Nuclear Magnetic Resonance : Volume 27 [1 ed.] 9781847553836, 9780854043170

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Nuclear Magnetic Resonance Volume 27

A Specialist Periodical Report

Nuclear Magnetic Resonance Volume 27 A Review of the Literature Published between June 1996 and May 1997 Senior Reporter G. A. Webb, Department of Chemistry,University of SurreK Guildford, UK Reporters J. R. P. Arnold, University of Leeds, UK P. C. Driscoll, University College, London, UK J. Fisher, University of Leeds, UK H. Fukui, Kitami Institute of Technology,Japan C. J. Jameson, University of Illinois at Chicago, USA K. Kamiehska-Trela, Polish Academy of Sciences, Warszawa, Poland C. L. Khetrapal,Indian Institute of Science, Bangalore, India S. M. Kristensen, University of Copenhagen, Denmark H. Kurosu,Nara Women'sUniversity,Nara CitK Japan L.Y Lian, University of Leicester, UK R. Ludwig, UniversitatDortmund, Germany M. J. W. Prior, University of Nottingham, UK K.V. Ramanathan,Indian Institute of Science, Bangalore, India W. Schilf, Polish Academy of Sciences, Warszawa, Poland M. E. Smith, University of Kent, Canterbury,UK T. Watanabe, Tokyo University of Fisheries, Tokyo,Japan J. Wojcik,Polish Academy of Sciences,Warszawa, Poland M.Yamaguchi,Kao Corporation,Tochigi Japan T Yamanobe, University of Gunma,Japan

THE ROYAL SOCIETY OF C HEMISTRY

Information Services

ISBN 0-85404-317-9 ISSN 0305-9804 Copyright

0The Royal Society of Chemistry 1998

All Rights Reserved Apart from any fair dealingf o r the purposes of research or private study, or criticism or review as permitted under the terms of the U K Copyright, Designs and Patents Act, 1988, this publication may not be reproduced, stored or transmitted, in any form or by any means, without the prior permission in writing of The Royal Society of Chemistry, or in the case of reprographic reproduction only in accordance with the terms of the licences issued by the Copyright Licensing Agency in the UK, or in accordance with the terms of the licences issued by the appropriate Reproduction Rights Organization outside the UK. Enquiries concerning reproduction outside the terms stated here should be sent to The Royal Society of Chemistry at the address printed on this page. Published by The Royal Society of Chemistry Thomas Graham House, Science Park, Milton Road, Cambridge CB4 4WF, UK For further information see our web site at www.rsc.org Typeset by Computape (Pickering) Ltd, Pickering, North Yorkshire, UK Printed by Athenaeum Press Ltd, Gateshead, Tyne and Wear, UK

Preface

The current volume consists of the usual collection of topics, reported on either annually or biennially, which will be familiar to readers of the Specialist Periodical Report on NMR. As in previous years I wish to express my sincere gratitude to the reporters for their very valiant attempts to provide a comprehensive coverage of the NMR literature over the twelve month period to which this volume relates. It is my great pleasure to welcome to the reporting team Drs. W. Schilf, R. Ludwig, S. M. Kristensen, €4. Kurosu and T. Yamanobe. At the same time my sincere thanks go to Drs. L. Y. Lian, J. R. P. Arnold and J. Fisher, who are retiring from the team, and to all the other reporters for their support and diligence in manuscript preparation for this volume. University of Surrey Guild ford October 1997

G. A. Webb

Contents

CHAPTER 1 NMR Books and Reviews By W. Schilf 1 Books 2 Regular Review Series 3 Edited Books and Symposia 4 Reviews in Periodicals 5 Reviews and Books in Foreign Languages CHAPTER 2 Theoretical and Physical Aspects of Nuclear Shielding By C. J. Jameson 1 Theoretical Aspects of Nuclear Shielding 1.1 General Theory 1.2 A b Initio Calculations 2 Physical Aspects of Nuclear Shielding 2.1 Anisotropy of the Shielding Tensor 2.2 Shielding Surfaces and Rovibrational Averaging 2.3 Isotope Shifts 2.4 Intermolecular Effects on Nuclear Shielding 2.5 Absolute Shielding 3 References CHAPTER 3 Applications of Nuclear Shielding By M . Yamaguchi 1 Introduction 2 Various Chemical and Physical Influences on Nuclear Shieldings 2.1 Computer Assisted Structural Assignment 2.1.1 Spectrum Simulation, Computer Assisted Assignments, and Related Techniques 2.1.2 Nuclear Shielding Calculations 2.2 Stereochemical Nuclear Shielding Non-Equivalence 2.2.1 Chirality Determination by Mosher’s and Related Methods 2.2.2 Other Stereochemistry Determination 2.3 Isotope Effects 2.4 Substituent Effects 2.4.1 Proton Substituent Effects 2.4.2 Carbon and Heteroatom Substituent Effects vii

1 i

1 4 18 35

44 44 44 60 63 63 67 69 69 75 76

83 83 83 83 83 84 85 85 86 87 87 87 88

...

Vlll

Contents

2.5 Intramolecular Hydrogen Bonding Effects and Related Effects 2.5.1 Proton Shifts 2.5.2 Heteronuclear Shifts 2.6 Bond Anisotrophy, Ring Current Effects and Aromatici ty 2.7 Intermolecular Hydrogen Bonding Effects, Inclusion Phenomena and Related Effects 2.7.1 Proton and Heteronuclear Shifts 2.7.2 Cyclodextrins (CDs) 2.7.3 Other Molecular Recognition 2.8 Shift Reagents 2.9 Miscellaneous Topics 3 Shielding of Particular Nuclear Species 3.1 Group 1 ('H, 2H, 3H, 677Li,23Na,39K,87Rb, 137Cs) 3.1.1 Hydrogen ('H) 3.1.2 Deuterium (2H) 3.1.3 Tritium (3H) 3.1.4 Lithium (677Li) 3.1.5 Sodium (23Na) 3.1.6 Potassium (39K) 3.1.7 Rubidium (85,87Rb) 3.1.8 Cesium (133Cs) 3.2 Group 2 (9Be, 25Mg) 3.2.1 Beryllium (9Be) 3.2.2 Magnesium (25Mg) 3.3 Group 3 and Lanthanoids e5Sc, "Y, '39La, I7'Yb) 3.3.1 Scandium (45Sc) 3.3.2 Yttrium (89Y) 3.3.3 Lanthanum ('39La) 3.3.4 Lanthanides (I4lPr, I7'Yb) 3.4 Group 5 (51V,93Nb) 3.4.1 Vanadium (5'V) 3.4.2 Niobium (93Nb) 3.5 Group 6 (95M0, Ig3W) 3.5.1 Molybdenum (95M0) 3.5.2 Tungsten (Ig3W) 3.6 Group 7 ("Mn, 99Tc) 3.6.1 Manganese (55Mn) 3.6.2 Technetium (99Tc) 3.7 Group 8 (57Fe, 1870s) 3.7.1 Iron (57Fe) 3.7.2 Osmium ('870s) 3.8 Group 9 (59C0, '03Rh) 3.8.1 Cobalt (59C0) 3.8.2 Rhodium ('03Rh)

88 88 89 89 89 89 89 90 91 91 92 92 92 92 93 93 93 94 94 94 94 94 94 94 94 94 95 95 95 95 95 96 96 96 96 96 96 96 96 97 97 97 97

ix

ConIenf s

3.9 Group 10 ("'Pt) 3.9.1 Platinum (19'Pt) 3.10 Group 11 (63Cu, Io9Ag) 3.10.1 Copper fj3cu) 3.10.2 Silver (lo9Ag) 3.1 1 Group 12 (67Zn, 133Cd,199Hg) 3.1 1.1 Zinc (67Zn) 3.1 1.2 Cadmium ('13Cd) 3.1 1.3 Mercury (199Hg) 3.12 Group 13 ("B, 27Al,69,71Ga,"'In, 205Tl) 3.12.1 Boron ("B) 3.12.2 Aluminium (27Al) 3.12.3 Gallium (69771Ga) 3.12.4 Thallium (2037205Tl) 3.13 Group 14 (I3C, 29Si,73Ge, 19Sn, 207Pb) 3.13.1 Carbon (13C) 3.13.2 Silicon (29Si) 3.13.3 ~i~ (115,117,119 Sn) 3.15.4 Lead (207Pb) 3.14 Group 15 (14,1'N,31P) 3.14.1 Nitrogen (l4,I5N) 3.14.2 Phosphorus (31P) 3.15 Group 16 (170, 33S,77Se,'25Te) 3.15.1 Oxygen (170) 3.15.2 Sulfur (33S) 3.15.3 Selenium (77Se) 3.15.4 Tellurium (12'Te) 3.16 Group 17 (19F,35y37~1) 3.16.1 Fluorine (I9F) 3.16.2 Chlorine (35737Cl) 3.16.3 Iodine ('271) 3.17 Group 18 (3He, 1297131Xe) 3.17.1 Helium (3He) 3.17.2 Xenon (12*9131Xe) 4 References

CHAPTER 4 Theoretical Aspects of Spin-Spin Couplings By H . Fukui 1 Introduction 2 A b Initio Calculations 2.1 Multiconfiguration Self-consistent Field Calculation 2.2 Coupled-Cluster Method 2.3 Hartree-Fock Calculation 3 Density Functional Theory 4 Empirical and Semiempirical Calculations

97 97 97 97 98 98 98 98 98 99 99 100 100 100 100 100 102 102 103 104 104 104 105 105 106 106 106 107 107 107 108 108 108 108 108 125

125 125

125 127 130 132 134

Conlents

X

4.1 Semiempirical CLOPPA Approach 4.2 Correlation Between Spin-Spin Couplings and Local Electronic Structures 5 Conformational Analysis 6 References

134 136 138 140

CHAPTER 5 Applications of Spin-Spin Couplings By K. Kamienska- Trela and J . Wbjcik 1 Introduction 2 Methods 3 One-Bond Couplings to Hydrogen 4 One-Bond Couplings Not Involving Hydrogen 5 Two-Bond Couplings to Hydrogen 6 Two-Bond Couplings Not Involving Hydrogen 7 Three-Bond Hydrogen-Hydrogen Couplings 8 Three-Bond Couplings Between Hydrogen and He teronuclei 9 Three-Bond Couplings Not Involving Hydrogen 10 Couplings Over More Than Three Bonds, and Through-Space 11 References

143

CHAPTER 6 Nuclear Spin Relaxation in Liquids and Gases By R. Ludwig 1 Introduction 2 General, Physical and Experimental Aspects of Nuclear Spin Relaxation 2.1 General Aspects 2.2 Experimental Aspects 2.3 Relaxation in Coupled Spin Systems 2.4 Dipolar Couplings and Distance Information 2.5 Exchange Spectroscopy 2.6 Quadrupolar Interactions 2.7 Intermolecular Dipolar Interaction in Diamagnetic and Paramagnetic Solutions 2.8 Slow Motions in Glasses 2.9 Models for Molecular Dynamics 3 Selected Applications of Nuclear Spin Relaxation 3.1 Pure Liquids 3.2 Non-Electrolyte Solutions 3.3 Electrolyte Solutions 3.4 Transition Metal Complexes 4 Nuclear Spin Relaxation in Gases 5 Self-Diffusion in Liquids 5.1 Experimental and Theoretical Aspects 5.2 Selected Examples

199

143 143 146 151 160 162 164 172 178 179 182

199 20 1 20 1 20 1 202 203 204 205 207 208 209 209 209 210 21 1 21 1 212 213 213 214

Contents

Xi

6 References

21 5

CHAPTER 7 Solid State NMR By M . E. Smith 1 Introduction 2 Technique Development 2.1 Theoretical 2.2 Experimental 3 Carbonaceous Materials 3.1 Coals, Pitches and Oil Shales 3.2 Fullerenes, Diamonds and Other Carbons 4 Organic Materials 4.1 General 4.2 Organometallics 4.3 Bio-Organic 4.4 Liquid Crystals, Membranes, Bilayers, Cell Walls and Woods 5 Organic-Inorganic Materials 5.1 General 5.2 Polysiloxanes 5.3 Soils and Humic Acids 6 Inorganic Materials 6.1 General 6.2 Silicates and Aluminosilicates 6.3 Microporous and Mesoporous Materials 6.3.1 Silicate-based Systems 6.3.2 Other Structural Studies 6.3.3 In Situ and Surface Reactions 6.4 Glasses 6.5 Ceramics 7 Miscellaneous 7.1 General 7.2 Dynamics and Intercalates 8 References

222

CHAPTER 8 Multiple Pulse NMR By L. Y. Lian 1 Introduction 2 Variation of the Radiofrequency Pulse 2.1 Composite and Decoupling Pulses 2.2 Solvent Suppression 3 Homonuclear Correlation Spectroscopy 3.1 Homonuclear Correlation 4 Dipolar Coupling, Chemical Exchange and Relaxation Time Experiments 4.1 Dipolar Coupling and Chemical Exchange

273

222 223 223 223 227 227 227 228 228 229 232 234 236 236 237 237 238 238 239 240 240 242 242 243 244 245 245 246 246

273 273 27 3 274 275 275 277 277

xii

Contents

4.2 Relaxation Time Measurements 278 5 Heteronuclear Experiments 279 5.1 Inverse Proton-Detected Correlation Spectroscopy 279 5.1.1 General 279 5.1.2 Heteronuclear Cross-Polarization Experiments 280 5.1.3 Isotope-Filtered Experiments 28 1 5.1.4 Isotope-Edited Experiments 28 1 5.2 Scalar Coupling Constants Using Heteronuclear Proton-Detection Experiments 282 6 Three- and Four-Dimensional NMR 284 6.1 Heteronuclear Triple ('H, 13C, "N) Resonance Three-Dimensional Experiments 284 6.2 Three-dimensional 13C-1Hor I5N-'H Experiments 286 6.3 Scalar Coupling Constants Using nD Heteronuclear Experiments With Proton-Detection 287 6.4 Homonuclear 3D Experiments 287 7 Analogues of nD Experiments 287 8 References 289 CHAPTER 9 NMR of Natural Macromolecules 292 By P . C . Driscoll and S. M . Kristensen 1 Introduction 292 2 Solution Structure Determination of Proteins 292 2.1 Landmark Protein Structures 293 2.2 NMR Spectroscopy of 'Large' Proteins 295 2.3 Deuterium Incorporation for Linewidth Narrowing 297 2.4 Selective Protonation Against a Deuteration Background 298 3 NMR Spectroscopy of Nucleic Acids 299 3.1 N M R o f D N A 299 3.2 Protein-DNA Complexes 299 3.3 N M R o f R N A 300 3.4 Protein-RNA Complexes 30 1 3.5 Aptamer RNA Complexes 302 3.6 An Aptamer DNA Complex 302 4 NMR of Protein-Protein and Other Ligand Interactions 303 5 Structure-Activity Relationships by NMR (SAR-by-NM R) 303 6 NMR Investigation of Macromolecular Solvation 305 7 Glycoproteins and Carbohydrate Binding 306 8 Technical Developments for Macromolecular NMR 307 8.1 Spin-Spin Couplings 307 8.1.1 Protein Coupling Constants 307 8.1.2 Nucleic Acid Coupling Constants 308 8.2 Direct Angle Measurements 308

Contents

xiii

9 10

11 12 13 14

15

8.3 Residual Dipolar Couplings 8.4 Adiabatic Decoupling 8.5 Side Chain Resonance Assignments Miscellaneous Aspects of Protein Side Chains Aspects of Protein Folding and Stability 10.1 Protein-Folding Pathways 10.2 Partially-Folded and Denatured States of Proteins NMR Studies of Proton Solvent Exchange New NMR Software Aspects of Solution Structure Calculation Nuclear Relaxation in Biological Macromolecules 14.1 Side Chain 13CRelaxation 14.2 Carbonyl 13C Relaxation 14.3 Rotational Diffusion Anisotropy 14.4 Conformational Restraints from Relaxation Data 14.5 Conformational Exchange 14.6 Theoretical Aspects 14.7 Applications of I5N and I3CRelaxation Measurements 14.8 Relaxation Studies of Other Nuclei References

CHAPTER 10 Synthetic Macromolecules By H . Kurosu and T. Yamanobe 1 Introduction 2 Characterization of Primary Structure of Polymers 3 Characterization of the Synthetic Macromolecules in the Solid State 3.1 Solid State 13CNMR Studies for Synthetic Macromolecules 3.2 Solid State Multi-Nuclear NMR Studies for Synthetic Macromolecules 3.3 Determination of Geometrical Parameters by Solid State NMR 4 Dynamics of the Synthetic Macromolecules in the Solid State 4.1 I3C NMR 4.2 I H NMR 4.3 2~ NMR 4.4 Other Nuclei NMR 4.5 Multi-Dimensional NMR 5 Characterization of the Synthetic Macromolecules in the Solution State 6 Dynamics of the Synthetic Macromolecules in the Solution State 7 Polymer Blends

309 309 3 10 3 10 31 1 31 1 3 12 313 314 315 316 316 318 320 321 32 1 322

323 325 326 337 337 337 344 344 346 347 347 347 348 349 349 350 350 350 35 1

xiv

Contents

8 9 10 11 12 13

7.1 Miscibility of Polymer Blends 7.2 Dynamics of Polymer Blends 7.3 Characterization of Polymer Blends Cross-Linked Polymers Polymer Gels Liquid Crystalline Polymers Diffusion Measurements for Polymeric Systems Imaging of Polymers References

35 1 352 352 353 354 355 355 356 356

CHAPTER 11 Conformational Analysis By J . R.P.Arnold and J . Fisher 1 Introduction 2 Methods 3 General 3.1 Rotation About Single Bonds 3.2 Six-Membered Rings 3.3 Other Ring Systems 3.4 Clusters 4 Restricted Mobility 5 Nucleosides and Nucleotides 6 Carbohydrates 7 Conformational Analysis of Bound Ligands 8 Organometallic Compounds 9 References

370

CHAPTER 12 Nuclear Magnetic Resonance Spectroscopy of Living Systems By M . J . W. Prior 1 Reviews and New Methodology 1.1 General Applications 1.2 Spectral Editing, Localisation and Instrumentation 1.3 Intracellular Ions, Metabolites and pH 2 Cells 2.1 Bacteria 2.2 Blood 2.3 Cultured Mammalian 2.4 Liver 2.5 Plant 2.6 Reproductive 2.7 Tumour 2.8 Yeast and Fungi 3 Plants and Algae 4 Tissue Studies 4.1 Brain and Spinal Cord 4.2 Eye 4.3 Heart 4.4 Kidney

386

370 370 37 1 371 372 373 374 377 378 379 380 380 38 1

386 386 386 387 388 388 389 390 39 1 39 1 39 1 39 1 393 394 395 395 398 399 404

Contents

xv

4.5 Liver 4.6 Pancreas 4.7 Lung 4.8 Muscle 4.9 Skin 4.10 Tumour 4.1 1 Whole Animal and Multiple-Tissue Studies 4.12 Reproductive 5 Clinical Studies 6 References

405 406 406 406 408 408 409 41 1 41 1 418

CHAPTER 13 Nuclear Magnetic Resonance Imaging By T. Watanabe 1 Introduction 2 Basic Principles, Education and Reviews 3 New Instruments 4 Pulse Sequences 5 Data Processing 6 Artifact, Noise and Optimization 7 Solid State NMR Imaging 8 0ther Nuclei 9 Diffusion, Flow and Velocity Imaging 9.1 Theoretical and/or Model Experimental 9.2 Diffusion, Flow and Mass Transport 9.3 Velocity and Its Profile 10 Solvent Assisted Imaging and Porosity 11 Water and Hydration 12 Polymers 13 Food and Food Processing 14 Botany, Plants and Seeds 15 In Vivo Imaging (Intact Insects, Fish, Bird Eggs) 16 In Vivo and Ex Vivo Imaging (Organs, Tissues) 17 References

431

CHAPTER 14 N M R of Paramagnetic Species By C. L. Khetrapal and K . V . Ramanathan 1 Introduction 2 Important Advances Having Bearing on Future Prospects 2.1 Discovery of New Thermotropic Liquid Crystals With Low Order Parameters 2.2 Orientation of Molecules by High Magnetic Fields 2.3 Natural Abundance 2H-NMR 2.4 Other Techniques for Spectral Simplification 2.4.1 Multiple Quantum Spectroscopy and Automatic Analysis Procedures

458

43 1 432 433 435 436 437 438 439 440 440 44 1 443 443 444 444 447 449 450 450 45 1

458 459 459 459 46 1 46 1

461

Contents

xvi

Multipulse and Multidimensional Techniques Reviews, Books and Monographs Theory, Erratum and General Studies New Techniques Including Combination of Various Techniques Chiral Systems Dynamic NMR Studies Discotics Polymeric Materials and Polymer Dispersed Liquid Crystals Membrane and Model Membrane Systems Diffusion Studies Anisotropies of Chemical Shift and Indirect Spin-Spin Coupling Relaxation Studies Molecular Order Molecular Structure and Conformation References 2.4.2

3 4 5 6 7 8 9 10 11 12 13 14 15 16

Author Index

464 466 467 468 469 469 470 47 1 472 473 474 474 475 478 479

485

Symbols and Abbreviations

These lists contain the symbols and abbreviations most frequently used in this volume, but they are not expected to be exhaustive. Some specialized notation is only defined in the relevant chapter. An attempt has been made to standardize usage throughout the volume as far as is feasible, but it must be borne in mind that the original research literature certainly is not standardized in this way, and some difficulties may arise from this fact. Trivial use of subscripts etc. is not always mentioned in the symbols listed below. Some of the other symbols used in the text, e.g. for physical constants such as h or T , or for the thermodynamic quantities such as H or S, are not included in the list since they are considered to follow completely accepted usage.

Symbols hyperline (electron-nucleus) interaction constant (i) hyperfine (electron-nucleus) interaction constant (ii) parameter relating to electric field effects on nuclear shielding (i) magnetic induction field (magnetic flux density) (ii) parameter relating to electric field effects on nuclear shielding static magnetic field of NMR or ESR spectrometer r.f. magnetic fields associated with vI ,vz spin-rotation coupling constant of nucleus X (used sometimes in tensor form): c2=1/3(Ci 2c3. components of C parallel and perpendicular to a molecular symmetry axis (i) self-diffusioncoefficient (ii) zero-field splitting constant rotational diffusion tensor components of D parallel and perpendicular to a molecular symmetry axis internal diffusion coefficient overall isotropic diffusion coefficient electric field eigenvalue of &or a contribution to i@) nuclear or electronic g-factor magnetic field gradient element of matrix representation of H Hamiltonian operator-subscripts indicate its nature nuclear spin operator for nucleus i components of Ii (i) ionization potential (ii) moment of inertia nuclear spin-spin coupling constant through n bonds (in Hz). Further information may be given by subscripts or in brackets. Brackets are used for indicating the species of nuclei coupled, e.g. J( I3C, H) or additionally, the coupling path, e.g. J(P0CF) reduced splitting observed in a double resonance experiment rotational quantum number reduced nuclear spin-spin coupling constant (see the notes concerning ' I J )

+

xvii

xviii mi

MO

SA

t T

P "IX 6X

AJ An A6 A", Au

Symbols and Abbreviations

eigenvalue of Ziz(magnetic component quantum number) equilibrium macroscopic magnetization of a spin system in the presence of BO components of macroscopic magnetization the number of average mol. wt. valence p orbital of atom A fractional population (or rotamers erc.) element of bond-order, charge-density matrix electric field gradient (i) nuclear quadrupole moment (ii) quality factor for an r.f. coil valence s-orbital of atom A electron density in SA at nuclear A (i) singlet state (ii) electron (or, occasionally, nuclear spin) cf I (iii) ordering parameter for oriented systems (iv) overlap integral between molecular orbitals elapsed time (i) temperature (ii) triplet state coalescence temperature for an NMR spectrum the glass transition temperature (of a polymer) spin-lattice relaxation time of the X nuclei (further subscripts refer to the relaxation mechanism) spin-spin relaxation time of the X nucleus (further subscripts refer to the relaxation mechanism) inhomogeneity contribution to dephasing time for M , or M,. total dephasing time for M , or M y ; (T;)-' = Ti + ( T i ) - ' decay time following 900-r-9090 pulse sequences spin-lattice and spin-spin relaxation time of the X nuclei in the frame of reference rotating with BI dipolar spin-lattice relaxation time mole fraction of compound atomic number of atom A (i) nuclear spin wavefunction (eigenfunction of I:) for a spin - nucleus (ii) polarizability nuclear spin wavefunction (eigenfunction of I-) for a spin nucleus magnetogyric ratio of nucleus X chemical shift of a nucleus of element X (positive when the sample resonates to high frequency of the reference). Usually in p.p.m. Kronecker delta ( = 1 if i = j , and = 0 otherwise) Dirac delta operator (i) time between field gradient pulses (ii) spectral width anisotropy in J (AJ = J I I- JI,for axial symmetry) population difference between nuclear states change of difference in S full width (in Hz) of a resonance line at half-height (i) anisotropy in u(Au = 011 - 01,for axial symmetry) (ii) differences in u for two different situations (i) susceptibility anisotropy (A, = X I I - xI,for axial symmetry (ii) differences in electronegativities relative permittivity permittivity of a vacuum (i) nuclear Overhauser effect (ii) asymmetry factor (e.g. in &qQ/h)

Symbols and Abbreviations

P

PO PB PN vi

vo

(iii) refractive index (iv) viscosity magnetic dipole moment permeability of a vacuum Bohr magneton nuclear magneton Larmor precession frequency of nucleus i (in Hz) (i) spectrometer operating frequency (ii) Larmor precession frequency (general, or of bare nucleus) frequency of ‘observing’r.f. magnetic field frequency of ‘irradiating’ r.f. magnetic field shielding parameter of nucleus i (used sometimes in tensor form). Usually in p.p.m. Subscripts may alternatively indicate contributions to (I. components of u parallel and perpendicular to a molecular symmetry axis diagrammatic contribution to (I paramagnetic contribution to u (i) pre-exchange lifetime of molecular species (ii) time between r.f. pulses (general symbol) correlation time mean time between molecular collisions in the liquid state angular momentum correlation time pulse duration translational magnetic relaxation correlation time (i) magnetic susceptibility (ii) electronegativity (iii) nuclear quadrupole coupling constant (= e‘qQ/h) carrier frequency in rad s-I as for v;,vo,v1 ,v2 but in rad sP1 modulation angular frequency (in rad s-I) sample rotation (rad S-I)

Abbreviations (a) Physical properties a.f. a.u. a.m. b.c.c. c.m.c. e.d. e.f.g. f.c.c. f.m. h.c.p. h.f. i.d. i.f. I.C.

mol. wt. 0.d. p.p.m.

xi x

audiofrequency atomic unit amplitude modulation body-centred cubic critical micelle concentration electron diffraction electric field gradient face-centred cubic frequency modulation hexagonal close-packea hyperfine inside diameter intermediate frequency liquid crystalline molecular weight outside diameter parts per million

xx r.f. r.m.s. s.h.f. u.h.f. ADC AEE AQ ARP BIRD CCPPA CH-COSY CHESS CHF CIDEP CIDNP COSY CP CPMG CSA CSI

cw

DAC DD DEPT DLB DNP DQ DQF ECOSY EHT ENDOR EOM ESR EXSY FC FID FLASH FPT FT GIAO HMQ HOHAHA HRPA IDESS IGLO INADEQUATE INDO INDO/S INDOR INEPT IR ISIS LIS LORG LSR

Symbols and Abbreviations

radio frequency root mean square super-high frequency ultra-high frequency analog-to-digital converter average excitation energy approximation acquire adiabatic rapid passage bilinear rotation decoupling coupled cluster polarization propagator approximation carbon-hydrogen correlation spectroscopy chemical shift selection coupled Hartree-Fock molecular orbital calculations chemically induced dynamic electron polarization chemically induced dynamic nuclear polarization correlation spectroscopy cross polarization Carr-Purcell pulse sequence. Meibom-Gill modification chemical shielding anisotropy chemical shift imaging continuous wave digital-to-analog converter dipole-dipole (interaction or relaxation mechanism) distortionless enhancement by polarization transfer differential line broadening dynamic nuclear polarization double quantum double quantum filter exclusive correlation spectroscopy extended Huckel molecular orbital theory electron-nucleus double resonance equations of motion electron spin resonance exchange spectroscopy Fermi contact free induction decay fast low angle shot finite perturbation theory Fourier transform gauge included atomic orbitals heteronuclear multiquantum homonuclear Hartman-Hahn higher random phased approximation improved depth selective single surface coil spectroscopy individual gauge for different localized orbitals incredible natural abundance double quantum transfer experiment intermediate neglect of differential overlap intermediate neglect of differential overlap calculations for spectroscopy internuclear double resonance insensitive nuclei enhanced by polarization transfer infrared image selected in vivo spectroscopy lanthanide induced shift local origin Ianthanide shift reagent

Symbols and Abbreviations

MASS MBPT MEM MIND0 MQ MQC MQF NMR NOE NOESY NQCC NQR PFG PRE QF QPD REX ROESY RPA SCPT SD SECSY SEFT SLITDRESS SOPPA SPI SPT SR TART TOCSY

uv

WAHUHA ZQ ZQC

magic angle sample spinning many body perturbation theory maximum entropy method modified INDO multiple quantum multiple quantum coherence multiple quantum filter nuclear magnetic resonance nuclear Overhauser enhancement nuclear Overhauser enhancement spectroscopy nuclear quadrupole coupling constant nuclear quadrupole resonance pulsed field gradient proton relaxation enhancement quadrupole moment/field gradient quadrature phase detection relativistically extended Huckel molecular orbital theory rotating frame Overhauser enhancement spectroscopy random phase approximation self consistent perturbation theory spin dipolar spin echo correlation spectroscopy spin echo Fourier transform slice interleaved depth resolved surface coil spectroscopy second order polarization propagator approach selective population inversion selective population transfer spin rotation (interaction or relaxation mechanism) tip angle reduced TI imaging total correlation spectroscopy ultraviolet Waugh, Huber and Haberlen (cycle of pulses) zero quantum zero quantum coherence

(b) Chemical species* acetylacetonat o acac ACTH adrenocorticotropic hormone (corticotropin) ADP adenosine diphosphate AMP adenosine monophosphate ATP adenosine triphosphate BSA bovine serum albumin CMP cytidine monophosphate CP cyclopentadieny 1 DAP dodecylammonium propionate DME 1,2-dimethoxyethane DMF dimethylformamide DML dimyristoyl-lecithin DMS dimethylsiloxane DMSO dimethyl sulfoxide DNA deoxyribonucleic acid DPG 2,3-diphosphoglycerate DPI dipalmitoyl-lecithin dPm dipivaloy lmethanato DPPH diphenylpicrylhydrazy1 Lower case initials are used when the species is a ligand.

xxi

Symbols and Abbreviations

xxii DSS DTBN EBBA EDTA EVA fod HAB HMPA HOAB IHP KDP MBBA NADH(P) NMF PAA PBA PBLG PC PCB PDMS PMA PMMA POM PS PTFE PVC PVF PVP RNA SDS TAB TCNQ TFA THF TMS UTP

2,2-dimethyl-2-silapentane-5-sulfonate (usually as the sodium salt) di-t-butyl nitroxide N-(p-ethoxybenzy1idene)-p-but y laniline ethylenediaminetetra-aceticacid ethylene-vinyl acetate 1, I , 1,2,2,3,3-heptafluoro-7,7-dimethyloctane-4,6-dionato 4,4’-bis(hepty1)azoxybenzene hexamethylphosphoramide p-n-heptyloxyazoxybenzene inositolhexaphosphate potassium dihydrogen phosphate N-@-methoxybenzy1idene)-p-butylaniline nicotinamide adenine dinucleotide (phosphate) N-methy lformamide p-azox yanisole pyrene butyric acid poly(L-benzyl pglutamate) phosphatidyl choline (lecithin) polychlorinated biphenyl polydimeth ylsiloxane poly(methacry1ic acid) poly(methy1 methacrylate) poly(oxymethy1ene) phosphatid ylserine polytetrafluoroethylene poly(viny1chloride) poly(viny1fluoride) poly(viny1 pyrrolidone) ribonucleic acid (tRNA, transfer RNA) sodium dodecyl sulfate trimethylammonium bromide tetracy anoquinodimethane trifluoroacetic acid tet rah ydrofuran tetramethylsilane uridine triphosphate

Amino -adic residues alanine Ala arginine Arg asparagine Asn aspartic acid ASP cysteine CYs glutamine Gln glutamic acid Glu glycine GlY histidine His hydrox yproline HYP isoleucine Ile

Leu LYS Met Phe Pro Ser Thr Trp TYr Val

leucine lysine methionine phen y lalanine proline serine threonin tryptophan tyrosine valine

1 NMR Books and Reviews COMPILED BY W. SCHILF

1

Books

R1

F. A. Bovey and P. A. Mirau, ‘NMR of Polymers’, Academic, San Diego, Calif., 1996,459 pp

2

Regular Review Series

Accounts of Chemical Research, 1996, vol. 29 R2

R3

R4

J. F. Haw, J. B. Nicholas, T. Xu, L. W. Beck and D. B. Ferguson, ‘Physical Organic Chemistry of Solid Acids: Lessons From in Situ NMR and Theoretical Chemistry’, p. 259 A. G. Marshall, Ion Cyclotron Resonance and Nuclear Magnetic Resonance Spectroscopies: Magnetic Partners for Elucidation of Molecular Structure and Reactivity, p. 307 J. Stubbe, J. W. Kozarich, W. Wu and D. E. Vanderwall, ‘Bleomycins: A Structural Model for Specificity, Binding, and Double Strand Cleavage’, p. 322

ACS Monographs, 1996, vol. 187 R5

T. S. Everett, ‘Nuclear Magnetic Resonance Spectroscopy of Organofluorine Compounds’, p. 1037

Advances in Chemistry Series, 1996, vol. 251 R6

H. A. Nasr-El-Din, ‘Flow of Suspension in Pipelines’, p. 177

Advances in Magnetic and Optical Resonance, ed. W. S . Warren, 1996, vol. 19 R7 R8 R9

F. Prig1 and U. Haeberlen, ‘The Theoretical and Practical Limits of Resolution in Multiple-Pulse High-Resolution NMR of Solids’, p. 1 S. J. Glaser and J. J. Quant, ‘Homonuclear and Heteronuclear HartmannHahn Transfer in Isotropic Liquids’, p. 59 P. T. Callaghan and J. Stepisnik, ‘Generalized Analysis of Motion Using Magnetic Field Gradients’, p. 325

Nuclear Magnetic Resonance, Volume 27

0The Royal Society of Chemistry 1998 1

2

Nuclear Magnetic Resonance

Advances in Spectroscopy, 1996, vol. 25 R10 C. M. Spickett, W. E. Smith and J. Reglinski, ‘Proton NMR Studies of Oxidative Stress in Disease’, p. 267 R11 M. Grootveld, A. Sheerin, M. Atherton, A. D. Millar, E. J. Lynch, D. R. Blake and D. P. Naughton, ‘Applications of High Resolution NMR Analysis to the Study of Inflammatory Diseases at the Molecular Level’, p. 295 Annual Reports on Medicinal Chemistry, 1996, vol. 3 1 R12 S. J. Archer, P. J. Domaille and E. D. Laue, ‘New NMR Methods for Structural Studies of Proteins to Aid in Drug Design’, p. 299 Annual Reports on N M R Spectroscopy, ed. G . A. Webb, 1996, vol. 32 R13 A. M. Gil, P. S. Belton and B. P. Hills, ‘Application of NMR to Food Science’, p. 1 R14 W. S. Price, ‘Gradient NMR’, p. 51 R15 D. J. Craik, K. J. Nielsen and K. A. Higgins, ‘Pharmaceutical Applications of NMR’, p. 143 R16 C. J. Groombridge, ‘NMR Spectroscopy in Forensic Science’, p. 21 5 Annual Reviews of Biophysics and Biomolecular Structure, 1996, vol. 25 R17 R. G. Bryant, ‘The Dynamics of Water-Protein Interactions’, p. 29 R18 A. Graeslund and M. Sahlin, ‘Electron Paramagnetic Resonance and Nuclear Magnetic Resonance Studies of Class I Ribonucleo tide Reductase’, p. 259 Annual Reviews of Physical Chemistry, 1996, vol. 47 R19 C. J. Jameson, ‘Understanding NMR Chemical Shifts’, p. 135 R20 K. T. Dayie, G. Wagner and J-F. Lefevre, ‘Theory and Practice of Nuclear Spin Relaxation in Proteins’, p. 243 R21 H. J. Dyson and P. E. Wright, ‘Insights into Protein Folding from NMR’, p. 369 Comprehensive Supramolecular Chemistry, ed. G. Alberti and T. Bein, Elsevier, Oxford, UK, 1996, vol. 7 R22 D. N. Theodorou, R. Q. Snurr and A. T. Bell, ‘Molecular Dynamics and Diffusion in Microporous Materials’, p. 507 Comprehensive Supramolecular Chemistry, ed. J. Davies, D. Eric and J. A. Ripmeester, Elsevier, Oxford, UK, 1996, vol. 8 R23 E. A. C . Lucken, F. Grandjean and G. J. Long, ‘NQR and Moessbauer Spectroscopy [In Supramolecular Chemistry]’, p. 225

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R24 D. D. Klug and J. S. Tse, ‘High-pressure Methods [In Supramolecular Chemistry]’, p. 307

Coordination Chemistry Reviews, 1996, vol. 148 R25 A. Mori, K. Kubo and H. Takeshita, ‘Synthesis and Metallophilic Properties of Troponoid Thiocrown Ethers’, p. 71 R26 Y. Habata and S. Akabori, ‘Alkylphosphoric Acid Armed Crown Ethers Having a Specific Cation Binding Ability’, p. 97 R27 K. Naemura, Y. Tobe and T. Kaneda, ‘Preparation of Chiral and Meso-crown Ethers Incorporating Cyclohexane-l,2-diol Derivatives as a Steric Barrier and their Complexation with Chiral and Achiral Amines’, p. 199 1996, vol. 149 R28 J. Fraissard, R. Vincent, C. Doremieux, J. Karger and H. Pfeifer, ‘Application of NMR Methods to Catalysis’, p. 1 R29 D. J. Nelson, ‘Aluminium Complexation with Nucleoside Di- and Triphosphates and Implication in Nucleoside Binding Proteins’, p. 95 R30 J. M. Aramini, J. A. Saponja and H. J. Vogel, ‘Spectroscopic Studies of the Interaction of Aluminum(II1) with Transferrins’, p. 193 1996, vol. 150 R31 I. Bertini and C. Luchinat, ‘NMR of Paramagnetic Substances’, p. 1 1996, vol. 151 R32 S. J. Berners-Price and P. J. Sadler, ‘Coordination Chemistry of Metallodrugs : Insights into Biological Speciation from NMR Spectroscopy’, p. 1 1996, vol. 154 R33 R. C. Fay, ‘Stereochemistry and Molecular Rearrangements of Some Six-, Seven-, and Eight-Coordinate Chelates of Early Transition Metals’, p. 99 1996, vol. 155 R34 P. S. Pregosin and R. Salzmann, ‘Structure and Dynamics of Chiral Ally1 Complexes of Pd(I1): NMR Spectroscopy and Enantioselective Allylic Alkylation’, p. 35 R35 E. Lindner, S. Pautz and M. Haustein, ‘Dynamic, Reactivity and Catalytic Behavior of Pseudo-Undercoordinated Ruthenium and Rhodium Complexes Stabilized by Intramolecular Solvents’, p. 145

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Macromolecular Symposia, vol. 107, 1996

R36 S. Penczek and A. Duda, ‘Selectivity as a Measure of “Livingness” of the Polymerization of Cyclic Esters’, p. 1 N M R Basic Principles and Progress, ed. P . Diehl, E. Fluck, H. Giinther, R. Kosfeld and J. Seelig, Springer, Berlin, Germany, 1996, vol. 34

R37 N. Chandrakumar, ‘Spin-1 NMR’ Progress in N M R Spectroscopy ed. J . W . Emsley, J. Feeney and L. H. Sutcliffe, 1996, vol. 28

R38 K. Asayama, Y. Kitaoka, G. Zheng and K. Ishida, ‘NMR Studies of High T, Superconductors’, p. 221 R39 J. M. Miller, ‘Fluorine-19 Magic-Angle Spinning NMR’, p. 255 R40 J. A. Peters, J. Huskens and D. J. Raber, ‘Lanthanide Induced Shifts and Relaxation Rate Enhancements’, p. 283 1996, vol. 29 R4 1 J. C. Lindon, J. K. Nicholson and 1. D. Wilson, ‘Direct Coupling of Chromatographic Separations to NMR Spectroscopy’, p. 1 R42 G . Varani, F. Aboul-ela and F. H. -T. Allain, ‘NMR lnvestigation of RNA Structure’, p. 51 R43 D. Farcasiu and A. Ghenciu, ‘Determination of Acidity Functions and Acid Strengths by I3C NMR’, p. 129 R44 F. Schick, ‘Bone Marrow NMR In Vivo’, p. 169 R45 A. C. de Dios, ‘Ab Initio Calculations of the N M R Chemical Shift’, p. 229

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Edited Books and Symposia

A CS Symposia Series

R46 J. L. Bonardet, M. C. Barrage and J. Fraissard, ‘NMR Techniques for Studying the Coking of Zeolite-Based Catalysts’, 1996,634,99 R47 I. Ojima, S. D. Kuduk, J. C. Slater, R. H. Gimi, C. M. Sun, S. Chakravarty, M. Ourevitch, A. Abouabdellah, D. Bonnet-Delpon, et al., ‘Syntheses, Biological Activity, and Conformational Analysis of FluorineContaining Taxoids’, 1996,639,228 R48 J. M. Bortiatynski, P. G. Hatcher and H. Knicker, ‘NMR Techniques (C, N, and H) in Studies of Humic Substances’, 1996,651, 57 R49 I. Bertini and C. Luchinat, ‘Electronic Isomerism in Oxidized Fe4S4HighPotential Iron-Sulfur Proteins’, 1996,653, 57

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R50 G. Sakane and T. Shibahara, ‘Characterization of Incomplete CubaneType and Cubane-Type Sulfur-Bridged Clusters’, 1996,653,225 R51 R. C. Rayne and M. O’Shea, ‘Neuropeptide Biosynthesis: Possible Molecular Targets for the Control of Insect Pests’, 1997,658,292 Advances in Carbanion Chemistry

R52 S. Bradamante and G. A. Pagani, ‘Benzyl and Heteroarylmethyl Carbanions: Structure and Substituent Effects’, 1996,2, 189 Bioactive Compound Design: Possibilities for Industrial Use, ed. M. G. Ford, R. Greenwood, G. T. Brooks and R. Franke, Bios Scientific Publishers, Oxford, UK, 1996

R53 H. Kubinyi, ‘Computer-Aided Drug Design. Facts and Fictions’, p. 1 Biochemical Aspects of Marine Pharmacology, ed. P. Lazarovici, M. Spira and E. Zlotkin, Alkan, Fort Collins, Colo., 1996

R54 Y. Kashman and A. Rudi, ‘Bioactive Sponge and Ascidian Secondary Metabolites’, p. 209 Bioenergetics: A Practical Approach, ed. G. C . Brown and C. E. Cooper, IRL Press, Oxford, UK, 1995

R55 K. M. Brindle, A. M. Fulton and S-P. Williams, ‘Studies of Cellular Energetics Using 3’P NMR’, p. 159 Biological Membranes ( A Molecular Perspective from Computation and Experiment), ed. K. M. Merz Jr. and B. Roux, Birkhauser, Boston, Mass., 1996

R56 M. F. Brown, ‘Membrane Structure and Dynamics Studied with NMR Spectroscopy’, p. 175 R57 R. R. Ketchem, B. Roux and T. A. Cross, ‘Computational Refinement Through Solid State NMR and Energy Constraints of a Membrane Bound Polypeptide’, p. 299 Biopolymer Mixtures, ed. S . E. Harding, S. E. Hill and J. R. Mitchell, Nottingham University Press, Nottingham, UK, 1995

R58 M. A. K. Williams, R. D. Keenan and T. K. Halstead, ‘The Use of NMR in Characterizing Biopolymer Mixtures’, p. 117 The Chemistry of Halides, Pseudo-Halides and Azides, ed. S . Patai and Z. Rappoport, Wiley, Chichester, UK, 1995 (Pt. 1)

R59 P. Taylor and B. Everatt, ‘NMR Spectroscopy’, p. 267

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R60 M. Geoffroy and E. A. C. Lucken, ‘Electron Spin Resonance and Nuclear Quadrupole Resonance’, p. 289 Complex Formation and Stereochemistry of Coordinating Compounds, Y. Buslaev, Nova Science Publishers, Commack, N. Y . , 1996

ed.

R61 G. Kirakosyan, ‘NMR in the Study of Inorganic Complexes of the Noble Metals’, p. 49 R62 V. I. Minkin and L. E. Nivorozhkin, ‘Stereodynamics and Degenerated Ligand Exchange in the Solutions of Tetracoordinated Chelate Complexes of Non-Transition Metals’, p. 77 Comprehensive Polymer Science, Second Supplement, ed. S. L. Aggarwal and S. Russo, Elsevier, Oxford, UK, 1996

R63 D. D. Werstler, ‘Two-Dimensional NMR Spectroscopy for the Structural Characterization of Polymers’, p. 197 Enzymology Labfax, ed. P. C. Engel, Academic, San Diego, Calif., 1996

R64 R. Cammack and J. K . Shergill, ‘EPR Spectroscopy in Enzymology’, p. 249 Evolutionary Biochemistry and Related Areas of Physicochemical Biology, ed. B. F. Poglazow, Bach Institute of Biochemistry, Moscow, Russia, 1995

R65 D. N. Ostrovsky, G. R. Diomina, E. I. Lysak and 1. N. Shipanova, ‘Novel Products and Participants of Oxidative Stress in Bacteria’, p. 599 Free Radicals: A PracticaZ Approach, ed. N. A. Punchard and F. J. Kelly, IRL Press, Oxford, UK, 1996

R66 D. P. Naughton, E. Lynch, G. E. Hawkes, J. Hawkes, D. R. Blake and M. Grootveld, ‘Detection of Free Radicals Reaction Products by High-Field Magnetic Resonance Spectroscopy’, p. 25 From Simplicity to Complexity in Chemistry - and Beyond, (Pt.Z), ed. A. Mueller, A. Dress and F. Voegtle, Vieweg & Sohn, Wiesbaden, Germany, 1996

R67 L. J. De Jongh, ‘Physical Properties of High-Nuclearity Metal Cluster Compounds: Model Systems for Uniform-Sized Metal Particles’, p. 163 Handbook of Metal-Ligand Interactions of Biological Fluids: Bioinorganic Medicine, ed. G. Berthon, Marcel Dekker, New York, 1995, vol. 1

R68 J. S. Valentine, ‘Metal-Protein Interactions. Generalities on Metal IonProtein Interactions and their Investigation Techniques’, p. 130

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Handbook on the Physics and Chemistry of Rare Earths, ed. K. A. Gschneidner Jr. and L. Eyring, Elsevier, Amsterdam, Neth., 1996 R69 J. H. Forsberg, ‘NMR Studies of Paramagnetic Lanthanide Complexes and Shift Reagents’, p. 1 Handbook of Polymer-Fibre Composites., ed. F. R. Jones, Longman Scientific & Technical, Harlow, UK, 1994 R70 J. N. Hay, ‘High Temperature Resins - Thermosetting Polyimides’, p. 96 High Pressure Science and Technology, Proceedings of the Joint X V AIRAPT and XXXIII EHPRG International Conference, 1995, ed. W. A. Trzeciakowski, World Scientific, Singapore, I996 R71 J. Jonas, ‘NMR Studies of Pressure-Induced Reversible Unfolding of Proteins’, p. 860 High Temperature Superconductivity: Models and Measurements, Proceedings of the 1994 GNSM School, ed. M. Acquarone, World Scientific, Singapore, 1996 R72 P. Carretta and A. Rigamonti, ‘NMR-NQR Studies in Cuprates: from the Antiferromagnetic to the Superconducting State’, p. 493. Immobilised Living Cell Systems: Modelling and Experimental Methods, ed. R. G. Willaert, G. V. Baron and L. De Backer, Wiley, Chichester, UK, 1996 R73 E. J. Fernandez, ‘Nuclear Magnetic Resonance Spectroscopy and Imaging’, p. 117 Introduction to Biophysical Methods for Protein and Nucleic Acid Research., ed. J. A. Glasel and M. P. Deutscher, Academic, San Diego, 1995 R74 B. W. Bangerter, ‘Nuclear Magnetic Resonance’, p. 317 Ionomers Characterization, Theory, and Applications, ed. S. Schlick, CRC, Boca Raton, Fla., 1996 R75 S. Schlick and G. Gebel, ‘NMR Spectroscopy of Bulk Perfluorinated Ionomers and Solutions: Information on Structure and Dynamics’, p. 165 R76 G. Martini, S. Ristori and M. Visca, ‘Self-Assembling of Perfluorinated Surfactants’, p. 2 19

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Lecture Notes of the Eighth Chinese International Summer School of Physics, Beijing, 1995, (Aspects of Modern Magnetism), ed. F. C. Pu, Y. J. Wang and C. H. Shang, World Scientific, Singapore, 1996

R77 Y. D. Zhang, J. I. Budnick and W. A. Hines, ‘Applications of Nuclear Magnetic Resonance in the Study of Magnetic Materials’, p. 236 Liquid Crystals in Complex Geometries Formed by Polymer and Porous Networks, ed. G. P. Crawford and S. Zumer, Taylor & Francis, London, UK, 1996

R78 M. Vilfan and N. Vrbancic-Kopac, ‘Nuclear Magnetic Resonance of Liquid Crystals with an Embedded Polymer Network’, p. 59 Moessbauer Spectroscopy Applied to Magnetism and Materials Science, vol. I i , ed. G. J. Long and F. Grandjean, Plenum, New York, 1996

R79 C. Sauer, ‘Magnetic and Structural Properties of Real Metal Layer Interfaces’, p. 3 1 NATO Advanced Study Institute Series, Series A , 1996, vol. 288

R80 Y. Bai and S. W. Englander, ‘The Cooperative Substructure of Protein Molecules’, p. 1 R8 1 P. J. Connolly, A. S. Stern and J. C. Hoch, ‘Solution Structure of the Long Neurotoxin LSIII with Possible Implications for Binding to the Acetylcholine Receptor’, p. 29 R82 C. G. Hoogstraten and J. L. Markley, ‘Approaches to the Determination of More Accurate Cross-Relaxation Rates and the Effects of Improved Distance Constraints on Protein Solution Structures’, p. 73 R83 L. J. Smith and C . M. Dobson, ‘Insights into Protein Dynamics by NMR Techniques’, p. 127 R84 K. T. Dayie, G. Wagner and J. -F. Lefevre, ‘Heteronuclear Relaxation and the Experimental Determination of the Spectral Density Function’, p. 139 R85 A. Ramamoorthy, F. M. Marassi and S. J. Opella, ‘Applications of Multidimensional Solid-state NMR Spectroscopy to Membrane Proteins’, p. 237 Series C , 1996, vol. 480

R86 J. A. Ripmeester and C. I. Ratcliffe, ‘Solid-state NMR in Inclusion Compounds. Synoptic Approaches to Structure Determination’, p. 101 1996, vol. 485 R87 H. -J. Schneider and J. Sartorius, ‘An Incremental Empirical Approach to Noncovalent Interactions in and with DNA’, p. 11

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R88 J. L. Dye, ‘Magnetic, Electrical and Spectroscopic Studies of Alkalides and Electrides. Experimental Methods and Examples’, p. 3 13 R89 Z. Chen, L. Mercier, J. J. Tunney and C . Detellier, ‘Dynamics of Supramolecular Assemblies in Solution and Solid State’, p. 393 Series E, 1996, vo1.320

R90 S. Hanessian, ‘Target-Driven Organic Synthesis: Reflections on the Past, Prospects for the Future’, p. 61 1996, Vo1.327 R9 1 Y. Morishima, ‘Unimolecular Micelles of Hydrophobically Modified Polyelectrolytes’, p. 33 1 N M R Spectroscopy Techniques: Second Edition, Revised and Expanded. [In: Practical Spectroscopy, 1996;21], ed. M. D. Bruch, Marcel Dekker, New York, 1996,616 pp

R92 D. D. Traficante, ‘NMR Concepts’, p. 1 R93 M. D. Bruch and C. Dybowski, ‘Spectral Editing Methods for Structure Elucidation’, p. 61 R94 R. E. Wasylishen, ‘NMR Relaxation and Dynamics’, p. 105 R95 M. D. Bruch, ‘Multidimensional NMR Spectroscopy of Liquids’, p. 145 R96 C. K. McClure, ‘Small Organic Molecules: Practical Tips and Structure Elucidation’, p. 239 R97 J. Rizo and M. D. Bruch, ‘Structure Determination of Biological Macromolecules’, p. 285 R98 L. W. Jelinski and M. T. Melchior, ‘High-Resolution NMR of Solids’, p. 417 R99 C. Dybowski, ‘Wide-Line and Line-Narrowing NMR Techniques’, p. 487 R100 A. J. Brandolini, ‘Chemical and Physical Characterization of Polymer Systems by NMR Spectroscopy’, p. 525 RlOl V. Seshan and N. Bansal, ‘In Vivo 31Pand 23Na NMR Spectroscopy and Imaging’, p. 557 Organosilicon Chemistry, 11, f Muenchen Silicontage], 2nd 1994, ed. N. Auner and J. Weis, VCH, Weinheim, Germany, 1996

R102 E. Brendler, K. Leo, B. Thomas, R. Richter, G . Roewer and H. Kraemer, ‘Disproportionation of Tetrachlorodimethyldisilane-NMR-Spectroscopic Identification of the Primary Products’ p. 69 R103 W. Koll and K. Hassler, ‘Synthesis and Spectroscopy of Phenylated and Halogenated Trisilanes and Disilanes’, p. 81 R104 U. Poschl, H. Siegl and K. Hassler, ‘Synthesis, Reactivity, and

Nuclear Magnetic Resonance

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Spectroscopy of Phenylated Cyclotetrasilanes and Cyclopentasilanes’, p. 113

R105 H. Stuger and P. Lassacher, ‘Oligosilanylsulfanes: New Functional Derivatives of Higher Silicon Hydrides’, p. 121 R106 C-R. Heikenwaelder and N. Auner, ‘Cycloaddition Reactions of 1, 1-Dichloro-2-neopentylsilenewith Pentafulvenes’, p. 399 R107 A. R. Bassindale, S. G. Glynn, J. Jiang, D. J. Parker, R. Turtle, P. G. Taylor and S. S. D. Brown, ‘Recent Explorations of the Chemistry of Pentacoordinate Silicon’, p. 41 1 R108 M. Muehleisen and R. Tacke, ‘Syntheses and Solution-State NMR Studies of Zwitterionic Spirocyclic h5Si - Organosilicates Containing Two Identical Unsymmetrically Substituted 1,2-Benzenediolat0(2-) Ligands’, p. 447 R109 0. Dannappel and R. Tacke, ‘Intramolecular Ligand Exchange of Zwitterionic Spirocyclic Bis[ 1,2-benzenediolato(2-)]organosilicates: Ab Initio Studies of the Bis[ 1,2-benzenediolato(2-)]-hydridosilicate(1-) Ion’, p. 453 RllO J. Belzner and D. Schaer, ‘Highly Coordinated Silicon Compounds Hydrazino Groups as Intramolecular Donors’, p. 459 R l l l J. Grobe, H. H. Niemeyer and R. Wehmschulte, ‘Alternative Ligands XXXIII: Heterobimetallic Donor - Acceptor Interactions in Si/Ni -Cages: Metallosilatranes’, p. 541 R112 J. Grobe, ‘Silyl Modified Surfaces - New Answers to Old Problems’, p. 591 R113 B. J. Hendan and H. C. Marsmann, ‘Silsesquioxanes of Mixed Functionality-Octa[(3-chloropropyl)-propyl-silsesquioxanes] and Octa[(3-mercaptopropy1)-n-propyl-silsesquioxanes] as Models of Organomodified Silica Surfaces’, p. 685 R114 V. M. Litvinov, ‘Poly(dimethylsi1oxane) Chains at a Silica Surface’, p. 779 Physical Phenomena at High Magnetic Fields-II, ed. Z. Fisk, World Scientific, Singapore,

R115 N. S. Sullivan, ‘NMR Studies of Quantum Solids at High Magnetic Fields and Low Temperatures’, p. 617 Physical Properties of Polymeric Gels, ed. J. P. Cohen Addad, Wiley, Chichester, UK, 1996

R116 J. P. Cohen Addad, ‘NMR and Statistical Structures of Gels’, p. 39 Physical Properties of Polymers Handbook, Woodbury, N. Y. , 1996

ed.

J. E. Mark, AIP Press,

R117 A. E. Tonelli, ‘NMR Spectroscopy of Polymers’, p. 27 1

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Polymer Spectroscopy, ed. A. H. Fawcett, Wiley, Chichester, UK, 1996

R118 A. H. Fawcett, J. G. Hamilton and J. J. Rooney, ‘NMR Characterization of Macromolecules in Solution’, p. 7 R119 A. E. Tonelli, ‘Conformation: The Connection Between the NMR Spectra and the Microstructures of Polymers’, p. 55 R120 0. W. Howarth, R. N. Ibbett, I. R. Herbert and M. A. Whiskens, ‘ “Model-Free” RIS [Rotational Isomeric State] Statistical Weight Parameters from I3C NMR Data’, p. 97 R121 R. K. Harris, ‘NMR Studies of Solid Polymers’, p. 117 R122 H. W. Spiess, ‘Multidimensional Solid-state NMR of Polymers’, p. 135 R123 J. L. Koenig, ‘NMR Imaging of Polymers’, p. 151 Presentations of the 23rd Steenbock Symposium, 1994, (High Pressure Effects in Molecular Biophysics and Enzymology), ed. J. L. Markley, D. B. Northrop and C. A. Royer, Oxford University Press, New York, 1996

R124 X. Peng, J. L. Silva, J. Zhang, L. E. Ballard, A. Jonas and J. Jonas, ‘HighPressure NMR Studies of the Dissociation of Arc Repressor and the Cold Denaturation of Ribonuclease A’, p. 96 Proceedings of the 14th American Peptide Symposium, Columbus, Ohio, 1995, (Peptides: Chemistry, Structure and Biology), ed. P. T. P. Kaumaya, T. P. Pravin and R. S. Hodges, Mayflower Scientific, Kingswinford, UK, 1996

R125 M. Kraft, 0. Schuckert, J. Wallach, M. 0. Westendrop, P. Bayer, P. Roesch and R. W. Frank, ‘A Synthetic Approach to Study the Structural Biology of Tat Proteins from HIV-1 and EIAV’, p. 21 Proceedings of the 10th Anniversary HTS Workshop, (Physics, Materials and Applications), ed. B. Batlogg, World Scientific, Singapore, 1996

R126 D. Pines, ‘Spin Fluctuations, Magnetotransport and dx2+ Pairing in the Cuprate Superconductors’, p. 471 Proceedings of the 9th Conversation, State University of New York, Albany, 1995, (Biological Structure and Dynamics), ed. R. H. Sarma and M. H. Sarma, Adenine Press: Schenectady, N. Y. , 1996

R127 C. W. Hilbers, R. H. A. Folmer, M. Nilges and R. N. H. Konings, ‘Structure and Function of the Single-Stranded DNA Binding Proteins of the Filamentous Bacteriophages M13 and Pf3. NMR Studies’, p. 1

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Proceedings of the 6th International Colloquium, 1993, (Phospholipids: Characterization, Metabolism, and Novel Biological Applications), ed. G. Cevc and F. Paltauf, AOCS Press, Champaign Ill., 1995 R128 B. W. K. Diehl and W. Ockels, ‘Quantitative Analysis of Lecithin: Phospholipid Analysis with 31PNMR Spectroscopy’, p. 29 Proceedings of the 9th International Conference on the Biochemistry of Exercise held in Aberdeen, 1994, (Biochemistry of Exercise I X ) , ed. R. J. Maughan and S. M. Shirreffs, Human Kinetics Publishers, Champaign, Ill., 1996 R129 J. Bangsbo, ‘Regulation of Muscle Glycogenolysis and Glycolysis During Intense Exercise: In Vivo Studies Using Repeated Intense Exercise’, p. 261 Proceedings of the 21st International Conference on Low Temperature Physics, Institute of Physics, Academy of Sciences of the Czech Republic, in Czech.J. Phys., 1996,46 R130 E. V. Thuneberg, ‘Vortex Sheet in Superfluid 3He-A’, p. 2937 R131 Y. M. Bunkov, ‘Spin Dynamics of Superfluid 3He in Non-Hydrodynamic Regime’, p. 3003 R132 K. Asayama, Y . Kitaoka, G. -Q. Zheng, K. Ishida, K. Magishi, T. Mito and Y . Tokunaga, ‘NMR of High T, Superconductors’, p. 3 187 Proceedings of the I I th International Congress on Cutulysis, Baltimore, 1996 in Studies in Surface Science and Catalysis, ed. J. W. Hightower, W. N. Delgass, E. Iglesia and A. T. Bell, Elsevier, Amsterdam, Neth., 1996, vol. 101, Pt.A, R133 J. F. Haw and J . B. Nicholas, ‘What NMR Has Told Us About Solid Acidity’, p. 573 R134 L. Le Noc, D. T. On, S. Solomykina, B. Echchahed, F. Beland, C . Cartier dit Moulin and L. Bonneviot, ‘Characterization of Two Different Framework Titanium Sites and Quantification of Extra-Framework Species in TS-1 Silicalites’, p. 61 1 R135 L. Heeribout, V. Semmer, P. Batamack, C. Doremieux-Morin, R. Vincent and J. Fraissard, ‘Broensted Acid Strength of Solids Studied by ‘H NMR: Establishing the Scale; Influence of Lewis Acid Sites’, p. 83 1 vol. 101, Pt.B R136 Y . Y . Tong, A. J. Renouprez, G. A. Martin and J. J. van der Klink, ‘Electron Availability and the Surface Fermi Level Local Density of States: An Alternative Way to See Catalytic Activity of Metals’, p. 901

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Proceedings of the 7th International Symposium in Amsterdam, 1995 (Platinum and Other Metal Coordination Compounds in Cancer Chemotherapy 2 ) , ed. H. M. Pinedo and J. H. Schornagel, Plenum, New York, 1996 R137 K. J. Barnham, S. J. Berners-Price, Z. Guo, M. P. Del Socorro and P. J. Sadler, ‘NMR Spectroscopy of Platinum Drugs: From DNA to Body Fluids’, p. 1 Proceedings of the International Symposium in La Grande Motte (France), 1993, (New Trends in Lipid and Lipoprotein Analyses), ed. J-L. Sebedio and E. G. Perkins, AOCS Press, Champaign Ill., 1995 R138 F. D. Gunstone, ‘Information About Fatty Acids and Lipids Derived by I3C Nuclear Magnetic Resonance Spectroscopy’, p. 250 Proceedings of the International Symposium on Growth Hormone Secretagogues, St.Petersburg Beach, Flo., 1994, (Growth Hormone Secretagogues), ed. B. B. Bercu and R. F. Walker, Springer, New York, 1996 R139 F. A. Momany and C. Y. Bowers, ‘Computer - Assisted Modeling of Xenobiotic Growth Hormone Secretagogues’, p. 73 Proceedings of the International Symposium, Indianapolis, 1994 ( N M R as a Structural Toolfor Macromolecules: Current Status and Future Directions), ed. R. B. D. Nageswara and M. D. Kemple, Plenum, New York, 1996 R140 R. R. Ernst, M. J. Blackledge, T. Bremi, R. Brueschweiler, M. Ernst, C. Griesinger, Z. L. Madi, J. W. Peng, J. M. Schmidt and P. Xu, ‘Intramolecular Dynamics of Biomolecules, Possibilities and Limitations of NMR’, p. 15 R141 J. D. Forman-Kay, S. M. Pascal, A. U. Singer, T. Tamazaki, 0. Zhang, N. A. Farrow and L. E. Kay, ‘Structural, Dynamic, and Folding Studies of SH2 and SH3 Domains’, p. 35 R142 G. Wagner, D. F. Wyss, J. S. Choi, A. R. N. Arulanandam, E. L. Reinherz, A. Krezel and R. A. Lazarus, ‘NMR Studies of Proteins Involved in Cell Adhesion Processes’, p. 51 R143 C. B. Post and M. L. Schneider, ‘Phosphotyrosyl Peptide-Enzyme Complexes: How Much Structure Can We Get from Transferred NOE’s?’, p. 91 R144 S. Grzesiek and A. Bax, ‘Recent Developments in Protein NMR Spectroscopy’, p. 117 R145 A. G. Redfield, ‘Field-Cycling NMR Applied to Macromolecular Structure and Dynamics’, p. 123 R146 B. Xia, H. Cheng, Y. K. Chae, L. Skjedal, W. M. Westler and J. L. Markley, ‘Iron-Sulfur Proteins: Investigations of Hyperfine-shifted Hydrogen, Carbon, and Nitrogen Resonances’, p. 251

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R147 A. J. Wand, ‘A Structural Biologist’s View of Precision and Accuracy of Structural Models of Proteins Based on NMR Data’, p. 307 Proceedings of the 4th International Symposium, Karachi, 1995, (Protein Structure Function Relationship), ed. Z. H. Zaidi and D. L. Smith, Plenum, New York, 1996 R148 J. L. Markley, B. Xia, Y. K. Chae, H. Cheng, W. M. Westler, J. D. Pikus and B. G. Fox, ‘NMR Approaches to the Study of Structure-Function Relationships in Iron-Sulfur Proteins: Rubredoxin, [2Fe-2s] Ferredoxins, and a Rieske Protein’, p. 135 Proceedings of the 10th International Symposium on Organosilicon Chemistry, Poznan, 1993, (Progress in Organosilicon Chemistry), ed. B. Marciniec and J. Chojnowski, Gordon & Breach, Basel, Switz., 1995 R149 K. Ruehlmann, U. Scheim and K. Kaeppler, ‘Substituent Constants of Groups at the Si-Atom’, p. 147 R150 A. R. Bassindale, ‘Coordination and Reactivity in Organosilicon Chemistry’, p. 191 Proceedings of the 8th International Symposium on Superconductivity, 1995, (Advances in Superconductivity VIII), ed. H. Hayakawa and Y. Enamoto, Springer, Tokyo, Japan, 1996 R15 1 P. Komarek, ‘Status and Future Prospects of High Current Superconductivity’, p. 1’9-14 Proceedings of the Loker Hydrocarbon Research Institute Symposium on Carbocation Chemistry, 1992, (Stable Carbocation Chemistry), ed. G. K. S . Praskash and P. V. R. Schleyer, Wiley, New York, 1997 R152 P. V. R. Schleyer, C. Maeker, P. Buzek and S. Sieber, ‘Accurate Carbocation Structures: Verification of Computed Geometries by NMR, IR, and X-Ray Diffraction’, p. 19 R153 H-U. Siehl, ‘Excursions into Long-Lived Vinyl Cations: NMR Spectroscopic Characterization of ‘aAryl Vinyl Cations’, p. 165 R154 M. Saunders, H . A. Jimenez-Vazquez and 0. Kronja, ‘Recent Applications of the Isotopic Perturbation Method for Determining the Details of Carbocation Structures’, p. 297 R155 D. A. Forsyth, ‘Isotope Effects as a Probe of Subtle Features of Carbocation Structure in Superacids’, p. 323 R156 P. C. Myhre and C. S. Yannoni, ‘CPMAS NMR of Carbocations at Cryogenic Temperatures’, p. 389

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Proceedings of the Symposium held at Stanford University in March, 1994, (Biological N M R Spectroscopy), ed. J. L. Markley and S. J. Opella, Oxford University Press, New York, 1997

R157 0. Jardetzky, ‘Simple Insights from the Beginnings of Magnetic Resonance in Molecular Biology’, p. 3 R158 M. Cohn, ‘Choice of Problems in the Early Days of Biological NMR Spectroscopy’, p. 16 R159 R. G. Shulman, ‘Early Days of Biochemical NMR’, p- 20 R160 J. J. H. Ackerman, ‘William D. Phillips Memorial Lecture’, p. 23 R161 C. M. Dobson, ‘The Role of NMR Spectroscopy in Understanding How Proteins Fold’, p. 82 R162 G. C. K. Roberts, L. -Y. Lian, I. L. Barsukov, S. Modi and W. U. Primrose, ‘NMR Approaches to Understanding Protein Specificity’, p. 94 R163 A. P. Hinck, W. F. Walkenhorst, D. M. Truckses and J. L. Markley, ‘NMR and Mutagenesis Investigations of a Model Cis:Trans Peptide Isomerization Reaction: Xaa’ ‘6-Pro’17 of Staphylococcal Nuclease and its Role in Protein Stability and Folding’, p. 113 R164 K. Akasaka, T. Yamaguchi, H. Yamada, Y. Kamatari and T. Konno, ‘NMR Approaches to the Heat-, Cold-, and Pressure-Induced Unfolding of Proteins’, p. 157 R165 Y. Arata, ‘NMR of Larger Proteins: Approach to the Structural Analyses of Antibody’, p. 183 R166 K. S. Matthews and R. Matthews, ‘Selective Chemical Deuteration of Aromatic Amino Acids: A Retrospective’, p. 205 R167 0. Kaplan and J. S. Cohen, ‘Nuclear Magnetic Resonance Spectroscopy Studies of Cancer Cell Metabolism’, p. 317 R168 L. Litt, M. T. Espanol, Y. Xu, Y. Cohen, L. -H. Chang, P. R. Weinstein, P. H. Chan and T. L. James, ‘Ex Vivo Multinuclear NMR Spectroscopy of Perfused, Respiring Rat Brain Slices: Model Studies of Hypoxia, Ischemia, and Excitotoxicity’, p. 340 Proceedings of the Symposium, Michigan State University, 1995, (Access in Nanoporous Materials), ed. T. J. Pinnavaia and M. F. Thorpe, Plenum, New York, 1995

R169 J. Kaerger, ‘Structure-Related Diffusion in Nanoporous Materials’, p. 175 Proceedings of the 20th Tunaguchi International Symposium, Division of Biophysics, Nagoya, 1994, (Tracing Biological Evolution in Protein and Gene Structures), ed. M. Go and P. Schimmel, Elsevier, Amsterdam, Neth., 1995

R170 T. Noguti and M. Go, ‘Modules of Barnase: The Physicochemical Basis for their Structures’, p. 161

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Proceedings of the 29th Washington State University International Particleboardl Composite Materials Symposium, Washington State University, 1995 R171 J. J. Marcinko, W. H. Newman, C. Phanopoulos and M. A. Sander, ‘The Nature of the MDI/Wood Bond’, p. 175 Proceedings of the Workshop on The Reaction Center of Photosynthetic Bacteria Structure and Dynamics, 1995, ( T h e Reaction Center of Photosynthetic Bacteria), ed. M-E. Michel-Beyerle, Springer, Berlin, Germany, 1996 R172 A. J. Hoff, T. N. Kropacheva, R. I. Samoilova, N. P. Gritzan, J. Raap, J. S. Van Den Brink, P. Gast and J. Lugtenburg, ‘Site-Directed Isotope Labeling as a Tool in Spectroscopy of Photosynthetic Preparations. Investigations on Quinone Binding in Bacterial Reaction Centers’, p. 405 Proceedings of the 4th World Surfactants Congress, 1996, vol. 1, Asociacion Espanola de Productores de Sustancias para Aplicaciones Tensioactivas, Barcelona, Spain R173 B. A. Parker and J . J . Crudden, ‘The Commercial Synthesis and Characterization of Novel Multifunctional Surfactant Chelates’, p. 446 Protein Engineering and Design, ed. P. R. Carey, Academic, San Diego, Calif., 1996 R174 G. M. Clore, and A. M. Gronenborn, ‘Determination of Structures of Larger Proteins in Solution by Three- and Four-Dimensional Heteronuclear Magnetic Resonance Spectroscopy’, p. 181 Proteins Labfax, ed. N. C. Price, Academic, San Diego, Calif., 1996 R175 B. Whitehead and J. P. Waltho, ‘NMR Structure Determination of Proteins’, p. 205 Protein Structure Prediction, A Practical Approach., ed. M. J. E. Sternberg, IRL Press, Oxford, UK, 1996 R176 N. Srinivasan, K. Guruprasad and T. L. Blundell, ‘Comparative Modeling of Proteins’, p. 11 1 Quantitative Aspects of Polymer Stabilizers, ed. G. E. Zaikov, Nova Science Publishers, Commack, N. Y., 1996 R177 Ya.A. Gurvich, 1. G. Arzamanova and G. E. Zaikov, ‘Experimental Methods for Estimation of Stabilizers Efficiency’, p. 1

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Signal Treatment and Signal Analysis in N M R , ed. D. N. Rutledge, in ‘Data Handling in Science and Technology’, vol. 18, Elsevier, Amsterdam, Neth., 1996 R178 L. J. Eveleigh, ‘Fourier Transform and Signal Manipulation’, p. 1 R179 K. M. Wright, ‘Maximum Entropy Methods in NMR Data Processing’, p. 25 R180 K. P. Whittall, ‘Analysis of NMR Relaxation Data’, p. 44 R181 R. S. Carmenes, ‘Nonlinear Regression’, p. 68 R182 J. Aubard and P. Levoir, ‘The Pade-Laplace Analysis of NMR Signals’, p. 100 R183 K. J. Cross, ‘Digital Filtering’, p. 120 R184 E. Kupce, ‘Binominal Filters’, p. 145 R185 M. Lupu and D. Todor, ‘Linear Prediction and Singular Value Decomposition in NMR Signal Analysis’, p. 164 R186 D. N. Rutledge, ‘A Windows Program for Relaxation Parameter Estimat i o n ’ , ~191 . R187 F. Mariette, J. P. Guillement, C. Tellier and P. Marchal, ‘Continuous Relaxation Time Distribution Decomposition by MEM’, p. 21 8 R188 D. L. Botlan, ‘Examples of the Use of Pade-Laplace in NMR’, p. 235 R189 B. P. Hills, ‘Analysis and Interpretation of NMR Water Proton Relaxation Data’, p. 248 R190 A. Coy and P. T. Callaghan, ‘Scattering Wavevector Analysis of Pulsed Gradient Spin Echo Data’, p. 281 RI 9 1 J-P. Grivet, ‘Accuracy and Precision of Intensity Determinations in Quantitative NMR’, p. 306 R192 G. Crisponi, ‘Least-Squares Estimation of Parameters Affecting NMR Line-Shapes in Multi-Site Chemical Exchange’, p. 330 R193 P. S. Belton, ‘Continuous Wave and Rapid Scan Correlation NMR’, p. 362 R194 M. A. Delsuc, ‘Data Processing in High-Resolution Multidimensional NMR’, p. 374 R195 S. A. Corne, ‘Neural Networks for 2D NMR Spectroscopy’, p. 407 R196 T. Brekke and 0. M. Kvalheim, ‘Analysis of Nuclear Magnetic Resonance Spectra of Mixtures Using Multivariate Techniques’, p. 422 R197 S. J. Doran, ‘Quantitative Magnetic Resonance Imaging: Applications and Estimation of Errors’, p. 452 R198 H. Nilgens and B. Bluemich, ‘Stochastic Spectroscopic Imaging’, p. 489 R199 H. Grahn and P. Geladi, ‘Application of Multivariate Data Analysis Techniques to NMR Imaging’, p. 513 Spectroscopic Methods for Determining Protein Structure in Solution, ed. H. A. Havel, VCH, New York, 1996, R200 A. M. Gronenborn and G. M. Clore, ‘Nuclear Magnetic Resonance Studies of Small and Medium Sized Proteins in Solution’, p. 190 R201 G. A. Morris, ‘Reference Deconvolution in NMR’, p. 346

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Surface Science, ed. R. J. MacDonald, E. C. Taglauer and K. R. Wandelt, Springer, Berlin, Germany, 1996

R202 G. Engelhardt, ‘Characterization of Zeolite Catalysts and Related Materials by Multinuclear Solid-state NMR Spectroscopy’, p. 321 R203 K. T. Jackson and R. F. Howe, ‘Spectroscopic Studies of Zeolite Single Crystals’, p. 331 Renal Toxicology of Metals, in: Target Organ Toxicology (vol. III)., ed. L. W. L. Chang, CRC Press, 1996

R204 D. R. Smith and F. McNeill, ‘In Vivo Measurement and Speciation of Nephrotoxic Metals’, p. 737 Tailor-Made Silicon-Oxygen Compounds: From Molecules to Materials, ed. R. Corriu and P. Jutzi, Vieweg, Wiesbaden, Germany, 1996

R205 J. A. Tossell, ‘Si-0, A1-0, and B - 0 Bonds in Molecules and Glasses’, p. 31 R206 M. S. Brandt, T. Puchert and M. Stutzmann, ‘Siloxene: The Physics View’, p. 117

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R207 P. K. Agrawal, ‘A Systematic NMR Approach for the Determination of the Molecular Structure of Steroidal Saponins’, Adv. Exp. Med. Biol., 1996,405,299 R208 P. K. Agrawal and A. K. Pathak, ‘Nuclear Magnetic Resonance Spectroscopic Approaches for the Determination of Interglycosidic Linkage and Sequence in Oligosaccharides’, Phytochern. Anal., 1996,7, 113 R209 K. Albert, ‘Hyphenation of Chromatographic Separation Techniques with Nuclear Magnetic Resonance Spectroscopy: Present Status and Future’, Analusis, 1996,24, M 17-M18 R210 A. D. Allen, J. D. Colomvakos, I. Egle, R. Liu, J. Ma, R. M. Marra, M. A. McAllister and T. T. Tidwell, ‘1995 R. U. Lemieux Award Lecture. Ketenes and Bisketenes: Organic Chemistry in Microcosm’, Can. J. Chem., 1996,74,457 R211 A. S. Altieri, K. E. Miller and R. A. Byrd, ‘A Comparison of Water Suppression Techniques Using Pulsed Field Gradients for High-Resolution NMR of Biomolecules’, Magn. Reson. Rev., 1996, 17, 27 R212 A. G. Anastassiou and H. S. Kasmai, ‘Preparation and Study of Unconventional IT- Excessives’, Trends Org. Chem., 1993,4, 617 R213 I. Ardelean, S. Stapf, D. E. Demco and R. Kirnmich, ‘The Nonlinear Stimulated Echo’, J. Magn. Reson., 1997, 124, 506 R214 R. K. Arni and R. J. Ward, ‘Phospholipase A2 - A Structural Review’, Toxicon, 1996,34, 827,

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R215 K. Asayama, Y. Kitaoka, G-q. Zheng, K. Ishida and K. Magishi, ‘NMR Study of High- T, Superconductors’, Physica B (Amsterdam), 1996, 223&224,478 R216 Z. Asfari, M. Nierlich, P. Thuery, V. Lamare, J-F. Dozol, M. Leroy and J. Vicens, ‘Calix[4]-Bis-Crownsand Calix[4]-Bis-Aza-Oxa-Crowns: From Receptors Design to Molecular Machines’, An. Quim. Int. Ed., 1996,92,260 R217 S. Aubert, R. Bligny and R. Douce, ‘NMR Studies of Metabolism in Cell Suspensions and Tissue Cultures’, Curr. Top. Plant Physiol., 1996, 16, 109 R218 D. E. Axelson, A. Kantzas and A. Nauerth, “H Magnetic Resonance Imaging of Rigid Polymeric Solids’, Solid State Nucl. Magn. Reson., 1996, 6,309 R219 J. J. P. Baars, H. J. M. Op den Camp, C. van der Drift, G. D. Vogels and L. J. L. D. van Griensven, ‘The Nitrogen Metabolism of Agaricus Bisporus’, Mushroom Sci., 1995, 14,811 R220 T. A. Babushkina, Yu.V. Goltyapin and S. I . Gushchin, ‘‘271NQR Spectra of Iodobenzoic Acid and Iodophenol Derivatives. H-bonds and C-I Characteristic Bonds of these Substances’, 2. Naturforsch., A: Phys. Sci., 1996,51,651 R221 A. D. Bain and I. W. Burton, ‘Quadrature Detection in One or More Dimensions’, Concepts Magn. Reson., 1996,8, 191 R222 D. Bakowies, M. Buehl, S. Patchkovskii and W. Thiel, ‘Theoretical Studies on Giant Fullerenes and on Endohedral Fullerene Complexes’, Proc. Electrochem. SOC.,1996,96- 10,901 R223 S. Bank, ‘Some Principles of NMR Spectroscopy and Their Novel Application’, Concepts Magn. Reson., 1997,9, 83 R224 S. E. Barrett, G . Dabbagh, L. N. Pfeiffer, K. W. West and R. Tycko, ‘Optically Pumped Nuclear Magnetic Resonance in the Quantum Hall Regimes’, Semicond. Sci. Technol., 1996,11, 1488 R225 L. P. Barthel-Rosa, J. H. Nelson, V. J. Catalan0 and J. Fischer, ‘Novel Compounds Formed from Reactions of [q5-Me5C5)MCl2I2(M=Ru, Rh) with Vinyldiphenylphosphine and Allyldiphenylphosphine’, Phosphorus, Surfur Silicon Relat Elem., 1996, 109-110, 169 R226 L. Barton, J. Bould, H. Fang and N. P. Rath, ‘Formation of Heterobimetallaheptaboranes from the Nido-metallahexaboranes (PPh3)2(CO)OsB5H9 and (PPh3)2(CO)IrB5H8’, Main Group Met. Chem., 1996, 19, 71 1 R227 L. Barton, H. Fang, D. K. Srivastava, T. A. Schweitzer and N. P. Rath, ‘Recent Studies of Group 14 Derivatives of Small Nido-Boranes’, Appl. Organomet. Chem., 1996,10(3&4), 183 R228 J. D. Bell, ‘Clinical Applications of Nuclear Magnetic Resonance Spectroscopy’, Spectrosc. Eur., 1996,8, 18,20 R229 P. S. Belton, ‘Spectroscopy Approaches to the Measurement of Food Quality’, Pure Appl. Chem., 1997,69,47 R230 H. Berke and P. Burger, ‘Nitrosyl Substituted Hydride Complexes - an Activated Class of Compounds’, Comments Inorg. Chem., 1994, 16,279 R231 C. Berthier, M. H. Julien, M. Horvatic and Y. Berthier, ‘NMR Studies of

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the Normal State of High Temperature Superconductors’, J. Phys., I, 1996,6,2205 R232 H. A. Berthon and P. W. Kuchel, ‘NMR Studies of Erythrocyte Metabolism’, Adv. Mol. Cell Biol., 1995, 11, 147 R233 L. Beyer, ‘The Chemical Composition of Soil Organic Matter in Classical Humic Compound Fractions and in Bulk Samples’, 2. PJanzenernaehr. Bodenkd., 1996,159, 527 R234 R. A. Beyerlein, C. Choi-Feng, J. B. Hall, B. J. Huggins and G. J. Ray, ‘Effect of Steaming on the Defect Structure and Acid Catalysis of Protonated Zeolites’, Top. Catal, 1997,4,27 R235 M. Beylot, 0. Peroni, F. Diraison and V. Large, ‘New Methods for In Vivo Studies of Hepatic Metabolism’, Reprod., Nutr., Dev., 1996,36, 363 R236 W. E. Billups, W. Luo, D. McCord and R. Wagner, ‘Synthesis of New Molecular Systems’, Pure Appl. Chem., 1996,68, 275 R237 P. R. Blake and M. F. Summers, ‘Insights into the Structural and Electronic Properties of Metalloproteins by Heteronuclear Magnetic Resonance’, Adv. Inorg. Biochem., 1994,10, 201 R238 A. L. Blumenfeld and J. J. Fripiat, ‘Acid Sites Topology in Aluminas and Zeolites from High-Resolution Solid-state NMR’, Top. Cutul., 1997, 4, 119 R239 K . Bock, T. Dreyer, S. Muller-Loennies and L. Molskov-Bech, ‘Evaluation of New Analytical Techniques for the Optimization of Brewing Processes’, Proc. Conv.-Inst. Brew. (Asia Pac. Sect.), 1996, 24,234 R240 H. W. G. M. Boddeke, R. E. Best, D. Stainhauser and K. Wyler, ‘From Neuron to Network. Measurement, Analysis, and Modeling. Part 2. Biological Neuronal Networks’, Tech. Mess., 1996,63, 337 R241 J-A. K. Bonesteel, ‘Nuclear Magnetic Resonance Analyses of Grignard Reagents’, Chem. Ind. (Dekker), 1996,64, 103 R242 D. Brinkmann, ‘Interplane Coupling and Spin Gap. An NMR/NQR Look on Typical Properties of High-temperature Superconductors’, 2. Nuturforsch., A: Phys. Sci., 1996,51, 786 R243 H. G . Brittain, ‘Spectral Methods for the Characterization of Polymorphs and Solvates’, J. Pharm. Sci., 1997,86,405 R244 E. Brosio, ‘Nuclear Magnetic Resonance: a Multiparameter Technique for in Situ Analysis’, Rev. Anal. Chem., 1995,14,227 R245 E. Brosio and R. Barbieri, ‘Nuclear Magnetic Resonance in the Analysis of Dairy Products’, Rev. Anal. Chem., 1996, 15,273 R246 S. P. Brown and S. Wimperis, ‘Two-Dimensional Multiple-Quantum MAS NMR of Quadrupolar Nuclei. Acquisition of the Whole Echo’, J. Magn. Reson., 1997, 124, 279 R247 E. Brunner and H. Pfeifer, ‘Spectroscopic Investigation of the Acidity of Solid Catalysts’, Anal. Methods Instrum., 1995,2, 3 15 R248 D. Burstein, ‘Stimulated Echoes: Description, Applications, Practical Hints’, Concepts Magn. Reson., 1996,8,269 R249 P. T. Buser, P. Hornstein, C. E. Zaugg and D. Atar, ‘The Rat Heart Langendorff-Model: Measurement of High Energy Phosphates Using 31P

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MRS Analysis of Calcium Responsiveness and of Structural Alterations of Contractile Proteins’, Pharmacol. Eval. Cardioprot. Subst., Freiburg Focus Biomeas., 1995, 143 R250 T. Butz, ‘Nuclear Quadrupole Interactions Studied by Time Differential Perturbed Angular Correlations of y-Rays’, 2. Naturforsch., A: Phys. Sci., 1996,51,396 R251 R. E. Cachau, ‘Protein Model Building Using Structural Similarity’, Adv. Comput. Biol., 1996,2, 65 R252 M. Careri and A. Mangia, ‘Multidimensional Detection Methods for Separations and Their Application in Food Analysis’, TrA C, Trends Anal. Chem., 1996,15,538 R253 T. R. Cech and A. A. Szewczak, ‘Selecting Apt RNAs for NMR’, R N A , 1996,2,625 R254 G. Celebre, G. Chidichimo, L. Coppola, C. La Mesa, R. Muzzalupo, L. Pogliani, G. A. Ranieri and M. Terenzi, ‘Water Self-Diffusion in Lyotropic Liquid Crystals: Pulsed Gradient Spin-Echo NMR and Simulation Techniques’, Gazz. Chim. Ital., 1996,126,489 R255 C . Cerf, ‘NMR Spectroscopy: From Quantum Mechanics to Protein Spectra’, Concepts Magn. Reson., 1997,9, 17 R256 C. A. Chang, ‘Macrocyclic Lanthanide Coordination Chemistry’, Proc. Natl. Sci. Counc., Repub. China, Part A : Phys.Sci. Eng., 1997,21, 1 R257 M. A. Chaubon, H. Ranaivonjatovo, J. Escudie and J. Satge, ‘Stable Metalla-Alkenes > M:C < and Dimetalla-Alkenes > M:M < (M = Si, Ge, Sn)’, Main Group Met. Chem., 1996, 19, 145 R258 D. B. Chesnut, ‘The Ab Initio Computation of Nuclear Magnetic Resonance Chemical Shielding’, Rev. Comput. Chern., 1996,8,245 R259 U. Chiacchio, G. Romeo and N. Uccella, ‘The Conversion of Five Membered 1, 2-N, 0-Heterocyclic Isoxazolidinium Cations’, Trends Heterocycl. Chem., 1996,4,261 R260 M. B. Comisarow and A. G. Marshall, ‘The Early Development of Fourier Transform Ion Cyclotron Resonance (FT-ICR) Spectroscopy’, J. Mass Spectrom., 1996,31, 581 R261 G. A. Cordell, L-Z. Lin and R. Roberto, ‘Proton and Carbon-13 NMR Studies of Steroids and Triterpenes’, Adv. Exp. Med. Biol., 1996, 405, 28 1 R262 S. A. Corne, ‘Artificial Neural Networks for Pattern Recognition’, Concepts Magn. Reson., 1996,8,303 R263 I. J. Cox, ‘Development and Applications of In Vivo Clinical Magnetic Resonance Spectroscopy’, Prog. Biophys. Mol. Biol., 1996,65,45 R264 L. K. Creamer and A. K. H. MacGibbon, ‘Some Recent Advances in the Basic Chemistry of Milk Proteins and Lipids’, Int. Dairy J. , 1996, 6, 539 R265 E. R. Cruz, ‘Structural Connectivities and Interactions Affecting Coupling Constants and Chemical Shifts in Organic Molecules’, Concepts Magn. Reson., 1996,8,385 R266 S. C. Cunnane and S. S. Likhodii, ‘I3C NMR Spectroscopy and Gas Chromatography--Combustion-Isotope Ratio Mass Spectrometry: Com-

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plementary Applications in Monitoring the Metabolism of 13C-Labeled Polyunsaturated Fatty Acids’, Can. J. Physiol. Pharmacol., 1996,74, 761 R267 A. Cusanelli, L. Nicula-Dadci, U. Frey and A. E. Merbach, ‘Ligand Effects on the Rate and Mechanism of Solvent Exchange at Rhodium(II1) and Iridium(III)’, Chimia, 1996,50, 618 R268 J. F. Davidson, ‘The Origin of Insights in Chemical Engineering: Planned and Unplanned Research’, Chern. Eng. Res. Des., 1996,74(2A), 28 1 R269 R. De Beer and D. Van Ormondt, ‘Background Features in Magnetic Resonance Signals: Addressed by SVD-based State Space Modeling’, Appl. Magn. Reson., 1994,6, 379 R270 E. M. M. De Brabander, A. G. Nijenhuis, R. Borggreve and J. Put, ‘Star Polycondensates. Large Scale Synthesis, Rheology, and Material Properties, Polyrn. News, 1997,22, 6 R27 1 J. D. de Certaines, ‘High Resolution Nuclear Magnetic Resonance Spectroscopy in Clinical Biology: Application in Oncology’, Anticancer Res., 1996,16,1325 R272 J . D. de Certaines, L. Nadal, G. Leray, H. Serrai and C. J. Lewa, ‘Proton Nuclear Magnetic Resonance Spectroscopy of Plasma Lipoprotein: Technical Problems and Potential Interest in Cancer Disease’, Anticancer Res., 1996,16, 1451 R273 A. C. de Dios and E. Oldfield, ‘Recent Progress in Understanding Chemical Shifts’, Solid State Nucl. Magn. Reson., 1996,6, 101 R274 H. J. M. de Groot, ‘Magic Angle Spinning Nuclear Magnetic Resonance of Photosynthetic Components’, Adv. Photosynth., 1996,3, 299 R275 P. J. G. M. De Wit, R. Lauge, G. Honee, M. H. A. J. Joosten, P. Vossen, M. Kooman-Gersmann, R. Vogelsang and J. J. M . Vervoort, ‘Molecular and Biochemical Basis of the Interaction Between Tomato and its Fungal Pathogen Cladosporium Fulvum’, Antonie van Leeuwenhoek, 1997, 71, 137 R276 K. B. Dillon, ‘Nuclear Quadrupole Resonance Spectroscopy’, Spectrosc. Prop. Inorg. Organomet. Compd., 1996,29, 179 R277 D. Dobrota, S. Kasparova and J. Horecky, ‘Studies of Myocardial Work and Metabolic Stress by 3’P NMR Spectroscopy’, Biologia (Bratislava), 1996,51,717 R278 D. G . Donne and D. G. Gorenstein, ‘A Pictorial Representation of Product Operator Formalism: Nonclassical Vector Diagrams for Multidimensional NMR’, Concepts Magn. Reson., 1997, 9, 95 R279 M. J. Duer and C. Stourton, ‘Further Developments in MQMAS NMR Spectroscopy for Spin-3/2 Nuclei’, J. Magn. Reson., 1997, 124, 189 R280 J. S. Duncan, ‘Magnetic Resonance Spectroscopy’, Epilepsia, 1996, 37, 598 R281 C. Dybowski and M. D. Bruch, ‘Nuclear Magnetic Resonance Spectrometry’, Anal. Chem., 1996,68, 161 R282 H. Eckert, ‘Solid State NMR as a Tool of Structure and Dynamics in Solid State Chemistry and Materials Science: Recent Progress and Challenges’, Curr. Opin. Solid State Mater. Sci., 1996, 1, 465

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R283 A. D. Ellington, F. Leclerc and R. Cedergren, ‘An RNA Groove’, Nut. Struct. Biol., 1996, 3, 98 1 R284 T. Engan, ‘Magnetic Resonance Spectroscopy of Blood Plasma Lipoproteins in Malignant Disease: Methodological Aspects and Clinical Relevance’, Anticancer Res., 1996, 16, 1461 R285 M. Engelhard and B. Bechinger, ‘Application of NMR-Spectroscopy to Retinal Proteins’, Isr. J. Chem., 1995,35, 273 R286 R. R. Ernst, ‘Nuclear Magnetic Resonance, a Powerful Tool for the Study of Biomolecular Dynamics’, Chimia, 1997,51, 33 R287 T. W-M. Fan, ‘Recent Advances in Profiling Plant Metabolites by MultiNuclear and Multi-Dimensional NMR’, Curr. Top. Plant Physiol., 1996, 16, 181 R288 B. Felden, C. Florentz, E. Westhof and R. Giege, ‘Usefulness of Functional and Structural Solution Data for the Modeling of tRNA-like Structures’, Pharm. Acta Helv., 1996,71,3 R289 R. J. Ferrier, R. Blattner, K. Clinch, R. H. Furneaux, J. M. Gardiner, P. C. Tyler, R. H. Wightman and N. R. Williams, ‘NMR Spectroscopy and Conformational Features [of Sugars]’, Carbohydr. Chem., 1996, 28, 307 R290 F. Fogolari, G . Esposito, S. Cattarinussi and P. Viglino, ‘Quantitative Analysis of Total Correlation Spectra: Application to Small Biomolecules’, Concepts Magn. Reson., 1996,8,229 R291 S. Forsen and J. Koerdel, ‘Biomolecular Structure and Dynamics Experiment and Theory’, J. Pharm. Biomed. Anal., 1996,14,233 R292 Y. Fraenkel, D. E. Shalev, J. M. Gershoni and G . Navon, ‘Nuclear Magnetic Resonance (NM R) Analysis of Ligand Receptor Interactions: The Cholinergic System-a Model’, Crit. Rev. Biochem. Mol. Biol., 1996, 31,273 R293 R. Freeman, ‘A Short History of NMR’, Khim. Geterotsikl. Soedin., 1995, (9), 1157-8 R294 H. Fuess, ‘Contributions of Crystallography to Materials Science’, Croat. Chem. Acta, 1996,69,1053 R295 B. J. Gaffney, ‘Origins of Biological Magnetic Resonance’, FASEB J . , 1996,10, 1448 R296 F. Garbassi, ‘Polymer Analysis and Characterization. Solid-state NMR. Does It Become Truly Popular?’, Polym. News, 1997,22, 15 R297 E. Gawlita, ‘Methods of Studies of Enzyme-Substrate Interactions’, Zesz. Nauk. - Politech. Lodz., Chem., 1994,44, 5 R298 N. E. Geacintov, M. Cosman, B. E. Hingerty, S. Amin, S. Broyde and D. Patel, ‘NMR Solution Structures of Stereoisomeric Polycyclic Aromatic Carcinogen - DNA Adducts: Principles, Patterns, and Diversity’, Chem. Res. Toxicol., 1997, 10, 11 1 R299 AA. Gencten, ‘Magic-Angle Spining NMR: An Experimental Approach’, Turk. J. Phys., 1996,20, 146 R300 J. G. Gilson, ‘Calculating the Fine-Structure Constant’, Phys. Essays, 1996,9,342

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R301 T. Glonek and T. E. Merchant, ‘31PNuclear Magnetic Resonance Profiling of Phospholipids’, Oily Press Lipid Libr., 1996,7, 37 R302 R. Goldberg, C. Morvan, A. Jauneau and M. C. Jarvis, ‘Methyl-Esterification, De-Esterification and Gelation of Pectins in the Primary Cell Wall’, Prog. Biotechnol., 1996, 14, 151 R303 L. Gomathi and S. Subramanian, ‘Elucidation of Secondary Structures of Peptides Using High Resolution NMR’, Curr. Sci., 1996,71, 553 R304 R. J. Gorte and D. White, ‘Interactions of Chemical Species with Acid Sites in Zeolites’, Top. Catal, 1997,4, 57 R305 G . D. Graham, ‘Brain Macromolecules: In Vivo Measurement by Proton Magnetic Resonance Spectroscopy’, Neuroscientist, 1996,2, 309 R306 D. Grate and C. Wilson, ‘Role REVersal: Understanding How RRE RNA Binds its Peptide Ligand’, Structure (London), 1997,5, 7 R307 F. Gualtieri, M. N. Romanelli and E. Teodori, ‘The “Frozen Analog” Approach in Medicinal Chemistry’, Stud. Med. Chem., 1996, 1, 271 R308 M. Gueron and J-L. Leroy, ‘Studies of Base Pair Kinetics by NMR Measurement of Proton Exchange’, Methods Enzymol., 1995,261,283-413 R309 N. K. Gulavita, A. E. Wright, P. J. McCarthy, S. A. Pomponi and R. E. Longley, ‘Cytotoxic Peptides from Marine Sponges’, J. Nat. Toxins, 1996, 5,225 R310 M. Guo, ‘Solid-state High-Resolution NMR Studies on the Miscibility of Polymer Blends’, Trends Polym. Sci. (Cambridge, U. K. ), 1996,4,238 R3 1 1 W. Guschlbauer, “‘Small is Beautiful”: Major Modifications in DNA Structure or Dynamics by Small Substituents or Ligands’, Acta Biochim. Pol., 1996,43, 77 R312 D. G. Gusev and H. Berke, ‘Hydride Fluxionality in Transition Metal Complexes. An Approach to the Understanding of Mechanistic Features and Structural Diversities’, Chem. Ber., 1996, 129, 1143 R313 D. J. S. Guthrie, “ H Nuclear Magnetic Resonance (NMR) in the Elucidation of Peptide Structure’, Methods Mol. Biol. (Totowa, N. J. ), 1997, 73, 163 R314 S. Hafner, D. E. Demco and R. Kimmich, ‘Magic Echoes and NMR Imaging of Solids’, Solid State Nucl. Magn. Reson., 1996,6, 275 R315 E. L. Hahn, ‘Radiation Damping of an Inhomogeneously Broadened Spin Ensemble’, Concepts Magn. Reson., 1997,9,65 R316 E. L. Hahn, ‘Concepts of NMR in Quantum Optics’, Concepts Magn. Reson, 1997,9, 69 R317 G. M. Hanna and J. J. Specchio, ‘Selected NMR Applications in Food Regulatory Analysis’, Food Test. Anal., 1995,1,43 R318 W. R. Harris, G . Berthon, J. P. Day, C. Exley, T. P. Flaten, W. F. Forbes, T. Kiss, C. Orvig and P. F. Zatta, ‘Speciation of Aluminium in Biological Systems’, J. Toxicol. Environ. Health, 1996,48, 543 R3 19 H. Haruyama and H. Hanzawa, “H Detected Heteronuclear Correlation: A Theme of Modern NMR Spectroscopy’, Annu. Rep. Sankyo Res. Lab., 1996,48,1 R320 J. H. Harwood, L. Christov, M. M. Guo, T. V. Holland, A. Y. Huckstep,

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D. H. Jones, R. E. Medsker, P. L. Rinaldi, T. Saito and D. S. Tung, ‘Investigation of Statistical Block, and Graft Copolymerizations Using NMR - Sensitive Initiators and Macroinitiators’, Macromol. Symp., 1996, 111,25 R321 C. Heimberg, R. Komoroski, J. E. 0. Newton and C. Karson, ‘I9F-MRS a New Tool for Psychopharmacology’, Prog. Psychiatry, 1995’47, 2 13 R322 C. Heitner-Wirguin, ‘Recent Advances in Perfluorinated Ionomer Membranes: Structure, Properties and Applications’, J. Mernbr. Sci., 1996,120, 1 R323 J. F. Hinton, K. Wolinski, P. Kozlowski and P. Pulay, ‘Are NMR Chemical Shift Calculations of Small Molecules Inexpensive? You Get What You Pay For!’, Bull. Magn. Reson., 1996,18, 127 R324 J. Hirakate and J. Oda, ‘Aminophosphonic and Aminoboronic Acids as Key Elements of a Transition State Analog Inhibitor of Enzymes’, Biosci., Biotechnol., Biochem., 1997,61,211 R325 B. L. Hirschbein and K. L. Fearon, r31PNMR Spectroscopy in Oligonucleotide Research and Development’, Antisense Nucleic Acid Drug Dev., 1997,7,55 R326 A. J. Hoff, ‘Magnetic Resonance: An Introduction’, Adv. Photosynth., 1996,3,209 R327 J. Homer, L. Paniwnyk and S. A. Palfreyman, ‘Nuclear Magnetic Resonance Spectroscopy Combined with Ultrasound’, Adv. Sonochem., 1996,4, 75 R328 M. J. Hostetler and R. W. Murray, ‘Colloids and Self-Assembled Monolayers’, Curr. Opin. Colloid Interface Sci., 1997,2, 42 R329 T. Ilkenhaus, H. Siegert and R. Schloegl, ‘The Mechanism of the Synthesis in Connection with Assignments for a Solid Reaction Cycle of the HPA Catalyst During Catalytic Reactions’, Catal. Today, 1996,32,337 R330 A. Il’yasov, E. Breier, G. Hagele, A. Vafina and B. Liorber, ‘NMR and ESR Study of Phosphorylated Oximes and Iminoxy Radicals’, Phosphorus, Surfur Silicon Relat. Elem., 1996, 109-110,437 R331 T. Iwama and T. Kataoka, ‘Recent Studies on 1, 2-Thiazetidine 1, 1-Dioxides (p-Sultams)’, Rev. Heteroat. Chem., 1996, 15’25 R332 J. H. Iwamiya and S. W. Sinton, ‘Stray-Field Magnetic Resonance Imaging of Solid Materials’, Solid State Nucl. Magn. Reson., 1996,6, 333 R333 V. K. Jain, ‘Mono-, Bi- and High-Nuclearity Organotin Complexes’, Proc.-Indian Acad. Sci., Chem. Sci., 1996,108, 165 R334 J. Jane, T. Kasemsuwan, J. F. Chen and B. 0. Juliano, ‘Phosphorus in Rice and Other Starches’, Cereal Foods World, 1996,41, 827 R335 J. A. Jones, ‘Measurement and Removal of Splittings in NMR Spectra by Data Processing’, Concepts Magn. Reson., 1996,8, 175 R336 V. S. Joshi, S. K. Chowdhury and A. Sarkar, ‘Stereochemistry of Molybdenium (11) n-Ally1 Complexes’, Proc.-Indian Acad. Sci.,Chem. Sci., 1996, 108,217 R337 N. Juranic, M. Moncrieffe, E. Kurian, F. G. Pendergast and S. Macura, ‘Study of Hydrogen Bonding Networks in Proteins by High Resolution NMR Spectroscopy’, J. Serb. Chem. Soc., 1996,61, 717

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R338 A. A. Kader, ‘Regulation of Fruit Physiology by Controlled/Modified Atmospheres’, Acta Hortic., 1995,398, 59 R339 S. Kakorin and E. Neumann, ‘Chemical Electrooptics and Linear Dichroism of Polyelectrolytes and Colloids’, Ber. Bunsen-Ges., 1996,100, 72 1 R340 S. Kasparova, D. Dobrota and J. Horecky, ‘Study of Myocardial Metabolism by 31PNuclear Magnetic Resonance Spectroscopy’, Biologia (Bratislava), 1996,51, 707 R341 M. Kataoka and Y. Goto, ‘X-Ray Solution Scattering Studies of Protein Folding’, Folding Des., 1996, 1(5), R107 R342 R. Kemp-Harper, P. Styles and S. Wimperis, ‘B1 - Selective Pulses’, J. Magn. Reson., Ser. A , 1996,123,230 R343 T. Kitayama, K. Tashiro and W. J. Simonsick Jr., ‘Characterization of Polymeric Materials’, Plast. Eng. (N. Y ) , 1997,40, 813 R344 R. A. Klemm, M. Ledvij and S. H. Liu, ‘Surface State and Normal Layer Effects’, Chin. J. Phys. (Taipei), 1996, M(2, Pt.2), 201. R345 J. M. Knight, I. C. Shaw and A. P. Jones, ‘Life Begins at 50’, Chem. Br., 1996,32,37 R346 W. D. Knight, ‘Four Decades of Small-Particle Physics’, Surf: Rev. Lett., 1996, 3, 1 R347 S-I. Kobayashi, ‘The Kubo Effects in Small Particles of Metals’, Surf: Rev. Lett., 1996,3, 3 R348 J. D. Kocsis and R. H. Mattson, ‘GABA Levels in the Brain: A Target for New Antiepileptic Drugs’, Neuroscientist, 1996, 2, 326 R349 S. Koenig and E. Sackmann, ‘Molecular and Collective Dynamics of Lipid Bilayers’, Curr. Opin. Colloid Interface Sci., 1996, 1, 78 R350 P. A. Kollman, ‘Observation of the A-DNA to B-DNA Transition During Unrestrained Molecular Dynamics in Aqueous Solution’, J. Mol. Biol., 1996,259,434 R35 1 F. Kong, ‘Synthesis, Conformation, and Glycosidic Coupling Reaction of l ?2- and 1,3- Anhydro Sugar Derivatives’, Youji Huaxue, 1997,17, 38 R352 A. P. Koretsky, K. R. Miller and J. M. Halow, ‘Hepatic High Energy Phosphate Metabolism in Transgenic Livers Expressing Creatine Kinase as Revealed by 31PNMR’, Adv. Mol. Cell Biol., 1995,11, 233 R353 H. Koshino, T. Nakajima, Y. Wakatsuki, K. Kobayashi and J. Uzawa, ‘1H-31 P Pulsed Field Gradient Heteronuclear Multiple-Bond Correlation (PFG-HMBC) Spectroscopy’, RIKEN Rev., 1996,12,37 R354 W. Kuhn, P. Barth, P. Denner and R. Mueller, ‘Characterization of Elastomeric Materials by NM R Microscopy’, Solid State Nucl. Magn. Reson., 1996,6, 295 R355 1. Kustanovich and A. Zvi, ‘Epitope Mapping Antibody-Antigen Complexes by Nuclear Magnetic Resonance Spectroscopy’, Methods Mol. Bid. (Totowa, N. J ) , 1996,66,25 R356 L. I. Kuznetsova, L. G. Detusheva, N. I. Kuznetsova, M. A. Fedotov and V. A. Likholobov, ‘Relation Between Structure and Catalytic Properties of Transition Metal Complexes with Heteropolyanion PW in Oxidative Reactions’, J. Mol. Catal. A: Chem., 1997,117, 389

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R357 K. F. LaNoue and C. Doumen, ‘Studies of Physiological Control of ATP Synthesis’, Adv. Mol. Cell Biol., 1995, 11, 207 R358 M. 0. Leach, ‘Introduction to In Vivo MRS of Cancer: New Perspectives and Open Problems’, Anticancer Res., 1996,16, 1503 R359 D. Leibfritz, ‘An Introduction to the Potential of ’H-, 31P- and I3lCNMR- Spectroscopy’, Anticancer Res., 1996,16, 1317 R360 G. Leofanti, G . Tozzola, M. Padovan, G. Petrini, S. Bordiga and A. Zecchina, ‘Catalyst Characterization: Characterization Techniques’, Catal. Today, 1997,34,307 R361 D. Li and N. L. Owen, ‘Structure Determination Using the NMR “Inadequate” Technique’, Adv. Mol. Struct. Res., 1996, 2, 191 R362 E. N. Lightfoot, J. L. Coffman, F. Lode, Q. S. Yuan, T. W. Perkins and T. W. Root, ‘Refining the Description of Protein Chromatography’, J. Chromatogr., A, 1997,760, 139 R363 G. Lindblom, ‘Nuclear Magnetic Resonance on Lipids and Surfactants’, Curr. Opin. Colloid Interface Sci., 1996,1, 287 R364 G . Lindblom, ‘Nuclear Magnetic Resonance Spectroscopy and Lipid Phase Behavior and Lipid Diffusion’, Oily Press Lipid Libr., 1996,7, 133 R365 M. Liu and J. C. Lindon, “ H NMR Dipolar Relaxation Times and the Derivation of Internuclear Distance’, Concepts Magn, Reson., 1996, 8, 161 R366 J. Livage, F. Babonneau, M. Chatry and L. Coury, ‘Sol-Gel Synthesis and NMR Characterization of Ceramics’, Ceram. In?.,1997,23, 13 R367 S. Louise-May, P. Auffinger and E. Westhof, ‘Calculations of Nucleic Acid Conformations’, Curr. Opin. Struct. Biol., 1996,6, 289 R368 J. H. Lunsford, ‘Characterization of Acidity in Zeolites and Related Oxides Using Trimethylphosphine as a Probe’, Top Catal., 1997,4,91 R369 B. A. Luxon and D. G. Gorenstein, ‘Comparison of X-Ray and NMRDetermined Nucleic Acid Structures’, Methods Enzymol., 1995,261,45-73 R370 A. A. MacDonald, S. H. Dewitt, S. Ghosh, E. M. Hogan, L. Kieras, A. W. Czarnik and R. Ramage, ‘The Impact of Polystyrene Resins in Solid-Phase Organic Synthesis’, Mol. Diversity, 1996,1, 183 R371 B. E. Mann, ‘Nuclear Magnetic Resonance Spectroscopy’, Spectrosc. Prop. Inorg. Organomet. Compd., 1996,29, 1 R372 J. T. Markert, K. Mochizuki and A. V. Elliott, ‘Infinite-Layer, T’-Phase, and 1-D- Ladder Copper Oxide Compounds’, J. Low Temp. Phys., 1996, 105, 1367 R373 D. Marsh, ‘Magnetic Resonance of Lipids and Proteins in Membranes’, Curr. Opin. Colloid Interface Sci., 1997,2,4 R374 G. J. Martin, ‘Tracing Back the Origin of Vanillin by SNIF-NMR’, Ind. Chem. Libr., 1996,8, 506 R375 G. J. Martin, M. L. Martin and Y-L. Martin, ‘Precise and Accurate Determination of Isotope Ratios by Nuclear Magnetic Resonance Spectroscopy’, Bull. Magn. Reson., 1996, 18, 9 R376 G. Martini and S. Ristori, ‘Spectroscopic Characterization of Perfluorinated Compounds’, Trends Phys. Chem., 1994,4, 117

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R377 G. A. Marzluf, ‘Genetic Regulation of Nitrogen Metabolism in the Fungi’, Microbiol. Mol. Biol. Rev., 1997,61, 17 R378 P. Maurer, E. Hohenester and J. Engel, ‘Extracellular Calcium-Binding Proteins’, Curr. Opin, Cell Biol., 1996,8, 609 R379 K. H. Mayo, ‘NMR and X-Ray Studies of Collagen Model Peptides’, Biopolymers, 1996,40,359 R380 R. J. McClure, K. Panchalingam, W. E. Klunk and J. W. Pettegrew, ‘Magnetic Resonance Spectroscopy of Neural Tissue’, Methods Neurosci., 1996,30,178 R381 H. M. Mcconnell and M. Martinez-Yamout, ‘Insight into Antibody Combining Sites Using Nuclear Magnetic Resonance and Spin Label Haptens’, Adv. Protein Chem., 1996,49, 135 R382 L. M. McDowell and J. Schaefer, ‘High-Resolution NMR of Biological Solids’, Curr. Opin. Struct. Biol., 1996, 6, 624 R383 K. A. McLauchlan, ‘Detection and Identification of Transient Free Radicals in Solution’, Appl. Mugn. Reson., 1996,11,357 R384 H. J. D. McManus, ‘Isotopic Techniques for Beverage Authenticity’, Food Test. Anal., 1996,2, 37-38 R385 F. Metz, M. Lanson, A. Merbach and U. Frey, ‘NMR Under High Gas Pressure’, Ind. Chem. Libr., 1996,8, 528 R386 B. Mikhova and H. Duddeck, ‘13C-NMR Spectroscopy of Coumarins and their Derivatives: A Comprehensive Review’, Stud. Nut. Prod. Chem., 1996,18,971 R387 S. S. Mitchell, K. J. Shon, B. Olivera and C. M. Ireland, ‘NMR Structures of Conotoxins’, J. Nut. Toxins, 1996,5, 191 R388 K. Mizoguchi, ‘Microscopic and Anisotropic Dynamics of Spin Carriers with/without Charge’, Springer Proc. Phys., 1996,81,70 R389 0. Monasterio and T. Nowak, ‘Applications of Nuclear Magnetic Resonance to Determine the Structure and Interactions of Ligands, Peptides and Enzymes’, Biol. Res., 1996,29, 141 R390 G. J. Moore and J. M. Matsoukas, ‘Designing Peptide Mimetics’, Epitheor. Klin. Farmakol. Farmakokinet., Int. Ed. 1995, 9 (2 and 3), 53. R391 M. M . Mossoba and D. Firestone, ‘New Methods for Fat Analysis in Foods’, Food Test. Anal., 1996,2,24-28,30-32 R392 B. Mulloy, ‘High-Field NMR as a Technique for the Determination of Polysaccharide Structures’, Mol. Biotechnol., 1996,6,244 R393 H. A. Nasrallah, T. E. Skinner, P. Schmalbrock and P-M. Robitaille, ‘In Vivo ’H-NMR Spectroscopy of the Limbic Temporal Lobe in Patients with Schizophrenia’, Prog. Psychiatry, 1995,47, 1 R394 M. Nath and S. Goyal, ‘Organotin (IV) Complexes of Schiff Bases: A Review’, Main Group Met. Chem., 1996,19,75 R395 J. L. Neira and M. Rico, ‘Folding Studies on Ribonuclease A, A Model Protein’, Folding Des., 1997,2, R1 R396 D. R. Nesselrodt and T. Baer, ‘2 + 1 Resonance Enhanced Multiphoton Ionization Spectroscopy as a Tool for Stereochemical and Conformational

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Analysis of Substituted Five- and Six-Membered Rings’, J. Mol. Struct., 1996,377,201 R397 K. Nicolay, A. van der Toorn and R. M. Dijkhuizen, ‘In Vivo Diusion Spectroscopy. An Overview’, N M R Biomed. , 1995,8,365 R398 C. Nicolini, ‘From Protein Nanotechnology to Protein Automata: Year Zero’, Electron. Biotechnol. Adv. (EL. B. A. ) Forum Ser., 1996,2, 1 R399 M. Nilges, ‘Structure Calculation from NMR Data’, Curr. Opin. Struct. Biol., 1996,6, 617 R400 Y. Nojiri, ‘Tilted Foil Technique Applied to Beta-NMR Studies’, Hyperjine Interact., 1996,100, 23 R401 L. Oehrstroem, ‘The Correlation Between Transition Metal NMR Chemical Shifts and the Stability of Coordination Compounds’, Comments Inorg. Chem., 1996,18,305 R402 H. Ogoshi and T. Mizutani, ‘Functional Porphyrins as Receptor Models’, Yuki Gosei Kagaku Kyokaishi, 1996,54, 906 R403 A. S. Oja and 0. V. Lounasmaa, ‘Nuclear Magnetic Ordering in Simple Metals at Positive and Negative Nanokelvin Temperatures’, Rev. Mod. Phys., 1997,69, 1 R404 P. Olivera-Pastor, P. Maireles-Torres, E. Rodriguez-Castellon, A. JimenezLopez, T. Cassagneau, D. J. Jones and J. Roziere, ‘Nanostructured Inorganically Pillared Layered Metal(1V) Phosphates’, Chem. Muter., 1996,8, 1758 R405 J. Otlewski, D. Krowarsch, ‘Squash Inhibitor Family of Serine Proteinases’, Acta Biochim. Pol., 1996,43,431 R406 K. J. Packer, ‘Reflections on Applications of NMR in Heterogeneous Catalysis and Surface Chemistry’, Top. Catal., 1996,3,249 R407 A. G. Palmer HI., J. Williams and A. McDermott, ‘Nuclear Magnetic Resonance Studies of Biopolymer Dynamics’, J. Phys. Chem., 1996, 100, 13293 R408 T. Parella, ‘High - Quality 1D Spectra by Implementing Pulsed Field Gradients as the Coherence Pathway Selection Procedure’, Magn. Reson. Chem., 1996,34,329 R409 M. S. G . Pavao, ‘Unique Sulfated Polysaccharides from Ascidians (Chordata, Tunicata)’, Braz. J. Med. Biol. Res., 1996,29, 1227 R410 D. A. Pearlman, ‘FINGAR: A New Genetic Algorithm-Based Method for Fitting NMR Data’, J, Biomol. NMR, 1996,8,49 R411 S. W. Pelletier, ‘Research in the Chemistry of Diterpenoid Alkaloids’, Pure Appl. Chem., 1997,69,119 R412 K. Peltonen and A. Dipple, ‘Polycyclic Aromatic Hydrocarbons: Chemistry of DNA Adduct Formation’, J. Occup. Environ. Med., 1995,37, 52 R413 P. Pendzig, W. Dieterich, D. Knoedler, A. Nitzan and R. Olender, ‘Charged Particle Dynamics in Disordered Systems. Monte Carlo Simulations of Glassy and Polymeric Electrolytes’, Muter. Sci. Forum, 1996,223, 61 R414 C. H. Pennington and V. A. Stenger, ‘Nuclear Magnetic Resonance of Cm and Fulleride Superconductors’, Rev. Mod. Phys., 1996,68,855

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R415 T. Peters and B. M. Pinto, ‘Structure and Dynamics of Oligosaccharides: NMR and Modeling Studies’, Curr. Opin. Struct. Biol., 1996,6, 710 R416 A. C. Petroff, ‘The Measurement of In Vivo and E x Vivo pH Using Nuclear Magnetic Resonance Spectroscopy’, Eur. J. Lab. Med. , 1996,4, 143 R417 J. W. Pettegrew, M. S. Keshavan, N. J. Minshew and R. J. McClure, ‘3’PMRS of Metabolic Alterations in Schizophrenia and Neuro-Development’, Prog. Psychiatry, 1995,47,45 R418 P. E. Pfeffer and Y. Shachar-Hill, ‘Plant/Microbe Symbioses’, Curr. Top. Plant Physiol., 1996, 16, 77 R419 M. Piccioli, ‘Mercury-199 NMR of the Metal Receptor Site in MerR and its Protein- DNA Complex’, Chemtracts: Inorg. Chem., 1995’7, 99 R420 U. Pindur and G. Fischer, ‘DNA Complexing Minor Groove-Binding Ligands: Perspectives in Antitumor and Antimicrobial Drug Design’, Curr. Med. Chem., 1996,3,379 R421 D. Pines, ‘Spin Fluctuations and dx2-y2Pairing in the High Temperature Superconductors’, China Cent. Adv. Sci. Technol. (World Lab.) Symp. I Workshop Proc., 1995,11, 1 R422 D. Pines, ‘Spin Fluctuations and dx2-y2Pairing in the Cuprate Superconductors: A Progress Report’, Lect. Notes Phys., 1996,475, 20 1 R423 D. Pines, ‘Spin Fluctuations and dx2+ Pairing in the High Temperature Superconductors’, Turk. J. Phys., 1996,20,535 R424 A. Polozov, A. V. Khotinen and E. N. Klimovitskii, ‘Phosphorinane and Enol Rings in One Molecule. Evidence for Reciprocal Stabilization of Half-Chair Conformations’, Phosphorus, Sulfur Silicon Relat. Elem., 1996, 109-110, 581 R425 D. Porschke, ‘Analysis of Chemical and Physical Relaxation Processes of Polyelectrolytes by Electric Field Pulse Methods: A Comparison of Critical Comments with Facts’, Ber. Bunsen-Ges., 1996,100, 715 R426 T. L. Poulos, ‘Ligands and Electrons and Heme Proteins’, Nat. Struct. Biol. 1996,3,40 1 R427 M. I. Povolotskii, A. B. Rozhenko, V. V. Polovinko and A. N. Chernega, ‘Features of Phosphabutadienes Structure: NMR Spectroscopy and X-Ray Investigation’, Phosphorus, Su,fur Silicon Relat. Elem., 1996, 109-110, 617 R428 P. Prelovsek and J. Jaklic, ‘Universality of Charge and Spin Response in Doped Antiferromagnets’, J. Korean Phys. SOC.,1996,29, S63 R429 J. W. Prichard, ‘The Nuclear Magnetic Resonance Revolution in Basic and Clinical Neuroscience’, Neuroscientist, 1995’1, 84 R430 A. Putnis, ‘Quantification of Disorder in Silicate Melts, Glasses and Crystals Using NMR Spectroscopy’, Phys. Chem. Miner., 1996,23, 247 R431 L. Quartara, V. Pavone, C. Pedone, A. Lombardi, A. R. Renzetti and C. A. Maggi, ‘A Review of the Design, Synthesis and Biological Activity of the Bicyclic Hexapeptide Techykinin NK2 Antagonist MEN 10627’, Regul. Pept., 1996,65, 55 R432 R. G. Ratcliffe, ‘In Vivo NMR Spectroscopy: Biochemical and Physiological Applications to Plants’, Curr. Top. Plant Physiol., 1996, 16, 1

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R433 R. G. Ratcliffe, ‘In Vivo NMR Studies of the Metabolic Response of Plant Tissues to Anoxia’, Ann.Bot. (London), 1997,79(Suppl.A), 39 R434 J. Reglinski and I. D. Watson, ‘An Analytical Perspective of NMR Spectroscopy of Biological Fluids and Cells’, Ann. Clin. Biochem., 1996, 33,290 R435 P. F. Renshaw, G. S. Sachs and R. G. Gonzalez, ‘In Vivo MRS Measurement of Lithium Levels in Brain’, Prog. Psychiatry, 1995,47, 179 R436 J. A. Ripmeester and C. I. Ratcliffe, ‘Solid-state NMR Spectroscopy [in Supramolecular Chemistry]’, Compr. Supramol. Chem., 1996,8,323 R437 G. C. K. Roberts, ‘The Other Kind of Biological NMR - Studies of Enzyme-Substrate Interactions’, Neurochem. Rex, 1996,21, 1117 R438 J. K. M. Roberts and J-H. Xia, ‘NMR Contributions to Understanding of Plant Responses to Low Oxygen Stress’, Curr. Top. Plant Physiol., 1996, 16, 155 R439 B. H. Robinson and G. P. Drobny, ‘Site-Specific Dynamics in DNA: Theory and Experiment’, Methods Enzymol., 1995,261,451-509 R440 A. K . Rodi, H. Ranoivonjatovo, J. Escudie and A. Kerbal, ‘Metallaimines > M:N-, Metallaphosphenes > M:P- and Metallaarsenes > M:As-’, Main Group Met. Chem., 1996,19, 199 R441 I. Roggatz, C. Karle, M. Taupitz and E. Roessler, ‘Dynamical Disorder in Glasses Studied by 2H and ‘H NMR’, Ber. Bunsen-Ges., 1996,100, 1554 R442 R. Rothchild, ‘Determining Enantiomeric Excess by Direct NMR Methods and by Indirect Methods’, Chem. Educ.[Electronic Publication], 1996, 1, 838071998.html URL: http://journals.springer-ny.com/sam-bin/swilma/cla. R443 J. Ruiz-Cabello, S. W. Collier and J. S. Cohen, ‘31P Nuclear Magnetic Resonance Spectroscopy of Cells and Tissues’, Phosphorus, SulJir Silicon Relat. Elem., 1996,109-110, 361 R444 N. G. Saito and Y. Paterson, ‘Nuclear Magnetic Resonance Spectroscopy for the Study of B-Cell Epitopes’, Methods (San Diego), 1996,9,516 R445 K. Sakaie, C. P. Slichter and J. H. Sinfelt, ‘Methods Using the Nuclear Quadrupole Interaction to Determine the Structure of Randomly Oriented Molecules’, J. Magn. Reson., Ser. A 1996, 119(2), 235 R446 L. Salles, J-Y. Piquemal, R. Thouvenot, C. Minot and J-M. Bregeault, ‘Catalytic Epoxidation by Heteropolyoxoperoxo Corn ,lexes: From Novel Precursors or Catalysts to a Mechanistic Approach’, J. Mol. Catall A: Chem., 1997,117,375 R447 H. Santos, P. Fareleira, A. Ramos, H. Pereira and M Miranda, ‘Nuclear Magnetic Resonance: A Noninvasive Technique in the Study of Life Processes in Situ’, Rev. Port. Quim., 1995,2, 3 R448 M. Sattler and S. W. Fesik, ‘Use of Deuterium ,abeling in NMR: Overcoming a Sizeable Problem’, Structure (London), 1996,4, 1245 R449 J. Sefcik and A. V. McCormick, ‘Kinetic and Thermodynamic Issues in the Early Stages of Sol-Gel Processes Using Silicon Alkoxides’, Cutal. Today., 1997,35,205 R450 F. Separovic, ‘Sensitivity and NMR Spectroscopy’, Chem. Aust., 1996’63, 436

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R451 D. C. Sherrington, ‘Polymer Resins - Synthesis and Structure’, Spec. Publ. - R. SOC.Chem., 1997,196,3 R452 D. Shortle, Y. Wang, J. R. Gillespie and J. 0. Wrabl, ‘Protein Folding for Realists: A Timeless Phenomenon’, Protein Sci., 1996, 5,991 R453 R. W. Singerman and R. C. Richardson, ‘Methods for Heteronuclear Thin - Film NMR’, J. Magn. Reson., Ser. A , 1996,123, 168 R454 J. Sjoeblom, R. Lindberg and S. E. Friberg, ‘Microemulsions - Phase Equilibria Characterization, Structures, Applications and Chemical Reactions’, Adv. Colloid Interface Sci., 1996,65, 125 R455 C. D. Slater and C. N. Robinson, ‘Substituent Effects on Chemical Shifts in the NMR Spectra of Side Chain Sites in Styrenes’, Trends Org. Chem., 1993,4,261 R456 C. P. Slighter, R. L. Corey, N. J. Curro, S. M. DeSoto, K. O’Hara, T. Imai, A. M. Kini, H. H. Wang, U. Geiser and J. M. Williams, ‘Nuclear Magnetic Resonance and Electron Spins: Some History, Ancient and in the Making’, Philos. Mug. B, 1996,74, 545 R457 E. D. Sloan Jr., ‘Gas Hydrate Tutorial’, Prepr. Pap. -Am. Chem. Soc., Div. Fuel Chem., 1997,42,449 R458 L. J. Smith and C. M. Dobson, ‘NMR and Protein Dynamics’, Int. J. Quantum Chem., 1996,59,315 R459 S. 0. Smith, ‘Magic Angle Spinning NMR as a Tool for Structural Studies of Membrane Proteins’, Magn. Reson. Rev., 1996, 17, 1 R460 L. Sobczyk, ‘Quasi-Symmetric 0-H.. .N Hydrogen Bonds in Solid State’, Mol. Phys. Rep., 1996, 14, 19 R461 0. Soederman and B. Balinov, ‘NMR Self-Diffusion Studies of Emulsions’, Surfuctunt Sci. Ser., 1996,61, 369 R462 S . Song and E. C. Alyea, ‘An Assessment of the Parameters Relevant to the Subdivision of CJ and II Electronic Eects in M--P Bonds’, Comments Inorg. Chern., 1996,18, 145 R463 H. W. Spiess, ‘Multidimensional Solid State NMR of Polymers’, Polym. Prepr. (Am. Chem. SOC.,Div. Polym. Chem), 1997,38,768 R464 P. A. Srere, C. R. Malloy, D. A. Sherry and B. Sumegi, ‘The Cooperative Behavior of Krebs Tricarboxylic Acid Cycle Enzymes’, Adv. Mol. Cell Biol., 1995, 11, 125 R465 J. A. Stanley, D. J. Drost, P. C. Williamson, D. Psy and T. J . Carr, ‘In Vivo Proton MRS Study of Glutamate and Schizophrenia’, Prog. Psychiatry, 1995,47,21 R466 L. Stefaniak and J. Jazwinski, ‘Meso-Ionic Compounds: Structure and NMR Parameters’, Khim. Geterotsikl. Soedin., 1995,9, 1180 R467 M. Stocker, ‘Characterization of Zeolitic Materials by Solid-state NMR State of the Art’, Stud. Surf Sci. Catal., 1996, 102, 141 R468 N. C. J. Strynadka and M. N. G . James, ‘Lysozyme: A Model Enzyme in Protein Crystallography’, EXS, 1996,75, 185 R469 B. Sulikowski, ‘Isomorphous Replacement in the Zeolitic Frameworks: Recent Advances and Implications’, Heterog. Chem. Rev., 1996,3,203 R470 B. Sundqvist, 0. Anderson, U. Edlund, A.Fransson, A. Inaba, P.

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Jacobson, D. Johnels, P. Launois, C. Meingast, et al., ‘Physical Properties of Pressure Polymerized C60’, Proc. -Electrochem. SOC.,1996, 96, 1014 R471 B. D. Sykes, ‘Application of NMR Spectroscopy to Muscle CalciumBinding Proteins’, Braz. J. Med. Biol. Res., 1996,29, 825 R472 P. Tekely, ‘Application of High-Resolution Carbon- 13 Nuclear Magnetic Resonance to Heterogeneous Macromolecular Solids’, Trends Phys. Chem., 1994,4,181 R473 M. E. Thellier, J-C. Wissocq and C. Ripoll, ‘NCR and SIMS Study of Whether Lithium Ions Have Limited Intracellular Access’, J. Trace Microprobe Tech., 1997,15,93 R474 B. Thomas, K. Scholz and K. Herzog, ‘Structure and Cation Sensitivity of Silicate Glasses - A Review’, Ber. Bunsen-Ges., 1996,100, 1628 R475 C. Tilcock, D. Utkhede and G. Meng, ‘Vesicles as Imaging Agents’, Surfactant Sci. Ser., 1996,62, 593 R476 V. P. Torchilin, ‘Surface-Modified Liposomes in y-[Ray Scintigraphic] and MR- Imaging’, Adv. Drug Delivery Rev., 1997,24, 301 R477 J. 0. Trent and S. Neidle, ‘Molecular Modeling of Drug-DNA Interactions: Facts and Fantasies’, Adv. DNA Sequence Specific Agents, 1996, 2, 29 R478 J. Tritt-Goc, ‘New Molecular State of Nitroprusside Salt Crystals- A Review’, Mol. Phys. Rep., 1996, 14, 119 R479 R. Tycko, D. P. Weliky and A. E. Berger, ‘Investigation of Molecular Structure in Solids by Two-Dimensional NMR Exchange Spectroscopy with Magnetic Angle Spinning’, J. Chem. Phys., 1996, 105,7915 R480 N. B. Ulyanow and T. L. James, ‘Statistical Analysis of DNA Duplex Structural Features’, Methods Enzymol., 1995,261,90-120 R481 G. Van Den Thillart and A. Van Waarde, ‘Nuclear Magnetic Resonance Spectroscopy of Living Systems: Applications in Comparative Physiology’, Physiol. Rev., 1996,76, 799 R482 D. G. Vander Velde, J. Matsuura and M. C. Manning, ‘Two-, Three-, and Four- Dimensional Nuclear Magnetic Resonance Spectroscopy of Protein Pharmaceuticals’, Pharm. Biotechnol., 1995,7, 179 R483 G. van der Velden and J. Bueulen, ‘NMR Studies of Modified EPDM Elastomers’, Polym. Prepr. (Am. Chem. Soc., Div. Polym. Chem.), 1997, 38,865 R484 R. A. Van Santen, ‘Theory, Spectroscopy and Kinetics of Zeolite Catalyzed Reactions’, Prepr.-Am. Chem. Soc., Div. Pet. Chem., 1997,42, 66 R485 L. van Wuellen, B. Gee, L. Zuechner, M. Bertmer and H. Eckert, ‘V. Physiochemical Methods of Glass Characterisation. Connectivities and Cation Distributions in Oxide Glasses: New Results from Solid State NMR’, Ber. Bunsen-Ges., 1996,100, 1539 R486 H. F. Vermaas, ‘Wood-Water Interaction and Methods of Measuring Wood Content. Part 1. Definitional Aspects to NMR’, Holzforsch. Holzverwert., 1996,48, 30 R487 M. Vihinen and C. I. E. Smith, ‘Structural Aspects of Signal Transduction in B-Cells’, Crit. Rev. Immunol., 1996, 16, 251

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R488 M. E. Wall and M. C. Wani, ‘Comptothecin and Taxol: From Discovery to Clinic’, J. Ethnopharmacol., 1996,51,239 R489 T. Wallimann, ‘31P-NMR-Measured Creatine Kinase Reaction Flux in Muscle: A Caveat!’, J. Muscle Res. Cell Motil., 1996, 17, 177 R490 A. J. Wand and S. W. Englander, ‘Protein Complexes Studied by NMR Spectroscopy’, Curr. Opin. Biotechnol., 1996,7,403 R491 A. H-J. Wang, ‘X-Ray Crystallographic and NMR Structural Studies of Anthracycline Anticancer Drugs: Implication in Drug Design’, A h . DNA Sequence Specific Agents, 1996,2,59 R492 C. Wang, G. Hwang, S. C . Siu, F. Aubke, B. Bley, M. Bodenbinder, C. Bach and H. Willner, ‘Solvolysis Reactions in Liquid Antimony(V) Fluoride. A Convenient and Versatile Synthetic Method’, Eur. J. Solid State Inorg. Chem., 1996,33,917 R493 D. Weuster-Botz and A. A. de Graaf, ‘Reaction Engineering Methods to Study Intracellular Metabolite Concentrations’, Adv. Biochem. Eng.l Biotechnol., 1996,54,75 R494 W. Wiegrebe, T. Kammermeier, A. Kaiser and P. Bielmeier, ‘Platinum Complexes of 1,3-Diphenylpropane-1,3-diamines - Cytostatic Compounds?’, Chem. Listy, 1996,90, 502 R495 S-P. Williams, A. M. Fulton and K. M. Brindle, ‘Experimental Approaches to Studying Enzymes in Vivo: The Application of Nuclear Magnetic Resonance Methods to Genetically Manipulated Organisms’, Adv. Mol. Cell Biol., 1995, 11, 65 R496 C. F. Wilson, M. E. Hagerman and R. W. Zoellner, ‘Probing Hydrogen Bonding and the Local Environment of Silanols on Silica Surfaces via Nuclear Spin Cross Polarization Dynamics. Comments’, Chemtructs: Inorg. Chem., 1995,7, 191 R497 W. D. Wilson, L. Ratmayer, M. Zhao, D. Ding, A. W. McConnaughie, A. Kumar and D. W. Boykin, ‘Design and Analysis of RNA Structure-Specific Agents as Potential Antivirals’, J. Mol. Recognit., 1996, 9, 187 R498 B. Winkler, ‘The Dynamics of H20 in Minerals’, Phys. Chem. Miner., 1996’23,310 R499 M. J. Wirth, R. W. P. Fairbank and H. 0. Fatunmbi, ‘Mixed SelfAssembled Monolayers in Chemical Separations’, Science ( Washington, D. C.), 1997,275,44 R500 P. Wzietek, H. Mayaffre, D. Jerome and S. Brazovskii, ‘NMR in the 2D Organic Superconductors’, J. Phys., I , 1996,6,2011 R501 Y. Xia, ‘Contrast in NMR Imaging and Microscopy’, Concepts Mugn. Reson., 1996,8,205 R502 T. Xu and J. F. Haw, ‘The Development and Applications of CAVERN Methods for In Situ NMR Studies of Reactions on Solid Acids’, Top. Cutul., 1997,4, 109 R503 T. Yamada and H. Sugi, ‘Nuclear Magnetic Resonance Spectroscopy of Skeletal Muscle and Muscle Proteins’, Jpn. J. Physiol., 1996,46,201 R504 C. Y. Yang, S . J. Cai, H. Liu and C. Pidgeon, ‘Immobilized Artificial

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Membranes- Screens for Drug-Membrane Interactions’, Adv. Drug Delivery Rev., 1997,23, 229 R505 G. Zimmer, K. F. Thier, M. Mehring and F. Rachdi, ‘NMR on Alkali Fullerides’, Appl. Magn. Reson., 1996,11,263 R506 S. Zumer, P. Ziherl and G. P. Crawford, ‘Ordering and Dynamics in Paranematic Surface Layers’, Mol. Cryst. Liq. Cryst. Sci. Technol., Sect. A , 1996,290,193

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Reviews and Books in Foreign Languages

Chinese R507 Z. Cheng and Z. Du, ‘In Vivo 31PMRS Studies on Tumors’, Junshi Yixue Kexueyuan Yuankan, 1996,20, 141 R508 J. Fan, ‘Introduction of Nuclear Magnetic Resonance with Application to Chemistry’, Guangzhou Huagong, 1996,24,38 R509 J. Hao, G. Li and H. Wang, ‘Application of Nuclear Magnetic Resonance Spectroscopy (NMR) in Surfactant Solution’, Riyong Huaxue Gongye, 1996,1, 37,44 R510 Z. Ma, P. Zhang, L. Li and C. Ye, ‘Progress of NMR Techniques Applied to Coal Chemistry’, Meitan Zhuanhua, 1996,19, 33 R511 X. Miao, C. Ye, X. Han and J. Hu, ‘Recent Advances in the Determination of Internuclear Distances from Two-Dimensional NMR Experiments’, Huaxue Tongbao, 1995,12,1 R5 12 L-J. Ming, ‘Dinuclear Metalloenzymes - Structure, Function, and NMR Spectroscopy’, Huaxue, 1996,54,69 R513 H. Wang, H. Zhang and G. Lu, ‘Interpretation of 2D NMR Spectroscopy and its Applications’, Guangpu Shiyanshi, 1994,11, 3 R514 H. Wang, H. Zhang and G. Lu, ‘3D NMR Spectroscopy’, Guangpu Shiyanshi, 1995,12, 1 R515 H. Wang, H. Zhang and G. Lu, ‘4D NMR Spectroscopy’, Guangpu Shiyanshi, 1995,12, 11 R516 Y. Wang and D. Shen, ‘The Application of Solid-state NMR Relaxation in the Study of Polymers’, Gaofenzi Tongbao, 1996,3, 152 R517 C. Xia and D. Li, ‘In Situ NMR Technique and Applications’, Bupuxue Zazhi, 1996,13,503 R518 J. Xie, Q. Pan and Z. Pan, ‘Determination of Diffusion Coefficients of Small Molecule Substances in Polymer Systems’, Hecheng Xiangiiao Gongye, 1996,19,240 R519 Y. Yang, ‘High - Resolution NMR Technique for Studying the Surface Acidity of Solid Catalysts and its Application’, Shiyou Huagong, 1997,26, 60 R520 J. Zhou, B. Yang, L. Li, H. Hu, J. Qiu and Z. Ye, ‘NMR Spectroscopy for Dynamic Nuclear Polarization’, Wuli, 1996,25, 160

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Czech

R521 J. Brus and P. Kotlik, ‘Application of NMR Spectroscopy in the Study of Alkoxysilane Polycondensation’, Chem. Listy, 1996,90, 316 Danish

R522 P. E. Hansen, ‘Isotope Effects’, Dan. Kemi, 1996,77, 13 R523 N. Westergaard, U. Sonnewald, S. B. Petersen and A. Schousboe, ‘Use of NMR Spectroscopy in Cellular Neurochemical Research’, Dan. Kemi 1994,75,22 Dutch

R524 R. Kaptein, ‘NMR Provides a Look at the Interactions Between Proteins and DNA’, Chem. Mag. (Rijswijk, Neth.), 1996,10, 378, 380 French

R525 P. Bradesi, A. Bighelli, F. Tomi and J. Casanova, ‘Analysis of a Complex Mixture by Carbon-13 NMR. Part I. ’, Can. J. Appl. Spectrosc., 1996, 41, 15 R526 P. Bradesi, A. Bighelli, F. Tomi and J. Casanova, ‘Carbon-13 NMR Analysis of Complex Mixtures. Part 2’, Can. J. Appl. Spectrosc., 1996, 41, 41 R527 J. Casanova, ‘The Contribution of NMR to Essential Oil Analysis. Example of Sesquiterpenes’, Riv. Ital. EPPOS 1996,7(Spec.Num.), 177 R528 J. M. Delacotte, C . Hardouin and C. Rolando, ‘Amber: Its Chemical Structure’, Analusis, 1996,24, M23 1 R529 H. Desvaux and P. Berthault, ‘Contributions of Off-Resonance RadioFrequency (RF) Fields to NMR Structural and Dynamic Studies in Solution’, J. Chim. Phys. Phys.- Chim. Biol., 1996,93,403 R530 M. Leduc and E. Otten, ‘NMR Visualization of the Lungs with Helium’, Recherche, 1996, (287), 41. R53 1 P. Lux, ‘High Performance Liquid Chromatography (HPLC)-Nuclear Magnetic Resonance (NMR) Coupling’, Analusis, 1996,24, M25 R532 M. Magliozzi and M. Farines, ‘Identification of Tetracyclic Triterpenic Alcohols by Mass Spectrometry and Proton NMR’, OI., Corps Gras, Lipides, 1996,3,443 R533 P. Panissod, C. Meny, J. P. Jay, M. Wojcik and E. Jedryka, ‘Structure of Metallic Multilayers and their Interfaces Observed by NMR’, J. Phys.IV, 1996, 6(C7, Multicouches Metalliques), C7/89-C7/106 R534 G. I. Shulman, ‘New Views on the Pathogenesis of Type I1 Diabetes Through the Use of NMR Spectroscopy’, Journ. Annu. Diabetol. HotelDieu, 1996, 11

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R535 A. Spassky, ‘DNA, Structure and Biological Function’, Rom. J. Biophys., 1995,5,341 R536 R. Thouvenot, ‘Multinuclear Magnetic Resonance: A Valuable Tool for Structural Analysis in Coordination Chemistry’, Actual. Chim., 1996, 7, 102 German

R537 W. Buchheim and E. Frede, ‘Influence of High Pressure Treatment of Emulsified Fats on Crystallization’, Lebensmittelind. Milchwirtsch., 1996, 117,228. R538 B. Bluemich and H. W. Spiess, ‘NMR Spectroscopy’, Spektrosk. Amorpher Krist. Festkoerper, 1995, 3, ed. D. Haarer and H. W. Spiess, Steinkopf: Darmstadt, Germany R539 R. Carle, ‘Chamomile Oil. Extraction and Quality Assessment’, Dtsch. Apoth. Ztg., 1996, 136 , 17,23 R540 H. J. Gabius, S. Andre, H. Kaltner, H. Ch.Siebert, G. Kayser, C. W. Von der Lieth, N. V. Bovin, U. Brinck, K. Kayser and J. F. G. Vliegenthart, ‘Synthetic Oligosaccharides and Neoglycoconjugates. Tools for Molecular Analysis of Lectin Recognition and for Tumor Diagnosis’, Bioforum, 1996,19,503,506 R541 A. R. Grimmer, ‘Application of Solid-state NMR in Materials Research’, CLB Chem. Labor Biotech., 1996,47,457. Methoden in der Proteinanalytik, ed. M. Holtzhauer, Springer, Berlin, Germany, 1996 R542 M. Holtzhauer, ‘NMR Spectroscopy for Structure Clarification of Peptides and Proteins in Solution’, p. 171 R543 G. G. Martin, Y. -L. Martin and J. Herz, ‘Statistical Concepts for Fruit Juice Analysis’, Fluess .Obst, 1996,63, 647 R544 H. Plenio and R. Diodone, ‘Covalently Bonded Fluorine as a n-Donor Ligand for Metal Ions’, GIT Labor-Fachz., 1997,41,314 R545 A. Porzel, ‘NMR Studies of Plants and Plant Constituents’, Nova Acta Leopold., Suppl., 1996,14,95 R546 B. Schneider, ‘In Vivo NMR Spectroscopy in the Elucidation of Biosynthetic Pathways of Low-Molecular-Weight Natural Compounds’, Bioforum, 1996,19, 120, 122-124, 126. R547 B. Thomas, K. Scholz and K. Herzog, ‘NMR Studies of the Microstructure of pH- and pNa-Sensitive Electrode Glasses’, Freiberg. Forschungsh. C, 1996, C465,7 Greek

R548 Th.Mauromoustakos, G. Mponas, M. Zerbou, E. Theodoropoulou, M. Bensaia, Kh.Dimitriou and M. Mikha-Skretta, ‘Determination of Adulteration and Geographic Origin of Food and Beverages Using NMR’, Chem. Chron., Genike Ekdose, 1996,58,612

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Italian R549 A. Bertario, ‘Modern Applications of Nuclear Magnetic Resonance’, Tecnol. Chim., 1996,16,92 R550 S. Polesello, ‘Magnetic Resonance Spectrometers’, Lab. 2000, 1994,8,42

Japanese R551 S. Akashi, ‘Studies on the Protein Structures by Mass Spectrometry’, J. Mass Spectrom. SOC.Jpn., 1997,45, 1 R552 S. Amiya, ‘Structural Interpretation of Synthetic Polymers’, Shin Kobunshi Jikkengaku, 1995, 5, 93, 162 R553 I. Ando, ‘Principles of NMR’, Shin Kobunshi Jikkengaku, 1995,5, 1 R554 I. Ando, H. Kuroko, S. Kuroki and N. Asakawa, ‘Solid State NMR’, Shin Kobunshi Jikkengaku, 1995,5211,324 R555 T. Asakura, K. Yamanoke and H. Kuroko, ‘Synthetic Polymers’, Shin Kobunshi Jikkengaku, 1995,5,238,325 R556 K. Azami and K. Yagishita, ‘Analytical Methods for Engine Oil Additives’, Toraiborojisuto, 1996, 41, 369 R557 T. Fukamizo, Y. Honda, I. Boucher and R. Brzezinski, ‘Structure and Function of Chitosanase from Streptomyces Sp. N174’, Ojo Toshitsu Kagaku, 1996,43,247 R558 K. Hatada, T. Kitagama, Y. Terawaki and T. Nishura, ‘FT - NMR of Polymer Solutions’, Shin Kobunshi Jikkengaku, 1995,5,23, 160 R559 S. Hikima, ‘Two-Dimensional NMR Measurement. Field-Gradient Method’, Idemitsu Giho, 1996,39,400 R560 R. Hirose, S. Hayashi, T. Miyataka and M. Shimada, ‘Development of Superconducting Magnet for High-Field NMR’, Oyo Butsuri, 1997, 66,20 R561 H. Horii, ‘Dynamic Interpretation’, Shin Kobunshi Jikkengaku, 1995, 5, 270,327 R562 F. Horii, ‘Orientation of Polymers as Revealed by Multidimensional SolidState NMR’, Kobunshi, 1996,45, 856 R563 M. Ichikawa, T. Shido and M. Harada, ‘Molecular Architecture of Bimetallic Active Centers and their Bifunctional Catalysis’, Shokubai, 1996,38,272 R564 T. Igarashi and T. Yasumoto, ‘Structural Study of Prymnesin’, Kagaku to Seibutsu, 1996, 34,495 R565 Y. Inoue, ‘Copolymerization Chain Distribution’, Shin Kobunshi Jikkengaku, 1995,5, 113,163 R566 K. Ishimori, ‘High-Resolution NMR on Ultratrace Nanoliter Scale’, Kagaku (Kyoto), 1996,51,394 R567 Y. Ito, T. Terada and S. Yokoyama, ‘New Techniques for NMR Structural Biology’, Nippon Noyaku Gakkaishi, 1996,21,450 R568 H. Kawashima and 0. Yamada, ‘The Recent Studies on the Coal Structure Using Solid State NMR’, Nippon Enerugi Gakkaishi, 1996,75, 698

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R569 K. Kijama, ‘Recent Advancement of Quasi-Drugs Analysis’, Fragrance J., 1997,25,33 R570 K. Kimura, ‘New Development of High Resolution Solid State Proton NMR. UFP-NMR’, Kagaku (Kyoto), 1996,51,794 R571 H. Kobayashi, ‘Pesticide Residue Analysis’, Bunseki, 1997, 1, 62 R572 Y. Kobayashi and H. Shimahara, ‘NMR Spectrum for Clarification of Histidine Tautomerism in Protein’, Seisan to Gijutsu, 1997,49,48 R573 M. Koketsu, Y. Enoki, L. R. Juneja, M. Kim and T. Yamamoto, ‘Isolation of Sialyloligosaccharides from Egg Yolk Using Enzymes and Some Biofunctional Activities of the Oligosaccharides Isolated’, Oyo Toshitsu Kagaku, 1996,43,283 R574 H. Kurosu and I. Ando, ‘Structural and Dynamical Analyses of Small and Large Molecules in the Solid State by High Resolution Solid State NMR’, Yuki Gosei Kagaku Kyokaishi, 1996,54,367 R575 Y. Kyogoku, ‘Role of NMR in Structural Biology. Determination of the Solution Structures of Biomacromolecules by NM R’, Seibutsu Butsuri, 1996,36,216 R576 K. Y. Lee, ‘To Aim at Catalyst Design. Catalyst Design of Heteropolyacids’, Shokubai, 1996,38,350 R577 T. Machiguchi and S. Yamabe, ‘The Problem of Non-Recognition for Dienes in Ketene Reactions. A Big Fault in Ketene History and its Solution’, Yuki Gosei Kagaku Kyokaishi, 1997,55,72 R578 S. Matsui, ‘NMR Imaging of Solids’, Shin Kobunshi Jikkengaku, 1995, 5, 363,382 R579 Y. Matsuoka, ‘Structural Analysis of the Resins in Adhesives’, Setchaku no Gijutsu, 1996, 16, 10 R580 K. Matsuta, ‘Anomalous Knight Shift and Spin-Lattice Relaxation Time for Short-Lived P-Emitter I3O in Pt’, Seisan to Gijutsu, 1997,49,45 R581 Y. Mikata, ‘Synthesis and Reaction of NAD(P)H Model Compounds with Interconversion of Central and Axial Chirality’, Yuki Gosei Kagaku Kyokaishi, 1997,55, 132 R582 E. Miki, ‘Structure and Physical Properties of Transition Metal Nitrosyls’, Kikan Kagaku Sosetsu, 1996,30,20 R583 T. Miyake, ‘Analysis of Solid Acid Catalysts by H-MAS NMR’, Shokubai, 1997,39,56 R584 Y. Motoyama, ‘Mechanism of Lewis Acid-Promoted Simmons-Smith Reaction’, Organomet. News, 1995,4, 128 R585 T. Murai, ‘Chiral Selones. Enantiomeric Excess Determination with 77Se NMR Spectroscopy’, Kagaku (Kyoto), 1996,51,790 R586 K. Nagata, F. Inagaki and A. Suzuki, ‘Tertiary Structure and Functional Sites of Bombyxin, an Insect Insulin-like Peptide. Comparison with those of Insulin’, Tanpakushitsu Kakusan Koso, 1996,41, 1485 R587 A. Naito, ‘Measurements of Interatomic Distances by High-Resolution Solid-state NMR’, Seibutsu Butsuri, 1996,36, 195 R588 A. Naito, ‘Progress in High Resolution Solid State NMR’, Kobunshi 1996, 45,340

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R589 R. Nakagaki, ‘Evolution of Magnetic Resonance and Magnetochemistry’, Kagakushi Kenkyu, 1996,23,251 R590 R. Nakagaki, Y. Fujiwara and Y. Tanimoto, ‘Magnetic Isotope Effect on Radical Reactions’, Kokagaku, 1996,22,46 R591 M. Nakahara, ‘Structure of Supercritical Water’, Kagaku (Kyoto), 1996, 51,691 R592 Y. Nakatani, ‘Conformational Changes of Transcription Factor TFIIB Induced by Binding to the DNA-TBP Complex’, Jikken Igaku, 1996, 14, 949. R593 M. Nishio, Y. Umezawa and M. Hirota, ‘The CH/x Interactions. Implications in Molecular Recognition’, Yuki Gosei Kagaku Kyokaishi, 1997,55, 18 R594 T. Ohno, ‘Nuclear Magnetic Resonance of Copper-Sulfide Spinels’, Kotai Butsuri 1996,31,483, R595 H. Saito, ‘Mechanism and Estimation of the Deterioration of Marine Lipids’, Chuo Suisan Kenkyusho Kenkyu Hokoku, 1996,8, 61 R596 K. Saito, ‘Application to the Calcium-Binding Regulatory Enzyme, Calmodulin. A Quantitative Study on Metalloenzymes’, Kikan Kagaku Sosetsu, 1995,27, 169 R597 Y . Sakano, ‘Enzyme Chemistry and Application of Carbohydrate-Relating Enzymes’, Oyo Toshitsu Kagaku, 1996,43, 113 R598 J. Sano, N. Ikushima, K. Takada and T. Shoji, ‘NMR Studies of (1,3)-pD- Glucooligosaccharide Derivatives’, DIC Tech.Rev., 1995,1, 19 R599 M. Sasaki, ‘Determination of Complete Structure of Moitotoxin’, Kagaku to Seibutsu, 1996, 34, 635 R600 N. Sayuki, ‘Change of Saltiness During Fermentation and Ripening of Miso’, Nippon Jozo Kyokaishi, 1997,92, 176 R60 1 K. Shimada, ‘Structural Interpretation of Natural Polymers’, Shin Kobunshi Jikkengaku, 1995,5, 137, 166 R602 H. Shinohara, ‘Metal Contained Fullerene’, Gendai Kagaku, 1997,313, 50 R603 N. Shinozuka, ‘The Global Environment and Analyses. Isolation and Characterization of Aquatic Humic Substances’, Kikan Kagaku Sosetsu, 1996,29,73 R604 S. Tabata, ‘Solid State NMR of Polymers’, Bunseki, 1996,7, 533 R605 M. Tagawa, F. Murai and Y. Murai, ‘Determination of the Absolute Structure of Ionone Type Glucosides from Actinidiaceae and Related Plants Using Glucosidation Shifts in C-13 NMR’, Tennen Yuki Kagobutsu Toronkai Koen Yoshishu, 1996,38,337 R606 T. Takayama, ‘Solid State NMR’, Bunseki, 1997,2, 104 R607 T. Takeuchi, ‘HPLC-750 MHz ‘H NMR Directly Linked System’, Kagaku (Kyoto) 1996,51,327 R608 H . Tou, Y. Kitaoka, K. Asayama, T. Sakakibara, K. Tenya, M. Ikeda, T. Tayama, H. Amitsuka, N. Kimura et al., ‘Odd-Parity Superconductivity in UPt,’, Kotai Butsuri, 1996,31,763 R609 A. Tsuji, ‘Membrane Proteins’, Shin Kobunshi Jikkengaku, 1995,5, 307 R6 10 T. Tsurumi, ‘Structure and Properties of Relaxors’, Nyu Seramikkusu, 1997,10, 17

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R611 T. Tsutsume, ‘Pulsed NMR Spectroscopy of Polymers’, Shin Kobunshi Jikkengaku, 1995,5,167 R612 M. Uehara and J. Akimitsu, ‘Carrier Doping to Spin Ladder System’, Oyo Butsuri, 1996,65, 397 R613 T. Umeki, ‘Acidity Evaluation of Solid Catalysts’, Idemitsu Giho, 1996, 39, 597 R614 J. Uzawa and H. Koshino, ‘Progress of NMR Techniques Using Pulsed Field Gradients’, Yuki Gosei Kagaku Kyokaishi, 1996,54, 354 R615 H. Waki, ‘ “Ion-Exchange Chemistry” in Analytical and Solution Chemistry Researches’, Nippon Ion Kokan Gakkaishi, 1996,7,66 R616 Y. Warita, ‘New Flavor and Fragrance Materials’, Koryo, 1996,190, 57 R617 T. Watanabe, ‘NMR Imaging’, Shin Kobunshi Jikkengaku, 1995,5,331 R618 H. Yamada, ‘Development of New Methods for the Synthesis of Oligosaccharide and Conformational Analysis of Oligosaccharide in Aqueous Solution’, Yuki Gosei Kagaku Kyokaishi, 1997,55,29 R619 T. Yamagishi, ‘Asymmetric Induction in Asymmetric Catalytic Reaction. Application of Asymmetric Hydrogenation and Electrostatic Interaction’, Organomet. News, 1995,4,113 R620 I. Yamamoto, Y. Yamamura, T. Ota, R. Matsushita, Y. Kigami, I. Yu, M. Takada and R. Morita, ‘Evaluation of Qualitative Change of Bone’, Clin. Calcium, 1996,6,954 R621 T. Yamazaki and T. Kitazume, ‘Interaction of Fluorine with Proton or Metals’, Yuki Gosei Kagaku Kyokaishi, 1996,54, 665 R622 H. Yasunaga, ‘Imaging Interpretation’, Shin Kobunshi Jikkengaku, 1995, 5,351,381 R623 H . Yasuoka, ‘High Temperature Superconductors Seen by NMR’, Nippon Butsuri Gakkaishi, 1997,52, 197 R624 H. Yokogawa, ‘Aerogel for Transparent Thermal Insulators. Manufacture and Characteristics of Moisture-Resistant Silica Having Ultramicropores’, Shinsozai, 1996,7,4 1 Korean R625 J. J. Chung, ‘RNA Structure Studied by NMR’, Saenghwahak Nyusu, 1995,15,101 R626 G. B. Lee, ‘Electronic and Molecular Structure Examination of Paramagnetic Hemoproteins Active Site by NMR Spectroscopic Method’, Saenghwahak Nyusu, 1995,15,96 R627 W. T. Lee, ‘Application and Structure Analysis of Protein Using Nuclear Magnetic Resonance Techniques’, Saenghwahak Nyusu, 1995,15,93 Polish R628 A. 2. Hrynkiewicz, ‘Nuclear Methods in Condensed Matter Research. Forty Years of Development and Applications in the Institute of Nuclear

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R629 R630

R631 R632

R633

Physics and in the Institute of Physics of the Jagellonian University’, Postepy Fiz., 1996,47, 157 T. Niedziela, W. Jachymek and C. Lugowski, ‘Bacterial Endotoxins Methods of Structural Analysis’, Postepy Hig. Med. Dosw., 1996,50,419 M. J. Potrzebowski, ‘Solid-state NMR Spectroscopic Studies of the Structure and Dynamics of Organophosphorus Dichalcogenides’, Wiud. Chem., 1996,50,925 G. Slosarek, ‘NMR Spectroscopy of Actin’, Wiad. Chem., 1996,50, 125 G. Slosarek and J. Barciszewski, ‘Structure and Properties of Systemin the Peptide with Plant Hormone Properties’, Postepy Biol. Komorki, 1996, 23,477 L. S. Stefaniak, ‘Mesoionic Compounds- Structure and NMR Spectral Parameters’, Wiad. Chem., 1995,49, 653

Russian

R634 A. V. Anisimov and N. R. Dautova, ‘Pulsed NMR and the Measurement of Water Diffusion in Plants’, Fiz. -Khim. Metody Issled. Strukt. Din.Mol. Sist., Muter. Vseross. Soveshch., 1994, 3, 41, ed. M. E. Gordeev, Mariiskii Politekhnicheskii Institut im.A. M. Gor’kogo, Ioshkar-Ola, Russia R635 E. V. Babaev, V. N. Torocheshnikov and S. I. Bobrovsky, ‘NMR Spectra of Indolizines and their c~-Complexes’,Khim. Geterotsikl. Soedin., 1995, 9, 1235 R636 S. P. Dmitriev and N. A. Dovator, ‘Orientational Shift of Magnetic Resonance Lines in the Spin Exchange of Alkali Metal Atoms’, Zh. Tekh. Fiz.,1996, 66, 183 R637 M. P. Filatova, S. B. Rykov, A. B. Sokolov, E. D. Skakovskii and L. Yu.Tichinskaya, ‘Preparation of Samples for Analysis of Wastewaters by NMR Spectroscopy’, Fiz.- Khim. Metody Issled. Strukt. Din. Mol. Sist., Mater. Vseross. Soveshch., 1994, 1, 48, ed. M. E. Gordeev, Mariiskii Politekhnicheskii Institut im.A. M. Gor’kogo: Ioshkar-Ola, Russia R638 V. S. Kartashov, ‘Methodological Aspects of Using NMR Spectroscopy in Pharmaceutical Analysis’, Furmatsiya, 1995,44, 37 R639 V. S. Kartashov, ‘Application and Prospects of NMR Spectroscopy for Pharmaceutical Analysis (Review)’, Khim. -Farm. Zh., 1996,30, 59 R640 A. S. Khachaturow, ‘High - Frequency I3C NMR Spectra of Polybutadiene’, in Sovremenny Aspekty YaMR Spektroskopii Polimerov, ed. A. S. Khachaturov, Nauchno-Issledovatel’skii Institut Sinteticheskogo Kauchuka im. Akademika S . V. Lebedeva, Sankt-Petersburg, Russia, p. 5, 1994 R641 G . E. Kibrik and A. Yu.Polyakov, ‘Investigation of the Molecular Dynamics by Multi- pulse Spin-locking in Nuclear Quadrupole Resonance’, Fiz. -Khim. Metody Issled. Strukt. Din. Mol. Sist., Mater. Vseross. Soveshch., 1994,3, 11 R642 N. K. Kochetkov, ‘Unusual Monosaccharides: Components of 0-Antigenic Polysaccharides of Microorganisms’, Usp. Khim., 1996,65,799 R643 L. B. Krivdin, G. N. Glushko and V. N. Efimov, ‘Stereochemical Applica-

1: N M R Books and Reviews

43

tion of Carbon- Carbon Spin-Spin Interaction Constants’, Fiz. -Khim. Metody Issled. Strukt. Din. Mol. Sist., Muter. Vseross. Soveshch., 1994, 1, 72, ed. M. E. Gordeev, Mariiskii Politekhnicheskii Institut im. A. M. Gor’kogo: Ioshkar-Ola, Russia R644 A. A. Lundin, ‘Asymptotic Similarities of Intermittent Correlation Functions and Problems of the Form of NMR Lines in Solids’, Zh. Eksp. Teor. Fiz., 1996, 110, 1378 R645 A. A. Lundin, ‘NMR Absorption Line Shapes in Solids’, Khim. Fiz., 1996, 15,36 R646 A. V. Minin, ‘Theory of Shallow Exploration by Using Nuclear Magnetic Resonance’, Fiz. Zemli, 1996, 10, 25 R647 N. Ya.Shteinshneider, ‘Study of Molecular Motion in Nafion-type Membranes by ESR and NMR’, Zh. Fiz. Khim., 1996,70,741 R648 G. N. Sinyakov and A. M. Shulga, “ H NMR Studies of Reduced Nickel Octaethylporphin Complexes’, Zh. Strukt. Khim., 1996,37, 507 R649 B. M. Vladimirskii and N. A. Temur’yants, ‘Nuclear Magnetic Resonance in Geomagnetic Field as a Possible Mechanism of Weak Electromagnetic Field Action upon Biological and Physicochemical Systems’, BioJizika, 1996,41,926 R650 V. K. Voronov, ‘Nuclear Magnetic Resonance’, Prirodu (Moscow), 1996, 2, 58 Spanish R651 J. Elguero, ‘Dynamic Phenomena in Crystals: Synergy Between X-Ray Crystallography and High-Resolution Nuclear Magnetic Resonance in Solids’, Rev. R. Acad. Cienc. Exactas, Fis. Nut. Madrid, 1994,88, 361 R652 A. J. Mondragon, ‘Synthesis Techniques and Analytical Methods Applied to Anthraquinone Dyes’, Afinidad, 1997,54, 109 R653 G. B. Rojas and J. M. Gomez Fatou, ‘Degree of Functionalization of Polyolefins’, Rev. Plast. Mod., 1996,71, 26 1 Turkish R654 H. Akgun, ‘NMR Spectroscopy’, FABAD Farm., Bilimler Derg., 1996, 21, 163 Ukrainian R655 A. V. Yatsenko and V. Yu.Kornienko, ‘Using Digital Filtration in WideLine NMR Spectroscopy’, Ukr. Fiz. Zh., 1996,41,636

2 Theoretical and Physical Aspects of Nuclear Shielding BY CYNTHIA J. JAMESON

1

Theoretical Aspects of Nuclear Shielding

1.1 General Theory - As the well-established methods employing multiple origins, GIAO, IGLO, LORG, IGAIM, and common origin C H F methods are applied to diverse molecular systems, using ever larger basis sets up to near Hartree-Fock limit, the limitations of calculations at the SCF level in accurately predicting the nuclear shielding become more evident. Furthermore, the challenge of applying these methods to heavier nuclei, or to nuclei having neighboring halogens and other atoms with large spin orbit coupling constants, demanded the development of theoretical methods for improved description of shielding in systems where electron correlation is important, and systems where relativistic effects are important. The methods that have been proposed in the past few years, reviewed in this chapter in the preceding volumes of the series, include direct methods applied to many body perturbation theory, use of multiconfigurational wavefunctions, coupled cluster approaches, and the application of density functional theory. This reporting period shows progress in all these areas. Since nuclear shielding depends acutely on the electronic distribution very close to the nucleus, the relativistic effects can be very significant. Most satisfying from a theoretical point of view is the use of fully relativistic methods based on fourcomponent wavefunctions and the complete Dirac equation.' However, these calculations would be impractical for those systems (containing atoms of high atomic number) in which relativistic effects on observed chemical shifts would be significant. Therefore, approaches that have been used to calculate relativistic effects on shielding have been based on two component wavefunctions. The quasi-relativistic method, on the other hand, uses the frozen core approximation. In this way, the highly relativistic core electrons are treated with the complete four-component atomic Dirac equation. The core electron density and its potential are extracted from these fully relativistic calculations. They are used in subsequent molecular calculations. The remaining valence electrons are treated with approximate relativistic theory based on a two-component Hamiltonian. When the spin orbit operator is neglected completely, then only the so-called scalar relativistic eflects are found. This terminology has been used by both Ziegler et al. and Malkin et al. These include both the direct effect and the geometry effect. Different minimum energy geometries are obtained in using

Nuclear Magnetic Resonance, Volume 27 0The Royal Society of Chemistry 1998 44

2: Theoretical and Physical Aspects of Nuclear Shielding

45

relativistic calculations than obtained using nonrelativistic calculations. The great sensitivity of shielding to bond distances implies that different shielding values will be obtained depending on whether the geometry corresponding to a nonrelativistic or relativistic calculation is used, this is an indirect relativistic effect. At a given molecular geometry, the shielding calculation itself may be done either with nonrelativistic or relativistic theory. This is a direct effect. Schreckenbach and Ziegler’ have considered only the direct effect; Kaupp et al. have considered both the geometry and the direct effects.3i4The scalar relativistic effects have also been called ‘spin-free’ relativistic effects by Nakatsuji et al? The spin orbit contributions alone have been calculated by Nakatsuji et and also by Malkin, Kaupp et a1.10911 Both scalar and spin orbit relativistic corrections have been considered by Nakatsuji et al. in a few case^.'^^^^' We describe their findings in more detail below. Recently, Fukui et al. derived the lowest order relativistic effect theory for nuclear magnetic shielding from a two-component positive energy Hamiltonian.l 3 They have shown that the previous (Morishima et al.,14 Endo et al.,15316 Nakatsuji et a].,’ 9 y 1 2 7 1 7 - 1 9 Malkin et a1.10,20-23)relativistic theory based on the twocomponent Hamiltonian is not gauge invariant. The Fukui et a]. theory is gauge invariant to the order of (Z/137)4 where Z is the atomic number of the heaviest atom in the m ~ l e c u l e . Briefly, ~ the nuclear shielding, retaining the nonrelativistic and the lowest order relativistic terms, is given by the following: O=Gd

+

0’

+ + +

+

+

=od(DS-I) ~ ~ ( D s - 1+ 1 )csd(ROO) oP(0P-I) ~ ( O P - 1 1+ ) oP(OP-III)+ o’(0P-IV) oP(FC-I) + oP(FC-11) + ~ ~ ( F C - 1 1+ 1 )o’(FC-IV) + g’(SD-I)+ CJ’( SD-11) CJ’ (SD-111) up(SD-IV) oP(ROO)

+

+

The formalism was presented by Fukui et al. in the sum-over-states form using third order perturbation theory in the basis o f the eigenfunctions of the nonrelativistic Schrodinger Hamiltonian in the absence of the fields. Each of the above terms involve one (first order perturbation theory), two (second order) or %SD(O9l7l), XFc(o>lyl), three (third order) of the following operators XDs(”l’o), %sz(l>o’l) 2oz(1,070) and &70p(o~~~o),X M c ( I , o , l ) roo(^^^^^) &GROO(1,0,0) &GRoo(o~l,o), X R 0 0 ( 1 7 1 , 0 ) , Xso(o’o’l), Xso(l’o’l), which are respectively the diamagnetic shielding (DS), spin dipolar (SD), Fermi contact (FC), spin Zeeman ( S Z ) , orbital Zeeman (OZ), orbital paramagnetic (OP), mass correction (MC), retarded orbit-orbit (ROO), and spin orbit (SO) operators. Of these, the operator that involves the gauge origin explicitly in the orbital angular momentum The operators operator is the orbital Zeeman term in the Hamiltonian, Xoz(170,0). that involve the gauge origin explicitly in the vector position of the electron are and the retarded orbit orbit terms the diamagnetic shielding term XD&’>’>’), X R o o ( 1 9 0 3 0 )and Thus, every term in the shielding involving the [ i. e., op(OP-I), op(OP-IV), oP(ROO), oP(FC-I), and operator Xoz(’,070) oP(SD-I)] will have counterpart terms involving & G D S ( ’ ~ ~ ~X ~ ) ,~ 0 0 ( ~ or~ ~ , ~ ) X R O O ( l , l , O )that should result in sums that are gauge invariant, in order that the observable shielding tensor itself be independent of chosen origin. 7

9

7

9

7

46

Nuclear Magnetic Resonance

The sum od(DS-I) + op(OP-I) had previously been established to be gauge invariant. These are the nonrelativistic diamagnetic and paramagnetic Ramsey terms, which involve the matrix elements of respectively HDs and HOP x Hoz respectively. The other sums that have been shown to be gauge invariant are as follows: od(DS-II) + op(OP-III) + op(OP-IV) is gauge invariant. These involve XDs x Y?Roo(o’o’o),Xop x XRoo(l,o,o),and S o p x X o z x XRoo(o’030) respectively. ~’~ X’O ~Z ) od(ROO) + oP(ROO) is gauge invariant. These involve . Y P R ~ ~ (and x roo(^.^,^) respectively. oP(FC-I) + oP(FC-11) is gauge invariant. These involve X F C x Sso(o’o’l) x Xozand XFC x $Yso(l’o,l) respectively. aP(SD-I)+ oP(SD-11) is gauge invariant. These involve XsDx Y?so(o’o~l) x Xozand X s Dx Xso(13031) respectively. All the remaining terms in the shielding are individually independent of the gauge origin [op(OP-11),op(FC-III), aP(FC-IV),oP(SD-111),and oP(SD-IV)]. The relativistic terms in the shielding can be grouped as follows: those that involve the spin orbit operutor {oP(FC-I)+ oP(FC-11),oP(SD-I) + oP(SD-11),and op(OP-11)) and those that do not ( ~ ~ ~ ( D s -+1 1op(OP-III) ) + oP(OP-IV), od(ROO) + oP(ROO), oP(FC-111),oP(FC-IV), oP(SD-111), and oP(SD-IV)}. Of those terms that do not involve the spin orbit operator, a smaller set involving only the mass velocity operator and the Darwin operator are called the ‘scalar’ relativistic terms in the hi el ding,^*^',*^ or called the ‘spin free’ relativistic terms,5 which would correspond to the gauge invariant sums [od(DS-II)+ op(OP111) + op(OP-IV)] and [od(ROO) + oP(ROO)] in the expressions for shielding and op(OP-IV). derived by Fukui et aI.I3 The Darwin terms are in c~~(DS-11) Nakatsuji et al. included the complex one-electron SO operator in the ‘ground state’ Hamiltonian and finds the spin orbit terms oP(FC-I) and oP(SD-I) only, which they labeled ‘FC’ and ‘SD’ respectively, thus neglecting op(FC-11),op(SDII), and op(OP-11). Malkin et a1.l’ on the other hand, include the Fermi contact operator in their ‘ground state’ Hamiltonian. The FC operator produces spin polarization in the formally closed shell system. The external magnetic field is then introduced as a perturbation, and the perturbed wavefunction is used to calculate the expectation value of the spin orbit operator. The spin dipolar terms have been left out entirely in the Malkin approach, so that in Ref. 10 they have only included oP(FC-I).However, because of the exchange-correlation functional used in the DFT method, the oP(FC-I) differs from Nakatsuji in that electron correlation is taken into account in oP(FC-I)of Ref. 10. One of the important results of the work of Fukui et al.I3 is first of all, a more complete relativistic theory based on the two component Hamiltonian. Second is the finding that the previous relativistic theory based on the two component Hamiltonian developed by other groups, including Morishima et al.,14 Endo et al.,15916 Nakatsuji et a1.,6 and Malkin et al.,” is not gauge invariant even in the limit of a complete basis set, because they included only the oP(FC-I) term without the counterpart oP(FC-11)term that makes the gauge invariant sum. The that comes from the vector potential part of the mechanical operator Sso(170’1), momentum 7c = p + eA, of a system in the presence of magnetic fields, included

2: Theoretical and Physical Aspects of Nuclear Shielding

Table 2.1

47

Contributions to the gauge invariant sum /&(FC-I) + d ( F C - I I )J involving the spin orbit contribution from the Fermi contact term, compared with the magnitudes of the nonrelativistic nuclear shielding

System HX

Nonrel." Rex 13

~(Fc-II)' ReJ 13

~ ( F c - I , P~ ( F c - I , P Ref 7

Ref I0

H in H F H in HCl H in HBr H in HI Fin HF C1 in HCl Br in HBr I in HI

28.64 30.81 31.18 3 1.74 41 3.6 952.0 2652.6 4562.8

7.42 x lo-' 8.04 x lo-' 1.47 x lo-' 2.04 x lo-' - 1.57 - 10.34 - 90.3 - 290.4

0.17 0.88 5.15 15.61

0.16 0.79 4.27 11.79

a

GIAO IGLO choice of gauge origin Gauge origin at the heavy nucleus These values are for only the one-electron terms in oP(FC-I)

by Fukui et al. in their relativistic shielding theory, appears in both oP(FC-11)and op(SD-11). It has been shown earlier by Nakatsuji et al.7 that the oP(SD-I) terms are small compared to oP(FC-I) in the cases they have considered. However, this may not always be the case, and gauge invariance requires the sum oP(SD-I) + oP(SD-11), whereas only oP(SD-I)had previously been included in the theory. The third important finding by Fukui et al. is that for the shielding of the heavy nucleus itself, the oP(FC-11) terms are not negligible. The previously neglected oP(FC-11)terms are small for the 'H shielding in the HX molecules, but are not small for the X shielding, as can be seen in Table 2.1. Systems to which relativistic corrections on shielding have been applied recently are (where X = F, C1, Br, I) l19Sn in SnX4: 'H in HX," I3Cin CX4 and in CH,X4-n,1013C in CX3+," 1 7 0 in [M04]"- (M = Cr, Mo, W, Mn, Tc, Rh, Ru, O S ) , ~and ? ~ I7O, 53Cr, 95M0,and 183Win Cr(C0)6, Mo(CO)~,and W(CO)6,2 183win wx6 and w o 4 2 - . 1 2 Some of the significant conclusions are the following. (a) There are large scalar relativistic effects found for the I7O shielding in transition metal 5d oxo-complexes,2*10(which had been found in earlier studies in these systems21323). In part this can be traced back to relativistically increased energy denominators for a few key contributions to the sum-over-states expression for op.At the same time, the relativistic expansion of the metal 5d orbitals facilitates charge transfer to the oxygen, and this increased charge separation reduces oPvia the r W 3dependence. Thus, both factors play a role in the observed periodic trends in 170shielding. It should be noted that H F and MP2 levels of theory fail miserably for these compounds, which are known to exhibit very large electron correlation effects already in their ground states." Table 2.2 shows a comparison of the I7O results for the transition metal do 0x0 complexes,

Nuclear Magnetic Resonance

48

Table 2.2 Scalar relativistic corrections to I7O shielding (ppm) in ‘uncoupled’ density functional calculations in transition metal 0x0 ions, based on calculations at experimental molecular geometries using the quasirelativistic method (QR). Ref. 2

I7O in

Nonrel

QR

UDFTGIAO’.‘

UDFTGIAO’.‘

459

- 446

- 253

-216 - 140 - 778 - 405 - 278 - 740 - 521

-

-219 - 799 -

450

- 367

-810 - 629

ReJ 3 Rel. correc.

13 37 79 21 45 88 70 108

Nonrel

QR

UDFTIGLO’

UDFTIGLO’

- 552

-

299 - 356 -881 - 464 - 385 - 839 - 659 -

535

- 260 - 156 - 862 -

427

- 289

-781 -531

Rel. correc.

Exp t .‘I QR UDFTGIAO‘

17 39 200 19 37 96 58 128

- 508 - 251 -

157

- 527 - 222

-112

- 832

- 922

-421 282 - 765 -517

-441 -261 - 798 - 488

-

Converted to absolute shieldings from chemical shifts compiled in Ref. 25 by using the absolute ”0 shielding scale based on G [ ’ ~ O CO, , v = 01 = -42.3+ 17.2 ppm, which defines o[”O in H20(liq, 300 K)] = 307.9f 17.2 ppm.’6 Note, however, that the most accurate calculations on the 170shielding in CO molecule using CCSD(T)-GIAO lead to o[’~O,CO, 300 K] = -59.3+2 ppm,” 17 pprn below the experimental value, but within the error bars of the latter Uncoupled DFT-GIAO using BP86 functional. Uncontracted Slater-type orbital basis, double 5 frozen core [core being defined as 1s for 0 atom, up to and including 2p, 3d, and 4f for first, second, and third transition row M atoms], valence MOs orthogonalized against all cores, triple 5 valence basis augmented by single < auxiliary core basis, extended by two sets of d polarization functions at M and one set o f f functions at 0 atom Although in use in the literature, the term ‘uncoupled DFT’ is considered inappropriate by Ziegler and co-workers (Ref. 2), since it is not analogous to uncoupled Hartree-Fock which neglects all electron correlation. Uncoupled DFT is uncoupled in the sense that all currentdependent terms in the exchange correlation energy functional are neglected ’Uncoupled DFT-IGLO with separate localization, using the gradient-corrected PW9 1 functional, nonrelativistic ECP on metal atom, IGLO-I1 basis on 0 atom ‘Uncoupled DFT-IGLO with separate localization, using PW9 1 functional, quasi-relativistic ECP on metal atom, IGLO-I1 basis on 0 atom ‘Uncoupled DFT-GIAO using BP86 functional, quasi-relativistic ECP on metal atom, IGLO-I1 basis on 0 atom r‘

’

calculated at experimental geometries using density functional theory for shielding in which the current contributions to correlation are neglected (that is, all the current-dependent terms in the exchange-correiation energy functional are neglected) called ‘uncoupled DFT’ by Malkin et al.24 (b) There are large scalar relativistic effects on the metal (M = Cr, Mo, W) shielding in transition metal 0x0 anions [M0,l2- and hexacarbonyls M(C0)6.2 These are shown in Table 2.3 to be much larger for ls3W (1306 ppm for IS3W in [WO4I2-) than for 53Cr and are substantially different for different molecules so that they are necessary to account for the chemical shifts. For

2: Theoretical and Physical Aspects of Nuclear Shielding

Table 2.3

Nonrelil QR' Expt.'

49

Scalar relativistic corrections to transition metal shielding (ppm) in 'uncoupled' density functional calculations (Ref 2 ) in transition metal 0x0 ions and hexacarbonyls, based on calculations at experimental molecular geometries using the quasi-relativistic method ( Q R )

- 2340 -

2265

- 509 -451

-1831 -1814 - 1795

825 2131

4900 5834

-

4075

- 3703 - 3505

Uncoupled DFT-GIAO using BP86 functional. Uncontracted Slater-type orbital basis, double s frozen core [core being defined as 1s for C and 0 atoms, up to and including 2p, 3d, and 4f for first, second, and third transition row M atoms], valence MOs orthogonalized against all cores, triple q valence basis augmented by single q auxiliary core basis, extended by two sets of d polarization functions at M and one set o f f functions at C and 0 atoms Ref. 27a

example, the chemical shift predicted for Is3W in W(CO)6 relative to the reference, [W04l2- is 370 ppm different from that predicted using nonrelativistic calculations. (c) There are additional (700 ppm for 183Win [WO4I2-) relativistic effects from spin orbit terms on the metal shielding, and these couple with the scalar relativistic effects.12 That is, calculations including both the SO terms and the scalar relativistic terms in the Hamiltonian give SO contributions that are different from calculations including only SO terms. (d) The electron correlation effects have to be included in calculations of the absolute shielding of transition metal nuclei. The comparison between density functional calculations which include correlation, and Hartree-Fock calculations which do not, in Table 2.4, shows that the absolute shieldings calculated with and without correlation differ by about 2000 ppm for 183Win [WO,]*-. (e) Relativity is seen to increase the diamagnetic shielding, by 970 ppm for 183W,for example (see Table 2.4). This can easily be understood by the relativistic contraction of the s and p core orbitals, especially the Is. Consequently, the relativistic change of the diamagnetic shielding is almost entirely due to the changes in the core contributions.2 As such, they will not contribute significantly to relativistic changes of the chemical shifts, since the changes of the core density are mostly independent of the chemical environment of the given nucleus. For example, in the comparison of the relativistic effects on diamagnetic shielding of 183Win WF6, [WO4I2-, and WC16, Hada et a l l 2 found the values to be very nearly identical, 809.83, 810.41, and 808.78 ppm, respectively, which differ by no more than 1.6 ppm. On the other hand, these authors found the relativistic effects on the total shielding (including the SO terms) to be 1393, 2053, and 1633 ppm, which decreases the predicted chemical shift of WF6, relative to the reference [WO4j2--,by 660 ppm.

50

Table 2.4

Nuclear Magnetic Resonance

Relativistic corrections to 183 W shielding (ppm) in [W 0 4 ] '-, based on calculations at experimental molecular geometry: scalar relativistic eflects with electron correlation using density functional theory and the quasi-relativistic method ( Q R ) (Ref. 2 ) compared with spin free relativistic unrestricted Hartree-Fock without electron correlation, with and without the spin orbit term (Ref. 12) With correlation, Ref 2

D ifference

DFT

Without correlation, Ref12 UHF

Difference

~~

r(W-O), A

u,Nonrel o,scalar rel. o,rel. with SO od,Nonrel od,scalar reI. op,Nonrel. op,scalar rel.

1.79 825" 21 3l''.h

8722" 9693".' - 7898",b - 7562",b

1306

97 1 336

1.83 2562" 39 17".d 46 16C.d.e

8895" 970Fd - 6332'." - 5788'*"

1355 699

810 544

'I Uncoupled DFT-GIAO using BP86 functional. Uncontracted Slater-type orbital basis, double s frozen core [core being defined as 1s for C and 0 atoms, up to and including 2p, 3d, and 4f for first, second, and third transition row M atoms], valence MOs orthogonalized against all cores, triple s valence basis augmented by single q auxiliary core basis, extended by two sets of d polarization functions at M and one set o f f functions at C and 0 atoms Quasi-relativistic method ' Basis sets are their set C: [10s9p4dlfl for W atom, (lOs7p)/[3s2p]for 0 atom Spin free relativistic no-pair Hamiltonian defined with external field projectors is used as zeroth-order Hamiltonian SO-UHF finite perturbation method using conventional spin orbit operator in the BreitPauli form, limited to the one-electron term

(f) The relativistic effects from spin orbit terms [arising from the one-electron part of oP(FC-I), neglecting aP(FC-11), and neglecting coupling with the scalar relativistic effects] have been found to be significant when the nucleus of interest has neighboring halogen (X) atoms. Earlier calculations for *'A1 in [A1 X4]-,17 29Siin Six4 and SiX13,8"Ga and '"In in [GaX4]- and [InX4]-,18 have come to the conclusion that the so-called 'normal halogen dependence' of chemical shifts in these cases is due to the oP(FC-I) relativistic term. More recent examples are found for 'H in HX, 13C in CHnX4-n10and in CX3+,I1 lI9Sn in S I I X ~ We .~ compare the results obtained for 'H in HX with and without electron correlation in the last two columns of Table 2.1. The effects for I3C in CH,X4-, and CX3+ ions are even more dramatic, as shown in Tables 2.5 and 2.6. The electron correlation effects in SnX4 are significant ( 1 00-400 ppm for X = H, Me, Cl) for the 19Sn shielding, while the relativistic effects are large when Br and I atoms are involved (See Table 2.7). Despite the apparent good agreement with experiment of the chemical shifts calculated including relativistic

'

2: Theoretical and Physical Aspects of Nuclear Shielding

Table 2.5

51

The one-electron spin orbit contribution from the Fermi contact term, oP(FC-I), ppm, compared with the magnitudes of the nonrelativistic nuclear shielding of I3C in CHnX4+, at experimental molecular geometries, except for the iodomethanes which were calculated at the optimized geometries

System

0,

d(FC-])cl.l'.lI

CH,,X,-n

Nonrel.",h Ref 10

SO contrib. Ref I0

CH3Cl CHzClz CHC13 CC14 CH3Br CH2Br2 CHBr3 CBr4 CH3I CHzIz CHI3 CI4

161.84 123.67 89.46 54.30 171.00 131.72 88.31 43.97 188.76 157.13 1 16.46 71.25

2.89 5.99 10.73 17.54 13.84 3 1.22 61.83 1 13.90 34.82 95.09 192.43 388.80

rF (FC-I)"." SO contrib. Ref 7 2.64

14.08

41.40

SOS-DFPT approach using IGLO choice of gauge origin, IGLO-I1 basis set Using Perdew and Wang exchange correlation potential (PW91) The one-electron spin orbit interaction operator is used Using Perdew and Wang exchange, Perdew correlation functional (PP) and a separate localization procedure for a and fl MOs. U H F calculations using gauge origin at the halogen atom, basis set is Huzinaga triple 6 set augmented with d functions for carbon. Correlation eects not included. Not shown are the small SD contributions also calculated by these authors.

Table 2.6 The one-electron spin orbit contribution from the Fermi contact term, c f ( F C - I ) , ppm, compared with the magnitudes of the nonrelativistic nuclear shielding of I3C in CX3+ at optimized (using quasi-relativistic ECPs and D Z P basis sets) molecular geometries, from Ref. 11. Uncontracted Partridge basis functions were used on C and X in SOSDFPTIIGLO method developed in Ref. 10 CJ ( T M S ) - CJ( CX,')

Nonrei.

d(FC-I) SO contrib.

CJ

CX,'

Toral

Calc."

( T M S ) - (T ( C X J&) Expt.'

CC13+ CBr3' CI3+

-55.5 -97.9 - 163.6

13.2 70.0 242.2

-42.3 -27.9 +78.6

226.6 212.2 105.7

236.3 207 95

System

Calculated o(TMS) Ref. 28

=

184.3 ppm

(T

52

Nuclear Magnetic Resonance

Table 2.7 Calculations of 'I9Sn shielding (ppm) in SnX4: relativistic unrestricted Hartree-Fock without electron correlation, with and without the spin orbit term (Ref. 9 ) and nonrelativistic calculations including electron correlation using density functional theory (Re$ 30) o,Nonrel. without correI.N.h Ref. 30 SnH4 3278 Sn(CH3)4 2823 SnC14 2957 SnBr4 Sn14

o,Nonrel. with correl.""'

0,Nonrel.

30 3107 2523 2524

9 3425 3105 2977 3147

without

SO contrib."

CT, Rel.

0,

without correI.(l

absolute'

9 13

9 3434

44 474 1608

3149 3447 4442

29 2722 2180 2328 28 18r 388 1

carrel."

'' Using IGLO-I11 basis for shielding calculations and optimization of molecular geometries

' Using SCF-GIAO

Using SOS-DFPT /IGLO with Perdew and Wang exchange correlation functional (PW9 1) Calculated at experimental molecular geometries, using UHF method with Huzinaga basis on Sn atom augmented by p and d functions, relativistic ECPs and double sets plus p and d functions on halogen atoms, from Ref. 9 Experimental values derived from spin rotation constants Converted to absolute shielding from the chemical shifts o(SnMe4) -cT(SnBr4) = -638 ppm and o(SnMe4) -o(Sn14) = - 1701 ppm (Ref. 31), by using o(SnMe4) = 2180 ppm from Ref. 29

corrections in the work of Kaneko et al., discrepancies of about 560-820 ppm are revealed by the experimental absolute shielding based on the I9Sn shielding scale of Ref. 29. Methods of including correlation in shielding calculations continue to be explored in ah initio32-37and density functional method^.^,^*- 40 Several models within the coupled cluster scheme (L-CCD,32CC2,33,CCSD(T)27934) have been investigated against a set of test molecules which have a wide variation in their contributions to shielding (and the related spin rotation constants) from electron correlation (H2, HF, N2, CO, FZ,and also H20, NH3, HCN, CH4, H2CO and HCCH). The most accurate method, so far, CCSD(T), is not generally practical, especially for medium to large systems, but can be considered as a reference point to investigate the other less complete, but less time-consuming models. The comparison between these models and CCSD(T) is shown in Tables 2.8, 2.9, and 2.10. The experimental values are absolute shielding values 00 which are isotropic averages in the gas at the zero-pressure limit. The error bars are associated with the determination of the absolute scale based on spin rotation constants for specific molecules (the CO molecule for I3C, NH3 for 15N, HF for 19F). Some important conclusions from the comparison of various ah initio methods of including electron correlation in shielding are: (a) The CC2 model is part of a new hierarchy of coupled cluster approximations in which the double excitation amplitudes are given by their first order

2: Theoretical and Physical Aspects of Nuclear Shielding

53

Table 2.8 Comparison of results of various ab initio methods of including electron correlation in the shielding of small molecules, in ppm 'H

'H

lYF

tiN

in H?

in H F

in H F

in N?

'

3

170

~

in CO

in CO

o,.,SCF-GIAO 26.48' 28.4 413.6 -112.4 -25.5 -87.7 or, SCF 26.493 28.332 414.1 5 - 1 I 1.40 -25.070 - 86.836 Of,MP2 26.646 29.145 424.40 -39.695 11.436 -44.671 Of,MP3 26.672 29.293 418.03 - 70.441 - 3.428 - 66.633 u ~L-CCD , 26.680 29.446 417.57 - 55.733 3.933 - 57.367 uc,cc2 28.9 424.2 -40.6 14.2 -38.2 or, FV-CAS 13.1' -37.1k sf, RASSCF 11.1' -43.Sk o,., CCSD(T) 26.680' 29.2 418.6 -58.1 5.6 -52.9 00(300 K)-E, -0.369 -0.358 - 10.42 -4.27 -2.39 -6.07 - 62.7(10) 2.9(20) - 59.3(20) 26.298(20) 28.48(6) 409.2 ~(,(300K) 1.0(9)r -42.3( 172)' 00(300 K), 26.363(4)" 28.575(6)h," 410.0(6)d -61.6(2)' Expt.

IYF in F.

ReJ

-167.9 -170.05 -169.57 -176.01 -194.53 -171.1

41 32 32 32 32 33 42 42 41 27 27

-186.5 -35.56 -225.5 -232.8(60)h

~~

Ref. 43, from spin rotation constant deduced from spin rotation constant (Ref. 44) ' Ref. 45 gives 28.8(5) ppm, derived from earlier spin-rotation constant Ref. 45, derived from spin rotation constant Ref. 46, from chemical shift relative to NH3 'Ref. 47, derived from spin rotation constant. See also Ref. 48 Ref. 26, derived from spin rotation constant Ref. 49, from chemical shift relative to H F ' Ref. 50, full configuration interaction with the basis set used here, the SCF value is -23.8 ppm (Ref. 42) with the basis set used here, the SCF value is -84.4 ppm (Ref. 42)

approximation and the single excitations are treated as zeroth order quantities. Using the test molecules in Table 2.8, it has been shown that the CC2 model, used with GIAOs for origin independence, does not represent an overall improvement over the relatively inexpensive MBPT(2) calculations. For C and H (except in CO) the differences between the CC2 and MBPT(2) results are small and the results agree reasonably well with experiment. For 0, N and F (and for I3C in CO) neither one of these methods are adequate; CC2 results differ from the CCSD(T) results by 5-20 ppm. (b) Linearized coupled cluster double excitation (L-CCD) theory includes the effect of double substitutions to infinite order. For H there is little change in going from MP3 to L-CCD, and agreement with CCSD(T) is good. For I3C, 15N, 1 7 0 and 19F, there are much bigger changes which improve the agreement with CCSD(T). The worst case in percentage terms is in CO. It appears that the L-CCD method could be used to obtain quite reliable values of shielding. These calculations by Cybulski and Bishop ensure gauge invariance by using large basis sets rather than GIAOs and magnetizabilities were calculated as (c) In the carbocation 1-cyclopropylcyclopropylidenemethy135CCSD(T) provides I3C chemical shifts that agree with experimental results to within 2.2 ppm,

54

Nuclear Magnetic Resonance

Table 2.9 Comparison of results of various ab initio methods of including electron correlation in the shielding of small molecules, in ppm 'H in HJO

I

'o

in HJO

328. I SCF-CIAO 30.7 327.96 SCF 30.701 344.87 or,MP2 30.968 336.02 B,, MP3 31.167 335.88 B,, L-CCD 31.247 cr,, c c 2 30.7 345.6 337.9 G,, CCSD(T) 30.9 - 13.6' 00(300 K)-o, -0.57' 324.3 00(300 K) 30.3 ~ ~ ( 3 K),Expt. 00 30.052( 1 5)L' 344.0( 172)' B,, B,,

/H in CH,

31.7 31.574 31.503 31.539 31.543 31.4 31.6

l. ( ~ >201 1.~ The span of PN is 1376 ppm; the EMPI calculated value is 1393 ppm whereas the H F and MP2 values are 1733 and 1223 ppm, respecti vely .

56

Nuclear Magnetic Resonance

A method for including electron correlation that is in widespread use is density functional theory. Density functional methods include correlation in the exchange-correlation energy functional used. The success of various density functional methods in predicting nuclear shielding in systems where the electron correlation effects on shielding are significant therefore depends on which functional is used in the calculation. In this sense, DFT methods are semiempirical in nature since many approximations and adjustments in applying the theory can be made. A complete density functional theory of nuclear shielding or any other magnetic property should include the explicit dependence on current density as well as the density itself. Nearly all the DFT calculations reviewed in this and in previous volumes of this series have used functionals in which the current dependence has been neglected. A new exchange correlation functional with an explicit dependence on current has been presented by B e ~ k e , ~that ' has not yet been implemented. Handy and co-workers7' have implemented a current density functional theory reviewed in Vol. 26 of this series, and initial results seemed to indicate that the current-dependent terms are small. The so-called Malkin correction7* in the SOS-DFPT-IGLO method provides a recipe that attempts to correct for the missing current-dependent terms by introducing correction terms into the energy denominators of the UDFT equations, leading to an improvement in agreement with experimental chemical shifts in a number of cases. These corrections to the shielding, too, appear to be small. For example for I7O in transition metal 0x0 complexes, the differences between UDFT and SOS-DFPT values are 10-50 ~ p m Deficiencies . ~ of presently used exchangecorrelation functionals rather than neglect of the current-dependent terms seem to be the main problem, as suggested by Handy et al.7' Kaupp et al. have investigated the performance of various functionals, basis sets and localization schemes in DFT calculations of I7O in transition metal 0x0 c ~ m p l e x e s They .~ found that larger basis sets change the results little, Malkin correction terms are small, and differences between different local and gradient corrected exchangecorrelation functionals are also minor. Use of GIAOs appear to be more reliable; when IGLO is used for distributed origins, results are very dependent on the localization scheme used. A population localization procedure rather than Boys localization was investigated. There is surprisingly great sensitivity to whether metal semi-core (3s and 3p) shells are localized separately or together with valence (3d) orbitals. It has been suggested that exchange functionals in current use could be improved by mixing with some fraction of Hartree-Fock exchange. The gradient corrected exchange functional of Becke (1988)73 together with the correlation functional of Perdew (1986)74,75(the so-called BP86 functional) or together with the correlation functional of Perdew and Wang (1991)76,77(the so-called BPW91 functional) have been compared with the performance of hybrid functionals. Two hybrid functionals commonly used in shielding calculations are B3LYP that has Becke's 3-parameter exchange DFT/Hartree-Fock hybrid7' together with the correlation functional of Lee, Yang and Parr.79 Another is B3PW1, Becke's 3parameter exchange together with the correlation functional of Perdew and Wang.76y77 Results are mixed and inconclusive. It has been suggested that hybrid

2: Theoretical and Physical Aspects of Nuclear Shielding

57

functionals, which include certain amounts of Hartree-Fock exchange could improve the agreement of the theoretical chemical shift range of transition metal nuclei compared to experiment. in a comparison of Io3Rh and 57Feshielding in various complexes Biihl found that the hybrid functional B3LYP gives better agreement with the experimental chemical shift range than BPW91.38,39 In contrast, Kaupp et al.3 have found for I7O shielding in transition metal 0x0 complexes that DFT-GIAO calculations with hybrid functionals (B3PW91, B3LYP, or the 'half-and half' BHLYP incorporating 50% H F exchange) give much more deshielded values than UDFT-GIAO results with the gradient corrected BP86 functional, and they are in poorer agreement with experiment. Whether or not use of hybrid functionals can generally be expected to give better performance in DFT calculations of shielding is still an open question. A formulation of shielding theory within the frozen core approximation has been pre~ented.~' The frozen core approximation neglects the core-core and corevirtual blocks in the first order density. A comparison with all-electron calculations using the same basis sets has been carried out to determine the accuracy of using the frozen-core approximation. In the calculations of shielding for nuclei in the third period of the periodic table (such as 33S and 35Cl),it was found that 3% and 8 % of the paramagnetic shielding for OC33S and H 3 k l respectively come from the 2p shell. When 3p, 3d shells (fourth period) or the 4p and 4d shells (fifth period) are included in the valence category, (53Cr,77Se,79381Br, 125Te)then only 0.5% or less of the total paramagnetic shielding comes from the core. The general conclusion is that if the valence shell is increased to include at least the ns, np, (n-l)p, and (n-l)d shells, where n is the number of the given period in the periodic table, the frozen core approximation can provide accurate shielding calculations in comparison to all-electron calculations using the same basis sets. This seems to indicate that the use of the frozen core approximation is a viable approach especially for the nuclei in the fourth and fifth periods. Of course for the heavier nuclei the relativistic effects have to be taken into account in a shielding calculation. Here too, the frozen core approximation plays a special role in that its use avoids the problems associated with the highly relativistic core electrons when the two component Hamiltonian is used.40 Applications of the frozen core approximation within quasi-relativistic (QR) methods has already been discussed above, with examples in Tables 2.2-2.4. Gauge transformations relating to translation of the origin of the vector potential are well known to change the diamagnetic and paramagnetic contributions to shielding. The computational methods used in the above reports generally adopt multiple origins in order to have practical gauge invariance of the shieldings. In a parallel approach to these, the physical description and basis for these magnetic response quantities are being explored via accurate determination of the three-dimensional electronic current density induced by an external, uniform magnetic field, as originally proposed by Jameson and Buckingham.80 Keith and Baderss are using such approaches for computing the magnetic response properties, shielding and magnetizability, in the context of atoms in molecules concepts to obtain an atomic partitioning that leads to an understanding of these magnetic properties at the atomic level.81In Keith and Bader's

58

Nuclear Magnetic Resonance

approach, the atomic contributions to the shielding of a nucleus have been determined by expressing the shielding as a function of the current density;" and the magnetizability is likewise partitioned into atomic contributions.82 The underlying ideas in the Keith and Bader's current density based approaches for practical computations of shielding is that the gauge origin of the first order molecular electron current density JB(r) can be chosen so as to obtain the best current density distribution for a given basis set. Of the novel approaches developed by Keith and Bader, IGAIM (individual gauges for atoms in molecules) has been used as an alternative to the well-established GIAO (gaugeincluding atomic orbitals) or IGLO (individual gauge for localized orbitals) or LORG (local origin/localized orbitals). IGAIM uses a multiple set of gauge transformations to compute the shielding as a sum of atomic contributions, which are in turn evaluated by choosing the nucleus position as gauge origin for JB(r) within the basin of each atom.83The multiple gauge origins used in IGAIM has been extended by Keith and Bader to the limit of a continuous set of origins.84 The CSGT (continuous set of gauge transformations) method uses a different gauge origin in real space for each point r where JB(r) is to be computed, by introducing continuous shift functions d(r). The choice d(r) = r in CSGT causes both the exact and approximate diamagnetic component of JB(r) to vanish everywhere. The vector currents determined in this manner satisfy the local current conservation requirement that V0 JB(r) = 0 with high numerical accuracy, enabling one to obtain faithful displays of the current flow induced in a molecule by an external magnetic field." A modification was offered in the CSDGT (continuous set of damped gauge transformations) method, to empirically shift the gauge origin towards the nucleus nearest to the point r.84 This dramatically improves the calculated values for nuclear shielding and leaves unchanged the already accurate values of magnetic susceptibility that is found in the CSGT method. The contrast between the current density distributions in a polar system such as LiH and a covalent system such as cyclopropane have been illustrated.82In LiH the primary current flows are separately contained within the atomic basis, whereas there are substantial flows across the CIC interatomic surfaces. In addition, the empirical additivity schemes for magnetizability have been shown to have a basis in physics: The transferable group contributions (x(CH3), x(CH2), etc.) to the mean susceptibility (average of the trace) are defined and calculated, without adjustment, using only the expectation values of the quantum mechanical observables for the electron and vector current densities, as required for the evaluation of the magnetic properties of an open system.82 Lazzeretti and Zanasi have carried out a detailed theoretical study of the CSGT method, which they have renamed CTOCD (continuous transformations of the origin of the current reviewed in volume 25 and 26 of this series, in which they consider only those choices of the d(r) shift function that formally eliminate either the diamagnetic or the paramagnetic contribution to the first order induced current density (respectively called CTOCD-DZ and CTOCDPZ methods). The first, implemented by numerical integration, when first i n t r o d ~ c e dturns , ~ ~ out to be equivalent to the Geertsen's polarization propagator based procedure,89 reviewed in volume 21 of this series, and can be carried out

2: Theoretical and Physical Aspects of Nuclear Shielding

59

using analytic procedure^.^^^^^ The second, annihilation of the paramagnetic contribution to the current density, can be implemented only in a numerical way, in this case the function d ( r ) is a continuous function of r, but is not unique, and depends on the basis set; even for a particular basis set its analytical form is not known a priori and only numerical values can be obtained for each point in real space, with which numerical integrations for shielding and magnetizability can be carried out.88*90Previous applications to CO2, CH4,88 and benzene” were reported in volume 25 of this series. The PZ scheme provides faster convergence to a basis set limit than the DZ scheme and the conventional common origin CHF for both magnetizability and nuclear magnetic shielding. With nearHartree-Fock quality basis sets all three methods, common origin, DZ1 and PZ1 provide quantitatively nearly identical current density streamlines and intensities for the HCCH m ~ l e c u l e . ~Presently ’ it has only been applied within the C H F scheme; but can be generalized to post-Hartree-Fock methods in a straightforward fashion. In a recent development, the CTOCD-PZ method was modified by using an empirical expression for shifting the origin towards or onto the nearest nucleus for only those points in the environment of the nuclei, a technique that was originally proposed by Keith and Bader with the CSDGT method,84 was applied to the CTOCD-PZ method.92 This method called CTOCD-PZ2 (with the PZ1 label being assigned to the unmodified version) greatly improves the nuclear magnetic shielding of all nuclei in the molecule; that is, the results for the nuclear magnetic shielding calculated by PZ2 using modest basis sets approach the results for near-Hartree-Fock limits in CHF calculations. Comparisons are made with CTOCD-PZ1 and with CTOCD-DZ1 and CTOCD-DZ2 methods. It has been established that that Lazzeretti’s CTOCD-DZ1 and CTOCD-DZ2 methods developed using the fully analytical C H F formulation are respectively equivalent to Keith and Bader’s numerical techniques, CSGT and CSDGT. Test cases used ~~ in comparisons were 13C, I5N, 170, I9F in a variety of r n o l e c ~ l e s .Both CTOCD-DZ 1 and CTOCD-PZ1 approaches fail in predicting the electron circulations close to the nuclei when small and medium size basis sets are used. On the other hand, the electron circulations in the interatomic regions are reasonably well-described and the unphysical characteristics of the streamlines obtained with the common origin method are removed.92 The PZ2 scheme is found to be competitive with GIAO, IGLO, and LORG procedures as far as accuracy of theoretical predictions is concerned. Gauge-invariance tests of all the components of the shielding tensor is an important objective criterion of the robustness of a method of theoretical calculation of magnetic properties and is a particular emphasis in the work of Lazzeretti and co-workers. In so doing, the adequacy of the basis set used can be tested separately from the extent of electron correlation contributions. Following this tradition, the gauge invariance of the properties of the SF6 molecule have been investigated, using both the familiar Coulomb gauge and the less used Landau gauge93 in the RPA scheme.94The values of nuclear magnetic shielding components obtained using the two gauges should be the same, in the HartreeFock limit. The difference between the numerical results for the origins at the ‘9F

60

Nuclear Magnetic Resonance

nuclei and at the center of mass for magnetizability and nuclear shielding in both gauges indicates that even the largest basis sets used are too weak for calculating magnetizability while they are good enough for the I9F shielding in the SF6 molecule.94 The contribution to the nuclear magnetic shielding tensor coming from the parity non-conservation terms of the molecular Hamiltonian are derived from a perturbation c a l c ~ l a t i o nA . ~decade ~ ago it was proposed to observe the NMR frequency shift which may occur between two enantiomers as a consequence of parity non-conservation. The calculated difference is very small since the PNC weak interaction occurs only when the electron is localized inside the nucleus. However, an additional contribution is that of the anapole term. The parityviolating nucleon-nucleon interactions lead to the existence of a first rank magnetic moment, the nuclear anapole. In the nucleus the violation of spatial parity produces a spiral spin structure and when an electron is inside a nucleus it feels an interaction due to the vector potential arising from the anapole. Thus, an increase of the PNC effects with the nucleus atomic number is expected. Due to the existence of PNC terms, two enantiomers must have intrinsically different shielding tensors. When only proper symmetry operations are concerned (proper rotations), the parity conserving part and the PNC parts of the tensor have the same zero and non-zero elements and are related by the same symmetry relationships. A difference comes when improper rotations and reflections must be considered. The number of independent terms of the PNC parts of the shielding tensors have been derived for each nuclear site symmetry. There are nine independent terms (six symmetric and three antisymmetric) in the PNC parts of CT when the nucleus sits at a site with point group symmetry C1,two symmetric terms for D, where n > 2 and three symmetric terms for D2 symmetry. Observing the very small predicted difference in the chemical shifts of the two enantiomers in a racemic mixture of a solute in an achiral solvent would be extremely difficult. 129Xeencaged in a chiral cryptate has been suggested as a possible test case.95 There is a recent review of theoretical and physical aspects of NMR chemical shifts, with emphasis on the shielding surface, effects of rovibrational averaging, and the connection between chemical shifts and environment (intermolecular chemical shifts).96 1.2 Ab Znitiu Calculations - Calculations of shielding of various nuclei, in addition to those reported above, can be grouped into two types, DFT calculations and uncorrelated ab initio calculations. DFT calculations on 1 2 5 ~ ~ , 4 0 , 9103Rh,38 7 91 zr,98 7 9 , 8 1 ~ ~ , 477se,40 0 59c0,99,100 35~1,40,10133s,40 and 3 1 ~ 1 0 2

and 'H.lo6 Systematic SOShave been reported as well as I7O, "N, 13C103-'05 DEPT/IGLO studies have been carried out by Olsson and Cremerlo4 on nuclei that have well-established absolute shielding scales, namely I3C, "N, and 170,in 20 molecular systems for which gas phase experimental data are available. This is an important study in that the very extensive results of 13C, "N and 1 7 0 in these molecules provide a comparative study of SCF-IGLO with various DFT schemes such as UDFT/IGLO, SOS-DEPT/IGLO(Locl) and (Loc~),as well as comparison with results from GIAO-MBPT(2) and GIAO-CCSD calculations of

2: Theoretical and Physical Aspects of Nuclear Shielding

61

with all results obtained employing the same geometry and basis sets. They suggest that SOS-DEPT calculations give shielding values that are too small all around, Olsson and Cremer suggest some scaling of the results by factors of 4/ 3 There are still problems with reproducing the chemical shift ranges of the transition metal nuclei such as lo3Rh,57Fe,and 59Co.38y99 For example, using the same exchange correlation functionals and the same basis sets, the DFT-GIAO method using various functionals, as implemented in the Gaussian94 software package, was found to perform better than SOS-DFPT/IGLO in calculations on a series of 59C0 sites with an experimental chemical shift range of 12000 ppm. SOS-DFPT/IGLO recovered less than 50% of the range,99 whereas, using GIAOs it was possible to obtain 6 9 4 3 % of the range.'" Although there are other systems for which GIAOs provide results that are in better agreement with experiment in comparative calculations of this type using the same set of molecules and the same basis set, and as discussed above, there are reasons why the package may be expected to perform better than SOS-DFPT/IGLO, the differences noted in the 59C0systems can not be so easily understood. Lacking an absolute shielding scale for 59C0,it is not possible to tell which calculations lead to results that are better in an absolute sense. Poorer results with SOS-DFPT/ IGLO may just be an indication that the basis sets used were inadequate; it is well-known that GIAO performs better than IGLO when basis sets are small. Furthermore, as discussed above, the exchange-correlation functionals are still inadequate; they do not provide accurate orbital energy differences which are crucial to the paramagnetic shielding, and the r-3 weighting in the shielding means that the densities have to be accurately described in the immediate vicinity of the nucleus. Authors sometimes report not the actual absolute shieldings that they calculated, but rather some difference such as [0(I3C,CH4) -0(13C, compound)]. This is a very poor way to report the results of a theoretical calculation. It obscures discrepancies with experiment, it could lead to errors in published tables, and comparison with other reports using other methods become difficult. The chemical shift range of selected 35Clcompounds, 800 ppm, is recovered in SOS-DFPT calculations. lo' Here again, no absolute shieldings are reported. 31P shielding tensor calculations were carried out for P2, PN, PCH, and PMo(NH2)3.1°2The span of the shielding tensor is the (always positive) difference between the most shielded and the least shielded component. Values of the span are large for these terminal phosphido sites and are of the same order of magnitude as those observed experimentally for PN, and for terminal phosphido complexes such as P=Mo[N('Bu)ArI3 and P(M(NN3) type compounds (up to 2400 ppm). Unfortunately, the authors failed to report the calculated shielding values. Instead, their calculated chemical shifts 'relative to 85% H3P04 are reported. It is not stated what absolute shielding value was used for the reference! This sloppy reporting of theoretical results makes it very difficult to compare results of different calculation methods on the same set of molecules. Other DFT calculations of 13Cand I7Ochemical shifts have been reported, without giving the values used for the shieldings of the reference c o m p ~ u n d s . ' DFT-GIAO ~~

62

Nuclear Magnetic Resonunce

calculation of the proton shieldings in transition metal hydrides seeks to find an explanation for the greatly increased shielding of ' H in hydridic sites next to metal atoms, such as [HM(CO),lm-, where M = Cr, Mn, Re, Fe, and Co.Io6It is suggested that paramagnetic contributions from the adjacent metal fragment are responsible, as already suggested in 1964 by Buckingham and Stephens.Io7 125Teshielding calculations by DFT-GIAO method recovered the observed range of chemical shifts (3000 ppm), with the largest discrepancies found in Fcontaining derivative^.^^ 71GaGIAO calculations at the SCF and MP2 level,lo8 and CCSD(T) calculations for GaH4- and GaH3 molecules at optimized geometries have been reported. The standard [Ga(0H2),l3 used experimentally is unsuitable as a theoretical reference due to the lack of consideration of water molecules beyond the first solvation shell in the calculations. On the other hand, there is an absolute shielding scale for 71Ga based on the atomic beam measurement at the same time as the aqueous solution at infinite d i l ~ t i o n , ' ~by ' using the calculated diamagnetic shielding for the free Ga atom = 2638.6 ppm, l o +

~ ( ~ l G[Ga(OD2)J3+ a, infinitely dilute in D2) = 1840(45) ppm. With this we can convert the experimental measurements to absolute shieldings, in Table 2.1 1. This Table shows that within the experimental errors, without taking into account the solvation effects, the agreement of calculations of 71Ga shielding at the MP2 level with experiment is reasonable. Uncorrelated calculations of shielding reported recently are the following: (a) using IGLO, 29SiI l 2 in various cations, "B and I3C calculations in structural studies,' 1 3 - ' I 5 (b) using GIAO, 13C and 15N in fullerenes and phosphoranes, 1 16- 1 18 I 1B and I3C in c a r b o r a n e ~ , "and ~ ~(c) ~ ~using ~ IGAIM, 13C and ' H shielding calculations in unsaturated hydrocarbons and organolithium compounds. ' 7 '

Table 2.11

Comparison of results of ab initio calculations in the absolute shielding of 71Gain small complexes (Ref. 108) against experiment, in ppm Calcd. ( M P 2 ) u("Ga)

Exptl. d'( f 45ppm)

1 175.5 1613.2 1625.0 1629.4 1827.3 1930.4 2593.2

1120 1593 1598 1620 1730 1840 2554

experimental chemical shifts (compiled by Ref. 108) have been converted to absolute shielding, based on the o("Ga, [Ga(ODz)h]3+infinitely dilute in DzO) = 1840(45) ppm

a

2: Theoretical and Physical Aspects of Nuclear Shielding

2

63

Physical Aspects of Nuclear Shielding

2.1 Anisotropy of the Shielding Tensor - The individual components of the chemical shift tensor 6ii, obtained experimentally as 6ii = (vii - vr,f)/vref are related to the shielding tensor components Gii by the relation 6 i i = (oref--oii)/ (1 - crref). Reports of chemical sh$t tensor components often have values correctly designated as Fii, and the reference substance is clearly identified, such as liquid TMS at 298 K, or ‘an external sample of solid CsCl’ at 295 K.122-’30 Unfortunately, some authors do not use the symbols and terms correctly. Some report numerical values for Siso and 6ii but for some unexplained reason Even worse, in incorrectly use mixed symbols 6is0 and q, for these q~antities.’~’ one paper the authors stated ‘we are therefore defining the isotropic chemical which does not shift and the isotropic shielding to be identical (6 = make sense at all. Some authors report numerical values of chemical shifts 6iSo and 6ii but incorrectly attach to these numbers the qsoand o i i symbols for shielding,’ 1-134 even going so far as to write the Hamiltonian with a factor . ( I + 0)m.’32- 134 Some authors report numerical values of chemical shifts, reverse the signs, and then incorrectly use the words shielding and the symbols q i .135-138 The incorrect statement 6 = - (crl + cr22 + 0 3 3 ) / 3 was given in one e ~ a m p 1 e . l ~ ~ Some report numerical values for (6ii--6iso) but incorrectly attach the term ‘shielding’ and the symbols q i to these Authors may state ~ ~ . . .’ and then ‘principal values of the chemical shift anisotropy c~~~ G~~( T are - ~ i ~ ~ .) . , . 14’ In order to put all these papers into give numerical values of (all consistent notation, one reported chemical shift tensor is taken from the papers cited above and shown in Table 2.13. Anisotropic chemical shift tensors of 207Pb in PbS04, PbMo04, PbCr04, PbTi03, PbZr03, Pb(N03)2, Pb(SCN)2 and PbS have been determined from precise powder lineshape analysis. 127Published Pb chemical shifts have errors, in part due to the large temperature dependence of the 207Pbchemical shifts in the previously used reference. A given nuclear site has absolute shielding CT which can be experimentally described by measuring a chemical shift relative to a particular reference substance refl:

or else by measuring a chemical shift relative to another reference substance ref2:

The chemical shift of ref2 measured relative to refl is 6reQ,refl = (Grefl -oren) / (1 - oref,). Combining these chemical shifts leads to 6 2 = [61- &reU,refl J (1 - Grefl)/ (1 -(T,,Q). The ratio (1 -crre-l)/(l -oren) is of course the ratio of the absolute resonance frequencies (Vrefl/VreQ). Therefore, conversions of chemical shifts from one reference to another should be as follows:

64

Nuclear Magnetic Resonance

When the chemical shift range of a nucleus is relatively small, the ratio ( V p f l / V , a ) is very close to unity, and is erroneously left out in conversions of chemical shifts from one reference substance to another. The factor should always be included, and in the case of 207Pb, the errors associated with leaving it out can be significant, as pointed out by Neue et al., more than 120 ppm if Pb metal is used as a reference instead of PbMe4.127PbMe4 is recommended as a convenient reference, set by choosing as zero a frequency of 0.209 205 97 times the 'H resonance frequency of neat liquid TMS at 298 K. This closely approximates the resonance frequency of PbMe4 in toluene solution without actual handling of the toxic substance. The chemical shift tensors in this study are not only more precisely determined than earlier ones, but are also directly comparable to each other because of having been obtained relative to exactly the same reference. They can serve as good test systems for relativistic shielding tensor calculations. The chemical shift tensors are reported in Table 2.12. The quantities span and skew are useful for characterizing the shielding tensor and the chemical shift tensor.142Span, Q, always a positive quantity, is the difference between the most shielded (~33)and the least shielded tensor component (ol ]), corresponding to the width of the resonance powder pattern in ppm.

Skew, K, a dimensionless quantity, is three times the difference between the isotropic shielding value and the middle shielding tensor component, divided by the span.

Converting shielding into chemical shift, leads to,

The skew K characterizes the shielding tensor without being affected by the choice of reference. We note in Table 2.12 that skew ranges from - 1 (for 0 2 2 = 033) to + 1 (for o l l = 022) in the examples of PbTi03 and PbMo04, respectively. Note also that the two inequivalent 207Pbsites in PbZr03 crystal have exactly the same skew, even though the individual tensor components are different and one site has a much broader powder pattern than the other. The essential symmetry of the shielding tensor in both sites are the same. Varner, Vold and Hoatson describe an efficient method for calculating powder patterns associated with the random distribution of tensor orientations. The method depends on calculating general powder patterns as sums of lineshapes from symmetric tensors. 129 (Although the shielding tensor is an asymmetric tensor (that is, it has a symmetric tensor and an antisymmetric tensor part) and

2: Theoretical and Physical Aspects of Nuclear Shielding

65

Table 2.12 '07Pb chemical shift tensors in various compounds, in pprn relative to Pb(CH3)4, as defined in the text, from precise analyses of powder patterns, Ref. 127

PbSOj PbMoOj PbCrO,, PbC03 PbTi03 PbZrO,(a) PbZr03(b) Pb(N03h Pb(SCN)? PbS

DI I

fJ12

033

g,.w

span, R

skew, K

- 3257.7 - 1880.4

- 3432.2 - 2067.2 - 2260.6 - 2481.1 - 1018.5 - 1135.7 - 642.4 - 3473.6 - 1837.7 + 113.2

- 3825.2 - 2067.2 - 2653.1 - 3075.2 -2148.2 - 1891.3 - 1887.6 - 3527.6 -2107.8 + 113.2

- 3505.0 - 2004.9

567.5 186.8 858.1 764.2 1129.7 869.8 1433.5 54 1275.4 0

+ 0.385

- 1795.0 -2311.0 - 1018.5 - 1021.5 -454.1 - 3473.6 - 832.4 + 113.2

-2236.2 - 2622.4 - 1395.1 - 1349.5 - 994.7 -3491.6 - 1592.6 + 113.2

- 1.0 -0.085 + 0.555 + 1.0 + 0.737 + 0.737 + 1.0 - 0.576 0

first principles calculations of the shielding tensor lead to the full asymmetric tensor, diagonalization of only the symmetric part leads to real eigenvalues for comparison with experiment. Only the symmetric tensor contributes to the spectrum.143)The highly efficient method of generating powder patterns from shielding components permits quick least squares fitting to experimental powder patterns. Chemical shift tensors have been reported for I7'Y in (q-C5Me5) complexes, spans are 919 to 1248 ppm, and the known chemical shift range, so far, is about 3000 ~ p m . ' ~The * chemical shift tensor for 133Csin CsVO3 has recently been r e ~ 0 r t e d . l I3Cd ~ ~ (and 31P)chemical shift tensors in tricadmium phosphates135 and in 5-coordinate Cd complexes containing nitrogen donor atornsl3' have been obtained from MAS spectra. All quoted numbers are 6ii (although symbols qs0 and oiiare incorrectly used with both the terms shifts and shielding indiscriminately in this paper,13' pay no attention to these). The principal components of the 95M0 chemical shift tensor in Mo(C0)6 are - 1843, - 1855, - 1865 ~ p m . ' ~ ~ The direction of greatest shielding 633lies along q22 of the electric field gradient tensor. The relative orientation of the EFG and CS tensors at Mo nucleus were obtained in this and other organometallic compounds. 59C0 chemical shift anisotropy in C ~ ( a c a c complex )~ has been investigated using MAS, off-MAS and simulation of the static powder spectrum.'4431Pchemical shift tensors in crystalline silicon phosphates, several polymorphs of Sip207 in the same sample have been obtained by 2D exchange NMR.l2' Complete assignment of 13Cshielding tensors in the entire molecule from single crystal studies has been developed to the highest level by D. M. Grant and coworkers. Single crystal NMR measurements provide complete tensor information and the increased resolution in the 2D chemical shift-chemical shift correlation method and the multiple-axis sample reorientation mechanism developed in this group permits the study of crystals containing a large number of magnetically different nuclei per unit cell. They have recently applied these techniques to shielding tensors in methyl g l y c o ~ i d e s and ' ~ ~ a-L-rhamnose (6-deox-~-mannose) monohydrate. 122 Many I3C chemical shift tensors have been obtained by Grant

66

Table 2.13

Nuclear Magnetic Resonance

Chemical shijt tensors in selected compounds, in ppm relative to stated reference substance. The individual components of the chemical shiJt tensor dii, obtained experimentally as dii = (vii- vre,)Jvref are related to the shielding densor components aii by the relution ljii = (arer- aii)/ (1 -grey). Span, st = (di]--d33)(1 ---~,.~y) !z (ail-633), skew, K = 3(622- 6iso)I(611-d33) where d11322>633.

System

Re$

Reference substance

6,,

d,.?

a,,,

&3

span,

skew,

R

K

I080

-0.16

155

- 0.48

138

Yb(q592 C5Me5)2(thf)z in THF s o h

123

solid CsCl

135

Cd(N03)2* 4H20

4282

167

41

163

24 1

+ 0.05

131

0.1 Msoln. Cd(C10412

68 1

426

- 42

355

723

+ 0.29

126

probably TMS

x

133.4

+ 0.20

"C in benzoic acid

129

6iso of solid

' ' ~ ( 0 )in acetone, 130 K

134

-165

-34

-488

-280

-320

62.3+~

8 . 9 + ~ -71.1+~

23

-255

22 1

I86

107

171

114

+ 0.39

TMS(g)

283

272

84

213

199

+ 0.89

CH'I'CCN, 140 K

132 TMS(g)

23 1

23 1

- 87

125

318

+I

"C(CN) in cis, cis-muconitrile

128

TMS

198

93

35

108.6

163

- 0.29

' ' ~ ( 0 )in anthraquinone in liq. cryst.

140

unknown

x

212.3

+ 0.275

aromatic "C in polymer (PET)

136

unknown

134

207

+ 0.07

glycine

96.4+~

235

1 9 . 5 + ~- 1 1 5 . 9 + ~

139

28

et al. using magic angle turning techniques. A recent improvement for resolving crystallographically non-equivalent sites has been applied to calcium formate, where the isotropic chemical shifts are separated only by 0.77 ppm.126Other 13C studies reported in this period include partially oriented polymers, *36 aromatic in liquid crystals. Nitrile carbons have been characterized in solid systems' 39CH3CN,'33 in cis, cis-muconitri1e,'28in CH3CN hydrogen-bonded to a ze01ite.l~~ 13C chemical shift tensors of acetone in the solid and adsorbed in zeolites have been characterized.'34 In the case of acetone, the molecule forms a complex with the Bronsted sites and the spectrum does not appear to change with coverage until the sites are saturated. The molecule may be considered to be immobilized in the zeolite. On the other hand, CH4 physisorbed in a molecular sieve at 300 K

2: Theoretical and Physical Aspects of Nuclear Shielding

67

reveals an anisotropic powder pattern that changes with temperat~re'~'and is probably an average similar to the powder patterns observed for Xe by Ripmeester et al.146Relaxation studies in solution can provide anisotropies of the chemical shift t e n ~ o r , ' ~ ~but ' ' ~ 'unless careful cross relaxation studies such as those that have been reported previously by Farrar et al. are carried out, these are generally not as reliable as single crystal or powder studies. An interesting study uses relaxation interference effects to obtain information about the 5N chemical shift anisotropy in a protein backbone,'37 provided order parameters for the backbone amides have been derived from "N relaxation measurements. Dihedral angles in solids and the orientation of the chemical shift tensor in the COO carbon in alanine have been determined from the I3C-labeled ~ 0 w d e r . l ~ '

2.2 Shielding Surfaces and Rovibrational Averaging - There has been a great interest in shielding surfaces and in the corrections to shielding due to nuclear motion since the 1970s. Earlier work on shielding derivatives and rovibrational corrections, driven by experimental observations of the temperature dependence and mass dependence have been reviewed p r e v i o ~ s l y . ' Recently, ~ ~ ~ ' ~ ~ the interest has spread to other workers. The shielding surfaces for simple hydrides (HF, HCl, H20, H2S, NH3, PH3, CH4, and SiH4)"' and other small molecules (H2, HF, N2, CO, F2)27have been calculated and the rovibrational averaging of these shielding surfaces have been carried out using theoretical potential energy surfaces of the molecules. In these calculations the primary purpose was to obtain a more accurate and direct connection between the calculated values and the experimentally observed quantities. The most accurate surfaces (shielding and potential energy) have been obtained at the CCSD(T) level for H2, HF, NZ,CO, F2 molecules by Sundholm, Gauss, and S ~ h a f e r and , ~ ~ these rovibrational corrections have been included in Table 2.14. In every case, the rovibrational corrections bring theoretically calculated isotropic shielding and tensor anisotropy values towards substantially better agreement with experiment. In the case of F2, the experimental potential energy curve has been used and in this particular case, the difference between the average shielding at 300 K and the shielding at the equilibrium molecular geometry, -35.56 ppm, is close to the previous experimental estimate of - 40 ppm. Agreement with previous experimental estimates is excellent, as shown in Table 2.14. It should be noted that the empirical value for C T ~in' F2 molecule was obtained from a single parameter fitting to the observed temperature dependence of the I9F chemical shift in F2 gas in the limit of zero pressure.'54 Thus, it actually stands for the effects of both the first derivative and the second derivative terms. This single parameter is found to be too large compared to current theoretical values for the first derivative of I9F shielding.27 Fukui et al. calculated shielding derivatives for CH4 and SiH4 m ~ l e c u l e s . ~ ~ ' Their vibrational corrections, (o),,=~- oe for various hydrides are shown in Table 2.15. The shielding surfaces and rovibrational averaging for NH3 and PH3 molecules were compared with the earlier work by Jameson and de D i o ~ , ' ~ ~ , ' ~ ~ but the authors appear to have overlooked the calculations of shielding surfaces

Nuclear Magnetic Resonance

68

Table 2.14 Rovibrational corrections (in ppm) to shielding in small molecules from ab initio calculations. (Ref. 27)

' H in H2 ' H in H F "F in H F

co 170 in co I3C in

I5N in N2 "F in Fz

-0.355

-0.014

-0.323

- 0.035 - 0.42

- 10.0 - 2.24

-0.15

- 0.369

- 2.39

-0.303, -0.375d -0.38 -9.15, - 10.5d - 1.9Id

43, 152 45 45, 152 149

- 6.07 -4.27

- 4.8Sd - 3.49d

149 149

-0.358 - 10.42

(- 0.087)b.' - 5.73 -4.03 - 30.87

- 0.35 -0.24 ( - 0.255);'" - 4.69

- 35.56

- 40'

49

'' from Ref. 152 from Ref. 153 experimental estimate from the temperature dependence of the chemical shift in the gas phase at the zero-pressure limit experimental estimate from the isotope shift experimental estimate of ( l ~ )- [ ~ I, ~ ~

Table 2.15 Rovibrational corrections (in ppm) various hydrides

"F in H F "Cl in HCI " 0 in H 2 0 33Sin H2S 77Sein H2Se ''N in NH3 31Pin PH3 I3Cin CH4 "Si in SiH4

-

10.0'

-

17.0

- 12.1 - 19.6

7.0 - 7.3 -4.7 - 2.0 -

(a),,o - ae and (

10.42

27

- 13.57 - 16.4'

160 162 161 155 156 58

-

- 58.9 - 8.8 1 - 12.78 - 3.59

r

~ - )ge for ~ ~

-

10.5'

152

-

13.0b

149

- 56.9b - 8.3h - 10.4b - 3.3b

149 149 149 152

a This value was also obtained by Ref. 27 b Experimental estimate from isotope shifts From vibrational analysis.of Osten and Jameson (Ref. 162) and shielding derivatives of Chesnut and Foley (Ref. 163)

and rovibrational corrections in CH4 that have been carried out previously by Raynes and The 13C shielding surface of CH3CI has been calculated by Buckingham and O l e g a r i ~ and ' ~ ~ the derivatives of this surface have been used by Raynes and Nightingale with the experimental harmonic force field for this molecule to calculate the various contributions to the thermal average shielding at 300 K.165 For the 35Clisotopomer the total nuclear motion correction to the 13C shielding

~

~

2: Theoretical and Physical Aspects of Nuclear Shielding

69

is - 3.1 14 ppm. The calculated temperature dependence of the 13C shielding is small, deshielding with increasing temperature, 0.66 ppb/K at 300 K for the CH335C1isotopomer.

2.3 Isotope Shifts - As in previous chapters of this series, we define the isotope shift according to the same IUPAC convention as the NMR chemical shift, as suggested by Gombler: 166 n ~ ~ ( m ' / m=~S(A )

. . .m'x) - 6 ( ~. .m. x)

where m' is the heavier isotope and m the lighter one and the NMR nucleus A is n bonds away from the substitution site. With this logical definition, most onebond isotope shifts are negative, that is, usually the heavier isotopomer resonates at lower frequency. Theoretical calculations of isotope shifts in the CH3C1 system have been carried out by Raynes and Nightingale. 165 The deuterium-induced I3C isotope shift has been obtained: -0.191, -0.386, and -0.571 ppm at 300 K for successive replacement of H by D in the 35Cl isotopomer of CH3Cl. These are very nearly additive, with deviations from additivity being of the order of 2 ppb. substitution leads to a 7 ppb change in the I3C shielding and this is the The 37/35C1 same for all deuterated versions. Calculations on CH3Br have not yet been carried out, but the isotope shift of -1.12 ppb upon 81/79Brsubstitution has been 0 b ~ e r v e d . lA~ ~few interesting isotope shifts observed for the first time are the following: 1A95Mo(13/12C) = -0.316 ppm in Mo(CO)~; this is consistent in sign and magnitude with the significant temperature dependence of - 0.29 ppm/K for the 95M0chemical shift in M O ( C O ) ~ 1A119Sn('5114N) .~~~ = -32 to -55 ppb have been observed in stannyl substituted aminopyridines, and in the same compounds 1A29Si(15/14N) = -9 to - 16 ppb, 1A15N(29128Si) = -2.4 to -6 ppb were observed.I6' Deuterium-induced isotope effects over 2-4 bonds in toluene, benzoic acid, and benzophenone reflect a dependence on the transmission pathway.'69 The isotope shift is related to the derivative of the shielding at a 13C nuclear site with respect to the stretching of a remote C-H bond. This derivative may be expected to depend on the nature of the electronic transmission from the remote bond to the 13C nuclear site. Likewise, a large isotope shift over five formal bonds between the remote 37'35C1substitution site and the 19F nuclear site, -0.54 ppb in 2,6dichloro-4-fluorophen01~~~ can be attributed to the shielding derivative being enhanced by transmission through the IT system. Deuterium isotope effects in hydrogen bonded systems are rather common. A deuterium induced 77Seisotope shift appears to occur via a through-space C-H . . . Se non bonded interaction in a dibenzo diselenocin compound.I7' 2.4 Intermolecular Effects on Nuclear Shielding - The nuclear magnetic shielding that is the topic of this chapter is associated with the linear response of the electrons in a molecule to an externally spatially uniform static magnetic field and the internal perturbation of a nuclear magnetic dipole moment. The non-linear

70

Nuclear Magnetic Resonance

response to a uniform or a non-uniform field, that is, the dependence of the shielding on the magnetic field and magnetic field gradients, has been given little a t t e n t i ~ n . ' ~Magnetic ~ - ' ~ ~ field dependent and field gradient dependent chemical shifts could be of practical interest in future generations of NMR instrumentation in which ever higher magnetic fields are used and field gradients are increasingly implemented as routine tools. Recently, Lazzeretti and co-workers have investigated the linear response to a static spatially uniform magnetic field gradient.176-179 The magnetic field induced at a nucleus (the component along the a direction) by the electrons perturbed by the magnetic field Bp and the magnetic field gradient By,is

The third rank tensor quant'ity o , , ~is~called the magnetic quadrupole contribution to the nuclear magnetic shielding. Molecular magnetic properties described via tensors of rank higher than two are not uniquely defined: they depend on the origin of the coordinate system. Natural choices for origins are either the center of mass or the nucleus in question. A computational scheme based on the RPA (random phase approximation) has been applied to these calculations. The authors point out the particular appeal of this theoretical method is that all timeindependent properties through second order are easily accessible by diagonalizing the non-Hermitian RPA matrix, i.e., from the spectrum of electron excitation energies and the corresponding transition amplitudes. The magnetic quadrupole contributions to the nuclear shielding of 13C and 'H in CH4177and 170and 'H in H20178have been reported earlier. More recently, the third rank tensors have been calculated for 15N and 'H in the NH3 molecule.'79 By comparing the third rank tensors calculated at the two gauge origins with the transformation law that relates them to one another at the Hartree-Fock limit, it is possible to test whether the basis sets used are sufficiently large. It has been shown that the uncontracted (15s8p4d/lOs3p) basis set used for NH3 satisfied the sum rules to better than 99% and also obeyed the transformation law extremely closely (better than 1 part in lo4 for all components). Basis sets of low or intermediate quality are insufficient to furnish reliable theoretical predictions of the third rank tensor properties. How large are these effects? The effects are hard to detect with any experimental apparatus developed so far, for external (laboratory) magnetic field gradients. However, magnetic field gradients arising from magnetic multipoles of neighboring groups within a molecule can give rise to such contributions that are not negligible. A good example is the experimentally well known pseudo-contact shifts described by Buckingham and Stiles18* and by McConnell.'*' The same can be said about the third rank tensors associated with the effects of external static electric fields and field gradients on nuclear shielding in a molecule. The effects are small and difficult to observe for molecules placed in external (laboratory) electric fields and electric field gradients; however, they are significant at the molecular level when the nucleus in question is in the presence of local electric fields and field gradients, e.g., due to neighboring polar groups.

2: Theoretical and Physical Aspects of Nuclear Shielding

71

The linear and quadratic response to external static electric fields and field gradients were first introduced by Buckingham. lS2 Using the Einstein summation convention,

The theoretical calculation of these third and fourth rank tensor quantities is even more demanding than the calculation of the shielding tensor itself. The physical picture is a simple one: a static homogeneous magnetic field and intrinsic nuclear magnetic moments induce stationary currents within the electronic charge distribution, whereas a static electric field polarizes it. Therefore, the distortion induced in the electron clouds by the latter gives rise to additional effects, which can be rationalized in terms of response tensors of higher rank. Analytical expressions for the third rank tensors can be obtained within the formalism introduced by Keith and Baders4 and articulated in more general terms by Lazzeretti et a1.,s6 that is, based on the formal annihilation of either diamagnetic or paramagnetic contributions to electron current density via continuous transformation of origin (CTOCD). In this theoretical framework, the condition of charge and current conservation can be fulfilled according to some form of continuity equation. Although faster convergence of procedures adopting GIAO basis sets seems to suggest that their use might be preferable in numerical studies,Is3 it has shown by Lazzeretti et al. that CTOCD schemes are easier to implement at any level of accuracy and become competitive provided that proper basis sets are employed.92Thus, the analytic expressions for the third rank tensors can be used to calculate origin-independent shielding polarizabilities that are virtually origin independent within the CTOCD-PZ scheme.’84 Total CTOCD-DZ and CTOCD-PZ shieldings tofirst order in the electricfield E, are independent of the coordinate system, as there is exact cancellation between terms arising from variation of diamagnetic and paramagnetic components. The 0’and 0’’components, sometimes called shielding polarizabilities and hyperpolarizabilities, are usually calculated not with analytic forms such as derived by Lazzeretti et al. but by numerical finite field differentiation of the analytically calculated a. The calculations of 0’ and a” including electron correlation, either by MP2lS5 or MCSCF (using a full valence complete active space (FV-CAS) or a restricted active space (RASSCF))42show that correlation affects dramatically the shielding polarizabilities and the effect is different for various components. The 0’and 0’’components calculated with and without electron correlation are compared for one example in Table 2.16. For example, dzZz, the component parallel to the bond, with the field along the bond, is largely insensitive for both 13C and 170.This is not surprising because this component involves polarizing the entirely diamagnetic parallel component of the shielding in the direction which maintains the symmetry (parallel to the bond). It is well known that the diamagnetic part (with the gauge origin at the nucleus in question) of the shielding is relatively insensitive to electron correlation. On the other hand, the xxz component involves polarizing the largely paramagnetic component, which in CO is known to be very sensitive to electron correlation,

72

Nuclear Magnetic Resonance

Table 2.16 Derivatives of " 0 nuclear shielding in a CO molecule with respect to the electric field. The positive z axis is along the bond from C to 0. Upon averaging the nuclear shielding over all orientations of the magneticJield with the electric field kept fixed relative to the molecular axes, the rotational mean shielding polarizabilities A , = - ( l / 3 ) d a w and B,, = - (1/6)d'aazz, respectively in ppm(ao2/e) = 1.944 6 9 ~ J O - ' ~ Vm- I a n d i n ~ p m ( a o ~ J = e )3~. 7 8 1 8 2 ~1 0 - 3 0 m 2 V - 2 ~~

~

SCF

Ref.

FV-CAS

42 1554.0 1380.0 2958.0 -2308.5 - 44.3 430.6 2413.7 -2946.9 1045.9 - 6376.2 - 184.9 - 8779.7 - 167.1 81 13.0

42 1184.4 987.3 1224.6 - 1755.1 -43.0 376.1 1724.7 - 1248.0 - 129.5 -4546.5 - 138.6 - 3604.5 - 527.2 1463.4

RASSCF

42 1336.4 1360.4 1273.4 - 1982.7 -43.8 373.1 1686.4 - 1307.7 -2352.8 -4501.8 - 150.1 - 3745.2 - 236.0 1873.9

SCF

MP2

SCF

185

185

186

1561.5 1315.0 2970.0 - 2330.1 - 44.2 432.6 2426.7 - 2544.6 991.3 - 6324.0 - 185.2 - 8813.8 - 166.2 8176.3

1242.4 448.3 540.0 - 1842.0 -43.7 376.7 1331.0 - 237.8 1093.0 - 3545.0 - 140.7 - 1550.0 - 389.4 - 5618.0

1526.7 2953.1

along a direction parallel to the bond. For both 13C and 170,introducing correlation changes this component by a considerable amount; for " 0 (orxxz changes from -2308 to - 1983 au. The second derivatives are harder to predict qualitatively and are also very sensitive to the level of correlation included, which can be observed by comparing the results from FV-CAS to the results from RASSCF. Nevertheless, the sign and order of magnitude of the effects of electron correlation at MP2 and RASSCF are similar. The response of the shielding to an external electric field gradient, d a p y 6 , sometimes called the quadrupole shielding polarizability, has been obtained for H20 molecule.'87 The components crrapy, c f a p y 8 , and crrapy6 were determined as parameters by fitting the results of shielding calculations of H20molecule in the presence of a set of charges minus that of the molecule in vacuum to an equation of the form of Eq. (1). This point charge method has been used earlier by Augspurger, Dykstra and Oldfield.'88 For the d a p y components the results of the fitting are comparable in sign and order of magnitude to calculations on H 2 0 using the finite field method,189but for d',py6 the point charge method leads to large discrepancies compared to the finite field method. Following the method of Dykstra, Oldfield, and P e a r ~ o n , ' ~ ' -the ' ~ ~average shielding of a H 2 0 molecule in liquid water was calculated in a molecular dynamics simulation by using Eq. (1) with the shielding polarizability parameters as constants. Using 21 6 water molecules in a cubic box with periodic boundary conditions in an NVT ensemble and a non-pairwise additive potential constructed by an energy partitioning

2: Theoretical and Physical Aspects of Nuclear Shielding

73

scheme (so-called NEMO potential), the ensemble averages of the electric field and field gradient at the 170and 'H nuclear sites as a function of temperature are calculated. (The electrostatics of a NEMO potential is represented with atomic charges, dipole moments and polarizability tensors.) The molecules are assumed to be rigid so the parameters in Eq. (I) are assumed to be constant. Furthermore, the surrounding water molecules are represented entirely by fields and field gradients, i.e., they possess no electrons with which to generate exchange and overlap contributions to shielding at the H 2 0 molecule of interest. The average geometry in the liquid is different from that of an isolated H 2 0 . This, plus the total contribution calculated from Eq. (1) amounts to about 10 ppm towards the experimental gas-to-liquid shift for the 170and about 0.7 ppm for the 'H. Since the experimental gas-to-liquid shift is 36 ppm (the liquid is deshielded relative to the gas) for I7O at 300 K,1939194 and 4.368 ppm at 298.2 K for 'H,lg5only a small portion of the actual gas-to-liquid shift is accounted for. Also the temperature coefficient of the chemical shifts in the liquid is found to have the correct sign but too small a magnitude compared to experiment. Another method of calculating the electric field and field gradient contributions to the shielding in a molecule in a liquid is to use a reaction field model. This idea was first introduced by Buckingharn.lg2Mikkelsen et al. present an update of the Buckingham model, considering a molecule within a spherical cavity in a homogeneous isotropic and linear dielectric medium. lg6 However, instead of the Onsager dipole model, they include higher multipole terms. They find that the isotropic shielding for I7O in H20 increases with increasing dielectric constant, whereas the proton shielding decreases. The calculated properties depend on the cavity size. Less than 50% of the gas-to-solution shift calculated in this manner is accounted for with the Onsager dipole model. Nevertheless, the sign of the gasto-liquid shift for I7O in water calculated by this method is opposite to that observed experimentally (9.4 ppm increase in shieldinglg7 rather than the observed 36 ppm decrease in shielding in going to the liquid). This model accounts for only a small portion of the observed gas-to-solution shifts of CH4 in solvents of various dielectric constant (13C deshielding by 5 to 12 ppm, 'H deshielding by 0.78 ppm up to shielding by 0.225 ppm).198Mikkelsen et al. also calculate the effects of the first solvation shell plus the dielectric medium outside the first solvation shell by including in the supermolecule calculation of the shielding the surrounding 4 water molecules.197This leads to a total of 16.4 ppm decrease in shielding for the I7O nucleus, to be compared with the experimental 36 ppm.1937'94 The proton shift is in better agreement with experiment, 3.97 ppmIg7 decrease in shielding to be compared with the experimental 4.368 ppm at 298.2 K.lg5 Magnetic anisotropy contributions to the intermolecular shielding can be attributed to so-called ring currents. Visualization of electron current densities induced in a molecule by an external magnetic field serves as an aid to understanding the numerical results of computation and the understanding of the general qualitative concepts such as aromaticity that are used widely for rationalization of experimental trends. Benzene is the usual reference system €or such discussions. However, cyclopropenyl cation is the smallest hydrocarbon for

74

Nuclear Magnetic Resonance

which the 4n + 2 rule for monocyclic ring systems is applicable. Thus it has been used as the prototype system, smaller than benzene so that large basis set calculations are easily done but analogous to benzene with respect to ring currents and aromaticity. Recently, this analogy has been called into question. 199 The CTOCD-DZ approach (CSGT as first introduced by Keith and BaderS4), where the current density at each point is computed with that point as origin, is known to give realistic current densities with even quite small basis sets, so is well suited to investigate this question. The current density map for the cyclopropenyl cation confirms the relative insignificance of the n electrons. The 7c current is a third of that in benzene and the cr current is a little larger than that in benzene. Also, the n contribution to the magnetizability component perpendicular to the molecular plane dominates the anisotropy of the magnetizability in benzene, whereas in cyclopropenyl cation by far the largest contribution to the anisotropy comes from the contribution of the cr valence electrons to this component. Interesting comparisons can be made when CH units are replaced isoelectronically with N or BH. The calculated shielding for C, N, B and H in the isoelectronic family of the cyclopropenyl cation can be rationalized in terms of the three-dimensional current density maps.'99 The origin of the chemical shift of 'H and 13C in (benzene)Cr(C0)3 compared to benzene has been the subject of controversy. Using the same CSGT approach, the magnetic susceptibility and the shieldings have been calculated in this complex.200 The shieldings were also calculated using GIAO and IGAIM methods. The geometries here and in (cy~lobutadiene)Fe(CO)~ as well as other related complexes were optimized in DFT/B3LYP. (Benzene)Cr(C0)3 is found to have a positive exaltation of the magnetic susceptibility characteristic of antiaromatic compounds. The calculated individual components of the I3C chemical shift in this complex agree reasonably well with experimental values. In large molecules such as peptides, the nonequivalence of proton shifts permit the assignment of spectra. An understanding of the contributions to the nonequivalence shifts ultimately will permit structure predictions from observed shifts. The proton shifts in a 10-membered diamide disulfide ring have been calculated using the DFT/B3LYP-GIAO method and analyzed in terms of magnetic anisotropy, electric field effects, van der Waals effects of near neighbors, an approach derived from the interpretation of intermolecular shielding effects in the gas phase proposed by Raynes, Buckingham, and Bernstein.20' The van der Waals term was investigated by computations on smaller fragments of identical structural geometry as the large molecule.202 Conformational effects on 13C shielding come from local structural geometry around the nucleus in question, but additional effects arise from orientations of neighboring polar groups. Facelli et al. continue their studies of systems designed toward an understanding of these contributions. Recently they carried out a series of GIAO calculations on nine 2X-substituted phenetole derivatives compared with the corresponding X-monosubstituted benzenes.203 The observed gas-to-solution shifts for '29Xe in various solvents have been interpreted in terms of various models, some of which are based on the reaction field theory.204-207 On the other hand, pairwise additive Xe-solvent models have

2: Theoretical and Physical Aspects of Nuclear Shielding

75

also been used, averaging over configurations sampled by a Metropolis Monte Carlo scheme.208This has been done for a mixture of Xe and Ar, for example.209 When the solvent molecule is large enough, it may be useful to consider pairwise additive Xe-atom (or ion) models, with the total Xe shielding at a given Xesolvent configuration coming from a pairwise additive sum over all Xe-atom (or ion) contributions. An example of this is a Xe atom in the presence of a solvent molecule that is a zeolite cage, in which the total Xe shielding for a particular Xe position in the cage is considered as a simple sum of Xe-0 and Xe-Na' ion contributions.963210 Another approach, when the solvent molecules can be partitioned into functional groups, is to consider the total Xe shielding for a particular Xe-solvent configuration as a pairwise additive sum of Xe-functional group contributions. In this approach, the configurations sampled when a CH3 group is attached to various molecular scaffolding are assumed to be identical, which of course, they are not. This method has recently been proposed and strictly empirical Xe chemical shift increments have been associated with individual functional groups such as CH2 and CH3 in cycloalkanes and normal alkanes for solutions of Xe in these solvents.21

2.5 Absolute Shielding - Because the electronic part of the spin rotation tensor is related to the paramagnetic part of the nuclear shielding (when the gauge origin is chosen to be at the nucleus in question) via an identity relation, the same algorithms that permit the computation of shielding tensors also permit the calculation of the spin rotation tensor. Direct comparison with experiment is possible in the case of the latter, especially for specific rotational and vibrational quantum numbers, whereas the experimental absolute shieldings with which shielding calculations are compared ultimately have their definitions linked to at least one spin-rotation tensor for the nuclear type, unless it is linked to an atomic beam measurement. Gauss et al. have calculated spin rotation constants for H2, HF, N2, CO, F2 and H2CO r n o l e ~ u l e s . ~To ~ ~facilitate ~'~ comparison with experiment, they have calculated theoretical values for specific rovibrational states with the required rovibrational corrections determined from CCSD(T) potential curves and spin rotation functions. Good agreement is obtained for H2, H F and FZ, while for N2 and CO the experimental numbers are deemed less accurate than the theoretical values. These are the first fully theoretical calculations of spin rotation constants for specific rovibrational states. Calculations of spin rotation constants for specific rovibrational states have been reported earlier by Sauer and Paidarova215 for HF, in which they used an empirical potential surface in the averaging. The absolute shielding of 19F in the SF2 and SFCl molecules have been derived from measurements of the spin rotation tensors in these molecules in a molecular beam, and are found to be unusually large positive, i.e., a highly shielded reminiscent of 19F in C1F. These absolute shielding tensors, shown in Table 2.17, provide good experimental values not contaminated by medium effects or reference substances for testing future calculations. Here the cc components are the out-of-plane components. The principal values of the

76

Nuclear Magnetic Resonance

Table 2.17 Experimental I9F absolute shielding tensors (ppm) obtained from measurements of spin rotation tensors. Components are along the inertial axes

Ref.

SFZ

SFCI

213

214

556( 19) 584(56) 1 16(38) 419(7 1)

781(11) 495(28) 227(28) 50 l(40)

shielding tensor, ozz,are related to the components along the inertial axes, G , ~ ,as follows:

+ ox, sin2e,, e,, + ox, cos2 o,,

o,, = o,,cos2o,, q , b = oZz sin2

where O,, is the angle between the z axis of the shielding tensor and the a inertial axis.

3

5

6

7 8 9 10 11 12 13 14 15 16 17 18

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R. B. Maharajh, J. P. Snyder, J. F. Britten, and R. A. Bell, Can.J. Chem., 1997,75, 140. D. G . de Kowalewski, V. J. Kowalewski, E. Botek, R. H. Contreras, and J. C. Facelli, Magn. Reson. Chem., 1997,35,351. T. R. Stengle, N. V. Reo, and K. L. Williamson, J. Phys. Chem., 1981,85,3772. T. R. Stengle, S. M . Hosseini, H. G. Basiri, and K. L. Williamson, J . Solut. Chem., 1984, 13,779. T. R. Stengle, S. M. Hosseini, and K. L. Williamson, J . Solut. Chem., 1986, 15, 777. J. H. Walton, J. B. Miller, and C. M. Roland, Appl. Mugn. Reson., 1995,8, 535. C . J. Jameson, A. K. Jameson, B. I. Baello, and H.-M. Lim, J. Chem. Phys., 1994, 100, 5965. C. J. Jameson, A. K. Jameson, and H.-M. Lim, J. Chem. Phys., 1996,104,1709. C . J. Jameson and H.-M. Lim, J . Chem. Phys., 1995,103,3885. M. Luhmer and K. Bartik, J . Phys. Chem. A , 1997,101, 5278. J. Gauss, K. Ruud, and T. Helgaker, J. Chem. Phys., 1996, 105, 2804. B. Gatehouse, H . S. P. Mueller and M. C. L. Gerry, J. Chem. Phys., 1997,106, 6916. J. Preusser and M . C. L. Gerry, J. Chem. Phys., 1997,106, 10037. S. P. A. Sauer and I. Paidarova, Chem. Phys., 1995,201,405.

3 Applications of Nuclear Shielding BY M. YAMAGUCHI

1

Introduction

The format of this report remains similar to that of previous years. Various chemical and physical influences on nuclear shieldings are considered in the first section. The shieldings of particular nuclear species are described in the following section according to their position in the Periodic table. Since there are huge number of articles on NMR spectroscopy during the period of this review, the coverage of this report is restricted to widely available and common journals, which are published in English, due to space limitation. 2

Various Chemical and Physical Influences to Nuclear Shieldings

2.1 Computer Assisted Structural Assignment - 2.1. I Spectrum Simulation, Computer Assisted Assignments, and Related Techniques - A review was given on the applications of artificial neural networks for pattern recognition in NMR spectra . The new scheme for the calculation of 1H NMR chemical shifts in substituted alkanes based upon partial atomic charges and steric interactions was reported.2 An automated approach was developed to extract amino acid spin systems from proteins or peptides by analyzing 3D HCCH-COSY/TOCSY spectra through a constrained partitioning a l g ~ r i t h r nA. ~program, LUCY, for structure elucidation from NMR correlation experiments was developed for COSY using an algorithm treatment of HMBC data based on 3JC,H long range C,H coupling^.^ A program, SIMPLTN, for the simulation of pulse and two-dimensional NMR was r e p ~ r t e dThe . ~ calculation of solid-state NMR line shapes for static solids or for magic angle spinning samples was reported.6 A new expert system, X-PERT, was reported for molecular structure elucidation using IR, and 'H and 13C NMR ~ p e c t r aA . ~complete program package for NMR data set processing, Gifa, was designed for processing, displaying, and analyzing one-dimensional, two-dimensional, and three-dimensional NMR data sets.8 A highly improved I3C NMR shifts prediction program, HIPPO-CNMRS, was reported.' A program to predict I3C NMR spectra was briefly introduced and the calculated spectra of all polychlorinated dibenzo-p-dioxines were listed as an example." A 'H NMR database extension of the complete spectroscopy database system SPECINFO was developed." An automated method for the prediction of I3C NMR chemical

Nuclear Magnetic Resonance, Volume 27 0The Royal Society of Chemistry 1998 83

84

Nuclear Magnetic Resonance

shifts which involves the combined use of database retrieval and multivariate calibration methods was described.I2 A novel and efficient approach to the calculation of powder 13CNMR lineshapes was p r e ~ e n t e d . The ' ~ prediction of the 19F NMR spectra of fluoroarenes using mathematical modeling techniques was r e p ~ r t e d . ' ~ 2.1.2 Nuclear Shielding Calculations - A review was given on the ab initio calculation of NMR chemical shielding. I 5 > I 6 A numerically accurate implementation of the gauge-including A 0 (GIAO) method for the calculation of NMR shielding in density functional theory was presented.I7 The direct (recomputation of two-electron integrals) implementation of the GIAO and the CSGT (continuous set of gauge transformations) methods for calculating nuclear magnetic shielding tensors at both the Hartree-Fock and density functional levels of theory was presented.'* The 'H NMR chemical shifts in low-valent transition metal hydrides were calculated by density functional theory and gauge-including AOs (DFT-GIAO). l 9 Ab initio calculations of H NMR chemical shielding were carried out the correlation-including GIAO MP2 level on nine small molecules.20 Ab initio HF-SCF calculations of the equilibrium geometries, energies, and I3C N M R shifts of various monomeric, dimeric, and tetrameric aggregates of the lithium ester enolate of methyl isobutyrate were Wave functions obtained at the RHF/6-3 1G(d) level of theory were used with the new method IGAIM (individual gauges for atoms in molecules) to calculate the isotropic 13Cand 'H NMR chemical shifts of a group of neutral unsaturated hydrocarbons and organolithium compounds.22 Ab initio GIAO and IGLO nuclear shielding calculations of I3C, "0, and 'H were performed on each of the four pyranose ring residues of the tetrasaccharide repeating unit in a single chain of the gellan poly~accharide.~~ The structures of a number of fluorocarbocations were calculated at the correlated MP2/6-31G" level and I3C and 19F NMR chemical shifts of fluorocarbocations were calculated using IGLO and IGLO-MP2 methods.24 A high level ab initio theoretical study was performed on the I5N NMR spectra and bond energies of pernitric acid, H02N02.25Ab initio IGLO study of the high shielding of 1 7 0 (and 13C, 15N) in linear heteronuclear n-systems (NO+, PhCO+, RCNO, N = C = 0-, RN = C = 0 and N 0 2 + ) was reported.26 ''N chemical shift tensors were calculated for benzamide with hydrogen bonding effects by Hartree-Fock and density functional methods.27Calculations of I7O shielding tensors in transitionmetal 0x0 complexes [M04]"- (M = Cr, Mo, W; Mn, Tc, Rh; Ru, 0 s ) and to the metal chemical shift in transition-metal carbonyls M(CO)6 (M = Cr, Mo, W) were performed based on density functional theory and a scalar relativistic Paulitype Hamiltonian.28The silylium cation Si(SiMe3)3 was investigated by HF, B3LYP, PISA-HF, SCRF, and the NMR/ab initio/IGLO approach in the gas phase and in benzene solution employing the 6-31G(d) basis set.29 Density functional theory (DFT)/IGLO 29Si NMR studies show that there is no significant silicenium ion nature in trialkylsilyl substituted arenium, bromonium, oxonium and nitrilium ions.30 The 31P chemical shift tensors of the transition metal phosphane complexes M(CO)5PX3 (M = Cr, Mo, W; X = H, CH3, F, C1)

'

+

3: Applications of Nuclear Shielding

85

were studied using a combination of density functional theory and ab initio effective core potential^.^' The effects of including correlation in the calculation of 31PNMR chemical shielding was studied for a variety of molecules.32Ab initio GIAO 31Pmagnetic shielding calculations were carried out on the hexacoordinate phosphorus intermediate and the corresponding reactant and product for the N - 0 migration reaction of (dimethoxyphosphoryl)threonine.3357Fe shielding tensors of substituted Fe-carbonyl complexes were computed employing the density functional based SOS-DEPT method with IGLO choice of gauge origins and with large basis set.34 The 59C0 chemical shieldings of several hexacoordinated Co(II1) complexes were calculated by SOS-DFPT-IGLO method.35 The 77Se shielding tensors and chemical shifts were calculated using density functional theory and the frozen-core a p p r ~ x i m a t i o nThe . ~ ~ 95M0 NM R chemical shifts of [MoO4-.SnI2- (n = 0, 1, 2, 3, 4) were analyzed theoretically by semi-empirical, CNDO and ab initio MO methods.37 9’Zr chemical shift was predicted for Zr@C28 at the GIAO-B3LYP level using medium-sized basis set and SCF optimized ge~metries.~’ lo3Rh chemical shifts of several rhodium complexes were calculated using the SOS-DFPT approach, large basis sets, and optimized g e o m e t r i e ~The . ~ ~ theoretical description of the Io3Rh chemical shift range of a number of organorhodium complexes was significantly better when the B3LYP hybrid functional is used instead of pure density f~nctionals.~’ The 19Sn NMR chemical shifts of SnX4 (X = H, C1, Br, I) and SnBr4_.In (n = 1, 2, 3) were calculated by the ab initio UHF method including the spin-orbit (SO) interaction combined with the finite perturbation m e t h ~ d . The ~ ’ ‘29Xechemical shifts of the complexes XeF2,, XeF2,- 1 and XeOnF6-2n (n = 1-3) were studied theoretically by ab initio finite perturbation method.42 Relativistic ab initio calculations of the 183Wmagnetic shielding constants and the chemical shift of WX6 (X = F, C1) and W042- were presented.43 Relativistic ab initio calculations of the 199Hgnuclear magnetic shielding constants and the chemical shift of HgX2 (X = C1, Br, I) were presented.a +

2.2 Stereochemical Nuclear Shielding Non-Equivalence - 2.2. I Chirality Determination by Mosher’s and Related Methods - The Mosher’s MTPA esters method or related modified method was applied to determine the absolute configuration of 2,6-dimethylheptyl sulfate from a marine ascidian from Policitor adriaticus D r a ~ c h e , ~epoxylycopaene ’ isolated from Botryococcus b r a ~ n i i a, ~new ~ eunicellin-based diterpenoid, cladiellaperoxide isolated from the soft coral Cladiella ~ p h a e r o i d e s the , ~ ~enantiomers of 1-(3,5-dimethoxyphenyl)-2-(4-methoxyphenyl)ethan01,~’2-substituted c y c l ~ p e n t a n o l sa, ~new ~ africane- and two monocyclofarnesane-type sesquiterpenoids isolated from the liverwort Porella sub~btusa,~’ keramaphidin B,51 monodeuterated diol diastereomers from 174-diacetylbenzene,52 several synthetic and natural chiral a m i n e ~altohyrtins ,~~ A, B, and C and 5-desacetylaltohyrtin A isolated from the Okinawan marine sponge Hyrtios a l t ~ mpenaresidins ,~~ A and B,55methyl (2Z,6R78R,9E)-3,6-epoxy-4,6,8-triethyl2,4,9-dodecatrienoate from the sponge Plakortis halich~ndrioides,~~ four alkaloids, 5’-des-O-methylharringtonine, 3’S-hydroxy-5’-des-O-methylharringtonine7 5’-des-O-methylhomoharringtonineand 5’-des-O-methylisoharringtonine,iso-

86

Nuclear Magnetic Resonance

lated from the leaves and stems of C. harringtonia var. d r ~ p a c e a , ’highly ~ functionalized 4-piperidones prepared through enantioselective synthesis by the asymmetric imino-Diels- Alder reaction of chiral 2-amino- 1,3-butadienes,’* (1 8R)-variabilin from the sponge Ircinia f e l i ~ C-1027 , ~ ~ chromophore,60 phor’ A-C from the boxazoles A and B from the marine sponge Phorbas S P . , ~saraines Mediterranean sponge Reniera sarai.62 A modification of the Mosher’s MTPA esters was reported.63 A graphical description of the aromatic magnetic field distribution in the conformers of MTPA and MPA esters and its use to correlate the average chemical shifts with the absolute stereochemistry was presented to compare MTPA with MPA as reagents for determination by NMR of absolute stereo~hemistry.~~ 2.2.2 Other Stereochemistry Determination - Axially chiral 1,l’-binaphthalene8,8’-diol was used as a chiral derivatizing reagent to determine the absolute configurations of a-chiral carboxylic acids by ‘H and I3C NMR.65 The absolute configuration and enantiomeric purity of chiral primary alcohols were determined by comparison of the ‘H NMR spectra of their esters with (R)- and (S)-9anthylmethoxyacetic acids.662-Fluoro-2-phenylacetic acid was found to be useful as a chiral derivating agent in I9F NMR spectroscopy, to determine the enantiomeric purity of 2,2’-dihydroxybinaphthyland its monoether derivative^.^^ An achiral deuterated derivatizing agent for enantiomeric analysis in liquid crystalline solvent was proposed.68 The enantiomeric purity of several tobacco alkaloids and nicotine like compounds was determined by ’H NMR in the presence of (-)-(R)-l,l’-binaphthyl-2,2’-diylphosphoric acid (BNPPA) as a chiral complexing agent.69 Simple enantiomeric determination procedure of amines using chiral selones by HMQC ‘H/77Se NMR was r e p ~ r t e d . ~A’ NMR method for the determination of the enantiomeric ratio of unprotected amino acids via complexation with chiral palladium compounds was r e p ~ r t e d . ~Enantiomers ’ of t-butylphenylphosphinothioicacid were found to be useful chiral solvating agents for ‘H NMR determination of enantiomeric excess of many classes of chiral organic compounds.72Permethylated P-cyclodextrin was used as chiral solvating agent to determine the enantiomeric purity of chiral aromatic hydrocarbons and trisubstituted allenes devoid of polar functional groups.73Enantiodifferentiation of methyl mandelate by p-cyclodextrin in the liquid phase was explored experimentally and t h e ~ r e t i c a l l yEnantiomerically .~~ pure (Rp)-tert-butylphenylphosphinothioic acid and quinine were used for the direct determination of the enantiomeric purity of diethyl 1-hydroxyalkylphosphonates.75The discrimination and analysis of the NMR spectra of optically active molecules dissolved in chiral liquid crystal solvents through two-dimensional correlation experiments was studied.76 The enantiomers of phycocyanobilin dimethyl ester was obtained by enantioselective chromatographic separation of their ring-D methyl imino esters and the enantiomeric purity was determined by ‘H NMR using the paramagnetic europium shift reagent.77 (S)-a-methoxyphenyl and (S)-a-methoxy-2-naphthyl acetic acids (MPA and 2-NMA) were used as NMR chiral shift reagents for the . ~ ~ atropisomeric enantiomers of stereochemistry analysis of alkyl s u l f ~ x i d e sThe

3: Applications of Nuclear Shielding

87

the antipsoriatic l0-(3-chlorophenyl)-6,8,9,1O-tetrahydrobenzo[b][ 1,8]naphthyridin-5(7H)-one (Sch 40120) with the shift reagent (R)-(-)-2,2,2-trifluoro- 1(9-anthry1)ethanol were detected by ‘H NMR.79 Two-dimensional ro tating-frame nuclear Overhauser enhancement (ROESY) NMR spectra were used to determine the absolute configuration of (+)-5diphenylphosphino-2,3 -dimethyl -7-phenyl-7-phosphabicyclo [2.2.I] he~t-2-ene.~’ (R)-0-Aryllactic acid amides derived from a-chiral primary amines and a-amino acid esters showed different chemical shifts in ‘H NMR depending on their configuration.8 Reliable 13C NMR method of making relative stereochemical assignments to certain N-[a-hetero-P-hydroxy(acetoxy)-P-(substituted pheny1)-1’oxopropyl]-2-oxazolidinones was reported.82

’

2.3 Isotope Effects - Deuterium isotope effects of I3C chemical shifts were studied in a series of enol and keto forms of P-keto amides and the corresponding thioamides,” in a series of benzene derivatives, viz. toluene, benzoic acid, and b e n ~ o p h e n o n e ,in~ ~polydeuterated isotopomers of trans-Nben~ylideneaniline.’~ Deuterium induced chemical shift differences on the 3C were reported for a series of Schiff bases of salicylaldehydes, 1-(phenyliminoThe temperature methyl)naphthalen-2-01 and 4-chloro-l,7-phenanthrolin-l0-01.~~ dependence of the deuterium isotope effect on the I3C NMR signals for various positions in the Ph ring of 2-(N,N-diethylaminomethyl)tetrachlorophenolwas studied in the moderately polar solvent CH2C12.87Low temperature ‘H, 2H, and 5N NMR measurements were performed to study hydrogen/deuterium isotope effects of intermolecular low barrier hydrogen bonded complexes.88 Hydrogen/ deuterium isotope effects on the 15N NMR chemical shifts and geometries of low barrier hydrogen bonds in bisisocyanide salts [M-CN-L-NC-MI-X+ (L = H, D) were studied.89 Deuterium induced isotope effects of a C-H * Se ‘hydrogen bond’ of 6H,12H-dibenzo[b,fl[1,5]diselenocin were studied by IR and 77Se NMR.90 I3C NMR isotope shift between CH3 79Br and CH3 81Br and of the linewidths of the two resolved resonances were studied.” Long-range deuterium isotope effects on the 31P NMR shielding tensor were studied for the perdeuteriated urea-phosphoric acid adduct (ND2)2CO-D3P04.92 Reflection in the ‘H NMR spectrum of 37C1/35C1isotope effects on the 19F NMR chemical shifts of l-chloro-2,4-difluorobenzenewas reported.93 Hydrogen/deuterium isotope effects on the geometry and the ”N NMR chemical shifts and geometries of strongly hydrogen bonded, solid hydrogen-bisisocyanide salts were studied experimentally and t h e ~ r e t i c a l l y . ~ ~

’

’

2.4 Substituent Effects - A review was given on effects of substituents on the NMR chemical shifts in the side chains of styrene derivative^.^^ 2.4.1 Proton Substituent Efects - Calculation of the effect of a linear electric field

of a polar substituent on proton chemical shifts based on partial atomic charges gave a complete account of fluorine substituent chemical shifts in rigid molecules for all long-range protons ( > 3 bonds).96

88

Nuclear Magnetic Resonance

2.4.2 Carbon and Heteroatom Substituent Efects

- Substituent effects were investigated on the 13C NMR spectra of 4-aryl-2,6-diphenylpyrylium and 1methyl-4-aryl-2,6-diphenylpyridiniumperchlorates and 4-aryl-2,6-diphenylpyridine^,'^ and on the I3C NMR chemical shifts for C-2, C-3, C-4, C-5, C-6, the halomethyl-substituted carbon (C-7) and the cyano or oxymic carbon (C-8) in 2halomethyl-2-hydroxy-tetrahydrofuransand -5,6-tetrahydr0-4H-pyrans.'* Prediction of I3C substituent chemical shifts in 14 series of para-substituted benzenes and in 2-substituted naphthalenes was based on principal component regression with chemical shift increments for the ipso, ortho, meta and para position of monosubstituted benzenes." 13C NMR spectroscopic comparison of sterically stabilized meta- and para-substituted o-tolyldi(adamant- 1-yl)methyl cations with conjugatively stabilized benzyl cations indicated small but significant variations in the chemical shifts of the charged carbon and its nearest neighbors on the adamantyl groups, the departures from additivity of substituent effect on the shifts of the aromatic carbons."' The influence of the oxime substituent on the I3C NMR chemical shifts was studied for a series of rod-like oligo(cyclohexy1idene)oximes."' I5N and 13C NMR were used to study some ortho-substituted phenylhydrazines at natural isotope abundance in DMSO-d6 solutions to analyze substituent chemical shifts."* Substituent effects on the 15N NMR parameters of azoles were s t ~ d i e d . ' ' The ~ replacement substituent constants, o + , for some five membered heteroaromatic rings were determined from " 0 NMR substituent chemical shifts of the carbonyl group in trifluoroacetyl derivatives, and from log ks for solvolyses of heteroaryl analogs of 1-tert-butylbenzyl bromide and ch10ride.l'~ I7O Chemical shift substitution parameters obtained previously from the investigation of the conformationally rigid 1,6-anhydro-~-~-hexopyanoses were applied to five a,P-~-hexopyranoses.'~~ Substituent effects of orthosubstituted nitrobenzenes and 2,4-dinitrobenzenes were studied by IR and 1 7 0 NM R spectroscopy.

Intramolecular Hydrogen Bonding Effects and Related Effects - A review was given on the NMR studies of hydrogen bonding networks in pr~teins.''~ Two-dimensional 'H NMR spectroscopy of two a-helical peptides which differ in their amphipathicity was used to investigate the relation between amide proton chemical shifts, amide proton exchange rates, temperature, and trifluoroethanol concentration to monitor intramolecular hydrogen bonds in helical peptides.'" The intramolecular 0 - H * N hydrogen bonding in 8-hydroxy-N,N-dimethyl-lnaphthylamine was studied by IR, 'H NMR, dipole moment, and X-ray diffraction study."' Solvent effect on intramolecular hydrogen bond in 8-quinolinol Noxide was studied by IR, UV, 'H and 13C NMR, dipole moment measurements and quantum mechanical calculations."' 'H NMR was used to study hydrogen bonding and hydrogen to deuterium isotope exchange in ureido sugars."' The SIMPLE (secondary isotope muitiplet NMR of partially labeled entities) NMR method was used to study strong intramolecular hydrogen bonds in the Me2S0 solutions of sugars having two syn-axial hydroxy groups, like the talopyranoses,'12 and to study intramolecular hydrogen bonds in rigid 1,3-diaxial diols.'13 2.5

2.5.1 Proton Shifts

3: Applications of Nuclear Shielding

89

NMR data (chemical shifts, NOES, coupling constants and variable temperature experiments), FT-IR data and MM2* calculations were used to demonstrate that 3-amido-l,6-anhydro-3-deoxy-~-~-glucopyranose acts as a hydroxyl-based interaction unit and provides conformational control of self-recognition processes by intramolecular hydrogen bonding. l4 Different folding patterns of two similar triamides were explained by intramolecular amide-amide hydrogen bonding propensity.' l 5 'H and I3C NMR revealed hydrogen bond like intramolecular specific interactions between the a-hydrogen of the vinyl group and endocyclic nitrogen in heteroaryl vinyl ethers having the vinyloxy group next to the endocyclic nitrogen. l 6

'

2.5.2 Heteronuclear Shifts - A solution and solid state "N NMR were used to IH, study hydrogen bonding in a Schiffs base, 1,4-C6H4(N:CC6H40H-2)2.'17 77Se, and 15N NMR were used to study the nature of the intramolecular Se-N nonbonded interaction of 2-selenobenzylamine derivatives. Hydrogen bondings in (2,2'-bipyridyl)-3,3'-diol and related compounds were studied by 15N and I7O NMR.'19

'

2.6 Bond Anisotropy, Ring Current Effects and Aromaticity - The biphenylene fused dihydropyrene was prepared and the aromaticity of its benzene rings was estimated.12' 5,lO-Dimethyl[13]annulenone, the first monocyclic annulenone larger than tropone, was synthesized and studied by 'H NMR.12' 12.2.2.21Metacyclophane- 1,9,17,25-tetrayne was prepared and studied by X-ray crystallography, fluorescence, 'H and 13C NMR, and Raman spectra.'22 Carboporphyrines were prepared from the tripyrrane and triformylcyclopentadienes and they were shown to be 18n arenes from their ring current comparison with that of porphyrins. 123

2.7 Intermolecular Hydrogen Bonding Effects, Inclusion Phenomena and Related Effects - 2.7.1 Proton and Heteronuclear Shifts - The 'H NMR spectra of hydrogen bonded complexes A-H * B (AH = HCI, AcOH, and CIH2CO2H; B = pyridine-15N) dissolved in 2:l mixtures of CDCIF2 with CDF3 were measured at 100- 150 K to study temperature dependent solvent electric field effects on proton transfer and hydrogen bond geometries. 124 Large-amplitude solid phase molecular motion was detected in 4-carboxjlbenzo-24-crown-8 ether and its KNCS complex via 13C CPMAS NMR.'25 Solvent to solute hydrogen bonding and solvent polarity effects were studied on the nitrogen NMR shielding of 1,2,4,5-tetrazine.l~~ 2.7.2 Cyclodextrins (CDs) - The a-cyclodextrin inclusion complex with alkyl(aqua)cobal~ximes,'~~ with (1R,5R)- and (1 S,SS)-c~-pinenes,'~~ with a,owith myo-inositol 2-phosphateI3' were studied by NMR. amino The P-cyclodextrin and/or substituted j3-cyclodextrin inclusion complexes with bile with two biliar acids (chenodeoxycholic acid and cholic acid),' 32 with n i ~ a r d i p i n e , 'with ~ ~ buserelin with sulfadirnetho~ine,'~~ with tolbutamide, 1 3 6 with diclofenac,' 37 with anthraquinone-2-sulfonic acid sodium

90

Nuclear Magnetic Resonance

salt, 13' with mandelic acid, a-methylbenzylamine and 2-phenylpropionic acid,139 with meso-tetrakis(4-carboxypheny1)porphyrin and its zinc complex,14o with with 1benzoic acid,I4' with g l i ~ l a z i d e , 'with ~ ~ ( +)- and (-)-fl~rbiprofen,'~~ adamantane carboxylic acid,'44 with i d e b e n ~ n e , ' with ~ ~ re ti no id^,'^^ with borne01,'~' with sulfafurazole,'41 with alkylcobaloxime (R = i-C4H9, n-C4H9, n-C5H 1 c-C6H1 PhCH2)I4' were studied by NMR spectroscopy. The complexation between the chiral inhalation anesthetics enflurane and isoflurane and octakis(3-O-butanoyl-2,6-di-O-n-pentyl)-y-cyclodextrinwas studied by NMR spectroscopy.'" NMR spectroscopy was also used to study the inclusion complexation of substituted phenyl and adamantane derivatives with a- and p-cyclodextrins,' of of pyridoxine with p- and model surfactants with p- and y-cycl~dextrins,'~~ y-cycl~dextrins,'~~ of polyisobutylene of various molecular weights with p- and y-cy~lodextrin,'~~ of (1 R)-( +)- and (IS)-(-)-a-pinene with a-, p- and y-cyclodextrin and with the corresponding permethylated derivative^,'^^ of substituted cyclohexanecarboxylic acids and phenylalkanoic acids with a-, p-, and y-cyclod e ~ t r i n s , 1' -bromoadamantane ~~ with a-, p-, and y-cycl~dextrins,'~~ of azo dyes with a-, p-, and y-cyclodextrins, heptakis(2,6-di-O-methyl)- and heptakis(2,3,6tri-0-methy1)- P-cyclodextrins.

',

'''

2.7.3 Other Molecular Recognition - The complexation of the sodium cation by a calix[4]arene tetraester, 5,11,17,23-tetra-p-tert-butyl-25,26,27,28-tetrakis((ethoxycarbonyl)methoxy)calix[4]arene was studied by 'H and 23Na NMR in a 50:50v:v mixture of deuterated acetonitrile and deuterated chloroform.'59 The interaction between urea and tetrabutylammonium acetate was investigated in dimethylformamide/dimethyl sulfoxide solutions using 'H and "N NMR.'@ NMR diffusion measurements and chemical shift data were used to study water hydration of 18-crown-6 and its potassium iodide complex in CDC13.'61 23Na NMR was used to determine the stoichiometry and stability of N a + complexes with 12-crown-4, 15-crown-6, dicyclohexyl- 18-crown-6 and dibenzo18-crown-6 in binary acetonitrile-dimethylsulfoxidemixtures.'62 Effect of alkyl chain length on self-preorganization of artificial nucleobase receptors was studied by ' H NMR.'63 23NaNMR was used to study alkali metal cation binding by selfassembled cryptand-type supermolecule. 164 The self-assembly of a [2]pseudorotaxane of a-cyclodextrin by the slippage mechanism was studied by 'H NMR.'65 ChiraI pyridine-based macrobicyclic clefts were prepared and enantiomeric recognition of ammonium salts was and evidenced by 'H NMR.'66 The binding of 8-anilino-1-naphthaleneslufonate 15 anions of substituted benzoic, aliphatic dicarboxylic, and N-acetyl-a-amino acids to a macrocyclic alkaloid d-tubocurarine in aqueous solution was studied by fluorometry, conductometry, and 'H NMR.'67 A variety of 'molecular chip' host molecules based on glycoluril were synthesized and their binding to resorcinol and catechol guests in chloroform investigated by NMR, IR and phase transfer.I6' NMR diffusion measurements and chemical shift data were used to study water hydration of 8-crown-6 and its potassium iodide complex in CDC13.169

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2.8 Shift Reagents - A review was given on lanthanide shift and relaxation agents and their applications in NMR spectroscopy and NMR irnaging.l7' A combination of chiral and achiral chemical shift reagents of europium was proposed for the determination of enantiomeric purity of complex corn pound^.'^^ The complexes Ln(L)3 of ortho, meta and para halogen-substituted dibenzoylmethane with lanthanides (Ln) were synthesized and the induced shifts in 'H NMR spectra on n-pentanol were studied.*72The chloride ion distribution in human red blood cell (RBC) suspensions was studied using cobalt(I1) glycine, [Co(Gly)3]-, as a shift reagent.'73 Interactions between Li+, N a + , Cs+, Ca2+ and Mg2+ and the shift reagent, TmDOTP5-, were studied by 'Li, 6Li, 23Na and 133CsNMR s p e c t r o ~ c o p y . ' ~H~ NMR spectra of the analgesic, famprofazone were studied in CDC13 solution at ambient temperatures with the achiral lanthanide shift reagent, tris(6,6,7,7,8,8,8-heptafluoro-2,2-dimethyl-3,5-octanedionato)europium(III), Eu(FOD)3 and with the chiral lanthanide shift reagent, tris[3-(heptafluoropropylhydroxymethylene)- ( + )-camphorato]europium(III), Eu(HFC)~."~ 2.9 Miscellaneous Topics - A review was given on the use of NMR for analysis of DNA protein recognition, using the lac repressor-operator system as the primary example,'76 on the use of NMR in the studies of complexes of DNA and DNA-binding on MAS NMR applications on the structural studies of proteins,'78 on 'H and 13C NMR studies of steroids and triterpenes and their g l y c ~ s i d e s , on ' ~ ~a systematic NMR approach for the determination of the molecular structure of steroidal saponins,'" on recent NMR studies of the layered organic superconductors of the (BEDT)2X family,'" on the principal interactions that affect NMR coupling constants and chemical shifts and their application to structure elucidation,'s2 on the use of NMR for studying deactivation of zeolite based catalysts, which occurs during cracking, hydrocracking, reforming, and isomerization reaction^,"^ on the recent progress in understanding chemical on solid-state NMR spectroscopy and its applications to supermolecular chemistry such as zeolites, catalysts, polymers, membranes, and enzymes, on recent progress and challenges of solid-state NMR in solid state chemistry and materials science,'86 on new solid-state NMR applications to surfactants and lipids,ls7 and on the correlation between transition metal NMR chemical shifts and the stability of coordination compounds.'88 A new type of highly water soluble in vivo NMR temperature probes based on paramagnetic lanthanide chelate complexes was reported. Thulium 1,4,7,10tetraazacyclododecane- 1,4,7,1O-tetrakis(methylene phosphonate) was recommended for "P and 'H NMR temperature probe.'" The remarkable pH dependences of the chemical shift separation (7.0 ppm/pH unit) was observed between the outer 'H NMR resonances on the spectrum of the paramagnetic complex [Yb(dotp>]'- [H8dotp = 1,4,7,10-tetraazacyclododecane-N,N',N",N''tetrakis(methy1enephosphonic acid)] in the pH range 5.0-7.5 at 39°C.19' The scaling factor for a number of compounds used as external reference for chemical shift values of 31Pand 19FNMR spectra were given.'92

Nuclear Magnetic Resonance

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3

Shieldings of Particular Nuclear Species

During the period of this review, the NMR spectra of most elements have at least received some chemical investigation. Due to the space limitation, structure determination and related studies of natural products or macromolecules will be excluded, for the most popular nuclei ('H, 13C, l4,I5N, I9F, 31P), for simple characterization by the common nuclei (2H, "B, 27Al, 29Si, "V, 77Se, 'I9Sn, 195Pt).Each article will be given only brief comments in the following section. 3.1 Group 1 ('H, 2H, 3H, 677Li,23Na,39K,"Rb, 133Cs- 3.2.2 Hydrogen ( ' H ) 'H NMR chemical shifts of the thiol protons of persulfur substituted mercaptobenzenes were found at unusually low field.lg3 The 'H MAS NMR spectra of chymotrypsin in aqueous solution and in ice were r e ~ 0 r t e d . I ~ ~ The positional isomers of monounsaturated long-chain fatty compounds containing allylic hydroxy groups were distinguished by 'H NMR through the chemical shift differences of the olefinic protons.'95 The 'H NMR chemical shift order of axial and equatorial methylene protons in 1,5-disubstituted 3,7-diazabicyclo[3.3.l]nonan-9-oneswas altered by substituents in the 1,5-p0sitions.'~~ High-speed solid-state MAS 'H NMR was applied to several membrane peptides incorporated into nondeuterated dilauroyl or dimyristoylphosphatidylcholine membranes suspended in H ~ 0 . l ~ ~ The polarizable solvent diiodomethane, CH212, was studied by its 'H NMR upfield shifts.'98 'H MAS NMR measurements were performed on a number of crystalline titanias, and on amorphous silica-supported ti tania and titania-silica, with the air of measuring the characteristic proton chemical shifts of hydroxy groups bound to titanias of different crystalline form.'99 A temperature dependent 'H MAS NMR was used to study the mobility of acidic protons in Ag3PW12040.200 'H MAS NMR of layered HNbW06.xH20 (x = 1.5, 0.5) was carried out at room temperature and at various spinning speeds (1-12 kHz).201 Adsorbate complexes formed by adsorption of methanol on zeolite H-ZSM-5 were investigated by 'H, 2H, I3C, and 27Al solid-state NMR at temperatures between T = 425 K and T = 86 K.202

3.2.2 Deuterium ('H) - SNIF-NMR (site-specific natural isotope fractionation studied by NMR) was described203 and applied to authenticate mustard to fractionate in the fermentation reaction to study the influence of the nature of the to analyze the natural vanilla to analyze the origin of 11 samples of (Z)-3-hexen01,~'~to authenticate maple syrup,208to detect added beet sugar in concentrated and single strength fruit juices.209 2H NMR was used to investigate the response of specifically choline-deuterated 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) to changes in surface electrostatic change in membranes consisting of mixtures of POPC plus various cationic amphiphiles plus polyadenylic acids.210[ 1.l]Ferrocenophanyllithium was shown by 2H NMR and isotopic perturbation to undergo a rapid intramolecular 1,12-proton transfer coupled with 1,12 Li ion transfer.*"

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2H NMR was used to investigate the rhodium catalyzed deuterioformylation of 1,l -diphenylethene.212 Pentachloro[a,a',a"-2H3]toluene was studied by 'H NMR in glassy crystal state.213 3.1.3 Tritium ( 3 H ) - 3H NMR was used to analyze 3H labeled azaline B [P-4,5-3H]-cholestan-3-one,215 3H labeled two nucleic acid,2163H labeled alkenes with high specific activity,217 3H labeled phospholipase A2 amide analog inhibitor.218Simple and facile syntheses of highly deuterated and tritiated LiBH4, NaBH4 and KBH4 were acheved and the products were characterized by "B, 'H, 2H, and 3H NMR.219i220 The determination of kinetic tritium isotope effects by dynamic 3H NMR was reported.2213H NMR study was carried out on the T2, HT, and DT isotopomers of dihydrogen dissolved in various nematic phases.222 3.1.4 Lithium (6s7Li)- 6Li and 15N NMR were used to study the solvation of lithium hexamethyldisilazide by N,N-dimethylethylenediamine,223to study [6Li, lSN]lithium dicyclohexylamide in the presence of T H F and hexamethylpho~ p h o r a m i d e to ,~~ study ~ the solution structures of monodentate chiral lithium amide in the presence of lithium halide,225and to study solution structure of 2[(dimethylamino)methyl]phenyllithium by singly and doubly labeled isotopomers.226 6Li, "N, and 13C NMR spectroscopic studies of [6Li,15N]lithium hexamethyldisilazide coordinated by 29 polyamines, polyethers, and aminoethers revealed a range of structural types.227 Monomeric lithium bis(dipheny1phosphino)amide, LiN(PPh2)2 solvated with T H F was characterized by X-ray crystallography, 6Li and 31PNMR, and theoretical study.2287Li NMR was used to study the N,C-dilithiated product of 2-allylpyrrole THF/HMPTA229and to monitor the reaction between [(Ph2SiOLi)20] and MgCb2THF in T H F which gives a ring expanded product .230 Three (8-methoxy- 1-naphthyl)arylgermanes were synthesized and characterized by X-ray crystallography and 'H, 13C, and 7Li NMR.231The effect on the solid-state 7Li chemical shifts and quadrupolar coupling constants of different locations of the lithium cation relative to the carbanion framework of delocalized carbanions was The 7Li NMR spectra for poly(ethy1ene glycol-400) distereate-LiC104 at different ionic ratio was 7Li NMR was used to determine the stoichiometry and stability of Li+ complexes with 12-crown-4, 15-crown-5, benzo-15-crown-5, 18-crown-6, dicyclohexyl- 18-crown-6 and dibenzo- 18-crown-6 in various acetonitrile-nitromethane mixtures at 27°C.2347Li NMR was used to study a LiKS04 single crystal grown by slow evaporation method.23s Lithium silylamide LiN(SiMe*OCMe3)2 was prepared and its three crystal phases were studied by X-ray crystallography and powder solid-state 6Li, 7Li, 13C, and 29Si MAS NMR and broad-line NMR spectra recorded at different temperatures.236

3.1.5 Sodium (23Na) - 23Na MAS NMR and synchrotron X-ray powder diffraction methods were used to study the binding of hydrofluorocarbon-1 34 (HFC 134, CF2HCF2H) in zeolite

Nuclear Magnetic Resonance

94

23Na, 27Al, and 'H NMR spectra were obtained on benzene solutions of varying sodium alkoxyhydridoaluminate compounds, Na H,Al- (OR),- , (x = 0-2; OR = OCH2CH20CH3).238 The ternary Na2RbC60 fulleride was studied by variable temperature solid-state 13C and 23Na NMR.23923Na MAS NMR was used to detect impurity phases in Na2Hf03.24023Na MAS, twodimensional MAS, and DOR NMR spectroscopy was applied to characterize the location of Na cations in dehydrated zeolite NaX (Si/Al = 1.23).24123Na MAS and DOR NMR was used to study dehydrated zeolite NaY loaded with two molecules of MO(CO)~per ~ u p e r c a g e . ~ , ~ +-

3.1.6 Potassium (39K) - 87Rb and 39K NMR and X-ray diffraction methods

were used to study K,Rbl -xX (X

=

Br, I) mixed crystals.243

3.1.7 Rubidium (R5,87Rb)- 13C and 87Rb NMR were used to study alkali

fullerides, RblC60 and Cs]C60,244and Rb3C60, K2RbC60 and R b ~ c s C ~The o.~~~ 87Rb NMR line shape of the Rb3C60 superconductor contained three distinct peaks.24687Rbsingle crystal NMR of RbC104 and Rb2S04 were reported.247 3.1.8 Cesium (133Cs)- 133CsNMR was used to study the complexation of crown

ethers with Cs cations in DMF.248The complexing properties of 1,3-~alix[4]-biscrown-6 towards Cs+ ions were studied by 133Csand 'H NMR.249 The temperature dependence of 133Csnuclear magnetic resonance in a CsMnC13.2H20 single crystal grown by the slow evaporation method was studied.250Magnitudes and relative orientations of 133Csquadrupole coupling and chemical shielding tensors were accurately determined from 133Cs MAS NMR spectra of the central and satellite transitions for four powder Cs salts.251 Ion-exchange of Na56Y with Cs cations was monitored by 133CsMAS NMR.252 +

3.2 Group 2 (9Be, 25Mg) - 3.2.2 Beryllium (9Be) - The reaction products of maleic and phthalic acids with Be(OH)2, generated in situ from BeS0, and Ba(OH)2, were identified by elemental analyses and 'H, 9Be, and 13C NMR.253 3.2.2 Magnesium (25Mg) - High-resolution 15Mg NMR data were reported for a single crystal of pure forsterite (Mg2Si04)at temperatures to about 1400°C.254 3.3 Group 3 and Lanthanoids (45Sc,89Y, 139La,"'Yb) - 3.3.1 Scandium (@Sc)45Scsolution NMR was used to show the internal motion of the scandium ions in two sc2c84 isomers.255 3.3.2 Yttrium (89Y) - X-ray structure analysis and "Y NMR measurements were used to study the hexagonal and rhombohedra1 phases of Y2Fe17.256 The synthesis, crystal structure, and 89Y, I3C, and 'H NMR of tetraaqua[2,6diacetylpyridinebis(acetylhydrazone)yttrium(III) nitrate trihydrate was reported.257The lanthanide coordination of the macrocyclic ligands cy(DTPA-EN) and cy(DTPA-EN-DTPA-EN) was studied in aqueous solution by 'H, 13C, 170, "Y, and 139LaNMR.258The 89Ychemical shifts and 89Y-'5Ncoupling constants

3: Applications of Nuclear Shielding

95

in aqueous solution of three yttrium complexes of polyaminocarboxylic acids: KYEDTA; K2YDTPA; and K3YTTHA, (EDTA = ethylene diamine tetra acetic acid, DTPA = diethylenetriaminepentaacetic acid and TTHA = triethylenetetraaminehexaacetic acid) were measured.259 3.3.3 Lanthanum (139La)- 'H, I3C, and 139LaNMR were used to study the interactions of La(II1) with D-glucitol and ribitol in aqueous solution.260 Yb) - The spin-echo NMR results were presented of '"Pr in Pro.2Gdo.8Ni and '47Sm in Sm,Gd'-"Ni (x = 0.02, 0.2, 0.5, 0.6, 0.8) at 1.4 K.261 The novel half-sandwich polyatomic species [{Yb6(q-CpS)618){ Li(thf)4)2] (Cp' = C5Me4(SiMe2But)) was synthesized and studied by "'Yb NMR.262 [Yb(q-C5Me5){si(SiMe3>3>(THF)2]was prepared and characterized by X-ray crystallography and 29Siand I7lYb NMR.263171YbCP/MAS NMR was used to study and characterize divalent ytterbium complexes264 and to study and characterize ytterbium(I1) cyclopentadienyl derivatives.265

3.3.4 Lanthanides (I4'Pr,

Group 5 (51V, 93Nb)- 3.4.1 Vanadium ("V) - Supported vanadium oxide catalysts were prepared by adsorption and calcination vanadium acetylacetonate complexes on the surfaces of silica and alumina and these surfaces were studied by 51VNMR.266Vanadium oxide-zirconia catalysts were prepared and characterized by "V solid-state NMR, XRD, and DSC.267 The V(V) complex of a hydrolytically stable trivalent pentadentate amine alcohol ligand was synthesized and characterized by 'H, 13C, and 51V NMR, vibrational and electronic spectroscopy.268 A cubane-type cluster (Et4N)[V2Fe2S4(Me2dtc)5](Mezdtc- = dimethyldithiocarbamate) was synthesized and characterized by X-ray crystallography and ' H and "V NMR.269Mixed ligand, monooxovanadium(V) complexes of Schiff bases with catechol, p-tert-butylcatechol or pyrogallol were synthesized and characterized by FTIR, UV-visible, 51VNMR and e l e c t r o ~ h e m i s t r yA . ~combined ~~ equilibrium study of tungstovanadates involving potentiometry and "V, 183W,and 1 7 0 NMR spectroscopy was able to identify 11 main species, giving their formation constants and pK, values where relevant.271The existence of the linear tri- and tetra-vanadate anions in aqueous solution was confirmed by 51V and 1 7 0 NMR and p ~ t e n t i o m e t r y . ~ ~ ~ Silicate anions were shown by 51V and 1 7 0 NMR to combine with aqueous [HV0412- in aqueous alkaline solution, forming the anion [H2VSi07I3-, [H3VSiO7I2- and various related monovanadooligosilicate species.27351V and 59C0quadrupole coupling and chemical shift anisotropy were measured for V(V) nitrilotriacetate complex, Co(0) acetylacetonate and NH4+ m e t a ~ a n a d a t e . ~ ~ ~

3.4

3.4.2 Niobium f9jNb) - Synthetic microporous analogs of the mineral nenadkevichite, with Ti/Nb molar ratios ranging from 0.8 to 17.1 and a purely titanous sample, were prepared and characterized by SEM, powder X-ray diffraction, Raman spectroscopy, diffuse-reflectance UV spectroscopy (DR-UV), and 23Na, 2ySi, and 93Nbsolid-state NMR.275

96

Nuclear Magnetic Resonance

Group 6 (95M0, lg3W) - 3.5.1 Molybdenum (95M0) - 'H, I3C, I7O, 95M0, and Ig3W NMR were used to study uronic acids and their complexation with molybdenum(V1) and tungsten(V1) o x ~ i o n s95M0 . ~ ~ ~NMR was used to study cationic phosphenium complexes of molybdenum.277 Cis-Mo(C0)4(X-2(pheny1azo)pyridine) (X = 4-CH30, 4-CH3, H, 4-C1, 5-Br, 5-CF3, 6-CH3) and cis-Mo(C0)4(2-(2-methylphenylazo)pyridine) were synthesized and characterized by cyclic voltammetry, visible and IR spectroscopy, and IH, 13C, and 95M0 NMR.278Mo-Cu-Se complexes with cubane-like cores, { MoCu3Se3X}, [{MoCu3Se3X}(PPh3,Se] (X = C1, Br, I) were synthesized and characterized by X-ray crystallography, IR, 31Pand 95M0NMR and UV-visible spectra.279

3.5

3.5.2 Tungsten (183W)- The formation of dinuclear tungstate and molybdate complexes of D-glycero-L-manno-heptose was studied in aqueous solution by 13C and 183W NMR.280 Alkenylvinylidene complexes [cyclic] mer-[(dppe)(C0)3W:C:CHC:CH(CH2)nCH2CH2] (dppe = Ph2PCH2CH2PPh2; n = 1,3,4) were prepared and characterized by IR and IH, 31P,I3C, and Is3W NMR.281 The formation of (n-Bu4N)[W(0)Cl5] and its 183W NMR spectrum was reported.282 The H202-cerium(IV) decatungstate anion (CeW 1 0 0 3 6 8 - ) reacting system was followed by in situ FT-IR and 183WNMR to study the structure of the polynuclear peroxo complex formed and its reversible behavior.283 The mixed-valence diamagnetic two-electron-reduced isopolytungstate [Wlo032]6was prepared and studied by 170and 183WNMR.284The oxothio polyanions y[SiWl0M2S2038]~- (M = Mo(V), W(V)) were prepared and studied by X-ray crystallography, 183WNMR, polarography, IR, and UV-visible spectra.285Sn(I1) tungstophosphate and tungstosilicate derivatives K H[Sn(II)3(a-PW9034)2]-32H20, C S ~ ~ ,5[Sn(II)3(a-SiW9034)2]*24.5H20, .~H~ and C S ~ H ~ [ S ~ (p-SiW9II)~( 034)2].30H20were prepared and characterized by elemental analyses, IR, H, I3C, 'I9Sn, and 183WNMR, and X-ray crystallography.286The novel dirhodiumsubstituted Keggin anion; [(P04)W11035{Rh~(OAc)~}]5was prepared and characterized by X-ray crystallography, UV/visible, 'H, 31P,and 183WNMR, and cyclic ~ o l t a m m e t r y . ~ ~ ~

'

3.6 Group 7 (55Mn, wTc) - 3.6.1 Manganese (5'Mn) - 59C0 and 55Mn NMR measurements were made on a range of CoMn materials: dilute powder alloy, thin-film alloys, and multilayers.288 3.6.2 Technetium (99Tc)- A new volatile technetium(VI1) oxofluoride, TcOF5, was prepared and characterized by I9F and 99Tc NMR and Raman spectroscopy.289

3.7 Group 8 (57Fe, lS7Os)- 3.7.1 Iron f5'Fe) - 57FeNMR was used to study ligand effects in cyclopentadienyliron complexes.290 The 57Fe(II) enriched complexes of tetramesitylporphyrin and octaethylporphyrin having various bisor mixed ligation were prepared and studied by 57Fe NMR and Moessbauer s p e c t r o ~ c o p y . ~2D(31P, ~' 57Fe){'HI-triple-resonance NMR spectroscopy was used at low temperatures (213 and 179 K) to study the conformers of

97

3: Applications of Nuclear Shielding

(q4-benzylideneacetone)- and (q4-diene)Fe(0)(C0)2L complexes (L phosphi tes).292

=

phosphines,

3.7.2 Osmium (1870s)- lS7OsNMR data were collected for 37 Os(arene)X2L type complexes, using inverse two-dimensional (31P,lg70s){'H} and ('H, lS7Os) NM R .293

3.8 Group 9 (59C0, Io3Rh) - 3.8.1 Cobalt (5yC0) - Mixed-metal tetrahedral clusters were prepared and studied by 59C0NMR.294The aggregation of [Co(Ren)(2,3,2-tet)]X3 (R-en = N-octyl- or N-dodecylethylenediamine, 2,3,2-tet = 3,7diazanonane-l,g-diamine,and X = C1 or C104) in H20 was studied by "Co, 35Cl, 2H, and 'H NMR.295 The spectroscopic (UV-visible, 'H, 31P and 59C0 NMR) properties of cis- and t r a n ~ - [ c o ( L - L ) ~ X (L-L ~ ] Y = O-CgH4(PMe2)2 or oC6H4(AsMe2)2, X = C1 or Br, Y = X or BF4) and cis-[Co{As(oC ~ H ~ A S M ~ ~ )(X ~ )=XC1, ~ ]Br Y or I) were compared.296 3.8.2 Rhodium ('03Rh) - Reactions of the cationic bis(che1ate)rhodium complex [Rh(P-0)2lf with SO2, CS2, and 0 2 / S 0 2 were studied by lo3Rh NMR.297The Rh(II1) complexes, trans-[Rh(L-L)zX;?]+ (L-L = o-C&(PMe& or oC6H4(A~Me2)2, X = C1, Br, or I) were prepared and characterized by elemental analyses, UV-visible and 'H, 31Pand Io3RhNMR.298

3.9 Group 10 (I9'Pt) - 3.9.1 Platinum (IY5Pt) - [Pt(L)C13]- (L = pyridine derivatives) were synthesized and studied by 13C and 195Pt NMR.299 [Pt(CH2:CHC02CH2Ph)(PPh3)2]was synthesized and characterized by 'H, I3C, 31 P and 195Pt NMR.300 Diplatinum(II1) tetrakis(P-diketonato) complexes with the unsupported Pt-Pt bond were synthesized and characterized by 195Pt NMR.301Pt(1V) complexes, [PtX2L][PF6]2 (L = [l 2]aneS4 = 1,4,7,10-tetrathiacyclododecane, [14]aneS4 = 1,4,8,11-tetrathiacyclotetrecane or [16]aneS4 = 1,5,9,13-tetrathiacyclohexadecane,X = C1, Br), were synthesized and studied by 195PtNMR and extended X-ray absorption fine structure studies.302 Mixedligand platinum(I1) complexes of [N(SPR2)2]- (R = Ph, OPh) were synthesized and characterized by elemental analyses, IR, 'H, 13C,and 19'Pt NMR, and X-ray cry~tallography.~'~ Seven dihydroxo bridged binuclear platinum(I1) sulfoxide complexes were synthesized and studied by 19'Pt NMR.304 19F-195Ptdouble resonance CP/MAS NMR spectra were investigated for polycrystalline M2[PtF6] (M = K, Rb, Cs, NMe4).305 3.10 Group 11 (63Cu, lWAg) - 3.10.1 Copper (63Cu) - 65Cu NMR and 63C~-27A1 spin echo, double-resonance measurements from Cu-exchanged ZSM-5 catalysts were reported.306 Homoleptic Cu(1) and Ag(1) complexes [Mn(L-L)2n](BF4)n(M = Cu or Ag; L-L = MeECH2EMe; E = S , Se or Te) were prepared and characterized by elemental analyses, FAB mass spectrometry, and IR and 'H, 77Se, 125Te,63Cu and Io9AgNMR.307

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Nuclear Magnetic Resonance

3.10.2 Silver (Io9AgJ - Homoleptic silver(1) stilbenes were synthesized and characterized by 'H and Io9Ag NMR.308Three ionic complexes of Ag(1) with 1methyl-2(3H)-imidazolinethionewere synthesized and characterized by mass, IR, and 'H, I3C, I5N, and 'O9& NMR.309 The reaction products of bis(diisopropy1amino)phosphenium triflate with Ag salts AgY [Y = CF3C02-, CF3S03-, CH3C02-] were studied by 'H, 13C, 31P, and lo9Ag NMR.310 (Trifluoromethyl)argentates(III) [Ag(CF3)nX4-J, with X = CN (n = 1-3), CH3, C 3 CCH, C1, Br (n = 2, 3), and I (n = 3), and of related silver(II1) compounds were prepared and characterized by X-ray crystallography and 'H, 13C, I9F, and Io9AgNMR.311 3.11 Group 12 (67Zn, '13Cd, '%g)

- 3.11.1 Zinc (67Zn) - A high-precision observation of 67ZnN M R in zinc metal at 295 K was reported.312

3.11.2 Cadmium (111***3Cd) - 'H and '13Cd NMR were used to investigate the Cd2+ binding sites on serum albumin (67 kDa) in competition with other metal ions.313 Metal displacement reactions of Cd7MT (MT = metallothionein) with Ag or Cu' and interprotein metal exchange reactions between Cd7MT and Agl2MT or Cu12MT were studied by "'Cd NMR.314 The seven-coordinate cadmium(I1) complex, [Cd(3,4-H2-dhb)2(H20)3]*(3,4-H3dhb)*2.5H20 (3,4-H3dhb = 3,4-dihydroxybenzoic acid), was prepared and characterized by X-ray crystallography and I3Cd NMR.3'5 Monomeric iodo-heterobimetallic isopropoxides ICdM2(OPri)9 (M = Ti, Hf) were prepared and characterized by solution 'H, 13C, and 'I3Cd NMR and solid-state I3C and '13Cd CP/MAS NMR, elemental analyses, cryscopic molecular weight determination, and X-ray crystallograph^.^'^ The principal elements of the 'I3Cd shielding tensor for a set of five coordinate compounds having mixed donor atoms coordinating to the cadmium were determined via '13Cd CP/MAS NMR.317 +

3.11.3 Mercury (199Hg) - The solution behavior of (1,3-dimethyluracil-5yl)mercury(II) with regard to acetate replacement by anions and by other model nucleobases was studied primarily by 'H and 199Hg NMR.318 Secondary interaction and n-n: conjugation in ferrocenylimine derivatives of mercury were probed by 199HgNMR.319Thienylmercury(I1) polypyrazolylborates were synthesized and characterized by elemental analyses, electric conductivity, molecular weight measurements, IR, and 'H, 13C, and 199Hg NMR.320 Vinylmercury hydrides were prepared for the first time and characterized by mass spectroscopy and 'H, 13C, and 199Hg NMR.321 Bis( 1,3-dirnethylimidazol-2-ylidene)mercury chloride was prepared and characterized by 'H, I3C, "N, and 199HgNMR and X-ray ~ r y s t a l l o g r a p h y . ~ ~ ~ HgL2C12 and HgL2Br2 (L = imidazolidine-2-thione, 1-3-diazine-2-thione and 1,3-diazepine-2-thione) were prepared and characterized by 'H, 13C, and 199Hg NMR.323 Methyl- and phenylmercury(I1) diphenylphosphinoates [HgR(S(O)PPh2}] (R = Me and Ph) were synthesized and characterized by IR and 'H, 13C, 31P and '99Hg NMR.324The reaction products of [2-(pyridin-2-yl)phenyl]-

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mercury(T1) acetate with 2-thiouracil were characterized by X-ray crystallography and H and Ig9HgNMR.32S[NMe4]2[Hg2(SPh)6] was prepared and characterized by X-ray crystallography, vibrational spectroscopy and solid-state 199Hg NMR.326199HgNMR measurements were performed both in the normal and in the superconducting state for an oriented HgBa2Cu04 + 8 superconducting powder sample with Tc = 96 K.327

'

3.12 Group 13 (llB, 27Al, 69371Ga,20%1) - 3.12.1 Boron ("B) - "B NMR was used to elucidate the nature of the complexation of borate with crosslinked dextran containing glucopyranoside residues, and with linear dextran and the Complexation of phenylmonomer derivative, a-methyl-~-glucopyranoside.~~~ boronic acid with alkyl glycopyranosides and related polyols was studied by "B NMR.329 The "B chemical shift assignment for the closo-carborane C,3-Me2-1,2-C2B3H3 structure was refuted by ab initio/IGLO, GIAO/NMR evaluations.330 The structural changes in the boron-oxygen network that result from chemical modification of glassy boron oxide by potassium oxide were examined by ''B DAS NMR and Raman s p e c t r o s ~ o p i e sA .~~ series ~ of boron-substituted mesoporous MCM-41 sieves was synthesized and studied by XRD, ''B and 29Si solidstate NMR.332 The crystal and molecular structures of boron chelate compounds with tropolone and 1,3-diketones were determined by X-ray crystallography and B NMR.333Molybdenum tricarbonyl complexes of 1-substituted borepins were B, and synthesized and characterized by X-ray crystallography, 'H 13C NMR.334 Reactions between S diimides R(NSN)R (R = R' = 'Bu, SiMe3, SnMe3; R = 'Bu, R' = SnMe3; R = SiMe3, R = SnMe3) and various organoboranes were studied by 'H, *'B, 13C, "N, 29Si and Il9Sn NMR.335 Reaction products between dichlorosilanes, RHSiC12 (R = H, Me, Ph), and the decaborane anion nido-BloH1?- in ethereal solvent were characterized by 'H, 29Si, and 11 B NMR, "B-''B COSY NMR, and EST mass spectroscopy.336The macropolyhedral compound neo-C4B18H22was examined by X-ray crystallography and 'H and "B NMR spectroscopy, and compared with neutral 7,8-C2BgH13 and the [7,8-C2BgH12]- anion.337 Bis(pyridine)difluoroboron, tris(pyridine)fluoroboron, and other (pyridine)haloboron cations were studied by 'H, "B, and I9F NMR.338 Strong evidence for the low temperature formation of an axially positioned NR3 (R = H, CH3) adduct of an open cage C2B7H9 structure was obtained via comparison of the experimentally obtained 13C and "B NMR data (R = CH3) with that obtained from ab initio/IGLO/NMR and ab initio/GIAO/NMR approaches (R = H, CH3).339Reaction products between nido-NBgH12 or nidoSB9HI and Lewis bases under a variety of conditions were characterized by mass spectrometry and 'H and "B NMR.340 "B and 31PMAS NMR were used for three borophosphates to monitor their phase c o m p ~ s i t i o n . ~'B ~ ' and 13C solidstate NMR of boron carbide with different isotope ratios, B4C("B/"B = 80.42/ 19.58; natural abundance isotope) and 1lB4C("B/"B = 99.5/0.5; "B enriched sample), was

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3.12.2 Aluminum (27A1) - The novel organoaluminium compounds (C5Me5)A1R2 (R = Me, Et, 'Bu) were prepared and characterized by 'H, 13C, and 27Al NMR and mass spectra.343 The acidity of a series of dealuminated H-Y zeolites was studied by 27Al and 29Si MAS NMR and XPS spectroscopy.344 Structures of glasses containing (20-30) mol% Ce02-(l 6-23) mol% A1203-(47-64) mol% Si02 prepared at 1550°C for 3 h in an atmosphere of N2 were investigated by FT-IR and 27Al MAS NMR.345 Solid-state 27Al and 29Si MAS NMR studies of the thermal transformation of the 2: 1 phyllosilicate mineral, pyrophylite, over the temperature range 1 50- 1350°C were reported.346 Two-dimensional triple-quantum 27Al MAS NMR spectra of VPI-5 were recorded in situ at room temperature and 85"C .347 K[Al(mal)2(H20)2]-2H20 [H2mal = CH2(C02H)2] was synthesized and studied by X-ray crystallography and 27Al, 'H, and 13C NMR.348 Several tripodal aminophenolate ligand complexes of Al(III), Ga(III), and In(II1) were prepared and characterized by 'H, I3C, 27Al, 71Ga, '"In NMR and UV s p e c t r o s ~ o p i e s . ~ ~ ~ Several four-coordinated aluminum organoamide complexes were synthesized and characterized by mass, IR, elemental analyses, and 'H, 13C, and 27Ai NMR.350 3.12.3 Gallium (69*71Ga)- Ga-substituted zeolite ZSM-20 was hydrothermally synthesized and characterized by 27A1,29Si,and 71GaMAS NMR.351 The 71GaNMR spectra of solutions of gallium tribromide in different aromatic solvents were recorded and dependences of chemical shift on concentration, temperature and solvent were observed.35271GaNMR was used to study liquid gallium embedded in an opal-like porous medium.353 The structure of acetato(meso-5,10,15,20-tetraphenylporphyrinato)gallium(III),Ga(tpp)(OAc), was studied by X-ray crystallography and 7'Ga NMR.354 An N403 tripodal trenbased (aminomethy1)phosphinato ligand, tris(4-(phenylphosphinato)-3-methyl-3azabuty1)amine (H3ppma), was synthesized and its complexation properties with the group 13 metals (Al, Ga, and In) were studied by X-ray crystallography and 27Al, 31P, 7'Ga, and '"In NMR.355 71Ga chemical shielding and quadrupole coupling tensors of the garnet Y3Ga5OI2 were measured by single crystal 71GaNMR.356 3.12.4 Thallium (203p205Tl) - 205TlNMR was used to show the existence of mixed complexes of the general formula T1(CN),Cln3-" - (M + n I 4 ) in aqueous solution.357Thallium hydridotris(3,5-dimethylpyrazol-l-yl)borate was studied by 203Tland 205TlNMR spectra of TlZrF5 'H, "B, I3C, "N, and 205TlNMR.35S9359 were measured.360 3.13 Group 14 (13C, 29Si,73Ge,'19Sn, 207Pb) - 3.13.1 Carbon (I3C) - A review was given on I3C NMR spectroscopy of coumarines and their derivatives361and on the determination of acidity functions and acid strength by I3C NMR.362 The C isotope content analysis of wine EtOH was discussed for the assignment of origin and the proof of adulteration of Italian, French, and German wines.363

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Biosynthetic origin of C-26 and C-27 of the phytoecdysteroids cyasterone and 29norcyasterone in Ajuga hairy roots were studied by I3C NMR using [I3C2]acetate as feeding.364A new method based on the I3C labeling and NMR spectroscopy was developed to study the human urinary excretion of diastereomeric acylglucuronides after the oral administration of 100 mg racemic [3-'3C]ketoprofen.365 I3C NMR chemical shifts of 5-Z-substituted 1-naphthonitriles (2 = H, F, C1, Br, NH2, NMe2, CN, NO2, OMe, CHO, C02Me) in CDCl3 and in neat trifluoroacetic acid were reported.366 Halomethyl cations were prepared and studied by 13C NMR and ab initio/DFT/GIAO-MP2 calculations.367 The isopropyl cation was prepared by the low temperature reaction of 2-bromopropane-2-13C with frozen SbFS, and its I3C spectrum was measured at 83 K using slow magic angle spinning.36B2-Triaxanemethyl cation and 2,l O-para[32.56]octahedranedimethyldication were prepared and studied by I3C NMR and IGLO and DFT calculations.369The first direct measurement of the ortho steric effect of the methoxy group on the 13Cchemical shifts in anisole was reported.370 'H and 13C N M R were used to study the interactions of alkali metal and tetraammonium halides with a ~ e t o n i t r i l e . ~13C ~ ' NMR chemical shifts of the terminal ally1 C atoms C-1 and C-3 of (1,2-bis(diphenylphosphino)ethane)(q3-1,3-diarylallyl)palladiurn tetrafluoroborates were correlated with 0 Hammett substituent constants.372 13C NMR chemical shifts of alkene carbones in 2-acylidene-3,5-diaryl-2,3-dihydro1,3,4-thiadiazoles and related benzothiazoles and selenazoles were measured and studied their relationship to other push-pull a l k e n e ~The . ~ ~principal ~ values of the I3C NMR chemical shift tensors in vanillin and 3,4-(Me0)&H3CHO were reported.374Complete 13C chemical shift tensors were measured in single crystals of the monosaccharides P-D-fructopyranose, a-L-sorbopyranose, and a-~-xylopyranose,~~' and a-L-rhamnose m ~ n o h y d r a t e , ~ ~ ~ and methyl a-D-galactopyranoside monohydrate, methyl a-D-glucopyranoside, methyl a-D-rnannopyranoside, methyl P-D-galactopyranoside, methyl p-D-glUC0pyranoside hemihydrate, and methyl P - ~ - x y l o p y r a n o s i d eusing ~ ~ ~ the twodimensional chemical shift correlation technique with a multiple axis sample reorientation mechanism. The principal components of the 13C chemical shift tensors for seven acylium ions were determined by both slow speed MAS NMR and theoretical methods.378 13C NMR measurements were performed on the three phases of A1C60 (A = K, Rb, Cs) and alkali NMR in c S I c 6 0 (133Cs)and RblC60 (B7Rb)379and four inequivalent carbons were identified by using high resolution 13C MAS NMR in cs4c60.380 The 613C:0 chemical shifts and the carbonyl stretching frequences vc = correlated the chemical structure for carbonyl containing compounds in various solvents.3B1The 40 13C chemical shift tensors of single crystal perylene in the a crystal form were determined with a precision of 0.30 The principal elements of the axially symmetric nitrile I3C chemical shift tensor, and the C N bond distance of solid CH3I3CN were determined from both static and sample spinning NMR experiments at 78 and 140 K.383The anisotropies, A& of the 'H and I3C nuclear shielding tensors of chloroform were determined experimentally and t h e ~ r e t i c a l l yThe . ~ ~measured ~ I3C chemical shifts of over forty carborane compounds correlated very well with a b initio/IGLO/

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NMR calculated values at both the DZ//3-21G and DZ//6-31G* (IGLO NMR// Gaussian geometry optimized) levtls of theory as well as with the ab initio/ GIAOiNMR values at the 6-31G f/6-31G* level of theory.385 The principal components of the carbonyl carbon chemical shift tensor of the hydrogen bonded 1 : 1 stoichiometric acetone-H-ZSM 5 adsorption complex were determined from an analysis of 13C NMR spectra of static and magic angle spinning powder samples at 78 and 130 K, respectively.386 3.13.2 Silicon (29Si) - A review was given on IR and 29Si NMR spectroscopic investigations on metallosiloxanes derived from o r g a n o ~ i l a n e t r i o l s . ~ ~ ~ The pentavalent lithium compound lithium 2,2’-biphenyldiyltrimethylsilicate was prepared and studied by 29Si NMR.388 Silylene, Tbt(Mes)Si (Tbt = C6H2(CH(SiMe3)2)3-2,4,6),which was generated by thermolysis of the extremely hindered disilene Tbt(M&s)Si:Si(Mes)Tbt, reacted with isocyanides CNR (R = C6H2’Pr3-2,4,6, Tbt, C6H‘Bu3-2,4,6) to give the corresponding silyleneisocyanide adducts Tbt(Mes)Si t C : N R , and the products were studied by I3C and 29SiNMR and B3LYP/6-3 1G(d) theoretical calculations.389 Several octa- and decasilane dendrimers, prepared starting from SiClMe(SiC12Me)2 and SiMe(SiC12Me)3, containing directly neighboring branchings were studied by 29SiNMR.390 29Si Solid-state NMR was used to characterize porous Si (PS) surfaces.391 Porous silicon was characterized by 29Si NMR under conditions of static samples, magic angle spinning, decoupling and cross polarization.392 29Si CP/ MAS NMR was used to obtain information on the amounts and relaxation behavior of the internal silanols of the silica substrate, and the residual silanols of the alkylsilane-derivatized phases.393The effects of La exchange in zeolite Y and zeolite X were studied by 29Si NMR.394High-resolution solid-state ‘H and 29Si NMR techniques were used to study the surface structure of Cab-0-Sil fumed silica.395 29Si NMR was used to study the acid catalyzed hydrolysis and esterification reactions of methyltrimethoxysilane in MeOH.396High-resolution 29SiNMR was used to identify and characterize the hydrolysis products of tetramethoxysilane and methyltrimeth~xysilane.~~~ Nonahalocyclopentsilanes, HSisX9, and octahalocyclopentasilanes, H2SiSX8(X = C1, Br, I), were prepared and characterized by IR and ‘H and 29Si NMR.398Sixty R3SiX/solvent (S) and R2HSiX/S systems (R = Me, Et, Bu; X = halo, OTf, etc.; S = CH2C12, DMPU, DMSO, sulfolane, HMPA, MeCN, pyridine, N-methylimidazole, NEt3) were studied with the help of I3C and 29SiNMR spectroscopy and ab initio/IGLO calculation for different concentration ratios of R3SiX/S and RzHSiX/S as well as different temperatures .399 3.13.3 Tin (1’5,117*119Sn) - The dimesityl(diisitylstanna)germene, = Ge( M ~ S(isityl ) ~ (Is) = 2,4,6-triisopropylphenyl),was prepared at low temperature and its tin-germanium double bond structure was evidenced at -20°C by lI9Sn NMR.400 A family of [6-0-( 1,2:3,4-di-O-~sopropyl~dene-a-~-galactopyranosyl)methylltin species Ph,Sn(CH20R)4-. (n = 1-3), Ph,SnMe3_,(CH20R)

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(n = 0-3) and Bu3Sn(CH20R) were prepared and investigated by 'I9Sn NMR.401 Dibutyltin and dioctyltin esters of ferrocenecarboxylic acid and dibutyltin ester of 1,l'-ferrocenedicarboxylic acid were synthesized and characterized by IR and 'H, I3C, 19Sn NMR.402[(iPr)2ATI]SnC1and { [(iPr)2ATI]Sn}[(q5-CsHS)-ZrC12(pC13)ZrCI2(q5-C5H5)](('Pr)2ATI = N-isopropyl-2-(isopropylamido)troponimine)were prepared and characterized by 'H, 13C, and Il9Sn NMR and X-ray crystal10graphy.~'~ The synthesis, X-ray crystallographic study, and 19Sn NMR spectrum of tetramethylammonium tris(thiobenzoat0-O,S)tin(II), (C4H12N)[Sn(C7H50S)3], were reported.404 The halogen exchange between two monoallyltin compounds was investigated by 'I9Sn 2D NMR EXSY.405 Reactions between Sn(E'Ph), (E' = S or Se; n = 2 or 4) and the bis(pyridine)dichalcogenides 2,2'-(CSH4NE)2 (E = Se or Te) were studied using 77Se, '19Sn, 12'Te NMR and X-ray crystal10graphy.~'~Bis(8-quinolinato)tin(II) was prepared and characterized by IR, 119 Sn Moessbauer and 'H, I3C, and l19Sn NMR spectroscopy.407The reactions between SnC12 and [Ph,P(S)S]2, Ph2P(S)SH and Ph2PS2NH4, respectively, were studied by 'H, I3C, 31P, 19Sn NMR.408 Ru(SnPh3)2(CO)2(iPr-DAB) was synthesized and characterized by UV-visible, IR, 'H, 13C, and '19Sn NMR, FAB mass spectroscopy, and X-ray ~rystallography.~'~ Triorganotin(1V) derivatives of several 4-I-5-pyrazolonato ligands were synthesized and characterized by elemental analyses, IR and 'H, I3C and '19Sn NMR.410 The six-coordinate tin compounds [SnX4(L-L)] (X = c1, L-L = MeS(CH2),SMe, O-C&(SMe)2, PhS(CH2),SPh (n = 2 or 3); X = Br, L-L = MeS(CH2)nSMe, o-C6H4(SMe),) were synthesized and characterized by X-ray crystallography and solution and solid-state I9Sn NMR.41 Two novel mesostructured materials based on tin(1V) sulfide, (C16TMA-SnS-Land C16TMA-SnS-M) (CI6TMABr = cetyltrimethylammonium bromide) were synthesized and characterized by elemental analyses, XRD, AFM, FTIR, '19Sn MAS NMR, 13C CP MAS NMR, energy-dispersive X-ray (EDX) Nonspinning and MAS '19Sn NMR spectra of the binary tin sulfides SnS and SnS2 and of a number of stoichiometric compounds from the ternary system Na2S-SnS2 were recorded.413 "'Sn and 'I9Sn NMR parameters of diastereotopic tins in model gem-distannyl compounds of the type F5C6ZC02SnR3 Sn2CHR were ~ r e s e n t e d . ~Pentafluorophenylcarboxylates, '~ (Z = absent, CH2, CH:CH, R = Bu, Ph), were prepared and studied by Ii7Sn Moessbauer spectroscopy, I17Sn CP-MAS NMR, and I3C, 19F, and lI9Sn NMR.41 Three singly Sn-substituted derivatives of aqueous silicate anions were determined by two dimensional heterocorrelated 29Si-117Sn NMR.416

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3.13.4 Lead (207Pb) - The high affinity Ca2+ binding sites of carp and pike

parvalbumins, as well as those of mammalian calmodulin and its C-terminal tryptic half molecule, were analyzed by 207PbNMR.4' The formation of lead oxides upon thermolysis of a Pb(III)/Zr(IV) alkoxide were studied by 207Pband I7O NMR.418Hydrated lead(I1) dimethylacetate was prepared and characterized by X-ray crystallography and 207PbNMR.4'9 Several six-membered heterocyclic organolead compounds were synthesized and studied by 'H, 13C, and 207Pb NMR.420 The PbC1,F6-,2- anions (n = 0-6) were

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Nuclear Magnetic Resonance

synthesized and characterized in MeCN solution by 19F and '07Pb NMR.421 207Pbsolid-state NMR powder spectra at 296 K were presented for PbS04, PbMo04, PbCr04, PbC03, PbTi03, PbZr03, Pb(N03)2,Pb(SCN)2, and PbS.422 3.14 Group 15 (14*15N,31P) - 3.14.1 Nitrogen (I4*I5N)- I4N NMR was used to study protonation effects of both saturated and unsaturated nitrogen environm e n t ~to, ~study ~ ~ the solvent effects on the I4N NMR shielding of 2-methyl-2nitrosopropane and its azodioxy dimer,424to study for all six possible thiazole and thiadiazole molecules in a variety of and to study for solvent induced nitrogen shielding variations in both the NR2 and cyano moieties of 15NNMR chemical shifts of eight cyanamide and of N,N-dimethyl~yanamide.~~~ substituted pyridine N-oxides and their complexes with methanol and dichloroacetic and trifluoromethanesulfonic acids were measured.427"N NM R data were reported for pyrazine, all methylpyrazines, and their 1- and 4-oxides and 1,413C and I5N NMR were used to study for two substituted trini tronaph thalene and ni tronaphthalenes 1,8-bis(4-toluenesulfonamido)-2,4,7l,8-bis(4-toluenesulfonamido)-2,4,5,7-tetranitronaphthalene and their salts with 1,8-dimethylamin0naphthalene.~~~ Solid-state I3C and 15N NMR were used to study polymorphism of 4,5-bis(4-methoxyphenyl)-2-(3-nitrophenyl)-1H-mida~ole.~ The ~ ' 15N chemical shift tensors and hydrogen bond geometries of I5N labeled 3,Ssubstituted pyrazoles were reported.43' 2-Aminopyridines72-amino-3methylpyridines and 2,6-diarninopyridines7 bearing N-trimethylsilyl, -stannyl or -plumby1 groups, and analogously substituted 2-picolines were studied by 'H, I3C, "N, 29Si,l19Sn, and 207PbNMR.432I3C, 14N,and I5N NMR chemical shifts were reported for a mesoionic t h i a t r i a ~ o l e .'H, ~~~ 13C, I4N, and 15N NMR were used to study some mesoionic 1,2,3-triazoles and related compounds.434 l-Phenyl-3-methyl-5-N-benzylideneaminopyrazolesand its derivatives were studied by 'H,13C, I4N, 15N,and I7O NMR.435 Approaches to observing extremely broad 14NNMR powder patterns of solids with improved sensitivity were described.436 I4N and 1 7 0 NMR spectra of a solution of nitrous oxide, N 2 0 in MeCN were measured.437The stoichiometric reaction of [N2H5][N3]with 1 equivalent of H2SO4 in water was followed by I4N NMR and the 14N NMR spectra of [N2H5][N3] and HN3 were reported.438 High precision I4N NMR shielding were reported for all five available oxazoles and oxadiazoles in a variety of solvents.439 15N NMR was used to study [Rh(NCBPh3)(PPh3)3]and [Rh(CNBPh3)(PPh3)3]and their derivatives.u0

3.24.2 Phosphorus (31P) - A series of 1,4,7-triazacyclononane-basedligands containing 1, 2, or 3 methylphosphinate side chains was prepared and studied for monitoring Mg" in biological samples by 31Pand 'H NMR.44131P NMR was used to calculate free [Mg2+]from p/a peak height ratio of ATP.44231PCP/MAS NMR spectra were acquired for various linear and branched di- and trinucleotides attached to a controlled pore glass solid [q4-P7Ni(C0)l3-, [q4-HP7Ni(C0)]*-, and [q2-P7PtH(PPh3)12- were prepared and characterized by X-ray crystallography and 31P NMR.444 Solid-state 31P NMR was used to study 5-phenyldibenzophosphole,its chalcogenides, and some

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of its transition metal c o m p l e x e ~ The . ~ ~ crystal structures and the principal values of 31P nuclear magnetic shielding tensor of (1-hydroxyalkyl)dimethylphosphine sulfides were determined.616 The urea-phosphoric acid adduct, (NH2)2CO-H3P04, was studied by variable temperature P NMR and semiempirical calculation^.^^ Vanadium phosphorus oxides (VPO) containing vanadium ions in the + 3 and + 4 oxidation states, namely VP04, (VO)2P2O7, VOHPO4-O.SH20 and VO(H2P04)2 were characterized using 31P solid-state NMR.448 The 31P chemical shift anisotropies were measured at 293 K for the triphenylphosphine ligands in solid octahedral Cr(0) c o m p l e ~ e s31P . ~ ~MAS NMR was used to determine 31Pchemical shift tensors of crystalline silicone phosphates4" and to measure the 31P chemical shielding tensors in the first terminal phosphido complexes containing a phosphorus-metal triple bond.45'

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Group 16 ( 1 7 0 , 33S, 77Se, '25Te)- 3.15.2 Oxygen ('70)- '70NMR spectra of 42 aliphatic and 13 cyclic enaminones with tertiary amino and of 55 primary and secondary enaminones with various substituents at the C-I, C-3, and N - p o ~ i t i o n s ~were ' ~ reported. A general synthetic approach for the synthesis of ''N and 1 7 0 doubly labeled pyrimidine nucleosides was reported.454 The effect of a cis-N-Me group in amides on the carbonyl 170chemical shift was in~estigated.~"The properties of substituted cyclobutene- 1,2-diones were examined by 170 NMR and theoretical calculations and compared to those of cyclopropenones and other models.456Two-dimensional 170,'H chemical shift correlation experiments were performed by polarization transfer via the J(OH) coupling in 2-hydroxymethyltetrahydrofuran and diethylene glycol monomethyl ether, and via different 2J(OH) couplings in methyl f ~ r m a t eThe . ~ ~1 ~7 0 NMR signal of formaldehyde was measured and the literature values of the 13Cand 'H signals were discussed.458 170NMR was used to study the effect of Na+ and Mg2+ ions on phosphoryl Solvent effects on 170chemical shifts in amides were studied using a multiple linear regression analysis.460 170NMR spectra of the isolated water molecules in hydrophobic poly(E-caprolactone) were reported.461 The rate constants and activation parameters for water exchange on hexaaqua and monohydroxy pentaaqua iridium(II1) were determined by 1 7 0 NMR as a function of temperature (358-406 K) and pressure (0.1-210 Mpa) at several acidities (0.5-5.0 m).462 The solvent effect on the NMR chemical shielding in liquid H 2 0 was calculated from a combination of molecular dynamics simula"0 NMR was used tions and quantum chemical calculations for ' H and 170.463 to study oxygen exchange of 1 7 0 labeled Na2Cr04 into solvent H20 according to the dimerization reaction.464 The 'H NMR chemical shifts and 170NMR chemical shifts of water in aqueous solutions of HCl, HBr, HI, HC104, HN03, H3P04, and H2S04465and in aqueous solutions of NH4Cl, NH4Br, NH41, NH4N03, NH4C104, (NH&S04, NH4H2HP04, and (NH4)2HP0266were measured and compared with different quantities. A wide range of 1 7 0 enriched phases AB03 and A2B03 (A = Li, Na, Ca, Sr, Ba, and La; B = Ti, Zr, Sn, Nb, and Al) and related compounds was synthesized and studied using I7O MAS 3.15

Nuclear Magnetic Resonance

106

NM R.467The 02-based reoxidation mechanism of three representative reduced polyoxymetalates was investigated using '70-labeled 0 2 with 1 7 0 NMR.46g A modified synthesis of carbonyl dibromide was elaborated and its 1 7 0 NMR and electron impact mass spectra were reported.469 3.25.2 Sulfur (j3S) - Natural-abundance solid-state 33S NMR with high-speed magic-angle spinning was reported.470 3.25.3 Selenium ("Se) - The new aminoammonioselenuranes were prepared and characterized by X-ray crystallography and 77Seand 5N NMR.471Palladium(I1) complexes of the selenium coronands 1,5,9,13-tetraselenacyclohexadecaneand 1,5,9,13,17,21 -hexaselenacyclotetracosane were analyzed by X-ray crystallography and 77Se, 'H, I3C, and 'H-I3C correlated NMR.47231P and 77Se high resolution solid-state NMR were used to study structural properties of 2-N,Ndiisopropylamino- 1,3,2h5-oxaselenaphospholane-2-selone.473 The phosphine derivatives of mixed-metal chalcogen clusters, CpCoFe(CO)S(p3-Se)2(PnP)(PnP = dppm or dppe) were prepared and characterized by elemental analyses, IR, and 'H, 13C, 31P, and 77Se NMR.474 The reaction products of (C0)6Fe2(p-EE') (E, E' = S, Se, Te) with diazoethane were characterized by elemental analyses, IR, and 'H, I3C, 31P,77Se and '25Te NMR.475The new mixed-metal, mixed-chalcogenide clusters [Fe2W(CO)Io(p3-Se)(p3-E)] (E = Te or S) were synthesized and characterized by X-ray crystallography, IR and I3C, 77Se, '25Te NMR.476Raman and 77SeNMR spectroscopy were used to confirm that when selenous acid is reduced by thiosulfate in H 2 0 , selenopentathionate and tetrathionate are formed.477 Organotungsten selenolato complexes were prepared and studied by X-ray crystallography and 77Se NMR.478 The (cyclopentadienyl)(carbonyl)oligoselenidotungsten(II) complexes, [CP(CO)~WI2Sen (n = 2, 3, 4) were prepared and characterized by X-ray crystallography, and H and 77SeNMR.479Several selenoether macrocyclic complexes of Co(III), Rh(III), and Ir(II1) were synthesized and characterized by elemental analyses, mass spectroscopy, IR, UV-visible, and 'H and 77Se NMR.4s0 Selenocyanato derivatives of hydro-closo-borates, (PPh4)2[(SeCN)BnH, 11 (n = 6, 10, 12) were prepared and characterized by X-ray crystallography and "B and 77SeNMR.48'

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3.15.4 Tellurium ('25Te) - 125Te and 'H NMR were used to study disubstituted vinylic telluride dichlorides and their corresponding tellurides.482 0-Alkyl dithiocarbonate (xanthate) derivatives of halomethyltellurium(IV), Me2TeX[S2COR], were characterized by IR, Raman, and 'H, I3C, and '25Te NMR.4s3 Il9Sn and 12'Te NMR were used to reveal that methyl, primary and secondary alkyl radicals, generated by reaction of phenyltelluroalkanes with tributyltin hydride are capable of displacing tributylstannyl radicals from (4-fluorophenyltelluro)tributylstannane to afford the 4-fluorophenyltelluroalkanes.484 The new mixed metal, mixed chalcogenide cluster CpCOFe2(C0)6(~3-S)(p3-Te) was prepared and characterized by elemental analyses, IR and 'H, I3C, and 12'Te NMR.485The new clusters Fe2M(CO)10(p3-S)(p3-Te)(M = W, Mo) were isolated

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and characterized by elemental analyses, IR, and 125TeNMR.4x6 The mixed tellurium/selenium Re6 clusters [NMe&[Re6(Teg - .Sen)(CN)6] (n = 0-8) were prepared and characterized by X-ray crystallography and 77Se and ’25Te NMR.487 Complexes of 2-(2-phenyltelluroethyl)pyridine and 2-{2-(4-methoxyphenyl)telluroethyl)pyridine with Co(I1 and 111) and Cu(1 and 11) were synthesized and characterized by molecular weight measurement, molar conductance, ESR, IR, ‘H and 12’Te NMR and electronic spectra in conjunction with magnetic susceptibility measurements and ESCA.488

3.16 Group 17 (I9F, 35937CI) - 3.I6.1 Fluorine (’9F) - A review was given on the study of protein structure and dynamics by 19F NMR,4x9 on 19F NMR of organofluorine comp0unds,4~~ and on 19F MAS NMR of inorganic fluorides, organic fluorides, and fluorop01ymer.s.~~~ 19F NMR was used to study fluorine containing aliphatic amino acids in proteins.492 19F NMR and genetic engineering techniques were used to study membrane-associated proteins labeled with fluorine labeled amino acids.493Wild type [4-F]Trp-labeled myoglobins (MbCO, Mb02, deoxyMb, metMb, and MbCN) and Hbs (HbCO, HbOz, and deoxyHb), as well as those of several mutants (W7F Mb, PWl5F Hb, pW37S Hb, and PY130F Hb, all as the carbonmonoxy adducts), were prepared via site-directed mutagenesis and their 19F NM R spectra were reported.494 Apoproteins of several flavoproteins were reconstituted with 2’-F-2’-deoxyarabinoflavins and studied by 19F NMR and absorption spectro~copy.~~’ Trifluoromethionine was used as a I9FNMR marker in protein.496Hexafluorobenzene was used as a sensitive 19FNMR indicator of tumor oxygenation.497 and 29 of its mono-, Ethyl 1,6dihydro- 1-ethyl-4-oxoquinoline-3-carboxylate di- and trifluoro and/or -chloro derivatives were synthesized and their ‘H, 13C and 19FNMR spectra were recorded.49xA series of norborn-7-yl fluorides were synthesized and their 19Fand 13CNMR spectra were recorded.499 High-resolution variable-temperature 19FMAS NMR spectroscopy of fluorocarbon polymers was r e p ~ r t e d . ~p-Fluoroacetophenone ” molecule was used as a probe to study zeolite acidity by 19Fsolid-state NMR.’” Fluorinated fullerenes CoF36 and C70F36px/405027503 and C60F18504 were prepared and studied by I9F NMR. Ab initio calculation and NMR spin echo measurement of I9F chemical shielding in the alkali metal fluorides was reported.505(1odocyano)iodine hexafluoroarsenate, [ICNI] [AsF6]-, was synthesized and characterized by elemental analyses, IR, Raman, and I9FNMR.506The camphor adducts of uranyl bis(P-diketonates) were prepared and characterized by elemental analyses, IR, ‘H, I3C{lH) and I9F NMR.507 Fluorocarbonyl peroxynitrate was synthesized and characterized by vapor pressure measurements, vibrational, 19F and 3C NMR, UV, and mass s p e c t r o s c ~ p i e s Gel-phase .~~~ I9F NMR was used to evaluate reactions in solid phase organic ~ynthesis.”~ +

3.16.2 Chlorine ( 3 5 . 3 7 ~-i )35/37CINMR chemical shifts and nuclear quadrupole couplings for some small chlorine compounds were studied experimentally and theoretically. 510

108

Nuclear Magnetic Resonance

3.16.3 Iodine (r271)- 'H and 1271 NMR, DTA, DSC, electric conductivity, and powder and single crystal X-ray diffractions were used for trimethylammonium iodide to study phase transitions and ionic motion^.^" 3.17 Group 18 (3He, 1297131Xe) - 3.17.1 Helium ( 3 H e ) - 3He NMR spectrometry was used to examine bisaddition to c60 containing an encapsulated 3He atom (3He@C60).512Two signals were observed in the 3He NMR spectrum of [email protected]'3 The [2 + 21 photocycloaddition of cyclic enones to c60 was studied by 'H, 3He, and 13C NMR, ESI mass, IR, and UV s p e c t r o ~ c o p y . ~ ' ~ 3He was dissolved into the organic solids and 3He NMR spectra were obtained to study rapid motion among 3.17.2 Xenon ('29,'3rXe)- A review was given on '29Xe NMR of adsorbed xenon for studying properties of zeolites and related r n a t e r i a l ~ . ~ ' ~ '29Xe NMR was used to study microheterogeneities and sorption environments in semicrystalline poly(4-methyl-1 -pentene) and high-density p ~ l y e t h y l e n e . ~ ' ~ Inclusion of NaCl in the large and small cavities of zeolite NaY was studied by X-ray diffraction and N and Xe adsorption as well as '29Xe and 23Na NMR.5'8 The adsorption of Xe in siliceous zeolite ZSM-12 was studied by static, MAS, and 2D-EXSY 129XeNMR.5'9 The structure of 12-tungstophosphoric heteropoly acid (H3PW12040) supported on silica has been studied by '29Xe NMR of adsorbed xenon.52o '29Xe and I3'Xe N M R were applied to study mesophases of cetyltrimethylammonium bromide in f ~ r m a r n i d e . ~ ~ '

4 1 2 3 4 5 6 7 8 9 10 11

12 13 14 15 16

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117 118 119 120 121 122 I23 124 125 126 127 128 129 130 131

132 133 134 135 136 137 138 139 I40 141 142 143 144 145

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4 Theoretical Aspects of Spin-Spin Couplings BY H. FUKUI

1

Introduction

Progress in theoretical investigation for nuclear spin-spin coupling constants is quite an interesting matter for both theoreticians and experimentalists. It is well known that the theoretical analysis of spin-spin coupling constants may increase notably the scope of NMR spectroscopy to study molecular structural problems if it is used to complement experimental observations. The aim of this review is to present readers with information about important developments in theoretical aspects of spin-spin couplings in the recent year. In the theoretical analysis of spin-spin coupling constants two different approaches are used. The first approach is a precise way based on ab initio calculations including electron correlation. The other approach is a way to find empirical or semiempirical correlations between spin-spin couplings and electronic structures based on an increasing number of experimental measurements. Recent developments in both approaches will be introduced in the following sections.

2

Ab Initio Calculations

During the last year only several papers have been published about ab initio calculations of nuclear spin-spin couplings, which used the multiconfiguration self-consistent field (MCSCF),' coupled-cluster (CC) approach,273and HartreeFock (HF) i.e., self-consistent field (SCF) m e t h ~ d . ~ - ~ 2.1 Multiconfiguration Self-Consistent Field Calculation - Kaski et al.' reported experimentally and theoretically determined CC spin-spin coupling tensors n j ( ' 3 C , ' 3 Cin ) benzene. This article should be accounted as one of the most excellent papers published in recent years for spin-spin couplings. Since the six carbons in benzene are magnetically equivalent, the CC spin-spin coupling constant n J ( ' 3 C , 1C) 3 between the ortho, meta, and para (n = 1, 2, and 3) positioned carbons were experimentally determined in two ways: firstly by utilizing the 2H/'H isotope effect on the carbon shieldings in neat monodeuteriobenzene and recording the 13C satellite lines in a 'H-decoupled 13C NMR spectrum, and secondly by recording the 'H-coupled 13CNMR spectrum of fully

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126

Nuclear Magnetic Resonance

'3C-enriched benzene (I3C6H6) in three kinds of liquid crystals and carrying out its complete analysis. Kaski et al. performed MCSCF linear response calculation^'-^ of the spin-spin coupling tensors, nj(13C,1 H) and nj(13C,13 C), in benzene for five coupling mechanisms: the diamagnetic and paramagnetic spin-orbit interaction terms (DSO and PSO), the Fermi contact term (FC), the spin-dipole term (SD), and the cross-term of the SD and FC mechanisms (SD/FC). The last SD/FC term does not contribute to the spin-spin coupling constant, i.e., the isotropic part of spinspin coupling tensor. A b initio calculations of the spin-spin couplings in benzene pose heavy requirements on computer time, the basis sets used, and the treatment of electron correlation. Correlated ab initio calculations of spin-spin couplings require the use of good atomic orbital basis sets, in particular for the FC and SD/ FC contributions. For molecules of the size of benzene this requirement becomes a serious bottleneck and one often cannot reach the basis set limit in the calculated properties. Kaski et al. utilized two different basis sets: firstly the TZP level set adopted originally from Huzinaga" and secondly the TZ basis set of Schafer et al." augmented with two polarization functions'2 on each atom and three tight s-type on each carbon atom. The first basis set includes 168 contracted Gaussian-type orbital (CGTO) functions, and the second one includes 252 CGTOs. In MCSCF calculation^^^ the electronic wave function consists of a linear combination of several Slater determinants constructed by moving electrons out from the doubly occupied (in the H F picture) molecular orbitals to the unoccupied (virtual) ones within the chosen active orbital space. Both the coefficients of the determinants and the orbitals are variationally optimized. The complete active space (CAS) wave function consists of all determinants that can be constructed within the active space, corresponding to full configuration interaction (FCI) calculation in that limited space. The size of a CAS expansion rapidly becomes prohibitive as more electrons and orbitals are included in the active space, and the need to constrain the number of determinants in the wave function arises. Then one uses the restricted active space (RAS) method in which the most common way is to partition the active space orbitals into the three subblocks, RASI, RAS2, and RAS3. The maximum number of holes can be specified in RAS1, which contains only orbitals that are doubly occupied in the SCF wave function. RAS2 corresponds to the active space in CAS calculations: no constraints to the orbital occupation numbers are put there. In RAS3 one can specify the maximum number of particles (electrons). For the MCSCF calculation to be successful, the active space must be chosen in a balanced wayI6 to contain the orbitals that are expected to participate most in electron correlation effects. Kaski et al.' calculated the spin-spin coupling tensors, nj('3C,1H) and nj(13C,'3C),in benzene with two different CAS- and three different RASMCSCF wave functions. The largest wave function consists of about one million Slater determinants. The calculated results for the CH and CC spin-spin coupling constants are given and compared to experimental ones in Table 4.I . Compared with the experimental results, even the best calculation gives too large (in magnitude) "J(C, C) couplings, but the trend in increasing the number of

4: Theoretical Aspects of Spin-Spin Couplings

127

Table 4.1 Experimental and calculated CH and Cc spin-spin coupling constants in benzene.' (Taken from ref. [ I J ) Experimental Coupling

C6H,-D

ZLI I I 6 i "

MIXTURE'

Phase 4"

Calculated

55.87(2) -2.486(24) 10.11 l(25)

158.550(6) 1.032(8) 7.517(5) -1.28(1) 55.98(1) -2.49(1) 10.099(9)

158.310(9) 1.04(1) 7.62(2) -1.23(2) 55.81l(4) -2.519(9) 10.090(6)

158.41(1) 1.09(1) 7.72(1) -1.44(1) 55.83(2) -2.434(7) 10.12(2)

176.7 -7.4 11.7 -4.6 70.9 -5.0 19.1

'

J(C,H) 'J(C, H)

3J(c,H) 4J(c,H)

'

J(C,C ) 'J(C, C) 3J(C,C)

~~

'' Value in hertz. The figure in parentheses after the experimental values is the standard deviation in units of the 1st digit Neat monodeuteriobenzene. The coupling constants were derived from the 'H-decoupled I3CNMR spectrum ' 13C6H6 dissolved in the liquid crystal ZLI 1157.The coupling constants were derived from the 'H-coupled 13CNMR spectrum " As in footnote c, but the solvent was liquid crystal MIXTURE '' As in footnote c, but the solvent was liquid crystal Phase 4 The results for the best MCSCF wave function

'

correlating orbitals showed convergence of these to the experimental values. The signs of "J(C,C) are consistently correct. This is not the case for "J(C,H), however, where the *J(C,H) value is calculated to have a negative sign contrary to experiment. The two-bond CH and CC couplings appear to be more difficult in calculation than the corresponding one- and three-bond couplings. 17*'* The calculated results for the anisotropies of C H and CC spin-spin couplings are given and compared to experimental ones in Table 4.2. Exactly the same pattern as with the isotropic couplings "J(C,C) is apparent also with the anisotropies A"J(C, C): the computed sign combination in the ortho, meta, and para couplings equals the experimental one. Unfortunately, the experimental values for AnJ(C,H) are not available for comparison. 2.2 Coupled-Cluster Method - Nooijen et a1.2 performed equation-of-motion coupled cluster (EOM-CC) calculations for nuclear spin-spin coupling constants. Recently, EOM-CC t h e ~ r y ' ~has - ~been ~ used to evaluate second-order properties like polarizabilitie~,~~ NMR chemical shifts,24and nuclear spin-spin coupling constant^.^^-^' In EOM-CCSD calculation of second-order properties one deals with equations that have dimensions of the space of single and double excitations, and which scale with the sixth power of the size of the basis set. To extend the applicability of the EOM-CCSD approach Bartlett and his co-workers considered additional approximations and proposed the partitioned EOM-CC (p-EOM-CC) method.28 The p-EOM-CC approach is particularly efficient for the evaluation of second-order properties if there is a large number of perturbations to be considered. The p-EOM-CC schemes are therefore very suitable to evaluate

Nuclear Magnetic Resonance

128

Table 4.2

Experimentally and theoretically determined anisotropies of the CH and Cc spin-spin couplings in benzens.a (Taken from ref. [ I ] ) A ' J ( C ,H ) A'J(C, H ) A 3 J ( C ,H ) A 4 J ( C ,H ) A ' J ( C ,C ) A'J(C, C ) A 3 J ( C ,C )

'

Calculated 28.0 exp in ZLI 1167 exp in MIXTURE exp in Phase 4 exp average

-9.2

3.3

-6.9

11.0 21.2 13.8 17.5 17.5

- 12.7

-5.2 -3.9 -2.5 -3.9

12.8 8.7 9.1 10.7 9.5

' Anisotropies in hertz with respect to the molecular C6 axis of symmetry, AJ = Jll

'The results for the best MCSCF wave function.

- JI

nuclear spin-spin coupling constants. For the SD contribution to the coupling, for example, there are six perturbations per nucleus in the system. In perturbation theory static second-order properties derive from the sum over states (or propagator) expression

Here, )0'1 and 19~)are the ground state and excited eigenstates of the unperturbed molecular Hamiltonian fi, with energies Eo and E X , respectively. The external perturbations are denoted 2 and 9. Equation (4.1)can be written alternatively as

where { i ) and ( j )denote ground state expectation values which serve to eliminate the ground state contribution from the sum over states. In the EOM-CC scheme second-order properties are obtained as Ex' = (Ol(1 + A ) ( i

-

(k))(fi

-

Eo)-'(j - @))lo) + x H y ,

(4.3)

where 10) is a Hartree;Fock single determinant reference state and A is a deexcitation operator. H and are the transformed Hamiltonian and the transformed perturbation operator, respectively. They are defined as

with a similar expression for j . The operator is the conventional connected excitation operator in coupled cluster theory, and (i) is given as

(2) with a similar expression for (3).

= (Ol( 1

+ A)flO)

(4.5)

129

4: Theoretical Aspects of Spin-Spin Couplings

Using inner projection techniques to expand the inverse Hamiltonian operator (I? - Eo)-' one obtains a matrix equation

EXY = a ( x ) F P h ( y )

+ a(y)H-'b(x).

Here, the various quantities are defined as

In the singles and doubles approximation to EOM-CC all operators, vectors, and matrices are limited to single and double excitations. In practice we obtain the socalled perturbed amplitude vector t by solving the linear equation system

for all perturbations z of interest and evaluating the second-order quantity ExY as an inner product Exy = a ( x ) . t ( y ) + a ( y ) . t ( x ) .

(4-9)

In the p-EOM-CC method the transformed Hamiltonian matrix H is approximated by replacing the double-double block of the matrix by a diagonal consisting of the differences of Hartree-Fock orbital energies. Nooijen et a1.2 presented p-EOM-CCSD and full EOM-CCSD results for the nuclear spin-spin coupling constants of BsH6, CH3F, CH3CN, and C2H4. The coupling constants are evaluated using Chipman's basis set29which consists of a [6s3pld]CGTO set on B, C, N, 0, and F and a [4slp] set on H. The results for the spin-spin coupling constants of CzH4are given and compared to experimental ones in Table 4.3. In is shown that the p-EOM-CCSD results are consistently close to the full EOM-CCSD ones. The calculated results reproduce well the experimental ones except 2J('H,1H) whose value is calculated to have a negative sign contrary to experiment. Perera and Bartlett3 calculated the 1J(13C,'3C) and 1J(13C,'H) in the 2-norbornyl carbocation with the EOM-CCSD method. The structure of the 2-norbornyl cation C,H11+ (Scheme 4.1) has been the focal point of one of the primary controversies in physical organic chemistry.31p33 Over the last 40 years, a large number of experimental and theoretical investigations have attempted to establish whether the classical (Scheme 4.1, I) or the nonclassical structure (Scheme 4.1, 11) is more stable (or even exists). The experimental evidence, based on a variety of spectroscopic technique^,^^-^* with NM R the most prominent, favors the symmetric bridged (nonclassical) structure for the 2-norbornyl cation in nonnucleophilic media, where direct spectroscopic measurements can be made.

130

Nuclear Magnetic Resonance

Table 4.3 The N M R spin-spin coupling constants of CzH4 (in H z ) . (Taken from ref: P J ) ~~~~

~

I J(

'

3C, H)

*J(' H, I H) J( 'H,' H)=iS

>J(I

H, I H),,,",

*J( I V , I H)

p-EOM-CCSD

Full EOM-CCSD

146.12 0.67 146.79 - 1.04 - 0.85 - 1.89 10.51 -0.68 9.83 16.30 - 1.57 14.73 - 1.40 - 1.79 -3.19

146.9 1 0.69 147.60 -0.62 -0.82 - 1.44 10.69 - 0.69 10.0 16.67 - 1.56 15.11 -1.11 - 1.84 - 2.95

Exptl."

~~

FC Non-FC Total FC Non-FC Total FC Non-FC Total FC Non-FC Total FC Non-FC Total

156.4

2.5

11.6

19.1

-

2.4

~~

'I

Ref. [30]

I Scheme 4.1

I1

(Taken from ref: [3 J )

Perera and Bartlett3 calculated the geometry of the 2-norbornyl cation at the SCF and MBPT(2) (second-order many body perturbation theory) levels using a standard DZP CGTO basis set39940 comprised of [4s2pld] for C and [2slp] for H. They found that the stable structure is nonclassical and that there is no classical form as a stationary point at the MBPT(2)/DZP level. The EOM-CCSD spinspin coupling constants calculated with the nonclassical structure showed a good agreement with the experimentally measured coupling values.37338 2.3 Hartree-Fock Calculation - San Fabian and his co-workers calculated vicinal fluorine-proton coupling constant 3J( 19F,1H)4 and vicinal proton-proton coupling constant 3J('H,1H)5by means of the ab initio SCF and semiempirical INDO/FPT methods. The vicinal coupling constants 'J(F,H) in the FCCH fragment in saturated compounds depend on a variety of molecular parameters. The main factor that

4: Theoretical Aspects of Spin-Spin Couplings

131

determines the magnitude of the 3J(F,H) couplings is the dependence on the torsion angle 4 between the coupled fluorine and proton nuclei, which is given by a Karplus type e q ~ a t i o n . ~ 'The - ~ second important factor is the effect of substituents attached to the FCCH In addition to these two important factors, there is a series of secondary factors that influence the magnitude of the 3J(F,H) couplings, such as interactions between substituents, the nature and orientation of P-substituents, etc. Fluoroethane is the simplest molecule with a vicinal coupling constant P in a saturated F-C-C-H fragment. Fluoroethane is, therefore, the parent molecule to which the substituent effects will be referenced. The coupling constant for the fluoroethane will be denoted by 3J(F,H)0. The effect upon 3J(F,H)0 of a substituent Xithat replaces the H at the position i in the fluoroethane molecule is defined as the individual substituent effect, A3J(F,H)iXi.According to a simple additivity model of substituent effects, the coupling constant A3J(F,H):;2'x3x4 in a X { X z / X 3 X 4 fluoroethane derivative (CFXIX2 - CHX3X4) would be given, in a two-substituents interaction model, by 'J(F, H)x1x'/x3x4 1234 =3 J(F,H)O +

4

4

I

i 1 nuclei are not an easy task. A large set of 1J('3C-55Mn)coupling data has for a large set of different been recently published by Torocheshnikov et manganese carbonyl complexes. These couplings have been now recalculated by the authors,137who used a revised lineshape fitting program, QUADR. The new J( 13C-"Mn) values differ considerably from those obtained previously. The couplings across C(0)-Mn bonds lie in the range of 128-189 Hz, those for C(sp2)-Mn bonds are of 57-114 Hz and the couplings across C(sp3)-Mn bonds are of 35-79 Hz. In the same paper'37 the 1J(13C-59Co) coupling of 126.2 Hz, measured for K3[Co(CN)6] in order to check the method applied, was reported. A line shape analysis performed by Kofod et for the 13CNMR spectrum of the pentacyanomethylcobalt(II1) anion gave 1J('3C-59Co)couplings of 127, 95 and 62 Hz for the cis cyano group, the trans cyano group, and the methyl group, respectively. The 13C nuclear spin relaxation study performed by Ejchart and Gryff-

155

5: Applications of Spin-Spin Couplings

Keller' 39 on 1-bromo-2- phenylacetylene yielded one-bond carbon-bromine scalar coupling in this compound 1J('3C-79Br)= -241 & 17 Hz. The 1J(33C-79'81Br) couplings for methyl bromide have been re-determined by Raynes et by the analysis of the 13C NMR linewidths influenced by scalar relaxation of the second kind. One-bond 13C-'05Rhcouplings along with J(31P-'05Rh)and J(13C(o)-31P) ones have been applied in order to establish the trans geometry of ((3-MBPA)2Rh(C0)Cl) and ((2-MBPA),Rh(CO)Cl) compounds, where 2-MBPA = 4,6-0benzylidene-2-deoxy-2-(diphenylphosphino)-a-~-altropyranoside, and 3-MBPA is 4,6 - 0- benzylidene - 2 - deoxy - 3 - (diphenylphosphino) - a - D- altropyranoside. 1J(13C-'0sRh)couplings of 74.6 and 37.7 Hz have been observed for terminal and nontenninal CO groups, respectively, in the spectrum of a new carbonyl acetate Rh(I1) complex, [Rh(CH3COO)(CH30CO)(CO)(CH30H)]2.142 1J(13C-1'9Sn)coupling values for tetramethyltin dissolved in 66 solvents have the changes observed were interpreted in been determined by Grishin et terms of the dispersion interactions. 1J('3C-'19Sn) and 'J('9F-1'9Sn) couplings have been determined in C P MAS NMR spectra of bis(3-(dimethylamino)propy1)difluorostannane dihydrate, { [Me2N(CH2)3]2SnF2.2H20),and in solution at temperatures below - 50°C. The data obtained indicate that in solution the compound exists in the form of two isomers. The coupling values observed for the major isomer are close to those found in the solid state.'@ 'J(13C-"9Sn) couplings of 350 Hz observed in the spectra of tri-n-butyltin pentafluorobenzoates, -phenylacetates and -cinnamates and 640 Hz in the corresponding triphenyltin derivatives provided evidence that all these compounds in solution are four-coordinated; much larger couplings were expected for five-coordinated compounds, of the order of 440-540 Hz and 750-850 Hz for butyl and phenyl derivatives, respectively.145 The spectra of some stannylated allenes such as e.g. (Me3Sn),C = C = C(Et)C(SnMe&BEt, have been re-measured recently by Wrackmeyer et in order to determine the accurate coupling 19Sn) couplings in the C(SnMe3)2BR2 values and signs. This also included 1J(13C-1 unit, whose small values were used by the authors as an indication that Sn-C hyperconjugation takes place in this fragment. J(' 3C-119Sn) couplings ranging from 508 Hz to 541 Hz have been measured by the same group of authors147for a series of ( E ) 1-dialkyl(or dipheny1)boryl-1-ferrocenyl-2-trimethylstannylal kenes. The coupling values increase in the order Me Ph < Et < i-Pr < t-Bu. The couplings of ca. 542-549 Hz have been found for (E)-3-ferrocenyl(alkyl)boryl-2trimethylstannylalkenes. The NMR studies on the structure of tin(1V) derivatives by the use of S('19Sn) and 1J(13C-'19Sn) data have been continued by Holecek and co-workers.'41 In the 13C(lH) spectrum of the cyanide-bridged compound (CO)5WCNCu(PPh3)3 measured at temperatures below - 20°C the exchange was slow coupling of 96 Hz between enough to allow the observation of the 1J(13C-183W) the 183Watom and the carbon of the CN High resolution solid state 13CPMAS and 'H SPEDA (single pulse excitation with delayed acquisition) NMR experiments have been applied by Ding and M c D ~ w e l l in ' ~ order ~ to investigate the structure of polycrystalline Zeise's salt,

-

Nuclear Magnetic Resonance

156

K(CH2CH2PtC13.xH20). The computer simulations of these spectra gave all interaction parameters in this salt including J(13C-195Pt)and J('H-'95Pt) coupling values, 192 and 65 Hz, respectively. A large coupling, 1J(13C-!99Hg)= 2741.2 Hz, has been reported by Arduengo et al. 15' for a mercury carbene complex, bis( 1,3-dimethylimidazo1-2-ylidene)mercury chloride. A linear relationship has been observed by Berg et a1.'52 between the 1J(*3C-205T1) couplings and the TI-CN force constants in the complexes of general formula T1(CN),Cln3 - m - n where n + m I 4 ; both parameters are also linearly correlated to the interatomic distance, dTI-C, which led the authors to the conclusion that these correlations reflect the TI-CN bond strength. The 'J(13C-205T1)coupling of 5287.3 Hz (1J('3C-203T1)= 5238.0 Hz) found in the I3C NMR spectrum of cyano rneso-tetra (4-methoxyphenylporphyrinato)thallium (111) provided evidence that the cyano group in this compound is, as a cyanide type, axially coordinated to the T1 atom.'53 that in some particular Recently, it has been shown by Wrackmeyer et cases one-bond couplings between 14N and 29Si nuclei can be measured directly from the 29Si spectrum. It concerns such compounds as, for example, N,N',N"tris-[(2'-dimethylsilylethyl)dimethylsilyl]borazine and N-boryl-2,2,5,5-tetramethyl1,2,5-azadisilacyclopentanewhere one or two alkylsilyl and a boryl group are attached to the nitrogen atom; due to the presence of these groups the electric field gradient at the 14N nuclei drops almost to zero. The coupling values, 1J(14N-29Si), are 8.1 and 6.4 Hz respectively, which is a typical magnitude of this type of couplings. Only a few examples of the couplings which involve a I5N nucleus coupled with other rare nuclei can be found in the literature. Couplings between "N and 29Si nuclei have been measured by Schwarze et af.155 for hexachlorodisilazane, 1J(15N-29Si) = 28.8 Hz, and by Wrackmeyer and Schwarze for the products and intermediates of the reaction between (Me3Si)ZNH and BH3.156The 1J(15N-31P) coupling values measured for E and 2 iminophosphines, RP=NR', cover However, as essentially the same region, 74 to 104 Hz ( E ) and 69 to 108 Hz (Z). shown by Gudat and N i e ~ k e , a' ~simultaneous ~ analysis of the 1J(15N-31P) and S(31P)values allows one to predict the geometry of the P = N bond reliably. New examples of J(' 5N-57Fe) couplings have been reported by Herberhold et al.;15s,159 the couplings of ca. 6 Hz have been found in Fe2(C0)6(p-NHCH3)(P-SH),'~~ Fe2(C0)6(p-NHCH3)(p-SCH3),'58 and Fe2(C0)6(p-SN-Si(CH3)3).159 Recently, Sanz et af.160~161 have published 1J(15N-205T1) data for the thallium complex of hydridotris(3,5-dimethylpyrazol-1-yl)borate, one of the frequently used ligands (the paper*60is the corrected version of the paper16'). Full spectral characteristics have been reported by Arduengo et for a carbene-phosphorus(V) adduct, perphosphoranide, which was formed in the reaction of the imidazol-2-ylidene with phenyltetrafluorophosphorane. The average 1J(19F-31P) coupling of 861 Hz found for this compound is significantly smaller than the coupling measured in C6H5PF4, 1J('9F-31P)= 963 Hz. The first example of the magnetic interaction between a covalently bound was fluorine and a silver ion has been reported by Plenio and D i ~ d o n e . 'It~ ~

'

5: Applications of Spin-Spin Couplings

157

observed in the spectra of two complexes formed by the partially fluorinated cryptands and Ag(1) salts. The cryptands were synthesized from 1,3-bZs(bromomethyl)-2-fluorobenzene and diaza- 18-crown-6 or benzodiaza- 18-crown-6. The values of the J('9F-'07/109A g) couplings were of 24-25 Hz. A 1J('9F-'870s)coupling of 98 Hz has been observed in the l9F-NMR spectrum of trans-[OsF2Py4] complex, a representative of a larger series of the transdihalotetrakis(pyridine)osmium (11) complexes. 164 Drews and P r e e t ~ ' ~166~ ?have shown that 1J(19F-'95Pt)couplings are very sensitive to the geometry of the platinum complexes. Thus, two different 1J(19F-195Pt)coupling values have been observed in the spectra of [PtF,C16- ,,-,Brm](TBA)2, n = 2-4, m = 0-4, TBA = tetra-n-butylammonium; couplings of ca. 1860 Hz have been found for the fluorines arranged along the symmetrical axes and of CQ. 1290 Hz for those along the asymmetric ones.165 Several papers have been published by Hassler and his on some new open-chain and cyclic polysilanes which have been characterized by IR and NMR spectroscopies, including 29Si-29Sispin-spin couplings. One-bond 29Si-29Si couplings, which vary from ca. 60 to 90 Hz, have been measured for a series of methylbromohydrogendi- and trisilanes, and for some methylbromohydrogenisotetrasilanes. 169 The 29SiINADEQUATE method has been applied to establish the structure of some silsesquioxanes, model compounds of organomodified silicasurfaces.I7O Wasylishen and his have continued their studies on MAS NMR spectra of tightly J-coupled spin pairs under slow spinning conditions. An analysis of the complex spinning sidebands observed in the 31P MAS NMR spectra of a phosphole tetramer and o-bis(dipheny1phosphino)benzene allowed them to deduce the signs of the J(31P-3'P) couplings in these compounds. 'J(31P-31P)= -362 Hz has been found for the phosphole tetramer and 3J(31P-31P) of + 160 Hz for o-bis(diphenylphosphino)benzene,which is in agreement with the data already published in the literature. A very large coupling, 1J(3'P-31P)= -405 Hz, has been observed by Eichele et al. '72 in a solid triphenylphosphine phosphadiazonium cationjc complex. The phosphorus nuclei involved are separated by more than 2.6 A; therefore, the authors came to the conclusion that no simple relationship exists between the 1J(31P-3'P)magnitude and the bond order and/or bond length. The absolute sign of this coupling has been determined by the 2D spin-echo experiment, which has been applied for this purpose for the first time. 1J(31P-31P)couplings measured by Blachnik and net^'^^ for the a-P4Se3(OC(0)Alk/Ar)2 and a-P4Se3(0C(0)Alk/Ar)2compounds vary around - 280 Hz. Similar 1J(31P-31P) values have been reported by the same group of authors for a-P4Se3(0R)2of - 300 Hz, and for P4Se3(SR)2of - 280 H z . ' ~ ~ A rJ(31P-31P) coupling of 273.5 Hz and three 2J(3'P-31P)couplings of 7.6 Hz, in the spectrum of the e m 30.5 Hz and 125.9 Hz observed by Caliman et compound P4C6-t-Bu6H2provided valuable assistance in establishing its molecular structure (see Fig. 5.3). The new cage compound, hexa-t-butyl- 1,4-dichloro- 1,4-distanna-2,3,5,6,7,8hexaphosphabicyclo[2.2.2]octane,C I S ~ ( ~ B U P - P ~ B ~ )has ~ Sbeen ~ C Icharacterized ,

Nuclear Magnetic Resonance

I58

Figure 5.3 = -214 Hz by the use of chemical shift and spin-spin coupling data; 1J(31P-31P) and 1J(31P-119Sn) = 1368 Hz have been measured for it.176 An analysis of the solid-state CP-MAS 31PNMR spectra of tertiary phosphine substituted tetracarbonylmanganese(1) complexes of the type PhCH2Mn(C0)4(PR3) performed by Christendat et al.' 77 yielded 1J(31P-55Mn)couplings which varied from 196 to 204 Hz; the couplings determined for the solution spectra of these compounds were by 50 Hz larger, which was ascribed by the authors to the changes in the torsion angle of the aryl rings. In a continuation of their studies on the structure of various complexes, von Philipsborn and his c o - w ~ r k e r s 'have ~ ~ published new NMR data for the conformational isomers of (q4-benzy1ideneacetone)- and (q4-diene)Fe(C0)2L complexes obtained for the first time by 2D (31P,57Fe)(1H)tripleresonance. Two general trends have been observed for the 'J(31P-57Fe)couplings measured for these compounds. The J(31P-57Fe)coupling in the phosphite complexes is larger than in the analogous phosphane ones and, when the J values for both isomers, basal and apical, are available, the larger coupling is observed for the isomer with the phosphorus ligand in the apical position. 1 31 in the spectrum of J( P-77Se) of 910 Hz measured by Goerlich et 1-adamantylphosphonoselenoic dichloride is in the range typical of a phosphine selenide, its magnitude corroborating the presence of a P = S e bond in this compound with only a small contribution for ylidic bonding of the type R1R22Pf-Se- (R' = 1-adamantyl, R2 = Cl). An analysis of one-bond 31P-77Se and two/three-bond 31P-31Pcouplings allowed Schuster et al. to establish the connectivity of the P and Se atoms in some new heteronorbornanes with phosphorus and selenium. 1J(31P-103Rh)couplings have been measured by Carlton181 for fifty-four carboxylate and thiolate complexes of rhodium including [Rh(02CR)(PPh3)3] (R = CH3, CF3), [Rh2(SC6F5)2(PPh3)4]and derivatives. The coupling values vary from 86.4 to 193.1 Hz. A full spectral analysis performed by Steinborn et for p-(5)-vinylenebis[dimethylglyoximato( 1-)-dimethylglyoximato(2-)- triphenylphosphine)rhodate]complex, the only example of a spectroscopically and structurally characterized dinuclear organometallic complex in which two electron-rich metal atoms are linked by an (E)-CH = CH unit, yielded a set of relevant couplings which included 1J(31P-'03Rh)= 73.2 Hz and 4J(3'P-103Rh)= 3.1 Hz. 1J(31P-'03Rh)couplings have been also collected by the same group of a ~ t h o r s ' for ~ ~two ~'~ large ~ series

'

159

5: Applications of Spin-Spin Couplings

of organorhodoximes of the type [Rh(dmgH)2(PPh3)R], where dmgH = dimethylglyoxime, R = 2-functionalized vinyl group,' 83 and substituted with allyl or propargyl groups;'g4 the coupling values are in most cases close to ca. 80 Hz. Further examples of the application of J(31P-103Rh)couplings include the homoleptic cisltrans bisdiphosphine-rhodium complexes, [(HOCH(CH2P(Ph)2)2)2Rh]BPh4 and the chiral rhodium-cyclooctadiene complexes {[(X,POCH(CH2)2)Rh(COD)]PFg] (X2 denotes 2R,4R-2,4-pentanedioxy substituent) studied by Scherer et a/.'" and heterobinuclear vinyl, allyl, and related complexes of rhodium/osmium studied by Sterenberg et al. lg6 A good correlation between the 1J(31P-'03Rh)coupling values and the Rh-P distance has been observed by Steyn et al. 187 in monocarbonylphosphinerhodium(1) complexes, [Rh(L,L'- BID)(CO)(PPh3)], where L,L'-BID denotes monocharged bidendate ligand with donor atoms L,L' (L, L' are various combinations of oxygen, nitrogen and sulfur). 1J(31p-l07/109A g) couplings in the solid-state CP MAS spectra have been determined by Bowmaker et al.'881189for 1:2 adducts of Ag(1) salts with tricyclohexylphosphine, [AgX{P(C6H11)3)2] (X = CN, I, Br, ) and 1,3bis(diphenylphosphino)propane, [AgX(dppp-P,P')(dpp-P), X = CN, I, Br, Cl. 190 The couplings in both series of the compounds increase in the order CN < I < Br C1; according to the authors, this reflects donating properties of the halogens to silver in the complexes studied. It is also worth noting that the J(31P-107/'09Ag) couplings derived in the solid-state CP MAS spectra differ from those determined in solution. The difference has been ascribed by the authors to the differences in the angle (3p-Ag-p in solution and in the solid state. 1J(31p-107/109A g) couplings measured at low temperatures have been analysed for the dinuclear [Ag2(pz)2(PPh3)2] and [Ag2(pz)2(PPh3)3] by Ardizzoia et = 513 Hz and 'J(31P-109Ag) = complexes where Hpz = pyrazole; 1J(31P-107Ag) 592 Hz observed for the first compound are in accord with the couplings reported for similar complexes in the literature. Large t4J(31P-119Sn)couplings observed by Mitchell and G ~ d r y in ' ~ the ~ spectra of Me2Sn(X)(CH2)3PPh2compounds, X = I (226 Hz), Br (263.3 Hz), C1 (270.5 Hz), indicate that a direct strong Sn-P bond interaction takes place in this case and that the four-bond contribution is rather negligible. 1J(31P-119Sn) couplings ranging from 1565 Hz up to 2027 Hz have been recorded for a series of the novel compounds, the P-stannylated iminophosphoranes R3Sn(E)P(= NSiMe3)N(SiMe3)2,where R = Me or Ph, E = NEt2, OMe or The magnitude of 1J(31P-'25Te) couplings as well as 'J(31P-77Se)ones strongly depends on the electronegativity of substituents at the phosphorus atom. The J(3'P-'25Te) couplings observed in t-BuP(Te)(F)N = C(NMe2)2 and PhP(Te)(F)N = C(NMe2)2 compounds, 2037.7 and 2092.7 Hz respectively, due to the presence of the fluorine atom belong to the largest observed for this type of

'

-

'

'

corn pound^.'^^ for a An analysis of 1J(31P-'83W)coupling values performed by Hersh et series of the tungsten carbonyl adducts led the authors to the conclusion that aryf-N-sulfonylphosphoramidesare highly electro-withdrawing ligands. The

160

Nuclear Magnetic Resonance

1 31 J( P-183W)data qualitatively corroborated the IR results, the latter being in this particular case more conclusive. A large set of the 'J(31P-'870s)couplings has been collected by Bell et for (q6-arene)osmium complexes. Some correlations between 'J(3'P-'870s) coupling values and the acceptor character of the phosphorus ligand, as well as a relationship between P-0s bond lengths and the couplings have been observed by the authors. 1J(3'P-195Pt) couplings varying from 3620 to 4060 Hz have been measured for a series of [Pt(CH2 = CHC02R)(PPh3)2] and [Pt(CH2 = C(CH3)C02R)(PPh3)2] complexes where R denotes alkyl substituents of various size. 197 The 1J(3'P-*95Pt)coupling of 2728 Hz observed in the spectrum of the platinum complex of the phosphorus containing calix[4]arene has proved its trans configuration. 19* Depending on a substituent at the Pt atom the complex Pt2X4(pyphos)4 (pyphos = 6-(diphenylphosphino)-2-pyridonate) can be either paramagnetic (X = Me) or diamagnetic (X = Cl). In the case of the methyl derivative, due to the paramagnetism of the compound, no signal in the 31P{'H}N M R spectrum has been observed. The 31P{1H}NMR spectrum of the chloro derivative, on the = 3590 Hz indicating that contrary, displayed a sharp signal with 1J(3'P-195Pt) this compound is a typical diamagnetic complex. ' 9 9 One-bond coupling between the 31P nucleus and the quadrupolar 1 9 7 A ~ nucleus has been determined from the solid-state CP MAS 31PNMR spectra of [AuC1(PMe3)] and [AuI(PMe3)] complexes: the corresponding J values are 648 and 553 Hz respectively, which is in a rough agreement with those already published in the literature.200 1J(77Se-77Se)couplings of 70 and 89 Hz have been observed by Bates and Morley201in the spectra of acyclic compounds, Se3(C5Me5)2and Se4(CSMe5)2, respectively. It is of interest to note that the two-bond Se-Se coupling in the latter compound is significantly larger than the one-bond coupling and is equal to 109 Hz. A 1J(77Se-'99Hg)coupling of ca. 2262 Hz has been found by Park et for the [HgSe2I2- anion in K(2.2.2-cryptand)2[HgSe2], the compound which was isolated from the reduction of HgSez by K in liquid NH3 in the presence of 2.2.2cryptand. The presence of two isomers, head-to-head and head-to-tail has been suggested for pivalamidate-bridged Pt(II1) dimer with an acetonate axial ligand, [Pt2(NH3)4(C5HloN0)2(CH2COCH3)(N03)](N03)2x(H~O)n, n = 1, 2.203 It has been confirmed by the observation of two sets of NMR parameters including two different Pt-Pt couplings, 1J('95Pt-'95Pt)= 3477 Hz for the H H isomer and 3625 Hz for the HT one. The I5N enrichment of this compound allowed the authors to measure a set of 1J(15N-195Pt) couplings for both isomers.

5

Two-Bond Couplings to Hydrogen

2J(1H-1H)and 'J('H-X) couplings (X = C, Si, Ge, Sn) in XH4 molecules have been calculated by Malkina et d 2 0 4 by the use of density functional theory.

5: Applications of Spin-Spin Couplings

161

An extensive study performed by Maharajh et ~ 1on the . conformation ~ ~ ~ of N,N'-[dimethyl-(2,2'-dithiobisacetyl)]ethylenediamine, a 10-membered diamide disulfide ring, yielded, among others, sets of 2J('H-'H) and 3J('H-'H) couplings for each of all three isomers in which this compound exists, i.e. for two 22 and one Z E conformer. Geminal and vicinal proton-proton couplings extracted from the 'H NMR spectra of the a-sulfinyl fragments of acyclic dialkyl sulfoxides and their complexes with (3-a-methoxyphenylacetic acid have been analysed by Buist and Behrouzian206 in an attempt to assess conformational preferences of these compounds. 2J(1H-'H) and 3J('H-'H) couplings have been determined by ~ ' ~1-methyl-azoniabicyclo[3.2.0]heptane chloride in order to Knaack et ~ 1 . for elucidate its stereochemistry. The geminal coupling of the methylene protons at C-2 in tetrahydro-1,3oxazines is a valuable probe of the stereochemistry of these and related compounds: 2J(1H2e-1H2a) is about - 7.5 Hz when the N-substituent is equatorial and 6 5 - 10.5 Hz when it is axial. Using this relationship and the relevant 2J(1H-'H)data Pihlaja et came to the conclusion that N-methyloctahydro2H-3,1-benzoxazine is not conformationally homogeneous but consists of a ca. 3:l mixture of the N-in and N-out forms at 198 K and a 7:3 mixture at ambient temperature. This is at variance with earlier reports where conformational homogeneity was suggested for this compound. Similar discrepancies have been observed for other compounds of this group. An extensive use of proton-proton couplings has been made in the conformational analysis of two carbothioamide-substituted meroterpenes (cannabino id^)^'^ and proton-proton couplings across two, three and four bonds have been measured for some green tea polyphenols.210 Proton-carbon 2J(1H-'3C) couplings have been measured and used in structural studies and in an investigation of hydrogen bonding properties of the UUCG tetraloop of the [13C/15NJ r(GGAC[UUCG]GUCC) hairpin.21 Geminal and vicinal 'H-I3C couplings have been applied to assign the 13C NMR spectra of two novel hexaruthenium clusters [ R ~ ~ ( p ~ - H ) ( q ~ - p ~ - C 0 ) ~ (p-CO)(CO)12(q5-C5R5)], where R = H or Me.212 Two- and three-bond 'H-15N couplings have been applied by Sveshnikov and Nelson2' in order to discriminate between structural isomers of N-methylated and tert-butylated tetrazoles. The magnitude and sign of 2J('H-3'P) couplings strongly depend on the coupling path; negative and large absolute values are observed for the trans arrangement and positive small couplings for the cis one. Isotopic perturbation of these couplings has been observed recently by Heinekey and van R ~ o n who , ~ ~ studied the structure and dynamic behaviour of dihydride complexes of the cobalt and iron group metals. It is already well established that 2J('H-3'P),and 3J('H-3*P)coupling values are large if the substituent is syn arranged to the lone pair at the phosphorus atom and close to zero for the anti arrangement. This relationship has been applied by Li et for structure elucidation of the four optical isomers of 1-mesityl-2,3dimethylphosphirane.

'

162

Nuclear Magnetic Resonance

2J(1H-31P)couplings of 6-8 Hz are characteristic of zwitterionic species obtained from i-Pr3P and various 2-cyanoacrylates such as i-Pr3P+CH2C-(CN)COOMe.215 2J(1H-31P)couplings of 15.3-1 6.5 Hz have been found in a series of a-aminoarylmethanephosphonic acids bearing fluoro, fluoroalkyl and fluoroalkoxy substituents in the benzene ring.216 An extensive use of NMR including an observation of the large two-bond 'H-Il9Sn couplings of ca. 100 Hz has been made by Cabezas and Oelschlager217 in the studies on the composition of stannylcyanocuprates and their addition products to 1-alkynyl ethers. Two-bond 1H-195Ptcouplings which vary from 58 to 80 Hz have been complexes measured by Otto et a1.218in the spectra of the tran~-[PtMeX(FPh3)~] (X = C1, I, NO3, CN, SCN, Py and N3). A linear relationship has been observed between the couplings and nucleophilic reactivity constants determined for these compounds.

6

Two-Bond Couplings Not Involving Hydrogen

A two-bond 7Li-31P coupling of 6.2 Hz has been observed in the 7Li{1H} spectrum of the dianion which was obtained by removal of two lithium cations This is the result of a slow quadrupolar from N,C,C-trilithi0-2,5-diallylpyrrole.~~~ relaxation rate of the 7Li nuclei left in the molecule and indicates an almost perfect tetrahedral environment around it. The first observation of 2J(13C-'3CN)coupling of 24.4 Hz in a vinylcyanohas been reported by cuprate, Bu3SnCH= 13C(OAlk)Cu(13CN)SnBu3(2Li), Cabezas and O e l ~ c h l a g e r This . ~ ~ ~result provided evidence that the cyanide and vinyl carbon atoms are bound to the copper atom. Two- and three-bond 13C-31P couplings have been applied to assign the 13C NMR signals in the spectrum of (RS)-and (SS)-O,O-(2,2'-binaphthyl)-N-(ol-benzylethyl)phosphamidatein a conformational study on this compound performed by Liu et a1.220 2J(13C-31P)couplings have been found to be useful in the determination of specific I3C enrichment in phosphorylated [1-'3C] glucose metabolites.221Hindered rotation around the P-N bond caused by repulsion between the lone pairs of electrons at the P and N atoms has been observed in di-tert-butyl-(N-pyrroly1)phosphine and some related compounds.222 The preferred orientation of the pyrrolyl group in the parent compound was deduced from the 2J('3C-31P) couplings; 2J(13C2-31P)= 35.4 Hz and 2J(13C5-31P)= -9.3 Hz were observed, which are typical values of C2 in syn and of C5 in anti position, respectively, in respect to the assumed axis of the P lone pair. 2J(13C-205T1) and 3J(13C-205T1) couplings of 212 and 283 Hz, respectively, have been found in the I3C NMR spectrum of benzoato meso-tetra-(4-methoxyphenylporphyrinato)thallium(III), Tl(tmpp)(C6H5C02), at -90°C when the rate of the intramolecular exchange of C6H5C02- was slow enough to allow observation of these couplings.223 Two- and three-bond 13C-207Pbcouplings of ca. 130 Hz and of 141-177 Hz

5: Applications of Spin-Spin Couplings

163

respectively, have been measured for lead (IV) carboxylates, PX4, where X = acetate, benzoate and cinnamate l i g a n d ~ . ~ ~ ~ The first examples of a J('5N-29Si) coupling in SiON systems have been reported by Mitzel et al.225 Couplings of 1.8 and 2.7 Hz were found in Si(ONMe2)4 and Si(ONEt2),, respectively. The two-path mechanism should be taken into consideration in this case since the coupling values indicate that not only two-bond coupling is present but also the direct Si N interaction takes place in these two compounds. Couplings across two and three bonds in which "N and 77Se nuclei are involved have been reported by Bernatowicz et ~ 1for some . ~seleno ~ and ~ diseleno azines and related compounds. A temperature dependence has been observed for two-bond "F-19F couplings measured for (q2-acetone pheny1hydrazonato)tetrafluorooxotungsten(~~).~~~ An analysis of the quite complex NMR spectra of the (trifluoromethy1)argentates(III), [Ag(CF3)&-J, where X = CN (n = 1-3), CH3, C E C C ~ H ~ ~ , C1, Br (n = 2, 3) and I (n = 3) has been performed by Eujen et yielding a full set of the coupling data including 2J('9F-'09Ag) couplings. This allowed the authors an insight into the geometry of the compounds studied. The two-bond 19F-'09Agcouplings which are equal to 100 Hz or somewhat larger for the Ag(1) compounds are significantly smaller in the Ag(II1) compounds; their values range from ca. 15 to 72 Hz. An extremely rare example of a two-bond coupling between 27Aland 31Pnuclei has been observed by Lowe et al.229in the aluminium complex [A1(H3ppma)2](N03),-2H20; 2J(27A1-31P) = 6.7 Hz, H3ppma denotes tris(4-(phenylphosphinato)-3-methyl-3-azabutyl)amineligand. 2J(29Si-3'P)and J(13C-29Si)couplings along with 13C and 29Si chemical shifts ' the proved to be a useful tool in the studies performed by Arshadi et ~ 2 1 . ~ ~on solvated silylium cations. An analysis of the 31P NMR spectra performed by Schrodel and S ~ h m i d p e t e r ~for ~ ' several derivatives of the cyclic trimers, (Ph3P= CP-X)3, X = C1, Br such as, for example, 1,3-bis(diphenylphosphanyl)2,4,6-tris(triphenylphosphorandiynyl-l,3,5-triphosphineniumchloride) yielded sets of J(3'P-31P)couplings including those across two bonds. 2J(31P-31P)couplings in the NMR spectra of complexes are strongly geometry dependent and therefore are often used for characterization of these compounds. They have been recently applied by Connac et al.232in order to characterize two novel rhenium complexes, chloro(oxo)bis[ 1-phenyl-2-(diphenylphosphino)ethenolato]rhenium(V) and nitridobis[1-phenyl-2- (diphenylphosphino)ethenolato](triphenylphosphine)]rhenium(V). The J couplings of 10 to 13 Hz have been found for the cis arranged phosphorus atoms and 210 Hz for the trans ones. A strong negative correlation between 2J(31P-3'P)and the sum of the phosphine pKa values has been observed by Keiter et al.233for the mixed-phosphine tricarbonyl iron complexes, trans-Fe(C0)3LL, where L = PPH3 and L' denotes a variety of PR3 or AsR3 ligands. The couplings also correlate with both the electronic factor x and the aryl effect parameter Ear but not with Tolman's cone angle 0.Large 2J(3'P-3'P) couplings of 95 and 135 Hz have been found for [(Me3Si)2NCa[p-P(H)-Si-i-Pr]3Ca(THF)3and {Ca(DME)[N(SiMe3)2l[p-PHSi-i-P1-31]2.~~~

164

Nuclear Magnetic Resonance

Very large two-bond 31P-1'9/'17Sncouplings, 2J(31P-'19/'17Sn)= 2579/2449 Hz observed in the low-temperature 31PNMR spectrum of [MeSi(Me2SiNp-tol)),SnAu(PPh3)I complex provided unquestionable evidence for the presence of a covalent Au-Sn bond in this compound.235 Three new chiral complexes, tin(I1) derivatives of A-type XWg034n- (X = 31P, 29Si) have been obtained by Xin and Pope.236 In the 183WNMR spectrum of K11H[Sn(11)3(PW9034)2]one of two signals present in the spectrum revealed a two-bond 31P-183Wcoupling of 1.7 Hz. Substituent effects and structural dependencies observed for experimental geminal * 9Sn-1 9Sn couplings have been reproduced by the theoretical RPA AM 1 calculations performed by Aucar et a1.237 During the reaction of equimolar amounts of [Pt(TMS0)2(OH)]?+ and [Pt(DESO)(OH)]22+ a rapid scrambling of the ligands takes place yielding all possible seven binuclear complexes; (TMSO = tetramethylene sulfoxide and DESO = diethyl sulfoxide). For three of them, i.e. for those where Pt atoms are non-symmetrically substituted, 2J(195Pt-'95Pt)couplings of 465 to 491 Hz have been observed in the 19'Pt NMR spectra by Marvin and A b b ~ t tThis . ~ ~allowed ~ the authors the assignment of the spectra of the compounds and elucidation of their conformation. The couplings for obvious reasons could not be observed for the symmetrically substituted complexes.

'

7

'

Three-Bond Hydrogen-Hydrogen Couplings

3J('H-'H) couplings are still the best experimental measure of the dihedral angle in peptides in solution. The available set of couplings is usually included in the refinement step of the final structure calculation. Representative examples of peptides and proteins for which 3J('H-'H) couplings were employed in secondary and/or solution structure elucidation are included in Table 5.1 (p. 166) and some papers are discussed. A method designed for the precise measurement of scalar couplings (kO.3 Hz) has been developed by Borgnat et al.239and applied to gramicidin. In the method called PARADISE (pure-phase achieved by retroactive acquisition in DANTE implemented selective excitation) the acquisition is started halfway through the pulse yielding sensitivity improvements of a factor 2 to 6. 3J(H~-Ha)couplings have been measured for staphylococca1 nuclease under different folding conditions and compared with the 'random-coil' values. A correlation of the magnitude of couplings with the order parameters of corresponding residues has been observed; both parameters depend on the accretion of the structure of the protein.240 Incorporation of the conformational database potential including 3J(HN-Ha) couplings into the target function has improved the quality of NMR protein structures.241 A method for determining the conformation of cyclic peptide by the use of 3J('H-'H) couplings obtained from 1D 'H NMR spectra has been published by Sefler et al.242A large set of 3J(1H-'H) couplings has been measured and used for a conformational analysis ~ ~ ~in of 36 linear and cyclic peptides containing sugar amino acids ( S A A S ) and

5: Applications of Spin-Spin Couplings

165

NMR studies of a series of peptides constrained to type VI P-turns containing antiparallel fl-ledder.2u Side chain flexibility and the backbone structure in type I antifreeze protein have been traced with the help of 3J('H-1H) couplings near freezing temperature^.^^' Simultaneous observation of several parameters including 3J('H-'H) couplings has shown that threonine residue in small peptides is conformationally restricted by an intraresidue hydrogen bond.246 Four 1,4diazepine-3-one-based dipeptidomimetic analogues have been conformationally examined by the use of 3J('H-1H) couplings.247The stereochemistry and conformation of a key bicyclic lactam- based Leu-Pro building block and the conformation of the surrounding peptide fragment have been assigned by Kao et af.248by the use of 2D NOE data and couplings from an NMR simulation. A special issue of Magnetic Resonance in Chemistry (1996) has brought several interesting papers2' 1,346-350 on the implementation of couplings in structural studies of nucleic acids. An almost complete set of homonuclear and heteronuclear conformational-independent couplings has been measured in ribonucleotides allowing optimizing and designing NMR experiments.349 A new parametrization for the Karplus equation has been obtained by the use of couplings measured for the model rigid nucleotides. A set of experiments to determine those couplings has been proposed.350 The method which allows unambiguous determination of the backbone angle y and stereospecific assignment of H5' protons by the use of 2J(C4,-Hsf) and 3J(H4,-Hs,) couplings in uniformly 13Clabelled oligonucleotides has been designed by Marino et af.351The CUPID method has been extended to five-member rings.3s2 CUPID-5 has been tested by the use of 42 sets of 3J(1H-'H)couplings measured for pyrrolidine rings. A J-coupling restrained molecular mechanics protocol (JrMM) has been proposed by Lam and A u - Y e ~ n g ; ~it' ~employs 3J(1H-1H)couplings to derive DNA endocyclic torsion angle constraints. The viability of the protocol has been demonstrated for a DNA h e ~ a m e r . ~The ' ~ errors in the value of 3J(1H-'H) couplings evaluated from DQF-COSY and P.E. COSY spectra and the limits of these methods regarding sugar conformations in larger DNA duplexes have been discussed.35s 3J(1H-'H) couplings have been used to trace quantitatively the dynamics of the NF?S pseudorotational equilibria of C - n u c l e ~ s i d e s . ~ ~ ~ The addition of dihedral angle constraints to the distance constraints decreases the uncertainty in the calculated structures. Therefore, the information obtained from 3J(1H-'H) couplings is frequently incorporated in structure calculation of oligonucleotides. Some examples are listed in Table 5.2 on p. 170. The structures of 4 new flavonol and 9 new a-ionol glycosides have been established by the extensive use of 'J('H-'H) vicinal couplings.364 The conformation of the glycerol backbone in phosphatidylcholines has been determined mainly with the help of 3J(1H-1H)couplings.36s 3J('H-'H) couplings have provided the conformational control of carbohydrate-carbohydrate selfassembly,366 and have been helpful in the structure determination of thirteen oligosaccharides obtained by depolymerization of porcine intestinal mucosal heparan sulfate.367 Some other oligosaccharides whose structures have been solved are listed in Table 5.3 on p. 170.

integrin inhibitor

a) the number of amino acid residues b) the total number of vicinal backbone and side chain proton-proton couplings measured

cyclo-[S-DL-DVP],5 conformers cyclo-[VY-DF-~R-P-~A] 18 analogs of c~cIo-[RGD-DF-V], superactive a& acetyl-pepstatin, HIV protease inhibitor [H-P-HV-P-HA-P-HL],-OH

Peptides and proteins for which the solution structure has been calculated

Boc-LV-AF-AF-AF-LV-OMe,left-handed helix substance P F7analogs: v E2(S)F, VZ2(S)F, AEF, AZF, indanylglycines Ac-EX-EALKK-EX-EALKK-NH~, X = V, I, A, with 2 lactam bridges Ac-(AAAAK)>-A-NH* methionine-rich segment of E. coli Ffh protein (resid. 410-434) immunogenic peptide from PND of the HIV-2 gp125 (resid. 294-332) cytotoxin I1 from Naju naja oxiana [ 13C/15NJregion-helix-loop-helix domain of E47 (resid. 332-397) [ 13C/15N] SH2 domain of hematopoietic cellular kinase pyrimidine-guanine sequence-specificRNase from Rana catesbeiana [ 13C/15N] RNA binding domain of E. coli rho protein (resid. 1- 130) [ 15N] flavodoxin from Desulfovibrio desulfuricans, oxidized [2H/13C/15N] IIB subunit of B. subtilis fructose transporter [2H/13C/15N] IIB domain of the E. coli mannose transporter [ 13C/15N]flavodoxin from E. coli,oxidized [ 13C/15N]murine-human chimera, MH35, of leukemia inhibitory factor [ 13C/15N]flavodoxin from Azotobacter chroococcum, oxidized [ 13C/15N]xylanase from Bacillus circulans

Peptides and proteins for which the secondary structure has been determined

Name

6

5

5 5 5

5 11 14 16 25 39 60 67 107 111 130 148 163 168 175 180 180 185

a)

Table 5.1 Peptides and proteins for which 3J('H-'H) couplings have been applied as a structural parameter

15 5

16 15

52 58 100 > 46 102 104 132 95 124 91 96 I03

2 6 14 16 17

b)

27 I

270

269

268

267

266

265

2 64

263

262

26 I

260

259

258

257

256

255

2 54

253

252

25 I

2 50

249

Reference

c

o\ m

17 20 21 21 21 22 23 23 25 26 30 32 33 33 34 35 35 36 36 37

11

4

9 10 10 10 10

32 > 46

15

9 28

13 > 25

7 10 12 ca. 25 4 14 19 19 12 20 14 8 19 > 18 12 36 11 > 26

6 I1 16 2

6 6 6 8

cycIo-[GLDV-BTD] 2 C-terminal backbone-cyclized analogs of substance P cyclo-[DP-FA-CGaa-FF], CGaa = C-glycosylated amino acid cyclo-[ANPNAA-Temp], Temp = diketopiperazine based template T'-bradykinin cyclo-[PFF-Aib-LI2 cyclo-[PGKAK]2 cyclo-[G-DSIP-1, analog of the delta-sleep-inducing peptide cyclo-(SGVARGDVGS-BTD], BTD = dipeptidomimetic residue amyloid P peptide (resid. 25-35) and its N27A analog conantokin-G, paralytic toxin from fish-hunting cone snails processing domain of the pro-ocytocin-neurophysin precursor (resid. 1-20) conantokin-T, paralytic toxin from fish-hunting cone snails buforin 11, antimicrobial peptide C-terminal fragment of the rat angiotensin I1 AT, A receptor (resid. 300-320) p-conotoxin GI I IB magainin 2 receptor binding domain of P . aeruginosa pilin strain P1 (resid.126- 148) [P 7,131 aA-conotoxin Plv* mitochondria1 transit peptide from green alga Chlamydomonas reinhardtii ZF-I, isolated zinc-binding module, complex 1:1 with Zn immunodominant region of protein G of bovine respiratory sync. virus race-specific elicitor AVR9 of the tomato pathogen C.fulvum, a cystine knot de now designed peptide with two distinct, compact P-sheet folds conotoxin GS, sodium channel antagonist from Conus geogruphus PiTX-Ka, selective blocker of A-type potassium channels from P . imperalor Pi 1, potassium channel blocking toxin from the scorpion Pandinus imperator neuropeptide Y, human [15N] headpiece subdomain of chicken villin (resid. 791 -825) CHABI I, two-disulfide derivative of charybdotoxin

b)

a)

Peptides and proteins f o r which 3J('H-'H) couplings have been applied as a structural parameter (continued)

Name

Table 5.1

300

299

29x

29 7

296

295

294

293

292

29 I

2 ~ 0

2XY

2x8

2x7

2x6

28.5

2x4

2x2

2x3

2x2

2x I

2x0

279

27x

277

276

275

274

273

272

Reference

2%

b

?

pheromone Er- 1 1 from ciliated protozoan Euplotes ruikovi N-terminal of HM2, hirudin-like peptide (resid. 1-47) [I 5-N] DNA binding domain of lac repressor headpiece (resid. 1-56) [13C/15N] E-domain of staphylococcal protein A F2, first F2 module from human fibronectin (resid. 315-374) [ 15-N] N-terminal DNA-binding domain of 434 repressor (resid. 1-63) [15-N] [RlOM] mutant of N-terminal DNA-binding domain of 434 repressor LqhaIT, highly insecticidal scorpion a-toxin from L. q. hebraeus HM2, hirudin-like peptide HM2 [N64V+ GI, mutant of hirudin-like peptide [13C/15N] type I11 antifreeze protein [15N] IFl, translation initiation factor from E. coli albolabrin, snake toxin containing RGD sequence [13C/15N] N-terminal SH3 domain of Grb2, complex with SOS peptide MCP-3, CC chemokine monocyte chemoattractant protein 3 [ 15Nl covalently linked pair of calcium-binding egf-like domain [ 13C/15N] IIB domain of glucose transporter of E. coli (resid. 15-92) [ 15N] lipoyl domain of E20 chain of OGDHC of E. coli [ 15N] N-terminal lipoyl domain of E2p of PDHC from A. Vinelandii [C77S]high-potential iron-sulfur protein from C. vinosum, reduced [ I3C/l SN] colicin E9 immunity protein (Im9) cytochrome cg from the green alga Monoraphidium braunii, reduced [ 13C/15N] [C40/82A] barstar [ 13C/15N] P2 protein, comp. of phenol hydroxyl., Pseudomonas sp. CF600 [ 13C/15N] [E41A] regulatory domain of skeletal troponin C, calcium loaded barley lipid-transfer protein, complex with palmitoyl CoA [ 13C/15N]immunoglobulin superfamily module of twitchin from C . eleguns [15-N] apocytochrome bS [13C/15N] non-classical homeodomain from rat LFBl/HNFl transcr. Factor [13C/15N] segment 4 of the rod domain of the g. f. from D . discoideum

Name

65 71 73 74 76 38+39 78 80 80 85 86 89 89 90 90 91 93 98 99 100

64

39 47 56 56 60 63 63 64 64

a)

48 >84 84 >89

> 127

70 72

l3 37 >71 >36 43 >42 >66 46 56 20 > 59

87 90 > 41 >64 > 64 66 >78

70 >42

97 >64 >45

6)

Table 5.1 Peptides and proteins for which 'J('H-'H) couplings have been applied as a structural parameter (continued)

327

326

325

323 324

322

320 32 I

319

31x

3'6 317

315

313 314

312

311

'09 310

30x

302

302

307

306

306

305

304

302 303

30I

Reference

-m 00

110 112 113 114 118 134 146 147 150 76x2 155 159 91 x 2 185 99x2

108

103 105

[ 13C/15N] SH2 domain of growth factor receptor-bound protein 2

ferricytochrome c from horse heart [ 1 5N] starch binding domain of glucoamylase from Aspergillus niger [13C/15N] domain I1 of TFIIS elongation factor (resid. 131-240) thioredoxin h from eukaryotic green alga C . reinhardtii, oxidized [ 15N] qCRP2-(LIM2), (resid. 82- 194) [ 13C/15N] SH2 domain from ~ 5 5 " kinase '~ [ 13C/15N] Fas (Apo- I /CD95) death domain (resid. 202-319) [ 13C/I 5Nj T-ag-OBD I lh(),DNA binding domain of SV40 T-antigen [ 13C/15N] amino-terminal extracellular domain of epithelial cadherin [ 15N] peptide deformylase from E. coli ribonuclease a-sarcin [ I3C/1 5N monocyte chemoattractant protein- I , dimer [ 13C/15N] Cu(I) rusticyanin from Thiobacillus ferrooxidans [ I3C/ I 5N] Bet v 1, major birch pollen allergen from Betula verrucosa [13C/15N] apo-SlOOB(PP), rat [ 13C/15N] interleukin-6, human [ 13C] type I1 DNA-binding protein B. subtilis phage SPOI-encod. dimer

a)

Name

65 > 100 45 84x2 > 173 34 44x2 83 88x2

> 128

> 80 44 17 > 130 58

> 137

58

>76

6)

Table 5.1 Peptides and proteins f o r which 3J('H-' H ) couplings have been applied as a structural parameter (continued)

345

344

343

341 342

340

33x 339

337

334 335

333

332

331

"'

329

328

Reference

!?

-5

2

3

g

9?'

%

E

A, 3

3

k

170

Nuclear Magnetic Resonance

Table 5.2 Nucleosides, nucleotides and oligonucleotides for which 3J(' H-'H) has been used as a structural parameter Name

a)

b) ~

5-cyclohexyL2'deoxyuridine 2',5'-CpA and 3',5'-d(CpA) complexed to RNase A d(CGTACG)Z 16 S-like (GGUG[UGAA]CACC) rRNA UGAA tetraloop

d(GCGAAT-3'-3'-(aT)-5'-5'-CGC)z d(GCATCCTAGC)-d(GCTAGGATGC) complex with calicheamicin y I oligosaccharide domain [~el-'~C RNA ] pseudoknot from mouse mammary tumor virus d(CGTAGGATATCCTACG)2 complex with head-to-head calicheamicin oligosaccharide domain panhandle RNA of influenza virus A

Reference

~~

1

7

2 12 12 20

18 54

20 32

60 128

348

32 34

155 34

362

357 358

354

359 3 60

363

a) number of nucleosides /nucleotides b) number of vicinal couplings measured

Table 5.3 Carbohydrates for which 3J('H-'H) couplings have been used as a structural parameter Name

Reference

0-antigen polysaccharide from the enteroinvasive E. coli 0143 0-antigenic polysaccharide from enteropathogenic E. coli 0 1 25 capsular polysaccharide adjuvant from Klebsiella 1-714 0-antigenic polysaccharide from the enteropathogenic E. cofi 0 142 oligosaccharide from the lipopolysaccharide of A . diazotrophicus strain PAL 5 capsular polysaccharide of Clostridium perfringes Hobbs 5 capsular polysaccharide from Alteromonas nigrifaciens IAM 1301OT 0-specific polysaccharide from lipopolysaccharide of A . calcoaceticus strain 7 4-O-methyl-P-~-glucuronicacid-containing rhamnogalacturonan two mannoamidines lipopolysaccharide (LPS) epitopes expressed by Haemophilus influenzae six ascarosides from Ascaris suum PGM, peptidoglycan monomer from Brevibacterium divaricatum

a) a) 370 a) a) 372 a) 373 a) 36x 369

'" 374

375

376 377

378 379 3x0

a) the 'J('H-I3C) couplings were also measured and used

In their studies on the reverse anomeric effect in N-glycosyloimidazoles Vaino et a ~ , have ~ ~ performed ' an analysis of time averaged 'J('H-*H) couplings for xylopyranosylimidazole and its methylimidazole homologue measured in CDC13. Analysing their data they came to the conclusion that the reverse anomeric effect is the result of small stabilizing intramolecular electrostatic contributions to the 'Cq conformer on N-protonation which will be severely attenuated in solvents more polar than chloroform. 3J('H-'H) couplings have been useful in assigning protons and in determining ring conformation of some alkaloids of the pharmacological importance such as thebaine and its derivatives (free base, hydrochloride, methiodide, and N - o ~ i d e s ) , 'the ~ ~ E and 2 isomers of strychnobrasiline, which belongs to the

5: Applicalions of Spin-Spin Couplings

171

pseudo 'seco' series of Strychnos alkaloids,383 and twelve quinolizidine alkal o i d ~ The . ~ ~tridimensional ~ structure of both conformers of monterine and granjine, antitumor bisbenzylisoquinoline alkaloids, have been calculated by the use of 3J(1H-1H)vicinal couplings.385The structure of myrmicarin 663, a new decacyclic alkaloid from ants, has been established on the basis of 3J('H-'H) couplings.386 Vicinal proton-proton couplings have also been determined for some anti biotics such as anhydroerythromycin A, a degradation product of the macrolide antibiotic erythromycin A.387Proton-proton couplings measured for the antibiotic moenomycin A have been used as an indication that all sugar units in this compound adopt the 4C1 conformation. It is worth mentioning that highly resolved ' H NMR spectra of good quality could be obtained only upon the sonification of a mixture of the compound, water and benzene.388 Structural information has been obtained for kanchanamycins, new polyol macrolide , ~ ~proton-proton ~ couplings antibiotics isolated from Streptomyces o l i v u c e ~ sand have been determined for monoensin, a carboxylic polyether polycyclic antibiotic with ionophoric properties, isolated from Streptomyces strains.390 The temperature dependence of the chemical shifts, S(19F), and the vicinal couplings, 3J(1H-1H),have been studied by Ojima et u1.39',392for fluorine containing analogues of paclitaxel and docetaxel in order to get insight into the conformation of these compounds. The experiments revealed highly dynamic behaviour of the molecules which was recognized in previous studies. A conformational analysis by the use of 3J('H-1H) couplings has been performed for 5a-cholestan-3~-o17 22 unsaturated C27 sterols and their acetate derivatives,393for prednisolone analogue, loteprednol e t a b ~ n a t eand , ~ ~for ~ two new diterpenoids, taxchinins L and M from Tuxus c h i n e n s i ~ . ~ ~ ~ An extensive study on the conformation of flavan-3-01s has been performed by Hemingway and c o - ~ o r k e r sby~ ~the~ ~combined ~~~ use of computational methods and analysis of the NMR parameters. In particular, they analysed solvent and temperature effects on the pyran ring proton couplings in the spectrum of (+)-catechin, the most common member of this group of comp o u n d ~The . ~ ~structure ~ of the covalent dimers of catechin has been elucidated with the help of 3J(1H-1H)couplings. by The effect of p hydrogens on vicinal proton-proton couplings, 3J(1H-'H), has by the use of SCF ab initio and semiempirical been analysed by Fabian et methods. The 3J(H2-H3)couplings determined for benzoquinone oxime derivatives are slightly greater than the 3J(H5-H6) couplings, the difference being usually interpreted in terms of the influence of the nitrogen electron lone pair. However, the recent studies performed by Perrin and Engler400for the parent benzoquinone oxime and some model compounds indicate that rather steric effects should be taken into account in order to explain the difference observed. Conformational studies which included analysis of 3J('H-'H) couplings have been performed by Gurumani et uL401for some 1-hetera-2,6-diphenylcyclohexan4-one oximes, by Hoffmann and Kahrs402for two (1,3-dioxan-4-yl)-methanes, the compounds which contain flexible backbone segments with a marked conforma-

Nuclear Magnetic Resonance

172

tional preference, by Avalos et al.403for three series of simple glycoamidines, and by Grindley et af.404 for highly hindered ethanes, meso- and racemic-2,2,2'2'tetramethyl-1,l '-biindanyls. The configuration and conformation of a series of 2-(acyloxymethy1)-1,3-dioxolanes have been studied by Malmusi et al.405Protonproton couplings have been determined for the cis and trans isomers of 2-iodomethyl-5-hydroxymethyl- 1,4-dioxane and the cis and trans isomers of 2-iodomethyl-6-hydroxymethyl-l,4-dioxane, the products of the reaction of its glycerol with iodine,406 for 5,5-dimethyl-2,3-diphenyl-N-hydroxypyrroline, two analogues and the corresponding nitrones407and for some dialkyl(2,5-dialkyl pirrolidin-2-y1)phosphonates and diethyl(2,5,5-trimethyl pirrolidin-2-y1)phosphonate .408 A full spectral analysis which also included measurements of coupling constants has been performed by Li et al.409for 4-0-tetrahydropyranylepiisopicropodophyllin. The structural dependence of 3J(1H-'H) couplings measured for norbornenes has been studied by Markovik et al.410Vicinal proton-proton couplings have been applied in structural analysis of some 2-aryl-trans-decahydroquinolin-2ones,41 some diastereoisomeric oxaspiro[4.4]nonane derivative^,^' three isomeric norbornanetetrols and one trio1 which are the main products of the performic oxidation of norborn-5-enediol (exo-2-syn-7-bicyclo[2.2.l]hept-5e n e d i ~ l ) ,and ~ ' ~10,l l-dihydro-5,10-ethano-5H-dibenzo[a,~cy~loheptene.~~~ Vicinal H-' H couplings in endo/exo-2,2-dichloro-7-isopropylidene-3-neopentyl-2-silabicyclo[2.2.l]hept-5-ene and E/Z-7,7-dichloro-4-isopropylidene-6neopentyl-7-silabicyclo[3.2.0]hept-2-ene,the products of the reaction between 1,l -dichlor0-2-neopentyl- 1-silene and 1,l-dirnethylpentafulvene, have been analysed by Auner and Heikenwa1der4l5 in order to confirm the structure of these compounds. A conformational analysis of thia crown ether derivatives by the use of NMR parameters including H-'H couplings and molecular mechanics has been performed by Meusinger et af.416The structure of benzimidazole cyanine dyes has been elucidated by the use of 3J('H-1H) couplings.417Proton-proton couplings have also been analysed for a series of E and 2 enamines, R'CH2NHC(C02R2) = CHC02R2.418 Vicinal proton-proton couplings have been determined experimentally in a study on the structure of lasalocid-alkali metal cation complex salts and compared with those resulting from the Monte Carlo simulations and those corresponding to conformations resulting from the PM3 computations in a methanol c ~ n t i n u u m . ~The ' ~ couplings have also been applied in order to characterize the aryl-substituted n-ally1 complexes of Pd(II).420

'

'

8

Three-Bond Couplings Between Hydrogen and Heteronuclei

It is generally assumed that vicinal 'H-I3C couplings follow the Karplus-type relationship by analogy with many other couplings across three bonds. However, the paper published recently by Parella et af.421shows that this relationship is not

5: Applications of Spin-Spin Couplings

173

always valid and the relevant data should be treated with great caution. Vicinal 'H-I3C couplings of ca. 4.5 - 6.5 Hz have been measured by this group of authors for a large series of compounds containing the rigid 'H-C-C = I3C moiety. Generally, no influence of the value of the dihedral angle between the C-H bond and the plane of the double bond on the magnitude of the couplings studied has been observed. A conformational analysis by the use of 3J('H-'3C) data has been performed for (4R,SR)-4,5- bis(alkylcarbamoy1)-1 , 3 - d i o ~ o l a n e sand , ~ ~two ~ 5-methoxy- 1,3dioxanes for which vicinal 'H-'H and 'H-I3C coupling data measured in the gasphase have been analysed and compared with the results of the ab initio MO calculations.423 3J('H-'3C) and 3J('3C-'9F)couplings have been reported for a large series of new trifluoromethyl trisubstituted 0 1 e f i n s . ~The ~ ~ knowledge of 3J(1H-'3C)coupling allows one to establish the relative configuration of the CF3 group and the proton even if only one isomer is available. 3J('H-'3C) couplings are very often applied in signal assignment of the 'H and I3C NMR spectra of complex compounds. 13C NMR spectra of a series of 3,7diazabicyclo[3.3.l]nonaneshave been interpreted by Gogoll et af.425by the use of these couplings and the spectra of three isomeric N-methyldiazabenzene salts by Newmark et af..426Todeschi et al.427have made assignments of the diastereotopic methylene protons in the 'H NMR spectra of five glutamic acid analogues substituted in position-3 or -4 by a methyl or a methylene group. The same couplings along with 3J('H-'H) couplings have been applied to determine rotamer populations in these compounds. 429 A detailed NMR study has been performed by Osborne and his on dimedone-aldehyde adducts. This also included measurements of protoncarbon couplings for dimedone itself and its tautomeric 3J('H-'3C) couplings have been applied to assign the geometry of E / Z isomers of novel conjugated enamines prepared from 9-arylmethyl- or 9-arylpropenyl-9H- carbazole with arylmethyleneaniline~.~~~ 3J('H-13C) couplings have been measured and analysed by Podanyi and M ~ r v a i ~for ~ ' three benzimidazolecarbamates substituted at C5 with the C3H7S(0),,(n = 0, 1,2) group and for a- pinene and trans-chrysantenyl acetate. Inter-chain, 3J('H-C-As-'3C) and intra-chain 3J('H-'3C) couplings have been measured for a series of lewisites including a new isomer cis, trans, trans-y~ewisite.~~~ Sasaki et af.,433,434 have succeeded in determining the structure of maitotoxin, the largest non- biopolymer known to date (M = 3422) and one of the most potent toxins using 273J('H-'3C)and 3J('H-'H) couplings. 2y3J('H-*3C)and 3J('H-'H) couplings have been measured and the latter used in the conformational analysis of a s p e r ~ i n . ~ ~ ' H(N)CA,CO, a sensitive E.COSY-type experiment, has been proposed yielding 3J('H-'3C ) coupling displacement in an indirectly detected I3C dimension allowing the accurate (better than f0.2 Hz) measurement of these couplings in the uniformly 13C,'5N labelled proteins.436 The different magnitudes of 3J('H-'3C)couplings have been observed for syn and anti periplanar arrangement

174

Nuclear Magnetic Resonance

of the side-chain amide protons in l3C/I5N labelled proteins.437This difference allows stereospecific assignment of those protons by the use of HZNCO-E.COSY experiment. Numerical 2D NMR multiplet simulation has been established as a tool for extracting high-precision 3J(1H-13C) and 3J('H-'5N ) couplings;438the couplings obtained by this method have been applied in an exhaustive conformational analysis of antamanide.439 Three-bond heteronuclear couplings yield information on the local conformation of the macromolecule and therefore are complementary to NOE observations which carry information on the overall macromolecule fold. One can observe the continuous efforts in this field of protein research which are illustrated by the data included in Table 5.4. Xu et ~ 1 . ~have ' ~ demonstrated the usefulness of 2J('H-'3C) and 3J(1H-13C) couplings in distinguishing between rigid and flexible oligosaccharides. Lacto-Nfucopentaose served as an example. 3J(1H-1H) and 3J('H-'3C ) couplings have been measured and compared with those predicted in the conformational analysis of four trisaccharides, anionic derivatives of selectins ligands - L ~ " ( G ~ cMore ).~~~ examples are listed in Table 5.5. A b initio calculations have been performed by San Fabian and G ~ i l l e m in e~~~ order to study angular dependence and substituent effects on vicinal protonfluorine couplings in a series of fluoroethanes. The Fermi contact contribution has been found to be the main factor which determines the coupling values. It has been shown by Bratovanov et al.122463 that 3J('H-29Si) couplings in vinylosilanes are significantly larger for the Erans compounds than for the corresponding cis ones, which allows a reliable assignment of the geometry of the double CC bond in spite of the fact that the ranges of these couplings overlap. Vicinal 'H-C-N-31P couplings, 3J(1H-31P)= 11.5 Hz, have been measured in derivatives of 1,5-dimethy1-2,3,3,4-tetrachloro1,5,2,4-diazadiphosphorinan-6one obtained in the reaction of this compound with catechol, 2,3-dihydroxynaphthalene, tetrabromocatechol, I ,2,4,5-tetrahydroxybenzene and hydroq~inone.~~~ 3J('H-31P)and 3J('H-13C)couplings have proved to be an efficient probe for the backbone torsion angles and y in nucleic a ~ i d s .Table ~ ~ 5.6 ~ ,enumerates ~ ~ ~ several oligonucleotides whose structures have been studied with the help of heteronuclear vicinal couplings. 3 ~ ( 1 ~ ~ 1 0 7 /g)1 0couplings 9~ of ca. 8 Hz have been observed by Drew et ~ 1 . in~ ~ ' the spectra of two disilver cryptates of the thiophene-spaced azacryptand hexa Schiff bases N[(CH2),N = CHRHC = N(CH2),]3N (n = 2 or 3, R = thiophene2,Sdiyl). A study performed by Zamora et al.482on (1,3-dimethyluraci1-5-yl)mercury(II) derivatives revealed that 3J(1H6-'99Hg)couplings strongly depend on the nature of the donor atom attached to the mercury atom; the largest vicinal coupling of 222 Hz has been found for (1 ,3-(CH&U-C5)HgNO3, the smallest one, of 107 Hz, for (1 ,3-(CH3)2UC5)2Hg.

a) b) c) d)

5 8 60 66 73 76 81 104 135 147 147 154 152

three [~(~)-C~,~(~)-C']enkephahns S-deoxo-Xaa3-amaninamide, three analogues [ 15N] [C58S] pNR-2/pS2, human [13C/15NJMoMODI-N (resid. 15-80) [13C/15N] high-potential sulfur protein I from E . halophila [ 15N] ribosomal protein L11 -C76 [13C/15N] SH3 domain of human p56 Lck tyrosine kinase [13C/15N] ribonuclease TI [13C/15N] P14a, pathogenesis related protein [ I3C/15N] flavodoxin from Desulfovibrio vulgaris, oxidized [ 13C/15N] flavodoxin from Desulfovibrio vulgaris, oxidized [ 13C/I 5N] FGF-2, basic fibroblast growth factor, human [ 13C/15NJ N-terminal cellulose-binding domain of C.Jimi CenC [ 13C/15N] transforming growth factor b1, homodimer [2H/13C/15N] EIN of of the E. coli PEP, sugar PTS 42 > 137 >37 161 > 75 160 493 349 > 109 103 d) >329 195 162 x 2 > 163

b)

'~cc

J H N I 3JCC

450

436

449

44x

447

446

445

443 444

442

45 I Jcc, 'JcN 3JHc, :JHN, 'Jcc, 3 J ~ N 4452 53 'JJCC, JCN

:HCI

'JHc :JHc

JHC, 3 J ~ ~ , JHN,

JHC, 'JHN

J H C , :JHN

JHN,

' 'JHC, JCC,~ J C N ' 'Jcc ' '~cc

JHC 'JHN

44 I

440

1

3

JHC, J H N

Reference

c)

number of residues total number of vicinal couplings measured (homonuclear .J H-IH) couplings are also included) -4 H - 1 5 N ) , l'JcC = "J(13C-13C), IIJCN = "J(I3C-I5N) types of cou lings measured, "JHC= "J('H-"C ), ''JHN = "J( PC ) couplings were measured only 3J(1H-1

259

112 x 2

a)

calculations

Peptides and proteins f o r which heteronuclear vicinal couplings have been used as a structural parameter in 3 0 structure

Name

Table 5.4

?

4 5.

9

?

g

s

5

2.

$

+k

=

2 nx7 13 nx5 nx6 n x 10

a-(1+2) and a-( 1'3) linked rhamnose oligosaccharides [ 13C] cell wall polysaccharide of Streptococcus mitis 522 [ 1 3C] osmoregulated periplasmic glucan of Burkholderia solanacearum GBSP 111, capsular polysaccharide from the type 111 group B Streptococcus phosphomannan core of exopolysaccharide of Pichia holstii NRRL Y-2448 backbone of lipopolysaccharide from Acinefobacter strain ATCC 17905

a) number of units, if n is present number of units in one repeat b) number of vicinal heteronuclear couplings measured c) type of vicinal heteronuclear couplings measured, 3 J H = ~ 'J('H-"C), 3JHp = 3J('H-3'P)," J c p

a)

"J('3C-31P)

2 12 20 8 6

b)

c)

Carbohydrates f o r which heteronuclear vicinal couplings have been used as a structural parameter

Name

Table 5.5

46 I

460

459

4%

451

456

Reference

m 4

-

32 >45 154 > 92 42

24 27 29 30+16

JHP

JHP

JHP,

JCP

JHC,'Jcp "'JH~

~

3JHI.

3

JCP ?JHP

'J H P

a) number of nucleosides/nucleotides b) total number of vicinal couplings measured including homonuclear 'J('H-'H) couplin s c) types of vicinal heteronuclear couplings measured . "JHc = "J(1H-'3C),"JHp = I1J(IH-$1P),'lJCc = "J(13C-1'C),IIJcI,= "J(13C-31P)

21

56 98 '52

JHP

54

3JHP

3JHP

'J H P

3JHP

'J H P

~~~~~

1.2.3JHc, 1.2.3 Jcc "'JH~

c)

44

51 38 21 82

ca. 30

1 11 12 15 16 16 16 16 16 16 16 19

ten [2'-' 3C]2'-deoxyribonucleosides d(GTAC[AAA]GTAC), hairpin r(GGC[GUAAUA]GCC) with hairpin loop [ 13C/15N]r(GGGC[GAGA]GCCUUAU), hairpin 5'-GCCUAG[CAAC]CUGGGC, T4 RNA hairpin mutant d(CTTCGAAG)2, CpG containing duplex d(CGGATCCG)2, complex with esperamicin A I r(GAG[GU/CUC)2 with GU mismatch r(GCG[GA]CGC)2 r(GGC[AG/GCC)2 d(ATCCTA-GTTA-TAGGAT), hairpin topoisomerase I1 site DNA strand, hairpin analog of anticodon loop of yeast tRNAIMC' hairpin corresponding to nt 1057-1081 of large subunit rRNA with UU mismatch [13C]site A of Exoli 16s ribosomal RNA, complex with paromomycin [13C/15N] HIV-1 TAR RNA, free DNA containing CCCG tetraloop and 16 nt DNA

b)

a)

Name

~~~~~

z

474

480

479

478

477

476

47s

4

c

2 472 473

G3

9

e3-

9. ?.

%

$

%-

?

470 47 I

46X 405,

467

466

465

I IX

Reference

Table 5.6 Nucleosides, nucleotides and oligonucleotides j o r which heteronuclear vicinal couplings have been used as a structural parameter

Nuclear Magnetic Resonance

178

9

Three-Bond Couplings Not Involving Hydrogen

3J(1'B-119Sn) couplings of 68 Hz and 65 Hz have been observed by Wrackmeyer et in the lI9Sn CPMAS NMR spectrum of 2'-bora-2'-isobutyl-l -stannaspiro[hexane-l,5'-tricycl0[6.3.3.0~'.~']tetradeca-3',6'diene. This indicates the presence of two conformational species in the solid state, a result different from that obtained from the single-crystal X-ray analysis. It is worth mentioning that this is the second example of a 3J(11B-"9Sn)coupling measured in the solid-state l19Sn CPMAS NMR spectra; the coupling is not observed in solution. A new experiment, an 'out and back' type quantitative HN(CO)CAC,li which allows one to determine 3J('3C-'3C) couplings between C, and aliphatic carbon atoms in perdeuterated proteins, has been designed by Hennig el and used to measure the couplings for the calmoduline residues. The (R,R)bis(tetrahydropyran-2-yl)methane can exist in the form of two conformers shown below in Fig. 5.4.

b

a

Figure 5.4

Temperature dependent measurements of the vicinal H-'H couplings performed for this compound by Hoffmann et af.485have indicated that it exists mainly in form a and only a small admixture of form b is present. This conclusion is in agreement with the observed 3J('3C-'3C) coupling of 3.4 Hz which is similar to the trans couplings found in some cyclohexane derivatives. A spin-echo difference HSQC-type experiment has been developed for the measurement of 3J(13C-'3C)and 3J('3C-15N)couplings important in determining the side-chain conformation in 13C,15Nlabelled proteins.486 With the help of 3J(l3C-I3C) couplings leucine side-chain rotamers have been revealed in a glycophorin A transmembrane ~ e p t i d e The . ~ ~ cross-peak ~ to diagonal-peak intensity ratio in (HN)CO(CO)NH spectrum has been used for an accurate 3C') coupling in 13C enriched proteins.488 The experimeasurement of a 3J(13C'-' ment was demonstrated for ubiquitin and HIV-1 Nef. Vicinal l3C-I3C couplings have been applied in studying a conformation of open chain compounds such as model 3,5-dimethylhexen-6-01, HOCH2CH(CH3)CH2CH(CH3)CH= CH2. The couplings for this compound have been calculated by a density functional (SOS-DFPT/IGLO) method and their Boltzmann averaging for individual conformers compared with the experimental data. A good agreement between these two sets of data has been observed .489

5: Applications of Spin-Spin Couplings

179

A conformational analysis of (2-hydroxypenty1)diphenylphosphine oxide and its acetate based on vicinal 3J(13C-3'P) and 3J('H-!H) couplings has been ' influence of the polarity of the performed by Genov et ~ 1 . ~A~ substantial medium on the magnitude of all the couplings measured has been observed for both compounds studied. New examples of 3J('3C-'19Sn)couplings have been published which indicate that the Karplus-type relationship is followed by this parameter. The compounds studied were di(-)menthyldimethyltin, di(-)menthyldiphenyltin, tri(-)menthyitin chloride and tri(-)menthyltin h ~ d r i d e . ~ ~ ' Lopez-Ortiz and c o - ~ o r k e r shave ~ ~ ~continued their study on l5N and 31P NMR of cyclotriphosphazenes by the use of 15N,31PHMQC correlations. This yielded not only one-bond 'sN-31Pcouplings but in two cases three-bond ones of ca. 1 Hz could be observed. The two trifluoromethyl groups in Ph(C6FS)PC(CF3)20H, due to the asymmetry of the phosphorus atom, are magnetically non-equivalent and, as a consequence, two significantly different 3J('9F-31P)couplings, 15.9 and 23.8 Hz, have been determined from the higher order I9F and 31PNMR spectra of this compound.493

10

Couplings Over More Than Three Bonds and Through Space

The conformations of dibenz[b.fJ[1.4loxazepine and 2-chlorobenzylidene malononitrile, representatives of tear gases, have been established on the basis of four(a,ortho), five- (a,rneta) and six-bond (a,para) proton-proton couplings.494 A detailed analysis of the 'H NMR spectra of trans- and cis-3a,4,5,6tetrahydro-6-phenyl-3H-cyclopenta[c]isoxazolesand trans- and cis-3,3a,4,5,6,7 hexahydro-7-phenylcyclohexa[c]isoxazolesperformed by Namboothiri et al.495 has yielded all possible 'H-'H couplings including those across four bonds. In particular, those between the hydrogen atoms attached to the carbons a to an sp2 centre provide new examples of this rather scarcely reported in the literature parameter. However, the authors emphasized that the spin-spin coupling data were not particularly informative as far as the conformation of the compounds studied was concerned. A full spectral analysis of the 'H NMR spectra has been performed by Rittner et al.496 for variously 3-monosubstituted 2-methylpropenes yielding the fourbond 'H-'H couplings. Generally, all coupling values are small and cover the range of 0.6 to 2.5 Hz. The four-bond 'W' couplings have been determined for lloctanes obtained from methylglyoxal in several 3,6-dioxa-8-azabicyclo[3.2. [tris(hydroxymethyl)aminomethane] buffer and compared with the four-bond couplings in cocaine, allococaine and morpholine .497 A homoallylic coupling 'J('H-'H) is always of great value in the assignment of the signals in the spectra of the studied compounds. It has been observed by in the spectra of dimedone-aldehyde adducts which allowed the Cremlyn et authors to assign the relevant signals unambiguously. An analysis of 'J('H-'H) Couplings along with that of NOE effects and I3C chemical shifts allowed Lunazzi

180

Nuclear Magnetic Resonance

et a/.498to assign the structures of rotational isomers in furan and thiophene o-amino thioaldehydes and aldehydes. A set of long-range 'H-'H couplings have been measured for several N,N'-dipyridyl ureas, the compounds which can be used as model systems for polypeptides and proteins,499 and for two azo dyes which can undergo azo-hydrazone t a u t o m e r i ~ m . ~ ~ ~ Couplings across seven bonds have been observed between the H-3 and H-7 protons in the 'H NMR spectra of flavone and 6-hydroxyflavone (0.27 and 0.52 HZ, respective~y).~~ Theoretical and experimental studies on the small internal potentials in various aromatic compounds by the use of long-range couplings have been continued by Schaefer and his group. One paper published has been devoted to benzal fl~oride.~"In another paper of this group of authors an analysis of the very subtle isotopic 35/37C1effects on the 19F NMR spectrum of 1-chloro-2,4-difluorobenzene has been performed502 yielding not only the isotope shifts of the "F NMR signals but also very precise "J('H-'H) and "J('H-I9F) coupling values (n = 4, 5 ) including their signs. It is of interest to note that the coupling values could be extracted from the 'H NMR, i.e. the X part, of the spectrum only. Long-range 'H-19F couplings, 'J('H-19F), of a relatively large value ca. 3 Hz, have been measured in the spectra of substituted azulenes whereas, surprisingly enough, those across three bonds have not been observed; a set of "J(13C-19F) couplings, n = 1 to 5, has been reported for the same group of compounds.503A conformational analysis has been performed by Barchi et ~ 1 . ~for' ~the complete series of 2' and 3' monofluorinated dideoxyuridines. Through space, long-range 'H-19F couplings have been observed for those compounds in which the fluorine atom was above the plane of the ring. The allylic-type 1H-31Pcoupling across four bonds of a positive sign has been reported for 6-p-tolyl and 6-cyclohexyl derivatives of methyl 5-[benzoylimino(diphenyl)-h5-phosphanyl]-2-oxo-2,3-dihydropyridine-4-carboxylates; 4J( H-31P) = + 2.5 and + 2.8 Hz, re~pectively.~'~ Very large 4J('H-' 17/'19Sn) and 4J('H-207Pb)couplings of the imine protons in the spectra of some novel inorganohave been observed by Aarnts et metallic complexes, Ru(E)(E')(CO),(i-Pr-DAB), where E represents a SnPh3 or PbPh3 group and E' = GePh3, SnR3 or PbR3 (R = Ph, Me) depending on E and i-Pr-DAB = N,N-diisopropyl- 1,4-diaza- 1,3-butadiene. This result was explained by the authors in terms of a delocalizaton of the charge over the axial ER3 group. The 'H-'99Hg couplings across four bonds can reach quite large values; for example, in some charged acetone derivatives they vary from 30 to 50 Hz. Somewhat smaller 4J('H-'99Hg)values, of 20 Hz only, have been observed for diand trimercurated derivatives of acetone, CH3COCH(HgC1)2 and CH3COC(HgC1)3.S07 New examples of through-space l3C-I9F spin-spin interaction have been recently reported. A 13C-'9Fcoupling of 6.2 Hz has been found by Sakharov et al.227 between the carbon of the trans methyl group and one of the fluorine ligands of (q2-acetone phenylhydrazonato)tetrafluorooxotungsten(VI). A I3C-l9F coupling of 5.5 Hz has been observed by Jones el dSo8 in the spectrum of 9,10,11,12-tetrafluoro-5,6-dihydrobenzo[b]naphth[2.l-~oxepinbetween the C1

5: Applications of Spin-Spin Couplings

181

and the F12 atoms; the through-space mechanism has been invoked by the authors to explain its magnitude. The 13C-19F couplings across formally six bonds of ca. 6 Hz have been observed in the spectra of a new class of synthetic fluorinated nucleosides, 2',3'-dideoxy-4'-fluoroalkylthymidineand 2',3'-dideoxy4'-fluoroalkylfluorouridine. Their magnitude as well as the magnitude of the 7J('H-'9F) coupling significantly depends upon the solvent in which the spectra are measured. This result has been invoked by the authors as evidence that the couplings observed are transferred through space."' Studies on determination of absolute signs of a variety of couplings have been continued by Wrackmeyer and his group. The compounds studied were 2,5dihydro-l,2,5-phosphasilaborolederivatives for which 1J(29Si-31P),2J(31P-31P), nJ('3C-31P),n = 1, 2, 3, and nJ(1H-31P),n = 2, 3, 4,have been measured,510and some new phosphabenzenes obtained by [4 + 21 cycloaddition of stannoles to 1-phospha-1-alkynes for which nJ(13C-31P),2J(29Si-31P),2J(31P-'19Sn) and nJ(1H-31P)have been dete~mined.~'Further examples include 2-trimethylsilyl(trimethy1~tannyl)methylpyridine~'~ and some cyclic organotin compounds5' for couplings , n = 2 to 5 , which absolute signs of nJ(13C-1'9Sn)and n+1J(1H-'19Sn) have been determined.

Figure 5.5

-

J( 15N 77Se) couplings across formally four bonds have been observed by Iwaoka and Tomoda514 in a series of 2-selenobenzylamine derivatives (see Fig. 5.5). The coupling values are very large and vary from 13.0 to 59.3 Hz. This indicates that the direct N*..Se interaction takes place in the compounds studied, the magnitude of the coupling increasing with the increase of the N Se bond order.

---

88

RRS(SS R) 7~(31p,31p)= 17 HZ

Figure 5.6

182

Nuclear Magnetic Resonance

A seven-bond 31P-31Pcoupling of 17 Hz has been observed in 31P NMR spectrum of R R S ( S S R ) diphosphite of 1,l’-bi-2-naphthol (see Fig. 5.6).Is5

11 1 2 3

4 5

6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35

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T. Schaefer, G. M. Bernard, Y . Bekkali and D. M. McKinnon, Can. J. Chem., 1996, 74, 1626. T. Schaefer, G. M. Bernard and F. E. Hruska, Can. J. Chem., 1996,74, 1810. T. Ueno, H. Toda, M. Yasunami and M. Yoshifuji, Bull. Chem. SOC.Japan, 1996, 69, 1645. J. Barchi JJ, L . 4 . Jeong, M. A. Siddiqui and V. E. Marquez, J. Biochem. Biophys. Method$, 1997,34, 1 1. E. Pelaez-Arango and F. Lopez-Ortiz, J . Chem. SOC.,Perkin Trans. I , 1996, 1481. M. P. Aarnts, D. J. Stufkens, A. Oskam, J. Fraanje and K. Goubitz, Inorg. Chim. Acta, 1997,256,93. Z. Popovii, B. Korpar-eolig, D. Matkovik-ealogovik, D. Vikik-Topii and M . Sikirica, Main Group Chem., 1996, 1, 373. C. R. Jones, J. J. Parlow and D. M. Schnur, J . Heterocyclic Chem., 1996,33, 1835. A. Mele, G. Salani, F. Viani and P. Bravo, Magn. Reson. Chem., 1997,35, 168. B. Wrackmeyer, G. Kehr, R. Koster and G. Seidel, Magn. Reson. Chem., 1996, 34, 625. B.,Wrackmeyer and U. Klaus, J . Organomet. Chem., 1996,520,211. B. Wrackmeyer, G. Kehr, H. Zhou and S. Ali, Magn. Reson. Chem., 1996,34,921. B. Wrackmeyer and U. Klaus, GIT Labor-Fachz, 1997,41,273. M. Iwaoka and S. Tomoda, J. Am. Chem. SOC.,1996,118,8077.

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6 Nuclear Spin Relaxation in Liquids and Gases BY R. LUDWIG

Introduction

1

The aim of this report is to cover the progress of work in the field of magnetic relaxation and self-diffusion in liquids and gases over a period of twelve months from June 1996 to May 1997, and is a continuation of the report from last year given by H. Weingartner.' As in previous periods, this review is limited to work on comparatively simple liquids and solutions of physico-chemical and chemical interest, as publications in the field of macromolecules and biological chemistry are covered elsewhere in this volume. Of course, such a distinction is sometimes problematic, as innovative work dealing with solutions of complex molecules may be of interest for research in the field covered here. Thus, at the risk of duplication, some interesting studies dealing with more complex systems are mentioned briefly. At the beginning of this chapter it is convenient to quote some authoritative reviews in the subject area. More specialized reviews will be discussed in the corresponding subsections. Also, some important general trends are briefly highlighted here. Details will be discussed later in this chapter. A nice review has been written by D. E. Woessner2 about Brownian motion and its effects in NMR chemical exchange and relaxation in liquids. Mo and Pochapsky3 have summarized the nuclear Overhauser effect as a powerful method for identifying structural features of organic compounds and determining secondary and tertiary structures of biological macromolecules. 'H NMR dipolar relaxation times and the derivation of internuclear distances have been discussed by Liu and L i n d ~ nHills' . ~ reviewed analysis and interpretation of NMR water proton relaxation data. NMR studies of the structure and dynamics of carbohydrates in aqueous solution have been summarized by van Halbeek and Sheng.6 Desvaux and Berthault7 have reviewed contributions to structural and dynamic studies in liquid state NMR using off-resonance rf-simulation. Gerothanassis and Tsamaktsides' gave a general overview about phenomena of nuclear electric quadrupole relaxation. Recent developments in high pressure high resolution NMR in liquids have been reported by Liidemann.' A book written by Bertini and Luchinat" provides a comprehensive survey of NMR methods for studying paramagnetic substances. From studies of dynamical processes which continue to be the major topic in ~

~ _ _ _ _

~~

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Nuclear Magnetic Resonance, Volume 27 0The Royal Society of Chemistry 1998 199

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the field under review, work on magnetic relaxation and self-diffusion over wide ranges of temperature and pressure may be singled out for special mention. Measurements at low temperatures yield a wealth of information beyond the extreme-narrowing regime and near the glass transition temperature. Magnetic relaxation and self-diffusion studies have contributed much to the current understanding of slow motional processes in the glass transition regime. Now, a concise picture of slow motions near the glass transition can be developed." l 3 Studies near the glass transition temperature require the application of sophisticated 1D and 2D techniques which are often adopted from solid-state spectroscopy. l 4 The applications of relaxation and self-diffusion techniques to solution systems are worthwhile to note. First, nonpolar solutes such as noble gases15 or benzeneI6 are used as sensitive probes for studying the role of water near apolar residues in larger molecules. Translational and rotational motions of water in solution can now be investigated with inireased experimental accuracy, thus allowing greater discrimination of subtle effects. Second, a combination of dipolar- and quadrupolar-relaxation-time experiments allows the determination of 2H, 14N and 170nuclear quadrupole coupling constants (NQCC) in the liquid In hydrogen-bonded systems, both these NQCC's and chemical shifts may depend largely on temperature, pressure and the molecular environment of the probe molecule. The results are particularly exciting, as accurate quantum-mechanical calculations of electric-field gradients and chemical shifts can now be carried out for quite complex systems. Theoretical calculations of these hydrogen-bond-sensitive properties can be performed on molecular clusters. In one method, clusters from molecular dynamics studies representing snapshots of the liquid structure are c h o ~ e n . ' In ~ ~another '~ method, ab initio-optimized molecular clusters are used in combination with a quantum statistical model to mimic the temperature-dependence behavior of quadrupole coupling constants and chemical shifts.20321 With many spectrometers now being routinely equipped with gradient coils for generating field gradients, the number of self-diffusion experiments in liquids and solution is steadily increasing. Recently developed new experimental techniques offer an interesting fresh perspective for studying very slow diffusion processes in all kinds of systems such as glasses, porous materials or biological structures. 11712.22 These experimental techniques are based on the use of the stray field of cryo-magnets to achieve large magnetic field gradients which enable the observation of very slow motions. Radiation-damping effects are still of interest. They arise from the influence of the bulk magnetization of the whole sample on the individual spins, and is favoured by high-Q coil arrangements. Radiationdamping effects were recognized in the early days of NMR,23but were generally considered as minor nuisances. With increasing magnetic field strength and increasing number of 'H NMR studies in protonated solvents, this effect is attracting renewed attention.24Ball et analyzed radiation damping artifacts in 2D COSY NMR experiments. Magnetic field gradient and e-switching field were used to minimize radiation-damping effects. The remaining multiplequantum (MQ) like artifacts in the indirectly t(1) domain could be referred to radiation-damping in the t(2) domain. This findings could be proven experimen-

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tally as well as theoretically with the modified radiation-damping theory of Vlassenbroek.26 In a simple COSY experiment, both radiation-damping and 'dipolar field' may occur as collective effects. These effects may act separately or together. Broekaert et proposed a scheme where both radiation-damping and dipolar-field effects can be suppressed. Simultaneous suppression of the water double-quantum signal and of the radiation-damping effect in doublequantum experiments is also proposed by Dalvit et aL2' Methods of reducing radiation damping during free induction decay are examined. Guo et al.29 demonstrated that half-frequency-spaced harmonic peaks in two-dimensional J-resolved NMR spectra of liquid water are induced by radiation damping. Experimental results have been exactly simulated based on the radiation-damping lineshape theory. In another study dealing with suppression of solvent water peaks in biological samples, Chen et expressed the dynamics of water magnetization under R F irradiation by the radiation-damping-modified Bloch equations.

2

General, Physical and Experimental Aspects of Nuclear Spin Relaxation

2.1 General Aspects - Sometimes well-accepted frameworks of NMR are found to be flawed. Warren and c o - w o r k e r ~ ~experimentally '.~~ observed anomolous intermolecular cross-peaks in two-dimensional solution NMR spectra. Resonances in the indirectly detected dimension as obtained with extremely simple pulse sequences on very simple samples, were simply impossible to explain with the conventional density matrix framework. Their revised density matrix treatment explicitly removes two fundamental assumption of the standard treatment. It includes the dipolar interaction between spins in solution and completely removes the high temperature approximation. The quantum treatment was compared to a corrected classical model and it was demonstrated that a combination of both pictures provides better predictive power as well as computational convenience. 2.2 Experimental Aspects - Accurate decay rate measurements for longitudinal and transversal modes are essential for many methods proposed for investigating molecular dynamics by NMR. Therefore, several papers deal with methods aimed at improving the accuracy and efficiency of relaxation time measurements. Jones et al.33 showed how Cramer-Rao theory may be used to determine the optimal sampling pattern for measuring the NMR spin-lattice and spin-spin relaxation times, TI and T2. present a method, based on the application of a constant Czisch et gradient field during the CPMG pulse sequence, which removes systematic errors in T2 measurements caused by off resonance effects. This improvement becomes important in protein NMR measuring "N and 13CT2 relaxation. In particular, cross-relaxation effects make it impossible to determine accurate values for longitudinal modes. N o r w 0 0 d ~proposed ~ a method that unables those effects to be largely eliminated and improves simultaneously the robustness of

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experiments to short (i.e. < 5 T I ) relaxation times. The same author also discussed a method which suppresses cross-relaxation effects in 'H relaxation measurement^.^^ For proton relaxation general expressions for all elements of the dipolar relaxation matrix are derived.37 The method is based on possible isolation of the mutual relaxation of an arbitrary pair or restricted set of spins from all other interactions. In biological systems it is highly desirable to distinguish between intracellular and extracellular sodium contents. Jung et al.38 used multiple-quantum filtering to obtain mono-exponential transverse relaxation of single-quantum coherences. A pulse sequence that accelerates the relaxation of sensitive nuclei through inverse polarization transfer from insensitive nuclei that have been subject to NOE during their detection is proposed by Homer et al.39 New pulse sequence for the direct measurement of heteronuclear cross~ ~ pulse , ~ ~ sequence uses proton relaxation is presented by Allard et ~ 7 1 . The detection of transient carbon magnetization with sensitivity-enhanced transfer of magnetization and pulsed-field gradients for coherence selection and water suppression. It is tested on a peptide with a selectively 13C-labeled a-carbon. The results agreed well with those obtained from the steady-state NOE and carbon longitudinal-relaxation rate. A new 300 MHz high-resolution, high-pressure NMR probe which operates in the pressure range of 100 to 900 MPa at temperatures of 243 to 373 K is described by Ballard et al.42 The potential biochemical applications of this probe are illustrated. Matenaar et al. designed a probe for measurements up to 200 MPa and 673 K for alkali ions in molten salts.43 described the design and construction of a single-coil, twoTonthat et channel probe for detection of low-field magnetic resonance using dynamic nuclear polarization (DNP). Measuring the D N P of protons in a manganese (11) chloride solution at 2.7 mT the signal amplitude was enhanced by a factor of a bout 200. A comparatively new development concerns NMR experiments in the presence of an electric current within the sample. Since 1980 the basis for such techniques has been systematically i n ~ e s t i g a t e dand ~ ~ experiments of this type have now been termed DCNMR (direct current NMR).46 Among the various possible experiments based on DCNMR, the determination of mobilities of charged particles appears to offer the most interesting perspectives, and in the earlier review periods sophisticated 1D techniques, termed electrophoretic NMR (ENMR)47 or magnetic resonance electrophoresis (MREP)48 have been developed. Holz and co-workers demonstrated that in the complex NMR spectrum of a multicomponent liquid 'mixture, the resonance lines of charged species can be filtered. In addition, the practicability of 13CENMR is shown.49

2.3 Relaxation in Coupled Spin Systems - For the description of motional processes, coupled nuclear magnetic relaxation is a well established method. The analysis of relaxation in coupled spin-systems is usually performed by a magnetization-mode formalism. BrUschweilerso has now investigated three-spin interactions in liquid-state NMR. The imaginary part of the magnetic dipolar cross-correlation spectral density generates terms which would not be explained

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by scalar J-coupling and chemical shifts. Thus the widely used liquid-state Hamiltonian needs modification. Meersmann and Bodenhausen observed relaxation-induced oscillations of spin-echo envelopes in scalar-coupled spin ~ y s t e m s . ~For ' strong second-order ~ curious effects when scalar coupling in the isotropic phase, Huth et ~ 1 . 'noticed applying selective pulses. Cross-correlation-induced J-coupling was studied by Brii~chweiler.~~ Dipolar and chemical shielding anisotropy cross-correlation leads to an additive contribution to the apparent scalar coupling constant, J. The effect of adiabatic double-resonance excitation on the indirect spin-spin coupling spectra of a liquid-like spin system is discussed by Capuani et ~ 7 1 . ~ ~ Canet and c o - ~ o r k e r spresented ~~ an analytical solution to the Solomon equations in three-spin groupings. The efficiency of the method is illustrated by the fit of experimental data, exhibiting an unusual evolution due to both intraand intermolecular dipolar couplings. The weak coupling in spin 1/2 systems of the type AX and AX2 can be used to investigate translational diffusion proce~ses.~~ Hughes and co-workerss7 examined Soerensen's 'universal bound on spin dynamics' in respect to the design of novel multiple-pulse NMR experiments. For weakly J-coupled and quadrupolar-coupled spin I = 1 and I = 3/2 systems it could be shown that the most commonly used NMR pulse sequences fail to achieve the maximum coherence transfer efficiency. Considerable attention over the years has focused on the development of techniques for heteronuclear spin decoupling in liquid-state NMR experiments. Geen and Boehlen" presented a novel kind of decoupling scheme which uses a single, inherently cyclic, amplitude-modulated pulse in place of the train of inversion pulses used more routinely. Further contributions in the field of coupled spin systems deal with '70-decoupled proton NMR,s9 double-quantum spectroscopy of two-spin-I AX systems,60 its application for inadequate spectra6' cross-correlation effects, in proton relaxation and magnetic field dependence of nitrogenproton J-splittings in p r o t e i d 3 as well as the influence of scalar-coupled deuterium upon relaxation of "N and its possible exploitation as a probe for side-chain interactions in proteins. 2.4 Dipolar Couplings and Distance Information - Con formational analyses of large molecules of biological interest takes in a large volume of the literature. Many aspects of these studies are relevant for the low-molecular weight systems. A nice example is the study of Liu and Lindon4 on 7-azaindole. In general, molecular geometries can be derived by cross-relaxation rates that depend on the internuclear distance. Usually, two routine types of experiments are used to determine macromolecular structures: NOESY64 investigates the longitudinal cross correlation, while ROESY65makes use of the cross-relaxation of transverse magnetization spin-locked to a strong r.f. field close to resonance. An important aspect of ROESY is that crosspeak intensity increases monotonically with correlation time. The weak r.f. field guarantees the extreme narrowing limit (oz,< < 1) for all values of z, and o of practical interest; unlike

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NOESY, therefore, crosspeak intensities will not tend to zero when wz, M 1, which often appears to be the case at high fields for small molecules. A second advantage is that NOE’s generated in a linear chain of spins alternate in sign which makes it possible to distinguish whether a weak ROE crosspeak derives from transfer via an intermediate spin, chemical exchange or is an authentic longrange ROE. In conventional NOESY spectra of larger molecules, all crosspeaks ate of the same sign regardless of the presence of ‘spin-diffusion’ or chemical exchange. The advantages of the off-resonance ROESY sequence are reviewed by Desvaux and Berthault.’ Several experiments have been described for structural and dynamic studies of biomolecules in the liquid state including the problem of internal dynamics. Shukla66 compared longitudinal and transverse magnetization transfer methods for a two-spin system representative of a methylene group exchanging between two chemically distinct sites. In particular, problems with the standard version of ROESY such as the influence of frequency-offsets on the relaxation rates are discussed which comprises either exchange rate determination or . ~ ~a treatment of intermolecular distance estimation. Ammalathi et ~ 1 presented data collection in a ROESY spectrum for interpretation-distance measurements. The intensity-ratio method is used in which correction factors due to the spinlock pulse offset were included. Cain et uf.68extracted quantitative information from two- and three-dimensional NOE spectra measured with short recycle delays. . ~ ~ a flexible program for the quantitative analysis of Gorler et ~ 1 introduced NOESY systems. Their program RELAX allows the simultaneous application of different modes describing the internal and overall motion of the molecule for individual spin pairs or group of spins. Mo and Pochapsky3 reviewed the determination of intermolecular interactions characterized by nuclear Overhauser effects. Combined selective and biselective pulses are used to invert single resonances together with nonselective pulses by Liu and L i n d ~ nThe . ~ distances obtained from such inversion recovery relaxation rate measurements are compared with values measured from nuclear Overhauser effect build-up rates. 2.5 Exchange Spectroscopy - Bain and Duns” presented a general theory of the effects of exchange and molecular dynamics on NMR spectra. The classical expression for this is as the square of the transition moment which the authors proposed to separate in two single terms. One term corresponds to the share of the initial magnetization that each spin coherence possesses at the start of the experiment. The second term describes how much that coherence contributes to the total detected signal. This general theory is illustrated for the case of mutual exchange in an AB spin system. Several papers have dealt with strategies and methodologies for data evaluation in exchange studies. Bryant and co-workers7’ investigated magnetic cross-relaxation and chemical exchange between microporous solid and mobile liquid phases. The NMR spinlattice relaxation rates are reported as a function of magnetic field strength, pH, and temperature. The exchange is explained by a two-stage process where the

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20 5

water proton exchange with the solid spin system is faster than the one with the bulk water phase. The spin-lock saturation transfer experiment was once introduced by Adams and Lerner.72L e i j ~ n ' sanalysis ~~ in terms of the Bloch equations has shown that the TI relaxation of the solvent is introduced in the decay of the exchangeable protons under conditions of relatively rapid exchange. An alternative experiment is proposed which yields a mono-exponential intensity decay for the exchanging protons at all exchange rates. The role of water exchange is studied extensively for gadolinium-, iridium and chromium-complexes.74-77 Some of these complexes present a new class of potential MRT contrast agents. As a consequence of slow rotation, the proton relaxivity of dendrimer complexes are considerably greater than those of smaller complexes. The importance of water interactions with proteins and peptides has been widely recognized. With the introduction of pulsed field gradients (PFG) in high resolution NMR, it is now possible to better quantify exchange m e ~ h a n i s m . ~ ~ , ~ ~ The heteronuclear version of H2O-selective PFG experiments, called e-PHOGSY, has been shown to represent a very sensitive experiment for the rapid detection of water bound to proteins and peptides.80 Dalvit" reported the homonuclear 1D and several new 2D versions of the ePHOGSY experiments and demonstrated their application to the protein chicken egg-white lysozyme. NMR investigations of hydrogen bonded complexes AHB give evidence of temperature-dependent solvent electric field effects on proton transfer and hydrogen bond geometries.82

2.6 Quadrupolar Interactions - Quadrupolar coupling constants are sensitive probes of hydrogen bonding. Their accurate knowledge is a major prerequisite when trying to extract dynamical information from relaxation data of quadrupolar nuclei. If the relaxing nucleus is covalently bound, the NQCC is determined by the electric field gradient (efg) arising from the intramolecular charge distribution at the nuclear site. Liquid phase values for NQCC can be obtained only in an indirect way. The standard procedure is to first determine correlation times for molecular reorientation from dipole-dipole relaxation rates. For example, the molecular reorientation time obtained from dipolar 13C-lH relaxation data is used to determine the deuteron NQCC in 13C-2Hfrom quadrupolar relaxation. In this particular case the procedure is correct, because the principle axis of the efg tensor coincides with the direction of the dipole-dipole interaction. The method also works for 'H-170 and 2H quadrupolar interaction in the OH group of water83 and alcohol^.'^ In pure liquids and in various binary mixtures it could be shown that the obtained *H NQCC show large and medium temperature effects.84Details are very difficult to interpret without the help of theoretical calculations. As noted in previous reports by Weingartner,' there are now theoretical methods to predict the efg in the liquid state. The first method is based on Molecular Dynamics Simulations (MD). From the bulk configurations, molecular clusters are chosen and used in

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Nuclear Magnetic Resonance

supermolecular ab initio calculations. This technique has been successfully to determine *H and I7O NQCC in liquid water. This applied by Huber et method was extended to calculate temperature dependent 'H and I7O chemical shifts in liquid water.8s The authors found the correct gas-to-liquid shifts, but the results depend strongly on the chosen intermolecular potential in the M D simulation. An interesting result is also that the chemical shift values depend in a more sensitive way on the intermolecular environment than the respective NQCC do. In a second method, molecular clusters were calculated by pure ab initio methods.20321 A Quantum Cluster Equilibrium (QCE) Model, which is fully based on quantum thermodynamics treatment, generates temperature- and pressuredependent molecular cluster populations. Changing cluster distributions lead to temperature-dependent H-bond-sensitive properties such as NQCC, chemical shifts and vibrational frequencies which are calculated for each of the clusters. With this procedure the temperature dependence of 2H, I4N and I7O NQCC in liquid formamide was calculated by pure theoretical methods.*l It could be shown that NQCC's show different temperature behavior depending on the degree of hydrogen bonding. The main advantage of this method is that larger molecular clusters show strong cooperative effects which cannot be considered by pairwise-additive potentials. Only the large cooperative enhancement led to values for NQCC which are typically known for the liquid phase. In this respect, effective I7O quadrupole moments for the calibrated computation of quadrupole coupling parameters were calculated. This procedure allows quadrupole coupling properties of quite reasonable accuracy to be obtained despite current uncertainties in the experimental I7Oquadrupole moment.86 Quadrupolar I7O relaxation time experiments were applied to study the et a/.'* studied the 1 7 0 NQCC and 13C hydration of amines and a m i d e ~ . Rubini *~ shielding tensor anisotropy for the carbonyl group in amides and amino acids in solution. The situation is somewhat different considering QF-relaxing monoatomic noble gases or ions in solution. In this case the efg is of intermolecular origin and gives an idea about the symmetry of the solvation shells. In a semiquantitative description arguments about the symmetry of the charge distribution at the nuclear site may be applied to estimate the efg. Spin-lattice relaxation of 7Li, 23Na,27Al, 7'Ga and '39La nuclei in electrolyte solutions have been investigated as functions of the isotopic composition of the ~ o l v e n t . 'Along ~ with the results for the 2H and I7O nuclei of the solvent molecules and the 14N nucleus of the nitrate anion, the authors obtained a semiquantitative description of the observed effects. It should be noted that among the alkali metal nuclei, 7Li is an exception, because in addition to the Q F interaction 7Li-'H dipolar interactions may contribute to the relaxation rate of 7Li in H20. Quantitative estimates of this interaction were given in several papers" and are picked up by Baumert et for comparison with theoretical results. Molecular dynamics simulations in conjunction with ab initio calculations were employed for 7Li in water at various temperatures. It was demonstrated that at low temperatures the solvation shell is more structured and therefore the efg decreases.

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The NMR of QF-relaxing noble gas nuclei in solution bears much similarity to that of mono-atomic ionic nuclei like alkali metal, alkaline earth metal, group I1 and halide nuclei. That I3'Xe can be used as a sensitive probe for changing electronic environment became of biological interest. Saba et a/. applied quadrupolar I3'Xe NMR relaxation to study macromolecular systems such as lecithin vesicles and the small protein c h a r y b d o t o ~ i n . ~ ~ In the case of studying longitudinal NMR relaxation times in liquid 'lNe, Huber and co-workers calculated the electric field gradient as a function of the neon-neon distance.93 Experimental studies since 199194 have clearly demonstrated that *'Ne relaxes by QF interaction. Therefore Huber et al. used a combination of molecular dynamics simulations and initio methods to calculate the efg, which is of intermolecular origin. With the help of a basis set including bond functions applied successfully in the calculation of a pair potential they could eliminate a strong and slowly decaying basis set superposition error.95

2.7 Intermolecular Dipolar Interaction in Diamagnetic and Paramagnetic Sohtion - NMR of paramagnetic substances has been reviewed by Bertini and Luchinat." Their book covers all aspects in the field of NMR of paramagnetic molecules. Relaxation phenomena, hyperfine shifts and relaxation in the presence of chemical exchange, magnetic coupled systems, Nuclear Overhauser effect and two dimensional spectra are presented within this review. It is now well established that the Solomon-Bloembergen-Morgen (SBM) theory invokes so many restrictions that its quantitative use is very limited. Many of the problems arise from the presence of zero-field splitting (ZFS) in addition to the Zeeman interaction. This is particularly so for non-rigid complexes of low symmetry, where both static and transient ZFS are present. The former is modulated by the overall reorientation of the complex; the latter is due to vibrational and rotational motions of the ligands." Meanwhile there exists an extensive literature on theories beyond the SBM level, although the various theoretical approaches have been quite different. The main approaches have come from the groups of Kowalewski at Stockholm, Bertini at Florence and Sharp at Ann Arbor, respectively, and have been extensively reviewed in preceeding reports in this series as well as other

review^.^^^^' now present a new model for nuclear spin relaxation in Kowalewski et paramagnetic transition metal complexes in solution, allowing the electron-spin relaxation to be outside the Redfield limit. The novel feature is that the transient ZFS, modulated by distortions of the solvation shell, is allowed to be of rhombic rather than cylindrical symmetry. The model, which assumes that the static ZFS is absent, is applicable to aqueous solutions of transition metal ions. Sharp et al.99 developed spin dynamics (SD) methods to compute NMR paramagnetic relaxation enhancements (NMR-PRE) produced by solutes with electron spin S 2 1 in solution. Their program is similar in spirit to conventional molecular dynamics calculations (MD), except that the spin motion is treated quantum mechanically. SD simulations provide accurate, flexible, and rapid calculations of NMR-

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Nuclear Magnetic Resonance

PRE phenomena with few of the assumptions or limitations of previous analytical theories. Low-field N M R of solvent pro tons, enhanced by dynamic polarization, has been measured by Lang et al. using a new paramagnetic solution.Io0The authors claim that the signal characteristics were the best ever obtained for stable radicals over a large temperature range. Foley et al. investigated the effect of paramagnetic ions on NMR relaxation of fluids at solid surfaces."' Longitudinal 29Si relaxation in aqueous alkali-metal silicate solutions were studied by Kinrade et u1.1°2 Their findings indicate that the primary causes of 29Si relaxation are interactions (dipolar and contact) with adventitious paramagnetic ions, dipoledipole relaxation by solvent protons, and an apparent spin rotation interaction.

2.8 Slow Motions in Glasses - Investigations of slow molecular motions near the glass transition temperature studied by NMR techniques become more 3 a dynamic disorder model to describe the popular. Mancini et d o proposed random changes of a local structure to environmental rearrangements. Applied to the spin relaxation of a two-level system, the model accounts for the crossover between homogeneous and heterogeneous relaxation and is in good agreement with recent NMR results of the rotational dynamics in supercooled liquids. A simple model of non-Markovian molecular reorientation is applied by Sillescut4 to multidimensional NMR experiments in supercooled liquids. The difference between 2D and reduced 4D spectra is explained with respect to the mechanism and dynamics of the molecular reorientation in complex liquids. The combination of relaxation and self-diffusion studies provide particularly useful information, because near the glass transition temperature, T,, translational and rotational motions become decoupled. This is nicely shown for lithium and proton self-diffusion in supercooled LiCI-H20 using ultrahigh magnetic field gradients. Proton diffusion as well as intermolecular modes causing 'H-'H dipolar relaxation and 'Li quadrupolar relaxation decouple from the viscosity.' It is demonstrated that 2H relaxation provides a powerful tool for studying dynamical processes in the liquid-to-solid-glass transition regime. For example, 2H NMR is used to investigate rotational diffusion of spherical colloidal particle^,"^ molecular reorientation and rate exchange in supercooled orthoterphenyl,'*' as well as molecular reorientation of mobile guest molecules dissolved in organic Field gradient NMR is used to study selfdiffusion in p o l y g l y ~ o l e 'and ~ ~ glycerol.I2 In the latter case N M R data are combined with incoherent neutron-backscattering results to cover overlapping time scales. Other papers dealt with relaxation phenomena in highly viscous liquids in the supercooled regime without giving particular attention to glass relaxation phenomena. Canet and co-workers found indications for changes of dynamical characteristics in pure quinoline and some of its derivatives."' Finding two activation energies, they suggest the existence of a dynamical transition in the liquid and relate this process to that proposed for some supercooled liquids. Various NM R spectroscopic techniques such as MAS, CP-MAS, CRAMPS,

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SATRAS, REDOR and SEDOR have been applied to investigate silicate glasses,'09-' phosphate glass ceramics'12 and borate and germanate glasses.' l 3 Studies of conducting polymer electrolytes based on 7Li, 13C and 'H relaxation have been performed.' l 4 > ' l 5

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2.9 Models for Molecular Dynamics - Some years ago, Lipari and Szabo' 16,' l 7 suggested a model-free approach to the interpretation of NMR relaxation in macromolecules. For both isotropic and anisotropic overall motion, it was shown that the unique information about fast internal motions contained in relaxation experiments can be completely specified by two model-independent quantities: a generalized order parameter, S, which is a measure of the spatial restriction of the motion, and an effective correlation time, z, which is a measure of the rates of motion. Recently, Briischweiler showed that the order parameter S can be interpreted on the basis of analytical or force-field-based models.' 18*' l 9 Now, a new protocol for the interpretation of side-chain dynamics is presented which is an extension of the previously proposed analytical Gaussian axial-fluctuation model. 2o Dzakula ef demonstrated that the motional probability distribution (CUPID) approach for analyzing the rotamer population from NMR spin-spin couplings and nuclear Overhauser enhancements allow the study of internal rotations in amino acids. Kliiner and Dolle'22 presented a hydrodynamic model to describe fully anisotropic rotational dynamics of asymmetric ellipsoids in liquids. The calculated results agree well with experimental value from 13Cnuclear relaxation data. For pure liquid benzene Python et al.'23 demonstrated the anisotropy of molecular reorientation using nuclear relaxation of the longitudinal 13C-'H two spin-order. Most relaxation parameters arising from dipolar interactions or quadrupolar interactions in benzene are related to the reorientation of in-plane vectors. The anisotropy can be obtained only by determining the relaxation mechanism arising from shielding anisotropy (CSA). This is because the main direction of the shielding tensor is perpendicular to the molecular plane. The intermolecular translational-rotational contribution to nuclear-spin relaxation in liquids is still under debate. '24-126

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3

Selected Applications of Nuclear Spin Relaxation

3.1 Pure Liquids - In a review, Hills' analyzed and interpreted NMR proton relaxation data of simple water. The dynamic structure of water coming out of ultra-pure water producing systems has been studied by 170NMR r e 1 a ~ a t i o n s . l ~ ~ The influence of hydrogen bonding on water rotation and proton mobility has been discussed by Agmon,' 28 who compared dynamical properties obtained from NMR spin-lattice relaxation and self-diffusion with those from Raman and other light-scattering spectra. Canet et af. claim"* indications for change of dynamical regime in pure liquids. For quinoline and some of its derivatives they obtained two activation

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energies from I3C spin-lattice relaxation times T1, and suggest the existence of a dynamical transition in the pure liquid system. Also with 13C relaxation Benayada et al. 29 determined rotational diffusion coefficients of monomeric polycromatic molecules. The analysis is based on well-known models for the anisotropic reorientation of planar asymmetric rotors. 1303131 Experimental measurements of diffusion and I3C NMR spin lattice relaxation is used to check models of n-alkanes to investigate their ligand-state dynamics.'32 The authors pointed out in particular the effects of global single-chain relaxation processes on the local intramolecular dynamics probed by the I3C NMR experiment.

'

3.2 Non-Electrolyte Solutions - A larger group of papers have dealt with water dynamics in aqueous solution of small apolar solutes or polar solutes with apolar g r 0 ~ p s . l13'~ ~It could be shown that the water reorientation is slowed down by apolar solutes whereas hydrophilic solutes like enhanced water reorientation. Hydrogen bonding has been investigated in binary mixtures of N,N-dimethyla~etamide/water,'~~ benzene in organic solvents' 3s and alcohol/ 37 water solutions.' The relaxation of quadrupolar nuclei such as 2H'33was measured in aqueous media. The relaxation rates could be accounted for by both spin-rotation and dipolar mechanisms. The effects of water hydration have been studied in aqueous mixtures of methan01,'~~ ethan01,'~~''~' propan01,'~~''~' and butan01,'~~ as well as amines and amides. 137,138 In most of the cases, 2H and 1 7 0 quadrupolar relaxation of water in the pure liquid and in the mixtures was used as a sensitive probe for structure changes. Hydration phenomena were also studied for macrocyclic systems such as crown ethers in organic solvent^.'^^"^^ Structure and dynamics of carbohydrates in aqueous solution have been reviewed by van Halbeek and Shuqun. ,I4' PVC'43 and other polyHigh-viscosity solvents such as p~lystyrene,'~' merS144-149 enable one to slow down the molecular motion of the solutes. Measurements outside the extreme-narrowing regime, where relaxation becomes frequency-dependent, are then possible. Making use of this principle, dynamics and coupling parameters are investigated by Rossler et al.'" have used the glass former to study the motion of guest molecules by 'H relaxation. In a series of papers, relaxation processes were analyzed in terms of contributions from the quadrupolar, chemical shift anisotropy and spin-rotation mechanism. In particular, CSA interactions have found broad attention. For amides, acids and amino acids measurement at four different magnetic fields allowed the determination of the contribution of the shielding anisotropy mechanism to the total relaxation rate. From the 1 7 0 NMR linewidth, it was possible to derive the 1 7 0 quadrupolar coupling constant. Both properties, the chemical shift anisotropy and the quadrupole coupling constants, were obtained in solution and compared with those obtained in the solid state.88 Batta et a].'" determined solution-phase 'H and I3C chemical shift anisotropies of a symmetric cryogenic disaccharide and alpha, alpha-trehalose. Dynamical behavior of carbohydrates was investigated by Kowalewski and co-workers. Is' The 13C results were analyzed with the Lipari-Szabo 'model-free' approach.' 6 , 3631

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6: Nuclear Spin Relaxation in Liquids and Gases

21 1

H ~ l z studied ' ~ ~ the temperature and urea effect on the self-association of ethanol in water. In accord with theoretical predictions, the association of ethanol increases with increasing temperature. Surface dynamics and fluid transport of liquids in porous materials are reported for silica g l a s ~ e s ' ~and ~ , porous '~~ rock^.'^^,'^^ Polar and non-polar liquids in porous glasses have been studied by proton and deuteron field-cycling NMR s p e c t r o ~ c o p y . ' ~ ~

3.3 Electrolyte Solutions - The effect of ions upon water dynamics is usually characterized by a limiting slope, B, of 'H, 2H or I7O relaxation rates of water as '~~ et ~ 1 . ' ~ 'used I7O spin-lattice a function of salt c ~ n c e n t r a t i o n . Yoshida relaxation times to derive the B-coefficients for alkali and tetraalkylammonium halides as a function of temperature. In a proceeding paper they studied ratios of the rotational correlation times of water molecules in pure water and electrolyte solutions for the same mixtures as a function of pressure and found quantitative agreement with conductivity measurements.I6' Ansari et a1.'62 determined rotational correlation times of all solvent compounds in the system methanol/ water/lithium chloride. Temperature effects on the rotational motion of the coordinated D20 in CsBr aqueous solution were investigated by *H and I7O relaxation measurement^.'^^ Because the main components of the electric field gradient tensors for 2H and I7O are perpendicular to each other the ratio T(~H)/T( 1 7 0 ) yields information about the anisotropic nature of the molecular motion of water in electrolyte solutions. It should be pointed out that for quantitative conclusions: the respective NQCC themselves may be temperature or pressure dependent17 and reasonable statements of anisotropic behavior of water can be made only for Di1/DI ratios larger than 2.1a In similar manner, Iida et al. measured 59C0 and 35Cl nuclear relaxation to determine critical micelle concentrations. A method is presented by Chizhik'66 for determining microstructural parameters such as coordination numbers of ions and mobilities of solvent molecules of diamagnetic aqueous solutions from NMR relaxation data. The results depend upon the relaxation rates of various nuclei belonging to solvent molecules and ions. Several dependences which govern the formation of ion hydration shells are given. Water exchange and rotational dynamics of Ga(II1) complexes have been studied as a function of temperature and pressure by Merbach et a1.'67 Proton-lattice relaxation time, TI, of water in aqueous solutions of ferrous and ferric ions and in the corresponding agarose gel system have been investigated in light of NMR relaxation theory.16' The important result is that at the microscopic level, changes in the solvation states of paramagnetic ions in aqueous or gel environment are greater than the difference in paramagnetism between ferric l ~ ~ 7Li spin-lattice relaxation times in and ferrous ions. Chung et ~ 1 . measured monoconducting gel electrolytes to deduce information about the dynamical process near the glass transition temperature. 3.4 Transition Metal Complexes - The study of ligand exchange upon metal ions has become one of the major topics in this subject area. T o get a better

212

Nuclear Magnetic Resonance

understanding of exchange processes, exchange times were measured extensively as a function of temperature, pressure and various magnetic field strengths. Merbach and c o - w ~ r k e r s 'have ~ ~ measured I7O longitudinal and transverse relaxation of aquo- and DTPA-complexes of Gd3+ and of a similar chelate complex serving as contrast agent in magnetic resonance imaging. The measurements have been performed at variable temperature, pressure and at several magnetic field strengths, and provide information on water exchange kinetics and reorientation times in such Sur and Bryant'72 studied ionic association and electron spin relaxation rates in aquo Gd3 complexes. Mg2+, Ca2+ and Ln3+ complexes were investigated by high resolution NMR '~~ transitionand water proton relaxivity measurements. 173 S ~ h u m a n nmeasured metal complexes to obtain information about the Li+ environment in TMEDA. Many dynamic shift and relaxation studies were performed using lanthanide complexes as contrast agents for magnetic resonance imaging. An extensive review is available by Peters, Huskens and R a b e ~ -and ' ~ ~this field is also regularly reviewed in this series. +

4

Nuclear Spin Relaxation in Gases

Spin-lattice relaxation rates of liquid 3He and 3He/4He mixtures were measured over the whole range of concentrations. It was shown that the wall contribution to relaxation depends on the square of the magnetic field.'76 Rudavskii et al.'77 demonstrated that relaxation of 3He-4He mixtures is governed by the Zeemanexchange mechanism. Texture dependence of the persistant NMR signal in superfluid 3He-B could be inferred by Bankov et 01.'~~ Feher and S k ~ b a ' ~ ~ discussed unpredicted phenomena of spin supercurrents and coherent precession of magnetization in superfluid 3He-B. Noble gases such as 3He or 129Xeare of current interest because they can be very highly spin polarized by optical pumping methods.'80"8' Optical pumping has been researched extensively in the past few decades following the pioneering '~~ there has been an increased amount of work of Kastner in the 1 9 5 0 ~ .Recently study involving the indirect pumping of nuclear spins via spin exchange with optically polarized valence electrons of another atom.Is3 The magnetic resonance signal for nuclei polarized in this fashion is greatly enhanced in comparison to that achieved with the typically small Boltzmann equilibrium polarization. Augustine et a1.'84for the first time examined the optical pumping phenomena in multi-tesla magnetic fields up to 7.04 T. It could be shown that '29Xe nuclear spin polarization can be more efficiently produced in comparison to lower fields and the kinetics are simpler to model theoretically. Methods for spin lattice relaxation and diffusion measurements based on magnetic resonance signals from laser-hyperpolarized 29Xe nuclei are introduced. The methods involve optimum use of the perishable hyperpolarized magnetization of '29Xe. They were applied to Iz9Xe in the gas phase, in vitro. The authors comment that their methods are in principle applicable for in vitro or ex vivo studies, which makes

'

6: Nuclear Spin Relaxation in Liquids and Gases

213

them important in the development of newly emerging hyperpolarized '*'Xe MRI applications. 3C nuclear relaxation times were measured by a high-pressure sapphire NMR cell for both neat C02 and a C02-CH4 mixture over a wide range covering gas, liquid and supercritical densities. Although the spin-rotation interactions still dominate the spin-lattice relaxation processes in CH4, the intermolecular dipolar interaction contributes approximately 5% to the overall relaxation rates at liquid densities. The chemical shift anisotropy and the intermolecular contributions to relaxation rates of C02 were experimentally determined to be negligible.l g 6 I3C relaxation times were also determined by Grant and co-workers for carbons of 1-decanol in dense carbon dioxide at pressures between 8 and 20 MPa along four isotherms between 288 and 348 K.ls7

5

Self-Diffusion in Liquids

5.1 Experimental and Theoretical Aspects - The most interesting developments for measuring diffusion are the availability of techniques in ultrahigh magnetic field gradients. Such ultrahigh gradients are present in the stray field of superconducting magnets188 or can be generated by specially constructed magnets with anti-Helmholtz coil arrangements."' Gradients up to 200 Tm allow the measurement of diffusion coefficients down to m2s-' which is three orders of magnitude below the values obtained in conventional experiments. Those large field gradients have been used to study slow motions in propylene glycol. ' O Kimmich and Fischer"' have described diffusion measurements in the fringe field of superconducting magnets. The fringe field provides extremely strong and stable field gradients which can be used for diffusion experiments in the presence of slow processes. Experiments in melts of entangled polymers show reasonable agreement with the predictions of the tube/reptation model. Diffusion-ordered 2D NMR spectroscopy (DOSY) was developed to aid in the analysis of complex mixtures.'92 The idea was to provide, at each chemical shift, a spectrum of diffusion coefficients of the various components through approximate inverse Laplace transforms (ILT) of pulsed-field-gradient NM R (PFG NMR) data sets. Even with low noise and comparable intensities, one typically cannot resolve two components in a diffusion spectrum having diffusion coeffi~ cients that differ by less than a factor of two. Wu, Chen and J o h n ~ o n ' ' proposed a 3D DOSY experiment in which PFG NMR diffusion measurements are combined with conventional 2D NMR to give the third dimension. This provides a major reduction of overlap, since the cross peaks are spread over the full 2D plane instead of along a single axis. A combination of a 2D proton-proton correlation spectrum (COSY) and a DOSY analysis produce 3D COSY-DOSY. It is well known that any magnetic-field gradient within the sample may developed a interfere with the NMR measurement. Norwood and c o ~ o r k e r s ' ' ~ method that uses the internal gradient itself to provide information about the heterogenous structure.

'

214

Nuclear Magnetic Resonance

present an analysis that relates the NMR spin-echo signal Kuchel et intensity to the magnitude of the magnetic field gradient, the spin-echo time, and the intrinsic molecular diffusion coefficient. Radiofrequency field gradient experiments were reviewed by Canet.'96 A method for measuring self-diffusion in liquids using a single magnetic-field-gradient pulse is presented by Robyr and B ~ w t e l lThis ' ~ ~ method relies on the refocusing of spatially modulated transverse magnetization by the dipolar demagnetizing field. Velan et af.'98reported a novel approach to the rapid measurement of molecular self-diffusion coefficients employing high resolution NMR. Multiple-Quantum (MQ) versions of the PGSE and LED pulsed-field-gradient NMR diffusion experiments are described for the coherence order 21 for isolated quadrupolar (spin 1) nulcei (7Li) in anisotropic systems such as DNA fibers.'99 Jones et af. demonstrated that phase cycling may remove the spatial dependence of NMR spin-echoes which are refocused by 90" pulses.200 Different imaging strategies for diffusion measurements with the centric phaseencoded Turbo-FLASH sequence are compared by Coremans et af.201 Ross et a1.202demonstrated that systematic errors associated with the CPMG pulse sequence may have significant effects on motional analysis of biomolecules. In particular, subsequent transfer of erroneous T2 values can produce large errors in derived motional dynamics, such as z, internal correlation times and S2 order parameter. A high-temperature, high-pressure NM R probe for self-diffusion measurements in molten salts has been developed. Since self-diffusion depends on both temperature and density, it is desirable to separate the two effects in experiment^.^^ 5.2 Selected Examples - In recent years, work on self-diffusion in pure liquids has begun to concentrate on measurements over wide ranges of temperature and pressure.203This is because measurements over limited ranges of temperature and pressure are often of little value in understanding molecular dynamics and testing theories. In the period under review, Harris et d 2 0 4 measured self-diffusion coefficients via the NMR spin-echo method for water below 0 degrees Celsius and at pressures up to 350 MPa in the liquid region bounded by the ice I and ice I11 phases. ~ ' ~ the density dependence Using the same technique, Enninghorst et ~ 1 . studied of self-diffusion in liquid pentane and pentane mixtures as a function of temperature and pressure. Equations for self-diffusion are tested and the results are compared with those from molecular dynamic calculations. Self- and mutual-diffusion coefficients of some n-alkanes were measured by Marbach and Hertz206at elevated temperatures and pressures and are explained in terms of simple model theories. Using similar methods, Schmoll et af.*07studied diffusion in the ternary system CaCl/HCl/H20. The validity of the Onsager reciprocity relation was confirmed within the limits of experimental error. A series of commercial silicones has been studied in the temperature range between 290 and 410 K at pressures up to 200 MPa.*08 Self-diffusion coefficients are discussed in terms of the rough sphere model and tested against the Rouse

6: Nuclear Spin Relaxation in Liquids and Gases

21 5

model. Ludemann and co-workers also investigated the concentration and temperature dependence of glucosides in aqueous solution.209 The numerous studies dealing with self-diffusion in liquid or liquid-like systems led to several review articles in this field. Ludemann’ reviewed developments in high-pressure, high-resolution NMR in pure liquids. Recent extentions of there studies that evidence the study of self-diffusion in binary mixtures are also presented. The compounds studied range from simple hydrocarbons to hydrogen bonded liquids like alcohols and water. Other review articles deal with the selfdiffusion of water in lyotropic liquid diffusion in microporous materials,211,212 and self-diffusion studies of emulsions.213 With the foregoing chapter describing methods of using high field gradient NM R, Fujara et al. investigated anomalous diffusion in polydimethylsiloxane melts214and viscous glycerol.12 Measuring self-diffusion with pulsed-gradient NMR, Knauss et studied water mobility in hydrated collagen. Using the same technique, water selfdiffusion in polymer and in plants2” was observed. Self-diffusion of paired ions was investigated by Mo et Applying the field-gradient N M R technique, found evidence of anomalous molecular diffusion due to structural Appel et confinement.

6

References 1

2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18

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133 134 135 136 I37 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 I60 161 162 163 164 165 166 167 I68

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H. Gilboa, B. E. Chapman and P. W. Kuchel, J. Mag. Reson., Ser. A , 1996,119, 1. C. Wakai and M. Nakahara, Bull. Chem. SOC.Japn., 1996,69,853. C. M . Kinart, W. J. Kinart, A. Bald and A. Szejgis, Phys. Chem. Liquids, 1995, 30, 151. T. Seto, T. Mashimo, I. Yoshiya, A. Shimizu, K. Fumino and Y. Taniguchi, J . Mol. Liq., 1996,70, 1. V. N. Izmailova, V. V. Rodin and P. V. Nuss, J . Russ. Acad. Sci., 1996,58, 581. K. Mizuno, K. Oda, Y. Shindo and A. Okumura, J. Phys. Chem., 1996,100, 10310. V. P. Solov’ev, N. N. Strakhova, 0. A. Raevsky, V. Riidiger and H.-J. Schneider, J. Org. Chem., 1996,61, 5221. 0. Mayzel, A. Gafini and Y. Cohen, Chem. Commun. (Cambridge), 1996,8,911. W. Zhu and M. D. Ediger, Macromolecules, 1997,30, 1205. S. Z. Mao, G. L. Ding, H. Z. Yuan, H. Q. Feng and Y. R. Du, Sci. China, Ser. A : Math. Phys. Astron. Techno]. Sci., 1997, 40, 408. E. I. Tylianakis, P. Dais and F. Heatley, J . Polymer Sci., Purt B: Polymer Phys., 1997, 35, 317. H. Kusanagi and K . Matsumura, Kobunshi Ronhunshu, 1996,53,308. S. H. Luff, Ber. Bunsenges. Phys. Chem., 1997,101,96. G. D. Smith, D. Y. Yoon, C. G. Wade, D. O’Leary, A. Chen and R. L. Jaffe, J . Chem. Phys., 1997,106,3798. K. Overloop, F. Vanstapel and P. Van Hecke, Magn. Reson. Med., 1996,36,45. J. Zhao, A. A. Jonse, P. T. Inglefield and J. T. Bendler, Polymer, 1996,37, 3783. J. Kowalewski, T. Nilsson and K. W. Tornroos, J . Chem. SOC.,Dalton Trans., 1996, 8, 1597. G. Buntkowsky, E. Rossler, M . Taupitz and H . M. Vieth, J . Phys. Chem., 1997, 101, 67. G. Batta, K. E. Kover, J. Gervay, M. Hornyak and G. M. Roberts, J. Amer. Chem. SOC.,1997, 119, 1336. L. Maler, G. Widmalm and J. Kowalewski, J. Phys. Chem., 1996,100, 17103. A. Sacco and M . Holz, J. Chem. Soc., Faraday Trans., 1997,93, 1101. L. Ballard and J. Jonas, Langmuir, 1996,12,2798. J. P. Korb, L. Malier, F. Cros, S. Xu and J. Jonas, Phys. Rev. Lett., 1996,77,2312. P. Mansfield and B. Issa, J. Magn. Reson., 1996, 122, 137. P. Mansfield and B. Issa, J. Magn. Reson., 1996, 122, 149. S. Stapf, R. Kimmich, R. 0. Seitter, A. I. Maklakov and V. D. Skirda, Coll. Surfaces A , Physicochem. Eng. Aspects., 1996, 115, 107. H. G. Hertz, in ‘Water A Comprehensive Treatise’, ed. F. Franks, Plenum, New York, 1973,Vol. 3. K. Yoshida, K. Ibuki and M. Ueno, J . Solution Chem., 1996,25,435. M. Ueno, N. Tsuchihashi, K. Yoshida and K. Ibuki, J. Chem. Phys., 1996, 105, 3662. M. S. Ansari, R. Ludwig, M. D . Zeidler, H. G. Hertz and M. Poschl, 2. Phys. Chem., 1997,199,99. K. Fumino, A. Shimizu and Y . Taniguchi, Mater. Sci.Res. Int., 1996,2, 54. C. W. R. Mulder, J. Schriever and J. C. Leyte, J. Phys. Chem., 1983,87,2336. M. Iida, M. Yamamoto and N. Fujita, Bull. Chern. Soc. Japn., 1996,69, 3217. V. I. Chizhik, Mol. Phys., 1997,90,653. E. Toth, S. Vanthey, D. Pubanz and A. E. Merbach, Inorg. Chem., 1996,35,3375. T. Tokuhiro, A. Appleby, A. Leghrouz, R. Metcalf and R. Tokarz, J . Chem. Phys., 1996,105,3761.

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S. H. Chung, P. Heitjans, R. Winter, W. Bzducha and Z. Florjanczyk, Ber. Bunsenges. Phys. Chem., 1996,100, 1639. E. Toth, S. Vanthey, D. Pubanz and A. E. Merbach, Znorg. Chem., 1996,35,3375. D. H. Powell, 0. M. Nidhubhghaill, D. Pubanz, I,. Helm, Y. S. Lebedev, W. Schleapfer and A. E. Merbach, J. Amer. Chem. Soc., 1996,118,9333. S . K. Sur and R. G. Bryant, J. Magn. Reson., Ser. B, 1996,111, 105. J. Huskens, D. A. Torres, Z. Kovacs, J. P. Andre, C. F. G. C. Geraldes and A. D. Sherry, Inorg. Chem., 1997,36, 1495. H. Schumann, Polyhedron, 1996,15,2327. J. A. Peters, J. Huskens and D. J. Raber, Prog. Nucl. Magn. Reson. Spectros., 1996, 28, 283. A. S. Van Steenbergen, S. A. J. Wiegers, J. A. A. J. Perenboom and J. C. Maan, Czech. J. Phys., 1996,46,233. E. Y. Rudavskii, N. P. Mikhin, A. V. Polev and V. A. Shvarts, Czech. J . Phys., 1996, 46,501. Y. M. Bankov, D. J. Cousins, M. P. Enrico, S. N. Fisher, G. R. Pickett, N. S. Shaw and W. Tych, Czech. J. Phys., 1996,46,233. A. Feher and P. Skyba, Czech. J. Phys., 1996,46,3019. W. Happer, E. Miron, S. Schaefer, D. Schreiber, W. A. von Wijngaarder and X. Peng, Phys. Rev. A , 1984,29,3092. T. K. Hitchens and R. G. Bryant, J . Magn. Reson., 1997,124,227. A. Kastner, J. Phys. Radium, 1950, 11,22. M. Gatzke, G. D. Cates, B. Driehuys, D. Fox, W. Happner and B. Saam, Phys. Rev. Lett., 1993,70, 690. M. P. Augustine and K . W. Zilm, J. Chem. Phys., 1996,105,2998. B. R. Patyal, J.-H. Gao, R. F. Williams, J. Roby, B. Saam, B. A. Rockwell, R. J. Thomas, D. J. Stolarski and P. T. Fox, J. Magn. Reson., 1997, 126, 58. S. Bai, C. L. Mayne, R. J. Pugmire and D. M. Grant, Magn. Reson. Chem., 1996,34, 479. S . Bai, C. M. V. Taylor, F. Lui, C. L. Mayne, R. J. Pugmire and D. M. Grant, J. Phys. Chem. B, 1997,101,2923. R. Kimmich, W. Unrath, G. Schnur and E. Rommel, J. Magn. Reson., 1991,91, 136. I. Chang, F. Fujara, B. Geil, G. Hinze, H. Sillescu and A. Tolle, J. Non-Cryst. Solids, 1994, 172-174,674 M. Appel, G. Fleischer, J. Karger, I. Chang, F. Fujara and A. Schonhals, Colloid Polymer Sci., 1997,275, 187. E. Fischer, R. Kimmich and N. Fatkullin, J. Chem. Phys., 1996,104,9174. K. F. Morris and C. S. Johnson, Jr., J. Amer. SOC.,1992, 114, 3139. D. Wu, A. Chen and C. S. Johnson, Jr., J . Magn. Reson., Ser. A , 1996, 121,88. M. A. Horsfield, S. A. Clark and T. J. Norwood, J. Magn. Reson., Ser. A , 1996,122, 222. P. W. Kuchel, A. J. Lennon and C. Durrant, J. Magn. Reson., Ser. B, 1996, 112, 1 . D. Canet, Prog. Nucl. Magn. Reson. Spectr., 1997,30, 101. P. Robyr and R. Bowtell, J. Magn. Reson., Ser. A , 1996,121,206. S . S. Velan and N. Chandrakumar, J. Magn. Reson., Ser. A , 1996, 123, 122. L. Vandam, B. Andreasson and L. Nordenskiold, Chem. Phys. Lett., 1996,262,737. R. P. 0. Jones, G. A. Morris and J. C. Waterton, J. Magn. Reson., 1997, 124,291. J. Coremans, M. Spanoghe, L. Budinsky, J. Sterck, R. Luypaert, H. Eisendrath and M. Osteaux, J . Magn. Reson., 1997,124,323. A. Ross, M. Czisch and G. C. King, J. Magn. Reson., 1997,124, 355.

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E. W. Lang and H. D. Ludemann, Prog. Nucl. Magn. Reson. Spectros., 1993, 25, 507. K. R. Harris and P. J. Newitt, J. Chem. Eng. Data, 1997,42, 346. A. Enninghorst, F. D. Wayne and M. D. Zeidler, Mol. Phys., 1996,88,437. W . Marbach and H. G. Hertz, 2. Phys. Chem, 1996,193,19. J . Schmoll and H. G. Hertz, 2. Phys. Chem., 1996, 194, 193. A. Thern and H. D. Liidemann, Z . Naturforsch., 1996,51, 192. A. Heinrichschramm, C. Buttersack and H. D. Ludemann, Carbohydrate Rex, 1996, 293,205. G. Celebre, G. Chidichimo, L. Coppola and C. Lamesa, Gaz. Chim. Ital., 1996, 126, 489. D. N. Theodorou, R. Q. Randall and A. T. Bell, Compr. Supramol. Chem., 1996,7, 507. G. H. Sorland, B. Hafskjold and 0. Herstad, J . Magn. Reson., 1997,124, 172. 0. Soederman and B. Balinov, Surfactant Sci. Ser., 1996,61,369. S . Pahl, G. Fleischer, F. Fujara and B. Geil, Macromolecules, 1997,30, 1414. R. Knauss, G. Fleischer, W. Grunder, J. Karger and A. Werner, Magn. Reson. Med., 1996,36,241. S . Matsukawa and 1. Ando, Macromolecules, 1996,29,7136. A. V . Anisimov and N. R. Dautova, Fiz. Khim. Metody Issled. Strukt. Din. Mol. Sist., Muter. Vseross. Soveshch, 1994,3,411. H. M o and T. C. Pochapsky, J . Phys. Chem. B, 1997,101,4485 M . Appel, G. Fleischer, J. Karger, F. Fujara and S . Siegel, Europhys. Lett., 1996,34, 483.

7 Solid State NMR BY M. E. SMITH

1

Introduction

It has again been a year when the number of publications where solid state NMR was employed has increased. The increasingly widespread access to high quality solid state NMR spectrometers is seeing many scientists now regarding solid state NMR as a primary characterisation tool, rather than a specialist technique. Hence many papers now show solid state NMR spectra simply to confirm a structure or follow a reaction pathway. This has been the case for a number of years in studying microporous aluminosilicates, but is now more generally true in solid state chemistry and materials science. Some of the most impressive progress in solid state NMR has continued to be in the structural and conformational information that can be extracted from large biomolecules. The two-dimensional (2D) multiple quantum (MQ) experiment for spin-half quadrupolar nuclei introduced last year has already made a significant contribution with further improvements, and many groups now routinely implement this approach because of the improved spectral resolution and the ability to extract NMR interaction parameters for such nuclei. It is also clear that a genuine multinuclear approach is blossoming. Although standard nuclei (e.g. 'H, '3C, 29Si,27Al,23Na)dominate the solid state NMR literature there is ever increasing application made of more 'difficult' nuclei. There are some changes to the structure of this report compared to last year. To cut down the size of this chapter and avoid duplication, reviews involving solid state NMR will be dealt with in the chapter on reviews. Solid state NMR applied to polymers will now be reviewed in the chapter on synthetic macromolecules, although polymer-based papers which are principally solid state NMR technique development are included here. Often solid state NMR is now used peripherally, as additional characterisation of materials, and not all of these papers will be covered here. Some of the other sections from last year have disappeared, but the topics are still covered under other headings. Sometimes for compactness the information is presented in tabular form. The period covered is roughly the year from spring 1996. It is hoped that a representative cross-section of papers is captured although it would be impossible to be exhaustive and any obvious omissions will be included next year.

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Technique Development

Section 2 is divided into two sections. The first deals with papers that were solely theoretical developments, with the second section examining experimentallybased work, although such work often also involves a theoretical contribution. 2.1 Theoretical - A number of problems in solid state NMR continue to merit theoretical consideration. Much of the rich anisotropic information contained in NMR spectra from solids can be extracted by simulation which was considered generally for powders.' The statistical errors in the principal components of the chemical shift anisotropy (csa) tensor extracted from spinning sideband intensities were calculated2 and a programme for simulating second-order quadrupolar powder patterns was p r e ~ e n t e d .Residual ~ dipolar effects under magic angle spinning (MAS) were calculated for spin- 1/2 nuclei with negative gyromagnetic ratios coupled to quadrupolar nuclei (e.g. 29Si-14N),4 and extraction of tensor information by simulating the lineshapes and sideband intensities when such residual coupling is present was considered for '3C-14N576and 13C-2H7 using slow MAS. Spin diffusion in polymers still plays an important role in domain sizing and a more accurate mathematical description was compared to numerical simulation.' A standardised spin diffusion plot was proposed that allows ready extraction of the domain size' and a combination of free induction decay (FID), TI and spin diffusion was used to iteratively optimise numerical models of heterogeneous polymers. l o Detailed calculations were presented for field dependent shifts of I3C and Floquet theory was applied to calculate the contribution to the residual 13C linewidth from homonuclear coupling amongst the abundant spins and the effects of off-resonance irradiation. An analytical solution was provided for offresonance effects on first-order quadrupole-perturbed spin-3/2 systems. l 2 Magnetic susceptibility effects in powders were c a l c ~ l a t e d and ' ~ a general theory for Tl in multiple spin systems modulated by strong rf-irradiation was given14 It was suggested that the drawings of M.C. Escher are helpful in understanding the complexity of some CP MAS NMR spectra.

'

2.2 Experimental - Progress was made on several experimental fronts during the last year. It is clear that there is increasing emphasis on multi-dimensional experiments that contain anisotropic tensor information that can be related to structure. Multiple resonance experiments are now more common, with increasingly exotic combinations of nuclei being used. The greatest progress during the past year has undoubtedly been with multiple quantum (MQ) experiments for producing much improved spectral resolution from non-integer spin quadrupole nuclei in solids. On the hardware front a coherent pulsed spectrometer16 was described and probes for single crystal measurement^,'^ applying tension to fibres in situ17 and for flowing reagents into," to follow catalytic reactions in situ were demonstrated. A solenoidal coil was described made from thin ribbon with a continuously variable width that minimises both axial and radial rf-inhomogeneity," and a surface coil was used for 1H-31Pcross-polarisation (CP) using

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adiabatic demagnetisation.20 There is continued interest in developing new pulses; shaped pulses were used for more efficient inversion of 2H lineshapes,2"22 broadband rf-pulses for double quantum (DQ) excitation23 and quadrupolar echoes from spin-1 systems could be formed at much lower rf powers from single time-dependent amplitude modulated pulses.24 Permutation of the phases of npulses was described for improved compensation of the errors in the pulselengths.25 The effects on the free induction decay from evolution of the magnetisation during finite length pulses were considered.26 Magic angle spinning (MAS) continues to be the most extensively used technique in solid state NMR with improved control by buffering and regulating the air supply, as well as employing multiple markings on the rotor for more accurately recording the MAS speed.27 To remove spinning sidebands the MAS rate can be made ~ a r i a b l eand ~ ~ a. ~ magic ~ angle turning (MAT) experiment was employed to suppress double angle rotation (DOR) sideband^.^' Spinning slightly off axis allows observation of just the centreband for "V and 59C0 which are simulated with both quadrupolar and csa interaction^.^^ Calibration of the temperature in MAS experiments still generates much discussion with further 207Pb studies of the isotropic chemical shift of Pb(N03):2 and squaric acid a potentially useful internal temperature standard for I3C CP MAS, having a sharp phase transition that can be varied in the range 373.2 to 520 K by the degree of d e ~ t e r a t i o n .Improved ~~ sequences for determining spin diffusion were proMultiple pulse line-narrowing combined with MAS in a combined rotation and multiple pulse sequence (CRAMPS), normally allows only moderate spinning speeds to be employed so that the quasi-static condition is met, which is now possible even at high MAS rates if windowless and semi-windowless sequences with appropriate observation windows are employed which are much less demanding on the specrometer and the accuracy of the s e t - ~ p . Line~~?~~ narrowing of some parts of the lines from abundant spins can be achieved by introducing a pre-acquisition delay3* and the formation of echoes in extensively dipolar coupled solids was i n ~ e s t i g a t e dA. ~sequence ~ was proposed for removal of inhomogeneous broadening ofmolecules bound to the surface of solid resins allowing J-coupling to be re~olved,~'and in fully I3C-labelled compounds '3C-'3C J-decoupling was necessary to reduce the 13C linewidth, which was helpful even in indirectly detected experiment^.^^ The application of magnetic field gradients to reduce artefacts and the length of phase cycles in multidimensional experiments has been transferred from solution to solid state NMR for the first time42 and ultrasonic narrowing was applied to 10 nm organic particles that reduced the 'H linewidth to 1 Hz thereby revealing J - ~ o u p l i n g . ~ ~ I3C is still by far the most studied nucleus and signal enhancement through CP from protons continues to be extremely important. To reduce sensitivity of the Hartmann-Hahn (HH) match condition and provide better spectral quantification linear rf-ramps have been applied44 and frequency-modulated CP greatly reduces the attenuation that fast MAS causes in normal CP.45If gradients exist in the rf-fields spatially localised C P matching occurs46 and alternatively localised information on a scale of 0.3 mm is achievable by applying magnetic field gradients synchronously with the MAS rotor.47 In elastomers CP is strongly

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influenced by molecular motion4' and cross-relaxation can be determined in CP MAS NMR experiments by delaying the contact.49 Spectral editing of 13C CPMAS spectra on the basis of the large differences in T1 between non-protonated and methyl carbons was reported" and selective removal of spinning sidebands to determine I3C csa's was discussed.51 Second-order recoupling of the heteronuclear dipolar coupling and csa gives rise to residual 13C line width^.^^ A 2D proton exchange experiment was applied to elastomers based on the residual dipolar coupling between CH and CH2 groups and was related to mechanical proper tie^.^^ Removal of the homogeneous line-broadening improves I3C spectral r e ~ o l u t i o n At . ~ ~very high applied magnetic fields the 'H-13C dipolar coupling can be correlated directly to the 'H isotropic chemical shift in high speed CPMAS experiments and was extended to two dimensions (2D).55 C-C bond-order parameters can be deduced from 2H NMR and in I3C-enriched samples from the homonuclear dipolar coupling.56 I3C spin-echo MAS NMR suppresses signals from the support and is used as part of a combinatorial synthesis approach.57 CP between spin-l/2 and spin-I nuclei (e.g. 2H) has been described using Floquet theory5' and for 2H-'H CP perdeuterated glycine is an ideal standard for setting the HH-match condition, and can also be used for shift referencing and checking the magic angle.59 The first 'H--171Yb CP-MAS spectra from ytterbium (11) complexes were and at low applied magnetic fields (2.35 T) setting up the H H condition for 171Yb indirectly on 199Hg was sufficiently accurate.61 195Ptcsa tensors were determined using polarisation transfer via 19F-195PtJ-coupling.62 Dynamic nuclear polarisation can offer significant enhancement of the NMR and also provide spectral editing.64 Optical pumping of noble gases can also provide significantly enhanced nuclear polarisation and provide spatially localised information with significant scope for application of this t e ~ h n i q u eThe . ~ ~effect of "F-decoupling on 'H NMR spectra was examined and extended to 13C-'H--19F triple resonance66 and a 1H-'3C-14N TRAPDOR experiment measured C-N distances.67REDOR measurements were increasingly developed allowing simultaneous distance measurements and longer distance to be determined in biomolecules.68 l3C--I9F REDOR was used to deduce the shapes of d e n d r i m e r ~ .Rotary ~~ resonance was also employed to deduce structural information with improved excitation of rotary echoes described,70 calculation of the magnetisation trajectory to produce initial inversion7' and an rf-driven rotary resonance experiment correlated isotropic and anisotropic chemical shift inf~rmation.'~1D rotational resonance was used to determine internuclear distances up to 0.44nm.73 Many combinations of interactions have been correlated in multi-dimensional experiments including quadrupolar-csa tensors,74 dipolar-isotropic chemical shift,74as well as giving the relative orientation of tensors, csa and dipolar75and csa tensors at different sites to follow s p i n - e ~ c h a n g eDetailed .~~ 133Csstudies of the correlation of the csa and quadrupolar tensors were made for simple caesium salts and in the case of Cs2Cr04 comparison was made to single crystal measurement^.^^ The dihedral angle and its distribution in organic chain molecules is an extremely important characterisation parameter and the csa-dipolar correlation experiment provides information on this,75 being applied to bis-

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phenol A p~lycarbonate.'~ In a doubly labelled peptide a 2D rotor synchronised sequence provided similar information via the cross-peak intensity although the effect ofthe 14N TI needs to be ~ o n s i d e r e dA . ~2D ~ rotor synchronised sequence can also give the csa tensor orientation in partially oriented polymers.80 Dipolar coupling is often selectively re-introduced to provide structural information" and a sequence for achieving this in weakly dipolar coupled systems was described that again provides information on tensor orientations,82 and for I3C-l5N labelled glycine recoupling was achieved by modulated rf.83 Indirect detection of which exploit 'H information can be achieved via observation of l3CS4and 19F85 the large chemical shift dispersion of the second nucleus. An improved 2D MAT experiment for deducing the csa was described.s6 Solid state NMR techniques were applied to determine oligonucleotide structuress7 and a 3D sequence with homonuclear spin-exchange and heteronuclear correlation was applied to a single crystal peptide." Sequences for deducing complete through space and through bond connectivities, using pulse sequences reintroducing dipolar-~oupling~~ and a solid state version of TOCSY9' were described. DQ experiments can simplify spectra in 13C-labelled compounds by removal of the homonuclear dipolar coupling in the first dimension, as well as the natural abundance background," providing information on the H-C-C-H torsional angle^.^',^^ DQ experiments on 3 1 P can distinguish end and pyrophosphate groups elucidating network c o n n e c t i v i t i e ~ .Information ~~'~~ about slow motions in solids can be extracted from 1D and 2D NMR spectra95 and the influences of homonuclear couplings on such spectra were discussed.96 Techniques that can be applied to obtain high resolution spectra from quadrupolar nuclei in solids were discussed The impact MQ-MAS has made on the study of quadrupolar nuclei is very significant and a number of papers considered improvements in the approach by optimising pulse length^,^^ producing purely absorptive lines by applying a Z-filter,"' acquiring the whole echo"' and the use of rotor-synchronised data acquisition that sums the sidebands giving better lineshape and sensitivity. '02 Modification of the MQ-MAS sequence to remove inhomogeneous second-order broadening was discussed. lo3 Schemes for more uniformly exciting the triple quantum transition over all particle orientations were ~onsidered"~ and quantitatively more reliable data was obtained by using an adiabatic coherence transfer that is insensitive to quadrupolar coupling constants (CQ) below 4 MHz for 23Na.'05It was suggested that MQ could be usefully combined with spinning at 30.6" or 70.1°,'04 and M Q excitation was combined with DOR.Io6The most encouraging aspect of the MQ MAS experiment is how readily a number of groups have implemented this approach and subsequently applied it to a wide range of materials with much improved spectral resolution from crystalline materials such as A1PO4- 14;'07 it has provided sufficient resolution to observe J-coupling to quadrupolar nuclei in the solid state.Io8 27Al MQ MAS in allows the NMR interactions to be deduced at a single applied magnetic field.'" The technique could even detect the initial amorphous decomposition product of Na2Hf03 at the -5% level"' and was used to follow the formation of a highly disordered Alp04 surface layer on y-A12O3."' 19F-27Al C P was used in an MQ-MAS experiment to identify

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sites. l 2 Detailed comparison was made of the complementary information provided by MQ-MAS and DAS experiments, and a scheme for deducing the csa from an MQ-MAS experiment de~cribed."~DOR, DAS and MQ-MAS were compared for "B to resolve different boron coordinations in glasses. l4 There promises to be further developments in this field in the coming year.

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3

Carbonaceous Materials

3.1 Coals, Pitches and Oil Shales - 13CNMR is much used for characterisation of the aromaticity of coals, being applied to a Feng Feng fat coa1,'15 Australian and Indonesian brown coals,' l 6 Bohemian and Moravian coals' l 7 and high sulfur-content Chinese coals."' 15N is now also being applied and variations in the CP dynamics and csa distinguish different species' with pyridinic nitrogens detected"' and in a Chinese coal nitrogen existed in pyridine and pyrrole forms."' "N NMR was used to follow the transformation of plant material to coal revealing that amides are converted to pyrrole forms.'20 In a range of cokes, chars and coal tar pitches the aromaticity determined from single pulse 13CNMR was higher than previously estimated by CP.12' In chars the short TI due to unpaired electrons allows rapid collection of 13C spectra, with 75% of the carbon still observable and the H/C ratio determined from single pulse NMR agreeing with elemental analysis.'21 Drying of coal causes partial decarboxylation'22 and mobility changes of different rank coals on soaking in pyridine were followed using 'H Carbonisation of coals can be followed by 13C'24and in situ 'H NMR. 125 During pyrolysis of sulfur and nitrogen-containing coal co-resites with phenol plus a second component it was observed that curing at 200°C almost completely eliminated the ether and methyol functionalities. 126 The aromatic cluster size determined by 13C NMR in coke deposits produced on coal liquefaction using CoMo-type catalysts based around surface modified alumina was related to the pore volume and the surface ~ 0 a t i n g . A l ~combination ~ of 1D and 2D solid state NMR methods characterised macromolecules produced by combustion of fuels.'28 13C NMR also monitored changes in the quinoline insolubles of coal tars on conversion to pitches.12' 2D 13C shift correlation allowed overlapping tensor information to be extracted and provided information on the orientation distribution of two mesophase pitches and showed a preferential alignment of the aromatic rings along the draw axis.130A DNP-CPMAS NMR sequence provided considerable signal enhancement from a char derived from a naphthalene pitch. 13' The cross-linking reaction of converting a pitch to carbon fibre was detected by 13C NMR.'32 13C NMR showed that pyrolysis of oil shales at 400°C leads to efficient loss of alkyl groups, along with some aromatisation to form polycyclic insoluble residues that can be converted to fullerenes. 133

''

3.2 Fullerenes, Diamonds and Other Carbons - Solvent molecules are often retained in C60 and can be observed by 'H NMR and splitting in the I3C spectrum, 134 with inefficient CP observed for Cho/benzene mixture^'^' but

Nuclear Magnetic Resonance

228

stronger CP for C70/toluene.'~~ At 1.1 GPa and heating to greater than 600 K c60 forms a dense insoluble material with fullerene cages connected via four-member rings that give a 13C MAS NMR signal at 77 ~ p m . The ' ~ ~effect of O2 intercalation in the c60 lattice was detected via the 13C spectrum.'38 c60 was found to be still rapidly rotating intercalated in the cavity of p-tert-butyl~alix[8]arene'~~ but showed more restricted motion between layers of a Mg/Al double hydroxide. I4O Chromatographic separation of fullerenes depends on whether the stationary phase is a long chain alkyl or phenyl-containing group which was characterised by I3C CP MAS.14' Alkali fullerides were extensively studied'42 and for AC60 (A = K, Rb, Cs) the TI and temperature dependence of the shift were very different for KC60 compared to the other two which was related to differences in the electronic structures. 143 13C MAS MMR revealed four carbon sites in Cs&O that collapse to a single line above 350 K,'44 and both 13C and 87Rb were used for Rb3C60, K2RbC60 and Rb2CsC60.'~~ Mercury was intercalated in Na2C60'46 and the metal-insulator transition in (NH3)KC60was detected at 40 K.'47 There were NMR studies of the complexes [N(CH3),C6,]. 1 .5thf'48 and (dibenzo-18-crown-6) KC60, with the latter producing an unexpectedly negative I3C shift.'49 In synthetic diamond DNP produced a lo3 enhancement of the 13C CP-MAS NMR ~igna1.I~'Lithium insertion into mesocarbon microbeads produced 7Li signals at 45 and 27 ppm, attributed to LiC6 and LiO.2C6 re~pectively.'~''H NMR was used to probe motion in M(NH3)xC, (M := Be, Mg, Al, Sc, Y, La) intercalation compounds. 52 The spherical shape of poly(styrene/divinylbenzene) particles was retained during pyrolytic conversion to a carbonaceous product which was followed by 13C MAS NMR.'53 In graphite oxide I3C NMR signals were detected at 60,70 and 130 ppm and showed C-OH bonds condense to C-OC 1ir1kages.l~~ Competitive adsorption on activated carbon between H20 and two phosphorus-containing species was followed by 2H and 3'P MAS NMR,'55 and the effect of activation on D20-adsorption on nutshell and coal-based carbon substrates was investigated by 2H MAS NMR and showed that on unactivated carbon there was negligible micropore ads0rpti0n.l~~

4

Organic Materials

4.1 General - 13C solid-state NMR is an important probe of structure of organic materials with colourless, red and orange-yellow fluorosceins related to lactonic, zwitterionic and quinoid s t r u c t ~ r e s . In ' ~ ~aryl alkyl ketones 13C NMR showed conformational changesI5* and in pure n-C36H74 with increasing molecular motion the peaks sharpen as increasing gauche conformation is present.'59 The structure of tetramethylene oxycarbonyl (2,4,4-trimethyl) pentyl methane in the region between the glass transition temperature and the melting point was examined. 160 Short contact times and dipolar dephasing were applied to determine the structure of peri-substituted naphthalene derivativesL6'and I ,8bis(dimethy1amino) naphthalene'62 and complexes of the latter with picric and hexafluorophosphoric acid.163 1D MAS lineshapes and 2D rotor-synchronised

7: Solid State N M R

229

exchange show a Cope rearrangement in fluorobullvalene. 164 Calculations of the 13C and 'H shift in (benzene)/CrC03 were compared to benzene.'65 'H MAS NMR allowed intramolecular cyclisation reactions to be followed'66 and 31P MAS NMR of P4-t-Bu showed proton transfer in reaction as a lactam base, confirmed by 13C CP-MAS NMR.'67 In dimedone keto-enol tautomerism was shown by coalescence in the 13C spectrum,I6' and in a series of aromatic Schiff bases enol-imine and keto-enamine tautomerism is observed, with the 13C MAS NMR spectra exhibiting residual dipolar effects.169 In aramide fibres isotropicanisotropic correlation VACSY experiments show a very narrow distribution of orientations in Ke~1ar.I~'15N NMR shows a hydrogenldeuterium isotope effect and the 15N chemical shift was related to the in hydrogen-bis-is~cyanides,'~' amount of hydrogen-bonding in a Schiffs base.I7* I3C MAS NMR was used to monitor reactions and structure in multiple crowns173and reaction of C 0 2 with organic compounds. 74 The breakdown of resorcinol-formaldehyde resins under alkaline conditions was characterised by I3C CP-MAS NMR.'75 ' H CRAMPS and spin-echo spectra resolved plastic and rigid phases in fumaric acid monoethyl ester. 176 Chemical shift tensors can provide important structural information such as in aryl aldehyde and formaldehyde, and the l3C--'H spin pair in 3,4-dibenzyloxy' ~ csa ~ benzaldehyde gave J = 26.4k0.5Hz with a *H CQ = 151.5k0.1 ~ H z . 13C tensors were also reported for benzenium, toluenium, e t h y l b e n ~ e n i u m 'and ~~ acylinium ions.'79In doubly-labelled pyrazoles the 15Namine and imine chemical shift tensors were reported' 8o and for polymorphism in 2-acetoamide-4-[bis(methoxy carbonyl)ethyl]amino-4'-nitroazo benzene the "N csa is significantly influenced by hydrogen-bonding. 8 1 Molecules bound to resin surfaces were investigated by 'H and 13C NMR, with the linewidth dependent on the resinsolvent combination'82 and susceptibility matching with a nano-MAS NMR probe provided better resolution. 183 Surface reaction of SNAr was monitored by I9F and I3C MAS NMR.lS4Relaxation times and changes in spectra can monitor atomic scale dynamics with 'H TI in 1,3-di-isopropyl benzene showing methyl group r e ~ r i e n t a t i o n 'and ~ ~ 'H and 13C following the chain dynamics in a c18 alkyl chain.'86 In catecholamine 'H Tl's showed NH3 and CH3 r e ~ r i e n t a t i o n ' ~ ~ and 19F relaxation in N(CH3)4(CC1CC00)2 revealed the CClF2 group dynamics.'88 Dynamics were investigated in P-cyclodextrin hydrates by 2Hlg9 and di-isobutyl phthalate in the glassy state by 'H.l9' In organic solids 13C T1 measurements are complicated by the transient nuclear Overhauser effect and 'H irradiation.'" Table 7.1 summarises some of the other solid state NMR work on organic compounds.

'

'

Organometallics - Solid state NMR is a very important characterisation tool for organometallic materials, with the bulk of the studies carried out using 'H I3C and 31Pbut with other sensitive spin-1/2 nuclei such as '13Cd and '19Sn becoming increasingly popular. Many of these studies are summarised in Table 7.2. Organometallics provide some interesting spectral phenomena, with for example the asymmetry in the csa of 3 1 Pin 5-phenylbenzophosphates reflecting the local site symmetry,225which could also be followed in complexes between

4.2

Nuclear Magnetic Resonance

230

Table 7.1 Nucleus

General organic materials Study

Ref

Structure and motion in bisphenol-A alkanoates (4-MeC6H4)3B303 and adducts with cyclohexane and isoquinoline bis( 5,5-dimethyl-2-oxo-I ,3,2-dioxaphosphorinan-2-y1) selenide 2-(2,2-dicyano-1-methyl-ethenyl) benzoic acid and 3-(2,2-dicyano-1methyl-ethyny1)- thiophene-2-carboxylic acid Oligothiophenes Methyl-3,4,6-tri-O-acetyl-2-deoxy-2[3-(2-phenylet~yl) ureido-P-Dglucopyranoside] 3,5-dimethylpyrazole-2,4,6-trimethyl benzoic acid cis and trans- 1,2-diaminocyclohexane 1,3,2h5, 41'-oxathiadiphosphetane c 14HI402P&-C7HX Imidazol- 1-ylacetic acid and rt -3-ethoxycarbonyl-2-imidazol-yl propionic acid 1,5-dimethyl-2,4,6,8-semibullvalene tetracarboxylic dianhydride Silane e.g. S [ ( ~ - B U ) ~ C ~ H ~ O ] ~ S ~ P ~ M ~ Polymorphism in 4,5-bis[4-methoxyphenyl]-2-(3-nitrophenyl)1Himidazole Triphenylmethyl iodide N-[2-[[[2-[(dimethylamino)methyl]-(4-thiazolyl)methyl] thiolethyll-N'meth 1 nitro-l,l-ethenediamine 5N' %'-di-(4bromophenyI)foramidine 3{5)-(dimethoxylphenyl) pyrazoles Triacylglycerols 1-hydroxycyclohexane phosphonic acid Reaction of porphyrin with, 1,1,1,5,5-tetrakis[(tris(dimethylarnino)phosphoranylidene)amino] phosphonium fluoride 2,3-di-o-methyl-~and L-tartaric acids and hexamethylene diamine Enantiomers of supalast tosilate 4-(3,5-dimethylpyrazol- 1-yl)benzoic acid trifluoroacetate 1,2-dimethoxybenzene Tetrahydronaphthalene derivatives N(o-phenylalky1)-substituted quinoxalin-2( 1H)ones and thiones Tri-(2-thionyl)borane Methyltrithiophosphonic acid and derivatives Di-(a-pyndyl) compounds 1,6-diarninopyrene-p-chloranil 4H-~yclopenta[2,1-b:3,4-b' dithiophene Aromatic acids doped with polyaniline

192 193 194 195 196 197 198 199 200 20 1 202 203 204 205 206 207 208 209 210 21 1 212 213 214 215 216 217 218 219 220 22 1 222 223 224

substituted phenols and triphenylphosphine.226 A very large 1J(P-P) coupling was reported for a triphenylphosphine phosphadiazonium cationic complex with the two-coordinate phosphorus-centre having a large csa of 576 ppm compared to 33 ppm for the PPh3 moiety.227 2J(P-P) couplings were reported for Cu(PPh3)(N03,BH4)complexes228and phosphido complexes with phosphorusmetal triple bonds are strongly deshielded and have very large csa's (-2000 ppm).229 Some cobalt complexes showed very different resolution in the 31P spectra due to variations in 59C0s e l f - d e c ~ u p l i n gand ,~~~ 31Pdecoupling allowed the 13Cd csa tensors in Cd(OAc)2.P(cyclohexyl)3 and CdC104.2P(cyclohexyl)3

'

23 I

7: Solid State N M R

Table 7.2 Organornetallic compounds Nucleus

Study

Ref

Cadmium (11) and mercury (11) thiolate complexes CH3C0O(CH2),SnCl3, (n = 3 - 5 ) bis-[ 1,2:3,4-d~~sopropyl~dene]-u-~-galactopyranosyl-6-0,6-0' thio phosphonyl disulfide and [5,5-dimethyl-2-thiono-l,3,2-dioxaphosphorinan-2-ylI diselenide 1,4-bis(o-aminobenzyl)-1,4-diazocyclohexanewith nickel (II), copper(1I) and palladium (11) { [(CH3CN)3YbFe(C0)4]2CH?CN) and [(CH?CN),YbFe(C0)4] co Me3AsBr2, Me3SbBr2 [w(q5-CSMeS)Me41PF6 [Mn(CO)(PhzPC2H4PPhz)2] F ~ C ~ Z C O ~ S I(Z I R=~ absent, , CH2, CH:CH; R = Bu, Ph) [(Phs>*Hg(~-SPh)zHg(~~h)*l' K4[Ptz(P10zH5)4].2H20,€&[Ptz(Pz05H2)4C12].2H20 and K4[Ptz(Pz05H2)4Brz] .2H20 AuBr-(PMe3) Naz[Bi2(3-carboxyl-3-hydroxypentane-1,5-dioate)].7H20 [CdI-(Sn2(OPr')9}].{ SnIZrz(OPr')9}z Diorganotin 1,3-dithioles-2-thione-4,5-dithiolates Stannocyclohexanes and spirotin compounds

249 250 25 1

+

Rh4(C0)9(p5~2:q6PhC2Ph)Cr(CO)3

252 253 254 255 256 257 258 259 260 26 1 262 263 264 265 266 267 268 269 270

[IndHP04) 4(H20)61(H20)5-H30(C3H2NS)~ [A~X{P(C~HI 1)3}],X = CN, I, Br, C1, SCN, NCO, NO3, C104 X = C1, Br, I AgX{P(C6Hll),~) bis[glycylglycinato]cadmium (11) di-tertbutyl(bis-triphenylsilyl), N-trimethylsilyl-N'-triphenyl sulfur di-imide Chromocenes, Cp2Crdeuterated CpzCr and decamethyl (Cp,*Cr) 27 1 272 (C6H7)Fe(C0)3BF4, C7H9Fe(C0)3BF4 [Mes*N(H)POMes*][GaC14],(Mes* = 2,4,6-tri-tertbutylphenyl) 273 Bis-(su1furimiido)tinand tris(su1furimido)-silicon,-germanium and 274 tin compounds LiN(PPh2),5.3thf 275 T I of [Zn(pt~)~l(BF,)~, [Fe(pt~)~](BF4)2; ptz = 1-n-propyl- 1H-tetra- 276 zole { (tBUPCzH4PtBUz)Ni(~6-C6Fs>) 277 si-P2cO2(co)6 6, Si-P2PdCo2(C0)78 278 [HB(3,5-Me'Pz)3]CdBH4, [HB(3,5-Me2Pz),Cd[H2B(pz)2], 279 [HB(3Phpz)3Cd[HzB(3,5-Me2Pz2)][HB(~-P~~z),C~[(BU'CO)~CH], [HB(3,5-Mezpz)3Cd[SzCNEt2];pz = pyrazol Zn'+, Cd' + ,and Hg2+ complexes with 2-(a-hydroxybenzyl) 280 thiamine monophosphate chloride ICd{M,(OPr'),}, {Cd(OPr')3}Ba{M2(OPr')9};M = Ti, Hf 28 1 [8-(dimethylamino)-methyl-1-naphthyl]phenylchlorosilanereaction 282 with fluoren-9-yl-lithium (M(dmb)2Y},, M = C u f , Agf; dmb = 1,8 diisocyano-p-methane, 283 Y = BF4-, PF6-, NOT-, ClO4-, CH3CO2(1 -hydroxyalkyl)dimethyl phosphine sulfides 284 SnC14(MeS(CHz),SMe) 285 AgS(CH2)3CH3 286

232

Nuclear Magnetic Resonance

to be determined.231Detailed studies of tertiary phosphine substituted alkyl and tetracarbonyl manganese (I) complexes allowed all the NMR interaction parameters (J, AJ, dipolar, CQ, csa) to be determined.232NMR showed that in 1:1 adducts between silver nitrate and di-iodo compounds the organic molecules act as donor l i g a n d ~ ,and ~ ~ ~that copper di-imine complexes have very similar solution and solid state structures.234Transformation of phosphine sulfides to phosphines, and to a rhodium complex were followed by 31PNMR,235and [ I . 11 ferrocenruthenoceno phases, oxidation products and dipeptide cadmium and zinc complexes were characterised by NMR.236 Organometallics often show catalytic activity and are deposited on surfaces. 31PNMR was used to examine several organometallic films237and changes in platinum speciation on coating Si02 and A1203 particles were observable by 19’Pt NMR, provided that the site symmetry of the platinum remained quasi-octahedra1.238 On silica surfaces complexes formed by (C0)2Ni[PPh2(C6H4)SiMe20Et]2,239PPh2CH2CH2(0Et)3,240 ZrH,241CpCr242and the surface reaction of Bu3SnOSnBu3 with siloxane bridges243were all characterised by solid state NMR. Reaction of Sn(n-C4Hg), with alumina forms (AIO), + &Bu3 --z compounds which were characterised by 13C and Il9Sn CIP-MAS,244and reaction of ether phosphine ruthenium (11) complexes with tetraethoxysilane and Al(0’Pr) produces numerous Si-@A1 linkages.245NMR followed the reaction of various sol-gel produced C5Me4H(CH2)nSiMek(OEt)3-k compounds with CpTiC13 and Cp*TiC13to form complexes,246and for ether-phosphine ligands that were sol-gel reacted with Si(OEt),, MeSi(OMe)3 and Me2Si(OEt), and ruthenium complexes, NMR showed that those with P-Ru bonds were more rigid.247The adsorption process of CO in fuel cells was followed quantitatively by NMR of 13C0 and discriminated between different bonding arrangements which were assigned.248 4.3 Bio-Organic - To elucidate the structures of large bio-molecules the dipolar coupling is being increasingly used to determine distances via REDOR and DRAMA sequences. Direct 1D spectroscopy is still useful and calculations of the 13C shift in amino acids were made through an ab-initio GIAO-CHF method,287 and the I3C csa tensor of enriched CO in 1,2-dimethylimidazole and 1methylimidazole gave clues as to the bonding of CO to hemeproteins.288The csa of carbonyl groups in peptides and polypeptides were investigated289and I9F csa’s of 5fluorotryptophan and tetradeutortryptophan labelled E-coli glucose/ galactose receptors were also determined.290 The hydration states of the salt nedocromil magnesium29’ and the hydrolysis kinetics of colloidal chitin292were followed. Bacteriorhodopsin is widely studied via NMR,293with changes in its conformation in the temperature range -40°C to 110°C followed by 13C NMR294 and specific l3C-labe1ling was employed to give structural informat i ~ n . DNA * ~ ~ was also widely investigated296with the orientation distribution of fibres derived from the csa measured from a new sequence,297and in specifically I3C-labelled oligomers a windowless homonuclear decoupling sequence provided distance measurements298and was developed into a double-quantum sequence that is applicable to a wider range of csa’s and offsets.299The orientation of an epitope in a strong magnetic field on the surface of a bacteriophage was

7: Solid State N M R

233

Table 7.3 Bio-organ ic Nucleus

Study

Ref

Cyclo-[S-his-S-Phe] Protein dynamics DRAMA and REDOR of 3-enol-pyuvylshikimate-3-phosphate synthase Cross-linking in peptidoglycan TIMeJHASc]. 1/2C3H,>0[SnMez(ASc)], SnBu,ASc NaDPH on lactobacillus casei dihydrofolate reductase Polysaccharide agarose and products with tresyl chloride Proteins and model systems Enkephalins REDOR of EPSP synthase Abbot-79175 a 5 lipoxygenome inhibitor Bovine serum albumin, y-globulin Sitosterol, stigmasterol Bile acid binding with barley P-glucan Delaviridine mesylate C30surface bonding phases with vitamin A acetate isomers Poly(L-glutamate) with n-fluoroalkyl sidechains Prion protein H 1 fragment Polypeptides Oligonucleotides Labelled amino-acids Relaxation of bacterial Rnase, lysozyme and bovine serum albumin Bibullvaleny1 A cyclovir and cytosine complex REDOR of phosphonamidate transition state analogs of themolysin 2J-hexanedione adducts of E-amine moieties Intercatechol crosslinks in tobacco hornworm cuticle

317

318 319 320 321 322 323 324 325 326 327 328 329 330 33 1 332 333 334 335 336 337 338 339 340 341 342 343

344 345 346 Dissolution of polysaccharides in agar 341 Leucine enkephalin Methyl 3,4,6-tri-o-acetyl-2-(3'-arylureido)-2-deoxy-~-~-glucopyranos~de 348 349 Bombyx mori silk fibroin 350 Zervamicins 351, Silk fibrion fibres 352 353 Peptides attached to macrobeads 354 a-, P-chitin 355 Hydrogen-bonding of amines 356 DRAMA in helical peptide 351 Orientation of helical peptides in membrane bilayers 358 Trimethoprim 359 REDOR of complex elongation factor Tu with magnesium gua 0s; e diphosphate 360 Cadmium substituted myoglobin 36 1 Biosynthesis in methanosphaera stadtmanae 362 Fibre and core tissue flax 363 Spin diffusion in drag line silk 364 Archaeological silk

Chymotrypsin in ice a,a trehalose

234

Nuclear Magnetic Resonance

inve~tigated.~"NMR provides structural information on the hydrogen-bonding in biological systems301and 1 7 0 was applied to oxalic acid dihydrate, and the chemical shift and quadrupole interactions were extracted and the 'H-170 CP dynamics inve~tigated.~'~ For assigning "N and I3C spectra uniquely in uniformly labelled proteins using mu1ti-dimensional NMR spectra resolution of better than 1 ppm is required for peptides with 30 amino acid residues.303The first 13C NMR spectra were obtained from frozen healthy and tumour tissues which showed differences in the intensity of methylene chains that are probably a result of changes in the dynamics.304As the pH is changed water in a Sephadex gel shows differences in ' H T1 as the exchange rate change^.^" As metal ions are added to alginic acid the gelatinous products were characterised by I3C NMR.306 Bio-synthesis of aliphatic bio-macromolecules by marine microalgae showed the formation of linear aliphatic oligomers C28-C34 linked by ether bridges.307 Signals from bacterial photosynthetic centres were enhanced by CINDP for 1 5 ~ 3 0 and 8 13~~309 Microbial conversion of glucose added to artificial soils was followed by 13C NMR with the cation type having a significant impact on the amount of c o n v e r ~ i o n . ~13C ' ~ NMR characterised insoluble precipitates in red wine bottles3'' and from aromatic bitters of I3C NMR compared soluble and insoluble chitin^.^'^ 'H T1, studies suggested some limited miscibility of waxy corn starch and wheat and cross-linking of starch with epichlorohydrin alone3I5 and 3-chloro-2-hydroxypropylammonium chloride in the presence of NH40H316 was optimised using 13C NMR spectroscopy. Table 7.3 lists other solid state NMR studies of such materials.

4.4 Liquid Crystals, Membranes, Bilayers, Cell Walls and Woods - NMR can probe successfully motion and order in interfaces, such as cell walls, bilayers and membranes. Incorporation of the steroid a l p h a ~ a l e n eand ~ ~ ~tri0ctani1-1~~~ into bilayers was followed by NMR. Orientation of phospholipid bilayers in strong magnetic fields can be followed through "N csa367and the secondary structure of incorporated maganin revealed by REDOR."* 'H--13C dipolar recoupling as used to determine the order parameter in lipid bilayers,"' MAS and heteronuclear Overhauser spectroscopy provided information about lipid interact i o n and ~ ~ 'H ~ ~MAS and NOESY give proton-proton distances."' For peptide K2CzoK2A-amideincorporated in 1,2-d2~-myristoyl-sn-glycero-3-phosphocholine H MAS at 14 kHz produces resolution of 68 Hz allowing conformation, folding and dynamics to be with a combination of *H and '*N providing an estimate of the exchange lifetime,373and the structure and dynamics of water in membranes followed by the cross-peaks in 2D MAS NMR.374Solid state NMR is now regarded as an integral part of a general approach for optimising membrane-protein structures375 and has been used to structurally refine gramcidin A transmembrane channels.376 For carboxylic ionophone lasalacid A dissolved in a lyotropic liquid crystal ROESY provided some structural information,377the I3C csa tensor provides information on the orientation of cis,cis-m~conitrile,~~~ and the effect of chain length and temperature on ordering

'

7: Solid State N M R

235

Table 7.4 Liquid crystals, membranes, bilayers, cell walls and woods Nucleus

Study

Gramicidin A in dimyristoylphosphatidylcholine Cardiotoxin in dimyristoylphosphatidic acid Cholesterol and cholesterol sulfate in dimyristoylphosphatidylcholine Lipid hydration in monomethyl diolecyl phosphatidyl ethanol amine dispersions Polysaccharide of allium cell walls 1 3 c I 'c Microbial cellulose 'H, "C, "N Naf transport in gramicidin channels I3c Transformation of cellulose in cotton lintens and softwood pulps 'H, "P Hydration properties of 1-palmitoyl-2-olecyl-phosphatidylethanol amine alone and in the presence of cholesterol I3 c Woods; yellow poplar and hard maple Alkoxyethyl phosphodiester derivatives 'H 1 3 c Retting of kenof fibres Ordering of dimyristoylphosphatidylcholine with temperature and 'H cholesterol Oriented histidine-containing polypeptides in phospholipid bilayers "N I3c Cell walls in wheat bran 31p Fluid phase effects in lipid bilayers I3c Location of cholesterol in phosphatidycholine membranes I Conformation of galactocerebroside in bilayers Membrane peptides 'H I 3c Cholesterol/lipid mixtures 1 5 ~ - 13 c Ligand site of a bacterial chemotaxis membrane receptor La-water-SDS-octanol system 'H Phospholipid headgroup dynamics in diolecylphosphatidyglycerol'H, 31P cyctochrome complexes 5-alkoxyisophthalic acid 'H Hydrogen-bonded carboxylic acid pyridyl complexes 'H 'H 31P 'H, 31p 'H

?H 'H

Complexes of 5-octadecyloxyisophthalic acid and cyclic oligo-amines Conformation of met- and leu-enkephalin in liquid crystals

Ref 396 397 398 399 400 40 1 402 403 404 405 406 407 408 409 410 41 1 412 413 414 41 5 416 417 41 8 419 420, 42 1 422 423, 424

of C n H z n + *P03H(n = 8-18) on Z r 0 2 was characterised by I3C NMR.379Other studies are summarised in Table 7.4. NMR has played a major role in characterising cellulose with both spectroscopy and relaxation times being useful. Cellulose in cell walls of Arabidopsis thaliana leaves was e~amined,~"'H T1,-weighting of the 13C spectra distinguishes ordered and disordered cellulose I,38' and calculations show that structural differences in cellulose are reflected in the shift of C6 and not of the Cz or C4 Reaction and degradation of cellulose were also followed by NMR3s3as were the linkages formed by cellulose-lignin reaction384and changes due to brown rot were followed by '3C CP-MAS.385Addition of theophylline to microcrystalline cellulose produced no change in the I3C CP MAS NMR spectrum.386Fungal action on wheat and tannins388was followed by 13C as was conversion of wheat straw to lignin by an enzyme.389Heat treatment to mimic burning examined the thermal transformation of ligno-cellulose in a I5N-

Nuclear Magnetic Resonance

236

enriched rye grass.390 Decomposition of organic material such as eucalyptus litter39' and carbohydrates in peat392 were also followed. Wood is a complex phase mixture and the three main components; cellulose, hemi-cellulose and lignin, on the length scale of spin diffusion (- nm) behave as separate phases.393 In bonding wood with 99% "N-labelled diphenylmethane di-isocyanate resins different nitrogen linkages dominate as the moisture is varied.394 The CP dynamics and 'H relaxation reflect mobility changes with hydration of citrus cell walls.395

5

Organic-Inorganic Materials

5.1 General - Sol-gel processing attracts interest for forming atomically mixed materials and NMR is used to probe variations in the atomic scale structure. Formation of mullite has attracted a lot of interest with NMR showing that for reaction of tetraethoxysilane (TEOS) with Al(N03)3 Si-0-Si bonds form rapidly that are then gradually broken to form a single silicon site, Si(OA1)30H.425The strong influence of formamide and D M F on aluminium incorporation426 and that optimum lower temperature processing maximises formation of the 30 ppm 27Al resonance have been noted.427 NMR also showed that for TEOS/A1Cl3 mixtures high pH improves silicon/aluminium mixing in mullite gels.428 For Si02-Ti02 sol-gel produced nanocomposites the Q-distribution for silicon suggests non-uniform mixing429and mechanical mixing of elemental aluminium with a Ti02.H20 hydrogel forms some alumina that is converted on heating, forming A1-0-Ti The stability of trifunctional siloxanes is reduced by addition of aluminium sec-butoxide as a result of the presence of A106432 and incorporation of phosphate groups in alkoxysilanes was characterised by 29Siand 31P NMR.433 Organotin hybrids were synthesised from the macro-cation [ ( B ~ S n ) l 2 0 ~ ~ ( 0 Hand )~]~ characterised + by 13C and '19Sn CP MAS NMR,434 and the complex [A12(p-OH)2(C14H604)4]-Na4H204 and its mono-hydrate were distinguishable from their 27Al NMR spectra.435The formation of Z r 0 2 from Zr(OPr)4 can be significantly changed by modification with 173-propanedioland 1,3-butanediol which was monitored by I3C NMR.436 The changing symmetry and local dynamics of three solid phases of LiN(SiMe20CMe3) were monitored by 6Li, 7Li, 13C and 29Si NMR.437The dynamics of lithium in a layered silicatepoly(ethy1ene oxide) intercalate were investigated by 7Li NMR.43sThe degree of ordering and surface interaction of octadecylphosphonic acid with Zr02, Ti02 and zirconated silica were probed by 13Cand 31Pand 'H WISE experiments.439 Silica-based materials occur widely and 29Si N M R characterises the distribution of organic groups in modified silica gelsu0 and 'H MAS NMR can also provide rapid characterisation of functionalised silica gels.441 Base-catalysed conversion of 1 12,2-tetrachloromethyl disilane to polycarbosilane between and 180°C and 450°C was followed by 13C and 29Si NMR.442Membranes formed by co-hydrolysis of (C6H5),,-Si(OC3H3)4-,, (n = 1,2) and Si(OCH2)3 depend on the organoalkoxide functionality,443and octameric units formed from functionalised silsesquioxanes were characterised by 13C and 29SiNMR.444Lipases entrapped in

7: Solid State N M R

237

sol-gels formed from RSi(OCH3)3alone or mixed with Si(OCH3)4show enhanced enzyme a c t i ~ i t y , ~and ' novel bridged bis-imide polysilsesquioxane xerogels were characterised by 29Si, 13C and "N NMR.446Pyrolysis of a polymer formed by hydrolysis/condensation of poly(diethyoxysily1enemethylene) to a silicon oxycarbide was followed by NMR,447 and 29Si NMR characterised the non-linear optical dye material formed by reaction of 4[N7N'-bis(2-hydroxyethy1)amino]-4'nitrostillbene and TEOS.448 Co-condensation of Si(OEt), and trifunctional alkylsilanes gives novel polymers with a high degree of cross-linking of which 13C and 29Si NMR are important probes, including pin-pointing the sol-gel transiti~n.""~

5.2 Polysiloxanes - The effect of 0 2 additions on plasma produced polysiloxanes was characterised by ' H 13C and 29Si MAS NMR450*451Thermal transformations of siloxanes are important and were followed for polydimethyland the chars formed by thermolysis s i 1 0 x a n e ~and ~ ~ p~lymethylhydrosilane,~'~ of polyhedral oligomeric silsesquioxane were examined by NMR.454Functionalisation of polysiloxanes can produce immobilised t h i ~ l s ,a ~m~i ~n e ~ thiol,~~~ a m i n e ~P-cyclodextrin457 ,~~~ and phenolic polymers.457Surface bonding of cyclic organosiloxanes to silica was followed by NMR,," which also checked the homogeneity of s i l i c a - ~ i l o x a n eand ~ ~ polyimide-siloxane460 ~ hybrids. H, 3C and 29Si NMR of silicone breast implants showed no difference in the atomic scale structure of virgin and explanted samples461and also showed the presence of methyltrifluoropropylsiloxane and diphenylsiloxane 5.3 Soils and Humic Acids - The organic fraction of soils is amenable to I3C CP-MAS NMR and there were reports from soils on vegetation,463crop litter,463 forest litter,463comparison of litter and humic compounds from different mineral horizons464and from the organic matter isolated from lakes which was shown to be largely aliphatic.465The form of isolated carbon was investigated466 and the effect of brown coal emissions on soil was probed by 13C NMR.467In excessively fertilised soil 27Al and 31P NMR provided detailed information on speciation, with phosphorus mainly associated with aluminium although some other phosphates occurred.468Binding of pesticides in sandy soils was investigated469 and the cadmium species formed on adsorption in montmorillonite clay elucidated by 'I3Cd NMR.470NMR also probed the organic leachates adsorbed onto alumina,47' Fe203472 and surfaces. Bioremediation to desorb hydrophobic organic compounds was followed by I3C NMR,473and the sorption of a-naphthol depends on the structure and composition of the organic substances in soils and sediments.474 13C and "N NMR spectra from fungal melanins were compared with soil organic matter.47513CNMR of a vertisol from Southern Mali showed a high level of aromatic compounds and a high degree of lignin d e c o m p ~ s i t i o n Fast . ~ ~ ~MAS was applied to humic acids to reduce the influence of spinning sidebands477and the changes of humic acids on exposure to UV were followed by NMR.478The role of the reaction of phenols and quinones with proteins in humic acid formation was studied by 15N CP-MAS,479 which was also used to examine the binding of "N-labelled aniline to fulvic and humic

238

Nuclear Magnetic Resonance

acids.480I3C NMR was used to analyse humic and fulvic acids fractionated from swamp water4*’ and the early diagenesis of Black Sea sediments.482

6

Inorganic Materials

6.1 General - ‘ H MAS NMR revealed two proton sites in Ag3PW12040 at 6.4 ’ ~ also and 9.5 ppm, with the former species mobile at room t e m p e r a t ~ r e , ~and characterised the silver and thallium salts of 12-tungstophosphoric, 12-molybdophosphoric and 12-tungstosilic CH30H molecules adsorded onto H3PW12040were probed by 13C ‘H and 31P NMR4” and 31P followed the thermal decomposition of H3PMo12040.12H20.486170NMR of H3PMo12040 showed rapid mixing of M o = O and Mo-0-Mo species.487 ‘H MAS NMR examined proton conduction in layered HNbW06.xH20 (x = 0.5, 1.5) showing that the conduction mechanism changed from diffusion of H 3 0 + at x = 1.5 to ‘H MAS NMR was exchange between cage protons and H 3 0 + at x = 0.5.488,4R9 also applied to preparation of MgO catalyst supports490and to identify surface species on silica and y-alumina in controlled formation of Z r 0 2 from ZrC14 ~ a p o u r . 29Si ~ ~ ’MAS NMR applied to Zr1-xSix02suggested a solubility limit of x = 0.15 below 950°C with tetragonal Z r 0 2 ~ t a b i l i s e d 31P . ~ ~was ~ also widely ~~~ conapplied in characterising plasma sprayed h y d r ~ x y a p a t i t e ,compounds taining P-S and P-Se bonds,494 adsorption of phosphorus compounds on oxides49’ and vanadium phosphorus oxide catalysts,49hwith other examples given in Table 7.5. Solid state NMR also characterised interstitial sites in yttrium d i d e ~ t e r i d and e ~ ~reactive ~ intermediate ~ilylenes.~~’ As an increasingly multinuclear approach is applied 7Li NMR showed two In solid solulithium coordinations in amorphous LiNbOmi2(0H)6~m.nH20.499 tions NMR was used to measure the cation distribution in Znl-xMnxA1204’00and for ZrV2-xPx07NMR showed V-0-P linkages preferentially form with REDOR giving P-V distances of 0.342 nm.’O1 ”V NMR showed heating of V205 results in V043- units with MgO, hydrotalcite and sepiolite but not A1203’02 and electric field gradients at vanadium sites were calculated in V2OS and y-LiV20s, with the chemical shift and quadrupolar contribution in V20s separated by measurements at 4.7 and 7.1 T.’03 The effects of arsenic compounds on hydration of Portland cement and their leaching was investigated by NMR.’04 23Na, 27Al and 31P including 23Na MQ NMR were applied to examine the local environments in Na3A1P309N and Na2Mg2P309N,”’ and ”N NMR followed the formation of I7O NMR continues cubic TaNo.’ by reaction of [ ( ~ B U C H ~ ) ~and T~N NH3.’06 ]~ to develop with MAS spectra from a range of ionic AB03 and A2B03compounds that have small CQ’S with the chemical shift largely determined by the B cation,’07 with other I7O NMR work reported from gel-produced hafnia and a series of hafnates.”’ The effects of coordination number on ’I3Cd chemical shifts were investigated in CdI2 and K2[CdI4Iso9 and cadmium (11) malonate compounds.’” 207PbNMR was reported from a series of compounds,’I’ as was the careful determination of the chemical shift tensor elements and the effect of temperature.’12 High speed MAS was applied to natural abundance 33S.’’3

7: Solid State N M R

239

Table 7.5 Inorganic materials Nucleus

Study

Ref

19F

CaIO(P04)6F2x(0H)2 - x CaHP04, CaHP04.2H20 Chemical reaction of Ca(OH)2 and Si02 under mechanical stress La2Lio5M3+o504 (M = Cu, Ni or Co), La2..,Sr,Cul - ,Li,04 Phosphoellenbergerite, holledahlite LiF, CsF AYbI3, (A = K, Rb, C S ) HxNbV05 a-tricalciurn orthophosphate Th6HxBr15(x = 5,7) Na2Nz02 (H30)2[V4(HP04)(Po,) @6Fi 2"C7H I 416 Ti203(H2P04)2.2H20 K(VO)(Se03)2H Fluoroenyllithiurn complexes Zinc phosphates Na2HP3O1o.Hz0 L ~ &a0 o 57Ti03 and L ~~IA I 3Ti o I 7(PO4)3 Ba(C103)?2 H 2 0 TI in NH4C104below 20 K SnS, SnS2and NaS-SnS2 compounds SrdA102112(Te03)2 H3PW12040 encapsulated in faujasite

514 515 516 517 518 519 520 52 1 522 523 524 525 526 527 528 529 530 531, 532 533 534 535 536 537

31p IH ' ~ i 'H, 31P I9F I7lYb "V, 95Nb 31P

IH 15N "F 31p 'H 7 ~ i ,IP 31P 7 ~ i 2H 'H " ~ n 27A17""e 31P

6.2 Silicates and Aluminosilicates - The effect of sulfate and alumina stabilisers on p-calcium silicates was determined by NMR,53swhich also probed aluminium substitution in calcium silicate hydrates.539An extensive study applied 29Si and 170MAS NMR to the hydration in calcium silicate hydrates.s40ps42The extent of tetrahedral aluminium in a Chinese montmorillonite was determined by NMR543 and the conversion of lutetium saturated montmorillonite to lutetium disilicate was f o l l o ~ e dIn. ~mullite ~ precursors the aluminium distribution was determined by 27Al NMR,545the evolution of the silicon environment in a mullite A14+2,Si2-2x010-x solid solution was followed by 29Si NMR,546and characterisation of mono- and diphasic mullite precursor powders was carried out by NMR.547 Thermal transformations of aluminosilicates were widely studied by NM R and included alkali-leached samples,s48 allophane formation from m e t a k a ~ l i n i t e , ~ ~ ~ Georgia kaolinite dehydroxylationSS0and the natural formation of metakaolinite by coal c o r n b u ~ t i o n . ~There ~' was a detailed NMR study of the thermal ' ~ the influence of mechanical grinding on transformation of p y r ~ p h y l l i t e ~and this process was examined.553Mechanical milling of Ca(OH)2 with Si02increases the acidity of the OH groups as indicated by 'H MAS NMR.554Formation of a consolidated mortar by mixing ground kaolinite with water glass was followed by NMR.555In fluorinated clays the I9F chemical shift reflects the occupancy of the octahedral layer.s56 133CsNMR shows different adsorption sites on the surfaces ~~ of kaolinite and illite.557 Acid dissolution of hectoriteSSSand ~ e p i o l i t e 'were followed by NMR, as was conversion of kanemite to mesoporous silica.560'H

Nuclear Magnetic Resonance

240

Table 7.6 Silicates and alurninosilicates Nucleus

Study

Ref

Monoclinicjtriclinic phase changes in Na2Mg5SixOZ I (OH), Ba, - xA12- $i2 + xOx Phase changes in tridymite Natrolite/thomsonite intergrowths in basaltic rocks Silicate hydrate containing tetraethylammonium and hexamethylbenzotripyrrolium Crystallisation of Nax[AlSi04]6(N02)2 y-Fez0,-Si02 nanocomposites Flocculation of colloidal silica with alumina polymers Viseite Reduced Upton montmorrilonite Na4A13Si9024C1 Crystallisation of basic sodalite Na~[AlSi041h(N03)2 Nax[A1Si04]6(103)2- .(OH,H@), Pillared beidellites

564 565 566 567 568 569 570 57 1 572 573 574 575 576 577 578

NMR from H 2 0 in channels in beryl produced a Pake pattern that suggests the absence of anisotropic motion on the NMR timescale.s6' 'H MAS NMR from nominally anhydrous minerals gave two signals from clustered OH and static H 2 0 molecules.562 The linewidth of 29Si MAS NMR signals was taken as a measure of disorder in a range of silicas.s63Other such studies are summarised in Table 7.6. 6.3 Microporous and Mesoporous Materials 6.3.2 Silicate-Based Systems - Solid state NMR has become widely used for characterisation of aluminosilicate molecular sieves. Last year MCM-41 was the most extensively studied such material by NMR with reports on its struct ~ r e boron , ~ s ~ b s~ t i ~t u t~i o~n titanium , ~ ~ ~ ~ i~n~c ~o r p ~ r a t i o n , ~ vanadium *~~~~*~ s u b s t i t ~ t i o n ,tin~ ~ ~ ~ ~ ~ ~ ~chromium ~~~ addition^,'^' effects of the removal of organic templatess9' and its dealumination to produce Na-A zeolite.s92 ZSM-5 was also much examined by NMR with studies reporting its interaction with molybdenum,593its low temperature c r y s t a l l i ~ a t i o nthe , ~ ~effects ~ of calcination,595nickel modification of HY-ZSM-5 zeolites96and 27AlMQ-MAS revealed two inequivalent A104 sites.597 Other structural studies by NMR included ZSM-11 ,598 MCM-22,599 SSZ-24,600HMS,"' the interaction of Pd2+ with NaX,601 the identification of five unique tetrahedral sites in VPI-8602 and dehydrated zeolite NaX which was characterised by 23Na.603The ability to isomorphously substitute allows a wide range of compositions with galliumsubstitution becoming increasingly popular and gallium has been incorporated in m ~ r d e n i t e , ~faujasite,60s '~ ZSM-5,606-608MFI p-zeolite,608 ferrieri te,608 offretite611 and ZSM-20.612 Titanium is also much substituted into such structures with studies of titanosilicates and amorphous M41 S,613within ETS-10 aluminium and gallium avoiding linkages with titanium,614niobium replacing titanium in ETS-46'5 and microporous titania-silica formed by co-hydrolysis of ,6093610

7: Solid State N M R

24 1

alkoxides producing an atomically mixed product according to 29Si MAS NMR.616Other substitutions studies included zinc,6o6titanium617 and iron6I8 in ZSM-5, iron in mesoporous silica,619cobalt in MF1620and vanadium incorporation in silicate molecular sieves in the presence of dodecylamine which produced a (SiO)3V:O coordination62' and vanadium present in VS-2 silicalite.622 Tin silicalite has a range of metal additions Boron incorporation as B 0 4 in titanoborosilicates was detected by 'B MAS NMR.624 One of the most important factors controlling the properties of microporous materials is the level of aluminium so that dealumination is a vital process. Dealumination was followed by NMR in a series of Y zeolites with vanadium attacking Si-0-A1 zeolite B,626and HZSM-5.627-629The nature of the extra-framework aluminium produced is extremely important and has been characterised in dealuminated m ~ r d e n i t e , ~MFI,631 ~' and HZSM-5,632with three types of aluminium site detected in dealuminated zeolite HY,633and 27Al, 29Si and 29Xe applied to characterise dealuminated HZSM-5.634Phosgene removes aluminium from Na-mordenite lattices635and the oxidation states in dealuminated mordeni te were examined.636The nature of the extra-framework aluminium is important in determining the activity, selectivity and stability of X and Y zeolites.637 In such lattices NMR provides detailed information on the atomic distribution638 with aluminium showing distinct site preferences and this was examined in dealuminated ZSM-5, mordenite and Y zeolite,639 as well as in f a ~ j a s i t e ~with ~ ' careful computer simulation of spectra a useful addition.64' Reactions to prepare zeolites can be characterised by NMR as illustrated by formation of zeolite 4A from kaolinite strongly depending on the dehydroxylation temperature,642 conversion of aluminosilicate PREFER to FER-type zeolite643and conversion of kanemite to mesoporous FSM-16644and ZSM-5.64s Many of the properties of these materials depend on the sites for adsorption and protonation within the cavities and 'H NMR can often directly observe these. With 'H NMR there were studies of the proton sites in dealuminated and weakly rehydrated zeolite HY,646 in ZSM-5, FeZSM-5, mordenite and zeolite Y,647faujasite,@' HZSM-5649 and the acidity of mordenites."' For HZSM-5 a combination of 'H MAS and 'H-27Al double resonance showed that the protons are associated with a l u m i n i ~ m . 'H ~ ~MAS ' ~ ~ NMR ~ ~ employing magnetic fields up to 18.8 T gave signals at 1.2 ppm (Si-OH) and 2.6 ppm (Al-OH) with four different bridging units detected in a range of zeolites.6s3The long-range interaction of cations with OH groups in HZSM-5 was detected by 'H MAS NMR.6s4 Cations within the cages were also investigated by NMR and included sodium in The effect of caesium oxide encapsulation and Mo(CO)~loaded in CsNaX and CsNaY was followed by 27Al and 29Si MAS NMR,6s7 and the caesium sites in exchanged Y were characterised by 133CsNMR.65s The adsorption sites of ZSM-12 were characterised by '29Xe NMR,659 and the effect of (C, &33)(CnH2n + I)(CH3)2N Br - on mesoporous molecular sieves was investigated.660 KFI-containing 18-crown-6 ether was characterised by NMR66' and vanadium in the cages of zeolite Y forms a V20s-like square pyramidal arrangement.662There were NMR studies of silica binders added to ultra-stable zeolite Y663and zeolites added to fire-retardant polymers.664

'

+

242

Nuclear Magnetic Resonance

6.3.2 Other Structural Studies - Aluminophosphates also form a range of microporous solids that are amenable to NMR and studies included VPI-5,665 AFI,667 STA-1,668 cobalt-substituted CoSAPO-36 and A1PO-36,666 c 0 S A P 0 - 4 6 , ~magnesium ~~ substituted MgAPO and MgSAPO-34 and -44,670 metal substituted MAPO-3 1 67' and the aluminophosphate precursor CAM-1 .672 Lamellar aluminophosphates containing organic molecules prepared from alcohols were characterised by NMR.6733674 Advanced N M R techniques provided additional structural information, with for SAPO-37 29Si-27A1TEDOR showing that silicon substitutes for phosphorus and 27Al-3'P 2D TEDOR revealing three aluminium species.675 The better resolution provided by MQ MAS of 27Al revealed structural detail in a microporous aluminium methyl p h ~ s p h o n a t e ~ ~ ~ and the structural changes accompanying the 70-80°C phase change in VPI-5.677 'Be and 31PMAS NMR were applied to BePO and BeAS0.67831P,19Fand I3C NMR were applied to the fluorinated gallophosphate ULM-3679 and Mn-1 containing cobalticenium cations was characterised.680 VzO5-layers were characterised by "V NMR supported on zirconia681,682as was the influence of potassium on V205 deposited onto t i t a ~ ~ i a 3'P . ~ ' ~MAS NMR was used to characterise microporous zinc phosphates,684 and vanadium phosphorus oxide precursors and catalysts.685NMR showed B03, B04 and A106 coordinations in microporous boron aluminium oxychlorides BAC( 10)686and BAC(3),687and ' H MAS NMR revealed the proton acid sites on niobic acid.688

6.3.3 In-Situ and Surface Reactions - It is crucial to understand the reactions that proceed in microporous materials and following these in situ by l3C NMR is generating a lot of interest. Laser heating can rapidly heat samples, with for 15 s, and was applied to methanol-to-gasoline example 600 K reached in conversion and ethylbenzene d i s p r o p o r t i ~ n a t i o n . Other ~ ~ ~ * I3C ~ ~ ~NMR studies included n-hexane conversion on platinum and palladium-supported materials with four parallel reaction pathways identified,69'p692dehydration of tert-butyl alcohol over HZSM-5,693propane-2 a1kylation of benzene over gallium modified HZSM-5,694decomposition of 2-chloroethyl sulfide on isomerisation of 1-butene by 12-tungstophosphoric acid supported on Si02,696conversion of butan-2-01 by AgTh2(P04)3,697decomposition of dichloromethane and chloroform on ZnY698 and methanol to hydrocarbon conversion on HSAPO-34.699 Carboxylic acids were formed from alcohols and olefins in HZSM-5 via trapping of alkyl carbenium ions and CO7Oo and in situ examination of isobutane alkylation over zeolites was p e r f ~ r m e d . Reactions ~~' on heterogeneous catalysts in general were studied,702 as was reaction of propane and propene in the ' ~ cumene disproportionation in zeolite presence of N O and 0 2 on C U / M F I , ~and p where intermediates were identified.704The adsorption process plays a crucial role in such surface reactions and adsorption was examined by NMR for dodecanes and dibenzylketones on ZSM-5,705 1- and 2-butene on NaGeX and SnSb0,706the state of acetyl chloride on a range of zeolite surfaces,7o7olefins and CO on HZSM-5 during the acylation process70s and for the carbonyl of acetone on HZSM-5 the 13Cshielding tensor was determined."' For surface groups the ability of various microporous zeotype materials to

-

7: Solid State N M R

243

protonate methanol was investigated7” and the interaction of surface hydroxyls and C2Cl4 was revealed by ‘H MAS NMR.711The adsorption of methanol on HZSM-5 produces some aluminium sites with large CQ’s712 and 2D NMR probed surface acid sites.713For alkylation of PhMe with MeOH or M e 2 0 over HZSM-11 I3C MAS NMR identified the surface adsorbed species.714Diffusion measurements determine mobility of molecules within zeolites and pfg experiments were performed7” on methanol in Na-X and C S N ~ - X ~ Oand , ~ ’CF4 ~ in ethene conversion in HZSM-5.7’7The relative mobility and reactivity of benzophenone and cyclohexane in NaX were characterised by 13C CP MAS NMR718 and of perdeuterated benzene in NaX and NaY from 2H T I m e a s u r e m e n t ~ . ~ ’ ~ Interactions of Mo(CO)~with PPh3 and and molybdenum on HZSM5721 were investigated by 27Al MAS NMR. Reduction of nitrogen oxides over supported V2O5 was followed720as was catalytic hydrohalogenation of freons over y-A1203and A1203-Sn02surfaces.722Adsorption of CF2HCF2Hon zeolites NaY and CsY were investigated by 23Naand 23Na-19FNMR.723The 27Al-31PJcoupling between trimethylphosphine and HY at the Lewis acid site was determined as 270f 10 Hz by the INEPT experiment.724The carbon residue in fluid cracking catalysts was characterised by NMR725and the existence of M ions in zeolite A discussed.726 The surface of cabosil silica was characterised by ‘H CRAMPS and MAS and 29Si C p MAS.727,728 Silanol groups on silica surfaces were characterised and condensation at 500°C was observed,729and the functionality of highly siliceous MCM-4 1 were examined by 29Si.730Silica surfaces were derivatised with trialktriarylphen~xymethane,~~’ methyl and e t h o ~ y s i l a n e s . ~ ~ ~ ~lmethane,~ ~’ A number of groups were anchored to silica surfaces including ~ a l i x a r e n e , ~ ~ ~ and the motion of n-octadecyl a ~ r i d i n e ,cyclodextrin-poly(vinylamine)736 ~~~ chains attached to colloidal silica were characterised by 13C TI measurements.737 ‘H MAS NMR was applied to organosilanes bound to silica gels738and the interaction of two surfactants (SDS and CTAB) with cyanopropyl-bound silica was characterised by NMR.739Me3A1 was adsorbed on A1203 surfaces via OH and surface complexes of silica-supported vanadium (V) as SiOVOX2 (X = C1 or O’Pr) were examined by 51V and 13C CP MAS.741Surface bonded hydrocarbon phases on Si02 were characterised by solid state NMR.742 The dynamics of surfactant molecules in mesoporous silicates were investigated by variable temperature I3C NMR and showed that the methylene units immediately next to the surface are immobile.743 Glasses - Structures of glasses can be probed by NMR with intermediaterange order now beginning to be examined in addition to short-range order. 27Al MAS NMR showed that in fast quenched Ca0-A1203 glasses A105 and A106 form along with the dominant A104,744and that in alumina-rich A1203-Si02 glasses and amorphous mullite (72wt% A1203-28wt% SiO2) that triclusters may be present and that less A105 is formed than previously believed.745In Ag+/Na+ exchanged Na2(%Si02 glasses 29Si MAS NMR showed that Q2/Q4 formation from Q3 occurs,746and in crystallisation of Li20.2Si02 glasses that the 29SiMAS NMR line was narrower from material crystallised from a glass formed at 0.31 6.4

244

Nuclear Magnetic Resonance

Table 7.7 Glasses Nucleus

Study

Ref

Na2&Ca&Si02-P205 bioglasses Mg&Ca0-Si02-P205-CaF2bioactive glasses Na+Mg@Si02 Na+Al2O3-SiO2 Na2&B203-Si02 Ce02-AIz03-Si02 R&La2O3-B2O3 (R = Mg, Ca, Ba) ( 5 0 - ( ~ / 2 ) ) N a ~ O . x B i5O-(x/2))P2O5 .~0~( Li4Si04-Li2W04,Li4Si04-Li3B03 A1203-Bz03-P205

765 766 767 768 769 770 77 1 772 773 774

GPa compared to a glass formed at ambient pressure.747 1D 29Si MAS NMR spectra are usually simulated with Gaussians but a 2D isotropic/anisotropic correlation spectrum makes no assumptions about the distribution but each Qspecies does have an approximately Gaussian distribution.748 For calciumcontaining silicate glasses in contact with simulated body fluid, phosphates are deposited as an apatite layer whose formation was followed by 31PNMR749,750 Interaction of water with glasses is an extremely important process and corrosion of potash-lime-silica glasses in acid solutions has been f~llowed,'~'and with deposition of a layer on water glass improved corrosion resistance is seen, with the layer containing two distinct sodium species.752In hydrated Na20-A1203Si02 'H CRAMPS and REDOR followed structural changes,753and 'H and 29Si MAS NMR showed changes in hydrogen-bonded and silanol groups as silicate and borosilicate gels evolved into glasses.754 Satellite transition spectroscopy of quadrupolar nuclei reveal different sites with such studies of "B and 27Al to the fore.755--757 Double resonance is being applied to investigate intermediate-range order with 'H-' 'B REDORS7 and 'B_27Al double resonance in Na20-B203-A1203 glasses establishing the connectivity, with spectral editing of B03 and B 0 4 possible from their differing spinlock characteristic^.^^^ In borate and borosilicate glasses "B DAS examined the effect of K20 additions on the B2O3 network759 and the effect of the fictive temperature on determining the B03/B04 ratio was probed by "B MAS.760In phosphate glasses 31P magnetisation transfer can provide information on the connectivity755 and the transition from chain-like to pyrophosphate units was examined with 31P MAS NMR.761Silicon oxycarbide glasses were investigated with NMR showing the role carbon762plays in pyrolysis of methyldimethoxysilane and tetraethoxysilane. In BaSiOC and BaAlSiOC 29Si and 27Al MAS NMR were applied, with a Si03C resonance observed indicating the direct incorporation of carbon in the network,763 and in BaSiOC and AlSiOC glasses formed from alkoxide precursors a wide range of bonding environments were observed, including Si-C.764Other studies of glasses are listed in Table 7.7

'

Ceramics - NMR showed that crystallisation of Li20-Al203-Si02 glasses into ceramics can be substantially altered by nitrogen dissolution, which also

6.5

7: Solid State N M R

245

influences the P-quartz to P-spodumene conversion and depends on whether Si3N4 or A1N is the source of nitrogen.775 Fluoroapatite glass-ceramics were characterised by I9F NMR776and the formation of a A12Ti05 matrix penetrated by K2Ti2A16016 whiskers was followed by 27Al MAS NMR.77727Al MAS NMR data on the AlO4/AlO6 ratio in y-A1203was compared to new computation^,^^' and was obtained to investigate the interaction of y-A1203 with EDTA.779 Amorphous aluminas were investigated by satellite transition NMR spectros c o ~ and y ~ 27Al ~ ~ MAS NMR was applied to silver-alumina ~atalysts.~''' H MAS and CRAMPS were applied to hydroxylated alumina surfaces, and could distinguish A120H and A130H,782the effect of impregnation of alumina with molybdenum and phosphorus,783 and the influence of sodium incorporation, which was also probed by 'H-"B double resonance.784Preparation of AlN via pyrolysis of poly(ethylimioa10ne)~~~ and the surface reactivity of AlN with water to form surface layers of AlO(0H) and Al(OH)3 were characterised by 'H-27Al CP.786 Formation of nanoscale mixtures of A1N and BN by reaction of MeNAlH3 and NH3BH3 under NH3 at 1273 K was followed by NMR787and the linewidth of "B-labelled B13C3 increased with enrichment indicating that the homonuclear dipolar coupling is the dominant line broadening mechanism.788 In a range of S i c compounds 29Si MAS NMR indicates that S i c 0 phases form789and the effect of stacking faults on the spectra of S i c polytypes was observed.790S i c formed by pyrolysis of polycarbosilanes was followed by 29Si and I3C NMR,79'*792 and Si02-C hybrids were formed by adsorbing SiC14 onto carbon particles followed by reaction with water ~ a p o u r SiCN . ~ ~ ~ceramics formed by heating polysilazanes at 1673 K7949795 and 2273 K,796 and laser combustion of he~amethyldisilazane~~~ were followed by NMR, and ultrafine Sic-Si3N4 mixtures showed no reaction at 1573 K but at 1773 K nitrogen dissolved in p-Sic is lost to form a layer at the grain boundaries containing SiC3N units.798 Laser synthesised Si3N4 was shown to be poorly crystalline by NMR and to contain Si-OH and Si-0-Si linkage^.^^^.^^^ Production of Si3N4 surface layers by reaction of silica gels with ammonia and trichlorosilane was followed by NMR.80' Formation of P'-sialon (Si6-ZA~,0zNg-z)still generates much interest and a multinuclear (27Al, 29Si, *'Mg, "Y) study examined the influence of A1203, MgO and Y2O3 sintering aids.802 In low cost p'-sialon production SiO is volatilised and the structure of the deposited solid was investigated by solid state NMR,'03 and p'-sialon formed by a high temperature self-propagating reaction had the same structure as that produced by conventional ~intering."~Oxidation of pl-sialon forms some amorphous silica and mullite that subsequently crystallises along with some alumina, accompanied by a decrease in the z-value of the ~ - ~ i a l o n . ' ~ ~

7

Miscellaneous

7.1 General - 29Si NMR of porous silicon showed detailed structure due to different hydrogenated species,806-808 with relaxation probably determined by the dipolar interaction.806 'H NMR was used to determine the proton-content of

246

Nuclear Magnetic Resonance

porous silicon807and I9F could detect fluorine species left in the pores from the electrolyte."' In YD, at x < 2 deuterium only occupies tetrahedral sites, although thermal disordering produces occupancy in addition to the octahedral site that becomes occupied at x > 2."' 27Al NMR of TiI-,Alx (0.25 < x < 0.55) identified the resonances from the a2 and y phases, together with the Knight shift, its anisotropy and the effect of strain on the NMR signal intensity.'" Paramagnetic Na43f clusters in sodalite cages produce a Fermi contact shift in the 29Siand 27Al NMR spectra from the hyperfine interaction." 7.2 Dynamics and Intercalates - Intercalation of molecules within other compounds can produce novel materials. Intercalation of Keggin ions has been reported in pillared and a-Zr(HP04)2.2H20.814 31PMAS NMR of the amine intercalate Z ~ ( O ~ P C S H @ ~ N ) , ( H P O suggested ~ ) ~ - ~ structural similarity to a-ZrP"' and characterised the n-butylamine intercalate of Ti(PhP02)x(HOP03)2-,. H20,'I6 and iron-containing compounds were intercalated in sodium montmorillonite which was characterised by NMR.'17 Double layer hydroxides intercalated a range of 0x0-anions producing nanocomposites,'" and phenylphosphoric 15N NMR was used to probe pyridine adsorption in clay mineralss2' and [Co(NH3),l3 could be extracted directly from aqueous solution by kanemite.821 Guest-host interactions were also probed by NMR for a P-cyclodextrin/ substituted ketone complex,'22 and in aluminosilicate sodalites/ethylene glycol complexes the aluminium-content greatly affected the i n t e r a ~ t i o n . '2H ~ ~ NMR is sensitive to the dynamics of guest molecules being applied to acetone in tris(5acetyl-5-thienyl) methane824'825and cy~lotriveratrylene,'~~ and KCNS in 4carboxybenzo-24-crown-8-ether.826 2H NMR was also used to investigate a 1,lodibromodecane/urea inclusion and the molecular dynamics of bis(q-arene) molybdenum complexes."' The dynamics of linear alkanes in nanotubes were investigated by 2H and I3C NMR,829 and for magnetically isolated uniaxially rotating molecules fine structure from 'H-'H dipolar and 'H--13CJ-coupling could be seen.83o +

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S. Hayakawa, S. Tsuru, H. Iida, C. Ohtsuki and A . Osaka, Phys. Chem. Glasses, 1996, 37, 188. S. Hayakawa, K. Tsuru, H . Iida, C. Ohtsuki and A . Osaka, J. Ceram. Soc. Jpn., 1996, 104, 1000. T. Boehm, J. Leissner and J. A. Chudek, Glass Sci. Techno/., (FrankfurtlMain), 1995, 68, 400. S. Yamazaki and S. Hayashi, Toso Kogaku, 1996,31,4. K. Herzog, B. Thomas and C. Jaeger, Freiberg Forschungsh., 1996, C465, 1 17. K. H. Yang and C.-S. Hwang, J. Non-Cryst. Solids, 1996,202, 61. C. Jaeger, G. Kunath-Fandrei, M. Feike and K. Herzog, Freiberg Forschungsh., 1996, C465,61. W. Muller-Warmuth, 2. Naturuforsch. A , 1996,51, 585. K. Herzog, J. Peters, B. Thomas and C. Jaeger, Ber. Bunsen-Ges., 1996, 100, 1655. L van Wullen, L. Zuchner W. Muller-Warmuth and H. Eckert, Solid State N M R , 1996, 6, 213. R. E. Youngman and J. W. Zwanziger, J. Phys. Chem., 1996,100, 16720. J. F. Stebbins and S. E. Ellsworth, J. Am. Ceram. Soc., 1996,79, 2247. J. Vogel, P. Wange and P. Hartmann, Glass Sci. Technol. (FrankfurtlMain), 1997, 70, 23. A. K. Singh and C. G. Pantano, J. A m . Ceram. Soc., 1996,79,2696. V. Langmann, W. Hoflbauer, N. Wartner, W. Mader and M . Jansen, Ber. BunsenGes., 1996, 100, 1635. A. M. Wootton, M. Rappenberger, M. H. Lewis, S. Kitchin, A. P. Howes and R. Dupree, J . Non-Cryst. Solids, 1996,204,217. D. Holland, M. W. G. Lockyer and R. Dupree, Brit. Ceram. Proc., 1996,55, 145. P. G. Galliano, J. M. Porto-Lopez, I. Sobrados and J. Sanz, Adv. Sci. Technol., 1995, 12, 81. A. R. Grimmer, G . Seifert, B. Thomas and P. Sarv, Freiberg Forschungsh., 1996, C465,61. K. Herzog, B. Thomas and C. Jaeger, Freiberg Forschungsh., 1996, C465,99. K. Herzog, C. Jaeger and B. Thomas, Freiberg Forschungsh., 1996, C465, 151. J.-L. Lin and C.-S. Hwang, J . Non-Crysf. Solids, 1996,202,61. R. K. Brow, D. R. Tallant and G . L. Turner, J. Am. Ceram. Soc., 1996,79,2410. L. Montagne, G. Palavit and G. Mairesse, Phys. Chem. Glasses, 1996, 37, 206. M. Takahashi, H . Toyuki, M. Tatsumisago and T. Minami, Solid State Ionics, 1996, 86-88, 535. W. A. Buckermann, W. Muller-Warmuth and C. Mundus, J . Non-Cryst. Solids, 1996,208,217. A. Nordmann, Y.-B. Cheng and M. E. Smith, Chem. Mater. 1996,8,2516. C . Jana and M . Braun, Biomuterials, 1996, 17, 2065. S. Kohn and M. Janzen, Ber. Bunsen-Ges., 1996,100, 1450. M.-H. Lee, C.-F. Cheng, V. Heine and J. Klinowski, Chem. Phys. Lett., 1997, 265, 673. J. Ryczkowski, React. Kinet. Catal. Lett., 1995,56,241. T. J. Bastow, C. Jaeger, G. Kunath-Fandrei and M. E. Smith, BUN. Magn. Reson., 1995, 17, 250. E. Hughes, Diss. Abstr. Int. B, 1996,56, 6710. G. Piedra, J. J. Fitzgerald, N. Dando, S. F. Dec and G. E. Maciel, Inorg. Muter., 1996,353474. H. Kraus and R. Prins, J. Catal., 1996,164, 260.

7 50 75 1 752 753 754 755 756 757 758 759 760 76 1 762 763 764 765 766 767 768 769 770 77 1 772 773 774 775 776 777 778 779 780 78 1 782 783

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784 785 786 787 788 789 790 79 1 792 793 794 795 796 797 798 799 800 801 802 803 804 805 806 807 808 809 810 811 8 12 813 8 14 815 816 817

27 1

F. Deng, G . Wang, Y. Du, C . Ye, Y. Kong and X. Li, Solid State N M R , 1997, 7, 281. S. Koyama, H. Takeda, Y. Saito, Y. Suguhara and K. Kuroda, J. Mater. Chem., 1996,6, 1055. S. A. Monie, D. J. Aurentz and C. G. Pantano, Mater. Res. Soc. Symp. Proc., 1996, 410,429. D. Dou, D. R. Ketchum, E. J. M. Hamilton, P. A. Florian, K. E. Vermillion, P. J. Grandinetti and S. G. Sheldon, Chem. Muter., 1996,8, 2839. T. Harazono, Y. Hiroyama and T. Watanabe, Bull. Chem. SOC.Jpn., 1996,69,2419. C . Dybowski, E. J. Gaffney, A. Sayir and M. J. Rabinowitz, Colliods Surf. A , 1996, 118, 171. H. Takeyama, H. Noma, Y. Adachi and M . Komatsu, Chem. Mater., 1997,7,766. L. V. Interrante, C. W. Whitmarsh, W. Sherwood, H.-J. Wu, R. Lewis and G. Maciel, NATO ASISer. E, 1995, 297, 173. Y. Yue and Y. Zhou, Bopuxue Zazhi, 1996,13, 567. R. K. Gilpin, M. E. Gangoda and M. Jaroniec, Carbon, 1997,35, 133. D. Bahloul, M. Pereira and C. Gerardin, J . Muter. Chem., 1997,7, 109. C. Gerardin, F. Taulelle and D. Bahloul, J . Mater. Chem., 1997,7, 1 17. J. Seitz, J. Bill, N. Egger and F. Aldinger, J. Eur. Ceram. SOC.,1996, 16, 885. Y. E. Kortobi, H. Sfihi, A. P. Legrand, E. Musset, N. Herlin and M. Cauchetier, Colloids Surf. A , 1996, 115, 3 19. M. Suzuki, X. Li, Y. Nakata, H. Nagai and T. Okutani, Surf. Rev. Lett., 1996, 3, 85. Y. Yue, D. Li and C. Ye, J . Muter. Sci. Lett., 1996, 15, 691. Y. Yue, D. Li and C. Ye, J . Muter. Sci. Lett., 1996, 15, 1079. P. van der Voort and E. F. Vansant, Pol. J . Chem., 1996,70,838. K. J. D. MacKenzie and R. H. Meinhold, J . Muter. Chem., 1996,6,821. T. C. Ekstroem, K. J. D. MacKenzie, V. V. White, I. W. M. Brown and G . C. Barris, J. Mater. Chem., 1996,6, 1225. Y. Yue, H. He, J. Klinowski, Y. Wu and H. Zhuang, J . Muter. Chem., 1996,6, 1391. K. J. D. MacKenzie, S. Shimada and T. Aoki, J . Muter. Chem., 1997,7, 527. T. Pietrass, A. Bifone, R. D. Roth, V.-P. Koch, A. P. Alivisatos and A. Pines, J . Non-Cryst. Solids, 1996,202, 68. W. K. Chang, M. Y. Liao and K. K. Gleason, J . Phys. Chem., 1996,100, 19653. D. Petit, J.-N. Chazalviel, F. Ozanam and F. Devreux, Appl. Phys. Lett., 1997, 70, 191. N. L. Aldolphi, J. J. Balbach, M. S. Conradi, J. T. Markert, R. M. Cotts and P. Vajda, Phys. Rev. B, 1996,53, 15054. M. E. Smith, M. A. Gibson, C. T. Forwood and T. J. Bastow, Phil. Mag. A , 1996, 37,4041. G. Engelhardt, M. Feuerstein, P. Sieger, D. Markgraber, G. Stucky and S. Voijislav, J. Chem. SOC.,Chem. Commun., 1996,729. C.-W. Hu, Q. Li, Y. H. Zhang, Y.-Y. Lie, Y.-F. Zhang, T.-D. Tang and E.-B. Wang, J. Chem. SOC.,Chem. Commun., 1996, 121. Y. Liu, C. Hu, Z. Wang, J. Zhang and E. Wang, Sci. China Ser. B, 1996,39,86. J. M. Merida-Robles, P. Olivera-Pastor, A. Jimenez-Lopez and E. RodriguezCastellon, J. Phys. Chem., 1996, 100, 14726. B. Zhang, D. M. Poojary, A. Clearfield and G. Deng, Chem. Muter., 1996,8, 1333. E. Jaimez, A. Bortun, G . B. Hix, J. R. Garcia, R. Julio and R. C. T. Slade, J . Chem. SOC.Dalton Trans., 1996,2285. I. Palinko, K. Lazar, I. Hannus and I. Kirisci, J . Phys. Chem. Solids, 1996,57, 1067.

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C. Forano, A. de Roy, C. Depege, M. Khaldi, F. Z. Metoui and J. P. Besse, Chem. h d . , 1997,69, 607. S. Carlino, M. J. Hudson, S. W. Husain and J. A. Knowles, Solid State lonics, 1996, 84, 117. L. Ukrainczyk and K . A. Smith, Environ. Sci.Techno/., 1996,30, 3167. M . T. J. Keene, J. A. Knowles and M. J. Hudson, J . Muter. Chem., 1996,6, 1567. H. Sfihi, A. P. Legrand and A. Guy, Colloids Surf. A , 1996,115, 1 15. S. B. Hong, M . A. Camblor and M. E. Davis, J . Am. Chern. Soc., 1997,119,761. P. S. Sidhu, J. Bell, G . H. Penner and K. R. Jeffrey, Can. J . Chem., 1995,73, 2196. P. S. Sidhu, J. Bell, G. H. Penner and K . R. Jeffrey, Can. J . Chem., 1996,74, 1784. G . W. Buchanan, A. Moghimi and C. I. Ratcliffe, Can. J . Chem., 1996,74, 1437. A. E. Aliev, S. P. Smart, I. J. Shannon and K . D. M. Harris, J . Chem. SOC.Furaduy Trans., 1996,92, 2179. D. O’Hare, S. J. Heyes, S. Barlow and S. Mason, J . Chem. SOC.Dalton Trans., 1996, 2989. P. Sozzani, R. Simonutti and A. Comotti, Mol. Cryst. Liq. Cryst. Sci. Technol. A , 1996,277,659. A. Kubo, F. Imashiro and T. Terao, J . Phys. Chem., 1996, 100, 10854.

819 820 82 1 822 823 824 825 826 827 828 829 830

8 Multiple Pulse NMR BY L.Y. LlAN

1

Introduction

The aim of this report is to cover the progress of work in the field of multiple pulse NMR over a period of twelve months from June 1996 to May 1997 and is a continuation of the report from last year. Many of the multipulse experiments reported over the last twleve months have been improvements of existing experiments, although much effort has been devoted to making improvements to methods for measuring relaxation times. With the very widespread use of pulsed field gradients, the two reviews by Canet' and Berger2 on the applications of pulsed field gradients are timely. For ease of reference, the new experiments described in this chapter are summarized in a table at the end of the chapter.

2

Variation of the Radiofrequency Pulse

2.1 Composite and Decoupling Pulses - Unwanted signal components in a NMR spectrum can be removed in various ways. These include phase cycling and pulsed field gradient. Phase cycling relies on systematically changing R F phases in the pulse cycle to alter the phases of signal components during subsequent pulses. The resulting signal is obtained by combining several experiments in such a way that undesired components are cancelled out. On the other hand, the pulsed field gradient method relies on the selection of in-phase signal, and rejection of unwanted signals. A third method for removing unwanted components is achieved by using radiofrequency gradient techniques. RF-gradient methods rely on variations in the B1 field strength to dephase unwanted magnetization components in a plane containing the z-axis, in contrast to the transverse phase modulation caused by Bo gradients. Sodickson and Cory3 discuss in detail the modifications to the standard BIRD and TANGO sequence, using R F gradients to uncouple resonances and to eliminate undesirable antiphase and multiple-quantum effects. Selective excitation and saturation occurs simultaneously in the method described. The 'H spectrum of complex molecules suffer from severe overlap; if it is possible to broadband decouple a proton spectrum then each proton resonance will appear as a singlet, thereby making interpretation of the data much simpler. Nuclear Magnetic Resonance, Volume 27 0The Royal Society of Chemistry 1998 273

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Although many methods for broadband proton-decoupling have been reported, there are disadvantages in many of these. Zangger and Sterk4 propose a method based on the use of weak gradient fields and selective pulses. Briand and Sorensen' describe a new set of pulse sequence elements that will enable simultaneous and independent rotation of I and 11s) spin systems with arbitrary flip angles and phases. These new sequences will mean that different classes of protons can be simultaneouly but independently phase-cycled. The proposed pulse sequence elements are based on the bilinear rotation (BIRD) pulse sequence. Spin inversion and excitation can be achieved using either radiofrequency pulses or an adiabatic sweep; the latter is attained by sweeping a continuous R F field B1 through resonance, starting from a large positive offset through to a large negative offset. An adiabatic sweep provides very wideband spin inversion without the need for a very intense R F field. In addition to the R F strength, the decoupling range depends also on the frequency-sweep rate and the shape of the amplitude modulation. Skinner and Bendal16give a detailed evaluation of the peak power and efficiency of adiabatic pulses. Adiabatic pulses have been used for providing broadband decoupling and is preferred since lower decoupling powers are required; hence reducing sample heating. However, when the B1 field is set low relative to the level necessary for complete decoupling, sideband intensities of the detected signals can be significant due to incomplete decoupling. Hwang et al.' discuss this sideband problem and propose methods for alleviating the problem, such as incrementing the lengths of the adiabatic passage. Kupce et ~ 1discuss . ~ in some detail sideband artifacts when using adiabatic pulses, with reference to the use of repetitive cycling of pulses within the decoupiing schemes. A two power-level decoupling scheme is proposed. Zhang et d 9apply a 'double WURST' decoupling sequence to simultaneously but separately decouple the 13C0 and 13Ca regions; a frequency-shifted decoupling scheme is combined with a standard decoupling method.

2.2 Solvent Suppression - Radiation damping is caused by the interaction of the water magnetization with the detecting network of a spectrometer, resulting in an induced magnetic field which is perpendicular and proportional to the transverse water magnetization. Radiation damping, which in biological samples affects only the water resonance, accelerates the decay of the free induction signal. The water resonance line is broadened, causing undesirable interference in the resulting NMR spectrum. The problem due to radiation damping becomes more acute at higher magnetic field strengths and with high sensitivity probeheads. Several methods have previously been reported which are aimed at eliminating the causes as well as consequences of radiation damping. Abergel et al." have reported a new method - the electronic radiation damping control system - which aims to remove the radiation damping field. A simple electronic device, which generates a magnetization-dependent field in the sample to compensate the radiation damping field at all times, is described. The authors, however, discuss how it is possible to amplify the radiation damping to enable the water magnetization to return back to equilibrium in a time shorter than the

8: Multiple Pulse N M R

27 5

characteristic radiation damping time. The approach described provides the same effect as the water flip-back pulses, which are now commonly used for minimizing signal attenuation due to amide proton-water exchange. Price and Arata' describe the use of a water-pre-sequence suppression method to overcome some of the problems caused by radiation damping. In their approach, which is simple to implement and apparently effective, the longitudinal relaxation behaviour is manipulated via the use of a variable train of homospoil pulses. This is done during the relaxation period. In order to study exchange processes between labile protons and the water protons, or interactions between the protein and water molecules, it is sometimes more convenient to perform one-dimensional experiments. For such purposes, good quality selective excitation of the solvent signal is important, but this is often made difficult by radiation damping, particularly at high-magnetic field strengths using high-quality probeheads. Bockmann and Guittet12 propose a new pulse sequence for efficient and selective excitation of the water signal without the requirement of special probeheads. The method is based on the suppression of radiation damping during the selective pulse, using the DANTE sequence combined with gradient echoes during the selective pulse. Dalvit13 describes modifications to the ROESY and NOESY experiments, by introducing selective 180" pulses on the water resonance, in order to observe, in one- and twodimensions, interactions between water and the protein spins. Radiation damping can create water double-quantum coherence in some experiments. The coupling of the spins with the coil generates MQ coherence in a way similar to bilinear scalar couplings. If radiation damping is large it cannot be refocused at the end of a spin-echo period and therefore causes interference in the resultant spectrum. Dalvit and Bohlen have suggested that a residual water signal in PFG double quantum experiments is observed in the resulting sepctrum. The origin of the undesired signal is due to the creation of double quantum coherence and to the presence of radiation damping. The authors suggest several methods to reduce the residual water signal including the use of magic angle gradient^'^ and by incorporating two weak z-pulsed field gradients at the beginning and end of the spin-echo period.15 Mescher et ~ 1 . describe ' ~ the MEGA sequence as a new water suppression technique; the method is based on Bo gradient dephasing of selective echoes. A comparison between MEGA and the two other commonly-used pulsed-field gradient based water suppression methods, WATERGATE and excitation sculpting, is made. The authors conclude that WATERGATE is the least tolerant to flip-angle errors of the selective pulses.

3

Homonuclear Correlation Spectroscopy

3.1 Homonuclear Correlation - The inclusion of the WATERGATE pulse for water suppression into many 2D homonuclear experiments (NOESY, COSY, TOCSY, etc) has improved the performance of these experiments enormously and made possible the use of dilute samples (under 1mM). The WATERGATE

276

Nuclear Magnetic Resonance

method is very effective at dephasing transverse magnetization at the water frequency, but has no effect upon magnetization that is aligned along the z-axis. At the end of the mixing period on a conventional TOCSY experiment, the water signal is not in the transverse plane for efficient water suppression by the WATERGATE method; Fulton et aZ.I7have described a modification to include a z-filter before the WATERGATE pulse to ensure that problems associated with radiation damping and spin-locking of the water magnetization, are alleviated. Wagner and Berger18 incorporate a weak pulsed field gradient for the entire mixing period in a NOESY experiment thereby reducing the phase cycling steps to two. For very concentrated solutions, therefore, considerable reduction in experimental time can be achieved. Excitation sculpting has been used by Callihan er aZ.I9 The pulse sequence described, TOCSY and NOESY, appears to be simpler to implement, more robust and provides good water suppression with little baseline distortions. ‘Directed’ TOCSY coherence transfer has recently been reported and has the advantage that it is more efficient and can lead to simplification of the spectra. The directed TOCSY selectively transfers in-phase coherence from one end of a chain of coupled spins into directed antiphase coherences along the chain. However, it is not easy to achieve this ‘one-way’ transfer by using isotropic mixing alone; Glaser et aZ.20 explores this issue in detail and describe the optimization of directed TOCSY by using a combination of isotropic and longitudinal mixing schemes. Horne and Morris21 address the question of tl noise in gradient-enhanced experiments. Although the t l noise is at lower levels in these experiments than in their phase cycle analogues, they nevertheless exist. The reduction in t, noise in gradient-enhanced experiments is due to the fact that only signals from a selected coherence pathway are detected and hence the tl noise detected is restricted to that arising from these selected pathways. On the other hand, in the phase-cycled experiments, t l noise from all possible pathways contributes to the resultant spectrum. Hence, the intrinsic t 1 noise caused by spectrometer instabilities still exists. The authors describe how their previously reported reference deconvolution methods can be applied in conjunction with gradient-enhanced experiments to give spectra with ultra-low tl-noise artifacts. There are two main disadvantages when pulsed field gradients are used: a loss in sensitivity and the inability to obtain pure-phase double absorption lineshape in two dimensional experiments. These problems are constantly being addressed leading to several solutions which are now routinely used. Ancian et a1.22describe their approach to overcome the lineshape problem in PFG-enhanced doublequantum filtered COSY experiments; they introduce a gradient pulse during the evolution period. Signals from the N and P-type pathways are collected alternately and added in the same data block. This combined data is later Fourier transfonned as a complex signal in the t2 domain and as a real signal in the t l domain. Further post-acquisition manipulation is required to ‘clean-up’ the data. also describe modifications to existing TOCSY, ROESY and Parella et NOESY pulse sequences to allow quick recording phase-sensitive data.

8: Multiple Pulse N M R

4

277

Dipolar Coupling, Chemical Exchange and Relaxation Time Experiments

4.1 Dipolar Coupling and Chemical Exchange - The derivation of dynamics information of macromolecules from NMR data requires the acquisition of relaxation rates and one of these is the cross-relaxation rate between a carbon or nitrogen and the attached proton. This cross-relaxation rate is usually calculated indirectly from the measured heteronuclear steady-state NOE and the long~ ~ a direct itudinal-relaxation rate of the heteronucleus. Allard et u I . describe measurement of the cross-relaxation rate between a heteronucleus and any of its neighbouring protons; the method uses selective pulses in order to separate the cross-relaxation rates from different protons. The study of the interactions between water and biomolecules has been the focus of attention in recent years and much effort is devoted to detecting waterproton interactions using NMR. In these experiments, the intermolecular interactions between the protein and water must be distinguished from the . ~ a ~novel intramolecular interactions and exchange effects. Wider et ~ 1describe 1 D difference experiment in which the separation of intermolecular solventprotein NOEs and chemical exchange effects from intramolecular NOEs is based on the different diffusion properties of the individual water molecules and the biological macromolecule. By using diffusion filters in NOE difference experiments, it is possible to observe the bound water molecules without the interference from intramolecular NOEs. Birlirakis et ~ 1 demonstrate . ~ ~ the use of the off-resonance-ROESY experiment for detecting these water-protein interactions. From the experiment described, it is possible to obtain quantitative protein-water exchange rates; the main feature of this experiment is the elimination of unwanted intramolecular dipolar cross-relaxation amongst the protein protons. Spin diffusion is a seious problem that complicates the interpretation of cross-relaxation data in macromolecules. If not specifically removed, this phenomenon occurs in all cross-relaxation experiments (for example, NOESYtype experiments). Juranic et al.27 describe a new isotope-assisted experiment in which a double INEPT-edited (DINE) selective inversion sequence, on 13C aliphatic groups, is introduced in the middle of the NOESY period in a NOESY['5N,'H] HSQC sequence. By varying the phase of the 13C excitation pulse in the DINE sequence, either CH,CH3 or CH2 are inverted; this experiment will delineate the spin diffusion paths according to whether they are CH, CH3 or CH2 mediated. Many exchange and ligand binding processes in biological systems involve significant changes in the translational diffusion coefficient; hence molecular diffusion can in principle be used to detect exchange and binding processes. Andrec and Prestegard2' combine spin-echo diffusion with selective-inversion exchange spectroscopy in order to quantify chemical exchange rates. The kinetics of exchange is encoded directly in the apparent diffusion coefficient. L e i j ~ nproposes ~~ a modification to a previously reported method for measuring proton exchange rates by saturation transfer with minimal interference due to water relaxation. In the proposed method, the solvent magnetization is

278

Nuclear Magnetic Resonance

randomized by a strong pulsed field gradient and never returned to the z-axis; the effect is that back-exchange with water is prevented, thereby providing a more accurate proton exchange rate. Grode and Mowery3' describe a simple modification that overcomes some of the difficulties due to spectral overlap in ID NOE difference spectroscopy; by appending a 2D J-resolved pulse as a read pulse following a low-power CW irradiation of the target nucleus, the affected resonances can be observed in a better resolved two-dimensional spectrum. Stott et d 3 1 discuss in detail the one-dimensional NOE experiment using pulsed field gradients. They investigate the spin dynamics behind these experiments, and demonstrate their differences with conventional experiments. Also discussed are the interferences and effects associated with selective population transfer, zero-quantum coherence, molecular diffusion, and strong coupling. Practical solutions to some of the problems are provided. Lix et al.32 describe briefly the artifacts in short mixing times 19F-'H heteronuclear Overhauser experiments. They suggest that the artifacts arise from transient changes in the sample susceptibility which in turn cause what appear to be multiple quantum peaks in these experiments. Pulse sequences that include composite 19F 180" pulses are proposed in an attempt to eliminate the artifacts.

4.2 Relaxation Time Measurements - "N, and 13C NMR relaxation times are widely used to probe the internal dynamics of proteins. Despite this, the proper analysis of the relaxation data acquired remains to be established. One of the main problems when analysing these NMR relaxation data is the uncertainty of the type of rotation diffusion to invoke - isotropic versus anisotropic - and difficulties in the initial establishment of the overall correlation time, particularly in the presence of conformational exchange. Tjandra et al.33 describe in detail the consequences of assuming isotropic diffusion for systems undergoing anisotropic tumbling; whilst this wrong assumption is of little consequence to the derived order parameters, it can result in misleading identification of exchange contributions. Lee et al.34also address the question of anisotropic diffusion and show how rotational diffusion tensors in proteins can best be determined using both backbone ''N and I3Ca spin relaxation rate constants. There is an increase in the use of 13C relaxation times for deriving dynamics information of a protein. Measurement of carbonyl (I3CO) relaxation rates is of particular use as the motion of the NH bond (the most commonly studied motion) is correlated with the motion of the CO bond. One of the main problems, however, is that 13C0 relaxation times are more difficult to measure. In uniformly 3C-labelled protein samples, the presence of i3Ca-i3C0scalar coupling may induce relaxation of the second kind. In addition, chemical shift anisotropy and other dipole-dipole interactions contribute to the relaxation of the carbonyl I3C nucleus. In an attempt to address some of the problems associated with measuring and analysing I3C carbonyl relaxation data, Engelke and R ~ t e r j a n s ~ ~ present data from relaxation measurements made at three different field strengths - 500, 600 and 800 MHz - and conclude that it is possible to describe, to a certain

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279

extent, the backbone dynamics of a protein using these relaxation data. Allard and Hard36 also describe the analysis of the 13C relaxation data for backbone carbonyls and analyse the contributions from different relaxation mechanisms to the longitudinal and transverse relaxation rates. For both, chemical shift anisotropy (CSA) is the dominant mechanism (64-73'/0), followed by the dipole-dipole (DD) relaxation due to protons (21 O h ) . The dipole-dipole relaxations due to both l3CUand I5N make contributions of between 9 and 2%. The authors conclude that, based on results obtained using their pulse sequence, the cross-correlation between CSA and DD relaxations are negligible. The CPMG pulse train is used for measuring transverse relaxation times; Czisch et ~ 1 . ~ 'have discussed in detail the detrimental consequences of offresonance effects of the 180" pulses used in the CPMG train. Systematic errors can arise in the T2 measurements due to these effects, leading to misinterpretation of relaxation data. It is the oscillatory nature of these effects that make them difficult to deal with; strongly affected and unaffected signals can be found at various frequencies within a CPMG spectrum. The authors propose the incorporation of contant gradients or pulsed field gradients during the CPMG period in order to remove these off-resonance effects. Proton relaxation, unlike, 15N and I3C: relaxation, is more complex since both intra- and intermolecular interactions may contribute and there is quite a variation in the internuclear distances. Even when using methods in which mutual dipolar relaxation can be isolated, cross-relaxation can still be a problem. Cross-relaxation can affect relaxation measurements either directly or indirectly. The approaches that have been used to suppress cross-relaxation rates include: the application of continuous irradiation or a sequence of selective 180" pulses to a band in the spectrum to suppress spin diffusion to that region, synchronous nutation of a pair of spins to suppress spin diffusion to other spins, and the use of one or more selective 180" pulses to suppress one or more selected cross-relaxation pathways. Norwood gives a detailed description of cross-relaxation and shows how the effects of cross-relaxation can be suppressed in 'H relaxation measurements; the measurements of the relaxation rates of proton longitudinal modes are described.38Almeida and O ~ e l l describe a~~ the measurements of 'H T,, using a I5N-'H heteronuclear method; no detailed analysis is given for the problems that can be associated with measuring proton relaxation times.

5

Heteronuclear Experiments

5.1 Inverse Proton-Detected Correlation Spectroscopy - 5.2.2 General - The heteronuclear single-quantum correlation experiment (HSQC) is the fundamental building block for most of the multi-resonance multidimensional experiments. There are three basic variations of this pulse sequence: with sensitivity enhancement by preservation of equivalent coherence pathways (PEP), with coherence selection by pulsed field gradients and a combination of both PEP and gradient coherence selection. The choice of which experiment to use must be governed by

280

Nuclear Magnetic Resonance

the sensitivity of each of these experiments. Gavin et attempt to address this problem and test the relative sensitivity of these three experiments using the natural abundance '3Ca-'H correlation. They conclude that the combined PEP and pulsed field gradient experiment gives the best sensitivity. The proton-detected heteronuclear single- and multiple-quantum-coherence spectroscopies are most commonly used to correlate proton chemical shifts with X-nucleus chemical shifts. There is another group of experiments - the heteronuclear zero- and double-quantum experiment. The spectra from these experiments are more difficult to interpret as the scale in the indirect dimension is either the sum or the difference in chemical shifts of two coupled nuclei; the chemical shift of the X-nucleus cannot be obtained directly. However, zero- and doublequantum-coherence experiments have additional information, such as the relaxation rate of double and zero-quantum coherence, and the signs and magnitude of passive J couplings that are otherwise difficult to obtain. Jurvet and Allard4' propose new pulses for phase-sensitive detection of heteronuclear zero- and d ouble-quan tum experiments. The presence of chemical exchange can be detrimental in that this process can reduce the signal intensity to the extent that the signals can no longer be observed. Chemical exchange broadening is commonly observed in many protein complexes, and this together with broadening due to increases in transverse relation rates can result in total loss of signals. In the presence of chemical exchange, several methods can be used to preserve spin coherence, such as the alignment of the magnetization along a large effective field by spin-locking techniques and by using CPMG-derived spin-echoes. Mulder et al.42 explore the use of this latter approach, in combination with the heteronuclear HSQC experiment. The pulse sequences described contain CPMG spin-echo trains during the polarization transfer periods of the INEPT sequence. The 13C-13C INADEQUATE experiment is one of the most widely used double-quantum experiment, provided there is enough sensitivity. Meissner et al.43 report on several experiments based on 'H-detected INADEQUATE pulse sequences. Two different pulse sequences are described: those where coherence is transferred between proton and carbon spins via one-bond JCH couplings and via long-range JCH couplings. Zangger and Sterk4 also describe a proton-detected INADEQUATE experiment. The authors propose a two-dimensional J-resolved experiment: the F1 domain contains a l3C-I3C scalar coupling scale rather than a double-quantum frequency. The initial transfer of polarization from the proton spins to carbon spins is via an INEPT sequence.

5.1.2 Heteronuclear Cross-Polarization Experiments - The heteronuclear crosspolarization (HCP) method for coherence transfer is being used in many multiple pulse experiments in place of the INEPT sequence. The main advantages of the HCP approach include better tolerance to rf inhomogeneity, slower relaxation due to less contribution of antiphase terms during transfer and suppression of exchange-broadening. However, it is difficult to combine and concatenate successive transfer steps, as is often required in constant-time triple-resonance experiments. The HCP method can be used as a semiselective transfer technique

8: Multiple Pulse N M R

28 1

since it is possible to control the rf power used to limit coherence transfer to certain scalar coupling networks. Zuiderweg et and Carlomagno et independently investigate the design of band-selective cross-polarization sequences using shaped pulses. The objective is to transfer magnetization between two spectral bands by cross-polarization between spins of the same species, for example 13Ca-13C0, and 'Ha-'HN. Novel coherence-transfer sequences, using Gaussian pulses of 225"45and 270"46 flip angles, are reported by both groups. Up to now, all the reported heteronuclear cross-polarization experiments require the use of the same multiple-pulse sequence in order to fulfil the Hartmann-Hahn condition; however, there are limitations to this method in situations where selectivity is required and also when the offset ranges for the two describe spin species that are spin-locked are very different. Carlomagno et the derivation of the 'kin' HEHAHA sequences which could in principle provide heteronuclear Hartmann-Hahn polarization transfer by using two different multiple-pulse sequences. 5.1.3 Isotope-Filtered Experimenets - Ogura et ~ 1 . ~describe ' several isotopefiltered experiments to detect protons bound to 12C and I4N; these experiments are useful for observing the unlabelled components of, for example, a I3C/"N labelled protein-ligand complex. The reported method uses a z-filter in combination with pulsed field gradient to filter out the 13C/1SN-attachedprotons. In addition, the method incorporates a wide-band inversion pulse to invert resonances over a wide-bandwidth, and a band-selective S and SS pulse as the observation pulses which serve to reduce water excitation. The main advantage of the proposed pulse schemes is the high efficiency of filtering. Whitehead et al.49describe a simple modification to the 2D experiment that allows detection of the unlabelled aromatic resonances when using 15N-labelled proteins. 5.1.4 Isotope-Edited Experiments - McIntosh et al?' describe an HMQC method

which allows stereospecific assignments of the asparagine and glutamine sidechains. A difference between two spectra collected with and without the evolution of the side-chain three-bond I3C-lH ('3C-CO-N-'H) couplings is obtained; the intensities of the resultant * 'NH2 side-chain resonances give the desired stereospecific assignment. Lohr and Ruterjans" describe another experiment, H2NCO-E.COSY, based on an E.COSY method, to acquire the same information; an 15N-'H HSQC experiment with band-selective excitation of the carbonyl carbons is used. "N-IH cross-peak which is coupled in the F1 by the 1J13co-(3, and 3H"Cy(for glutamine) and 3H'CCP(for asparagine) in the F2 dimension in a E.COSY-1i ke manner. In order to obtain ultra-high resolution HSQC spectra, Willker52et al. propose the use of region-selective HSQC experiments and J-scaling in the tl dimension. The J-scaling is obtained by adding an extra 180" pulse and incremented delay within the evolution period. Band-selective excitation is also used by K r i ~ h n a m u r t h yin~ ~order to obtain

282

Nuclear Magnetic Resonance

high-resolution TOCSY data for measurements of proton-phosphorus coupling values. The pure-phase double-pulsed field gradient spin-echo (DPFGSE) train is used for band selection. The excitation profile here depends entirely on the inversion profile of the band-selective n: pulses with the DPFGSE trains. The pure-phase nature of the band-selective DPFGSE spectrum with no additional phase cycling makes this excitation sculpting method convenient to use and for incorporation into other standard 2D experiments. This band selective approach has also been i n ~ o r p o r a t e dinto ~ ~ pulse sequences that will allow effective transfer of proton magnetization across four bonds involving a small heteronuclear coupling (J approx. 3-8 Hz) without substantial loss due to modulation by homonuclear couplings of similar magnitudes. In 13C-editedexperiments, differences exist between the spectra obtained using either the HSQC and HMQC-type polarization transfers. The main difference is due to the additional 180" pulses in the HSQC sequence; when these additional pulses are not ideal, sensitivity of the resonances towards the edge of the "C spectrum tends to be reduced. However, it is easier to accommodate field gradient pulses in the HSQC experiments; this has important implications since better quality water suppression and cleaner spectra can be obtained. In an attempt to overcome the difficulties of non-ideal 180" pulses, Ogura et aZ.55describe the use of broadband shaped inversion (hyperbolic-secant inversion) and refocusing pulses.

5.2 Scalar Coupling Constants Using Heteronuclear Proton-Detection Experiments - Heteronuclear coupling constants provide valuable constraints for the characterization of molecular conformation, bonding and dynamics. Conventionally, the E.COSY-type experiments are most useful for generating small coupling constant values. Kozminski and N a n have ~ ~ described ~ HMQC- and HSQCbased two-dimensional experiments that have good sensitivity and that will generate E.COSY-type cross-peaks to allow accurate measurements of heteronuclear long-range coupling constants. They describe in detail the use of two new pulse sequence elements: arbitrarily scaled shift and coupling information (ASSCI) and HECADE (heteronuclear couplings from SSCI-domain experiments with e.COSY-type cross-peaks). The first element is designed to scale chemicalshift differences and heteronuclear coupling splittings to optimize signal dispersion and resolution. The second element reduces phase distortion. 13C-13C coupling constants are frequently determined using the INADEQUATE experiment. However, the inherent insensitivity of the experiment, due partly to the fact that it is carried out at I3C natural abundance, has prompted the development of more sensitive methods; one approach is to use the INADEQUATE experiment with proton detection. Kozminski and N a n ~ ~ ~ describe a proton-detected experiment for the measurement and unambiguous assignment of long-range 13C-'3Ccoupling constants at natural abundance. The method is useful for small molecules at very high (molar range) concentrations. Reif et aZ.58also describe a proton-detected INADEQUATE experiment which enables determination of the 'J, 2J and 'J coupling carbon-carbon coupling constants.

8: Multiple Pulse N M R

283

Tjandra and Bax59describe a method for measuring the dipolar contributions to the 'JCH splittings using the magnetic-field dependence of J modulation in a 2D I3C-'H CT HSQC spectrum. The ability to measure the dipolar couplings in systems with large susceptibility anisotropy is important since the magnitude of the dipolar couplings contains information on the orientation of the internuclear vector relative to the susceptibility tensor and hence could potentially contain structural information. Although three-bond couplings have usually been used to provide structural information through known relationships between coupling constants and dihedral angles, the one-bond coupling such as the 'JCaHaand 'JCaN values have been shown to correlate to torsion angles in a polypeptide chain. As the variations in one-bond couplings due to the torsion angle, H-bonding and dipolar contributions are all small, therefore accurate measurement of the one-bond splitting is necessary. Tolman and Prestegard60761 describe in detail two methods for measuring "N-' H one-bond coupling constants, one based on resonanceintensity and the other on frequency-resolution. The first method6' is a minor modification to the "N-lH HSQC experiment. In these experiments the coupling is extracted from the resonance intensity rather than by direct measurement of an experimental splitting. The method is based on the differential relaxation effects during the refocused INEPT period between the sine- and cosine-modulated signal; during the refocusing periods, the cosine-modulated signal will relax as transverse "N and longitudinal 'H magnetization while the sine-modulated signal will relax as transverse I5N and tranverse 'H magnetization. In their frequency-resolution method,61 an accordion approach is adopted in order to improve the resolution in the indirect dimension. A modification of the 2D J-resolved experiment is proposed; the indirect evolution period is a composite of two evolution periods which are implemented in an accordion style. Essentially the one-bond coupling is obtained from the "N-'H HSQC spectrum in which the one-bond coupling is allowed to evolve by removing the 'H 180" pulse during the evolution period. Kelly et discuss modifications to the 15N-lH HSQC spectrum to give a 3D J-resolved HSQC spectrum in order to derive coupling constant values in badly overlapping 2D HSQC spectra. O t t i ~ ~shows g ~ ~how small JHC can be obtained from double quantum/zero quantum experiment in linear spin systems. Excitation sculpting was designed as a method for delivering constant phase and amplitude excitation over a given bandwidth, optimizing selective inversion, and purging unwanted sidelobes. The building block for excitation sculpting is the double-pulsed-field gradient spin-echo pulse sequence (DPFGSE). Krishnamurthya proposes the use of excitation sculpturing to improve resolution and provide cross-peaks which are J-scaled in the carbon dimension in a 13C-lH HSQC spectrum. The proton band selection is based on excitation sculpturing using the double-pulsed field gradient spin-echo technique. The sequence provides pure absorptive lineshapes, and long-range heteronuclear coupling constants which are scaled in the carbon (indirect) dimension. The concept of the DPFGSE excitation sculpting method has been adapted to

284

Nuclear Magnetic Resonance

give the gradient-bilinear rotation decoupling (GBIRD) sequence, in which the BIRD pulse is flanked by two RF gradients, giving selective retention of the X-bound proton magnetization and attenuation of all other magnetization components in the system. Xu and Evans65 describe the application of GBIRD into a 2D pulsed field gradient heteronuclear hl half-filtered TOCSY experiment and a selective one-dimensional pulsed field gradient TOCSY experiment that will enable determination of long-range J X H couplings.

6

Three- and Four-Dimensional NMR

6.1 Heteronuclear Triple (lH,13C,15N) Resonance Three-Dimensional Experiments - Two main issues are constantly addressed in the development of new experiments - sensitivity and resolution. The inherent sensitivity of an experiment is one of the main criterion as to whether a method of practical use. The sensitivity is most dependent on the duration of an experiment, the efficiency of the coherence transfer scheme, the effects of pulse imperfections, etc. In an attempt to improve the HN(C0CA)NH . ~ the ~ use of overlapping coherence transfer experiment, Bracken et ~ 1examine steps. Overlapping evolution periods are used. The main advantage is derived from a reduction in the number of 180"pulses in these modified experiments. One of the main causes for reduction in sensitivity in many triple resonance experiments is the unfavourable relaxation and I3C-l3C scalar coupling properties of the I3Ca centre. While the constant-time experiment removes 13C-13C scalar, it also introduces a long constant-time period during which I3C transverse relaxation occurs, leading to a significant loss in signal. Improvements to the sensitivity of the HNCA and HN(C0)CA experiments are reported by Matsuo et d7Instead of using constant-time to remove 13C-13Cscalar coupling, the authors use homonuclear multi-band decoupling of I3Cpfrom all other carbons (hence the experiments are known as CPd-HNCA and CPd-HN(CO)CA). The Cp decoupling shortens the initial C" evolution period significantly when compared with the constant-time experiment. The main disadvantage is the presence of Bloch-Siegert shifts of the C" signals. The I3C homonuclear multiband decoupling is achieved using a WURST-2 decoupling pulse. The same group has also used the adiabatic WURST-2 homonuclear Cp decoupling to improve the resolution and sensitivity in HCCH-TOCSY experiments6* where again I3C-l3C coupling deteriorates the sensitivity of the experiment. The I3Cp decoupling used collapses the Ca multiplets for all the residues except the serines and threonines. The multiple-quantum coherences can exhibit better relaxation properties than the corresponding single-quantum magnetization states, the latter being generally employed in modern triple resonance experiments. The main drawback with using the MQ states during indirect frequency evolution periods is that they are modulated by scalar coupling interactions with passive spins. The resulting splittings in the indirect dimension reduce the effective sensitivity. In order to ~~ overcome the problems associated with using MQ states, Swapna et u I . have

8: Multiple Pulse N M R

28 5

described a suite of modified experiments in which the multiple-quantum states are used in conjunction with pulsed field gradient and constant-time periods. The two and three-bond homo- and heteronuclear couplings are decoupled by simultaneous proton and carbon constant-time evolution. The 3D HCACO experiment has been previously reported; this experiment is best performed in D20. In order to overcome the unnecessary inconvenience of using two samples, Zhang and Gmeiner7' describe gradient versions of the HCACO and (H)CACO-TOCSY experiments which are designed to improve water suppression and sensitivity. The same authors7' also describe the 3D NOESY-(HCAC0)NH experiment that transfers NOES from the 'Ha to the backbone 'HN in the succeeding residue. The WATERGATE method is used for water suppression . The main advantage of the method proposed is that NOE's from 'Ha that appear at the water frequency can be measured. The use of phase labelling of C-H and C-C spin systems allows discrimination of spin systems from different amino-acids. Variations of known experiments to show how this phase-labelling can be introduced have been described. Feng et u I . ~ *provide a practical guide to the use of HACANH and HACA(C0)NH type experiments, which provide data for establishing intraresidue and interresidue connections between backbone 'H, I3C and I5N atoms with high sensitivity. The authors concentrate on connectivities involving glycine resiues. Rios et u I . ~ ~ show how phase labelling can be achieved in the constant-time PFG-CBCA (C0)NH experiment. The assignments resonances from aromatic and arginine side-chains are not easily achieved using the standard triple resonance experiments which are designed for backbone resonance assignments. Several groups have reported new methods for assigning these side-chain resonances. The sequence specific sidechain assignments of histidine and tryptophan resonances were discussed by Sudmeier et u I . , using ~ ~ a modified version of the HCN experiment. Under certain conditions, when the side-chain protons are not undergoing chemical exchange with the solvent, the HCN experiment can be used to get good connectivities for the side-chain carbon, nitrogen and proton resonances. Rao et d7' describe several pulse schemes for the sequential assignment of the arginine side-chain H" protons. Lohr and R ~ t e r J a n propose s~~ several new experiments, based on the previously reported ct-HCACO experiment, which uses the l3CY spin of the aromatic group as the focal point. The NMR spectral assignment and structure determination of very large proteins can be made possible by the use of deuterated protein samples and much effort is devoted to developing experimental methods for assigning spectra of deuterated proteins. The use of a protein sample depleted of protons presents a different set of problems as many of the NMR assignment strategies rely on the use of proton magnetization. Gardner et al.77 describe the(H)C(CO)NH-TOCSY experiment, which uses a TOCSY-transfer between the protonated carbon of the methyl groups and the C" to make connectivities between the protonated methyl groups and the backbone amide protons in an otherwise deuterated protein sample. Ikegami et U I . also ~ ~ describe modifications to existing experiments (the HN(CA)NH experiment) for application to deuterated protein samples. Dotsch

286

Nuclear Magnetic Resonance

et ai.79 describe the 0-carbon-edited HNCOCACB experiment for deuterated proteins; this experiment is based on the HNCOCACB experiment and allows selection of spin systems from amino acid residues glycine, serine, cysteine and alanine, all these amino acids lack a Cy carbon. In addition, these experiments can also be used to provide sequential, connectivities for aromatic residues where the Cy resonates far away from the Ca and Cp regions. Dijkstra et a1.80 describe the (CO)N(CO)CAH 3D experiment that correlates '5N(i + 1) with I3Ca(i) and'Ha(i) of the protein backbone; the main disadvantage of this experiment is the loss in sensitivity, due to the fact that the pulse sequence begins with excitation of the carbonyl carbon spin, and also the requirement for a longer relaxation delay.

6.2 Three-dimensional I3C-'H or I5N-'H Experiments - The unambiguous assignment of intermolecular NOE's is crucial for obtaining high-quality structural information, particularly when conformational heterogeneity exists. Zhang et a/." report on a suite NOESY-based experiments with improved spectral resolution. Talluri and Wagner82 describe the implementation of an earlier reported method for water suppression in I5N-'H HSQC experiments which uses a water flipback pulse with a WATERGATE sequence. They show how the water resonance can be aligned at the f z axis by making use of radiation damping; a significant improvement in the overall sensitivity of the experiment is observed particularly for resonance of amide groups that experience fast exchange with water. Wijmenga et ai.83also describe improvements to the 3D TOCSY-HSQC experiment in order to obtain better sensitivity. Gradient water suppression was used and the water magnetization vector was not defocused but kept in the f z axis prior to acquisition.. The original heteronuclear cross-polarization HCCH-TOCSY experiment uses '~ the phase cycling and trim pulses to suppress artefacts. Wijmenga et ~ 1 . modify sequence to incorporate gradients to provide for water suppression and coherence pathway selection. In addition, a previously reported double-sensitivity enhancement strategy, whereby each transfer step is modified into an enhanced sequence, is introduced and significant improvement in the sensitivity is demonstrated. Despite the extra dimensions when using I3C-isotope edited experiment, the presence of I3C-l3Ccoupling can still limit the resolution in the 13C dimension in these experiments when using '3C-labelling samples. This resolution can be improved by removing the modulation caused by these couplings using the constant-time approach. Shaw et ai." demonstrate a new constant-time modification to the HQQC (heteronuclear quadruple-quantum coherence) experiment and show that increase in resolution without loss of sensitivity (as a result of the introduction of constant-time delays) can be achieved in the HQQC experiment. Hu and Zuidenvegs6 describe the constant-time (H)CCH-COSY experiment to obtain chemical shift correlations between neighbouring I3C nuclei to obtain stereospecific assignments of the valine and leucine methyl groups.

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6.3 Scalar Coupling Constants Using nD Heteronuclear Experiments with Proton-Detection- Assignment of resonances and determination of the structures of ribonucleic acids(RNAs) are made using scalar coupling information. The HCN-experiment has been a crucial experiment to provide links between the ribose protons and a particular base. On the other hand, the HCP-based experiments can be used to obtain sequential assignment of all ribose protons, ribose carbon and intervening phosphorus resonances in the RNA backbone. Nevertheless, spectral overlap can still be a problem and Ramachandran et aLs7 describe another set of experiments where the HCN and HCP-based experiments are acquired simultaneouly in order to save data acquisition time. The xl information is useful in describing the three-dimensional structure of a protein and its derivation is based on obtaining sufficiently precise measurements of the small coupling constants. Hu and Bax88 demonstrate the measurement of 3JNcyin isotopically enriched proteins , using the HNCG experiments. Grzesiek and Baxs9 describe an improvement to the (HN)CO(CO)NH experiment which will allow measurements of the small 3Jc.cp coupling values. The method descibed uses a TOCSY-type magnetization transfer, instead of the COSY-type transfer, in order to extend the measurement of this coupling constant in systems where the relaxation rates are less favorable. 6.4 Homonuclear 3D Experiments - The double-quantum experiment is not very often used due in part to the poor sensitivity of the experiments and also because of the rather inconvenient double-quantum representation in the indirect dimension. Nevertheless, development continues in this area and Dalvit” describes two new experiments which includes either a NOESY or TOCSY step at the beginning of the pulse sequence, followed by the multiplequantum coherence transfer step. Pulsed field gradients are also used in these experiments.

7

Analogues of nD Experiments

Pellecchia et aL9’ describe the 2D H(C)C02 and the HCC02 experiment for assignments of side-chain carboxylate groups; these experiments are based on the previously reported ct-HCACO experiment. In studies of oligosaccharides, one-dimensional versions of many multidimensional experiments are frequently desired in order to achieve high resolution. Very often, ‘excitation sculpting’ is used where only a selected region of the spectrum is excited, hence restricting coherence transfer to involve only these excited nuclei. Gradwell et al.92 describe the use of excitation sculpting in the construction of 1D ROESY, TOCSY-ROESY, and ROESY-TOCSY experiments. The selective pulse is achieved by applying a double-pulsed field-gradient spin-echo sequence. Wagner and Bergerg3 describe a selective triple resonance experiment which provides connectivity between two heteronuclear atoms using proton detection. Gradient and selective pulses are used to achieve selectivity.

288

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Table 8.1 New or improved double and triple resonance experiments Experiment

A ims

References

3D (H)N(COCA)NH with improved sensitivity CPd HCCH-TOCSY; CPd-HNCA; CPd-HN(C0)CA 3D (HA)CANH, (HA)CA(CO)NH HMQC with PFG and Constant-time 3D yd-HCACOi3D yd (H)CACO-TOCSY 3D NOESY-(HCAC0)NH

Sequential NH-NH connectivities

66

Connectivities involving C" and with Cp decoupling Improved sensitivity triple resonance experiments HCACO in HzO

67,68

Transfers NOES from I H" to IHNof succeeding residue Spin system topology discrimination

71

Spin system topology discrimination Connectivities in histidine and tryptophan side-chains Connectivities in arginine side-chain

73 74

Connectivities between aromatic ring and aliphatic spins Sequential assignment of protonated meihyl groups i n perdeuterated proteins Connectivities in deuterated proteins Correlation of I5N(,+I ) , '3Ca(,)and IHa(,,backbone resonances Sequential connectivities between NH and C",Cp for residues alanine, glycine, serine, cysteine and aromatic residues Improved resolution triple resonance experiments Spin system assignment

76

PFG-CT-HACANH; PFGHACA(C0)NH (phase-labelling) PFG-CBCA( CO)NH(phase-labelling) 3D HCN Arg-(H)C(C)TOCSY-N"H" and Arg-H(CC)TOCSY-N"H" 3D HCBCG; H(CD)CGCB); (HB)CB(CG)CDHD (H)C(C0)NH-TOCSY HN(CA)NH (modified) 3D (CO)N(CO)CAH P-carbon-edited D-HNCOCACB NOESY-based triple resonance experiments 3D TOCSY-HSQC (sensitivity-enhanced) 3D HCCH-TOCSY (doubly sensitivity-enhanced) 2D HQQC constant-time experiment

Scalar connectivities in "C-labelled proteins Heteronuclear I3C-IH scalar coupling (methyl groups) 3D CT-(H)CCH-COSY Stereospecific assignments of Val and leu methyl groups in selectivelylabelled proteins Simultaneous HCN and HCP-based HC(N,P); HC(N,P)-CCH-TOCSY experimnents Double-tuned Isotope-filtered Isotope-filtered experiments EZ-HMQC-NH2 Stereospecific assignment of asparagine and glutamine side-chains HINCO-E.COSY Stereospecific assignment of asparagine and glutamine side-chains ['H-'3C]DINE-NOESY[1H-'5N]HSQC Isotope-assisted NMR cross-relaxation network editing HNCG 3 ~ N c ycoupling constant 2D H(C)C02 and the HCCO, Assignment of side-chain carboxylate groups 3D (H)C(CCO)NH

69 70

72

75

77 78 80 79

81 83 84 85 86 87 55 50 51

27 88 91 45

8: Multiple Pulse N M R

8 1

-

7

3 4 5 6 7 8 9 10

11 12 13 14 15 16

17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41

289

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F. A. A. Mulder, C. A. E. M. Spronk, M. Slijper, R. Kaptein, and R. Boelens, J. Biom. N M R . 1996,8,223. A. Meissner, D. Moskau, N. C. Nielsen, and 0. W. Sorensen, J . Magn. Reson. 1997, 124,245. K. Zangger, and H. Sterk, J . Magn. Reson. 1996, Series A 121, 56. E. R. P. Zuiderweg, L. Zeng, B. Brutscher, and R. C. Morshauser, J . Biom. N M R . 19!96,8, 147. T. Carlomagno, M. Maurer, M. Sattler, M. G. Schwendinger, S. J. Glaser, and C. Griesinger, J . Biom. N M R . 1996,8, 161. T. Carlomagno, B. Luy, and S. J. Glaser, J . Magn. Reson. 1997,126, 110. K. Ogura, H. Terasawa, and F. Inagaki, J . Biom. N M R . 1996,8,492. B. Whitehead, M. Tessari, P. Dux, R. Boelens, R. Kaptein, and G. W. Vuister, J . Biom. N M R . 1997,9,313. L. P. McIntosh, E. Brun, and L. E. Kay, J. Biom. N M R . 1997,9,306. F. Lohr, and H. Ruterjans, J . Magn. Reson. 1997,124,255. W. Willker, U. Flogel, and D. Leibritz, J . Magn. Reson. 1997, 125, 216. V. V. Krishnamurthy, J . Magn. Reson. 1996, Series B 113,46. V. V. Krishnamurthy, J . Magn. Reson. 1996, Series B 112, 75. K . Ogura, H. Terasawa, and F. Inagaki, J. Magn. Reson. 1996, Series B 112, 63. W. Kozminski, and D. Nanz, J. Magn. Reson. 1997,124,383. W. Kozminski, and D. Nanz, J. Magn. Reson. 1996, Series A 122,245. B. Reif, M. Kock, R. Kerssebaum, J. Schleucher, and C. Griesinger, J . Magn. Reson. 1996, Series B 112, 295. N. Tjandra, and A. Bax, J. Magn. Reson. 1997,124,512. J. R. Tolman, and J. H. Prestegard, J. Magn. Reson. 1996, Series B 112,245. J. R. Tolman, and J. H. Prestegard, J. Magn. Reson. 1996, Series B 112, 269. G. P. Kelly, F. W. Muskett, and D. Whitford, J. Magn. Reson. 1996, Series B 113, 88. G. Otting, J. Magn. Reson. 1997, 124, 503. V. V. Krishnamurthy, J . Magn. Reson. 1996, Series A 121, 33. G. Xu, and J. S. Evans, J . Magn. Reson. 1996, Series A 123, 105. C. Bracken, 111, A. G. P. and J. Cavanagh, J . Biom. NMR. 1997,9,94. H. Matsuo, E. Kupce, H. Li, and G. Wagner, J . Magn. Reson. 1996, Series B 113, 91. H. Matsuo, E. Kupce, and G. Wagner, J . Magn. Reson. 1996, Series B 113, 190. G. V. T. Swapna, C. B. Rios, Z. Shang, and G . T. Montelione, J . Biom. N M R . 1997, 9, 105. W. Zhang, and W. H. Gmeiner, J. Biom. N M R . 1996,7,247. W. Zhang, and W. H. Gmeiner, J . Biom. NMR. 1996,8,357. W. Feng, C. B. Rios, and G. T. Montelione, J . Biom. N M R 1996,8,98. C. B. Rios, W. Feng, M. Tashiro, Z. Shang, and G. T. Montelione, J . Biom. NMR. 1996, 8, 345. J. L. Sudmeier, E. L. Ash, U. L. Gunther, X. Luo, P. A. Bullock, and W. W. Bachovchin, J . Magn. Reson. 1996, Series B 113, 236. N. S. Rao, P. Legault, D. R. Muhandiram, J. Greenblatt, J. L. Battiste, J. R. Williamson, and L. E. Kay, J. Magn. Reson. 1996, Series B 113, 272. F. Lohr, and H. Ruterjans, J . Magn. Reson. 1996, Series B 112,259. K. H. Gardner, R. Konrat, M. K. Rosen, and L. E. Kay, J. Biom. N M R . 1996, 8, 351. T. Ikegami, S. Sato, M. Walchli, Y. Kyogoku, and M. Shirakawa, J . Magn. Reson. 1997,124,214.

8: Multiple Pulse N M R

79 80 81 82 83 84 85 86 87 88 89 90 91 92 93

29 1

V. Dotsch, H. Matsuo, and G. Wagner, J. Magn. Reson. 1996, Series B 112, 95. K. Dijkstra, G.. J. A. Kroon, E. AB, R. M. Scheek, and J. Kemmink, J. Magn. Reson. 1997,125, 149. 0 . Zhang, J. D. Forman-Kay, D. Shortle, and L. E. Kay, J. Biom. N M R . 1997,9, 181. S. Talluri, and G. Wagner, J . Magn. Reson. 1996, Ser. B 112,201. S. S. Wijmenga, C. P. M., van Mierlo, and E. Steensma, J. Biom. N M R . 1996,8, 319. S. S. Wijmenga, E. Steensma, and C. P. M. van Mierlo, J. Magn. Reson. 1997, 124, 459. G . L. Shaw, T. Muller, H. R. Mott, H. Oschkinat, I. D. Campbell, and L. Mitschang, J. Magn. Reson. 1997, 124,479. W. Hu, and E. R. P. Zuiderweg, J. Magn. Reson. 1996, Series B 113,70. R. Ramachandran, C. Sich, M. Grune, V. Soskic, and L. R. Brown, J . Biom. N M R . 1996,7, 251. J. S. Hu, and A. Bax, J. Biom. N M R . 1997,9,323. S. Grzesiek, and A. Bax, J. Biom. N M R . 1997,9,207. C . Dalvit, J. Magn. Reson. 1996, Series B 112, 186. M. Pellecchia, H. Iwai, T. Szyperski, and K. Wuthrich, J . Magn. Reson. 1997, 124, 274. M. Gradwell, H. Kogelberg, and T. A. Frenkiel, J. Magn. Reson. 1997,124, 267. R. Wagner, and S . Berger, J. Magn. Reson. 1996, Series A 120,258.

9 NMR of Natural Macromolecules P. C. DRISCOLL AND S. M. KRISTENSEN

1

Introduction

In this, our second year of reporting for this series, the commission to review the applications of NMR to the study of macromolecules has become no less daunting than we indicated last time around. The format of the foregoing report is much as before with a very heavy focus upon the role of NMR spectroscopy in the determination of the three-dimensional solution structures of biological macromolecules, primarily proteins and nucleic acids, and their complexes. However attendance at various recent biological NMR meetings has evidenced a very strong and apparently expanding level of activity in the realm of the investigation of macromolecular dynamic properties through the measurement and interpretation of nuclear relaxation, cross-relaxation and cross-correlation phenomena. In view of this the latter major part of this report is devoted to a thorough description of some of the recent and important developments in this particular aspect of our speciality. We would also like to highlight here the exciting developments in the use of biological NMR for the purposes of ‘highthroughput’ screening of ligand fragments that can subsequently be chemically tethered to derive high affinity inhibitors of enzymes or macromolecular interactions - so-called structure-activity relationships by NMR (‘SAR-byNMR’). As is described below the apparent potential of this method for the experimental (rather than ab initio) discovery of new therapeutic agents is likely to greatly excite our colleagues in the pharmaceutical industry, and possibly restimulate their investment in this powerful spectroscopy.

2

Solution Structure Determination of Proteins

Solution structure determinations of biological macromolecules by NM R spectroscopy continues apace, and a complete and comprehensive documentation of reports of new protein and nucleic acids structures is beyond the scope of what these reviewers can devote their time to. To a very large extent to do so would be to duplicate the effort of the large staff of the Brookhaven Protein Data Bank, where the vast majority of newly determined structures are deposited along with accompanying experimental distance and torsion angle restraints and resonance chemical shift assignments. As for last year’s report, we will restrict ourselves to Nuclear Magnetic Resonance, Volume 27 0The Royal Society of Chemistry 1998 292

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an attempt to list some of the highlights of the structure determination activity. This collection is biased towards those structures that appear in journals with the highest impact factors, or have attracted our attention because of some particular aspect of the methodological approach. By its very nature this is then a subjective list of highlights and we plead with fellow spectroscopists not to feel slighted by any omission.

2.1 Landmark Protein Structures - The determination of the structure of the prion protein is certainly one of the most newsworthy discoveries for the field of NMR spectroscopy, and is known to have made the front page of at least one major European newspaper. Prion protein is currently targeted as the pathogenic agent in a series of neurodegenerative disorders that includes the sheep condition scrapie, bovine spongiform encephalopathy (BSE or ‘mad cow disease’) and in humans Creutzfeldt-Jakob disease (CJD). A new variant CJD has recently been identified in the United Kingdom where a number of deaths of young people have been associated with this disease that usually only occurs much later in life. The current opinion is that this new form of CJD may have arisen from the long term ingestion of BSE-infected beef meat, and as a result there is the real prospect of a major public health problem in the medium- to long-term. Prion proteins are thought to exist in two conformations, the benign cellular form and a modified infectious ‘scrapie’ form. The somewhat controversial ‘protein only’ hypothesis that is one of the main models for the disease pathology states that a modified form of the normal prion protein is sufficient to trigger the infectious state. Wiithrich and colleagues successfully produced the autonomously folding Cterminal portion (residues 121-231) of the mouse prion protein PRP by expression into the periplasmic space of Escherichia cofi.’ The PRP structure determined by triple resonance NMR contains a two-stranded antiparallel P-sheet and three a-helices. The domain contains the majority of sites for which mutations in familial prion disease patients have been found. The mutations cluster around, within and adjacent to regular secondary structure elements. The authors claim that the presence of the P-sheet element is in contradiction to previous sequence-based predictions of the structure, and could be important for the initiation of the transition from the cellular form to the scrapie form.’-4 NMR spectroscopy has already provided important contributions to mapping the structural biology of the human immunodeficiency virus (HIV). Now Summers and co-workers have determined the solution structure of the aminoterminal core domain of the HIV-1 capsid protein5 and thereby contributed a useful molecular replacement model to solve the crystal structure of capsid protein dimer.6 The solution structure of the N-terminal 151 residues of the capsid protein was solved using triple resonance NMR methodology. The fold is unlike any other viral coat protein previously defined. The arrow-head shaped domain has seven a-helices, two b-hairpins and an exposed, partially ordered loop. The N-terminal proline residue Pro-1 forms a salt bridge with a conserved, buried aspartate residue (AspS1) suggesting that the amino terminus of the protein rearranges upon proteolytic maturation. A cellular rotamase, cyclophilin A, is packaged into the HIV-1 virion and its binding site is identified from the

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structure in the exposed loop surrounding Pro90, which in the free monomeric domain is kinetically trapped into separate cis- and trans-conformations, and leads to the suspicion that the rotamase catalyses the interconversion of two loop structures. Programmed cell death, otherwise known as ‘apoptosis’ is one of the most topical areas of cell biological research, the mechanisms of which if unravelled will likely provide a great boon to the development of anti-tumour agents for the treatments of cancers. In one well studied model of apoptosis the cell death signalling involves the self-association of the cytoplasmic ‘death’ domains of the transmembrane cytokine receptor Fas (APO-l/CD95) and the interaction with a third protein FADD containing a homologous death domain. The first structure of a death domain has been solved by triple resonance NMR by Huang et al.7 The structure reveals a fold comprising six antiparallel amphipathic a-helices arranged in a novel topology. An important step in the progress towards successful determination of the structure was the characterisation of the pH profile of the aggregation properties of the expressed domain. Using the solution structure the authors performed site-directed mutagenesis and were able to identify the region of the death domain involved in the self-association and the binding to the downstream partner FADD. The WW domain, so-called because it contains two conserved tryptophan residues, is a newly identified protein module that binds proline-rich peptide motifs in vitro. It is commonly found, often in several tandemly linked copies, in intracellular signalling and regulatory proteins. Macias et al. have determined the structure of the WW domain from YAP65 (Yes kinase associated protein) in complex with proline-rich peptides containing the core motif PPXY.’ The structure of the domain is a slightly curved three-stranded antiparallel P-sheet. Two prolines pack against the first Trp residue forming a ‘buckle’ on the convex side of the P-sheet. On the other side three exposed residues (Tyr, Trp and Leu) make up the binding site of the peptide ligand. The structure of the domain is compared with Src homology 3 (SH3) domains, which also appear to use stacked aromatic rings to provide a surface for the binding of proline-rich peptides. The family of Bcl-2 related proteins are critical regulators of cell survival that are localised to the outer mitochondrial, outer nuclear and endoplasmic reticulum membranes. The mechanism of action of these proteins is a focus of a great deal of research. We highlighted last year Fesik and co-workers’ description of the three dimensional NMR solution and X-ray crystal structures of human Bcl-XL, an inhibitor of programmed cell death.’ The structure revealed a topological homology to the membrane translocation domain of bacterial toxins, and Minn et al. subsequently demonstrated that Bc1-x~possessed the capability to form ion channels in synthetic lipid membranes.” This result provoked speculation that the Bcl-2 proteins may function to regulate the permeability of intracellular membranes. It is known that heterodimerisation between members of the Bcl-2 family is a key event in the regulation of the protein function. Fesik’s group have developed their interest in the structural characteristics of these proteins and determined the solution structure of the complex of Bcl-XL with a peptide corresponding to the death promoting region of the Rcl-2 related protein Bak.”

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The bound peptide adopts an amphipathic a-helical structure that interacts through hydrophobic and electrostatic interactions. Mutations in Bak that would disrupt these contacts are shown to inhibit the ability of Bak to heterodimerise with Bcl-XL. Other protein solution structure determinations released in the past twelve months that are worthy of note are as follows: papilloma virus E2 protein;12 human thioredoxin complexed with a peptide from its target Ref- 1;13714pathogenesis-related protein P14a;I5 a non-classical homeodomain from the rat liver LFBl/HNFl transcription factor;16 a yeast killer toxin with an ancestral Pycrystallin precursor fold;l7 J-domain and the Gly/Phe-rich region of the E. coli DnaJ chaperone;I8 HTLV-I1 matrix protein (along with comparative analysis of matrix proteins from the different classes of pathogenic human retroviru~es);'~ cysteine-rich intestinal protein CRIP;20 archaeal TFIIB from Pyrococcu.~furi o s ~ s ; ~histone ' HMfB from the hyperthermophile Methanothermus fervidus;22 tomato heat stress transcription factor HSF24;23 human interleukin-6;24 CheY binding domain of CheA;2Sthe 'Link' module - a hyaluronan-binding domain involved in extracellular-matrix stability and cell-migration;26the Src homology 3 domain from the tyrosine kinase Fyr~;~'tandem pair of calcium-binding E G F domains from fibrilliq2' skeletal muscle troponin C regulatory domain Glu41 +Ala mutant;29 type I11 anti-freeze protein;30 a synthetic troponin-C 14T - a representative domain from the actin heterodimeric d ~ m a i n ; ~villin ' severing and bundling protein illi in;^^ antitumor compound PT523 and NADPH in a ternary complex with human dihydrofolate r e d ~ c t a s e ;DNA-binding ~~ domain of N F A T c ; ~ribosomal ~ RNA binding protein S15 from Therrnus N-terminal thioredoxin-like domain from protein disulfide isotherrnophil~s;~~ m e r a ~ ec-Jun ; ~ ~ leucine zipper h ~ m o d i m e rglycophorin ;~~ A transmembrane helix dimer in detergent m i ~ e l l e s ; ~chromatin '~~~ binding ('chromo') domain from mouse modifier protein l;40 E. coli polynucleotide phosphorylase S1 RNAbinding domain;41an example twitchin immunoglobulin superfamily domain;42 an example of the repeating segment of the F-actin cross-linking gelation factor ABP- 120;43 nidogen binding LE module of laminin y- 1 chain;44 Kunitz-type domain from human type VI collagen a 3 chain;45 a three-helix bundle spectrin repeat46 bovine SlOOB protein dimer in the calcium-free state:' domain I1 of elongation factor TFIIS;48ball peptides that make inactivation gates for mammalian voltage-dependent potassium channels;49 the homopentamer structure of P-subunit of verotoxin VT-1 from E. coli;" and human pNR-2/pS2 - a single trefoil motif p r ~ t e i n . ~ ' 2.2 NMR Spectroscopy of 'Large' Proteins - From the perspective of the structural biologist it is important to remain acquainted with the current molecular weight limits for the application of triple resonance heteronuclear NMR spectroscopy, both in respect of the ability to actually solve the NMR solution structure, and to obtain backbone resonance assignments from which often the secondary structure can be delineated. Again we choose to highlight some of the recent reports of the activity in this field. Torchia and co-workers have targeted several large proteins for solution

296

Nuclear Magnetic Resonance

structure determination, and have been notably successful in the case of two homodimeric systems, the 22.2 kDa HIV-1 protease, complexed with the inhibitor DMP32352 and the 25 kDa disulfide-linked transforming growth factor-p 1 h ~ m o d i m e rBoth . ~ ~ struStures were determined to very high resolution by NMR standards (0.6 and 0.7 A root mean square difference to the mean coordinate structure, respectively for core backbone atoms) without the requirement to resort to deuterium labelling and compare very favourably with related X-ray crystal structures. Summers and co-workers reported the solution structure of the 28 kDa symmetrical homodimer 3-0x0-A5-steroid isomerase enzyme54 which has a novel fold. From the structure these authors were able to establish a structure activity relationship for residues in the active site. The three-dimensional solution structure of the monomeric 259-residue 30 kDa N-terminal domain of enzyme I (EIN) of the phosphoenolpyruvate-sugarphosphotransferase system of E. coli has been determined by Garrett at al? Enzyme I, which is autophosphorylated by phosphoenolpyruvate, reversibly phosphorylates the'phosphocarrier protein HPr, which in turn phosphorylates a group of membrane-associated proteins, known as enzymes 11. To facilitate and confirm NH, "N, and 13C assignments in this case the authors made extensive use of perdeuterated "N and 15N-/'3C-labelled protein to narrow line widths. Ninetyeight percent of the 'H, "N, and I3C assignments for the backbone and first side chain atoms of protonated EIN were obtained using a combination of double and triple resonance correlation experiments. The structure determination was based on a total of 4251 experimental NMR restraints, and the precisip of the coordinates for the final 5$l simulated annealing structures was 0.79 A for the backbone atoms and 1.060Afor all atom:. The structure of EIN is ellipsoidal in shape, approximately 78 A long and 32 A wide, and comprises two domains: an a@ domain (residues 1-20 and 148-230) consisting of six strands and three helices and an a-domain (residues 33-143) consisting of four helices. The two domains are connected by two linkers (residues 21-32 and 144-147), and in addition, at the C-terminus there is another helix which serves as a linker between the N- and C-terminal domains of intact enzyme I. The authors describe a comparison with the recently solved X-ray structure of EIN which indicated that there are no significant differences between the solution and crystal structures within the errors of the coordinates. The NMR spectrum for this protein shows a particular signature for the active site His189 which has a trans conformation about ~ 1 a, g + conformation about x 2 , with its NE2atom accepting a hydrogen bond from the hydroxyl proton of Thr168. The authors conclude that since His189 is thought to be phosphorylated at the NE2 position, its side chain conformation would have to change upon phosphorylation. It appears that backbone resonance assignments can be obtained for significantly larger proteins than those for which the structures that can (yet) be obtained. Particularly outstanding in this respect are the reports of assignments and secondary structure mapping for the human carbonic anhydrase I,56 perdeuterated monomeric 38.5 kDa flavoenzyme UDP-N-acetylenol-pyruvylglucosamine reductase (MurB) in substrate free- and b o ~ n d - s t a t e sand , ~ ~homodimeric 39 kDa P-hydroxydecanoyl thiol ester d e h y d r a ~ eThe . ~ ~ backbone and side chain assign-

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ments and secondary structure has been mapped for the 41 kDa homo-hexamer structure of 62 residue 4-oxalocrotonate tautomerase in double 13C,1SN-labelled f01-m.~~ These assignments provided the basis for subsequent studies of the polypeptide backbone dynamics through "N-relaxation measurements in both the free and inhibitor bound states.60 2.3 Deuterium Incorporation for Linewidth Narrowing - One of the fundamental limits to the application of 1H,13C,'SN-tripleresonance NMR techniques is the dipolar coupling of I3C atoms with the attached protons. This phenomenon is especially troublesome for a-carbons, the relatively broad linewidths of which tend to limit coherence transfer and sensitivity of any pulse sequence that involves this pivotal position in the amino acid/polypeptide backbone structure. A workaround for this problem has been proposed in which recombinant protein samples are prepared from the heterologous host (usually E. coli bacteria) grown up in high levels of deuterium oxide (D20). In the last volume of this series we reviewed some of the pioneering work in this area of 'perdeuteration'. Some groups are routinely using high levels of perdeuteration (ca. 70%) to produce samples that facilitate the application of triple resonance NMR experiments for resonance assignment. One of these, headed by Stephen Fesik, has produced an excellent overview of the application of perdeuteration in protein NMR structure determination.61 In a broad-ranging article, Venters et al. have described in detail various practical aspects of the use of perdeuteration in NMR studies of large proteins.62They present an assessment of the effects of perdeuteration upon 13Ca, 13C', lsNH and 'HN relaxation times, and the advantageous consequences for the sensitivity of various triple resonance pulse sequences. In describing the application of perdeuteration to the 259 residue 29 kDa metalloenzyme human carbonic anhydrase 11, the authors propose a general strategy for obtaining the backbone and side chain resonance assignments, and secondary structure pattern of perdeuterated proteins. There is a slow but steady stream of new triple resonance NMR pulse sequences that are designed to be optimal for perdeuterated protein samples including an improved sensitivity version of the HN(CA)CO experimenf3 and experiments for the determination of amino acid class based on the CBCACONH pulse sequence amino acid type identification in D - p r ~ t e i n s . ~ Perhaps ~ ~ ~ ' the most comprehensive description of development and application of pulse sequences designed for perdeuterated samples is given by Shan and co-workers.68 This expansive work describes the near complete ( > 90Y0)backbone resonance assignments of the protein component of the 64 kDa trp repressor-operator complex containing two NMR distinct tandem repressor dimers bound to a 22 basepair DNA oligonucleotide. The authors discuss the use of constant time evolution periods for improved resolution and analyse the utility of enhanced sensitivity strategies in the context of high molecular weight deuterated biomolecules. Deuteration of proteins also allows new avenues to investigate molecular dynamics, through measurement of 2H relaxation times. Kay and co-workers have previously demonstrated that useful measurements of methyl group deuterons can be made in 2H,13Cdouble-labelled proteins. Now Pervushin er al. have

298

Nuclear Magnetic Resonance

investigated the 2H relaxation in side chain NH2 groups of a DNA-binding homeodomain protein, by dissolving a "N-labelled sample in a 50:50 mixture of D 2 0 and The relaxation properties are contrasted for the free and DNAcomplexed form of the homeodomain. A more formal analysis of the influence of a scalar coupled deuteron upon the relaxation of a directly coupled "N nucleus and its exploitation as a probe for asparagine and glutamine side chain interactions in proteins has been presented by Boyd et al.70

2.4 Selective Protonation Against a Deuteration Background - Perdeuteration undoubtedly allows for improved sensitivity and resolution in triple resonance 'through bond' pulse sequences designed for the elucidation of 'H, 13C and '*N resonance assignments. For structure determination using NMR however, the spectroscopist requires to unravel the network of 'H-lH 'through space' nuclear Overhauser effects that one generally obtains from protonated samples. Several groups have explored the consequences for the quality of NOESY spectra and the subsequent structure determinations in using partially or perdeuterated (containing ' H nuclei only in sites of solvent exchangeable protons) protein samples. Certainly it is clear that dilution of ' H within the protein using the latter approach yields to a dramatic reduction in the number of dipolar couplings in such samples, leading to strongly diminished spin-diffusion effects, and NOESY sp!ctra that give reliable distance estimates for protons separated by as much as 7 A. These results suggested that it might be possible to determine low resolution protein structures from the distance restraints obtained from perdeuterated samples alone. These concepts have not however directly lead to any new structures of large molecular weight proteins in the past year, which tends to suggest that over-optimistic claims were made for these procedures. Indeed several groups have performed work to improve the yield of structurally significant restraints from deuterated samples. The common theme of these reports is the introduction of protonated '3C-methyl groups in a background of a perdeuterated '3C,'5N-labelled protein. For example, Rosen et al. reported a strategy for selective protonation of methyl groups in otherwise perdeuterated proteins in which fully protonated pyruvate is used as the sole carbon source for the over-expression of the target protein in bacteria grown in D20 containing m e d i ~ m . ~The ' biosynthetic pathways at work result in essentially complete deuteration at the a-carbon position and greater than 80% deuteration at the pcarbon of nearly all the amino acids. In contrast, the methyl groups of Ala, Val, Leu and Ile(y2 only) remain highly protonated. The same group later reported a (H)C(CO)NH-TOCSY pulse sequence for the facile resonance assignment of these protonated methyl groups, demonstrated on a small (14 kDa) protein but recorded at low temperature (3 "C) to mimic the correlation of a much larger protein (rotational correlation time 18.8 n ~ ) In . ~addition ~ they reported a demonstration of the calculation of the solution structure of the small protein under these condition^.^^ The global protein fold i s obtained from a set of methyl-methyl, methyl-NH and NH-NH distance restraints. The authors show that the inclusion of methyl-NH and methyl-methyl distance restraints greatly improves the precision and accuracy of the structures obtained compared to

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those calculated on the basis of the NH-NH distances alone. The application of the strategy to larger proteins, up to molecular masses up to 40 kDa, is discussed, with the conclusion that whilst improved precision and accuracy of the calculated protein folds can be generally expected the precise nature of the results may depend critically on the particular pattern of a- and P-secondary structure elements in the target structure. A related strategy has been proposed independently by two other groups. Metzler et af. describe the potential for structure determination of large proteins on the incorporation of 1H,13C,15N-labelled Ile, Leu and Val into a perdeuterated "N-labelled protein.74 Smith et al. have analysed a conceptually very similar strategy - protonation of specific amino acid types (including aromatic amino acids) in a background of perdeuteration - and include both experimental demonstrations and model protein structure calculations in their expo~ition.~' In spite of the high level of activity in the development of these techniques it remains to be seen if the promise of these ideas will be translated into general utility in global fold determinations of large molecular weight proteins by NMR.

3

NMR Spectroscopy of Nucleic Acids

The application of NMR spectroscopy to the study of nucleic acid conformation and function continues apace. On a general note, Schultze et al. reported a concern at the poor quality of RNA structure reporting in public structure databases particularly in relation to chirality err01-s.~~. In an intriguing development Kubinec et af. introduced site specific tritium labels into a DNA oligomer and a so-called hammerhead RNA77as a preliminary test of the suitability of 3H NMR for the investigation of DNA-bound water molecules. 3.1 NMR of DNA - Again this field appears, to the outsider at any rate, to be dominated by the output of Pate1 and co-workers who in the last twelve months have reported several DNA structures including those of consensus binding site DNA oligonucleotides bound to enediyne antibiotics calichemeamicin y1 I and esperamcin A1;78,79Bombyx mori single repeat telomeric DNA which forms a Gquadruplex;" oligodeoxynucleotide duplexes containing the exocyclic lesions;81782 and two aminopyrene DNA ad duct^.^^^'^ Meanwhile Feigon and co-workers reported on the solution structures of an intramolecular DNA triplex containing an N-7-glycosylated guanine which mimics a protonated cytosine DNA triple^,^' and a pyrimidine-purine-pyrimidine triplex containing the sequence-specific intercalating non-natural base D-3 DNA.s6 Hilbers' group described the solution structure of a DNA hairpin with G*A mismatch base pair in the and a study of an oligonucleotide that displays pH dependent double-helix f--t triplehelix transitions.88

3.2 Protein-DNA Complexes - The following descriptions highlight some of the landmark results in this area of activity over the past twelve months. The structure of a complex between the DNA binding domain of the GAGA factor

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Nuclear Magnetic Resonance

(GAGA-DBD) and an oligonucleotide containing its GAGAG consensus binding site has been determined by NMR by Omichinski et al.89 The GAGADBD comprises a single classical Cys2-His2, zinc finger core, and an N-terminal extension containing two highly basic polypeptide segments, BRl and BR2. The zinc finger core binds in the major groove and recognises the first three GAG bases of the consensus in a manner similar to that seen in other classical zinc finger-DNA complexes. Unlike the latter, which require tandem zinc finger repeats with a minimum of two units for high affinity binding, the GAGA-DBD makes use of only a single finger complemented by BR1 and BR2. BR2 forms a helix that interacts in the major groove recognising the last G of the consensus binding site, while BRl wraps around the DNA in the minor groove and recognises the A in the fourth position. The solution structure of the DNA binding domain of lac repressor (headpiece 1-56; HP56) has been refined using data from 2D and 3D NMR spectroscopy by Kaptein, Boelens and c o - w o r k e r ~The . ~ ~conformation of the NMR structures of free and DNA-complexed lac repressor headpiece were compared. The regions comprising the secondary structure elements show close correspondence for both conformations except for the loop between helix I1 and I11 which changes considerably upon complexation of the headpiece. The change in the conformation of the loop in lac HP56 is essential for binding of the side chains of residues Asn25 and His29 to the lac operator DNA. The lac headpiece residues that are intolerant to mutations were analysed. Most of these mutation-sensitive residues are important for a correct folding of the headpiece region, and a number of these residues are also involved in contacting the operator DNA. A second series of NMR studies of the free and DNA-bound states of the lac repressor headpiece showed that formation of the hinge helix requires protein-protein interactions and occurs only when the repressor binds to the full lac operator." The solution structure of the 18-kDa single-stranded DNA binding protein encoded by the filamentous Pseudomonas bacteriophage Pf3 has been refined using 40 ms mixing time "N- and I3C-edited NOESY spectra and many homoand heteronuclear J - c ~ u p l i n g sThe . ~ ~ new structure is highly precise, but some variation was found in the orientation of a P-hairpin, denoted the DNA binding wing, with respect to the core of the protein. 15N relaxation parameter analysis showed that the DNA binding wing is much more flexible than the rest of the protein, but its mobility is largely arrested upon binding of the protein to dA6. Furthermore, the complete DNA binding domain of the protein was mapped by recording two-dimensional TOCSY spectra of the protein in the presence and absence of a small amount of a spin-labelled oligonucleotide. The roles of specific residues in DNA binding were assessed by stoichiometric titration of dA6, which indicated for instance that Phe43 forms base stacking interactions with the singlestranded DNA. Finally, all results were combined to form a set of experimental restraints, which were subsequently used in restrained molecular dynamics calculations aimed at building a model for the Pf3 nucleoprotein complex.

3.3 NMR of RNA - The relative ease with which it is now possible to prepare isotope enriched RNA oligonucleotide has led to a steady increase in the numbers

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of reports of NMR studies of RNA motifs and their complexes with chemical biochemical ligands. Several good reviews of this activity have appeared recently93y94along with a study that critically evaluates the accuracy of the structures derived.95 A number of studies are worthy of highlighting here: Aboulela et al. have examined the uncomplexed form of the cis-acting RNA regulatory element TAR, the target of the regulatory protein tat of the HIV-1 Varani and co-workers have determined the solution structure of the acceptor stem of E. coli tRNAAla to probe the role of the G3mU70 base pair in synthetase recognition:' Greenbaum et al. have the structure of the donor site of a trans-splicing RNA;99 and Feigon and co-workers made the solution structure of the conserved 16 S-like ribosomal RNA UGAA tetraloop."' Hilbers' group examined an RNA duplex containing tandem G*A mismatched basepair motifs,"' and Kolk et al. studied the structure of an isolated central hairpin of the hepatitis 6 virus antigenomic ribozyme.Io2 Pardi and co-workers described unusual dynamics and pK, shift at the active site of a lead-dependent ribo~yme.''~ The conformational change in the catalytic core of the hammerhead ribozyme upon cleavage of an RNA substrate has been investigated by Simorre et a1.,'04 and the network of heterogeneous H-bonds in a set of GNRA tetraloops has been elucidated by Jucker et al.'05 Pardi's group also published new papers concerning methods for assigning base resonances in '3C,'SN-double-labelled RNA.'06-'0* Protein-RNA Complexes - Many proteins involved in pre-mRNA processing contain one or more copies of a 70-90-amino-acid a/P module called the ribonucleoprotein domain. RNA maturation depends on the specific recognition by ribonucleoproteins of RNA elements within pre-mRNAs and small nuclear RNAs. The human U1A protein binds an RNA hairpin during splicing, and regulates its own expression by binding an internal loop in the 3'-untranslated region of its pre-mRNA, preventing polyadenylation. Varani and co-workers report the NMR-derived solution structure of the complex between the regulatory element of the U l A 3'-untranslated region (UTR) and the U l A protein RNA-binding domain. '09,' l o The structure reveals that specific intermolecular recognition involves the interaction of the variable loops of the ribonucleoprotein domain with the well-defined helical regions of the RNA."' Formation of the complex then orders the flexible RNA single-stranded loop against the protein P-sheet surface, and reorganises the carboxy-terminal region of the protein to maximise surface complementarity and functional group recognition. Varani's group also describe the identification of a hybrid peptoid/peptide oligomer of nine residues (denoted CGP64222) that was able to block the formation of the TatITAR RNA complex in vitro at nanomolar concentrations."* NMR studies demonstrated that the compound binds similarly to the mode adopted by polypeptides derived from the Tat protein and induces a conformational change in TAR RNA at the Tat-binding site. The solution structure of a HIV-1 Rev peptide bound to stem-loop IIB of the '3C,15N-isotope labelled Rev response element (RRE) RNA has been solved by NMR spectroscopy by Battiste et a1.Il3 The Rev peptide has an a-helical conformation and binds in the major groove of the RNA near a purine-rich 3.4

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internal loop. Several peptide arginine side chains make base-specific contacts, and an asparagine residue contacts a G*A base pair. The phosphate backbone adjacent to a G*G base pair adopts an unusual structure that allows the peptide to access a widened major groove. The structure formed by the two purine-purine base pairs of the RRE creates a distinctive binding pocket that the peptide can use for specific recognition. Aminoglycoside antibiotics that bind the 30s ribosomal A-site RNA cause misreading of the genetic code and inhibit translocation. Puglisi and co-workers have determined the solution structure of the antibiotic paromoycin bound to an oligonucleotide from the 16s A-site."4,'15 The ligand binds in the major groove of the RNA within a pocket created by an A*A base pair and a single bulged adenine. Specific interactions are observed between chemical groups important for antibiotic activity and conserved nucleotides in the RNA, and the structure thereby helps to explain the binding of a range of aminoglycosides to the ribosome, mechanisms of resistance and ribosome function.

3.5 Aptamer RNA Complexes - One of the most exciting developments over the previous twelve months has been the plethora of studies relating the structure and dynamic properties of '3C,15N-isotopelabelled RNA aptamer complexes with bound co-factors and peptides.lI6 RNA aptamers are short oligonucleotides artificially derived for a specific ligand binding function by in vitro selection techniques. Claiming to be the first of its kind, Fan et al. reported the structure of 35mer RNA aptamer complexed with flavin mononucleotide (FMN).' l 7 The conserved internal RNA loop zippers up on complex formation with the isoalloxazine ring of FMN, which intercalates into the helix between a C O G mismatch and a G.U.A base triple. Specific hydrogen bonding and ring stacking interactions are revealed which help to rationalise the ligand-binding affinity. A series of reports describing the experimental approach and structural outcome of the study of the RNA aptamer complex with AMP have been presented by Pate1 and co-workers."* 12' Studies on a similar complex have also appeared by ~ ~ aptamer ~ ' ~ adopts ~ an L-shaped structure with two Dieckmann et ~ 1 . ' The nearly orthogonal stems, each capped proximally by a G.G mismatch pair, binding the AMP ligand at their junction in a GNRA-like motif. Patel's group have also reported the structure determination of an RNA aptamer complex with an aminoglycoside a n t i b i ~ t i c . 'The ~ ~ solution structures of RNA aptamer complexes with the HIV-1 Rev peptide have been investigated by both Ye et ~ 2 i . I ~ ~ and Peterson and Feigon.126

3.6 An Aptamer DNA Complex - The first structure of DNA aptamer complex has been recently presented by Lin et ai.'27 The NMR study which reveals the DNA stem-loop complex with argininamide, indicates that the hairpin loop DNA binding site undergoes an adaptive conformational transition on complex formation, as the tip of the loop folds down towards the stem and encloses the bound ligand between reversed Hoogsteen A*C and Watson-Crick G*C basepairs. The argininamide makes a series of hydrogen bonding and stacking interactions, without the involvement of salt bridges to the backbone phosphates.

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NMR of Protein-Protein and Other Ligand Interactions

It is increasingly important that biological NMR spectroscopists tailor their efforts not only at technological developments in the field but also at the resolution of biological problems that can be addressed by studies of interacting molecules in the NMR tube. For example, Garrett et al. used the assignments of the 30 kDa EIN domain, one of the largest solution structures determined to date to map the interaction site of the 9.5 kDa histidine-containing phosphocarrier protein HPr.I2*The complex is in fast exchange, which permits the monitoring of chemical shift changes of the backbone NH and I5N resonances of EIN upon complex formation by recording a series of 'H,"N correlation spectra of uniformly "N-labelled EIN in the presence of increasing amounts of HPr at natural isotopic abundance. In a similar manner the interaction between domain 1 of the T-cell antigen CD2 and its adhesion molecule partner CD48 was mapped by monitoring differential line broadening in '5N,1H spectra.'29 McInnes et al. used transferred NOES to examine the complex formed between transforming growth factor-a and a soluble form of the epidermal growth factor receptor;13'; Kriwacki et al. used mass spectrometry and NMR to investigate the nature of the complex between p21 and the cyclin-dependent kinase CDK2;'317'32and Scheuring et al. discovered using fluorine-19 NMR a curious system of a threeway asymmetric complex of inhibitor bound to a trimeric enzyme.133Kalbitzer and co-workers have performed an elegant and detailed phosphorous-3 1 NMR study of conformational transitions in p21'"" and its complexes with effector ~~ protein RAF-RBD and GTPase GAP.134Roberts and c o - ~ o r k e r s 'have targeted a number of interesting cytochrome p450 enzyme-ligand complexes for a variety of NMR studies, many of which include the use of Fe(heme)-induced paramagnetic relaxation of the bound ~ u b s t r a t e . ' ~ ~Using - ' ~ ~ a variant of cytochrome b562 containing the His10 2 t M e t mutation Barker and Freund have provided the first NMR characterisation of 6-coordinate, bis-methionine-ligated heme centre in both ferrous and ferric oxidation states.14' NMR spectroscopic studies of such bis-methionine-coordinated cytochrome have not previously been feasible, since the only other cytochrome with such a ligand arrangement, bacterioferritin, is too large to be studied by current NMR methods. Kaslik et al. have used NMR and other physical techniques for further characterisation of serpin binding to the proteinase t r y p ~ i n . ' ~ '

5

Structure-Activity Relationships by NMR (SAR-by-NMR)

Possibly one of the most dramatic developments in recent applications of biological magnetic resonance has been described by Stephen Fesik and coworkers from the Pharmaceutical Discovery Division, Abbott Laboratories, Illinois. Called structure-activity relationships-by-NMR, or SAR-by-NMR for short, the procedure provides a straightforward method for identifying high affinity ligands that can aid in the drug discovery process.'42 The impetus for SAR-by-NMR comes from the realisation that current modes of ab initio

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inhibitor design by computational methods alone may fail to identify the true thermodynamic parameters that control the free-energy of ligand-binding. Rather the SAR-by-NMR approach attempts to build up high affinity ligands from the experimental observations of often-times weakly interacting fragments that bind in separate sub-sites of the protein structure. The promise of the method, at least from this admittedly outsiders point of view, is likely to rejuvenate interest in the pharmaceutical industry in biological macromolecular NMR spectroscopy. We describe here the SAR-by-NMR strategy in outline. First, a library of low molecular weight compounds (2000- 10 000 compounds with average molecular weight ca. 200) is screened to identify molecules that bind to the protein. Primarily binding is detected by the observation of ''N or 'H amide chemical shift changes in two-dimensional "N-'H-HSQC spectra upon the addition of the ligand to a sample of the target protein, which has been produced in "N-enriched form. The HSQC spectra can be recorded quite rapidly, and this allows for the operation of the screening procedure in a high throughput manner. When one (weakly) binding molecule has been identified, a series of analogues can then be screened to optimise the binding to that site. Subsequently, a second ligand is sought that interacts at a different, nearby site, either in the presence or absence of the first ligand. Again optimisation of the second site binding fragment can be performed with structurally related small molecular weight compounds. When these two such lead fragments have been obtained the three dimensional structure of the ternary complex is determined to high resolution either by NMR or X-ray crystallography. In the final phase of the procedure, the known ternary complex structure is used to direct the synthesis of compounds containing linked lead fragments, with the goal of producing high affinity ligands. The argument is made that this directed mode of 'combinatorial chemistry', being based on experimentally defined lead fragments, rather than a more random search, requires lower levels of investment in synthetic medicinal chemistry than other methods. The SAR-by-NMR approach relies on the fact that although the untethered fragments may only display protein binding affinities in the millimolar to micromolar range, the binding affinity of the linked compound is in principle the product of the binding constants of the individual fragments plus a term that is due to the changes effected by the linking. The authors describe the application of the SAR-by-NMR method to the discovery of novel ligands of FKSO6-binding protein (FKBP), an inhibitor of the serine-/threonine-phosphatase calcineurin, a target of the well-known immunosuppressants that lead to blockade of T-cell activation. They discovered a compound that binds to FKBP with a Kd of 19 nM by linking two molecules with binding affinities of 2 pM and 100 pM. This compound was discovered from fragments that were rapidly identified and optimised in approximately two months. In total only five linked compounds were synthesised, all of which displayed sub-micromolar affinities for FKBP. It seems clear that this type of result will excite interest in the development and application of the SAR-by-NMR methodology for drug discovery, particularly with regard to the construction of suitable low molecular weight chemical libraries, and robotics and spectrometer technology to enhance the throughput rates during the screening process. Separately, Archer et al. have reviewed

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concepts in NMR that are important for structural studies of proteins to aid in drug-design. 143

6

NMR Investigation of Macromolecular Solvation

The subject of the nature of hydration of biomolecules continues to be a particularly fruitful area for biological NMR spectroscopists. Wiithrich and coworkers review the state of this field,'44 particularly with respect to the comparison of experimentally derived parameters describing the rate processes governing exchange of water molecules between the bulk solvent and the hydration sites on macromolecules with long duration explicit solvent molecular dynamics simulations, for example, of a protein-DNA complex.145This study highlights an essential water molecule that mediates an intermolecular contact. In the simulation this 'interior' water molecule has a residence time of the order of Ins, at the lower end of the range determined by NMR. The same group has introduced a novel method for the observation of hydration waters in biological macromolecules, based on the use of pulse-field-gradient diffusion filters.'46 The use of the diffusion filter in NOE difference measurements enables the observation of hydration waters without interference from intramolecular NOEs, and allows their identification under a single set of solution conditions, and at short mixing times. Otting and co-workers have explored the hydration in the minor groove of a number of double-stranded DNA fragments containing T-/A-rich sequence motifs in the central portion.14' From the results of this study the authors conclude that the hydration water in the minor groove is significantly more mobile at the end of the AT-rich inner segments, and that minor groove hydration near GC base pairs is kinetically less restrained than for AT-rich DNA segments. Single base pair mutations dramatically affect the lability of the hydration water, illustrating a high sensitivity of water-DNA NOEs towards small conformational differences. The presence of water molecules in HIV protease complexes with two inhibitors KNI-272 and DMP323 has been investigated by Torchia and cow o r k e r ~ . ' ~ *The , ' ~NOE ~ and ROESY data recorded for the KNI272 complex is consistent with the presence of two long-lived water molecules that are also observed in the crystal structure of the same complex. Analysis of the crossrelaxation rates indicates that the water molecules have residence times of greater than 1 ns and perhaps as long as 7 ns, indicating that they form an integral component of the intermolecular interface. For the DMP323 complex, in which the urea oxygen atom has been designed to replace a commonly observed water molecule, the situation is more complex, but again the NMR data are consistent with two further crystallographically observed water molecules with short residence times (-500 ps). The exchange rates of some exchangeable hydroxyl groups in the inhibitor binding site are consistent with entry of solvent molecules into the binding site on the milli- to microsecond timescale. Liepinsh et al. have examined the more general (hydrophobic) solvent binding

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properties of lysozyme. 50 The specificity-determining substrate binding site of hen egg white lysozyme can be readily identified in solution by NMR using small organic solvent molecules as detection probes. Protein-solvent magnetisation exchange in NOESY-type experiments can be detected and analysed in terms of single or multiple solvent binding sites, information that could be useful in the context of rational drug design, or SAR-by-NMR screening programs. In a similar manner Otting and co-workers have examined magnetisation exchange between solvent-binding cavities of lysozyme and the protons of hydrogen, methane, ethylene, and cylcopropane applied at 1-200 bar pressure.’” The gases can therefore be used to identify partially hydrated hydrophobic cavities in proteins. The gases reside in the cavities with lifetime longer than 1 ns, indicating diffusion in the protein is slowed with respect to diffusion in solvent. The authors speculate that cavity binding may be a major aspect of the anaesthetic effect of small gas molecules.

7

Glycoproteins and Carbohydrate Binding

It has generally proved difficult to obtain recombinant forms of glycoproteins in an isotope-labelled form that would be suitable for detailed structural investigation by heteronuclear NMR spectroscopy. However recently there have been some breakthroughs in this area. The conformational properties in solution of the glycans on the a subunit of recombinant human chorionic gonadotropin (hCG) have been described by Weller et a!., using high-resolution multinuclear NMR studies on uniformly I3C,l’N-enriched recombinant glycoprotein expressed in mammalian CHO cells.152 Glycosylation at Asn52 is essential for signal transduction, whereas the N-glycan at Am78 stabilises the structure of the protein. The glycan important for full biological activity of hCG appears to extend into solution both in the isolated a subunit and in complex with the p subunit. The disposition of this glycan with respect to the protein backbone suggests that glycosylation maintains this activity either by interacting with a lectin-like region of the hCG receptor or by reducing the affinity of the hormone for the hCG receptor and preventing its down-regulation. Debeer et al. have performed an independent investigation of a similar n a t ~ r e . ”In ~ their study, an almost complete ‘H NMR and a partial 13C NMR spectral assignment for the amino acids and the N-glycans of ahCG and of an enzymatically deglycosylated form, which had a single GlcNAc residue at each of its two glycosylation sites, has been achieved. The secondary structure of ahCG in solution, which was determined based on NOE data, is partially similar to that of the a subunit in the crystal structure of hCG, but large structural differences are found for amino acid residues 33-58. In the crystal structure of hCG, residues 33-37 and 54-58 of the a subunit are part of an intersubunit seven-stranded P-barrel and residues 41 -47 constitute a 310-helix.In contrast, in free ahCG in solution, amino acids 33-58 are part of a large disordered loop, indicating that in intact hCG, interactions with the p subunit of hCG stabilise the conformation of the a subunit. The NMR data for ahCG and its deglycosylated counterpart are very similar, indicating that

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removal of carbohydrate residues other than GlcNAc-1 does not notably affect the conformation of the protein part. However, numerous 'H NOEs between the GlcNAc-1 residue at Asn78 and several amino acid residues show that this GlcNAc residue is tightly packed against the protein, being an integral part of the structure of the a subunit. An analysis of 'H NOEs across the glycosidic linkages of the glycan, resonance-line widths, and 'H and I3C chemical shifts of the other monosaccharides suggests that the remainder of the glycans at Asn78, and the glycans at Asn52 are largely extended in solution. The stabilisation of the protein fold provided by the 0-linked glycosylation in The study reports the cytokine GCSF has been studied by Gervais et assignments of 'H and I3C resonances of the bound saccharidic chain and demonstrates the a-anomeric configuration of the N-acetylgalactosamine-threonine linkage. It also provides results suggesting that the carbohydrate moiety reduces the local mobility around the glycosylation site which could be responsible for the stabilising effect observed on the glycoprotein. By use of heteronuclear H,I3C NMR methods, the three-dimensional structure and dynamics of the glycoconjugate estrone-3-glucuronide (E3G) uniformly 3Cenriched in the glucuronic acid moiety has been probed both in free solution and in association with an anti-E3G antibody single-chain F, fragment.'55 The glycan is found to exist in multiple conformations in free solution, with particularly large torsional fluctuations about the glycosidic linkage y ~ .Resonance assignments and distance restraints for the glycoconjugate in the bound state were obtained from heteronuclear proton-carbon-carbon-proton-COSY and isotope-edited NOESY techniques, respectively. Quantitation of the NOE data with a full-relaxation matrix approach showed that the antibody selects a conformation from the solution repertoire which does not correspond with either of the two lowest energy conformations of the free glycan. The glucuronide moiety undergoes a stacking interaction with an aromatic ring in the binding site, and both ringcurrent shifts and nuclear Overhauser effects computed from the predicted bound-state conformation are in good agreement with experiment. The role of aromatic amino acids in carbohydrate binding of plant lectins has been examined by laser photo-chemically induced dynamic nuclear p o l a r i ~ a t i o n . ' ~ ~ ~ ' ~ ~

'

8

Technical Developments for Macromolecular NMR

8.1 Spin-Spin Couplings - Methods to determine scalar coupling constants in proteins and nucleic acids continue to appear, particularly with respect to the determination of structurally significant torsion angles in isotope-enriched molecules. 8.1.1 Protein Coupling Constants - Bax and co-workers have introduced new pulse sequences for 2D experiments which yield the facile determination of x1 angles of aromatic residues through the estimation of 3Jc3cy and 3 J N ~ y couplings.'58 They later developed this approach for the more general task of identification of aliphatic residues with a 3JNcycoupling substantially larger than

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Nuclear Magnetic Resonance

1 Hz, indicative of a trans arrangement between N and Cy.'59Two versions of an experiment to measure in a quantitative manner three-bond scalar couplings between carbonyl/carboxyl carbon resonances 3Jcrc1,are also presented, an experiment which is useful for the determination of xI for Asp residues, and the distinction of backbone 4 angles which are smaller than - 120" from those larger than - 120".'60~'6' Lohr and Ruterjans describe a method for the determination of 3JHacrin '3C,15N-isotope-enriched proteins which can complement more traditional methods of the estimation of the backbone 4 angle.162Schmidt et al. present ~ 3~J ~, p ~ , heteronuclear relayed E.COSY methods for the estimation of 3 J ~and in proteins, useful for the evaluation of 4 and xl dihedral angles.'63 In an interesting study devoted to the observation x1 angles, Gronwald et al. used measurements of 3J,p scalar couplings for threonine residues in the icebinding site of the a-helical type I antifreeze protein near the solution freezing temperature to characterise the nature of the interfacial ~ 0 n t a c t .Hennig l ~ ~ et al. describe a sensitive method for the determination of homonuclear l3C-I3C Jcouplings between aliphatic carbons in perdeuterated ~ r 0 t e i n s . The I ~ ~ measurements can be used to define the x 2 rotamers of aliphatic side chains, and characterise the structures of Arg, Lys, Leu, Ile and Pro residue side chains, often involved in intra- and intermolecular interactions. 8.1.2 Nucleic Acid Coupling Constants - The determination of a variety of vicinal homo- and heteronuclear coupling constants that can be obtained for unif~rmly-'~C-labelledDNA oligonucleotides is presented by Zimmer et al. 166 2 0 and 3D HCCH-E.COSY type experiments were used to measure 3JHHcouplings around the deoxyribose ring, a refocused HMBC experiment was used for estimation of 3J,-~about the glycosidic torsion angle x and a P-FIDS-CT-HSQC p 3 J ~ coupling p constants about the experiment was used to determine 2 J ~ and backbone torsion angle E for a 10 base pair DNA duplex. Marino et al. describe in detail the conformational analysis of the backbone angle y (05'-C5'-C4'-C3') and stereospecific assignment of HS'(pro-S)/HS'(pro-R) protons in a uniformly '3C,'5N-labelled 19mer RNA oligonucleotide though 2J and 3J measurements in E-COSY type multidimensional heteronuclear NMR experiments. From the small values of the 3JH4tH5f couplings measured for this hairpin it was concluded that all the y angles assume a gauche+ (60") rotamer conformation. The determination of base and sugar heteronuclear scalar couplings in uniformly isotope-enriched 3C,"N-nucleotide 5'-monophospha tes and various unlabelled cyclic nucleotides is discussed by Ippel et a1.'6g The experiments described yield an almost complete set of homo- and heteronuclear coupling constants in ribonucleotides, the knowledge of which is useful for the design and interpretation of experiments aimed at larger nucleic acid structures. 8.2 Direct Angle Measurements - A completely novel approach to the determination of torsion angles within proteins and nucleic acids has been proposed by Griesinger and c o - ~ o r k e r s . 'The ~ ~ method is based upon the measurement of dipole-dipole cross-correlated relaxation of double and zero-

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quantum coherences for two bond vectors that straddle the torsion angle in question. The relaxation rates can be directly related to the angular geometry without the requirement of a Karplus type curve, and depend upon only the rotational correlation time as an empirical parameter. The method is demonstrated with CaH(i-I) and NH(i) multiple quantum coherence to extract the peptide backbone angle \~r,which is not directly measurable by any three-bond scalar coupling. In principle the method may be generalised to measure the angle between any two bond vectors arbitrarily far apart in the structure, and it can be anticipated that developments of these types of measurements will make an important impact on the solution structure determination of biological macromolecules. 8.3 Residual Dipolar Couplings - In last year's survey we reported new observations of the finite non-isotropic magnetic susceptibility of proteins, 'residual' dipolar couplings manifested in field-strength dependence of one-bond heteronuclear couplings JNH and JCH.These measurements potentially contain long-range structural information of a type that could revolutionise the determination of biological macromolecular structure. At present magnetic field strengths effects are very small, particularly for diamagnetic systems, and there has been no great increase in reports of this type of measurement in the last twelve months, though have been some technical description of methodology for extracting 1 J ~ ~ 1 7 0 and ' 1 7 1 J ( - H ~values. ~ ~ However one interesting development has arisen. Prestegard and colleagues expanded their examinations of residual dipolar couplings in cyanometmyoglobin, a paramagnetic system, for which measurements of the residual dipolar couplings can be measured with high accuracy.173 The ensuing analysis reveals deviations between the experimental measurements and predictions based on the available crystallographic and solution structures which are largely systematic and well correlated within a given a-helical secondary structure element. A rationalisation of these discrepancies can be made by invoking a model of collective motions and small displacements of representative helices from the reported average positions in the solid state. The authors suggest that this type of motion is difficult to observe by any other established method, and yet is of the type that is especially important to explain biological f ~ n c t i 0 n . In l ~ ~a commentary, however, Bax and Tjandra warn that the data can be readily explained on the basis of a more rigid structure with a repositioned magnetic anisotropy tensor - they describe practical aspects of the NMR experiments that could lead to discrepancies with the orientation obtained from the protein X-ray structure.'74

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'

8.4 Adiabatic Decoupling - In the previous year's report we discussed the renewed interest in novel modes of broadband heteronuclear and (multi-site) selective homonuclear spin-decoupling procedures based on adiabatic fast passage with linear frequency sweep RF irradiation schemes. 175-177 Technological developments have continued with the introduction of figure-of-merit descriptor and cycling sideband assessment for adiabatic decoupling schemes, 17' and the proposal for bi-level decoupling patterns for the reduction of cycling side-

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bands.'79 Weigelt et al. describe the application of SESAM decoupling to the suppression of zero-quantum coherence effects in protein NMR spectra.Ig0 In two separate reports Matsuo and co-workers describe the use to selective homonuclear '3Cf3-decoupling for the improvement in sensitivity and resolution in 3D HNCA, HN(C0)CA"' and HCCH-TOCSY182 pulse sequences widely used in applications to I3C,"N-isotope enriched proteins.

8.5 Side Chain Resonance Assignments - Whilst procedures for the determination of backbone and aliphatic carbon- 13 resonances in isotope-enriched proteins are highly developed and essentially routine, a similar consensus of approach for the determination of aromatic carbon-13 resonance assignments does not yet exist. Two approaches which target this particular problem are described by ~ Lohr et Zerbe et ~ 1 . " and Specialised pulse sequences have also been described for the sequence specific assignment of side chain arginine N"H resonances,lgS and stereospecific assignment of side chain asparagine and glutamine amide NH2 resonances.' 86*187

9

Miscellaneous Aspects of Protein Side Chains

Wang et al. have reported their elegant studies that provide solution NMR evidence that the HIV- 1 protease catalytic aspartyl groups have different ionisation states in the complex formed with the asymmetric drug KNI-272.'88*'g9 Because KNI-272 is asymmetric the two protease monomers have distinct NMR spectra in the complex. Ionisation states of a variety of acidic side chains where studied by pH titrations and the observation of H / D isotope effects on the aspartyl carbon chemical shifts. Rajarathman describe 'H NMR experiments that indicate that in interleukin-8 the buried side chain of Glu-38 interacts with the backbone amides of Gln-8 and Cys-9 in the N-terminal functional domain. 190 The ternary complex of Lactobacillus casei dihydrofolate reductase (DHFR) with folate and NADPf exists as a mixture of three interconverting forms (I, IIa and IIb) whose relative populations are pH dependent, with an effective pK 6. The role of Asp26 in this pH dependence has been investigated by measurement of the 13Cchemical shifts of [2,4a,7,9-'3C4]-folate in its complex with the mutant DHFR Asp26 -+Asn and NADP+.19' A study of the pH dependence of the 13C chemical shifts of DHFR selectively labelled with [4-'3C]-aspartic acid in its complex with folate and NADP+ indicates that no Asp residue has a pK value greater than 5.4. The authors propose that the protonation/deprotonation controlling the equilibria involves the 0 4 position of the folate and that Asp26 influences this indirectly by binding in its CO2- form to the protonated N 1 group of folate in forms I and IIa thus reducing the pK involving protonation at the 0 4 position to -6. Pellechia et al. describe two new 2D NMR pulse sequences H(C)C02 and HCC02 for the assignment and monitoring of pH titrations of carboxylate groups in '3C,15N-labeled~ r 0 t e i n s . I ~ ~

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The structural role of a conserved buried Arg10-Glu35 salt bridge in the 434 repressor DNA-binding domain has been characterised by a comparative NMR analysis of the wild-type and ArglO t Met mutant proteins.'93 The solution structures of each form exhibit the same protein fold, with the primary deviation between the two structures represented by a translation of helix I along its axis relative to the helix 11-turn-helix I11 motif. This change is paralleled by a small decrease in the protein stability, and changes in the pK of the Glu19 side chain and the population of the hydrogen bond between this side chain and the backbone amide of Asn 16. Feeney and co-workers demonstrate that the 'H,''N-HSQC N M R spectra of complexes of Lactobacillus casei dihydrofolate reductase containing methotrexate recorded at 1 "C show four resolved signals for the four NqH protons of the Arg57 residue consistent with hindered rotation in the guanidino group resulting from interactions with the a-carboxylate of m e t h 0 t r e ~ a t e . IIncreasing ~~ the temperature causes exchange line-broadening and coalescence of signals. Rotation rates for the Ci-N" and W-Cc bonds have been calculated from lineshape analysis and from ZZ-HSQC exchange experiments. 195 The authors propose that the unusual pattern of the relative rates of rotation about these two bonds, which are reversed in the protein complexes compared with their values in free arginine, indicate that there are concerted rotations about the Cr-N" bond of the Arg57 guanidino group and the C'-C" bond of the glutamate a-carboxylate group of methotrexa te. Mulder et al. have described a general scheme for the suppression of exchange broadening in I5N,'H HSQC spectra by the incorporation of Carr-PurcellMeiboom-Gill (CPMG)-derived pulse trains to reduce dephasing losses during periods of coherence transfer.'96 In applying such strategies to a protein-DNA complex the authors demonstrate improved sensitivity for many backbone and side chain NH resonances, particularly for protons located at the protein-DNA interface and for arginine guanidino groups undergoing conformational exchange.

10

Aspects of Protein Folding and Stability

10.1 Protein-Folding Pathways - As we commented in last year's review, NMR continues to provide an avenue for the description of protein folding pathways, though increasingly NMR is used in combination with a variety of other physical and chemical techniques, including for example mass spectrometry. Recent developments in our understanding of the mechanism of protein folding, and the extent to which NMR spectroscopy is playing a role in its elucidation are provided by Dyson and Wright,19' and Miranker and D 0 b s 0 n . I ~Dobson ~ and co-workers have reported an extension of the ideas presented previously for the monitoring of the folding of proteins in real-time using NMR s p e c t r o ~ c o p y , ' ~ ~ this time using 2D heteronuclear spectra of the refolding of nitrogen-15 labelled up-bovine a-lactalbumin.200 The intensities and line shapes of the cross peaks reflect the time course of the folding events that occur during the acquisition of

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the spectrum. Plaxco et a!. have described the folding of a fibronectin type 111 module, which occurs very rapidly ( < 1 s at 5 "C) in spite of the complex all P-sheet topology, and the presence of eight proline residues.*" Lu et al. followed the refolding of a partially structured state of hen lysozyme form in 60% (v/v) 2,2,2- trifluoroethanol (TFE) by hydrogen exchange pulse labelling monitored by NMR and other techniques.202The results are compared with the refolding in 6 M guanidine hydrochloride (GuHCl). Under similar conditions the kinetics of refolding are very similar in each system, in spite of the very much higher level of secondary structure present in the TFE-denatured state. From this observation it is concluded that there is rapid equilibration of the structures formed in the initial stages of the folding pathway(s). In addition it is noted that whilst addition of GuHCl to the refolding buffer decreases the rate of folding, low levels of TFE accelerate folding, which is consistent with a view that the slow steps of protein folding for lysozyme are associated more with the reorganisation of hydrophobic interactions than with the hydrogen bonded structure. The relationship between specific aspects of a protein sequence and the protein's stability have been examined in detail by Pfuhl et al., who looked at a N-terminal extension of a titin immunoglobulin superfamily domain,203 and Truckses et af., who considered the effect of a single amino acid substitution on Staphylococcus aureus nuclease A and the coupling to a cis-/trans- proline is~merisation.~'~ Gronenborn et al. explored the effects on protein structure and stability of a library of core mutants at five residue positions of the GB1 domain of streptococcal protein G.205-207The overall structural integrity of several of the isolated mutants, as assessed by NMR, ranged from very close to wild type to fully unfolded. Interestingly, the stability of the mutants is not strictly correlated with the number of changes or side chain volume.

10.2 Partially-Folded and Denatured States of Proteins - There has been very great interest in using NMR spectroscopy to investigate the conformational properties of unfolded or partially folded states of proteins. This is an area where NMR excels over other techniques such as X-ray diffraction. Detailed characterisation of denatured states of proteins is necessary to understand the interactions that funnel the large number of possible conformations along fast routes for folding. For example, Freund et af. have presented an NMR procedure that detects almost all sequential NOEs between amide hydrogen atoms (HN-HN NOE), including those in random coil regions in a protein, barnase, in urea solutions.208 A semi-quantitative analysis of these NOEs identified partly structured regions that are in remarkable agreement with those found to form early on the reaction pathway. The results strongly suggest that the folding of barnase initiates at the first a-helix and the p-turn between the third and the fourth strands. This strategy of defining residual structure also worked for guanidinium hydrochloride-denatured chymotrypsin inhibitor 2 and colddenatured barstar. The cold-denatured state becomes significantly populated in the presence of increasing concentrations of urea and lower temperatures. In the presence of 3 M urea, the double mutant of barstar in which Cys40 and Cys82 are both mutated to Ala (C40/82A) is completely and reversibly denatured at 278 K,

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a temperature that is accessible to NMR experiments. This cold-denatured state of barstar was assigned by heteronuclear NMR experiments and structural parameters such as NOE, coupling constants and chemical shifts were derived.209 This approach reveals residual structure populating the a-region of the 4 , conformational space in the regions corresponding to the first and the second a-helices and near the end of the second P-strand of native barstar, whereas the C-terminal region that corresponds to the fourth helix and the third P-strand is in a random coil conformation. The results suggest that the first and the second helices are potential initiation sites for the folding of barstar. The spectra of denatured or partially folded states of proteins are characterised by very poor chemical shift dispersion, particularly for the 'H resonances. Zhang et al. have devised a suite of triple resonance NMR pulse sequences that allow the extraction of 'H-'H NOE cross-peaks but encoding their position in the spectrum via the attached backbone I3C' or "N chemical shift, for which the loss of dispersion is The techniques could also be applied to highly overlapped regions of the spectra of fully folded proteins. Smith and co-workers have over the course of a series of articles developed a statistical model of the so-called 'random coil' state of a polypeptide chain, that can be used to test against the outcome of experimental measurements of unfolded proteins and pep tide^.^"-*'^ The model thereby provides a framework for the identification of residual structure inherent in non-native states of proteins.

11

~

NMR Studies of Proton Solvent Exchange

Measurements of the rates of exchange with solvent of labile protons continue to provide insights in the biophysical properties of biological macromolecules in a variety of states, some of which are highlighted here. Liepinsh et at. have explored the solvent exchange rates of the hydroxyl protons of threonine, serine, tyrosine, the amino protons of lysine, and the guanidinium protons of arginine over the pH range 0.5 to 8.5 and for the temperatures in the range 4-36 "C, along with the exchange catalysis by phosphate, carbonate, carboxyl-, and a r n i n o - g r ~ u p s . ~ ' ~ They discovered that the proton exchange rates are sufficiently fast that the rota1 magnetisation transfer between biomolecules and free bulk water is not rate limited by the proton exchange rate, but by the intramolecular cross-relaxation rates between the exchangeable and non-exchangeable protons of the biomolecules. Since the cross-relaxation rates between surface hydration water molecules and biomolecules are usually vanishingly small because of too rapid exchange with the free bulk water, the authors propose that the contrast in magnetic resonance imaging is a fingerprint of the number of the exchangeable protons from OH and NH groups of the tissue, as far as the contrast depends on the magnetisation transfer between biomolecules and water. Chung et al. describe their work which examines the hydrogen exchange properties of proteins in native and denatured states monitored by both mass spectrometry and NMR.2'5 Different conformational states of several proteins

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were prepared by varying solution conditions. Alternate protein conformers were found to contain different numbers of 2H atoms, with measurements in the gas phase yielding results that are consistent with NMR spectra in the liquid state. Andrec et af. report a new approach to the quantitation of chemical exchange rates, based on a selective-inversion exchange HMQC experiment in which a short spin-echo diffusion filter has been inserted into the exchange period.216In this way, the kinetics of exchange are encoded directly in an apparent diffusion coefficient which is a function of the position of the diffusion filter in the pulse sequence. The utility of the method is illustrated with application to the exchange of protein amide protons with bulk water. A detailed theoretical analysis of this experiment indicates that, in addition to the measurement of simple exchange rates, the experiment is capable of measuring the effect of mediated exchange, for example the transfer of magnetisation from bulk water to an amide site mediated by an internal bound water molecule or a labile protein side chain proton in fast exchange with bulk water. Morikis and Wright have described detailed hydrogen/deuterium exchange rates for the CO complex of soybean leghemoglobin.2'" The data for 61 individual amide protons are analysed in terms of the locaf packing and stability of a-helical secondary structure elements in the protein structure, and the potential relationship of these parameters to the ligand-binding activity of the protein. The stability of backbone amide protons with respect to exchange has been investigated in a folding intermediate and the native state of an antibody single chain variable domain fragment (scF,) of an antibody again by combining NMR and mass Differential stabilisation core amides of the V L and V H domains within the scF, are described.

12

New NMR Software

Several new software packages have been described in the past year that are particularly relevant to the biological NMR spectroscopist. RELAX is a program for back calculation of NOESY spectra based on the complete relaxation matrix formalism.219 The programs AQUA and PROCHECK-NMR are separate interfaced software tools for the manipulation and cross-checking of NMR solution structure restraints and stereochemical quality of output conformer coordinates respectively.220 MOLMOL is a molecular model visualisation program with particular emphasis on the display and examination of NMR solution structures and derived input and output From the same stable as MOLMOL (and DIANA and CALTBA, etc:.) comes OPAL, a general purpose molecular mechanics program suitable for energy refinement and simulation of biological macromolecule dynamics in GARANT is a program for the automated resonance assignment of NMR spectra of proteins, incorporating an evolutionary algorithm and local optimisation r o ~ t i n e .In~ ~ ~ , ~ ~ contrast SERENDIPITY uses graph theory to extract secondary structure and backbone resonance assignments from triple resonance NM R spectra of proteins. 226

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315

Aspects of Solution Structure Calculation

A number of developments in solution structure calculations based on NMRderived experimental restraints have been reported in the previous year.227,228 In particular, a number of new strategies based upon simulated annealing protocols have been described. Of particular note is the introduction of simulated annealing for solution structure determination in torsion angle coordinate space. Development and implementation of this strategy within the program X-PLOR showed that compared to two other commonly used algorithms, molecular dynamics in Cartesian space and metric-matrix distance geometry combined with Cartesian molecular dynamics, the method shows increased computational efficiency and success rates for large proteins, and it shows a dramatically increased radius of convergence for DNA.229 For a protein consisting of 126 residues, structure determination by torsion-angle molecular dynamics has a success rate of 85%, a more than twofold improvement over other methods. In the case of the 12 base pair DNA duplex, torsion-angle molecular dynamics had a success rate of 52% while Cartesian molecular dynamics and metric-matrix distance geometry always failed. New potential functions have been developed to incorporate additional types of NMR derived experimental data into X-PLOR. Wittekind et al. report the structure calculation of an Src Homology 3 domain with and without chemical shift potential terms applied.230Building on the previously reported chemical shift potentials, Kuszewski et al. have described a new potential involving multiple proton chemical-shift restraints for non-stereospecifically assigned methyl and ethylene protons.231Using a similar strategy to the chemical shift potentials, Clore and co-workers have a developed a numerical dihedral angle conformational database potential which attempts to restrain the protein structure dihedral angles to regions of conformational space that are highly populated in high resolution crystal structures (as described by the PROCHECK database).2327233 For high quality solution structures, use of this potential in the refinement can yield improved stereochemical scores for the solution structure, when judged against crystal structures, at little cost to violations of the restraint terms. The feasibility of determining the relative populations of multi-conformer structures from NOE-derived distances alone has been assessed by Bonvin and B r ~ n g e rThey . ~ ~ found ~ that without cross-validation of the NOE restraints, any population ratio can be refined to a similar quality of the fit. Complete crossvalidation provides a less biased measure of fit and allows the estimation of the correct population ratio when used in conjunction with very tight distance restraints. With the qualitative distance restraints most commonly used in NMR structure determination, cross-validation is unsuccessful in providing the correct answer. Nilges and co-workers have described an extensive strategy for structure determination of proteins that is largely automated, called ARIA for Ambiguous Restraints for Iterative Assignment.235 The methods are implemented in XPLOR, start from an essentially complete proton chemical shift assignment and a partial list of assigned NOE cross-peaks which is subsequently augmented by

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automatically interpreting peak lists generated by automated peak-picking. The central task of ARIA is the assignment of ambiguous NOEs during the structure calculation using a combination of ambiguous distance restraints and an iterative assignment strategy. In addition, ARIA calibrates ambiguous NOEs to derive distance restraint bounds, merges overlapping data sets to remove duplicate information, and uses empirical rules to identify erroneous peaks. The method has been demonstrated for the structure determination of the spectrin pleckstrin homology domain, for which ARIA generated structures of good quality, and of sufficiently high accuracy to solve the X-ray crystal structure of the same domain by molecular replacement, were obtained.236Nilges has also been instrumental in a re-examination of the use of floating assignments for the stereospecific assignand developing general strategies for ment of methylene and isopropyl calculating symmetrical multimer solution structures.2:3s In other developments the conformational sampling properties of the program DIANA have been tested against a long-time molecular dynamics calculation in explicit water,239with the conclusion that DIANA produces conformer bundles that are consistent with M D simulations using realistic potential functions over the nanosecond timescale. The limits of structure calculation with variable target function have been reported,240724’and the effects of achievable experimental improvements on the quality of distance restraints by ‘magnetisation exchange network editing’ on solution structure accuracy have been examined.242

14

Nuclear Relaxation in Biological Macromolecules

In the last few years, the development in the field of dynamics and nuclear relaxation of bio-macromolecules has been spectacular with an explosive increase in the number of publications per year. Within the last year, there has been several very good reviews of the field. Palmer, Williams and M ~ D e r m o t have t~~~ written a superb review of nuclear magnetic resonance studies of biopolymer dynamics covering both the liquid state and the solid state. Dayie, Wagner and L e f e ~ r have e ~ ~written ~ a concise, chronological, and mathematically very explicit review of the ‘theory and practice of nuclear-spin relaxation in proteins’ covering from the earliest studies of relaxation by Felix Bloch to the present time. J a r d e t ~ k y ~has ~ ’ written a review of protein dynamics and conformational transitions in allosteric proteins and Bertini, Luchinat and Aime246have written a book on NMR of paramagnetic substances with emphasis on proteins and relaxation. A number of more specialised reviews which touch on the topic of biomolecular relaxation include a review by Bryant247concerning the dynamics of water-protein interactions, a review by Varani, Aboulela and Allain94 concerning NMR of RNA structure and finally a review by Aramini, Saponja and V 0 g e 1 concerning ~~~ spectroscopic studies of the interaction of aluminum(II1) with transferrins. 14.1 Side Chain 13C Relaxation - Lately, there has been much interest in the development of methods for measuring I3C, ”N and 2H relaxation rates of side

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chain nuclei.249 This is because the side chains provide a large number of potential labels for investigating the dynamic properties of a protein, but also because the dynamic properties of the side chains are generally thought to be more correlated to protein function than those of the backbone. In particular, the side chain carbon nuclei constitute a large number of sites where the dynamics can be probed. However, because of the difficulties in interpreting the relaxation behaviour of 13C nuclei in the presence of relaxation interference effects seen in CH2 and CH3 groups, most quantitative studies in the past have focused on the methine sites. The practical difficulties in suppressing I3C-l3C cross-relaxation effects and 13C-13Cscalar coupling are also complicating factors when studying 3C-enriched proteins. LeMaster and K u ~ h l a n ~have ’ ~ developed a powerful double 13C,2H-labelling scheme for the investigation of side chain dynamics in proteins. It involves the expression of the protein in a particular strain of E. coli which is grown in 55%/ 45% D20/H20 with 55-60% deuterated [ 1,3-13C]-glycerolor [2-’3C]-glycerolas the primary carbon source. The resulting protein is then labelled with 13Cand I2C in an alternating manner which together with the fractional deuterium labelling provides a large number of isolated ’H-I3C spin pairs for which relaxation properties can readily be analysed. The authors demonstrate the method on E. coli thioredoxin and show that in particular the methylene carbons exhibit a large variety in the dynamic behaviour. It is also demonstrated that the mobility of a site is very dependent on the number of bonds separating it from the backbone so that the order parameter decreases out through the side chain for most residues. This is both the case for solvent-exposed residues and residues in the core, but with a steeper decrease in order parameters for solvent-exposed residues. The authors make the very interesting observation that sites with conformational exchange mainly cluster around side chain to main-chain hydrogen bonds and bifurcated main-chain hydrogen bonds. It is suggested that rearrangement and/or breaking of these hydrogen bonds could be the origin of the conformational exchange contributions to R2. An important aspect of side chain dynamics is the establishment of motional models which explain the experimental relaxation data. Several different models have over the years been suggested for describing the dynamics of an inter-atomic vector. This includes diffusion and jump motions of the inter-nuclear vector, wobbling in a cone, and limited rotational diffusion within a rotameric state with jumps between diflerent states. A major difficulty is that within the experimental uncertainty of the often sparse relaxation data, it is usually not possible to distinguish two or more different motional models with the consequent risk of over-interpreting the experimental data. Common ways of avoiding over-interpretation of the relaxation data is to parameterise the relaxation times either within a ‘model-free’ framework or by calculating values of the spectral density function at certain frequencies. However, none of these approaches provide a physical interpretation. Bremi et aL2” have described a powerful protocol for the interpretation of side chain relaxation data in terms of a specific physical model. The method involves the calculation of a long molecular dynamics trajectory and a subsequent analysis

’

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Nuclear Magnetic Resonance

of the trajectory in order to find a realistic motional model. In the present study, it is shown that the side chain dynamics of the phenylalanines in cyclic decapeptide antamanide can be described in terms of a Gaussian axial fluctuation model (GAF) with occasional jumps between different rotamer states of x1 and ~ 2 Second, the NMR correlation functions are calculated from the trajectory and expressed in terms of the motional parameters to provide a connection between the physical parameters describing the dynamics and the experimental relaxation data. Thirdly, the sensitivity of the relaxation parameters to the motional parameters are assessed by calculating synthetic relaxation data from the motional parameters determined from the trajectories and then recalculating the motional parameters from the relaxation parameters with added noise. This step in the protocol is crucial because it tells whether motional parameters can reliably be estimated from the available set of relaxation measurements or whether more relaxation parameters are needed in order to estimate the motional parameters. Finally, if the model parameters can be reliably recalculated from the synthetic relaxation data, the experimental relaxation data are parameterised according to the model. The protocol is obviously quite demanding on computer power, as the molecular dynamics trajectory must be long compared with the time scale of the relevant motions. 14.2 Carbonyl 13C Relaxation - The backbone carbonyl carbon is an exciting target for relaxation studies because of the abundance of carbonyl sites throughout the protein. However, the more complicated relaxation behaviour of the carbonyl carbon, when compared to backbone amide I5N and I3Ca relaxation, has until recently slowed down progress in this area. In contrast to backbone I5N and 13Ca relaxation rates, the relaxation rates of the carbonyl carbon is dominated by the chemical-shift anisotropy (CSA) relaxation mechanism but also have significant dipole-dipole relaxation contributions from several near-by nuclei,'including the a proton(s), the amide proton and the amide ''N nitrogen as well as the 13Ca and l3CPnuclei if the protein is uniformly I5N- and 13C-labelled. Thus, in order to parameterise the relaxation data in terms of a motional model, detailed information about the chemical-shift tensor and inter-nuclear distances to spatially close nuclei are required. A further complication arises in the interpretation because the different relaxation interactions are not co-linear and consequently may have independent correlation functions. Within the framework of the model-free approach, each interaction accordingly has its own spectral density function characterised by a generalised order parameter and an effective correlation time so that the number of unknown dynamic parameters to be estimated for each site is at least two for each relaxation pathway if no further approximations or assumptions are made. Two major studies of both the theoretical aspects of carbonyl carbon relaxation as well as the practical implementation of relaxation experiments have recently been presented. Engelke and R i i t e ~ j a n shave ~ ~ ~presented a detailed analysis of the different contributions to the relaxation of 13C' based on knowledge about the chemicalshift tensor taken from a solid-state study of a model compound and inter-atomic

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distances derived from the standard peptide backbone geometry. The analysis indicates that dipolar interactions between I3C’ and 13Ca, ‘Ha and the amide proton give significant contributions to both longitudinal (R1) and transverse (R2) relaxation rates whereas contributions from dipolar interactions with the I3Cpand the amide ”N nitrogen are negligible. The authors stress that cross correlation between the CSA mechanism and the dipolar interaction with the I3Ca is important to consider. R1 and R2 relaxation rates of ribonuclease T1 were measured at 500 MHz, 600 MHz and 800 MHz with HCACO-like pulse schemes. The relaxation rates were interpreted within the Lipari-Szabo model-free framework by assuming a simple Lorentzian spectral density function for all the dipolar interaction with an order parameter S2 0.8 and then fitting the order parameter and the effective correlation time for the CSA interaction. This leads to order parameters somewhat lower (around 0.75) and with more variation along the sequence than those commonly seen in backbone ”N amide studies. Finally, a reduced spectral density mapping procedure is used to show that a number of I 3 C sites show exchange contributions to R2 in the order of up to 4 s-’. Allard and Hard253have performed a study of the 13C’-relaxationproperties of the DNAbinding protein Sso7d at 500 MHz and 600 MHz by a very different suite of pulse schemes based on the HNCO experiment. Because the experiments rely on the detection of the amide proton rather than the alpha proton, they are less susceptible to an incompletely suppressed water resonance. On the other hand the interpretation is further complicated by the significant dipolar interactions between the 13C’ and the amide proton. The authors have developed a pulse scheme for the measurement of the 1H-13C’heteronuclear NOE and by means of this experiment demonstrate that the dipolar interaction between I 3 C and spatially close protons is a significant relaxation pathway. The importance of cross correlation between the CSA mechanism and the dipolar 13C-13Cainteraction is investigated by recording R1 and R2 experiments with and without selective 180” pulses on I3Ca. In contrast to the findings of Engelke and R i i t e r j a n ~ ?no ~~ differences in the R1 and R2 relaxation rates were observed, and it is suggested that cross correlation does not affect the relaxation rates significantly under the given experimental conditions. The relaxation data were analysed within the model-free framework to extract order parameters for the CSA interaction. In these calculations, it was assumed that the dynamics could be modelled by one effective correlation time identical for all spectral density functions, an order parameter for the CSA interaction and the 13C’-13Caand 13C’-15N dipolar interactions, and finally an order parameter for the dipolar interaction with a virtual proton at a distance calculated as the r-6-averaged distance of the protons close in space. This procedure results in an average order parameter of 0.88 for the CSA interaction in good agreement with 15N relaxation studies but higher than the average order parameter estimated by Engelke and R i i t e r j a n ~ . ~ ’ ~ In both studies, it is recognised that a major problem in the analysis is the lack of detailed knowledge about the chemical-shift tensor for the I3C’ sites in the different amino-acid residue types in a folded protein, and that variations in the chemical-shift tensor with sequence and structure could introduce significant errors in the derived dynamic parameters.

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14.3 Rotational Diffusion Anisotropy - There has been considerable interest in the characterisation of the rotational diffusion anisotropy of proteins by means of heteronuclear relaxation measurements. A motional model including anisotropic rotational tumbling may provide information about the rotational diffusion tensor and is obviously a physically more adequate model for the description of the rotational diffusion of non-spherical proteins. Anisotropy modelling may also provide important structural information about the relative orientations of domains in multi-domain proteins where inter-domain distance restraints are sparse. Tjandra et al.254 have with their study of the ternary complex of the HIV-1 protease dimer and the DMP323 inhibitor for the first time demonstrated the determination of a fully asymmetric rotational diffusion tensor. The inertia tensor of the complex has relative ratios of 1.0:0.85:0.44 of the principal components and is thus highly asymmetric and it is shown to have a rotational diffusion tensor nearly co-linear with the inertia tensor and with relative sizes of the principal tensor components of 1.0:1.11:1.42. The Fisher (F) test is used to demonstrate that the improvement in fitting the data to a fully anisotropic rotational diffusion tensor compared to an axial symmetrical tensor is statistically significant. In the study, relaxation data were recorded at 360 MHz and 600 MHz and from the field dependence of R I and R2 rates. It was found that on average, the chemical-shift anisotropy of the peptide-bond amide nitrogens are at least 170 ppm, which is about 7% higher than the commonly used value of 160 ppm. However, since the CSA relaxation mechanism contributes only about 20% to the I5N relaxation rates at moderate field strengths, the effect of such a difference is significant only for relaxation data of very high accuracy, as in the present study, or in studies performed at a very high magnetic field strength. Phan et al.255have performed I5N relaxation measurements of a fibronectin type I module pair at three field strengths and have demonstrated that it is possible to model the relaxation data with a symmetrical rotational diffusion tensor with DiI/D1 of 1.9. This is consistent with hydrodynamic simulations of a model of the two modules forming a rigid elongated structure. Recently, Lee et al.256have demonstrated the simultaneous use of "N and I3C relaxation data in the characterisation of the rotational diffusion tensors of the proteins calbindin, G-CSF and ubiquitin. It is shown that both because of the larger data set and because of the more uniform distribution of "N and I3C bond vectors, as compared to 15N bond vectors alone, a superior and more robust anisotropic modelling is obtained when both 15N and 13C relaxation data is included in the analysis. It is stressed, that even with the use of a model including non-isotropic rotational diffusion, the goodness of the fits obtained is not as good as expected given the experimental uncertainties and it is suggested that the uncertainties of the relaxation data may be underestimated by as much as 400%. Errors could also arise from uncertainties in the orientation of the 15N and 13C bond vectors and from internal motions which are not included in the model. Fushman et al.257have addressed the problem of protein aggregation which is very commonly encountered at the millimolar concentrations applied in protein NMR studies and have derived a method that takes into account both a fast

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monomer-dimer equilibrium and anisotropy of the overall rotation of the dimer. The relative orientation of the two monomers in the dimer are assumed to be random in order to model a non-specific aggregation process. By comparing with a traditional model-free analysis, it is demonstrated that within this framework of non-specific aggregation, the overall correlation time is very dependent on the aggregation state whereas both the generalised order parameters and the internal correlation times are only a little affected. The large majority of relaxation studies of proteins still assume isotropic rotational diffusion and it has accordingly been particularly important to investigate the effects on model-free parameters of not taking into account have rotational diffusion anisotropy in the model description. Tjandra et shown that a moderate rotational diffusion anisotropy, when applying the isotropic approximation, has only a little effect on the extracted order parameters, whereas it can result in the identification of artificial exchange contributions to the R2 relaxation rates and artificial internal motions on the nanosecond time scale. However, the study by Lee et ul.256also shows that the determination of anisotropic rotational diffusion parameters of proteins with modest anisotropy (such as calbindin and ubiquitin) requires relaxation data of extremely high precision.

14.4 Conformational Restraints from Relaxation Data - Tjandra et ~ 1 . ~have ~ ' taken the use of rotational diffusion anisotropy to the extreme in a study of the N-terminal domain of enzyme I (EIN). For a molecule with an axially-symmetric rotational diffusion tensor and in the absence of conformational exchange and large-amplitude internal motions, the R2/R1 ratio for a given I5N nucleus is determined by the two principal components, DII and Dl,of the rotational diffusion tensor and the angle, 0, between a given 'H-I5N bond vector and the symmetry axis of the rotational diffusion tensor. The authors show how it is possible to determine Dil and DI directly from the ensemble of R2/R1 ratios and how the angle 8 subsequently can be determined for each 'H-I5N bond vector. The 0 angles are then used as structural restraints together with other NMRderived restraints in a simulated annealing protocol. It is demonstrated that inclusion of the anisotropy data alters the relative orientation of the a and a/P sub-domains whereas the overall quality of the structure is not affected. The conclusion drawn from the study is that such data are of particular value in the establishment of the relative orientation of the domains in multi-domain proteins and in the establishment of long-range order in DNA and RNA where NOEderived distance restraints can be sparse. 14.5 Conformational Exchange - Conformational exchange processes on the micro- to millisecond time scale may contribute to the measured transverse relaxation rate and are thus important to consider in the analysis of relaxation data. Traditionally, an exchange contribution to the transverse relaxation rate is included in the modelling on a statistical basis, i.e. either if the given transverse relaxation rate is significantly larger than the average value within an ensemble or alternatively if the fit of the model to the experimental data is significantly

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Nuclear Magnetic Resonance

improved when an explicit exchange term is included in the fitting procedure. However, when transverse relaxation rates are measured at two or more magnetic field strengths, the quadratic dependence of the field strength of exchange contributions enables an alternative way of identifying exchange phenomena. This has been demonstrated within the framework of spectral density mapping or reduced spectral density m a ~ p i n g . ~ A ~ ~related . ~ ~ ' method is demonstrated by Phan et al.255in which the quantity R2-(R1/2) is plotted as a function of the square of the magnetic field strength, enabling the determination of the exchange rate from the slope of the line. This method requires knowledge of R1 and R2 relaxation rates only, in contrast to the spectral density mapping approaches. have investigated the temperature dependence of ''N exchange Mandel et contributions in ribonuclease H 1 within the framework of a simple two-site exchange model in which the exchange rate constants have a simple Arrhenius dependence of the temperature. It is neatly shown, that a lower limit to the activation energy of the exchange process can be estimated from the slope of an Arrhenius plot of ln(R,,) against l/(RT) and that the sign of the slope indicates whether the normalised exchange rate constant k, = kl/pZ = k2/p1is smaller or larger than 3.2/~~pMG. Here, p1 and p2 are the fractional populations of the two states, kl and k2 are the two first-order rate constants and T C ~ M Gis the delay between the I5N CPMG refocusing pulses in the R2 experiment. In the case of ribonuclease H 1, the conformational exchange processes were estimated to have lower limits to the activation energies in the range from 20 kJ.mo1-' to 50 kJ.mo1-' and normalised exchange rate constants larger than 2 . 7 lo3 ~ s-I. Conformational exchange processes may be important for protein function. In an 15N relaxation study of the human CD2 adhesion domain by Wyss et a1.,262a strikingly high density of exchange terms has been observed on the surface of the protein known to bind to the CD58 adhesion domain. Habazettl et al.263have performed a comprehensive I5N relaxation study of the 10 kDa N-terminal fragment of the E. Coli Ada protein. In particular, they have measured backbone I5N R I Prelaxation rates at different spin-lock field strengths and have been able to determine a characteristic time constant of around 60 ps for the conformational exchange process of Gln-73 which is positioned close to the active site. Several studies show increased exchange terms upon introduction of certain point have studied the increased conformational exchange mutations. Beeser et contributions of the Y35G mutant of BPTI by varying the CPMG delay in the R2 experiment. Wong et al.265have studied the C4A/C82A double mutant of barstar and interpreted the increased exchange contributions as a concerted movement of the residues in the first helix and a twisting of the P-sheet. De Lorimer et a1.266 have observed lowered order parameters and increased exchange contributions in the disrupted-core mutant L78K of thioredoxin when compared to the wild-type protein. 14.6 Theoretical Aspects - Since the pioneering work by Akke, Briischweiler and Palmer,267 there has appeared only few statistical mechanics studies of the relation between relaxation parameters and thermodynamic properties. However, within the last year two studies have appeared about the relation between

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relaxation order parameters and conformational entropy. Yang and Kay268have derived relationships between the order parameter and the conformational entropy for eight different motional models and have applied the methodology to the estimation of the changes in conformational entropy associated with the folding-unfolding process of an SH3 domain. Li et ul.269 have investigated the relationship between the order parameter and the conformational entropy within the framework of a one-dimensional vibrator motional model. Finally, Mandel et a1.261have performed an analysis of the temperature dependence of the order parameter and applied the method to ribonuclease H 1 . A study by Sunada and is concerned with the calculation of order parameters by normal-mode analysis and especially the contributions from highfrequency motions. Daragan and may^^^' have performed a theoretical analysis of internally restricted correlated rotations in peptides and proteins using I3C and have proposed the use of Gaussian spectral 15N relaxation data. Ishima et d272 density functions in the description of internal motions in proteins. 14.7 Applications of 15N and I3C Relaxation Measurements - Apart from the reports mentioned above, nuclear relaxation measurements have been performed on a large number of different molecules and systems. A substantial number of studies are concerned with the changes in dynamics induced by the binding of a ligand. Olejniczak et ul.273have studied the PTB domain from IRS-1 with and without bound p hospho tyrosine-cont aining peptide and observed motional restrictions upon peptide binding. Boelens and c o - w ~ r k e r have s ~ ~studied ~ ~ ~ the ~~ dimeric HU protein and have observed motional restriction of a P-hairpin upon binding to DNA. Hodsdon and C i ~ t o l have a ~ ~measured ~ I5N relaxation data for the uncomplexed and complexed form of intestinal fatty-acid binding protein and observed motional restriction upon binding in three spatially close stretches in the binding region. Slijper et ul.277have observed reduced mobility of backbone and side chain I5N sites on the binding surface of lac-repressor headpiece (1-56) upon binding to DNA. Markus et ul.278 have studied the C-terminal RNArecognition domain of ribosomal protein L11 and have observed motional ' carried restriction of a flexible loop upon binding to RNA. Stivers et ~ 1 . ~have out an investigation of the uncomplexed and inhibitor-bound forms of 4oxalocrotonate tautomerase and observed increased exchange terms upon inhibitor binding as well as both increased and decreased order parameters. The changes in order parameters are interpreted in terms of changes in conformational entropy. Pintar et ul.279have measured I5N R , and R2 values and collected analytical ultracentrifugation data for both the uncomplexed and phosphotyrosine-peptide bound forms of the Fyn SH2 domain. They showed that the free domain is at least a dimer under the given experimental conditions and that complex formation shifts the monomer-dimer equilibrium towards the monomer. Yu et ~ 1 . ~have ~ ' studied both free and DNA-bound forms of the C-terminal domain of E. coli topoisomerase and surprisingly observed a general reduction in order parameters upon complex formation except for a few residues in loop have regions for which the order parameters increased. Fushmann et investigated ribonuclease T1 in free form and in complex with 2'-GMP and it is

3 24

Nuclear Magnetic Resonance

shown that complex formation results in increased motional restriction. A nanosecond long molecular dynamics simulation is used in the interpretation of the data. In a number of studies, relaxation measurements have shed light over the 1have. observed ~ ~ dynamics of loops and linker regions in proteins. Martin et ~ significant internal mobility in the S1 and S4 loops of the substrate-binding site. Pfuhl et d 2 0 3 have shown that an N-terminal extension to the immunoglobulinlike domain M5 of titin increases the stability of the domain and restricts the mobility of the BC and F G loops. Feng et al.283have observed increased mobility in loops and C-terminal region of a variant of human interleukin-3. Ubbink et al.284 have by means of "N relaxation measurements identified a 13-residue unstructured tail in Thiobacillus versutus ferrocytochrome c550 and Matsuo et al.285 have identified a mobile C-terminal tail in the h-cro repressor protein. Jeon et a/.286 have identified a flexible linker in the C-terminal one-third of the have demonstrated that IF3 a-subunit of RNA polymerase. Moreau et consists of two domains connected with a flexible linker. Spitzfaden et a/.288have investigated the inter-domain interactions of a fibronectin type 111 module pair by means of 15N relaxation measurements and show that the two domains have a well-defined relative orientation and forms a rigid elongated structure. However, by introduction of a glycine linker between the two domains, the rigidity of the structure is lost. McEvoy et have identified flexible linker regions in the CheY-domain from chemotaxis kinase CheA. Farrow et al.289have described a comprehensive I5N relaxation study of the Nterminal SH3 domain from Drk in both the folded state and in the unfolded state. Pellecchia et a1.18 have performed I5N relaxation studies of fragment 2-108 of the DnaJ molecular chaperone of E. coli. It is shown that the Gly/Phe-rich region 77-108 does not form a global fold. However, the relaxation data show that residues 90-103 show reduced mobility compared to the rest of the Gly/Phe-rich have carried out an 15N relaxation study of four region. Alexandrescu et states of staphylococcal nuclease A including the uncomplexed protein, the complex with 3',5'-bisphosphate, the OB-fold fragment and an unfolded 131 residue fragment. Konrat er a/.291have performed 15N relaxation measurements of the Chave studied the terminal LIM domain from quail CRP2 and Muhlhahn et "N dynamics of the human macrophage-migration inhibitory factor. Liu et al.293 have studied a reactive-site hydrolysed form of Cucombita maxima trypsin inhibitor by means of 15N relaxation techniques. Kelly et ~ 1 . have ' ~ ~ investigated both the reduced form and the oxidized form of E. coli glutaredoxin-1 by I5N relaxation and Papavoine et al.295 have performed an "N relaxation study of the major coat protein from bacteriophage M13 in detergent micelles. Alattia et al.296 have carried out a I3C natural abundance relaxation study of pike parvalbumin. Zhu et al.297 have performed 15N relaxation studies of adenosines in two DNA dodecamers and found order parameters around 0.8 and fast internal motions. P a q ~ e has t ~ carried ~ ~ out a 13C relaxation study on selectively labelled DNA and has interpreted the relaxation data within the framework of the model-free method.

~

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14.8 Relaxation Studies of Other Nuclei - There has been a number of reports about interactions between water and biological macromolecules. Venu et al.299 have studied both wild-type and the G36S mutant of BPTI by means of nuclear magnetic relaxation dispersion (NMRD) measurements of the water and show that changes in NMRD can be accounted for by the loss of a single of the four have investigated the water accessibility internal water molecules. Kroes et d.300 of the copper site in azurins by means of NMRD measurements. Wang et ~ 1 . ' ~ ~ have studied water-protein NOE and ROE effects in the HIV-1 protease/KNI272 inhibitor complex and the measurements show the presence of ordered water molecules in the complex interface. Denisov et ~ 1 . ~ "have investigated the kinetics of DNA hydration by NMRD measurements of water 2H and I7O. The measurements are consistent with a few highly ordered water molecules with residence times around 1 ns at 4 "C. Other water molecules have residence times much shorter than 1 ns. Bryant247makes a similar observation in a NMRD and NOESY study of a DNA duplex. It is suggested that the ordered water molecules contribute to the stability of the complex. Otting and c o - w o r k e r ~have ' ~ ~ studied several double-stranded DNA sequences by means of NOESY and ROESY techniques. The observation of positive NOE signals between water and DNA protons indicate the presence of ordered water molecules with residence times of at least 0.5 ns which is in good agreement with the above NMRD studies. Conte et have looked for bound waters on a RNA duplex and found ordered water molecules in the base of both the major and the minor groove with effective correlation times of about 0.5 ns. Birlirakis et d 3 0 3 proposed an off-resonance ROESY experiment for the quantitative characterization of water-protein exchange processes. Gillespie and S h ~ r t l e ~ ' ~have ,~'~ introduced PROXYL spin labels at 14 unique positions in the denatured A1 3 16 fragment of staphylococcal nuclease A and increased transverse relaxation rates for amide protons were used to derive 700 distance restraints between spin labels and amide protons which were subsequently used in a structure calculation. The calculated structure was found to be very similar to the native structure of the enzyme. Huber et ~ 1 . ~ "have studied the 'H relaxation rates near the paramagnetic centre in Chromatioum vinosum highpotential ferrodoxin and have related these rates to distances to the paramagnetic centre. The data indicate an apparent difference between the solution and X-ray structures around Phe-48. Kr~shelnitski~'~ has investigated the temperature dependence and field dependence of 'H transverse relaxation rates. Nikonowicz et ~ 1 . ~have ' ~ compared the 'H longitudinal relaxation rates in unlabelled and 2H/'5N-labelled RNA and demonstrates that exchange is the major contributor to relaxation but that 'H-'H dipolar relaxation also contributes significantly. Bonechi et d 3 0 9 have investigated the temperature dependence of ' H longitudinal relaxation rates to characterise DNA-ligand interaction in the fast-exchange limit. Luck et ~ 1 . ~ have " measured I9F relaxation times of 5-fluorotrypthophan and tetradeutero-5-fluorotrypthophanlabelled E. coli glucose/galactose receptor and the contributions from dipolar relaxation with protons on the trypthophan ring was estimated. The relaxation data which was interpreted within the framework

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of the model-free method are consistent with highly rigid 19F sites with fast internal motions on the picosecond time scale. Finally, Aramini et have performed a 207Pbstudy of 207Pbbound to parvalbumin and calmodulin. *"Pb is suggested as a probe for investigating calcium-binding proteins.

15 1

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12 13 14

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290 29 1 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310

31 1

10 Svnthetic Macromolecules BY H. KUROSU AND T. YAMANOBE

1

Introduction

NMR is one of the most important instruments for characterizing macromolecules because physical properties of polymers are affected by primary and secondary structure of the polymers. In this chapter, NMR works concerned about synthetic macromolecules are reviewed by categorizing tacticity, polymerization mechanism, polymer alloy, liquid crystal, gel, polymer network, imaging, diffusion, absorption and so on. A previous reviewer of this chapter, A. H. Fawcett edited 'Polymer Spectroscopy" which covers NMR methods and applications about characterization, conformation, statistical mechanics using rotational isomeric state model, imaging and multidimensional techniques. Harwood2 described 13C and 31P NMR studies on polymers and copolymers derived from several enriched initiators. They provided information about the influence of solvent on the initiation step in copolymerization, the selectivity and the chemical behavior of radicals. The molecular weight and its distribution measured by NMR are also reported. Other reviews are published about characterization of polym e r ~ ',~ polymerizing -~ rnechanisms,l2 polymer processing,13 liquid crystals,I4 ionomer,I5 polydimethylsiloxane,16 imaging,I7 polymer gels'* and crosslinked polyacrylates. l 9

2

Characterization of Primary Structure of Polymers

Determination of primary structure is one of the most important aspects in polymer characterization, because physical properties of polymer are affected by primary structure. NMR is the unrivalled method for this determination. Primary structure includes tacticity, branch, irregularity, cotacticity, sequence distribution. Works on primary structure are summarized in Table 10.1.

Nuclear Magnetic Resonance, Volume 27 0The Royal Society of Chemistry 1998 337

338

Nuclear Magnetic Resonance

Table 10.1 N M R studies of primary structure of polymers ~~~~

Polymer

~

Nucleus Contents

ref.

H, C degree of acetylation 20 acetylated chitosan acrylic resin (Paraloid) H resin component 21 alternating copolymer H, C sequence distribution 22 chemically reduced poly(viny1 chloride) H, C stereoregularity, composition 23 copolyether, poly( 1,IO-decanediol-coH,C end group, sequence distribution 24 2,2-diethyl-2,3-propanediol) copolyperoxide,poly(a-methylstyrene-coH,C sequence distribution 25 styrene),poly(a-methy 1styrene-co-methyl methacrylate) deacetylated chitosans H,C sequence distribution 26 dendrimer, theory branching 27 fluoropol ymer H,C,F characterization, triple resonance 28 hydroxy-terminated polybutadiene H,C endgroup 29 liquid crystalline polyether C conformation 30 poly((2S,S)-benzyl-~-3-methylmalate) C stereosequence 31 poly((octamethyltetrasily1ene)methylene) H, C, Si sequence distribution 32 poly((R)-3 hydroxy- 1-octenyl sulfone) C tacticity, sequence distribution 33 poly( 1,3-hexadiene) H, C configuration 34 poly( 1,5-hexadiene), poly( 1,5-hexadiene- C sequence distribution, composition 35 co-ethylene), poly( 1,5-hexadiene-coethy lene-co-styrene) poly( 1-chloro- 1 -fluoroethylene) H, C, F tacticity 36 H, C, F tacticity 37 poly( 1-chloro- 1-fluoroethylene) 38 poly( 1-chloro- 1-fluoroethylene),poly(1- H, C, F stereosequence distribution chloro- 1-fluoro-ethylene-co-isobutylene) H, C tacticity 39 poly( 1-octene) poly( 1-octene) C tacticity 40 poly( 1-phenyl- 1-silabutane) H, C, Si tacticity 41 poly(2,2-dimethyltrimethylenecarbonate- C sequence distribution 42 co-L,L-lactide) poly(2,5-di-n-butoxy- 1,4-phenylene) H, C characterization 43 poly(2,5-dimethyl-3-vinylfuran) H, C tacticity 44 poly(2,5-dimethyl-3-vinylthiophene) H,C tacticity 45 poly(2-(3-thienyl)ethanol-butoxycarbonylH tacticity, defect 46 methylurethane) poly(2-(ter-butyldimethylsiloxy)ethyl C tacticity 47 methacry late) poly(2-hydroxyethyl methacrylate-co-2- C composition, stereochemistry, 48 ethoxyethyl methacrylate) configuration poly(2-hydroxyethylmethacrylate-coH, C stereochemistry, configuration, methacrylic ester) sequence distribution 49 sequence distribution 50 poly(3,3,3-trifluoro- 1,2-epoxypropane)- F block-pol y(N-phen ylmaleimide) poly (3,3-dialkylcyclopropenes) C stereoregularity 51 poly(3-(alky1thio)thiophenes) H regioregularity 52 poly(3-alkyl-co-3,4-dialkylthophene) H sequence distribution 53 poly(3-butylthiophene), C regioregularity 54 poly(3-octylthiophene), pol y (3-dodecylthiophene) poly(3-cyclohexyloxy-2-hydorxypropyl H, C sequence distribution, composition 55 acry late-co-styrene) poly(3-hexanoyloxyethyl-2,5-thienylene) H,C regiochemistry 56

10: Synthetic Macromolecules

339

Table 10.1 N M R studies of primary structure of polymers (continued) Polymer

Nucleus Contents

poly(3-methyl-1,2-butadiene) poly(3-phenyl-4,4'-biphenol-c0terephthalic acid), poly(3,3'-diphenyl4,4'-biphenol-co-2,6-naphthalenedicarboxylic acid) poly( 3-tetrahydrofurfuryloxy-2H, C hydroxypropyl methacrylate) poly(3-vinyl-1-methylindole) poly(4,(2-hydroxy-2-methylpropanoyl) phenoxyethyl-2-(2-propenylamino)-2methyl propanoate-co-styrene) poly(4-acetoxy st yrene) poly(4-hydroxybutyrate-co-3hydroxybutyrate) poly(4-methyl-1,3-pentadiene-c0 C -ethylene) poly(5-ethyl-1,3-dioxan-5-yl-methyI C acrylate), poly(5-ethyl-1,3-dioxane-5yl-methylmet hacry late) poly( 5-indanyl acrylate), poly(5-indanyl H, C acrylate-co-glycidylmethacry late) poly (5-methoxy -2-vinylthiophene) poly(5-vinyl-1,3-benzodioxole) poly(6-deoxy-methacrylamido-~glucopyranose) poly(6-vinyl-I ,Cbenzodioxane) H, c Cb0polymer C poly(acety1ene-co-diethy l C dipropargylmalonate) poly (acrylhydrazide-amide) C poly(acrylonitri1e-co-methacrylate) H

poly(acry1onitrile-co-methyl acrylate-co- H itaconic acid) poly(adipic anhydride), poly(adipic C anhydride)-block-poly( E-caprolactone) poly(alky1 thiophene-3-carboxylate) H poly(amide-imide) C H poly(anthraquin0ne diimine) poly(ary1 ether ketone) C poly(benzoquinone imine) H poly(bicyclo(2,2,l)hept-2-ene C (norbornene)), poly(bicyclo-(2,2,1) hepta-2,5-diene(norbornadiene)) H, c poly(butadiene) poly(buty1vinyl ether-co-4-ethoxyphenyl C 4-(4-(vinyloxy)butoxyl)benzoate-co-4ethoxyphenyl4-( 1 1-(vinyloxy) undecy1oxy)benzoate) poly(D,L-lactide) C poly(dimethylcyclosi1oxane-co-diphenyl-Si cyclosiloxane)

ref.

characterization sequence distribution

57 58

sequence distribution, characterization stereoregularity sequence distribution, characterization

59 60 61

tact icit y sequence distribution

62 63

sequence distribution

64

tacticity, dyad, triad

65

composition

66

stereochemistry tacticity tacticity

67 68 69

tacticity characterization sequence distribution

70 71 72

sequence distribution sequence distribution, Markov statistics tacticity, composition

73 74

sequence distribution

76

tacticity consti tutional regularity stereochemical structure protonation of carbonyl stereochemical structure tac ticit y

77 78 79 80 81 82

characterization stereoregularity

83 84

tacticity, sequence distribution tacticity

85 86

75

Nuclear Magnetic Resonance

340

Table 10.1 N M R studies of primary structure of polymers (continued) Polymer

Nucleus Contents

poly(ester-co-imide), C poly(N-(o-carboxyalkylene) trimellitic imide-co-2,6-dihydroxynapht haleneco-p-hydroxybenzoic acid) poly(ethene-co-4-vinylcyclohexene) C pol y(ethene-co-styrene) H poly(ether ketone ether ketone ketone) H,C poly(ether ketone) F poly(ethy1ene oxide) H poly(ethy1ene oxide) H poly(ethy1ene oxide) H,C poly(ethy1ene oxide-stat-propylene H, C oxide) H poly(ethy1ene terephthalate), poly(cyclohexanedimethano1-coterephthalate) poly(ethylene terephtha1ate)-block-liquid C crystalline polyester poly(ethylene-2,6-naphthalate), C poly(ethylene-2,6-naphthalate-co-poly(4-h ydrox ybenzoate) poly(ethylene-2,6-naphthalate)/ H poly(ethy1ene terephthalate) poly(ethyIene-2,6-naphthalate-c0C hexamethylene 2,fj-naphthalate) poly (eth ylene-alt-styrene) H poly(ethy1ene-co-1-butene) C poly(ethy1ene-co-dimethylaminoethyl C met hacrylate) poly(ethy1ene-co-n-butyl methacrylate), H, C poly(ethy1ene-co-acrylic acid), poly(ethy1ene-co-methacrylic acid), poly(ethy1ene-co-methyl acrylate), poly(ethy1ene-co-vinylacetate), poly(ethy1ene-co-n-butyl methacrylate) poly(ethy1ene-co-propylene) H, C poly(ethylene-co-propylene) C poly(ethy1ene-co-propylene) C poly(ethy1ene-co-propylene) H,C poly(ethy1ene-co-propylene), C poly(ethy1ene-co-propen-co-hexene) poly(ethy1ene-co-propylene), C 1), poly(ethy1ene-co-propylene-co-butenepoly (ethylene-co-propylene-co-2ethylidiene) poIy(ethylene-co-styrene) C pol y(ethy lene-co-propylene) C

poly(hexakis(methoxymethy1)melamine) C poly(hexamethylene-2,3-di-O-methyl-D,-H, C L-tartaramide) poly(L-lactic acid) C

ref.

sequence distribution

87

regioselectivity sequence distribution defect structure endgroup conformation endgroup endgroup sequence distribution

88 89 90 91 92 93 94 95

endgroup

96

characterization

97

sequence distribution

98

transesterifcation

99

sequence distribution

100

sequence distribution sequence distribution sequence distribution

101 102 103

branch

104

sequence distribution reaction probability sequencial distribution end group, degradation sequence distribution, branch

105 106 107 108 109

composition

110

regioregularity configuration, sequence distribution linkage stereochemistry

111 112 113 114

molecular weight,characterization 115

10: Synthetic Macromolecules

34 1

Table 10.1 N M R studies of primary structure of polymers (continued) Polymer

Nucleus Contents

poly(L-lactic acid) H, c poly(L-1ysine)-block-poly(ethy1ene glycol) H poly(1actic acid) H,C

ref.

poly(1actide) poly(1actide-co-E-caprolactone) pol y (m-phenylene) poly(ma1eic anhydride-co-styrene)

H, c C H, c C

poly(methy1 methacrylate) poly(methy1 methacrylate) poly(methy1 methacrylate)/siloxane poly(methy1 methacrylate)-blockpoly(st yrene) poly(methy1 methacry late-co-2-h ydroxy ethylmethacry late) poly(methy1 methacrylate-co-ally1 methacrylate) pol y(me thylmet hacry late) poly(methylmethacry1ate)-graft-curdlan pol y(methy lphen y lsilylene), poly(methy1-p-tolylsilylene), poly(cyclohexylmethy1silylene) poly(methylpheny1silylmethylene)

H H Si H

molecular weight, end group conformation sequence distribution, composition, microtacticity stereosequence, hexad chain microstructure characterization, linkage sequence distribution, configuration end group tacticity cross link, IPN composition, molecular weight

H

tacticity, sequence distribution

127

H

stereoregularity

128

C C Si

tacticity, heptad characterization tacticity

129 130 131

C

stereochemistry, configuration, tacticity tacticity, sequence distribuition

132

poly(N,N-diisopropylamino- 1-pentene), H poly(N,N-diisopropylamino-1-penteneco- 1-hexene) poly (N,N-diphen y lacrylamide) H poly(n-butyl methacrylate) H, c poly(N-cyclohexylacrylamide-co-styrene)H, C poly(N-substituted acrylamide-co-styrene-C co-methyl methacrylate) poly(N-vinylformamide-co-sodium-3- C acrylamideo-3-methylbutanoate), pol y( N-vinylformamide-co-sodium-2acrylamide-2-methylpropanesulfonate), acrylate) pol y(norbornene-co-cyclopentene) C pol y(norbornene-co-ethy lene) C poly(o1efin sulfone), poly((R)- 1-octen-3-01C sulfone) H, C, P poly(organophosphazene) poly(oxyethy1ene)telechelics H, C poly(oxymethy1ene-co-dimethylsiloxane) H poly(oxytrimethy1ene) H pol y(p-aniline) H, C pol y (p-chlorostyrene-co-maleic C anhydride) poly(p-hydroxy benzoate-co-bisphenol A C terephthalate)

116 117 118 119 120 121 122 123 124 125 126

133

tacticit y tactici t y composition, sequence distribution sequence distribution, photosensitive polymer composition

134 135 136 137

sequence distribution sequence distribution stereochemistry

139 140 141

characterization characterization sequence distribution conformation, ab initio conformation sequence distribution

142 143 144 145 146 147

sequence distribution

148

138

Nuclear Magnetic Resonance

342

Table 10.1 N M R studies of primary structure of polymers (continued) Polymer

Nucleus Contents

ref.

poly(p-phenylene), polyelectrolyte poly(p-phenylene-alt-2,5-diheptyl-pphen y lene)

H H

constitutional homogeneity sequence distribution

149 150

H C

primary structure, defect composition, phase separation

151 152

H, C tacticity H regioirregularity H, C stereoregularity C sequence distribution C tacticity, sequence distribution H, C, Si molecular weight, branch H sequence distribution

153 154 155 156 157 158 159

H

characterization

160

H

composition

161

C H

tacticity stereochemical structure, irregularity sequence distribution, tacticity sequence distribution end group, irregular structure, byproducts sequence distribution sequence distribution

162 163

poly(pheno1-co-p-phenylphenolco- formaldehyde) poly(poly(a-(alkoxymethy1)acrylate)) poly(propen-co-ethy lene) poly(propy1ene oxide) poly(propy1ene-co-allene) poly( R- 1-octen-3-ol-co-sulfone) poly(silylenemethy1ene) poly(sodium acrylate -co-lauryl methacrylate) poly( styrene)-block-poly(tert-butylmethacry1ate)-blockpoly(methy1 methacrylate) poly(styrene-co-2,3-diphenyl-1,3butadiene) pol y(styrene-co-acrylamide) poly(styrene-co-acrylonitrile) poly(st yrene-co-acrylonitrile) poly(styrene-co-methyl methacry late) poly(succinimide)

C C H, C

poly(terephtha1aldehyde) poly(terephthalaldehyde), poly(isophthalaldehyde), poly(terephthalaldehyde-co-1,12dodecanedial) poly (tetrafluorobenzo[c]thiophene) poly(tetrahydofurfury1 methacrylateco-methyl methacrylate) poly(tetramethy1ene carbonate) poly(urethane urea) poly(viny1 acetate-co-ethyl methacrylate) poly(viny1 alcohol) poly(viny1 alcohol) poly(viny1 chloride) poly(viny1 chloride) poly(viny1 chloride) poly(viny1 ether)-block-poly(viny1ether)block-poly(methy1 tri(ethy1ene glycol) vinyl ether) poly(viny1 formal)

H,C H

poly(viny1idene chloride-co-methyl acrylate) poly(viny1idene cyanide-co-cyanovinyl acetate), poly(methacrylonitri1eco-methyl a-acetoxyacrylate)

H, C, F characterization

164 165 166 167 168

C

tacticity

169 170

H,C C H,C C C C C C H

characterization, end group sequence distribution composition, sequence distribution composition tacticity tacticity, degradation tacticity, pentad t acticity degree of polymerization

171 172 173 174 175 176 177 178 179

H, c H, c

stereosequence, 180 sequence distribution composition, sequence distribution 181

C

sequence distribution

182

10: Synthetic Macromolecules

343

Table 10.1 N M R studies of primary structure of polymers (continued) Polymer

Nucleus Contents

poly(viny1idenecyanide-co-methyl a-acetox yacrylate),poly(methacrylonitrile-co-methyl a-acetoxyacrylate),poly(acrylonitrileco-methyl a-acetoxyacrylate) poly(viny1idenefluoride) poly(a4sobut yl-P-D,L-aspartate) poly(a-methyl- P-propiolactone) poly(a-methyl-P-propiolactone)

C

sequence distribution

183

F, C H C C

endgroup configuration, crystal structure tacticity, stereosequence sequence distribution, stereocopolymer stereosequence distribution sequence distribution

184 185 186 187

endgroup sequence distribution, biodegradation sequence distribution end group, sequence distribution

190 191

tacticity configuration sequence distribution

194 195 196

sequence distribution sequence distribution

197 198

regioregularity characterization

199 200

characterization

20 1

defect characterization endgroup minor structure composition

202 203 204 205 206

C poly(a-methyl-P-propiolactone) poly(a-methylstyrene-coC methacrylonitrile),poly(a-methylstyreneco-acrylonitrile) poly(P-propiolactone) H,C poly(y-butyrolactone) H,C poly(y-butyrolactone-co-E-caprolactone)C poly(y-thiobutyrolactone), polyH, C (c-caprolactone) poly(c-caprolactone) H,C poly(E-caprolactone), poly(1actide) A1 poly(E-caprolactone-co-l,4,8-trioxaspiroC [4,6]undecan-9-one) poly(c-caprolactone-co-D,L-lactide) C poly(E-caprolactone-co-lactide), poly((R)- C 3-hydroxybutyric acid) poly(w-(3-thienyl)alkanesulfonates) H, C polyacetylene, poly(alkyldipropargy1H, C (4-sulfobutyl)-ammonium betaine) polyacrylonitrile-graft-poly(ethy1ene C oxide) polyaniline C polyaramide H, C polybromostyrene H polybutene C polycaprolactone-graft-poly(maleic H anhydride) polycarbonate H,C polycarbonate H polycarbonate, poly(2,2-bis(4-hydroxy C pheny1)propane) polycarbonate, poly(oxybenzoate-co-p- H, C terephtahlate) H, C poly(ethy1ene oxide), poly(propy1ene oxide) polydimethylsiloxane Si polydimethylsiloxane, polydimethyl H, C, Si siloxane-block-poly(methy1 methacry late) H polyester blends H polyester/melamine

ref.

188 189

192 193

sequence distribution,liquid crystal 207 endgroup 208 conformation, dihedral angel, C 13 209 labeled bisphenol A transesterification, composition, 2 10 sequence distribution degradation 21 1 degradation characterization

212 213

transesterification degradation

214 21 5

Nuclear Magnetic Resonance

344

Table 10.1 N M R studies of primary structure of poIymers (continued) ~~

Polymer polyglutarimide polyisobutylene polyiso but ylene polyisoprene-block-polyst yrene poly(acetic acid)-graft-poly(ma1eic anhydride) polyoxyethylene-graft-nylon 6 polypropylene polypropylene polypropylene polypropylene polypropylene polypropylene polypropylene polypropylene polypropylene polypropylene polypropylene polypropylene-block-polystyrene polysaccharides polysiloxane

Nucleus Contents degree of imidization degradation end group characterization composition

chemical composition tacticity, pentad tact ici t y tacticity terminal microstructure, tacticity tacticity end group t acticity tacticity tactici ty, pentad tacticity tacticity, pentad tacticity primary structure H,C,N, characterization, hydrogen Si bonding polysiloxane C, Si degree of substitution polystyrene H, C tacticity, regioselectivity polystyrene-block-polyisoprene H sequence distribution polystyrene H tacticity polystyrene H, C tacticity polystyrene H tacticity polystyrene H, C, P end group polystyrene, poly(styrene-co-ethylene) C tacticity, sequencial distribution polystyrene-block-poly(ethy1eneimine) C molecular motion pol ysuccinimide H ,C microstructure polyurethane end group, sequencial distribution H, C polyvinylchloride-graft-polypyrrole H number of branch syndiotactic polystyrene H tacticity, polymerization mechanism terpolyperoxide(po1y( styrene-co-methyl- H sequence distribution co-methacrylate-co-a-methylstyrene)) vinyl-bridged polysilsesquioxane C, Si characterization endgroup a,w-dichloro-poly(methyIphenylsi1ane) Si

3

~

ref. 216 217 218 219 220 22 1 222 223 224 225 226 227 228 229 230 23 1 232 233 234 235 236 237 238 239 240 24 1 242 243 244 245 246 247 248 249

250 25 1

Characterization of the Synthetic Macromolecules in the Solid State

3.1 Solid State I3C NMR Studies for Synthetic Macromolecules - Solid state NMR is a powerful tool to characterize the structure of macromolecules. High resolution solid state I3C NMR is widely used to obtain information about structure and mobility of macromolecules. The main properties of poly(pphenylenevinylene) (PPV) in its neutral and doped states are discussed by means

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of high resolution solid state 13C NMR and resonance Raman scatter~ I I ~ ( R R SI3C ) . ~CP/MAS ~~ NMR, 2D WISE and 'H spin diffusion experiments allow one to gain new insight into the structure and dynamics of solid polyelectrolyte-surfactant complexes, a material with pronounced mesophase formation.253The super molecule organization and molecular motion of high temperature membrane model compound, 5-(octadecyloxy)isophthalic acid, was studied by DSC and variable temperature solid state I3C NMR.254Dicyclopentadiene(DCPD) thermosetting resin has been characterized by 13C CP/MAS N M R technique.255 Solid state 13C NMR methods have been applied to study a gelspun ultrahigh molecular weight polyethylene fiber. Discussions on the chain conformation and the rate of motion are carried out based on the 13C chemical shift and spin-lattice relaxation time, respectively.256The crystal structure of form I of syndiotactic polypropylene are studied by solid state I3C NMR.257The mechanical properties of ternary systems consisting of polypropylene, EPDM and different types of inorganic fillers have been investigated. Solid state N M R studies provide a first insight into the interactions on the molecular scale by observation of molecular mobilities.258Two forms of a novel accordion-shaped non-linear optical polymer based on cis- and trans-l,2-diaminocyclohexaneand 0-xylyl linkages were characterized by solution and solid state NMR.259Role of long alkane spacers in poly(ester imide)s derived from N-(4'-hydroxyphenyl)-4hydroxyphthalimide are studied by I3C CP/MAS NMR.260 The molecular conformation and the phase structure of syndiotactic polypropylene gel were studied by IR and solid state high resolution I3C NMR. About 64% of solvent molecules in the gel are incorporated in the crystal-amorphous interphase as bound solvent and another 34% are in the amorphous phase as free solvent.261 The surface of colloidal silica of 22 nm and 100 nm was modified with a silane coupling agent, n-octadecyltriethoxysilane. The solid state 13C NMR spectrum shows that the covalently bonded n-octadecyl chains on the silica surface adopt a largely extended all-trans conformation.262The I3C NMR spectra of the different crystal modifications of poly(4-hydrobenzonate)~and their copolymers have been obtained by means of CP/MAS technique.263Frozen state I3C NMR measurements have been made for different frozen solutions of poly(viny1 alcohol) with different tacticities to characterize intramoleculer hydrogen bonds.264 'H-I3C cross relaxation of trifluoroethylene-vinylidene fluoride copolymer were determined by CP/MAS NMR.265 Methods for structure changes during the photopolymerization of polyol acrylates were studied. Methods included CP/MAS I3C NMR and twisted intramolecular charge transfer fluorescence probing.266Polyazulene formed by photolysis of azulene is analyzed by CP/MAS I3C NMR spectroscopy. The spectrum is compared to that of azulene to confirm the polymer structure.267The phase structure of random copolymers of ethylene and ethylene-d4 with 1-octadecene and other 1 -alkenes was studied. The CP/MAS 13CNMR spectra show that a fraction of the central sections of C16H33 side chains in ethylene-d4 copolymers are in ordered environments at 298K.268 The structure of uniaxially oriented poly(ethy1ene terephthalate) with different draw ratios was studied in the solid state using I3C NMR. From the analysis of the NMR spectra, the angle q between the phenylene para C-C axis and the chain

346

Nuclear Magnetic Resonance

axis was 16" & 10" and 29" f 5" for the oriented components was determined.269 Solid state I3C MAS NMR was used to detect morphology changes in HDPE induced by electron beam irradiation, powdering at 77 K, and molding at high temperature and pressure.270 The structure of conducting polymer is also analyzed by 13Csolid state NMR.271'272 Synthetic macromolecules have been studied by two-dimensional (2D) '3C NMR spectroscopy. The molecular orientation of a series of differently processed industrial fibers of poly(ethy1ene terephthalate) was investigated by I3C solid state rotor-synchronized 2D CP/MAS NMR.273'H and 13C(lD and 2D) NMR spectroscopy of PMMA degraded by exposure to X-,rays revealed 34 chemical shifts which could be assigned.2743275 The microstructure of polymers prepared in the presence of nickel and palladium compounds as catalysts was investigated by 13C and 2D NMR spectroscopy.2762D MAS I3C NMR spectroscopy and FTIR microscopy were used to measure the orientation in uniaxially drawn poly(ethylene terephthalate) film as a function of draw ratio.277 The analysis of orientational alignment in solids was performed by 2D isotropic-anisotropic correlation spectroscopy.278 2D heteronuclear proton-fluorine correlation solid state spectroscopy is demonstrated on a sample of poly(viny1idene difluoride). The incorporation of magnetization filters into the preparation period enables one to measure the wideline separation experiments(W1SE) spectra for the amorphous or the crystal parts of the sample separation.279The WISE NMR were also used to characterize interfaces in core-shell polymers.2s0 13C CP/MAS NMR techniques have been used to evaluate the structure of four hyper-crosslinked polystyrene resins.339

3.2 Solid State Multi-Nuclear NMR Studies for Synthetic Macromolecules Many attempts to characterize the structure of materials have been carried out by not only 13Cbut also "N, 29Si,I9F, 1 7 0 and 'HNMR in the solid state. Polycrystal powder samples of 2-acetamido-4-{bis{ (2-methoxycarbonyl)ethyl)amino)-4'-nitro azobenzene have been investigated using solid state and solution state 13C and "N NMR in an attempt to understand the effect of polymorphism.28' 29Si, "N, I3C and 'H NMR spectra are valuable for characterizing polysiloxane structures, and provide evidence for the involvement of the amine ligand in hydrogen bonding with surface silanols.282Solid state variable temperature MAS 'H NMR measurements were carried out on deuterated polyethylene. Results showed that the 'H chemical shift induced by conformational and morphological changes of the polyethylene sample is within the linewidth of 0.5 ppm. The resonance frequency of the proton varies linearly with the inverse HDPE was studied by solid state square of the deuterium decoupling 'H NMR spectral fitting, relaxation and spin diffusion methods.284I9F NMR, WAXS, DSC measurements have been employed to determine the crystallinity of melt-quenched poly(tetrafluoroethy1ene) samples of different molecular 13C, 'H and 29SiNMR was used to show that the absorbed water in Twaron 1055 fiber is located in small pores in the skin region of the fibers, and in larger core defects.286 Hexamethylenediamine-glutaryl dichloride copolymer was examined by "N and I3C NMR spectroscopy and the coexistence of both a and y crystal

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forms was observed.287 170NMR is used to examine oxidative degradation in polymers: polypropylene, EPDM, polyisoprene and nitrile rubber are used to illustrate.288 The polysilane-to-polycarbosilane transformation of 1,1,2,2-tetrachlorodimethyldisilane has been characterized in detail by 29Siand 13C CP/MAS NMR.289Variable temperature (up to 150°C) solid state I9F NMR spectroscopy with high speed MAS (up to 25kHz) was used to obtain spectra with significantly high resolution for fluorocarbon polymers such as Kel-F. Sufficient resolution was archived to determine the concentration of each carbon in the five-carbon sequence as well as monomer component present in the polymer.290The reversed ~ ~ 'a model phase materials were studied by I3C and 29SiNMR s p e c t r o ~ c o p y .As system for the composite interface, grafted n-alkylsilane on various silica substrates was studied by 29Si NMR.292Mesomorphic behaviour of polydiethylphosphazenes were studied by 13C,14Nand 2H NMR.293The structural analysis method for the determination of molecular bond directions and the orientational distribution relative to the oriented axis of silk fibroin fiber was studied on the basis of the solid state "N NMR chemical shift anisotropy tensor.294 The variation in the mobile fraction seen in 'H-NMR free induction decay was analyzed using the Thomson-Gibbs equation to give the hard block lamellae thickness distribution in a poly(ester-urethane) elastomer.295Local structures of high surface area sodium titanate materials have been examined as a function of pH using solid state I7O NMR.357

3.3 Determination of Geometrical Parameters by Solid State NMR - Geometrical parameters such as bond length and torsion angle can be determined by solid state NMR. Double-quantum solid state NMR methods for determination of torsion angles in unoriented polymers was used to study the morphology of amorphous and thermally crystallized poly(ethy1ene terephthalate), doubly I3C enriched in the glycol moiety.296The solid state shape, size, and intermolecular packing of a fifth-generation dendritic macromolecule were determined by a combination of site-specific stable-isotope-labeling, rotational-echo doubleresonance (REDOR) NMR and distance-constrained molecular dynamics simul a t i o n ~ Torsion . ~ ~ ~ angles in unoriented polymers which contain segments with pairs of I3C-labeled sites separated by only one or two bonds were determined by a double-quantum solid-state NMR experiment.298 Interchain '3C-'3C distance between 13C labels and between I3C label and natural-abundance 13C have been determined using dipolar restoration at the magic angle (DRAMA) with XY8 phase alternation and controlled ample excitation for dephasing rotational amplitude (CEDRA) for p o l y ~ a r b o n a t e s . ~ ~ ~

4

Dynamics of the Synthetic Macromolecules in the Solid State

I3C NMR - I3C NMR spin-lattice relaxation times Ti are used to investigate the effect of low molecular weight diluents, including N,N-dimethylformamide, N-methylformamide, propylene carbonate, y-butyrolactone, triglyme and tetraglyme, on the local polymer segmental motion in a polyether-urethane 4.1

348

Nuclear Magnetic Resonance

network.300 A rhombohedra1 two-dimensional polymer of c60 obtained under high pressure was measured by high resolution I3C NMR.301 The effect of molecular motion in crosslinked elastomers on the heteronuclear crosspolarization rate for the case of the spin-lock procedure was in~estigated.~'~ The high resolution solid I3C and 'H NMR linewidths of semicrystalline poly(6hydroxybutyrate), in the amorphous phase and in the melt are studied as a function of temperature and magnetic field strength. Measurements of the I3C spin-spin relaxation times under the same experimental conditions show that the natural linewidth is a minor contributor to the line-broadening observed in the I3C spectra of the solid polymers.303 The conformation ranges, motion and morphology of polyesters were discussed on the basis of the solid state 'H and I3C NMR relaxation times and variable temperature spectra.304 The double melting endotherm of spunbonded isotactic polypropylene fabrics was investigated by monitoring changes in the solid state NMR spectrum that result from thermal annealing.305 Segmental relaxations in urea inclusion compounds with diblock butadiene-caprolactone copolymer were observed by I3C NMR.306 Molecular motions underlying the mechanical a-transition in poly-.c-caprolactone were investigated using solid-state 13C NMR spectroscopy.307 Solid state 13C NMR analyses have been performed to obtain information about the microphase separated structure for polyurethane elastomer, which is prepared from p-phenylene diisocyanate(PPDI), poly(tetramethy1ene oxide)(PTMO) and 1,4butanediol(BD). 13C spin-lattice relaxation time analyses have revealed that three components with different TIC values exist for the PPDI and BD residues, while two components are observed for the PTMO carbons.308 Relaxation time measurement of polybutadiene indicates that polybutadiene has a highly flexible domain and the vinyl configuration sequence distribution was confirmed from the relaxation data of CH2 and CH3.309The interpolymer interaction, morphology and chain dynamics of the poly(acry1ic acid)/poly(ethylene oxide) complex are examined by using I3C CP/MAS NMR methods.329Thermally induced molecular motion and premelting in the solid state of n-hexatriacontane were studied by 13C CP/MAS NMR.354

'H NMR - Mobility of amorphous polymers such as poly(viny1 chloride), atactic polypropylene and ethylene-propylene-dieneterpolymer were studied by proton spin-lattice relaxation time, proton spin-lattice relaxation time in the rotating frame and dipolar dephasing pulse s e q ~ e n c e . ~ Polyethylene, " polypropylene and polystyrene have been analyzed in the melt state using protonNMR T2 relaxation methods using the Carr-Purcel Meiboom-Gill (CPMG) spinecho pulse s e q ~ e n c e . ~2D ' wideline separation (WISE) NMR presents information about dynamics (via 'H wideline) with structure(via I3C chemical HDPE was studied by solid state 'H NMR spectral fitting, relaxation and spin diffusion methods.313Molecular dynamics studied performed by 'H NMR spinlattice relaxation time measurements suggest the occurrence of a mutual interaction between aqueous micelles of macromonomer and sodium dodecylH NMR relaxation and pulsed gradient spin echo diffusion measurements have been performed on virgin and unfilled vulcanized SBR, and networks

4.2

'

'

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349

after various extents of devulcanization by an ultrasound te~hnique.~'The room temperature lattice dynamics in a series of 12-doped poly(2-butoxy-5-methoxy phenylenevinylene) conducting polymers were studied by 30MHz H NMR.328 The 'H NMR relaxation times of poly(ethy1ene oxide) grafted on silica were determined in order to discuss the dependence of the temperature and grafting ratio on the relaxation times.331'H T1 and TIp, together with FID, have been measured for natural and epoxidized rubber, plus a series of vulcanized samples.340 'H NMR - Variable temperature 2H NMR T1experiments were performed on backbone deuterated atactic polystyrene in four solvents at two Larmor freq~encies."~Drawn nylon 6 fibers hydrated with D20 were studied by 2H NMR and the presence of three types of water and two classes of exchangeable portions were found.3l 7 Dynamical mechanical analysis, 2H NMR and dielectric spectroscopy techniques were used to identify the nature of the local motions involved in the secondary relaxations of a thermotropic aromatic p o l y e ~ t e r . ~ ' ~ The stress relaxation and the segmental orientation induced after a sudden strain on the networks were studied by step-strain experiments and 'H NMR.319The mobility of poly(methy1 methacrylate)-silicate interpenetrating networks were studied by 2H NMR.320Comparisons of 2H NMR spin-lattice relaxation time, T I , and spin-spin relaxation time, T2, for the adsorbed, swollen polymer at different temperatures were made to obtain information about the backbone motion of surface-bound polymer.321Dynamics of linear alkanes of different chain-length in nanotubes were studied by 13C and 2H NMR.322 Molecular mobility and mechanical properties of glassy polymers were studied by I3C and 2H NMR.323 Using 2H NMR, the molecular mobility of the deuterated groups of selectively deuterated poly(ethylene-2,6-naphthalenedicarboxylate) was investigated as a function of temperature.324 The conformation and mobility of the spacers of smectic poly(ester imide)s were investigated using 2H and 13CCP/MAS NMR.325

4.3

Other Nuclei NMR - A 7Li NMR spin-lattice relaxation investigation over the temperature range 200-340K is reported for a polycrystal sample of LiCF3S03 and a sample of poly(ethy1ene oxide)-LiCF3S03 with an 0:Li molar ratio of 3.5: 1 .326 Dynamics in a poly(ethy1ene oxide) based nanocomposite polymer electrolyte were studied by solid state 7Li NMR.327The mechanism of motion of the ethylene side groups in the high temperature modification of poly(diethy1phosphazene) is identified and compared to the arrangement of side groups in the low temperature modification by 'H/I3C/l4Ntriple resonance solid state NMR.330 In monoconducting gel electrolytes prepared from polymeric lithium complex plasticized with polyethylene glycol, DMSO, or propylene carbonate, 7Li NMR T1 at two resonance frequencies (24.5 and 77.5 MHZ) have been measured for various components over the temperature region 0.75 to 2 Tg( = 200K).332Measurement of the T1 relaxation process for both the 7Li and 19 F nuclei of solid polymer electrolytes provides some insight into the effects that salt concentration and plasticizer addition have on the environment of the cation and the triflate anion.333

4.4

3 50

Nuclear Magnetic Resonance

4.5 Multi-Dimensional NMR - Geometry and time scale of the complex rotational dynamics of amorphous polymers at the glass transition were studied by multidimensional NMR exchange experiments (three-dimensional difference correlated exchange spectroscopy (DICO)).335Study of geometry and main chain motions in poly(ethy1 methacrylate) were performed by 3D difference correlated NMR.3362D WISE(wide1ine separation) NMR have been used for investigating dynamics of polymers in the solid state.337,338

5

Characterization of the Synthetic Macromolecules in the Solution State

The dissolved state of polyacrylonitrile(PAN) in various solvents was elucidated by analyzing 13CNMR chemical shift difference for two arbitrarily chosen NMR peaks and by considering solvent effect on electro-magnetic parameters with aid of solvation phenomena of PAN in solvents.352 Poly(ethy1ene-co-vinyl acetate), EVA was analyzed by 13Chigh-resolution NMR. The analyses of this copolymer permitted the copolymer component to be obtained, and a study of molecular mobility was carried out by solid state NMR.353 The 'H, I3C and "N NMR spectra have been measured of coupling products of benzendiazonium salts with nitromethane, nitroethane, 1-nitropropane, 2-nitroethanol and of their sodium salts, and the chemical shifts have been unambiguously assigned.354 The orientation of polybutadiene chains in thermoplastic elastomers based on hydrogen bonding complexes, i.e., polybutadiene statistically modified by 4-(3,5dioxo- 1,2,4-triazoline-4-yl)isophthalic acid, is investigated under uniaxial deformation by two-dimensional small-angle neutron scattering, 2H NMR, optical birefringence and IR dichroism spectroscopy.355The segmental orientation in a semi-interpenetrating polymer network based on crosslinked polybutadiene swollen to different degrees by free butadiene oligomers(of molar masses below the entanglement limit) is studied as a function of uniaxial strain for both the oligomer chains and the network chains by using 2H NMR.356A 7Li NMR study in hexane of various mono- and difunctional organolithium compounds confirms their trend to associate in hydrocarbon solvents and for a,o-dilithiopolyisoprene, the influence of the chain length on the formation of aggregated species involving 2 4 lithium atoms.358

6

Dynamics of the Synthetic Macromolecules in the Solution State

Dynamic properties of styrene-methylene methacrylate (MMA) statistical copolymer solutions in benzene, a solvent isorefractive with MMA, were studied by dynamic light-scattering spectroscopy(DLS) and by pulsed-field-gradient NMR (PFG-NMR).341The 'H TI for the phenyl protons H(p) and the methyl protons H(m) in poly(2,6-dimethyl-p-phenylene oxide)(I) were measured at different polystyrene(I1) and I.342 The dynamics of poly(viny1 acetate) in toluene solution was examined by I3C and 'H relaxation.343 13C T were determined in solution for a series of

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p ~ l y b u t a d i e n e s . 3C ~ ~T ~ 1, T2 and NOE values were measured as a function of temperature at two magnetic fields for poly(viny1 chloride) in three solvents: chloroform, dioxane and DMS0.345A dilute-solution TI study was performed on a bisphenol polycarbonate related to the polycarbonate of bisphenol A except the isopropylidene unit is replaced by a cyclohexylidene NMR relaxation time investigations of water 'H and 2H in aqueous poly(ethylene glycol) solutions are presented for the water content range of 3-90 ~ t % 2H . NMR ~ ~ relaxation ~ times and self-diffusion coefficients of poly(P-deuterostyrene-P-2-vinylpyridine)and poly(a-deuterostyrene) were measured for the polymers in solution as a function of c ~ n c e n t r a t i o nThe . ~ ~ whole ~ spectra were used to obtain the averaged second order Legendre polynomials by 2H NMR for free oligomer and network chains in polybutadiene model network.349 To verify the micro-phase partitioning model, the predictions of boron speciation are compared to "B NMR observations in solution with a fifth generation poly(amidoamine) starburst polymer, which is a boron-specific chelating polymer.350NMR was used to study the sol-gel transition in a plasticized system based on methacrylic acid-methylene methacrylate copolymer.351

7

Polymer Blends

7.1 Miscibility of Polymer Blends - There are many reports on the investigation for miscibility of polymer blends studied by NMR. The miscibility of poly(ethylene naphthalene-2,6-dicarboxylate) (PEN) with poly(buty1ene terephthalate) (PBT) was studied by 13C CP/MAS NMR complemented with DSC measurements. The result shows that PEN and PBT blends with weight ratios SO/ 20, 50/50 and 20/80 are miscible in the molecular The miscibility of polyvinylphenol (PVPh) or terpenephenol (TPh) with polyoxymethylene (POM) was examined by high-resolution solid state 13C N M R spectroscopy. It was found that the driving force for the mixing of POM and PVPh is the hydrogenbonding interaction between the phenolic PH group of PVPh and the ether oxygen of POM, and that the mixing is preferentially induced in the noncrystal phase.360 The phase behaviour of poly(viny1 chloride)/poly(Ph methacrylate) blends has been investigated by glass transition temperature and T1,H measurement~.~ The ~ ' study of EPDM/atactic polypropylene blend compatibility was investigated by CP/MAS I3C NMR spectra, variation contact time experiment analyze, T1rH, and dipolar dephasing experiment.362The compatibilizing effect of graft copolymer, linear low-density polyethylene-y-polystyrene (LLDPE-y-PS), on immiscible LLDPE/PS blends has been studied by means of I3C CP/MAS NMR and DSC techniques.371Competitive domain-structure development and homogenization under annealing were investigated via time-resolved light scattering and 'H NMR in melt-quenched blends of partially miscible poly(ethylene naphthalene-2,6-dicarboxylate)(PEN) and poly (ethylene terephthalate) (PET) loaded with/without PEN-PET random copolymer as a c ~ m p a t i b i l i z e r . ~ ~ ~ ESR, FTIR and solid state "N NMR spectroscopies were used to characterize the structure and relative strength of the interactions between metal sulfonate and

352

Nuclear Magnetic Resonance

amide groups in blends of lightly sulfonated polystyrene ionomers and an N-methylated polyamide, poly(N,N'-dimethylethylene sebacamide) and low molecular weight model complexes.383 7.2 Dynamics of Polymer Blends - Self-diffusion and T2 measurements have been performed on a series of blends of narrow fraction linear and cyclic polydimethylsiloxane polymers in the melt by pulsed NMR techniques.363 The two components of the segmental dynamics of poly (vinylethylene) (PVE) and polyisoprene (PIP) miscible blends, are resolved and analyzed.364Solid state I3C CP/MAS/DD NMR measurements have been carried out at 300K on melt-mixed blends of poly(ethy1ene oxide)/atactic poly(Me methacrylate) (PEO/a-PMMA) in the concentration range 10/90 to 75/25 and determined TI,H, TI,C, TIH and Dynamic mechanical and solid state 13C NMR analyses have been used to assess molecular scale heterogeneity in a raw elastomer(butadiene-acrylonitrile copolymer elastomer), a microcrystal polymer(PVC), and their 50/50 blend.366'H T I was used to characterize the molecular motions of' PEO chains in compatible PEO(hydrated)/PMMA(deuterated) blends.367 The interpolymer interaction, morphology and chain dynamics of the poly(acry1ic acid)/poly(ethylene oxide) (PAA/PEO) complex are examined by using I3C CP/MAS NMR.368 Relaxation time distribution profiles were obtained for polystyrene/polyethylene, novolak/ phenoxy resin, and hydroxylated polystyrene/poly(Et methacrylate) blends as a means of characterizing the amorphous and crystal domains of the blends.277 Compatibilization of the PBA/PMMA core/shell latex interphase was investigated by solid state 13CN M R 'H TI, measurements.278

7.3 Characterization of Polymer Blends - The structure of the elastomeric ethylene-propylene-diene terpolymer/atactic polypropylene blends was assigned by NMR using DEPT and HETCOR(heteronuc1ear correlation) sequences.369 'H-CRAMPS NMR techniques are used to study the phase structure of complexed and decomplexed blends of poly[(N-ethylcarbazol-3-yl)methyl met hacryla te] and pol y { 2-[(3,5-dinitro benzoy 1)oxylet hyl met hacry late} (mole ratio = l:l).370 Solid state I3C NMR was used to investigate the structure, crystallinity and phase morphology of 1,l -dihydroperfluorooctyl acrylate/Me acrylate copolymer blends.372Solid state 13CNMR spectroscopy involving MAS with and without CP was employed for interaction studies in natural rubber(NR)/EVA and NR/mercapto-modified EVA (EVASH) blends.374Chain packing in neat and modified poly(ethy1ene naphthalene-2,6-dicarboxylate)(PEN), sequence distribution of PEN-co-poly(4- h ydrox ybenzoa te), and their miscibility and transesterification in their blends with polycarbonate and other polyesters were studied via the solid state 13CNMR spectroscopy.375Core-shell latexes with a core of poly(Bu acrylate) (PBuA) and a shell of poly(Me methacrylate) were studied by solid state 13CCP/MAS NMR at different temperatures.376Solid state multipulse proton NMR, wideline deuterium NMR and 2D NMR in solution have been used to study blend formation in resist formulations of novolaks and the radiation-sensitive dissolution inhibitor poly(2-methyl-1-pentene ~ u l f o n e ) . ~ ~ ~ The dynamic mechanical properties, phase and interface of tieblock copolymer

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isoprene/styrene were studied by NMR and mechanical measurement^.^^' Pure gas and hydrocarbon vapor transport properties of blends of two glassy polyacetylene-based polymers, poly( 1-trimethylsilyl- 1-propyne) (PTMSP) and poly( 1-phenyl- 1-propyne) (PPP) have been determined.381 Natural abundance I5N NMR experiments show direct evidence for metal-pyridine interactions in blends of pyridine-containing polyurethanes and metal acetates.382 A blend of Zn-neutralized sulfonated poly(dimethylpheny1ene oxide) with an aminecontaining silicone copolymer was prepared and characterized using dynamic mechanical analysis, DSC and solid state 'H, 13Cand 29SiNMR data.384

8

Cross-Linked Polymers

Influence of y-rays on the morphology of polyethylene was investigated using solid state I3C NMR through TIC, T2C and line width. While crosslinking in the irradiated polyethylene takes place mainly in the noncrystalline regions, distortion and damage to the folded chain of the crystal lattice were observed in the crystalline regions.385 Qualitative and quantitative analysis of branches and crosslinks were studied for photoinitiated crosslinking of low density polyethylene.386 Structure and dynamics of hyper-crosslinked polystyrene were studied by solid state NMR.387*3*8 Unsaturated polyesters derived from maleic anhydride and 2,2-di(4-hydroxypropoxyphenyl)propane were copolymerized with styrene. Their crosslinked structures were analyzed by solid state CPMAS NMR.389 Curing processes were studied for dicyclopentadiene thermosetting resin. Solid state CPMAS NMR measurements were carried out to investigate the structure and dynamics of polymer matrix during curing in rigid and mobile phases.390Curing mechanism of bisphenol A dicyanate ester in the presence of an electrolytically surface treated XAS carbon fiber was studied. The resin forms the symtriazine network structure in the c ~ r n p o s i t e . Arriola ~~' et al. copolymerized 13C labeled crosslinker with acrylic acid under various temperatures, pH and percent solids and determined reactivity ratios and their sensitivity to the variables.392Solid state NMR and fluorescence spectroscopy were used to study the detailed structure of poly(meth)acrylate networks. Both techniques give complementary information. With these techniques information about the mobility of individual atoms and the homogeneity of the polymeric networks is obtained.393 Sotta et al. relate the cross-links to a nonzero average of the homonuclear and heteronuclear dipolar couplings. They presented the way to estimate the degree of crosslinks through the residual dipolar couplings and applied this method to cross-linked poly(styrene-co-butadiene) elastomers.394 Structural change during heating under air and nitrogen was investigated for vulcanized natural rubber.395 Proton relaxation parameters were measured for natural and epoxidized rubbers and a series of vulcanized samples. The obtained relaxation parameters were discussed in terms of the mobility of the various parts of the samples and of their components.396 Single pulse excitation experiments have been applied to highly crosslinked poly(diviny1benzene) resins in order to quantify the various types of carbon atom present.397The multiphase behavior of

3 54

Nuclear Magnetic Resonance

poly( 1,3-dioxolane) in linear and network form as a function of molecular weight and crosslink degree of the sample was investigated.398 Evidence that methyl groups are precursors to certain crosslinks was obtained via a methylene peak of solid NMR spectra for heat treated methyl pendent poly(p-phenylene benzobisthiazole) fibers.399 Selective labeling of polymers with 13C was applied to PMRl5 resin in order to investigate reactions of curing and d e g r a d a t i ~ n . ~ "A .~~~ pyrolysis of crosslinked polymethylhydrosiloxanes under an argon flow has been investigated by 29SiMAS NMR.402

9

Polymer Gels

The existence of the inclusion type polymer-solvent complexes was probed in gels and solids of syndiotactic PMMA, in gels of isotactic PMMA and PVC.403The mechanism of ion transport for polyelectrolyte gels such as calcium alginate was investigated by proton N M R microscopy. The diffusion coefficient of copper in these gels was obtained from NMR data.404Also the absorption of heavy metals by alginate gels was investigated by NMR microscopy. The relaxation mechanism of water protons in the presence of heavy metal ions are discussed.405The effect of pressure on electric conductivity and NMR relaxation behavior were measured for poly(acrylonitri1e) gel. Activation volumes for NMR relaxation and ionic conductivity were discussed in terms of possible effects of the polyacrylonitrile on the ionic solvation The diffusion process of water in swollen and in supercoiled polyacryloamide gels and in polysaccharides agarose gels were measured. Restricted diffusion effects are evidenced in both gels. The results were interpreted in the framework of diffusion model through permeable walls.407 Reiche et al. found a strong correlation between plasticizer mobility and ion diffusion and with ionic conductivity for poly(ethy1ene glycol) dimethylacrylate.m8 2H NMR measurements of deuterated poly(dimethylsi1oxane) elastomers were carried out. The obtained data were compared to the predictions of a model describing elastomer deuterium transverse deplaning data as a linear superposition of contributions from elastic and pendent chains.409Procedures to use the line broadening of the 13C NMR peak for radioactive waste treatment were described by Saidel.410Adsorption properties of polybutadiene on carbon black aggregates are investigated. The gel-like behavior of bridged aggregates was ~bserved.~" Gelation of epoxy resin crosslinked by formation of siloxane bridges from two amino-epoxy-silane were investigated by 29Si NMR.412 Statistical properties of poly(3-n-octylthiophene) gels were investigated above T, and fusion temperatures by varying the crosslink functionality and concentration^.^'^ Evidence of the formation of surfactant micelles inside spherical poly(N-isopropylacrylamide) microgels was obtained by NMR.414The existence of polymer solvent complexes was confirmed from NMR relaxation parameters for syndiotactic PMMA gels in bromobenzene and for PVC gels in di-butyl phthalate or diethyl ~ x a l a t e The . ~ ~structure ~ and formation mechanism of carbon gel in carbon black-filled isoprene rubber composites were investigated by the pulse NMR t e ~ h n i q u e . An ~ ' ~ association between water and the CH proton at the

10: Synthetic Macromolecules

355

volume phase transition was discussed for the crosslinked poly(N-isopropylacrylamide) spherical microgel particle^.^"

10

Liquid Crystalline Polymers

The distribution of the nematic director was determined by 'H NMR for meltprocessed 4-hydroxybenzoic acid-6-hydroxy-2-naphthoicacid c ~ p o l y r n e r s . ~ ' ~ From 'H and 13C NMR relaxation times and spectra, the conformation, molecular motion and morphology of columnar type rigid-rod polyesters which are prepared by polycondensation of 4,4'-dihydroxylbiphenyl with substituted terephthaloyl chloride were d i s c ~ s s e d . ~ The ' ~ ~ ~chain ~ * conformation of the spacer was studied based on the y-gauche effect of 13CNMR chemical shift for thermotropic liquid crystalline polyethers based on 1-(4-hydroxy-4'-biphenyl)-2(4-hydroxypheny1)propane and a , o - d i b r o m ~ a l k a n e s .The ~ ~ ~ structure and dynamics of surfactant molecule reorganization in mesophase silicates were investigated by VT solid state NMR. Evidence for the electrostatic binding between the electropositive end of surfactant and the silicate substrate were pro bed .422

11

Diffusion Measurements for Polymeric Systems

The diffusional Deborah number defined as the ratio of relaxation time to diffusion time was determined as a function of concentration and temperature in the dodecane transport process in polystyrene. Diffusion time and relaxation time were measured by NMR and a dynamic mechanical analyzer, respectively. Correlation between the Deborah number and the transport mechanism was discussed.423Diffusion constants of an imide salt were determined by 19Fand 'Li NMR for poly(oxypropy1ene)-lithium bis(trifluoromethylsu1fonylimide) polymer electrolytes.424Self-diffusion coefficients of polyethylene glycol and HDO in D20 in swollen methylenebisacrylamide-crosslinked poly(N,N-dimethylacrylamide) gels were determined. The diffusion behavior was reasonably explained by the modified free volume theory.425Rheo-NMR methods were used to measure the velocity profiles of the polystyrene solutions in the vicinity of a demixng transition. The obtained velocity profiles were discussed by using the power law fluid The component and concentration dependencies of the selfdiffusion coefficients for a series of star block copolymers of A2B (A: polyisoprene, B:polystyrene) type in solution were measured by NMR. The diffusion coefficients were discussed based on the scaling procedure.427Segmental diffusion in polydimethyl~iloxane~~~ and poly(ethy1eneo~ide)~~~ melts determined by NMR was discussed based on the reputation model. A model was proposed which treats spin diffusion and spin-lattice relaxation in heterogeneous polymers using the same parameters and applied to determine the domain sizes and interfacial thickness in heterogeneous polymers.430

356

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Nuclear Magnetic Resonance

Imaging of Polymers

Imaging techniques are increasingly applied to polymer systems. Several techniques were presented for imaging of polymer systems; spin diffusion,43* magic sandwich echo,432 magic quadrupolar interaction,434 I9F MAS NMR,435and means of incorporating NMR parameters.436 Polymer gels were investigated by imaging techniques in terms of the proton distribution of polyacrylamide h y d r ~ g e l ,motional ~~~ mapping of nanocomposite gels comprising poly(ethy1ene oxide) grafted silica43*and the polymerization process of acrylamide gels.439Aging processes were directly investigated by imaging for natural rubber440 and carbon black-filled natural rubber.441 An anisotropic diffusion of CC14 was observed for samples of injection molded isotactic polypropylene. The highly oriented skin layer is proven to be resistant to solvent penetration.M2 A new class of paramagnetic magnetic resonance imaging contrast agents were developed by copolymerization of EDTA dianhydride and diamine monomers. These polyamides showed the obviously higher relaxation e~ectiveness.~~

13 1

2

3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22

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R. V. Law, D. C. Sherrington, C . E. Snape, Macromolecules, 30,2868-2875 (1997). F. E. DuPrez, E. J. Goethals, P. J. Adriaensens, J. M. Gelan, D. J. M. Vanderzande, Macromolecules, 29,4000-4005 (1 996). M. B. Polk, D. L. Vanderhart, F. E. Arnold, T. D. Dang, J . Polym. Sci., Part B: Polym. Phys., 34,1881-1889 (1996). M. A. B. Meador, J. C. Johnston, A. A. Frimer, P. J. Cavano, Polym. Prepr., 38, 827-828 (1997). M . A. B. Meador, J. C. Johnston, P. J. Cavano, Macromolecules, 30, 515-519 (1 997). R. Kalfat, F. Babonneau, N. Gharbi, H. Zarrouk, J . Muter. Chem., 6, 1673-1678 (1996). J. Spevacek, M. Suchoparek, Macromol. Symp., 114,23-34 (1997). K. Potter, E. W. McFarland, Solid State Nucl. Magn. Reson., 6, 323-331 (1996). N. Nestle, R. Kimmich, Colloids Surf.,A, 115, 141-147 (1996). C. A. Edmondson, M. G. Wintersgill, J. J. Fontanella, F. Gerace, B. Scrosati, S. G. Greenbaum., Solid State Ionics, 85, 173-179 (1996). L. Pavesi, M. Balzarini, Magn. Reson. Imaging, 14,985-987 (1996). A. Reiche, J. Tuebke, K. Siury, B. Sandner, G. Fleischer, S. Wartewig, S. Shashkov, Solid State lonics, 85, 121-127 (1996). K. McLoughlin, C. Szeto, T. M. Duncan, C. Cohen, Macromolecules, 29, 5475-5483 (1996). V. A. Saidel, C. C. Ponta, Prog. ColloidPolym. Sci., 102(Gels), 98-100 (1996). J. P. C. Addad, P. Frebourg, Polymer, 37,4235-4242 (1996). A. Vainrub, F. Devreux, M. Sarkar, P. D. Palasz, A. N. Burgess, J . Sol-Gel Sci., Technol., 6,279-285 (1996). A. Viallat, B. Pepin-Donat, E. Rebourt, Synth. Met., 84, 575-576 (1997). Y. Gao, S. C. F. Au-Yeung, S. Zhou, C. Wu., J . Macromol. Sci., Phys., B36, 417-422 (1997). J. Spevacek, M. Suchoparek, Macromolecules, 30,2178-2181 (1997). N. Kida, M. Ito, F. Yatsuyanagi, H. Kaido, J . Appl. Polym. Sci., 61, 1345-1350 (1 996). C. Wu, S. Zhou, S. C. F. Au-Ueung, S. Jiang, Angew. Makromol. Chem., 240, 123-136 (1996). M. Gentzler, J. A. Reimer, M. M. Denn, Polym. Prepr., 37,764 (1996). M. Guo, H. R. Kricheldorf, Poiym. Prepr., 38,274-275 (1997). M. Guo, H. R. Kricheldorf, Polym, Prepr., 38,276-277 (1997). J. Cheng, S. Z. D. Cheng, Polym. Prepr., 38,794-795 (1997). L.-Q. Wang, J. Liu, G. J. Exarhos, B. C. Bunker, Langmuir, 12,2663-2669 (1996). D. Kim, N. Peppas, Korean J. Chem. Eng., 13, 123-128 (1996). C. Roux, W. Gorecki, J. Y. Sanchez, E. Belorizky, Macromol. Symp., 114, 21 1-216 (1997). S. Matsukawa, I. Ando, Macromolecules, 29,7136-7140 (1996). B. Manz, P. T. Callaghan, Macromolecules, 30, 3309-3316 (1997). S. H. Anastasiadis, K. Chrissopoulou, G. Fytas, G. Fleischer, S. Pispas, M. Pitsikalis, J. W. Mays, N. Hadjichristidis, Macromolecules, 30, 2445-2453 (1997). S. Pahl, G. Fleischer, F. Fujara, B. Geil, Macromolecules, 30, 1414-1418 (1997). E. Fischer, R. Kimmich, N. Fatkullin, J . Chem. Phys , 104,9174-9178 (1996). J. Wang, K. S. Jack, A. L. Natansohn, Polym. Prepr., 38,843-844 (1997). F. Weigand, D. E. Demco, B. Bluemich, H. W. Spiess, J . Magn. Reson., Ser A, 120, 190-200 (1996).

399 400 40 1 402 403 404 405 406 407 408 409 410 41 1 412 41 3 414 41 5 416 417 418 419 420 42 1 422 423 424 425 426 427 428 429 430 43 1

10: Synthetic Macromolecules

432 433 434 435 436 437 438 439 440 44 1 442 443

369

F. Weigand, D. E. Demco, B. Bluemichi, H. W. Spiess, Solid State Nucl. Magn. Reson., 6 , 357-365 (1996). F. Weigand, S. Hafner, H. W. Spiess, J. Magn. Reson., Ser A , 120,201-205 (1996). M. Klinkenberg, P. Bluemler, B. Bluemich, J. Magn. Reson., Ser. A , 119, 197-203 (1 996). C. A . Fyfe, Z. Mei, H. Grondey, Magn. Reson. Imaging, 14,887-889 (1996). M. Hepp, J. B. Miller, Solid State Nucl. Magn. Reson., 6, 367-374 (1996). G. -L. Ding, L. -Y.Li, Y. -R. Du, C. -H. Ye, Magn. Reson. Imaging, 14, 947-948 (1 996). M. E. Brik, J. J. Titman, J. P. Bayle, P. Judeinsteln, J. Polyrn. Sci., Part B: Polym. P ~ Y s .34,2533-2542 , (1996). S. Ahuja, S. L. Dieckman, N. Gopalsami, A. C. Raptis, Macromolecules, 29, 5356-5360 (1996). P. Barth, S. Hafner, Magn. Reson. Imaging, 15, 107-1 12 (1997). M. Knoergen, U. Heuert, H. Schneider, P. Barth and W. Kuhn, Polym. Bull., 38, 101-108 (1997). R. J. Abbott, J. A. Chudek, G. Hunter, L. Squires, J. Muter. Sci. Lett., 15, 1108-lllO(1996). M. Ouyang, R. Zhou, G . Fu, Polyrn. Adv. Technol., 7,671 -674 (1996).

11 Conformational Analysis BY J. R. P. ARNOLD AND J. FISHER

1

Introduction

Here we survey reports concerned with conformational analysis using NMR methods. The main inputs to experimental data for structural analysis are generally chemical shifts, scalar couplings and nuclear relaxation. With the increasing availability of significant computing power and user-friendly software, detailed conformational analyses are becoming routine. We start this review therefore by looking a t developments in methodology some of which are likely to extend even further the scope of such studies. This is followed by a review of general examples of conformational analysis in small organic molecules, nucleosides and nucleotides, carbohydrates and organometallics. The corresponding sections are not necessarily exclusive or inclusive, but serve to present the main broad categories of conformational analysis as it is currently being performed. The determination of the solution structures of large biomolecules, such as proteins, polypeptides and oligonucleotides represent a special type of conformational analysis, which we do not explore in this particular review.

2

Methods

The shielding effects of the carbonyl group have been used in chemical shift simulations to define the major conformer in a metacyclophane-dione system.’ Contributions of ring currents, with solvent and intramolecular electrostatics, have been included in calculations of chemical shifts in an RNA stem-loop, to reveal how the shifts evolve during a long molecular dynamics run.2 Subpicosecond fluctuations were observed in the shifts, mostly attributable to internal electrostatics and ribose pucker changes. Isotope-induced changes in chemical shift are not often used in conformational analysis, mainly because they can be difficult to interpret. Deuterium-induced shifts of hydroxyl * H signals due to intramolecular hydrogen bonds in rigid 1,3diols3 have been found to be relatively large, providing an opportunity for exploring the origins of isotope shifts and calibration of earlier measurements from conformationally mobile systems. Scalar coupling constants are generally the most important experimental data in ‘traditional’ conformational analysis, provided that they are adequately parameterised. For such purposes, rigid systems are often used to distinguish Nuclear Magnetic Resonance, Volume 27 0The Royal Society of Chemistry 1998 370

37 1

11: Conformational Analysis

substituent effects from angular ones. Thus in a series of bridgehead substituted bicyclo[ 1.1 .I]pentanes, a 3Jc-H dependence on the substituent electronegativity was e ~ i d e n tAngular .~ dependence and substituent effects have been investigated in vicinal I9F-'H couplings5; calculations using ab initio methods have been compared with experimental data and the relative importance of the various terms in the parameterisation assessed. The effects of p hydrogens on vicinal 'H-'H couplings have also been explored using ab initio calculations,6 and the fl effect is evidently considerably complex. I3C-labelled proteins offer a considerable number of scalar couplings which have angular dependence, and extraction of accurate 3J1HN-ct) and values from spectra generated by a new heteronuclear relayed E.COSY experiment has been d e m ~ n s t r a t e d . ~ Further refinement of nOe-based biomolecular structural calculations, involving groups of equivalent and non-stereo assigned diastereotopic protons, has been presented,' with discussion of the relative merits of 'r-6 averaging' versus 'r-6 summation' treatments. As so often, much depends on how well the overall structure is defined by the nOe data. Molecular dynamics calculations are increasingly being applied to conformational studies, and this requires the availability of reliable force fields. A new force field has been derived for alkyl chlorides' for use in MM3 calculations, presented with comparisons with experimental measurements. MM3 parameter improvement has also been demonstrated in trans-1,2-disubstituted cyclohexyl derivatives. l o Allowance for the effects of external perturbations on molecular dynamics-derived structures has been explored' an electrostatic perturbation of a porin protein offers a possible mechansim for pore closure. Conformational characterisation of 5-membered rings by analysis of NMR data using a continuous probability distributionI2 has been demonstrated, showing greater computational efficiency than previous procedures. 3J(H~-ct)

';

3

General

In this section studies in which the conformation of small molecules, mainly organic but with many examples from inorganic chemistry, have been investigated are covered. These studies have involved, for example, the monitoring of chemical shifts and resonance linewidths as temperature is varied, the measurement of homo- and heteronuclear coupling constants, the simulation of NMR spectra and molecular modelling.

3.1 Rotation About Single Bonds - The solution and solid state properties of (2- hydroxypenty1)diphenylphosphine oxide and its acetate have been determined It is clear that the conformational by NMR and X-ray ~rystallography.'~ preferences of these molecules differ with physical state and this is rationalised by the hydrogen bonding potential in each state. In measuring vicinal proton-proton coupling constants it has been established that the preferred solution conformation is not the expected all staggered arrangement but the twisted staggered conformer. The populations of the different conformational states have been

372

Nuclear Magnetic Resonance

found to be strongly dependent on the polarity of the solvent. The same authors have in a similar study investigated the conformational preferences of a range of hydroxyalkyl phosphonates and carboxylic ester derivatives thereof in solvents of different polarities and in the presence of specific metal ions; Li+, N a + , Zn2+.I4 In C6D6 and CDC13 the most stable conformer was (ga) with the phosphoryl group gauche to the hydroxy group and anti to the alkyl group. In more polar solvents the population of the less stable (ag) conformer in which the phosphoryl group is anti to the hydroxy is increased. This information was derived by the measurement of vicinal proton-proton coupling constants, and phosphorouscarbon coupling constants. The ease of rotation about bonds connected to furan ring^'^>'^ has been analysed by measurement of nOe effects, specific long range couplings and lineshape analysis. l 6 A series of methylated glutamic acids which are agonists at glutamate receptors have been studied.17 The conformations generated from 'H and 13Canalyses may be grouped according to the distance between the amino and carboxylic acid, or two carboxylic acid groups and the two backbone torsion angles. Keto- and thioketo- (thio)enol tautomerism has been studied using deuterium solvent changes2' and 1 7 0 chemical shifts." induced

3.2 Six-Membered Rings - As might be expected there have been a large number of investigations of six membered rings. Many of these have been of all carbon (ring) system^,'^-^' but there have also been a significant number of nitrogen32--43,58 and ~ x y g e n ~ ~containing -~' systems, and also several phosp h o r o ~ s , ~and ~ , sulfur4' ~' containing six membered rings studied. Molecular orbital calculations have been used to corroborate NMR studies which showed that both axial and equatorial 1-methyl-1-cyclohexyl cations exist in chair conformations.22 The NMR investigations involved recording spectra in super acids and at low temperature. Variable temperature and variable solvent experiments have been used to probe the conformational preferences of trans-2fluorocyclohexanol.23 Direct integration and proton-proton vicinal coupling analysis have enabled the proportions of axial-axial and equatorial-equatorial conformers to be determined under different conditions. A series of fused carbon containing 6-membered rings have been investigated. These include decalones,26 and dihydroanthracene.27 Proton and 3C NMR studies of three diastereoisomers of 3-amino-2-decalones have enabled the conformation of the rings to be determined and have established that the amino group (or BOC protected amino group) is equatorial in all isomers.26 A boat conformation has been established for the central ring of 9-( 1 -amino-2,2dimethylpropyl)-9,1O-dihydroanthracenefrom NMR and MM3 studies. This anthracene derivative has been shown to have the potential for use as a chiral solvating agent.27 - ~ ~ 'quinolines ~' and Substi tu ted p i p e r i d i n e ~ , ~ * >d~i h~y. ~d *r ~ p y r i d i n e s ~ ~and related corn pound^^^-^^ have been studied using 'H and 13C NMR in order to determine conformational preferences in these for both substituents and the ring. The conformation of ethyl and isopropyl groups at the 3 position of 4-

'

I ] : Conformational Analysis

373

hydroxypiperidines have been established by measuring the upfield shift observed . ~ ~ orientational at the C2 and C4 positions relative to the methyl d e r i ~ a t i v eThe preferences of the N-substituent of a range N-(phenylcarbamoyl)piperidin-4-ones have been determined by 'H NMR and supported by X-ray crystallographic studies.33 The phenylcarbamoyl moiety has been shown to be coplanar with respect to the piperidone ring. When the piperidone ring is symmetrically substituted it is found to have a 'sofa' conformation but this becomes a twistboat when the symmetry is broken. A calcium channel agonist, 4-isoxazolyl-1,4-dihydropyridine, has been analysed via a combination of variable temperature 'H and nOe experiment^^^ supported by AM1 calculations. Ring and nitrogen inversion have been implicated to account for the conforma13C chemical shift tional equilibria of 3-phenyl-l ,2,3,4-tetrahydroi~oquinolines.~~ measurement and prediction has enabled this analysis. A series of 1-hetera-2,6-diphenylcyclohexan-4-one oximes have been studied by 'H NMR.45Coupling constant analysis has indicated that when the 2,6 diphenyl groups are cis the ring adopts predominantly a chair conformation. The boat conformation becomes more significant when the phenyl groups are trans. The chair/twist-boat equilibrium has been investigated for trans-4-(trifluoromethy1)-2,2,6-trimethyl-1,3-dioxanevia a combination of 3C chemical shift measurement and molecular mechanics calculation^.^^ The predicted chair to twist-boat equilibrium predicted by MM3 calculations was found, as in previous studies, not to be consistent with experimental data. Variable temperature 'H, 31Pand 1H{3'P}NMR experiments and semiempirical calulations have been employed to analyse the conformation of cis- and trans-3(methoxy-carbonyl)-2-methoxy-2-oxo1,2-0xaphosphorinane.~~The "P spectra for each isomer showed no variation with temperature but the 'H spectra suggested some significant changes for the cis isomer but none for the trans isomer.

'

3.3 Other Ring Systems - The conformational consequences for having cyclopropane like rings fused on to larger rings have been investigated in a number of Four bond H-'H couplings between cyclopropyl hydrogens and non-cyclopropyl hydrogens have been calculated by semiempirical methods, for model compounds, in order to help assign the spectra of 17,18cyclosteroids. 52 The four bond couplings follow an angular dependence reminiscent of allylic couplings. The conformation of the epoxypropyl side chain of asperlin has been determined by a combination of 2D nOe experiments and molecular modelling procedure^.^^ An analysis of vicinal coupling constants has established that this molecule does not adopt a single conformation. T e t r a ~ h e n y Ialkylph~sphonate,'~ ,~~ and N-nitropyrrolidine~~~ have all been the subject of conformational analysis investigations. MM2 and MM3 calculations together with nOe and low temperature 'H NMR experiments have indicated significant conformational flexibility in the diastereoisomers of tetraphenylpyrrolidine studied. The data supports the presence of both envelope and twist conformers. The results of ab initio calculations have been found in agreement with those of CD and 'H N M R investigations of N-nitropyrrolidine and its 2-

'

374

Nuclear Magnetic Resonance

methyl and 2,Sdimethyl derivative^.^^ The latter compound has both nitrogens planar in the ground state whilst those of the first named compound are pyrimidal. In each case however a twisting of the nitroamino group about the NN bond is observed. Natural and modified nucleosides and nucleotides continue to attract attention.60-63Considerable effort is being made in the preparation and analysis of modified sugar60-62and base63 moieties. The furanose ring has been modified by incorporating 3C at the C2' position for conformational studies utilising both 'H-I3C and 13C-13C coupling constants, of deoxyadenosine, cytidine and thymidine.61 The consequences for sugar puckering of a 2'OH and 3' deoxy modification have been studied6' with the conclusion that the dominant conformation is north (N). The conformation of 7-iodo-2'-deoxytubercidin has been determined and compared with related compounds 2'-deoxytubercidin, and 2'deoxyadenosine.63 The conformations are closely related and the glycosidic torsion angle is anti in all cases. Seven,64eight,65p68nine,69 ten,70 e l e ~ e n ~ land > ~ t* ~ e l v emembered ~ ~ ' ~ ~ rings of a wide range of compositions have been the subject of conformational analyses. A diazacyclooctane and its Bis-BH3 adduct has been studied using 'H and 13C NMR and molecular mechanics calculation^.^^ It is clear that even at very low temperatures the major conformational class of this compound is twist-chairchair rapidly interconverting via the chair-chair, with the minor form most likely a set of twist-boat-boats. This finding led to conclusions to be drawn regarding the binding of Bis-BH3. The conformation of two rather unusual but related eight-membered rings has been determined by variable temperature 'H and "P{ 'H) NMR experiment^.^^?^* The eight membered ring of 12H-dibenzo[d,g][1,3,2]dio~agerrnocin~~ and 12Hdibenzo[d,g][1,3,2]dioxaphosphocins6*have been found to exist in a boat-chair conformation both in solution and solid state, the free energy of activation for ring inversion of the germanium compound being 55.6 kJ mol-'.67

'

Clusters - A number of ~ a l i ~ [ and 4 ]c a~l i ~x [ 6~ ] a~r e~n e~~ have ~~~ >~~been ~ investigated. A two step synthesis of tetramethoxy calix[4]arenes has been reported together with the 'H NMR analysis of these compound^.'^ In C6D6 solution there is a shift in the calixarene conformational equilibrium from 96/4 conelcone mixture exclusively to the cone conformer. This is a clear indication that a well-defined calixarene cavity can been formed from flexible precursors. The dynamics of phosphorylated p-tert-butylcalix[6]arenes have been probed by ' H and 31P 2D NMR experiment^.^^ When the calixarene is monophosphorylated (or thiophosphorylated) the calixarene skeleton is rigid, the disubstituted equivalents are less so. The disubstituted calixarenes appear to be involved in at least three dynamic processes; macrocyclic ring inversion, hydrogen bond array reversal, and pinched conformer interconversion. The free energy of activation for each of these events has been estimated. The stability of four conformers of tetraacetoxy-p-tert-butylcalixarene in dimethylsulfoxide solution has been established by variable temperature H NMR.77At high temperature the cone conformation is the most unstable. 3.4

11: Conformational Analysis

375

Table 11.1 Examples of molecules f o r which conformations have been determined using N M R Compound

Comments

(2-hydroxypenty1)diphenylphosphine oxide Dialkyl(2-hydroxyalky1)phosphonates 4-(2-furyl)-2-(methylamino) pyrimidine Furan and thiophene o-amino thioaldehdyes Methylated glutamic acids Anils of salicylaldehydes

'JHH,

MM, H-bonding dominant

Metal binding, solvent effects 'H, PM3, MD, hindered rot. about C-N bond 'H, 13C,nOe, stereospecific5J lineshape analysis 'H, I3C, shift calc. "C Deuterium induced shifts. Taut omerism Tautomerism. I3C shift calc. 170shifts P-ketoamides, P-ketothioamides Deuterium induced "C shifts Triphen ylethenethiol Tautomerism. 'H in DMSO 4,1O-di-tertbutyl-5,9-diisopropyl-4,5,9, MM2, AMI, I3C to determine 19-tetraazatetracyclo rotamer populations [6.2.2.2.3,6]tetradecane 1-methyl- 1-cyclohexyl cation GIAO-MP2/DZPDZ computed I3Cchemical shifts. Hyperconjugation analysed in chair trans-2-fluorocyclohexanol 'H, I3C, conformer populations in range of solvents. AG, AH, AS compared with MP2 calcs silyl-cyclohexane MP4/MP2 calcs. for energy diff. axial-equatorial. Energies comp. with NMR results trans-4-substituted cyclohexene oxides 'H, axial conformer dominates 3-amino-2-decalones 'H, 13C.Ring junction cis 9-(1-amino-2,2-dimethylpropyl)'H, "C, MM3 9,lO-dihydroanthracene Cyclic glutamic acid analogues 'H, I3C, Mol. dynamics a-methylglutamic acid and 'H,"C, Ca conf. preferred in aq. sol. a-cyclicglutamic acid ' W between amino and COOAbscisic acid analogues COSY, nOe, chair and twisted boat identified for isomers Monterine and Granjine 'H, nOe, dynamic NMR 'JHH. Free energy of activation by NMR CP-55,940 -cannabinoid Intramol. H-bond detected in full receptor ligand conf. analysis 3-ethyl- and 3-isopropyl-4I3C alkyl group conf. deduced hydrox ypiperidines 'H, I3C,orientation of phenylcarbamoyl N-(phenylcarbamoyl)piperidin-4-ones determination 'H,'3C,15N, Conf. of benzoxamine Ofloxacin and piperazinyl ring determination 'H of model NADH compds. N-substitued (S)-3-(p-tolylsulfiny1)-1,4 -dihydropyridines I3C chem. shifts pyrimidine ring Thymidine-radiation damage products for conf. analysis 'H VT. chair/boat analysis [3.3lcyclophanes 'H VT, nOe. AM1 calc. Rotational 4-isoxazolyl-1,4-dihydropyridine energy barriers higher than calc.

ReJ

13 14 15

16 17 18 19 20 21 22 23 24 25 26 27

29 28 30 40

31 32 33 42

35 36 41 34

376

Nuclear Magnetic Resonance

Table 11.1 Examples of molecules for which conformations have been determined using N M R (contd) Compound

Comments

Ref.

Quinidine

MM, AM1 agree with 2 sol. state conformers 13Cchemshifts calc. MM 'H,''C, COSY, HETCOR. 'J show trans geom. 'H, 13C,NOESY, full conf. analysis

37

I3Cchem. shifts calc., MM3, MP2

46

3JHHshow folded conf. 95% populations 'Hof bicyclic lactam 'H, nOe, sel. decoup., D-isotope effect on "c. Spectral simul. 'H, 13C,3JCH. Envelope stable conf.

44 47 48

31P,'H, 'H{31P),VT. cis isomer conf. temp. depend 'H, chair-chair equilib. monitored D20sol., 'H VT, NOESY. Chem. shifts, 'J su gest half-chair for one ring. 4JHH, I%, noe ~. ring has 6S,7R in c ~ D Oxirane configuration nOe, MM2, MM3, AMI, PM3, VT 'H, I3C, MM2

43

'H Chair-chair interconv. energy barrier det. by NMR

56 59

1,2,3,4-tetrahydroisoquinolines 2-aryl-frans-decahydroquinolin-4ones 1-X-2,6-diphenylcyclohexan4-one;

x= 0,s

tran~-4-(trifluoromethyl)-2,2,6trimethyl-l,3-dioxane Heptan- 1,3,5,7-tetrol-diacetonides Leu-enkephalin analogue Thioamide cannabinoids (4R,5R)-4,5-bis(alkylcarbamoyl)1,3 -dioxolanes cis- and trans-3-methoxy-carbonyl-2methoxy-2-0x0- 1,2-oxaphosphorinane 3-substituted- 1,3,2-oxaphosphorinanes Daunomycin

17,18-cyclosteroids Asperlin 2,3,4,5-tetraphenyl pyrrolidines dialkyl(2,5-dialkypyrrolidin-2-y1) phosphonates N-nitropyrrolidines dibenzo[a,e]cycloocta-1,Sdiene; 5,6,12,13-tetrabispyrazolo[1,2-a:1',2'-el [ 1,2,5,6]tetraazocinediium dihalides 3'-deox yribonucleosides 2'-13C labelled deoxyribonucleosides

'H, nOe. North conformer dominates 13C-'H, I3C-l3cCOUphgS. 3 J ~ ~ / PSEUROT analysis (S,S)-isodideoxyadenosine 'H, 1D, 2D, pseudorotational params. conf. about glycosidic, anti 7-iodo-2'-deoxytubercidin 'H, aq. sol. Pucker and glycosidic torsion angle determination 7-membered lactam dipeptide mimics 'H, mol. modelling 1,3,3,5,7,7-hexamethy1-1,5'H, I3C, VT. Free energy of activation diazacyclooctane/Bis-BH' adduct for twist-chair-chair to chair-chair intercon. Cyclooctanone-3,3-d2 Isotope effects in 13Cto estim. effect of heavy atom on boat-chair conformation 12H-dibenzo[d,g][1,3,2]dioxagermocin 'H VT. Boat-chair in sol. and solid 12H-dibenzo[d,g]1,3,2]dioxaphosphocins "P{ 'H} VT, boat-chair 1,2,6,7-tetrahydro-4H-3,5'H, I3C VT. Ring inversion and benzo-dioxonin racemisation expl. NMR results (hydroxynitrory1)decanol-acetoneTi salt 'H, 13C,TOCSY, HSQC, HMBC, show Ti complexation

38 39 45

49

51 50 52 53

54 55

60 61 62 63 64 65

66 67 68 69

70

11: Conformational Analysis

377

Table 11.1 Examples of molecules for which conformations have been determined using N M R (contd) Compound ~~

Comments

Rex

'H, X-ray

71

~

dibenzo[c,h]bicyclo[4.4.llundecanes; with disub. cyclopropanes 1-azacyclododecan-2-one cis,cis,trans-1,5,9-~yclododecatriene Tetramethoxy calix[4]arenes

'H, I3C. VT. trans isomer only H. Rapid exchange 'H in C6D6to determ % cone conformation 'H VT. C2v sym. at room temperature Calix[cj]arene; aniline bridge Phosphorylated p-tert-butylcalix[6]arenes IH, 31P,2D. Free energy for macrocyclic ring interconv. measured Tetraacetoxy-p-tert-butylcalix[4]arene H in DMSO. VT. Not flexible at room temperature [ 1.2.1.2]( 1,3)Naphthalenophanes 'H. Mobile but 1,2-alternate of naphthalenes preferred Calix[4]resorcinarenes H, interconversions between cones, metal binding location bis(benzo-crown ethers) - K + binding H, "C for conf. change of complexes 18-crown-5;Ammonium ions Conf. from nOe. No change of complex Cyclodextrins; phenyl and adamantyl 'H, D20. nOe. Free energy of binding inclusion from NMR Naphthafurophanes IH, preliminary conformation Deformylgeissoschizine 'H. 2,3-diphenyl-l,3-thiazolidin-4-ones 'H, I3C, chem. shift comparisons

'

'

' '

72 73 74 75 76 77 78 79 80 81 82 83 58 57

Metal binding studies have been performed for four calix[4]resorcinarene esters and two calix[4]resorcinarene amides." Dynamic NMR experiments have indicated that metal cations bind in syn fashion using two pairs of binding sites which are separated across the macrocyclic ring. The binding of potassium ions to bis(benzo-crown ether) derivatives has also been studied by NMR." The crown ethers were linked by NH(CH2), - NH chains where n = 2-6,8 or 10. The complexation of alkali and ammonium cations with 18-crown-5 have been analysed with the aid of nOe experiments." No significant change in conformation is observed on cation binding.

4

Restricted Mobility

'H spectra of (But)3CH and (But)3COH at - 150 "C show signals for each of the methyl groups, and one of these is split into 3 equal components ranging over 1 ppm.*' This shows that one of the methyl groups is rotating slowly on the NMR timescale, with a barrier to 120" rotation of 22.2 kJ mol-'. Hindered rotation is very obvious in the ethane system 2,2,2',2'-tetramethyl-l,1 '-biindanyls6 in a study which used scalar coupling, chemical shifts, lineshape analysis and energy calculations. The racemic form crystallises into a conformation consistent with STO-3G and AM1 calculations but not MM3, and this is also the major species in solution, whilst the meso-isomer shows slow exchange between two enantio-

378

Nuclear Magnetic Resonance

meric conformers. Barriers to rotations around N-Ar and N-C, bonds in 4,6-bisand 2,4,6-tris-(N,N-dialkylamino)-s-triazineshave been reported.87 Hindered rotation around the aryl-naphthalene bonds in arylnapthalene lignans potentially gives rise to separable rotational enantiomers, but measured barriers of 16.9 to 21.5 kJ mol-' for this rotation mean half-lives of less than 10 min for the individual atropisomers.88 An unusual example of the effect of hydrostatic pressure on conformational behaviour has been given by a study of cis-1,12-diacetoxy [ 12]para~yclophanes.~~ The logarithm of the rate of internal rotation (i.e. of the aromatic ring) was found to be proportional to the applied pressure, up to the apparatus limit of 300 MPa. From this, AV* is negative so that the partial molar volume of the transition state is actually smaller than that of the ground state. Nitrogen inversion and N - 0 bond rotation has been scrutinised in a series of acyclic di- and tri- substituted hydroxylamine~.~~ A N-benzyl group with an ortho hydroxyl group increases the barrier to N inversion by 10 kJ mol. - This is indicative of the breaking of the intramolecular hydrogen bond required for inversion to proceed. The role of strain in the rates of nitrogen inversion in polycyclic tertiary amines has been studied." A strain-related parameter was used in MM3 calculations, to show significant deviations from calculated values for the inversion rates in some azabicycles. This was attributed to orbital effects. Hindered rotation of the phenyl group in the Diels-Alder adduct of phencyclone with N-n-pr~pylmaleirnide'~>~~ has been noted. In enaminonitriles derived from aliphatic amines, the barrier to rotation about the C,i,,I-NH bond was found to higher than in those derived from aromatic a m i n e ~ Rotational .~~ barriers about the exocyclic C-N bond in 2-aryl-substituted 4-(N,N-dimethylaminomethylene)-2-oxazolin-5-oneshave been examined,95 the barrier heights showing a correlation with the Hammet o-constant of p-substituents of the 2-aryl ring. A significant barrier to amide rotation of 64.4 kJ mol-' has been determined in a 1-a~yl-2,3-dihydroazepine.~~ In a dibenzo[c,h][1,6]-diazecine, a rotational barrier of 43.5 kJ mol-' for the exocyclic N-S bond has been mea~ured,~' attributed to steric hinderance with no contribution from N-inversion. Unusually low N-N rotational barriers have been found in N-nitroso-2,4-diaryl3-azabicyclo[3.3.l]nonan-9-ones,due to significant deviation from planarity of the nitrosamino system.98 In a diterpenoid carboamide, restricted rotation around the C-CONEt2 and C-N bonds has been noted.99 The rotational barrier for the Ar-C(0)But bond in a disubstituted acyl durene is high enough to allow chromatographic separation of the configurational isomers."' Solvation effects on conformation and rotational barriers have been investigated in fluorinated compounds using 19F NMR and various computational methods. 101,102

'

5

Nucleosides and Nucleotides

The determination of sugar puckers in larger unlabelled oligonucleotides has been discu~sed.''~The use of uniform 13C/'5N-labelling, as in RNA in recent

11: Conformational Analysis

379

years, provides many more conformationally informative scalar couplings. '04 This can mean a better description of the conformation, and derivation of improved Karplus equations. A computational algorithm for the analysis of pseudorotation in furanose rings has been presented. ' 0 5 Modified nucleosides and nucleotides are important subjects for investigation, since physiologically useful data can result, and such compounds have potential therapeutic use. The solution conformation of 5-fluorocytidine has been reported.'06 A bicyclodeoxynucleoside has been synthesised and its restricted conformational flexibility demonstrated. '07 Glycosidic bond angle preferences in a series of purine-like C-nucleosides have been explored. log Diribonucleoside monophosphate analogues containing phosphonate linkages have been found to be conformationally similar to their natural counterparts. '09 The minor but naturally-occurring nucleotide dihydrouridine has been shown to adopt the 2'-endo conformation, just as it is observed to adopt in tRNA.'" The conformational behaviour of another minor tRNA nucleotide, 5-methylaminomethyluridine, has also been investigated.' Nucleic acids themselves are targets for a number of both therapeutic and carcinogenic agents. A dinuclear platinum complex forms an adduct with d(GpG) which has novel orientations for the bases.' l 2 The potent carcinogen dibenzo[a,l]pyrene forms an adduct with A bases, the conformational behaviour of which has been investigated.Il3

''

6

Carbohydrates

Heteronuclear 3D gradient assisted NMR techniques have been developed for the assignment of signals of exchangeable protons in uniformly I3C-labelled oligosaccharides. l4 The extra conformational information that these can provide is illustrated by a disaccharide which has considerable internal motion. Using more traditional NMR techniques, exchangeable protons have provided conformational information for a tetrasaccharide system GAl which has long hydrocarbon attachments. The conformational behaviour of 2-deoxy-2-fluoro-D-ribose has been found to be similar to that of D-ribose.'16 Conformational analysis has been carried out on a galabioside and its thio glycoside analogue^."^ A folded conformation in DMSO solution has been found in an acylated flavonon glucohammoside,"8 due to intramolecular hydrophobic interactions. Conformational preferences in sugar thioureas have been noted.' I9?l2O A reverse anomeric effect has been investigated in an N-glycosylimidazole,'*' which is attributed to a small intramolecular electrostatic effect on N-protonation. The effect of this is highly dependent on the polarity of the solvent. Solvent effects have also been investigated in the conformations of a series of monosaccharides.' 22 The flexibility of glycosidic linkages has been i n ~ e s t i g a t e d , ' ~ since ~-'~~ this has important consequences for the overall conformation of an oligosaccharide. 13C and 'H relaxation has been applied to the characterisation of dynamic behaviour in carbohydrates.'26 Other carbohydrate systems subject to detailed conformational analysis

'

'"

380

Nuclear Magnetic Resonance

include mono-glycosylated 3-N-alkyl~atechols,'~~ novel 1,3-oxazacyclophosphamides, 12' glyc~amidines,'~~ a heparin-derived tetrasaccharide,' 30 myo-inositol methyl P-C-lactoside,133 phosphates,13' 2:4,5di-O-isopropylidene-myo-inositol,'32 methyl a-L-arabinopyran~sides,'~~ mann~amidines,'~' N-acylglucosamine derivatives of sialyl Lewis X,'36 derivatives of N-acetyl-D-allosamine and -D-gluc~samine'~'and rhamnose oligosaccharides.'38 7

Conformational Analysis of Bound Ligands

Most of the studies cited in this review concern the conformations of molecules which are in free solutions. However, for molecules which become bound to target sites (e.g enzyme co-factors, substrates and inhibitors) the solution conformation may not necessarily correspond to the bound one. Hence the conformation of a bound state is often of great interest, and may hold important clues to the specificity of binding. Various NMR methods can be used, depending on the strength of the binding and the rates of exchange involved. Thus the NMR signals of the bound ligand may be analysed indirectly (e.g. by transferred nOe) or directly (as in a tightly-bound complex). The conformation of coenzyme A bound to chloramphenicol acetyltransf e r a ~ e 'has ~ ~ been determined using nOe methods. The conformation and tautomeric forms of folate bound to L. cusei dihydrofolate reductase have been studied using 13Cchemical shifts.'40Conformations of aminoglycoside antibiotics bound to aminoglycoside 3'-pho~photransferase'~' and 16s ribosomal RNA'42 have been reported. Blood group A trisaccharide bound to Dolichos biflorus adopts a single conformation, whilst the free form has two families of low-energy conformers. Different conformers of C-lactose and 0-lactose have been identified bound to ricin-B.'&

8

Organometallic Compounds

Intramolecular hydrogen bonding has been invoked to cause the adoption of ordered conformations in bis(amino acid) derivatives of 1,l'-ferrocenedicarboxylic acid.'45 Aromatic-aromatic interactions between ligands in Cu(1) complexes of diimines derived from 1,2-diaminocyclohexane and substituted benzaldehydes have been implicated in the structure and catalytic function.'& Restricted rotation has been noted about P-C and Pd-P bonds in palladium tris(o-toly1)phosphinemonoamine complexes.147 A pyrazolyl-bridged iridium dimer shows a slow ring inversion which interconverts two diastereomeric forms.'48 A series of dppm-bridged complexes of platinum(I1) with Au(I), Ag(1) and Hg(I1) centres have been synthesised and characterised. At ambient temperatures the complexes have static structures, but become fluxional at higher temperadissociation of chloride is implicated in this. t u r e ~ .A' ~reversible ~

I I : Conformational Analysis

38 1

Conformational exchange in the newly synthesised cis-PtCl*[1,l ’-bis(undeceny1se1eno)ferrocenel has been characterised. 50 A ckno wledgements We would like to thank the Wellcome Trust for personal support to JRPA.

9 1 2

3 4

9 10 11 12 13 14 15 16

17

18 19 20 21 22 23 24 25 26 27

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382 28 29 30 31 32 33 34 35 36 37 38 39 40 41

42 43 44 45 46 47 48 49 50 51 52 53 54 55 56

Nuclear Magnetic Resonance

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11: Conformational Analysis

57

58 59

60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80

81 82 83 84

85 86

383

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384

Nuclear Magnetic Resonance

87

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88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 I07 108 109 110

111 112 113 114 115 116

117 118 119 120

11: Conformational Analysis

121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144

145 146 147 148 149 150

385

A. R. Vaino, S. S. C. Chan, W. A. Szarek, and G. R. J. Thatcher, J. Org. Chem., 1996,61,4514. P. Hobley, 0. Howarth, and R. N. Ibbett, Magn. Reson. Chem., 1996,34,755. B. J. Hardy, A. Gutierrez, K. Lesiak, E. Seidl, and G. Widmalm, J. Phys. Chem., 1996,100,9187. S. Koepper and B. Meyer, Liebigs Ann., 1996, 1131. A. Poveda, J. L. Asensio, M. Martin-Pastor, and J. Jimenez-Barbero, Chem. Commun., 1996,421. L. Maeler, G. Widmalm, and J. Kowalewski, J. Phys. Chem., 1996, 100, 17103. S. Mabic and J-P. Lepoittevin, J. Carbohydr. Chem., 1996, 15, 1051. T. Oshikawa, M. Yamashita, K. Mitsuji, K. Kaneoka, T. Usui, N. Osakabe, C. Takahashi, and K. Seo, Heterocycl. Commun., 1996,2,261. M. Avalos, R. Babiano, P. Cintas, C. J. Duran, J. L. Jimenez, and J. C. Palacios, Tetrahedron, 1996,52,9263. D. Mikhailov, K. H. Mayo, I. R. Vlahov, T. Toida, A. Pervin, and R. J. Lindhardt, Biochem. J., 1996,318, 93. L. G. Barrientos and P. P. N. Murthy, Carbohydr. Res., 1996,296,39. S. J. Lee, S. J. Cho, K. S. Oh, C. Cui, Y. Ryu, Y-T. Chang, K. S. Kim, and S-K. Chung, J . Phys. Chem., 1996,100, 10111. G. Rubinstenn, P. Sinaye, and P. Berrhault, J . Phys. Chem. A, 1997,101,2536. R. Lanzetta, M. Parrilli, C. Garzillo, A. di Matteo, and G. del Re, J. Chem. SOC., Perkin Trans. 2, 1996, 505. Y. Bleriot, A. Genre-Grandpierre, A. Imberty, and C. Telier, J . Carbohydr. Chem., 1996, 15,985. J. Y. Ramphal, M. Hiroshige, B. Lou, J. J. Gaudino, M. Hayashi, M. S. Chen, L. C. Chiang, F. C. A, Gaeta, and S. A. DeFrees, J. Med. Chem., 1996,39, 1357. P. Fowler, B. Bernet, and A. Vasella, Helv. Chim. Acta, 1996,79,269. B. J. Hardy, S. Bystricky, P. Kovac, and G. Widmalm, Biopolymers, 1997,41,83. I. L. Barsukov, L-Y. Lian, J. Ellis, K-H. Sze, W. V. Shaw, and G. C. K. Roberts, J. Mol. Biol., 1996,262, 543. B. Birdsall, M. G. Casarotto, H. T. A. Cheung, J. Basran, G. C. K. Roberts, and J. Feeney, FEBS Lett., 1997,402, 157. J. R. Cox and E. H. Serpersu, Biochemistry, 1997,36,2353. D. Fourmy, M. I. Recht, S. C. Blanchard, and J. D. Puglisi, Science, 1996,274, 1367. F. Casset, T. Peters, M. Etzler, E. Korchagina, N. Nifantev, S. Perez, and A. Imberty, Eur. J. Biochem., 1996, 239, 710. J-F. Espinosa, F. J. Canada, J. L. Asensio, M. Martin-Pastor, H. Dietrich, M. Martin-Lomas, R. R. Schmidt, and J. Jimenez-Barbero, J. Am. Chem. SOC., 1996,118,10862. R. S . Herrick, R. M. Jarret, T. P. Curran, D. R. Dragoli, M. B. Flaherty, S. E. Lindyberg, R. A. Slate, and L. C. Thornton, Tetrahedron Lett., 1996,37, 5289. R. W. Quan, 2.Li, and E. N. Jacobsen, J . Am. Chem. SOC.,1996,118,8156. R. A. Widenhoefer, H. A. Zhong, and S. L. Buchwald, Organometallics, 1996, 15, 2745. G. W. Bushnell, D. 0. K. Fjeldsted, S. R. Stobart, and J. Wang, Organometallics, 1996,15,3785. C. Xu, G. K. Anderson, L. Brammer, J. Braddock-Wilking, and N. P. Rath, Organometallics, 1996, 15,3792. X-A. Mao, J-Z. Yao, B-S. Tian, and Y-Y. Chen, Magn. Reson. Chem., 1996,34,109.

12 Nuclear Magnetic Resonance Spectroscopy of Living Systems BY M. J.W. PRIOR

1

Reviews and New Methodology

1.1 General Applications - The history of in vivo applications of NMR has been reviewed with 414 references.' A review of 31PNMR has been produced with many references2 The study of biodynamics and NMR has been reviewed with 12 references3 and the application of NMR in vivo to the study of biosynthetic pathways has been reviewed with 10 reference^.^ The experimental approaches to enzymatic studies in vivo using NMR to investigate genetically manipulated organisms has been reviewed' and the application of NMR to the study of biochemistry, in vitro and in vivo, has been reviewed with 39 references.6 A review which includes discussion of 'H, I3C and 3'P NMR methods in vivo has been p r ~ d u c e d .The ~ study of the tricarboxylic acid cycle in vivo using molecular biology and I3C NMR has been reviewed with 18 references.' A review of in vivo NMR has been produced with 18 references.'The application of 'H NMR to the study of oxidative stress has been reviewed with 49 references." A review of the application of NMR to comparative physiology has been produced with 277 references." The use of NMR for the determination of metabolite diffusion has been reviewed with 52 references.12 A method for solid-state NMR detection of protonated, compared to nonprotonated phosphate, which has a potential use in vivo as an indicator of bonemineral dynamics, has been d e ~ e l o p e d . The ' ~ conversion of a whole-body NMR imaging system into a EPR spectrometer suitable for the detection of free radicals in a 200 g rat has been r e p ~ r t e d . ' ~

1.2 Spectral Editing, Localisation and Instrumentation - A comparison of five different methods for the quantification of two-dimensional N M R spectroscopic images has been performed." A new sequence for lactate editing in 'H spectra which uses homonuclear polarisation transfer has been developed.16 The double quantum editing sequence 90: - r - 180; - r - 90; - 7-1 - 90: - r - 180; - rAcq(r = 1/45) has been used to obtain localised spectra of the lactate CH3 protons in the human leg by making the first 90" pulse and the two 180" pulses slice selective." A modified Fourier series window method has been used to obtain 13C NMR spectra from the canine myocardium in vivo following the infusion of [3-13C]pyruvate.'8 A new water suppression sequence which utilises a Nuclear Magnetic Resonance, Volume 27 0The Royal Society of Chemistry 1998 386

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train of homospoil pulses has been shown to allow the observation of protein resonances which occur near or under the water peak." The spin-spin coupling constant and chemical shift of the 'H spectrum of citrate has been found to be affected by divalent cations.20 Multiple-window spectrum estimation has been applied to in vivo 'H, 31Pand * 3C NM R spectroscopy. Some advantages over conventional Fourier-transform analysis are no baseline distortion from truncated data, broad baseline humps are removed and large solvent peaks may be subtracted. The method may, therefore, be particularly useful for analysis of in vivo data.21The method of localised spinecho 'H NMR has been described for use in vivo.22 A spectra-editing technique developed for the detection of ethanolamine in vivo has been d e m ~ n s t r a t e dA. ~ ~ method for the simultaneous acquisition of 'H stimulated echo mode spectra with 31Pimage selected in vivo spectra from the same volume of interest has been described .24 A system which allows the detection of gamma photons inside a wide bore 9.4 T magnet has been developed. Data was simultaneously obtained by NMR spectroscopy and positron emission tomography from the perfused rat heart.25 The use of dielectric resonators for application to NMR signal detection in vivo has been investigated.26 1.3 Intracellular Ions, Metabolites and pH - A review of the use of NMR measurements of intracellular ions applied to neuroscience has been p r ~ d u c e d . ~ ' The methods for the determination of intracellular Ca2+ (Ca2+i) using 19F NMR, including synthesis of indicators and necessary NMR equipment, has been described.28The basis of NMR determinations of intracellular pH (pHJ has been reviewed.29 A description of the measurement of intracellular magnesium (Mg2+i) from 31P NMR spectra has been p r ~ d u c e d . ~The ' measurement of Mg2+i from the chemical shifts of the a-ATP and P-ATP resonances (6ab) has been compared to a method which uses the chemical shift of Pi and the peak height ratio of a-ATP and p-ATP resonances (hp/a). Over the physiological range of Mg2+ concentrations (0.25 to 1.25 mM) 6ab changes by 0.6 ppm whereas, hpIa changes 2.5-fold. The new method was used to measure Mg2+; in the working rat heart.32 A new type of indicator for the determination of [Mg"] in biological samples using 31P NMR has been produced. A series of 1,4,7-triazacyclononane-based ligands were synthesised and the macrocycle with 3 methylphosphinates (NOTMP) appeared to be the most useful. The value of Mg-NOTMP complex was 0.35 mM at physiological pH and temperature which is suitable for measurements of [Mg2+] in cells. Measurements of [Mg2'] using NOTMP were made in blood plasma.32933 The use of triple-quantum-filtered 23Na NMR has been assessed for the determination of intracellular Na+ (Na+i) in the perfused rat heart in the absence of an extracellular shift reagent to help distinguish the extracellular Na signals. Signal changes in constant perfusion interventions probably reflected changes in Na+i but this was not the case during no flow i ~ c h a e m i a . ~ ~ The visibility of intracellular ADP has been investigated in human and avian erythrocytes. In human erythrocytes, which are organelle free, all acid extractable +

388

Nuclear Magnetic Resonance

ADP and ATP was NMR visible in the intact cell. In chicken erythrocytes, which contain a nucleus and mitochondria, all acid extractable ADP was NMR invisible, indicating sequestration or binding in intracellular organelles. The NMR data required time domain analysis with the VARPRO program, incorporating prior knowledge of peak structure, to provide reliable data.35Differences in the nucleotide compartmentation and energy state between in situ rat heart and isolated perfused rat heart have been observed. In the perfused heart the level of PCr determined by 31PNMR was in agreement with values determined in tissue extracts though, the amount of NMR visible ATP was 71 YOof that in extracts. In the perfused rat heart the ratio of PCr/ATP measured by NMR was 1.5 compared to 2.7 in the heart in situ. The ratio of PCr/ATP in tissue extracts of the perfused heart was 1.4compared to 1.9 in extracts from the heart in situ. It was also shown that >95% of ADP and >99% of AMP is in a bound form, i.e. not visible to NMR, in the perfused heart and the heart in sit^.^^

2

Cells

The application of NMR to the analysis of erythrocytes and biopsies of malignant tumour cells has been re~iewed.~' 2.1 Bacteria - A review has been produced on novel products and participants of oxidative stress in bacteria which focuses on the accumulation of the novel compound 2-C-methyl-~-erythritol-2,4-cyclopyrophosphate.~~ The mechanism of metabolism of monomethyl sulfate in a Hyphomicrobium species and an Agrobacterium species has been studied in real time using ['3C]MeS04. The results indicate a hydroxylation of MeS04 via a monooxygenation mechanism and not via the hydrolysis of MeS04 to produce methanol.39 Glucose metabolism in Fibrobacter succinogenes has been investigated by I3C NMR and enzymic analysis. The use of 13C NMR in vivo was able to detect the ' metabolism of [ l-'3C]glucose and [2-"C]glucose in presence of f ~ m a r a s e . ~The the presence of celloboise has been followed with I3C N M R in Fibrobacter The incorporation of [ I 3C]C02, [2-I3C]acetate, [ l-13C]acetate, suc~inogenes.~' [3-13C]serine or [ 1-'3C]formate into whole cells of Methanosphaera stadtmanae has been detected using CPMAS I3C NMR. The method allowed the detection of signals not observed in solution state NMR.42 The effects of denitrification by nitrite on immobilised cells of Pseudomonas fluorescens ATCC 17822 (biotype 11) has been investigated by 3'P NMR. Cells were able to maintain a pH gradient of 0.4 to 0.5 units until intracellular nitrite reached 27 mM when the pH gradient collapsed.43 A new bioreactor system has been developed for the study of micro-organism metabolism which enables high cell densities to be achieved with adequate oxygenation. 31P NMR measured intracellular Pi, NADH, nucleotide diphosphates (NDP), nucleoside triphosphates (NTP), uridine diphosphoglucose (UDP-glucose), a cyclic pyrophosphate, two sugar phosphate pools and extracellular Pi during anaerobic glucose fermentation by Zymomonas mobilis. The

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cyclic pyrophosphate has not been measured in vitro due to the instability of the compound. Furthermore, the aerobic glucose metabolism of Corynebacterium glutamicum following a pulse of [l-'3C]glucose was investigated by l3C NMR which detected the dynamics of labelling of lactate, glutamate, succinate and lysine with a time resolution of 10 minutes.44 3'P NMR has been used in conjunction with a fluorescent pH indicator to detect changes in the pH, of Propionibacterium acnes exposed to UV or blue light. Lethal doses, leading to less than 15% of cell survival, caused a reduction of the pH gradient across the cell membrane. Sub-lethal doses lead to an increased pH,, and a transmembrane pH gradient, which was r e ~ e r s i b l e . ~ ~ The unidirectional rate constant of ethanol diffusion through the lipid membrane of Zymomonas mobilis has been determined using 'H selective NMR spin magnetisation transfer.46 The pathways of L-arginine metabolism have been determined using multinuclear one- and two-dimensional NMR methods in the Gram negative bacterium Helicobacter Py10ri.~~ Blood - A review of NMR studies on the metabolism of erythrocytes has been produced.47 Pulsed field gradient NMR has been used to determine the maximum transport rate (10.1 mol dmW3 cell water s-') and concentration at half saturation (577 mM) for urea efflux from erythrocytes. A comparative NMR study of the diffusional water permeability (Pd) of red blood cells from the adult and foetal guinea pig (Cavia porcellus) has been performed. There was no significant difference in the Pd of adult, pregnant female and foetal guinea pig erythrocytes measured by a doping NMR technique. Basal permeability to water and the activation energy of water diffusion were also measured along A dose depenwith the inhibition of permeability by p-chloromercuriben~ene.~~ dent enhanced water exchange rate in erythrocytes exposed to the anti-anginal, anti-arrhythmic agent amiodarone has been mea~ured.~'The spin-spin relaxation rate of water in erythrocytes has been shown to be related to the permeability of the membrane to water. The effects of mefloquine and quinine on the spin-spin relaxation time of erythrocytes have been measured in a study of the effects of these drugs on membrane permeability." Changes in the isotropically-tumbling neutral lipids of activated splenic and thymic T lymphocytes has been followed with 2D 'H NMR. After 72 h of activation with phorbol myristate acetate and ionomycin the lipid content of the cells was similar but, after 120 h of activation the lipid signal was 3-fold higher in thymic T cells. An increase in choline, phosphocholine and glycerophosphocholine was seen in both cell types at 24 h stimulation but, only glycerophosphocholine was maintained after 72 h s t i m ~ l a t i o n . ~ ~ In a study of the interaction of bismuth(II1) complexes with glutathione spinecho 'H NMR showed that bismuth citrate reacts with glutathione in erythro~ investigation to determine the flux of universally cytes in vivo and in v i t r ~ . ' A labelled [ '3C]glucose into 2,3-bisphosphoglycerate (BPG) has been investigated with I3C and 31PNMR in human erythrocytes. l3C NMR detected l3C-label1ed glucose, lactate and BPG whereas, 3'P NMR was used to determine total BPG.

2.2

390

Nuclear Magnetic Resonance

The system was also modelled by computer ~ i m u l a t i o n The . ~ ~ level of ATP detected by "P NMR in erythrocytes from pregnant anaemic women has been shown to be reduced. The rate of decrease of ATP following washing from plasma was augmented and there was a lower pHi. The results were accounted for by a higher rate of glycolytic enzymes.55 The rate of anaerobic glycolysis, especially the 2,3,-diphosphoglycerate shunt, has been determined in human erythrocyte cell suspensions using 31P NMR at three temperatures. At 277 K there was negligible diphosphoglycerate phosphatase activity whereas, the activity was 4.4 x l o w 4and 7.7 x low4mol dmP3 h-' at 295 K and 310 K, re~pectively.~~ In a study of human erythrocyte metabolism in renal failure 3'P NMR was used to detect intracellular phosphorous metabolites and indicated that the pHi is decreased in the acute stage compared to chronic renal failure.57 I9F NMR has been used to study the fluoroquinolone lumefloxacin in a suspension of human erythrocytes. Peaks for intracellular and extracellular lumefloxacin were seen and the intracellular peak was broadened." 35Cl NMR has been used in conjunction with the chemical shift reagent cobalt(I1) glycine to measure the intracellular, compared to extracellular C1- content in a suspension of human erythrocyte^.^^ Spin-echo 'H NMR has been used in a study of the accumulation of inorganic and organic arsenic species in rabbit erythrocytes. 31PNMR was used to monitor effects on the energy metabolism of the cells.60 2.3 Cultured Mammalian - 'H NMR has been used to study the process of programmed cell death (apoptosis) in Jurkat T-cell lymphoblast cultures. A greater than twofold increase in the methylene resonance (1.3 ppm) was observed when apoptosis was induced by serum deprivation, glucocorticoid and doxorubicin treatment. No increase in this resonance occurred with necrotic cell death. A similar result was found in Hut-78 T-cell leukaemia, J-Y natural killer T-cell leukaemia, Daudi B-cell lymphoma, HeLa and 3T3 fibroblast cell lines.6' 'H NMR has been used to investigate the NMR-visible mobile lipid signals from a transformed murine blastoma cell line. Attenuation of cellular proliferation by confluence or low pH caused an increase in lipid signal which was amplified at high cell densities by removal of serum. Changes in the NMR visible pools of the lipid metabolites choline, phosphocholine and glycerophosphocholine measured by 2D 'H NMR suggested that the NMR-visible mobile lipid signals arise from phospholipid metabolism.62 An increase in intracellular N a + (Na+i) has been detected by 23Na NMR in 3T3 fibroblasts 3 min after stimulation with serum growth factors. The rise in N a + j lasted for 20 min and was prevented by the inhibition of either the bumetanide-sensitive Na +-K -C1- cotransport or the amiloride-sensitive Na H a n t i p ~ r tThe . ~ ~role of voltage-sensitive Ca2+ channels in mediating Ca2 influx during ischaemia has been investigated in the neuronal cell line NGlO8- 15 which does not express glutamate-sensitive Ca2+ channels. 19F and 31P NMR and 23Na double quantum filtered NMR was used to detect Ca2+i, cell energy metabolism and intracellular N a + (Na+i), respectively in cells loaded with the Ca2-t indicator 1,2-bis-(2-amino-5-fluorophenoxy)ethane-N,-tetraacetic acid (5FBAPTA). Ischaemia induced a fall in pH, PCr and ATP, and a rise in +

+ .

+-

+

12: Nuclear Magnetic Resonance Spectroscopy of Living Systems

39 1

Na+i. An increase in Ca2+iwas only seen when PCr was depleted and ATP was at 5 5 % of control values. An increase in Ca2+i was seen upon depolarisation which could be prevented by nifedipine. However, nifedipine had no effect upon the increase in Ca2+iduring ischaemia.@ 2.4 Liver - 31PNMR has been used to monitor immobilised hepatocytes in a bioreactor. The metabolism of 7-ethoxycoumarin was followed and the effects of cyclosporine pretreatment on carbon tetrachloride toxicity were investigated with the system.65 2.5 Plant - Measurements of the pHi of tobacco (Nicotiana tabacum) cells grown in culture have been made with 31PNMR to investigate the possibility of using the intracellular to extracellular distribution of [14C]benzoic acid to determine pHi.66 The phytohormone-induced affects on the primary nitrogen metabolism in transformed root cultures of Datura stramonium have been measured with "N and 31PNMR. The enhanced production of y-aminobutyric acid (GABA) induced by phytohormone treatment was not associated with a change in cytoplasmic pH although, acidification of the cytoplasm (artificially or by hypoxia) did cause increased GABA levels.67 The metabolism of ["Nltropinone in transformed root cultures of Datura stramonium has been followed with "N NMR. The metabolites ["Nltropine and simple ["Nltropine esters but, not [lSN]hyoscyamine,were observed.68

2.6 Reproductive - 31PNMR has been used in a study of immobilised sertoli cells isolated from 18 to 21 day old rats. Perfused cells maintained ATP levels for more than 10 h and cells which had been in cold storage overnight showed partial regeneration of ATP. Measurements of Ca2+i, Mg2+,,lactate and pyruvate, and oxygen consumption were by conventional biochemical means.69The antispermatogenic effects of gossypol have been investigated in murine TM4 Sertoli cells and compared to the effects on TM3 Leydig cells using 31Pand 23Na NMR. Acute affects on the energetic status of the cells was only apparent in high doses of gossypol whereas, chronic treatment with lower doses did reduce the energetic status and increase Na'i. These effects were greatest in the TM3 cell though, inhibition of growth was greatest in TM4 cells. The results suggest that the antispermatogenic effects of gossypol are unlikely to be the result of effects on energy m e t a b o l i ~ r n . ~ ~ 2.7 Tumour - 31PNMR has been used to examine the metabolism of human breast cancer cells (MCF7 and T47D) compared to human mammary epithelial cells proliferating at the same rate. An increased level of phosphocholine, phosphoethanolamine and their glycerol derivatives were observed in malignant cells.71The intracellular levels of ATP and Pi, and pH,, have been observed in harvested cells of the human lymphoma cell line M 0 l t - 4 . ~31P ~ NMR studies of the effects of recombinant human tumour necrosis factor-a on Molt-4 cells and HL-60 cells has revealed a decrease in ATP/Pi with treatment.73 31P N M R has also been used to characterise the phosphorus metabolites of Erlich ascites

392

Nuclear Magnetic Resonance

tumour cells and sarcoma 180 cells. The effects of iodoacetic acid and 2,4dinitrophenol on cell metabolism, and the effects of gossypol pretreatment were also i n ~ e s t i g a t e dThe . ~ ~ incorporation of the phosphonium analogue of choline in quiescent and mitogenically stimulated Rat-2 fibroblasts has been investigated with 31P NMR. In quiescent cells the phosphonium analogue was mostly incorporated in the phosphodiester pool. In mitogenically stimulated cells a significant proportion of the label was incorporated in the phosphomonoester pool; increases in phosphomonoesters has generally been associated with growth and oncogenic t r a n ~ f o r m a t i o nThe . ~ ~ ratio of phosphocholine to phosphoethanolamine has been shown to be lower in stationary cultures compared to proliferating cultures of tumour cells. Phosphoethanolamine began to rise as the stationary phase was approached, whereas, phosphocholine decreased during log growth, though, this could be reversed by the addition of ~ h o l i n e . ~ ~ The cytotoxic activity of cyclocreatine in rat C6 glioma and OC238 human ovarian carcinoma cells has been studied using 31P NMR. An accumulation of phosphocreatine and phosphocyclocreatine was observed in rat C6 glioma cells but not in OC238 human ovarian carcinoma cells. The accumulation of phosphocyclocreatine and subsequent cellular swelling could have been the cause of cytotoxicity in glioma cells but not in the OC238 human ovarian carcinoma cells.77The effects of 2-deoxy-~-glucose(2DG) or 3-O-methyl-~-glucose(3MG) on the energy metabolism of Ehrlich ascites tumour cells has been measured by 31 P NMR. Accumulation of 2-deoxy-~-glucose-6-phosphate (2DG6P) and depletion of the ratio of P-ATP/Pi was observed in cells exposed to 2DG. Coadministration of 3MG reduced the accumulation of 2DG6P from 2DG but caused a greater fall in depletion of P-ATP/Pi compared to 2DG alone. Photosan 11, administered with 2DG, caused an increase in 2DG phosphorylation and a decrease in P-ATP/Pi.78 An increase rate of uptake of 7Li into human 1321 N1 astrocytoma cells on microcarrier beads, compared to the rate of uptake of 7Li into human erythrocytes, has been detected with 7Li NMR utilising dysprosium tripolyphosphate as a shift reagent to separate intracellular from extracellular signals. Intracellular volume was assessed with 23Na NMR and cellular viability was determined by 31PNMR.79 The effects of a cationic lipophilic phosphonium salt (tetraphenylphosphonium chloride) on the human malignant cell line DU4475 have been measured with 'H NMR. A dose and time dependent increase in the CHZ/CH3 peak ratio was observed.80Multidrug resistance in Adrimycin- and taxol-resistant K562 cells has been investigated with 'H NMR. The fatty acid methylene/methyl and choline/ methyl ratios were higher in the multidrug resistant cell lines compared to sensitive cells. The ratios of fatty acids were partially recovered to control values when cells were maintained in media containing no antineoplastic agents. Furthermore, treatment with verapamil, which may reverse multidrug resistance, also caused a partial recovery of fatty acid ratios in the 'H spectra.81The effects of the differentiating agents SLM9123 and other retinoid compounds on the 31P metabolites of HL-60 cells have been studied with 31PNMR. Cells were exposed for 1,3 or 5 days to the compounds and exposure for 5 days caused an increase in ATP and phosphomonoesters PME, and a decrease in pHi.82

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2.8 Yeast and Fungi - The influence of aeration on the cytoplasmic pH of Saccharomyces cerevisiae at cell densities ranging from 0.9% vol/vol to 45% vol/ vol has been investigated using 3iP NMR.83 31P NMR has been used to investigate the effects of the alkalinisation or anaerobic conditions on Saccharomyces cerevisiae in high or low cell densities. Alkalinisation resulted in the degradation of polyphosphate to shorter polymers whereas anaerobic conditions lead to the hydrolysis of polyphosphate to Pi.84 The role of the yeast vacuole during phosphate starvation has been studied in Saccharomyces cerevisiae using 31PNMR. During phosphate starvation wild-type Saccharomyces cerevisiae can continue to grqw for two to three generations. 31PNMR showed that cytosolic phosphate was maintained at the expense of vacuolar phosphate, which was demonstrated to be due to the loss of vacuolar polyphosphate. In Aslp 1 cells, which have a defective vacuole, growth ceased immediately in the absence of extracellular ph~sphate.~’ 31P NMR measurements of polyphosphate in yeast cells has shown that the chain length of polyphosphate was altered by growth conditions and the total amount of polyphosphate was unaffected.86 Phosphorus metabolism in two isogenic strains of Penicillium chrysogenum, with different levels of penicillin synthesis, has been studied with 31P NMR. Changes in pHi did not affect the accumulation of phosphorus metabolites in either strain.87 31PNMR saturation transfer has been used to measure the steady state flux between Pi and ATP in yeast cells genetically modified to overexpress an adenine nucleotide translocase isoform. Modified cells had an increased rate of the flux of Pi to ATP and an increase in the ratio of moles of ATP synthesised per atom of oxygen consumed (P:O ratio) when they were incubated with glucose. There was no increase in the flux or the P:O ratio when cells were incubated with ethanol alone.” The metabolism of glucose and xylose as a function of oxygenation has been studied in cell suspensions and agarose-immobilised cells of Saccharomyces cerevisiae and Pichia stipitis using 31Pand I3C NMR. Intracellular pH, the rate of glucose metabolism and ethanol production of Saccharomyces cerevisiae cell suspensions was the same in aerobic and anaerobic conditions whereas, pHi and, glucose and xylose metabolism was higher in aerobic cell suspensions of Pichia stipitis compared to anaerobic cell suspensions. The rate of glucose and xylose metabolism, and ethanol production of immobilised cells of Pichia stipitis was the same as that of the anaerobic cell suspensions. Immobilised cells of Saccharornyces cerevisiae metabolised glucose at twice the rate of free cell s ~ s p e n s i o n s . ~ ~ The metabolism of [ l-13C]glucoseby the sophorose lipid producing yeast Candida apicola has been investigated with 13C NMR in harvested, whole cells. In logarithmic phase the label appeared predominantly in C-2 of ethanol, whereas in late logarithmic phase there was significantly reduced ethanol formation, the labelling of glycerol became dominant and signals from olefinic carbons and CH3 groups indicated incorporation into fatty acids.” The effects of amphotericin B, 2-deoxy-~-glucose and 2-fluoro-2-deoxy-~glucose on the metabolism of glucose, and the reciprocal effects, have been investigated in Saccharomyces cerevisiae.” In Candida albicans the effects of amphotericin B on anaerobic glucose metabolism has been measured in blastos-

Nuclear Magnetic Resonance

394

pores. During exponential phase amphotericin B decreased glucose consumption, ethanol, trehalose and glycerol production until metabolism was blocked after 25 minutes. Almost no effects were observed on glucose metabolism in cells during stationary phase.92 The effects of trehalose accumulation on the intracellular water structure of Saccharomycescerevisiae has been investigated by the examination of changes of T2 for intracellular water. In trehalose containing Saccharomyces cerevisiae cells up to 80% of water is in a bound state.93

3

Plants and Algae

The methodology of high resolution NMR studies in plant cells and tissues has been reviewed.94 A review on the biochemical and physiological applications of NMR to the study of plants has been p r ~ d u c e d . ~The ' recent advances in the profiling of plant metabolites has been reviewed with 76 reference^.^^ A review, with 58 references, of N M R methods for the study of seed hydration, fermentation and measurements of water self-diffusion has been produced. The possibility of following enzymic reactions and measuring Na i was also discussed.97 3 1 PNMR has been used to investigate the response of the Antarctic green alga Parasiola crispa to water stress. The addition of the non-ionic osmoticum polyethylene glycol to the media resulted in an increase of Pi, a decreased polyphosphate signal shifted down field and an eventual appearance of extracellular Pi. Phosphorus metabolism and binding of cations to polyphosphate was suggested to be involved in the tolerance of Parasiola crispa to desi~cation.~' The action of the cytoskeletal protein modifiers colchicine and cytochalasin B on the state of water in seeds has been investigated. The changes in spin-spin relaxation indicated an increase in free water.99 Several methods for the detection of sucrose concentrations in plants have been assessed. Chemical shift selective imaging, heteronuclear correlation via 13C-'H coupling and homonuclear correlation via 'H-'H coupling was used to examine developing pea (Pisum sativum L.) seeds and sucrose phantoms. Chemical shift selective imaging gave the best results. loo Germinating barley seeds have been examined by I3C NMR which detected maltose, sucrose, fructose and oils. During the first six days of germination the oil content decreased, maltose increased and the levels of fructose and sucrose remained constant. Sugars were also detected in the vascular bundle of seeds and in the solubilised endosperm."' The spatial distribution of carbohydrates and amino acids in the hypocotyl of castor bean seedlings has been measured by correlation-peak imaging. High levels of glucose were detected in the phloem area of the vascular bundles, high levels of sucrose were seen in the cortex parenchyma and lower levels of sucrose were observed in the pith parenchyma. Glucose was lower in the cortex parenchyma than the pith parenchyma. Lysine and arginine were mainly visible in the vascular bundles and valine was detected in the cortex parenchyma. Glutamate/glu tamine was detected in the cortex parenchyma and the vascular bundle.'02 The location of sucrose and oils have been detected in the maize seed using imaging and localised spectroscopy. Oils were found in the embryo and pericarp and most of -+

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the sucrose was detected in the e n d ~ s p e r m . " Magic-angle ~ spinning 'H NMR has been used to detect water and lipid in barley grains. Additionally, combined rotational and multiple pulse 'H NMR of barley grains was used to detect water, lipid, protein and carbohydrate components.Io4 The metabolic processes controlling the assimilation of ammonium ions in root nodules has been investigated using 31Pand 15N NMR."' The incorporation of 'N-labelled inorganic nitrogen sources in carrot (Daucus carota L.) somatic embryos has been investigated with 15NNMR in a study of stage specific nitrogen metabolism which also included the techniques of amino acid analysis and I4Clabelling. I5N NMR detected histidine, amino sugars, glutamine, arginine, urea, alanine, a-amino nitrogen, serine, aliphatic amines and several unknown compounds in the proembryogenic masses and various embryo developmental stages. The level of arginine and aliphatic amines peaked during globular and torpedo stages and substantially decreased in the germinating stage. ' 0 6 The metabolism of ammonium ions and nitrate has been studied in seedlings of Norway spruce (Picea abies) using I4N and "N NMR. Tissue concentrations of NH4+ reached a plateau when NH4+ was 5 mM in the growth medium. Estimates of the pH of NH4+ stores were 3.7-3.8 units in roots and stems and 3.4-3.5 units in needles based on measurements of the NH4+ quintet. 15N from NH4+ was incorporated first into the amide of glutamine and then into a-amino groups, mostly of glutamine, arginine and alanine. Almost no "N signals from needles were seen.'" The use of Gd3+ as a shift reagent to distinguish intracellular from extracellular I4N NMR signals in the measurement of nitrate metabolism has been investigated. It was found that Gd3' allowed the investigation of nitrate over extended periods but, it affected growth and nitrate uptake. Further investigation revealed that Gd(DTPA-BMA), a chelated form of G d 3 + , is likely to be a suitable form for physiological measurements.''* I l B NMR has been used to detect borate monoester and diester signals along with boric acid in radish roots, apple fruit, cabbage leaves, and komatsuna roots and l e a ~ e s . ' ' ~

4

Tissue Studies

4.1 Brain and Spinal Cord - A review of a broad range of 13CNMR techniques for the study of brain metabolism has been produced. The article is aimed at those who have little knowledge of NMR techniques."' The analysis of brain amino acids by magnetic resonance in vivo and microdialysis has been performed. An age dependent response to oxygen and glucose deprivation has been shown to occur in brain slice preparations taken from either 21- or 7-day-old rats. In slices from 21-day-old rats there was a greater loss of ATP and phosphocreatine (PCr) after a 20 min insult and these slices were more vulnerable to postischaemic depolarisation compared to the slices from 7-day-old rats. Furthermore, slices from the 7-day-old rats were less affected by exposure to nitric oxide compared to slices from the 21-day-old rats.112The preparation of adult rat brain slices has been developed and utilised in the study of the effects of hyperoxia,

'

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Nuclear Magnetic Resonance

hypercapnia or hypoxia pre-treatment on the outcome of exposure to 20 min of no-flow hypoxia. PCr and ATP became undetectable, and the ratio of lactate to N-acetylaspartate increased, during 20 min of no-flow hypoxia. Metabolite levels, The except pH, recovered to control values within 2 hours of re-~xygenation."~ role of external Ca2+ on the recovery of aglycaemic hypoxia in cortical slices from 10-day-old rats has been investigated with 'H and 31PNMR. A decrease in PCr, ATP, lactate and pHi was observed following 30 min of aglycaemic hypoxia and an incomplete recovery occurred after 30 min in control media. In Ca2+-free media, or media containing diltiazem or verapamil, the recovery of ATP and PCr was increased.' l 4 The levels of PCr and ATP have been measured in the grey and white matter of the piglet brain. The ratio of PCr/ATP is reported to be 0.77 for the grey matter and 2.18 for the white matter."' The energy metabolism of the rat brain following frontal lobectomy has been investigated with 31PNMR to examine the effects of monosialic ganglioside treatment. Frontal lobectomy caused a decrease in ATP and an increase in ADP during the compensatory period. These changes were not observed with monosialic ganglioside treatment.' l 6 The compartmentation of Pi in the brain has been investigated with 31PNMR and the MarquardtLevenberg non-linear curve fit algorithm for data analysis. During complete ischaemia four intracellular compartments of Pi at separate pH values were detected.'17 The effects of hypoxia on the new-born piglet brain have been assessed with 31PNMR in vivo and measurements of Na+-Kf ATPase activity in v i m . 31PNMR was used to monitor the maintenance of hypoxia at a level which decreased the PCr/Pi ratio to 25% of control values. Piglets were then allowed 0 hours recovery, 6 hours of normoxic recovery or 48 hours of normoxic recovery. PCr/Pi was 57% of controls after 6 hours recovery and had returned to normal values by 48 hours. In extracts the rate of ATP hydrolysis was 58.3 pM Pi mg-' protein h-' in controls and 45.8, 47.4 and 48.7 pM Pi mg-' protein h-' in 0 hour recovery, 6 hour recovery and 48 hour recovery, respectively. The results suggest that a recovery in the PCr/Pi ratio does not reflect the extent of recovery of the tissue."' An investigation of the assessment of brain oxygenation in relation to brain energy metabolism has been carried with 31PNMR. The redox state of cytochrome aa3, measured with near infrared spectrophotometry, was used to determine tissue oxygenation. Reduction of the fraction of inspired oxygen (FI02) from 0.21 to 0.15 resulted in a significant increase in reduced aa3 but, no significant changes in PCr or ATP. When FJ02 was 0.10, PCr decreased significantly and reached a minimum when F I 0 2 was 0.04 whereas, aa3 was almost totally reduced at FI02 of 0.08. When FI02 was 0.10 or 0.08, no change in ATP was detected."' 13C NMR has been used to investigate cerebral metabolic compartmentation caused by acute hyperammonaemia.I2O The measurement of glutamine synthetase activity, by NMR in vivu, has been performed in a study of the effect of glutamine synthetase activity on levels of ammonia in brain during hyperammonaemic encephalopathy. 12' Localised NMR spectroscopy has been used to measure the rate of C4-glutamate isotopic turnover from an infusion of [l-'3C]glucose in the somatosensory cortex of the rat brain during forepaw stimulation. It was found

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that the percent increase in the rate of cerebral oxidative glucose metabolism was equal to the percent increase in tricarboxylic acid cycle turnover and the percent increase in the rate of oxygen consumption. The results imply that oxidative glucose metabolism provides the majority of energy during sustained cerebral activation.'22 The rate of turnover of y-aminobutyric acid (GABA) has been demonstrated to be reduced in the brains of anaesthetised rats treated with vigabatrin. 'H and I3C-edited NMR showed that GABA concentrations were increased 2-fold 24 hours after treatment and GABA-transaminase was inhibited by 60% though, no effect on the tricarboxylic acid cycle was 0 b s e r ~ e d . I ~ ~ An investigation of the use of in vivo detection of N-acetylaspartate (NAA) as a marker of neuronal cell loss has been carried out. Lesions in the forebrain of rats were created with kainic acid treatment and brains were examined by 'H NMR. Estimates of neuronal loss by measurement of NAA in vivo were equivalent to measurements by the conventional method of determination of neuronal enzyme activity.'24 'H NMR has been used to examine the metabolite changes in the cold-injury brain trauma model. Accumulation of acetate, lactate and glutamine occurred during the first 24 hours. After 24 hours the glutamine decreased below control levels, alanine increased and N-acetylaspartate decreased. Treatment with the free radical scavenger 1,2-bis(nicotinamide)-propane repressed the development of oedema, lactate and alanine increases, and the decrease of NAA. Some measurements of oedema in ischaemic stroke and peritumoural oedema in the clinical environment where also made. 12' The effects of the four vessel occlusion model of reversible cerebral ischaemia in the rat has been investigated using 1D and 2 D 'H NMR in vivo. 31PNMR was also used and showed a decrease in PCr, ATP and pH, with a rise in Pi during 30 min of ischaemia. A decrease in NAA/total creatine and an increase in lactate/total creatine were detected by ID and 2 D 'H NMR. Furthermore, 2D NMR indicated a decrease in aspartate, an increase in inositol-choline derivatives during ischaemia and, an increase in alanine and a decrease in glutamateglutamine during reperfusion. 126 Localised 'H NMR has been used to monitor the concentrations of metabolites in the rat brain before, during and after 10 min of global ischaemia. Whilst the concentrations of NAA, total creatine (Cr), choline-containing compounds (Cho) and myo-inositol remained constant there was a rapid decline in glucose mirrored by the rise in lactate during ischaemia. The recovery of lactate levels followed first order kinetics.'27 Water suppressed volume-selective 'H NMR has been used to observe the differences between the live and dead mouse brain.12* An increase in neocortical lactate has been observed in ' H NMR spectroscopic imaging of the rat brain following unilateral common carotid artery occlusion. Increases in lactate were seen in both hemispheres though, the rise was greater in the clamped hemisphere and did not recover following reperfusion. A decrease in neocortical water and NAA following ischaemia was accounted for by changes in the values of T2.129 The MDX mouse, a model of Duchenne muscular dystrophy, has been examined with 'H NMR to assess the nature of disease related mental retardation, There were no significant differences in the NAA content of MDX brains compared to normals; however, there was a reduced level of choline and myo-

398

Nuclear Magnetic Resonance

inositol compounds which suggests that there is no loss of neurones but a decrease in glia or there are developmental abnormalities in dystrophic brain.I3' Differences in the relaxation rates of 'H NMR detected metabolites of the normal compared to the hyponatraemic rat brain have been investigated. A decrease in the longitudinal rate constant for Cr and an increase in the transverse rate constant for NAA were observed. In addition, a 14% decrease in metabolite concentrations and a 200% increase in lactate occurred 4 hours after the induction of hyp~natraemia.'~'The effects of nimodipine on brain energy metabolism during and following transient forebrain ischaemia in the gerbil has been investigated using 31P NMR. Measurements of cerebral blood flow and whole blood viscosity were also made. Pre-treatment with nimodipine improved the ratio of PCr/Pi and P-ATP/Pi during ischaemia and after reperfusion. Nimodipine also reduced whole blood viscosity though, improved cerebral blood flow was only apparent during administration of the drug.13* In a study of the disruption of respiratory rhythm which occurs during acute hypoxia the effects of hypoxia on brain stem energy metabolism has been observed in vivo by 31P NMR. A 43% decrease in PCr with no decrease in ATP was seen during 62% depression of respiratory rhythm. 133 The distribution of the fluorinated anaesthetics halothane and isofluorane has been studied with I9F NMR chemical shift imaging. A heterogeneous distribution of anaesthetic concentration was observed and total concentration increased with continuous anaesthetic delivery. 134 The use of ~-deoxy-2-fluoro-~-g~ucose (2DFG) and a functional probe for NMR studies of brain metabolism has been investigated. Metabolites of 2DFG were identified and the dose dependent uptake was i n ~ e s t i g a t e d . ''~H~ NMR has been used to investigate the environment of ethanol in the rat brain. Following the i.p. administration of ethanol signal intensities were measured with and without off-resonance saturation. A decrease in the ethanol peak to 67% with off-resonance saturation indicated the presence of bound, NMR invisible, ethanol which may affect the interpretation of in vivo data when water suppression is used.'36 3'P NMR has been used to examine the porcine spinal cord at 4.7T. Clear resonances for ATP, PCr, Pi, PME and PDE were detected along with a broad resonance which was assigned to myelin phospholipids. 137 4.2 Eye - Glucose and phosphorous metabolism has been examined in the normal, mature (8-month-old) rat lens compared to the streptozotocin-induced diabetic lens or the immature (2-month-old) lens. In contrast to immature lenses the normal mature lens contained sorbitol-3-phosphate (S3P) and fructose-3phosphate (F3P), and these compounds were greatly increased in the diabetic lens. When sorbitol production was inhibited both sugar phosphates disappeared. Incubation of lenses with [I-'3C]glucose resulted in the production of [I-'3C]lactate and [3-I3C]lactate indicating the production of [l-'3C]S3P and [ 1-13C]F3P which were then converted to [I -'3C]-cr-glycerophosphate and [ 1-'3C]dihydroxyacetone phosphate, respectively. 13* An investigation of the effects of oxidative stress on the intact rabbit lens in organ culture has utilised 13C NMR to follow the uptake of L-[3-'3C]cysteine from the incubation medium into

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the cysteinyl residue of glutathione. Increasing levels of oxidative stress caused by the addition of t-butylhydroperoxide resulted in the decrease of ([3-13C]cysteinyl)glutathione and a loss of 13C resonance intensity. Removal of oxidative stress resulted in partial recovery of ([3-'3C]cysteinyl)-glutathioneand this recovery was enhanced by 2-mercaptoethanol. 139 The T I and apparent T2 relaxation rates of water in the intact mouse lens have been compared to those of water in the soft contact lens.14' The values of T I relaxation of water in the normal and dehydrated isolated lens have been investigated by 'H NMR to assess the free and bound water contents.14' Heart - A review of patterns in energy metabolism of the mammalian myocardium adapted to chronic physiological conditions has been produced.142 The use of 31P NMR in the evaluation of metabolic parameters in the Langendorff perfused heart has been reviewed.'43 A review of studies of the control of cardiac respiration using isolated heart mitochondria and submitochondrial particles compared to studies in perfused heart and intact organisms has been produced.14 The metabolism of [3-13C]pyruvateand [3-13C]propionate in the rat heart has been followed in vivo with heteronuclear spin-echo and heteronuclear multiple quantum coherence spectroscopy. [3-I3C]Pyruvate was converted to [3-I3C]lactate in the blood and [3-13C]lactatewas metabolised in the heart. The transfer of the I3C label to alanine and acetyl CoA was 200-600% greater in normal compared to ischaemic hearts. Ischaemic hearts had a greater amount of label in the cytoplasmic lactate pool. Isoprenaline-induced ischaemia slightly decreased pyruvate oxidation but increased anaplerosis of pr~pionate.'~'The metabolism of [2-I2C]butyrate in the heart has been followed with 13C NMR in a study of the effects of redox potential on the transport of metabolites across the mitochondria1 membrane of intact hearts. The entry of 13C label into glutamate was used as a measure of flux through the tricarboxylic acid (TCA) cycle. The influence of the malate-aspartate shuttle was examined by exposure of hearts to 2.5 mM lactate in addition to [2-I2C]butyrate to induce a high redox state. The addition of lactate did not affect TCA cycle flux but increased the interconversion of a-ketoglutarate to glutamate. When hearts were exposed to [3-13C]lactateand unlabelled butyrate the label appeared in alanine and not in glutamate indicating an augmented redox state driving the malate-aspartate s h ~ t t 1 e . l ~ ~ 31P NMR has been used to measure the accumulation of 2-deoxyglucose-6phosphate (2DG6P) to estimate the rate of the glucose transporter in the heart of the hypertensive rat. Glucose transport was 3-fold higher, and hexokinase activity was 1.6-fold higher, in the hypertensive heart. In the presence of insulin accumulation of 2DG6P in the hypertensive heart was 86% of that in control hearts.'47 The accumulation of 2DG6P in the hypertrophied dog heart has been measured with 31PNMR to examine the effects of chronic pressure overload. In severe left ventricular hypertrophy ATP content of the heart was reduced by 40% and PCr content was reduced by 6O%, arterial lactate and noradrenaline levels were increased. Although no 2DG6P was detected in controls there was a timedependent accumulation in the hypertrophied dog heart which was increased

4.3

Nuclear Magnetic Resonance

400

with pressure over10ad.I~~ Changes in the ATP utilisation during graded hypoxia and reoxygenation have been measured in the heart of new-born and mature lambs. The phosphorylation potential was found to decrease in the new-born but not mature lambs in response to graded hypoxia. The ATP consumption during hypoxia increased more in mature lambs. 149 The effects of glycogen content on the post-ischaemic recovery of the rat heart have been studied using 3 1 PNMR. A high pre-ischaemic glycogen content was shown be beneficial to the recovery of the heart when reperfusion occurred before the onset of ischaemic contracture, otherwise the high glycogen content resulted in a lower pH, at the onset of ischaemia resulting in a lower recovery of cardiac function. I5O Glycogenolysis has been measured in the perfused rat heart during low-flow or no-flow ischaemia. I3C NMR showed that the rate of glycogenolysis was higher in the no-flow ischaemic heart and the rate was lower in isoproterenolpretreated hearts in both ischaemic groups. A sharp rise in Pi was observed by 31P NMR in ischaemic hearts though, the rise of Pi was smaller in low-flow ischaemia, and isoproterenol attenuated the rise of Pi in all cases. A rise in AMP also occurred in ischaemic hearts and was attenuated by is~proterenol.'~' In rat hearts perfused with 1 1 mM glucose during low-flow ischaemia 31PNMR was used to measure cellular energetics and intracellular and extracellular volumes, 23NaNMR was used to measure N a + , and s7Rb NMR was used to measure R b + influx to estimate Na+-K+ ATPase activity. In hearts perfused with 11 mM glucose ATP was two-fold higher, [Rb+] was three-fold higher, "a+] was fivefold lower and functional recovery was two-fold higher compared to controls.'52 Changes in the extracellular and intracellular ions of the perfused rabbit heart during no-flow ischaemia have been investigated with NMR, ion selective electrodes and the 4-electrode method to measure whole-tissue resistance. During the first 8 min of ischaemia the concentration of extracellular K + ([K'],) rose, PCr fell by 8O%, ATP decreased by 25%, and pHi and extracellular pH (pH,) fell by 0.5 units. There was a small change in the concentration of intracellular Ca2+ [Ca2+],and whole-tissue resistance during this period. However, after 20 min of ischaemia, when [Ca2+], had increased 3-fold and pH, was 6.0, whole-tissue resistance increased signifi~antly.'~~ The effects of hypertrophy and heart failure on the concentration of intracellular Na ("a '3,) levels were found significantly higher "a+], in hypertrophied hearts but not in hypertrophied failing hearts, compared to controls. The highest "a+], was seen 3-4 weeks after banding and decrease thereafter. Hypertrophied hearts also had a higher [Na +I1 during hypoperfusion. When intraventricular volume was increased [Na +I1 increased only in normal hearts.'54 The effects of inhibition of Na+-K+-2Cl- cotransport on myocardial N a + and Ca2 levels during ischaemia and reperfusion have been investigated. The influx of N a + into the heart during ischaemia was increased in Kf-free media containing oubain. When amilioride was also added to the perfusate the influx of N a + was decreased. Perfusion of hearts with K'-free media containing bumetanide prior to ischaemia resulted in increased Na + during ischaemia and reperfusion. Furthermore, bumetanide increased the level of Ca2+,during ischaemia and reperfusion. The results are consistent with the hypothesis that during ischaemia +

+

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40 1

the increase in intracellular N a + is due to changes in Na+ leakage more than changes in the Na+-K+ pump, that the Na+-H+ exchanger exacerbates this increase and that the Na+-K '-2C1- cotransporter is active during ischaemia and contributes additional loss of Na+i during reperfusion.155The effects of N a + transporters on cellular swelling during ischaemia in the isolated rat heart has been investigated using ' H NMR to measure water and 59C0 NMR to measure the extracellular marker cobolticyanide. Although 50 pM oubain did not affect cellular swelling during 30 min of ischaemia, 400 pM oubain or 200 pM iodoacetate caused cellular shrinkage during ischaemia. When 100 pM furosemide, 1.5 pM ethylpropylamiloride or 50 pM lidocaine was used to inhibit passive Na+ transporters cellular swelling was reduced. The results indicate the role of passive N a + transporters in the cause of oedema during myocardial i ~ c h a e r n i a . 'The ~ ~ Na+-K+ balance of KCN poisoned rat heart has been investigated with 31P NMR to measure energy metabolism, 23Na NMR to measure N a + i accumulation and 87Rb NMR to measure Rb+ efflux as an estimate of K + efflux. Treatment of hearts with 1 mM KCN caused a decrease in intracellular PCr, ATP and R b + , and an increase of intracellular Pi and Na'. KCN induced K" efflux was inhibited by glibenclamide and a-cyano-4-hydroxycinnamate. The intracellular accumulation of Na was attributed to the inhibition of Na+-K+-ATPase by Pi.157The effects of angiotensin I1 on H + fluxes after acid loading or during post-ischaemic reperfusion have been investigated in the Langendorff-perfused ferret heart; pH; was measured by 31PNMR from the resonances of Pi or deoxyglucose-6-phosphate. Angiotensin I1 stimulated the Na+-H+ antiport and the cardiac angiotensin AT, receptor was implicated in H + efflux by use of the AT, receptor blocker GR-117289. Angiotensin had a less pronounced effect on HC03--dependent pH, recovery after acid loading. During reperfusion angiotensin improved pHi recovery but, an increased influx of N a + was implicated in impaired contractile recovery.'58 A study of the effects of low extracellular K + on an isovolumetric isolated perfused heart preparation has been performed. When hearts were perfused for 30 min with media containing 0 mM K + ventricular fibrilIation occurred, there was a decrease in ATP and PCr and an increase in Pi. Perfusion of hearts with media containing 2 mM K + resulted in less dramatic effects upon energy metabolites and contractions. The reduction of [Ca2+J in the perfusate reduced the effects of low K + and an increased [Ca2'] had the converse effect. Perfusion of hearts with low [K+] also caused a decrease in the NMR-detected [Kf],.15931P NMR has been used in an investigation of Mg2+-stimulated cardiac purine nucleoside formation and release in the retrogradely perfused pig hearts. When the [Mg2+] of the perfusate was increased from 0.6 to 6.0 mM the coronary vascular resistance and spontaneous heart rate fell and the release of adenosine and inosine increased. Excess Mg2+ did not alter pHi or ATP concentration but lowered ADP and AMP concentrations. The Mg2+-stimulated adenosine release was assigned to be predominantly due to the membrane-bound ecto isoform of 5'-nucleotidase. I6O 19FNMR in conjunction with the Ca2+ indicator SFBAPTA has been used to measure the concentrations of Ca2+ ([Ca2+]) in sarcoplasmic reticulum of the +

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Nuclear Magnetic Resonance

Langendorff perfused rabbit heart.'61 An investigation of K + levels in the perfused rat heart, and in hepatocytes, has been carried out using 133Cs+as a K + substitute. 133CsNMR was used to measure exchange rates and cellular compartmentation.'62 The detection of intracellular Pi by in viva 31P NMR has been compared to the amount of Pi detected in extracts to determine the quantity of bound Pi in the normal and ischaemic rat heart.'63 The angiotensin-converting enzyme inhibitor quinapril has been studied in rats after myocardial infarction. 31PNMR detected a reduction in PCr in the infarcted heart which was prevented by quinapril. However, exposure to quinapril led to an increased susceptibility to acute hypoxia in infarcted and sham operated hearts.164 Ischaemic preconditioning is a process by which the heart can become less sensitive to the effects of long term total ischaemia following prior exposure to short periods of ischaemia and reperfusion. However, it has been demonstrated using 31P NMR to measure pHi and high energy phosphates that the prior exposure to hypoxia alone does not induce the same protection of the energy metabolism and contractile function during and following total i~chaemia.'~' The effects of ischaemic preconditioning or cardioplegia on the outcome of ischaemia have been compared using 'P NMR. Tschaemic preconditioning accelerated the onset of contracture and the decline in ATP whereas, cardioplegia delayed the onset of contracture and the decline in ATP. Furthermore, ischaemic preconditioning reduced the extent of intracellular acidification, but cardioplegia only delayed the onset of acidification. However, both methods improved recovery of left ventricular developed pressure. 16' The effects of ischaemic preconditioning and phosphokinase C (PKC) activation on acidification during ischaemia in the rat heart has used 31P NMR to measure pHi and high energy phosphates. No differences in the high energy phosphates were observed between hearts from any group during reperfusion. However, PKC activation by 1,2-dioctanol-sn-glycerol, but not by 4b-phorbol 2-myristate 13-acetate, produce an attenuation of the acidification of the heart and allowed better recovery of developed pressure similarly to the effects of ischaemic preconditioning. 167 The effects of several ischaemic preconditioning protocols has been examined with 31P NMR in the perfused rat heart. Effective protocols resulted in reduced ATP degradation, reduced intracellular acidosis and maintenance of residual PCr during ischaemia. Furthermore, these effective protocols caused vasodilatation, a PCr overshoot and a Pi undershoot during reperfusion in the preconditioning protocol. The departure from equilibrium for the energy producing reactions persisted until the prolonged period of ischaemia and appeared to be reinforced by multiple periods of ischaemic preconditioning. A new type of cardioplegic solution for long-term preservation of hearts has been developed. The solution, which contains impermeant agents, free radical scavengers and metabolic substrates, was tested on isolated rat hearts assessed with 31P NMR.'69 The effects of diltiazem on the viability of cold preserved rabbit hearts has been assessed with 31PNMR. Diltiazem administration prior to immersion of hearts in Euro-Collins solution at 4°C preserved the high energy phosphate metabolites equally well for 12 or 24 hours.'70 The role of Na+i in the preservation of hearts during hypothermic ischaemia has been investigated.

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Measurements were made of cell volumes with 'H and 59C0 NMR, of pH and cellular energetics with 31PNMR and of Na+i with 23Na NMR. Storage with solutions containing amiloride reduced cellular swelling and accumulation of Na+i but hearts stored in solutions containing amiloride or mannitol failed to resume contraction when reperfused. Storage in low N a + -containing solution was disadvantageous to high energy phosphates during storage and reperfusion. 1 7 ' The perfusion parameters of the modified Kety model have been detected for the diffusable tracer gadoteridol in isolated normally perfused hearts, hearts subjected to 20 min ischaemia and hearts with adenosine-induced increased p e r f i ~ s i 0 n . lA~ ~new method for measurement of cardiac blood flow, which utilises coloured microspheres and spectrophotometry, has been adapted for use in NMR in v i ~ 0 . IThe ~ ~ regional myocardial oxygen tension of the perfused rat heart has been determined with 3 D spatially resolved I9F NM R measurements of perfluorooctyl bromide relaxation rates.174In an investigation of the effects of inhibitors of NO synthetase, L-N-monomethylarginine or L-N-arginine methyl ester, on the outcome of ischaemia in the rabbit heart 31P NMR detected an improved maintenance of high energy metabolites and a lower acidosis in the treated groups.'75 The effects of nitrite infusion on the perfused rat heart have been investigated with 'H NMR to measure changes in the oxymyoglobin y CH3 Val El 1 signal and the metmyoglobin signal at - 3.9 ppm. Infusion of < 10 mM nitrite did not affect these signals and 31PNMR did not detect a change in high energy phosphates and pH though, the rate pressure product fell by 26%. When > 10 mM nitrite was infused the oxymyoglobin y CH3 Val El 1 signal fell and the metmyoglobin signal at - 3.9 ppm increased. There were also significant changes in the rate pressure product, high energy phosphates and lactate production. The infusion of > 10 mM nitrite did not affect oxygen consumption and indicates that myoglobin oxidation does not limit myocardial respiration but does reduce energy production. 17' The role of the PCr energy reserve in the reduced cardiac function of the failing heart has been investigated with 31P NMR in isolated Langendorff-perfused hearts. Dilated cardiomyopathy was induced in turkey hearts by furazolidone and resulted in a 73% reduction in baseline isovolumetric contractile performance. ATP and PCr concentration was reduced and the creatine kinase (CK) reaction velocity, measured by magnetisation transfer, was reduced by 7 1YO.The results support the hypothesis that decreases in the energy reserve via the CK system contributes to reduced cardiac function in the failing heart.'77 A study of the effects of the inhibition of CK on the contractile function of the heart has used 31PNMR to measure pHi, ATP, PCr and Pi. Iodoacetamide was used to deplete CK activity whilst the contractile reserve of the heart was measured by the increase of rate pressure product (RPP) from baseline to that during perfusion with high [Ca2+].An inverse relationship was observed between RPP and the free energy release from ATP hydrolysis (DG,). The maximal RPP was achieved at a AG-p of 52-53 KJ mol-', equal to the free energy requirement of the sarcoplasmic reticulum Ca2+ adenosine triphosphatase (Ca2+-ATPase). The results suggest that the limitation of CK causes a decrease in AG-, which limits

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Nuclear Magnetic Resonance

the activity of Ca2+-ATPase and restricts the contractile performance of the heart.'7831PNMR has been used to monitor the effects of NO on changes in PCr and ATP during two high Ca2+ challenges. The first Ca2+ challenge increased the rate pressure product and caused a decrease in PCr but, did not affect the level of ATP. In hearts which were then treated with the NO donor Snitrosoacetylcysteine (SNAC) a second Ca2 challenge failed to produce an increase in the rate pressure product, did not affect the level of PCr and the level of ATP became decreased. In experiments performed in vitro SNAC directly affected the activity of creatine kinase.I7' The effects of creatine kinase activity of the recovery of the rat heart following 10 min of global ischaemia has used 31P NMR to measure changes in PCr and ATP. Pretreatment of hearts with myristic acid allowed full recovery of developed pressure within 10 min of reperfusion. Pretreated hearts also had normal levels of PCr and ATP, and no loss of creatine kinase activity throughout reperfusion. A higher level of catalase was found in pretreated hearts. A porcine model of post infarction left ventricular remodelling has been investigated with spatially resolved 31PNMR to measure high energy phosphates. Left ventricular mass and volume, ejection fraction, the ratio of scar surface area to left ventricular surface area and left ventricular wall stresses were calculated from magnetic resonance imaging, anatomical data and measured left ventricular pressure. Coronary ligation caused congestive heart failure (CHF) in 6 of 18 animals whereas the remaining 12 had left ventricular remodelling (LVR) without CHF. The ratio of PCr/ATP in the subepicardium, the mid myocardium and the subendocardium was 2.10, 2.06 and 1.92, respectively in controls; 1.99, 1.80 and 1.57, respectively in LVR hearts; and 1.41, 1.33 and 1.25, respectively in C H F hearts. The myocardial free ADP were significantly increased only in C H F hearts. The alterations in myocardial energetics induced in ventricular fibrillation have been investigated with 3'P NMR in the perfused ferret heart. A limitation of energy metabolism through oxidative phosphorylation in combination with increased energy demands were indicated to be the cause of the rundown in energy metabolism during digitalis-induced fibrillation. Electricallyinduced ventricular fibrillation did not impair myocardial energy metabolism and caused a less severe Ca2+ overload compared to digitalis-induced fibrillation.'g2 31PNMR has been used to measure energy metabolism during P-adrenergic stimulation of the rabbit heart. Microdialysis was used to estimate the levels of adenosine and adenosine-5-phosphate in interstitial fluid. An increase in adenosine in interstitial fluid and a decrease in bioenergetic status was observed after P-adrenergic stimulation though, no change in [ATP], [Mg2'] or pH were observed. Multivariate statistical analyses of 31PNMR spectra have been used in the assessment of energy status of beating isolated rat hearts in a study of the effects of acidosis during ischaemia and reperfusion. +

Kidney - The effects of 0.3 mM or 1.2 mM Mg2+ on the post ischaemic recovery of the perfused kidney has been measured with 31PNMR. Exposure of kidneys to 0.3 mM Mg2+ prior to, and after, 1 h of no flow ischaemia decreased post-ischaemic recovery of ATP and increased accumulation of Pi compared to

4.4

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kidneys exposed to 1.2 mM Mg2+ throughout the experiment. The accumulation of N a + was also improved in kidneys exposed to 1.2 mM Mg2+ though, no differences were seen in the levels of Ca2+ibetween the g r ~ u p s . ' ' ~'H NMR has been used to detect lactate and trimethylamine N-oxide in perfused kidneys after cold storage to determine the locality and quantity of injury.ls6 The protective effects of a dietary glycine supplement in rats treated with the proximal tubule toxin maleate or the antineoplastic agent ifosfamide have been investigated. 31P NMR analysis of the renal cortex revealed a decrease in Pi and various phospholipids when a glycine supplement was not used.187 Liver - The metabolism of ibuprofen has been followed in vivo by 13C NMR in rats. The pharmacokinetics of 2,2,5,5-tetrarnethylpiperidine-1 -0xy1-3carboxylic acid (PCA) in the mouse liver has been followed with EPR in control conditions, during restricted blood flow to the kidneys, after exposure to CC14 or exposure to lipopolysaccharide. Restriction of renal blood flow had the biggest impact on PCA clearance though, CC14 and lipopolysaccharide treatment had significant effects.189 The effects of ischaemia on the phosphorous metabolites and Na +, levels of the rat liver have been investigated with 31Pand 23Na NMR. Occlusion of the hepatic artery and portal vein caused a decrease in ATP and an increase in Pi within 5 min with no further change. Exposure to 15 or 35 rnin of ischaemia, but not 65 min exposure, allowed some, temporary, recovery of ATP during reperfusion. The level of Na+i increased at a rate of 1.O mM min-' during the first 15 min of i~chaemia."~The role of oxygen free radicals in ischaemic reperfusion injury to the liver has been studied in rats with and without cirrhosis.lg' Three relaxation components of water have been measured in rat liver following excision or coldstorage. The relaxation rate of the structured water component changed with liver water content but, the relaxation rates of free and bound water remained ~ 0 n s t a n t . I'H ~ ~NMR at 1.9 T has been used to examine pig liver excised after perfusion with cooled Euro-Collins solution; further examination of PCA extracts at 9.7 T where used to re-evaluate the peak assignment^.'^^ The lactate content of isolated rat liver following flushing and preservation on ice has been examined by 'H NMR. An increase in lactate was seen over a 24 h period and alanine was also detected. The chemical shifts of both peaks were, however, shifted by -0.1 ppm. '94 31PNMR has been used in a study of rat liver under hypothermic perfusion with an oxygenated lactobionate/raffinose-based solution containing adenosine and inorganic phosphate. Liver ATP levels were low immediately after removal and increased slightly over the first 3 h of perfusion. By 24 h ATP levels had increased significantly and were maintained for up to 48 h of perfusion. ATP was maintained at a lower level for 48 h when phosphate was replaced by citrate in the perfu~ate.''~ The phosphorous metabolism of the rat liver and the hibernating ground squirrel liver under hypothermic perfusion has been studied with 31P NMR. High levels of nucleotides were detected in both cases and no differences between the two liver types were observed.'96 In a study of rat liver 31PNMR detected the decrease in ATP during 10 and 30 min periods of ischaemia and 4.5

'"

406

Nuclear Magnetic Resonance

revealed the greater, though, incomplete recovery of ATP levels following the 10 min period compared to the 30 min period of zero blood flow. 13C NMR was used to observe the incorporation of [l-'3C]glucose in the liver during reperfusion and demonstrated that its incorporation was a function of blood glucose concentration and not liver function. 19' The hepatic nucleotide triphosphate regeneration of pig liver following hypothermic reperfusion has been investigated with 31PNMR. A decline in nucleoside triphosphate (NTP) signals beIow the detection threshold was observed during 4 hours of cold storage and reperfusion resulted in a recovery of these signals to 70% of previous values. Increases in Pi, 3-phosphoglycerate and 2,3-diphosphoglycerate during storage were reversed during reperfusion. Cellular damage, indicated by decreases in glycerophosphocholine and glycerophosphoethanolamine, was minimal during storage but increased upon reperfusion. 19* 4.6 Pancreas - 31PNMR measurements of signals from the P-phosphate of ATP (P-ATP) have been made in the pancreas during and following 1, 2 or 3 hours of warm ischaemia. Cardiac arrest or cessation of blood flow caused a progressive decrease in P-ATP for 40 min after which the signal was not detected. P-ATP levels returned to control values upon reperfusion and the rate of return was fastest in the 1 hour ischaemia group.'" Lung - The relaxation times of water in acute hydrostatic pulmonary oedema have been measured in the rat lung following treatment with noradrenaline. TI and T2 were significantly prolonged in hydrostatic pulmonary oedema though, the T2 curves for peripheral lung tissue had a fast and a slow component. The fast T2 component was most closely related to the changes in interstitial water .2oo

4.7

4.8 Muscle - A review has been produced which discusses the problems associated with the interpretation of 31P NMR data on creatine kinase flux in The recovery of pHi and 31Pmetabolite levels in excised hamster muscle has been studied following tetanic stimulation of muscle form normal and dystrophic animals.*02 The changes in phosphorus metabolites of rat skeletal muscle stimulated via the sciatic nerve at 1, 10 and 100 Hz have been detected with 3'P NMR. At 1 and 10 Hz stimulation muscle contraction decreased to 46% and 26% of maximal force, respectively and was accompanied by a decrease in PCr and an increase in Pi. Muscle pH decreased and recovered during 10 Hz stimulation. At 100 Hz stimulation contraction force decreased to 6% of maximal force and there was a transient decrease in PCr and increase in Pi.203 The role of pHi on muscle fatigue has been investigated with 31PNMR. In previous studies of this phenomena in isolated muscle and muscle fibres contradictory results have been reported but, these studies were performed at different temperatures. The role of temperature and pH; were investigated in isolated mouse extensor digitorum longus under tetanic stimulation between 13 and 25" in normocapnia and hypercapnia conditions. Hypercapnia decreased pHi by the

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same amount at 15 and 25" though, the inhibition of force was greater at the lower temperature. A similar pattern of temperature dependent inhibition of force by pHi was observed in glycerinated fibres from rabbit psoas at maximum Ca2 activation.204 The metabolic changes in mouse hind limb muscle which occur during injury repair following exercise have been investigated with 31P NMR. Changes in PCr, ATP, ADP, Pi and phosphomonoesters were detected. There was a rise in Pi which peaked after 3 days that correlated to tissue repair assessed by histological examination.20531P NMR has been used to measure the effects of succinylcholine treatment on energy metabolism in the hind limb muscle of the rat following sciatic nerve section. Succinylcholine increased the ratio of Pi/ATP in the denervated muscle though, these effects were greatly reduced by pretreatment with vercuronium, midazolam or magnesium sulfate.206 The effects of dimethylfomamide (DMF) on the energy metabolism of rat muscle has been investigated with 31PNMR. Muscle tension was reduced in fatigue tests and 31P NMR detected reduced PME and Pi, along with increased pHi, in DMF-treated muscle indicating a lower activation of energy metabolism.207 The contractile activity and phosphorus metabolism of transgenic mouse muscle with increased creatine kinase activity has been investigated. Despite a 47% increase in creatine kinase activity in the transgenic mouse gastrocnemius muscle a 28% increase in the rise time of a 5 s isometric contraction was the only observed difference in contractile activity. No differences in the 31P metabolism of the transgenic muscle were observed compared to controls. Indicating that creatine kinase activity is not a limiting factor in muscle metabolism or contractile function.208 The influence of extracellular pH (pH,) on the pHi of muscle has been studied in the rat. An infusion of 150 mM HCI over a period of 2 to 4 h did not affect pHi. Chronic acid loading (4 mM NH4CI 1OOg-' day-' for 5 days) produced a small change in pHi of 0.05 pH units whereas, chronic uraemia had no effect on muscle pHi.209 Differences in the phosphorus metabolism of muscle (biceps fermoris) has been detected in pigs with different halothane-susceptible genotypes. Halothane-sensitive homozygo te (hh) pigs were subdivided into two groups; those with high PME (hhpme+)and those with low PME (hhpme-).The hhpme+ pigs were significantly different from halothane negative homozygous (HH) pigs with respect to pH, PCr and PME. The hhpme-pigs were significantly different to HH pigs with respect to pH and PCr.2'0 I3C and 31P NMR measurements of muscle from homozygous halothane-sensitive pigs has also been reported.21 The uptake of '3C-label from an infusion of [2-I3C]acetate in muscle and heart has been followed with 'H-decoupled, nuclear Overhauser enhanced 13CNMR in anaesthetised rabbits in vivo. Stable enrichment was seen in C-2, C-3 and C-4 of glutamate and the half-time for enrichment was 17 min for C-4 and 50 min for C2 and C-3. Flux through total anaplerotic pathways, relative to citric acid cycle flux, was higher in quiescent skeletal muscle (26%) compared with hearts (3%) though, anaplerotic flux is higher in the heart when the rate of the citric acid cycle flux is taken into account.212 +

408

Nuclear Magnetic Resonance

Skin - Measurement of TI and T2 relaxation rates for water has been used to study inflammation of the rat skin following UVB irradiation and vesicant application.213The isolated frog skin has been examined by 31P NMR under anaerobic perfusion of the epidermal side. A fall in PCr and pH; was accompanied by an increase in Pi and sugar phosphates on the serosal side of the skin. Ventilation after anaerobic perfusion accelerated the rate of recovery of 31P

4.9

metabolite^.^'^ 4.10 Tumour - A review of 31PNMR methods for studies of tumour metabolism has been produced.215Recent reports of the use of NMR in cancer studies, together with the techniques for measurements in tumours, has been reviewed.216 The physiological states in cancer cells and tissues have been defined in terms of Statistical Thermodynamics and Brownian Motion Therory. Physiological transitions were shown to be indicated by nuclear spin-relaxation times and spectral line widths yielding correlation times, microscopic thermodynamic functions and metastatic potential^.^'^ 'H NMR has been used to monitor the growth of gliomastoma cells implanted in the rat brain.218Measurements of tumour blood volume have been made using Oxypherol (a perfluorocarbon emulsion) and 19F NMR. The results correlated with blood volume estimates obtained from a technique using radioisotope labelled albumin.219The effects of melanin content on the TI relaxation rate of 31Pmetabolites has been investigated in a melanotic (ROX-t) tumour line and an amelanotic (COX-t) tumour line. When 200 mm3 tumours were examined, ROX-t tumours had shorter T I values than COX-t tumours. However, in 1000 mm3 tumours, which had significant necrosis, there was no difference in the T I values for the two tumour types.220The effects of anaesthetics on the metabolism of the 9L rat glioma has been examined with 31P NMR. The anaesthetic xylazine alone or in combination with ketamine caused hyperglycaemia. Co-administration of glucose enhanced this affect and caused intracellular acidification but, when Pi was also added to the combination an intracellular alkalinisation occurred. The combination of ketamine and acepromazine had no affect on blood glucose or tumour pHi.22X 31PNMR has been used to examine mouse mammary carcinomas following cyclophosphamide treatment. The ratio of nucleotide triphosphates to Pi was raised in the treated tumours compared to untreated controls. The phosphomonoester (PME) peak was resolved into two resonances one of which corresponded to phosphocholine (PC). The remaining phosphomonoesters, contained in the second peak, were elevated with respect to the PC peak in treated tumours. Similar elevations of PME peak have been reported following radiation therapy.222The intradermal ESb-MP murine T-cell lymphoma has been examined in solid tumours, in syngeneic DBA/2 mice, and in cultured cell suspensions at 1 I .7 T using 31PNMR. Growing tumours had relatively high PME, NTP, and Pi and low levels of phosphodiesters (PDE) and no PCr; tumour pH was 6.7-6.9 units. Cell suspensions had low PDE and no PCr, higher nucleoside monophosphates and diphosphates, low PME and a pHi of 7.4 units. Treatment with 5 Gy irradiation and i.v. transfer of immune spleen cells from allogenic B10.D2 donors resulted in 100% remission and NMR could distinguish between respon-

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ders and non-responders on the basis of increased pHi after treatment.223 The high energy phosphorus metabolites of the murine fibrosarcoma FSaII have been measured with 3’P NMR in relation to size and tissue oxygenation. The ratios of P-NTP/Pi and PCr/Pi showed a positive correlation with median tissue oxygen tension measured with 02-sensitive needle electrodes. The pH of tumours declined during growth and a tissue acidification was observed in tumours larger than 350 mm3. Intracellular acidification and the loss of high energy phosphate occurred when tissue oxygenation fell below 10 mm Hg.224The oxygenation and high energy phosphorus metabolites of the KHT murine sarcoma have been measured using the relaxation rate of sequestered perfluorocarbon emulsions to determine oxygenation with I9FNMR, and using 31PNMR to measure energetic status, For most of the tumours studied an increase in tumour size led to a decrease in tumour oxygenation, and the energetic status and pH of tumours was generally related to the tissue oxygen level. However, this was not true of all cases and it was concluded that measurements of oxygenation and energy metabolism within the same tumour would be necessary to clarify this anomaly.225 A I9F NMR method for the determination of tumour oxygenation based on changes in the relaxation rates of hexafluorobenzene injected directly into the tumour have been described.226 The effects of tumour blood flow on ammonium ion concentrations in RIF-1 tumours has been investigated with 14NNMR. Reduction of tumour blood flow, by hydralazine or blood vessel ligation, revealed a correlation between ammonium ion concentration and the 31P-detectedPCr/Pi ratio.22731PNMR has been used in a study of the effects of hyperthermia, in combination with hydralazine treatment, on the growth and energy metabolism of FM3A tumours. A correlation between the reduction in the ATP/Pi ratio and tumour growth delay was observed.228The metabolism of 5-fluorouracil (SFU) in human hypopharynx and colon carcinoma xenographs has been followed with I9F NMR. Tumour growth delay and fluoronucleotide (FNuc) levels were significantly higher in the colon carcinoma xenographs. Pretreatment with methotrexate or thymidine increased FNuc levels in both tumour types but tumour growth delay was only increased in the colon carcinoma ~ e n o g r a p h s The .~~~ metabolism and clearance kinetics of 5FU has been measured in the mouse liver and S180 implanted turn our^.^^' 4.11 Whole Animal and Multiple-Tissue Studies - The levels of ATP and PCr detected by 31PNMR in left ventricular myocardium, left cerebral cortex and right thigh skeletal muscle have been compared to those found in freeze-clamped extracts. The level of PCr in myocardial and cerebral tissue detected by NMR was in agreement with the amount found by chemical assay, though, the amount of ATP detected by NMR was lower than that in extracts. The amount of PCr in extracts of muscle was below that of the amount detected by NMR.231The use of 133Csas a probe of intracellular space has been investigated with 133CsNMR. Blood samples taken from rats administered CsCl i.p. showed separate resonances from intracellular and extracellular 133Cs.Only one resonance from 133Cswas detected in brain, muscle and kidney representing the accumulation of intracellular 133Csin these tissues.232The effects of halocarbon hepatotoxicity

410

Nuclear Mugnetic Resonance

and renal ischaemic reperfusion injury have been investigated using image-guided localised 'H and 31P spectroscopy to measure biochemical markers of tissue damage. The role of oxidative stress in halocarbon hepatotoxicity and renal ischaemic reperfusion injury was assessed by observation of the effects of free radical scavengers.233 The effects of temperature stress on energy metabolism in the common carp (Cyprinus capio) has been studied with 31PNMR. The dynamics of recovery from anoxia changed with temperature and no recovery was seen in carp subjected to temperature 31P NMR was used in a separate study to determine the bioenergetics of carp muscle under cold-C02 anaesthesia. The levels of PCr, ATP and pHi were lowered in the anaesthetised carp compared to controls. Furthermore, 31PNMR was used to examine the changes of phosphorous metabolites in carp muscle post-mortem.235 31PNMR has been used to determine the energy metabolites of the tail muscle of the crayfish, Procambarus clarkii. Signals for sugar phosphates, Pi, arginine phosphate (AgP) and ATP were detected and a decrease in AgP was observed upon inducing escape behaviour. Recovery of AgP was fastest in young The marine organism red abalone (Haliotosis rufescens) has been studied with 31PNMR and 31PNMR saturation transfer to determine the changes in phosphorous metabolite concentrations and the arginine kinase flux during a 2 hour exposure to hypoxia or pentachlorophenol (PCP). Changes in Pi and AgP concentrations were similar when red abalone was exposed to hypoxia or PCP. However, in contrast to exposure to PCP, hypoxia increased the arginine kinase flux which continued to increase during the first hour of recovery.23731PNMR spectra of red abalone in ambient (35%), hyposaline (25%) and hypersaline (45%) sea water during exposure to PCP showed no effect due to salinity. During recovery from exposure to PCP, though, sea water salinity effected the onset and intensity of effects."' The high energy phosphate content of the adductor muscle and body trunk of the oyster, Crassostrea gigas, has been measured with 31PNMR. The levels of AgP and PDE in the body trunk were higher than those of the adductor muscle. The pHi of the adductor muscle and the body trunk were 7.48 and 7.33, r e s p e ~ t i v e l y . ~The ' ~ ~effects ~ ~ ~ of lethal and sublethal doses of KC1 on the zebra mussel (Dreissena polymorpha) have been investigated with 31PNMR. Exposure to 8.6 mM KC1 or the molluscicide Bayluscide caused a decrease in ATP, AgP and pH, and an increase in Pi. Doses of KC1 below 8.6 mM caused similar responses though, these effects were reversible on exposure to KC1-free water. Hyperbaric oxygen was able to prevent the effects of 8.6 mM KCI but, mussels died on return to KC1-free, normobaric oxygen conditions. Hypoxia caused similar effects to 8.6 mM KCl.24' 31Pand I3C NMR have been used to examine the metabolism of the 15 day old chick embryo. 31P spectra contained signals from ATP, PCr, Pi, PDE and PME whereas, the natural abundance I3C spectra contained signals primarily from fatty acids. Infusion of [l-'3C]glucose caused an increase in the phosphorus metabolites and an increase in fatty acid signals and the appearance of signals from glycogen.242 The 'H NMR signals of the proximal histidyl N5H of myoglobin in Arenicola marina have been used to determine the level of tissue oxygenation under hypoxic conditions.243An investigation of cryopreservation of

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41 1

the developing zebra fish embryo, as a model of a multicompartmental system, has examined the uptake and distribution of the cryoprotectants dimethyl sulfoxide, propylene glycol and methanol. Dimethyl sulfoxide and propylene glycol showed no or little permeation of the system within 2.5 hours whereas, methanol permeated the entire embryo in 15 minutes. The yolk syncytial layer was implicated in a critical role in limiting the permeation of the cryopro tectant s .244 4.12 Reproductive - The perfused human placenta has been examined with 31P NMR. During control perfusions there was an initial increase in ATP and a fall in Pi, though, the levels of these metabolites continued to be constant for the remaining 11 hours of perfusion. Other biochemical markers of viability were measured in the perfusate and remained constant. Treatment with 0.1 mM dinitrophenol slightly reduced ATP and other biochemical markers though, treatment with 0.1 mM iodoacetate and 0.1 mM dinitrophenol blocked ATP production and caused a substantial metabolic impact.245

5

Clinical Studies

A review of the application of high resolution NMR to the field of oncology, in conjunction with the use of pattern recognition, has been produced.246The study of interactions and organisation of the regulatory systems which allow the energy balance to be maintained in skeletal muscle has been reviewed with 65 references.247 A review and discussion of the methodologies of quantitative determination of metabolites in humans using NMR has been produced with 25 1 references.248 The clinical applications of NMR in liver disease, cancer and diseases of the central nervous system have been reviewed with 10 references.249 The NMR methods available for the study of clinical brain disorders has been reviewed with 37 references.250The use of NMR for clinical investigations has been reviewed with 37 reference^.^" A review with 76 references of methods for the determination of metabolite concentrations in the human brain has been produced.252Methods for monitoring antiepileptic drug treatment, including the detection of brain y-aminobutyric acid (GABA) levels, have been reviewed.253 The measurement of [13C]glucose metabolism in the brain by 13C NMR, compared to "F-deoxyglucose studies using positron emission tomography, has been reviewed with reference to alterations in glucose metabolism which occur in epilepsy.254The study of glutamate and other metabolites by NMR and their role in schizophrenia has been reviewed.255Furthermore, reviews of the use of 31P NMR in the study of impaired frontal lobe function and membrane alterations in schizophrenia256and the application of NMR to the study of the limbic temporal lobe of patients with schizophrenia have been produced.257A review of the methods for the measurement of psychotropics and antidepressants in brain tissues using 19F NMR has been produced.258 The methods for the determination of the level and distribution of Li' in the human brain have been reviewed.258A review of the measurement of high energy metabolites and

412

Nuclear Magnetic Resonance

phospholipid metabolism of the brain in Alzheimer's disease has been produced with 24 references.260 Localised 'H NMR spectra of the human testis has been performed a t 2.0 T using a short echo-time STEAM sequence. Signals were detected from trimethylammonium groups, total creatine (Cr), myo-inositol and aliphatic resonances that reflect mobile amino acids in cytosolic proteins as well as containing residual lipid contamination.261 A method for the measurement of the concentrations of high energy phosphate compounds in the human heart has been developed. The localised 31PNMR signals are calibrated against a 'H NMR data set acquired from the same volume. The method was validated using measurements on phantoms and measurements on human calf muscle. In the normal heart the concentration of ATP and PCr were 5.8 f 1.6 and 10 f2 mmol kg- wet weight, respectively.262The quantification of tissue citrate in the normal prostate gland has been achieved using experimentally determined relaxation parameters and tissue water content as an internal standard. Localised 'H NMR also detected choline-containing compounds (Cho) and Cr resonances and a four-fold higher concentration of citrate in the peripheral zone compared to the central gland.263 The removal of lipid artefacts from 'H NMR spectroscopic images of the human cerebral cortex using the Papoulis-Gerchberg algorithm has been investigated. The methodology permitted the acquisition of spectroscopic images of the brain without lipid suppression.264 A study of the reproducibility of measurements of metabolite peak areas in the human brain by 'H NMR has been performed. Measurements of NAA, Cho and Cr where made in co-operative ~ ) in the left and right hemispheres of the volunteers from voxels (8 ~ m - located brain on two separate days. The coefficient of variance (CV) for measurements from separate days was 9% to 18%. After minor corrections to the spectrometer six measurements where taken from the right hemisphere of volunteers on four separate days. The CV for consecutive measurements on the same subject was 4.4% to 17.2% and the CV for measurements made on separate days ranged from 7.7% to 25.8%.265 The values for TI and apparent T2 of NAA, Cr and Cho in the human brain at 4 T has been measured. The value for TI was only slightly larger than that at 1.5 T reported in the literature. The determined value of the apparent T2 for NAA, Cr and Cho was less than that reported for measurements at 1.5 T. Potential contributing factors have been discussed.266 Changes in the levels of free fatty acids in the brain after electroconvulsive therapy have been detected with 'H NMR.267A decrease in the ratios of NAA/ Cho and NAA/Cr has been detected in the brains of 10 alcoholic patients compared to age matched controls.268A difference in the phosphorous metabolites in the brains of polydrug abusers has been detected with localised 31PNMR. Phosphomonoesters were decreased by 15% and the p-NTP signal was decreased by 10%. No other peak changes were observed.2693'P NMR examinations of schizophrenic patients have revealed lower prefontal levels of PME and higher levels of phosphodiesters (PDE). Lower levels of PME were also seen in patients with depression.270 In two patients with wandering symptoms, one with Binswanger-type cerebral infarction and one with sequelae of cerebral bleeding and multiple lacunar infarction, 31PNMR was used to observe changes in the

'

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41 3

phosphorus metabolites of the brain caused by treatment with fasudil hydrochloride. Pretreatment 31P spectra showed decreased PME and PDE with increased ATP; these peaks were returned to normal values with treatment.27' The effects of the combination of lithium with choline for rapid cycling bipolar disorder have been examined with 'H NMR. Those patients that responded to choline had a substantial rise in the Cho peak in the basal ganglia.272 The time-domain analysis of the metabolite concentrations in the normal human brain has been performed on data obtained with a single-voxel spin-echo technique.273Point resolved spectroscopy (PRESS) has been developed for the detection of GABA. The determination of the concentration of GABA in a single region of a phantom and in the brains of 10 volunteers has been demonstrated.274 The use of metabolite levels detected by 'H NMR in the assessment of patients with intractable epilepsy has been described.275 'H NMR measurements in the primary motor cortex of patients with amyotrophic lateral sclerosis has revealed a decrease in NAA compared to the levels detected in the parietal neocortical region and compared to NAA levels in these regions in matched control subjects.276 The concentrations of several metabolites measured in biopsy samples from the human brain have been compared to the concentrations found by in vivo 'H NMR; samples from epilepsy patients and normal volunteers were examined.277 'H NMR examinations of patients with neoplastic or infectious brain lesions have been compared to biopsy samples taken from the same region. It was found that the Cho peak at 3.2 ppm reflected cellular destruction.278The use of 'H NMR to assess prognosis after near-drowning has been described. Measurements of decreased NAA, Cr, lactate and glutamate/glutamine were used to distinguish between good and poor outcome.279 'H NMR has been used to measure metabolite concentrations in the brains of infants suspected of perinatal hypoxic-ischaemic cerebral injury. Those infants who developed serious cerebral injury or died had low Cho and NAA concentrations and the T2 values for all metabolites was increased.280 The effects of exposure of normal brain tissue to irradiation during radiotherapy for brain tumours have been investigated with localised 'H NMR. Choline and creatine compounds were unchanged compared to controls, however, the concentration of NAA was decreased from 13.2 mmol dm-3 in controls to 8.6 mmol dm-3 in irradiated patients indicating the loss of neuronal tissue.28' In another study of the effects of irradiation on the 'H metabolites of the brain cyclohexane has been used as an external standard. The concentration of Cho, Cr and NAA in irradiated subjects (before, during or after treatment) were not found to be significantly different to control values.282Localised 'H NMR has been used to examine and compare children suffering from different lysosomal diseases, those with x-linked adrenoleukodystrophy and normal volunteers. Principal component analysis of the data increased the discrimination of the pathologies based upon the metabolic profiles detected by 'H NMR.283The macromolecular content of the human brain has been mapped using an inversion pulse and a variable recovery time before the application of localisation and spectroscopic imaging. The resonances at 2.05 and 0.9 ppm were mapped with a resolution of 1.5 cm3 and a resonance at 1.3 ppm was observed in subacute stroke patients.284

414

Nuclear Magnetic Resonance

Frontal grey matter and frontal white matter of the brain of normal volunteers (aged 19 to 78 years) have been investigated for age related changes in metabolite concentrations. In the grey matter NAA remained constant with age but, Cr, Cho, myo-inositol and the percentage of cerebrospinal fluid increased whilst brain water content decreased. No significant changes were observed in the white matter.285The effects of oral administration of cytidine 5'-diphosphate choline on the Cho resonance of the brain in 25-year-old and 59-year-old subjects has been studied with 'H NMR. In younger subjects Cho increased by 18% and in older subjects Cho decreased by 6% despite a similar rise in plasma choline in both groups.286Age related changes in the brains of children have been measured with 'H NMR in the frontal lobe, parietotemporal lobe, temporal lobe and cerebellum. The ratio of NAA/Cho increased rapidly from age 0 to 2 years in all areas except the cerebellum. Changes in NAA/Cho where more gradual after 3 years. The Cho/Cr ratio decreased with age in all areas except the cerebellum. Quantification of metabolites revealed that the NAA concentration was lowest in the temporal lobe and that Cho and Cr were highest in the cerebellum.287The NMR localisation method PRESS has been used to obtain measurements of the concentration of 31Pmetabolites using brain water as an internal concentration reference. Measurements of PME (5.6 f0.9 mmol kg-I wet weight), Pi ( I .4 f0.4 mmol kg-' wet weight), PDE (2.3k0.6 mmol kg-' wet weight), PCr (2.9k0.3 mmol kg-' wet weight), NTP (2.8k0.6 mmol kg--' wet weight) and total phosphate (21.4k2.8 mmol kg-' wet weight) where made in the brains of healthy infants of gestational plus postnatal age 34 to 39 weeks.288 A water-suppressed J-refocused coherence transfer sequence for the observation of glutamate in human brain has been developed on a 4.1T system. Spectroscopic imaging using this sequence allowed the observation of differences in glutamate content of grey and white matter of the human brain.289The grey and white matter contribution to the signals detected in voxels of a spectroscopic image of the human brain has been assessed using information from 'H NMR water images of the brain. Values for the Cr, NAA and Cho content of gray and white matter were obtained and the extent and location of metabolic abnormalities were measured for a patient with multiple sclerosis.290 The dynamic uncoupling and recoupling of perfusion and oxidative metabolism during focal brain activation has been investigated with 'H NMR. Neuronal activation (4-6 min) in the primary visual cortex caused a 40% decrease in steady state glucose due to a 21% increase in utilisation. A transient increase in lactate of 170% occurred 2.5 min after the onset of stimulation. Uncoupling of blood flow and oxidative metabolism was indicated by blood hyperoxygenation which returned to basal levels over 3 minutes.29' The effects of aldose reductase inhibitors on diabetic neuropathy has been investigated by measurement of motor nerve conduction velocity and measurement of TI relaxation values. In diabetics the TI relaxation values for nerve, but not muscle or adipose tissue, were increased compared to controls. There was a positive correlation between the TI values and glycaemic control and a negative correlation between TI and motor nerve conduction velocity. Administration of an aldose reductase inhibitor improved glycaemic control and TI values of the

12: Nuclear Magnetic Resonance Spectroscopy of Living Systems

41 5

sural nerve in diabetics though, it did not reverse the loss of motor nerve conduction velocity.292 Proton-decoupled 31P NMR has been used to determine the J-coupling constants for ATP in human myocardium and calf muscle. Using chemical shift imaging with slice selective, excitation measurements were obtained which showed a significant difference between J,p for muscle ATP and Jupfor heart ATP which could not been explained by differences in the binding of ATP to magnesium.293The Mg2+ content of skeletal muscle, measured with 31PNMR, has been shown to be constant throughout the menstrual cycle and unrelated to the concentration of Mg2+ in the blood.294In a study of 33 male and 32 female volunteers 31PNMK revealed that males had significantly lower free intracellular Mg2+ levels. Furthermore, the level of free intracellular Mg2+ and the ratio of PCr/Pi fell with increasing Minnesota Heart Health Program Questionnaire score.295The chemical shifts of the a- and P-phosphates of ATP and the value of J,p have been shown to be different in gastrocnemius compared to soleus muscle. The results indicate a higher free intracellular Mg2+ concentration in the gastrocnemius muscle.296A split in the 'H NMR peak at 1.3 ppm in spectra of fatiguing skeletal muscle has been assigned to lactate in two environments; i.e. in glycolytic and in oxidative fibre populations.297 A decrease in the Pi signal from human skeletal muscle has been observed with 31PNMR in the first 30 s of ischaemia following exercise. The level of Pi was decreased by comparison to the value found at the end of exercise whilst the level of PCr in the muscle under ischaemia was the same as that observed after exercise.298 A new pulse sequence for the detection of 'H and 3'P metabolites has been used to measure changes in lactate and phosphorous metabolites in the forearm with exercise.299Measurements of changes in the Pi peak of leg muscle following exercise have been performed on long-distance runners. During exercise 3'P NMR detected a split Pi peak which indicates different pH environments. The pattern of recovery of the Pi peak to control values was dependent on the post exercise events. When unloaded exercise was performed during recovery the Pi peak at the lower pH recovered rapidly and the Pi peak at the higher pH was reduced but still present. In passive recovery, where no exercise was performed, the Pi peak at the higher pH disappeared more rapidly than the Pi peak at the lower pH.300A split in the ATP signals from the human finger flexor muscle, and from the human gastrocnemius and biceps muscle, has been detected using 'Hdecoupled 31PNMR following exercise. The changes in the chemical shifts of the signals from y-ATP and P-ATP were 0.4 ppm and Oil ppm, respectively. The pHi calculated from the shifts of ATP was in good agreement with that obtained from the shift of Pi peak.301 The effects of short-term intermittent hypoxic training on muscle energetics during submaximal exercise have been investigated with 31P NMR in elite combination skiers. The level of PCr/(PCr + Pi) and pHi during submaximal exercise were significantly increased by training in hypoxic conditions (in a hypobaric chamber with conditions equivalent to an altitude of 2000m) and the post-exercise recovery rate of PCr was significantly increased.302A study of the rate of PCr resynthesis after exercise in trained and untrained volunteers has been

416

Nuclear Magnetic Resonance

carried out using four levels of exercise. 31PNMR detected a difference in the end exercise pH and ADP concentration for athletes compared to untrained volunteers after the two most severe exercise regimes. The recovery rate of PCr was faster in the athletes.303The effects of caffeine on creatine loading in muscle has used 31P NMR to determine the metabolic responses. Caffeine administration did not affect the increased muscle PCr content caused by creatine loading and no differences were seen in the 31Pmetabolites during exercise. However, caffeine did prevent the increased dynamic torque production caused by creatine admini~tration.~’~ The effects of oral administration of phosphocreatine on skeletal muscle during graded exercise has been followed with 31P NMR. Administration of phosphocreatine resulted in a smaller depletion of muscle phosphocreatine at higher work rates and a smaller cytosolic acidification during work and recovery.305 The failure of erythropoietin to improve the peak oxygen uptake of muscle despite an increase in haemoglobin content of the blood following therapy has been investigated. The cellular bioenergetics of muscle was followed with 31P NMR in patients after erythropoietin treatment for chronic renal failure. Despite a 50% increase in blood haemoglobin content the ratio of PCr/Pi for the vastus medialis at rest was unchanged from the values obtained from patients before erythropoietin treatment and was significantly lower than the ratio detected in control subject. Similarly, the cellular bioenergetics and muscle acidification following exercise for treated and untreated patients were not significantly different and were significantly lower than control values. However, at a given pHi no differences in the 31Pdata were seen between control and treated subjects implying a deficiency in ability to limit the decrease in pHi during exercise affects the bioenergetics of patients treated with erythropoietin for chronic renal A rare mitochondrial myopathy has been investigated with 31PNMR fai1~re.j’~ to examine the metabolic changes in muscle. There was a low PCr and high Pi content at rest and a small acidification of pHi upon exercise.307Treatment with coenzyme Qlo (CoQ) for mitochondrial myopathy has been investigated with 31P NMR to assess the response to exercise. Eight patients were treated with I50 mg CoQ d-I for six months. Patients were examined at rest, during exercise and immediately after exercise. An improved post exercise PCr/Pi ratio was seen in one patient, though, no reason could be found for this result.308 Natural abundance 13C N M R has been used to measure the glycogen to creatine ratio found in muscle of patients with glycogenolysis and other myopathies. High values of the glycogen to creatine ratio was found in muscle glycogenoses with no overlap of values with other diseased or normal The recovery of muscle glycogen after exercise has been measured in volunteers using 13C NMR at 1.5 T to examine the effects of glucose feeding compared to fructose feeding. The rate of glycogen recovery was 4.2% h-I after glucose compared to 2.2% h- after fructose.310A moderate glucose accumulation has been detected in skeletal muscle during a 2 h hyperglycaemic (22 mmol dm-3) clamp with somatostatin infusion.311 The use of 13C-labelled tracer fatty acids for the study of in vivo fatty acid I3C NMR has been used to assess the status by I3C NMR has been de~cribed.~” triglyceride content of the liver of patients with hepatic steatosis by the

12: Nuclear Magnetic Resonance Spectroscopy of Living Systems

417

determination of the total CH2-peak area of the liver spectra compared to spectra from a lipid phantom.313The effects of triglyceride infusion on glucose metabolism under euglycaemic hyperinsulinaemic clamp have been studied with simultaneous I3C and 31PNMR. The infusion of triglycerides had no effect on whole body glucose uptake for 3.5 hours but, glucose uptake then decreased continuously until it was 46% of control values after 6 hours. The rate of glycogen synthesis and oxidative glucose metabolism were unaffected for 3 hours after which they declined to 50% and 6O%, respectively. The decrease in muscle glycogen synthesis was preceded by a decrease in the muscle glucose-6-phosphate concentration after 1.5 hours of lipid The rate of glycogen synthesis and the level of glucose-6-phosphate in exercise-induced glycogen depleted muscle of normoglycaemic insulin resistant young people has been measured with I3C and 31PNMR, respectively. The initial rate of glycogen recovery during the first hour, which is insulin independent, was the same for both insulin resistant and normal subjects. However, the following 4 hours of glycogen resynthesis, which has been shown to be insulin dependent, was significantly reduced in the insulin resistant subjects.315 The contributions of hepatic glycogenolysis and gluconeogenesis to glucose production in the early postprandial period have been studied with I3C NMR. Following measurements of hepatic volume and glycogen content gluconeogenesis accounted for 55% of the rate of whole body glucose production whereas, glycogenolysis contributed 45% to this rate.31613CNMR has been used to study the storage of liver glycogen following a mixed meal. Liver glycogen content rose from 207 to 316 mmol dm-3 at an average rate of 0.34 mmol dm-3 min-'. Hepatic glucose output was completely suppressed within 30 minutes of the meal but increased again after 60 minutes. The pattern of change mirrored the plasma glucagon/insulin ratio.317The roles of glucagon and insulin in the regulation of hepatic glycogen synthesis and turnover in humans has been investigated with 13C NMR. It was shown that small changes in the portal vein concentrations of glucagon and insulin independently affect the hepatic glycogen synthesis and turnover. A two-fold increase in glycogen synthesis and a 73% reduction in glycogen turnover occurred under hyperglycaemia when insulin was at basal levels and glucagon secretion was inhibited.318 The detection of the glucose resonance at 5.23 pprn by 'H NMR at 4 T has been d e m ~ n s t r a t e d .Glucose ~'~ transport in the brain has been followed with 'H NMR. A rapid increase in blood glucose resulted in the appearance of elevated glucose peaks in the brain after a time lag.320Kinetic analysis of relative brain glucose concentrations yielded values for plasma glucose concentration at half maximal transport (K,) of 4.8k2.4 mM, a maximal transport rate (Tmax)of 0.8k0.45 pmol g-' min-', and a cerebral glucose consumption rate (CMR,],) of 0.32 k0.16 pmol g- min- . If cerebral glucose concentration was assumed to be 1 pmol g-' in euglycaemia then the results were K, = 3.9k0.82 mM, T,, = 1.16f0.29 pmol g-' min-' and CMR,], = 0.35+0.10 pmol g-' min-'. Pattern-recognition analysis of ' H NMR spectra from normal brain and five types of the most common adult supratentorial brain tumours has been demonstrated to distinguish each tissue type in 104 out 105 cases.321The automated

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Nuclear Magnetic Resonance

classification of human brain tumours by neural network analysis of 'H NMR data has been shown to distinguish tumour and normal tissue, classify malignant and non-malignant gliomas, and classify other tumour types to matched histology with an 82% accuracy.322 Factors influencing the spatial resolution and the information content of H spectroscopic images have been discussed with reference to the effect of these factors on detection and classification of turn our^.^^^ Changes in the lipid signals of bone marrow in leukaemia patients have been studied with 'H NMR. Low or absent 'H NMR lipid signals in leukaemic patients were shown to be reversible upon successful treatment.324The lipid content of the bone tumours, and their effect upon bone marrow, have been investigated with fat and water selective NMR imaging and 'H localised NMR ~ p e c t r o s c o p y'H . ~ ~NMR ~ has been used to examine the lipid resonances in brain tumours. Seventy five non-irradiated tumours were examined and lipids were detected in 29% of anaplastic astrocytomas grade 111, 60% of glioblastomas and 50% of metastatic tumours. Lipids were also detected in brain abscesses and epidermoid cysts, but, not in benign turn our^.^^^ Two methods for the extraction of information from N M R spectra which allows discrimination between normal and tumour tissue has been described. Discrimination was achieved using features of the whole spectrum or the peaks from the phospholipid precursors in the phosphomonoester region.327An improvement in the localised 'P NMR spectra of human cancers following the application of 'H-decoupling and nuclear Overhauser enhancement techniques has been reported and discussed.328 H-decoupling and nuclear Overhauser enhancement has been applied to 31P NMR to examine the phosphorous metabolites of 20 soft tissue sarcomas. Prominent NTP signals and low Pi indicated a high proportion of viable cells in 15 of the tumours which also had high amounts of phosphoethanolamine compared to phosphocholine. In these tumours no glycerophosphoethanolamine was detected and only 4 tumours contained glycerophosphocholine.329 Localised 19F NMR spectroscopy has been used to obtain measurements of the concentration of fluoro-p-alanine, the end product of 5-fluorouracil catabolism, in the liver of patients receiving a bolus of 5 - f l u o r o ~ r a c i l Simultaneous .~~~ acquisition of 3D localised 31Pand 19F NMR spectra from the liver of patients receiving bolus 5-fluorouracil chemotherapy have been performed.331

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Cady, E. B.; Wylezinska, M.; Penrice, J.; Lorek, A. and Amess, P. Magn. Reson. Imaging 1996,14(3), 293-304. Pan, J. W.; Mason, G. F.; Pohost, G. M. and Hetherington, H. P. Magn. Reson. Med. 1996,36(1), 7-12. Hetherington, H. P.; Pan, J. W.; Mason, G. F.; Adams, D.; Vaughn, M. J.; Twieg, D. B. and Pohost, G. M. Magn. Reson. Med. 1996,36(1), 21-29. Frahm, J.; Krueger, G.; Merboldt, K-D. and Kleinschmidt, A. Magn. Reson. Med. 1996,35(2), 143-8. Suzuki, E.; Shibata, T.; Yasuda, K.; Takeda, N.; Inouye, H.; Ishizuka, T. and Yasuda, K. Znt. Congr. Ser. l995,1084(Diabetic Neuropathy), 393-8. Jung, W.-I.; Widmaier, S.; Seeger, U.; Bunse, M.; Staubert, A.; Sieverding, L.; Straubinger, K.; van Erckelens, F.; Schick, F.; et a1 J . Magon. Reson. Ser. B 1996, 110(1), 39-46. Rosenstein, D. L.; Ryschon, T. W.; Niemela, J. E.; Elin, R. J.; Balaban, R. S. and Rubinow, D. R. J. Am. Coll. Nutr. 1995, 14(5), 486-90. Ward, K. M.; Rajan, S. S . ; Wysong, M.; Radulovic, D. and Clauw, D. J. Magn. Reson. Med. 1996,36(3), 475-480. Widmaier, S.; Hoess, T.; Jung, W-I.; Staubert, A.; Dietze, G. F. and Lutz, 0. Magn. Reson. Mater. Phys., Biol., Med. 1996,4(1), 47-53. Shen, D.; Gregory, C. D. and Dawson, M. J. Magn. Reson. Med. 1996,36(1), 30-38. Iotti, S.; Lodi, R.; Gottardi, G.; Zaniol, P. and Barbiroli, B. Biochem. Biophys. Res. Commun. 1996,225(1), 191-194. Shin, Y. J. Ungyong Mulli 1995,8(3), 273-7. Yoshida, T.; Watari, H. and Tagawa, K. N M R Biomed. 1996,9(1), 13-19. Widmaier, S.; Jung, W-I.; Bunse, M.; Van Erckelens, F.; Dietze, G. F. and Lutz, 0. N M R Biomed. 1996,9(1), 1-7. Kuno, S-Y.; Inaki, M.; Tanaka, K.; Itai, Y. and Asano, K. Eur. J . Appl. Physiol. Occup. Physiol. 1994,69(4) 301 -4. Takahashi, H.; Inaki, M.; Fujimoto, K.; Katsuta, S.; Anno, I.; Niitsu, M. and Itai, Y. Eur. J . Appl. Physiol. Occup. Physiol. 1995,71(5), 396-404. Vandenberghe, K.; Gillis, N.; Van Leemputte, M.; Van Hecke, P.; Vanstapel, F. and Hespel, P. J . Appl. Physiol. 1996,80(2), 432-7. Frassineti, C.; Iotti, S . ; Lodi, R.; Zaniol, P. and Barbiroli, B. In Vivo 1996, 10(4), 429-433. Marrades, R. M.; Alonso, J.; Roca, J.; Gonzalez de Suso, J. M.; Campistol, J. M.; Barbera, J. A.; Diaz, 0.;Torregrosa, J. V.; Mascians, J. R.; et a1 J . Clin. Invest. 1996, 97(9), 2101-21 10. Jehenson, P.; Marsac, C.; Duboc, D.; Stansbie, D.; Bonne, G.; Cousin, J.; Benelli, C.; Leroux, J. P.; Lindsay, G. and Syrota, A. J . Chim. Phys. Phys. -Chim. Biol. 1995, 92(10), 1801-5. Gold, R.; Seibel, P.; Reinelt, G.; Schindler, R.; Landwehr, P.; Beck, A. and Reichmann, H. Eur. Neurol. 1996,36(4), 191 - 196. Jehenson, P.; Duboc, D.; Labrune, P.; Fardeau, M.; Odievre, M. and Syrota, A. J. Chim. Phys. Phys. -Chim. Biol. 1995 92(10), 1797-800. Van Den Berg, A. J.; Houtman, S.; Heerschap, A.; Rehrer, N. J.; Van Den Boogert, H. J.; Oeseberg, B. and Hopman, M. T. E. J . Appli. Physiol. 1996,81(4), 1494-1500. Roussel, R.; Velho, G.; Carlier, P. G.; Jouvensal, L. and Bloch, G. Am. J . Physiol. 1996,271(3, Pt. l),E434-E438. Cunnane, S. C.; Likhodii, S. S . and Moine, G. Lipids 1996, 31(Suppl., Fatty Acids and Lipids from Cell Biology to Human Disease), S 127s 130.

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Petersen, K. F.; West, A . B.; Reuben, A.; Rothman, D. L. and Shulman, G . I. Hepatology (Philadelphia) 1996,24(1), 1 14- 117. Roden, M.; Price, T. B.; Perseghin, G.; Petersen, K. F.; Rothman, D. L. and Cline, H. J . Clin. Invest. 1996,97(12), 2859-2865. Price, T. B.; Perseghin,, G.; Duleba, A.; Chen, W.; Chase, J.; Rothman, D. L.; Shulman, R. G. and Shulman, G. I . Proc. Natl. Acad. Sci. U . S. A . 1996, 93(11), 5329-5334. Petersen, K. F.; Kitt, F.; Price, T.; Cline, G. W.; Rothman, D. L. and Shulman, G. I. Am. J. Physiol. 1996, 270(1, Pt. l), E186-El91. Taylor, R.; Magnusson, I.; Rothman, D. L.; Cline, G. W.; Caumo, A.; Cobelli, C. and Shulman, G . 1. J. Clin. Invest. 1996,97(1), 126-32. Roden, M.; Perseghin, G.; Petersen, K. F.; Hwang, J-H.; Cline, G. W.; Gerow, K.; Rothman, D. L. and Shulman, G. I. J. Clin. Invest. 1996,97(3), 642-8. Gruetter, R.; Garwood, M.; Ugurbil, K. and Seaquist, E. R. Magn. Reson. Med. 1996,36(l), 1-6. Gruetter, R.; Novotny, E. J.; Boulware, S. D.; Rothman, D. L. and Shulman, R. G. J. Cereb. Blood Flow Metab. 1996, 16(3), 427-438. Preul, M. C.; Caramanos, Z.; Collins, D. L.; Villemure, J-G.; Leblanc, R.; Olivier, A.; Pokrupa, R. and Arnold, D. I. Nat. Med. ( N . Y . ) 1996,2(3), 323-5. Usenius, J-P.; Tuohimetsa, S.; Vainio, P.; Ala-Korpela, M.; Hiltunen, Y . and Kauppinen, R. A. NeuroReport 1996,7(10), 1597-1600. Bovee, W. M. M . J.; Karlsen, 0. T. and Rozijn, T. H. Anticancer Res. 1996, 16(3B, Proceedings of the Special Symposium on ‘Lipid Metabolism and Function in Cancer’, 1995), 15 15- 1520. Schick, F.; Einsele, H.; Lutz, 0. and Claussen, C. D. Anticancer Res. 1996, 16(3B, Proceedings of the Special Symposium on ‘Lipid Metabolism and Function in Cancer’, 1995), 1 545- 155 1. Schick, F.; Duda, S. H.; Lutz, 0. and Claussen, C. D. Anticancer Res. 1996, 16(3B, Proceedings of the Special Symposium on ‘Lipid Metabolism and Function in Cancer’, 1995), 1569- 1574. Gotsis, E. D.; Fountas, K.; Kapsalaki, E.; Toulas, P.; Peristeris, G. and Papadakis, N. Anticancer Res. 1996, 16(3B, Proceedings of the Special Symposium of ‘Lipid Metabolism and Function in Cancer’, 1995), 1565- 1567. Tate, A. R.; Crabb, S.; Griffiths, J. R.; Howells, S. L.; Mazucco, R. A.; Rodrigues, L. M. and Watson, D. Anticancer Res. 1996, 16(3B, Proceedings of the Special Symposium of ‘Lipid Metabolism and Function in Cancer’, 1995), 1575-1579. Negendank, W. G.; Li, C-W.; Padavic-Shaller, K.; Murphy-Boesch, J. and Brown, T. R. Anticancer Res. 1996, 16(3B, Proceedings of the Special Symposium of ‘Lipid Metabolism and Function in Cancer’, 1995), 1539- 1544. Li, C-W.; Kuesel, A. C.; Padavic-Shaller, K.; Murphy-Boesch, J.; Eisenberg, B. L.; Schmidt, R. G.; von Roemeling, R. W.; Patchefsky, A. S.; Brown, T. R. and Negendank, W. G. Cancer Res. 1996,56(13), 2964-2972. Li, C-W.; Negendank, W. G.; Padavic-Shaller, K. A.; O’Dwyer, P. J.; MurphyBoesch, J. and Brown, T. R. Clin. Cancer Res. 1996,2(2), 339-45. Li, C-W. and Gonen, 0. Magn. Reson. Med. 1996,35(6), 841-847.

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13 Nuclear Magnetic Resonance Imaging BY TOKUKO WATANABE

1

Introduction

Topics covered in this and the last' annual report are limited to nuclear magnetic resonance imaging (NMRI) or microimaging or microscopy by employing a vertical high resolution NMR machine or a horizontal MRI machine for animal use because of the increasing number of papers concerned with this category. The previous five annual reports of this chapter aimed to cover the whole field of nuclear magnetic resonance imaging, including clinical research by employing a whole-body horizontal MRI The author has the impression that NMR imaging or microscopy has experienced a tremendous increase in its use in a diverse range of investigations ranging from basic research to applications in a wide variety of objects in liquid and solid states. This has increased the number of references and range of journals reviewed. This review mainly covers works whose abstracts have appeared in Chemical Abstracts NMR Selects between June 1996 and May 1997. Journals that concentrate on the development and applications within NMRI include Journal of Magnetic Resonance, Journal of Magnetic Resonance Imaging and Magnetic Resonance in Chemistry, Solid State Nuclear Magnetic Resonance, Magnetic Resonance in Medicine, NMR in Biomedicine, Magnetic Resonance Imaging, as well as more clinical publications, Radiology, American Journal of Roentgenology, Journal of Computer Assisted Tomography, Topics in Magnetic Resonance Imaging, American Journal of Neuroradiology, Neuroimage and Investive Radiology. Theoretical aspects of the field are often documented in Medical Physics and hardware developments regularly make an appearance in the Review of Scientific Instruments. Concepts in Magnetic Resonance, which presents fundamental aspects of the technique, and Magnetic Resonance Quarterly, which contains review articles of various topics of the field, are recommended from the educational view point. The abstract from the Annual Meeting of International Society for Magnetic Resonance in Medicine (ISMRM) is recommended as a means of deriving concise, up to date information on development within the subjects. New development in clinical MRI system is also useful in NMRI and should be paid attention to. RadioGraphics, the journal of scientific exhibits, technology and continuing education in radiology, is very educative for not only medical doctors but also basic scientists. A text book covering the field,

Nuclear Magnetic Resonance, Volume 27 0The Royal Society of Chemistry 1998 43 1

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Nucleur Magnetic Resonance

'Principles of Nuclear Magnetic Resonance Microscopy' by P. Callaghan is excellent.7 In 1996, many commemorative papers were given for the celebration of both the one hundredth anniversary of the discovery of the X-ray by Roentgen in 1895 and the fiftieth anniversary after the success of the first detection of the NMR signal by Bloch's group and Purcell's group independently in 1946. Articles concerning historical reviews and advances of NMR spectroscopy and imaging were given by pioneers in the early days and at the present In the clinical field currently pursued technologies and requirements for process tomography (X-ray CT, MRI, ultrasound and angiography) were reviewed from the view point of the quality of the diagnosis and roles for MRI were identified."," As mentioned above, the NMRI technique has infiltrated various non-clinical research fields, such as physicochemical, biological or physiological, geological, environmental, industrial applications during this review period. Especially, application in intact plants is successful and the flow of water or solutes such as sugar and water distribution in various kind of plants were investigated by flow sensitive NMR microscopy. The application to intact plants and agricultural crops is going to increase in the future. Generally, NMRI applied to dynamic phenomena such as diffusion, flow and/or velocity in various media has been greatly progressed both in theoretical treatment and in application. Heterogeneities in the porous structure, the relationship between the structure and mass transport in porous solids and the spatial distribution of pores were topics of interest during this review period. With regard to NMR imaging of solid materials, a number of challenges have to be overcome with the difficulties of solid state NMR imaging before wide spread use. To date a variety of strategies have been proposed for obtaining solid state N M R imaging. Issue 4 (July) of Vol. 6 of Solid State Nuclear Magnetic Resonance is a special edition for solid state imaging. In the application of NMRI techniques to problems of relevance to the process industries, the particular strengths of NMR techniques are their ability to distinguish between different chemical species and to yield information simultaneously on the structure, concentration distribution and flow processes occurring within a given process unit. Examples of specific applications in the areas of materials and food processing, transport in reactors and two phase flow were discussed. l 2

2

Basic Principles, Education and Reviews

MR imaging and volume localized spectroscopy in medical and material applications was reviewed with the explicit introduction of the principle of NMR and ESR imagings.I3 The basic experimental techniques, such as how to build spatial information, processing magnetization, the definition of field of view, resolution and contrast, the limitations on resolution, and experimental protocols of Fourier Imaging and projection reconstruction imaging were described. Gradient and spin echo imaging, as well as chemical shift selective imaging were dealt with and the principles of multiple selective Hadamard excitation discussed,

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as were some novel alternatives for selective excitation. Pulse sequences for three dimensional imaging as well as four dimensional spatial spectral imaging were briefly introduced. Metabolite imaging, multiple quantum imaging, volume localized spectroscopy, two dimensional volume localized zero quantum spectroscopy, stray field imaging for solids was also introduced. The article finally calls attention to the novel approach of magnetic resonance force microscopy as well. Recent developments in different techniques for three dimensional (3D) imaging, which include serial sectioning, X-ray tomographic methods and NM R scanning, was reviewed.I4 This provides a significant improvement of the tools available for studying and understanding the mechanical functions of cancerous bone. A full characterization of all elastic mechanical properties of the cancerous bone has been made possible by 3D reconstruction in combination with newly developed methods for large scale finite element analysis. Radiofrequency field gradient experiments were reviewed, including high resolution NMR spectroscopy and imaging.” The effect of experimental conditions on the data obtained from diffusion weighted NMR experiments was reviewed.I6 The origin and forms of the Stejskal and Tanner experiment were presented, and the relative merits of bipolar to monopolar diffusion weighting gradient pulses were discussed, as were those of spin echo and stimulated echo weighting schemes. Criteria for successful diffusion weighted imaging were given. From the view point of safety, exposure to static magnetic field was estimated for the employees of N M R - ~ n i t s . ’The ~ phenomena that were detected and measured in magnetic resonance microscopy experiments and that highlight applications that have contributed to cardiovascular research were reviewed.’* NMR in vivo spectroscopy and imaging of bone marrow was reviewed.”

3

New Instruments

New instruments with the sensitivity of the SQUID as an NMR detector were developed.20 Superconducting quantum interference devices (SQUID’S),which are the most sensitive detectors of magnetic fields, can be used to great advantage to measure NMR signals at low fields and frequencies. DC (direct current) SQUID operated in flux locked mode significantly improved the low field NMR results performed using an R F (radio frequency) SQUID, resulting in an increase in sensitivity and reduction in the signal acquisition time by a factor of more than 100. A simple one dimensional T I contrasted NMR image of a two component sample consisting of mineral oil and tap water at room temperature was demonstrated.20This using SQUID’Sin NMR imaging at low fields is promising for both medical applications and for materials’ nondestructive evaluation. Specific ferrite machining techniques were presented for a new NMR system composed of ferrite permanent magnets and an open H shape.21A prototype positron emission tomography (PET) scanner compatible with clinical MRI scanners and NMR spectrometers was developed.22 Simultaneously acquired PET and MR phantom images show no significant artifacts or distortions. Measurements with a point source demonstrate that this PET system has a

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reconstructed resolution of 2.1 mm, a coincidence time resolution of 26 ns and a typical energy resolution of 45%. The resolution in NMR microscopy is limited by a combination of the inherent low sensitivity of NMR, the destruction of spin magnetization gratings by molecular diffusion, and variations in the local magnetic field strength introduced by spatial variations of the bulk susceptibility. Many hardwares were developed for higher resolution and higher accuracy of NMRI. A quadrature multiple R F coil system was developed for use in a vertically polarized NMR imaging system to maximize signal to noise ratio over a given field of view.23 Conceptual coil conductor patterns were formulated and the theoretical analysis of magnetic field patterns was performed. Test results with the prototype were acquired to verify the theoretical work performed. In order to acquire the magnetic field maps on the surface of a cylinder or sphere rapidly and accurately, an array of NMR coils multiplexed to a single radiofrequency receiver was used as NMR probes.24 This array significantly decreases the time necessary to map Bo and improve field map accuracy. A limitation of this approach is that NMR resonant circuits are inherently narrow band which limits the apparatus to a specific field strength and only points in space defined by the array layout. Small birdcage resonators for high field NMR m i c r o ~ c o p y multituning ,~~ of birdcage resonators,26 and shielded R F resonators for NMR/MR127 were developed. From the current densities calculated in shielded ellipsoidal R F coils by using a new method, accurate field distributions can be calculated and the effects of shielding the probe deduced.27Preliminary experimental results for circular cross section R F resonators confirm the accuracy of the calculated fields. The method of current density calculation is applicable to coils of various cross sectional shapes. Strong radiofrequency field gradients with spatial resolution better than five micro m were developed.28 A 3DFT gradient echo technique has been developed which, in conjunction with series resonant gradient coil circuits, can produce three dimensional NMR images with T E < 100 P S . ~ ’ The method involves a read gradient waveform composed of two sinusoids of different frequencies. The important features of the new method are that with suitable phase encoding all octants of k space are sampled, the R F pulse is applied when the gradients are all zero, and the echo forms when the gradient is essentially constant. This method will allow more extensive applications of solid imaging techniques to biological samples in vivo. Constant time imaging methods, which are the optimal approach to recording images when the factors, such as the destruction of spin magnetization gratings by molecular diffusion and variations in the local magnetic field strength introduced by spatila variations of the bulk susceptibility, are important, was introduced, analyzed in the presence of molecular diffusion, and demonstrated to yield high resolution images.30 Large oscillating field gradients were used to three demensional NMR imaging.31 To implement the method, a microscopy probe was constructed for a standard bore 400 MHz NMR spectrometer (the latter was also implemented at 600 MHz), which is described. A Radiofrequency ESR spectrometer/imager is described32 modified from a Surrey Medical Imaging Systems NM R spectroscopy/imaging console.

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43 5

Pulse Sequences

The high field magnetic resonance (MR) characteristics of fluids in porous reservoir rocks exhibit short T2 relaxation times and broad natural line widths. These characteristics severely restrict which NMRI methodology can be used to obtain high resolution porescale images of fluids in porous rock. A MR microscopy protocol based on 3D backprojection using strong imaging gradients was developed to overcome many of these constraint^.^^ Software has been developed to perform 3D erosion/dilation and to extract the pore size distribution from binarized 3D images of fluid filled porosity. Resolution as high as 25 pm per pixel has been obtained for fluid systems in Bentheim and Pontainebleau sandstones. A fast volumetric imaging technique has been demonstrated for imaging fluids contained in porous media. Acquisition time was reduced by 3D PEPI hybrid,34 Hadamard NMRI,35and fast NMRI with B1 gradient.36 The 2D n-modified EPI or PEPI technique forms part of a novel 3D imaging technique which incorporates a z axis phase encoding procedure to yield a 3D PEPI hybrid.34 Full isotropically resolved data sets with good SIN ratio may be acquired in several minutes using the 3D PEPI hybrid. This is in contrast to acquisition times of several hours for standard 3D imaging techniques. Hadamard NMRI with slice selection was developed on a conventional Bruker MSL 300 spectrometer, with the result that the inherent systematic noise was eliminated and data acquisition times were comparable to those of ultrafast imaging technique^.^^ Although stochastic NMR imaging is’ one of the less common NMR imaging techniques, stochastic rf excitation is characterized by some remarkable features and is of interest for imaging of large objects, because the rf excitation power is at least two orders of magnitude lower in comparison to conventionally pulsed NM R imaging schemes. New imaging methods for specific purposes were developed, such as gradient echo sampling of FID and echo,37radial spectroscopic imaging38and a diffusion weighted multi spin echo pulse sequence.39 A multislice NMR imaging pulse sequence capable of measuring both the reversible and irreversible contribution to the transverse relaxation rate (R(2)’ and R(2)) in a single scan was described.37 The method, termed GESFIDE (gradient echo sampling of FID and echo) is based on sampling the descending and ascending portions of a Hahn echo with a train of gradient echoes. R(2) and R(2)’ were computed by exploiting the differential evolution of the transverse magnetization before and after the phase reversal pulse. Salient features of the method are its insensitivity to R F pulse imperfections and its high precision and efficiency. A family of fast chemical shift imaging (CSI) techniques, which take advantage of the cylindrical symmetry found, for instance, in some plants, was i n t r ~ d u c e dRapid . ~ ~ measurement of the radially dependent spatial distribution of metabolites and the minimal experimental duration can be accomplished substantially, compared to conventional CSI and correlation peak imaging. Radial spectroscopic ‘H NMRI of metabolites in Ancistrocladus heyneanus, a tropical liana plant, was shown, using both radial chemical shift imaging and radial correlation peak imaging. The reduction of experimental duration compared to the conventional techniques was by a factor

Nuclear Magnetic Resonance

436

of 63 and 3 1, respectively. A diffusion weighted multi spin echo pulse sequence by combining CPMG imaging and pulsed field gradient NM R was presented, which allowed for simultaneous measurement of T2, the fractional amplitude, and the diffusion constant of different fractions.39 Monte Carlo simulations demonstrate an improvement of this sequence with respect to the accuracy of diffusion constant and fractional amplitude for slow exchange. Burst imaging and DUFIS realize fast imaging without rapid switching of magnetic field gradients. Interestingly, when one dimensional Fourier transform is applied, Burst imaging becomes similar to line projection scanning, a concept proposed earlier by Mansfield and M a ~ d s l e y . ~The ' line scanning interpretation was applied to two dimensional Burst imaging, and the relationship between its two dimensional k space trajectory and line scanning interpretation was discussed.41 'Diffusion diffraction' experiments on water, yielding 'q space' plots, were conducted on suspensions of oxygenated (diamagnetic) human erythroc y t e ~ From . ~ ~ the relevance of diffusion diffraction of water, the shape of the q space plots, diffusion anisotropy, and the pseudo first order rate constant characterizing the covalent inhibition of water to NMR based histological characterization of tissues, erythrocyte alignment in the small vessels of the brain was noted. A computer program has been developed for evaluating the NMR signal response of various imaging parameters and its efficiency in fat suppression of the RODEO (Rotating Delivery of Excitation Off resonance) pulse sequence.43 Both spoiled and refocused RODEO pulse sequences have been considered. Excellent fat suppression can be achieved by choosing appropriate imaging parameters. Proton decoupled, NOE enhanced, phospholipid saturated 31Pspecta localized to defined regions within the normal liver by using three dimensional chemical shift imaging were demonstrated, resulting in enhancement significantly inprove the signal to noise ratio and enhance resolution of metabolites in in vivo 3'P MRS.44

5

Data Processing

Two real time NMR image processing systems using high speed personal computers have been developed.45The first was made with a MS DOS (Microsoft Disk Operating System) PC system (CPU, Pentium; clock frequency, 100 MHz) and a homebuilt frame memory board. The second was made with a MS Windows (Microsoft Windows 95) PC system (CPU, Pentium; clock frequency, 133 MHz). The reconstruction time for one 128 x 128 image was 280 ms for the DOS system and 120 ms for the Windows system, while the image display time was 30 ms for the DOS system and 120 ms for the Windows system. NMR imaging experiments for observing unsteady particle or bubble motion in fluids were performed using these systems. A PC based NMR off line data processing system is developed and described in With this software system, one dimensional (lD), two dimensional (2D), and NMR imaging (MRI) data can be processed easily, and give reliable results. The use of principal component

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analysis in spectral quantification was extended to the estimation of frequency and phase shifts in a single resonant peak across a series of spectra.47 The estimated parameters can be used to correct the spectra accordingly, resulting in more accurate peak area estimations. Further, the removal of the variations in phase and frequency caused by instrumental and experimental fluctuations makes it possible to determine more accurately the remaining variations, which bear biological significance. The procedure is demonstrated on simulated data, a 3D chemical shift imaging dataset acquired from a cylinder of inorganic phosphate (Pi), and a set of 736 31PNMR in vivo spectra taken from a kinetic study of rat muscle energetics.

6

Artifact, Noise and Optimization

The effect of magnetic field inhomogeneity on image quality was d i s c ~ s s e d . ~ ' - ~ ~ The field inhomogeneity leads to a distortion of the image when the reciprocal space is sampled on an oblique plane. This effect is especially strong in echo planar imaging (EPI). Reduction of .the distortions by the multishot EPI acquisition and the specific artifacts related to resonance offset, signal amplitude variations, gradient reversal, or transverse interference in multishot EPI was analyzed and illustrated using phantom and human head irnage~.~'Various methods for avoiding the artifacts are described, including echo time shifting, variable excitation tip angle, one directional sampling, and the application of steady state free precession. Quasi immunity of B1 gradient NMR microscopy to magnetic susceptibility distortion^,^^ negative edge enhancement with diffusion at permeable susceptibility interface^,^' and pulse sequence dependent diffusion related edge enhancement4 in NMR microscopy were discussed. Self diffusion of nuclear spins has been suggested to cause edge enhancement in images especially on a microscopic scale. According to previously published work, edge enhancement is caused, theoretically, by motional narrowing due to the boundaries and spin self diffusion during the data acquisition period. More careful examination reveals that edge enhancement due to motional narrowing develops only under a few specific condition^.^' It is found that edge enhancement depends greatly on the data acquisition mode; therefore, the images obtained are different depending on the pulse sequence employed. The new phenomenon observed has been termed selective spectral suppression since the observed edge enhancement results from the selective attenuation of certain frequency components in the nuclear signals due to diffusion dependent signal attenuation for a given pulse s e q ~ e n c e . ~ ' Gradient acoustic noise in MR imagers was characterized and predicted.52 Correction of motional artifacts in diffusion-weighted images using a reference phase map,53 optimization of signal-to-noise ratio for quadrature unmatched R F coils,54 and correction for rf inhomogeneities in multiecho pulse sequence MRI dosimetry" was described. Spectroscopic proton image data recorded with the aid of a gradient echo spectroscopic imaging pulse sequence were reported.56 A postdetection processing methodwais suggested which permits correction of artifacts due to inhomogeneity, susceptibility, and chemical shift resonance

438

Nuclear Magnetic Resonance

offsets. That is, apart from the spectral information available in this way, better spatial resolutions can be achieved. The method was demonstrated by resonance offset corrected images of the human finger in vivo. Moreover, resonance line selective and spectroscopically resolved diffusion weighted images and diffusivity maps rendered with the aid of the same postdetection procedure were shown.

7

Solid State NMR Imaging

Solid state NMR imaging techniques have been steadily improving over the years. Today high resolution images of rigid solids are now accomplished by many different means. One of such techniques to solid state NMRI is based on magic echoes. The theoretical background of magic echoes, their spatial encoding and the magic echo imaging pulse sequences presently in use are re~iewed.~' In this review the applicability of these methods for the investigation of materials is demonstrated and perspectives for materials science are outlined. A magic echo imaging method is presented which allows quasiconventional 'H NMR Fourier imaging of rigid solids involving constant time phase encoding as well as frequency encoding under multiple pulse line narrowing condition^.^^ With the effective transverse relaxation time in solids, T2eE, as a contrast parameter, the immobilization in cold drawn polycarbonate within a shearband is made visible. A new approach to solid state imaging using tetrahedral magic echoes (TME) is proposed and compared with the previously reported modified magic echo (MME) appro ache^.^^ The TME narrowing is substantially superior to the MME narrowing for solids where the heteronuclear dipolar interaction between H and a second spin species is comparable in magnitude to the homonuclear 'H-'H dipolar interaction. Three approaches to reducing image artifacts, i.e., gradient decoupling, time sequenced second averaging and over sampling, are described that are specific to multiple pulse line narrowing methods of NMR imaging.60 Stray field magnetic resonance imaging is reviewed.61The authors described their implementation of a two dimensional version of the stray field imaging method on a commercial instrument capable of collecting wideline NMR data and the use of this method in the examination of solid materials of interest in the aerospace industry. Hydration and hardening processes of Portland cement (type I) were studied by analysis of the one dimensional projections (profiles) obtained periodically with the 'H NMR stray field imaging technique over two days.62 Multinuclear NMR imaging of * 'B quadrupolar solids was demonstrated with the fringe field method.63For abundant nuclei, the combination of multiple pulse line narrowing and pulsed field gradients have greatly improved both the resolution and sensitivity of the imaging experiment, but often at the expense of the chemical information in the material. Means of incorporating NMR parameters in the imaging experiment to generate image contrast which provides information about local variations in the chemistry of the material were imaging technique with magic sandwich echoes is used d i s c ~ s s e dA. ~ 'H-NMR ~ to acquire localized wideline spectra and then to obtain localized molecular mobility contrast for imaging of solid polymers (compositions of polystyrene and

'

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high impact strength polystyrene, and polycarbonate and low density polyethylene).65The van Vleck second (M(2)) and fourth (M(4)) moments of the rigid components show considerable variation with the spatial composition of the investigated samples. A new 'H NMR imaging method, in which the relaxation time provides the contrast, is demonstrated to be suitable for investigating the effect of shear bands strongly localized inhomogeneities of the plastic deformation on the local mobility of polymeric materials in the solid state.66 The immobilization of a shear band in cold drawn polycarbonate (PC) is visualized for the first time. Vacancy induced atomic motion in 3He-4Hemixture crystals in coexistence with the liquid was revealed by 3He NMR imaging in the temperature range between 0.45 K and 1.3 K.67 The spatial distribution of the density 3He, and that of TI and T2 relaxation times in the solid and in the liquid along the vertical direction of the experimental cell, i.e., perpendicular to the solid liquid interface, were imaged. See Sections 8 (other nuclei) and 12 (polymers) as well for solid state NMRI.

8

Other Nuclei

Papers concerning 23Naand 31PNMRI are reviewed in the section, with in vivo applications as well. 2D-NMRI: The quadrupole splitting of the resonance was exploited to provide a quantitative characterization of the local strain of deuterated poly (butadiene) oligomers incorporated into elastic rubber bands.68 By application of a double quantum filter only the magnetization of the strained areas of the rubber sample was imaged. The double quantum filtered signals from areas could be obtained, where the local strain was too small to be detected as a line splitting with the spectroscopic technique. I9F-NMRI: 19F-NMRmicroscopic imaging together with 19Fsolid state MAS NMR spectroscopy was demonstrated as a reliable and readily accessible technique with which the distribution and diffusion of blowing agents in rigid insulating foams can be detected and m ~ n i t o r e d In . ~ the ~ case of fluorocarbon blowing in polystyrene and polyurethane foam samples the quantitative effective diffusion coefficients and activation barriers of the blowing agents were directly calculated from the imaging data. In in vivo systems a 19F nucleus has a great advantage because of no background signal in intact tissues and a wide spread range of the chemical shift. The distribution of fluorinated anesthetics, halothane and isoflurane, in rabbit brain was mapped during the course of their uptake using 2D-19F chemical shift imaging technique^.^' Sevofluran uptake, distribution and elimination in rat brain was also in~estigated.~' 23Na-NMRI: NMR spectroscopy and imaging of 23Na nuclei in cartilage,72 ordered environment^^^ and brining pork74 were investigated. Measurement of the sodium concentration and estimation of the cartilage matrix fixed charge density in control, acid neutralized, and enzyme digested bovine nasal cartilage, a model for human cartilage were carried out and the mean ion activity coefficient of sodium in cartilage was ~ a l c u l a t e d The . ~ ~ ingress of sodium ions into post

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rigour porcine muscle during brining was followed by one dimensional 23Na NMR imaging. The ingress is well described by Fick's second law, with an inter diffusion coefficient that decreases exponentially with the sodium ion content (between 8 and 20 mg / g cured pork). 27A1-NMRI: Dissolution kinetics of aluminum containing drugs at physiological doses and their removal from the human stomach have been followed by 27Al NMR spectroscopy and the time course of gastric emptying has been visualized with 27Al NMRI under normal conditions and in the presence of an antimuscarinic agent.75The gastric pH is directly visualized only by 27AlNMRI. 3'P-NMRI: Mitochondria1 inorganic phosphate (Pi) has been shown to be undetectable by 31P NMR in the isolated rat liver perfused under physiological conditions. Vidal et al. have demonstrated that Pi in mitochondrial compartment can be detected by NMR under normothermic conditions (37 degrees C) in acidic (pH 6.5, bicarbonate free) perfused liver using 50 nM of valinomycin or 10 pM of N,N' dicyclohexylcarbodiimide (a mitochondrial H ATP synthase i n h i b i t ~ r ) . ~ ~ 3He and '29XeNMRI: The magnetization effects and NMR signal dependence of two noble gases, 3He and '29Xe, are modelled across a range of gradient echo imaging parameter^.^^ The possibility of using hyperpolarized '29Xe for functional MRI is discussed in view of the results from the blood flow analysis. The short lived nature of the hyperpolarization opens up new possibilities, as well as new technical challenges, in its potential application as a blood flow tracer. An efficient method for the introduction of laser polarized xenon into systems of biological and medical interest for the purpose of obtaining highly enhanced NMR/MRI signals was de~cribed.'~ Using this method, the first observation of the time resolved process of xenon penetrating the red blood cells in fresh human blood was made. The potential of certain biologically compatible solvents for delivery of laser polarized xenon to tissues for NMR/MRI is discussed in light of their respective relaxation and partitioning properties. +

9

Diffusion, Flow and Velocity Imaging

9.1 Theoretical and/or Model Experimental - NMRI and PGSE NMR studies have shown that it is necessary to consider heterogeneities in the porous structure over different length scales in order to be able to understand the relationship between structure and transport in porous solids. Moreover, the spatial distribution in pore structure is seen to influence strongly mass transfer processes occurring within the porous medium. Numerical simulations have been performed of transport within Cluster Cluster Aggregate (CCA) structures.79 A comparison of methods of simulating the diffusion process was presented, the results of which were compared with NMRI and PGSE NMR measurements of the tortuosity of commercial catalyst pellets. A multifractal description of porous media is also proposed in the form of a Composite CCA structure.79 The information on molecular displacements over distances comparable to cell dimensions can be used to infer tissue microstructure and microdynamics. The expected effects of temperature, restriction, hindrance, membrane permeability,

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anisotropy and tissue inhomogeneity on the diffusion measurements were analyzed in order to interpret biological tissues which differ markedly from the theoretical ‘infinite isotrope medium’.80 Diffusion tensor imaging, q space imaging and diffusion spectroscopy of metabolites can further enhance the specificity of the information obtained from diffusion NMR experiments. ‘Mansfield (k space) diffraction’ was compared with the ‘diffusive (q space) diffraction’ and their similarity and differences were noted by Callaghan.81The diffusive diffraction concept is extremely helpful in elucidating the Pulsed Gradient Spin Echo NMR experiment for fluid molecules in porous media and has been applied successfully to the model isolated pore (the ‘single slit’ case) and the orientationally disordered interconnected pore glass (the ‘powder grating’ case). The flow of water through the pore spaces of model objects, which were computer-simulated for 2D and 3D ‘random Swiss cheese percolation’ and ‘random site percolation’ pore networks, was studied with the aid of NMR microscopy in the velocity mapping variant.82 The results for the model objects were juxtaposed to those for lacunar materials such as pumice, sponge, sand, and flow velocity mapping in random percolation glass bead a g g l ~ r n e r a t e s . NMR ~~-~~ model objects evidenced for a power law dependence of the volume averaged velocity on the probe volume radius.83 A pulse sequence for six dimensional spin density/velocity NMR imaging was employed for the combined record of the three dimensional spin density distribution and the three dimensional velocity vector field of water percolating through the pore space.84 The Mansfield and Issa model of voxel pair coupling is extended using electrical circuit simulation to interacting voxel clusters comprising all configurations of contiguous voxels up to and including four voxels. This information is used to simulate flow through porous rock samples by calculating the expected velocity distributions found in porous rocks using the PEP1 rapid NMR imaging technique.” A stochastic model of fluid flow in porous rocks based upon the experimental observation of water flow through a Bentheimer sandstone core was proposed.86 The how maps were measured by NMR imaging techniques. The stochastic theory led to a Gaussian velocity distribution with a mean value in accord with Darcy’s law and a prediction of a linear relationship between flow variance and mean fluid flow through rock. Examination of a flow coupling mechanism between isolated voxel pairs leads to a complementary explanation of the Gaussian velocity distribution and further details of the Mansfield Issa equati01-1.~~ A theoretical framework for the description of the phenomenon of electro osmosis was developed.*8 The main emphasis of the work is to develop relations that describe the time and spatial resolution of the velocity of the liquid in contact with a charged surface when a train of electric field pulses are applied parallel to the surface. The method becomes a powerful tool in the field of colloid chemistry. 9.2 Diffusion, Flow and Mass Transport - The influence of pore structure on mass transfer through porous alumina catalyst pellets was r e p ~ r t e d . ~NMR ’ imaging is shown to be a useful technique for gaining insight into the effect of the manufacturing process on the mass transfer properties, transport heterogeneity and anisotropic diffusion, of porous catalyst pellets. The molecular displacement

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profiles of water molecules in cellulose fiber samples with different water contents were measured as a function of the diffusion observation time ( 5 to 1200 m ~ ) . ~ * The displacement profile characterizes the average pathway of liquid molecules imbibed in a microporous medium. Areal distributions of oil and water in an immiscible fracture flow were resolved on the basis of their NMR T1 relaxation times." In order to quantify the volume of nonaqueous phase liquid (n hexane) present in a bed of water saturated sand contained within a vertical column, it is demonstrated how NMRI can be used and the data was analyzed by three models, i.e., the linear mass transfer model, the pore diffusion model and the shrinking core The pore diffusion model gave best agreement with the experimental data. Proton NM RI of Fushun bituminous coal swelling deuterated pyridine d(5) and acetone d(6) illuminated proton distribution of the mobile phase within the coal macromolecular networks93 and some information on the transport and swelling behavior of coal was obtained. The time dependent swelling and deswelling of Illinois No. 6 coal by pyridine were measured by combined NMR and NMRI technique^.'^ The results indicate that pyridine transport in this coal proceeds via Case I1 diffusion for swelling and via Fickian diffusion for deswelling. The differences between the swelling and deswelling characteristics are discussed from the viewpoint of coal's intrinsic structural properties and stored geologic pressure effects. T1 maps were employed to measure the rate of axial spreading of paramagnetic tracers (GdC13) inside the 6mm bead pack in the range of flow rate from 0.015 mL/s to 0.175 mL/s." Tracer concentration profiles and spatial variations in the dispersion coefficient were observed. NMR relaxation and imaging have been applied to study preparation processes of ceramic porous samples.96 Relaxation analysis gives a clear characterization of the materials, with high sensitivity. Waterflooding is a widely employed technique in enhancing oil and gas recovery. NMR imaging has shown itself to be an important tool for improving analysis of flow behaviour during waterflooding in heterogeneous The shape of the displacing front during water injection in highly heterogeneous reservoir carbonates was e ~ a l u a t e d . ~The ' thickness of the concentration polarization layers formed during crossflow membrane filtration of an oil water emulsion was quantitatively measured and the formation and development of the oil polarization layers was visualized non invasively using NMR chemical shift selective micro imaging.98A chemical shift selective NM R flow imaging sequence using stimulated echoes for data acquisition is presented to yield two dimensional velocity distribution maps of the oil droplets and of the water ~ e p a r a t e l yIt. ~was ~ then used to investigate the fluidity of concentration polarization layers formed from the oil droplets during crossflow membrane filtration. Phase flow encoded NMRI was used to study the pipe flow behavior of cellulose fiber suspensions when cationic polyacrylamide (C PAM) had been added as a flocculant.''' The addition of C PAM increases the fiber flocculation and the shear strength of the fiber flocs. The break up process of fiber flocs in highly turbulent flow is of great importance to produce paper with an even fiber distribution. NMRI was used to study the ingress of water into poly(tetrahydr0The study offers strong furfuryl methacrylate co hydroxyethyl methacrylate).

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evidence that the diffusion is Fickian in nature. The diffusion coefficient, D, obtained by fitting the underlying diffusion profile according to the equation for Fickian diffusion, is 1.5 x 10-"m2 s-l, which is in good correlation with the value of 2.1 x 10- I'm2 s- I , obtained from mass uptake measurements.

9.3 Velocity and Its Profile - Spatially resolved velocity profiles and spatially nonresolved velocity distributions of steady flow in a tube and bead packs were measured.'02 The velocity histogram was calculated from spatially resolved velocity phase encoded images acquired in a 6 mm bead pack. A Fourier flow method was used to measure the velocity distribution directly in a 0.25 mm bead pack. The method, based on NMR velocity imaging, allowed the direct measurement of velocity, and consequent calculation of shear rate, at a spatial resolution of around 10 pm, sufficient to resolve apparent slip at the inner wall from shear banding within the bulk of the fluid.lo3 The observation of shear banding, under Couette flow, of the worm like surfactant system, cetylpyridiniumchloride (1 OOmM) / sodium salicylate (60mM) was reported.'03,'04 Two special magnetic resonance imaging techniques, Fourier encoding velocity imaging (FEVI) and two or three dimensional multistripe/multiplane tagging imaging, were applied to the Rayleigh/Benard problem of thermal convection for the first time.lo5 The main perspective of this work is that the combined application of FEVI and multistripe/multiplane tagging imaging permits quantitative examinations of thermal convection for arbitrary boundary conditions and with imposed through flow apart from the direct visualization of convective flow in the form of movies. Strategies for NMR based rheometry are discussed with particular attention given to ease of implementation, robustness, and measurement of The techniques are based on NMR velocimetry of Poiseuille flow, and together with measurements of the pressure drop. In this article methods for NMR velocimetry are briefly reviewed. lo6 Apparent slip was observed in 0.2% aqueous solutions of xanthan gum made from the material supplied by UNAM but not in that supplied by Aldrich or Kelco.lo7The slip appeared to be a function of molecular weight, possibly through sensitivity to the aspect ratio of the molecule. NMR offers a powerful technique to measure dynamic moisture profiles in porous building materials in a nondestructive way.'" A French limestone (Terce Sculpture) sample was saturated by capillary, and its drying was monitored by NMR imaging.'09 The results clearly showed the existence of two different stages in the drying process, and the physical key factor in the problem of staining was the amount of water evaporated during the first stage.

10

Solvent Assisted Imaging and Porosity

The local determination of porosity is an extremely valuable target because of different applications in petrophysics. In fact, obtaining a reliable profile of porosity or saturations could considerably improve the evaluation of transport properties of porous media, especially if applied to multiphase flow tests (i.e., for relative permeability characterization). However, the best procedure to adopt for

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this kind of study is currently under debate, involving different experimental choices both for acquisition and hardware solutions. In order to assess usefulness of application of N M R imaging methods as a porosity measurement tool for heterogeneous samples, selected carbonate cores, characterized by fractures and large vugs, were investigated using different instrumental solutions.' l o The quantitative characterization of macro porous materials with regard to pore width and pore width distribution was accomplished for the first time by using 'H NMR microscopy in combination with suitable methods of digital image analysis.' The authors present the newly developed algorithm and discuss the first experimental results in use of large pored glass filter systems filled with silicon oil as intrusion fluid. A novel method of determining median pore size and pore size distributions as a function of spatial position inside a porous sample was developed.'12 NMR cryoporometry, which is a method of measuring pore sizes and pore size distributions in the range of less than 40 Angstrom to over 2000 Angstrom pore diameter by the technique of freezing a liquid in the pores and measuring the melting temperature by NMR, was used in conjunction with NMRI to measure pore sizes with one, two and three dimensional spatial resolutions.' l 2 CPMG imaging is applied to the visualization of porosity and wetting heterogeneities in water saturated sandstone samples at 0.1 T.Il3 The formation of a filter cake during mechanical dewatering (filtration and expression) of sludge is studied using one dimensional NMRI of porosity profiles. l4

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11

Water and Hydration

In a recent study by Fyfe et al., chemical shift selective NMR imaging was used to monitor the location and concentration of water and Me2SO in test samples. The technique was applied to quantification of Me2S0 in rat kidney and liver at temperatures commonly used for introducing cryoprotectants into tissues. NMR micro imaging and proton relaxation times were used to monitor differences between the hydration state of the nucleus and cytoplasm in the Rana pipiens oocyte.''6 Individual isolated ovarian oocytes were imaged in a drop of Ringer's solution with an in plane resolution of 80 pm. Measurements of plasma and nuclear membrane potentials with KC1 filled glass microelectrodes demonstrated that the prophase I oocyte nucleus was about 25 mV inside positive relative to the extracellular medium. A model for the prophase arrested oocyte is proposed in which a high concentration of large impermeant ions together with small counter ions set up a Donnan type equilibrium that results in an increased distribution of water within the nucleus in comparison with the cytosol. Hydration of food was visualized by NMRI.Il7

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12

Polymers

New methods for probing structure and dynamics of heterogeneous solid polymers, such as amorphous polymers, elastomers, and core shell systems, on a

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different length scale by multidimensional NMR and NMRI was described.l18 On the molecular level high resolution multiple quantum spectroscopy of solids probe connectivities of different functional groups on length scales below 1 nm. On a mesoscopic scale NMR spin diffusion techniques probe phase separation and interfacial effects in polymer blends and block copolymers. On a macroscopic scale NMR imaging techniques allow one to spatially resolve differences in order and mobility in the necking region or in shearbands of deformed polymers. The experimental techniques for characterizing elastomer materials, parameter selective NMR images (TI, T2, T1, images) were reviewed in detail and the methods required for the data analysis are explained.'lg A special emphasis is put on the analysis of experimental errors within the framework of NMR imaging. The information from parameter selective images was correlated to crosslink density in rubber materials, sulfur cured and carbon black filled technical rubbers with different degrees of crosslink density and oxidative aging. Time evolution of spatial distribution: NMR and its imaging are powerful tools to study the dynamic behavior of dissolution process of polymers in their theta solvents. Biodegradable polymers have attracted much attention as implantable drug delivery systems. Uncertainty in extrapolating in vitro results to in vivo systems due to the difficulties of appropriate characterization in vivo, however, is a significant issue in the development of these systems. To circumvent this limitation, noninvasive magnetic resonance techniques, EPR and MRI, were applied to characterize drug release and polymer degradation in vitro and in vivo.'20 MRI makes it possible to monitor water content, tablet shape, and response of the biological system such as edema and encapsulation. The results of the MRI experiments give the first direct proof in vivo of postulated mechanisms of polymer erosion. 13CNMR relaxation times and NMRI of polystyrene (PS) in its theta solvent, cyclohexane, are measured at different ternperatures.l2' A two step model for the dissolution is proposed. Swelling effects in polymers were reported relating to time-dependence.122Polyacrylamide hydrogel (PAMG) is a kind of water absorbing functional material. Water distribution and structure of networks in gamma irradiated crosslinked PAMG samples was investigated in comparison with those in PAMG.'23 Metal ion uptake and transfer: In recent years, heavy metal uptake by biopolymer gels such as calcium alginate or chitosan has been studied for the recovery of heavy metals from aqueous solutions. To understand the mechanism of ion transport in these biopolymer systems, the transport of copper ions and rare earth ions into calcium alginate gels, immobolized cell biosorbents, and kombu (Laminaria japonica) algal biomass was investigated by using 'H NMR 127 Most of the work done on absorption phenomena in such microscopy. materials was concerned with equilibrium concentrations of different heavy metal ions and their dependence on parameters such as temperature, pH and concentrations of competing ions. By NMR microscopy, both spatially and temporally resolved kinetic data of the absorption process was measured for the first time. It was demonstrated that rare earth ions are absorbed with a steep reaction front that can be described very well with a modified shrinking core model, while copper ions are absorbed with a more diffuse f r ~ n t . ' ~ Based ~ * ' ~ on ~ NMR

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imaging results of the spatial and temporal development of ion exchange processes in alginate gels, the question of appropriate modelling of these processes is discussed and Stefan's model (shrinking core model) was found to fit the behaviour of rare earth and actinoid ions.Iz6 The diffusion coefficient of copper in these gels was calculated from the NMR data to fit a combined diffusion reaction model involving a diffusion term (D) and a kinetic binding term (k).I2' Gels for NMRI dosimetry: In recent radiotherapy techniques, such as boron neutron capture therapy (BNCT) and proton therapy, the high nonuniformity of the spatial distribution of absorbed dose makes mandatory 3D dose determinations in order to carry out good treatment planning. The investigation of proper dosemetric techniques is desirable. For such dosimetric techniques a chemical dosemeter (ferrous sulfate solution) incorporated in a polymer gel was develIonizing radiation causes a variation in certain parameters of the oped. 128system such as the relaxation rates of hydrogen nuclei, measurable by NMRI or the gel optical absorption in the visible spectrum. Fricke infused agarose gel phantom containing loB in the amount typically accumulated in tumours for BNCT was a n a 1 y ~ e d .The I ~ ~ isodose curves were obtained from NMR analysis of a phantom after irradiation in the thermal column of a nuclear reactor. A method for depth dose profiling in tissue irradiated by a proton beam is also suggested (resolution of the Bragg peak position; within 0.1 mm, widening in the peak ramp; about 1 mm). An automated fast MRI method for localized measurement of dose distribution using NMR-Fricke gel dosimetry was developed and the influences on the measurement accuracy was e~a1uated.l~' Diffusion of iron is one of the major problems limiting the usefulness of NMR gel dosimetry. From the results of dual gel samples using a 4.7T micro imaging MR scanner and a fast TI imaging sequence (the acquisition of a 64 x 128 x 8 data sets in less than 15 min) it is proposed tha,t a gel consisting of 1.5% agarose (for stability), 3% gelatine and O.lmM xylenol orange (to combat diffusion and allow a visual evaluation) is a suitable base for NMR dosimetry gels and the use of a fast TI imaging sequence reduces acquisition times and therefore the potential impact of diffusion.l 3 Monitoring of Process: 'H NMR spectra and images have been acquired during polymerization of a mixture of soluble reactive methacrylamide (monomer) and N,N' methylenebisacrylamide (cross linking molecule) by adding ammonium persulfate (initiator) and tetramethyl-ethylenediamine (accelerator) to form long chain, cross linked p01ymers.l~~ To verify homogeneous polymerization, multidimensional NMRI was utilized for in situ monitoring of the process for the first time. The in situ NMR measurements were performed during sulfur vulcanization of unfilled SBR by using a vulcanization device which was constructed for use in combination with a standard microimaging probe in a vertical bore NMR magnet.'33 A complex aging regime takes place in the course of thermal aging of natural rubber, depending on the kind and the content of the free crosslinker, the aging temperature, the duration of the aging period and the reactivity of the atmosphere (air or nitrogen). A different aging process was observed by NMR and parameterselective NMRI.'34 Material property imaging

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for the investigation of aging processes in elastomer materials (rubber samples consisting of four pieces of natural rubber with different oxidative aging) was proposed based on conventional parameter selective imaging.'35 Structure formation: The influence of polyelectrolytes on structure formation in liquid crystalline Na dodecylsulfate/decanol/water systems was investigated by means of small angle X-ray diffraction, theology, NMR spectroscopy, and microscopy. 13' The spatial heterogeneity of the molecular mobility of the competitive vulcanization of natural rubber and high cia polybutadiene blends was studied to show the presence of domains of widely different molecular m o b i l i t i e ~ . 2D ' ~ ~NMR was used to image stress in strained elastomer bands made from natural rubber.'38 Deuterated poly (butadiene) oligomers were incorporated into the rubber network by swelling as spy molecules for probing the local chain orientation. The quadrupole splitting was spatially detected by spectroscopic 2D imaging and double quantum (DQ) filtered imaging. The first method can easily be implemented and is experimentally robust, but it suffers from low sensitivity to small strains while strong signals from isotropic regions restrict the dynamic range of the measurement. The second method is very sensitive to small strains, but only qualitative information is obtained unless a whole set of differently filtered DQ images is evaluated.

13

Food and Food Processing

NMRI is coming to be regarded as an integral technique in pre and post harvest investigations of physiological changes in fruit and vegetables, since MRI systems with cryornagnets large enough to accommodate samples of interest to postharvest researchers become more accessible. Furthermore, the non invasive, non destructive attributes of ' H MRI, and its ability to provide highly resolved spatial information concerning the distribution and magnetic environment of water in soft tissues, makes it an attractive technique for probing such samples in food materials. Fruits: Applications pertaining to the study of fruits and vegetables were reviewed, as well as recent developments that employ NMR principles as on line sensors in postharvest sorting and processing ~ i t u a t i 0 n s . lEffects ~ ~ of time and storage atmosphere on relaxation properties in persimmon fruit (Diospyros kaki cv Fuyu) were investigated during the five weeks following commercial harvest. I4O The experimental conditions required for discrimination of various types of tissue in fruits of cultivated strawberry (Fragaria X Ananassa) at high fields (ca. 7 T) have been in~estigated.'~'In marked contrast to soft fruits of other species, from which informative images have been derived at high fields using a variety of pulse sequences and acquisition parameters, appreciable image intensities from parenchymal and vascular tissues in healthy strawberry fruits were obtained only with a spin echo imaging sequence using large sweep widths (ca. 100,000 Hz), and consequently small values for TE ( < 5 ms), indicating predominantly short T2 values for these tissues. Freezing effects in fruit tissue of kiwifruit142and parenchyma apple'43were observed. In fresh and frozen thawed

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immature kiwifruits the formation of ice and the dynamics of freezing was visualized by loss of signal in affected areas of the fruit in SE irnaging.l4* Freezing commenced at the epidermis and gradually progressed towards the core. T2 relaxation was faster, and diffusion coefficient greater in frozen thawed fruit compared with fresh fruit. The power of the NMR relaxation technique is illustrated by using the changes in the distribution of NMR water proton transverse relaxation times to monitor the subcellular compartmentation of water and ice during the drying and freezing of parenchyma apple tissue.'43 It is quite interesting that in this paper authors assessed the potential of NMR and NMRI for non invasively monitoring the subcellular and intercellular redistribution of water in cellular tissue during drying and freezing processes and concluded that nonspatially resolved NM R relaxation and diffusion techniques still provide the best probes of subcellular water compartmentation in tissue, despite exciting advances in NMR micro imaging and NMR microscopy. Vegetables: NMRI, differential calorimetry and temperature measurements were used to monitor cylindrical potato sections frozen at 11C and 42C.144 Multiecho imaging together with monoexponential T2 decay fitting was applied to determine reliable proton density and T2 distributions over a white button mushroom at three magnetic field strengths (9.4,4.7, and 0.47 T).'45 Based on the results, it is concluded that imaging mushrooms at low fields (around or below 0.47 T) and short echo times has strong advantages over its high field counterpart, especially with respect to quantitative imaging of the water balance of mushrooms. The influence of the tissue structure of mushrooms, for example, tissue density (susceptibility inhomogeneity) and cell shape on the amplitude, T2 and T I images are analyzed with Gd DTPA solutions and acquiring saturation recovery multispin Echo images.146 Meat and Fish: The automated acquisition and processing of a set of magnetic resonance images which quantify the spatial distribution of the TI and T2 values, proton density (M(0)) and magnetization transfer (MT) rate has been developed and applied to pork cured in a brine solution.'47 The dependence of the NMR relaxation times on meat swelling induced by sodium chloride is also discussed. Changes in the fresh and frozen fish muscle from cod (Gudus rnorhua) and haddock (Melunogrurnrnus ueglefinus) were investigated by high resolution NMR and NMR114*.It was not possible to detect formaldehyde by NMR either in the stored fish samples or in spiked water or salt extracts even at high levels of formaldehyde addition, probably due to polymerization. Depending on the condition of the storage trials, dimethylamine or trimethylamine was detected. 'Fresh' cod and haddock samples purchased from a local supermarket showed high levels of TMA indicating a breakdown of trimethylamine oxide to TMA by bacteria. NMRI showed the presence of frozen and unfrozen areas in the fish non destructively. The power of M R technology combined with micromanipulation for elucidating key physiological factors in cryobiology was demonstrated in direct quantitative measurements of cryoprotectant permeation into a multicompartmental system by using chemical shift selective NMR microscopy and NMR s p e c t r o ~ c o p y . 'The ~ ~ developing zebrafish embryo was used as a model. NMR images of the spatial distribution of three cryoprotectants (dimethyl

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sulfoxide, propylene glycol, and methanol) demonstrated methanol permeation into the entire embryo within 15 min. Water in Food: Hydration of food was visualized by NMRI’” and the relationship between firming and water mobility in starch-based food systems during storage was discribed.”’

14

Botany, Plants and Seeds

The number of applications in this field showed a tendency to increase during this period. Water distribution and flow of water and solutes such as sugar in various kind of intact plants were investigated by flow sensitive NMR microscopy, to discuss phloem loading and xylem function. 152-155 Phloem loading comprises the entire pathway of phloem mobile solutes from their place of generation (or delivery) to the sieve tubes in a sequence of transport steps across or passing by several different cell types. Since the symplastic continuity from mesophyll to sieve tubes may be very different for different plant species or even in different vein orders, data from one species are not transferable to another species. The flow rates and flow speeds in phloem and xylem in the intact Recinus seedling was revealed, which directly proved the existence of an internal circulating solution Water flow in the xylem vessels of intact maize plants was measured as Water contents in healthy xylem, reaction zones (column boundary layers) and decayed wood were determined in the fungal region of the wood of sycamore, Acer Pseudplutunus L.,from TI or T2 weighted NMR images in comparison with gravimetrically obtained data. 15’ Results obtained from both early and late stages of decay were much more variable than those from healthy wood or from reaction zones, and reflected both the low water content of decayed wood (and hence poor signal to noise ratios for NMR data) and the changing physical environment as the wood was degraded. In order to discriminate black walnut (Juglunsnigru L.)seeds which germinate following stratification, NMR spectroscopy and imaging were effectively used.’ 56 The empty seeds were selected. Seeds lacking in a large amount of lipid produced images with very low intensity relative to those containing abundant lipids and failed to germinate. Among seeds containing large amounts of lipid, germinable seeds were indistinguishable from non germinable ones. Location (distribution and fluctuation) of sugars during germination was examined in Barley seeds’57and pulse sequences, such as Chemical shift selective imaging (CHESS), heteronuclear correlation via I3C-’H coupling (HMQC), and homonuclear correlation via ‘H-’H coupling (DQF), of NMR and MRI were quantitatively evaluated to measure sucrose concentration in plants.”* The difference of the physical state of water and metabolic activity between chilled and non-chilled tulip bulbs was discussed’59. Microimaging and NMR relaxometry was used for analysis of the microstructure and inhibition kinetics of pea seeds (Pisum Sativum L.).I6OThermal response is also an interesting topic. ‘61y162 Tissue specific thermal responses of geranium stems to hyperthermia were investigated in vivo and apparent activation energy and entropy for each image

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voxel (39 x 39) x 500 pm3.I6l The changes in T2 thermodynamics were caused primarily by direct temperature dependent variations in the physical state of tissue water. Thermodynamic analysis of the physical state of water during freezing in plant tissue was reported, based on the temperature dependence of proton spin-spin relaxation.162

15

In Vivo Imaging (Intact Insects, Fish, Bird Eggs)

One of the most attractive, valuable uses of in vivo NMR microscopy is to trace the growth and differentiation process occurring in intact individuals.163-165 NMR microscopy (gradient echo and chemical shift selective pulse sequences) was used to image the parasitoid wasp Venturia canescens (Hymenoptera: Ichneurnonidae)within larval and pupal instars of its host, the Indian meal moth, Both the location and shapes of Plodia interpunctella (Lepidoptera:Pyralidae).163 the parasitoid in the developing process from the L(l) larva to a pupal stage within the host and the digestive, nervous, and tracheal systems of the host were identified. Destruction of the host tissues by the parasitoid was visible. It was found that the parasitoid first ate the fat body and digestive system of the host, allowing the host to continue to grow, and only progressed to the vital organs when its own development had neared pupation. Coherent and incoherent flows in fertilized quail and bantam eggs have been studied in the course of incubation until the end of the sixth day.'64y165The methods employed were multiplane tagging time of flight and a bipolar gradient echo NMR imaging pulse sequence supplemented in the coherence evolution interval. The water flow in a breathing carp was visualized.166The distribution of phosphate and pH gradient in the midgust of a lepidopteran larva, Spodoptera litura (Noctuidae) was visualized by 31PNMR m i c r o ~ c o p y .The ' ~ ~ technical background of the method is outlined and resolution to a pixel size of 0.39 mm2 was obtained.

16

In Vito and Ex Vivo Imaging (Organs, Tissues)

In vivo imaging: Single neuron was microimaged by NMRI.16s-169The apparent diffusion coefficient (ADC) of water was measured in single Aplysia californica neurons by using NMR microscopy encoded in each of two perpendicular gradient directions. 169 Comparisons of the mean ADCs of the gross nuclear and cytoplasmic compartments in five cells, and 50 subregions within these cells, showed no significant difference between the diffusion measurements in the majority of cases. The results indicate that the ADC in these single neurons is isotropic at the spatial and temporal resolutions used in these studies. Single neuron under hypotonic perturbation showed no significant change of ADC.I6* Images of the normal human skin were obtained in vivo at voxel sizes as small as 19 x 78 x 800 pm3, by means of customized 3D gradient and partial flip angle spin echo pulse sequences and very small transmit/receive coils on a 1.5T clinical imager equipped with high power whole body gradient~.'~'Metastatic hemangio-

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sarcoma in canine eye was imaged by 'H and 23Na NMR with historologic correlation. 71 Background Myocardial ischemic insult causes depression of fatty acid beta oxidation and increased fatty acid esterification with triglyceride (TG) accumulation. To evaluate whether the extent of T G accumulation in the canine heart after 24 hours of ischemia could be detected, myocardial 'H NMR spectroscopic imaging was a p ~ 1 i e d .Determination l~~ of water diffusion in the rat brain is noninvasively measured. 173-176 By using a NMR microscope (7 T), determination of the apparent diffusion coefficient (ADC) or the mean diffusivity with a high accuracy was aimed during a pathological cycle (starting after induction and up to 37 days) of experimental allergic en~ephalomyelitis.'~~ Dynamic changes in the status of tissue water as a function of time after mechanical brain injury induced by partial unilateral transaction of the fimbria f ~ r n i x ,diffusion '~~ weighted NMR imaging changes caused by electrical activity of the brain.175and brain d e h y d r a t i ~ n were ' ~ ~ evaluated by in vivo imaging in rats. Lactate accumulation during moderate hypoxic hypoxia in necrotical rat brain'77 and in middle cerebral artery occluded rats'78 were investigated by 'H NMR spectroscopic images. In the latter case intracellular pH was investigated by 31PNMR chemical shift imaging.'78 Ex vivo imaging: Trabecular microstructure was analyzed quantitatively by 400 MHz NMRI.17' Cartilage degradation18' was measured and the concentration of glycosaminoglycans in cartilage was directly imaged by a TI-weighted sequence with Gd-DTPA.

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9

10 11 12

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14 Oriented Molecules C .L. KHETRAPAL AND K.V. RAMANATHAN

1

Introduction

The report covers the literature published on Oriented Molecules for the biennial period ending May 1997. The entire literature on the subject can be easily traced back from volume 25' and systematically referring to the relevant earlier volumes. The field of oriented molecules has been rapidly undergoing changes in terms of its development and applications like any other fast growing field of science. The first decade starting from the discovery of NMR spectroscopy of molecules oriented2 in the nematic phases of liquid crystals in 1963 was devoted to the understanding of the methodology with emphasis on the determination of molecular geometries and chemical shielding anisotropies specially of small molecules with high symmetry. During the subsequent decades, attempts were made to extend it to relatively large molecules with lower symmetries and to the development of the procedures for the analyses of relatively complicated spectra. The use of the techniques of specific- or per-deuteration with heteronuclear decoupling, multiple quantum spectroscopy, near magic angle spinning, various two-dimensional procedures and the use of mixed liquid crystals in this respect are worthy of mention. However, the spectral complexities encountered in molecules with more than eight strongly interacting spins were responsible for the limited applications of the technique for the studies of complex systems. Consequently, interest in structure-determination reduced substantially during the third decade whereas other diverse fields such as theory of molecular ordering, new methodology, weak molecular interactions, polymer liquid crystals, polymer dispersed liquid crystals, relaxation studies, membrane and model membrane systems attracted more attention. During the period under the present review tremendous developments in the field have taken place so as to revive the interest in the structural studies and they promise a bright future in addition to the continuing interest in the diverse fields mentioned above. Four advances worthy of mention in this respect.are : Discovery of new thermotropic liquid crystals with low order parameters, use of high magnetic fields, natural abundance 2H-NMR spectroscopy and other spectral simplification techniques. Since these developments promise a bright future for the technique in particular and NMR in general, they are discussed first followed by the coverage of the literature in other areas, as in the earlier volumes in the same format.

Nuclear Magnetic Resonance, Volume 27 0The Royal Society of Chemistry 1998 458

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459

Important Advances Having Bearing on Future Prospects

2.1 Discovery of New Thermotropic Liquid Crystals With Low Order Parameter -Neat phases of quaternary ammonium halides based on trioctadecyl amine have been shown to exhibit nematic liquid crystalline behaviour within certain temperature range^.^ These liquid crystals have low order parameters and provide 'weakly' coupled proton NMR spectra of the dissolved molecules4 such as cis,cismucononitrile. It has also been observed that solutes such as dimethyl sulfoxide and methyl iodide induce another phase identified as smectic phase within certain temperature and concentration ranges of the solutes (Figure 14.1). The important feature of this thermotropic liquid crystalline phase is that the order parameters of the neat phases as well as those of the dissolved molecules are small. This indicates possible use of such phases for obtaining first order spectra.

2.2 Orientation of Molecules by High Magnetic Fields - As mentioned earlier, major problems associated with the widespread use of the technique for the determination of molecular structure arise from two factors namely the need to solubilize the compound in appropriate liquid crystal solvents and the fact that the spectra become rapidly complex with the increase of the number of interacting nuclei because of the fact that they are in general strongly coupled. The availability of NMR instruments operating at high magnetic fields which can cause a small degree of alignment of molecules in isotropic solution due to the anisotropic magnetic susceptibility, has proved to be beneficial since it takes care of both these difficulties. Considerable work in this direction has been reported in the period under review, though the feasibility of such studies has been reported much earlier.5-" Such advances are likely to prove valuable particularly in biomolecular structure determination since the alignment information can be combined with the NOE and the scalar coupling data in order to obtain refined solution state structure. The availability of very high field spectrometers (1 7.6T) has made investigations of magnetic field alignment of duplex and quadruplex DNA worthwhile. l 2 The observation of small magnetic alignment of nucleic acids and proteins in solution appears more feasible via heteronuclear couplings than by 2H-NMR. Magnetic field alignment of diamagnetic protein "N-enriched human ubiquitin has been observed by measuring 'JNH at three different magnetic field strengths and using two different measuring technique^.'^ The results indicate two contributions to magnetic field dependence of the 'JNH splittings, an orientation independent contribution caused by a dynamic frequency shift and an orientation dependent contribution resulting from I5N-'H dipolar couplings. The first 24.6 T (- 1 GHz) resistive magnet with improved homogeneity has been installed and the 2H-NMR spectra of powders and oriented samples have been employed to demonstrate the use of ultra high magnetic fields.I4 Orientation of benzofuran by magnetic field has been studied in an isotropic liquid phase.15 The solvent dependence of H-H dipolar couplings in strong magnetic field has been used to characterise aromatic-aromatic interactions of benzene, hexafluorobenzene, naphthalene and some mono substituted benzenes. l 6 The solvent dependence of the dipolar couplings allows the determination of the association

Nuclear Magnetic Resonance

460

1

(isotropic)

347u

Figure 14.1 I3C NMR spectra of seven mass percent of l3CHj? in N-methylN,N,N- trioctadecyl-ammonium iodide as a function of temperature. As indicated, the lines marked (*) and (.) arise from the molecules in the nematic and the induced smectic phases respectively

14: Oriented Molecules

46 1

thermodynamics of an aromatic compound in a suitable system. The results show that benzene, naphthalene and some mono substituted benzenes tend to stack parallel to hexafluoro benzene and for the benzene-naphthalene complexes, evidence for the T-type structure has been found. 2.3 Natural Abundance *H-NMR - The use of 2H-isotopic substitution either partially or fully has been one of the oldest procedures suggested for the simplification of the spectra of oriented molecules. The initial reports were published as early as 197317 when the use of preferential isotopic substitution followed by heteronulcear decoupling for such a purpose was demonstrated. Due to the practical difficulties associated with the isotopic substitution, the technique has not been used in a routine manner. However, with the availability of high field and high sensitivity spectrometers, it has been observed recently that the 2H-NMR spectra of liquid crystals in the natural abundance of deuterium can be recorded in a reasonable time. l 8 A typical spectrum of 4’-hexyloxy-4-cyanobiphenyl in the nematic phase is shown in Figure 14.2. A subsequent obvious extension of this work for the dissolved molecules such as acetone has been made.” The natural abundance 2H-NMR spectrum of acetone dissolved in mixed liquid crystals of opposite diamagnetic anisotropies in the critical mixture where the coexistence of the spectra due to two orientations of the liquid crystal director is observed, has also been obtained and is included in Figure 14.2. Such experiments may be used in future in which the orientation information derived from the deuterium spectra can be employed for the analyses of the complicated proton spectra of oriented molecules. 2.4 Other Techniques for Spectral Simplification - Among the various other techniques developed to simplify the complex NMR spectra of oriented molecules in order to enhance the scope of the method, the following have been employed during the period under review:

2.4.I Multiple Quantum Spectroscopy and Automatic Analysis Procedures Multiple quantum spectroscopy, suggested and applied for the simplification of NMR spectra of oriented molecules in the late 1 9 7 0 ’ ~ is , ~ still ~ considered a powerful technique despite the experimental difficulties. It has been used as an aid for the analysis of the single quantum 10 spin proton NMR spectrum of biphenyl2’ oriented in a liquid crystal. The 8-quantum spectrum was first analysed to obtain dipolar couplings and the chemical shifts which in turn were used to derive the precise spectral parameters for the single quantum spectrum. Typical spectra are reproduced in Figure 14.3. The vibrationally corrected geometrical parameters were determined. The effective internal rotational potential was found to be shifted slightly towards a more planar configuration relative to the gas phase potential with an equilibrium dihedral angle of 37”. The multiple quantum NMR technique has also been employed to analyse the single quantum proton spectrum of butane dissolved in a liquid crystal and the information on the conformational and orientational behaviour including transgauche energy difference and the conformer probabilities obtained.22 The first

Nuclear Magnetic Resonance

462

4 , . ,

Hz Figure 14.2

0 KHz

20

40

,

, , ,

, ,‘, ,

5000

0

-20

- 40

, , , -5000 I

( a ) Natural abundance 2H N M R spectrum of 4’-hexyloxy-4-cyanobiphenyl in the nematic phase obtained with proton decoupling recorded ut 333 K with 180000 scans. ( b ) Natural abundance ’H N M R spectrum of four weight percent acetone dissolved in a I : ] mixture ZLI-1I14 (trans-p-pentyl-4- (cyanophenyl)cyclohexane) and ZLI1167 ( a ternary eutectic mixture of propyl, pentyl and heptyl bicyclohexyl carbonitrile) at 305.6 K with 15000 scans. The coexistence of the spectra due to two orientations of the liquid crystal director is observed. (Trace ( a ) reproduced with permission from Ref. 18)

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Frequency/kHz

Frequency /kHz Figure 14.3 Calculated (Bottom truce) and experimental (middle trace) single quantum spectra of partially oriented biphenyl. Top trace corresponds to the eight quantum spectrum of the same compound. (Reproduced with permission from J. Magn. Reson. 1996, A118,264)

464

Nuclear Magnetic Resonance

determination of the 13C-13Cdipolar couplings (in the natural abundance of the 13C) in nematic liquid crystalline phase (4-n-pentyl-4'-cyanobiphenyl) has been reported.23 It utilises the double quantum 13C-technique. The 13C-13Cdipolar couplings have been interpreted in terms of the structure and order parameters of the cyanobiphenyl fragment. An automatic method for the analysis of multiple quantum spectra of oriented molecules has been described24and the derived parameters used for the analysis of the single quantum spectrum. The utility is demonstrated for the proton spectrum of bromobenzene, ethynylbenzene and napthaquinone dissolved in nematic solvents. The restrictions of the formulated procedures are also discussed. The use of automated WIN-DAISY programme for the analysis of the spectra of molecules oriented in liquid crystalline solutions is demonstrated and applied to the proton and the "F-spectra of 3-methyl-3-cyanocyclopropeneand bis-trifluoromethyl mercury re~pectively.~~

2.4.2 Multipulse and Multidimensional Techniques - Such techniques have been developed and applied for the spectral simplification, sensitivity enhancement and deriving the information which is otherwise difficult to obtain. Several multipulse sequences providing homonuclear dipolar decoupling using low radio frequency irradiation power have been compared.26 Proton-proton decoupled I3C-spectra of singly 3C-labelled benzene dissolved in liquid crystals are studied. Two classes of multiple-pulse sequences that produce either broad band decoupled I3C-spectra or separated local field spectra are studied. A pulsesequence optimisation procedure which uses a gradient search method with analytical derivatives is d e m ~ n s t r a t e dand ~ ~ applied to the optimisation of a pulse sequence proposed earlier2' for deuterium decoupling in oriented phases and tested for pentadeuterobenzene oriented in a nematic phase. The sensitivity improvements that can be obtained by appending a Carr-Purcell-Meiboom-Gill pulse train to 2H-multipulse experiments in liquid crystals have been discussed.29 Typical results are illustrated in Figure 14.4.New radio frequency pulse schemes for deriving the orientation distribution function of chemical shielding anisotropy tensors in the NMR of ordered solids have been reported and combined with sample spinning at magic angle for side band ~eparation.~'The side bands associated with the molecular order are separated using only five r.f. pulses and avoiding three-dimensional Fourier-transformation. It has been demonstrated that the stimulated echo-pulse sequence can be employed for the examination of slow collective motion in ordered systems.31 The performance of various two-dimensional NMR methods for the measurement of C-H dipolar couplings in liquid crystalline phases has been a n a l y ~ e d . ~ ~ The utility of proton-detected local field (PDLF) spectroscopy for the determination of C-H dipolar couplings in liquid crystals has been demonstrated. The technique, PDLF, alone and in combination with variable angle spinning has been applied to 4-pentyl-4'-biphenyl-carbonitrile and the results in terms of reliability and resolution that can be achieved with and without spinning of the sample are discussed. A multi-dimensional NMR technique to measure and assign 13C-lH dipolar couplings in nematic phases is described and applied to

14: Oriented Molecules

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s/N=3.0

a

-

+ uKx)[)

Moo0

44

ZOOOO

loo00

0

-loo00

-zoo00

-30000

-aKm

Hz b

Figure 14.4

( a ) ' H natural abundance magnitude spectrum of the liquid crystal, 4-cyano-4'-pentyl-biphenylrecorded with a conventional quadrupolarecho sequence. ( b ) Spectrum of the same sample under identical conditions acquired using a Carr-Purcell-Meiboom-Gill ( C P M G ) train consisting of 10 refocusing pulses. The spectrum was obtained by Fourier transforming the sum of the autocorrelation functions associated with the 10 echoes. The delay time (22) in the CPMG train was set to 800 ps to obtain suficient resolution for most of the peaks. (Reproduced with permission from J . Magn. Reson., 1996,

B112,51)

Nuclear Magnetic Resonance

466

4-pentyl-4-biphenyl-carb0nitrile.~~ The orientations and conformations of enkephalins have been studied by magic angle and near magic angle spinning and two dimensional NMR spectroscopy in a lyotropic liquid crystal solvent formed by cesium perfluorooctanoate and The results for the neuropeptide metenkephalin (Tyr-Gly-Gly-Phe-met) indicate that the conformation is in a folded form like p-turn and the molecule is preferentially oriented along the direction perpendicular to the line connecting two phenyl rings in Tyr and Phe. In a similar manner, the conformation of leucine enkephalin oriented in a lyotropic liquid crystal has also been studied.36 The conformation of a carboxylic ionophore lasalocid A has also been determined in a lyotropic liquid crystal by magic angle spinning and two-dimensional experiment^.^^ The information derived from ROESY measured under magic angle spinning was analysed according to distance-geometry algorithm. The solvent was cesium perfluorooctanoate in D 2 0 and the resulting structure of lasalocid A was cyclic indicating cation complexation within a hydrophobic region of the liquid crystal. The state-correlated 2D NMR ~ p e c t r o s c o p yhas ~ ~ ~been ~ ~ applied to 4-(npentyloxy)-4'-cyanobiphenyl (50CB), its 1 :1 mixture with 1-(4'-cyanopheny1)-4The propylcyclohexane (PCH3) and 4'-methoxybenzylidene-4-acetoxyaniline.40~41 dipolar pattern for individual protons could be separately discussed as cross sections along the F,-axis. Since the cross section in the state correlated 2Dspectrum is determined by the local dipolar couplings of individual protons, spectral simulation can be performed for such spin systems with limited number of protons rather than for the entire proton system of the molecule, making analysis of a proton NMR spectrum of a liquid crystal far easier. The experiment with varying mixing times provides a means to explore diffusion in liquid crystal phases. In 4-(n-pentyloxy) 4-cyanobiphenyl, the local order is found to decrease towards the end of the aliphatic chain. Secondary splittings of the ring protons provide an estimate of the torsion angle between the two phenyl rings to be around 47-52" at 67.1"C. In the 1:l mixture, the local orders of both the rings and the aliphatic chain of (50CB) are significantly increased while those of the rings of PCH3 are decreased. In the remaining part of the report, the coverage of literature follows the standard format. The reviews, books and monographs published during the period are reported first followed by theory, erratum and general studies, new techniques including combination of various techniques, chiral systems, dynamic NMR studies, discotics, polymeric materials and polymer dispersed liquid crystals, membrane and model membrane systems, diffusion studies, anisotropies of chemical shift and indirect spin-spin coupling, relaxation studies, molecular order and molecular structure and conformation.

3

Reviews, Books and Monographs

Many special publications to commemorate the 50 years of the discovery of NMR in bulk materials have been brought out during the period. The eightvolume encyclopedia of NMR published by John Wiley and Sons has a ~ p e a r e d . ~ '

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It contains several articles on oriented systems. The National Academy of Sciences, India has brought out a special issue on NMR.43It contains 3 papers on oriented systems. A book on NMR probes of molecular dynamics has been published.& It contains chapters on 2H-NMR studies of dynamics in solids and liquid crystals besides 11 chapters on other topics. A review with 21 references for the structural analysis of oriented polymers and other macromolecular systems is available.45 Experimental methods such as multidimensional NMR, labelling and multiple quantum spectroscopy permitting the determination of dipolar couplings by NMR in liquid crystalline phases have been surveyed.46A comparison of different methods to determine chain-length in biomembranes from selectively or per deuterated systems has been made.47 A review containing 62 references on the deuterium NMR of the structure and dynamics of membrane components is available.48 The results on the water selfdiffusion in lyotropic liquid crystals using pulsed field gradient spin-echo NMR have been reviewed and the article contains 46 reference^.^^ It describes generalised theoretical analysis of NMR self-diffusion experiments in lyotropic liquid crystals, experimental results on binary systems and some recent findings of water self-diffusion in lyotropic liquid crystal systems, obtained by computer simulation techniques.

4

Theory, Erratum and General Studies

The results from a molecular dynamics simulation on a solute in a liquid crystalline solvent have been employed to test theoretical models for a conformationally dependent potential of mean torque used to calculate average nuclear dipolar interaction^.^' Monte Carlo simulations have been used to study orientational behaviour of solutes in a uniaxial nematic liquid crystaL5' The dependence on the solute size and shape has been investigated. The results are compared with mean field models and the earlier experimental studies. A new approach to perform molecular dynamics simulation for several cyanobiphenyl liquid crystals has been used.52 The molecular potential is obtained by considering the phenyl rings in the liquid crystal molecules as enlarged, spherical extended atoms. The method permits more rapid simulations than those using full atom-atom potentials, without the loss of structural or orientational information. The nematic properties of cyanobiphenyl liquid crystals have been investigated. Diffusion coefficients in directions both parallel and perpendicular to the director have also been calculated. The consequences of relaxing the rotational isomeric state approximation in predicting the transitional properties of nematogenic systems formed by two mesogenic moieties linked by a flexible alkanes have spacer, as in the homologous series of a,o-bis(4-cyanobiphenyl-4-yl) for a mesogenic molecule with rigid core and flexible been a n a l y ~ e dA. ~model ~ chain is proposed and tested in molecular dynamics calculation^.^^ Simulations have been performed on a system composed of 256 molecules with three different members of methylenic units in the chain in order to explore the effect of chain length on static and dynamic properties. Sensitivity improvements in mechani-

468

Nuclear Magnetic Resonance

cally oriented biological membranes by incorporating more oriented material in a given sample volume has been achieved.55An erratum to table 6 of reference 56 has been given and the calculated quadrupole and polarisability tensor in their principal frames reported.56,57

5

New Techniques Including Combination of Various Techniques

In addition to the development and applications of new techniques, during the period under review, efforts have been made to combine various physical techniques in order to derive additional and more reliable information. A method for the determination of H-I3C-dipolar couplings and order parameter along the in C-H bond axes of the liquid crystal N-(p'-methoxy-benzy1idene)-p-n-butylaniline its nematic phase by using transient oscillations observed in the cross-polarisation experiments has been proposed.58 A two-dimensional NMR method based on the depolarisation of rare spins for the determination of oscillation frequencies has also been proposed and employed. Dipolar oscillations as a function of mixing time observed in cross-polarised peptide samples in oriented lipid bilayers leading to improvement of resolution and sensitivity have been i n ~ e s t i g a t e dThe . ~ ~ spinning side bands observed in the I3C-MAS NMR spectra in systems requiring more than two elements of the ordering matrix (such as cis,cis-mucononitrile) oriented in liquid crystalline media and of the neat samples in the solid state have been A method for obtaining the orientation of the carbon chemical shift studied.60761 tensor is thus proposed and demonstrated for &,cis-mucononitrile. The phase diagram of binary mixtures of the poly(oxyethy1ene) surfactant, nonaethylene glycol mono (1 1-oxa-l4,18,22,26-tetramethylheptacosyl) ether in D 2 0 has been mapped using optical microscopy and deuterium NMR.62 A combination of H and 2H-NMR, polarised-light optical microscopy and synchrotron X-ray diffraction techniques has been employed to determine the structures of the mesophase formed at room temperature by four anionic cyanine dyes in water.63 The neat phases of a series of quaternary ammonium halides based on trioctadecylamine have been investigated by optical microscopy, It is differential scanning calorimetry (DSC) and 2H-NMR spectro~copy.~ observed that the phase behaviour depends primarily on the structure of the fourth substituent on nitrogen and the thermal history. The use of the combination of optical microscopy and NMR has also been made to establish the formation of an induced smectic phase by addition of solutes such as dimethyl sulfoxide and methyl iodide to the quaternary ammonium salt, N-methyl-N,N,Ntrioctadecylammonium i ~ d i d e The . ~ phase behaviour of tetrabutylammonium salts of perfluoroalkanecarboxylate soaps has been explored by using optical microscopy and 2H-NMR.64 Thermotropic and lyotropic mesomorphism of 4dodecyloxy-2-hydroxybenzoic acid and sodium 4-dodecyloxy-2-hydroxybenzoate have been investigated by a combination of techniques such as optical microscopy, differential scanning calorimetry and NMR.65 While the free acid shows thermotropic nematic and smectic C mesophases, its sodium salt shows lyotropic, hexagonal, lamellar and intermediate phases. A deuterium NMR study of

'

14: Oriented Molecules

469

polymorphism in hexa(p-alkoxy-phenoxymethyl) benzene with 5, 6 , or 7 carbons in the alkoxy chains and several of their deuteriated isotopomers has been undertaken and the polymorphism examined with the help of other physical techniques such as optical microscopy and X-ray diffraction in addition.66

6

Chiral Systems

NMR occupies an important position amongst the various techniques available for the enantiomeric analyses. In general the methods are based on the association of chiral compounds with chiral reagents, producing new species which exhibit different NMR spectra for each enantiomer. An alternative NMR approach is based on the study of the spectra of chiral molecules dissolved in binary mixtures of nematic and cholesteric thermotropic liquid ~ r y s t a l s . ~During ~ - ~ ~ the period under report, a new NMR method using chiral lyotropic liquid crystals obtained by the dissolution of poly-y-benzyl-L-glutamate (PBLG) in various organic solvents7* has been proposed. Partially deuterated chiral molecules under such conditions exhbit different deuterium NMR spectra for each enantiomer due to the fact that the enantiomers interact with the chiral centres of the PBLG helix and consequently each of them orients differently. This technique has been employed for the enantiomeric analysis and the precise evaluation of the isomeric ratios. High resolution proton and natural abundance I3C-spectra of a rigid chiral molecule (f)-p-(trichloromethy1)-P-propiolactone has thus also been investigated.71.72From the NMR and the X-ray data, the full order matrix has been determined and analysed in detail for each optical isomer of the molecule. The technique has also been employed for various other systems.73 It has been shown that with the chiral dopant, potassium hexadecanoyl-lprolinate, the magnitude and sense of the helical twist are dependent on the host chiral detergent.74 The 13C-NMR reveals that the magnitude of the twist is directly proportional to the relative cis-trans populations of the diastereorotamers. 2H-NMR in a chiral liquid crystal solvent has also been used to measure the diastereo ~ e l e c t i v i t yThe . ~ ~ discrimination and analysis of the NMR spectra of optically active molecules dissolved in chiral liquid crystal solvents through 2Dcorrelation experiments has also been reported and the potential of the method demonstrated for (f)-3,3,3-trichloroepoxy-propanedissolved in a thermotropic cholesteric solvent.76 It is also shown that 2D-heteronuclear correlation experiments provide powerful methods for correlating 13C and ‘H-spectral data of the two enantiomers. A specific example of (f)-2-bromo-propanoic acid dissolved in a lyotropic polypeptide liquid crystal is given.

7

Dynamic NMR Studies

Strictly speaking, the entire field of NMR of molecules oriented in the liquid crystalline media falls under the category of ‘dynamic NMR’ since it is based on the partial ordering of the molecules caused by anisotropic molecular motions. If

470

Nuclear Magnetic Resonance

one uses this as the criterion, the title of this section of the report may appear confusing. However, some specific dynamic studies on molecules dissolved in liquid crystals starting with theoretical investigations are presented in this section. A molecular dynamics simulation of biphenyl dissolved in a liquid crystal solvent has been carried out in order to get insight into the stability of the phases.77 Correlation between the molecular motions and liquid crystalline phase transitions in two hydrogen-bonded carboxylic acid-pyridyl complexes (between 4-pentyl benzoic acid and 4-pentylcyclohexanoic acid with 1,2-bis-(4-pyridyl ethane) has been presented.78779 The formation of a liquid crystalline phase in the former and the lack of such a phase in the latter has been interpreted. Dynamics and molecular order of the liquid crystalline complexes of 5-octadecyloxy isophthalic acid and cyclic oligo-amines have been investigated by 2H-NMR.80 The systems form stable, enantiotropic liquid crystalline phases at high temperature and the dynamics in these phases can be described by a single motional model. The model involves fast rotation around the director coupled with a rapid phenyl flip. The [1,9] sigmatropic rearrangement has been studied by dynamic NMR for two 2-acyloxytropone mesogens and for 2-acetyloxytropone in CDC13 as well as in a nematic phase.81>82 The activation energies in the nematic solvent are found to be slightly higher than those in CDC13. Variable temperature 13C-NMR has been used to investigate structure and dynamics of surfactant molecule reorganisation in mesophase silicates and information on the formation mechanism of the mesophase materials derived.83 The orientational distribution function for the CCD3 bond in the perdeuterated polymethacrylate chain of a liquid crystalline side group polymer has been determined by 2H-NMR in the frozen smectic A phase.84 I3C-NMR spectroscopy combined with rapidly decelerated sample spinning has been employed to observe the preferred microscopic alignment at two different directions during the macroscopic reorientation of nematic liquid crystals in magnetic field.85The ratio of the molecules with two kinds of preferred alignments is determined by the two non-equilibrium dynamics as well as diamagnetic susceptibility anisotropy of the liquid crystal sample. The liquid crystal samples investigated are 4-n-penty1-4-cyanobipheny1,4-cyanophenyl-1-trans-4-n-pentylcyclohexane and l-(trans-4-n-pentylcyclohexyl)-4-cyanocyclohexane.Dynamic NMR studies of 1,3,5,7 tetraoxacyclooctane using 'H, 2H, and I3C-NMR have been undertaken in the liquid crystal and isotropic solutions as well as in the solid state.86 In solution, the molecules exist as a mixture of boat-chair and crown conformers. Pseudo rotation and inversion are extremely fast in the boat-chair form while the inversion in the crown conformer is relatively slow. Inversion rate and equilibrium constants between the two forms over a wide temperature range have been determined in several isotropic and liquid crystalline solvents.

8

Discotics

In general 2H-NMR is employed for the study of discotic liquid crystals, though the use of 13C-NMR has also been made in the case hexaoctanoyloxytriphenylene.87 2H-NMR studies of the discotic material, 2,3,7,8,12,13 hexakis (octadeca-

14: Oriented Molecules

47 1

noy1oxy)-truxene specifically deuterated in the a-position of the alkyl chain along with the polarising microscope studies show the appearance of the uniaxial discotic mesophase within the temperature range of 90-191°C.88 *H-NMR of spectra of benzene-d6 dissolved in the protonated material are interpreted using a model in which benzene molecules occupy two solvation sites intercalated within the columns and dissolved in the aliphatic chains. The exchange of C6D6 between the two sites is slow on the NMR time scale in the crystalline phase whereas it is fast in the mesophase. 2H-NMR investigations of C6D6 in the discotic mesogen octa-0-decanoyl-Pcellobiose shows an increase in the 2H-quadrupole splitting of C6D6 when the sample is heated.89 This is interpreted in terms of fast dynamic equilibrium between different solvation sites in the carbohydrate liquid crystal. The mesomorphic properties of five homologues of the labelled 1,2,5,6,8,9,12,13octaalkyloxydibenzopyrene (I) series and their charge transfer complexes with 2,4,7-trinitro-9-fluorenone (11) have been investigated." The *H-NMR of the labelled compound (I) was used to determine the nature and rate of the molecular reorientation. Addition of the electron acceptor (11) increases the stability range of the mesophases. Trifluoroacetic acid has been shown to form molar complexes with alkyloxy discotic compounds, thereby, enhancing their mesomorphic properties due to the formation of oxonium ion cornplexe~.~' Molecular dynamics in the columnar and lamellar mesophases of a liquid crystal of biforked molecules has been studied by proton relaxation measurements at different temperatures combining standard and fast field cycling technique^.^^

9

Polymeric Materials and Polymer Dispersed Liquid Crystals

Considerable interest in this area has developed during the period under report compared to earlier years. Due to the importance and technological applications of these materials, it is considered worthwhile to include publications related to this field under a specific special section. The Direction Exchange with Correlation for Orientation - Distribution Evaluation and Reconstruction (DECODER) method has been applied to oriented systems such as extruded polymers for the purpose of quantifying order in these systems.93 The experiment correlates the '3C-anisotropic chemical shifts at two different orientations with respect to the magnetic field by utilising a rapid reorientation of the entire sample during mixing time of a two-dimensional experiment. The incorporation of ultraslow MAS to orient the sample considerably reduces the experimental requirement of the DECODER experiment. Mesomorphic behaviour of a partially deuterated side chain liquid crystal polymethacrylate, poly [4-[6-methacryloyloxyhexyl-oxy]-4'-methoxy-azobenzene] has been investigated by means of 2H-NMR, DSC and optical microscopy techniques. Evidence for a phase transition occurring in the middle of the nematic phase has been found.94 I3C-NMR above and below the clearing temperature of the liquid crystal 4-n-hexyloxyphenyl 4-methoxybenzoate constrained to an oriented, low concentration polymer network is reported.95 The results support

472

Nuclear Magnetic Resonance

the model of neatly cylindrical shaped liquid crystal domains surrounded by thin walls of cross linked network. Main chain dynamics and order have been studied in a liquid crystalline side group polymer.96 The slow chain dynamics above the glass transition studies indicates a diffusive motion constrained by the partial orientational order of the mesophase. Two-dimensional NMR Wideline Separation (WISE) pulse sequence has been employed for the correlation of structure and motion of polymer dispersed liquid crystals (PDLC).97It is observed that fast motions occur in both aliphatic and aromatic portions of cyanobiphenyl and cyanoterphenyl liquid crystals. It has been shown that the thermodynamics of PDLC lattice model can be studied in detail by Monte Carlo simulation^.^^ It has also been demonstrated that the Monte Carlo method for calculating the line shapes in the 2H-NMR spectra of model nematic droplets that mimic PDLC systems is a powerful tool to understand experimental data.99 The molecular organisation and ordering inside the droplet have been determined and the dependence on the system size evaluated. The frequency and temperature dependence of the longitudinal proton relaxation time have been studied in liquid crystal droplets embedded in a solid polymer matrix in the nematic and isotropic phases over a broad Larmor frequency range employing a fast field cycling technique.'" It is shown that the spin-lattice relaxation time is dominated by the cross-relaxation at the liquid crystal-polymer interface in the entire frequency range.

10

Membrane and Model Membrane Systems

A large number of publications have appeared on the membrane and the model systems essentially providing information on the membrane interactions and the dynamics. A method using ultra thin polymers and unilamellar vesicles for the preparation of oriented lipid bilayers has been presented and the NMR study of the peptidemembrane interaction undertaken."' It has been demonstrated that an integral membrane-protein can be uniaxially magnetically oriented in a lanthanide containing bicelle system with substantially improved chemical shift dispersion as compared to the bicelle systems that orient with bilayer normally perpendicular to the direction of the applied magnetic field.'02 2Hand 23Na NMR studies of the lamellar phase of sodium dodecyl sulfate/pentanoI/water/ dodecane have been undertaken and the bilayer bending rigidity studied. lo3 The shear-alignment studies of the hexagonal lyotropic liquid crystalline phase formed by a solution of hexa-(ethylene glycol) monododecylether in D20 using 2H-NMR reveal that the reorientation of the domains depends not on the shear rate but on the shear strain.'04 The phase behaviour and hydration studies of 1-palmitoyl-2-oleoyl-snglycero-3-phospho-ethanolamine/cholesterol/D~0 has been investigated by 2H and 31PNMR studies.'05 The phase transitions in didodecyldimethyl ammonium bromide-H20 system have been studied by multinuclear NMR and optical microscopy and the coexistence of two lamellar phases has been observed.*06 Replacement of H 2 0 by D20 in this system has been employed to study the

473

14: Oriented Molecules

isotope effect on the co-existence of the two different types of surfactant bilayers at room temperature and the structural transition from vesicles to lamellar liquid crystal observed at low surfactant concentration with increasing temperature. The 2H-NMR and DSC methods have been employed to study the phase diagram for the system cetylpyridinium bromide/n-butanol/n-octane/water system.'07 From similar studies in the sodium dodecylsulfonate/n-pentanol/watersystem, it has been found that the liquid crystal structures do not change with the contents of water under 303 K. log 2H-NMR studies of sodium dodecylsulfate/decanol/water system have been used to investigate the phase diagram of the s y ~ t e m . ' ~First ~~''~ order transition to a lyotropic biaxial nematic has been observed. The conformational behaviour of the acyl chains of 1:l binary mixtures containing phospholipids has been investigated using FT-IR and 2H-NMR.' It is mainly influenced by head group interactions. Pulsed field gradient spin-echo NMR, water self-diffusion, D20-NMR line-shape and optical microscopy have been used to characterise the lamellar microstructures of Aerosol OT/Water System.' l 2 Two-dimensional deuterium exchange spectroscopy has been employed to study lipid bilayers."3~"4 A quantitative analysis demonstrates the sensitivity of the technique to the local curvature and the shapes of the multilayers. A study of the bilayer of 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine on a spherical solid support consisting of silica heads at hydration states of the bilayer provides strong evidence that the lateral diffusion of lipids is the most dominant mechanism in determining the spectral evolution in two-dimensional exchange NMR of spherical, solid supported bilayers. Lateral diffusion coefficients have been determined. Segmental order parameters in liquid crystalline lipids have been interpreted in terms of orientation distribution. Dipolar (13C-13Cand '5N-'3C) couplings and the chemical shift anisotropy for the amide carbon and the "N-labelled sites have been measured in an isotopically labelled lactam analogue of ganglioside in an oriented bilayer system using both one and two-dimensional NMR.' l 6 A switching of the sign of the order parameter of the bilayer director from - 1/2 to 1 induced by the binding of the paramagnetic Eu3 ions to the phospholipid head groups in magnetically oriented membrane model systems has been observed.' l 7 The Dipolar Sign Term by Indirect Coupling Transformation (DISTINCT) technique has been employed to determine the signs of heteronuclear dipolar couplings between J-coupled 3C and 'H-nuclei in lipids.' " It is a switching angle spinning experiment that employs scalar couplings to make spin-dependent heteronuclear coherences observable.

''

' ''

+

'

11

Diffusion Studies

Methods for accurate anisotropic diffusion measurements in liquid crystals have been described.' l9 The self-diffusion of water in the nematic micellar phase of cesium penta-decafluorooctanoate-water system has been investigated by 2Hpulsed gradient spin-echo NMR. 120 The principal components of the macroscopic diffusion tensor have been determined as a function of temperature and concentration.

Nuclear Magnetic Resonance

474 12

Anisotropies of Chemical Shift and Indirect Spin-Spin Coupling

Only three publication^'^'-^^^ on the determination of the chemical shielding anisotropy and a single paper on the anisotropy of the indirect spin-spin couplings'24 are reported in this section. One of the publications12' makes use of the ENEMIX method, utilising mixed liquid crystals of opposite diamagnetic anisotropies at the relative concentration of the two types of the liquid crystals being those where the proton-proton dipolar couplings of methane v a n i ~ h . ' ~ ~ ' ' ~ ' For chloroform, it has been observed that though the 13C-chemical shielding anisotropies are in reasonable agreement with those calculated theoretically, there are significant deviations for the proton chemical shielding anisotropies so obtained. The deviations have been interpreted in terms of the formation of hydrogen bonds between the chloroform proton and the cyanide group of the liquid crystal ZLI-I 167 used in the studies. The experiments when performed'28 using NEMIX m e t h ~ d ' * ~ -(where ' ~ ' the shift anisotropies in systems with threefold or higher symmetries are measured directly from the coexistence of the spectra corresponding to the orientations of the director along and perpendicular to the magnetic field, without the use of a reference compound or without the change of experimental conditions), yield results which are consistent with the values determined by theoretical calculations. NMR studies of xenon gas as a function of temperature, in the liquid crystal ZLI- 1 I32 confined to sub-micron cylindrical cavities provide a clear indication of nematic to isotropic phase transition of the confined liquid crystal.122In the nematic phase at 21 "C, the resonance line of the dissolved '29Xeshows a chemical shielding anisotropy of 15 ppm. The quadrupole splitting observed in the 13'Xe NMR spectrum of the confined liquid crystal solution of xenon gas is slightly greater than that found in the bulk. The two-dimensional exchange experiment demonstrates that the xenon atoms probe different liquid crystal directors within a single cavity on a 20 ms time scale and that inter-pore exchange occurs on a time scale of 400 ms. The proton and 13C-NMR spectra of 1,4-dichloro-2-butyne in isotropic and nematic phases have been studied and the '3C-chemical shielding ' ~ aniso~ anisotropy for the acetylenic carbons obtained as 233 f 10 ~ p m . The tropies of the I3C-l3C coupling tensors in benzene have been obtained by liquid crystal proton and 13C-NMR using dipolar couplings corrected for both harmonic vibrations and def0rmati0ns.l~~ The results obtained in 3-thermotropic liquid crystal solvents are in good agreement with each other. The anisotropies of the ortho, meta and para I3C- I3C indirect spin-spin couplings are about 17, -4 and + 9 Hz, respectively.

13

Relaxation Studies

The effects of uniaxial-biaxial phase transition on the spectral densities measured from the deuteron Zeeman and quadrupolar spin-lattice relaxation times are examined in two partially deuterated samples of 4-n-pentyloxy benzylidene-4'-

14: Oriented Molecules

47 5

heptylaniline (one deuterated at the methine site and the other with the aniline ring deuterated).132 Orientational dynamics of individual molecules in nematic liquid crystals have been interpreted by modified models and the frequency dependence of the spectral densities obtained from NMR relaxation experiments e ~ p 1 a i n e d . l ~ ~ Proton spin-lattice relaxation dispersion using a fast field cycling NMR technique has been r e ~ 0 r t e d . More l ~ ~ than two chemically non-equivalent nitrogen nuclei have been detected from the quadrupole dip spectrum of 4,4’-bi~-heptyloxyazoxybenzene. The biaxial smectic C local structure comprises of bimolecular unit cell in this case. From the analysis of experimental dispersion of the spin-lattice relaxation time with frequency, angle and temperature, it is concluded that the molecular dynamics in the nematic mesophases is different than that in the smectic A phase. 135 In the nematic phase of 4-cyanobenzoate-4-octylbenzoyloxy phenyl, major contribution to the spin-lattice relaxation comes from the order director fluctuation and not from the self-diffusion . On the other hand, in the smectic-A phase, self-diffusion provides a predominant relaxation mechanism. Study of angular and frequency dependences of the longitudinal proton spinrelaxation of the liquid crystalline cyanobiphenyls has been undertaken. 136 The 13C-relaxation times have been employed to study the critical feature arising from the fluctuations of the order parameter in the smectic A-nematic phase transitions 37 The angular of 4-cyano-4’-n-octylbiphenyl and 4-cyano-4’-n-nonanylbiphenyl. dependence of the longitudinal 23Na spin relaxation in a lyotropic calamitic nematic phase has been examined using a simple rotor technique.13* The results indicate the micelles to be biaxial. 2H- relaxation data in the nematic and smectic A phases of 4-n-pentyloxy-benzylidene-4-heptylanilineand 4-n-butoxybenzylidene-4’-n-octylaniline-2,3,5,6-d4 support a model which includes director fluctuations and rotational diffusion of an asymmetric rigid rotor in a biaxial potential of mean The activation energies for the tumbling motion of the molecule is found to be larger than that for the spinning motion.

14

Molecular Order

Studies of the molecular orientation in liquid crystals and the molecules dissolved therein form a major part of this report. They involve theoretical computations, dipolar and quadrupolar splittings, relaxation and diffusion data and the lineshape and the line-width studies. The effect of steric hindrance on reorientational dynamics has been examined in well-defined geometries both theoretically and experimentally. 141 2H-NMR has been used to study the ordering of deuterated cyclic aliphatic solutes such as cyclohexane, methylcyclohexane, 1,1 -dimethylcyclohexane, 1,4cis/trans-dimethylcyclohexane,cis and trans-decalins in nematic s01vents.l~~ It is shown that their orientational ordering can be accurately described in terms of purely hard body interactions with the solvent molecules. The orientational order in a liquid crystal mixture consisting of benzene and 4-n-pentyl-4’-cyanobiphenyl employing molecular dynamics simulations and NM R has been examined.143The

476

Nuclear Magnetic Resonance

temperature dependent order parameters obtained from the NMR experiments have been used to determine solute-solvent and solvent-solvent interaction parameters. Proton, 2H and I9F-NMR studies of fluoromethane in three liquid crystal solvents have been undertaken and the anisotropic couplings interpreted in terms of the bond additivity.I4 For the accurate description of the solute orientation, 'non-rigid' contributions such as vibration-rotation interaction and vibrational corrections - both harmonic as well as anharmonic - have to be included. The presence of anisotropic contributions to the C-F indirect spin-spin coupling is indicated. The order parameters and the carbon shielding tensors of p-bis(0-methylstyryl) benzene in the nematic phase of ZLI-1167 have been determined as a function of temperature by '3C-NMR.'45 The solutes, ortho, meta and para dichlorobenzenes, ortho dicyanobenzene, furan, tetrathiofulvalene and fluorobenzene have been studied in two zero electric field gradient mixtures of liquid crystals (56.5 wt % of ZLI-1132, an eutectic mixture of alkylcyclohexylcyanobenzene and alkylcyclohexylcyanobiphenyl in N-(4-ethoxybenzylidene)-4'-n-butylaniline (EBBA) and 70 wt YO of (4-n-pentyl)-4'-cyanobiphenyl (5CB) in EBBA) using proton NMR.'46 The results indicate similar anisotropic potential in both the mixtures. The rest of the orientation studies reported herein are on liquid crystals themselves. Nematic, smectic, cholesteric and ferroelectric liquid crystals have all been studied. Orientational order parameters and spectral densities of motion in the nematic, smectic A and smectic B phases of p'-hexyloxybenzylidene-pfiuoroaniline, fully deuterated in the chain and partially deuterated in the aniline ring have been determined.147The orientational order of the C-D bonds and the spectral densities determined suggest that on entering the highly ordered smectic phases, the internal motions of the first two methylene groups in the chain slow down. Motional parameters derived from quantitative fittings of the quadrupole splitting and spectral density data in three different nematogens of various chain lengths have been reported.'48 The compounds containing four-rings in the main core (three aromatic and one-alicyclic) and substituted by a lateral alkoxy branch in one of the inner rings have been shown to have large enantiotropic nematic ranges.'49 The order parameters for two of the aromatic rings with para substitution have been determined by I3C-NMR. The lateral alkoxy chain does not seem to play any significant role in the ordering of the mesogenic core. The order parameters of the inner and the outer aromatic rings are dependent on the terminal substituent and also on temperature. The orientational ordering of the two lateral chains in three substituted compounds of the 2,3,-n-dialkoxy-4-(4chlorobenzoyloxy)-4'-(4-methylbenzoyloxy)-azobenzene series has been investigated by one and two dimensional '3C-NMR.'50 The ordering behaviour of the two lateral alkoxy chains in the nematic range is found to be quite different from that of the terminal chains. It is concluded that the two alkoxy chains are folded back along the mesogenic core involving cis-conformation for the first fragment. 'Hand 2H-NMR studies on doubly re-entrant liquid crystal 4-cyanobenzoyloxy[4-o~tylbenzoyloxy]-p-phenylene and its chain deuterated homologue have been undertaken and the phase transitions in~estigated.'~'It is found that the rotational viscosity changes drastically at the phase transition but the orienta-

14: Oriented Molecules

477

tional order parameter of the molecular core changes smoothly through the phase changes - re-entrant nematic - smectic A of partially bilayered typenematic while a first order discontinuity has been detected for a smectic A of monolayer type to re-entrant nematic phase transition. The order fluctuations in liquid crystals are characterised by the standard stimulated - echo three pulse sequence and information on the order parameter derived.152The smectic A to smectic C phase transitions for two binary mixtures namely 4'-(2-~hloroalkoxy)4-heptyloxybiphenyl with 4-butyloxyphenyl-4'-decyloxybenzoate have been studied.Is3 The order parameters of the mesogenic core have been determined by 13C-NMR. The order parameter at the transition temperature is found to be discontinuous for a first order smectic A-smectic C transition and continuous for a second order transition. !3C-NMR is used to determine the order parameter of four binary liquid crystal systems as a function of temperature and concentration and the tricritical behaviour of their SA-N transition studied.154 The temperature dependence of the order parameters obtained through I3C-NMR for MBBA and 4-n-pentyl-4'-cyanobiphenyl has been studied and its physical significance discussed. 5 5 The pretransitional behaviour in I3C-NM R chemical shifts of liquid crystals observed within a few tenths of a degree above the nematic to isotropic transition temperature has also been examined. The orientational ordering of liquid crystals containing a difluoro substituted phenyl ring has been studied by 13C-NMR.156Due to the complexity of the "F-coupled spectra, variable angle spinning has been used to resolve the C-F splittings. 2H-NMR has been employed to investigate orientational order in the nematic and smectic phases of 15' The dy4-(2-methylbutyl) phenyl 4'-n-heptylbipheny1-4-carboxylate-d18. namics of the aromatic molecular core is studied in the temperature interval including SA-SB transition. Diffusion constants related to the molecular spinning and tumbling motions are evaluated. The mesomorphic properties of the p-nalkoxy-benzylidene-p'-fluoroanilinehave been investigated by 2H-NMR in the homologues with the number of carbons in the chain being 4 3 and 8.lSsThe quadrupole splittings in deuterated 4-n-hexyloxy-4'-cyanobiphenylhave been reassigned and a re-evaluation of the fittings of the splittings with the molecular mean field made.'59 Molecular order in confined liquid crystal materials has also been investigated. A deuterium NMR study of pentyl cyanobiphenyl liquid crystal confined to controlled pore glass matrix has been made.160The line-width in the confined samples is always narrower than in the bulk sample. The molecular anchoring and orientational wetting properties of a liquid crystal close to nematic-isotropic transition confined to cylindrical channels of alumina membranes have been investigated.I6l The cavity walls of the confining pores were chemically modified with an aliphatic acid to establish surface anchoring. Radical changes in 2H-line shapes in the nematic phase show the existence of a discontinuous homeotropicto-planar anchoring transition induced by either changing the length of the surfactant, the density of the surfactant on the surface or by varying temperature. The dipolar correlation effect on the stimulated echo of nematic probes has been employed for the study of orientational director fluctuations in a nematic liquid crystal confined in Bioran porous glasses.162No macroscopic preferential order

478

Nuclear Magnetic Resonance

of the director could be detected in the confined material since the local director is aligned by surface interactions rather than by the magnetic field. The remaining publications in this section pertain to the orientational studies in the cholesteric, lyotropic and ferroelectric liquid crystals. The components of the order tensor of cholesteryl myristate from the proton NMR data are determined using the method of moments.1637164 2H-NMR spectra have been investigated in uniaxial and biaxial nematic phases of selectively deuterated decylammonium chloride, potassium laurate and water and the results interpreted in terms of theory for quadrupole spectra in micellar phases.165Evidence for a variation of the local order parameter of the molecules within the micelle between uniaxial phases has been obtained. In the cylindrical phase, amphiphilic molecules are less closely packed than in the discotic phases at lower temperatures. Proton NMR has been employed to study the orientational behaviour of a ferroelectric mixture.'66 The alignment of the mesogenic unit is reflected in the splitting of the NMR signal into a doublet. The angular dependence of the linewidth of the NMR signal on the tilt angle of the director has been calculated. A ferroelectric switching has been detected by measuring the angular dependence of the line-width in the switched state.

15

Molecular Structure and Conformation

During the period under report, the publications related to the study of structure and conformation of molecules using NMR spectroscopy of oriented molecules range from simple systems such as pyridinium head group to complex systems like 4-cyano-4'-(2,2,2-trifluoroethoxy)-biphenyl. 167-173 Temperature dependence of the 2H-NMR spectra in deuterated pyridinium head group has been studied in a lyotropic liquid crystalline phase of 85 wt % dodecyl pyridinium iodide-water system.167The quadrupole splittings of the three non-equivalent 2H-sites indicate that the motionally averaged inclination angle of the pyridine ring increases by about 6" on heating from 24 to 40°C. The rustructure of s-trioxane has been determined from the 'H and 13C-NMR spectra in three-nematic liquid crystals.168 It is concluded that the molecule oscillates between two equivalent chair conformers and the methylene protons a r t tilted outwards from the three-fold symmetry axis. Values of the rCH = 1.11 1A , the HCH bond angle = 110.3" and methylene rocking angle = -2.1" have been obtained. It may be mentioned that the molecule had been studied earlier also but no corrections for harmonic vibrations or deformations were made. 174 The conformation of the ethyl group relative to the phenyl plane in 4-chloroethyl benzene has been investigated. 169 The derived dipolar couplings have been compared with the values calculated by the additive potential and maximum entropy molecular mean field theoretical models. It is concluded that the inclusion of geometry relaxation on rotation in this case is particularly important to determine the potential for rotation about the ring-C bond. The 'H, 2H and 13C-NMR spectra of phenyl acetate ('3CO-enriched) and phenyl acetate-(C2H3) dissolved in a nematic liquid crystal solvent have been analysed and the results

14: Oriented Molecules

479

interpreted using the additive potential model to derive information on the molecular c o n f ~ r m a t i o n . 'A~ ~comparison of the results with those of the molecular orbital calculations leads to the conclusion that a potential with a minimum at 54.4" 0.1" is the most probable. The conformation of phenyl benzoate oriented in a nematic phase has been studied from the proton NMR s p e ~ t r u m . ' ~The ' minimum energy conformations are found to be distributed over a wide range of the torsion angles. The dipolar couplings between pairs of protons in n-hexane dissolved in a nematic liquid crystal solvent are used as constraints in a Monte Carlo sampling of conformation and orientation in n - h e ~ a n e . 'Rotation ~~ about each C-C bond in the molecule is modelled by complete sinusoidal torsional potential rather than by the three-state rotational isomeric states model. A comparison of the results of the two models shows that the conformational distributions for both the models are not very different from those in the neat liquid. However, the calculated conformational distribution appears to be very sensitive to the exact shape used for the C-C bond rotation potential. This highlights the need for careful consideration of the shape of the potential when modelling rotation about the C-C bonds. The results are compared with those published earlier. ' 7 5 The conformational distribution in 4-cyano-4'-(2,2,2-trifluoroethoxy)biphenyl is investigated by analysis of the dipolar couplings obtained from the deuterium decoupled proton NMR spectrum of a partially deuterated sample in a nematic solvent'73 with the maximum entropy method. It is observed that the compounds with the ethyl and the trifluoroethyl groups have very similar conformational distributions.

*

16 1

2 3 4

5 6 7 8 9 10 11

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14: Oriented Molecules

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81 82

48 1

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482 83 84

85 86 87 88 89 90 91 92 93 94 95 96 97 98 99

1 00 101 102 103 1 04 105 106 107 108 109 110 111 112 113 114 115 116

Nuclear Magnetic Resonance

L. Q. Wang, J. J, Liu, G . J. Exarhos and B. C. Bunker. Langmuir, 1996,12,2663. G. Germano, C. A. Veracini, C. Boeffel, H. W. Spiess, Mol. Cryst. Liq. Cryst., 1995, 266,47. M. L. Magnuson and B. M. Fung, Liq. Cryst., 1996,20,293. L. Calucci, H. Zimmermann, R. Poupko and Z. Luz, J. Phys. Chem., 1995, 99, 14942. S. Zamir, N.Spielberg, H. Zimmermann, R. Poupko and Z. Luz, Liq. Cryst., 1995, 18,781. D. Sandstrom, M. Nygren, H. Zimmermann and A. Maliniak, J . Phys. Chem., 1995, 99,6661. D. Sandstrom, R. Stenutz, G. Widmalm and A. Maliniak, J . Chem. Soc., Faraday Trans., 1996,92,1 1 I. S. Zamir, D. Singer, N. Spielberg, E. J. Wachtel, H. Zimmermann, R. Poupko and Z. Luz, Liq. Cryst., 1996,21,39. L. Calucci, H.Zimmermann, E. J. Wachtel, R. Poupko and Z. Luz, Liq. Cryst., 1997,22,621. C. Cruz, J. L. Figueirinhas, P. J. Sebastiao, A. C. Ribeiro, F. Noack, H. T. Nguyen, B. Heinrich and D. Guillon, Z . Naturforsch., 1996,51a,155. R. H.Lewis, H. W. Long, K. Schmidt-Rohr and H. W. Spiess, J. Magn. Reson., 1995,A115,26. R. Muzzalupo, G. A. Ranieri, D. Catalano, G. Galli and C. A. Veracini, Liq. Cryst., 1995,19,367. A. Riede, S.Grande, A. Hohmuth and W. Weissflog, Liq. Cryst., 1997,22, 157. G. Germano, C.A. Veracini, C. Boeffel, H. W. Spiess, Mol. Cryst. Liq. Cryst.,l995, 266,47. R. L. Silvestri and J. L. Koenig, Moi. Cryst. Liq. Cryst., 1995,259,101. C. Chiccoli, P. Pasini, F. Semeria, E. Berggren and C. Zannoni, Mol. Cryst. Liq. Cryst., 1995,266,241. A. Golemme, S. Zumer, J. W. Doane and M. E. Neubert, Phys. Rev., 1988, A37, 559. D. Schwarze-Haller, F. Noack, M. Vilfan and G . P. Crawford, J. Chem. Phys., 1996, 105,4823. S.Auge, H. Mazarguil M. Tropis and A. Milon, J . Magn. Reson., 1997,124,455. K.P. Howard and S. J. Opella, J. Magn. Reson., 1996,B112,91. P. 0.Quist, Langmuir, 1995,11, 2201. M. Lukaschek, D. A. Grabowski and C. Schmidt, Langmuir, 1995,11,3590. R. Marinov and E. .I. Dufourc, J. Chim. Phys., 1995,92,1727. F.Caboi and M. Monduvi, Langmuir, 1996,12,3548. G-Z. Li, J-C. Hao, L-Q. Zheng, F. Li, S-X. H a 0 and H-Q. Wang, Chem. J . Chinese Univ., 1995,16, 595. F.Li, G-2. Li, H-Q. Wang and S-X. HaO, Chem. J . Chinese Univ., 1996,17,1446. P. 0.Quist, Liq. Cryst., 1995,18,623. S . Gustafsson, P.0. Quist and B. Halle, Liq. Cryst., 1995,18,545. W. Ziegler and A. Blume, Spect. Chim. Acta, 1995,A51, 1763. L. Coppola, R. Muzzalupo, G. A. Ranieri, and M. Terenzi, Langmuir, 1995, 11, 1116. F.Macquaire and M. Bloom, Phys. Rev. E., 1995,51,4735. C. Dolainsky, M. Unger, M. Bloom and T. M. Bayerl, Phys. Rev. E., 1995,51,4743. K . Schmidt-Rohr and M. Hong, J. Phys. Chem., 1996,100,3861. B. A. Salvatore, R. Ghose and J. H. Prestegard, J. Am. Chem. SOC.,1996,118,4001

14: Oriented Molecules

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483

R. S. Prosser, S. A Hunt, J. A. DiNatale and R. R. Vold, J. Am. Chem. SOC.,1996, 118, 269. M. Hong and K. Schmidt-Rohr, J. Magn. Reson., 1995, B109,284. I. Furo and H. Johannesson, J. Mugn. Reson., 1996, A119, 15. H. Johannesson, I. Furo and B. Halle, Phys. Rev. E., 1996,53,4904. J. Vaara, K. Oikarinen, J. Jokisaari and J. Lounila, Chem. Phys. Lett., 1996, 253, 340. H. W. Long, M. Luzar, H. C. Gaede, R. G. Larsen, J. Kritzenberger, A. Pines and G. P. Crawford, J. Phys. Chem., 1995,99, 11989. A. Grayff-Keller, P. Szczecinski and A. Ejchart, Pol. J. Chem., 1995,69,627. J. Kaski, J. Vaara and J. Jokisaari, J. Am. Chem. SOC.,1996,118,8879. Y. Hiltunen and J. Jokisaari, Mol. Phys., 1983,50, 1013. Y. Hiltunen and J. Jokisaari, J. Mugn. Reson., 1987,75,213. J. Lounila, M. Ala-Korpela and J. Jokisaari, J. Chem. Phys., 1990,93, 8514. C. L. Khetrapal, N. Suryaprakash and S. Vivekanandan, Chem. Phys. Lett. (To be published). C. L. Khetrapal and A. C. Kunwar, Chem. Phys. Lett., 1981,82,170. C. L. Khetrapal and A. C. Kunwar, Mol. Cryst. Liq. Cryst., 1981,72, 113. P. Diehl, J. Jokisaari and F. Moia, J . Magn. Reson., 1982,49,498. X. Shen and R. Y. Dong, Mol. Cryst. Liq. Cryst., 1995,262,293. E. A. Joghems and G. vander Zwan, J. Phys. II France, 1996,6,845. E. Anoardo and D. J. Pusiol, Phys. Rev. Lett., 1996,76, 3983. P. J. Sebastiao, A. C. Ribeiro, H. T. Nguyen and F. Noack, J. Phys. II France, 1995, 5, 1707. J. Struppe and F. Noack, Liq. Cryst., 1996,20,595. H. Yoshida, Mol. Cryst. Liq. Cryst., 1995,259, 55. P. 0. Quist, J. Phys. Chem., 1996,100,4976. R. Y. Dong and X. Shen, J . Chem. Phys., 1996,105,2106. R. Y. Dong, J. Phys. Chem., 1996,100,15663. J. P. Korb, L. Malier and F. Cros, J. Chim. Phys., 1995,92, 1709. A. F. Terzis, C. D. Poon, E. T. Samulski, Z. Luz, R. Poupko, H. Zimmermann, K. Muller, H. Toriumi and D. J. Photinos, J. Am. Chem. SOC.,1996,118,2226. D. Sandstrom, A. V. Komolkin and A. Maliniak, J. Chem. Phys., 1996, 104, 9620. J. B. S. Barnhoorn and C. A. De Lange, Mol. Phys., 1996,88, 1. R. Tarroni and C. Zannoni, Chem. Phys., 1996,211,337. T. Chandrakumar, L. Smith and E. E. Burnell, J. Phys. Chem., 1995,99,7054. C. Forte, C. Gandolfo, M. Geppi and C. A. Veracini, Mol. Cryst. Liq. Cryst., 1995, 266, 213. R. Y. Dong and G. M. Richards, Mol. Cryst., 1995,262,339. P. Berdague, F. Perez, J. P. Bayle, M. S. Ho and B. M. Fung, New. J. Chem., 1995, 19, 383. F. Perez, J. P. Bayle and B. M. Fung, New. J. Chem., 1996,20,537. S. Miyajima and T. Hosokawa, Phys. Rev., 1995, B52,4060. F. Grinberg and R. Kimmich, J. Chem. Phys., 1995,103,365. T. Brauniger and B. M. Fung, J. Chem. Phys., 1995,102,7714. C. W. Cross and B. M. Fung, Liq. Cryst., 1995, 19, 863. M. L. Magnuson, B. M. Fung and J. P. Bayle, Liq. Cryst., 1995,19,823. M. L. Magnuson, B. M. Fung and M. Schadt, Liq. Cryst., 1995,19,333. D. Catalano, E. Ciampi, K. Fodor-csorba, C. Forte, M. Geppi and D. Imbardelli, Liq. Cryst., 1996, 21, 927.

484

Nuclear Magnetic Resonance

158

L. Calucci, 0. Francescangeli, C. Gandolfo, L. Komitov and C. A. Veracini, Liq. Cryst., 1997, 22, 99. R. Y. Dong, X. Shen and G. M. Richards, Phys. Rev. E., 1995,52, 1753. S. Kralj, A. Zidansek, G . Lahajnar, I. Musevic, S. Zumer, R. Blinc and M. M. Pintar, Phys. Rev. E., 1996,53, 3629. G. P. Crawford, R. J. Ondris-Crawford, J. W. Doane and S . Zumer, Phys. Rev. E., 1996,53,3647. F. Grinberg and R. Kimmich, J . Chem. Phys., 1996,105,3301. V. A. Andreev, Y. A. Marazuev, L. V. Nedbaeva, and I . V. Oleynikova, Mof.Cryst. Liq. Cryst., 1995,265,477. V. A. Andreev and I. V. Oleyikova, Izv. Akad. Nauk. Ser. Khim., 1995, 1269. F. P. Nicoletta, A. Golemme, N. Picci and G. Chidichimo, Gass. Chim. Ztaf., 1996, 126, 279. M. Winkler, A. Gil and D. Geschke, Liq. Cryst., 1996,21,203. M. Tansho, S. Ikeda, H. Ohki and R. Ikeda, J . Phys. Chem., 1995,99,4335. A. L. Esteban and M . P. Galache, Magn. Reson. Chem., 1995,33,831. G. Celebre, G. D. Luca, M. Longeri, D. Catalano, M . Lumetti and J. W. Emsley, Mol. Phys., 1995,85,221. E. K. Foord, J. Cole, M. J. Crawford, J. W. Emsley, G. Celebre, M. Longeri and J. C. Lindon, Liq. Cryst., 1995, 18,615. J. W. Emsley, M. I. C. Furby and G . D. Luca, Liq. Cryst., 1996,21, 877. M . Luzar, M. E. Rosen and S. Caldarelli, J. Phys. Chem., 1996, 100, 5098. J. W. Emsley, G . Celebre, G. D. Luca, M. Longeri, D. Catalano and C. A. Veracini, Gazz. Chim. Ital., 1996, 126,429. M. Cocivera, J. Chem. Phys., 1967,47,3061. J. Alejandre, J. W. Emsley, D. J. Tildesley and P. J. Carlson, J. Chem. Phys., 1994, 101,7027

159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175

A uthor Index

In this index the number in parenthesis is the Chapter number of the citation and this is followed by the refirence number or numbers of the relevant citations within that Chapter.

Aalonen, P. (10) 105 Aarnes, H. (12) 107 Aarnts, M.P. (3) 409; ( 5 ) 506 Abbott, E.H. (3) 304; ( 5 ) 238 Abbott, R.J. (10) 442 Abboud, J.-L.M. (3) 460 Abboud, K.A. (3) 257 Abduijalil, A.M. (12) 18 Abe, A. ( 5 ) 423 Abergcl, D. (8) 10 Abernathy, S.M.(6) 99 Abetz, V. (10) 349,355,356 Abeygunawardana, C. (9) 59,60 Abhiraman,A.S. (10) 312,338 Abildgaard, F. (5) 343 Ablett, S. (13) 106 Abouabdcllah, A. ( 5 ) 392 Aboulcla, F. (5) 479; (9) 94,96, 97,112 Abraham, R.J. (3) 2,96; (4) 47, 77,78,80; (1 1) 23 Abrahams, I. (7) 272 Acher, F. ( 5 ) 427 Achiba, Y. (3) 255 Achour, M.N. (2) 175 Ackerman, J.J.H. (12) 232 Ackerman, J.L. (7) 20; (12) 13 Ackermann, M.N.(3) 278 Adachi, M. (7) 243 Adachi, Y. (7) 790 Adam, 0. ( 5 ) 370 Adam, W.R (12) 162 Adami, P. (12) 173 Adams, B. (6) 72; (7) 57 Adams, D. (12) 290 Adams, J.L.(7) 57 Adams, P.D. (9) 228 Adams, P.N. (10) 202

Adams, R.C. (7) 662 Adamsons, K. (10) 11 Adcock, W. (3) 499; ( 5 ) 130 Addad, J.P.C. (10) 18 Addink, R. (10) 207 Adcrmann, K. ( 5 ) 291 Adolphi, N.L. (7) 497,809 Adriacnscns, P. (10) 169, 180,398 Acnouts, K. (7) 426 Affandi, D. ( 5 ) 190 Alkhami, A. (3) 162,234 Afonin, A.V. (3) 116 Agccv, S.V.(7) 12 Agmon, N. (6) 128 Agrawal, P.K. (3) 180 Agris, P.F. (1 1) 110 Aguilar-Parrilla, F. (3) 89,94,43 I; (7) 163, 171, 180, 198 Ahlberg, P. (3) 21 1; ( 5 ) 102 Ahlrichs, R. (2) 50; (4) 11 Ahlsdorf, B. (7) 469 Ahmedov, M.A. (10) 55,59 A h , S. (6) 32 Ahuja, S. (10) 439; (13) 132 Aiba, S. (10) 191 Aikcn, N.R. (12) 75,76; (13) 168, 169 Aimc, S. (2) 135; (3) 191; (9) 246 Aisa, A.M.A. ( 5 ) 182-184 Akabori, S. (1 1) 77 Akagi, K. (12) 228 Akai, T. (7) I5 1 Akapo, S.A. (7) 458,742 Akasaka, K. (14) 18,38-41 Akgun, H. (12) 7 Akhtar, M.N. ( 5 ) 129 Akhtcr, H. (7) 504 Akin, D.E. (7) 362,388,407 485

Akino, M. (12) 137 Akira, K. (3) 365 Akkc, M. (9) 261,267 Akolckar, D.B. (7) 667 Akporiayc, D. (3) 394 Aksncs, D.W. ( 5 ) 67 Alafandy, M. (3) 407 Ah-Korpela, M. (12) 273,322; (14) 127 Alam, P. ( 5 ) 387 Alani, T.M.(3) 396,397; (10) 288 Alamo, R.G. (7) 159; (10) 334 Alarcon, S.H. (7) 169 Al-Arfaj, A.R. (5) 129 Alattia, T. (9) 296 Alba, M.D. (7) 544 Albarct, C. (9) 287 Albert, K. (7) 186,332,353,441, 449,734,735,738; (10) 244, 29 1 Albrecht, M. (3) 164 Albrecht-Schmitt, T.E. (3) 487 Alcantar, C. (3) 167 Aldcrfcr, J.L. (1 I ) 106 Aldcrman, D.W. (2) 122, 145; (3) 375-377 Aldingcr, F. (7) 796 Aldrich, H.S. (7) 160 Alecci, M. (12) 14 Alcgria, A. (10) 364 Alei, M. (2) 194 Alejandre, J. (14) 175 Alemiin, C. ( 5 ) 422; (7) 213; (1 1) 49 Alcmany, L.B. (3) 5 13 Alctras, A.H. (12) 18 Aletras, V. (3) 3 15 Alcwood, P.F. ( 5 ) 282,286,295

Nuclear Magnetic Resonance

486 Alexander, P. (13) 12 Alcxandrcscu, A.T. ( 5 ) 240; (9) 290

Alcxcy, V. (3) 167 Alfonso, I. (3) 324 Alger, J.R (12) 284 Alheid, H. (7) 152 Ali, M. (7) 383 Ali, S.(2) 168; (3) 432; (5) 512 Ali, S.A. (1 1) 90 Aliev, A.E. (7) 827 Alikacem, N. (7) 46 1,462 Alivisatos, A.P. (3) 392; (7) 806 Aliyu, N.H. (7) 233 Allain, F.H.T. (9) 94,95, 109, 110 Allan, P. (3) 11 Allard, P. (5) 17; (6) 40,41; (8) 24,36,41; (9) 253 Allavena, M. (2) 132, 134; (3) 386; (7) 709 Allen, K.M. (7) 147 Allen, N.S.(10) 128 Allinger, N.L. (4) 82; (1 1) 9 Allison, T.J. (5) 259 Allman, T. (3) 5 Alloul, H. (3) 379; (7) 142, 143 Almacr, S. (13) 151 Almeida, F.C.L. (8) 39 Almcida, J.S. (12) 43 Almcida, L.P.A. ( 5 ) 372 Almcndros, G. (7) 390,475 Almugheiry, M.A. (13) 85 Alonso, J. (12) 306 Alpert, N.M. (12) 146 Al-Taweel, S.M. (3) 334 Altmann, K. (10) 372 Altona, C. (4) 84; (5) 346 Alturky, M. (3) 407 Alvarado, V. (13) 95 Alvarcz, A. (7) 559 Alvarez, F. (10) 364 Alvarez, R. (7) 129 Alvero, R. (7) 544 Alvizzati, E. (10) 227 Ammo, H. (12) 140 Amantea, A. (3) 454 Am&, S.(13) 26 Amari, T. (10) 96 Amburgey, J.C. (5) 343 Amess, P. (12) 288 Amh, N.S. (3) 278 Amin, S. (9) 84 Amir-Aslani, A. ( 5 ) 475 Amir-Ebrahimi, V. (10) 82, 139 h i l l a t h i , E. (6) 67 Amoli, H.S. (3) 172 A~OWCUX, J.-P. (3) 241,347; (7)

99, 100, 107, 112,597,603, 676,677 Anastasiadis, S.H.(10) 427 Ancian, B. (8) 22 Andersen, N.H. (1 1) 34 Anderson, G.K. (1 1) 149 Anderson, J.E. (1 1) 85 Anderson, M. (12) 117 Anderson, M.W. (3) 275; (7) 581, 613-615,699,710 Anderson, O.M. ( 5 ) 67 Anderson, P.A. (7) 726 Anderson, S.E. (12) 155 Anderson Evans, C. (5) 13 1 Andersson, A. (3) 232; (7) 528 Andersson, 1. (3) 271,272 Ando, 1. (6) 216; (7) 289,333; (10) 283,339,387,425 Ando, S.(7) 289 Ando, W. ( 5 ) 104 Ando, Y. (12) 282 Andre, J.P. (6) 173 Andreae, F. ( 5 ) 440 Andreasson, B. (6) 199 Andrec, M. (8) 28; (9) 216 Andreev,V.A. (14) 163,164 Andrcs, H. (3) 219,220 Andrcs, R. ( 5 ) 73 Andrescn, J.M. (7) 121, 125, 126, 725 Andro, T.M.(1 1) 34 Andrushkevich, T.V. (7) 486 Anet, F.A.L. (4) 37 Angelini, G. (3) 222 Angemair, K. ( 5 ) 200; (7) 260 Anglister, J. ( 5 ) 307 Angus, D.I.(3) 499; ( 5 ) 130 Angyal, S.J. (3) 112 Anisimov, A.V. (6) 217 Anno, I. (12) 303 Anoardo, E. (14) 134 Anpo, M. (7) 622 Ansari, M.S. (6) 162 Anlhoni, U. (7) 157 Antich, P.P. (3) 497; (12) 174,226 Antonietti, M. (10) 253 Antos, G. (7) 650 Anttila, U. (1 1) 58 Antuch, W. (9) 17 Antz, c . (9) 49 Antzutkin, O.N.(7) 297; (14) 30 Anulewicz, R (7) 197 Aoki, S.(3) 54 Aoki, T. (7) 805 Aoki, Y. (12) 228 Aoyama, Y. (3) 329 Apostol, M.(3) 244

Appel, M. (6) 107, 190,219 Appelmans, K.E. (12) 286 Apperlcy, D.C. (3) 92; (7) 3 17, 383,395,400 Apple, T. (7) 447 Appleby, A. (6) 168 Arai, N. (7) 354 Arais, M.E. (7) 389 Aramcndia, M.A. (7) 490 Aramini, J.M. (3) 417; ( 5 ) 360; (9) 248,3 11 Aranyosi, P. ( 5 ) 500 Arata, Y. (8) 11; (12) 19 Archer, D.B. (5) 330 Archer, F. (1 1) 17,28,29 Archer, S.J.(5) 443,452; (9) 40, 53,143 Arcinue, E. (12) 279 Ardclean, I. (7) 46 Ardizzoia, G.A. ( 5 ) 191 Arduengo, A.J., I11 (3) 322; (5) 151,162 Argalane, S.(7) 697 Arias, J. (2) 119; (3) 339,385 Aria~-Blan~~, M.J. (3) 142 Aries,F. (11) 113 Ariga, T. (10) 208 Arishima, T. (7) 2 10 Arkhangclsky, I.V.(7) 134 Arkin, C.R (7) 206 Arleud, G.J. (5) 290 Armes, S.P. (10) 179 Armiger, L.C. (12) 163 Arnal, M.L. (10) 233 Arnaud,R(ll) 102 Arnold, D.1. (12) 321 Arnold, F.E. (10) 399 Arora, A. (5) 365 Amola, D.J.(10) 392 Arrowsmith, C.H. (5) 33 1; (9) 48, 68 Arrowsmith, D. (10) 88 Arroyo, P.A. (7) 626 Arsalani, N. (10) 143 Arseniev, A.S. ( 5 ) 255 Arshadi, M.(3) 399; (5) 230 Arstall, M.A. (12) 179 Arthur, H.L. (12) 148 Arthur, S.D.(10) 276 Arulmozhi, V. (1 1) 28 Arumugam, S. (7) 373 k a n a & , M. (4) 37 Arvanitoyannis, I. (10) 191 As&, H. (7) 222 Asakawa, Y. (3) 50 Asakura, T. (7) 349; (10) 269 Asano, K. (12) 302

487

Aufhor Index Asby, R.D. (10) 63 Ascenso, J.R. (10) 237 Asensio, J.L. (1 1) 125, 144 Asfari, Z. (3) 249 Asgedom, G. (3) 270 Ash, E.L. (8) 74 Ashe, A.J., I11 (3) 334 Ashish, ( 5 ) 246 Ashram, M. (1 1) 78 Ashtekar, S. (7) 669,670 Ashton, P.R. ( 5 ) 121 Askenasy,N. (12) 156,171 Aso, Y. (7) 328 Assa-Munt, N. (5) 254 Assink, R.A. (3) 396,397; (10) 288 Astrand, P.O. (2) 187 Atalar, E. (12) 262 Atar, D. (12) 143 Atkins, E.D.T. (10) 58 Atlan, H. (12) 63 Aubagnac, J.-L. (I 1) 59 Aubrecht, K.B. (3) 224 AUCN,G.A. (4) 63-65,67; (5) 237; (1 1) 4 Aucr, F. (7) 245 Auerbach, S.M. (7) 719 Auge, S. (14) 48, 101 Auger, M. (7) 372,396,397,461, 462 Augspurgcr, J.D. (2) 186, 188, 190 Augustc, F. (7) 4 17 Augusthe, M.P. (6) 44, 184 Auner, N. ( 5 ) 4 15 Aupers, J.H. (7) 263 Aurentz, D.J. (7) 174,786 Auriemma, F. (1 0) 257 Au-Yewg, S.C.F.(2) 99,100; (3) 35; ( 5 ) 353,354; (10) 414,417 Avalos, M. ( 5 ) 403; (1 1) 129 Avella, N. (10) 78 Avgeropoylos, A. (10) 219 Avis, J.M. (9) 110 Avrin, W.F. (13) 20 Aw, B.-H. (3) 80 Awrcy, D.E. (5) 33 1; (9) 48 Axen, A. (3) 196; ( 5 ) 425 Azcrad, R. (5) 427; (1 1) 17,28,29 Aziz, S.G. (3) 172 Amar, A.J. (7) 559 Amar, F. (3) 58 Azuma, Y. (12) 235,239,240 Baard, Y. (7) 723 Baba, T. (2) 13, 151; (3) 200; (7) 483,654

Babb, S.M. (12) 286 Babcock, E.E. (12) 190,212 Babiano, R. (5) 403; (1 1) 129 Babitch, I.V. (3) 266 Babonneau, F.(7) 442,444,453, 459; (10) 289,402 Babu,G.N. (10)61, 137 Bacchini, P. (7) 387 Bach, 1. (7) 277 Bach, R. (7)246 Bache, R.J. (12) 148 Bachelard, H.S. (12) 28 Bacher, A. (9) 133 Bachiller, P.R.(6) 32 Bachinlein-Mans, J. (7) 437 Bachmann, P. (6) 64 Bachovchin, W.W. ( 5 ) 336; (8) 74 Bacic, G. (13) 120 Backlund, P. (7) 478 Bacskay, G.B. (4) 52,68,70; ( 5 ) 55 Bader, M.G. (10) 39 1 Bader, RF.W. (2) 81-85 Badey, B. (10) 69 Badia, P. (12) 186 Baducchcl, B. (3) 189 Baello, B.I. (2) 208 Bacrends, E.J. (3) 409 Bagby, M.O. (3) 195 Baggiolini, M. (9) 190 Bagryantsev, V.F.(3) 503 Bahloul, D. (7) 794,795; (10) 289 Bai, S. (6) 186, 187 Bai, X. (7) 139 Baik, D.H. (10) 247 Bailey, J.L. (12) 209 Bain, A.D. (3) 5; (5) 40; (6) 70 Baird, M.C. ( 5 ) 70 Bairich, D.H. (7) 67 1 Baitoul, M. (10) 252 Bak, K.L. (4) 16 Bak, M.I. (12) 179 Baker, W.E. (10) 386 Bakos, J. (5) 185 Balaban, A.T. (3) 333 Balaban, RS. (12) 26,266,294 Balasubramanian, S. (10) 46,66 B a l m , Y.S.(7) 416 Balbach, J. (7) 809; (9) 200 Belbontin, G. (10) 227 Balcazar, J.L. (7) 202 Bald, A. (6) 135 Baldassani, A.M. (13) 171 Baldisseri, D. ( 5 ) 343 Baldus, M. ( 5 ) 34; (7) 89,90 Baldwin, B.S. (7) 407 Baldwin, B.W. (3) 52

Baldwin, C.A. (13) 92 Baldwin, M.(7) 334 Baldwin,N.J. (12) 219,225 Balinov, B. (6) 2 13 Balkan, A. ( 5 ) 121 Ball, G.E. (6) 25 Ball, L.J. ( 5 ) 443; (9) 40 Ballard, C.C. (2) 5,6; (3) 44 Ballard, L. (6) 42, 154 Ballestcros, P. (7) 202 Ballingand, J.-L. (12) 179 Balluff, M. (10) 149 Bally, 1. ( 5 ) 290 Balschi, J.A. (13) 172 Balb, C.F.J. (10) 90 Baltisbergcr, J.H. (7) 109, 113 Baltusis, L. (7) 183 Balzano, F. (3) 73, 143 Balzarini, M. (10) 407 Banci, L. ( 5 ) 3 19; (6) 96 Banciu, M.D. ( 5 ) 414 Bandyopadhyay, T. (4) 6; (5) 118; (11)6t

Banerjee, A, (12) 180 Bank, S. (7) 342,361; (1 2) 42 Bankov, Y.M. (6) 178 Bansal,N. (12) 174 Banse, F. (7) 434 Baptista, J.L. (7) 428 Baraldi, E. (9) 8 Baranwal, R. (7) 444 Barba, L. (3) 410 Barbarella, G. (7) 196 Barbaw, Y. (7) 683 Barbcni, M. (3) 207 Barber, J. ( 5 ) 387 Barbera, J.A. (12) 306 Barbiroli, B. (12) 298,305 Barchi, J. ( 5 ) 504 Barclay, G.G. (10) 203 Bardet, M. (6) 67; (7) 393; (1 1) 36 Barich, D.H. (3) 368,378; (7) 178, 179 Barkan, D. (7) 359 Barker, A.L. (6) 33 Barker, E.B. (4) 34 Barker, P.B. (13) 26,53 Barker, P.D. (7) 726; (9) 140 Barlow, S. (7) 828 Barlucnga, J. (3) 58 Barnes, C.L. (3) 507 Barnhoorn, J.B.S. (3) 222; (14) 144 Barr, T.L. (7) 161, 162 Barra, A.L. (2) 95 Barrage, M.C. (3) 183 Barras, J. (7) 135

Nuclear Magttelic Resonance

488

Barregard, L. (13) 17 Barrclle, M. (3) 67; (1 1) 102 Barrerc, B. (12) 133 Barrcs, 0. (7) 561 Barrie, P.J. (7) 261,272,280,288, 322

Barrientos, L.G. (1 1) 13 1 Banis, G.C. (7) 803 Barsukov, LL. (1 1) 139 Barszczewicg A. (2) 189 Bartels, C. (9) 224,225 Barth, P. (10) 440,441; (13) 119, 134, 135

Bartholomae, G. (3) 189 Barthomeuf, D. (7) 60 1 Barthwal, R (1 1) 50 Bart&, K. (2) 2 1 1 Bartlett, P.A. (5) 242 Bartlett, R.J. (4) 2,3, 19-23, 25-28,40; (5) 106 Bartley, J.P. (5) 379 Bartoli, M.H. (5) 385; (11) 40 Bartolomei, M. (3) 153 Bartoshevich, Y.E.(12) 87 Bartram, P.W. (7) 695 Baruzzi, G. (10) 154 Bashford, C.L. (12) 35 Bashir, A. (13) 180 Basiri, H.G. (2) 205 Baskar, G. (10) 314 Basnak, I. (5) 121,357 Basran, J. (9) 191; (11) 140 Basset, J.-M. (5) 491; (7) 241, 243,244

Basti, M.M. (11) 110 Bastiaan, E.W. (14) 5 , 9 Bastien, I.J. (4) 34 Bastow, T.J. (3) 3 12,467; (7) 507, 508,532,780,810

Basu, A.K. (9) 83 Batamack, P. (7) 649,650,688 Batchelor, R.J. (3) 472 Bates, C.M. (5) 201 Bates, T.E. (12) 114 Batta, G. (6) 15 1 Battiste, J.L. (8) 75; (9) 113, 185 Battisti, C. (12) 50 Battles, J.A. (9) 58 Bau, R (7) 280 Bauduin, N. (12) 276 Bauer, A. (3) 253 Bauer, C.J. (3) 492; (5) 355; (1 1) 103

Bauer, H. (3) 189 Bauer, W. (3) 228; (7) 275; (12) 173

Baum, M. (5) 96

Baumann, H. (5) 386 Baumann, W. (5) 74 Baumet, L. (5) 302 Baumert, R (6) 91 Baumgart, F. (12) 229 Baumgarlncr, R (9) 44 Bausch, J.W. (2) 114, 120; (3) 330 Bauza,G. (12) 81 Bax, A. (2) 137; (5) 88,486,488; (6) 63,65; (8) 33,59,88,89; (9) 158-161, 172, 174,254, 258; (14) 13 Bayer, E. (10) 244 Bayed, T.M. (14) 114 Bayie, J.P. (10) 438; (14) 67, 149, 150,155 Baz, T. (3) 97 Beauchamp, A.L. (3) 299; (5) 232 Beaume, F. (10) 323 Becerro, A.I. (7) 544 Bech, L.M. (5) 323 Bechinger,B. (7) 56,357,409 Bechtel, B. (3) 257 Beck, A. (12) 308 Beck, T.W. (12) 204 Bccke, A.D. (2) 70,73,78 Becker, E.D.(2) 128; (7) 378; (14) 60 Becker, K. (7) 388 Bcckerle, M.C. (9) 20 Bcckett, M.A. (7) 193 Beckham, H.W. (10) 307,312,338 Beckman, H. (7) 200 Beckman, R.A. (5) 329 Beckmann, P.A. (7) 185 Beer, R.H. (3) 282 Beeser, S.A. (9) 264 BCguc, J.-P. (5) 391 Beguin, C.G. (1 1) 102 Behar, K.L. (12) 110, 122,123, 284 Behrens, S.(5) 273 Behringer, K.D.(7) 239,240,733 Behrouzian, B. (5) 206 Bein, T. (7) 662 Beinkma, J.J. (9) 156, 157 Bekkali, Y.(5) 501; (1 1) 101 Bekker, T. (7) 334 Belahmer, Z. (7) 138 Belcuig, M.P.(3) 459 Belgrand, P. (7) 522 Bell, A.G. (3) 293; (5) 196 Bell, A.T. (3) 306; (6) 211; (7) 74, 600 Bell, J. (7) 824,825 Bell, J.D. (12) 198,249 Bell, L.G. (5) 42

Bell, RA. (2) 202 Bell, T.N. (7) 722 Bellcc, N. (3) 321 Bellwq, A.-M. (7) 4 17 Bellows, C.F. (12) 180 Bcloeil, J.C. (12) 126, 133 Bclorizky, E. (6) 100; (10) 424 Belostolskii, A. (1 1) 9 1 Belous, A.M. (12) 55 Belsky, K.A. (5) 13 1 Belton, P.S. (7) 345 Belzile, N. (7) 465 Belzner, J. (5) 100 Benayada, B. (6) 129 Benazzi, E. (7) 244 Bcncko, V. (12) 65 Bcndall, M.R (2) 173; (8) 6 Bendini, E.(I 0) 163 Bendler, J.T. (6) 148; (10) 346 Benedctti, E. (5) 277 Benedict, H. (3) 88,89,94; (7) 171 Bcnelli, C. (12) 307 Benesi, A.J. (7) 174 Benetis, N. (6) 97 Bcncz, A. (7) 245 Bcnticld, R.E. (10) 13 1 Benga, T.(12) 49 Benian, G.M. (5) 324; (9) 42 Bennett, A.E. (7) 81,82 Bcnnett, E.A. (5) 379 Bcnsimon, C. (3) 299; (7) 2 17; (11)97

Bcnson, J.W. (5) 233 Bentovim, L. (9) 75 Bentrop, D. (5) 3 17 Bentrude, W.G.(1 1) 5 1 Bentrup, F.W. (13) 153 Benziger, J.B. (7) 685 Bequin, C. (4) 46 BCrm-Stoed, RK. (5) 256 Bcrdague, P. (14) 75, 149 Bereau, V. (3) 285 Berenger, G. (12) 126 Berg, A. (5) 293,3 16; (9) 284 Berg, K.E. (3) 357; (5) 152 Berger, N. (7) 493 Berger, S. (5) 10, 128; (8) 2, 18, 93 Berger, U.V. (12) 124 Bcrggren, E. (14) 98 Berglund, H. (9) 35 Bergman, R G . (5) 43 Bergquist, P. (10) 384 Bergstrom, C.H. (10) 140 Berke, H. (5) 7 Berlin, A. (7) 223; (10) 272 Berlin, K. (3) 123

Author Index Berlose, J.-P. (5) 250 Bcrman, E.(12)63 Bermel, W.(5) 484;(6)25;(9) 165,180 Bernard, D.( 12) 276 Bemard, E.(12) 184 Bernard, G.M.(2) 170;(3)93;(5) 59,501,502;(11) 101 Bernard, M. (12) 169 Bernassau, J.-M. (5) 3 12 Bematowicz, P. (5) 226 Berndt, K.D.(5) 291;(9)239 Bcrnc, R.M.(12) 183 Berners-Price, S.J. (5) 190 Bernet, B.(1 I) 137 Bernhagen, J. (9)292 Bcmier, P.(7) 138 Bernstein, H.J. (2)64,201 Bernstein, M.P. (3) 227 Bero, M.(10) 120 Beroza, P. (5) 341 Bcrr, S.S.(12) 183 Berrhault, P. ( I 1) 133 Berrocal, M.(7)389 Berthault, P. (6) 7 Berthier, G. (2) 175 Bertholdt, U.(5)87, 158,159 Berthon, H.A. (1.2)48 Bertini, I. (5) 317,319,444;(6) 10,96;(9) 246 Bertucci, C.(3) 143 Bessada, C.(7)538 Bcsse, J.P. (7)818 Bethell, H.W.L. (12)158 Bcthunc, D.S.(2) I17 Bcusen, D.D.(7)319,326,341 Beveridge, R (7) 184 Beycr, H.K.(7)645 Beyer, L.(7)463,464,469 Beyemann, M.(3) 108 Bhat, S.V. (3) 201;(7)488,489 Bhat, T.N.(9)148 Bhat, V.(3) 201;(7)488,489 Bhattacharya, A.K. (7)492 Bhattacharya, M. (10)206 Bhavani, N. (5) 4 1 1; ( I 1) 39 Bhuvaneshwari, R (10)39 Biaglow, J.E. (12)22 1 Bianchini, C.(5) 50,5 1 Bibby, D.M.(7) 628,634 Bibler, J. (7) 175 Bick, A. (7)374 Biedrzycka, Z.(3) 126,424-426, 439 Biekofsky, RR (3)455 Bieiecki, A. (7)506 Bienert, M. (3) 108

489 Bicnz, S.(5) 12,463 Bicrwisch, J. (3) 193 Biesemans, M. (3)407,415; (5) 16,144,145;(7)250,257 Bifone, A. (3)392;(7)806;(13) 78 Bifdco, G.(5) 362 Biggs, W.R (7) 141 Bigi, A. (2) 135 Bijanzadeh, H.R (5) 418 Bildsoe, H.(2) 123;(3) 247,251; (7)77 Bilcccn, D.(13) 75 Biliaderis, C.G. (5) 376 Bill, J. (7)796 Billeter, M. (5) 306,326;(9) 1-3, 16,144,145,193,221-225 Billingham, N.C. (10) 179 Billups, W.E. (3)513 Binder, H. (5) 176 Bincsh, N. (3) 201;(7)488,489 Birattari, C.(13) 129 Birczynski, A. (7)534 Birdsall, B.(3) 492;(7)322;(9) 191,194,195;(11) 140 Birlirakis, N. (8)26;(9)303 Bisang, C.(5) 275 Bish, D.L.(7)556 Bishop, D.M.(2)32, 185 Bister, K.(5) 333;(9)291 Bitan, G. (5) 273 Bitterer, F. (5) 93 Bizzani, P.C. (10)56 Bjoerksten, J. (1 1) 1 1 Blachtuk, R (5) 173, 174 Black, J.R (3)307 Blackband, S.J. (12)244,263;(13) 149,168,169 Blackledge, M.J.(5) 332 Blakc, A.J. (3)302;(5) 225 Blake, RC.,I1 (5)341 Blanchard, S.C.(5) 478;(9) 114, 115; (1 1) 142 Blandamcr, M.J. (3) 15 1; (1 1) 82 Bldcnbcrg, F.G. (12)61 Blanquct, S.(5)338;(9)287 Blasco, T.(7)502 Blaszczyk, J. (3) 473;(7) 194 Blaustein, M.P.(5) 296 Blazyk, J. (7) 368 Blease, T.G.(10)211 Blcchta, V.(7)246 Bleriot, Y.(5) 377;(1 1) 135 Bleuzen, B. (6)75 Bliek, C.(5) 408;(1 1) 55 Blinc, R (14) 160 Blixt, J. (3)357;(5) 152

Bloch, G. (12)17,31 1 Bloch, P. (5)20;(7)40 Bloembergen, N.(6)23 Bloemmk, M.J. (1 1) I12 Blow N. (7)691,692,694 Blommen, M.J.J. (5) 240;(9)290 Bloom,M. (14) 113,114 Bloor, D.(1 0) 169 Bluemel, J. (7)239,240,242,271, 733 Bliimel, M.(5) 449;(9)240 Bluemich, B. (7)47,48;(10) 302, 394,431,432,434;(13)35.65, 68,133,138 Bluemlcr, P. (10)434;(13) 35,68, 138 Blum, F.D.(10)321,348 Blum, H. (12)180 Blume, A. (14)11 1 Blume, H.P. (7)463,469 Blumenfield, A.L. (7)639 Blust, R (12)234 Bobroff, S.(13) 113 Boch, C.(12)98 Bocian, W.(3)433,434;(5) 116 Bock, K. (5) 460,461 Bockmann, A. (8) 12 Bodart, P. (13)62 Boddenberg, B. (3) 518;(7) 655 Bodenhausen, G.(5)38;(6)51, 52;(7)24,45 Bodurka, J. (12) 141 Boecker, C.A. (5) 233 Boeffel, C. (10)280;(14)84,96 Biihlcn, P. (5) 450 Bahler, B. (5) 101 Boehm, M.J. (7)392 Bochm, T.(7)751 Boehnlein-Maus, J. (3)236 Boclens, R (3)176;(5)292,303, 309;(8)42,49;(9)90,91,153, 196,226,274,275,277,282 Boender, G.J. (7)55 Bocrs, E.(3) 258 Boerschkc, RC. (7)465 Bogacs. C. (1 0) 161 Bogacs, L.(10)161 Bohin,J.-P. (5) 458 Wen,J.M. (6)28,58;(8) 14, I5 Bohloul, D.(7)442 Bohmer, R (6) 105 Bohner, M.(7)522 Boicelli, A. (13) 171 Bojarski, A.J. (1 1) 15 Boker, M.(7)276 Bolas, N.M.(13)'32 Bolin, K.A. (5) 252;(9)21 I

Nuclear Magneiic Resoriame

490 Bolis, G. ( 5 ) 302 Bolon, P. (1 1) 62 Boltalina, O.V. (3) 502-504 Bolton, P.H. (14) 12 Bolvig, S. (3) 83; (1 1) 19 Boman, A. (3) 232; (7) 528 Bonafous, L. (7) 538 Bonagamba, T.J. (3) 233; (6) 115; (7) 28; (12) 205 Bonardet, J.L. (3) 183,516 Bondareva, V.M.(7) 486 Bonechi, C. (9) 309 Bongcrt, D. (5) 176 Bonhommc, C. (7) 442,444; (10) 289 BOMC,G. (12) 307 Bonnet-Dclpon, D. (5) 392 Bonneviot, L. (7) 624 Bonvin, A. ( 5 ) 303; (9) 90,234 Boogcrs, 1. (7) 307 Boone, H.W. (10) 79, 81 Booth, R. (12) 278 Borau, V. (7) 490 Borgen, G. (1 1) 72 Borgcr, R. (12) 234 Borgia, G.C. (13) 96, 110 Borgnat, P. ( 5 ) 239 Borisova, I.V. (7) 282 Borlc, A.B. (12) 69 Borncmann, J. (1 3) 26 Borrcdon, J. (12) 126 Bomnann, H. (7) 270 Borsa, F. (3) 327 Borschcvski, A.Y. (3) 502 Bortolotti, V. (13) 110 Bortun, A.I. (7) 526,816 Bortun, L. (7) 526 Bosacck, V. (7) 707 Bosch Van Oudtshoorn, M.C.(3) 137 Botck, E. (2) 203; (4) 65; (5) 237 Bothncr-By, A.A. (14) 5-8, 10, 11 Botsi, A. (3) 155 Bolt, S.G. (3) 444 Botta, C. (10) 53 Botta, M. (3) 191 Bottcro, J.Y. (7) 571 Botto, R E . ( 13) 94 Bottomley, P.A. (12) 262 Botuyan, M.V. (5) 341 Bou, J.J. (7) 213 Bouaziz, S.(9) 80 Boubcl, J.C. (6) 108 Boucckkine, A. (2) 175 Bou~Wrine-Yaker,G. (2) 175 Bouchard, M.(7) 396

Bouchaycr, E. (5) 290 Bouchruha, H. (10) 33 1 Bougis, P.E. (7) 397 Bouhdid, A. (3) 415; ( 5 ) 145; (7) 257 Boulangcr, Y. ( 5 ) 270 Boullanger, P. (10) 69 Boulwarc, S.D. (12) 320 Bourbigot, S. (7) 664 Bourgcois, 1. (8) 22 Boutiller, J.M. (10) 358 Bovee, W.M.M.J. (12) 323 Bovens, E. (3) 258 Bovcy, F.A. (10) 5 Bowden, G.J. (6) 25 Bowcn, J.P. (1 1) 9 Bowers, J.L. (3) 190 Bowcry, A. (13) 22 Bowlcs, R.K. (7) 330 Bowmakcr, G.A. (3) 326; (5) 188, 189,200; (7) 258,260,267, 268 Bowman, C.N. (10) 350 Bowtell, R.W. (6) 197; (13) 169 Boyd, J. (9) 70,255 Boyd, S.( 5 ) 123 Boyer, L. (3) 67 Boykin, D.W. (3) 106 Brackcn, C. (8) 66 Bradamante, S.(7) 223; (10) 272 Braddock-Wilking,J. (1 1) 149 Brade, H. (5) 375,461 Bradc, L. ( 5 ) 375 Bradshow, J.S. (3) 166 Braga, A.L. (3) 482 Braibante, M.E.F. ( 5 ) 496 Braich, R (3) 443; (7) 336 Brambrilla, R. (10) 152 Bratnham, J. (1 2) 79 Brammcr, L. (1 1) 149 Brancoline, A. (13) 97 Brandao, P. (3) 275; (7) 6 15 Brandolini, A.J. (10) 9 Brandt, D.E. ( 5 ) 233 Brandt, K.B. (7) 578 Brar,A.S. (10) 173, 181 Bras, M.L.(7) 664 Brasch, N.E. (3) 464 Brasili, L. ( 5 ) 405 Bratovanov, D. (5) 12 Bratovanov, S. ( 5 ) 463 Brauer, D.J. (3) 3 11; (5) 93,228 Braucr, M. (12) 270 Braun, J. (3) 221; (7) 212 Braun, M. (7) 514,776 Braun, T.P. (7) 523 Braune, A. (5) 128

Braunigcr, T. (14) 153 Braunstcin, P. (3) 294 Bravo, P. ( 5 ) 509 Bray, A.M. (7) 173 Brazovskii, S.(3) 181 Brcch, S.J. (7) 266 Brcdas, J.-L. (10) 195 Brceze, A.L. (5) 3 18 Brcmi, T. (6) 120; (7) 41; (9) 251; (14) 27 Bremncr, T. (10) 3 1 1 Brendler, E. (3) 390 Brcneman, C.M. (1 1) 94 Brcrcton, I.M. (12) 233 Bressot, C. (3) 249 Brew, K. (9) 200 Brcwstcr, M.E. ( 5 ) 394 Brcy, W.S. (3) 257 Brczczinski, L.J. (3) 61 Briand, J. (8) 5 Bridges, A.N. (3) 336 Brierchcck, D.M. ( 5 ) 259 Bright, J.R (5) 305 Bnk, M.E. (10) 438 Brindle, K.M. (12) 5,88 Brindlc, R. (7) 441,449,734,735, 738; (10) 291 Bringmann, G.(13) 38 Brisson, J.-R ( 5 ) 459 Britten, J.F. (2) 202; (5) 205 Britton, M.M. (13) 104 Broadhurst, R.W. ( 5 ) 315,443; (9) 40,75 Brockcn, H. (13) 108 Brcclawiak, E. (7) 640 Brodowski, G. (10) 149 Broekacrt, P. (6) 26,27 Bronnimann, C.E. (3) 346; (7) 552 Brooke, G.M.(10) 169 Brooks, K.J. (12) 114 Brosio, E. (1 2) 97 Brothers, P. (9) 54 Brouet, V. (3) 379; (7) 142, 143 Brougham, D.F.(7) 272 Brousseau, L.C. (7) 174 Brow, RK. (7) 771 Brown, C.A. (2) 117 Brown, D.A. (7) 272 Brown, E.L.J. (9) 27 Brown, G.D. ( 5 ) 122 Brown, G.R (10) 176,305 Brown, H.C. (4) 32 Brown, I.W.M. (7) 803 Brown, J.M. (9) 152 Brown, L.R (8) 87 Brown, M.J. (7) 2 I 22 Brown, S.D. (7) 126 ',

Aufhor Index Brown, S.P. (7) 101, 103 Brown, T. (9) 302 B r o w , T.R. (12) 75,328-330; (13) 44,47 Broyde, S. (9) 83, 84 BNW, D.W. (14) 65 Briischweiler, R. (6) 50, 53, 118-120; (9) 251,267 Bruhl, I. (13) 136 Bruix, M. ( 5 ) 339,358 Bdwicki, T. ( 5 ) 384 Brulatout, s. (12) 126 Brun, E. (8) 50; (9) 187 Brunar, H. (9) 85 Brunel, D. (7) 657 Brunet, F. (7) 5 18 Brunger, A.T. (9) 228,229,234 Brunissen, A. ( 5 ) 250 Brunner, E. (7) 7 11 Brunottc, F. (12) 276 Bmtscher, B. (8) 45 Bruycre, T. ( 5 ) 448; (9) 15 Bruzik, K.S. (7) 413 Bryant, D.J. (12) 198 Bryant, R.G. (6) 71, 172, 181; (7) 305; (9) 247 Bryce, J. (10) 8 1 Bryson, J.W. (7) 249 Bubb, W.A. ( 5 ) 497; (12) 54 Bucala, R. (9) 292 Buchanan, G.W. (3) 125; (7) 216, 826; (1 1) 97 Buchanan, M. (12) 25 Buchholz, H.A. (3) 369 Buchlcr, P. (7) 504 Buchwald, S.L. (1 1) 147 Buck, M. (9) 202,212 Buckel, W. ( 5 ) 128 Buckermann, W.A. (7) 774 Buckingham, A.D. (2) 80,107, 164, 180, 182,201; (3) 464 Buddrus, J. (3) 71 Budingcr, T.F.(13) 78 Budinsky, L. (6) 201 Budnick, J.I. (3) 256 Buechner, M. (5) 185 Buhl, M. (2) 38,39,98, 108, 117; (3) 34,38-40; (5) 115 Buhler, B. ( 5 ) 33 Buenger, R. (12) 160 Buffinger, D.R (3) 246 Buhl, J.-C. (7) 569,575-577 Buhr, A. ( 5 ) 3 14 Buisson, J.P.(10) 252 Buist, P.H. ( 5 ) 206 Bujoli, B. (7) 529 Bujoli-Doenfi; M. (7) 529

49 1 Bulai, A. (10) 90 Bull, L.M. (7) 113,719 Bullock, J.F. (7) 18 1; (10) 28 1 Bullock, P.A. ( 5 ) 336; (8) 74 Bunker, B.C. (7) 743; (10) 357, 422; (14) 83 Bunsc, M. (12) 16,293,301 Buntkowsky, G. (6) 150; (12) 141 Burford, N. (5) 172; (7) 227, 273 Burgalh, A. (10) 27 Burger, P. (3) 164 Burgess, A.N. (10) 412 Burgina, E.B. (7)486 Burgoyne, J. (14) 62 Burke, A.L. (10) I65 Burkcrt, U. (4) 82 Burkham, J. (3) 216; (9) 77 Burkhart, F. ( 5 ) 274 Burkhoff, D. (1 2) 34 Burmeister, M.J.(7) 454 Bumell, E.E. (3) 222; (14) 21,22, 51,146

Burrell, P.M. (2) 46,49, 153 Burrichtcr, A. (3) 24 Burrows, H.D. (10) 267 Burstcin, D. (13) I80 Burton, G. (1 1) 52 Buschow, K.H.J. (3) 256 Buscr, P.T. (12) 143 Bush, C.A. (5) 454,457 Bush, S. (7) 52 Bushncll, G.W. (1 1) 148 Bushwellcr, J.H. (9) 294 Busico, V. (10) 222 Buslacv, Y.A. (5) 227 Busncl, J.P. (7) 425 Busza, A.L. (12) 194-196 Butcher, C.H. (7) 122 Butcher, S.E.(5) 359; (9) 100 Butler, LS. (3) 3 15, 449; (5) 177; (7) 232,280 Butlcr, W.M. (5) 42 Buttcrsack, C. (6) 209 Buttle, L.G. (7) 259 Buvat, P. (10) 54 Buxton, P.C. (5) 387 Bycron, M. ( 5 ) 324; (9) 4 1,42 Bynum, K. (1 1) 92,93 Byrd, E.F.C. (2) 37; (3) 32 Bym, S.R (7) 207 Bystrich, S . ( 5 ) 456; (1 I ) 138 Bytheway, I. (4) 52,68; (5) 55 Bywater, M.J. (3) 302 Bzducha, W. (6) 114, 169; (10) 332 Bzhezovskii, V.M. (12) 55

Cabal, M.-P. (3) 58 Cabczas, J.A. ( 5 ) 2 I7 Cabildo, P. ( I 1) 59 Caboi, F. (14) 106 Cadet, J. (6) 67; (1 1) 36 Cadioli, B. (2) 160 Cadot, E. (3) 285 Cady, E.B. (12) 280,288 Cagiao, M.E. (10) 90 Cahilll, S. (9) 257 Cai, F.F. (7) 149 Cai, R (7) 139; (10) 135 Cai, Y. (3) 269; ( 5 ) 210 C a i r n , A. (3) 2 12 Cain, R.J. (6) 68 Cairns, E.J. (7) 248 CaIa, P.M. (12) 155 Calabrcsse, C. (12) 81 Caldarelli, S. ( 5 ) 114,239; (14) 32, 33,46,172 Caldas, V. ( I 0) 305 Caldwcll, C.R. (13) 161 Caldwcll, G.W. ( 5 ) 268, 382 Calirnan, V. ( 5 ) 175 Callaghan, P.T. (10) 426; (13) 7, 81,103,104,107, 167 CaHcbcrt, F. (7) 450,45 I Callihan, D. (8) 19 Calogcropoulou, T. (7) 406 Calucci, L. (14) 66,81,86,91, 158 Calvo, F. (12) 8 1 Cambie, R.C. (1 1) 99 Camblcr, M.A. (7) 599,602,823 Cambon, H. (7) 657 Cameron, C.G. (10) 142 Cameron, T.S. (5) 404; (7) 273; (11) 86 Cammarata, G. (13) 171 Cammas, S.(10) 117 Campbell, A.P. (5) 251,254,288 Campbcll, G.C. (7) 167 Campbell, I.D. (5) 305,313; (8) 85; (9) 26-28,70, 129,201, 255,279,288 Campbell, J.R (10) 384 (7) 628,634 Campbell, S.M. Campistol, J.M. (12) 306 Campo, J.A. (5) 72 Campos-Olivas, R ( 5 ) 339 Camu, F. (3) 407 Canada, F.J.(1 1) 144 Canavesi, A. (7) 223; (1 0) 272 Canet, D. (6) 55,56, 108, 123, 196; (7) 84; (8) 1; (13) 15,28, 49 Canet, I. (14) 69,70 Canfield, R (9) 152

Nuclear Magnetic Resoname

492

Canioni, P. (13) 76 Cannon, J. (12) 265 C m o n , P.J. (6) 38; (12) 34 Cano, F.H. (7) 202 Cano, M. (5) 72 Canters, G.W. (9) 284,300 C a n t i , P.L. (10) 163 Cao, J. (3) 5 14 Cao, R. (3) 279 Cao, Z. (5) 120 Capitani, D. (3) 222 Capka, M. (7) 246 Caporusso, A.M. (3) 73 Capozzi, F. (5) 3 17 Caprihan, A. (13) 45 Capuani, S. (6) 54 Capul, C. (12) 213 Caputo, M.C. (2) 94, 177-179 Caputo, T.M. (9) 294 Caraceni, P. (12) 69 Caramanos, Z. (12) 32 1 Caravan, P.(3) 349 Carbajo, R.J. (3) 281 Cardenas, A. (7) 433 Cardy, C.M. (5) 3 13; (9) 28 Carites, J.C. (12) 186 Carlccr, R. (5) 4 17; (10) 180 Carlier, P.G. (12) 17,311 Carlino, S. (7) 819 Carlomagno, T. (8) 46,47 Carlson, G.P. (3) 136 Carlson, P.J. (14) 175 Carlstrom, G. (9) 301 Carlton, L. (3) 440; (5) 181 Carniichael, I. (4) 6; (5) 118; (1 1) 61

Carofiglio, T. (3) 140 Carpenter, J.P. (10) 250 Carpenter, T.A. (13) 155 Carpenticr, Y.A. (7) 366 Carr, C.A. (12) 124 Carr, T.J. (12) 255 Carricdo, G. (5) 492 Carroll, P.J. (2) 114, 115 Carroll, T.J. (7) 715 C ~ p tP.-A. , (3) 26 Carss, S.A. (7) 66 Carter, A.N. (12) 79 Cartcr, C. (9) 6 Cartledge, F.K. (7) 504 Carvill, A.G. (10) 82, 139 Cary, C.J. (3) 52 Casarini, D.(7) 158, 192,196; (11) 100

Casarotto, M.G. (9) 191; (11) 140 Casas, J.S. (3) 309,324,325; (7) 321

Cascio, W.E. (12) 153 Case, D.A. (5) 341,348; (6) 118 Cascllato, U. (3) 309 Casenshy, B. (3) 238,352 Caseri, W.R. (7) 73 1 Casida, M.E. (2) 72 Casillas, C.G. (10) 381 Casset, F. (1 1) 143 Cassctta, A. (3) 410 Castano, M.V. (7) 32 1 Castcl, A. (3) 23 1 Castellano, E.E.(3) 325 Castellano, RK. (1 1) 74 Castiglione, F. (14) 24 Castineiras, A. (3) 324 Castro, C.D. (12) 84 Castro, M.A. (7) 544 Castro, S. (7) 452 Casu, M. (6) 92 Catalano, D. (14) 54,77, 8 1, 82, 94,157,169,173

Catellani, M. (10) 53 Cates, G.D. (6) 183 Cativicla, C. (7) 215 Cauchcticr, M. (7) 797 Caulfield, J.B. (13) 172 Caullet, P. (7) 643 Caulton, K.G. (3) 4 18 Caumo, A. (1 2) 3 17 Caus, T. (1 2) 169 Cavallaro, C. (3) 145 Cavalli, L. (4) 47 Cavanagh, J. (8) 66 Cavano, P.J. (10) 400,401 Cavasotto, C.N. (4) 64 Cavazza, M. (14) 81,82 Cave, A. (5) 385; (9) 296; (1 1) 40 Cecchi, P. (3) 320 Celebre, G.(6) 210; (14) 24,49, 56,57,77, 169, 170, 173

Celina, M. (1 0) 288 Ccnti, G. (7) 703 Ccrdan, R. (8) 26; (9) 303 Ceri, H. (10) 234 CerioN, G.(3) 456 Cermak, J. (7) 246 Cernohous, J.J. (10) 160 Cemusak, I. (2) 199 Ccrny, Z. (3) 238,352 Ccrtaines, J.D. (12) 202 Ccrvcllo, J. (5)406 Chabert, B. (10) 292 Chabrol, B. (12) 283 Chadha, RK. (5) 124 Chadwick, C.A. (9) 152 Chadwick, J.C. (10) 227 Chadwick, M.M. (10) 286

Chadwick, M.P. (5) 442; (9) 5 1 Chae, S.A. (10) 270 Chaffce, K.P. (7) 454 Chapeau, F. (12) 207 Chai, M. (10) 41 Chaibi, J. (7) 436 Chakrabarty, D.K. (3) 486; (7) 669,670

Chakravarty, S. (5) 391,392 Chakravorty, A.K. (7) 548 Chaloncr, P.A. (3) 300; (5) 197 Chambers, RD. (7) 66 Champagnat, J. (12) 133 Champmartin, D. (2) 147,148; (6) 88

Champness, N.R (3) 307 Chan, J.C.C. (2) 99, 100; (3) 35 Chan, P.H. (12) 113 Chan, S.S.C. (5) 381; (1 1) 121 Chan, T.-Z. (5) 13 1 Chandrakumar, N. (5) 29; (6) GO, 61,198; (13) 13

Chandrakumar, T. (14) 21, 146 Chandrasekaran, A. (7) 204 Chandrasekhar, S. (7) 642 Chaneac, C. (7) 570 Chang, B.S. (9) 9, 11 Chang, C.-C. (3) 350 Chang, C.H. (9) 52, 149 Chang, C.-J. (3) 136 Chang, I. (6) 12, 107, 189, 190 Chang, L. (12) 285 Chang, L.-H. (12) 113 Chang, P.S. (3) 113; (1 1) 3 Chang, T.C. (10) 2 13 Chang, W.K. (3) 391; (7) 807 Chang, Y.-T. (1 1) 132 Changani, K.K. (12) 198 Chang-Fong, J. (3) 67 Changl, L. (12) 278 Chanon, M. (5) 4 14 Chao, H.M. (5) 245; (9) 164 Chapcllc, S. (3) 280 Chapman, B.E. (6) 133; (12) 46 Chapron, Y. (3) 130 Charan, S.(10) 173 Charcy, B. (7) 561 Charistos, D. (7) 567 Charles, C.L. (10) 138 Charles, S. (3) 444 Charlton, C. (4) 46 Charlton, J.L. (1 1) 88 Charnaya, E.V.(3) 353 Charpentier, P.(5) 207 Chase, J.R (12) 122,315 Chase, P.B. (12) 204 Chassaing, G. (5) 250

Author Index Chatclain, T. (7) 66 1 Chattopadhyaya, J. (5) 356 Chaubon, M.-A. (3) 400 Chaudhry, A. (6) 37 Chaudrct, B. ( 5 ) 9 1 Chauduri, S.R.(7) 732 Chauhan, K. (7) 203 Chauhan, V.S. (5) 249 Chaung, Y. (12) 176 Chauvel, J.P.(2) 62,63 Chazalviel, J.-N. (7) 808 Chain, W.J. (5) 348,362; (8) 34; (9) 256 Chc, M. (7) 238 Cheah, K.Y. (13) 89 Chec, G.-L. (I 1) 88 Cheeseman, J.R. (3) 18 Cheetham, A.K. (7) 719 Chcn, A. (6) 146,193 Chcn, C. (3) 269 Chen, C.-N. (12) 188 Chen, C.P. ( 5 ) 258 Chen, C.S.(12) I88 Chen, D.Y. (10) 393 Chcn, F. (7) 543 Chcn, G. (7) 356 Chcn, H. (3) 149; (10) 162 Chen, H.B. (10) 213 Chen, H.L. (3) 127 Chen, J. (7) 139, 149,674,686 Chen, J.-H. (3) 354; (5) 153; (6) 30 Chen, K.G. (12) 159 .Chen, L. (9) 34 Chcn, M.S. (1 1) 136 Chcn, P. (4) 76; (13) 151 Chcn, Q. (10) 103,283 Chen, S.M. (7) 149 Chen, T. (7) 589,590,638 Chcn, T.-A. (10) 52 Chen, T.H.(7) 632 Chen, W. (5) 220; (7) 160; (10) 256; (12) 161,167,315 Chen, W.-H. (7) 704 Chcn, Y. (3) 149 Chen, Y.C. (10) 213 Chen, Y.-H. ( 5 ) 223 Chen, Y.L. (7) 141 Chen, Y.-Y. (1 1) 150 Chen, Z. (3) 25; (7) 474 Chen, Z.-J. (7) 371,399 Chcng, C.-F. (7) 587,588,672, 778 Cheng, F.Y. (12) 138 Cheng, H.-M. (12) 138 Cheng, H.N. (10) 107,240 Cheng, J. (3) 55; (7) 737; (10) 30,

493 256,262,421 Cheng, J.-W. ( 5 ) 465 Chcng, L. (7)479 Cheng, S.(7) 140 Chcng, S.Z.D. (10) 30,421 Chcng, Y. (10) 77 Chcng, Y.-B. (7) 775 Chcng, Z. (12) 215 Chenon, M.-T. (5) 61 Cheong, C. (5) 284,363 Cheong, H.-K. ( 5 ) 363 Cherkasova, T. (5) 142 Cherniak, R ( 5 ) 373 Cherry, S.R.(13) 22 Chervin, 1.1. ( 5 ) 432 Chesnick, AS. (12) 26 Chcsnut, D.B. (2) 37,69, 163; (3) 15,20,32 Cheung,H.T.A. (9) 191; (11) 140 Chcynier, V. (5) 398 Chezeau, J.-M. (3) 501 Chi, S.-W. ( 5 ) 253 Chiang, L.C. (1 1) 136 Chiang, M.Y. (3) 350 Chiantorc, 0. (10) 21 Chiavacci, C. (3) 143 Chiba, A. (12) 214,236 Chiccoli, C. (14) 98 Chichibu, S. (12) 214,236 Chidambaran, R (1 3) 9 Chidichimo, G. (6) 210; (14) 49, 165 Chien, E.Y.T. (3) 494 Chien, J.C.W. (10) 230 Chilulrwi, S.V.V. (7) 669 Chimichi, S.(3) 102; ( 5 ) 84 Chin, I.-J. (10) 216 Chin, J. (7) 173 Chinachots, P. (7) 3 14 Chinayon, S.(12) 57 Chinchilla, R (3) 8 1 Chipera, S. (7) 556 Chiprnan, D.M. (4) 29 Chippendalc, A.M. (3) 11; (7) 181, 266; (10) 28 1 Chittibabu, K.G.(10) 46 Chiu, T.-M. (12) 267 Chiihk, V.I. (6) 89, 166 Cho, G. (10) 370 Cho, H. (3) 216; (9) 77 Cho, H.-N. (1 0) 200 Cho, S.G. (7) 68 1; (1 I) 24 Cho, S.J. (11) 132 Cho, Y.K. (12) 181 Cho, Z.H. (13) 51, 122 Choh, S.H. (3) 235,250 Choi, B.-S. ( 5 ) 363

Choi, D.-C. (10) 200 Choi, H.W. (10) 216 Choi, S.-H. (10) 167 Choi, S.-K. (7) 448; (10) 200 Choi, S.M. (13) 30 Choi, Y. (10) 130 Cholli, A.L. (10) 46 Chopin, L. (7) 27 Choplin, A. (7) 241 Chopra, N. (3) 406 Chorev, M. (5) 247 Cholhia, C. ( 5 ) 324; (9) 42 Chou, P . J . ( 5 ) 258 ChQU,S.-H. ( 5 ) 465 Choudhary, V.R (7) 609,6 10 Chow, A. ( 5 ) 123 Chrissopoulou, K. (1 0) 427 Christellcr, J.T. (1 3) 167 Christendat, D. ( 5 ) 177; (7) 232 Chrisknscn, A.M. (7) 343; (9) 19 Christensen, J.D.(12) 269,272, 274 Christensen, K.A. (3) 291 Christiansen, 0.(2) 33 Christofidcs, J.C. (3) 112 Christofori, A. (10) 227 Christopher, C.T.G. (6) 102 Christopherscn, C. (7) 157 chnstov, L. (10) 2 Chu, F. (10) 91 Chu,K.J. (10) 112 Chu, M.L. (9) 45 Chu, P.P. (7) 140; (10) 377 Chuang, 1 . 4 . (7) 455,456; (10) 235,282 Chudek, J.A. (7) 75 1; (10) 442; (13) 141,163 Chujo, R (7) 364 Chung, E.W. (9) 215 Chung, H. (13) 179 Chung, I. (10) 87 Chung, J. ( 5 ) 34 1 Chung, J.C. (12) 121 Chung, K.H. (7) 470,510 Chung, S.H. (6) 114, 169; (7) 253; (i0) 332 Chmg, S.-K. (1 1) 132 Chuprina, V.P. (3) 176 Churchill, T.A. (12) 194 Ciampi, E. (14) 82, 157 Cicplak, P. (1 1) 46 Cimino, G.(3) 62 Cingolani, A. (3) 410 Cintas, P.(5) 403; (1 1) 129 Cippullo, R (10) 222 Cisero, M.(3) 207 Cistola, D.P. (9) 276

Nuclear Magnetic Resonance

494 Cizmcciyan, D. (7) 718 Claesscns, H.A. (3) 393 Claramunt, R.M. (3) 103,358, 359; ( 5 ) 3,72, 160, 161; (7) 163; (1 1) 59 Claridge, T.D.W. ( 5 ) 224; (1 1) 47 Clark, C.J. (13) 139, 140, 142 Clark, C.R. (3) 464 Clark, J.B. (12) 114 Clark, S.A. (6) 194 Clarke, J. ( 5 ) 324; (6) 44; (9) 42 Clarke, K. (3) 442; (12) 31, 147, 150,152 Clarkc, P. (7) 310,391,466 Clark Lewis, I. (9) 190 Clauss, J. (14) 79 Claussen, C.D. (12) 324,325 Clauw, D.J. (12) 295 Clay, D. (10) 125 Clayden, N.J. (10) 277,285,295 Clearficld, A. (7) 526,s 15 Clezeau, J.M. (7) 107 Cline, G.W. (12) 316-318 Cline, H. (12) 3 14 Clorc, G.M. ( 5 ) 24 1,453; (9) 13, 14,55,89, 128,205-207, 23 1-233,258 Close, J.D. (5) 44 Clough, R.L. (10) 288 Clouse, M.E. (3) 190 Clyburne, J.A.C. (7) 273 Cobelli, C. (12) 3 17 Cocivera, M.(14) 174 Codd, S.L. (13) 2 9 , 3 1 Coddington, J.M. (7) 628,634 Cody, J.A. (3) 487 Coelho, M.R.G. (10) 309 Cohen, B.M. (12) 269,272,274, 286 Cohcn, C. (10) 409 Cohen, J.S. (12) 1 Cohen, Y. (3) 161, 169; (6) 140 Cohen-Addad, J.P. (10) 367,411 Cohn, M. (12) 77 Coke,M. (7) 340 Colangclo, C.M. (9) 2 1 Cole, J. (14) 170 Cole, K.C. (1 0) 13 Coleman, A.W. (3) 147 Coles, G.D. (7) 330 Collier, S.W. (1 2) 1 Collins, D.L. (12) 321 Collins, J.H. ( 5 ) 296 Collum, D.B. (3) 223,224,227 Colmenero, J. (10) 364 Colombet, P. (7) 538 Colucci, W.J. (4) 85,86

Colwcll, S.M. (2) 7 1 Commcrs, D. (7) 440 Comrneyras, A. (4) 36 Comotti, A. (7) 829; (10) 293,322 Conancc, R. (7) 505 Concannon, B.A. (7) 304 Confort-Gouny, S. (1 2) 283 Cong, X. (7) 540-542 Conga, C.S. (7) 129 COM,G.L. (9) 302 Connac, F. (5) 232 Connil, M.-F. (5) 491 Connolly, T.J. (7) 217 Connor, C. (10) 286 Connors, K.A. (3) 156 Conradi, M.S.(7) 809 Constantine,K.L. (9) 57 Constantine, S.P. (3) 262 Constantinidis,1. (12) 227 Conk, M.R.(5) 355; (9) 302; (1 1) 103 Contel, M. ( 5 ) 235 Contreras, R.H. (2) 203; (3) 455, 460; (4) 61-65,67; ( 5 ) 237; (1 1) 4, 52 Convert, 0. ( 5 ) 250 Cook, C.U. (12) 115 Cook, G.D. (3) 11 Cook, RL. (7) 477 Cooke, D. (7) 346 Coolcn, H.K.A.C. (1 1) 84 Coopcr, S.L. (10) 382 Coopcr, T.G. (13) 156 Coopcr, W.T. (7) 739 Copa-Patino, J.-L. (7) 389 Copie, V. (7) 255; (9) 58 Coppola, L. (6) 210; (14) 49, 112 Corberan, V.C. (7)605 Corbin, D.R (3) 237; (7) 678,723 Cordcll, G.A. (3) 179 Cordonnier, M.-A. ( 5 ) 49 1 Corell, C. (7) 599 Coremans, J. (6) 201 Coriani, S. (2) 42,87 CoM, N.(7) 478 Corker, J. (7) 241 Coma, A. (7) 59, 136,599,626, 714 Cornago, P. (1 1) 59 Come, S.A. (3) 1 Cornet, R. (2) 56 Cornfold, M.(12) 278 Cornwell, C.D. (2) 45 Corradi, M.M. (3) 263 Corradini, P. (10) 257 Corrales, T. (10) 128 Correze, J.L. (12) 126

Cortycs-Corbcran, V. (7) 608 Cory, D.G. (6) 24; (7) 42; (8) 3; (13) 30,60 Cosgrove, T. (10) 363 Coskun, M.(10) 55,59 Coslcdan, F. (3) 23 1 Cosman, M. (9) 82,84 Costa, V.E. (3) 17 1 Cotc, B. (7) 744 Cottcn, M. (14) 14 Cotton, J.D. (5) 177; (7) 232 Cot&, R.M. (7) 809 Coulter, M.S. (4) 42 Courdurier, G. (7) 697 Couroct, D. (7) 683 Courtieu, J. (3) 68,76; (14) 67-73, 75,76 Cousin, J. (12) 307 Cousins, D.J. (6) 178 Couture, M.M.J. (5) 444 Couturcs, J.P. (7) 538,546,547, 744 Couty, R (7) 563 Covcncy, F.M. (6) 48 Cowans, B. (7) 206 Cowburn, D. (9) 257 Cowic, M. (5) 186 Cowlcy, A.R (7) 266 Cox, J.R. (1 1) 141 Cox, P.J. (3) 401 Coy, A. (13) 42 Coyle, J.T. (12) 124 Coiranc, P.J. ( 5 ) 221; (12) 169, 283 Crabb, S. (12) 327 Crabtrec, G.R (9) 34 Crabtree, RH. (5) 89 Craig, B.N. (3) 113; (1 1) 3 Craik, D.J. (5) 282,286,295; (12) 162,218 Cramail, H. (10) 243 Cramers, C.A. (3) 393 Craven, I.E. (10) 147 Craw, J.S. (4) 70 Crawford, G.P.(14) 100,122, 161 Crawford, M.J. (14) 170 Creighton, T.E. (9) 36 Crcmer, D. (2) 103-105; (3) 29, 399; ( 5 ) 230 Crcmcr, S.E. (1 1) 43 Crcmlyn, RJ. ( 5 ) 428,429 Creomes, A.F.L. (7) 350 Crini, G. (7) 736 Crispino, A. (3) 45 Cristofolini,L. (3).239 Crocker, M. (3) 199 Crockett, R (7) 636

A uthor Index Crolts, R.D. (3) 302 Crook, A.M.E. (13) 163 Crooks, P.A. (3) 69 Croot, L. (10) 277 Cros, F. (6) 155; (14) 141 Cros, P. (10) 69 Crosby, D.G. (12) 238 Cross, C.W. (14) 52, 154 Cross, H.R (3) 442; (12) 31, 150, 152

Cross, R.J. (3) 5 12 Cross, T.A. (7) 373,375,402; (14) 14,59 Crouzy, S. (3) 130 Crozier, S.(13) 25,27 Crumbaugh, G.M. (7) 616 CNZ, C. (14) 92 Cruz, E.R. (3) 182; (5) 2

Csepregi, C.Z. (5) 500 Cucinotta, V. (3) 138 Cuenod, C.A. (12) 266 Cui, C. (1 1) 132 Cui, W.W. (5) 376 Cuiec, L. (1 3) I 13 Culf, AS. (3) 216,218; (9) 77 Cullinan, D. (9) 8 1,82 Cullis, P.M. (3) 15 1; (1 1) 82 Cumming, D.A. (5) 344; (9) 24 C d g s , C.C. (2) 102; (3) 451; (7)229 CUMiUlC, S.C. (12) 312 Curran, S.A. (10) 152 Curran, T.P. (I 1) 145 Curtis, M D . (5) 42 Ckanelli, A. (3) 462; (6) 74,76 Cushman, M. (9) 133 Cutie, S.S. (10) 392 Cybulski, S.M.(2) 32, 185 Cygan, R.T. (7) 557 Czajka, 8. (7) 722 Czaplicki, J. (14) 48 Czirkina, LA. (5) 11 1 Czisch, M. (6) 34,202; (8) 37; (9) 44,45,292

Dadok, J. (14) 7 Dafardar, M.H. (7) 548 Dahlquist, F.E. (9) 25 Dahlquist, K.D. (9) 114 Dahn, H. (2) 59; (3) 26,458 Dai, H.L. (13) 72 Dais, A.J. (10) 337 Dais, P. (5) 435; (6) 143; (10) 345; (1 1) 53

Dakltar, J. (7) 627 Dalal, N.S.(7) 33

495

Dale, G., 111 (10) 28 Dale, J. (1 1) 72 Dalvit, C. (6) 28, 81; (8) 13-15,90 Damha, M.J. (3) 443 D~~oM S. (7) , 250 Damskc, J.S.S.(7) 307 Damude, L.C. (3) 406 Dana, G. (7) 435 Danankov, V.A. (10) 388 Dance, I.G. (3) 326; (7) 258 Dando, N.(7) 782 Dang, T.D. (10) 399 Daniels, E.S.(10) 378 Danielson, M.A. (3) 489 Dann, S.E.(3) 41 1; (7) 285,536 Darabi, H.R. (3) 122 Daragan, V.A. (9) 271 Durn, J.-C. (5) 91 Darben, P.A. (5) 379 Darbon, H. (5) 3 12 Darby, N.J. (9) 36 Dardel, F. (5) 338; (9) 287 Dardin, A. (10) 319,355 Darensbourg, D.J. (5) 149 Dartigucnavc,M. (5) 232 Da Silva, N.M. (10) 362,369 Date, T. (7) 349 Dattilo, P. (13) 110 Daub, E. (3) 496 Daunch, W.A. (3) 470; (7) 5 13 Dauphin, G. (5) 390,4 19 Dauphin, J.-F. (8) 22 Dauplais, M. (5) 300 D'Auria, G.(5) 283 Dautova, N.R. (6) 2 17 Davidovich, R.L. (3) 360 Davidson, B.R (12) 198 Davidson, F. (7) 167 Davidsson, 0.(3) 21 1; (5) 102 Davies, A.P. (5) 210 Davies, D.G. (6) 65 Davies, N.A. (7) 5 Davies, P.L. (5) 245,308; (9) 30, 164

Davies, S.E.(3) 300; (5) 197 Davis, A.L. (5) 210; (9) 277 Davis, H.T. (13) 95, 102 Davis, J.H. (7) 56,372,396 Davis, L.M.(7) 380 Davis, M.E. (7) 823 Davis, P.J. (9) 155 Davis, R.J. (7) 616 Davis, S.J. (9) 129 Davis, W.M. (7) 255 Dawson, M.J. (12) 297 Day, A.J. (9) 26 Day, R.O. (7) 204

Dayie, K.T. (9) 244,262

Deak, G.(10) 161 De Almeida, M.M.B. (7) 663 De Almeida, W.B. (1 1) 37 Dean, P.A.W. (3) 404,406 de Armda Campos, I.P. (3) 482 Debanne, M.T. (9) 130 Debarquin, F. (13) 109 deBeer,R(12) 15 Debeer, T. (9) 153 de Bleijser, J. (6) 83 Deborah, D.S. (10) 2 Debou~y,J.-C. (3) 130 De Brosse, C. (3) 82 de Bruin, T.J.M. (3) 101

Dec,S.F.(3) 346; (7) 552,782 Decanniere, C. (12) 210,211 DcCaprio, A.P. (7) 342 dc Camciro, J.W. (1 1) 22 de Certaines, J.D. (12) 207,246 Deckelbaum, RJ. (7) 366 Declercq, J.-P. (5) 424 de Cock, E. (9) 287 Decorps, M. (13) 177 dc Dios, A.C. (2) 30,68, 150, 155, 156,192; (3) 16,185

de Donato, P. (7) 561 Deflieux, A. (10) 243 DeFrees, S.A. (1 1) 136 dc Freitas, D.M. (3) 173; (12) 59 Dcgani, H. (12) 71 Dcga-Szafran, 2.(3) 427 Degeorges,A. (12) 8 1 De Giulio, A. (3) 45 Degl'Innocenti, A. (5) 498; (1 1) 16 de Graaf, A.A. (12) 44,46 de Groot, H.J.M. (7) 55,73,500 Dcguchi, K. (3) 243; (7) 335 Deh, M.K. (5) 135 de Haan, J.W. (3) 242,393; (7) 647,656

Dchnert, u.(5) 100 Dejager, P.A. (13) 39 dc Jong, R (5) 349; (9) 168,308; (11) 104

de Kanter, F.J.J. (3) 388 de Kcijzer, A.H.J.F. (3) 388 deKok,A. (5)316 de Kowalewski, D.G. (2) 203; (3) 460; (5) 496 Delahais, V. (3) 46 Delair, T. (10) 69 Delamare, J. (13) 2 1 de Lamotte, S.F. (3) 147 De Lange, C.A. (3) 222; (14) 144 dc la Rosa, M.A. (5) 3 19 dcl Castillo, B. (3) 146

Nuclear Magnetic Resonance

496 dc Lecuw, F.A.A.M. (4) 84 DeLeon, L. (12) 32 De Lcouw, J.W. (7) 307 Delepierre, M. ( 5 ) 297,347 Delfino, J.M. (1 1) 38 Delgas, W.N. (7) 662 Delikatny, E.J. (12) 62,80 De Lima, G.M. (3) 262 Delivoria-Papadopoulos, M. (12) 118 Della, C.C. (10) 56 Della, E.W. (4) 67; (11) 4 Delmottc, L. (3) 412,501; (7) 107 Delnomdedieu, M. (12) 60 Delobcl, R. (7) 664 Dc Lorimcr, R (9) 266 Delort, A.-M. (12) 40,41,92 Delossantos, C. (9) 81,82 Delpcch, F. (5) 9 1 Delpuech, J.J. (6) 129 dcl Re,G. (1 1) 134 Dclsuc, M.A. (3) 8; (8) 40 DeLuca, C.I. ( 5 ) 308; (9) 30 De Luca, F. (6) 54 De Luca, G. (14) 56,57 Dcmangc, P. (14) 48 Dcmco, D.E. (7) 23,46,48,53; (10)302,394,431,432; (13) 57,65 dc Meijcrc, A. (3) 369 DeMcmber, J.R (4) 36 Dc Mcnczcs, S.M.C. (10) 369 Dcmcnt’cva,D.V. ( 5 ) 255 Dcrnilly, D. (13) 160 Dcmiroglou, A. (7) 323 Dcmou, P. ( 5 ) 45 Dcmoustier-Champagne, S. (10) 25 1 Dcmura, M. (7) 349; (10) 269 Dcnavit-Saubic, M. (12) 133 Deng, F. (7) 176,652,784 Deng, G. (7) 8 15 Deng, H.(7) 253 Deng, Y.(3) 269 Den Hollander, J.A. (13) 172 Denison, T.J.(12) 26 Dcnisov, G.S. (3) 88, 124; ( 5 ) 83; (6) 82 Denisov, V.P. (9) 299,301 Denisov, V.R. (7) 265 D~M,M.M.(10)418 &MU, P.(13) 119 Dedcnc, C.J. (3) 278 Dc Olivcira, A.L. (3) 233 De Paoli, M.A. (6) 115 Depegc, C. (7) 818 Deprc, c.(12) 175

Dc Ramos,C.M.(7) 306 Dereppc, J.M. (13) 109 Derewinski, M. (7) 608 &Rider, M.L.( 5 ) 352; (1 1) 12 Deropp, J.S. (13) 142 Dc Rosa, S. (3) 45 De Ross, C. (10) 257 Dcrouanc, E.G. (7) 691,692,694 dc Roy, A. (7) 8 18 Dcrrcr, S. (1 1) 64 Derrick, P.J. (10) 248 Dervan, P.B. (9) 85,86 Desai, N.G. (12) 268 Descorps, M. (12) 102, 129 Dcshpandc, M.V. (7)292 de Silva, E.N. ( 5 ) 200; (7) 260 dc Silva, N.M. (10) 3 10 De Shone, F. (5) 364 Deslauriers, R. (12) 157 d’Espinosc dc la Caillere, J.B. (7) 522,730 Dcssaux, 0. (7) 450,45 1 Desvaux, H. (6) 7 Detellier, C. (3) 159,260 De Tommasi, N. (5) 364 Devargas, L. (13) 107 Dcvaux, J. (10) 25 1 Dcvaux, P.F. (7) 370 Devcdas, P. (7) 609 Dcvi, M.S. (10) 39,40 Devi, S. (10) 124 de Vos, D. (3) 415,420; ( 5 ) 145; (7) 257 Dcvrcux, F. (7) 808; (10) 412 dc Vroom, E. (5) 349; (9) 168; (1 1) 104 Dewald, B. (9) 190 Dewar,M.J.S. (4) 66 Dewey, H. (7) 671 de Wit, P.J.G.M. (5) 293 dc Witte, B. (7) 426,440 Diamond, R (1 1) 8 Diancz, M.J. (1 1) 120 Dias, A.R. (10) 237 Dias, H.V.R. (3) 403 Dim, A. (5) 3 19 Diaz, M.(2) 119; (3) 339,385 Diaz, 0. (12) 306 Diaz, P. (7) 559 Diaz-Cabana, M.-J. (7) 599 Diaz Perez, V.M. (1 1) 119 Diaz-Quijada, G.A. (10) 199 Dibattista,J.P. (3) 2 15 Di Bello, C. (5) 283 Di Blasio, B. ( 5 ) 277 Dickinson, C.Z. (12) 155 Dickinson, L.C. (7) 314,379,439

Dickman, M.H. (3) 287 Dickson, R.M. (4) 5 1 Didicr, J.G. (10) 108 Didillon, B. (7) 238 Dicckman, S.L. (10) 439; (13) 132 Dicckmann, T. ( 5 ) 359; (9) 100, 116, 122, 123 Dichl, P. (3) 521; (14) 131 Dictrich, H. (1 1) 144; (12) 301 D i c k , G.F.(12) 16,296 Dicz, E.(3) 455,460; (5) 399; (1 1) 6 Dicz, M.A. (7) 129 Diezemann, G. (6) 105 Diglio, G. (2) I35 Dijkhuizcn, R.M. (12) 12; (13) 174 Dijkstra, K. (8) 80; (9) 36, 156 Dikiy, A. ( 5 ) 3 17 Dillon, P.F. (12) 2 Dimandja, J.-M.D. (7) 458,742 di Matteo, A. (1 1) 134 Dimilrijevic, R. (7) 565 DiNatalc, J.A. (14) 1 17 Ding,D. (7) 638 Ding, D.-T. (7) 65 1 Ding, G.-L. (6) 142; (10) 437; (12) 128; (13) 93,121,123 Ding, S. ( 5 ) 150; (7) 49 Dmglc, T.W. (4) 76 Dinglcy, A.J. (12) 52 Diodone, R (5) 133, 163 Diomina, G.R (12) 38 Dirkcn, P.J. (3) 467; (7) 507 Dimfield, E.A. (5) 131 Di Sant’Agncsc, P.A. (12) 245 Di Talia, P.(5) 277 Diler, B. (13) 28 Diu, D.T. (7) 632 Diz, A.C. (4) 62 Dizon, J. (12) 34 Djcdaini-Pilard, F. (3) 152 Djuran, M.I.(7) 261 Do,Y.(7) 5 10 Doane, J.W. (14) 99, 161 Dobson, C.M. (9) 198-202, 21 1-213,215 Dodd, R.B. (7) 362 Dodd, S. (12) 218 Doddrell, D.M. (2) 173; (12) 233; (13) 25.27 Dodi, K. (7) 280 Dodziuk,H. (3) 128 Elk, A, (6) 122 Dlirfler, U.( 5 ) 146, 147 Docrlitz, H. (10) 324 Doerrenbach, F. ( 5 ) 93 Doi, Y. (10) 198

Author Index Doidge-Hamison, S.M.S.V. (7) 263 Dolainsky, C. (14) 114 Dolgushin, F.M. (7) 265 Dollase, T. (7) 38 Domach, M.M. (12) 84 Domaille, P.J. ( 5 ) 340,443; (9) 40, 52, 143; (14) 6 Domard, A. (10) 20,69 Domb, A. (1 3) 120 Dombinski, R (7) 194 Domha, M.J. (7) 336 Dommisse, R (5) 417; (12) 234 Donaire, A. ( 5 ) 444 Donati, A. (9) 309 Donati, C. (6) 103 Dondur, V. (7) 565 Dong, R.Y. (14) 132,139,140, 148,159 Donker, H.C.W. (13) 145,146 Donne, D.G. (9) 297 Donnerstag, A. ( 5 ) 388 Donohue Rolfe, A. (9) 50 Dopke, J.A. (3) 336 d’Orchymont, H. ( I 1) 26 Dorclcijcrs, J.F. (5) 292 DorCmicux-Morin, C. (7) 649,650 Dome, L. (7) 461 Dorrcndinger, L.S. (7) 571 Doscotch, M.A. (10) 119 Dostovalova, V.I. (3) 10 Dotsch, V. (8) 79; (9) 34,64-67 Douce,P.(12) 111 Doughty, D.A. (1 3) 33 Douglas, A.L. (3) 397 Doulicz, J.P. (7) 56,408,417; (14) 47 Doumcn, C. (12) 144 Douthwaite, RE. (7) 148 Douy, A. (7) 425,546,547 Dowd, T.L. (12) 185 Downing, A.K. ( 5 ) 3 13; (9) 28 Doylc, P.M. (5) 267,272 Doz01, J.-F. (3) 249 Dragoli, D.R (1 1) 145 Drake,J.E. (3) 483 Drake,R.J.(3) 483 Drakopoulou, E. (5) 300 Draper, D.E. (5) 445,477; (9) 278 Drcschcr, C. (3) 334 Drew, M.G.B. (5) 481 D~ws,H.-H. ( 5 ) 165,166 Drexler, U. (7) 220 Driega, A.B. (7) 216 Driehuys, B. (6) 183 Drijber, RA. (7) 473 Dnscoll, P.C. (9) 129 Drobny, G.P. (7) 298,299

497

Droege, P.A. (3) 507 Drohat, A.C. ( 5 ) 343 Drost, D.J. (12) 255,270 Drouin, M. (7) 283 Drumel, S. (7) 529 bury, C.J. (10) 169 Du, Y.-R (6) 142; (7) 65 I, 652, 784; (10)437; (13) 121,123 Du, 2.(12) 72,73,215,230 Duan, Z. (7) 732 Dubinshy,V.Z.(12) 116 D u b , D. (12) 307,309 Dubois, P. (10) 76,192, 195, 196 Duboudin, J.-G. (3) 414 Ducc,S.L.(13) 117, 150 Duchet, J. (10) 292 Duda, A. (10) 12, 192 Duda, S.H. (12) 325 Dudas, M.J. (7) 474 Duddeek, H. (3) 361; (1 1) 69 Duer, M.J. (7) 95, 104,209,418, 420,42 1 ; (1 4) 78,79 Ducvcr, T.A. (10) 165 Ducwcl, H. (3) 496 Duewell, S.(12) 26 Dufand, V. (7) 241 Mour, S.(13) 76 Dufourc, E.J. (7) 56,398,404, 408,411,417; (14) 47,105 Dufourcq, J. (7)4 11 Duhandiram, D.R (9) 68 Duleba, A. (12) 315 Dumas, R. (12) 276 Dumoulin, M.M. (10) 13 Dumy, P. (5) 278 Duncalf, D.J. (10) 248 Duncan, D.C. (3) 284,468 Duncan, J.S. (12) 251 Duncan, T.M. (10) 409 Dunckcr, D.J. (12) 148 Dunham,W.R (6) 80 Dunlap, R.B. (3) 70 Dunlop, C. (7) 748 Dunn,J.F. (12) 130 Dunning, T.H., Jr. (4) 12,39 Duns,G.J. (6) 70 Duo, D. (7) 787 Duplan, J.C. ( 5 ) 37 Duprcc, R. (7) 501,566,726,764, 765 DuPrez, F.E. (10) 398 Dupuis, M. (4) 72 Duque, C. (3) 59 Durh,C.J. (5) 403; (1 1) 129 Durand, M.E.(12) 241 Durkhard, D.J.M. (7) 747 Durrant, C. (6) 195

Durst, T. (7) 2 17 Dutton, P.J. (1 1) 79 Duus, F. (3) 83; (1 1) 19 Duus, 1.0.(5) 460 Dux, P. (8) 49 Duzcnli, C. (13) 55 Dvinskkh, S.V. (7) 19 Dvoryantsev, S.N. (12) 165 Dybowski, C. (2) 127; (3) 422; (7) 32,254,5 12,789 Dykstra, C.E. (2) 186,188, 190 Dyson, H.J. (5) 254,341; (9) 197 Dzakula, 2.(5) 352; (6) 121; (1 1) 12 Dzicmbowska, T. (3) 110; (5) 78 Eaccs, J.G. (10) 277 Eady,RR(5)265 Earl, W.L. (7) 556 Eastman, P.(13) 128 Eaton, S.F.(9) 294 Ebelhauser, R (7) 533 Ebcrstadt, M. (5) 3 14,335; (9) 7, 11 Ebisawa, K.(7) 355 Ebisu, T. (12) 131 Ebrahimian, S. (9) 54 Eccles, C.D. (13) 167 Eckert, H.(3) 186; (6) 109; (7) 501,611,758 Eckman, RR. (10) 284,313 Eckstein, K.( 5 ) 180 Eddaoudi, M. (3) 147 Edelstein, W.A. (1 3) 52,54 Eden, M. (7) 92 Edge, M. (10) 128 Mger, M.D. (6) 141; (10) 316 Edlund, U. (3) 232,399; (5) 230, 321; (7) 137,403,528; (9) 56 Edmondson,C.A. (10) 406 Edwards, A.M. ( 5 ) 33 1; (9) 48 Edwards, J.C. (7) 128 Edwards, P.P. (7) 726 Edzes, H.T. (13) 145,146 Ecckhaut, G.J. (10) 295 Effendy, ( 5 ) 188-190; (7) 267,268 Efimov, V.N.( 5 ) 107 Efstratindis, V. (10) 219 Egan, D.A. (9) 12 Egawa, Y.(10) 360 Eggenberger, R (6) 18,19,94 Egger, N.(7)796 Eggert, H. ( 5 ) 119 Eggleston, I.M. ( 5 ) 278 Egorov, A.A. (12) 87 Egorova-Zachernyuk,T.A. (7) 350

Nuclear Magnetic Resoiiance

498 Ehrlich, L.S. (9) 6 Eiam-ong, S. (12) 57 Eichclc, K. (2) 60, 124, 128; (3) 445; ( 5 ) 172; (7) 177,225,227, 273,378; (14) 60 Eichhorn, B.W. (3) 444 Eichner, P. (7) 5 15 Eijgelshoven, M.H.J. (12) 181 Eikcns, W. (3) 478 Einsele, H. (12) 324 Einstein, F.W.B. (3) 472 Eisenberg, B.L. (12) 329 Eisenberg, M. (9) 81,82 Eiscndrath, H. (6) 201 Ejchart, A. ( 5 ) 139; (14) 123 Ekstroem, T.C. (7) 803 El-Aasser, M.S. (10) 378 Elbayed, K. (3) 294 El-Dewik, A. (7) 5 11 Eley, C.D. (7) 383 El-Faer, M.Z. (1 1) 73 Elgucro, J. (3) 103,359,43 1; ( 5 ) 3,65, 160, 161; (7) 163, 180, 198,215; (1 1) 59 Elin, R.J. (12) 294 Elisecv, A. (3) 151; (1 1) 82 Elkins, N. (12) 159 Ellcna, J.F. ( 5 ) 259 Ellermann, J. (3) 228; (7) 275 Ellington, A.D. (9) 125 Ellis, G. (3) 114; ( 5 ) 366 Ellis, J. (1 1) 139 Ellis, P.D. (2) 131; (3) 3 17; (7) 279,360 Ellsworth, M.W. (7) 737; (10) 262 Ellsworth, S.E. (7) 760 Ellwanget, A. (7) 735; (10) 244 Elmalak, 0. (13) 120 El-Nahhal, I.M. (7) 455,456; (10) 235,236,282 Elsenbaumer, R.L. (10) 77 Eltis, L.D. (5) 3 17,444 Elyashberg, M.E. (3) 7 Emblcton, G. (9) 155 Embrey, K.J.( 5 ) 387 Emeis, C.A. (3) 199 Emerson, C.S. (12) 183 Emglang, B.K. (12) 209 Emig, P. ( 5 ) 207 Emoto, S.E. (12) 117 Ernsley, A.M. (7) 383 Emsley, J.W. (3) 76; (4) 44; (14) 24,50,76, 77, 169-171, 173, 175 Emsley, L. ( 5 ) 239; (7) 393; (14) 32 Endo, K. (2) 14-16; (3) 243; (7)

2 14 Endo, T. (10) 208 Endrc, Z.H. (12) 233 Endud, S. (7) 592 Enevoldsen, T. (2) 183 Engelhard, M. (7) 295 Engelhardt, G. (3) 24 1; (7) 603, 811 Engclkc, J. (8) 35; (9) 240,252 Engelman, D.M.( 5 ) 487; (9) 38, 39 Engelmann, A.R (4) 61 Engler, R.E. ( 5 ) 400 Englert, G. (14) 2 Enninghorst, A. (6) 205 Enrico, M.P. (6) 178 Enright, G. (7) 2 I6 Epaud, RM.(7) 399 Era, S. (12) 140 Erata, T. (7) 354 Erbel, P.J.A. ( 5 ) 265 Ergin, M.(7) 482 Erickson, J.W. (9) 148 Eriksen, A.B. (12) 107 Eriksson, L.A. (2) 20; (4) 50 Ennakov, V.L. (7) 24 Ernest, M. (7) 52 Emi, B. ( 5 ) 26 1,262,3 14 Emst, H. (7) 689,690,7 17 Emst, M. (7) 334; (14) 26 Emst, R.R. (2) 126; (5) 48; (6) 64, 120; (7) 34,39,4 1,72,78,86; (9)251; (10)209;(14)27 Emst, S. (7) 653,716,717 Emst, T. (12) 278,279,285 Erofecv, L.N. (10) 35 1 Erten, H. (10) 55 Ertl, G. (12) 164,173 Escape, J.M. (1 3) 49 Escudie, J. (3) 400 Esculcas, A.P. (3) 275,347; (7) 581,615,637,677 Eskin, M.N.A. ( 5 ) 376 Esp~01,M.T. (12) 113 Espartero,J.L. (10) 118 Espinosa, J.-F. (1 1) 144 Esposito, G. ( 5 ) 278 Esteban, A.L. (3) 455,460; (14) 168 Estrada, M.D. (1 1) 120 Ettorre, G.C. (13) 10 Etzler, M. (1 1) 143 Eugene, M.(12) 8 1 Eujen, R. (3) 3 11; (5) 228 Evanochko, W.T.(13) 172 Evans, A.B. (3) 464 Evans, B.W.(7) 400

Evans, 1. (7) 241 Evans, J.C. (4) 34 Evans, J.N.S. (7) 25 Evans, J.S. ( 5 ) 22; (8) 65 Evans, P.D.(9) 50 Evans, P.J. (10) 131 Everall, N. (10) 285 Everett, T.S. (3) 490 Evgcnia, A. (10) 57 Evleh, E.M. (2) 134; (3) 386; (7) 709 Exarhos, G.J. (7) 743; (10) 422; (14) 83 Eychenne, C. (7) 434 Fabian, J.S. (3) 460 Fabian, W.M.F. ( 5 ) 440 Fabryova, V. (12) 56 Facchielli, L. (13) 129 Facchine, K.L. (14) 10 Facclli, J.C. (2) 203; (3) 27,370, 382 Facey, G.A. (7) 216,217 Fbler, J. ( 5 ) 463 Fairbrother,W.G. (3) 278 Fairbrother,W.J. ( 5 ) 304 Fairman, R. (5) 256 Faklcr, B. (9) 49 Falcigno, L. ( 5 ) 283 Falke, J.J. (3) 489 Fallon, G.D. (3) 419 Falvello, L.R(3) 8 1 Falzone, C.J. ( 5 ) 325 Fan, P. (9) 117 Fan, T.W.-M. (12) 96 F a , W.-L. (12) 160 Fane, A.G. (13) 98,99 Fanghaenel, A. (3) 193 Fantazzini, P. (13) 96, 110 Fantini, J. ( 5 ) 22 1 Farahani, K. (13) 22 Farcasiu, D. (3) 362 Fardeau, M. (12) 309 Farfan, N. (3) 333 Farghali, H. (12) 65,69 Farmer, B.T., I1 ( 5 ) 334; (9) 57,62, 74, I08 Farnan, I. (7) 748 Farooqui, S.A. (6) 101 Farquharson, M.J. (3) 338 Fmant,RD. (11) 116 Farrar, T.C. (6) 17,20,21,86 Farre, R (7) 661 Farrell, N. (1 1) 112 Farrow,N.A. (9) 260; 289 Fatkullin, N. (6) 22,19 1;( i 0) 429

Author Index Faulkner, D.J. (3) 56 Faurc, C. (7) 398 Faurc, R. (5) 414 Fauvelle, F. (3) 130 Favaretto, L. (7) 196 Favier, J.C. (10) 358 Fawcett, A.H. (10) 1,33,141, 157 Fawcett, J. (3) 63 Fazakcrlcy, V.G. (11) 109 Fcderico, A. (12) 50 Fedetov, V.D. (7) 338 Fedorov, L.A. (3) 10 Fedobv, M.A. (2) 101; (3) 510 Fancy, J. (3) 492; (5) 442; (7) 322; (9) 51, 191, 194, 195; (11) 140 Fchcr, A. (6) 179 Fehlhammcr, W.-P. (3) 89,94; (7) 171 Feigon, J. (5) 359; (9) 76,85,86, 100,116,122,123,126 Feijen, E.J.P. (3) 344; (7) 633 Fcike, M. (7) 23,93,94,755 Feio, G. (13) 62 Feiweier, T. (6) 11 Fcjes, P. (7) 623,635 Felder, E.R. (9) 112 Feldman, W. (7) 505 Feldmann, C. (7) 524 Felix, V. (7) 345 Fell, B. (7) 173 Felli, LC. (5) 444 Fellmann, P. (7) 370 Felsenfeld, G. (9) 89 Penelonov, V.B. (3) 520 Feng, F. (7) 63, 131,651 Feng, H. (7) 176; (10) 371 Feng, H.Q. (6) 142; (13) 121 Feng, L. (1 0) 226 Feng, R. (12) 72,73 Feng, W, (8) 72,73 Feng, X. (7) 92 Feng, Y. (7) 598; (10) 383 Feng, Y.P.(9) 283 Fenwick, K.M. (7) 395 Ferey, G. (7) 525,679 Fcrmandjian, S. (5) 469,475 Fernandes, E. (7) 203 Fernhdcz, C. (3) 347; (5) 448; (7) 99, 100, 107, 112,597,676, 677; (9) 15 Femandcz, L. (7) 563 Femandez, M. (3) 58 Fernandez, Y. (12) 2 13 Fernandez-Santin, J.M. (10) 185 Ferrando, A. (10) 163, 164 Ferrara, A. (1 1) 52

499

Ferrara, P. (5) 3 12 Fcrrarini, A. (14) 53,56,57 FCITUO,M.B. (2) 93,94, 177-179 Fcrrcira, A. (3) 275; (7) 614,615 Ferreiro, M.J. (3) 66 Fcrro, D.R (10) 5 1 Ferro, L. (7) 142,143 Fersht, A.R. (5) 320; (9) 208,209, 265

Fcsik, S.W. (5) 335; (9) 7,9-12, 61,142,273,280

Fettinger, J.C. (3) 444 Fetzer, J.C. (7) 141 Feuerslcin, M.(3) 241; (7) 603, 81 1

Feunk, E. (7) 129 Fcx, T. (3) 509 Fiala, R. (9) 117, 1 19, 124 Ficheux, D.(3) 147 Fichtner, K.-P. (12) 223 Fiebig, K.M. (9) 212,213 Fiedler, H.-P. (5) 389 Field, R.A. (9) 155 Fierke, C.A. (9) 62 Figucirinhas, J.L. (14) 92 Fijolek, H.G. (7) 286 Filippidis, A. (7) 567 Fill, M. (9) 10 Findeis, B. (5) 235 Findeiscn, A. (1 1) 57 Findeisen, M. (5) 388 Fink, G. (10) 105 Finkler, S.(7) 295 Firestonc, L. (13) 7 1 Firlej, L. (7) 138 Fischer, A. (3) 446; (5) 198,464; (7) 20 1,284

Fischer, E. (6) 22, 191; (10) 429; (14)31

Fischer, J.E. (3) 244 Fischcr, M. (9) 133 Fisher, B.J. (13) 155 Fisher, J. (4) 77 Fisher, K. (3) 255 Fisher, RJ. (9) 14 Fisher, S.N.(6) 178 Fisher, S.W. (12) 241 Fitlaw, J.F. (7) 698 Fitzgerald, J.J. (3) 346; (7) 552, 782

Fitzpatrick, J.H. (12) 117 Fjeldsted, D.O.K. (1 1) 148 Flaherty, M.B. (1 1) 145 Flanagan, J.M. (9) 173 Fleischer, G. (6) 107, 190,214, 215,219; (10) 341,408,427, 428

Fleischhauer, J. (5) 207,485; (10) 189

Flcmming, H.C. (7) 472 Flctcher, M.C. (1 1) 8 Flint, H. (3) 29 1 Flogel, U. (8) 52 Flores, R (12) 279 Florian, P. (7) 253,748,787 Florin, A.E. (2) 194 Flojanczyk, Z. (6) 114, 169; (10) 332

Fliikiger, K. (5) 261,262 Fw-Fw, C. (7) 163,198,215 Fodor-Cmrbti, K. (14) 157 Foglia, F. (6) 75 Fokken, S. (10) 89 Foley, C.K. (2) 163 Foley, I. (6) 101 Foley, J.M. (12) 208 Foley, N.(7) 156 Folkendt, M.M. (2) 62 Folmer, RH.A. (9) 92,237 Fonc, M. (7) 737; (10) 256,262 Fong, S. (5) 324; (9) 42 Fonseca. I. (7) 202 Fontaine, X.L.R (3) 337,340 Fontanella, J.J. (10) 406 Fonte, P. (1 1) 83 Foord, E.K.(14) 50, 170 Forano, C. (7) 818 Forano, E. (12) 40,4 1 Forbes, L.K.(13) 27 Ford, W.T.(10) 388 Ford, Y.Y. (12) 67,68 Forder, C. (10) 179 Forchlich, R (1 1) 96 Foreman, J.B. (4) 79 Forge, V. (9) 200 Forgo, P. (5) 380; (12) 145 Forini, F. (3) 131,132 Forman-Kay, J.D. (8) 81; (9) 210, 289

Fornasicr, R. (3) 140 Forrest, B. (1 1) 1 10 FOKO,L. (3) 379 Forshaw, P. (7) 156 Forsylh, M. (7) 53 1,532; (10) 300, 333

Fort, J.J. (7) 327 Forte, C. (14) 147,157 Fortier, P.L. (9) 287 Fortin, D. (7) 283 Forwood, C.T. (7) 8 10 Fougereux, J.A. (13) 160 Foulkes, J. (7) 135 Fountain, M.A. (5) 466 Fountas, K. (12) 326

Nuclear Magnetic Resonance

500

Fouquct, E. (3) 405 Fourmy, D.(5) 478;(9) 114,115; (I 1) 142 Fownicr, M. (7)487 Fowlcr, P.W.(2)57,58,160, 199; (11) 137 Fox, D. (6) 183 Fox, J.M. (7) 146 Fox, M.A. (2)120;(3)330 Fox, P.T. (6) 185;(1 3) 43,77 Fraanje, J. (3) 409;(5) 506 Fraenkel, G. (5) 103,123 Frahm, A.W. (5) 68 Frahm, J. (12)127,261,291 Fraissard, J. (3) 183,516;(7)649, 650,688 Fralix, T.A. (12) 153 Frampton, C.S. (3)296 Francesangeli, 0.(14) 158 Francis, P. (3)492 Francke, W. (5) 386 Frank, H.(6)24 Frank, M.K.(9)205 Frank, R.(9)49 Frankel, A.D. (9) 113 Frankland, A.D. (3)263 Fransen, J.R (1 1) 79 Frantz, S.(12)164 Franzoni, L. (5) 285 Frappier, F. (5) 383 Frassineti, C. (12)305 Frausto da Silva, J.J.R (5) 76 Frazier, C.E.(7)394,405 Frebourg,P.(10)411 Freedberg, D.I. (9) 148, 149,188, 189 Freeman, B.D. (10)381 Freeman, R (5)23;(8)8;(9) 178, 179 Frenkiel, T.A. (5) 442;(8)92;(9) 51,194,195 Frenking, G.(2)I 1 1, 116;(5) 489 Frenna, V. (3) 102;(5) 84 Frentescu, L.(1 2) 49 Freml, T.(3)189 Fresh, M. (3) 145;(1 1) 42 Freude, D.(7)646,690,716 Freud, C. (9)218 Frcund, S.M.V. (5) 320,324;(9) 41,42,140,208,209,265 Frey, H.(10) 27 Frey, U.(3)462;(6)74,76;(9) 151 Freyhardt, C.C. (7)602 Friary, R.J. (3) 79 Fricke, R.(3)351;(7)612 Friedrich, J. (1 2) 177

Friedrich, M.S. (5) 31 1; (9)57, 230 Fries, K. (3)236;(7)437 Frimcr, A.A. (10)400 Fripiat, J.J. (7)521,639 Frisch, A. (4)79 Frisch, M.J. (3)18 Frith, W.J. (13)106 Fritz-Zieroth, B.(12)228 Froba, M.(7)586 Froese, C.(2) 110 Fronzoni, G.(4)18 Fruchier, A. (3)103;(5) 3,65 Frund, F. (7)463 Frydman, L.(7)99,170;(10)278 Frye, J. (3)243 Fu, G.(10)443 Fu, H. (7)589 Fu, R.(7)24,45,191 Fu, RQ. (6)52 Fu, S.(10)241 Fu, Y.(10)256 Fucini, P.(5) 327;(9)43 Fuelbcr, C.(7)48,53;(10)302, 394 Fuelop, F. (5) 208 Fuentes, J. (I 1) 119,120 Fuganti, C.(3) 207 Fujara, F. (6)11, 107, 189,190, 214,219;(10)428 Fuji, K.(5) 395 Fujibayashi, T. (12)206 Fujihara, H.(3) 471 Fujimori, K.(10) 122,147 Fujimoto, K.(12)303 Fujimoto, Y.(3)59,364 Fujinawa, T.(7)222 Fuji@ N.(3)295;(6)165 Fujiwara, H.(3) 116, 158;(7)347, 377,423,424;(14)34-37 Fukazawa, Y. (1 1) 1 Fukuda, S.(3) 60 Fukui, H. (2) 13,151 Fukushi, Y.(3)65 Fukushuna, E.(13)45 Fukushima, Y.(7)560,644 Fukuzalu, M.(12)200 Fulber, C. (13) 133 Fulcher, R.G. (13) I5 1 Fuller, B.J. (12) 194-196,198 Fulton, A.M. (12)5,88 Fulton, D.B.(8) 17 Fumagalli, M.L. (1 3) 129 Fumino, K.(6) 136,163 Fung, B.M. (7)38;(14)52,85, 149, 150,153-156 Furby,M.I.C. (14) 171

Furet, E. (6)75 Funhata, K.(5) 15 Furman, G.B.(6)62 Fumcaux, R.H. (7)330 Furo,l. (14) 119,120 Furukawa, N.(3)47I Furukawa, Y.(3)5 1 1 Furuya, H. (5) 423 Fusck, J. (3)238,340,352 Fushman, D. (9)257,281 Futsaether, C.M.(12)45 Fyfe, C.A. (7)598,675;(10) 435; (13)69 Fytas, G. (10) 427 Gaarc, K.(3)394

Gabclica, Z.(7)607,624 Gabius, H.J. (9)156, 157 Gabold, P.(3)228;(7)275 Gabrielse, W.(2) 136;(7)80;(10) 273 Gabuda, S.P.(3)360 Gacs-Baitz, E.(2) 169;(3) 84;(5) 99 Gade, L.H.(5) 235 Gadgil, V.R (7)203 Gadian, D.G. (12)275 Gadre, A. (3) 156 Gaede, H.C. (14) 122 Gaeta, F.C.A. (1 1) 136 Gafhey, E.J. (7) 254,789 Gahi, A. (3) 161, 169;(6) 140 Gaggelli, E. (12)50 Gape, S.M.(5) 322;(9)29 Gaillard, J. (9)306 Gaines, A. (7)482 Gaines, D.F. (3) 336 Gajhede, M. (5) 342 Galache, M.P. (14) 168 Galakhov, M.(5) 73 Galasso, V. (4) 17,18 Galbis, J.A. (10) 114 Galembeck, F. (7)452 Galeone, A. (5) 362 Galetti, G.C.(7)387 Galiasso, R (7)607 Galinanes, M.(12)166 Galiardo, A. (1 0) 49 Gallazzi, M.C. (7)67;(10) 330 Gallez, B. (12)189 Galli, A. (7)703 Galli, G.(14) 94 Galliano, P.G. (7)766 Gallie, E.A. (7)465 Gallis, J.L. (13)76 Gallucci, J. (5) 123

Author hidex Galya, L.G. (7) 678 Gamasa, M.P. (3) 28 1 Gambarini, G. (13) 129 Gamble, G.R. (7) 362,388,407 Gamcsik, M.P. (12) 227 Gan, Z.H. (2) 126; (7) 34,72,86 Ganapathy, S. (7) 292,s 17 Gandolfo, C. (14) 147, 158 Gandour, RD. (4) 85,86 Ganeshan, K. (3) 443; (7) 336 Gangoda, M.E.(7) 793 Ganguly, P. (7) 5 17 Gann, S.L. (7) 97 Gans, P. (5) 290 Gao, J.-H. (6) 185; (1 1) 118; (13) 43,77 Gao, P. (7) 33 1 Gao, Q. (7) 673,674 Gao, S.(7) 696 Gao, W. (7) 379,439 Gao, Y. (10) 414 Gao, Z.M. (5) 465 Garbassi, F. (10) 7 Garbcr, M. (9) 35 Garbow, J.R. (3) 5 Garcia, A.R. (6) 132 Garcia, C. (9) 287 Garcia, J.R. (7) 526,816 Garcia, M.E.F. (10) 201,333 Garcia, R. (7) 129 Garcia-Alonzo, F.J.( 5 ) 492 Garcia-Alvarcz, M. (10) 185 Garcia Fcrnandcz, J.M.(1 1) I 19, 120 Garcia-Garibay, M.A. (3) 144; (7) 718 Garcia Martinez, E. (3) 309 (3) 325; (7) Garcia-Tasende, M.S. 32 1 Garden, S.J. (3) 401 Gardner, K.H. (8) 77; (9) 68, 71-73 Gargaro, A.R ( 5 ) 442; (9) 5 1, 194, 195 Garigiputi, R.S. (7) 57 Garlick, P.B. (12) 25; (13) 22 Garnier,A. (12) 151, 168 Garrett, D.S. (5) 453; (9) 55, 128, 258 Garribba, P. (13) I0 Garrido, L.(7) 20; (12) 13 Garros, G. ( 5 ) 4 14 Garwood, M. (8) 7, 16; (12) 3 19 Garzillo, C. (1 1) 134 Gasbarrini, A. (1 2) 69 Gase, U. (9) 23 Gaspar, P.P. (5) 214

50 1 Gatchousc, B. (2) 213 Gates, D. (3) 442; (12) 31 (7) 558,573 Gates, W.P. Gato, K. (3) 54 Gatzkc, M. (6) 183 Gaudct, G. ( I 2) 40,4 1 Gaudin, F. (9) 298 Gaudino, J.J. (1 1) 136 Gaudron, P. (12) 164 Gaur, H.A. (10) 273 Gauss, J. (2) 27,33-36,41,50,67, 2 12; (4) 24 Gaulhier, A.D. (5) 382 Gautier, N. (3) 78,356 Gavalcr, J. (12) 69 Gavilanes, J.G. (5) 339 Gavin, J.A. (8) 40 Gawinccki, R (3) 97,106 Gay, LD. (3) 472 Gayathri, C. (14) 6 , l l Gazzano, M. (2) 135 Gdaniec, M. (4) 8 1; (1 1) 98 Geacintov, N.E. (9) 84 Gcbcl, G. (1 0) 15 Gcckcler, K.E. (10) 143 Gedde, U.W. (10) 84 Gedeon, A. (3) 5 16 Gedye, R.N. (7) 465 Gcc, B. (6) 109 Gecn, H. (6) 58 Gccrling, P. (7) 250 Geers, R. (12) 210,211 Gccrts, H. (7) 468 Gccrtscn, J. (2) 89; (4) 13, 14,20 Gehrig, P. (9) 2 18 Gehring, A.U. (7) 476 Geiduschek, E.P. (5) 345 Geiger, A. (6) 9 1 Gci1,B. (6) 11, 105, 189,214; (10) 428 Geise, H.J. (5) 417 Gelan, J. (10) 169, 180,398 Gelbaum, L. (7) 358 Gelin, F. (7) 307 Gemmecker, G. (5) 262,3 14 Gendron, R (10) 13 Geneste, P. (7) 657 Geng, Y.H. (10) 271 Gcnge, A.R.J. (3) 41 1; (7) 285 Genov, D.G. ( 5 ) 490; (1 1) 13, 14 Gcnre-Grandpierre, A. ( 5 ) 377; (11) 135 Gentzler, M. (10) 418 Georgc, RD. (10) 372 Gcorgescu, J. (9) 292 Georfiou, P.E. (1 1) 78 Gcorgopoulos, C. (9) 18

Geppi, M. (14) 147, 157 Gerace, F. (10) 406 (6) 173 Gcraldes, C.F.G.C. Gerard, J.F.(10) 292 Gerardin, C. (7) 794,795 Gcrbcr, S. (6) 18, 19 Germanas, J.P. ( 5 ) 244 Germann, M.W. ( 5 ) 360 Germano, G. (14) 84,96 Gcrothanassis, I.P. (3) 460; (6) 8; (7) 280,288,322 Gcrow, K. (12) 3 18 Gerry, M.C.L. (2) 213,214 Gerstmann, S. (7) 270,274 Gervais, V. (9) 154 Gcrvay, J. (6) 151 Gerzain, M.(7) 216 Geschke, D. (14) 166 Gcsell, J. ( 5 ) 287 Gesenberg, C. (3) 5 13 Gettes, L.S.(12) 153 Geyer, M. (9) 49, 134 Gharbi, N. (7) 436,453; (10) 402 Gharbi-Bcnarous, J. ( 5 ) 427; (1 I ) 17,28,29 Ghcnciu, A. (3) 362 Ghi, P.Y. (10) 170; (13) 101 Ghiran, I. (12) 49 Ghiviriga, I. (3) 86; (1 1) 18,87 Ghose, R. (14) 116 Giannelis, E.P. (10) 327 Giannctto, G. (7) 607 Giannolis, E.P. (7) 438 Gibbs, S.J.(13) 11,74, 106 Gibson, A.M. (3) 302 Gibson, M.A. (7) 8 10 Gibson, M.S. (3) 373 Gidley, M.J. (7) 346 Giclcn, M. (3) 407,415; ( 5 ) 16, 145; (7) 257 Gierasch, L.M. (7) 88,357 Gierling, K. (3) 297 Gies, H. (7) 598 Gil, A.M. (7) 345; (14) 166 Gil, RR.(3) 179 Gilbert, T.M. ( 5 ) 43 Gilbertson, S.R (7) 235,356 Gilboa, H. (6) 133 Gilboe, D.D. (12) 117 Gilcva, N.G. (10) 90 Gilham, D.E.(9) 139 Gillard, RD. (7) 233 Gillen, K.T. (10) 288 Gilles, I. (1 1) 59 Gillespic, J.R (9) 304,305 Gillcspie, P. (9) 86 Gillct, B. (12) 126, 133

Nuclear Magnetic Resonance

502

Gillics, D.G. (13) 32,63 Gillics, R.J. (12) 76 Gillis, D.J. (5) 70 Gillis, N. (12) 304 Gilman, J.W. (7) 454; (10) 174 Gilmcr, T.C. (10) 125 Gilon, C. (5) 273 Gilpin, RK. (7) 793 Gilquin, B.(5) 300 Gilson, D.F.R. (3) 449; (5) 177; (7) 232

Gimcno, J. (3) 28 1 Gimeno, M.C. (5) 235 Gimi, R.H. (5) 392 Gincs, J.M. (3) 142 Gioia Lobbia, G. (3) 320 Giordano, F. (3) 142,320 Giotto, M.V. (3) 233 Giralt, E. (5) 422; (1 1) 49 Girault, J.-P. (5) 427; (1 1) 17,28, 29

Gkibct, C.G. (4) 62-64 Giroud, M. (12) 276 Gitti, RK. (5) 454; (9) 5,6 Gittleman, C.S. (7) 600 Giurg, M. (5) 226 Gladden, L.F. (7) 420,421; (13) 12,79,89,92; (14) 78,79

Glaser, J. (3) 357-359; (5) 152, 160,161 Glaser, R. (7) 15 Glaser, S.J. (5) 35 1; (8) 20,46,47; (9) 167

Gleason, K.K. (3) 391; (7) 807 Gleason, W.B. (7) 291 Glennon, J.D. (7) 734 Glick, G.D. (6) 68 Glikamp, L A . (3) 137 Glockshuber, R. (9) 1-3 Gltkkle, A. (5) 57 Glowinkowski, S.(7) 190 Glushka, J. (5) 373 Glushko, G.N. (5) 107-110 Gmeiner, W.H.(5) 257; (8) 70,71 Go, N. (9) 270; (1 1) 105 Gobbo, M. (5) 276 Gobelto, R (2) 135 Goda, F. (12) 189 Goddard, R (7) 277 Godelitsas, A. (7) 567 Goday, E. (3) 167 Godry, B. (5) 192 Gorler, A. (6) 69 Goerlich, J. (3) 446; (5) 179,493; (7) 284

Goethals, E.J. (10) 398 Goetz, S.(7) 574

Goff, C.M. (3) 248 Gofiedi, G. (10) 163 Gogoll, A. (3) 196; (5) 425 Goguen, P.(7) 18,698 Golchin, A. (7) 310 Gold, R. (12) 308 Goldenberg, D.P.(9) 264 Goldenberg, W.S.(7) 480 Goldfarb, V. (5) 3 11; (9) 57,74, 230

Goldoni, F. (10) 56 Golemme, A. (14) 99, 165 Goljcr, I. (12) 56; (14) 12 Gololobov, Y.G. (5) 215 Golotvin, S.S.(14) 15 Golubev, N.S.(3) 88, 124; (5) 83; (6) 82; (7) 198 Golubeva, L.Y. (12) 165 Gombler, W. (2) 166 Gomers, P.T.(10) 237 Gomes, A S . (10) 97 Gbmez, S. (5) 237 Gomez-Paloma, L. (5) 348,362 Gomez-Sal, M.P. (5) 73 Gonen, 0. (12) 33 1 Gonzalez, A. (3) 5 13 G o d l e z , C. (5) 358 Gonzalez, RG. (12) 124,259 Gonzalez-Calbet, J.M. (7) 599 Gonzalez de Andres, A.I. (7) 129 Gonzalez dc Suso,J.M. (12) 306 Gonzalez-Vila, F.J. (7) 390,475 Goodman, B.A. (13) 141 Goodman, J.M. (I 1) 64 Goodman, M. (5) 280 Goodman, S.L.(5) 269 Goodson, B.M. (13) 78 Gopalsami, N. (10) 439; (13) 132 Goralski, T. (1 2) 6 1 Gorbalenya,A.E. (9) 6 Gorbuty, M.L. (7) 119 Gore, J.C. (13) 175 Gore, RJ. (13) 128 Gorecki, W.(10) 424 Gorelsky, S.I.(7) 134 Goren, S.D.(6) 62 Gorcnstcin, D.G.(8) 9; (9) 297 Gorin, A. (9) 125 Gorke, U. (13) 56,164,165 Gorier, A. (9) 219 Gorny, K. (3) 246 Gorshkova, RP. (5) 374 Gorte, RJ. (2) 132,134; (3) 383, 386; (7) 709

Goruez, C.C. (7) 473 Goschl, M. (3) 130 Goto, H. (7) 222

Goto, Y. (12) 206

Gotsis, E.D. (12) 326 Gottardi, G. (12) 298 Gottlieb, H.E. (5) 495; (I 1) 91 Gottwald, J. (7) 23 Gotzel, G. (3) 341 Goubitz, K. (3) 409; (5) 506 Goudemand, P. (7) 450,45 1 Goudemant, J.-F. (12) 175 Cough, S.L. (5) 267 Goujon, J.M. (12) 186 Gounelle, Y. (14) 71,72 Goux, A. (1 0) 95 Gozansky, E.K. (9) 297 Gozc, C. (3) 244,380; (7) 144; (10) 71,301

Graafsma, H. (7) 668 Grabias, T. (7) 187 Grably, S.(12) 151 Grabowski, D.A. (14) 104 Grabowski, Z. (3) 126,425,439 Grace, A.A. (12) 158 Gradwell, K. (8) 92 Graeslund, A. (6) 40; (8) 24 Graf, L. (9) 141 Graf, R (7) 23,53,93 Graf von Roedem, E. (5) 243 Graham, G.D. (12) 284 Graham, S.(12) 131 Grandclaude, D. (6) 55; (13) 36 Grande, S.(14) 95 Grandinetti, P.J. (7) 253,748,787 Granger, P. (3) 294 Grant, D.J.W. (7) 291 Grant, D.M. (2) 122, 145; (3) 27, 370,375-377,382; ( 6 ) 186, 187; (7) 72, 119, 130

Grant, RP. (9) 288 Grassi, A. (10) 231 Grasso,G. (3) 138 Gratzowski, H. (7) 300 Gray, M.L. (13) 180 Gray, W.R (5) 289 Grayson, M. (2) 58, 167; (3) 91; (5) 140 Graziani, R.(3) 309 Grdadolnik, S.G. (5) 3 14 Greatrex, R (2) 120; (3) 330 Grech, E.(3) 109,429; (5) 78, 80-82; (7) 172,221

Grechowiak, J.R (7) 596 Green, C.J. (1 2) 196 Grecn, M.A. (7) 148 Green, M.H.L.(7) 148 Green, S.St. C. (5) 2.16 Green, T.A.P. (13) 3 1 Greenbaum, N.L. (9) 99

Author Index Greenbaum, S.G. (10) 406 Greenblatt,J. (8) 75; (9) 185 Greenwood, J. (7) 300 Greenwood, P.F. (7) 48 1 Gregory, C.D.(12) 297 Gregory, D.M. (7) 87,298,299 Grennberg, H. (3) 196; ( 5 ) 425 Grest, G.S. (6) 132 Greville, M.(7) 532 Grey, C.P. (3) 237; (7) 723,724; (10) 320 Griesbach, A. (12) 223 Griesinger, C. ( 5 ) 105,350,351, 484; (8) 20,46,58; (9) 165-167, 169 Griffm, A.C. (14) 78,79 Griffin, A.G. (7) 420,421 Griffm, R (5) 36 Griffm, R.G.(2) 102; (3) 451; ( 5 ) 171; (7) 71,82, 105, 108,229, 255,369,533 Griffiths, J.M. (7) 255 Grifiths, J.R (12) 35,327 Griffiths, L. (3) 2,96 Grifiths, P.C. (10) 363 Grimmer, A.R (3) 34 1; (7) 767 Grinberg, F. (14) 31, 152, 162 Grindley, T.B. ( 5 ) 404; (1 1) 10,86 Grischenko, O.V. (12) 55 Grishin, Y.K. ( 5 ) 143 Grisi, F. (10) 64 Grobelny, J. (10) 389 Grobet, P.J. (3) 266,344; (7) 468, 633 Grob-Pisano,C. (7) 78; (10) 209 Groch, K.M. (7) 304 Grode, S.H. (8) 30 Grodzicki, M. (3) 291 Grohal, J.R.(7)286 Grohmann, A. (7) 255 Grollman, A.P. (9) 81,82 Grondey, H. (7) 598,675; (10) 435; (13) 69 Gronenborn, A.M. ( 5 ) 241,453; (9) 13, 14,5589, 128, 205-207,23 I-233,258 Gronski, W. (10) 349,356 Gronwald, W. ( 5 ) 245; (9) 164 Grootendorst,E.J. (7) 500 Grootveld, M.(13) 148 Grosenick, H. (3) 150 Gross,D. (13) 160 Gross, J.D.(7) 369 Gross, M. (9) 215 Gross, R.A. (10) 63, 186-188,220 Gross, W.L. (12) 179 Grossmann,G. (3) 446; (7) 200,

5 03

201,220,284,494 Grotendorst, J. (12) 46 Grove, A. ( 5 ) 345 Grove, D.M. (3) 101 Grozinger, C. (7) 379,439 Gruender, W. (6) 2 15 Gruetter, R. (12) 3 19,320 Grune, M. (8) 87 Gnuunayr, K. (3) 77 Gruss, U. ( 5 ) 2 16 Grutzock, M.W. (7) 539 Gryff-Keller, A. ( 5 ) 139; (14) 123 Grzesiek, S.( 5 ) 88,486,488; (6) 63; (8) 89; (9) 149, 158, 161; (14) 13 Grzybowski, B. (7) 683 Gschwind, RM. (5) 262 Gu, B. (7) 472 Gu, J. (3) 472 Gu, Z. (7) 301,355 Gualerzi, C.O. (5) 309 Gualtieri, A.F. (3) 237 Guarrotxena, N. (10) 177,178 Gubser, C.C. (9) 93, 109, 111 Gudat, D. (2) 1 18; (3) 3 10; (5) 157 Gudmundsson, B.O. (3) 226 Guedes da Silva, M.F.C. ( 5 ) 76 Guegan, P. (10) 160 Guelton, M. (7) 683 Gucnncugues, M. ( 5 ) 300 Guenot, P. (3) 152 Giintert, P. (9) 17, 144, 145, 222-225,239 Guenther, G. (7) 493 Giinther, H. (5) 29,33,101; (6) 61; (7) 729 Guenther, R. (1 1) 1 10 Guering, P. (10) 3 1 Guern, J. (12) 66 Guezcnnec, C.Y. (12) 111,133 Guggenberger, G. (7) 476 Guidoin, R. (7)46 I, 462 Guidotti, B.R. (7) 73 1 Guiheneuf, T.M. (13) 74, 147 Guilemin, J.-C. (3) 321 Guilfoyle, D.N. (13) 34 Guillaume, M. (5) 424 Guilleme, J. (4) 4,5; (5) 399,462; (1 1) 5,6 Guillemot,J.-C. (5) 3 12 Guillermo,A. (10) 367 Guillon, D. (14) 92 Guillot, G. (13) 113 Guimaraes, A.R (12) 124 Guisset, M.(7) 609,6 I0 Guittet, E. (8) 12,26; (9) 303 Guizard, C. (7)433,460

Gulandris, V. (7) 459 Guliants, V.V. (7) 685 Gulik-Keywicki,T. (7) 4 I7 Gulini, U. (5) 405 Gullion, T. (7) 27 Gunatillake, P.A. (10) 246 Gundersen, L.-L. (1 1) 72 Gung, B.W. (3) 115 Gunnewegh, E.A. (7) 707 Gunther, U.L. (8) 74 Guo,J. (7) 150,543,549,551 Guo, J.X. (6) 29 Guo, M. (10) 2,98,99,214,238, 254,263,304,359,375,380, 419,420 Guo, W. (7) 415 Guo, X. (7) 593,721 Guo, Y. (3) 62 Guo, Z.Y. (7) 632 Gupta, C.M.(5) 365 Gupta, RK. (12) 185; (13) 116 Gurcvitz, M. ( 5 ) 307 Gurumani, V. ( 5 ) 40 1; (11) 45 Guschlbauer, W. (1 1) 109 Gusev, D.G. ( 5 ) 7 Gustafsson, S. (14) 110 Guth, J.L.(7) 643 Gutieffez, A. (7) 387; (1 1) 123 Guticrrcz, E. (7) 559 Gulknccht, R (5) 261,262 Gutmann, I. ( 5 ) 410 Gutsze,A. (12) 141 Guvot, A. (10) 95 Guy, A. (7) 822 Guy, H.R (9) 49 Guyot, S.( 5 ) 398 Gurman, J. (10) 65 Gwaltney, S.R (4) 28 Gwathmey, J.K. (12) 177 Ha, J.M. (7) 594 Ha, M.-A. (7) 400,4 10 Ha, N.T.H. (10) 122 Haakansson, M. (3) 21 1 Haase, A. (13) 38,130,152 Haasnoot, C.A.G. (4) 84 Habata, Y. (1 1) 77 Habaue, S. (10) 134, 153 Habazettl, J. (9) 263 Habenschuss, A. (7) 160 Haber, J. (7) 537,689 Hada, C. ( 5 ) 414 Hada, M. (2) 5-9, 12, 17-19; (3) 41-44 Haddleton, D.M. (10) 248 Hadjichristidis,N. (10) 219,427

Nuclear Magnetic Resonance

504

Hadjiliadis, N. (3) 3 15; (7) 280 Hadjoudis, E. (3) 155 Hacbcrlcn, U. (2) 143 Hacgele, G. ( 5 ) 216; (14) 25 Haendcl, H. (7) 332 Haenicke, W. (12) 261 Haensler, M. (3) 194 Hkssgcn, D. ( 5 ) 193 Hacrd, T. (6) 4 1 Hacrkocncn, M. (10) 115,116 Hamster, M. (7) 344 Hiirtcl, U. ( 5 ) 128 Haessner, R (5) 388 Haher, S. (7) 23,36,37,53; (10) 433,440; (13) 57,58, 135 Hafskjold, B. (6) 212 Hagcdorn, M. (1 2) 244; ( 13) 149 Hagcn, A. (7) 7 I7 Hagen, W.R. (6) 79 Haggkvist, M. (13) 90 Haginhara, H. (10) 223 Hagiwara, T. (10) 50 Hahm, C. (3) 246 Hahn, J. (7) 220 Haida, M. (12) 200 Haiduc, I. (3) 333,408 Haishi, T. (1 3) 45 Hajduk, P.J. (9) 142 Hajck, M. (1 2) 248 Haji,L.(10)71,301 Hikansson, M. (5) 102 Halay, J.L. (10) 3 18,323 Halcrow, M.A. (7) 209 Halfhill, M.J. (10) 276 Hall, E.S.(10) 119 Hall, F.H. (4) 4 1,42 Hall, H.K. Jr. (10) 7 9 , s 1 Hall, L.D. (4) 45; (13) I1,74, 106, 147, 150,155 Hall, P.J. (7) 126 Hallc, B. (9) 151,299,301; (14) 110,120 Halloin, J.M. (13) 156 Hake, M.R. (13) 29,3 1 Halstead, T.K. (7) 189 Halut, S. (3) 285 Halvorson, H.R.(12) 30 Hamaide, T. (10) 95, 194 Haman, S. (1 1) 102 Hamana, H. (10) 50 Hamano, Y. (1 1) 35 Hambley,T.W. (11) 112 Hamdan, H. (7) 592 Hamerton, I. (10) 39 1 Hamill, S.J. ( 5 ) 324; (9) 42 Hamilton, E.J.M. (7) 787 Hamilton, J.A. (7) 366,415

Hamilton, J.G. (10) 82, 139 Hamilton, T.P.(3) 25 Hamman, S. (3) 67; (4) 46 Hammarslrtim, A. ( 5 ) 291; (9) 180 Hammer, B.E. (13) 24,95, 102 Hammer, J. (7) 368 Hamor, T.A. (5) 357 Hampel, F. (3) 228; (7) 275 Hamy, F. (9) 112 Hamza, A.I. (3) 346; (7) 552 Han, H. (10) 58 Han, K.-H. ( 5 ) 289 Han. O.C. (7) 527 Han, O.H. (1 0) 270 Han, R. (12) 82 Han, S. (10) 270 Hanada, K. (1 0) 342 Hancock, R. (12) 62,80 Handcl, T.M. ( 5 ) 256,340 Handford, P.A. (5) 3 13; (9) 28 Handy, N.C. (2) 71 Hangar, A.B. (9) 104 Hanhinen, P. (1 1) 58 Hanna, J.V. (3) 240; (7) 110,481 Hanna, R.A. (7) 504 Hannus, I. (7) 635,817 Hansen, H.-J. (5) 115 Hansen, L.L. (12) 70 Hanscn, P.E. (3) 83; ( 5 ) 209; (1 1) 19,48 Hanson, G. (12) 233 Hanson, J.C. (3) 237 Hanssum, H. (12) 78 Hantz, E. ( 5 ) 347 Hao, J.-C. (14) 107 Hao, S.-X. (14) 107, 108 Happncr, W. (6) 180, 183 Harada, A. (3) 154; (10) 117 Harada, J. (12) 206 Harada, M. (12) 287 Haraldseth, 0. (13) 176 Harazono, T. (3) 342; (7) 788 Harbison, G.S. (7) 296 Hard, K. ( 5 ) 292; (9) 153 Hard, T. (8) 36; (9) 35,253 Hardcastlc, S.E. (7) 161 Harden, D.B. (1 1) 15 Harding, C.J. (5) 481 Harding, S.E. (9) 279 Hardy, B.J. (5) 456; (1 1) 123, 138 Hardy, D.L. (12) 23 Hardy, L.C. ( 5 ) 426 Harian, C.J. (10) 155 Harkcma, S. (1 1) 76 Harkins, R.N. (9) 130 Harlan, J.E. (9) 9, 11 Harlow, R.L.(3) 322; (5) 151

Harmsen, B.J.M. (9) 92 Harris, C.J. ( 5 ) 267,272 Harris, K.D.M. (7) 827 Harris, K.R. (6) 204 Harris, P. (5) 138; (7) 380 Harris, R (11) 114 Harris, R.K. (3) 92,326; (7) 5,66, 85, 155, 156, 169, 181, 192, 226,258,383,568; (10) 279, 281,340,396 Harris, S.J. (7) 734 Harris,T.A. ( 5 ) 233 Hanison, J.J. (10) 205 Harrison, W.J. (14) 63,64 Hartbrich, A. (12) 44 Hartl, F. (3) 409 Hartman, J.S.(3) 338,373; (7) 550 Hartmann, B. ( 5 ) 469 Hartmann, J. (I I) 97 Hartmann, P. (2) 125; (3) 450; (6) 112; (7) 94,493,761 Hartridgc, A. (7) 492 Harvcy, G. (7) 636 Harvcy, P.D. (7) 283 H ~ c yP.J. , ( 5 ) 188-190; (7) 267, 268 Harwood, H.J. (10) 2,28,38,242 Hasclcy, S.R. ( 5 ) 375 Hasclmaicr, R. (6) 15,93 Hashimoto, T. (3) 50; (12) 287 H a s h i m c , D. (7) 269 Haskell, W. (10) 338 Hassan, A. (1 1) 90 Hassc, A. (12) 102, 173 Hasslcr, K. (3) 398; ( 5 ) 92, 167, 168

Hassncr, A. ( 5 ) 495; (1 1) 91 Haslings, J.J. (3) 271-273 Hatanaka, H. (9) 26 Hatano, K. ( 5 ) 104 Hatcher, M.E. (7) 298 Hatchcr, P.G. (7) 120,307,467; (13) 94 Hatori, K. (10) 130 Hattori, M. (10) 352 Haudrechy, A. (14) 75 Hauct, T. (1 2) 186 Haupt, C.I. (12) 264 Hausen, H.-D. ( 5 ) 176 Haushalter, K.A. (3) 160 Havilin, RH. (3) 492 Haw, J.F. (3) 368,378; (7) 18, 178,179,671 Hawker, C.J. (10) 91 Hawkes, G.E. (7) 272,288 . Hay, A.S. (5) 430 Hay, J.N. (10) 391

Author Index Hayakawa, S.(7) 749,750 Hayashi, H. (10) 261 Hayashi, J. (7) 354 Hayashi, K. (13) 4 1 Hayashi, M.(1 1) 136 Hayashi, N . (1 1) 1 1 1 Hayashi, S.(2) 144; (3) 274; (7) 31,681,752

Hayashi, T. (12) 199 Hayashibara, T. (11) 1 Haycock, D.E. (13) 106 Hayner, M.W. (5) 233 Hayncs, H.W. (7) 127 He, H. (7) 135, 154, 161, 162,549, 55 1,583,588,592, 665,672, 804 Hc, J. (7) 604 He, P. (7) 150 He, P . 4 . (10) 385 He, Q. (6) 47 Hc, W.-Y. (12) 74,82 He, Y. (7) 287,739 Headrick, J.P. (12) 36, 163, 183, 23 1 Hcaly, E.F. (4) 66 Hcaly, P.C. (5) 188-190,200; (7) 260,267,268 Hcarmon, R.A. (3) I 1 Hearse, D.J. (12) 166 Heath, G.A. (3) 301 Heath, J. (12) 147 Heath, S.L.(3) 348 Heatley, F. (6) 143; (10) 21 1 Hcaton, N.J. (14) 29 .Hebrant, M. (5) 390 Heckmann, G. (5) 176 Hedberg, K. (2) 1 17 Hedbcrg, L. (2) 117 Hedeen, R.A. (13) 52 Hedgcs, N.D. (7) 346 Hedi, Z. (7) 453 Hcdiger, S.(7) 39 Heeribout, L. (7) 649,650 Heerma, W. (7) 350 Heerschap, A. (12) 20,310 Hcfiner, S.A. (10) 379 Hcikcnwaldcr, C.-R. (5) 4 15 Heii, S.R. (6) 49 Heiliger, L.(2) 28; (3) 367 Heilmann, S.M. (10) 61,137 Heimberg, C. (12) 258 Hcine, V. (7) 778 Heinekey, D.M. (5) 44,45,48,49, 53 Hcinemann, F.W. (5) 182,183 Hciner, A.P. (7) 382 Heinicke, J. (5) 416

505 Hcinrich, B. (14) 92 Heinrichschramm, A. (6) 209 Heitjans, P. (6) 114, 169; (10) 332 Heizmann, G. (9) 1 12 Helgaker, T. (2) 42, 189, 196, 197,

Hcrrod, N.J. (13) 147 Hersh, W.H. (5) 195 Herstad, 0. (6) 2 12 Hcrtz, H.G. (6) 90,93, 159, 162,

212; (4) 7, 16,54 Hcllcr, J. (7) 334 Hcllermark, C. (10) 84 Hellicr, P.C. (3) 166 Hellinga, H.W. (9) 266 Hellmann, J. (10) 355 Helm, L. (6) 75,77, 171 Helmakamp, M.M.(7) 602 Helmc, M. (7) 73 Helpcm, J.A. (12) 30 Hemcry, A. (10) 3 1 Hemery, P. (10) 358 Hcrningway, RW. (5) 396,397 Hemmingson, J.A. (7) 381 Hendan, B.J. (5) 170 Hendayma, S. (7) 739 Hcndcrson, C.M.B. (7) 566 Hcndcrson, W. (3) 326; (7) 258 Hcndra, P.J. (10) 285 Hengst, L. (9) 13 1 Hennel, F. (13) 48 Hennessy, 0. ( 12) 2 18 Hcnnig, L.(5) 388 Hennig, M. (5) 484; (9) 165, 169 Hcnrichs, P.M. (10) 284,313 Henrikscn, 0. (12) 252 Henry, M. (7) 436 Henry, P.F. (7) 146 Henry, R A . (7) 199; (10) 259 Hensmann, M.(9) 279 Henson, N.J. (7) 719 Henton, D.E. (10) 392 Hcnz, M. (3) 454 Hcpp, M.A. (2) 127; (3) 422; (7) 512; (10) 436; (13) 64 Hcras, J.V. (5) 72 Herbcrhold, C. (5) 327; (9) 43 Herbcrhold, M. (5) 87, 147, 158, 159; (7) 270,274 Heringa, K.D. (3) 420 Herkcr, M. (7) 271 Hcrlin, N. (7) 797 Herman, T. (10) 184 Humecz, I. (3) 498; (5) 132 Hernandez, G. (3) 70 Hernandez, M. (7) 389 Hernandcz-Coronado, M.J. (7) 389 Herold, R.H.M. (3) 199 Hcrr, T.E. (2) 93 Hcrrick, R.S. (1 1) 145 Hemnann, C. (9) 134 Hemnann, V. (13) 133

Hcrvh, M. (5) 3 19 Hcrzog, K. (6) 110; (7) 94,753,

206,207

755,757,768,769

Herzog, U. (3) 390; (5) 169 Heseltinc, T.H. (6) 25 Hespel, P. (12) 304 Hesse, M. (1 1) 70 Hessler, G. (5) 93,243,274 Hctherington, H.P. (12) 289,290 Hcucr, A.S. (10) 335,336 Heuert,U. (10)441; (13) 134 Heugel, S. (12) 164 Hew, H.A. (5) 349,467; (9) 101, 102, 105, 168; (1 1) 104 Hcwitt, R.C. (14) 17 Hcwlins, M.J.E. (12) 39 Hcyding, RD. (10) 268 Hcyes, S.J. (7) 103, 147,828 Heyong, H. (3) 332 Hibbs, D.E. (7) 193 Higgins, T.P. (12) 39 Higuchi, H. (3) 121 Higuchi, R. (3) 47 Higuchi, S. (7) 151 Hiluchi, K. (10) 329,368 Hilbcrs, C.W.(5) 349,474,480; (9) 87,88,92, 101, 102, 168, 237,295; (1 1) 104 Hileman, R.E. (5) 367 Hill, A.M. (3) 298,308 Hill, B.P. (6) 5 Hill, C.L. (3) 284,468 Hill, D.J.T. (10) 48, 170; (13) 101, 117 Hill, E.A. (3) 436 Hill, J.M. (5) 286,295 Hill, N.M.S. (1 1) 80 Hillcr, H.-H. (12) 173 Hiller, W. (7) 271; (10) 93 Hills, B.P. (13) 143 Hilmersson, G. (3) 21 1; (5) 102 Hiltuncn, K. (10) 115, 116 Hiltuncn, Y. (12) 322; (14) 125, 126 Himei, H. (7) 640 Himmelreich, U. (12) 90 Hinck, A.P. (5) 445,452; (9) 52, 53,278 Hindemann, D.K. (2) 45 Hindman, J.C. (2) 195 Hinds, M.G. (5) 264 Hines, J.V. (5) 361

506 Hincs, W.A. (3) 256 Hingerty, B.E. (9) 83,84 Hinkle, AS. (5) 44 Hino, A. (1 2) 93 Hinzc, G. (6) 105, 189 Hiraiwa, N. (3) 12 1 Hirama, M. (3) 60 Hirano, S. (7) 499 Hirano, Y. (7) 485 Hiraoki, T. (3) 417; (9) 3 11 Hiroaki, H. (5) 446 Hiroshige, M. (1 1) 136 Hirota, S. (5) 71 Hiroyarna, Y. (3) 342; (7) 788 Hirsch, 0. (7) 94 Hirschingcr, J. (7) 503 Hush, D. (9) 99 Hirsh, D.J. (7) 368 Hitchcock, P.B. (3) 262,263,300; (5) 175, 197 Hitchens, T.K. (6) 181 Hitotsuyanagi, Y. (3) 57 Hix, G.B. (7) 8 16 Hjiycj, L. (12) 213 Ho, C. (3) 493; (7) 337 Ho, J.-C. (10) 210 Ho, M.S. (14) 149 Ho, S.N. (9) 34 Ho, S.Y. (10) 213 Hoatson, G.L. (2) 129; (3) 13; (7) 21,22 Hobley, P. (1 1) 122 Hobson, S.T.(7) 446 Hochgraefe, M. (7) 598 Hockings, P.D.(13) 139 Hodeau, J.-L. (10) 71,301 Hodgc, C.N. (9) 149 Hodgcs, R.S. (5) 25 1,288; (7) 372 Hodgkmson, P. (6) 33 Hodor, P. (12) 49 Hodsdon, M.E. (9) 276 Hoecker, H. (10) 42 Hocfnagel, M.A. (3) 258 Hocgler, C. (7) 171, 180 Hoei, Y. (10) 106 Hoelgcr, C. (3) 89,94,43 1 Hoclter, D. (10) 27 Hocrr, D.C. (3) 214 Hoess, T. (12) 296 Hoevath,A. (10) 149 Hoffbauer, W. (7) 763 Hoffmann, M. ( 5 ) 243,274 Hoffmann, RW. (5) 402,485, 489; (1 1) 44 Hohann, M. (2) 120; (3) 330 Hogc, B. (3) 3 1 I ; (5) 228 Hoge, G.S. (7) 235

Nuclear Magnetic Resotiatice Hohmuth, A. (14) 95 Hoitnk, A. (7) 392 Holak, T.A. ( 5 ) 327; (9) 43-45,56, 218,292 Holdcron, S.( I 0) I99 Holder, S.J. (10) 131 Holderberg, A.W. (3) 310 Holdt, H.-J. ( 5 ) 86 Holccek, V. (5) 148 Holik, M. (3) 99 Holl, M.M.B. (7) 506 Holland, D. (7) 765 Holland, T.V. (10) 2 Hollestein, S. (1 1) 70 Hollingshurst, J. (10) 363 Holman, B.L. (12) 269 Holmes, A.B. (1 1) 64 Holmes, M.C. (14) 62,64 Holmes, R.R. (7) 204 Holst, 0. ( 5 ) 375,461 Holstein, P. (7) 66 (5) 149 Hollcamp, M.W. Holtman, D. (12) 1 15 Holub, J. (2) 115; (3) 340 Holy, A. (1 1) 109 Holz, M. (6) 15,45,46,49,93, 153 Holzman, T.F. (9) 12 Holmucller, P. (12) 192 Horn, K. (5) 258 Homans, S.W. (9) 50, 152, 155; (11) 114 Homcr, J. (6) 39 Hommcl, H. (7) 730 Hommcl, RK. (12) 90 Hommcl, U. (5) 271 Honda, K. (3) 243 Honek, J.F. (3) 496 Honcywell, J.D.(7) 233 Hong, E. (7) 5 10 Hong, I.K. (13) 5 1 Hong, J. (5) 344; (9) 24 Hong, M. (3) 279; (14) 26,32,33, 115, 118 Hong, S.B. (7) 823 Hong, T.-N.(5) 153,223 Honig, H. (3) 9 Hoogendoorn, A.M. (3) 199 Hoogcslegcr, F.J. (3) 101 Hoogstraten, C.G. (9) 242 Hook, J.M. (7) 5 11 Hopfl, H. (3) 333 Hopkins, T.L. (7) 343 Hopman, M.T.E. (12) 3 10 Hoppe, H. (9) 101 Horc, P.J. (6) 33 Horii, F. (10) 175,264,308,360,

385 Horn, H. (4) 11 Horn, M. (12) 164 Home, E. (7) 734 Homc, T.J. (8) 21 Homcmann, S.(9) 1-3 Hornstein, P. (12) 143 Hornyak, M. (6) 151 Horsfield, M.A. (6) 194 Horsman, A. (12) 263; (13) 169 Horstink, L.M. (9) 295 Horton, J.W. (12) 190 Horvath, T. (3) 202; (7) 7 12 Hoshino, Y. (7) 732 Hosokawa, T. (14) 15 1 Hosomi, N. (12) 132 Hossain, M.A. (12) 119 Hossain, M.B. (7) 203 Hossain, M.M. (3) 486 Hosscini, S.M. (2) 205,206 Hosur, M.V. (13) 9 Hosw, R.V. (13) 9 Hou, L. (13) 94 Hourqucbic, P. (10) 54 Houston, M.E.( 5 ) 25 1 Houtman, S. (12) 3 10 Hovnanian, N. (7) 433 Howard, A.E. (1 1) 46 Howard, K.P. (7) 367; (14) 102 Howard, M.J. (5) 3 15 HOW&, O.W. (3) 271-273; (5) 481; (10) 92; (11) 122 Howe, F.A. (12) 35 Howc, P.W.A. (9) 109,110 Howe, RF. (7) 5 11,628,634 Howell, D.K. (5) 97 Howell, E.E. (7) 358 Howcll, N. (1 3) 148 Howells, S.L. (12) 327 Howes, A.P. (7) 764 Howic, R A . (3) 401 Howlett, G.J. (5) 298 Howlin, B.J. (3) 23; (10) 391 Hoyc, T.R (3) 53; (10) 160 Hoyt, D.W. (9) 130 Hrabal, R. (8) 17 Hricovini, M. (7) 384 Hruska, F.E. (2) 170; (3) 93; (5) 59,502 Hsatani, K. (10) 74 Hsich, Y.-Y. (3) 354 Hsu, E.W. (12) 244; (13) 149, 168, 169 HSU,Ma-L.(7) 130 Hsu, V.L. (5) 345 Hu,C. (7) 55 I , 638,812,813 ’ Hu, H. (7) 63,64, 150

Author Index Hu, H.B. (13)46 Hu, J. (3)374;(7)63,64,13 I, 176 Hu, J.G. (7)293 Hu, J.H. (7)5 1 Hu, J.S. (5)486;(8)88;(9) 158-160 Hu, J.Z. (7)50, 191 Hu, K. (12) 164 Hu, S.(3) 306 Hu, S.W. (7)720 Hu, W.(7)402;(8) 86 Huai, N.A.(1 3) 46 Huang, B.H. (5) 335;(9) 7;(10) 162 Huang, F.-Y. (7)358 Huang, J.K. (9)293 Huang, R. (12)72,73 Huang, R-F.(5) 258 Huang, S.(5) 445,477 Huang, S.R.(9)278 Huang, T.-H. ( 5 ) 258;(7) 358,675 Huang, V.T. (13) 15 1 Huang, Y. (3)449;(9)293 Huang, Y.X. (7)428 Huang, 2.(7)139 Huang, Z.-E. (7) 149 Hubbard, S.F. (13) 163 Hubbard, T.J.P. (9)41 Huber, H. (3)463;(6) 18, 19,85, 94,95 Hubcr, J.G. (9)306 Hubcr, R (9)44 Huch, V. (3) 236,316;(7)262, 28 1,437 Iiuckstep, A.Y.(10)2 Hudalla, C. (7)501 Hudson, H.R. (5) 216 Hudson, K.J. (7)668 Hudson, M.J. (7)819,821 Hue, L.(12) 175 Huls, D.(5)29, 101;(6)61 Huerta, S.(7)389 Huffman, J.C. (3)418 Hughes, C.E.(6) 57;(13) 73 Hughes, D.W. (5) 40 Hughes, E.(7)78 1 Hughes, R (7)725 Hui, Z.(12) 18 Huis, L. (14)9 Hull, W.E. (12)223 Hulrne, C.(1 1) 47 Hult, A.(10) 84 Humbert, B. (7) 571 H u b e r t , F. (13)28,36,49 Humblot, F.(7) 244 Humpfer, E.(5)20;(7)40 Hunger, M. (3)202,241;(7)603,

507 Ikcda, Y. (7)545,705;(10)50 653,712 Hunt, S.A.(14)55,117 Ikegami, T.(8)78 Hunter, B.K. (10) 268 Ikemoto, N.(5) 470;(9)78,79 Huntcr,G.(10)442;(13) 141,163 Ikura, M.( 5 ) 337 Huntress, W.T. (6) 13 1 Ilyasov, A.(14)25 HUO,Q.-S. (7)591 Ilyina, E.(5) 294 Huo, S. (7)373 Lm,S.S. (10)100 Huo, S.Q.(3) 3 19 Imamura, T. (7) 15 1 Hursthouse, M.B. (7) 193 Imanari, M. (14)38-41 Husain, S.W. (7)819 Imanishi, T.(1 1) 35 Hush, N.S.(4)52,68-70;(5)55 Imashiro, F.(3)213;(7)830 Huskens, J. (3) 170,441;(6)173, lrnbardclli, D.(14) 157 175;(12)33 Imbcrty, A.(5) 377;(1 1) 135,143 Hussain, M.S.(1 1) 43 Improta, S.(9)203 Huss-D~~cII,K. (12) 105 Inaba, A.(7) 133 Hutchings, G.(7)725 Inaba, I. (7) 123 Hutchinson, R.A.(10) 104 Inabe, T. (7)222 Hutchison, D.(3)421 Inagaki, F. (8)48,55;(9)26 Hutchison, J.L. (10)3 17 Inagaki, S.(7)560,644 Hutchison, R.B.(12)159 Inaki, M.(12)302,303 Huth, J. (6)52 Infantes, L. (7) 198 Huttner, G.( 5 ) 185 Inglefield, P.T. (3) 5 17;(6) 148; Huve, L. (3) 501 (10)346,384 Hudnaga, S.(4) 10 Ingman, P. (3)521 Hwmg, C.-S. (3) 345;(7)754,770 Ingwall, J.S. (12)177-179 Hwmg, J.-H. (12)284,3 18 h i , T.(7)620 Hwang, K.-1. (5)289 Inokuti, M. (4)58 Hwang, T.L. (8) 7 Inomata, H. (2) 13,151 Hyde, E.I. (5) 3 10 Inoue, H.( 13) 4I Hydcr, F. (12)122,123 Inouc, M.(7)364 Hynie, S.(1 2)65 Inouc, T.(1 3) 59 Inouc, Y.(7)654;(12)93 Hyvoncn, M. (9)8 Inouye, H. (1 2) 292 Intcrrante, L.V. (7)447,791;(10) 158 Iannotti, D.A.(7)392 Iatrou, H. (10)219 Inubushi, T.(12) 197;(13) 178 Ibancz, A.F.(1 1) 38 lotti, S.(12)298,305 Ibbctt, R N .(10)92;(1 I) 122 Ippcl, J.H. ( 5 ) 349;(9) 168;(1 1) 104 Ibbott, G.S.(13)128 Ipscn, H. (5)342 Ibcrs, J.A. (3) 487;(5)202 Ibrom, W. ( 5 ) 68 Iribaran, 1. (7)213;(10) 114 Irie, T. (3) 134 Ibuki, K. (6) 160,161 Irvine, J.T.S.(7)263 Ichihara, S . 4 (12) 132 Ichimura, N.(5) 423 Irwin, A.E.(7)306 Isab, A.A.(3)323;( 5 ) 129 Ichinose, K. (3)261 Idioyatullin, D.S.(7)35 lsaka, H. (10)32 Iglesias, G.Y.M.(1 1) 38 Isayev, A.I.(10) 315 Iglesias, M.T. (10)65 Isbell, S.A.(13) 115 Isbester, P.K. (3)500;(10) 290 Ihrig, A.M. (4)43 Iida, H. (7)749,750 Isfort, 0.(6) 1 1 Iida, K. (3)60 Ishibashi, M.(3)55 Iida, M. (3)295;(6) 165 lshida, H. (3) 5 1 1 Ishida, N.(12) 101,103;(13) 157, Iijima, M. (10)47,94 159 Ikeda, K. (7) 116 Ishihama, A. (9) 286 Ikeda,R.(3)511;(14) 167 Ishihara, Y. (6)87 Ikeda, S.(14)167 Ishii, F. (10)265 Ikcda, T.(10)223

Nuclear Magnetic Resonance

508 Ishii, H. (13) 178 Ishii, T. (1 1) 77 Ishii, Y. (2) 141; (7) 75 Ishima, R. (9) 272 Ishimaru, A. (3) 50 Ishizuka, T. (12) 292 Ismail, I.M.K. (7) 454 Ismail, K. (7) 126 Isobc, T. (7) 430,431,516,554 Isracli, Y. (3) 159,260 Issa, B.(6) 156, 157; (13) 34, 85-87

Itai, Y. (12) 302,303 Ito, M. (LO) 416 Ito. T. (10) 269 Ito, Y. (9) 75 Itokawa, H. (3) 57 Itsubo, A. (10) 96 Ittel, S.D.(10) 276 Iuliucci, R.J. (3) 382; (7) 89 Ivancic, M. (5) 345 Ivanov, P.M. (3) 157; (1 1) 54 lvanova, E.P. (5) 374 Ivanova, 1.1. (7) 69 1,692,694,7 14 Ivcrscn, T. (7) 403 Iwahara, J. (9) 272 Iwai, H. (8) 91; (9) 192 Iwamiya, J.H. (13) 61 Iwaoka, M.(2) 171; (3) 90, 118; (5) 514

Iwashita, N.(7) 15 1 Iwata, C. (1 1) 35 Iwata, S. (3) 33; (12) 197 Iwaya-Inoue, M. (13) 159 lycr, P.S. (7) 6 11 Iyer, V.S. (3) 120 Izatt, R.M. (3) 166 Izmailova, V.N.(6) 137 Izquicrdo, M.(12) 102 Izumo, H.(3) 50 Jaballas, J. (2) 119; (3) 339,385 Jack, K.S. (10) 430 Jackman, L.M.(7) 203 Jacks, A.J. (5) 330 Jacob, A. (12) 98 Jacobi, M. (10) 349,356

Jacobs, P.A. (3) 344; (7) 633 Jacobs, P.D.(7) 127 Jacobsen, E.N. (7) 234; (1 1) 146 Jacobson, A. (9) 147 Jacobson, U. (10) 386 Jacobson, P. (7)137 Jacques, C. (12) 184 Jacquicr, V. (10) 194 Jacquot, J.-P. (5) 290,332

Jacgcr, A. (7) 245,247,449; (10) 29 1

Jaegcr, C. (2) 125; (3) 450; (6) 112; (7) 93,94,574,753,755, 757,768,769,780 Jaeger, S. (3) 478 Jacnchcn, J. (7) 647 Jacrovic, N. (7) 215 Jaffe, R.L. (6) 146; (10) 145 JaKcr, F.A. (12) 26 Jagannathan, N.R (12) 268 Jager, W.F.(10) 266,393 Jagcrovic, N.(1 1) 59 Jagodzirlska, E. (5) 78 Jagodzinski, T.S. (3) 83; (5) 209; ( I 1) 19,48 Jahnkc, W. (5) 240; (9) 290 Jaimc, C. (3) 141, 157; (11) 27 Jaime, W. (12) 91 Jaimcz, E. (7) 8 16 Jab, R.M. (5) 249 Jain, V. (12) 78 Jaklin, A. (3) 45 Jakob, K.H. (13) 133 Jakob, P.M. (13) 38 Jakobscn, H.J. (2) 123; (3) 247, 25 1,356; (7) 77 James, H. (10) 170 Jamcs, R. (5) 3 18 Jamcs, T.L. (12) 113 Jamcson, A.K. (2) 46,48,49,65, 68,153, 155,156,208,209 Jameson, C.J. (2) 46,48,49,54, 65,68,80,96,149, 150, 152-156, 161, 162,208-210; (3) 184 Jamin, N.(5) 300 Jana, C. (2) 125; (3) 450; (7) 514, 776 Janaik, C. (5) 124 Janck, M. (7) 558 Jankowiak, R (11) 113 Janoschek, R (3) 89,94,456; (7) 171 Janousek, Z. (3) 337 Jans, A.W.H. (13) 145 Jansen, B.A.J. (3) 101 Janscn, J.C. (10) 207 Janscn, M. (7) 524,530,763; (1 1) 3 Jansen, P. (10) 374; (12) 46 J~~scM J. ,(7) 152 Janssen, M.U. (3) 113 Janssen, RG. (1 1) 76 Janvicr, P. (7) 529 Janzcn, E.G.(5) 407 Janzen, M. (7) 777

Janzen, R A . (7) 473 Jardetzky, 0. (9) 245 Jardinc, W.G. (7) 410 Jariwala, C.P. (7) 420,421; (14) 78,79

Jaroniec, M.(7) 793 Jaroszcwski, J.W. (12) 1,70 Jarrell, H.C. (5) 459 Jarrct, R.M.(4) 38; (1 1) 145 Jarrctt, W.L.(7) 159; (10) 334 Jarvct, J. (5) 17; (6) 40; (8) 24 Jarvic, T.P. (7) 299,648 Jarvis, M.C. (7) 395,400,410 Jascja, M.(5) 3 10 Jasso, A.R. (10) 128 Jassri, H. (3) 386 Jaszunski, M. (2) 189 Jaumicr, P. (7) 250 Jayanthi, S. (10) 25 Jayaraj, A.F. (3) 371 J a p e s , I. (7) 425,546,547 Jaiwinski, J. (5) 116 Jcanncrat, D.(5) 38 Jcdlinski, 2. (10) 190 Jccner, J. (6) 26,27,64 Jeffrey, K.R (7) 824,825 Jehenson, P. (12) 307,309 Jchng, J.-M. (7) 685 Jeitncr, T.M. (12) 62,80 Jelenski, L.W. (13) 158 Jclics, L.A. (12) 154 Jelinek, T. (3) 340 Jelinski, L.W. (7) 17; (12) 100 Jcndcn, D.J. (12) 278,285 Jcnkins, B.G. (12) 124 Jcnkins, D.M. (7) 574 Jcnneskens, L.W. (3) 101 Jcnnings, H.J. (5) 459 Jennisscn, H.P. (7) 323 Jcnscn, A.W. (3) 514 Jenscn, H.J.Aa. (4) 7,8, 16,54,55 Jcon, Y.H. (9) 286 Jeon, Y.J. (10) 247 Jeong, L . 4 . (5) 504 Jeong, S.Y. (3) 235,250 Jeremic, D. (5) 70 Jcrmoumi, T. (7) 443 Jcrorne, D. (3) 18 1 Jerome, R (10) 76, 192, 195, 196 Jcschck, G. (3) 38 1 Jeske, G. (7) 201 Jesse, L. (12) 245 Jessel, T. (1 2) 23 Jessri, H. (2) 134; (7) 709 Jctton, R.E. (3) 14 Jho, J.Y. (10) 102 Jia, X. (5) 345

Author Index Jiang, F. (9) 118-121 Jiang, L.C. (9) 124 Jiang, S. (10)417 Jiang, Y.J. (3) 370 Jiang, Z. (10) 162 Jikihara, T. (7) 347,424; (14) 36 Jimenez, C. (7) 490 Jimdncz, J.A. (3) 103; (5) 3 JimCnez, J.L. (5) 403; (1 1) 129 Jimencz-Barbero, J. (1 1) 125, 144 Jimenez-Lopez, A. (7) 814 Jimenez-Vazquez, H.A. (3) 5 12, 513,515

Jimcno, M.-L. (3) 103; (5) 3; (1 1) 59

Jiminez Blanco, J.L. (1 1) 119, 120 Jin, J . 4 (10) 328 Jin, W. (3) 403 Jing, X.B. (10) 271 Jinno, K. (7) 141 Jinsart, W. (12) 57 Joghems, E.A. (14) 133 Johannesson, H. (14) 119, 120 Johansson, R. ( I 1) 117; (12) 281 John, J. (10) 206 John, R (10) 121 Johnels, D. (3) 232,399; (5) 230; (7) 137,528

Johnson, C.S., Jr. (6) 47, 192, 193 Johnson, G. ( 12) 2 1 Johnson, J.M. (9) 33 Johnson, L.K. (10) 276 Johnson, M.J.A. (2) 102; (3) 451; (7) 229

Johnson, M.O. (8) 16 Johnson, P.E. (5) 45 1 Johnson, RD. (2) 117 Johnsson, A. ( 12) 45 Johnston, B.K. (10) 215 Johnston, J.C. (10) 400,401 Johnston, S.T. (10) 3 15 Jokela, R. (1 1) 58 Jokisaari, J. (2) 130; (3) 384,521; (4) 1,59; (5) 112; (12) 273; (14) 121,124-127,131 Jolivet, J.P. (7) 570 Jonas, D.(1 3) 13 1 Jonas, J. (6) 42, 111,154, 155 Joncqk, A. (5) 269 Jones, A.A. (3) 517; (10) 384 Jones, A.D. (4) 78 Jones, A.P. (12) 9 Jones, B.E. (5) 200; (7) 260 Jones, C. (5) 372 Jones, C.R. (5) 508 Jones, D.H. (5) 46; (10) 2 Jones, D.L. (4) 45

509

Jones, D.N.M. (1 1) 8 Joncs, F.N. (10) 113 Jones, G.A. (7) 678 Jones, G.R. (5) 114 Joncs, J.A. (5) 39; (6) 33 Joncs, J.R. (3) 218; (10) 391 Jones, P.F. (7) 454 Jones, P.G. (3) 446,478,479; (5) 179, 194, 198,215,464; (7) 201,284 Jones, RA. (9) 80, 118, 120; (13) 176 Jones, R.C. (10) 13 1 Jones, R.P.O. (6) 200 Jong, S.-J. (7) 704 Jonse, A.A. (6) 148; (10) 346 Jonsen, P. (7) 7 Jonsson, B.H. (9) 56; (13) 88 Jonsson, P. (13) 17 Joosten, M.H.A.J. (5) 293 Jordan, L.R (12) 163 Jordan, P.A. (3) 348 Jorgenson, P. (2) 196 Joseph, R. (10) 388 Joseph-Nathan, P. (7) 168 Josephy, M. (13) 174 Joshi, M.D. (5) 45 I Joshi, P.N. (7) 582,666 Josien, H. (5) 250 Jossang, A. (5) 385; (1 I ) 40 Jossang, P. (5) 385; ( I 1) 40 Joule, J.A. (10) 146 Jourquin, J. (12) 210,211 Jousseaume, B. (5) 491; (7) 250 Jouvensal, L. (12) 17,3 11 Joy, RW. (12) 106 Joyce, D.C. (13) 139 Juang, C.L. (7) 296 Jucker, F.M. (5) 467; (9) 105 Judeinsteln, P. (10) 438 Jue, T. (12) 176,243 Juillard, J. (5) 390,419 Jukka,V.(IO) 115 Julio, R. (7) 8 16 Jumel, K. (9) 279 Jun, S. (7) 470 Jung, G. (5) 389 Jung, K.J. (6) 38 Jung, M.(I 1) 66 J u g , W.-I. (12) 16,22,293,296, 30 1 Jungk. S.J. (4) 85 Junius, F.K. (9) 37 JuraniC, N. (3) 107; (5) 127; (8) 27 Jurga, S. (7) 190 Jurkschat, K. (5) 144 Jurvet, J. (8) 4 1

Juza, M. (3) 150 Kabalka, G.W. (7) 153 Kabalov, Y.K. (7) 574 Kacmarck, L. (3) 117, 119; (5) 79 Kadkhdace, M. (12) 233 Kagcr, J. (6) 107, 190,215,219; (7) 716,717

Kaeriyama, K. (10) 150 Kafarski, P. (3) 75 Kahl, S.B. (5) 30 Kah~nann,J.D. (9) 27 Kahr, B. (7) 206 K h s , B.C. (5) 402,485; (1 1) 44 Kai, A. (7) 40 1 Kaib, M. (5) 386 Kaido, H.(10) 416 Kaikkonen, A.P. (6) 89 Kainosho, M. (2) 14 1; (3) 255; (7) 75

Kaiser, V. (7) 200,2 11 Kaji, H. (10) 175,264 Kakkar, A.K. (7) 237 Kalbitzcr, H.R (3) 192; (6) 69; (9) 49,134,219

Kalekar, S. (5) 373 Kalfat, R (7) 453; (10) 402 Kaliaguire, S. (7) 582,624,666 Kalidimo, C.G. (7) 288 Kalisch, B.W. (5) 360 Kallus, S. (7) 680 Kalurachchi, K. (9) 308 Kamachi, M. (3) 154 Kamada, K. (12) 125 Kamariotaki, M. (3) 3 15 Kambour, R.P. (10) 384 Kameda, T. (7) 289 Kamei, S. (12) 271 Kamenikova, L. ( 12) 65 Kamerling, J.P. (9) 153, 157 Kamiehski, B. (3) 423; (5) 77 Knmihira, M. (7) 325 Kaminsky, W. (10) 88 Kamitani, M. (7) 555 Kanamori,K. (12) 121 Kanamori, M. (12) 235,239,240 Kanazawa, Y. (12) 135 Kancko, H. (2) 5,6,9, 12; (3) 41, 43,44

Kaneoka, K. (1 1) 128 Kanetakis, J. (6) 104 Kang, B. (3) 269; (5) 141 Kang, H.S. (5) 36 1 Kang, S.J. (7) 448 Kmg, Y.-H. (12) 160 Kannan, S. (3) 507

Nuclear Magnetic Resotiatice

510 Kano, H. (12) 101,103; (13) 157, 159 Kano, T. (7) 377; (14) 37 Kanowski, M. (3) 245; (7) 145 Kao, H.-M. (7) 724 Kao, J. ( 5 ) 248 Kaplan, D.L. (10) 187,188 Kaplan, L.J. (12) 180 Kaplan, 0. (12) 1 Kapoor, M.P. (7) 624 Kappler, F. (12) 75 Kaprinidis, N. (3) 5 14 Kapsalaki, E. (12) 326 Kaptein, R. (3) 176; ( 5 ) 292,303, 309; (8) 42,49; (9) 90,91, 153, 156, 157, 196,220,226,274, 275,277 Karaghiosoff, K. (5) 180 Karagianis, G. ( 5 ) 298 Karaliota, A. (3) 3 15 Karasav, Yu.Z. (3) 7 Karch, E.E. ( 5 ) 233 Kardos, J. (9) 141 Karimi Nejad, Y. ( 5 ) 447; (9) 241, 282 Karkhaneei, E. (3) 162,234 Karle, C. (6) 13 Karlik, S.J. (12) 27 Karlsen, O.T. (12) 323 Karlsson, A. (3) 21 1; ( 5 ) 102 Karn, J. ( 5 ) 479; (9) 96,97, 112 Karnechev, A.S. (7) 16 Karra, V.R. (7) 660 Karson, C. (12) 258 Kashirn, R.K. (10) 77 Kashino, S. (3) 5 I 1 Kashiwagi, T. (10) 174 Kashiwaya, Y. (3) 442; (12) 3 1 Kaski, J. (4) 1; (5) 112; (14) 124 Kaslik, G. (9) 141 Kaspar, A. (13) 75 Kasper, D.L. (5) 459 Kasperczyk, J. (10) 120 Kassab, E. (2) 132, 134; (3) 386; (7) 709 Kastner, A. (6) 182 Kataoka, K. (10) 47,94, 117 Katch, E. (7) 333 Kathmann, E.E. (10) 138 Kato, K. (12) 51, 140 Kato, M. (10) 47,94 Katoh, A. (7) 218 Katritzky, A.R. (3) 86; (1 1) 18,87 Katsuta, S. (12) 303 Katti, S.B. (1 1) 60 Katz, J. (6) 38; (12) 34 KauCfmann, J.-M. (3) 407

Kauhan, J.D. (9) 52, 148, 149, 158, 188,189 Kaufinan, M.J. (12) 269 Kaupp, M. (2) 3,4, 11,21-23; (3) 31 Kauppincn, R. (12) 273,281,322 Kaushik, V.K. (10) 75 Kautcn, R.J. (12) 238; (13) 144 Kawabata, A. (10) 96 Kawahara, H. (14) 40 Kawai, F. (12) 235,239,240 Kawai, G. (1 1) 111 Kawai, H. (12) 93 Kawakami, Y. (7) 618 Kawasaki, N. (3) 51; (10) 191 Kawase, T. (3) 122 Kawashima, H. (7) 123, 133 Kawauchi, S. ( 5 ) 423 Kay, C.M. ( 5 ) 251,337 Kay, L.E. ( 5 ) 344; (8) 50,75,77, 81; (9) 24,25,68,71-73, 113, 185, 187,210,249,260,268, 289 Kayscr, F. (5) 16 Ke, Y.C. (10) 80 Kean, R.T. (10) 119 Kearns, D.R( 5 ) 345 Keates, J.M. (2) 138; (3) 265; (7) 60 Keelcr, J. (8) 3 1 Kcenc, M.T.J. (7) 821 Kehr, G. (2) 168; (3) 432; (5) 146, 222,510,512 Keifer, P.A. (7) 182, 183 Kcisala, J. (12) 273 Keiter, E.A. ( 5 ) 233 Keitcr, R.L. (5) 233 Keith, T.A. (2) 81-85; (3) 18 Keki, S. (10) 161 Keleman, S.R.(7) 119 Keller, W. (9) 6 Kelley, J.J. (9) 294 Kelley, RA. (12) 179 Kelley, RF. (5) 304 Kelley, S.S. ( 5 ) 397 Kelly, G.P.(8) 62 Kelly, M. (9) 75 Kelly, R.J. (1 1) 47 Keltner, J.R. (1 2) 274 Kemminli, J. (8) 80; (9) 36 Kemmler, M. (7) 245 Kempe, R.( 5 ) 74 (7) 503 Kempf, J.-Y. Kemp-Harper, R. (13) 73 Kempter, C. ( 5 ) 389 Keniry, M.A. (3) 177 Kenji, I. (10) 50

Kenmotsu, M. (3) 243 Kennedy, J.D. (2) 31; (3) 337,340 Kennedy, M.A. (7) 360; (9) 173 Kennedy, S. (1 2) 245 Kcnncdy, W.P.(9) I3 Kcntgcns, A.P.M. (7) I1 1,432 Kcnwright, A.M. (7) 10,192,400; (10) 202 Keon, C.A. (3) 442; (12) 3 1 Keppcler, B. (3) 297 Kera, Y. (3) 283 Kcreszturi, G. (3) 498; ( 5 ) 132 Kerkhof, P.J.A.M. (13) 114 Kerr, W.L. (13) 142,144 Kerssebaum, R ( 5 ) 105; (8) 58 Kerzina, Z.A. ( 5 ) 2 12 Keshavan, M.S. (12) 256 Keskinen, K. (7) 597 Kessler, H.(3) 4 12; ( 5 ) 243,262, 269,273,274,314,441; (7) 107 Kessler, J.M. (3) 445; (7) 225 Kestner, T.A. (3) 500 Kctchem, R.R. (7) 375,376,787 Kettani, A. (9) 80 Keul, H. (1 0) 42 Khaldi, M. (7) 818 Khalid, A. (3) 488 Khan, A. (7) 263 Khan, I.M. (7) 175 Khandpur, A.K. (10) 160 Khanhari, RK. (7) 291 Khasrou, L.N. (3) 483 Khatkevich, A.N. ( 12) 165 Khazaeli, S. (3) 248 Khetrapal, C.L. (2) 128; (7) 378; (14) 1, 3,4, 19,60,61, 128-130 Khodabaudeh, S. (7) 602 Khokhlova, L.P. (12) 99 Khong,A. (3)513,515 Khowmik, P.K. (10) 58 Khozina, E.V.(7) 35 IOda,N. (10)416 Kidena, K. (7) 124 Kiebooms, R (10) 169 Kierncr, T. (7) 275 Kiessling, L.L. ( 5 ) 455 Khara, K. (7) 566 Kihlbcrg, J. (3) 509 Kiihne, S. (7) 298 Kikuchi, K. (3) 255 Kikuchi, 0. (5) 104 Kikutani, T. (10) 184 Kilbum, D.G. (5) 45 1 Kilburn, J. (I 1) 57 Kilby, P.M. (9) 47 Kim, D. (10) 423

Author Index Kim, H. (5) 253 Kim, LK. (10) 100 Kim, J.-B. (7) 620 Kim, K. ( 5 ) 244 Kim, K.M. (10) 87 Kim, K.S. (1 1) 132 Kim, P.S. ( 5 ) 299 Kim, s. (12) 221 Kim, S.C. (5) 284 (10) 200,315 Kim, S.-H. Kim, S.-K. ( 5 ) 289 Kim, S.-M. (5) 289 Kim, S.S.(13) 122 Kim, S.Y.(10) 366 Kim, T.K. (10) 87 Kim, Y. (7) 557,572; (11) 115 Kim, Y.H. (7) 527 Kim, Y.S.(7) 385; (10) 216 Kim, Y.-W. (7) 556 Kimishima, T. (1 0) 168 Kim,W.H. (10) 46 Kimmich, R. (6) 22, 158, 188, 191; (10) 405,429; (13) 50,56,57, 82-84, 105, 124-126, 164, 165; (14) 31, 152, 162 Kimura, A. (7) 347,377,423,424; (14) 34-37 Kimura, H.(7) 335 Kimura, K. (7) 43 Kimura, M. (14) 40 Kimura, T. (1 3) 4 I Kinage, A.K. (7) 609,610 Kinart, C.M. (6) 135 Kinart, W.J. (6) 135 Kindler, N. (7) 530 King, G.C. (6) 34,202; (8) 37 King, G.F. (9) 37,238; (12) 52 King, M.T. (3) 442; (12) 3 1 King, N.J.C. (12) 52 King, W.A. (5) 52; (7) 256 King, X. (10) 226 Kinncy, A.B. (10) 19 Kinrade, S.D. (3) 416; (6) 102 Kinter,D. (12) 117 Knby, R.A. (7) 216 Kirchner, B. (6) 95 Kiricsi, I. (7) 635,8 17 Kirkpatrick, R J . (7) 540-542,557, 558,572,573; (10) 357 Kirpekar, S.(4) 55 Kirst, G.O. (12) 98 Kirszensztejn, P. (7) 722 Kishore, K. (10) 25,249,361 Kishore, R. ( 5 ) 246 Kiso, Y. (9) 148,188,189 Kist, H. (7) 500 Kitada, N. (12) 228

51 1 IOtagawa, I. (3) 54 Kitagawa, S. (3) 243; (7) 509 Kitamaru, R. (10) 261,385 Kitayama, T. (10) 6 Kitazawa, Y. (12) 140 Kitchin, S. (7) 189,566,726,764 Kitt,F.(12)316 Kiwata, R. (7) 210 Kjellbcrg, A. ( 5 ) 369 Kjclstad, B. (12) 45 Klabunde, K.J. (5) 95 Klaid, B. ( 5 ) 380 Klapoetke, T.M. (3) 438,506 Klaus, E. (5) 483; (7) 23 I, 264 Klaus, U. (3) 335; ( 5 ) 483,5 1 I , 5 13; (7) 264 Klaus, W. (5) 446 Klausmcycr, K.K. ( 5 ) 149 Klaus-Mrcstani, C. (5) 144 Kleanthous,C. (5) 3 18 Klei, B. (13) 137 Klein, A. (10) 378 Klein, B.K. (9) 283 Klcin, J. (3) 150 Klcin, R.S. (1 1) 108 Kleinberg, RL. (6) 101 Kleineidam, R.G.(9) 157 Klcinpeter, E. (5) 86 Kleinschmidt, A. (12) 29 1 Klemm, A. (13) 82 Klemm, L.H.(5) 64 Klemperer, W. (2) 44,52 K I ~ I c W ~ CJ.Z (3) , 429; ( 5 ) 80-82; (7) 22 1 Klinkait, T. (9) 112 Klinkcnbcrg, M. (10) 434; (13) 68, 138 Klinowski, J. (3) 332; (7) 135, 136, 154, 161, 162,564,583,587, 588,592,665,672,778,804 Kloegen, S. (1 1) 96 Klof, J.M. (10) 274 Klooster, W.T. ( 5 ) 54 Klop, C.J. (10) 218 Klostermann, K.(7) 200 Kliiner, RP. (6) 122 Klug, C.A. (7) 69,235,319,326, 356; (10) 297,299 Klumpp, G.W. (3) 388 Klunk, W.E. (12) 260 Klymachyov, A.N. (7) 33 Knaack, M. (5) 207 Knaub, S.R.(12) 58 Knauf, M.A. (5) 449 Knauss, R. (6) 215 Knevel, A.M. (3) 136 Knicker, H. (7) 120,390,463,467,

475 Knicp, R (3) 34 1 Knight, C.G.T. (3) 416 Knight, J.M. (12) 9 Knirel, Y.A. ( 5 ) 374 Knoch, F.A. (3) 228; (7) 275 Knoergen,M. (10)441; (13) 134 Knothe, G. (3) 195 Knott, V. (5) 3 13; (9) 28 Knowlcs, J.A. (7) 819,821 KO, RK. (13) 122 Kobayashi, J. (3) 5 1,55 Kobayashi, K. (3) 255; (5) 28 1 Kobayashi, M. (3) 54 Kobayashi, R (4) 16 Kobayashi, S. (12) 93 Kobe, J.M.(7) 713 Koch, M.(7) 71 I Koch, V.-P.(3) 392; (7) 806 Kochetkov, N.K. (5) 6 Kodweiss, J. (2) 109 Koebbemann, C. (7) 463 Kijck, M. ( 5 ) 105; (8) 58 Kocckcnbcrgcr, W. (1 2) 102; (1 3) 154 Koehler, F.H. (7) 242,271 Koehler, K.F. (5) 432 Koll, W. (5) 92 Kocnig, J.L. (10) 395; (13) 137; (14) 97 Koepf-Maier, P. (12) 229 Koepper, S.(1 1) 124 Koergel-Knabner, I. (7) 467 Kostcr, R. ( 5 ) 5 10 Koctzlc, T.F. (4) 74; ( 5 ) 54 Kohl, P. ( 5 ) 138 Koga, K. (3) 225 Kogclberg, H. (8) 92 Kohda, D. (9) 26 Kohn, S.C. (7) 562,566,777 Kohnke, F. (1 1) 83 Kohno, T. ( 5 ) 28 1 Koikc, Y. (7) 236 Koiko, Y. (7) 269 Koizumi, M. (12) 101, 103; (13) 157,159 Kojima, M. (12) 135 Kojima, S.(7) 328 Kojima, Y. (3) 255; (7) 430,43 1 Kokotailo, G.T. (7) 598 Kolbert, A.C. (7) 52,334; (10) 108 Kolehmainen, E. (3) 97,270,435; (5) 60,62,212,413 Kolf, S.(5) 164 Kok, M.H. (9) 102 Koll, A. (3) 87 Koller, H.(7) 656

Nuclear Magnetic Resoriarice

512 Kollman, P.A. (1 1) 2,46 Kollwitz, M. (2) 36 Kolocassides, K.G. (12) 166 Kolodziejski, W. (7) 59, 136 Kolp, B. (5) 440 Kolsaker, P. (7) 195 Kolstad, J.J. (10) 119 Kolthoff, C.E. (9) 152 Komadel, P. (7) 558 Komarek, J. (7) 596 Komatsu, H. (2) 171; (3) 90 Komatsu, M. (7) 790 Komatsu, T. (7) 630 Kominami, H. (3) 283 Komitov, L. (14) 158 Komolkin, A.V. (14) 143 Komor, E. (12) 102; (13) 154 Komori, M. (1 3) 4 1 Komori, T. (3) 47 Komoroski, RA. (12) 258 Komoto, T. (3) 430; (7) 205 Konak, C. (10) 341 Konakazawa, T. (10) 269 Kondo, M. (12) 203 Kondo, S.(3) 121 Kong, M. (12) 74,82 Kong, Y. (7) 784 Konings, R.N.H. (9) 92,237,277, 295

Konradov, A.A. (12) 116 Konrat, R. (5) 333; (8) 77; (9) 72, 29 1

Konstantinovic, S. (5) 410 Konzclman, J. (10) 22 Koole, L.H. (10) 127 Koon, C.L. (7) 725 Koons,J.M. (3) 517; (7) 1 Koostcr, W.T. (4) 74 Kooyman, P.J. (7) 629 Kopinga, K. (13) 108,114 Kopiske, C. (7) 277 Koppel, I. (3) 465,466 Koppenhafer, S.L.(12) 172 Kopplcr, D. (13) 38 Koprowski, M.(5) 82 Koradi, R (9) 22 1 Korai, Y. (7) 130 Korb, J.P. (6) 71, 155; (7) 305; (14) 141

Korchagina, E.(1 1) 143 Kordatos, K. (3) 239 Koretsky, A.P. (12) 84,208 Korobka, A. (9) 81,82 Korpar-colig, B.(5) 507

Koshlap, K.M. (9) 85,86 Kosikova, B. (7) 384 Koskela, T. (2) 130 Kosmella, S.(13) 136 Kossler, S. (3) 189 Kosslick, H. (3) 351; (7) 612 Kostellow, A.B. (13) 116 Kostyanovsky, G. (5) 432 Kotaka, T. (10) 373 Kothandaraman, H. (10) 39,40 Kothe, G. (14) 29 Kotila, S. (3) 3 10 Kotz, J. (13) 136 Koufaki, M. (7) 406 Koutcher, J.A. (12) 222 Kovac, P. (5) 456; (11) 138 Kovacs, K. (7) 623 Kovacs, 2.(6) 173 Kovari, L.C. (9) 6 Kover, K.E. (6) 151; (12) 145 Kowalewski, J. (4) 48,56,57; (6) 97,98, 149, 152; (1 1) 126

Kowalewski, V.J. (2) 203 Kowallik, P. (12) 173 Koyama, N. (10) 198 Koyama, S.(7) 785 Kozhovnikov, I.V. (7) 487 Kozlova, S.G.(3) 360 Koimihski, W. (3) 290,293; (5) 11-13, 115, 196,463; (8) 56, 57

Krafczyk, R. (5) 162 Kragclund, B.B. (5) 323 Krajcarski, D.(5) 378 Krajewski-Bertrand, M. (10) 344 Kraka, E. (2) 103 Kral, A. (3) 48 Kralik, L. (5) 14 Kralj, S.(14) 160 Kramer, K.J. (7) 343 Kraus, H. (7) 111,783 Krause, E. (3) 108 Krautler, B. (5) 333; (9) 29 1 Krawictz, K.T.R. (7) 698 Krcbs, J. (5) 484; (9) 165 Kreis, R (12) 279 Kremenovic, A. (7) 565 Kremer, F. (10) 318 Kremer, T. (3) 228 Kresinski, R.A. (5) 490; (1 1) 13 Kreuger, G. (12) 29 1 Kreutzer, U. (12) 243 Kricheldorf, H.R (10) 171, 190, 193,260,304,325,419,420

Kortobi,Y.E. (7) 797 Kosa, J.L. (9) 20

Krieger, C. (7) 164

Kose, K. (13) 45

Krishna, K.R (1 1) 33

Krill, J. (5) 464

Krishna, P.M. (1 1) 33 Krishnamoorthi, R (9) 293 Krishnamurthy,V.V. (5) 21; (8) 53,54,64

Kritzenbcrger, J. (14) 122 Krivdin, L.B. (4) 64; (5) 5, 107-1 11

Kriwacki, R W . (9) 131,132 Kriz, 0. (3) 238,352 Krizek, D.T. (1 3) 162 Kroakman, B. (7) 392 Krocker, S. (5) 36; (7) 108 Goes, S.J. (9) 300 Kron, T. (13) 131 Kroon, G.J.A. (8) 80 Krssak, M. (12) 192 Kruck, T. (3) 343 Kriiger, C. (5) 93; (7) 277 Krucgcr, K. (3) 446; (7) 200,20 I , 21 1,220,284,494

Kruft, M.-A.B. (10) 127 Krugh, T.R (5) 466 h e , S. (9) 157 Krushelnitskii, A.G. (7) 338; (9) 307

Krysciak, J. (7) 608 Ku, D.D.(13) 172 Kubacka, A. (7) 537,689 Kubas, G.J.(5) 52; (7) 256 Kubin, J. (12) 118 Kubinec, M.G. (3) 216; (9) 77 Kubo, A. (3) 213; (7) 830 Kubo, M. (7) 640 Kubono, A. (10) 184 Kuchel, P.W. (6) 133, 195; (12) 46,48,54; (13) 42

Kuchenbrod, E. (13) 152 Kuduk, S.D.(5) 391,392 Kuebler, S.C.(10) 335,336 Kiihnle, F.N.M. (5) 271 Kuemmcrlen, J. (7) 363 Kuesel, A.C. (12) 75,329 Kugelmass, S.D. (13) 179 Kuhn, W. (10)441; (13) 119, 134 Kukolich, S.G. (2) 53 Kulaev, 1. (12) 86 Kulik, AS. (10) 338 Kulovaara, M.(7) 478 Kumar, A. (7) 29; (1 1) 60 Kumar, A.T.A. (13) 91 Kumar, J. (1 0) 46 Kumar, M. (5) 124 Kumar, N. (7) 606 Kumar, RA. (5) 470; (9) 78,79, 118,119

Kumar, S.(7) 132; (8) 19; (13) 20 Kumaravel, G. (7) 184

Author Index Kumashuo, K.K. (7)498 Kumzerov, Yu.A. (3)353 Kunath-Fandrei, G.(7)94,574, 755,780 Kuncrt, 0.(9)23 Kung, H.C.(14) 12 Kuni, N.(7)347,423,424;(14) 34-36 KWO, S.-Y. (12)302 Kunoff, E.M. (6)62 Kuntsevich, A.D.(5)432 Kunwar, A.C.(14) 129,130 Kuo, E.L. (12) 121 Kupce, E. (8)8,67,68;(9) 175-179,181,182 Kupriyanov, V.V. (12) 157 Kurata, A. (7)364 Kurian, E. (3) 107 Kuribayashi, S.(12)135 Kurita, D.(1 2) 200 Kuroda, K. (7)785 Kuroda, Y.(3) 163 Kuroki, S.(7)289 Kurosu, H.(7)289;(10)283,339, 387 K w t z , J.W. (5) 455 Kusanagi, H.(3) 461;(6) 144 Kushlan, D.M. (9) 250 Kushmerick, M.J. (12)247 Kusnetscv, M.A. (3)369 Kustanovich, I. (5)307 Kusuoka, H.(12) 182 Kuszcwski, J. (5) 241;(9)13, 23 1-233 Kutosovsky, Y.E. (13) 95, 102 Kulscher, B. (5) 207 Kutubuddm, M. (1 0) 244 Kuwahara, D.(7)30 Kuwata, K. (12) 140 Kvicalova, M.(7)246 Kvickc, A. (7)668 Kwak, S.Y. (10)366 Kwan, S.(7)539 Kweon, J. (10)I10 Kwon, Y.-U. (7)527 Kydd, R.A. (7)578 Kyogoku, Y.(8)78;(9)285,286 Kytokivi, A. (7)491 Laaksoncn, A. (2)29;(4)48 Laali, K.K. (3)24 Laatikaincn, R.(14) 16 Laban, I. (3)326;(7)258 Labinger, J.A. (5)46 Labouriau, A.(7)556 Labrune, P.(12)309

513 Lacadena, J. (5) 339 Lacroix, P. (12)207 Ladonnc, F. (13) 160 Lafcr, B. ( 12)272 Lafonlainc, E.(7) 142, 143;(10) 255,390;(14)67,68 Lagicr, C.M. (3) 92,447;(7)226 Laguna, M. ( 5 ) 235 Lahajnar, G. (14) 160 Lahcini, M. (7)250 Lahcij, E.J. (13) 114 Lai, A. (6)92 Lai, J.C.K. (12)110 Lai, Y.-H. (4)76 Laihia, K. (5) 212,413 Laine,C.(11)58 Laine, RM.(7)444 Laing, W.A. (13) 167 Lakomaa, E.-L. (7)49 1,740 Lallcrnand, J.Y. (8) 10; (9)287 Lalowicz, Z.T. (7)534 Lam, P.Y.S. (9)52 Lam, S.L. (5) 353,354 Lamarc, V. (3)249 Lamartina, L. (3)102;(5) 84 Lambert, J. (5) 26 Lmbcrt, J.-F. (7)238 Lambcrt, R.K.(13) 107 Lambla, M. (10)280 Lamborg, C.M. (3)278 Lambrenghr, O.C. (13) 10 Lamers, P.H.(10)215 La Mesa, C. (6)210;(14) 49 Lammcrs, H.(3)258 La Monica, G.(5) 191 Lancelin, J.-M. (5)290,332 Lancelot, G. (9)298 Landeck, M.(13) 152 Lander, C.M. (12)62,80 Landcrsjo, C.(5) 368,371 Landfcstcr, K. (10)280,376 Landron, C.(7)744 Landsbcrg, B.M. (2)56 Landwehr, P.(12)308 Lane, A.N.(5)355;(9)302;(1 1) 103 Lanfranchi, M. (3)28 1 Lang, D.P. (7)112 Lang, E.W. (6)203 Lang, K. (6) 100 Lang, S.J. (7)495 Langedijk, J.P.M. (5) 292 Langcr, R.(1 3) 120 Langford, C.H.(7)477 Langlois, Y.(14)75 Langmann, V.(7) 763 Lankhorst, D. (6)83

LaNoue, K.F. (12) 144 Lansbwy, P.T. (7)82 Lam, R (5)26 1,262 Lanzetta, R (I 1) 134 Lanzi, M. (10)56 La Penna, G.(14)50,54 Lapidot, A. (1 2) 120 Lapous, D. (I 2) 66 Lappcrt, M.F. (3)263 Lark, P.D. (13) 139 LaRosa-Thompson, J. (7)539 Larossi, D.(10)56 Larsen, J.N. (5) 342 Larscn, R G . (7)334;(14) 122 Larscn, S. (5) 138 Larsson, P.T. (6)98 Lartigcs, B.S.(7)571 Lartigue, C.(10)367 Larue, V. (I 1) 29 Laskowski, R A . (9)220 Lasperas, M.(7)657 Laszlo, J.A.(7)3 15 Latypov, S.K. (3) 64,66 Lau, J. (3) 160 Lau, W.S. (9)200 Laubc, J. (3) 478 Laue, E.D. (5) 443;(9)40.75, 143 Law, T.M.(9)294 Laughlin, P.J.(10)202 Laukien, F.H.(7)42 Laupretre, F.(10)318,323,344 Laurent, Y.(7)505 Lauri, G.(5) 242 Lauricclla, R.(5)408 Lauricre, C.(12)66 Lauterwcin, J. (3) 105,276,457; ( 5 ) 31 Lavanchy,N. (12) 151,168 Lavandera, J.-L.(1 1) 59 Lavasseur, R (12)207 Laviellc, S.(5) 250 Lavinc, B.K. (7)739 Law, RV.(10)339,387,397 Lawless, G.A. (2) 138;(3)239, 262,263,265;(7)60 Lawrence, A.J. (6)71;(7)305 Lazar, K. (7)817 Lazdins, J. (9) I12 Lazeti, M. (3) 230 Lazzarctti, P. (2)58,86-88,90,91, 93,157,158,176-179,184 Lazzari, M.(10)21 Lazzaroni, R (3) 73,212 Le, H.(3)494 Leach, M.O. (12)24,216 Leahy, J.W. (3) 61 LcBars, E.(12) 129;(13)’177

5 14 Lebedev, Y.S. (6) 171 Le Bihan, D. (12) 266; (13) 80 Leblanc, R.(12) 32 1 LcBlond, N. (3) 289 Le Borgnc, A. (10) 85 Lebuis, A.M. (3) 23 1 Lechappe, J. (13) 160 Lecomte, J.T.J. (5) 325 Lecomte, S. (5) 6 1 h e , A.M. (2) 71 Lee, B.M. (9) 5 , 6 Lee, C. (2) 79, 134; (3) 386; (7) 709 Lec, C.E. (10)328 Lee, C.-G. (10) 229 Lce, C.H. (10) 328 Lee, D.C. (3) 216; (9) 77 Lec,D.H. (10) 102; (13) 122 Lee, F.S. (2) 191 Lce, G.H. (3) 350; (10) 240 Lee, H. (2) 119; (3) 339,385 Lcc, H.-J. (10) 110 Lcc, J. (9) 133 LW, J.-H. (10) 200 Lee,K. (1 1) 115 Lce,K.-B. (10) 110 LCC,K.-C. (7) 402 Lec, K . 4 . (7) 527 Lee, L.K. (8) 34; (9) 256 Lee, M.-H. (7) 778 Lee, M.-L. (5) 128 Lee, S. (6) 31 Lee, S.B. (3) 301 Lce,S.-G. (3) 259 Lce,S.J. (11) 132 Lee,S.-R. (10) 193 Lee, T.-Y. (7) 704 Lec, V. (5) 3 1 1; (9) 230; (1 1) 47 Lee,Y. (10) 216,247 Lee, Y.K. (7) 92 Leeflang, B.R. (9) 153 Lecining, P. (3) 86; (1 1) 18 Leenhecr, J.A. (7) 471 Lefeber, C. ( 5 ) 74 Lcfcbvrc, A. (5) 469 Lefebvre, F. (7) 24 1,243,244 Lefevre, J.F. (9) 244 Lefiant, S.(10) 252 Le Gal-Cdffet, M.-F. (5) 330 Legault, P. (8) 75; (9) 103, 104, 185 Leghrouz, A. (6) 168 Legoy, M.-D. (3) 49 Legrand, A.P. (7) 522,730,797, 822 Lcgros, F. (3) 407 Lc Gucmeve, C. (3) 197; (7) 4 14

Nuclear Magnetic Resona~ice Lehman, J. (7) 238 Lehmann,RG. (10) 212 Lchmann, S. (5) 182; (1 1) 97 Lehmann, V. (13) 160 Lchncrt, R.J. (10) 285 Lehtincn, C. (10) 109 Leibfritz, D. (8) 52; (12) 6,98 Leigh, J.S. (6) 59 Ledon, M. (6) 73; (8) 29 Lcipoldt, J.G. ( 5 ) 218 Leipzig, K. (10) 347 Leisen, J. (10) 335 Leissner, J. (7) 75 1 Leister, W.H. (3) 214 k i t e , C.A.P. (7) 452 Lciting, B. ( 5 ) 326,334; (9) 16 Lcjczak, B. (3) 75 Lemaitrc, J. (7) 522 Lemaster, D.M. (9) 250 Lemcn, L. (13) 77 Lemcslc, M. (12) 276 LeMoyec,L.(12)81 Lcn, 2. (5) 120 Lcndi, K. (6) 124, 126 Lcnk, R. (12) 3,217 Lcnnon, A.J. (6) 195 Lenz, R.W. (10) 58, 155 Lco,G.C. (5) 268 Lcon, G. (7) 607 Lconard, A. (7) 408 Leonard, S. (12) 270 Lepoittcvin, J.-P. (1 1) 127 Lcporini, D. (6) 103 Lcrchc, M.H. (5) 323 Led, A. (7) 154 Lcrner, D.A. (3) 146 Lcmcr, L. (6) 72 Le Rolland, B. (7) 538 Leroux, J.P. (12) 307 Lc Rumcur, E. ( I 2) 207 Lcsagc, A. ( 5 ) 239 Lcscot, E. ( 5 ) 469,475 Lcshcheva, I.F. (5) 143 Lcsiak, K. (1 1) 123 LeSOt, P.(3) 76; (14) 71-73,76 Le Tallec, N. (12) 207 Leumann, C. (1 1) 107 b u g , P.-H. (3) 80 Leupin, W. (9) 147 Lcuhcr, M. ( 5 ) 262 Levantc, T.O.(14) 27 Lcvason, W. (3) 296,298,307, 308,411,480; (7) 285 Levin, J.M. (12) 269 Levin,V.Y. (10)315 Levitt, M.H. (7) 92,297; (14) 23, 30

Levy,L.A. (12) 161 Levy, P. (12) 129; (13) 177 Lcwa, C.J. (12) 202 Lcwandowski, E.D. (12) 146 Lewis, J.E. (7) 602 Lewis, J.R ( 5 ) 2 10 Lcwis, L.M. (9) 2 1 Lcwis, M.H. (7) 764 Lewis, R. (7) 791 Lewis,R.H. (14) 93 Lcwis, R J . ( 5 ) 282 Leyte, J.C. (6) 83, 164 Li, B. (5) 395; (7) 287 Li, C.-W. (12) 328-331; (13) 44 Li, D. (5) 120; (7) 799,800 Li, F. (14) 107, 108 Li, G.-Y. (7) 70 Li, G.Z. (14) 107, 108 Li, H. (3) 314; (7) 585,589,590, 638; (8) 67; (12) 53,230 Li, H.J. (9) 63, 181 Li, H.X. (7) 584,619,632,651 Li, J. (3) 412; (10) 271 Li, K.-B. (3) 3 Li,L.(7)50,51,63,64,115,131, 150, 176, 191,543; (10) 28, 36-38 Li, L.-Y. (10) 437; (12) 128; (13) 93,123 Li, M.-D. (3) 350 Li, M.X. ( 5 ) 322; (9) 29 Li, Q. (5) 409; (7) 8 12 Li, R (7) 327,674; (10) 148 Li, S. (5) 98; (7) 314,673,674 Li, S.M. (10) 118 Li, T.Q. (13) 90, 100 Li, W. (5) 248 Li, X. ( 5 ) 2 14; (7) 784,798 Li, X.S. (7) 579 Li, Y. (7) 25.68; (12) 232 Li, Z. ( 5 ) 120; (7) 234; (1 1) 78, 146 Li, Z.G. (9) 269 Lian, L.Y. ( 5 ) 318; (9) 136-139; (1 1) 139 Liang, G. (2) 113; (4) 35 Liang, H. (9) 9-12 Liang, M. (10) 321 Liang, S. (3) 369 Liao, D. (3) 269 Liao, D.I. (5) 453; (9) 55 Liao, F.-L. (5) 223 Liao, M.Y. (3) 391; (7) 807 Liao, Y.-D. (5) 258 Liboska, R (1 1) 109 Lichtenhan, J.D. (7) 454 Lic, Y.-Y. (7) 812

A irrhor Index Licpinsh, E. (9) 147, 150, 151,214 Liepold, A. (7) 58 1 Lightfoot, P. (7) 233,668 Li Hsu, Y.F. (4) 4 1,42 Likhodii, S.S.(12) 312 Likholobov, V.A. (7) 278 LikiC, V.A. ( 5 ) 127 Lilla, G. (3) 222 Lilly, G.J. (14) 74 Lim, A.R. (3) 235,250 Lim, H.-M. (2) 208-210 Limbach, H.-H. (3) 88,89,94, 124,221,431; ( 5 ) 83; (7) 163, 171, 180, 198,208,212; (12) 141 Lime, M.J. (13) 161, 162 Lin, C.-C. (3) 354; (5) 153 Lin, C.H. (9) 127 Lin, H.J. (3) 354 Lin, J. (3) 152 Lin, J.-L. (7) 770 Lin, L.Z. (3) 179 Lin, s.-L. (3) 345 (7) 358 Lin, T.-H. Lin, W. (3) 173; (12) 53 Lin, W.-Y. (7) 591 Lin, X. (7) 521 Lin, 2. (3) 275; (7) 614,615,676 Lindblom, G. (3) 187 Lindblom, L. ( 5 ) 216 Linden, A. (3) 290,293; ( 5 ) 115, 196 Lindfers, L.-E. (7) 606 Lindgrcn, T. (7) 403; (10) 8 1 Lindhardt, R.J.(1 1) 130 Lindner, E. (3) 297; (7) 245,247, 449; (10) 291 Lindon,J.C. ( 6 ) 4 ; ( l l ) 116;(14) 170 Lindsay, G. (12) 307 Lindybcrg, S.E. ( I 1) 145 Liney, G.P. (12) 263 Lingren, T.A. (10) 1 19 Linhardt, R.J. (5) 367 Lintuluoto, J.M. (3) 163 Lious-Joseph, A. (8) 10 Lipari, G. (6) I 16, 1 17 Liping, W. (7) 63 1 Lipkowitz, K.B. (3) 74 Lippens, G. ( 5 ) 458; (6) 27 Lippert, B. (3) 3 18; (5) 482 Lipton, A S . (2) 131; (3) 317; (7) 279,360 Lis, T. (3) 109 Litt, L. (12) 113 Litten, C.J. (1 1) 107 Litvak, G.S. (7) 486

515 Litvinov, V.M. (10) I6 Liu, A.H. (7) 255 Liu, C. (7) 728 Liu, C.C. (3) 395; (7) 727 Liu, F. (2) 122, 145; (3) 375-377 Liu, H.(3) 279; (12) 155 Liu, H.W. (7) 140; (10) 377 Liu, I.-C. (3) 354 Liu, J. (7) 743; (10) 422 Liu, J.H. (9) 293 Liu, J.J. (14) 83 Liu, J.-T. (7) 140 Liu, K.-T. (3) 104 Liu, L. (5) 220 Liu, M. (6) 4 Liu, P. (7) 621 Liu, Q. (3) 269; (5) 409; (7) 447 Liu, S. (3) 332; (7) 564,583,585 Liu, S.-B. (7) 140,704 Liu, S.H. (10) 377 Liu, W. (7) 593,721 Liu, X.N. (10) 244 Liu, Y. (7) 813 Liu, Y.C. (12) 188 Liu, Y.H. (3) 3 19 Liu, Z. (7) 616 Livage, J. (7) 436 Livant, P. (1 1) 65 Livc, D. (9) 117, I19 Lix, B. ( 5 ) 25 1; (8) 32 Lizak, M.J. (7) 20; (12) 13 Llaguno, E.C. (7) 471 Llamas-Saiz, A.L. (7) 163 Llauro, M.-F. (10) 95, 194 Llauro-Darricades, M.F.(10) 107 Lobbia, G.G. (3) 410 Lobo, L.S. (7) 637 Lobo, R.F. (7) 602 Lochert, I.J. (4) 67; (1 1) 4 Locke, J.A.M. (10) 131 LockcU, C.J. (12) 194-196 Lockhart, J.C. (1 1) 80 Lockley, W.J.S. (3) 218 Lockycr, M.W.G. (7) 765 Locuyer, C. (7) 241 Mi, R. (12) 298,305 Lodovico, L. (1 1) 16 Loefgrcn, B. (10) 105,109 Liihr, F. (5) 436,437,449; (1 1) 7 Locns, J. (7) 576 Liiw, R. (5) 234,484 Liiwendahl, M.(3) 21 1; ( 5 ) 102 h e m k i n , A. (3) 68; (14) 70-73 Loewcnslein, H. (5) 342 Loftus, P. (4) 77 Logan, M. (7) 5 1 1 Logan,T.M. (8) 19

Lohmeier-Vogel, E.M. (1 2) 89 Lohof, E. (5) 243 Lohr, F. (8) 51,76; (9) 162, 163, 184,186,240 Loiscau, T. (7) 679 Lomakin, S. (10) 174 Lomas, J.S. (3) 100 London, R.E. (7) 290; (9) 310; (12) 161 Long, G.J. (7) 272 Long, H.W.(14) 93,122 Long, J.R. (7) 533 Long, R.C. (12) 209 Long, X. (7) 585 Longcri, M. (14) 24,56,57, 169, 170,173 Longo, A. (10) 164 Longo, P. (1 0) 64, 10 1, I 11,23 1 Lookman, R. (7) 468 LopaLa, R.(7) 722 b p e z , C. (3) 103; (5) 3; (7) 163 Lopez, D. (10) 23 Lopez, P. (7) 202 Lopcz-Carrasqucro, F. (10) 185 Lop~~L-Casko, A. (1 I ) 120 Mpcz de la Paz, M. (3) 114; (5) 366 Mpcz-Ortiz, F.(3) 28 1; ( 5 ) 492, 5 05 Lorek, A. (12) 288 Lorenz, P. (13) 11 1 Lortcl, S.(12) 142 Lou, B. ( I 1) 136 Loubinoux, 1. (12) 126 Lou& A.J. (4) 74; (5) 54 Louis, H.A. (9) 20 Lounasmaa, M. ( I 1) 58 Lounila, J. (3) 384; (14) 121, 127 Louris, J.N. ( 5 ) 64 Lovschall, J. (14) 69 Low, D.G. (9) 155 Lowc, D.A. (3) 499; (5) 130 Lowc, M.P. (3) 355; (5) 229 Lowe, R.(9) 165 Low,M. (12) 263 Loy, D.A. (3) 396; (10) 250 Lu, G. (5) 141 Lu, G.Q. (7) 579 Lu, H.(9) 202 Lu, J. (3) 269 Lu, L. (7) 150; (14) 3 , 4 Lu, N. (2) 61 Lu,Q.(3)512,514;(5)481 Lu, S.Y. (10) 391 Lu, X. (10) 241 Lu, X.J. (5) 310 Lu, Y.-J. (3) 282

Niiclear Magnetic Resonance

516

Luan, Z. (3) 332; (7) 583 Luaricclla, R. (1 1) 55 Luca, G.D. (14) 169,17 1,173 Lucas, C. ( 5 ) 491 Lucas, R. (5) 452; (9) 53 Lucastro, G. ( 5 ) 302 Lucchcsc, Y. ( 5 ) 232 Lucchini, V. (3) 140 Luchinat, C. ( 5 ) 3 17,444; (6) 10, 96; (9) 246,300 Lucht, B.L. (3) 223,227 Luck, L.A. (7) 290; (9) 310 Luckhurst, G.R. (14) 53 Luders, K. (7) 145 Ludwig, R. (6) 17, 20,21, 84,86, 91,162 Ludcmann, H.-D. (6) 9,203,208, 209; (7) 390,463,475 Lucdcrs, K. (3) 245 Lucning, U. (1 I) 75 Lueschcr, K. (13) 25,27 Lucssc, s. (10) 347 Luff, S.H. (6) 145 Luginbuhl, P. (5) 301; (9) 144, 145,222,223 Lugtenburg, J. (7) 73,350 Luhmer, M. (2) 21 1; (7) 730 Lui, C.Y. (4) 36 Lui, F. (6) 187 Lui, W. (3) 5 13 Lukaschck, M. (14) 104 Luk'yanchuk, 1. (7) 138 Lumctti, M. (14) 169 Lumsdcn, M.D. (2) 60; (7) 177 Lun, F. (7) 63 1 Lunazzi, L. (5) 498; (7) 158; (1 1) 100

Lunberg, P. (12) 105 Lundquist, P.-0. (12) 105 Luncva, N. (9) 84 Lungu,A. (10) 266,393 Lunsford, J.H. (5) 94 Luo, E. (7) 638 Luo, H. (10) 103 Luo, L. (3) 149 Luo, L.B. (3) 127 Luo, N. (10) 172 Luo, S. (7) 255 Luo, X. ( 5 ) 336; (8) 74 LUO,X.-L. ( 5 ) 52; (7) 256 Luporini, P. (5) 301 Lupsc, c. (12) 49 Luri, D.J. (12) 14 Luslbadcr, J. (9) 152 Lustcnbcrgcr, P. (3) 290 Luster, J. (7) 476 Lutz, F. ( 5 ) 93

Lutz, N.W. ( 5 ) 22 1 Lutz, 0. (2) 109; (12) 16,301, 324,325 Luu-duc, P. (4) 46 Luxon, B.A. (9) 297 Luy, B. (8) 47 Luypacrt, R. (6) 20 1 Luylcn, I. ( 5 ) 356 Luyz, 0. (12) 296 Luz, Z. (5) 66; (7) 76, 164,339; (14) 66,86,87,90,91, 142 Luzar, M. (14) 122,172 Luzgin, M.V. (7) 700,708 Lyazghi, R (5) 4 19 LyEka, A. ( 5 ) 148; (10) 354 Lynch, S.R. (5) 2 1 1 Lyndcn-Bell, R.M. (4) 30 Lyng, H. (12) 220 Lysak, E.1. (12) 38 tysck, R (3) 435; ( 5 ) 62 Lyvcr, R. (3) 256 Lzz0,L. (10) 101 Ma, J.F. (3) 22; (13) 37, 170 Ma, L. ( 5 ) 220 Ma, W. (10) 220 Ma, Z.R. (13) 93 Maan, J.C. (6) 176 Maas, L.C. (12) 274 Maas, W.E. (6) 24; (7) 42 Mabic, S. (1 1) 127 Mabillc, C. (10) 3 1 McAlistcr, M.S.B. (9) 129 McAlpinc, S.R (3) 144 MacArthur, M.W. (9) 21 1,220 Macartney, D.H. (3) 165 McAteer, K. (7) 360 McBride, B.W. (12) 242 McBride, D.(12) 278 McCallam, S.J. (12) 14 McCamlcy, A. (10) 248 McCarthy, J.J. (7) 472 McCarthy, M.J. (13) 142, 144 McCarhy, S.P. (10) 186,220,246 (12) 18 McCartney, W.C. McClain, M.D. (10) 250 McClure, J. (9) 6 McClure, R.J. (12) 256,260 McClure, S.G. (7) 466 McConncll, H.M. (2) 18I McCOMCII,P. (5) 328 McCord, E.F. (10) 104,276 McCormick, J.E. (3) 492 McCoy, M. (1 1) 57 McDcrmott, A. (7) 308,309,355; (9) 243

McDonagh, T. (5) 344; (9) 24 Macdonald, J.B. (2) 26 MacDonald, J.G. (10) 305 Macdonald, P.M. (3) 210,252, 443; (7) 336,658 McDonald, R ( 5 ) 186 McDonncll, P.A. ( 5 ) 268 McDowcli, C.A. ( 5 ) 150; (7) 49 McDowcll, J.A. ( 5 ) 471 McDowell, L.M. (7) 319,326,341, 359 Macedo, A. (6) 78 McEvoy, M.M. (9) 25 McFaddcn, G.B. (7) 9 McFaddin, D.C.(10) 268 MacFall, J.S. (13) 140 McFarland, E.W.(10) 404; (13) 72,127 MacFarlane, D.R (7) 53 1,532; (10) 300,333 McFarlane, H.C.E. (2) 25 McFarlane, W. (2) 25,3 1; (3) 80 McGcary, RP. (1 1) 64 McGeorge, G. (7) 181,226; (10) 28 1 McGhce, B.J. (7) 725 McGill, W.B. (7) 473,474 McGraw, G.W. (5) 396 Machacck, J. (3) 352 Machida, I. (7) 130 Machizuki, H. (7) 499 Macho, V. (7) 422; (14) 80 Machovic, V. (7) 117 Macias, M.J. (9) 8,235 Maciel, G.E. (3) 395; (7) 455,456, 727,782,791; (10) 235,236, 282; (12) 104 McInncs, C. (9) 130 McIntosh, L.P. (5) 266,451; (8) 50; (9) 187 McIntyre, D.D. (10) 234; (12) 89, 106 McIntyre, J.S. (4) 34 Mack, H.-G. (3) 508 Mackay, M. (3) 199 McKcc, V. ( 5 ) 48 1 MacKenzic, K.J.D. (7) 427,548, 550,802,803,805 MacKenzic, K.R (5) 487; (9) 38, 39 McKinnell, D. ( 5 ) 121 McKinnon, D.M. ( 5 ) 501; (1 1) 101 McKnight, A.L. (10) 133,224 McKnight, C.J. ( 5 ) 299 McLain, S.J. (10) 276 McLay, N. (14) 74 Maclean, C. (14) 5,9, 1 1'

517

Author Index MacLeod, P.J. ( 5 ) 404; (1 1) 86 McLoughlin, K. (10) 409 McMillan, P.F. (7) 744 Macosko, C.W. (10) 160 McPartlin, M. ( 5 ) 235; (7) 261 McPhail, A.T. ( 5 ) 13I Macquaire, F. (14) 113 Macquet, J. (7) 444 Macura, S. (3) 107; (5) 127; (8) 27 McVay, R. (2) 47 McWherter, C.A. (9) 283 Madaio, A. (3) 62 Madden, L.V. (7) 392 Maddinelli, G. (13) 97, 110 Madejova, J. (7) 558 Madcr, K.(I 3) 120 Mader, W. (7) 763 Madhu, P.K. (7) 29 Maeda, H. (12) 282 Maeda, M. (3) 428 Maeda, T. (5) 28 1 Mackawa, M. (3) 283 Maeler, L. (1 1) 126 Maemets, V. (3) 465,466 Maennle, F. (7) 208 Maerker, C. (1 1) 22 Maglio, G. (10) 78 Magnuson, M.L. (7) 38; (14) 85, 155,156 Magnusson, G. (1 1) I 17 Magnusson, I. (12) 3 17 Magusin, P.C.M.M. (7) 54; (10) 25 8 Mahaffy, C.A.L. (3) 14 Maharajh, R.B. (2) 202; (5) 205 Mahi, L. ( 5 ) 37 Mahicu, B. (3) 407 Mahler, A. (10) 171 Mahmood, U. (1 2) 222 Mahon, M.F. (3) 476,485 Maigret, B. (7) 503 Maillct, D. (13) 101 Mainyama, Y. (7) 222 Mair, R.W. (13) 103 Mairesse, G. (7) 772 Maisel, H.E. ( 5 ) 146; (7) 92 Majors, A.W. (1 1) 65 Majors, P. (13) 91 Mak, T.C.W. (3) 127 Makarkina, A.V. (14) 15 Makkar, H.P.S. (7) 388 Maklakov, A.I. (6) 158 Makriyannis, A. (7) 365,406; (1 1) 31 Maksimovskaya, R.I. (7) 486 Mal, T.K. (9) 70 Malagoli, M. (2) 86-88,90,93,

177,178 Malarski, 2. (3) 109, 110 Malcolm, R.K. (10) 33,141,157 Malek, A. (3) 252; (7) 658; (12) 245 Maler, L. (6) 152 Malet, R. (5) 420 Maley, W.E. (7) 368 Malfrcyt, P. (5) 4 19 Malhotra, M. (1 0) 181 Malicr, L. (6) 155; (7) 142, 143; (14) 141 Malik, K.M.A. (7) 193 Maliniak, A. (14) 88,89,143 Malito, J. ( 5 ) 8 Malivcrncy, C. ( 5 ) 424 Malkiewicz, A. (1 1) I10 Malkin, V.G. (2) 3,4, 10, 11,20, 21,23,24,72, 101; (3) 34,463, 5 10; (4) 49,50,53; (5) 204; (6) 85 Malkina, O.L. (2) 3,4, 10, 1 1,20, 21,23,24,72, 101; (3) 34,463, 510; (4)49,50,53; (5) 204; (6) 85 Mallet, R.T. (12) 160 Mallett, M.J.D. (13) 29,3 1 Malley, M.F. (9) 57 Malli, G. (2) 110 Malliavin, T.E. (3) 8 Mallick, K.K. (7) 492 Mallouk, T.E. (7) 174 Malloy, C.R. (12) 8, 190,212 Malmusi, L. (3) 13 1; ( 5 ) 405; (1 1) 42 Maltby, P.A. (4) 74; ( 5 ) 54 Maltha, A.M. (7) 500 Malveau, C. (7) 84 Malyshev, I.Y. (12) 165 Mammi, S. ( 5 ) 276 Man, P.P. (7) 435 Mancini, S.(6) 103 Mancuso, A. (12) 131 Mandal, A.B. (10) 314 Mandcl, A.M. (9) 261 Mandelkern, L. (7) 159; (10) 334 Mandelson, J.H. (12) 269 Manevich, Y. (12) 221 Manharan, B. (3) 475; ( 5 ) 75 Manimekalai, A. (I 1) 32 Maniwa, Y. (3) 255 Manneschi, L. (12) 50 Mannila, E. (3) 48 Manoj, M.K. (1 I) 95 Manolova, N. (10) 1 18 Manor, D. (1 2) 123 Manque, R. (7) 607

Mansfield, P. (6) 156, 157; (13) 34,40,85-87, 169 Manton, D.J. (12) 263 Miinttiiri, P. ( 5 ) 413 Mantz, R.A. (7) 454 Manz, B. (10) 426 Mao, B. (9) 83 Mao, H.Y. (9) 113 Mao, S.Z. (6) 142; (13) 121 Mao, X. (6) 46; (7) 520 Mao, X.-A. (6) 29,30; (1 1) 150; (12) 128 Mapelli, C. ( 5 ) 3 11; (9) 230 Maquet, J. (7) 442; (10) 289 Marat, K. (3) 416; ( 5 ) 126,376; (6) 102 Maraviglia, B. (6) 54 Maracuev, Y.A. (14) 163 Marbach, W. (6) 206 Marban, E. (12) 182 Marchand, R (7) 505 Marchand-Brynaert, J. (10) 25 1 Marchessault, R.H. (10) 303 Marchetti, F. (3) 410 Marcian, L. (1 3) 171 Mardon, H.J. (9) 288 Marck, R. (5) 14 Marck, T. (7) 276 Marg, B. (3) 285 Mariani, M. (9) 226,282 Marichal, C. (7) 503 Marignan, J. (7) 443 Marinas, J.M. (7) 490 Marinelli, L. (6) 54 Marinez, LA. (10) 114 Marinid, 2. (5) 380 Marino, J.P. (5) 350,35 1; (8) 20; (9) 166, 167 Marinov, R. (7) 404; (14) 105 Marion, D. ( 5 ) 332 Marked, J.T. (7) 809 Markgrabcr, D. (7) 8 1 1 Marklcy, J.L. (5) 352; (6) 121; (9) 141,204,242;(11) 12 Markov, V.Yu. (3) 504 Markovid, Z. ( 5 ) 410 Marks, D. (7) 58 Markus, M.A. ( 5 ) 445; (9) 32,278 Markwell, R.D. (5) 177; (7) 232 Marler, B. (7) 598,643,680 Maroto-Valer, M.M. (7) 121, 125 Maroun, R G . (5) 475 Marques, L. (10) 7 1 Marquez, V.E. ( 5 ) 504 Marrades, R M . (12) 306 Marriott, T. (3) 5 13 Marrs, D.J. ( 5 ) 48 1

Nuclear Magnetic Resonance

518 Marsac, C. (1 2) 307 Marsan, M.P. (7)329; (14) 48 Marschmcycr, S. (7) 627 Marsden, P.K. (12) 25; (13) 22 Marshall, I. (12) 265 Marshall, W.J. (3) 322; ( 5 ) 151, 162 Marsmann, H.C. ( 5 ) 170 Martello, L.B.(12) 238 Martcns, J.A. (3) 344; (7) 633 Martin, A. ( 5 ) 73,378 Martin, D. (12) 276 Martin, F. (7) 390,475 Martin, G.G. (3) 204,206,208, 209 Martin, G.J. (3) 203,204,206,209 Martin, J.R. (9) 282 Martin, M.A. (3) 146 Martin, M.L. (3) 203,205 Martin, M.-T. ( 5 ) 383 Martin, P.T. (3) 278 Martin, Y.-L. (3) 203,204,206, 208 Martindalc, J.A. (3) 246 Martinc, H. (12) 91 Martinck, J. (12) 65 Martinez, A. (3) 59; (7) 626 Martinez, A.T. (7) 387 Martinez, G. (10) 177, 178 Martinez dc Ilarduya, A. ( 5 ) 422; (7) 213; (10) 185; (1 1) 49 Martincz dcl POLO, A. ( 5 ) 339 Martinez-Richa, A. (7) 168 Martin-Lomas, M. (1 1) 144 Martinoni, B. ( 5 ) 271 Martin-Pastor, M. (1 1) 125, 144 Martins, J.C. (3) 415; ( 5 ) 16, 144, 145; (7) 257; (10) 97 Martins, M.A.P. (3) 98 Martirosian, E.R. (3) 7 Marucci, G. ( 5 ) 405 Maruhashi, Y. (1 0) 269 Maruyama, T. ( 5 ) 433 Marvin, J.R. (3) 304; ( 5 ) 238 Maryanoff, B.E. ( 5 ) 268 Marynaski, M.J. (13) 128 Marzilli, L.G. (5) 71 Masaya, K. (12) 132 Mascavage, L. (1 1) 57 Mascians, J.R. (12) 30( Masciocchi, N. ( 5 ) 191 Mashima, K. (5) 199 Mashimo, S.(6) 127 Mashimo, T. (6) 136 Mason, G.F. (12) 110, 22, 123, 289,290 Mason, J. (2) 46, 142

Mason, R.P. (3) 497; (12) 174,226 Mason, S.S.(2) 131; (3) 317; (7) 279,828 Masood, M.A. (10) 224 Masoud, H. ( 5 ) 378 Maspcro, A. ( 5 ) 19 1 Masscy,J. (10) 315 Masscy, V. (3) 495 Massiah, M.A. (9) 19 Massiot, D. (3) 356; (7) 102,425, 505,529,538,546,547,744 Massol, M. (1 2) 2 13 Masson, P. (10) 107 Mastlkhln, V.M. (3) 520; (7) 596 Masuda, H. (10) 150 Masuda, K. (10) 175,264; (12) 135 Masurc, M. (10) 31 Mataka, S. (1 1) 71 Matasyoh, J.C. ( 5 ) 407 Matchcttc, M.A. (3) 248 Mateer, D.L. (14) 63 Matecscu, G.D. (4) 35 Matei, C. (12) 222 Matci, H. ( 1 2) 49 Matcnaar, U. (6) 43 Matha, B. (5) 273 Mathernc, G.P. (12) 183 Matheron, C. (1 2) 40,4 1 Mathias, L.J. (7) 159; (10) 287, 334 Mathicu, Y. (12) 66 Mathur, P. (3) 474-476,485,486; ( 5 ) 75 Mathur, S. (3) 3 16; (7) 262,28 1 Malkovic-calogovic, D. (5) 507 Matlengicwicz, M. (10) 129 Matoka, D.J. (2) 114 Matsaru, S. (10) 106 Matsubara, K. (3) 134; ( I 0) 166, 245 Matsuda, H. (2) 15 1 Matsuda, T. (13) 4 1 Matsudaira, P.T. ( 5 ) 299; (9) 32 Matsui, S.(13) 59 Matsukawa, S. (6) 216; (10) 425 Matsumon, N. (5) 433,434 Matsumoto, A. (10) 360 Matsumoto, H. (12) 119 Matsumoto, K. ( 5 ) 203 Matsumoto, T. (10) 360 Matsumura, K. (6) 144 Matsunaga, T. (12) 109 Matsunami, J. (5) 203 Matsuo, E. (13) 159 Matsuo, H. (8) 67,68,79; (9) 63, 64, 181, 182,285; (12) 132

Matsushima, S. (12) 282 Matsushita, K. (12) 5 1 Matsuzawa, S. (10) 106 Mattcr, H. (5) 380 Mattern, R.-H. (5) 280 Matthaci, D. (13) 130 Matthews, R.C. ( 5 ) 97 Mattincn, J. ( 5 ) 208 Mattson, RH. (12) 253 Matubayashi, N. (6) 16 Matulova, M. (3) 280 Matyska, M.T. (7) 141,742 Maudslcy, A.A. ( I 2) 131,264; (13)40 Maufict, 0. (5) 469,475 Maurcr, M. (8) 46 Maurer, T. (3) 192; ( 5 ) 264 Mauritz, K.A. (7) 429 Maus, D.C. (7) 255 Mavromoustakos, T. (7) 406 May, F.E.B. ( 5 ) 442; (9) 5 1 Mayaffrc, H. (3) 181 Mayer, A. (12) 98 Maycr, H.A. (3) 297; (7) 245,247 Maycr, I. (4) 71 Maycr, M.R. ( 5 ) 325 Maycr, P.T. (7) 327 Mayer, R. ( 5 ) 48 Maycr, U. (9) 44,45 Mayerhoff, D.J. (12) 136 Mayhew, S.G. ( 5 ) 449 Maync, C.L. (6) 186, 187; (10) 205; (1 4) 68 Mayo, K.H. ( 5 ) 294; (9) 271; (1 1) 130 Mays, J.W. (10) 427 Mayzcl, 0. (3) 161, 169; (6) 140 Mazarguil, H. (14) 10 1 Mazhar-ul-Haquc, (1 1) 43 Mazid, M.A. (7) 261 Mazikov, R.K. (6) 93 Mazitov, R. (6) 90 Mazucco, R.A. (12) 327; (13) 139 Mazza, S. (10) 111 Mazzanti, A. ( 5 ) 498; (1 1) 16 Mazzola, E.P. (5) 496 Mcador, M.A.B. (10) 400,401 Meadors, K. (13) 22 Meadows, R P . ( 5 ) 335; (9) 7,9, 11, 12, 142 Mcakin, P. (10) 300 Mealli, C. ( 5 ) 50, 5 1 Meccrrcyes, D. (1 0) 192 Meddour, A. (3) 68; (14) 70,73, 75 Mcdsker, RE. (10) 2 Mcdycki, W. (7) 188

AufhorIndex Mcchan, A.J. (12) 84 Mccrsmann, T. (6) 5 1 Mccrson, F.Z. (12) 165 Mehring, M. (3) 244,380; (7) 144, 523; (10) 71 Mchta, M.A. (7) 298 Mci, Z. (10) 435 Meiboom, S. (14) 17 Meik, Z. (2) 169; (3) 84,85; ( 5 ) 58,99 Meier, B.H. ( 5 ) 34; (6) 64; (7) 78, 89,90,363 Meier, E.J.M. (3) 290 Mcier, G. (12) 77 Mciering, E.M. (9) 33 Mcijs, G.F. (10) 24,246 Mcillc, S.V.(10) 34 Meinhold, R.H. (7) 427,548,634, 802 Mciningcr, M. (13) 38 Meinnel, T. ( 5 ) 338 Mcissncr, A. (5) 20,27; (7) 40; (8) 43 Mcl, Z. (13) 69 Meldal, M. ( 5 ) 460 Mcle, A. ( 5 ) 509 Meli, A. ( 5 ) 5 1 Melvin, B.K. (12) 83 Mclvin, L.S. (1 1) 3 1 Melvin, O.A. (3) 401 Mcrngcr, W. (7) 167 Men, A.J. (7) 632 Mena, M. (5) 73 Mendcz, B. (10) 233 Mcndonca-Prcviato, L. ( 5 ) 372 Mcndoza-Dim, G. (7) 168 Mendz, G.L. (12) 47 Mencndez, J.C. (3) 146 Menez, A. (5) 300 Mcnezes, S.M.C. (10) 29,83 Meng, Y. ( 5 ) 98 Mengcr, F.M. (3) 198 Menicagli, R. (3) 73 Merbach, A.E. (3) 462; (6) 74-77, 167,170, 171 Mcrboldt, K.-D. (12) 261,291 Merckx, R. (7) 468 Mcric, P. (12) 126 Merida-Robles, J.M. (7) 814 Merkle, H. (1 2) 148 Merle, M.H. (3) 363 Merlet, D. (3) 76; (14) 71-73,76 Memng, M. (10) 30 1 Memtt, M.E. (7) 343 Mertel, L. (13) 171 Menvin, L.H.(7) 199; (10) 259, 3 72

519

Mcschcr, M. (8) IG Mcshkov, S.V. ( 5 ) 374 Mesilaakso, M. (5) 494 Mcssala-Rannanpiho,M. ( 5 ) 413 Messcrlc, B.A. ( 5 ) 19 Mcssner, W. (2) 109 Mestcrs, C.M.A.M. (7) 701 Mctcalf, R. (6) 168 Metcalfc, J.C. (12) 158 Mctiu, H.1. (7) 719 Mctoui, F.Z. (7) 8 I8 Metz, G. (7) 44,295 Mctz, K.R. (3) 190 Mctzgcr, J.W. ( 5 ) 389 Metzger, P. (3) 46 Mctzlcr, A. (12) 102 Metzler, W.J. ( 5 ) 334; (9) 57,74 Meunicr, S. (5) 312 MCUI~CC, J.-C. (3) 4 14 Mcusingcr, J. (7) 627 Mcusingcr, R. (5) 416; (12) 90 Mcycr, A.J. (3) 151; (1 1) 82 Mcycr,B.(lI) 124 Mcycr, R.A. (12) 208 Meycrs, C.A. (5) 3 11; (9) 230 Mcyers, R.L. (12) 115 Mczzina, E. (3) 102; ( 5 ) 84 Michacl, M. (10) 92 Michaclis, T. (12) 261 Michal, C.A. (7) 17 Michcl, D. (7) 13 Michicls, P. (9) 104 Michnicka, M. (9) 308 Micura, R. (3) 77 Midland, M.M. ( 5 ) 397 Mielcarck, J. (3) 133 Mielke, C.H. (12) 25 Mierke, D.F. ( 5 ) 247,276 Miessner, H. (3) 351; (7) 612 Mihalyi, RM. (7) 645 Mqangos, c. (lo) 23 Mijs, W.J. (10) 207 Mikashita, N. (7) 349 Mkhailov, D. (1 1) 130 Mikhailov, V.I. (6) 89 Mikhaleva, 1.1. ( 5 ) 279 Mikhin, N.P. (6) 177 Mikhova, B.P. (3) 361; (1 1) 54 Mikkclscn, K.V. (2) 196, 197 Miknis, F.P. (7) 122, 127 Mikolajczyk, M. (3) 72 Mikros, E. ( 5 ) 435; (1 1) 53 Milant, P. (7) 162 Mildncr, T. (7) 690,7 16 Mildvan, A.S. (9) 59, GO Milewska, M.J. (4) 81; (1 1) 98 Milius, W. (3) 335; (5) 117, 146,

147, 155, 159,483; (7) 219, 264,270 Millan, J. (10) 177 Millar, G.J. (7) 579 Millar, J.M. (5) 45 Millard, M.M. (13) 161,162 Millcr, B.L. (12) 278 Miller, D.O. (1 1) 78 Millcr, 1. (13) 43 Millcr, J.B. (2) 207; (10) 436; (13) 64 Millcr, J.L. (1 1) 2 Millcr, J.M. (3) 491 Miller, R K . (12) 245 Millcr, S.C. (9) 204 Millcr, T. (12) 42 Millcr, T.L. (7) 361 Millet, J.-M. (7) 697 Millhauscr, G.L.( 5 ) 252 Milligan, L.P. (12) 242 Millili, G.P. (7) 386 Mills, J.E. ( 5 ) 382 Milnc, J. (3) 477 Milon, A. (3) 45; (7) 329; (14) 48, 101 Milonc, L. (3) 191 Milton, M.J. (1 I ) 114 Mima, H. (3) 47 1 Mimouni, M. (5) 390 Minami, T. (7) 773 Minchenko, V.A. (5) 109 Ming, W. (10) 241 Mingozzi, I. (10) 227 Mingyang, J. (7) 63 1 Minn, A.J. (9) 10, 11 Minoja, A.P. (7) 66 Minshew, N.J. (12) 256 Mintas, M. ( 5 ) 69 Mioc, U.B. (7) 565 Miola, C. (10) 194 Miranda, P.M.C. (12) 35 Miranker, A.D. (9) 198,215 Mirau, P.A. (10) 5,379 Mirmira, S.R( 5 ) 468 Miron, E. (6) 180 Mironov, Y.V. (3) 487 Mishra, O.P. (12) 118 Mishra, P.K. (14) 7,8, 10 Misiura, K. (3) 473 Misono, M. (7) 485 Mitch, W.E. (12) 209 Mitchell, D.J. (7) 298 Mitchcll, J.B.O. ( 5 ) 267 Mitchell, M.B. ( 5 ) 7 1 Milchcll, R.H. (3) 120 Mitchell, T.N.(5) 192 Mifjavila, S. (12) 213

520 Mitrakos, P. (3) 210 Mitroma, Y. (1 1) 7 1 Mitschang, L. (8) 85 Mitsuji, K. (1 1) 128 Mittard, V. ( 5 ) 332 Mitzcl, J.M. (7) 127 Mitzel, N.W. (5) 225 Miura, K. (2) 151 Miyajima, S. (7) 222; (14) 151 Miyakc, Y.(3) 255 Miyaniob, A. (7) 640 Miyamoto, T. (3) 47 Miyashita, K. (1 1) 35 Miyazaki, Y. (3) 328 Miyoshi, K. (3) 277 Miyoshi, T. (10) 329,368 Mizogami, M. (12) 206 Mizuno, K. ( 5 ) 203; (6) 138 Mizuno, T. (12) 203 Mizutani, J. (3) 65 Mo, H. (6) 2 18 Mo, H.P. (6) 3 Mo, Z. (7) 115 Modi, S. (9) 136-139 Modro, A.M. (3) 459 Modro, T.A. (3) 459 Mochlc, K. (5)4 16 Moellcr, C. (7) 419 Mocllcr, K.D. (5) 248 Mocshauscr, R.C. (8) 45 Moffat, J.B. (7) 484,696 Moghimi, A. (3) 125; (7) 826 Mohamcd, B. (12) 184 Mohan, V.K. (10) 249 Mohanazadch, F. (3) 172 Mohn, K.R. (2) 109 Moia, F. (14) 131 Moinc, G. (12) 3 12 Mokrosz, J.L. (1 1) 15 Molcro, J.A. (7) 617 Molinski, T.F. (3) 6 1 Molko, D. (6) 67 Molla, E. ( 5 ) I 17; (7) 219 Mollcr, K. (7) 662 Molnar, Z. ( 5 ) 463 Moloncy, M.G. ( 5 ) 224 Molyneaux, D.A. (13) 23 Momany, G. (9) 6 Momasaki, S. (3) 50 Momcteau, M. (7) 288 Momozono, Y. (12) 135 Moncrieffe, M. (3) 107 Mondal, M.I.P. (7) 40 1 Mondello, M. (6) 132 Monduzzi, M. (14) 106 Monctti, M. (7) 300 Mongc, A. ( 5 ) 72

Nuclear Magnetic Resonaiice Monic, S.A. (7) 786 Monkman, A.P. (10) 146,202 Monks, S.A. ( 5 ) 298 Monncric, L. (10) 318,323 Monnct, C. (10) 194 Mons, H.-E. ( 5 ) 29; (6) 61 Monsan, P.F. ( 5 ) 370 Montagnc, L. (7) 772 Montal, M.(7) 357 Montciro, J.F.L.(7) 626 Montclionc, G.T.(8) 69,72,73 Montez, B. (3) 494 Montheard, J.-P. (10) 182, 183 Monti, D. (13) 129 Monti, G. (3) 447 Montics, J.R. (12) 169 Montoro, M.A. (3) 482 Moobeny, E.A. (4) 86 Moody, C.M. (3) 492; ( 5 ) 272 Mooibrwk, S.(2) 26 Moon, C.H. (7) 470,5 10 Moonen, C.T.W. (13) 39 Moorc, C.D.( 5 ) 325 Moore, C.M. (12) 274 Moorc, D.P. (12) 198 Moorc, E.A. (3) 505; (7) 5 19; (10) 326 Moorc, G.R. (3) 348; (5) 3 18 Moore, J.A. (1 1) 94 Moore, P.B. (5) 476 Moorc, RB. (7) 429 Moore, S.J. ( 5 ) 71 Mooren, M.M.W. (5) 474; (9) 87 Moors, E.H.M. ( 5 ) 467; (9) 105 Mor, M. (3) 142 Morccllct, M. (7) 736 Morcau, M. (9) 287 More;tu,N.J. ( 5 ) 61 Morein, F.G.(7) 439 Moreno-Maiias, M. (3) 372; ( 5 ) 420 Morct, M. ( 5 ) 191 Morgan, C.J.(9) 215 Morgan, G.G. ( 5 ) 48 1 Morgan, K.R. (7) 330 Morgan, W.D. (9) 194, 195 Mori, H. (7) 210 Mori, K. (3) 55 Mori, T. (10) 96 Mori, W. (5) 199 Morihashi, K. ( 5 ) 104 Morikawa, S.(12) 197; (13) 178 Monkis, D. (9) 2 17 Morimoto, H. (3) 216-221; (9) 77 Morimoto, M. (3) 283 Morin, F.G. (7) 379 Morin, P.E. ( 5 ) 33 1; (9) 48

Morini, C.C. (12) 205 Morini, G. (10) 227 Morisaki, M. (3) 364 Morisato, A. (10) 38 1 Morishima, I. (2) 14 Moricy, C.P. (5) 201 Morokuma, K. (2) 102; (3) 451; (7) 229 Moromoto, H. (7) 212 Moroz, B.L. (7) 278 Momlla, G.A. (13) 116 Moms, G.A. (6) 200; (8) 21 Moms, J.R (7) 465 Moms, K.F.(6) 192 Moms, L.C. (5) 373 Moms, R.E. (7) 668 Moms, RH. (4) 74; ( 5 ) 54,56 Momson, W.H. (7) 362 Mortaignc, B. (10) 255,390 Mortimcr, M. (3) 505; (7) 5 19; (10) 326 Morton, C.J. (9) 26,27 Morton, M.D. (12) 5 8 Morvai, M. ( 5 ) 43 1 Mosca, M. ( 5 ) 277 Moscr, E. (1 2) 192 Mosimann, L.L. ( 5 ) 233 Mosingcr, E. ( 5 ) 448; (9) 15 Moskau, D. ( 5 ) 27; (8) 43 Motctt, I. (12) 175 Motevalli, M. (3) 230; (7) 272 Mothes, D. (12) 186 Moto, T. (6) 87 Motooka, K. (13) 159 Motoyama, I. (7) 236 Mott, H.R (8) 85; (9) 129 MOU,C.-Y. (7) 140 Moudrakovski, I.L.(2) 146; (3) 5 19; (7) 278,659,660 Mougerel, J.C. (7) 643 Moulis, J.M. (9) 306 Mountford, C.E. (12) 62,80 Moura, I. (6) 78 Moura, J.J.G. (6) 78 Mourits, F. (2) 198 Mousley, D.P. (1 1) 80 Moussa,I. (3) 363 Moussavi, M. (6) 100 Mowery, M.R (8) 30 Moxon, E.R. (5) 378 Moy, F.J. ( 5 ) 450 Moyano, J.R.(3) 142 Mucci, A. (3) 131, 132; ( 5 ) 405; (10) 56; (1 1) 42 Muchmore, S.W. (9) 9, 10 Muegge, C. (3) 108 Muehlstadt, M. ( 5 ) 416

Author Index Muelhaupt, R. (10) 35, 89 Miiller, A. ( 5 ) 207; (7) 76 Mucller, A.H.E. (3) 21 Mueller, A.J. (10) 233 Mucller, H.S.P. (2) 213 Mueller, J.L.(3) 373 Miiller, K. ( 5 ) 66; (7) 164; (14) 142 Miiller, K.J. (6) 90 Mueller, K.T. (7) 648 Muellcr, L. (5) 3 11,334; (9) 57, 74,106-108,230 Muellcr, M. (10) 3 18 Muellcr, W.T. (5) 328 Mueller-Warmuth, W. (7) 152, 569,575,756,758,774 Miinchcnberg, J. ( 5 ) 194 Mucntcr, J.S. (2) 44,52 Muggc, C. (13) 111 Muhandiram, D.R. (8) 75; (9) 25, 113,185 Muhid, M. (7) 592 Muhlhahn, P. (9) 292 Mujceb, A. (1 1) 50 Mukoyama, Y. (1 1) 77 Mukuno, K. (1 1) 89 Muldcr, C.W.R. (6) 164 Mulder, F.A.A. (8) 42; (9) 196, 282 Mulkcrn, RV. (12) 115 Mullan, N.N. (1 1) 5 1 Mullcr, D. (3) 34 1 Mullcr, H.J. (13) 174 Muller, H.P. (13) 82-84, 105 Muller, 1. (7) 329; (14) 48 Muller, R. (1 3) 1 19 Muller, T. (8) 85 Mulquiney, P.J. (12) 54 Munaon, E.J. (10) 290 Mundus, C. (3) 413; (7) 535,569, 575,774 Munoz, M.E. (10) 23 Munoz Botclla, S. (3) 146 Munoz-Guerra, S. ( 5 ) 422; (7) 213; (10) 114, 185; (1 1) 49 Munoz-Paez, A. (7) 544 Munson, E.J. (3) 500; (7) 291; (10) 119 Murakami, M. (10) 132 Murakami, Y.(12) 181 Murata, M. ( 5 ) 433,434 Murata, S . (7) 116, 124 Muratani, T. (7) 116 Murphy, E. (12) 153, 161,167 Mwhy-Bmsch, J. (12) 328-330; (13) 44 Murray, B.A. (3) 168

52 1 Murray, D.R. (7) 702 Murray, R.K., Jr. (3) 369 Murta Vallc, M.L. (7) 663 Murthy, K.S. (10) 249 Murthy,N.S. (10)317 (1 1) 13 1 Murthy, P.P.N. Murthy, Y.V.S.N. (3) 495 Murugavl, R. (3) 387 Murzin, A.G. ( 5 ) 443; (9) 40,4 1 Mwzina, N.V. ( 5 ) 443; (9) 40 Musacv, D.G. (2) 102; (3) 45 I; (7) 229 Muscvic, I. (14) I 60 Musio, R. (4) 75 Muskett, F.W. (8) 62 Mussct, E. (7) 797 Musso, H. (4) 83 Muto, Y. (1 1) 1 1 1 Mutter, M. ( 5 ) 278 Mutzcnhardt, P. (6) 55,56, 123 Muzzalupo, R (14) 49,94,112 Myers, L.C.(9) 263 Myers, S.M.(2) 131; (3) 317; (7) 279 Nabirahni, M.A. (I 1) 68 Nachtcgaal, G. (7) 747 Nachtigal, C. (3) 48 1 Nadin, A. (1 1) 64 Nafpliotis, L.(1 0) 232 Nagai, H. (7) 798 Nagai, K. (9) 109, 1 10 Nagamoto, Y. (12) 127 Nagana Gowda, G.A. (14) 3,4 Nagaoka, K. (7) 364 Nagaoka, S. (12) 140 Nagapudi, K. (10) 307 Nagasaki, Y. (10) 47,94 Nagasawa, A. (3) 277 Nagase, S. (3) 255,389; ( 5 ) 134 Nagashima, F. (3) 50 Nagata, T. (12) 109 Nagayama, K. (9) 272 Nagcl, J. (9) 275 Nagy, J.B.(7) 623,635,706 Nahijima, M. (3) 57 Nair, V. (1 1) 62 Nairn, K.M. (7) 53 1,532 Naito, A. (7)43,294,325; (14) 38-41 Najcra, C. (3) 8 1 Nakagawa, T. (3) 364 Nakahara, M. (6) 16, 134 Nakai, T. (7) 30 Nakaic, C.R. (5) 285 Nakajima, N. (10) 366

Nakajima, T. (2) 8,9, 17; (3) 41 Nakamoto, S.(12) 170 Nakamura, A. (5) 199 Nakamura, G.K. (9) 123 Nakano, M.(10) 156 Nakano, T. (7) 555 Nakaoki, T. (10) 26 1 Nakata, Y. (7) 798 Nakatani, H. (14) 38 Nakatani, Y. (7) 329 Nakalo, T. (10) 166,245 Naliatsuji, H. (2) 5-9, 12, 17-19; (3) 4 1-44 Nakayama, A. (10) 19 1 Nakazawa, H. (3) 277 Nakazawa, T. ( 5 ) 23 Namboothiri, I.N.N. ( 5 ) 495 Nanny, J.R. (3) 14 Nan& D. (3) 292; ( 5 ) 11-13, 115, 178,463; (8) 56,57; (14) 26 Napierala, M.E.(10) 142 Narita, K. (3) 158 Narita, T. (10) 50 Narula, S.P. ( 5 ) 124 Narumi, J. (2) 15 I Nascimbcn, L. (12) 177 Nash, I.A. (1 1) 47 Nasrallah, H.A. (12) 257 Natan, M.J. (7) 286 Natansohn, A. (10) 370,430 Nalarajan, D. ( 5 ) 4 1 1; ( I 1) 39 Natclc, N.R. (1 1) 34 Naulct, N. (3) 204,208 Naumann, C. (3) 249 Naumov, D.Y. (7) 568 Naumovski, L.(12) 6 1 Navon, G. (12) 156, 171; (13) 78 Nawrot, B. (1 1) 1 10 Nazarcnko, E.L.(5) 374 Nazlan, M. (7) 592 Neckers, D.C. (10) 266,393 Ncda, I. ( 5 ) 198 Ncdbaeva, L.V. (14) 163 Ncdcz, C. (7) 244 Nceman, M. (12) 77 Negcndank, W.G. (12) 328-330; (13)44 Neil, J. (12) 232 Nchasov, A.N. ( 5 ) 279 Nclliappm, V. (10) 378 Nclscn, S.F.(1 1) 2 I Nelson, J.H. (2) 124; (3) 445; ( 5 ) 35,213,481; (7) 225,230 Ncnoff, T.M. (7) 678 Ncplaz, S.(5) 475 Ncstlc, N. (10) 405; (13) 50, 124-126 Ncto, A. ( 5 ) 173

522

Ncttesbcim, D. (9) 9, 11 Ncttlcton, E.J. ( 5 ) 224; (9) 215 Nctzel, D.A. (7) 122,127 Ncubaucr, S. (1 2) 164 Neubauer, T. (7) 627 Neubcrt, M.E. (14) 99 Ncuc, G. (2) 127; (3) 422; (7) 32, 5 12 Neuhaus, D.(9) 109, 110; ( 1 1) 8 Ncvalainen, T. ( 5 ) 60 Ncwby, C.S. (7)340 Ncwitt, P.J. (6) 204 Ncwlson, L.T.J. (10) 276 Newman, R.H. (7) 380,381,385 Ncwmark, R.A. (5) 426; (10) 61, 137 (12) 258 Newton, J.E.O. Newton, M.G. (10) 57 Ng, S.(9) 9; (10) 333,340,396 Ng, T.C. (12) 219,225 Nguyen, H.T. (14) 92, 135 Nguyen,V. (13)21 Ni, F. (8) 17 Ni, J. (7) 405 Nicasko, G. (5) 285 Nicholas, J.B. (3) 368, 378; (7) 179 Nicholson, L.K. (9) 52 Nicola, N.A. (5) 264 Nicolaou, K.C. (5) 362 Nicolay, K. (12) 12; (13) 174 Nicolc, D. (6) 129 Nicoletta, F.P.(14) 165 Nicolopoulos, S. (7) 599 Nicula, S. ( 5 ) 278 Niculadadci, L. (6) 74 Nidhubhghaill, O.M.(6) 171 Niccke, E. (2) 118; (5) 157 Nieel, J.C.S. (10) 159 Niegcr, M. (3) 310; (5) 193,212 Niclscn, K.J. (5) 282 Nielscn, N.C. ( 5 ) 27; (8) 43 Nielscn, P.H. (7) 157 Nicmcla, J.E. (12) 294 Niendorf, T. (13) 16 Nierlich, M. (3) 249 Nietlispach, D. (9) 75 Nicto, J.M.L. (7) 502 Nicto, P.M. (9) 194, 195 Nicuwenhuis, S.A.M. (7) 350 Nifantev, N. (1 1) 143 Nightingale, M. (2) 165 Niimi, T. (1 1) I 1 1 Niitsu, M. (12) 303 Nijs, C.L. (10) 295 Nikas, D. (12) 278 Nikols'kii, A.B. (7) 265

Nuclear Magneiic Resonance Nikonowicz, E.P. (9) 308 Nilgens, H.(13) 35 Nilges, M. (9) 36,37,92,227, 235-238 Nilsson, T. (6) 98, 149 Nilsson, U. (1 1) 1I7 (12) 149 Ning, X.-H. Nishimoto, M. (1 I) 35 Nishimura, K.(3) 261; (7) 325; (10) 96 Nishina, M. (12) 5 I Nishio, E.(3) 283 Nishio, T. (7) 218 Nishitani, H. (12) 287 Nishiyama, T. (1 1) 35 Nissann, R.A. (7) 199; (10) 259 Nissim, I. (12) 187 Nixon, J.F. ( 5 ) 175 Noack, F. (14) 92, 100, 135, 136 Noble, G.W. (7) 668 Noble, RD. (7) 443 Nobrega, R. (10) 20 1 Noegel, A.A. (5) 327; (9) 43 Noerdelaas, A.A.M. (7) 307 Noguchi, H.(3) 225 Nohr, R.S. (10) 305 Noiret, N. (3) 78 Nojima, S. (10) 306 Nollc, A.(2) 109 N o h , RJ.M. (1 1) 84 Noltemeyer, M. ( 5 ) 100 Noma, H. (7) 790 Nomura, M. (7) 116,124 Nonin, S.(9) 121 Nonomura, T. (5) 433,434 Nooijen, M.(4) 2,27,28 Norbert, H.J.D. (3) 208 Norby, P. (3)237 Norden, A. (7) 169 Nordcnskiold, L. (6) 97, 199 Nordio, P.L. (14) 53 Nordmann, A.(7) 775 Norman, P.R (7) 155,156 Norrby, E. ( 5 ) 254 Norrild, J.C. ( 5 ) 119 Norris, D.G. (13) 16 North, M. (7) 3 17 Norton, R.S.( 5 ) 264,298 Norwood, T.J. (6) 35-37, 194; (8) 38; (12) 23 Nosaka, T. (3) 190 Notheis, C. (3) 390 Nourmohammadian,F. ( 5 ) 4 18 Novack, K.M.(10) 97 Novak, B.M.(10) 156 Novak, P. (2) 169; (3) 84,85; ( 5 ) 58,99

Novcr, L. (9) 23 Novotna, M. (7) 117 Novotny, E.J. (12) 320 Nowak, A.K.(7) 70 1 Nowakowski, J. (1 1) 2 Nowak-Wydra, B. (5) 209; (1 1) 48 Nowicka-Schcibc, J. (3) 109,429; ( 5 ) 81 Nuber, B. (7) 252 Nugier-Chauvin, C. (3) 78 Numajiri, H. (6) 87 Nunes, T. (10) 267; (13) 62 Nunez-Regueiro, M. (10) 71,301 Nuss, P.V. (6) 137 Nygren, M. (14) 88 Nyholm, P.-G. (7) 413 Nymand, T.M. (2) 187 Nyquist, R.A. (3) 381 Nyulaszi, L. (3) 321 Oadcs, J.M. (7) 3 10,39 1,466 Oas, T.G.(9) 264 Obcrer, L. ( 5 ) 27 1 Obcrhammer, H. (3) 508 Obcrson dc S o w , M. (7) 601 Obika, S. (1 1) 35 OBrien, J. (10) 51 Occelli, M.L. (7) 61 1,625 O'Connell, E.M.(10) 382 O'Connell, M.P. ( 5 ) 304 OConnell, T.M. (7) 290; (9) 3 10 OConnor, S.J.M. (10) 142 O'Connor-McCourt, M. (9) 130 Oda, K. (6) 138 Oda, M.(3) 122 Oda, T. (12) 119 Odberg, L. (1 3) 90, 100 Oddershede, J. (2) 183; (4) 13, 14, 55

Odgaard, A. (13) 14 Odievre, M. (12) 309 Odom, J.D.(3) 70 O'Donncll, J.H. (10) 48, 170 O'Donnell, J.M. (12) 137,24 1 ODonoghue, S.I. (9) 37,235,238 O'Dwyer, P.J.(12) 330 Ochrstrocrn, L. (3) 188 Oelschlager, A.C. (5) 217 Ocpen, S.B.(7) 729 Ocseberg, B. (1 2) 3 10 Ogata, H. (7) 222 Ogata, N. (3) 47 Ogata, T. (10) 43 Ogawa, K. (7) 349 Ogawa, T. (10) 132 Ogoshi, H. (3) 163

Author In&x Ogura, K. (8) 48,55 Oh, D.-B. (5) 253 Oh, K.S. (1 1) 132 Oh, S.-W. (3) 326; (7) 258 OHare, D. (7) 828 Ohashi, Y. (7) 269 O m,A. (5) 74 Ohkanda, J. (7) 2 18 O W ,H. (14) 167 Ohlenschlager,0.(9) 28 1 Ohmon, H. (3) 158 Ohms, G. (3) 446; (7) 200,201, 2 1 1,220,284,494 Ohsumi, Y. (12) 85 Ohta, A. (3) 428 Ohta, H. (7) 141 Ohta, Y.(12) 200 Ohtani, H. (10) 123 Ohtsuki, C. (7) 749,750 Ohuchida, S. (7) 269 Oikarinen, K. (3) 384; (14) 121 oimann, s. (7) 220 Oishi, M. (12) 27 1 Ojima, I. (5) 391,392 Ojima, J. (3) 121 Okabe, M. (10) 106 Okada, H. (2) 15 Okada, K. (7) 550 Okada, M. (3) 154 Okada, T. (10) 43 Okajima, K. (10) 352 Okamoto,M. (10) 373 Okamoto, Y. (10) 134,153,167 Okawa, H. (10) 151 Okozaki, R.(3) 389; (5) 134 Okkel', L.G.(3) 520 Okouchi, S. (6) 87 Okubo, H. (13) 159 Okuda, J. (10) 89 Okuhara, T. (7) 485 Okui, N. (10) 184 Okumura, A. (6) 138 Okushita, H. (10) 221 Okutani, T. (7) 798 Olah,G.A. (2) 28, 112,113; (3) 24,30,367,369; (4) 3 1,33*37 Oldfield, E. (2) 188, 190-192; (3) 185,494 O'kary, D.J. (3) 113; (6) 146; (1 1) 3 Olechnowicz, R (12) 141 Olegario, R (2) 164 Olejniczak, E.T.(5) 335; (9) 7,273 Olejniczak, Z. (7) 534,537,605, 608,689 OlejIllk, Z. (3) 109 Olender, Z. (7) 76

523 Olcschuk, C.J.(1 1) 88 Oleynikova, I.V. (14) 163,164 Oliva, L. (10) 101, 11 1 Oliveira, A.B. (1 1) 37 Oliveira, C.M.F. (10) 201 Oliver, C.F. (9) 137 Oliver, Y. (12) 184 Olivera, B.M. (5) 289 Olivera-Pastor, P. (7) 8 14 Olivicr, A. (12) 321 Olivier, L. (7) 339 Olivicri, A.C. (3) 6,92,447; (7) 2-5,7, 169,226 Olmeijer, D.L. (10) 142 Olscn, D.R. (1 2) 220 Olscn, J. (4) 8 , 9 Olson, D.M.( 5 ) 233 Olsson, L. (2) 104, 105 Omelanczuk, J. (3) 72 (9) 89 Omichinski, J.G. Onak, T. (2) 119; (3) 339,385 Onaka,S.(11)41 Ondris-Crawford, R.J. (14) 161 O'Neil, J.D.J. (5) 126 Oniciu, D.C. (1 1) 87 Ono, S . (7) 430,499 Ono, Y. (3) 200; (7) 483,654 Onyszchuk, M.(3) 23 1 Opella, S.J. ( 5 ) 287; (7) 88, 300, 357,367; (8) 39; (14) 102 Opie, L.H. (12) 150 Oppusunggu, D. (2) 46,65 Ordung, I. (3) 229; (5) 2 19 Orendt, A.M. (3) 370 Orion, I. (7) 614; (10) 252 Oritani, T. (I 1) 30 Orlich, G. (13) 154 Ortenzi, C. (5) 301 Ortiz Meilet, C. (1 1) 119, 120 Ortuiio, R.M. (5) 412 Orvig, C. (3) 349,355; (5) 229 Osada, S.(1 1) 41 Osaka, A. (7) 749,750 Osakabe, N. (1 1) 128 Osakada, K. (10) 168 Osawa, E. (4) 83 Osbome, A.G. (5) 428,429 Osbome, M.J. (5) 318 Oschkinat, H.(8) 85; (9) 8,75, 133,154,235 Oshikawa, T. (1 1) 128 Oshima, K. (3) 329 Oskam, A. (5) 506 Osmark, P. (5) 342 Osse, J.W.M. (13) 166 Ossenkamp, G.C. (2) 60; (7) 177 Oskaw, M. (6) 201

Ostelow, W. (13) 1 1G Oslen, H.J. (2) 149, 152, 162 Ostcr, T. (5) 193 Oskrman, R (3) 79 Ostrovsky, D.N. (12) 38 Oswald, RE. (9) 66,67 Otomo, T. (9) 286 Ott, D. (5) 484; (9) 165 Otter, B.A. (1 1) 108 Ottcy, M.H. (7) 313 Ottigcr, M. (9) 183 Ottmg, G. (5) 18, 19,28,263,291; (8) 63; (9) 147, 150, 151, 180, 214 Otto, S. (5) 218 Ottocy, M.H. (10) 26 Ottosson, C.-H. (3) 29,399; ( 5 ) 230 Otvos, J.D.(3) 3 14 Ouillon, I. (10) 182, 183 Oumi, Y. (7) 640 Ourcvitch, M. (5) 391,392 Ourisson, G. (7) 329 Ouyang, M. (10) 443 Ovejcro, G. (7) 6 17 Overduin, M. ( 5 ) 337 Overhand, M.(5) 27 1 Ovcrloop, K. (6) 147 Ovcrweg, A.R (3) 242; (7) 656 Owen, N.L. (5) 120 Owens, L.M. (12) 153 Ozaki, T. (7) 289,335 Ozanam, F. (7) 808 Ozawo, K. (12) 197 Ozdemir, E. (10) 55 Ozilgen, M. (13) 144 Ozin, G.A. (3) 252; (7) 658 Paci, M. (5) 309 Padavic-Shaller, K. (12) 328-330; (13) 44 Padden, B.E. (7) 291 Padias, A.B. (10) 8 1 Padilla, A. (9) 296 Pae, Y.I.(3) 267; (7) 681,682 Paff, J. (13) 35 Pagila, R.N. (9) 130 Pahl, S. (6) 2 14; (10) 428 Paidarova, I. (2) 215 Paine, M.J. (9) 138 Paiva, A.C.M. ( 5 ) 285 Pajanne, E. (4) 58 Pajuelo, F.(3) 372; (5) 420 Pak, P.K. (7) 35 1,352; (10) 294 Palacios, J.C. (5) 403; (1 1) 129 Palasz, P.D.(10) 412

5 24

Palavit, G. (7) 772 Palcnik, R.C. (3) 257 Palfreyman, S.A. (6) 39 Palinko, I. (7) 8 17 Palkc, W.E. (14) 77 Palmcr, A.G., I11 (8) 34; (9) 243, 256,261,267 Palmcr, I. (9) 158 Palmcr, R.B. (1 1) 34 Palmonari, C. (1 3) 96 Palumbo, R. (10) 78 Palyulin, V.A. (1 1) 25 Pamin, K. (7) 537,689 Pampcl, A. (3) 194; (7) 344,374 Pan, J.W. (12) 289,290 Pan, M. (7) 602 Pan, Y. (7) 320 Panchalingham, K. (12) 260 Pandiarajan, K. ( 5 ) 401; (1 1) 45 Pancpucci, H. (3) 233; (6) 115; (7) 28; (12) 205 Pang, W.-Q. (7) 591 Panigcl, M. (12) 245 Pantano, C.G. (7) 762,786 Pantcli, N. (2) 43 Pantophlct, R. (5) 375 Paolctti, L.C. (5) 459 Paolillo, L. (5) 283 Papa, J. (7) 607 Papadakis, N. (12) 326 Papavoinc, C.H.M. (9) 92,295 Papp, H. (7) 627 Paquct, F. (9) 298 Parag, P.G. (1 1) 94 Paramonov, N.A. (5) 374 Pardi, A. (5) 467; (9) 103-108 Pardo, C. (5) 65 Pardo, J. (9) 33 Parella, T. (3) 372; ( 5 ) 412,420, 421; (8) 23 Parent, M.A. (7) 484 ParentqV. (10) 195 Parigi, G. (9) 300 Parisc, J.B. (7) 678 Parisi, M. ( I 1) 83 Park, C.B. (5) 284 Park, C.K. (10) 328 Park, C.-W. (5) 202 Park, D.H. (7) 587,588 Park, H. (10) 110 Park, J.M. (3) 139 Park, K.K. (3) 139 Park, M.Y. (3) 267; (7) 682 Park, S.S. (10) 100 Park, Y.H. (10) 247 Parkar, A.A. (9) 26 Parker, D. D. (1 0) 395

Nilclear Magnetic Resonance Parkcs, H.G. (12) 130 Parkington, M.J. (3) 469 Parkinson, J.A. (5)387 Parlow, J.J. (5) 508 Parolis, H. (5) 460 Parolis, L.A.S. (5) 460 Parr, R.G. (2) 79 Parras, A. (7) 490 Parrilli, M. (1 1) 134 Parris, W.E. (9) 7 1 Parrot-LopCx, H. (3) 147 Parvez, M. (1 1) 56 Pasau-Clacrbout,A. (7) 691,692 Pascal, Y. (5) 419 Pasch, H. (10) 93 Pascual, J. (9) 46 Pasini, P. (14) 98 Pastor, S.D. (1 1) 67,68 Pastorc, A. (9) 46,203 Pastukhov, A.V. (10) 388 Palarin, J. (7) 661,680 Patchcfshy, A.S. (12) 329 Patel, B.P. (5) 89 Patcl, D.J. (5) 470; (9) 78-84,99, 117-121, 124, 125, 127 Palcl, P.P. (12) 172 Palernostro, G. (12) 147 Pathiraja, A. (10) 24 Patin, H. (3) 78 Patrick, P. (12) 184 Patrickos, C.S. (10) 179 Patterson, J.E. (7) 427 Patyal, B.R.(6) 185; (13) 77 Pauli, J. (13) 111 Pauthc, M. (7) 459 Pavck, T. (12) 148 Pavcnti, M. (5) 430 Pavcsi, L. (10) 407 Pavilikova, H. (7) 117 Pavlovic, M.(12) 22 1 Pawelkc, Z. (3) 109 Pawlaczyk, J. (3) 135, 148 Pawson, T. (9) 71 Paycn, J.-F. (12) 129; (13) 177 Payne, G.S.(12) 24 Paync, N.G. (5) 45 Peacock, A.J. ( 10) 3 13 Pcarcc, R.B. (13) 155 Pearlman, D.A. ( 5 ) 4 1 Pcarson, J.G. (2) 190-192; (3) 494 Pcchinc, J.-M. (3) 68; (14) 68, 70 Pechy, P. (2) 59; (3) 26,458 Pcdcn, C.H.F. (10) 357 Pedone, C. (5) 277 Pedonc, P.V.(9) 89 Pedotti, S. (3) 138 Pcclcn, K. (3) 409

PceIcn, S. (5) 265 Pcctcrs, M.P.J. (7) 432 Pcgg, D.T. (2) 173 Pcggion, E. (5) 276 Pcirson, N.F. (3) 505; (7) 5 19 Pcjchal, V. (5) 148 Pel, L. (13) 108, 114 Pclacz-Arango, E. (5) 492,505 Pcll, M.A. (5) 202 Pcllecchia, C. (10) 228 Pcllecchia, M. (8) 91; (9) 18, 192 Pcllcgrini, M. (5) 247, 276 Pcllon, J.G. ( 5 ) 21 1 Pcltre, M.J. (7) 601 Pclupessy, P. (7) 45 Pcnades, S. (3) 114; (5) 366 Penczek, S. (10) 192 Pcndcrgast, F.G. (3) 107 Pcng, B.-X. (5) 417 Pcng, C. (5) 38 Peng, P. (7) 641 Pcng, S.-M. (3) 350 Pcng, W.-J. (5) 97 Pcng, X. ( 5 ) 409; (6) 180 Pcng, Z. (7) 3 1 1 Pcng, Z.-H. (5) 417 Pcnklcr, L.J. (3) 137 Pcnlidis, A. (10) 165 Penncr, G.H. (7) 824,825 Pcnnington, C.H. (3) 246 Pcnricc, J. (1 2) 288 Pcpin, J.-L. (12) 129; (13) 177 Pcpin-Donat, B.(10) 413 Pcppas, N. (10) 423 Pcranthancr, S. (7) 703 Pcrcha, P.A. (10) 61 Pcrdcw, J.P. (2) 74-77 Pcrcira, A.A. (12) 55 Pcreira, J. (6) 37 Pcrcira, M. (7) 794 Pcrcnboom, J.A.A.J. (6) 176 Pcrcra, S.A. (4) 2,3,25-27; (5) I06 Pcrcs, M. (12) I l l , 133 Pcrcz, F. (14) 149, 150 Percz, S. (1 1) 143 Pcrczalvarado, G.C. (9) 20,54 Perez-Alvarez, T. (7) 321 Perez-Ganido, S. (1 1) 120 Pcrcz-Gonzalcz, J. (13) 107 Pcrcz-Lcbloc, M.I. (7) 389 Pcrcz-Martinez, J.I. (3) 142 Pcrham, RN. ( 5 ) 3 15; (7) 300 Pcristeris, G. (12) 326 Pcrjessy, A. (3) 106 Pcrkins,P. (13) 151 Pcrlcpcs, S. (3) 3 15

A ufhorIndex Pcrly, 0. (3) 152, 155 Perrin, C.L. (5) 400 Perry, D.L. (2) 127; (3) 422; (7) 5 12 Pcrry, M.C.(6) 39 Perseghin, G.(12) 3 l 4 , 3 15,3 18 Persson, P.-A. (7) 137 Pertinhez, T.A. ( 5 ) 285 Peruchena, N.M. (4) 67; (1 1) 4 Peruzzini, M. (5) 50,5 1 Pervin, A. (1 1) 130 Pcrvushin, K. (5) 306; (9) 69, 193 Pcrzanowski, H.P. (3) 323 Pcseh, J.J. (7) 742 Petcrkofsky, A. ( 5 ) 453; (9) 55, 128 Petcrs, A. (13) 169 Peters, A.R. (12) 15 Pctcrs, A.W. (7) 648 Peters, G. (3) 305; (7) 62 Peters, J.A. (3) 170,258; (6) 175; (7) 757 Peters, L. (10) 232 Peters, T. (1 1) 143 Peterscn, B.O. ( 5 ) 461 Petcrscn, K.F. (12) 313,314,316, 318 Petcrsen, S.B. (12) 220 Peterson, E.W. (12) 159 Peterson, R.D. (9) 126 Petigny, 0. (7) 66 1 Petit, D. (7) 808 Petrakis, L. (2) 66 Petmud, M. (3) 414 Petroff, O.A.C. (12) 29,123,277; (13) 175 Petros, A.M. (9) 12 (7) 237 Petrucci, M.G.L. Petrzebowski, M.J. (7) 25 1 Pettegrew, J.W. (12) 256,260 Petter, R.C. (7) 184 Pettcrsson, L. (3) 271,272 Pettinari, C. (3) 410 Petuskey, W.T. (7) 744 Pcukert, u. ( 5 ) 174 Pezek, J.J. (7) 141 Pezolet, M. (7) 397 Pfaadt, M. (7) 419,422; (14) 80 Pfeffer,P.E. (12) 108 Pfefferle, C. (5) 389 Pfeiffer, S. ( 5 ) 447; (9) 240,241 Pfiefcr, H. (7) 7 11 Pflcidcrer, B. (7) 20; (12) 13 Pfihl, M. (9) 46,203,284 Pham, M. (1 1) 98 P h a , Q.-T. (10) 182,237 Phan, I.Q.H. ( 5 ) 305; (9) 255

525 Philippou, A. (7) 581,614 Phillips, J.R. (3) 303 Phillips, L. (4) 44 Photinos, D.J. (14) 142 Photis, F. (10) 345 Phung, C.G. (2) 122, 145; (3) 375-377,382 Pi,Z. (10)41 Piacente, S . ( 5 ) 364 Pianct, I. (3) 405 Pianka, M. (5) 216 Picard, F. (7) 462 Picchi, M.P.(9) 309 Picci, N. (14) 165 Piccinini, F. (2) 88 Picciolo, M. (5) 444 Pichot, C. (10) 69 Pickett, G.R. (6) 178 Pickford, A.R. (5) 305 Picord, F. (7) 397 Picoul, W. (14) 75 Pidun, U. (2) I1 1 Piedra, G.(7)782 Piekarska-Bartoszewicz, B. (3) 111; (5) 125; (7) 197,348 Picmontesi, F. (10) 154 Piepcr, N. ( 5 ) 144 Pierard,C.(12) 111, 133 Pictrass, T. (3) 392; (7)806; (13) 78 Pihlaja, K. ( 5 ) 208 Pikkcmaat, J.A. (5) 346 Pilatus, U. (12) 244; (13) 149 P h i , M.R.A. (3) 507 Pinchuk, V.A. (5) 215 Pincock, J.A. (5) 404; (I 1) 86 Pines, A. (3) 392; (6) 44; (7) 52, 74, 109, 113,334,806; (13) 78; (14) 20,26,28,32,33, 122 Pinheiro, T.J.T. (7) 418 Pinilla, E. (5) 72 Pinnau, 1. (10) 381 Pinnavaia, T.J. (7) 580,586 Pintar, A. (9) 279 Pintar, M.M. (14) 160 Pinto, B.M. (3) 472; (10) 199 Pinto-Coelha, C.(7) 561 Piriou, F. (I 1) 26 Pislewski, N. (7) 187 Pispas, S. (10) 427 Pitkcathly, M. (9) 279 Pitsikalis, M. (10) 427 Pitt, A. (14) 64 Pizza, C. (5) 364 Pla, J.C. (5) 496 Plack, V. (5) 493 Plakatouras,J.C.(3) 3 15

Planas, M. ( 5 ) 4 12 Plass, W. (3) 268 Platzek, 1. (3) 189 Plaxco, K.W. (9) 199,201 Plcban, L.A. (12) 277 Plcixats, R (3) 372; (5) 420 Plcnio, H. ( 5 ) 133, 163 Plcsck, J. (2) 115 Plcsniak, L.A. (5) 266 Plics, E. (7) 245 Plinta, H.-J. ( 5 ) 198 Pluckthun, A. (9) 218 Plyasova, L.M. (7) 486 Pneczek, S.(10) 12 Pochapshy, T.C.(6) 3,2 I8 Pocock, K.F. (7) 3 11 Podhyi, B. (3) 498; (5) 132,431; (12) 145 Pcdkorytov, I.S. (6) 89 Podlogar, B.L. ( 5 ) 268 P~er~chke, K.-R (7) 277 Poschl, M. (6) 162 Poeschl, U.(3) 398; (5) 168 Pogliani, L. (14) 49 Pohost, G.M. (12) 289,290; (13) 172 Pokrupa, R. (12) 321 Polam, J.R. (3) 291 Poland, R.E.(12) 285 Polctaeva, I. (5) 187 Polev, A.V. (6) 177 Politou, A.S. (9) 203 Polk, M.B. (7) 132; (10) 399 Pollack, R.M. (9) 54 Pollak, S . (9) 152 Pollcrs, I. (10) 180 Pollock, J.R (5) 260 Polonski, T. (1 1) 98 Polshakov, V.I. (5) 442; (9) 5 1, 194 Polson, J.M. (14) 2 1,22,5 I Polson, S.M. (5) 71 Polturak, E. (1 3) 67 Pombciro, A.J.L. (5) 76 Pomerantz, M. (10) 77 Pomery, P.J. (10) 48, 170 Pon, R T . (5) 360 Ponce, A.L. (7) 521 Poncelet, G. (3) 344; (7) 559,633 Poncharreau, R ( 12) I86 Ponchel, A. (7) 683 Poncc, V. (7) 500 PongraEiC, M. (5) 69 PO-, J.-L.(3) 8; (8) 40 Ponstingl, H.(5) 263 Ponta, C.C. (10) 410 Poojary, D.M. (7) 815

526 Poon, C.D. (14) 142 Pop, E. (5) 394 Popc, J.M. (13) 98,97, 13 I Popc, M.T.(3) 286,287; (5) 236 Popiclarz, R. (10) 266 Poplc, J.A. (2) 64 Popov, M.A. (7) 14 Popovid, 2. (5) 507 Port, A. ( I 1) 27 Portcla, M.F. (LO) 243 Portman, M.A. (12) 149 P o ~ ~ o - ~ PJ.M. c z , (7) 766 Poschl, E. (9) 44 Poshni, F.I. (3) 237; (7) 723 Pospicswski, P. (7) 187 Possani, L.D. (5) 297 Possc, S. (12) 266 Potchcn, E.I. (13) 156 Polrzcbowski, M.J. (3) 473; (7) 194 Pott, T. (7) 41 1 Poltagc, C. (7) 155, 156 Pottcr, K. (10) 404; (13) 72, 127 Pottcrat, 0.( 5 ) 389 Potts, J.R. (5) 305 Pouliqucn, D. (13) 160 Poulscn, F.M. ( 5 ) 323,342 Pound, R.V. (6) 23 Poupko, R. (5) 66; (7) 76, 164, 339; (14) 66,86, 87,90,91, 142 Pouwcls, P.J.W. (9) 157 Poveda, A. (1 1) 125 Powcll, A.K. (3) 348 Powcll, C. (10) 392 Powcll, D.H. (6) 171 Powcll, D.R. (1 1) 2 1 Powell, H.R. (7) 209 Powcrs, J.P. (I 1) 46 Powcrs, R. (5) 450 Powlowski, J. (5) 32 1 Poycr Lcc, J. (5) 407 Prabakar, S. (3) 397 Pradcl, A. (3) 413; (7) 535 Pradhan, A. (7) 704 Prakash, A.M. (7) 669,670 Prakash, G.K.S. (2) 28, 112, 113; (3) 24,30,367,369; (4) 37 Prakash, M.R. (12) 124 Prakash, 0. (9) 293 Prakasha, T.K. (3) 322; (5) 151; (7) 204 Prandolini, M.J. (6) 25 Prasad, S. (7) 671 Prassides, K. (3) 239 Pratima, R (7) 29; (14) 58 Pratt, E.A. (3) 493; (7) 337

Nuclear Magnetic Resonance Pratt, L.M.(7) 175 Pratum, T.K. ( 5 ) 25 Prcccc, S.R. (3) 296,298 Prectz, W. (3) 305,481; (5) 164-166; (7) 62 Prehoda, K.E. (9) 204 Prendcrgast, F.G. (5) 127 Prenzler, P.D. (3) 301 Prcslcgard, J.H. ( 5 ) 487; (8) 28, 60.61; (9) 38,39, 170, 171, 173,216;(14) 116 Preston, C.M. (7) 477 Prcty, W. (6) 12 Preul, M.C. (12) 321 Prcusscr, J. (2) 214 Prcviato, J.O. (5) 372 Price, T.B. (12) 314-316 Price, W.S. (8) 11; (12) 19 Prichard, J.W. (12) 29,250,284; (13) 175 Pridgcn, L.N. (3) 82 Priclmcicr, F. (12) 127 Primrose, W.U. (3) 218; (9) 136-139 Prins, R. (7) 111,636,783 Prinz, M. (5) 491 Prior, D.A.M. (13) 14 1 Prisncr, T. (9) 134 Priston, M.J. (12) 58 Privalov, A.F. (7) 19 Privalov, V.I. (7) 134 Probert, M.A. (9) 155 Probst, N. (10) 260 Prochnicka-Chalufour, A. (5) 297 Proctor, E. (12) 194, 195 Proctor, M. (5) 324; (9) 4 1,42 Prodhan, S. (7) 5 17 Prognon, P. (3) 147 Prongay, A.J. (9) 6 Proscrpio, D. (7) 506 Prosscr, R.S. (14) 29,55, 117 Proto, A. (1 0) 64,23 I Prusincr, S.B. (7) 334 Pruski, M. (7) 13,112 Pryor, K. (5) 334 Psy, D. (12) 255 Ptaszynski, J. (7) 537,689 Pubanz, D. (6) 77,167,170 Puchala, A. (3) 435; ( 5 ) 62 Puckett, J.M., Jr. ( 5 ) 71 Pugh, D.J.R. (9) 27 Puglisi, G. (3) 145 Puglisi, J.D. (5) 478; (9) 114, 115; (1 1) 142 Pugmirc, R.J. (3) 27,370; (6) 186, 187; (7) 119, 130 Pulay, P. (3) 17

Puranik, V.G. (3) 486 Pursch, M. (7) 186,332,353,449, 738; (10) 291 Purvis, G.D., Ill (4) 40 Puschl, A. (7) 157 Pusiol, D.J. (14) 134 Puuktnnen, M. (7) 534 Puyear, S. (3) 17 Puzo, G. (5) 370 Pwscock, A.J. (10) 284 Pyda, M. (7) 160 Python, H. (6) 55, 123 Pyykko, P. (2) 1

Qi, P.X. (5) 329 Qian, H. (5) 321 Qian, S.W. (5) 452; (9) 53 Qin, J. (9) 13 Qiu, F. (5) 103 Qiu, J. (7) 63,64, 131, 150,593, 72 1 Qiu, K. (7) 5 1 Qiu, S. (7) 674 Qu, B. (10) 386 Qu, X. ( I 0) 386 Qu,Y. (11) 112 Quacquarini, G. (5) 3 19 Quan, R.W. (7) 234; (1 1) 146 Quang-Tho, P. (10) 183 Quignard, F. (7) 24 1 Quinoa, E. (3) 64,66 Quinting, G . R (10) 135 Quirk, J.J. (3) 480 Quist, P.O. (14) 103, 109, 110, 138 Qurcshi, A.H. (13) 23 Quyoum, R ( 5 ) 70

Raanby, B. (10) 386 Raap, J. (7) 350 Rabagliati, M. (10) 239 Rabastc, F. (12) 92 Rabb, D.M. (3) 113; (1 1) 3 Rabe, G.W.(3) 264; (7) 61 Rabcr, D.J. (3) 170; (6) 175 Rabillcr, C. (3) 205 Rabinowitz, M.J. (7) 789 Rabis, A. (7) 2 11 Rabkina, A.Yu. (10) 86 Rachdi, F. (3) 244,380; (7) 144; (10) 71,301 Rachwal, S. (5) 394 Radda, G.K. (3) 442; (12) 31, 130, 147,150, 152 Radei, P.A. (5)30

Author Index Radford, S.E. (9) 202,2 15 Radhafuishnan, 1. (9) 99 Radiotis, T. (1 0) 176 Radkc, C.J. (7) 600 Radley, K. (14) 74 Radloff, D. (10) 253 Radulovic, D.(12) 295 Raduncr, E. (7) 636 Radzcwich, C.E. (5) 53 Racvsky, O.A. (6) 139; (1 1) 8 1 Raghunathan, P. (12) 268 Ragunathan, A. (7) 224 Rahim, S. (3) 477 RaiC, S.( 5 ) 69 Raihanc, M. (10) 182, 183 Rainc, A. (9) 75 Rainc, A.R.C. (5) 443; (9) 40 Raithby, P.R. (1 1) 64 Rajamohanan, P.R. (7) 292,5 17 Rajan, S.S. (12) 295 Rajarajan, G. (1 1) 32 Rajarathnam, K. (9) 190 Rajashankar, K.R. ( 5 ) 249 Rajic, N. (7) 684 Rak, A. (9) 35 Rakiewicz, E.F. (7) 648 Rail, W.F. (12) 244; (13) 149 Ramachandran, R. (8) 87 Ramagc, P. ( 5 ) 448; (9) 15 Ramakmar, S. ( 5 ) 249 Ramamoorthy, A. (7) 88 Raman, E.R. (13) 173 Raman,S.V. (6) 60 Ramanathan, C. (7) 20; (12) 13 Ramanathan, K.V. (2) 128; (7) 378; (14) 1, 19,58,60, 61 Ramasamy, R. (12) 32 Ramaswamy, G.N. (7) 407 Ramirez, R.G.(3) 408 Ramm, M.T. (1 1) 21 Ramnarain, S. (9) 152 Ramos, A. (9) 93,98 Ramos, M.( 5 ) 65 Ramphal, J.Y.(1 1) 136 h e y , N.F. (2) 172 Ramwino, M.C. (3) 153 Ranaivonjatovo, H. (3) 400 Rance, M. (8) 34; (9) 256 Randall, E.W. (13) 62,63 Randall, R.Q. (6) 21 1 Randl, O.G.(6) 12 Randrianarivclojosia, M. (5) 383 Rangarajan, G. (7) 224 Ranieri, G.A. (14) 49,94,112 Rankin, D.W.H. (5) 225 Rao, B.A. (7) 185 Rao, C.P.(3) 270

527 Rao, N.S. (8) 75; (9) 68, 113, 185 Rao, P.V.C. (10) 75 Rapp, W. (7) 353 Rappcnbcrger, M.(7) 764 Rappoport, Z. (3) 456; (1 I ) 20 Raptis, A.C. (10) 439; (13) 132 Raptis, R. (3) 301 Rasala, D.(3) 97, 106,435; (5) 62 Rashkov, 1. (10) 118 Rasmusscn, P. (1 0) 125 Rasoanaivo, P. (5) 383 Rasul, G. (2) 28, 112, 113; (3) 24, 30,367,369 Ratclifle, C.I.(2) 146; (3) 125, 5 19; (7) 659,826 Ratcliffc, R.G. (12) 67,68,95, 108 Rath, D.P. (12) 18 Rath, N.P. ( I 1) 149 Raticr, M. (3) 414 Ratilaincn, J. (14) 16 Ralnani, R. (3) 483 Rauhut, G. (3) 17 Rauk, A. ( I 1) 22,56 Raulcl, R. (13) 36,49 Rausch, M.D. (10) 230 Ravalec, X. (1 2) 202 Ravard, A. (3) 69 Ravikumar, A. (7) 292 Ravindranathan, S. (10) 343 Rawdah, T.N. (1 1) 73 Raya, J. (3) 294 Raychaudhuri, S. (9) 269 Rayncs, W.T. (2) 43,47,5 1,57, 58, 157-159, 165, 167, 174, 193,201; (3) 91; (4) 14; (5) 140 Razavi, A. (10) 232 Rebck, J., Jr. (1 1) 74 Rebourt,E. (10)413 Rccchia, C.H. (3) 246 Rccht, M.I. ( 5 ) 478; (9) 114, 115; (11) 142 Reddy, B.S.R. (10) 66 Rcddy, D.V. ( 5 ) 245; (9) I64 Rcddy, R. (6) 59 Rcddy,S. (10) 3 12 Rcdmon, L.T. (4) 40 Reed, S.I. (9) 131 Reedijk, J. (1 1) 1 12 Rces, N.H. (3) 80 Rectz, M.T. (7) 445 Reevc, J.N. (9) 22 Rcfsgaard, H.H.F. (7) 3 12 Regano, C. (7)213; (10) 114 Regcr, D.L. (2) 131; (3) 3 17; (7) 279 Regina, G. (13) 10

Rcglinski, J. (12) 10,37 Rchahn, M.(10) 149 Rchak, P. (7) 94 Rchdcr, D. (2) 27 Rchrcr,N.J. (12) 310 Rcibcnspics, J.H. ( 5 ) 149 Rcich, B. (13) 130 Rcich, D.(7) 569 Rcich, H.J. (3) 226 Rcichc, A. (10) 408 Rcichc, J. (1 3) 136 Rcichert, D. (7) 76 Rcichmann, H. (12) 308 Rcid, B.R (5) 465 Rcid, D.S.(13) 144 Rcid, G. (3) 302,307,4 1 1,480; (7) 285 Rcif, B. ( 5 ) 105; (8) 58; (9) 169 Rcilly, A. ( 5 ) 3 I8 Rcilly, D.(5) 304 Rcimcr, J.A. (3) 306; (7) 65,248; (10)418 Rcinclt, G. (12) 308 Rcincr, C. (6) 42 Rcinhoudt, D.N. (1 1) 76 Rcinmuth, A. (10) 5 1 Rcis, M.A.M. (12) 43 Rcjzek, M. (3) 49 Rckc, R.D. (10) 52 Rcmaud, G.S. (3) 204,206 Rcmcnar, J.F. (3) 227 Rcmcrowski, M.L. (9) 295 Rcmcur, E.L. (12) 202 Rcmigercau, B. (13) 143 Rcmy, M.J. (3) 344; (7) 633 Rcn, J. (3) 174 Rcng, J.W. (9) 259 Rcnicro, F. (3) 363 Rcnncr, c. ( 5 ) 327; (9) 43,292 Rcnncr, M.K. (3) 53 Rcnshaw, P.F. (12) 259,269,272, 274,286 Rcntsch, D. ( 5 ) 136, 137 Rcntsch, G.H. (3) 292; (5) 178 Rcnzoni, D.A.C. (9) 27 Reo, N.V.(2) 204 Rcschclilowski, W. (7) 58 1 Rcsconi, I. (1 0) 154 Rcttig, S.J. (3) 355; (5) 229 Rcubcn, A. (12) 313 Rcutcr, H. (1 1) 63 Rcvcl, B. (7) 450,45 1 Rcvcn, L. (7) 379,439 Revillon, A. (10) 237 Revnyak, D.(7) 105,229 Rcynolds, J.L. (10) 121 Rhce, I.J. (7) 35 I, 352; (lo) 294

528

Rhcingold, A.L. (5)233; (7)254 Riandc, E.(10) 65 Ribas, C. (3)58 Ribciro, A.A. (5)32 Ribeiro, A.C. (14)92, 135 Ribes, M. (3)413;(7)535 Ribet, M. (7)138 Ribot, F.O. (7)434 Ricaud, P.M. ( 5 ) 3 15 Ricci, G. (10)34 Rim, A. (9).156,157 Rice, D.M.(7) 183 Ricc, G.L. (7)741 Rice, L.M. (9)228,229 Richards, G.M. (14) 148,159 Richards, J.C. (5) 378 hchardson, J.M. (9)50 Richardson, J.P. (5) 259 Richcns, D.T.(3)462;(6)76 Richcrt, R. (6) 106 Richcrt, T.(3) 294 Richlcr, R. (7)442 hchtcr, J. (6)43;(13) 130 Richter, R. (10) 289 Richter, W.(6)31 Rico, M. ( 5 ) 339,358 Riddcll, F.G. (1 2) 79 Ridcnour, C.F. (12)104 Rideout, D.C. (12)80 Riedc, A. (14)95 Riedi, P.C. (3) 288 Riedl, T. (7) 154 h e k , R. (8)25;(9) 1-3,144, 146 Riemenschncidcr,J.L. (4)35 Rienstra, C.M.(7)7 I, 82 Rigby, A.M. (7)701 Rigby, S.P. (13) 79,89 Rigolc, M. (7)683 Rigsby, L.L.(7)362 Riguera, R. (3) 64,66 Riley, C.M.(12)5 8 Riley,J.P. (2) 174 Rilo, H.L. (12)69 Rim, O.K.(1 1) 24 Rinaldi, P.L. (3) 470;(7)5 13; (10) 2,28,36-38,41,242 Rios, C.B. (8)69,72,73 Riou, D. (7)525 Ripamonti, A. (2) 135 Ripmeester, J.A. (2) 146;(3)519; (7)659 Rise, F. (1 1) 72 Risinger, R. (12)266 Rissanen, K. ( 5 ) 212 Rissc, W.(10)5 1 httby, M. (4)20 Ritter, U.(3) 387

Nuclear Magnetic Resonance Rittncr, R. (4)78;(5)496 Ritz, P. (7)61 1 Rivas, G. (9) 46 Rivicr, C.(13) 113 Rivier, J. (5)289 Riviere, M.( 5 ) 370 Riviere, P. (3) 23 I Rizzarelli, E. (3) 138 Rim,A. (2)42, 189

Ro,Y.M.(13)51 Robcr, R.E. (1 0) 242 Roberie, T.G. (7)648 Robert, J.B. (2) 95;(6)108 Robert, R (12)186 Roberts, A.B. ( 5 ) 452;(9)53 Roberts, E.L.( 5 ) 3 15 Robe&, G.C.K. (9)47, 135-139, 191;(11) 139, 140 Robcrts, G.M. (6) 15 1 Roberts, J.D. (3) 160 Roberts, J.E. (7)685;(10) 378 Roberts, J.K.M. (12)94 Robertson, J.G. (9)57 Robertson, K.N. (7)273 Robins, R.J. (12)67,68 Robins, T.(9)12 Robinson, C.N.(3) 95 Robinson, C.V. (9)215 Robinson, D. (13)55 Robinson, J.A. (5)275 Robinson, K.D. (5) 214 Robinson, V. (3)496 Robitaille, P.-M.L. (12)18,241, 257 Robourt, E. (10) 146 Robson, R.L.(5) 265 Roby, J. (6) 185 Robyr, P. (6) 197;(7)78;(10)209 Roca, J. (12)306 Rocchi, R. ( 5 ) 276 Rocha, J. (3) 275,347;(7)121, 233,428,581,614,615,637, 676,677 Rocha, M.F.(10) 243 Rochon, F.D. (3)299 Rockwell, B.A. (6)185 Rockwell, G.D. (1 1) 10 Rodbumrung, W.(3) 497;(12)226 Roden, M.(12) 314,318 Roder, F. (12) 173 Rodin, V.V. (6)137 Rodrigus, L.M. (12)35,327 Rodrigucz, I. (7)657 Rodriguez, J. (7)389,526,553 Robiguez, L.(2)61 Rodriguez, O.P.(1 1) 43 Rodriguez-Baeza, M.(10)144

Rodrigucz-Castellon,E. (7)814 Rodrigucz-Galan, A. (10) 114 Roesky, H.W. (3)387 Rosslcr, E. (6)13,106, 150 Roetteic, H.(3)164 Rocwer, G. (3) 390;( 5 ) 169;(7) 442;(10)289 Rofe, C.J.(13) 107 Roffmann, W.U. (13)25,27 Rofstad, E.K. (12)220 Rogers, J.S. ( I I) 68 Rogers, P.S. (5)393 Roggatz, 1. (6)13,106 Rogowski, RS.(5)296 Rohr, K.S. (14)26 Roland, C.M. (2)207 Roman, B.B.(12)208 Roman, S.K. (12)80 Romannikov, V.N. (7)700,708 Romao, C.C. (10)237 Rommel, E. (6) 188 Rommereim, D.N. (7)304 Romming, C.(7)195 Romotowski, T.(7)596 Ronova, J.A. (10)86 Roodt, A. ( 5 ) I87,2I 8 Rooney, J.J. (10) 82, 139 Rooncy, W.D. (12) 131, 136 Roongta, V. (5) 294 ROOS,B.O. (4) 15,48 Roos, K. (7)58 1 Root, A. (7)491,740 Root, T.W. (10)382 Ropson, N. (10)76, 195 Roque, L.C.(3)482 Rosanske, R. (7)27;(14) 14 Rosario, R.M. (10)243 Ross, M.T. (10)128 Rosato, A. (5) 444 Rosc, J. (3) 294 Roscmeycr, H.(1 1) 60,63 Rosen, M.E. (14)172 Rosen, M.K.(8)77;(9) 71-73 Rosenburg, I. (I 1) 109 Ros~nkrmtz,T.S. (12)1 18 Rosenstein, D.L. (12)294 Rosenlhal, U. (5) 74 Rosier,A. (12)210 Rosowsky, A. (9)33 Rospenk, M. (3)87 Ross, A.(6)34,202;(8) 37;(9) 56,292 Ross, B.D. (12)121,279

Ross,H.(1 1) 75 Rosseinsky, M.J. (7) 146-148 Rossen, W.(13)91. Rossi, A. (12)142,151, t68

Author Index Rossi, C. (9) 309 Rossi, F. (5) 277 Rossini, S. (7) 196 Rossmann, A. (3) 363 Rossmann, M.G. (9) 6 Rosso, C. (3) 140 Roth, K. (3) 189 Roth, R.D. (3) 392; (7) 806 Rothchild, R. (3) 175; (11) 92,93 Rothemund, S. (3) 108 Rothman, D.L.(12) 122, 123,254, 284,313-318,320

Roubaud, V. (5) 408; (1 1) 55 Rouchcr, P. (12) 126 Roulct, T. (3) 405 Rousscl, J.C. (13) 113 Roussel, R. (12) 3 11 Rowt, B. (7) 375 Row, C. (10) 424 Roveri, N. (2) 135 Rovnyak, D. (2) 102; (3) 45 1 Roy, S. (10) 124 Rozijn, T.H. (12) 323 Rum, B. (5) 393 Rum, J. (12) 230 Ruan, R. (13) 151 Ruban, A. (2) 118 Rubini, P. (2) 147, 148; (6) 88 Rubinow, D.R. (12) 294 Rubinstcnn, G. (1 1) 133 Ruch, B.E. (5) 170 Rudavskii, E.Y.(6) 177 Rudin,A. (10) 311 Rudkcvich, D.M. (1 1) 74 Rudzinski, J.M. (1 1) 41 Rueda, D.R (10) 90 Rudigcr, V. (3) 151, 156; (6) 139; (11) 81,82

Ruessel, C. (7) 493 Rutcjans, H. (5) 436,437,447, 449; (8) 35,51,76; (9) 23, 162, 163, 184, 186,240,24 1,252, 281; (11) 7 Ruf'ini, L. (3) 153 Rufinska, A. (7) 252,277,445 Ruhnau, F.C. (7) 67; (10) 330 Ruiz, F.A. (5) 72 Ruiz, M.C. (4) 62-64 Ruiz-Cabello, J. (12) 1 Ruiz-Morales, Y. (2) 97, 106; (3) 19 Rule, G.S. (5) 259 Rullmann, J.A.C. (3) 176; (5) 292; (9) 220 Rummens, F.H.A. (2) 198 Rungaphinya, W.(10) 147 Ruppersberg, J.P. (9) 49

529

Rupprccbt, A. (7) 297; (14) 30 Rush, B.M.(7) 248 Rush, S. (10) 5 1 Russcll, K.E. (10) 268,386 Rusznik, I. (5) 500 Ruthcrford, T.J. (1 1) 114 Rutledgc, P.S. (1 I) 99 Ruud, K. (2) 42, 189, 196, 197, 212; (4) 16

Ryan, T.A. (3) 469 Rybinskaya, M.I. (5) 212 Rychlicki, H. (10) 154 Rychnovsky, S.D.(1 1) 46 Ryczkowski, J. (7) 779 Rydygcr, K. (1 3) 50 Ryoo, R. (7) 667 Rys, B. (1 1) 69 Ryschon, T.W. (12) 294 Ryu,K. (3) 47 Ryu, Y. (11) 132 Ryynhen, R. (5) 4 13 S a m , B. (6) 183,185 Saba, G. (6) 92 Sabat, M. (3) 3 18; (5) 482 Sabo-Eticnne, S. (5) 91 Sacco, A. (6) 153 Sachleben, R.J. (7) 170; (10) 278 Sachs, G.S.(12) 259,272 Sachscnroeder, H. (7) 71 1 Sadlcj, A.J. (2) 158 Sadlcr, P.J. (3) 313; (5) 267,272; (7) 261; (12) 53

Saez, J. (5) 385; (1 1) 40 Sagan, S. (5) 250 Sage, D. (10) 292 Sahota, S.K. (12) 112 Said, R. (3) 205 Saidcl, V.A. (10) 410 Saito, H. (7) 43,294,325 Saito, I. (7) 123 Saito, M. (10) 352 Saito, T. (10) 2,41,242 Saito, Y. (7) 141,785 Sakaguchi, M. (12) 235,239,240 Sakaino, Y. (3) 430; (7) 205 Sakamoto,K. (1 1) 1 11 Sakamoto,

Y.(7) 644

Sakano,K. (1 2) 85 Sakharov, S.G. (5) 227 Sako, K. (1 1) 4 1 Sakuma, C. (3) 428 Sakurai, M. (12) 93 Salahub, D.R (2) 4, 10,20,21,23, 24,72; (4) 49,50,53; (5) 204 Salani, G. (5) 509

Salchirad, F. (7) 699 Salgado, J. (9) 300 Saljoughlan, M.(3) 217 Salloum, M.J. (7) 473 Salticl, A.R (5) 328 Salvadori, P. (3) 73, 143; (13) 129 Salvan, A.-M. (12) 283 Salvaticrra, D. (3) 141, 157 Salvatore, B.A. (14) 116 Salvini, T.F. (12) 205 Salvioli, G. (3) 131, 132 Samadi-Maybodi,A. (7) 568 Saman, D. (3) 49 Samoilenko, A.A. (13) 62 Samoshin, V.V. (1 1) 25 Samoson, A. (7) 106 Sample, J.L. (7) 286 Samulski, E.T. (1 0) 3 17,3 19,355; (14) 142

San,J. (4) 4,s

San,R.J. (10) 49 Sananes,M.T. (3) 448 Sancelme, M. (12) 92 Sanchez, A. (3) 198,309,324, 325; (7) 32 1

Sanchcz, C. (7) 434 Sanchez, J.Y. (10) 424 SanchCz-Fcrrando, F. (3) 14 1;(5) 421; (8) 23

Sanchcz Gonzalcz, A. (3) 309 Sanchez-Soto,RJ.(7) 553 Sanctuary, B.C. (3) 3; (7) 12 Sandcr, L.C. (7) 186 Sandcrs, J.C.P. (3) 421 Sanderson, P.N. (1 1) 116 Sandman, K. (9) 22 Sandncr, B. (10) 408 Sandor, P. (2) 163; (3) 91; (5) 140 Sands, RH. (6) 80 Sandstrom, A. (5) 356 Sandstrom, D. (7) 92; (14) 23,88, 89,143

San Fabiin, J. (3) 455; (5) 399, 462; (1 1) 5,6

Sanford, D.G. (5) 336 San Gil, R.A.S. (10) 309 Sangiorge, C.L. (3) 233 Sankar, S . S . (10) 38 1 Sankarapandian,M. (10) 361 Sannes, M.T. (7) 496 Sannohe, H. (1 1) 77 Sano, T. (7) 618 Santa, H. (14) 16 SantaLucia, I. (5) 473 Santamaria, A. (10) 23 Santamaria, C. (5) 73 Santa Maria, M.D. (5) 72

Nuclear Magttelic Resonance

530 Santillan, R. (3) 333 Santini, C. (3) 320; (5) 491 Santoro, J. (5) 339 Santos, H. (12) 43 Santos, R.A. (7) 304 Sanz,D. (3) 103, 358,359; (5) 3, 72, 160, 161; ( I 1) 59 Sanz, J. (7) 553,766 Saponja, J.A. (9) 248 Sarastc, M. (9) 8,46 Sarkar, A. (7) 732 Sarkar, M. (10) 412 Sarkar, S.K. (7) 57 Sarv, P. (7) 597,767 Sasabc, H. (10) 151 Sasaki, M. ( 5 ) 433,434 Sasayama, S. (13) 4 1 Satabin, P. (1 2) 11 1 Satgc, J. (3) 23 1,400 Sathyanarayana, D.N.(5) 63,499 Sato, K. ( 5 ) 281; (7) 210 Sato, N. (3) 59 Sato, S. (3) 5 11; (8) 78 Satoh, N. (7) 43 Satoh, T. (1 1) 111 Satpathy, U.S. (10) 75 Sattlcr, M. (8) 46; (9) 9, 11,6 I Satyanarayana, C.V.V. (3) 475, 476,485; (5) 75; (7) 670 Sauer, S.P.A. (2) 215 Saundcrs, M.(3) 512,513,515; (4) 38 Saupc, A. (14) 2 Sauriol, F. (5) 435; (1 1) 53 Sauvagc, A. (7) 60 1 Sauvt, G. (5) 270 Saviano, G. (5) 277 Saviano, M. ( 5 ) 277,283 Sawada, S. (3) 328 Sawada, T. (1 1) 71 Sawada, Y. (7) 151; (10) 130 Sawaguchi, T. (10) 217,225 Say, B.J. (7) 10; (10) 340,396 Sayari, A. (7) 621,660 Sayir, A. (7) 789 scamuzzi, s. (3) 212 Scaroni, A.W. (7) 120 Schaafsma, T.J. (13) 166 Schaaper, W.M. ( 5 ) 292 Schadt, M. (14) 156 Schaefcr, J. (7) 69,235,319,320, 326,341,343,356,359,368; (10) 297,299 Schacfer, S. (6) 180 Schaefer, T. (2) 170; (3) 93; ( 5 ) 59,501,502; (1 1) 101 Schaeffer, F. (5) 347

Schiir, D. (5) 100 Schafcr, A. (2) 27 Schah-Mohammcdi, P. (3) 88 Schakel, M. (3) 388 Schaller, T. (3) 305; (5) 483; (7) 62,231,264,518 Schantz, S. (10) 365 Schapcr, I. (3) 508 Scharf, K.D. (9) 23 Schamgl, N. (10) 190 Schattenmann,F.J. (10) 72 Schauer, R. (9) 157 Schaumbcrg, K. (3) 353; (7) 157, 312,515 Schauss, G. (7) 47 Schcck, R.M. (8) 80 Schemer, D. (3) 508 Schemer, K. (13) 75 Schcler, U. (3) 92; (7) 47,66, 85, 226; (10) 279 Schcllcr, D. (10) 189 Schcndcl, S.L. (9) 10 Schenctti, L. (3) 131, 132; (5) 405; (10)56; (11)42 Schcnker, K.V. (14) 28 Schcnzcl, K. (5) 167 Scherer, J. ( 5 ) 185 Schcrer, M. (3) 343 Schcurer, C. (5) 48 Schcuring, J. (9) 133 Schcying, G. (13) 111 Schick, F. (12) 16,293,324,325; (13) 19 Schicsscr, C.H. (3) 484 Schiffcnbaucr, Y.S. (12) 77 Schiffcr, J. (5) 485 Schilf, W. (5) 85 Schindlcr,R. (12) 308 Schippcr, D. (9) 282 Schinmachcr, V. (12) 223 Schlaf, M.(4) 74; (5) 54 Schlagcr, 0. (7) 252 Schlcapfcr, W. (6) 171 Schlcich, T. (1 2) 139 Schlcucher, J. (5) 105; (8) 58 Schleyer, P.von R.(2) 120; (3) 228,330; (4) 26; (7) 275; (1 1) 22 Schlick, S. (10) 15 Schloegl, R. (3) 245 Schlotterbeck,G. (7) 353 Schlotz, T.D. (12) 172 Schmalbrock, P. (12) 257 Schmidbaur, H. (3) 253; ( 5 ) 200; (7) 260 Schmidpeter, A. (5) 23 1 Schmidt, A. (3) 228; (7) 275; (10)

383 Schmidt, C. (14) 104 Schmidt, E.J. (13) 67 Schmidt, E.W. (3) 56 Schmidt, H.L. (3) 363 Schmidt, J.M. (5) 438,439; (9) 163,240; (1 1) 7 Schmidt, M. (3) 253 Schmidt, M.R. (3) 336 Schmidt, M.W.I. (7) 467 Schmidt, P. (10) 42 Schmidt, R.G.(12) 329 Schmidt, R.R. (1 1) 144 Schmidt-Naake, G. (10) 189 Schmidt-Rohr, K. (7) 9 1; (10) 298; (14) 93, 115, 118 Schmitt, J. (7) 472 Schmilt, w . (5) 441 Schmitz, G. (12) 44 Schmitz, R.F. (3) 388 Schmoll, J. (6) 207 Schmucckcr, M.(7) 427,745 Schmulzlcr, R. (3) 446; (5) 162, 179,194, 198,215,464,493; (7)284 Schnackerz, K. ( 12) 164 Schneidcr, B. (12) 4 Schncidcr, D. (5) 96 Schncidcr, H. (7) 427,745; (10) 441; (13) 134 Schncidcr, H.-J. (3) 151, 156; (6) 139; (11) 81,82 Schneider, W.G. (2) 64 Schncll, 1. (7) 93 Schncllbach, M.(7) 242 Schneller, T. (7) 247,449; (10) 29 1 Schn~tzc,F.-W. (7) 627 Schnick, W. (5) 155 Schnur, D.M.( 5 ) 508 Schnur, G. (6) I88 Schobcrth, S.M. (12) 46 Schocgl, R (7) 145 Scholfield, C.J. (1 1) 47 Scholten, A.B. (3) 393 Scholz, K. (6) 110 Schombcr, B.M. (5) 53 Schonhals, A. (6) 107, 190 Schopfer, U. (5) 489 Schott, M.K. (9) 49 Schott, 0. (5) 326; (9) 16 Schou, C. (5) 342 Schrak, RR. (7) 229 Schreckcnbach,G. (2) 2,40,97, 106; (3) 19,28,36 Schreiber, A. (7) 280 Schreiber, D. (6) 180

Author Index Schreicr, S. (5) 285 Schreycck, L. (7) 643 Schnever, J. (6) 164 Schrobilgcn, G.J. (3) 289,421 Schrock, R.R. (2) 102; (3) 45 1; (7) 255; (10) 72 Schroder, M. (3) 302 Schrodel, H.-P. (5) 23 1 Schroder, F. (5) 386 Schroepfcr, G.J., Jr. (5) 393 schroth, (1 1) 97 Schrotter, J.C. (7) 460 Schumann, M. (5) 144 Schuctz, M. (3) 228 Schuff, N. (12) 264 Schulcr, P. (5) 407 Schulman, L. (3) 79 Schulte, J. (3) 105,276,457; (5) 31 Schultc, P. (5) 484; (9) 165 Schulten, H.-R. (7) 463,469 Schultheiss, J. (9) 23 Schultz, J. (9) 8 Schultzc, P. (9) 76,85 Schulz, P. (7) 661 Schulz, R.J. (13) 128 Schulzc, D. (7) 701 Schumann, H. (6) 174 Schurig, V. (3) 150 Schurko, R.W. (5)35, 172; (7) 227,230 Schuster, D.I.(3) 512,514 Schustcr, I. (3) 366; (13) 67 Schuster, M. (5) 180 Schwab, J.M. (9) 58 Schwalbe, H. (5) 35 1,484; (8) 20; (9) 165, 167,211-213 Schwartz, P. (12) 124 Schwarz, G. (10) 260 Schwarz, H.B.(7) 716,717 Schwarz, J.B. (7) 386 Schwarz, M. (7) 152 Schwarz, W. (5) 176,234 Schwarx, B. (3) 229; (5) 154-156, 219 Schwarze-Hallcr,D. (14) 100 Schweins, T. (9) 134 Schwcisguth, D.C. (5) 476 Schwcitzcr, B.I. (8) 19 Schwcitzcr, R.C.(3) 12 Schwendinger,M.G. (8) 46 Schwerdt, J.H. (3) 79 Schwerk, U. (7) 13 Schwcsinger, R. (7) 2 12 Sciacovelli, 0. (4) 75 Sciaky, M. (12) 169 Scnischen, L.B. (7) 718

w.

53 1

Scoganmiglio, G. (3) 62 Scollan, N.D.(12) 242 Scott, B.L. (5) 52; (7) 256 Scolt, J.D. (10) 274 Scott, R (7) 374 Scott, R.A. (9) 2 1 Scott, S.L. (7) 74 1 Scowen, I.J. (5) 235; (7) 261 Scranton, A.B. (10) 19 Scriven, L.E. (13) 95, 102 Scrosati, B.(10) 406 Scudder, M.L. (3) 326; (7) 258 Scuseria, G.E.(4) 13, 14 Scaquist, E.R(12) 319 Scarle, P.A. (3) 6 1 Searlcs, D. (6) 18, 19 Scbald, A. (3) 264,305; (7) 61,62, 92,23 1

Sebastian, R (14) 16 Sebastiao, P.J. (14) 92, 135 Secheresse, F. (3) 285 Seco,J.M. (3) 64 Scddon, A.P. (5) 450 Scddon, K.R. (3) 469 Scderholm, C.H. (2) 66 Seebach, D. (5) 27 1 Seeger, U. (12) 293 Seela, F. (1 I) 60,63 Seelig, J. (1 3) 75 Secvogel, K. (7) 277 Scflcr, A.M. (5) 242 Segre, A.L. (3) 222 Seibel, P. (12) 308 Seidcl, A. (3) 5 18; (7) 655 Scidel, G. (5) 5 10 Seidel, S.W. (7) 255 Seidl,E.(ll) 123 Seidl, P.R. (10) 29,83 Seiferlmg, D. (6) 46 Seifert, G. (7) 767 Scigneuret, M. (3) 197; (7) 414 Scino, H. (1 0) 73 Scip, S.(5) 261 Seitlcr, R.O. (6) 158 Seitz, J. (7) 796 Seivert, M.(7) 691,692 Sekar, P. (3) 474,476,485,486 Sekine, M. (1 1) 1 11 Sckino, H. (4) 19,25 Scllnr, R.J.(12) 265

Selvaratnam, S . (3) 80 Selzer, T. (1 1) 20 Scmenova, N.A. (12) 116 Semeria, F. (14) 98 Semlyen, J.A. (10) 363 Scmmcr, V. (7) 650 Sen, S . (6) 113

Scntcal, L. (5) 270 Sengstschmid,H. (5) 23 S e M , H.(5) 446 Senna, M. (7) 430,431,5 16,554, 555

Seno, M. (1 0) 2 17,225 Scnos, A.M.R (7) 428

Seo,K.(1 1) 128 Scok, Y.J. (5) 453; (9) 55, 128 SWk, Y.-S. ( I 1) 24 Scpa, J. (2) 132-134; (3) 383,386; (7) 6,709

Seppaelae, J. (10) 105 Scppala, J.V. (10) 116,140 Sera, A. (1 1) 89 Scrcda, S. (7) 273 Scrcdcnko, V.A. (3) 503 Scrganov, A. (9) 35 Scrgecv, N.A. (7) 26 Scrgcieva, 0.R (5) 111 Sergeycv,N.M. (2) 167; (3) 91, 437; (5) 140

Scrianni, AS. (4) 6; (5) 118; (1 1) 61

Scmclz, F.G. (10) 35,89 Serpersu, E.H. (1 1) 14 1 Scrra, M.J. (5) 466 Serrano, D.P. (7) 617 Scrralrice, G. (6) 129 Scshadri, K. (9) 152,155 Sclhson, I. (5) 32 1; (9) 56 Scto, H. (5) 15 Seto, T. (6) 136 Scttambolo, R.(3) 2 12 Sette, M. (5) 309 Sevcrino, A. (7) 637 Seydoux, R (13) 78 Seymour, A.-M.L. (12) 147,166 Sfihi, H. (7) 797,822 Sgravenmadc, E.J. (13) 173 Shaabani, A. (5) 418 Shabanova, E. (3) 353; (7) 5 15 ShabcsLary, N. (3) 248 Shachar-Hill, Y.(12) 108 Shafer, R.H. (3) 177 Shah, S.A.A. (3) 230 Shaka, A.J. (8) 31 Shaller, C. (12) 75 Shamsipur, M.(3) 162,234 Shan, X. (9) 68 Shang, Z. (8) 69.73 Shankar, R. (5) 124 Shanks, J.V. (12) 83 Shannon, I.J. (7) 827 Shao, P.L. (7) 429 Shao, Q.(7) 139 Shao, Y. (11) 118; (13) 22

Nuclear Magnetic Resonance

532 Shapiro, J.I. (12) 159 Shapiro, M.J. (7) 173, 184 Sharma, N. (14) 3 Sharma, RK. (12) 78 Sharma, U. (1 I) 50 Sharon, 1. (12) 63 Sharp, J.C. (13) 169 Sharp, K.G. (10) 320 Sharp, RR (6) 99 Shashkov, AS. ( 5 ) 374 Shashkov, S . (10) 408 Shavila, Y. (13) 148 Shaw, A.A. (8) 22 Shaw, G.L. (8) 85 Shaw, G.S. (9) 3 1 Shaw, I.C. (12) 9 Shaw, N.S. (6) 178 Shaw, W.H., Jr. (10) 104 Shaw, W.V. (1 1) 139 Shchepkin, D.N. (3) 124; ( 5 ) 83; (6) 82 Shchipanova, I.N. (12) 38,86,87 Shea, K.J. (7) 446 Shehan, B.P. (12) 162,218 Shcldon, J.G. (12) 88 Shcldon, S.G.(7) 787 Shelimov, B. (7) 238 Shen, D. (12) 297 Shen, H. (5) 409 Shen, H.C. (10) 381 (12) 74,82 Shen, H.-L. Shen, L. (3) 374; (7) 287 Shen, L.F. (13) 46 Shcn, N.X. (3) 256 Shen, Q.(5) 220 Shen, Q.H. (10) 158 Shcn, X. (14) 132,139,159 Shen, Y. (10) 197 Shen, Y.J. (12) 134; (13) 70 Shen, Z. (10) 197 Sheng, S . (6) 6 Shenouda, N.S.(7) 320 Shenton, M.J. (10) 363 Sheppard, N. (4) 30 Sherr, D. (12) 7 1 Shenif, B.L. (7) 574 Shemff, N. (10) 24,246 Sherrington, D.C. (10) 339,387, 397 Shcrry, A.D. (3) 174, 190,441; (6) 173; (12) 8,32,33, 190,212 Sherwocd, W. (7) 791 Sheth, H. (5) 288 Shcu, Y.-H. (3) 354; (5) 153,223 Shevchcnko, I.V. (5) 464 Shi,F. (10) 63 Shi, G.( I 1) 118

Shi, J. (5) 141 Shi, J.F. (10) 384 Shibata, A. (7) 746 Shibata, M. (10) 80 Shibata, T. (9) 75; (12) 292 Shicls, J.C. (7) 298,299 Shigcmrtsu, K. (3) 65 Shigemori, S. (13) 178 Shiloach, J. (9) 14 Shirn, J.Y. (1 1) 9 Shimada, S. (7) 805 Shimaoka, A. (7) 364 Shimidzu, T. (10) 221 Shimizu, A. (6) 127,136,163 Shimizu, K.(3) 261 Shimura, M. (10) 342 Shin, I.D.(10) 306 Shin, Y.J. (12) 299 Shindo, M. (3) 225 Shindo, Y. (6) 138 Shingler, V.(5)321 Shingu, T. (5) 395 Shinmyom, T. (1 1) 4 1 Shinohara, S . (12) 135 Shinoharr, T. (7) 430,43 1 Shinohara, Y. (3) 365 Shintaro, S . (6) 127 Shiohara, K. (10) 134 Shiono, T. (1 0) 223 Shioya, S. (1 2) 200 Shiozaki, R. (3) 283 Shipil', P.N. (7) 265 Shirahama, K. (12) 85 Shirakawa, M. (8) 78; (9) 285 Shofer, S.L. (12) 237 Shoji, A. (7) 289,335 Shon, K.-J. (5) 289 Shonk, T.K. (12) 279 Shoo, Q.-F.(7) 149 Shoolery, J.N. (7) 183 Shore, J.S. (7) 74 Shore, S.G.(7) 253 Shorer, M. (7) 472 Shortle, D. (8) 81; (9) 210,304, 305 Shostakova, A.K. (7) 282 Shoubridge, E.A. (12) 64 Shuetz, M.(7) 275 Shuker, S.B. (9) 11,142 Shukla, H.P. (12) 174 Shukla, R. (6) 66 Shulman,G.l. (12)313,315-318 Shulman, R.G. (12) 122,315,320 Shustov, G.V. (1 1) 56 Shvaleva, A.L. (1 2) 99 Shvarts, V.A. (6) 177 Shvcts, V.I. (7) 350

Si, Y.-K. (12) 74,82 Sibel'dina, L.A. (12) 86, 87 Sich, C. (8) 87 Sichirollo, A.E. (13) 129 Sicinska, W. (3) 126,425,426, 439 Siddcck, M. (12) 122 Siddiqui, M.A. (5) 504 Sidelnikov, V.N. (7) 693,700 Sidhu, P.S. (7) 824,825 Sidorov, L.N. (3) 502,503 Sieber, S . (1 1) 22 Sicbert, F. (7) 295 Siebert, H.C. (9) 156,157 Siegal, G.(5) 306; (9) 193 Siegbahn, P. (4) 48 Siegel, S.(6) 219; (13) 22 Sieger, P. (7) 8 11 Sicgl, H. ( 5 ) 168 Siehl, H.U.(2) 35 Sicpmann, J.I. (10) 119 Sieralta, A. (3) 37 Sierra, M.G. (7) 226 Sierzputowska, H. (1 1) 110 Sicvcrding, L. ( I 2) 293 Sigwalt, P. (10) 358 Sihombing, R (7) 48 1 Sijbesma, W.F.H. (12) 43 Sikirica, M. (5) 507 Silbernagcl, B.G. (6) 132 Silks, L.A. (3) 70 Sillard, R. (5) 291 Sillescu, H. (6) 14, 104, 105, 189 Silva, T.H.A. (1 1) 37 Silvcrman, R W . (13) 22 Silvestri, RL. (14) 97 Silvestru, C. (3) 408 Simericl, C. (5) 347 Simion, D.V. (2) 200; (7) 165 Simkovic, I. (7) 3 15,3 16 Simon, A. (3) 501; (7) 523 Simon, C.K.S. (3) 230 Simon,J. (10) 24 Simonetti, M. (5) 283 Simons, RS. ( 5 ) 90 Simonsick, W.J., Jr. (10) 6 Simonutti, R (7) 67,384,829; (10) 293,322,330 Simorre, J.P. (9) 104, 106-108 Simova, S.(3) 151; (11) 82 Simpelkamp, 1.(7) 445 Simpkins, S. (12) 196 Simpson, C.K. ( 5 ) 195 Simpson, E.J. (13) 141 Simpson, M.W. (7) 266 Sims,M. ( 5 ) 272 Sinaye, P. (1 1) 133

Author lndex Singcr, D. (14) 66,90 Singh, A.K. (3) 488; (7) 762 Singh, K.K. (11) 95 Singh, N. (7) 5 11 Singh,P.B. (5) 443; (9) 40 Singh, RM. (1 1) 95 Singha, N.C. (5) 63,499 Sinnema, A. (7) 487 Sinnwell, V. (5) 386 Sinton, S.W. (13) 61; (14) 20 Siri, D. (5) 408; (1 1) 55 Siri, F.M. (12) 154 Sirkecioglu, 0. (7) 126 Sitkowski, J. (3) 117, 119, 128, 427; (5) 78,79; (7) 172

Sitprija, V. (12) 57 Siury, K. (10) 408 Siuzdak,G. (9) 132 Sivadinarayana, C. (7) 609,610 Skelton, B.W. (5) 188, 189; (7) 267,268

Skelton, N.J. (5) 304 Skene, T.M. (7) 391

Skibbe, U. (13) 167 Skibsled, J. (2) 123; (3) 247,25 I; (7) 77

Skibsted, L.H. (7) 312 Skidmore, M.A. (3) 484 Skinner, G.A. (3) 63 Skinncr, T.E. (8) 6; (12) 257 Skirda, V.D. (6) 158 Skjacrback, N. (5) 282 Skjemstad, J.O. (7) 391,466 Skjctnc, T. (7) 195 Sklenif, V. (5) 14 Skokan, E.V.(7) 134 Skolimowski, J. (5) 85 Skottner, A. (13) 176 Skwarczynski, M. (3) 75 Skyba, P. (6) 179 Skyrnnikov, N.R. (6) 125 Slade, R.C.T. (7) 816 Slate,, R.A. (11) 145 Slater, C.D. (3) 95 Slater, J.C. (5) 392 Slates, R (13) 22 Slattery, J. (12) 265 Slawin, A.M.Z. (3) 303 Slechta, J.D. (12) 58 Sligar, S.G.(3) 494 Slijper, M. (3) 176; (5) 303; (8) 42; (9) 90,91, 196,277

Slornozynska, U.(7) 34 1 Smaihi, M. (7) 433,443,460 Small, G.J. (11) 1 13 Small, G.W. (3) 12 Smart, S.C. (12) 23

533

Smart, S.P. (7) 827 Smidsrocd, 0. (7) 313; (10) 26 Smirnov,S.N. (3) 88,124; (5) 83; (6) 82

smimov,V.S. (7) 35 Smirnow, L.P. (10) 35 1 Smith, A.E. (5) 367 Smith, A.M. (14) 64 Smith, B.M. (10) 350 Smith, B.O.(9) 75 Smith,B.R. (13) 18 Smith, D. (12) 118 Smith, D.M. (5) 202 Smith, E.G. (6) 48 Smith, F.W. (9) 116 Smith, G.A. (12) 28 Smith, G.D. (6) 146; (10) 145 Smith, J.A. (5) 348 Smith, K.A. (7) 820 Smith, K.J. (5) 3 10 Smith, L. (14) 146 Smith, L.J. (9) 21 1-213 Smith, M.E. (3) 240,467; (7) 110, 507,508,531,532,775,780, 810; (10) 333 Smith, M.L. (2) 127; (3) 422; (7) 512 Smith, P.B. (10) 392 smith,S.L. (4) 43 Smith, S.O. (3) 178; (7) 44 Smith, S.R. (1 1) 67 Smith, T.A.D. (4) 80; (1 1) 23 Smith, T.W. (12) 179 Smith, W.E. (12) 10 Smith, W.S. (1 1) 110; (12) 238 Smithgall, T.E. (5) 257 Smrecki, V. (3) 85 Snape, C.E. (7) 121, 125,126, 725; (10) 339,387,397 Sncddon, L.G. (2) 114,115 Snijder, H.J. (13) 146 Snijkers-Hendrickx, I.J.M. (7) 432 Snurr, RQ. (7) 716,717 Snyder, J.P. (2) 202; (5) 205 Snyder, L.C. (14) 17 Soares, B. (10) 374 Soares,C.M. (1 1) 1 1 Soares, R.F. (7) 452 Sobczyk, L. (3) 87, 109 Sobrados, I. (7) 163,215,553,766 Sodickson, A. (8) 3 Soedman, 0. ( 6 ) 213; (13) 88 Sdjanaatmadja, U.M.S. (9) 156, 157 Sonnichscn, F.D. (5) 245,308; (8) 32; (9) 30, 164 Soffc, N. (9) 70

Soga, K. (10) 223 Sogani, M. (12) 140 Soghomonian, V. (14) 14 Soh, J.R. (3) 267; (7) 681,682 Soimakallio, S. (12) 273,281 Sok, J. (3) 327 Sokolova, E.V. (7) 574 Solana, I. (3) 292; (5) 178 Solca, J. (6) 95 Soldatov, A. (7) 137 Soler, L.P. (5) 19 Soliemani, H. (5) 4 18 Soliveri, J. (7) 389 Solotnov, A.F. (1 1) 8 1 Solov'ev, E.E. (7) 16 Solov'ev, V.P. (6) 139; (1 I) 81 Solujic, L. (3) 445; (7) 225 Solum, M.S. (7) 119 Somberg, H. (3) 7 Somoza, J.R (9) 204 Son, T.-D. (12) 91 Son, Y. (10) 247 Song, G. (1 1) 1 18 Song, H.F.(12) 188 Song, H.K. (13) 170 Song, J. (5) 300 Song, W. (10) 230 Song,Y.Q.(13) 78 Song, Z. (7) 297; (14) 30 Soni, S.D. (1 I) 106 Sopchik, A.E. (1 1) 5 1 Sordo, J. (3) 309,324,325; (7) 32 1

Sorcnscn, O.W. (5) 20,27; (7) 40; (8) 5,43

Sorensen, T.S. (2) 200; (7) 165; (1 1) 22 Sorgc, C.(7) 463,469 Sorgenfrei, B.L. (13) 54 Sorimachi, K. (5) 330 Sorland, G.H. (6) 212 Sosa, C.P. (2) 103 Soskic, V. (8) 87 SoSnicki, J.G. (5) 209; (1 1) 48 Sosnowski, J.J. (3) 369 Soti, F. (3) 86; ( I 1) 18 SOlta, P. (10) 394 Soubayrol, P. (7) 435 Sourgen, F. (5) 475 Sousa-Aguiar, E.F. (7) 626,663 Southon, T.E. (12) 107 Sovago, J. (10) 57 Sozzani, P. (7) 67,829; (10) 293, 322,330

Spagnolo, P. (5) 498; (1 I) 16 Spangfort, M.D. (5) 342 Spangler, M. (3) 79

Nuclear Mapretic Resonance

534

Spannenberg, A. ( 5 ) 74 Spanoghc, M. (6) 201 Spanswick, R.M. (12) 100; (13) 158 Spassky, N. (1 0) 85 spassov, S.L. (1 1) 54 Spencer, D.D. (12) 277 Spencer, G.M. (7) 263 Spcnccr,N. ( 5 ) 121,357 Spcnscr, 1.D. ( 5 ) 40 Sperandio, D. ( 5 ) 115 Spevacek, J. (7) 338; (10) 403,415 Spiccia, L.(3) 419 Spiccr, L.D.(9) 62,266 Spickctt, C.M. (12) 10 Spiclbcrg, N. (14) 87,90 Spiclman, D.(12) 6 1 Spiess, F.W. (10) 253 Spicss, H.W. (7) 23,36,37,47, 53,93, 94,419,422; (10) 4, 280,3 12,318,319,335,336, 338,355, 376,394, 43 1-433; (13) 58,65,66, 1 18; (14) 80, 84,93,96 Spinelli, D. (3) 102; ( 5 ) 84 Spisni, A. ( 5 ) 285 Spitz, R. (10) 95, 107 Spiitfaden, C. (9) 20 1,288 Spitmcr, N. (9) 240 Spom, M.B. ( 5 ) 452; (9) 53 Spraul, M. ( 5 ) 20; (7) 40 Springuel-Huet, A. (3) 5 16 Spronk, C.A.E.M. (8) 42; (9) 91, 196 Sprovicro, E. (4) 65; ( 5 ) 237; ( I 1) 52 Spruijt, B.M.(13) 174 Spurio, R. ( 5 ) 309 Spyros, A. (10) 303 Squircs, L. (10) 442 Srcedhara, A. (3) 270 Srcjic, R. (7) 565 Srcrc, P.A. (12) 8 Srikrishnan,T. (1 I) 106 Srivastava, N. (1 1) 50 Srivastava, R.C. (4) 74; ( 5 ) 54 Srowronska, A. (7) 194 Stabaki, D.(3) 3 15 Stadlcr, R.(10) 319,349,355,356 Stael, G.C. (10) 353 Slahl, M. (2) 111; ( 5 ) 344,489; (9) 24 SLahl, S.J.(8) 33; (9) 52, 148, 149, 158,188,189,254 Staley, S.W. (14) 10 Standaert, T.A. (12) 149 Stmdnes, A. (5) 67

Standte, B. (7) 7 1 1 Stanica, D. (3) 344; (7) 633 Stanley, G.G. ( 5 ) 97 Stanley, J.A. (12) 255 Stansbie, D. (12) 307 Stanton, J.F. (2) 33,35,41,67; (4) 2 1-24 Stapf, S. (6) 158 Starck, P. (10) 109 Storich, M.R.( 5 ) 343; (9) 22 Stark, R.E. (7) 371,399 Starke, 1. ( 5 ) 86 Starkmann,B.A. (3) 492 Starovasnik, M.A. (5) 304 Staszewska, 0.( 5 ) 116 Staubach, B. (3) 71 Staubcrt, A. (12) 293,296 Stcadman, S. (lo) 287 Stebbins, J.F. (3) 254; (6) 113; (7) 109,113,748,760 Stoc, W.J. (3) 473 Steedman, W. (7) 126 Stcel, P.J. (1 1) 87 Stccnbcrgcn, C. (12) 161, 167 Steensma, E. (8) 83,84 Stefani, H.A. (3) 482 Stcfaniak, L. (3) 117, 119, 128, 423,427,429,433,434; ( 5 ) 4, 77-82,85, 116,226; (7) 172, 22 1 Stcfanova, R. (3) 292; ( 5 ) 178 Stcgmann, H.B. ( 5 ) 407 Stegmann, R.(2) 116 Stchling, U.M. (10) 133 Stcin, E.G.(9) 229 Stein, K.M. (10) 133 Stcin, M. ( 5 ) 332 Stein, P.C. (10) 53 Steinbcck, C.(3) 4 Stcinbeck, M. (4) 74; ( 5 ) 54 Steinborn, D. ( 5 ) 182-184 Stcinbrunn, M.B. (3) 129 Stcincbrunncr,G. (3) 463; (6) 85, 95 Steiner, E. (2) 160, 199 Stelm, 0.( 5 ) 93 Stcnger, V.A. (3) 246 Stcngcr-Smith,J.D. (7) 199; (10) 259 Stengle, T.R. (2) 204-206 Sknland, C.J. (5) 252 Slenutz, R (14) 89 Stepanov, A.G. (7) 693,700,708 Stephan, H. (5) 389 Stcphan, M.P. ( 5 ) 372 Stcphcns, P.J. (2) 107 Stcphenson, D.S.( 5 ) 113

Stcphenson, G.A. (7) 207 Stcrck, J. (6) 201 Stcrcnbcrg, B.T. ( 5 ) 186 Sterk, H. (5) 24,58,440; (8) 4,44 Stcuer, B. (3) 48 1 Sleuemagel, S. (7) 100,653 Stevens, E.D. (1 1) 68 Stevenson, R.J. (1 I ) 99 Stcwart, J.J.P. (4) 66 Stcwnrt, M.J.(7) 159; (lo) 334 S t y , G.J.J. ( 5 ) 187 Stcynberg, J.P. (5) 396 Stibr, B. (2) 115; (3) 337,340 Sdlbs, P. (13) 42 Stiles, P.J. (2) 180 Stirling, A. (7) 640 Stivcrs, J.T. (9) 59, GO Stluka, C. (14) 8 Stobart, S.R.(1 1) 148 Stockman, B.J. ( 5 ) 260 Stochr, C.M. (3) 74 Stojakovic, D. (7) 684 Stokcs, B.T. (12) 137 Stokoe, R.B. (7) 3 17 Stolarski, D.J. (6) 185 Stoll, A.L. (12) 272 Stolpcn, A.H. (6) 59 Stone, A.G. (7) 392 Storek, W. (3) 351; (7) 612 Sbrrs, RW. (12) 61 Stott, F.J. ( 5 ) 443; (9) 40 Stott, K. (8) 31 Stourton, C. (7) 95, 104,420,421; (14) 78,79 Stout, B.E. (7) 306 Stowcll, J.G. (7) 207 Stoyanova, R.(12) 75; (13) 47 Straka, J. (7) 338 Slrkhova, N.N. (6) 139 Strange, J.H. (6) 48; (13) 29,3 I, 112 Straubingcr, K. (12) 293 Swaus, D.A. (10) 224 Straws, S.K. (7) 41 strazewski, P. (3) 454 Strcater-Knowlem,I.M. (1 3) 172 Strcck, R (3) 381 Strcct, J.C. (12) 222 Strcct, J.M. (3) 502,503 Strckowski, L. ( I 1) 15 Slrclenko, Y.A. (3) 437 Strelkova, T.V.(10) 86 Strickland, G.C. (7) 193 Stripe, W.A. (4) 6; ( 5 ) 1 18; (1 1) 61 StroehI, D. ( 5 ) 86 Strohschein, S. (7) 332.

Author Index Stromberg, P.C. (12) 241 Struchkov, Yu.T. (7) 265 Strunk, K. (3) 193 Struppc, J. (14) 136 Stubbs, M. (12) 35 Stucki, J.W. (7) 558,573 Stucky, G.D. (7) 678,811 Studelska, D.R. (7) 326,356 Stufkcns, D.J. (3) 409; ( 5 ) 506 Stumpp, E. (7) 152 Sturat, J.W. (1 1) 110 Stutz, B. (2) 109 Styblo, M. (1 2) 60 Stylcs, P. (13) 73 styrcz, s.(3) 97 Su, W. (3) 279 Subrayan, R.P. (10) 113 Suchanski, W. (7) 190 Suchoparck, M. (10) 403,415 Sudhakar,R.J. (7) 62 1 Sudmcicr, J.L. (8) 74 Sudmeijer, 0. (10) 227 Sudol, M. (9) 8 Sugasawa, K. (3) 225 Sugcla, H. (9) 285 Sugimoto, K. (7) 210 Sugimoto, M. (2) 17, 19; (3) 42 Sugisawa, H. (7) 335 Sugiyama, T. (1 1) 30 Suguhara, Y. (7) 785 Suh,B.J. (3) 327 Suits, B.H. (2) 133; (3) 383; (7) 6 Sulikowski, B. (7) 537,605, 608 Sullivan, A.C. (3) 230 Sumegi, B. (12) 8, 145 Sumiyama, K. (7) 430 Swnmcrs, M.F. (9) 5,6, 19-22,54 Summers, S.P. (3) 257 Sumpter, R.M. ( 5 ) 393 Sun, B. ( 5 ) 171; (7) 255 Sun, H. (12) 53 Sun,H.D. ( 5 ) 395 Sun, H.Z. (7) 261 Sun, J. (12) 160 Sun, M. ( 5 ) 357 Sun,P.C. (7) 632 Sun, Y. (7) 591 sun, z.-Y. (3) 493; (7) 337 Sunada, S.(9) 270 Sundarcsrur, S. (7) 685 Sundelin, J.-P. (5) 413 Sundholm, D. (2) 27,34,50 Sundquist, B. (7) 137 Sundquist, W.I. (9) 5 , 19 Suntola, T. (7) 740 Suontamo, R. (3) 435; ( 5 ) 62 Sur,S.K. (6) 172

535 Suri, A.K. (9) 117,124 Suryaprakash, N. (2) 128; (7) 378; (14) 4,60. 128 Sutcliffe, L.H. (13) 32 Sutcliffc, M.J. (9) 136-139 Sum, D. (7) 39; (14) 28 Suter, U.W.(7) 78,731; (10) 209 Sutovich, K.J. (7) 648 Suty, H. (7) 571 Suzuki,E. (9) 123; (12) 292 Suzuki, H. (3) 389; (5) 134 Suzuki, K. (7) 430,43 1 Suzuki,M. (3) 158; (7) 798 Suzuki, S. (3) 154,255 Svcnsson, A. (3) 509 Svcshnikov, N.N. (5) 2 13 Svirkin, Y.Y. (10) 188 Svoboda, J. (6) 98 Svyalkin, V.A. (1 1) 25 Swagcr, S. (4) 4 1,42 Swaminathan, M.(5) 401; (I 1) 45 Swann, M.J. (10) 169 Swapna, G.V.T. (8) 69 Swartz, H.M.(12) 189; (13) 120 Swcahan, B.C. (1 I ) I 16 Swenson, RP. (5) 260 Swift, G. (10) 187,188 Swirsky, Y. (13) 67 Sy, L.-K. ( 5 ) 122 Sybilska, D. (3) 128 Sykcs, B.D. (3) 108; ( 5 ) 245,251, 254,288,308,322; (8) 32; (9) 29-31, 164, 190 Sykorova, I. (7) 1 17 Symms, M.R.(13) 32 Sypcr, L. ( 5 ) 226 Syrota, A. (12) 307,309 Syvitski, R.T. (3) 416 Szabo, A. (2) 137; (6) 116,117; (9) 260 Szabo, E. (9) 141 Szakan, B. (3) 135, 148 Szafran, M. (3) 427 Sixinlay, J. ( 5 ) 500 Szarek,W.A.(5)381;(11) 121 Szczecinski, P. (14) 123 szczcpaniak, L. (12) 212 Szczcsniak,E. (7) 190 Szczodrowska, B. (3) 110 SZC, K.-H. ( I 1) 139 Szcimics, G. ( 5 ) I13 Szejgis, A. (6) 135 Szergold, E.S.(12) 75 Szcto, C. (10) 409 Szetsi, S.K. (3) 321 Sziligyi, L. (5) 380; (9) 141 Sznclcr, E. (1 1) 69

Szostak, R (7) 175 Szpyt, I. (7) 627

szymarlski, s. (5) 47 Szyperski, T. ( 5 ) 448; (8) 91; (9) 15,18,183,192 Tabary, X. (5) 61 Tabayashi, K. (14) 18 Tabei, K. (3) 428 Tachibana, K. (5) 433,434 Tagawa, K. (1 2) 300 Tahara, S. (3) 65 Tailin, W. (7) 63 1 Taillades, G. (3) 413; (7) 535 Tajouri, T. (10) 33 1 Takabayashi, A. (10) 73 Takahashi, C. (1 1) 128 Takahashi, H. (12) 303 Takahashi, K.(12) 140, 197; (13) 178 Takahashi, M.(7) 773 Takai, H. (3) 158 Takai, M. (7) 354 Tnkanashi, Y. (1 2) 203 Takano, I. (3) 57 Takashima, A. (5) 28 1 Takashima, H.(2) 7,8, 18, 19; (3) 42 Takasu, T. (1 2) 27 1 Takata, T. (10) 208 Takayama, T. (7) 236,269 Takeda, H. (7) 785 Takeda, K. (7) 83,618 Takeda, N. (3) 389; (5: 134; (7) 289; (12) 292 Takeda, S. ( 5 ) 199 Takcgoshi, K. (7) 83; ( 0) 329, 368 Takeguchi, T. (7) 620 Takehana, Y. (10) 123 Takcmura, H. (1 1) 41 Takeya, K. (3) 57 Takcyama, H. (7) 790 Taki, I. (12) 282 Takikawa, H. (3) 55 Talaga, P. (5) 458 Tallant, D.R (7) 77 1 Tallarck, U. ( 10) 244 Tallcc, N.L. (12) 202 Tallincau, C. (12) 186 Talluri, S. (8) 82 Talvitic, A. (3) 48 Tamm, N.B. (7) 134 Tamura, A. (12) 193 Tan, RY. (9) 113 Tanaka, H. (7) 746

Nuclear Magnetic Resonance

536 Tanaka, K. (3) 158; (5) 395; (12) 302

Tanaka, M.(5) 199 Tanaka, R. (3) 59 Tanaka, S.(2) 8, 19; (3) 42 Tanaka, T. (3) 60 Tanaka, Y. (1 2) 228 Tancredi, T. (5) 277 Tancv, P.T. (7) 580,586 Tang, J. (10) 206 Tang, P. (7) 296; (13) 71 Tang, T.-D. (7) 8 12 Tang, W. (3) 149 Tang, W.X. (3) 127 Tang, X.W. (13) 30 Tani, K. (5) 199 Tanigaki, K. (3) 239 Tanigaki, N. (10) 150 Tanigaki, T.(12) 200 Taniguchi, M. (1 1) 71 Taniguchi, Y. (6) 136, 163 Tanner, S.F.(7) 7 Tannus, A. (8) 7, 16; (12) 205 Tanouchi, M. (12) 287 Tansho, M. (14) 167 Tao, J. (3) 402 Tapia, 0. (1 1) 1 1 Tapparo, A. (3) 348 Tarnasov, V.P. (10) 35 1 Tarroni, R (2) 139,140; (14) 145 Tasaki, K. (7) 69; (10) 297,299 Tashiro, K. (10) 6 Tashiro, M. (8) 73; (1 1) 71 Taslicr, R.C. (12) 112 Tassini, M. (12) 50, 171 Tasz, M.K. (1 1) 43 Tate, A . R (12) 327 Tatemitsu, H. (1 1) 4 1 Tato, M. (5) 285,302 Tatoud, R (12) 8 1 Tatsumi, K. (7) 151 Tatsumisago, M. (7) 773 Tattershall, B.W. (5) 174 Taulelle, F. (7) 525,679,795 Taupitz, M.(6) 13, 106, 150 Tausch-Trcml, R. (12) 229 Tauskcla, J.S. (12) 34,64 Tavares, M.I.B. (10) 309,310, 353,362,369,374

Taylor, C.M.V. (6) 187 Taylor, J.A. (7) 466 Taylor, M.J. (1 1) 99 Taylor, R (3) 502-504; (12) 3 17 Taylor, RE. (7) 74; (13) 78 Taylor-Robinson, S.D.(12) 198 T a m p a , M.P. (10) 388 Teaslcy, M.F. (10) 276

Tcbby, J.C. (5) 490; (1 1) 13, 14 Tecrstra, D.K. (7) 574 TcIT, D.J. (3) 418 Tcichmann, S. (9) 75 Tcjima, T. (2) 17 Tekcly, P. (7) 84,571; (10) 3 Telcman, 0. (7) 382 Tcllicr, C. (5) 377; (1 1) 135 Temcriusz, A . (3) 1 11; (5) 125; (7) 197,348

Temuz, M.M. (10) 59 Tenenholz, T.C. (5) 296 Tcng, Y. (5) 98 Tenhuncn, M. (12) 28 1 Tcnnant, L. (9) 13 1 Terada, T. (9) 75 Tcrada, Y. (12) 197 Tcrao, T. (2) 141; (3) 213; (7) 75, 83,830

Tcrasaki, 0. (7) 644 Terasawa, H. (8) 48,55 Tcrcmzi, M.(14) 49 Tercnzi, M. (14) 112 Tcrlouw, A. (13) 166 Tcrraza, C.A. (1 0) 239 Tcrreno, E. (3) 191 Tcrskikh, V.V. (3) 520; (7) 596 Tcrucl, H. (3) 37 Tcrvo, J. (7) 478 Tcrzis, A.F. (14) 142 Tesche, B. (7) 445 Tessari, M.(8) 49 Tessicr, C.A. (5) 90; (10) 4 1 Tcssicr, J.J. (13) 147 Tcstini, M.(13) 10 Teyssic, P. (10) 76 Teze, L. (10) 323 Thaddeus, P. (2) 55 Thakur, K.A.M. (10) 119 Than, C. (3) 217,219,220 Thanabal, V. (5) 328 Thatchcr, G.R.J. (5) 381; (1 1) 121 Thclcm, M. (13) 35 Theodoropoulou, E.(7) 406 Theodorou, D.N. (6) 21 1 Thcm, A. (6) 208 Thibaudcau, C. (5) 356 Thicle, H. (3) 7; (14) 25 Thlianakis, E.I.(10) 345 Thoene, C. (3) 478,479 Thonnessen, H. (5) 179, 194,2 15 Thomas,A. (10) 290 Thomas, B. (3) 390; (6) 110; (7) 94,753,757,767-769 Thomas, D.J.(12) 60 Thomas, K.M. (7) 156 Thomas, R.J. (6) 185

Thomas, W.A. (4) 80; (5) 1;(1 1) 23

Thominc, S. (12) 66 Thompson, A . R (7) 3 15 Thompson, C.B. (9) 9-1 1 Thompson, G.D. ( 12) 2 1 Thompson, L.K. (7) 416 Thompson, R1.G. (1 0) 2 1 1 Thompson, T. (1 2) 270 Thompson, T.V. (7) 155, 156 Thomson, T. (3) 288 Thorn, K.A. (7) 480 Thornburg, L.D. (9) 54 Thornton, J.M. (5) 267,272; (9) 21 1,220

Thornton, K.H. (5) 328 Thornton, L.C. (1 1) 145 Thornton-Pctt, M. (3) 337,340 Thorpc, T.A. (12) 106 Thuery, P. (3) 249 Thuring, H. (9) 281 Thursficld, A. (7) 710 Tian, B.-S. ( I 1) 150 Tian, D. (10) 196 Tian, F. (7) 402; (14) 59 Tian, J. (10) 371 Tian, R (12) 178 Tiddcslcy, D.J. (14) 50 Tiddy, G.L.T. (14) 62-65 Tidwcll, T.T. (3) 456 Tie, H. (7) 619 Tielunk, E.RT. (3) 415; (5) 145; (7) 257

Ticmcy, J. (1 1) 57 Ticrsch, B. (13) 136 Ticzzi, E. (9) 309 Tildesley, D.J. (14) 175 Tillack, A. (5) 74 Timellinc, G. (1 3) 96 Timofeeva, M.N. (3) 520 Timoshcva, N.V. (7) 204 Timpl, R (9) 44,45 Tinant, B. (5) 424 Thg, Y.-L. (12) 71 Tinoco, I., Jr. (5) 21 1,361,468; (1 1) 2

Tiripicchio, A. (3) 28 1 T h e , C. (5) 347 Titman, J.J. (10) 438 Tittlebaum, M.E. (7) 504 Tjan, S.B. (10) 159 Tjandra, N. (2) 137; (5) 88; (6) 63; (8) 33,59; (9) 158, 172, 174, 254,258; (14) 13 Tjcerdcma, RS. (12) 237,238 TkaE, I. (5) 227 Tkatchcnko, I. (10) 237 '

Author index Tobiason, F.L. ( 5 ) 396,397 Tocik, 2. ( 1 1) 109 Toda, H. (5) 503 Todd, P. (10) 350 Todcschi, N. ( 5 ) 427; (1 1) 17,28 Toke, L. ( 5 ) 500 Tolle, A. (6) 189 Toi, H. (3) 329 Toida, T. (5) 367; (1 1) 130 Toiron, C. (5) 358 Tokitoh,N. (3) 389; ( 5 ) 134 Tokuhiro, T. (6) 168 Tokumitsu, T. (12) 136 Tolgycsi, W.S. (4) 34 Tollc, A. (6) 104 Tolman, J.R. (8) 60,61; (9) 170, 171,173 Tomaselli, M. (7) 39,78; (10) 209 Tomasevich, G.R. (2) 55 Tomasovic-Canovic, M. (7) 565 Tomesch, J. (7) 173 Tomida, M. (10) 166,245 Tomimoto, M. (I 1) 105 Tomita, Y.A. (7) 324 Tommc, P. ( 5 ) 45 1 Tomoda, S. (2) 171; (3) 90, 118; ( 5 ) 5 14 Tompa, K. (7) 276 Tomutsa, L. (13) 33 Toncllato, U. (3) 140 Tonelli, A.E. (10) 8,306 Tong, H. (7) 139 Tong, K.I. (5) 337 Tong, L. (9) 6 Tong, T.-H. (7) 38 Tonthat, D.M. (6) 44 Torchia, D.A. ( 5 ) 445,452; (9) 52, 53,58, 148, 149, 188, 189,260, 278 Tordjeman, P. (10) 323 Tordo, P. ( 5 ) 408; (1 1) 55 Torgeson, D.R (3) 327 Toriumi, H. (14) 142 Tomcna, C.F. (4) 78 Tornieporth-Oetting, I.C. (3) 438 T o m a x , K.W. (6) 149 Torocheshnikov, V. ( 5 ) 136,137 Torregrosa, J.V. (12) 306 Torres, D.A. (6) 173 Torres, P.D. (3) 368,378; (7) 178, 179 Torresi, R M . (6) 115 Torri, G. (7) 736 Toscano, R.A. (3) 408 Tosukhowong, P.(1 2) 57 Toth, E. (6) 77, 167, 170 Toth, G. (3) 498; ( 5 ) 132

537 Toulas, P. (1 2) 326 Tower, R.A. (12) 233,242 Toyota, M. (3) 50 Toy-Palmer, A. ( 5 ) 341 Toyuki, H. (7) 773 Tpkarz, R. (6) 168 Tracey, I. (1 2) 130 Tracht, U. (3) 518; (7) 655 Train, S.G.( 5 ) 97 Tran, D. (2) 1 19; (3) 339 Tran, T.-A. ( 5 ) 280 Tranchant, J.-F. (7) 398 Trautwcin, A.X. (3) 291 Traycr, I.P. (5) 3 10 Treleaven, W.D. ( 5 ) 97 Tremilla, J.M.(7) 664 Trevanian, G. (5) 475 Trilisenko, L. (12) 86 Trillo, J.M. (7) 544 T d , L. (9) 14 Tripathy, S.K.(10) 46 Tritto, I. (10) 5 1 Trivedi, D.C. (7) 224 Trivcdi, J.S. (7) 327 Trivcdi, R (3) 486 Trivcllonc, E. (3) 62 Troeltzsch, C. (7) 734 Troendle, F.J. (3) 175 Trofmcnko, S.(3) 359; ( 5 ) 160, 161 Tronc, E. (7) 570 Trongon, D. (7) 582,624 Tropini, B. (12) 129; (13) 177 Tropis, M. (14) 48, 101 Trucks, G.W.(3) 18 Truckses, D.M. (9) 204 True, N.S.(2) 62, G3 Trujillo, J. (3) 58 Trwnbo, D.L. (10) 44,45,60,62, 67,68,70 Truyen, B. (12) 2 1 1 Tsai, D.J.S. (5) 131 Tsai, T.X. (7) 704 Tsamaktsides, C.G. (6) 8 Tsang, M.L.S. (5) 452; (9) 53 Tsang, M.W.H. (3) 63 Tsapatis, M. (7) 602 Tse, T.Y.(12) 100; (13) 158 T s d i , Y.C. (9) 280 Tsclikas, Y.( 10) 2 19 Tscng, L.-H. (7) 353 Tseng, W.-Y. (7) 140 Tsipis, C. (7) 567 Tsotinis, A. (7) 406 Tsuchihashi, N. (6) 161 Tsuda, M.(3) 5 1,55 Tsuda, Y. (12) 132

Tsuge, S.(10) 123 Tsuji, C. (12) 200 Tsuji, M.K. (12) 115 Tsuru, S.(7) 749,750 Tsutsumi, A. (10) 265 Tuan, V.A. (3) 351; (7) 612 TU~LII, Y.-F. (3) 104 Tuck, D.G. (3) 352 Tucker, A. ( 5 ) 426 Tuckcr, D.J. (10) 122, 147 Tucker, K.D. (2) 55 Tudoret, M.-J. ( 5 ) 70 Tuebke, J. (10) 408 Tuel, A. (3) 448; (7) 496 Tu@, C. (10) 139 Tugarinov, V. (5) 307 Tun~k,S.P.(7) 265 Tuohimctsa, S.(12) 322 Turwttc, M. (7) 283 Turnbull, L.W. (12) 263 Turner, B.G. (9) 19 Turner, D.H. ( 5 ) 466,471-473 Turner, G.L. (7) 771; (10) 357 Turner, M.J. (10) 363 Turncr, T.F. (7) 122 Tuzi, S.(7) 294,325 Tweig, D.B. (12) 290 Tych, W. (6) 178 Tycko, R (7) 65,79,303 Tyger, W.H. (10) 215 Tylianakis, E.I. (6) 143 Tymiak, A.A. (7) 183 Tyrrell, E. (3) 63 Ubbink, M. (9) 284 Ubcrti, A.M. (3) 17 1 U ~ l l o - B ~ C t G. b , (3) 73, 143, 212 Ueda, M. (10) 43,73 Ueda,N. (3) 122 Uedaira, H. (6) 87 Uckama, K. (3) 134 Ucmura, H. (5) 203 Ueno, M. (6) 160,161 Ucno, T. (5) 503 Uguina, M.A. (7) 617 Ugurbil, K. (12) 148, 181,319 Uhm, H.L. (3) 449 Uhrinova, S. (5) 459 Ukrainczyk, L. (7) 820 Ullmann, G. (3) 194; (7) 344 Ullrich, A. (3) 193; (14) 45 Ulug, A.M. (13) 26,53 Umbert, D. ( 13) 36 Umeda, T. (1 1) 89 Umemoto, S.(10) 184

Nuclear Magnetic Resonance

538

Unger, M. (14) 114 Ungvaiy, F. (10) 57 Uno, T. (10) 153, 184 Unrath, W. (6) 188 Unseld, K. (13) 133 Upadhyay, V.K. (10) 75 Uppenbrink, J. (5) 272 Uraoka, A. (13) 59 Urbano, F.J. (7) 490 Urbina, F. (5) 369 Ursini, C.V. (5) 9 Uryu, T. (10) 130 Usenius, J.-P. (12) 273,281,322 Usenius, T. (12) 281 Usha, M.G. (7) 302 Ushio, T. (7) 214 Usui, S.(1 1) 1 Usui, T. (1 1) 128 Utkin, Yu.N. (5) 255 Uytterhoeven, J.B. (7) 426,440 Vaananen, T.L.J. (10) 116, 140 Vaara, J. (2) 130; (3) 384; (4) 1; (5) 112; (14) 121, 124

Vaarum, K.M. (10) 26 Vacatcllo, M. (10) 222 Vachoud, L. (10) 20 Vagabov, V. (1 2) 86 Vageli, 0. (9) 275 vahtras, 0. (4) 7,54 Vai, A. (13) 129 Vaia, R A . (7) 438 Vainio, P. (12) 273,281 Vain0,A.R (5) 381; (11) 121; (12) 322

Vainrub, A. (10) 412 Vais, RA. (10) 327 Vajda, P. (7) 809 Valdes, C. (3) 58 Valensin, G. (12) 50 Valenzuela, RX. (7) 608 Valiyaveettil, S.(7) 419,422; (14) 80

Vance, J.E. (7) 290; (9) 310; (12) 161

Vandam, L. (6) 199 Vandelli, M.A. (3) 131, 132, 145; (11)42

Van den Bcrg, A.J. (12) 3 10 VandenBerg,C. (13) 166 Vandenberg, J.1. (12) 158 Vandenberghe, K. (12) 304 Van den Boogaart, A. (12) 35,273 VandenBoogcrt,H.J. (12)310 Van den Thillart, G. (12) 1 1 Van dcr Graf, M. (12) 20 VanderHart, D.L. (7) 9; (10) 174, 399

van der Helm, D. (7) 203 van der Hooven, H.W. (5) 293 Van dcr Linden, A. ( 12) 234; (13) 173

van dcr Maarcl, J.R.C. (6) 83 van der Marel, G.A. (5) 349,474, 480; (9) 87,88, 168,277; (11) 104 van dcr Merwc, P.A. (9) 129 Van dcr Oost, J. (9)284 van der Pas,J. (10) 159 Vandersande, F. (12) 2 10 vanderToom,A. (12) 12 VandcrVeen, J. (5) 233 Van der Velde, D.G. (12) 58 Van der Voort, P. (3) 266; (7) 801 van der Walal, P. (7) 629 Vanderzande, D.J.M. (10) 169, 180,398

Van der Zwan, G. (14) 133 Van der Zwan, J. (9) 282 Van der Zwan, M. (5) 459 van de Sandc, J.H. (5) 360 van de Ven, F.J.M. (5) 252; (9) 295

van de Ven, L.J.M. (3) 393; (7) 647

van Dongen, M.J.P. (5) 474,480; (9) 87.88

Vallet, C. (3) 205 Vallet-Regi, M. (7) 599 Vallier, M. (3) 4 14 Van, Q.N. (8) 3 1 Vanas, H. (13) 39,145,146,166 Van Audcrkcrkc, J. (12) 234 van Beck, J.D. (7) 363 Van Beelcn, D.C. (3) 420 van Bckkum, H. (3) 258; (7) 487,

Vandoorn, T. (13) 29 Van Dusschoten, D. (13) 39,166 van Duynhoven, J.P.M. (1 1) 76 Vanek, T. (3) 49 Vaneldik, L.J. (9) 47 van Erckelens, F. (12) 293,301 van Geeresteinujah,E.C. (9) 226 van Genderen, M.H.P. (7) 419,

629,707 van Boom, J.H. (5) 349,474,480; (9) 87,88,91, 168,277; (11) 104

van Gorkom, L.C.M. (7)399,s 1 1 van Grieken, R (7) 6 17 van Halbeek, H. (5) 373; (6) 6 van Haveren, J. (12) 32

422; (14) 80

Van Hecke, P. (6) 147; (12) 210, 21 1,304

van Hummel, G.J. (1 1) 76 Van Kessel, G.M.M. (10) 227 Vanko, G. (7) 623 Van Lecmputte, M. (1 2) 304 van Lceuwen, P.W.N.M. (1 1) 84 van Mierlo, C.P.M. (8) 83,84 van Neervcn, RJ.J. (5) 342 Van Nuland, N.A.J. (9) 156,200 van Oirschot, J.T. (5) 292 Vanovcrschcldc, J.-L. (12) 175 Van Reempts, J. (1 3) 173 Van Rijn, J. (3) 420 van Rook M. (5) 49 van ROSSU~, B.-J. (7) 55 Vansant, E.F. (3) 266; (7) 801 van Sankn, R.A. (3) 242; (7) 647, 656

Van Sluis, R (12) 24 Vanstapel, F. (6) 147; (12) 304 Van Stcenbergen, AS. (6) 176 Van Thiel, D.H. (12) 69 van Tilborg, P. (5) 309 Van Waardc, A. (12) 11 van Wcll, H.F.J.M. (2) 136; (7) 80 van Westrcnen, J. (1 2) 32 van Wolpit, J.H.M.C. (7) 647 van Wullen, L. (7) 758 van Zijl, P.C.M. (12) 254; (13) 26, 53; (14) 5,7, 10, 11

van Zuylcn, C. (9) 153 Varani, G. (5) 479; (9) 93-98, 109-1 12

Varaprath, S.(10) 212 Varghese, B. (3) 475; (5) 75 Varma, K.S. (7) 193 Varma-Nair, M. (7) 160 Varner, S.J. (2) 129; (3) 13 Varshavsky, Y.S.(5) 142, 187 Varum, K.M. (7)3 13 Vasanthan, N. (10) 306 Vasella, A. (1 1) 137 Vashchcnko, A.V. (3) 116 Vasviiri-Debreczy,L. (3) 498; (5) 132

Vathyam, S.(6) 3 1 Vaughn, M.J. (12) 290 Vaupel, P. (1 2) 224 Vauthey, S.(6) 77,167,170 Vazqucz, L. (3) 146 VmquCz-Lopez, E.M. (3) 324,325 Veale, M.F. (12) 52 Vecchio, G. (3) 138 Vedrhe, J.C. (7) 697. Vcech, R L . (3) 442; (12) 3.1 Vccman, W.S. (2) 136; (7) 54,67,

Author Index 80; (10) 258,273,330

Vcga, S. (3) 431; (7) 58,71, 180 Vcisz, O.B.(13) 162 Vcith, M. (3) 236,3 16; (7) 262, 28 1

Velan, S.S.(6) 198 Velez, P. (9) 10 Velho, G. (12) 3 11 Venkataraman, T.N. (7) 5 17 Venkatasubban, K.S.(3) 175 Venkatasubramanian, P.N. (12) 134; (13) 70

Venminerva, N. (13) 10

w. (13) 29

Venters, R.A. (9) 62 Ventura, C.A. (3) 145 Vcntura, M. (5) 412 Ventura, P. (3) 132 Venu, K. (9) 299,301 Vcnugopal, V. (3) 507 Vcpsiil&inen, J. (5) 413 Vcracini, C.A. (14) 54, 81,82,84, 94,96,147,158,173

Vcrbech, R. (7) 158 Verberckmoes, A.A. (3) 266 Vcrboom, W. (1 1) 76 Verbruggcn, I. (5) 144 Vcrcautcrcn, J. (5) 398 Verccllonc, A. (5) 370 Verchere, J.-F. (3) 280 Verdegem, P.J.E. (7) 73 Verdine, G.L. (9) 34,263 Vereschagina, Y.A. (1 1) 25 Vcrheydcn, P. (5) 16 Verhoye, M.R. (13) 173 Vermillion, K.E. (7) 787 Versini, G. (3) 363 Versluis, K. (7) 350 Vert, M. (10) 118 Vervoort, J. (5) 265,293,316 Veszprcmi, T. (3) 32 1 Vetrreivet, R. (7) 640 Viallat, A. (10) 4 13 Viani, F. (5) 509 Vicens, J. (3) 249 Vicent, C. (3) 114; (5) 366 Vidal, G. (13) 76 Vidoto, E. (7) 28 Vidoto, E.L.G. (7)28; (12) 205 Vieth, H.M.(3) 245; (6) 150; (7) 19,145

Vieth, M. (7) 437 Vig, A. (5) 500 Vikic-TopiC, D.(2) 169; (3) 84, 85; (5) 69,99,507 Vila, F. (5) 408; (1 1) 55 Vilar, W.D. (10) 29,83

539

Vilcs, J.H. (3) 3 13; (5) 267,272 Vilfan, M. (10) 14; (14) 100 Villa-Garcia, M.A. (7) 526 Villalain, J. (7) 412 Villar, H.O. (4) 72 Ville, H. (12) 210,211 Villemure, J.-G. (12) 32 1 Vincedon, M. (7) 393 Vincent, R (7) 649,688 Vinogradov, E.V. (5) 375,461 Vion-Dury, J. (12) 283 Virgili, A. (3) 14 1; (5) 406,421;

Vorherr, T. (5) 484; (9) 165 Vorkapid-Furat, J. (5) 69 Voscgaard, T. (2) 123; (3) 247, 25 1,356; (7) 77

Vossen, P. (5) 293 Vome.semskii, V.N. (5) 432 V o m , J.A. (13) 156 Vrvancic-Kopac, N. (10) 14 Vuister, G.W. (8) 49 Vural, J.M. (7) 366 Vyas, RR (7) 292; (9) 83

(8) 23; (1 1) 27

Vis, H. (9) 226,274,275 Vita, C. (5) 300 Vital, J. (7) 637 Viltal, J.J. (3) 404,406 Vivekanandan, S.(14) 19, 128 Vivi, A. (12) 50, I71 Vizethum, F. (7) 493 Vladimusky, 0. (10) 274 Vladimirsky, Y. (10) 274 Vlahov, 1.R (1 1) 130 Vlascek, K.(7)468 Vlasov, A.V. (7) 265 Vlassenbroek, A. (6) 26,27 Vlcek, A,, Jr. (3) 409 Vlicgcnthart, J.F.G. (9) 153, 156, 157

Voevodskaya, T.I. (5) 143 Vogel, H.J. (3) 417; (9) 248,31 I; (10)234; (12) 89, 106

Vogel, J. (2) 125; (3) 450; (6) 112; (7) 94,493,761

Vogcl, P. (5) 114 Vogclsang, R (5) 293 Voges, M.H. (5) 53 Voigt, A. (3) 387 Voijislav, S.(7) 8 11 Vold, R.L. (2) 129; (3) 13; (7) 21, 22

Vold, R.R.(14) 55, 117 Volke, F. (3) 194; (7) 344,374 Volkova, N.N. (10) 35 1 Voll, D. (7) 427 Voll, s. ( I 2) 173 Vollrath, F. (7) 363 Volobueva, O.B. (12) 99 Vondergonna, V. (2) 1.18 Von der Lieth, C.W. (9) 156 von Keinlin, M.(12) 102; (13) 38 von Meerwall, E. (10) 315 von Philipsborn, W. (3) 290,292, 293; (5) 136, 137, 178, 196

von Roemeling, R.W. (12) 329 von Wijngaarder, W.A. (6) 180 Vorgias, C.E. (9) 274,275

Waali, E.E. (10) 274 Wachendorf, C. (7) 463 Wachowski, L.(7) 722 Wachs, I.E. (7) 685 Wachtel, E.J. (14) 66,90,9 1 Wada, T. (10) 151 Wada, Y. (12) 85 Wade, C.G. (6) 146 Wodc, H.J. (10) 248 Wagener, K.B. (10) 22 Wagner, G. (7) 695; (8) 67,68,79, 82,93; (9) 32-34,63-67, 175-177,18 1,182,244,259, 262,263 Wagner, J.R (1 1) 36 Wagner, R (8) 18 Wakai, C. (6) 16, 134 Wakarchuk, W.W. (5) 266 Waki, H. (3) 328 Waluta, H.(7) 545,705 Wako, H. (1 1) 105 Walchi, M. (8) 78 Wald, L.L. (12) 274 Walker, D.G. (3) 214 Walker, F.A. (3) 291 Walker, J. (9) 5 Walker, P. (12) 276 Walker, R.T. (5) 121,357 Walker, T.B.(10) 152 Wall, D. (9) 18 Wallace, J.C. (7) 122 Wallimann, T. (12) 20 1 Walter, K. (9) 12 Walter, 0. (5) 3 19 Walther, G. (3) 351; (7) 612 Walton, J.H. (2) 207 Wand, A.J. (5) 329; (9) 269 wandrey, (12) 44 Wang, B. (5) 195 Wang, C. (10) 241; (12) 181 Wang, D. (7) 543 Wan& D.-N. (10) 172 Wang, E. (7) 812,813; (9) 86 Wang, F. (7) 549,55 1

c.

540 Wang, F.S. (10) 27 1 Wang, G. (7) 784 Wang, H.C.(7)254 Wang, H.-Q. (14) 107, 108 Wang, H.T. (10) 38 Wang, I. (7) 704 Wang, J. (7) 8,416,586,589,590, 638; (10) 430; (1 1) 148 Wang, J.Z. (7) 584,6 19,632,65 1 Wang, K. (7) 638 Wang, K.U. (14) 12 wang, L. (7) 118; (10) 220 Wang, L.H. (12) 196 Wang, L.-Q.(7) 743; (10) 422; (14) 83 Wang, M.(5) 98,220 Wang, P.C.(12) 188 Wang, Q. (3) 288; ( 5 ) 70 Wang, S. ( 5 ) 98; (7) 520 Wang, S.H. (7) 74, 109, 113 Wmg, S.-L. (5) 223 Wmg, S . 4 . (3) 354; ( 5 ) 153,223 Wang, w. (9) 80 Wang, X. (7) 235 Wang, Y.(2) 74-76; (3) 269,350; (10) 148; (12) 181,219 W a g , Y.-H. (12) 74 Wang, Y.X. (5) 477; (9) 52, 148, 149,188,189 Wang,Z. (7) 813; (10) 126 Wmgc, H.-T. (1 0) 28 Wangc, P. (7) 761 Ward, K.M.(12) 295 Wardcll, J.L. (3) 401; (7) 263 Wardlaw, J. (12) 265 Warcing,J.R (7) 173 Warmslcy, J.F. (5) 428,429 Warnc, M.A. (3) 2,96; (4) 78 Wamock, W. (7) 329 Warren, J.J. (5) 393 Warrcn, W.S. (6) 3 1,32; (14) 20 Warschawski, D.E. (7) 369,370 Warshcl, A. (2) 19 1 Wnrtcwig, S. (10) 408 Wartner, N. (7) 763 Wasylishen, RE.(2) 26,29,60, 124, 128; (3) 445; ( 5 ) 35,36, 171, 172; (7) 108, 177,225, 227,228,230,273,378; (14) GO

Watanabc, K. (7) 600; (1 1) 111 Watanabe, M. (7) 236,269 Watanabc, S.(1 1) 1 1 1 Watanabc, T.(3) 342; (7) 5 16, 545,554,705,788; (13) 1 Watari, H. (12) 140,300 Waters, E.J. (7) 3 1 1

Nuclear Magnetic Resoriarice Waterson, C. (10) 248 Weisemam, R (9) 28 I Waterton, J.C. (6) 200 Wciskirchcn, R (5) 333; (9) 29 I Watkins, J.M. (14) 65 Wcisledcr, D. (3) 195 Watson, D. (12) 327 Wciss, AS. (9) 37 Watson, I.D. (12) 37 Wciss, H. (3) 21 Watts, A. (7) 418 Weiss, R.A. (10) 383 Waugh, M.P. (2) 138; (3) 239, Weiss, R.G. (12) 262; (14) 3,4 265,504; (7) 60 Wcissberg, P.L.(12) 158 Wawer, A. (3) 11 1 Wcissflog, W. (14) 95 Wawcr, I. (3) 1 1 1, 117; (5) 80, Weisshoff, H.(3) 108 125; (7) 172, 197,208,221, Wcitckamp, D.P. ( 5 ) 46; (14) 20 348 Wcitkamp, J. (7) 653,7 16,7 17 Waymouth, RM. (10) 35,133,224 Wcitz, I.S. (5) 247 Wayne, F.D. (6) 205 Welch, M.D. (7) 564 Wazeer, M.1. (1 1) 90 Wcliky, D.P. (7) 79 Wcaner, L.E. (3) 214 Wclker, M. (6) 18, 19,94 Wcalhcrbce, J.A. (5) 452; (9) 53 Wellard, RM.(12) 162 Webb, G.A. (2) 99; (3) 23,35, Wcller, C.T.(9) 152 117, 119, 126,374,423-425, Wcllcr, M.T. (7) 536 429,433,434,439; ( 5 ) 77-82, Wclzcl, P. ( 5 ) 388 85, 116,226; (7) 172,221,287; Werner, D.E. (3) 2 16,22 1; (7) (10) 391 212,334; (9) 77 Wcn, G. (1 1) 41 Webb, T.R (I 1) 65 Wcn, H. (12) 26 Webbcr, J.B.W. (13) 112 Webcr, C.(5)275 Wcn, L. (9) 293 Webcr, D.J. (5) 296,343 Wen, Q. (7) 479 Wcbcr, E.J. (7) 480 Wen, W.-Y. (3) 517 Wcndlcr, S.L.(7) 394 Wcbcr, J. (6) 75 Wenkcr, J. (5) 452; (9) 53 Wcbcr, R. (3) 440 Wcnz, G. (3) 129 Wcbcr, U. (14) 25 Wcrmuth, J. ( 5 ) 269 Wcbstcr, F.X. (3) 2 15 Wcmcr, A. (6) 215 Wcbstcr, M. (3) 308 Wcrner, H. (3) 245; ( 5 ) 96; (7) 145 Wegncr, P. (7) 245 Wcmer, J.M. ( 5 ) 313; (9) 28 Wchlan, M.(3) 89,94; (7) 171 Wcrncr, M.H. ( 5 ) 113; (9) 14 Wehlcr, T. (7) 166 Werner-Zwanzigcr, U. (7) 1 14 Wchrli, F. (13) 37, 170, 179 Wcrshaw, R.L. (7) 471 Wcluli, S.L. (13) 179 Wcrstiuk, N.H. (2) 121; (3) 22 Wci, D. (7) 595; (10) 126 Wcrstler, D.D. (I 0) 10 Wei, H. (12) 148 Wcsscls, P.L.(3) 137,459 (10) 210 Wci, K.-H. Wci, X. (3) 287 West, A.B. (12) 3 13 Wcst, B.O.(3) 419 (3) 136 Wei, Y.-C. West, J. (8) 19 Weig, A. (13) 154 Wcigand, F. (10) 431-433; (13) 58, Wcst, M.( 5 ) 407 65,66 Westerhausen, M.(5) 234 Westlcr, W.M. (6) 121; (9) 141; Weigelt, J. (5) 28; (9) 180 (12) 117 Wcil, D.A. (10) 61 Weslley, B.R. (5) 442; (9) 51 Weinberg, J.M. (12) 187 Wcstlund, P.-0. (6) 97,98 Weiner, M.W. (12) 131, 136,264 Wcstman, J. (7) 166 Wcingiirtner, H. (6) 1, 11, 15 Weinhold, F. (6) 20.2 1,86 Wetsel, W. (12) 167 Weinmann, H.-J. (3) 189 WcWCr-Botz, D. ( 12) 44 Weinstein, P.R ( 12) 1 13 Whalcy, M. (6) 71; (7) 305 Whclan, G.S.(3) 168 Weintraub, A. (5) 368,369,371 White, A.H. ( 5 ) 188-190; (7) 267, Weintraub, 0. (3) 431; (7) 180 Weis, J. (13) 56,83,84, 105, 164, 268 White, A.M. (4) 36 I65

Author Index White, D. (2) 132-134; (3) 383, 386; (7) 6,709 White, G.F. (12) 39 White, J.L. (10) 337 White, L.A. (10) 138 White, L.T. (12) 146 White, P.S. (3) 438 Whik, V.V. (7) 803 Whitecotton, B.R. (13) 20 Whitchead, B. (8) 49 Whiteman, E.L.( 5 ) 325 Whitfield, H.J. (3) 240,467; (7) 110,507,508 Whitford, D. (8) 62 Whitla, W.A. ( 5 ) 172; (7) 227,273 Whitman, C.P.(9) 59,60 Whitman,G.J.R. (12) 180 Whitmarsh, C.W. (7) 791 Whittaker, A.K. (10) 170; (13) 101 Whittaker, D.V. (3) 137 Whittaker, M.R. (1 0) 48 Wibcrg, A. (7) 195 Wick, M. (12) 127 (3) I 13; (1 I) 3 Wickersham, B.M. Widcnhocfcr, R.A. (1 1) 147 Wider, G. ( 5 ) 326; (8) 8,25; (9) 1-3, 16,69, 144, 146, 178, 179 Widmaier, S. (12) 293,296,301 Widmalm, G. ( 5 ) 368,369,371, 456; (6) 152; (11) 123, 126, 138; (14) 89 Widmer, H. ( 5 ) 271 Wieczorek, M.W. (3) 473; (7) 194 Wiedenbruch, R. ( 5 ) 48 Wiegers, S.A.J. (6) 176 Wieghardt, K. (7) 252 Wicland, T. ( 5 ) 44 1 Wicnch, J.W. (3) 423,433,434; ( 5 ) 77,116 Wicruszeski, J.-M. ( 5 ) 458; (6) 27 Wiesner,U. (10) 253,318; (13) 66 Wigert, R.J.(7) 386 Wijmenga, S.S. ( 5 ) 265,349,474, 480; (8) 83,84; (9) 87,88, 10 I , 168; (1 1) 104 Wild4 D.E. (12) 244; (13) 149 Wilke,N. (12) 181 Wille, A.E. (2) 115 Wille, S.(2) 46,65, 153 Willem, R. (3) 405,407,415; ( 5 ) 16,144,145; (7) 250,257 Willem, E.F.A. (5) 474; (9) 87 Williams, B. (13) 141 Williams, D.J. (3) 303; (1 1) 83 Williams, J. (9) 243 Williams, J.A. ( 5 ) 3 10 Williams, J.C. (7) 318

54 1 Williams, J.L. (13) 179 Williams, J.P. (12) 36,23 1,233 Williams, M.A. (5) 442; (9) 5 1; (10) 326 Williams, P.G. (3) 216-221; (7) 212; (9) 77 Williams, P.J. (7) 31 1 Williams, P.S.(3) 175 Williams, RE. (2) 120; (3) 330 Williams, RF. (6) 185 Williams, RV. (7) 203 Williams, S.(1 3) 148 Williams, S.C.R (12) 21,23; (13) 2-6 Williams, S.-P. (12) 5 , 8 8 Williams, S.R (12) 112, 194 Williamson, G. ( 5 ) 330 Williamson, J.R. (8) 75; (9) 113, 185 Williamson, K.L. (2) 204-206; (4) 41,42 Williamson, M.P. ( 5 ) 330; (7) 349 Williamson, P.C.(12) 255,270 Willis, A.E. (7) 300 Willis, J.A. (12) 139, 237 Willis, R.C.(9) 71 Willis, R.J. (12) 163 Willker, W. (8) 52 Willner, H. (3) 508 Wilmanns, M. (9) 236 Wilrns, M.P. (3) 409 Wilson, A.E. (3) 199 Wilson, G.E. (7) 320,359,392 Wilson, K.S. (9) 274,275 Wilson, P.J. (2) 99; (3) 23,35 Wilson, R.W. (12) 23 Wilson, S.R. (3)512,514;(12) 233 Wilson, W.K. ( 5 ) 393 Wiltscheck, R. ( 5 ) 240; (9) 290 Wimmer, 2. (3) 49 Wimmet, T.F.(4) 73 Wimperis, S. (6) 57; (7) 101, 103; (13) 73 Wind, R.A. (7) 119,304 Windmuller, B. (5) 96 Windust, J. (9) 155 Winge, D.R.(9) 20 Wingfield, P. (8) 33; (9) 52, 148, 149,158,188,189,254 Winkelbach, H.R. (10) 88 Winkler, H. (3) 291 Winkler, M. (14) 166 Winnewisser, G. (2) 56 Winter, P.M. (13) 71 Winter, R. (6) 114,169; (10) 332 Wintersgill, M.G. (10) 406

Wise, D. (12) 34 Wiseman, R.W. (12) 204 Wisniewski, M. (10) 85 Wison, M.A. (7) 48 1 Witanowski, M. (3) 126,424-426, 439 Wittcbort, R.J. ( 5 ) 56; (7) 302 Wittekind, M. (5) 3 1 1; (9) 57,74, 230 Wiltig, R.M. (12) 46 Wittinghofer, A. (9) 134 Wocssncr, D.E. (6) 2, 130 Wofsy, S.C. (2) 52 Wolcsanski, P.T. (7) 506 Wolf, C.R (9) 138, 139 Wolf, E. (5) 40 Wolfe, G.M. (7) 299 Wolfc, 1. (7) 646,690 Wolfe, S.A. (9) 34 Wolfenson, A.E. (6) 115 Wolff, J.J. (1 1) 21 Wolinsky, K. (3) 17 Wokowicz, P.E. (1 3) 172 Wollenberg, K.F. ( 10) 2 18 Wollers, J. (3) 420 Won, H.Y. (10) 216 Wong, J. (7) 585,586 Wong, K.B. ( 5 ) 320; (9) 208,209, 265 Wong, S. (7) 438; (10) 327 Wong, S.L. (9) 9 Wong-Moon, K.C. (7) 98,675 Woo, A.J. (7) 259 Woo, S.(10) 270 Wood, R. (3) 209 Wood, T.C. ( 5 ) 259 Woodall, L.J. (7) 726 Woodgale, P.D. (1 1) 99 Woods, B.T. (12) 267 Woods, R.J. (5) 459 Wooley, K.L. (7) 69; (10) 297 Woolins, J.D. (3) 303 Wootton, A.M. (7) 764 Wozniak, K. (7) 161, 162 Womiak, T.J. (7) 207 Wrackmeyer, B. (2) 168; (3) 229, 335,432; ( 5 ) 57,87, 117, 146, 147, 154, 156, 159,219,222, 483,510-513; (7) 219,264, 270,274 Wray, V. (4) 44 Wright, C.S. (9) 156, 157 Wright, J.E. (9) 33 Wright, J.L.(3) 291 Wright., P.A. (7) 668 Wright, P.E. (6) 119; (9) 131, 132, 197,217

Nuclear Magnetic Resonarice

542

Wright, S.J. (2) 47 Wroblewski, K. (12) 22 1 Wu, B. (10) 155 wu, c.(10) 414,417 Wu, D.(3) 269; (5) 141; (6) 193; (7) 287; (10) 148 Wu, E.X. (12) 21 Wu, G. (2) 60, 102; (3) 451; (5) 36, 171; (7) 96, 105, 108, 177, 228,229 WU, H.4. (7) 791 Wu, J. (4) 6; (5) 118,301; (8) 9; (9) 132; (1 1) 61 Wu, M.(5) 472,473 Wu, P. (7) 630 Wu, R. (3) 70 Wu, T. (7) 392 Wu, X. (7) 50,51; (10) 52,283 Wu, Y. (3) 514; (7) 20,804; (12) 13 Wu, Y.J. (3) 319 Wu, Z.R (9) 54 Wucrthwcin, E.-U. (1 1) 96 Wiithrich, K. (5) 301,306,326, 448; (8) 8,25,91; (9) 1-4, 15-18,69, 144-146, 178, 179, 183,192, 193,221-225,239 Wunderlich, B. (7) 160 Wurtman, R.J. (12) 286 Wuttke, J. (6) 12 Wutz, C. (10) 260,325 Wuyan, B. (12) 129; (13) 177 Wylezinska, M . (12) 288 Wyrwicz, A.M. (12) 134; (13) 70 ,Wysocka, W. (5) 384 Wysong, M.(12) 295 Wyss, D.F.(9) 262 Wzictek, P. (3) 18 1

Xia, J.-H. (12) 94 Xia, 2.-F. (12) 190 Xiao, W.(3) 402 Xic, M.(10) 348 Xie, X. (10) 148 Xie, X.-Q. (1 1) 3 1 Xin, F. (3) 286; (5) 236 Xing, B. (7) 473,474 Xiong, H. (12) 138 Xiong, J. (12) 104, 138 Xiong, J.H. (13) 77 Xu, C. (11) 149; (12) 191 Xu, D. (10) 103; (12) 176 Xu, G. (5) 22; (8) 65 Xu, G.Y. (5) 344; (9) 24 XU,J. (10) 186-188,226 Xu, L.(7) 662; (10) 108

Xu, M. (3) 327 Xu, P. (5) 195 xu, Q.W. (5) 454,457 Xu, R. (7) 673,674,686,687 Xu, S.(6) 111, 155 Xu, T. (3) 368,378; (7) 178, 179 XU,X.-C. (7) 70 Xu,Y. (7)593,687,721; (10) 386; (13) 7 1 Xu, Z. (7) 109, 113 Ya, X. (12) 148 Yahi,N. (5) 221 Yahnke, M.S.(7) 248 Yakimansky, A.V. (3) 21 Yamabayashi, H. (12) 200 Yamabe-, T. (3) 430 Yamada,H. (10) 153; (11) 89 Yamada, J. (3) 364 Yamada, K. (3) 47 Ymadaya, M. (7) 640 Yamaguchi, 1. (10) 168 Yamaguchi, K. (5) 199 Yamaguchi, Y. (3) 277 Yamamoto, G. (3) 121 Yamamoto, H. (1 1) 30 Yamamoto, K. (2) 15, 16; (7) 214 Yamamoto, M. (3) 295; (6) 165 Yamamoto,N. (10) 191 Yamamoto,T. (10) 168 Yamanaka, K.(6) 127 Yamanaka, S.A. (10) 250 Yamane, H. (12) 135 Yamane, M. (7) 746 Yamanoke. T. (7) 205 Yamashita, H. (7) 622 Yamashita, M. (1 1) 128 Yamashita, S. (7) 545,705 Yamashita, Y. (7) 123,133 Yamato, Y. (12) 135 Yamaura, K. (10) 106 Yam&, H. (10) 352 Yamazaki, S.(7) 752 Yamazaki, T. (9) 52, 188, 189,286 Yamdagni, R. (7) 477

Yan,A. (7) 604 Yan, B. (7) 342,361 Yan, B.L.(12) 42 Yan, X. (12) 230 Yan, Y. (7) 732 Yanchunas, J. (9) 57 Yang,B. (7)63,64,115, 131,150 Yang, C.Z. (10) 382 Yang, D.P.(7) 365 Yang, D.W.(9) 249,268 Yang, G. (10) 103

Yang, J.J. (7) 455-457; (10) 235, 236,282

Yang, K.H. (7) 754 Ymg,L. (5) 184;(10)211;(12) 157

Yang,N. (7)50,51, 176,593,721 Yang, N.L. (2) 61 Yang, Q.-X. (7) 358 Yang, S. (10) 226 Yang, T.C. (5) 223 Yang, w. (2) 79 Yang, Y. (3) 269; (10) 226,255; (11) 1

Yang, Y . 4 . (10) 390 Yang, Z. (10) 206; (12) 72.73 Yanovsky, A.I. (7) 265 Yao, J.-Z. (1 1) 150 Yao, K.-M. (10) 197 Yao, S.(13) 98,99 Yao, Z. (5) 95 Yaojun, S. (7) 63 1 Yap, G.P.A. (5) 233 Y m c v a , I.V. (1 1) 25 Yashima, E. (10) 167 Yashima, T. (7) 630 Yashimoto, Y. (6) 16 Yasuda, I. (3) 57 Yasuda, K. (12) 292 Yasumori, A. (7) 746 Yasumoto, T. (5) 433,434 Yasunami, M. (5) 503 Yatsimirsky, A.K. (3) 167 Yatsuyanagi, F. (10) 416 Yavari, 1. (5) 418 Yazaki. Y. (12) 85 Yazawa, M.(3) 417; (9) 31 1 Ye, C. (3) 374; (7) 50,51,63,64, 115,131, 176,191,520,784, 799,800; (10) 371 Ye, C.-H. (7) 150,651,652; (10) 437; (12) 128; (13) 46,93, 123 Ye, X.M. (9) 125 Ycagcr, D.L. (4) 9 Yec, A.A. (5) 126 Yco, J.H. (7) 351,352; (10) 294 Yesinowski, J.P. (3) 436 Yi, G . 4 . (5) 253,284 Yi, Y. (5) 120 Ying, S.-H. (10) 172 Yingcai, L.(7) 63 1 Yip, P.F. (5) 467; (9) 105 Yiihautala, M.(2) 130; (3) 521 Yoder, J.C. (5) 149 Yogo, A. (3) 213 Yokohama, T. (7) 545 Yokoi, T. (5) 395 Yokoyama, S. (9) 75,272’; (1 1)

Author Index 111 Yokoyama, T. (7) 705 Yokoyama, Y. (12) 235,239,240 Yom, J.W. (5) 195 Yonczawa, T. (2) 14 Yong, Y. (7) 687 Yongbi, N.M. ( I 2) 24 Yonnet, J.P. ( I 3) 2 1 Yoo, s.(9) 5 Yoon, D.Y. (6) 146; (10) 145 Yoon, H.S. (9) 9, 11, 12 Yoon, S.H. (7) 130 Yoshida, E. (1 0) 204 Yoshida, H. (14) 137 Yoshida, K. (6) 160, I61 Yoshida, T. (7) 218; (10) 130; (12) 300 Yoshida, Y. (10) 50 Yoshifuji, M. ( 5 ) 503 Yoshikawa, M. (7) 602; (10) 221 Yoshimura, K. (3) 328 Yoshimura, N. (12) 119 Yoshinaga, K. (10) 308 Yoshinara, Y. (7) 142 Yoshinari, Y. (3) 379 Yoshioka, S. (7) 328 Yoshiya, I. (6) 136 Yoshizaki, K. (12) 203 Yosomiya, R. (10) 80 You, A. (9) 34 Young, D.W. (3) 492 Young, J.J. (3) 166 Youngcr, S.J. (7) 480 Youngman, R.E. (3) 33 1; (7) 114, 759 Ystynyuk, Y.A. (7) 282 Yu, G. (10) 162 Yu, H.A. ( 5 ) 344; (9) 24 Yu, J. (7) 686,687 Yu, L.P. (9) 280 Yu, X. (12) 146 Yuan, F. (9) 263 Yuan, H. (7) 543 Yuan, H.Z. (3) 3 19; (6) 142; (13) 121 Yuan, T. (3) 417; (9) 31 1 Yuan, Z. (7) 585,589,590 Yuan, Z.Y. (7) 584,619,632 Yue, Y. (7) 591,673,674,686, 792,799,800,804 Yun, Y.J. (7) 594 Yvcs, M. (12) 184 Zabarylo, S.V.(3) 443; (7) 336 Zabc, H. (3) 288 Zachmann, H.G. (10) 98,263,324,

543 359 Zaddach, H. (5) 432 Zadcrcnko, P. (7) 202 Zaghib, K. (7) 15 1 Zahcdi-Niaki, M.H. (7) 666 Zajicck, 1. (1 1) 109 Zalibcra, L. (12) 56 Zamaracv, K.I. (7) 693,700,708 Zambelli, A. (10) 64,228,23 1 Zambianchi, M. (7) 196 Zamir, S. (14) 66,87,90 Zamora, F. (3) 3 18; (5) 482 Zanasi, R. (2) 58,86-88,90-93, 157,158,160,177,178,184 Zanctti, N.C. (2) 102; (3) 45 1; (7) 229 Zangger, K. ( 5 ) 24; (8) 4,44 Zaniol, P. (12) 298,305 Zannoni, C. (2) 139, 140; (14) 98, 145 Zanobini, F. ( 5 ) 50,5 I Zanotti, G. (5) 277,44 1 Zapata, M. (10) 144 Zapol'skii, A.S. (3) 503 Zappala, M. (3) 145 Zarevucka, M. (3) 49 Zarrouk, H. (7) 436; (10) 402 Zasloff, M. (5) 287; (7) 357 Zaugg, C.E. (12) 143 Zavin, B.G. (10) 86 Zavodszky, P. (9) 141 Zawrotny, M.E.(9) 54 Zax, D.B. (7) 11,438,506; (10) 327 Zdanowska-Fraczck, M. (7) 188 Zwh, W. (7) 476 Zefirov, N.S. (1 1) 25 Zchndcr, M.M. (10) 209 Zcidler, M.D. (6) 17,43,84, 162, 205 Zcigler, R.C. (lo) 154 Zelenkina, O.A. (1 1) 25 Zemlyanskii, N.N. (7) 282 Zeng, L. (8) 45 Zeng, Q.D. (9) 2 1 Zcpf, D. ( 2 ) 109 Zcrbe, 0. ( 5 ) 301; (9) 183 Zcri, A.C. (12) 205 &rial, A. (9) 154 Zerroukhi, A. (10) 182,183 Zctta, L. (10) 34 Zhan, C.-G. (3) 33 Zhang,B. (7)595,815;(12) 191 Zhang, B.L. ( 5 ) 452; (9) 53 Zhang, c. (7) 444 Zhang, H. (7) 549,55 1 Zhang, H.M. (7) 302

Zhang, J. (7) 813; (12) 148, 181 Zhang, J.-G. (5) 264 Zhang, L. (3) 28 1; ( 5 ) 98 Zhang, M. (3) 417; (7) 118 Zhang, M.J. (9) 3 11 Zhang, 0. (8) 8 1 Zhang, 0.W. (9) 2 10,260,289 Zhang, P. (7) 115, 118,748 Zhang, P.Z. (13) 93 Zhang, Q. (3) 279,419 Zhang, Q.W. (7) 302 Zhang, S. (8) 9; (10) 388 Zhang, S.G. (7) 622 Zhang, T. (7) 127 Zhang, W. (7) 586; (8) 70,71; (13) 71

Zhang, W.X.( 5 ) 257 Zhang, X. (3) 374; (10) 162 Zhang, X.D.(13) 46 Zhang, X.H. (9) 120 Zhang, X.X. (3) 166 Zhang,Y. (12) 148,181 Zhang, Y.D. (3) 256 Zhang, Y.-F. (7) 8 12 Zhang, Y.H. (7) 812 Zhang, Z.Y. (3) 127 Zhao, H. (3) 512; (9) 120 Zhao, J. (6) 148; (10) 241,346, 3 84 Zhao, P.-Y. (12) 190 Zhao, Q.-Y. (3) 49 Zhao, X. (7) 115,520 Zhao, X.S. (7) 579 Zhao, Y. (7) 585 Zhcng, G. (3) 374 Zheng, L.-Q. (14) 107 Zheng, Y.B. (10) 80 Zhcng, Z. (7) 447 Zhong, H.A. (1 1) 147 Zhong, J.H. (13) 175 Zhou, B. (1 1) 118 Zhou, H. (2) 168; (3) 432; ( 5 ) 222, 5 12 Zhou, J. (7) 63,64, 131, 150, 176, 191,441,595 Zhou, M.M. (9) 273 Zhou, P. (9) 34 Zhou, R (10) 443 Zhou, S. (10) 414,417 Zhou, X. (3) 472 Zhou, X.-F. ( 5 ) 4 17 Zhou, Y. ( 5 ) 98; (7) 792 Zhu, C.X. (9) 280 Zhu, F.Q. (9) 297 Zhu, G. ( 5 ) 328 Zhu, H. (7) 291; (12) 137 Zhu, K.J. (10) 197

Nuclear Mapteiic Resonance

544

Zhu, L.M.(5) 465 Zhu, M. (7) 342 Zhu, Q. ( 5 ) 280 Zhu, Q.-R. (10) 385 Zhu, W. (6) 141; (10) 299,3 16 Zhu, W.L.(9) 21 Zhu, Z. (3) 1IS Zhuang, H. (7) 804 Z~UO , (3) 452,453 J.-C. Zidansek, A. (14) 160 Ziebarth, RP. (3) 246 Ziegeweid, M.A. (14) 26 Ziegler, A. (12) 102 Zieglcr, K.(5) 277 Ziegler, T. (2) 2,40,97,106; (3) 19,28,36; (4) 5 1 Ziegler, W. (1 4) 1I 1 Ziessow, D. (12) 229 (8) 7 Zijl, P.C.M. Zilbcrberg, N. ( 5 ) 307 Ziliox, M.(7) 44

Zilm, K.L. (7) 256 Zilm, K.W. ( 5 ) 45,52; (6) 184 Zimmer, D.P. (5) 350; (9) 166 Zimmer, M. (3) 236; (7) 437 Zimmermann, G.R.(9) 106-108; (14) 66 Zimmermann, H. ( 5 ) 66; (7) 76, 164,339; (14) 86-88,90,91, 142

Zimmermann,U. (13) 152 Zinchenko, S.V.( 5 ) 5 Zinchenko, V.D. (12) 55 Zinin, V. (14) 25 Zinth, W. (9) 45 Ziolkowski, J. (7) 500 Zippi, E.M.(7) 153 Ziyad, M.(7) 697 Zobov, V.E.(7) 14 Zoebisch, E.G. (4) 66 Zolnai, Z. (8) 27 Zolotukhin, M. (10) 90 Zonta, A. (7) 445

Zotti, G. (7) 223; (10) 272 Zschunke, A. (13) 1 I 1 Zsunga, M.(10) 161 Zubkov, V.A. (5) 374 Zuchner, L. (7) 758 Zuideweg, E.RP. (6) 68; (8) 45, 86 Zukerman-Schpector, J. (3) 325 Zularrf, M. (1 1) 63 Zumbruk, T. (7) 323 Zumbulyadis, N. (7)58; (10) 296 Zumer, S. (14) 99, 160, 161 zuo, C.S. (3) 190 Zwbano, M.M. (7)215 Zuriaga, M. (3) 447 Zwanziger, J.W. (3) 331; (7) 114, 759 Zweckstettcr, M. (9) 45 Zydowicz, N. (10) 20 Zymanczyk-Duda, E. (3) 75 Zysmilch, M.G. (7) 308,309