Table Of ContentBiological Magnetic Resonance
Volume 19
Distance Measurements in
Biological Systems by EPR
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Biological Magnetic Resonance
Volume 19
Distance Measurements in
Biological Systems by EPR
Edited by
Lawrence J. Berliner
OhioStateUniversity
Columbus, Ohio
Gareth R. Eaton
and
Sandra S. Eaton
University of Denver
Denver, Colorado
KLUWER ACADEMIC PUBLISHERS
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eBookISBN: 0-306-47109-4
Print ISBN: 0-306-46533-7
©2002 Kluwer Academic Publishers
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To Pier Luigi Nordio
CONTRIBUTORS
Albert H. Beth • DepartmentofMolecularPhysiologyandBiophysics,
VanderbiltUniversity, Nashville, Tennessee 37232
Petr P. Borbat • BakerLaboratory ofChemistry and ChemicalBiology,
Cornell University, Ithaca, New York 14853
Gary W. Brudvig • DepartmentofChemistry, Yale University, P.O. Box
208107, New Haven, Connecticut 06520-8107
Sergei A.Dzuba • InstituteofChemical Kinetics andCombustion, Russian
Academy of Sciences,Novosibirsk, Russia
Gareth R. Eaton • Department ofChemistry and Biochemistry, University
of Denver, Denver, Colorado 80208
Sandra S. Eaton • DepartmentofChemistry and Biochemistry, University
of Denver, Denver, Colorado 80208
Jack H. Freed • BakerLaboratory ofChemistry and Chemical Biology,
Cornell University, Ithaca, New York 14853
Arnold J. Hoff• DepartmentofBiophysics, LeidenUniversity, Leiden, the
Netherlands
Eric J. Hustedt • Department ofMolecular PhysiologyandBiophysics,
Vanderbilt University, Nashville, Tennessee 37232
GunnarJeschke• Max-Planck-Institute forPolymerResearch, Postfach
3148, D-55021 Mainz, Germany
K. V. Lakshmi • Department ofChemistry, Yale University, P.O. Box
208107, New Haven, Connecticut 06520-8107
Gertz I. Likhtenshtein • DepartmentofChemistry, Ben-GurionUniversity
of the Negev, P.O.B. 653, Beer-Sheva 84105, Israel
vii
viii
Contributors
Hassane S. Mchaourab • DepartmentofMolecularPhysiology and
Biophysics, Vanderbilt University School of Medicine, Nashville,
Tennessee 37232
Joseph C. McNulty • Departmentof Chemistry and Biochemistry,
University of California, Santa Cruz, California 95064
Glenn L. Millhauser • DepartmentofChemistry and Biochemistry,
University of California, Santa Cruz, California 95064
EduardoPerozo • DepartmentofMolecularPhysiologyandBiological
Physics, University of Virginia Health Science Center, Charlottesville,
VA 22906
MartinPannier • Max-Planck-Institute forPolymerResearch, Postfach
3148, D-55021 Mainz, Germany
Arnold Raitsimring • DepartmentofChemistry, UniversityofArizona,
Tucson, Arizona 85721
Yeon-Kyun Shin • DepartmentofBiochemistry and Biophysics, Iowa
State University, Ames, Iowa 50011
Hans W. Spiess• Max-Planck-Institute forPolymerResearch,Postfach
3148, D-55021 Mainz, Germany
Wenzhong Xiao • Department ofChemistry, University ofCalifornia,
Berkeley, California 94270
Preface
Distance measurements in biological
systems by EPR
The foundation for understanding function and dynamics of biological
systems is knowledge of their structure. Many experimental methodologies
are used for determination of structure, each with special utility. Volumes in
this series on Biological Magnetic Resonance emphasize the methods that
involve magnetic resonance. This volume seeks to provide a critical
evaluation of EPR methods for determining the distances between two
unpaired electrons.
The editors invited the authors to make this a very practical book,
with specific numerical examples of how experimental data is worked up to
produce a distance estimate, and realistic assessments of uncertainties and of
the range of applicability, along withexamples of the power of the technique
to answer biological problems.
The first chapter is an overview, by two of the editors, of EPR
methods to determine distances, with a focus on the range of applicability.
The next chapter, also by the Batons, reviews what is known about electron
spin relaxation times that are needed in estimating distances between spins
or in selecting appropriate temperatures for particular experiments. Albert
Beth and Eric Hustedt describe the information about spin-spin interaction
that one can obtain by simulating CW EPR line shapes of nitroxyl radicals.
The information in fluid solution CW EPR spectra of dual-spin labeled
proteins is illustrated by Hassane Mchaourab and Eduardo Perozo.
Wenzhoug Xiao and Yeon-Kyun Shin show a way to determine dipolar
interactions by Fourier deconvolution of nitroxyl CW EPR spectra. Glenn
Millhauser describes the use of the rigid spin label abbreviated TOAC. The
broadening of CW EPR of spin labels caused by paramagnetic metals reveals
depth of the radical beneath the surface and the electrostatic environment, as
described by Gertz Likhtenshtein. The use of effects to determine
distances is described by the Eatons. Arnold Raitsimring shows how to
apply the “2+1” pulse sequence for distance and spatial distribution
measurements of paramagnetic centers. Double-Quantum ESR is applied to
distance measurements by Petr Borbat and Jack Freed. Pulsed double
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x Preface
electron-electron methods, sometimes called PELDOR or DEER are
described by Gunnar Jeschke, Martin Pannier and Hans Spiess. K. V.
Lakshmi and Gary Brudvig discuss spin-spin interactions in the
photosynthetic reaction center revealed by CW EPR spectra. The distance
information that is obtainable from out-of-phase electron spin echoes of
photo-inducedradical pairs is explained by Sergei Dzuba and Arnold Hoff.
Some related topics have been discussed in other volumes of
Biological Magnetic Resonance and consequently are not included in the
present volume. In particular, we call the reader’s attention to the Mims and
Peisach review of ESEEM in Volume 3, the review of biological
applications of time domain EPR by Thomann, Dalton, and Dalton in
Volume 6, the four reviews of ENDOR by Hoffman and coworkers,
Huttermann, Möbius, and Thomann and Bernardo in Volume 13,
progressive saturation and saturation transfer EPR by Marsh, Pali, and
Horvath in Volume 14, and of ENDOR by Makinen, Mustafi and Kasa in
Volume 14. Other reviews are cited in the appropriate chapters.
Site-directed spin labeling and time-domain EPR are enabling
technologies for using spin-spin interactions to estimate distances. Now that
commercial pulsed EPR spectrometers are available, both the CW and
pulsed EPR the techniques that are described in this volume can be applied
by many researchers. We hope that this volume guides users to the
technique(s) most suitable for the problem to be solved.
Sandra S. Eaton
Gareth R. Eaton
Denver, Colorado
Lawrence J. Berliner
Columbus, Ohio
Contents
Section I. Introduction
Chapter 1
Distance Measurements by CW and Pulsed EPR
Sandra S. Eaton and Gareth R. Eaton
1. Structural StudiesofBiomolecules............................................................. 2
1.1. Structure andDynamics....................................................................... 3
1.2. Rationale forDistance Measurements byEPR.................................... 4
2. DipolarInteractions................................................................................... 6
3. ExchangeInteraction.................................................................................. 9
4. Determination of Electron-Electron Distances from Dipolar Interaction
Measured by EPR ...................................................................................... 10
4.1. Pairwise Interaction Between Two Slowly-Relaxing Spins in an
Immobilized Sample .......................................................................... 12
4.2. Pairwise Interaction Between Two Slowly-Relaxing Spins in a Slowly-
Tumbling Macromolecule in Fluid Solution...................................... 17
4.3. Pairwise Interaction Between a Slowly-Relaxing Spin and a More
Rapidly-Relaxing Spin in an Immobilized Sample........................... 18
4.4. Out-of-Phase Echo for Spin-Polarized Radical Pairs......................... 20
4.5. Collisions Between Slowly-Relaxing Label and More Rapidly-
Relaxing Spin in Fluid Solution......................................................... 20
5. Distributions of Distances........................................................................... 21
6. Accuracy and Precision of Distances Measured......................................... 21
References................................................................................................... 21
Chapter 2
Relaxation Times of Organic Radicals and Transition Metal Ions
Sandra S. Eaton and Gareth R. Eaton
1. Introduction................................................................................................ 29
1.1. Scope of this Chapter.......................................................................... 29
1.2. Why You Should Care about Relaxation Times................................. 31
2. Terminology............................................................................................... 32
3. Experimental Measurements of Relaxation Times .................................... 36
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