1
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Teucher M, Kucher S, Timachi MH, Wilson CB, Śmiłowicz D, Stoll R, Metzler-Nolte N, Sherwin MS, Han S, Bordignon E. Spectroscopically Orthogonal Spin Labels in Structural Biology at Physiological Temperatures. J Phys Chem B 2023; 127:6668-6674. [PMID: 37490415 PMCID: PMC10405217 DOI: 10.1021/acs.jpcb.3c04497] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2023] [Revised: 07/08/2023] [Indexed: 07/27/2023]
Abstract
Electron paramagnetic resonance spectroscopy (EPR) is mostly used in structural biology in conjunction with pulsed dipolar spectroscopy (PDS) methods to monitor interspin distances in biomacromolecules at cryogenic temperatures both in vitro and in cells. In this context, spectroscopically orthogonal spin labels were shown to increase the information content that can be gained per sample. Here, we exploit the characteristic properties of gadolinium and nitroxide spin labels at physiological temperatures to study side chain dynamics via continuous wave (cw) EPR at X band, surface water dynamics via Overhauser dynamic nuclear polarization at X band and short-range distances via cw EPR at high fields. The presented approaches further increase the accessible information content on biomolecules tagged with orthogonal labels providing insights into molecular interactions and dynamic equilibria that are only revealed under physiological conditions.
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Affiliation(s)
- Markus Teucher
- Faculty
of Chemistry and Biochemistry, Ruhr University
of Bochum, Bochum 44801, Germany
| | - Svetlana Kucher
- Faculty
of Chemistry and Biochemistry, Ruhr University
of Bochum, Bochum 44801, Germany
- Department
of Physical Chemistry, University of Geneva, Genève 1211, Switzerland
| | - M. Hadi Timachi
- Faculty
of Chemistry and Biochemistry, Ruhr University
of Bochum, Bochum 44801, Germany
| | - C. Blake Wilson
- Department
of Physics, University of California, Santa
Barbara, Santa
Barbara, California 93106, United States
- Institute
for Terahertz Science and Technology, University
of California, Santa Barbara, Santa
Barbara, California 93106, United States
| | - Dariusz Śmiłowicz
- Faculty
of Chemistry and Biochemistry, Ruhr University
of Bochum, Bochum 44801, Germany
| | - Raphael Stoll
- Faculty
of Chemistry and Biochemistry, Ruhr University
of Bochum, Bochum 44801, Germany
| | - Nils Metzler-Nolte
- Faculty
of Chemistry and Biochemistry, Ruhr University
of Bochum, Bochum 44801, Germany
| | - Mark S. Sherwin
- Department
of Physics, University of California, Santa
Barbara, Santa
Barbara, California 93106, United States
- Institute
for Terahertz Science and Technology, University
of California, Santa Barbara, Santa
Barbara, California 93106, United States
| | - Songi Han
- Institute
for Terahertz Science and Technology, University
of California, Santa Barbara, Santa
Barbara, California 93106, United States
- Department
of Chemistry and Biochemistry, University
of California, Santa Barbara, Santa Barbara, California 93106, United States
| | - Enrica Bordignon
- Faculty
of Chemistry and Biochemistry, Ruhr University
of Bochum, Bochum 44801, Germany
- Department
of Physical Chemistry, University of Geneva, Genève 1211, Switzerland
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2
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Gerbaud G, Barbat B, Tribout M, Etienne E, Belle V, Douzi B, Voulhoux R, Bonucci A. Refining the Dynamic Network of T2SS Endopilus Tip Heterocomplex Combining cw-EPR and Nitroxide-Gd III Distance Measurements. Chembiochem 2023; 24:e202300099. [PMID: 36999435 DOI: 10.1002/cbic.202300099] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2023] [Revised: 03/16/2023] [Accepted: 03/30/2023] [Indexed: 04/01/2023]
Abstract
The type 2 secretion system (T2SS) is a bacterial nanomachine composed of an inner membrane assembly platform, an outer membrane pore and a dynamic endopilus. T2SS endopili are organized into a homo-multimeric body formed by the major pilin capped by a heterocomplex of four minor pilins. The first model of the T2SS endopilus was recently released, even if structural dynamics insights are still required to decipher the role of each protein in the full tetrameric complex. Here, we applied continuous-wave and pulse EPR spectroscopy using nitroxide-gadolinium orthogonal labelling strategies to investigate the hetero-oligomeric assembly of the minor pilins. Overall, our data are in line with the endopilus model even if they evidenced conformational flexibility and alternative orientations at local scale of specific regions of minor pilins. The integration of different labelling strategies and EPR experiments demonstrates the pertinence of this approach to investigate protein-protein interactions in such multiprotein heterocomplexes.
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Affiliation(s)
- Guillaume Gerbaud
- BIP-Bioénérgetique et Ingénierie es Protéines, IMM, Aix Marseille Université, CNRS, 13009, Marseille, France
| | - Brice Barbat
- LCB-Laboratoire de Chimie Bactérienne, IMM, Aix Marseille Université, CNRS, 13009, Marseille, France
| | - Mathilde Tribout
- LCB-Laboratoire de Chimie Bactérienne, IMM, Aix Marseille Université, CNRS, 13009, Marseille, France
| | - Emilien Etienne
- BIP-Bioénérgetique et Ingénierie es Protéines, IMM, Aix Marseille Université, CNRS, 13009, Marseille, France
| | - Valérie Belle
- BIP-Bioénérgetique et Ingénierie es Protéines, IMM, Aix Marseille Université, CNRS, 13009, Marseille, France
| | - Badreddine Douzi
- LCB-Laboratoire de Chimie Bactérienne, IMM, Aix Marseille Université, CNRS, 13009, Marseille, France
- Present address: INRAE, DynAMic, Université de Lorraine, 54000, Nancy, France
| | - Romé Voulhoux
- LCB-Laboratoire de Chimie Bactérienne, IMM, Aix Marseille Université, CNRS, 13009, Marseille, France
| | - Alessio Bonucci
- BIP-Bioénérgetique et Ingénierie es Protéines, IMM, Aix Marseille Université, CNRS, 13009, Marseille, France
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3
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Ketter S, Joseph B. Gd 3+-Trityl-Nitroxide Triple Labeling and Distance Measurements in the Heterooligomeric Cobalamin Transport Complex in the Native Lipid Bilayers. J Am Chem Soc 2023; 145:960-966. [PMID: 36599418 PMCID: PMC9853854 DOI: 10.1021/jacs.2c10080] [Citation(s) in RCA: 7] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
Increased efforts are being made for observing proteins in their native environments. Pulsed electron-electron double resonance spectroscopy (PELDOR, also known as DEER) is a powerful tool for this purpose. Conventionally, PELDOR employs an identical spin pair, which limits the output to a single distance for monomeric samples. Here, we show that the Gd3+-trityl-nitroxide (NO) three-spin system is a versatile tool to study heterooligomeric membrane protein complexes, even within their native membrane. This allowed for an independent determination of four different distances (Gd3+-trityl, Gd3+-NO, trityl-NO, and Gd3+-Gd3+) within the same sample. We demonstrate the feasibility of this approach by observing sequential ligand binding and the dynamics of complex formation in the cobalamin transport system involving four components (cobalamin, BtuB, TonB, and BtuF). Our results reveal that TonB binding alone is sufficient to release cobalamin from BtuB in the native asymmetric bilayers. This approach provides a potential tool for the structural and quantitative analysis of dynamic protein-protein interactions in oligomeric complexes, even within their native surroundings.
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4
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Goldfarb D. Exploring protein conformations in vitro and in cell with EPR distance measurements. Curr Opin Struct Biol 2022; 75:102398. [PMID: 35667279 DOI: 10.1016/j.sbi.2022.102398] [Citation(s) in RCA: 22] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2022] [Revised: 04/20/2022] [Accepted: 04/30/2022] [Indexed: 11/18/2022]
Abstract
The electron-electron double resonance (DEER) method, which provides distance distributions between two spin labels, attached site specifically to biomolecules (proteins and nucleic acids), is currently a well-recognized biophysical tool in structural biology. The most commonly used spin labels are based on nitroxide stable radicals, conjugated to the proteins primarily via native or engineered cysteine residues. However, in recent years, new spin labels, along with different labeling chemistries, have been introduced, driven in part by the desire to study structural and dynamical properties of biomolecules in their native environment, the cell. This mini-review focuses on these new spin labels, which allow for DEER on orthogonal spin labels, and on the state of the art methods for in-cell DEER distance measurements.
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Affiliation(s)
- Daniella Goldfarb
- Department of Chemical and Biological Physics, Weizmann Institute of Science, Rehovot, 761001, Israel
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5
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Keeley J, Choudhury T, Galazzo L, Bordignon E, Feintuch A, Goldfarb D, Russell H, Taylor MJ, Lovett JE, Eggeling A, Fábregas Ibáñez L, Keller K, Yulikov M, Jeschke G, Kuprov I. Neural networks in pulsed dipolar spectroscopy: A practical guide. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2022; 338:107186. [PMID: 35344921 DOI: 10.1016/j.jmr.2022.107186] [Citation(s) in RCA: 14] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/21/2021] [Revised: 02/23/2022] [Accepted: 02/25/2022] [Indexed: 06/14/2023]
Abstract
This is a methodological guide to the use of deep neural networks in the processing of pulsed dipolar spectroscopy (PDS) data encountered in structural biology, organic photovoltaics, photosynthesis research, and other domains featuring long-lived radical pairs and paramagnetic metal ions. PDS uses distance dependence of magnetic dipolar interactions; measuring a single well-defined distance is straightforward, but extracting distance distributions is a hard and mathematically ill-posed problem requiring careful regularisation and background fitting. Neural networks do this exceptionally well, but their "robust black box" reputation hides the complexity of their design and training - particularly when the training dataset is effectively infinite. The objective of this paper is to give insight into training against simulated databases, to discuss network architecture choices, to describe options for handling DEER (double electron-electron resonance) and RIDME (relaxation-induced dipolar modulation enhancement) experiments, and to provide a practical data processing flowchart.
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Affiliation(s)
- Jake Keeley
- School of Chemistry, University of Southampton, Southampton SO17 1BJ, United Kingdom
| | - Tajwar Choudhury
- School of Chemistry, University of Southampton, Southampton SO17 1BJ, United Kingdom
| | - Laura Galazzo
- Department of Physical Chemistry, University of Geneva, Quai Ernest Ansermet 30, CH-1211 Geneva, Switzerland
| | - Enrica Bordignon
- Department of Physical Chemistry, University of Geneva, Quai Ernest Ansermet 30, CH-1211 Geneva, Switzerland
| | - Akiva Feintuch
- Department of Chemical Physics, Weizmann Institute of Science, Rehovot 7610001, Israel
| | - Daniella Goldfarb
- Department of Chemical Physics, Weizmann Institute of Science, Rehovot 7610001, Israel
| | - Hannah Russell
- SUPA School of Physics and Astronomy and BSRC, University of St Andrews, North Haugh, St Andrews KY16 9SS, United Kingdom
| | - Michael J Taylor
- SUPA School of Physics and Astronomy and BSRC, University of St Andrews, North Haugh, St Andrews KY16 9SS, United Kingdom
| | - Janet E Lovett
- SUPA School of Physics and Astronomy and BSRC, University of St Andrews, North Haugh, St Andrews KY16 9SS, United Kingdom
| | - Andrea Eggeling
- Department of Chemistry and Applied Biosciences, Swiss Federal Institute of Technology in Zurich, Vladimir Prelog Weg 2, CH-8093 Zürich, Switzerland
| | - Luis Fábregas Ibáñez
- Department of Chemistry and Applied Biosciences, Swiss Federal Institute of Technology in Zurich, Vladimir Prelog Weg 2, CH-8093 Zürich, Switzerland
| | - Katharina Keller
- Department of Chemistry and Applied Biosciences, Swiss Federal Institute of Technology in Zurich, Vladimir Prelog Weg 2, CH-8093 Zürich, Switzerland
| | - Maxim Yulikov
- Department of Chemistry and Applied Biosciences, Swiss Federal Institute of Technology in Zurich, Vladimir Prelog Weg 2, CH-8093 Zürich, Switzerland
| | - Gunnar Jeschke
- Department of Chemistry and Applied Biosciences, Swiss Federal Institute of Technology in Zurich, Vladimir Prelog Weg 2, CH-8093 Zürich, Switzerland
| | - Ilya Kuprov
- School of Chemistry, University of Southampton, Southampton SO17 1BJ, United Kingdom.
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6
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Abstract
Different types of spin labels are currently available for structural studies of biomolecules both in vitro and in cells using Electron Paramagnetic Resonance (EPR) and pulse dipolar spectroscopy (PDS). Each type of label has its own advantages and disadvantages, that will be addressed in this chapter. The spectroscopically distinct properties of the labels have fostered new applications of PDS aimed to simultaneously extract multiple inter-label distances on the same sample. In fact, combining different labels and choosing the optimal strategy to address their inter-label distances can increase the information content per sample, and this is pivotal to better characterize complex multi-component biomolecular systems. In this review, we provide a brief background of the spectroscopic properties of the four most common orthogonal spin labels for PDS measurements and focus on the various methods at disposal to extract homo- and hetero-label distances in proteins. We also devote a section to possible artifacts arising from channel crosstalk and provide few examples of applications in structural biology.
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7
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Meichsner SL, Kutin Y, Kasanmascheff M. In‐Cell Characterization of the Stable Tyrosyl Radical in
E. coli
Ribonucleotide Reductase Using Advanced EPR Spectroscopy. Angew Chem Int Ed Engl 2021. [DOI: 10.1002/ange.202102914] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Affiliation(s)
- Shari L. Meichsner
- Department of Chemistry and Chemical Biology TU Dortmund University Otto-Hahn-Strasse 6 44227 Dortmund Germany
| | - Yury Kutin
- Department of Chemistry and Chemical Biology TU Dortmund University Otto-Hahn-Strasse 6 44227 Dortmund Germany
| | - Müge Kasanmascheff
- Department of Chemistry and Chemical Biology TU Dortmund University Otto-Hahn-Strasse 6 44227 Dortmund Germany
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8
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Meichsner SL, Kutin Y, Kasanmascheff M. In-Cell Characterization of the Stable Tyrosyl Radical in E. coli Ribonucleotide Reductase Using Advanced EPR Spectroscopy. Angew Chem Int Ed Engl 2021; 60:19155-19161. [PMID: 33844392 PMCID: PMC8453577 DOI: 10.1002/anie.202102914] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2021] [Revised: 04/11/2021] [Indexed: 12/21/2022]
Abstract
The E. coli ribonucleotide reductase (RNR), a paradigm for class Ia enzymes including human RNR, catalyzes the biosynthesis of DNA building blocks and requires a di‐iron tyrosyl radical (Y122.) cofactor for activity. The knowledge on the in vitro Y122. structure and its radical distribution within the β2 subunit has accumulated over the years; yet little information exists on the in vivo Y122.. Here, we characterize this essential radical in whole cells. Multi‐frequency EPR and electron‐nuclear double resonance (ENDOR) demonstrate that the structure and electrostatic environment of Y122. are identical under in vivo and in vitro conditions. Pulsed dipolar EPR experiments shed light on a distinct in vivo Y122. per β2 distribution, supporting the key role of Y. concentrations in regulating RNR activity. Additionally, we spectroscopically verify the generation of an unnatural amino acid radical, F3Y122., in whole cells, providing a crucial step towards unique insights into the RNR catalysis under physiological conditions.
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Affiliation(s)
- Shari L Meichsner
- Department of Chemistry and Chemical Biology, TU Dortmund University, Otto-Hahn-Strasse 6, 44227, Dortmund, Germany
| | - Yury Kutin
- Department of Chemistry and Chemical Biology, TU Dortmund University, Otto-Hahn-Strasse 6, 44227, Dortmund, Germany
| | - Müge Kasanmascheff
- Department of Chemistry and Chemical Biology, TU Dortmund University, Otto-Hahn-Strasse 6, 44227, Dortmund, Germany
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9
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Bahrenberg T, Yardeni EH, Feintuch A, Bibi E, Goldfarb D. Substrate binding in the multidrug transporter MdfA in detergent solution and in lipid nanodiscs. Biophys J 2021; 120:1984-1993. [PMID: 33771471 PMCID: PMC8204392 DOI: 10.1016/j.bpj.2021.03.014] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2020] [Revised: 03/07/2021] [Accepted: 03/15/2021] [Indexed: 10/21/2022] Open
Abstract
MdfA from Escherichia coli is a prototypical secondary multi-drug (Mdr) transporter that exchanges drugs for protons. MdfA-mediated drug efflux is driven by the proton gradient and enabled by conformational changes that accompany the recruitment of drugs and their release. In this work, we applied distance measurements by W-band double electron-electron resonance (DEER) spectroscopy to explore the binding of mito-TEMPO, a nitroxide-labeled substrate analog, to Gd(III)-labeled MdfA. The choice of Gd(III)-nitroxide DEER enabled measurements in the presence of excess of mito-TEMPO, which has a relatively low affinity to MdfA. Distance measurements between mito-TEMPO and MdfA labeled at the periplasmic edges of either of three selected transmembrane helices (TM3101, TM5168, and TM9310) revealed rather similar distance distributions in detergent micelles (n-dodecyl-β-d-maltopyranoside, DDM)) and in lipid nanodiscs (ND). By grafting the predicted positions of the Gd(III) tag on the inward-facing (If) crystal structure, we looked for binding positions that reproduced the maxima of the distance distributions. The results show that the location of the mito-TEMPO nitroxide in DDM-solubilized or ND-reconstituted MdfA is similar (only 0.4 nm apart). In both cases, we located the nitroxide moiety near the ligand binding pocket in the If structure. However, according to the DEER-derived position, the substrate clashes with TM11, suggesting that for mito-TEMPO-bound MdfA, TM11 should move relative to the If structure. Additional DEER studies with MdfA labeled with Gd(III) at two sites revealed that TM9 also dislocates upon substrate binding. Together with our previous reports, this study demonstrates the utility of Gd(III)-Gd(III) and Gd(III)-nitroxide DEER measurements for studying the conformational behavior of transporters.
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Affiliation(s)
- Thorsten Bahrenberg
- Departments of Chemical and Biological Physics, Weizmann Institute of Science, Rehovot, Israel
| | - Eliane Hadas Yardeni
- Departments of Biomolecular Sciences, Weizmann Institute of Science, Rehovot, Israel
| | - Akiva Feintuch
- Departments of Chemical and Biological Physics, Weizmann Institute of Science, Rehovot, Israel
| | - Eitan Bibi
- Departments of Biomolecular Sciences, Weizmann Institute of Science, Rehovot, Israel.
| | - Daniella Goldfarb
- Departments of Chemical and Biological Physics, Weizmann Institute of Science, Rehovot, Israel.
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10
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Giannoulis A, Ben-Ishay Y, Goldfarb D. Characteristics of Gd(III) spin labels for the study of protein conformations. Methods Enzymol 2021; 651:235-290. [PMID: 33888206 DOI: 10.1016/bs.mie.2021.01.040] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Gd(III) complexes are currently established as spin labels for structural studies of biomolecules using pulse dipolar electron paramagnetic resonance (PD-EPR) techniques. This has been achieved by the availability of medium- and high-field spectrometers, understanding the spin physics underlying the spectroscopic properties of high spin Gd(III) (S=7/2) pairs and their dipolar interaction, the design of well-defined model compounds and optimization of measurement techniques. In addition, a variety of Gd(III) chelates and labeling schemes have allowed a broad scope of applications. In this review, we provide a brief background of the spectroscopic properties of Gd(III) pertinent for effective PD-EPR measurements and focus on the various labels available to date. We report on their use in PD-EPR applications and highlight their pros and cons for particular applications. We also devote a section to recent in-cell structural studies of proteins using Gd(III), which is an exciting new direction for Gd(III) spin labeling.
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Affiliation(s)
- Angeliki Giannoulis
- Department of Chemical and Biological Physics, Weizmann Institute of Science, Rehovot, Israel
| | - Yasmin Ben-Ishay
- Department of Chemical and Biological Physics, Weizmann Institute of Science, Rehovot, Israel
| | - Daniella Goldfarb
- Department of Chemical and Biological Physics, Weizmann Institute of Science, Rehovot, Israel.
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11
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Tkach I, Diederichsen U, Bennati M. Studies of transmembrane peptides by pulse dipolar spectroscopy with semi-rigid TOPP spin labels. EUROPEAN BIOPHYSICS JOURNAL : EBJ 2021; 50:143-157. [PMID: 33640998 PMCID: PMC8071797 DOI: 10.1007/s00249-021-01508-6] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/08/2020] [Revised: 01/25/2021] [Accepted: 01/29/2021] [Indexed: 12/01/2022]
Abstract
Electron paramagnetic resonance (EPR)-based pulsed dipolar spectroscopy measures the dipolar interaction between paramagnetic centers that are separated by distances in the range of about 1.5-10 nm. Its application to transmembrane (TM) peptides in combination with modern spin labelling techniques provides a valuable tool to study peptide-to-lipid interactions at a molecular level, which permits access to key parameters characterizing the structural adaptation of model peptides incorporated in natural membranes. In this mini-review, we summarize our approach for distance and orientation measurements in lipid environment using novel semi-rigid TOPP [4-(3,3,5,5-tetramethyl-2,6-dioxo-4-oxylpiperazin-1-yl)-L-phenylglycine] labels specifically designed for incorporation in TM peptides. TOPP labels can report single peak distance distributions with sub-angstrom resolution, thus offering new capabilities for a variety of TM peptide investigations, such as monitoring of various helix conformations or measuring of tilt angles in membranes.
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Affiliation(s)
- Igor Tkach
- Max Planck Institute for Biophysical Chemistry, RG Electron-Spin Resonance Spectroscopy, 37077, Göttingen, Germany.
| | - Ulf Diederichsen
- Department of Organic and Biomolecular Chemistry, University of Göttingen, 37077, Göttingen, Germany
| | - Marina Bennati
- Max Planck Institute for Biophysical Chemistry, RG Electron-Spin Resonance Spectroscopy, 37077, Göttingen, Germany
- Department of Organic and Biomolecular Chemistry, University of Göttingen, 37077, Göttingen, Germany
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12
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Soetbeer J, Millen M, Zouboulis K, Hülsmann M, Godt A, Polyhach Y, Jeschke G. Dynamical decoupling in water-glycerol glasses: a comparison of nitroxides, trityl radicals and gadolinium complexes. Phys Chem Chem Phys 2021; 23:5352-5369. [PMID: 33635938 DOI: 10.1039/d1cp00055a] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Our previous study on nitroxides in o-terphenyl (OTP) revealed two separable decoherence processes at low temperatures, best captured by the sum of two stretched exponentials (SSE) model. Dynamical decoupling (DD) extends both associated dephasing times linearly for 1 to 5 refocusing pulses [Soetbeer et al., Phys. Chem. Chem. Phys., 2018, 20, 1615]. Here we demonstrate an analogous DD behavior of water-soluble nitroxides in water-glycerol glass by using nitroxide and/or solvent deuteration for component assignment. Compared to the conventional Hahn experiment, we show that Carr-Purcell and Uhrig DD schemes are superior in resolving and identifying active dephasing mechanisms. Thereby, we observe a partial coherence loss to intramolecular nitroxide and trityl nuclei that can be alleviated, while the zero field splitting-induced losses for gadolinium labels cannot be refocused and contribute even at the central transition of this spin-7/2 system. Independent of the studied spin system, Uhrig DD leads to a characteristic convex dephasing envelope in both protonated water-glycerol and OTP glass, thus outperforming the Carr-Purcell scheme.
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Affiliation(s)
- Janne Soetbeer
- Laboratory of Physical Chemistry, ETH Zürich, Vladimir-Prelog-Weg 2, CH-8093 Zürich, Switzerland.
| | - Marthe Millen
- Laboratory of Physical Chemistry, ETH Zürich, Vladimir-Prelog-Weg 2, CH-8093 Zürich, Switzerland.
| | - Konstantin Zouboulis
- Laboratory of Physical Chemistry, ETH Zürich, Vladimir-Prelog-Weg 2, CH-8093 Zürich, Switzerland.
| | - Miriam Hülsmann
- Bielefeld University, Department of Chemistry, Universitätsstr. 25, D-33615 Bielefeld, Germany
| | - Adelheid Godt
- Bielefeld University, Department of Chemistry, Universitätsstr. 25, D-33615 Bielefeld, Germany
| | - Yevhen Polyhach
- Laboratory of Physical Chemistry, ETH Zürich, Vladimir-Prelog-Weg 2, CH-8093 Zürich, Switzerland.
| | - Gunnar Jeschke
- Laboratory of Physical Chemistry, ETH Zürich, Vladimir-Prelog-Weg 2, CH-8093 Zürich, Switzerland.
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13
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Teucher M, Qi M, Cati N, Hintz H, Godt A, Bordignon E. Strategies to identify and suppress crosstalk signals in double electron-electron resonance (DEER) experiments with gadolinium III and nitroxide spin-labeled compounds. MAGNETIC RESONANCE (GOTTINGEN, GERMANY) 2020; 1:285-299. [PMID: 37904822 PMCID: PMC10500692 DOI: 10.5194/mr-1-285-2020] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 06/18/2020] [Accepted: 10/31/2020] [Indexed: 11/01/2023]
Abstract
Double electron-electron resonance (DEER) spectroscopy applied to orthogonally spin-labeled biomolecular complexes simplifies the assignment of intra- and intermolecular distances, thereby increasing the information content per sample. In fact, various spin labels can be addressed independently in DEER experiments due to spectroscopically nonoverlapping central transitions, distinct relaxation times, and/or transition moments; hence, they are referred to as spectroscopically orthogonal. Molecular complexes which are, for example, orthogonally spin-labeled with nitroxide (NO) and gadolinium (Gd) labels give access to three distinct DEER channels that are optimized to selectively probe NO-NO, NO-Gd, and Gd-Gd distances. Nevertheless, it has been previously recognized that crosstalk signals between individual DEER channels can occur, for example, when a Gd-Gd distance appears in a DEER channel optimized to detect NO-Gd distances. This is caused by residual spectral overlap between NO and Gd spins which, therefore, cannot be considered as perfectly orthogonal. Here, we present a systematic study on how to identify and suppress crosstalk signals that can appear in DEER experiments using mixtures of NO-NO, NO-Gd, and Gd-Gd molecular rulers characterized by distinct, nonoverlapping distance distributions. This study will help to correctly assign the distance peaks in homo- and heterocomplexes of biomolecules carrying not perfectly orthogonal spin labels.
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Affiliation(s)
- Markus Teucher
- Faculty of Chemistry and Biochemistry, Ruhr University Bochum, Universitätsstraße 150, 44801 Bochum, Germany
| | - Mian Qi
- Faculty of Chemistry and Center for Molecular Materials (CM2), Bielefeld University, Universitätsstraße 25, 33615 Bielefeld, Germany
| | - Ninive Cati
- Faculty of Chemistry and Center for Molecular Materials (CM2), Bielefeld University, Universitätsstraße 25, 33615 Bielefeld, Germany
| | - Henrik Hintz
- Faculty of Chemistry and Center for Molecular Materials (CM2), Bielefeld University, Universitätsstraße 25, 33615 Bielefeld, Germany
| | - Adelheid Godt
- Faculty of Chemistry and Center for Molecular Materials (CM2), Bielefeld University, Universitätsstraße 25, 33615 Bielefeld, Germany
| | - Enrica Bordignon
- Faculty of Chemistry and Biochemistry, Ruhr University Bochum, Universitätsstraße 150, 44801 Bochum, Germany
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14
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Assafa TE, Nandi S, Śmiłowicz D, Galazzo L, Teucher M, Elsner C, Pütz S, Bleicken S, Robin AY, Westphal D, Uson I, Stoll R, Czabotar PE, Metzler-Nolte N, Bordignon E. Biophysical Characterization of Pro-apoptotic BimBH3 Peptides Reveals an Unexpected Capacity for Self-Association. Structure 2020; 29:114-124.e3. [PMID: 32966763 DOI: 10.1016/j.str.2020.09.002] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2020] [Revised: 07/13/2020] [Accepted: 08/29/2020] [Indexed: 01/11/2023]
Abstract
Bcl-2 proteins orchestrate the mitochondrial pathway of apoptosis, pivotal for cell death. Yet, the structural details of the conformational changes of pro- and antiapoptotic proteins and their interactions remain unclear. Pulse dipolar spectroscopy (double electron-electron resonance [DEER], also known as PELDOR) in combination with spin-labeled apoptotic Bcl-2 proteins unveils conformational changes and interactions of each protein player via detection of intra- and inter-protein distances. Here, we present the synthesis and characterization of pro-apoptotic BimBH3 peptides of different lengths carrying cysteines for labeling with nitroxide or gadolinium spin probes. We show by DEER that the length of the peptides modulates their homo-interactions in the absence of other Bcl-2 proteins and solve by X-ray crystallography the structure of a BimBH3 tetramer, revealing the molecular details of the inter-peptide interactions. Finally, we prove that using orthogonal labels and three-channel DEER we can disentangle the Bim-Bim, Bcl-xL-Bcl-xL, and Bim-Bcl-xL interactions in a simplified interactome.
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Affiliation(s)
- Tufa E Assafa
- Faculty of Chemistry and Biochemistry, Ruhr University Bochum, Bochum, Germany
| | - Sukhendu Nandi
- Faculty of Chemistry and Biochemistry, Ruhr University Bochum, Bochum, Germany
| | - Dariusz Śmiłowicz
- Chair of Inorganic Chemistry I - Bioinorganic Chemistry, Faculty of Chemistry and Biochemistry, Ruhr University Bochum, Bochum, Germany
| | - Laura Galazzo
- Faculty of Chemistry and Biochemistry, Ruhr University Bochum, Bochum, Germany
| | - Markus Teucher
- Faculty of Chemistry and Biochemistry, Ruhr University Bochum, Bochum, Germany
| | - Christina Elsner
- Faculty of Chemistry and Biochemistry, Ruhr University Bochum, Bochum, Germany
| | - Stefanie Pütz
- Faculty of Chemistry and Biochemistry, Ruhr University Bochum, Bochum, Germany
| | - Stephanie Bleicken
- Faculty of Chemistry and Biochemistry, Ruhr University Bochum, Bochum, Germany
| | - Adeline Y Robin
- Walter and Eliza Hall Institute of Medical Research, Parkville, VIC, Australia; Department of Medical Biology, The University of Melbourne, Melbourne, VIC, Australia
| | - Dana Westphal
- Walter and Eliza Hall Institute of Medical Research, Parkville, VIC, Australia; Department of Medical Biology, The University of Melbourne, Melbourne, VIC, Australia; Department of Dermatology, Medical Faculty and University Hospital Dresden, TU Dresden, Dresden, Germany
| | - Isabel Uson
- Crystallographic Methods, Institute of Molecular Biology of Barcelona (IBMB-CSIC), Barcelona, Spain; ICREA, Baldiri Pg. Lluís Companys 23, 08010 Barcelona, Spain
| | - Raphael Stoll
- Faculty of Chemistry and Biochemistry, Ruhr University Bochum, Bochum, Germany
| | - Peter E Czabotar
- Walter and Eliza Hall Institute of Medical Research, Parkville, VIC, Australia; Department of Medical Biology, The University of Melbourne, Melbourne, VIC, Australia
| | - Nils Metzler-Nolte
- Chair of Inorganic Chemistry I - Bioinorganic Chemistry, Faculty of Chemistry and Biochemistry, Ruhr University Bochum, Bochum, Germany
| | - Enrica Bordignon
- Faculty of Chemistry and Biochemistry, Ruhr University Bochum, Bochum, Germany.
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15
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EPR of site-directed spin-labeled proteins: A powerful tool to study structural flexibility. Arch Biochem Biophys 2020; 684:108323. [DOI: 10.1016/j.abb.2020.108323] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2019] [Revised: 02/17/2020] [Accepted: 02/24/2020] [Indexed: 12/20/2022]
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16
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Breitgoff FD, Keller K, Qi M, Klose D, Yulikov M, Godt A, Jeschke G. UWB DEER and RIDME distance measurements in Cu(II)-Cu(II) spin pairs. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2019; 308:106560. [PMID: 31377151 DOI: 10.1016/j.jmr.2019.07.047] [Citation(s) in RCA: 28] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/07/2019] [Revised: 07/12/2019] [Accepted: 07/15/2019] [Indexed: 06/10/2023]
Abstract
Distance determination by Electron Paramagnetic Resonance (EPR) based on measurements of the dipolar coupling are technically challenging for electron spin systems with broad spectra due to comparatively narrow microwave pulse excitation bandwidths. With Na4[{CuII(PyMTA)}-(stiff spacer)-{CuII(PyMTA)}] as a model compound, we compared DEER and RIDME measurements and investigated the use of frequency-swept pulses. We found very large improvements in sensitivity when substituting the monochromatic pump pulse by a frequency-swept one in DEER experiments with monochromatic observer pulses. This effect was especially strong in X band, where nearly the whole spectrum can be included in the experiment. The RIDME experiment is characterised by a trade-off in signal intensity and modulation depth. Optimal parameters are further influenced by varying steepness of the background decay. A simple 2-point optimization experiment was found to serve as good estimate to identify the mixing time of highest sensitivity. Using frequency-swept pulses in the observer sequences resulted in lower SNR in both the RIDME and the DEER experiment. Orientation selectivity was found to vary in both experiments with the detection position as well as with the settings of the pump pulse in DEER. In RIDME, orientation selection by relaxation anisotropy of the inverted spin appeared to be negligible as form factors remain relatively constant with varying mixing time. This reduces the overall observed orientation selection to the one given by the detection position. Field-averaged data from RIDME and DEER with a shaped pump pulse resulted in the same dipolar spectrum. We found that both methods have their advantages and disadvantages for given instrumental limitations and sample properties. Thus the choice of method depends on the situation at hand and we discuss which parameters should be considered for optimization.
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Affiliation(s)
- Frauke D Breitgoff
- ETH Zürich, Lab. Phys. Chem., Vladimir-Prelog-Weg 2, 8063 Zürich 3 Switzerland.
| | - Katharina Keller
- ETH Zürich, Lab. Phys. Chem., Vladimir-Prelog-Weg 2, 8063 Zürich 3 Switzerland.
| | - Mian Qi
- Faculty of Chemistry and Center for Molecular Materials (CM(2)), Bielefeld University, Universitätsstraße 25, 33615 Bielefeld, Germany
| | - Daniel Klose
- ETH Zürich, Lab. Phys. Chem., Vladimir-Prelog-Weg 2, 8063 Zürich 3 Switzerland
| | - Maxim Yulikov
- ETH Zürich, Lab. Phys. Chem., Vladimir-Prelog-Weg 2, 8063 Zürich 3 Switzerland
| | - Adelheid Godt
- Faculty of Chemistry and Center for Molecular Materials (CM(2)), Bielefeld University, Universitätsstraße 25, 33615 Bielefeld, Germany.
| | - Gunnar Jeschke
- ETH Zürich, Lab. Phys. Chem., Vladimir-Prelog-Weg 2, 8063 Zürich 3 Switzerland
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17
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Goldfarb D. Pulse EPR in biological systems - Beyond the expert's courtyard. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2019; 306:102-108. [PMID: 31337564 DOI: 10.1016/j.jmr.2019.07.038] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/02/2019] [Revised: 06/07/2019] [Accepted: 07/08/2019] [Indexed: 05/14/2023]
Abstract
Application of EPR to biological systems includes many techniques and applications. In this short perspective, which dares to look into the future, I focus on pulse EPR, which is my field of expertise. Generally, pulse EPR techniques can be divided into two main groups: (1) hyperfine spectroscopy, which explores electron-nuclear interactions, and (2) pulse-dipolar (PD) EPR spectroscopy, which is based on electron-electron spin interactions. Here I focus on PD-EPR because it has a better chance of becoming a widely applied, easy-to-use table-top method to study the structural and dynamic aspects of bio-molecules. I will briefly introduce this technique, its current state of the art, the challenges it is facing, and finally I will describe futuristic scenarios of low-cost PD-EPR approaches that can cross the diffusion barrier from the core of experts to the bulk of the scientific community.
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Affiliation(s)
- Daniella Goldfarb
- Department of Chemical and Biological Physics, Weizmann Institute of Science, Rehovot, Israel.
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18
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Yardeni EH, Bahrenberg T, Stein RA, Mishra S, Zomot E, Graham B, Tuck KL, Huber T, Bibi E, Mchaourab HS, Goldfarb D. Probing the solution structure of the E. coli multidrug transporter MdfA using DEER distance measurements with nitroxide and Gd(III) spin labels. Sci Rep 2019; 9:12528. [PMID: 31467343 PMCID: PMC6715713 DOI: 10.1038/s41598-019-48694-0] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2019] [Accepted: 08/08/2019] [Indexed: 11/09/2022] Open
Abstract
Methodological and technological advances in EPR spectroscopy have enabled novel insight into the structural and dynamic aspects of integral membrane proteins. In addition to an extensive toolkit of EPR methods, multiple spin labels have been developed and utilized, among them Gd(III)-chelates which offer high sensitivity at high magnetic fields. Here, we applied a dual labeling approach, employing nitroxide and Gd(III) spin labels, in conjunction with Q-band and W-band double electron-electron resonance (DEER) measurements to characterize the solution structure of the detergent-solubilized multidrug transporter MdfA from E. coli. Our results identify highly flexible regions of MdfA, which may play an important role in its functional dynamics. Comparison of distance distribution of spin label pairs on the periplasm with those calculated using inward- and outward-facing crystal structures of MdfA, show that in detergent micelles, the protein adopts a predominantly outward-facing conformation, although more closed than the crystal structure. The cytoplasmic pairs suggest a small preference to the outward-facing crystal structure, with a somewhat more open conformation than the crystal structure. Parallel DEER measurements with the two types of labels led to similar distance distributions, demonstrating the feasibility of using W-band spectroscopy with a Gd(III) label for investigation of the structural dynamics of membrane proteins.
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Affiliation(s)
- Eliane H Yardeni
- Department of Biomolecular Sciences, Weizmann Institute of Science Rehovot, Rehovot, 76100, Israel
| | - Thorsten Bahrenberg
- Department of Chemical and Biological Physics, Weizmann Institute of Science, Rehovot, 76100, Israel
| | - Richard A Stein
- Department of Molecular Physiology and Biophysics, Vanderbilt University, Nashville, TN, USA
| | - Smriti Mishra
- Department of Molecular Physiology and Biophysics, Vanderbilt University, Nashville, TN, USA
| | - Elia Zomot
- Department of Biomolecular Sciences, Weizmann Institute of Science Rehovot, Rehovot, 76100, Israel
| | - Bim Graham
- Monash Institute of Pharmaceutical Sciences, Monash University, Parkville, VIC, 3052, Australia
| | - Kellie L Tuck
- School of Chemistry, Monash University, Wellington Road, Clayton, Victoria, Australia
| | - Thomas Huber
- Research School of Chemistry, The Australian National University, Canberra, ACT 2601, Australia
| | - Eitan Bibi
- Department of Biomolecular Sciences, Weizmann Institute of Science Rehovot, Rehovot, 76100, Israel.
| | - Hassane S Mchaourab
- Department of Molecular Physiology and Biophysics, Vanderbilt University, Nashville, TN, USA.
| | - Daniella Goldfarb
- Department of Chemical and Biological Physics, Weizmann Institute of Science, Rehovot, 76100, Israel.
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19
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Shah A, Roux A, Starck M, Mosely JA, Stevens M, Norman DG, Hunter RI, El Mkami H, Smith GM, Parker D, Lovett JE. A Gadolinium Spin Label with Both a Narrow Central Transition and Short Tether for Use in Double Electron Electron Resonance Distance Measurements. Inorg Chem 2019; 58:3015-3025. [DOI: 10.1021/acs.inorgchem.8b02892] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Affiliation(s)
- Anokhi Shah
- SUPA, School of Physics and Astronomy, University of St Andrews, St Andrews KY16 9SS, U.K
- BSRC, University of St Andrews, St Andrews KY16 9ST, U.K
| | - Amandine Roux
- Department of Chemistry, Durham University, South Road, Durham DH1 3LE, U.K
| | - Matthieu Starck
- Department of Chemistry, Durham University, South Road, Durham DH1 3LE, U.K
| | - Jackie A. Mosely
- Department of Chemistry, Durham University, South Road, Durham DH1 3LE, U.K
| | - Michael Stevens
- College of Life Sciences, University of Dundee, Dow Street, Dundee DD1 5EH, U.K
| | - David G. Norman
- College of Life Sciences, University of Dundee, Dow Street, Dundee DD1 5EH, U.K
| | - Robert I. Hunter
- SUPA, School of Physics and Astronomy, University of St Andrews, St Andrews KY16 9SS, U.K
| | - Hassane El Mkami
- SUPA, School of Physics and Astronomy, University of St Andrews, St Andrews KY16 9SS, U.K
| | - Graham M. Smith
- SUPA, School of Physics and Astronomy, University of St Andrews, St Andrews KY16 9SS, U.K
| | - David Parker
- Department of Chemistry, Durham University, South Road, Durham DH1 3LE, U.K
| | - Janet E. Lovett
- SUPA, School of Physics and Astronomy, University of St Andrews, St Andrews KY16 9SS, U.K
- BSRC, University of St Andrews, St Andrews KY16 9ST, U.K
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20
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Bordignon E, Kucher S, Polyhach Y. EPR Techniques to Probe Insertion and Conformation of Spin-Labeled Proteins in Lipid Bilayers. Methods Mol Biol 2019; 2003:493-528. [PMID: 31218631 DOI: 10.1007/978-1-4939-9512-7_21] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Electron paramagnetic resonance (EPR) spectroscopy of spin-labeled membrane proteins is a valuable biophysical technique to study structural details and conformational transitions of proteins close to their physiological environment, for example, in liposomes, membrane bilayers, and nanodiscs. Unlike in nuclear magnetic resonance (NMR) spectroscopy, having only one or few specific side chains labeled at a time with paramagnetic probes makes the size of the object under investigation irrelevant in terms of technique sensitivity. As a drawback, extensive site-directed mutagenesis is required in order to analyze the properties of the protein under investigation. EPR can provide detailed information on side chain dynamics of large membrane proteins or protein complexes embedded in membranes with an exquisite sensitivity for flexible regions and on water accessibility profiles across the membrane bilayer. Moreover, distances between the two spin-labeled side chains in membrane proteins can be detected with high precision at cryogenic temperatures. The application of EPR to membrane proteins still presents some challenges in terms of sample preparation, sensitivity and data interpretation, thus it is difficult to give ready-to-go methodological recipes. However, new technological developments (arbitrary waveform generators) and new spin labels spectroscopically orthogonal to nitroxides increased the range of applicability from in vitro toward in-cell EPR experiments. This chapter is an updated version of the one published in the first edition of the book and describes the state of the art in the application of nitroxide-based site-directed spin labeling EPR to membrane proteins, addressing new tools such as arbitrary waveform generators and spectroscopically orthogonal labels, such as Gd(III)-based labels. We will present challenges in sample preparation and data analysis for functional and structural membrane protein studies using site-directed spin labeling techniques and give experimental details on EPR techniques providing information on side chain dynamics and water accessibility using nitroxide probes. An updated optimal Q-band DEER setup for nitroxide probes will be described, and its extension to gadolinium-containing samples will be addressed.
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Affiliation(s)
- Enrica Bordignon
- Faculty of Chemistry and Biochemistry, Ruhr University Bochum, Bochum, Germany.
| | - Svetlana Kucher
- Faculty of Chemistry and Biochemistry, Ruhr University Bochum, Bochum, Germany
| | - Yevhen Polyhach
- Laboratory of Physical Chemistry, ETH Zurich, Zurich, Switzerland
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21
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Ritsch I, Hintz H, Jeschke G, Godt A, Yulikov M. Improving the accuracy of Cu(ii)–nitroxide RIDME in the presence of orientation correlation in water-soluble Cu(ii)–nitroxide rulers. Phys Chem Chem Phys 2019; 21:9810-9830. [DOI: 10.1039/c8cp06573j] [Citation(s) in RCA: 30] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Detailed analysis of artefacts in the Cu(ii)–nitroxide RIDME experiments, related to orientation averaging, echo-crossing, ESEEM and background-correction is presented.
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Affiliation(s)
- Irina Ritsch
- Laboratory of Physical Chemistry
- Department of Chemistry and Applied Bioscience
- ETH Zurich
- 8093 Zurich
- Switzerland
| | - Henrik Hintz
- Faculty of Chemistry and Center for Molecular Materials (CM2)
- Bielefeld University
- 33615 Bielefeld
- Germany
| | - Gunnar Jeschke
- Laboratory of Physical Chemistry
- Department of Chemistry and Applied Bioscience
- ETH Zurich
- 8093 Zurich
- Switzerland
| | - Adelheid Godt
- Faculty of Chemistry and Center for Molecular Materials (CM2)
- Bielefeld University
- 33615 Bielefeld
- Germany
| | - Maxim Yulikov
- Laboratory of Physical Chemistry
- Department of Chemistry and Applied Bioscience
- ETH Zurich
- 8093 Zurich
- Switzerland
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22
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Prokopiou G, Lee MD, Collauto A, Abdelkader EH, Bahrenberg T, Feintuch A, Ramirez-Cohen M, Clayton J, Swarbrick JD, Graham B, Otting G, Goldfarb D. Small Gd(III) Tags for Gd(III)–Gd(III) Distance Measurements in Proteins by EPR Spectroscopy. Inorg Chem 2018; 57:5048-5059. [DOI: 10.1021/acs.inorgchem.8b00133] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Georgia Prokopiou
- Department of Chemical Physics, Weizmann Institute of Science, Rehovot 76100, Israel
| | - Michael D. Lee
- Monash Institute of Pharmaceutical Sciences, Monash University, Parkville, VIC 3052, Australia
| | - Alberto Collauto
- Department of Chemical Physics, Weizmann Institute of Science, Rehovot 76100, Israel
| | - Elwy H. Abdelkader
- Research School of Chemistry, Australian National University, Canberra, ACT 2601,Australia
| | - Thorsten Bahrenberg
- Department of Chemical Physics, Weizmann Institute of Science, Rehovot 76100, Israel
| | - Akiva Feintuch
- Department of Chemical Physics, Weizmann Institute of Science, Rehovot 76100, Israel
| | - Marie Ramirez-Cohen
- Department of Chemical Physics, Weizmann Institute of Science, Rehovot 76100, Israel
| | - Jessica Clayton
- Department of Physics, University of California, Santa Barbara, California 93106-9530, United States
| | - James D. Swarbrick
- Monash Institute of Pharmaceutical Sciences, Monash University, Parkville, VIC 3052, Australia
| | - Bim Graham
- Monash Institute of Pharmaceutical Sciences, Monash University, Parkville, VIC 3052, Australia
| | - Gottfried Otting
- Research School of Chemistry, Australian National University, Canberra, ACT 2601,Australia
| | - Daniella Goldfarb
- Department of Chemical Physics, Weizmann Institute of Science, Rehovot 76100, Israel
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23
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New limits of sensitivity of site-directed spin labeling electron paramagnetic resonance for membrane proteins. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2018; 1860:841-853. [DOI: 10.1016/j.bbamem.2017.12.009] [Citation(s) in RCA: 26] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/12/2017] [Revised: 11/27/2017] [Accepted: 12/09/2017] [Indexed: 01/27/2023]
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24
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Mahawaththa MC, Lee MD, Giannoulis A, Adams LA, Feintuch A, Swarbrick JD, Graham B, Nitsche C, Goldfarb D, Otting G. Small neutral Gd(iii) tags for distance measurements in proteins by double electron–electron resonance experiments. Phys Chem Chem Phys 2018; 20:23535-23545. [DOI: 10.1039/c8cp03532f] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Small Gd(iii) tags based on DO3A deliver narrow and readily predictable distances by double electron–electron resonance (DEER) measurements.
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Affiliation(s)
| | - Michael D. Lee
- Monash Institute of Pharmaceutical Sciences
- Monash University
- Parkville
- Australia
| | - Angeliki Giannoulis
- Department of Chemical Physics
- Weizmann Institute of Science
- Rehovot 76100
- Israel
| | - Luke A. Adams
- Monash Institute of Pharmaceutical Sciences
- Monash University
- Parkville
- Australia
| | - Akiva Feintuch
- Department of Chemical Physics
- Weizmann Institute of Science
- Rehovot 76100
- Israel
| | - James D. Swarbrick
- Monash Institute of Pharmaceutical Sciences
- Monash University
- Parkville
- Australia
| | - Bim Graham
- Monash Institute of Pharmaceutical Sciences
- Monash University
- Parkville
- Australia
| | - Christoph Nitsche
- Research School of Chemistry
- The Australian National University
- Canberra
- Australia
| | - Daniella Goldfarb
- Department of Chemical Physics
- Weizmann Institute of Science
- Rehovot 76100
- Israel
| | - Gottfried Otting
- Research School of Chemistry
- The Australian National University
- Canberra
- Australia
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25
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Wu Z, Feintuch A, Collauto A, Adams LA, Aurelio L, Graham B, Otting G, Goldfarb D. Selective Distance Measurements Using Triple Spin Labeling with Gd 3+, Mn 2+, and a Nitroxide. J Phys Chem Lett 2017; 8:5277-5282. [PMID: 28990781 DOI: 10.1021/acs.jpclett.7b01739] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Distance measurements by pulse electron paramagnetic resonance techniques, such as double electron-electron resonance (DEER, also called PELDOR), have become an established tool to explore structural properties of biomacromolecules and their assemblies. In such measurements a pair of spin labels provides a single distance constraint. Here we show that by employing three different types of spin labels that differ in their spectroscopic and spin dynamics properties it is possible to extract three independent distances from a single sample. We demonstrate this using the Antennapedia homeodomain orthogonally labeled with Gd3+ and Mn2+ tags in complex with its cognate DNA binding site labeled with a nitroxide.
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Affiliation(s)
- Zuyan Wu
- Research School of Chemistry, Australian National University , Canberra ACT 2601, Australia
| | - Akiva Feintuch
- Department of Chemical Physics, Weizmann Institute of Science , Rehovot 76100, Israel
| | - Alberto Collauto
- Department of Chemical Physics, Weizmann Institute of Science , Rehovot 76100, Israel
| | - Luke A Adams
- Monash Institute of Pharmaceutical Sciences, Monash University , Parkville VIC 3052, Australia
| | - Luigi Aurelio
- Monash Institute of Pharmaceutical Sciences, Monash University , Parkville VIC 3052, Australia
| | - Bim Graham
- Monash Institute of Pharmaceutical Sciences, Monash University , Parkville VIC 3052, Australia
| | - Gottfried Otting
- Research School of Chemistry, Australian National University , Canberra ACT 2601, Australia
| | - Daniella Goldfarb
- Department of Chemical Physics, Weizmann Institute of Science , Rehovot 76100, Israel
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26
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Gmeiner C, Klose D, Mileo E, Belle V, Marque SRA, Dorn G, Allain FHT, Guigliarelli B, Jeschke G, Yulikov M. Orthogonal Tyrosine and Cysteine Site-Directed Spin Labeling for Dipolar Pulse EPR Spectroscopy on Proteins. J Phys Chem Lett 2017; 8:4852-4857. [PMID: 28933855 DOI: 10.1021/acs.jpclett.7b02220] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Site-directed spin labeling of native tyrosine residues in isolated domains of the protein PTBP1, using a Mannich-type reaction, was combined with conventional spin labeling of cysteine residues. Double electron-electron resonance (DEER) EPR measurements were performed for both the nitroxide-nitroxide and Gd(III)-nitroxide label combinations within the same protein molecule. For the prediction of distance distributions from a structure model, rotamer libraries were generated for the two linker forms of the tyrosine-reactive isoindoline-based nitroxide radical Nox. Only moderate differences exist between the spatial spin distributions for the two linker forms of Nox. This strongly simplifies DEER data analysis, in particular, if only mean distances need to be predicted.
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Affiliation(s)
- Christoph Gmeiner
- Laboratory of Physical Chemistry, ETH Zurich , Zurich 8093, Switzerland
| | - Daniel Klose
- Laboratory of Physical Chemistry, ETH Zurich , Zurich 8093, Switzerland
| | - Elisabetta Mileo
- Aix Marseille Univ , CNRS, BIP, Laboratoire de Bioénergétique et Ingénierie des Protéines, Marseille 13402, France
| | - Valérie Belle
- Aix Marseille Univ , CNRS, BIP, Laboratoire de Bioénergétique et Ingénierie des Protéines, Marseille 13402, France
| | - Sylvain R A Marque
- Aix Marseille Univ , CNRS, ICR, Institut de Chimie Radicalaire, Marseille 13397, France
- N. N. Vorozhtsov Novosibirsk Insititute of Organic Chemistry , 630090 Novosibirsk, Russia
| | - Georg Dorn
- Institute of Molecular Biology and Biophysics, ETH Zurich , Zurich 8093, Switzerland
| | - Frédéric H T Allain
- Institute of Molecular Biology and Biophysics, ETH Zurich , Zurich 8093, Switzerland
| | - Bruno Guigliarelli
- Aix Marseille Univ , CNRS, BIP, Laboratoire de Bioénergétique et Ingénierie des Protéines, Marseille 13402, France
| | - Gunnar Jeschke
- Laboratory of Physical Chemistry, ETH Zurich , Zurich 8093, Switzerland
| | - Maxim Yulikov
- Laboratory of Physical Chemistry, ETH Zurich , Zurich 8093, Switzerland
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27
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Manukovsky N, Feintuch A, Kuprov I, Goldfarb D. Time domain simulation of Gd3+–Gd3+ distance measurements by EPR. J Chem Phys 2017; 147:044201. [DOI: 10.1063/1.4994084] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Affiliation(s)
- Nurit Manukovsky
- Department of Chemical Physics, Weizmann Institute of Science, Rehovot 7610001, Israel
| | - Akiva Feintuch
- Department of Chemical Physics, Weizmann Institute of Science, Rehovot 7610001, Israel
| | - Ilya Kuprov
- School of Chemistry, University of Southampton, Southampton SO17 1BJ, United Kingdom
| | - Daniella Goldfarb
- Department of Chemical Physics, Weizmann Institute of Science, Rehovot 7610001, Israel
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28
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Joseph B, Tormyshev VM, Rogozhnikova OY, Akhmetzyanov D, Bagryanskaya EG, Prisner TF. Selective High-Resolution Detection of Membrane Protein-Ligand Interaction in Native Membranes Using Trityl-Nitroxide PELDOR. Angew Chem Int Ed Engl 2016; 55:11538-42. [DOI: 10.1002/anie.201606335] [Citation(s) in RCA: 69] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2016] [Indexed: 12/31/2022]
Affiliation(s)
- Benesh Joseph
- Institut für physikalische und theoretische Chemie und Biomolekulares Magnetresonanz Zentrum; Universität Frankfurt; Max-von-Laue-Strasse 7 60438 Frankfurt am Main Germany
| | - Victor M. Tormyshev
- N. N. Vorozhtsov Novosibirsk Institute of Organic Chemistry SB RAS; Novosibirsk 630090 Russia
- Novosibirsk State University; Novosibirsk 630090 Russia
| | - Olga Yu. Rogozhnikova
- N. N. Vorozhtsov Novosibirsk Institute of Organic Chemistry SB RAS; Novosibirsk 630090 Russia
| | - Dmitry Akhmetzyanov
- Institut für physikalische und theoretische Chemie und Biomolekulares Magnetresonanz Zentrum; Universität Frankfurt; Max-von-Laue-Strasse 7 60438 Frankfurt am Main Germany
| | - Elena G. Bagryanskaya
- N. N. Vorozhtsov Novosibirsk Institute of Organic Chemistry SB RAS; Novosibirsk 630090 Russia
| | - Thomas F. Prisner
- Institut für physikalische und theoretische Chemie und Biomolekulares Magnetresonanz Zentrum; Universität Frankfurt; Max-von-Laue-Strasse 7 60438 Frankfurt am Main Germany
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29
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Joseph B, Tormyshev VM, Rogozhnikova OY, Akhmetzyanov D, Bagryanskaya EG, Prisner TF. Selective High-Resolution Detection of Membrane Protein-Ligand Interaction in Native Membranes Using Trityl-Nitroxide PELDOR. Angew Chem Int Ed Engl 2016. [DOI: 10.1002/ange.201606335] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- Benesh Joseph
- Institut für physikalische und theoretische Chemie und Biomolekulares Magnetresonanz Zentrum; Universität Frankfurt; Max-von-Laue-Strasse 7 60438 Frankfurt am Main Germany
| | - Victor M. Tormyshev
- N. N. Vorozhtsov Novosibirsk Institute of Organic Chemistry SB RAS; Novosibirsk 630090 Russia
- Novosibirsk State University; Novosibirsk 630090 Russia
| | - Olga Yu. Rogozhnikova
- N. N. Vorozhtsov Novosibirsk Institute of Organic Chemistry SB RAS; Novosibirsk 630090 Russia
| | - Dmitry Akhmetzyanov
- Institut für physikalische und theoretische Chemie und Biomolekulares Magnetresonanz Zentrum; Universität Frankfurt; Max-von-Laue-Strasse 7 60438 Frankfurt am Main Germany
| | - Elena G. Bagryanskaya
- N. N. Vorozhtsov Novosibirsk Institute of Organic Chemistry SB RAS; Novosibirsk 630090 Russia
| | - Thomas F. Prisner
- Institut für physikalische und theoretische Chemie und Biomolekulares Magnetresonanz Zentrum; Universität Frankfurt; Max-von-Laue-Strasse 7 60438 Frankfurt am Main Germany
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30
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Evans EGB, Pushie MJ, Markham KA, Lee HW, Millhauser GL. Interaction between Prion Protein's Copper-Bound Octarepeat Domain and a Charged C-Terminal Pocket Suggests a Mechanism for N-Terminal Regulation. Structure 2016; 24:1057-67. [PMID: 27265848 DOI: 10.1016/j.str.2016.04.017] [Citation(s) in RCA: 57] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2016] [Revised: 04/19/2016] [Accepted: 04/20/2016] [Indexed: 11/29/2022]
Abstract
Copper plays a critical role in prion protein (PrP) physiology. Cu(2+) binds with high affinity to the PrP N-terminal octarepeat (OR) domain, and intracellular copper promotes PrP expression. The molecular details of copper coordination within the OR are now well characterized. Here we examine how Cu(2+) influences the interaction between the PrP N-terminal domain and the C-terminal globular domain. Using nuclear magnetic resonance and copper-nitroxide pulsed double electron-electron resonance, with molecular dynamics refinement, we localize the position of Cu(2+) in its high-affinity OR-bound state. Our results reveal an interdomain cis interaction that is stabilized by a conserved, negatively charged pocket of the globular domain. Interestingly, this interaction surface overlaps an epitope recognized by the POM1 antibody, the binding of which drives rapid cerebellar degeneration mediated by the PrP N terminus. The resulting structure suggests that the globular domain regulates the N-terminal domain by binding the Cu(2+)-occupied OR within a complementary pocket.
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Affiliation(s)
- Eric G B Evans
- Department of Chemistry and Biochemistry, University of California, Santa Cruz, Santa Cruz, CA 95064, USA
| | - M Jake Pushie
- Department of Geological Sciences, University of Saskatchewan, Saskatoon, SK S7N 5E2, Canada
| | - Kate A Markham
- Department of Chemistry and Biochemistry, University of California, Santa Cruz, Santa Cruz, CA 95064, USA
| | - Hsiau-Wei Lee
- Department of Chemistry and Biochemistry, University of California, Santa Cruz, Santa Cruz, CA 95064, USA
| | - Glenn L Millhauser
- Department of Chemistry and Biochemistry, University of California, Santa Cruz, Santa Cruz, CA 95064, USA.
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31
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Collauto A, Feintuch A, Qi M, Godt A, Meade T, Goldfarb D. Gd(III) complexes as paramagnetic tags: Evaluation of the spin delocalization over the nuclei of the ligand. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2016; 263:156-163. [PMID: 26802219 DOI: 10.1016/j.jmr.2015.12.025] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/13/2015] [Revised: 12/28/2015] [Accepted: 12/30/2015] [Indexed: 05/15/2023]
Abstract
Complexes of the Gd(III) ion are currently being established as spin labels for distance determination in biomolecules by pulse dipolar spectroscopy. Because Gd(III) is an f ion, one expects electron spin density to be localized on the Gd(III) ion - an important feature for the mentioned application. Most of the complex ligands have nitrogens as Gd(III) coordinating atoms. Therefore, measurement of the (14)N hyperfine coupling gives access to information on the localization of the electron spin on the Gd(III) ion. We carried out W-band, 1D and 2D (14)N and (1)H ENDOR measurements on the Gd(III) complexes Gd-DOTA, Gd-538, Gd-595, and Gd-PyMTA that serve as spin labels for Gd-Gd distance measurements. The obtained (14)N spectra are particularly well resolved, revealing both the hyperfine and nuclear quadrupole splittings, which were assigned using 2D Mims ENDOR experiments. Additionally, the spectral contributions of the two different types of nitrogen atoms of Gd-PyMTA, the aliphatic N atom and the pyridine N atom, were distinguishable. The (14)N hyperfine interaction was found to have a very small isotropic hyperfine component of -0.25 to -0.37MHz. Furthermore, the anisotropic hyperfine interactions with the (14)N nuclei and with the non-exchangeable protons of the ligands are well described by the point-dipole approximation using distances derived from the crystal structures. We therefore conclude that the spin density is fully localized on the Gd(III) ion and that the spin density distribution over the nuclei of the ligands is rightfully ignored when analyzing distance measurements.
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Affiliation(s)
- A Collauto
- Department of Chemical Physics, Weizmann Institute of Science, Rehovot 76100, Israel
| | - A Feintuch
- Department of Chemical Physics, Weizmann Institute of Science, Rehovot 76100, Israel
| | - M Qi
- University Bielefeld, Faculty of Chemistry and Center for Molecular Materials, D-33615 Bielefeld, Germany
| | - A Godt
- University Bielefeld, Faculty of Chemistry and Center for Molecular Materials, D-33615 Bielefeld, Germany
| | - T Meade
- Department of Chemistry, Northwestern University, Evanston, IL 60208, USA
| | - D Goldfarb
- Department of Chemical Physics, Weizmann Institute of Science, Rehovot 76100, Israel.
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32
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Collauto A, Frydman V, Lee MD, Abdelkader EH, Feintuch A, Swarbrick JD, Graham B, Otting G, Goldfarb D. RIDME distance measurements using Gd(iii) tags with a narrow central transition. Phys Chem Chem Phys 2016; 18:19037-49. [DOI: 10.1039/c6cp03299k] [Citation(s) in RCA: 35] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Methods based on pulse electron paramagnetic resonance allow measurement of the electron–electron dipolar coupling between two high-spin labels.
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Affiliation(s)
- A. Collauto
- Department of Chemical Physics
- Weizmann Institute of Science
- Rehovot 7610001
- Israel
| | - V. Frydman
- Department of Chemical Research Support
- Weizmann Institute of Science
- Rehovot 7610001
- Israel
| | - M. D. Lee
- Monash Institute of Pharmaceutical Sciences
- Monash University
- Parkville
- Australia
| | - E. H. Abdelkader
- Research School of Chemistry
- Australian National University
- Canberra
- Australia
| | - A. Feintuch
- Department of Chemical Physics
- Weizmann Institute of Science
- Rehovot 7610001
- Israel
| | - J. D. Swarbrick
- Monash Institute of Pharmaceutical Sciences
- Monash University
- Parkville
- Australia
| | - B. Graham
- Monash Institute of Pharmaceutical Sciences
- Monash University
- Parkville
- Australia
| | - G. Otting
- Research School of Chemistry
- Australian National University
- Canberra
- Australia
| | - D. Goldfarb
- Department of Chemical Physics
- Weizmann Institute of Science
- Rehovot 7610001
- Israel
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33
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Abdelkader EH, Lee MD, Feintuch A, Cohen MR, Swarbrick JD, Otting G, Graham B, Goldfarb D. A New Gd(3+) Spin Label for Gd(3+)-Gd(3+) Distance Measurements in Proteins Produces Narrow Distance Distributions. J Phys Chem Lett 2015; 6:5016-5021. [PMID: 26623480 DOI: 10.1021/acs.jpclett.5b02451] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
Gd(3+) tags have been shown to be useful for performing distance measurements in biomolecules via the double electron-electron resonance (DEER) technique at Q- and W-band frequencies. We introduce a new cyclen-based Gd(3+) tag that exhibits a relatively narrow electron paramagnetic resonance (EPR) spectrum, affording high sensitivity, and which yields exceptionally narrow Gd(3+)-Gd(3+) distance distributions in doubly tagged proteins owing to a very short tether. Both the maxima and widths of distance distributions measured for tagged mutants of the proteins ERp29 and T4 lysozyme, featuring Gd(3+)-Gd(3+) distances of ca. 6 and 4 nm, respectively, were well reproduced by simulated distance distributions based on available crystal structures and sterically allowed rotamers of the tag. The precision of the position of the Gd(3+) ion is comparable to that of the nitroxide radical in an MTSL-tagged protein and thus the new tag represents an attractive tool for performing accurate distance measurements and potentially probing protein conformational equilibria.
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Affiliation(s)
- Elwy H Abdelkader
- Research School of Chemistry, Australian National University , Canberra, ACT 2601, Australia
| | - Michael D Lee
- Monash Institute of Pharmaceutical Sciences, Monash University , Parkville VIC 3052, Australia
| | - Akiva Feintuch
- Department of Chemical Physics, Weizmann Institute of Science , Rehovot 76100, Israel
| | - Marie Ramirez Cohen
- Department of Chemical Physics, Weizmann Institute of Science , Rehovot 76100, Israel
| | - James D Swarbrick
- Monash Institute of Pharmaceutical Sciences, Monash University , Parkville VIC 3052, Australia
| | - Gottfried Otting
- Research School of Chemistry, Australian National University , Canberra, ACT 2601, Australia
| | - Bim Graham
- Monash Institute of Pharmaceutical Sciences, Monash University , Parkville VIC 3052, Australia
| | - Daniella Goldfarb
- Department of Chemical Physics, Weizmann Institute of Science , Rehovot 76100, Israel
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34
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Doll A, Qi M, Wili N, Pribitzer S, Godt A, Jeschke G. Gd(III)-Gd(III) distance measurements with chirp pump pulses. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2015; 259:153-62. [PMID: 26340436 DOI: 10.1016/j.jmr.2015.08.010] [Citation(s) in RCA: 45] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/01/2015] [Revised: 08/13/2015] [Accepted: 08/14/2015] [Indexed: 05/15/2023]
Abstract
The broad EPR spectrum of Gd(III) spin labels restricts the dipolar modulation depth in distance measurements between Gd(III) pairs to a few percent. To overcome this limitation, frequency-swept chirp pulses are utilized as pump pulses in the DEER experiment. Using a model system with 3.4 nm Gd-Gd distance, application of one single chirp pump pulse at Q-band frequencies leads to modulation depths beyond 10%. However, the larger modulation depth is counteracted by a reduction of the absolute echo intensity due to the pump pulse. As supported by spin dynamics simulations, this effect is primarily driven by signal loss to double-quantum coherence and specific to the Gd(III) high spin state of S=7/2. In order to balance modulation depth and echo intensity for optimum sensitivity, a simple experimental procedure is proposed. An additional improvement by 25% in DEER sensitivity is achieved with two consecutive chirp pump pulses. These pulses pump the Gd(III) spectrum symmetrically around the observation position, therefore mutually compensating for dynamical Bloch-Siegert phase shifts at the observer spins. The improved sensitivity of the DEER data with modulation depths on the order of 20% is due to mitigation of the echo reduction effects by the consecutive pump pulses. In particular, the second pump pulse does not lead to additional signal loss if perfect inversion is assumed. Moreover, the compensation of the dynamical Bloch-Siegert phase prevents signal loss due to spatial dependence of the dynamical phase, which is caused by inhomogeneities in the driving field. The new methodology is combined with pre-polarization techniques to measure long distances up to 8.6 nm, where signal intensity and modulation depth become attenuated by long dipolar evolution windows. In addition, the influence of the zero-field splitting parameters on the echo intensity is studied with simulations. Herein, larger sensitivity is anticipated for Gd(III) complexes with zero-field splitting that is smaller than for the employed Gd-PyMTA complex.
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Affiliation(s)
- Andrin Doll
- Laboratory of Physical Chemistry, ETH Zurich, Vladimir-Prelog-Weg 2, CH-8093 Zurich, Switzerland
| | - Mian Qi
- Faculty of Chemistry and Center for Molecular Materials, Bielefeld University, Unversitätsstraße 25, 33615 Bielefeld, Germany
| | - Nino Wili
- Laboratory of Physical Chemistry, ETH Zurich, Vladimir-Prelog-Weg 2, CH-8093 Zurich, Switzerland
| | - Stephan Pribitzer
- Laboratory of Physical Chemistry, ETH Zurich, Vladimir-Prelog-Weg 2, CH-8093 Zurich, Switzerland
| | - Adelheid Godt
- Faculty of Chemistry and Center for Molecular Materials, Bielefeld University, Unversitätsstraße 25, 33615 Bielefeld, Germany
| | - Gunnar Jeschke
- Laboratory of Physical Chemistry, ETH Zurich, Vladimir-Prelog-Weg 2, CH-8093 Zurich, Switzerland.
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35
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Garbuio L, Zimmermann K, Häussinger D, Yulikov M. Gd(III) complexes for electron-electron dipolar spectroscopy: Effects of deuteration, pH and zero field splitting. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2015; 259:163-73. [PMID: 26342680 DOI: 10.1016/j.jmr.2015.08.009] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/26/2015] [Revised: 08/06/2015] [Accepted: 08/07/2015] [Indexed: 05/15/2023]
Abstract
Spectral parameters of Gd(III) complexes are intimately linked to the performance of the Gd(III)-nitroxide or Gd(III)-Gd(III) double electron-electron resonance (DEER or PELDOR) techniques, as well as to that of relaxation induced dipolar modulation enhancement (RIDME) spectroscopy with Gd(III) ions. These techniques are of interest for applications in structural biology, since they can selectively detect site-to-site distances in biomolecules or biomolecular complexes in the nanometer range. Here we report relaxation properties, echo detected EPR spectra, as well as the magnitude of the echo reduction effect in Gd(III)-nitroxide DEER for a series of Gadolinium(III) complexes with chelating agents derived from tetraazacyclododecane. We observed that solvent deuteration does not only lengthen the relaxation times of Gd(III) centers but also weakens the DEER echo reduction effect. Both of these phenomena lead to an improved signal-to-noise ratios or, alternatively, longer accessible distance range in pulse EPR measurements. The presented data enrich the knowledge on paramagnetic Gd(III) chelate complexes in frozen solutions, and can help optimize the experimental conditions for most types of the pulse measurements of the electron-electron dipolar interactions.
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Affiliation(s)
- Luca Garbuio
- Laboratory of Physical Chemistry, ETH Zurich, Zurich, Switzerland
| | | | | | - Maxim Yulikov
- Laboratory of Physical Chemistry, ETH Zurich, Zurich, Switzerland.
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36
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Evans EGB, Millhauser GL. Genetic Incorporation of the Unnatural Amino Acid p-Acetyl Phenylalanine into Proteins for Site-Directed Spin Labeling. Methods Enzymol 2015; 563:503-27. [PMID: 26478497 PMCID: PMC4841275 DOI: 10.1016/bs.mie.2015.06.008] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
Site-directed spin labeling (SDSL) is a powerful tool for the characterization of protein structure and dynamics; however, its application in many systems is hampered by the reliance on unique and benign cysteine substitutions for the site-specific attachment of the spin label. An elegant solution to this problem involves the use of genetically encoded unnatural amino acids (UAAs) containing reactive functional groups that are chemically orthogonal to those of the 20 amino acids found naturally in proteins. These unique functional groups can then be selectively reacted with an appropriately functionalized spin probe. In this chapter, we detail the genetic incorporation of the ketone-bearing amino acid p-acetyl phenylalanine (pAcPhe) into recombinant proteins expressed in E. coli. Incorporation of pAcPhe is followed by chemoselective reaction of the ketone side chain with a hydroxylamine-functionalized nitroxide to afford the spin-labeled side chain "K1," and we present two protocols for successful K1 labeling of proteins bearing site-specific pAcPhe. We outline the basic requirements for pAcPhe incorporation and labeling, with an emphasis on practical aspects that must be considered by the researcher if high yields of UAA incorporation and efficient labeling reactions are to be achieved. To this end, we highlight recent advances that have led to increased yields of pAcPhe incorporation, and discuss the use of aniline-based catalysts allowing for facile conjugation of the hydroxylamine spin label under mild reaction conditions. To illustrate the utility of K1 labeling in proteins where traditional cysteine-based SDSL methods are problematic, we site-specifically K1 label the cellular prion protein at two positions in the C-terminal domain and determine the interspin distance using double electron-electron resonance EPR. Recent advances in UAA incorporation and ketone-based bioconjugation, in combination with the commercial availability of all requisite reagents, should make K1 labeling an increasingly viable alternative to cysteine-based methods for SDSL in proteins.
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Affiliation(s)
- Eric G B Evans
- Department of Chemistry and Biochemistry, University of California Santa Cruz, Santa Cruz, California, USA
| | - Glenn L Millhauser
- Department of Chemistry and Biochemistry, University of California Santa Cruz, Santa Cruz, California, USA.
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37
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Campbell JP, Ryan JT, Shrestha PR, Liu Z, Vaz C, Kim JH, Georgiou V, Cheung KP. Electron Spin Resonance Scanning Probe Spectroscopy for Ultrasensitive Biochemical Studies. Anal Chem 2015; 87:4910-6. [DOI: 10.1021/acs.analchem.5b00487] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Affiliation(s)
- Jason P. Campbell
- National Institute of Standards and Technology, 100 Bureau Drive, MS 8120, Gaithersburg, Maryland 20899, United States
| | - Jason T. Ryan
- National Institute of Standards and Technology, 100 Bureau Drive, MS 8120, Gaithersburg, Maryland 20899, United States
| | - Pragya R. Shrestha
- National Institute of Standards and Technology, 100 Bureau Drive, MS 8120, Gaithersburg, Maryland 20899, United States
| | - Zhanglong Liu
- National Institute of Standards and Technology, 100 Bureau Drive, MS 8120, Gaithersburg, Maryland 20899, United States
| | - Canute Vaz
- National Institute of Standards and Technology, 100 Bureau Drive, MS 8120, Gaithersburg, Maryland 20899, United States
| | - Ji-Hong Kim
- National Institute of Standards and Technology, 100 Bureau Drive, MS 8120, Gaithersburg, Maryland 20899, United States
| | - Vasileia Georgiou
- National Institute of Standards and Technology, 100 Bureau Drive, MS 8120, Gaithersburg, Maryland 20899, United States
- Department
of Electrical and Computer Engineering, George Mason University, 4400 University Drive, Fairfax, Virginia 22030, United States
| | - Kin P. Cheung
- National Institute of Standards and Technology, 100 Bureau Drive, MS 8120, Gaithersburg, Maryland 20899, United States
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38
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Vincent Ching HY, Demay-Drouhard P, Bertrand HC, Policar C, Tabares LC, Un S. Nanometric distance measurements between Mn(ii)DOTA centers. Phys Chem Chem Phys 2015; 17:23368-77. [DOI: 10.1039/c5cp03487f] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
The distance between two Mn(ii)DOTA complexes attached to the ends of polyproline helices of varying lengths was measured by 94 GHz PELDOR spectroscopy with good accuracy demonstrating their effectiveness as spin-labels.
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Affiliation(s)
- H. Y. Vincent Ching
- Institute for Integrative Biology of the Cell (I2BC)
- Department of Biochemistry
- Biophysics and Structural Biology
- Université Paris-Saclay
- CEA
| | - Paul Demay-Drouhard
- Ecole Normale Supérieure-PSL Research University
- Départment de Chimie
- Sorbonne Universités – UPMC Univ Paris 06
- CNRS UMR 7203 LBM
- F-75005 Paris
| | - Hélène C. Bertrand
- Ecole Normale Supérieure-PSL Research University
- Départment de Chimie
- Sorbonne Universités – UPMC Univ Paris 06
- CNRS UMR 7203 LBM
- F-75005 Paris
| | - Clotilde Policar
- Ecole Normale Supérieure-PSL Research University
- Départment de Chimie
- Sorbonne Universités – UPMC Univ Paris 06
- CNRS UMR 7203 LBM
- F-75005 Paris
| | - Leandro C. Tabares
- Institute for Integrative Biology of the Cell (I2BC)
- Department of Biochemistry
- Biophysics and Structural Biology
- Université Paris-Saclay
- CEA
| | - Sun Un
- Institute for Integrative Biology of the Cell (I2BC)
- Department of Biochemistry
- Biophysics and Structural Biology
- Université Paris-Saclay
- CEA
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39
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40
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Dalaloyan A, Qi M, Ruthstein S, Vega S, Godt A, Feintuch A, Goldfarb D. Gd(iii)–Gd(iii) EPR distance measurements – the range of accessible distances and the impact of zero field splitting. Phys Chem Chem Phys 2015; 17:18464-76. [DOI: 10.1039/c5cp02602d] [Citation(s) in RCA: 60] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Gd rulers were designed in the 2–8 nm range for in-depth evaluation of Gd(iii) complexes as spin labels for EPR distance measurements.
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Affiliation(s)
- Arina Dalaloyan
- Department of Chemical Physics
- Weizmann Institute of Science
- Rehovot
- Israel
| | - Mian Qi
- Bielefeld University
- Faculty of Chemistry and Center for Molecular Materials
- D-33615 Bielefeld
- Germany
| | - Sharon Ruthstein
- Department of Chemistry
- Faculty of Exact Sciences
- Bar-Ilan University
- Ramat Gan
- Israel
| | - Shimon Vega
- Department of Chemical Physics
- Weizmann Institute of Science
- Rehovot
- Israel
| | - Adelheid Godt
- Bielefeld University
- Faculty of Chemistry and Center for Molecular Materials
- D-33615 Bielefeld
- Germany
| | - Akiva Feintuch
- Department of Chemical Physics
- Weizmann Institute of Science
- Rehovot
- Israel
| | - Daniella Goldfarb
- Department of Chemical Physics
- Weizmann Institute of Science
- Rehovot
- Israel
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41
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Feintuch A, Otting G, Goldfarb D. Gd3+ Spin Labeling for Measuring Distances in Biomacromolecules. Methods Enzymol 2015; 563:415-57. [DOI: 10.1016/bs.mie.2015.07.006] [Citation(s) in RCA: 53] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
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42
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43
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Kaminker I, Bye M, Mendelman N, Gislason K, Sigurdsson ST, Goldfarb D. Distance measurements between manganese(ii) and nitroxide spin-labels by DEER determine a binding site of Mn2+ in the HP92 loop of ribosomal RNA. Phys Chem Chem Phys 2015; 17:15098-102. [DOI: 10.1039/c5cp01624j] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
Abstract
W-band (95 GHz) double electron–electron resonance (DEER) distance measurements between Mn2+ and nitroxide spin labels were used to determine the location of a Mn2+ binding site within an RNA molecule.
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Affiliation(s)
- Ilia Kaminker
- Department of Chemical Physics
- Weizmann Institute of Science
- Rehovot 76100
- Israel
| | - Morgan Bye
- Department of Chemical Physics
- Weizmann Institute of Science
- Rehovot 76100
- Israel
| | - Natanel Mendelman
- Department of Chemical Physics
- Weizmann Institute of Science
- Rehovot 76100
- Israel
| | - Kristmann Gislason
- Department of Chemical Physics
- Weizmann Institute of Science
- Rehovot 76100
- Israel
| | - Snorri Th. Sigurdsson
- University of Iceland
- Department of Chemistry
- Science Institute Dunhaga 3
- 107 Reykjavik
- Iceland
| | - Daniella Goldfarb
- University of Iceland
- Department of Chemistry
- Science Institute Dunhaga 3
- 107 Reykjavik
- Iceland
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44
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Razzaghi S, Qi M, Nalepa AI, Godt A, Jeschke G, Savitsky A, Yulikov M. RIDME Spectroscopy with Gd(III) Centers. J Phys Chem Lett 2014; 5:3970-5. [PMID: 26276479 DOI: 10.1021/jz502129t] [Citation(s) in RCA: 65] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/15/2023]
Abstract
The relaxation induced dipolar modulation enhancement (RIDME) technique is applied at W-band microwave frequencies around 94 GHz to a pair of Gd(III) complexes that are connected by a rodlike spacer, and the extraction of the interspin distance distribution is discussed. A dipolar pattern derived from RIDME experimental data is a superposition of Pake-like dipolar patterns corresponding to the fundamental dipolar interaction and higher harmonics thereof. Intriguingly, the relative weights of the stretched patterns do not depend significantly on mixing time. As much larger modulation depths can be achieved than in double electron-electron resonance distance measurements at the same frequency, Gd(III)-Gd(III) RIDME may become attractive for structural characterization of biomacromolecules and biomolecular complexes.
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Affiliation(s)
- Sahand Razzaghi
- †Laboratory of Physical Chemistry, Department of Chemistry and Applied Biosciences, ETH Zurich, Vladimir-Prelog-Weg 2, 8093 Zurich, Switzerland
| | - Mian Qi
- ‡Faculty of Chemistry and Center for Molecular Materials, Bielefeld University, Universitätsstraße 25, 33615 Bielefeld, Germany
| | - Anna I Nalepa
- §Max-Planck-Institut für Chemische Energiekonversion, Stiftstrasse 34-36, D-45470 Mülheim an der Ruhr, Germany
| | - Adelheid Godt
- ‡Faculty of Chemistry and Center for Molecular Materials, Bielefeld University, Universitätsstraße 25, 33615 Bielefeld, Germany
| | - Gunnar Jeschke
- †Laboratory of Physical Chemistry, Department of Chemistry and Applied Biosciences, ETH Zurich, Vladimir-Prelog-Weg 2, 8093 Zurich, Switzerland
| | - Anton Savitsky
- §Max-Planck-Institut für Chemische Energiekonversion, Stiftstrasse 34-36, D-45470 Mülheim an der Ruhr, Germany
| | - Maxim Yulikov
- †Laboratory of Physical Chemistry, Department of Chemistry and Applied Biosciences, ETH Zurich, Vladimir-Prelog-Weg 2, 8093 Zurich, Switzerland
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Raitsimring A, Dalaloyan A, Collauto A, Feintuch A, Meade T, Goldfarb D. Zero field splitting fluctuations induced phase relaxation of Gd3+ in frozen solutions at cryogenic temperatures. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2014; 248:71-80. [PMID: 25442776 PMCID: PMC4495766 DOI: 10.1016/j.jmr.2014.09.012] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/31/2014] [Revised: 09/14/2014] [Accepted: 09/16/2014] [Indexed: 05/18/2023]
Abstract
Distance measurements using double electron-electron resonance (DEER) and Gd(3+) chelates for spin labels (GdSL) have been shown to be an attractive alternative to nitroxide spin labels at W-band (95GHz). The maximal distance that can be accessed by DEER measurements and the sensitivity of such measurements strongly depends on the phase relaxation of Gd(3+) chelates in frozen, glassy solutions. In this work, we explore the phase relaxation of Gd(3+)-DOTA as a representative of GdSL in temperature and concentration ranges typically used for W-band DEER measurements. We observed that in addition to the usual mechanisms of phase relaxation known for nitroxide based spin labels, GdSL are subjected to an additional phase relaxation mechanism that features an increase in the relaxation rate from the center to the periphery of the EPR spectrum. Since the EPR spectrum of GdSL is the sum of subspectra of the individual EPR transitions, we attribute this field dependence to transition dependent phase relaxation. Using simulations of the EPR spectra and its decomposition into the individual transition subspectra, we isolated the phase relaxation of each transition and found that its rate increases with |ms|. We suggest that this mechanism is due to transient zero field splitting (tZFS), where its magnitude and correlation time are scaled down and distributed as compared with similar situations in liquids. This tZFS induced phase relaxation mechanism becomes dominant (or at least significant) when all other well-known phase relaxation mechanisms, such as spectral diffusion caused by nuclear spin diffusion, instantaneous and electron spin spectral diffusion, are significantly suppressed by matrix deuteration and low concentration, and when the temperature is sufficiently low to disable spin lattice interaction as a source of phase relaxation.
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Affiliation(s)
| | - A Dalaloyan
- Weizmann Institute of Science, Rehovot, Israel
| | - A Collauto
- Weizmann Institute of Science, Rehovot, Israel
| | - A Feintuch
- Weizmann Institute of Science, Rehovot, Israel
| | - T Meade
- Northwestern University, Evanston, IL 60208, USA
| | - D Goldfarb
- Weizmann Institute of Science, Rehovot, Israel.
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Edwards D, Huber T, Hussain S, Stone K, Kinnebrew M, Kaminker I, Matalon E, Sherwin M, Goldfarb D, Han S. Determining the Oligomeric Structure of Proteorhodopsin by Gd3+-Based Pulsed Dipolar Spectroscopy of Multiple Distances. Structure 2014; 22:1677-86. [DOI: 10.1016/j.str.2014.09.008] [Citation(s) in RCA: 63] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2014] [Revised: 08/15/2014] [Accepted: 09/04/2014] [Indexed: 12/30/2022]
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47
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New developments in spin labels for pulsed dipolar EPR. Molecules 2014; 19:16998-7025. [PMID: 25342554 PMCID: PMC6271499 DOI: 10.3390/molecules191016998] [Citation(s) in RCA: 55] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2014] [Revised: 10/07/2014] [Accepted: 10/13/2014] [Indexed: 11/17/2022] Open
Abstract
Spin labelling is a chemical technique that enables the integration of a molecule containing an unpaired electron into another framework for study. Given the need to understand the structure, dynamics, and conformational changes of biomacromolecules, spin labelling provides a relatively non-intrusive technique and has certain advantages over X-ray crystallography; which requires high quality crystals. The technique relies on the design of binding probes that target a functional group, for example, the thiol group of a cysteine residue within a protein. The unpaired electron is typically supplied through a nitroxide radical and sterically shielded to preserve stability. Pulsed electron paramagnetic resonance (EPR) techniques allow small magnetic couplings to be measured (e.g., <50 MHz) providing information on single label probes or the dipolar coupling between multiple labels. In particular, distances between spin labels pairs can be derived which has led to many protein/enzymes and nucleotides being studied. Here, we summarise recent examples of spin labels used for pulse EPR that serve to illustrate the contribution of chemistry to advancing discoveries in this field.
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Upadhyay A, Das C, Shanmugam M, Langley SK, Murray KS, Shanmugam M. Electronic and Magnetic Properties of a Gadolinium(III) Schiff Base Complex. Eur J Inorg Chem 2014. [DOI: 10.1002/ejic.201402219] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
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49
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Di Valentin M, Albertini M, Zurlo E, Gobbo M, Carbonera D. Porphyrin triplet state as a potential spin label for nanometer distance measurements by PELDOR spectroscopy. J Am Chem Soc 2014; 136:6582-5. [PMID: 24735449 DOI: 10.1021/ja502615n] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
This work demonstrates, for the first time, the feasibility of applying pulsed electron-electron double resonance (PELDOR/DEER) to determine the interspin distance between a photoexcited porphyrin triplet state (S = 1) and a nitroxide spin label chemically incorporated into a small helical peptide. The PELDOR trace shows deep envelope modulation induced by electron-electron dipole interaction between the partners in the pair, providing an accurate distance measurement. This new labeling approach has a high potential for measuring nanometer distances in more complex biological systems due to the sensitivity acquired from the spin polarization of the photoexcited triplet state spectrum.
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Affiliation(s)
- Marilena Di Valentin
- Dipartimento di Scienze Chimiche, Università di Padova , via Marzolo 1, 35131 Padova, Italy
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Ji M, Ruthstein S, Saxena S. Paramagnetic metal ions in pulsed ESR distance distribution measurements. Acc Chem Res 2014; 47:688-95. [PMID: 24289139 DOI: 10.1021/ar400245z] [Citation(s) in RCA: 56] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
The use of pulsed electron spin resonance (ESR) to measure interspin distance distributions has advanced biophysical research. The three major techniques that use pulsed ESR are relaxation rate based distance measurements, double quantum coherence (DQC), and double electron electron resonance (DEER). Among these methods, the DEER technique has become particularly popular largely because it is easy to implement on commercial instruments and because programs are available to analyze experimental data. Researchers have widely used DEER to measure the structure and conformational dynamics of molecules labeled with the methanethiosulfonate spin label (MTSSL). Recently, researchers have exploited endogenously bound paramagnetic metal ions as spin probes as a way to determine structural constraints in metalloproteins. In this context Cu(2+) has served as a useful paramagnetic metal probe at X-band for DEER based distance measurements. Sample preparation is simple, and a coordinated-Cu(2+) ion offers limited spatial flexibility, making it an attractive probe for DEER experiments. On the other hand, Cu(2+) has a broad absorption ESR spectrum at low temperature, which leads to two potential complications. First, the Cu(2+)-based DEER time domain data has lower signal to noise ratio compared with MTSSL. Second, accurate distance distribution analysis often requires high-quality experimental data at different external magnetic fields or with different frequency offsets. In this Account, we summarize characteristics of Cu(2+)-based DEER distance distribution measurements and data analysis methods. We highlight a novel application of such measurements in a protein-DNA complex to identify the metal ion binding site and to elucidate its chemical mechanism of function. We also survey the progress of research on other metal ions in high frequency DEER experiments.
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Affiliation(s)
- Ming Ji
- Department of Chemistry, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, United States
| | - Sharon Ruthstein
- Department of Chemistry, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, United States
- Department of Chemistry, Faculty of Exact Science, Bar Ilan University, Ramat-Gan 5290002, Israel
| | - Sunil Saxena
- Department of Chemistry, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, United States
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