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Yang X, Elrod LC, Le T, Vega VS, Naumann H, Rezenom Y, Reibenspies JH, Hall MB, Darensbourg MY. Controlling O2 Reactivity in Synthetic Analogues of [NiFeS]- and [NiFeSe]-Hydrogenase Active Sites. J Am Chem Soc 2019; 141:15338-15347. [DOI: 10.1021/jacs.9b07448] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Xuemei Yang
- Department of Chemistry, Texas A&M University, College Station, Texas 77843, United States
| | - Lindy C. Elrod
- Department of Chemistry, Texas A&M University, College Station, Texas 77843, United States
| | - Trung Le
- Department of Chemistry, Texas A&M University, College Station, Texas 77843, United States
| | - Valeria S. Vega
- Department of Chemistry, Texas A&M University, College Station, Texas 77843, United States
| | - Haley Naumann
- Department of Chemistry, Texas A&M University, College Station, Texas 77843, United States
| | - Yohannes Rezenom
- Department of Chemistry, Texas A&M University, College Station, Texas 77843, United States
| | - Joseph H. Reibenspies
- Department of Chemistry, Texas A&M University, College Station, Texas 77843, United States
| | - Michael B. Hall
- Department of Chemistry, Texas A&M University, College Station, Texas 77843, United States
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2
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Wili N, Richert S, Limburg B, Clarke SJ, Anderson HL, Timmel CR, Jeschke G. ELDOR-detected NMR beyond hyperfine couplings: a case study with Cu(ii)-porphyrin dimers. Phys Chem Chem Phys 2019; 21:11676-11688. [DOI: 10.1039/c9cp01760g] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The pulse EPR method ELDOR-detected NMR gives information about electron–electron couplings in Cu(ii) porphyrin dimers.
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Affiliation(s)
- Nino Wili
- Laboratorium für Physikalische Chemie
- ETH Zürich
- 8093 Zürich
- Switzerland
| | - Sabine Richert
- Centre for Advanced Electron Spin Resonance (CÆSR)
- University of Oxford
- Oxford
- UK
| | - Bart Limburg
- Chemistry Research Laboratory
- University of Oxford
- Oxford
- UK
| | | | | | | | - Gunnar Jeschke
- Laboratorium für Physikalische Chemie
- ETH Zürich
- 8093 Zürich
- Switzerland
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3
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Cox N, Nalepa A, Lubitz W, Savitsky A. ELDOR-detected NMR: A general and robust method for electron-nuclear hyperfine spectroscopy? JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2017; 280:63-78. [PMID: 28579103 DOI: 10.1016/j.jmr.2017.04.006] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/18/2017] [Revised: 04/04/2017] [Accepted: 04/05/2017] [Indexed: 06/07/2023]
Abstract
ELDOR-detected NMR (EDNMR) performed at higher magnetic fields is becoming an increasingly popular alternative to conventional ENDOR for the characterization of electron-nuclear hyperfine interactions owing to its enhanced sensitivity. However there are two key problems that limit its widespread adoption, with factors controlling: (i) lineshape distortions and; (ii) overall spectral resolution, still largely understood only at a qualitative level. Indeed highly anisotropic (dipolar) coupled species are particularly problematic in the EDNMR experiment. Nor is it clear as to whether line intensities measured in EDNMR can provide quantitative information. Here we describe how all these problems can be overcome for a nitroxide radical as model system. We introduce a simulation procedure/protocol for the simulation of EDNMR line-shapes collected over a range of high turning angle (HTA) pulse lengths. It is shown that spectral line-shapes can be robustly reproduced and that the intensities of spectral lines and the spin nutation behavior can be quantitatively assessed. This broadens the scope of the EDNMR experiment as a generally applicable, quantitative double resonance method.
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Affiliation(s)
- Nicholas Cox
- Max-Planck-Institut für Chemische Energiekonversion, Stiftstr. 34-36, 45470 Mülheim an der Ruhr, Germany; Research School of Chemistry, The Australian National University, Canberra, Australia.
| | - Anna Nalepa
- Max-Planck-Institut für Chemische Energiekonversion, Stiftstr. 34-36, 45470 Mülheim an der Ruhr, Germany
| | - Wolfgang Lubitz
- Max-Planck-Institut für Chemische Energiekonversion, Stiftstr. 34-36, 45470 Mülheim an der Ruhr, Germany
| | - Anton Savitsky
- Max-Planck-Institut für Chemische Energiekonversion, Stiftstr. 34-36, 45470 Mülheim an der Ruhr, Germany.
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4
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Ramirez Cohen M, Mendelman N, Radoul M, Wilson TD, Savelieff MG, Zimmermann H, Kaminker I, Feintuch A, Lu Y, Goldfarb D. Thiolate Spin Population of Type I Copper in Azurin Derived from 33S Hyperfine Coupling. Inorg Chem 2017; 56:6163-6174. [DOI: 10.1021/acs.inorgchem.7b00167] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Affiliation(s)
- Marie Ramirez Cohen
- Department of Chemical
Physics, Weizmann Institute of Science, Rehovot 76100, Israel
| | - Netanel Mendelman
- Department of Chemical
Physics, Weizmann Institute of Science, Rehovot 76100, Israel
| | - Marina Radoul
- Department of Chemical
Physics, Weizmann Institute of Science, Rehovot 76100, Israel
| | - Tiffany D. Wilson
- Department of Chemistry, University of Illinois, Urbana, Illinois 61801, United States
| | - Masha G. Savelieff
- Department of Chemistry, University of Illinois, Urbana, Illinois 61801, United States
| | - Herbert Zimmermann
- Abteilung Biophysik, Max Planck-Institut für Medizinische Forschung, Heidelberg 69120, Germany
| | - Ilia Kaminker
- Department of Chemical
Physics, Weizmann Institute of Science, Rehovot 76100, Israel
| | - Akiva Feintuch
- Department of Chemical
Physics, Weizmann Institute of Science, Rehovot 76100, Israel
| | - Yi Lu
- Department of Chemistry, University of Illinois, Urbana, Illinois 61801, United States
| | - Daniella Goldfarb
- Department of Chemical
Physics, Weizmann Institute of Science, Rehovot 76100, Israel
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5
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Roncaroli F, Bill E, Friedrich B, Lenz O, Lubitz W, Pandelia ME. Cofactor composition and function of a H 2-sensing regulatory hydrogenase as revealed by Mössbauer and EPR spectroscopy. Chem Sci 2015; 6:4495-4507. [PMID: 29142700 PMCID: PMC5665086 DOI: 10.1039/c5sc01560j] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2015] [Accepted: 05/26/2015] [Indexed: 01/22/2023] Open
Abstract
The regulatory hydrogenase (RH) from Ralstonia eutropha H16 acts as a sensor for the detection of environmental H2 and regulates gene expression related to hydrogenase-mediated cellular metabolism. In marked contrast to prototypical energy-converting [NiFe] hydrogenases, the RH is apparently insensitive to inhibition by O2 and CO. While the physiological function of regulatory hydrogenases is well established, little is known about the redox cycling of the [NiFe] center and the nature of the iron-sulfur (FeS) clusters acting as electron relay. The absence of any FeS cluster signals in EPR had been attributed to their particular nature, whereas the observation of essentially only two active site redox states, namely Ni-SI and Ni-C, invoked a different operant mechanism. In the present work, we employ a combination of Mössbauer, FTIR and EPR spectroscopic techniques to study the RH, and the results are consistent with the presence of three [4Fe-4S] centers in the small subunit. In the as-isolated, oxidized RH all FeS clusters reside in the EPR-silent 2+ state. Incubation with H2 leads to reduction of two of the [4Fe-4S] clusters, whereas only strongly reducing agents lead to reduction of the third cluster, which is ascribed to be the [4Fe-4S] center in 'proximal' position to the [NiFe] center. In the two different active site redox states, the low-spin FeII exhibits distinct Mössbauer features attributed to changes in the electronic and geometric structure of the catalytic center. The results are discussed with regard to the spectral characteristics and physiological function of H2-sensing regulatory hydrogenases.
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Affiliation(s)
- Federico Roncaroli
- Max-Planck-Institut für Chemische Energiekonversion , Stiftstraße 34-36 , 45470 Mülheim an der Ruhr , Germany . ; .,Department of Condensed Matter Physics , Centro Atómico Constituyentes , Comisión Nacional de Energía Atómica (CNEA) , Argentina
| | - Eckhard Bill
- Max-Planck-Institut für Chemische Energiekonversion , Stiftstraße 34-36 , 45470 Mülheim an der Ruhr , Germany . ;
| | - Bärbel Friedrich
- Institut für Biologie/Mikrobiologie , Humboldt-Universität zu Berlin , Chausseestraße 117 , 10115 Berlin , Germany
| | - Oliver Lenz
- Institut für Biologie/Mikrobiologie , Humboldt-Universität zu Berlin , Chausseestraße 117 , 10115 Berlin , Germany.,Institut für Chemie , Technische Universität Berlin , Max-Volmer-Laboratorium , Straße des 17. Juni 135 , 10623 Berlin , Germany
| | - Wolfgang Lubitz
- Max-Planck-Institut für Chemische Energiekonversion , Stiftstraße 34-36 , 45470 Mülheim an der Ruhr , Germany . ;
| | - Maria-Eirini Pandelia
- The Pennsylvania State University , Department of Chemistry , State College , PA 16802 , USA . .,Max-Planck-Institut für Chemische Energiekonversion , Stiftstraße 34-36 , 45470 Mülheim an der Ruhr , Germany . ;
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6
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Bruch EM, Warner MT, Thomine S, Tabares LC, Un S. Pulse Electron Double Resonance Detected Multinuclear NMR Spectra of Distant and Low Sensitivity Nuclei and Its Application to the Structure of Mn(II) Centers in Organisms. J Phys Chem B 2015; 119:13515-23. [PMID: 25730710 DOI: 10.1021/acs.jpcb.5b01624] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Abstract
The ability to characterize the structure of metal centers beyond their primary ligands is important to understanding their chemistry. High-magnetic-field pulsed electron double resonance detected NMR (ELDOR-NMR) is shown to be a very sensitive approach to measuring the multinuclear NMR spectra of the nuclei surrounding Mn(II) ions. Resolved spectra of intact organisms with resonances arising from (55)Mn, (31)P, (1)H, (39)K, (35)Cl, (23)Na, and (14)N nuclei surrounding Mn(2+) centers were obtained. Naturally abundant cellular (13)C could be routinely measured as well. The amplitudes of the (14)N and (2)H ELDOR-NMR spectra were found to be linearly dependent on the number of nuclei in the ligand sphere. The evolution of the Mn(II) ELDOR-NMR spectra as a function of excitation time was found to be best described by a saturation phenomenon rather than a coherently driven process. Mn(II) ELDOR-NMR revealed details about not only the immediate ligands to the Mn(II) ions but also more distant nuclei, providing a view of their extended structures. This will be important for understanding the speciation and chemistry of the manganese complexes as well as other metals found in organisms.
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Affiliation(s)
- Eduardo M Bruch
- Service de Bioénergétique, Biologie Structurale et Mécanismes (CNRS UMR-8221), Institut de Biologie et de Technologies de Saclay, CEA-Saclay , F-91191 Gif-sur-Yvette, France
| | - Melissa T Warner
- Service de Bioénergétique, Biologie Structurale et Mécanismes (CNRS UMR-8221), Institut de Biologie et de Technologies de Saclay, CEA-Saclay , F-91191 Gif-sur-Yvette, France.,Department of Biology, Tufts University , Medford, Massachusetts 02155, United States
| | - Sébastien Thomine
- Institute for Integrative Biology of the Cell (I2BC), Saclay Plant Sciences, Université Paris-Saclay, CEA, CNRS, Université Paris-Sud , Gif-sur-Yvette, F-91198 France
| | - Leandro C Tabares
- Service de Bioénergétique, Biologie Structurale et Mécanismes (CNRS UMR-8221), Institut de Biologie et de Technologies de Saclay, CEA-Saclay , F-91191 Gif-sur-Yvette, France
| | - Sun Un
- Service de Bioénergétique, Biologie Structurale et Mécanismes (CNRS UMR-8221), Institut de Biologie et de Technologies de Saclay, CEA-Saclay , F-91191 Gif-sur-Yvette, France
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7
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Cox N, Nalepa A, Pandelia ME, Lubitz W, Savitsky A. Pulse Double-Resonance EPR Techniques for the Study of Metallobiomolecules. Methods Enzymol 2015; 563:211-49. [DOI: 10.1016/bs.mie.2015.08.016] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
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8
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Vedha SA, Solomon RV, Venuvanalingam P. Atomic partitioning of M-H2 bonds in [NiFe] hydrogenase--a test case of concurrent binding. Phys Chem Chem Phys 2014; 16:10698-707. [PMID: 24756140 DOI: 10.1039/c4cp00526k] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The possibility of simultaneous addition of η(2)-H2 to both the metals (Ni and Fe) in the active site of the as isolated state of the enzyme (Ni-SI) is examined here by an atom-by-atom electronic energy partitioning based on the QTAIM method. Results show that the 4LS state prefers H2 removal than addition. Destabilization of the atomic basins of the thiolate bridges and decrease of the electrophilicity of the Fe and Ni, resulting in poor back donation to the CO ligand, are the bottlenecks that hamper dihydrogen activation simultaneously. The study helps to understand why such states are seldom accessed in the activation of dihydrogen. Moreover, Ni has been found to be the natural choice for the dihydrogen binding.
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Affiliation(s)
- Swaminathan Angeline Vedha
- Theoretical & Computational Chemistry Laboratory, School of Chemistry, Bharathidasan University, Tiruchirappalli 24, India.
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9
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Ogo S. H2and O2Activation-A Remarkable Insight into Hydrogenase. CHEM REC 2014; 14:397-409. [DOI: 10.1002/tcr.201402010] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2014] [Indexed: 12/15/2022]
Affiliation(s)
- Seiji Ogo
- International Institute for Carbon-Neutral Energy Research (WPI-I2CNER); Kyushu University; 744 Moto-oka, Nishi-ku Fukuoka 819-0395 Japan
- Department of Chemistry and Biochemistry; Graduate School of Engineering; Kyushu University; 744 Moto-oka, Nishi-ku Fukuoka 819-0395 Japan
- Core Research for Evolutional Science and Technology (CREST); Japan Science and Technology Agency (JST); Kawaguchi Center Building; 4-1-8 Honcho Kawaguchi-shi Saitama 332-0012 Japan
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10
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Affiliation(s)
- Wolfgang Lubitz
- Max Planck Institute for Chemical Energy Conversion, Stiftstr. 34-36, 45470 Mülheim an der Ruhr, Germany
| | - Hideaki Ogata
- Max Planck Institute for Chemical Energy Conversion, Stiftstr. 34-36, 45470 Mülheim an der Ruhr, Germany
| | - Olaf Rüdiger
- Max Planck Institute for Chemical Energy Conversion, Stiftstr. 34-36, 45470 Mülheim an der Ruhr, Germany
| | - Edward Reijerse
- Max Planck Institute for Chemical Energy Conversion, Stiftstr. 34-36, 45470 Mülheim an der Ruhr, Germany
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11
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Kaminker I, Wilson TD, Savelieff MG, Hovav Y, Zimmermann H, Lu Y, Goldfarb D. Correlating nuclear frequencies by two-dimensional ELDOR-detected NMR spectroscopy. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2014; 240:77-89. [PMID: 24530956 DOI: 10.1016/j.jmr.2013.12.016] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/12/2013] [Revised: 12/26/2013] [Accepted: 12/27/2013] [Indexed: 06/03/2023]
Abstract
ELDOR (Electron Double Resonance)-detected NMR (EDNMR) is a pulse EPR experiment that is used to measure the transition frequencies of nuclear spins coupled to electron spins. These frequencies are further used to determine hyperfine and quadrupolar couplings, which are signatures of the electronic and spatial structures of paramagnetic centers. In recent years, EDNMR has been shown to be particularly useful at high fields/high frequencies, such as W-band (∼95 GHz, ∼3.5 T), for low γ quadrupolar nuclei. Although at high fields the nuclear Larmor frequencies are usually well resolved, the limited resolution of EDNMR still remains a major concern. In this work we introduce a two dimensional, triple resonance, correlation experiment based on the EDNMR pulse sequence, which we term 2D-EDNMR. This experiment allows circumventing the resolution limitation by spreading the signals in two dimensions and the observed correlations help in the assignment of the signals. First we demonstrate the utility of the 2D-EDNMR experiment on a nitroxide spin label, where we observe correlations between (14)N nuclear frequencies. Negative cross-peaks appear between lines belonging to different MS electron spin manifolds. We resolved two independent correlation patterns for nuclear frequencies arising from the EPR transitions corresponding to the (14)N mI=0 and mI=-1 nuclear spin states, which severely overlap in the one dimensional EDNMR spectrum. The observed correlations could be accounted for by considering changes in the populations of energy levels that S=1/2, I=1 spin systems undergo during the pulse sequence. In addition to these negative cross-peaks, positive cross-peaks appear as well. We present a theoretical model based on the Liouville equation and use it to calculate the time evolution of populations of the various energy levels during the 2D-EDNMR experiment and generated simulated 2D-EDMR spectra. These calculations show that the positive cross-peaks appear due to off resonance effects and/or nuclear relaxation effects. These results suggest that the 2D-EDNMR experiment can be also useful for relaxation pathway studies. Finally we present preliminary results demonstrating that 2D-EDNMR can resolve overlapping (33)S and (14)N signals of type 1 Cu(II) center in (33)S enriched Azurin.
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Affiliation(s)
- Ilia Kaminker
- Department of Chemical Physics, Weizmann Institute of Science, Rehovot, Israel
| | - Tiffany D Wilson
- Department of Chemistry, University of Illinois, Urbana, IL, United States
| | - Masha G Savelieff
- Department of Chemistry, University of Illinois, Urbana, IL, United States
| | - Yonatan Hovav
- Department of Chemical Physics, Weizmann Institute of Science, Rehovot, Israel
| | - Herbert Zimmermann
- Abteilung Biophysik, Max-Planck-Institut für Medizinische Forschung, Heidelberg, Germany
| | - Yi Lu
- Department of Chemistry, University of Illinois, Urbana, IL, United States
| | - Daniella Goldfarb
- Department of Chemical Physics, Weizmann Institute of Science, Rehovot, Israel.
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12
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Möbius K, Lubitz W, Savitsky A. High-field EPR on membrane proteins - crossing the gap to NMR. PROGRESS IN NUCLEAR MAGNETIC RESONANCE SPECTROSCOPY 2013; 75:1-49. [PMID: 24160760 DOI: 10.1016/j.pnmrs.2013.07.002] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/17/2013] [Revised: 07/15/2013] [Accepted: 07/15/2013] [Indexed: 06/02/2023]
Abstract
In this review on advanced EPR spectroscopy, which addresses both the EPR and NMR communities, considerable emphasis is put on delineating the complementarity of NMR and EPR concerning the measurement of molecular interactions in large biomolecules. From these interactions, detailed information can be revealed on structure and dynamics of macromolecules embedded in solution- or solid-state environments. New developments in pulsed microwave and sweepable cryomagnet technology as well as ultrafast electronics for signal data handling and processing have pushed to new horizons the limits of EPR spectroscopy and its multifrequency extensions concerning the sensitivity of detection, the selectivity with respect to interactions, and the resolution in frequency and time domains. One of the most important advances has been the extension of EPR to high magnetic fields and microwave frequencies, very much in analogy to what happens in NMR. This is exemplified by referring to ongoing efforts for signal enhancement in both NMR and EPR double-resonance techniques by exploiting dynamic nuclear or electron spin polarization via unpaired electron spins and their electron-nuclear or electron-electron interactions. Signal and resolution enhancements are particularly spectacular for double-resonance techniques such as ENDOR and PELDOR at high magnetic fields. They provide greatly improved orientational selection for disordered samples that approaches single-crystal resolution at canonical g-tensor orientations - even for molecules with small g-anisotropies. Exchange of experience between the EPR and NMR communities allows for handling polarization and resolution improvement strategies in an optimal manner. Consequently, a dramatic improvement of EPR detection sensitivity could be achieved, even for short-lived paramagnetic reaction intermediates. Unique structural and dynamic information is thus revealed that can hardly be obtained by any other analytical techniques. Micromolar quantities of sample molecules have become sufficient to characterize stable and transient reaction intermediates of complex molecular systems - offering highly interesting applications for chemists, biochemists and molecular biologists. In three case studies, representative examples of advanced EPR spectroscopy are reviewed: (I) High-field PELDOR and ENDOR structure determination of cation-anion radical pairs in reaction centers from photosynthetic purple bacteria and cyanobacteria (Photosystem I); (II) High-field ENDOR and ELDOR-detected NMR spectroscopy on the oxygen-evolving complex of Photosystem II; and (III) High-field electron dipolar spectroscopy on nitroxide spin-labelled bacteriorhodopsin for structure-function studies. An extended conclusion with an outlook to further developments and applications is also presented.
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Affiliation(s)
- Klaus Möbius
- Max Planck Institute for Chemical Energy Conversion, Stiftstrasse 34-36, D-45470 Mülheim an der Ruhr, Germany; Department of Physics, Free University Berlin, Arnimallee 14, D-14195 Berlin, Germany.
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13
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Krämer T, Kampa M, Lubitz W, van Gastel M, Neese F. Theoretical Spectroscopy of the NiIIIntermediate States in the Catalytic Cycle and the Activation of [NiFe] Hydrogenases. Chembiochem 2013; 14:1898-905. [DOI: 10.1002/cbic.201300104] [Citation(s) in RCA: 51] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2013] [Indexed: 11/05/2022]
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14
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Kampa M, Pandelia ME, Lubitz W, van Gastel M, Neese F. A Metal–Metal Bond in the Light-Induced State of [NiFe] Hydrogenases with Relevance to Hydrogen Evolution. J Am Chem Soc 2013; 135:3915-25. [DOI: 10.1021/ja3115899] [Citation(s) in RCA: 85] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Mario Kampa
- Max-Planck-Institut für Chemische Energiekonversion, Stiftstrasse 34-36, D-45470 Mülheim
an der Ruhr, Germany
| | - Maria-Eirini Pandelia
- Max-Planck-Institut für Chemische Energiekonversion, Stiftstrasse 34-36, D-45470 Mülheim
an der Ruhr, Germany
| | - Wolfgang Lubitz
- Max-Planck-Institut für Chemische Energiekonversion, Stiftstrasse 34-36, D-45470 Mülheim
an der Ruhr, Germany
| | - Maurice van Gastel
- Max-Planck-Institut für Chemische Energiekonversion, Stiftstrasse 34-36, D-45470 Mülheim
an der Ruhr, Germany
| | - Frank Neese
- Max-Planck-Institut für Chemische Energiekonversion, Stiftstrasse 34-36, D-45470 Mülheim
an der Ruhr, Germany
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15
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Reijerse E, Lendzian F, Isaacson R, Lubitz W. A tunable general purpose Q-band resonator for CW and pulse EPR/ENDOR experiments with large sample access and optical excitation. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2012; 214:237-43. [PMID: 22196894 DOI: 10.1016/j.jmr.2011.11.011] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/29/2011] [Revised: 11/11/2011] [Accepted: 11/12/2011] [Indexed: 05/22/2023]
Abstract
We describe a frequency tunable Q-band cavity (34 GHz) designed for CW and pulse Electron Paramagnetic Resonance (EPR) as well as Electron Nuclear Double Resonance (ENDOR) and Electron Electron Double Resonance (ELDOR) experiments. The TE(011) cylindrical resonator is machined either from brass or from graphite (which is subsequently gold plated), to improve the penetration of the 100 kHz field modulation signal. The (self-supporting) ENDOR coil consists of four 0.8mm silver posts at 2.67 mm distance from the cavity center axis, penetrating through the plunger heads. It is very robust and immune to mechanical vibrations. The coil is electrically shielded to enable CW ENDOR experiments with high RF power (500 W). The top plunger of the cavity is movable and allows a frequency tuning of ±2 GHz. In our setup the standard operation frequency is 34.0 GHz. The microwaves are coupled into the resonator through an iris in the cylinder wall and matching is accomplished by a sliding short in the coupling waveguide. Optical excitation of the sample is enabled through slits in the cavity wall (transmission ∼60%). The resonator accepts 3mm o.d. sample tubes. This leads to a favorable sensitivity especially for pulse EPR experiments of low concentration biological samples. The probehead dimensions are compatible with that of Bruker flexline Q-band resonators and it fits perfectly into an Oxford CF935 Helium flow cryostat (4-300 K). It is demonstrated that, due to the relatively large active sample volume (20-30 μl), the described resonator has superior concentration sensitivity as compared to commercial pulse Q-band resonators. The quality factor (Q(L)) of the resonator can be varied between 2600 (critical coupling) and 1300 (over-coupling). The shortest achieved π/2-pulse durations are 20 ns using a 3 W microwave amplifier. ENDOR (RF) π-pulses of 20 μs ((1)H @ 51 MHz) were obtained for a 300 W amplifier and 7 μs using a 2500 W amplifier. Selected applications of the resonator are presented.
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Affiliation(s)
- Edward Reijerse
- Max-Planck-Institut für Bioanorganische Chemie, 45470 Mülheim an der Ruhr, Stiftstr. 34-36, Germany.
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Stein M. Comment on "A nickel(II)-based radical-ligand complex as a functional model of hydrogenase". Chemistry 2011; 17:15046-8; author reply 15049-50. [PMID: 22170220 DOI: 10.1002/chem.201002985] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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17
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Pandelia ME, Ogata H, Lubitz W. Intermediates in the catalytic cycle of [NiFe] hydrogenase: functional spectroscopy of the active site. Chemphyschem 2010; 11:1127-40. [PMID: 20301175 DOI: 10.1002/cphc.200900950] [Citation(s) in RCA: 92] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
The [NiFe] hydrogenase from the anaerobic sulphate reducing bacterium Desulfovibrio vulgaris Miyazaki F is an excellent model for constructing a mechanism for the function of the so-called 'oxygen-sensitive' hydrogenases. The present review focuses on spectroscopic investigations of the active site intermediates playing a role in the activation/deactivation and catalytic cycle of this enzyme as well as in the inhibition by carbon monoxide or molecular oxygen and the light-sensitivity of the hydrogenase. The methods employed include magnetic resonance and vibrational (FTIR) techniques combined with electrochemistry that deliver information about details of the geometrical and electronic structure of the intermediates and their redox behaviour. Based on these data a mechanistic scheme is developed.
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Affiliation(s)
- Maria-Eirini Pandelia
- Max-Planck Institut für Bioanorganische Chemie, Stiftstrasse 34-36, 45470, Mülheim an der Ruhr, Germany
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Potapov A, Pecht I, Goldfarb D. Resolving ligand hyperfine couplings of type 1 and 2 Cu(ii) in ascorbate oxidase by high field pulse EPRcorrelation spectroscopy. Phys Chem Chem Phys 2010; 12:62-5. [DOI: 10.1039/b919069d] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Ogata H, Lubitz W, Higuchi Y. [NiFe] hydrogenases: structural and spectroscopic studies of the reaction mechanism. Dalton Trans 2009:7577-87. [DOI: 10.1039/b903840j] [Citation(s) in RCA: 168] [Impact Index Per Article: 11.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Erhardt S, Macgregor SA. Computational Study of the Reaction of C6F6 with [IrMe(PEt3)3]: Identification of a Phosphine-Assisted C−F Activation Pathway via a Metallophosphorane Intermediate. J Am Chem Soc 2008; 130:15490-8. [DOI: 10.1021/ja804622j] [Citation(s) in RCA: 76] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Stefan Erhardt
- School of Engineering and Physical Sciences, Heriot-Watt University, Edinburgh EH14 4AS, U.K
| | - Stuart A. Macgregor
- School of Engineering and Physical Sciences, Heriot-Watt University, Edinburgh EH14 4AS, U.K
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