1
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Bindra JK, Malavath T, Teferi MY, Kretzschmar M, Kern J, Niklas J, Utschig LM, Poluektov OG. Light-Induced Charge Separation in Photosystem I from Different Biological Species Characterized by Multifrequency Electron Paramagnetic Resonance Spectroscopy. Int J Mol Sci 2024; 25:8188. [PMID: 39125759 PMCID: PMC11311511 DOI: 10.3390/ijms25158188] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2024] [Revised: 07/15/2024] [Accepted: 07/19/2024] [Indexed: 08/12/2024] Open
Abstract
Photosystem I (PSI) serves as a model system for studying fundamental processes such as electron transfer (ET) and energy conversion, which are not only central to photosynthesis but also have broader implications for bioenergy production and biomimetic device design. In this study, we employed electron paramagnetic resonance (EPR) spectroscopy to investigate key light-induced charge separation steps in PSI isolated from several green algal and cyanobacterial species. Following photoexcitation, rapid sequential ET occurs through either of two quasi-symmetric branches of donor/acceptor cofactors embedded within the protein core, termed the A and B branches. Using high-frequency (130 GHz) time-resolved EPR (TR-EPR) and deuteration techniques to enhance spectral resolution, we observed that at low temperatures prokaryotic PSI exhibits reversible ET in the A branch and irreversible ET in the B branch, while PSI from eukaryotic counterparts displays either reversible ET in both branches or exclusively in the B branch. Furthermore, we observed a notable correlation between low-temperature charge separation to the terminal [4Fe-4S] clusters of PSI, termed FA and FB, as reflected in the measured FA/FB ratio. These findings enhance our understanding of the mechanistic diversity of PSI's ET across different species and underscore the importance of experimental design in resolving these differences. Though further research is necessary to elucidate the underlying mechanisms and the evolutionary significance of these variations in PSI charge separation, this study sets the stage for future investigations into the complex interplay between protein structure, ET pathways, and the environmental adaptations of photosynthetic organisms.
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Affiliation(s)
- Jasleen K. Bindra
- Argonne National Laboratory, Chemical Sciences and Engineering Division, 9700 South Cass Avenue, Lemont, IL 60439, USA; (J.K.B.); (T.M.); (M.Y.T.); (J.N.)
| | - Tirupathi Malavath
- Argonne National Laboratory, Chemical Sciences and Engineering Division, 9700 South Cass Avenue, Lemont, IL 60439, USA; (J.K.B.); (T.M.); (M.Y.T.); (J.N.)
| | - Mandefro Y. Teferi
- Argonne National Laboratory, Chemical Sciences and Engineering Division, 9700 South Cass Avenue, Lemont, IL 60439, USA; (J.K.B.); (T.M.); (M.Y.T.); (J.N.)
| | - Moritz Kretzschmar
- Lawrence Berkeley National Laboratory, Molecular Biophysics and Integrated Bioimaging Division, Berkeley, CA 94720, USA; (M.K.); (J.K.)
| | - Jan Kern
- Lawrence Berkeley National Laboratory, Molecular Biophysics and Integrated Bioimaging Division, Berkeley, CA 94720, USA; (M.K.); (J.K.)
| | - Jens Niklas
- Argonne National Laboratory, Chemical Sciences and Engineering Division, 9700 South Cass Avenue, Lemont, IL 60439, USA; (J.K.B.); (T.M.); (M.Y.T.); (J.N.)
| | - Lisa M. Utschig
- Argonne National Laboratory, Chemical Sciences and Engineering Division, 9700 South Cass Avenue, Lemont, IL 60439, USA; (J.K.B.); (T.M.); (M.Y.T.); (J.N.)
| | - Oleg G. Poluektov
- Argonne National Laboratory, Chemical Sciences and Engineering Division, 9700 South Cass Avenue, Lemont, IL 60439, USA; (J.K.B.); (T.M.); (M.Y.T.); (J.N.)
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2
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Bindra JK, Niklas J, Jeong Y, Jasper AW, Kretzschmar M, Kern J, Utschig LM, Poluektov OG. Coherences of Photoinduced Electron Spin Qubit Pair States in Photosystem I. J Phys Chem B 2023; 127:10108-10117. [PMID: 37980604 DOI: 10.1021/acs.jpcb.3c06658] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2023]
Abstract
This publication presents the first comprehensive experimental study of electron spin coherences in photosynthetic reaction center proteins, specifically focusing on photosystem I (PSI). The ultrafast electron transfer in PSI generates spin-correlated radical pairs (SCRPs), which are entangled spin pairs formed in well-defined spin states (Bell states). Since their discovery in our group in the 1980s, SCRPs have been extensively used to enhance our understanding of structure-function relationships in photosynthetic proteins. More recently, SCRPs have been utilized as tools for quantum sensing. Electron spin decoherence poses a significant challenge in realizing practical applications of electron spin qubits, particularly the creation of quantum entanglement between multiple electron spins. This work is focused on the systematic characterization of decoherence in SCRPs of PSI. These decoherence times were measured as electron spin echo decay times, termed phase memory times (TM), at various temperatures. Decoherence was recorded on both transient SCRP states P700+A1- and thermalized states. Our study reveals that TM exhibits minimal dependence on the biological species, biochemical treatment, and paramagnetic species. The analysis indicates that nuclear spin diffusion and instantaneous diffusion mechanisms alone cannot explain the observed decoherence. As a plausible explanation we discuss the assumption that the low-temperature dynamics of methyl groups in the protein surrounding the unpaired electron spin centers is the main factor governing the loss of the spin coherence in PSI.
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Affiliation(s)
- Jasleen K Bindra
- Chemical Sciences and Engineering Division, Argonne National Laboratory, 9700 South Cass Avenue, Lemont, Illinois 60439, United States
| | - Jens Niklas
- Chemical Sciences and Engineering Division, Argonne National Laboratory, 9700 South Cass Avenue, Lemont, Illinois 60439, United States
| | - Yeonjun Jeong
- Chemical Sciences and Engineering Division, Argonne National Laboratory, 9700 South Cass Avenue, Lemont, Illinois 60439, United States
| | - Ahren W Jasper
- Chemical Sciences and Engineering Division, Argonne National Laboratory, 9700 South Cass Avenue, Lemont, Illinois 60439, United States
| | - Moritz Kretzschmar
- Molecular Biophysics and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States
| | - Jan Kern
- Molecular Biophysics and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States
| | - Lisa M Utschig
- Chemical Sciences and Engineering Division, Argonne National Laboratory, 9700 South Cass Avenue, Lemont, Illinois 60439, United States
| | - Oleg G Poluektov
- Chemical Sciences and Engineering Division, Argonne National Laboratory, 9700 South Cass Avenue, Lemont, Illinois 60439, United States
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3
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Ren Y, Hore PJ. Conditions for EPR detection of chirality-induced spin selectivity in spin-polarized radical pairs in isotropic solution. J Chem Phys 2023; 159:145104. [PMID: 37819000 DOI: 10.1063/5.0171700] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2023] [Accepted: 09/19/2023] [Indexed: 10/13/2023] Open
Abstract
Chiral molecules can act as spin filters, preferentially transmitting electrons with spins polarized along their direction of travel, an effect known as chirality-induced spin selectivity (CISS). In a typical experiment, injected electrons tunnel coherently through a layer of chiral material and emerge spin-polarized. It is also possible that spin polarization arises in radical pairs formed photochemically when electrons hop incoherently between donor and acceptor sites. Here we aim to identify the magnetic properties that would optimise the visibility of CISS polarization in time-resolved electron paramagnetic resonance (EPR) spectra of transient radical pairs without the need to orient or align their precursors. By simulating spectra of actual and model systems, we find that CISS contributions to the polarization should be most obvious when at least one of the radicals has small g-anisotropy and an inhomogeneous linewidth larger than the dipolar coupling of the two radicals. Under these conditions there is extensive cancellation of absorptive and emissive enhancements making the spectrum sensitive to small changes in the individual EPR line intensities. Although these cancellation effects are more pronounced at lower spectrometer frequencies, the spectral changes are easier to appreciate with the enhanced resolution afforded by high-frequency EPR. Consideration of published spectra of light-induced radical pairs in photosynthetic bacterial reaction centres reveals no significant CISS component in the polarization generated by the conventional spin-correlated radical pair mechanism.
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Affiliation(s)
- Yi Ren
- Department of Chemistry, University of Oxford, Oxford, United Kingdom
| | - P J Hore
- Department of Chemistry, University of Oxford, Oxford, United Kingdom
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4
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Kanda T, Ishikita H. Energetics of the Electron Transfer Pathways in the Homodimeric Photosynthetic Reaction Center. Biochemistry 2022; 61:2621-2627. [PMID: 36322126 PMCID: PMC9671125 DOI: 10.1021/acs.biochem.2c00524] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2022] [Revised: 10/09/2022] [Indexed: 11/06/2022]
Abstract
Photosynthetic reaction centers from a green sulfur bacterium (GsbRC), the PscA/PscA proteins, and photosystem I (PSI), PsaA/PsaB proteins, share structural similarities. Here, we report the redox potential (Em) values of GsbRC by solving the linear Poisson-Boltzmann equation and considering the protonation states of all titratable sites in the entire GsbRC protein and identify the factors that shift the Em values with respect to PSI. The Em values for one-electron reduction of the accessory (A-1) and adjacent (A0) chlorophylls in GsbRC are 100-250 mV higher than those in PSI, whereas the Em values for the Fe4S4 cluster (FX) are at the same level. The PsaA-Trp697/PsaB-Trp677 pair in PSI, which forms the A1-quinone binding site, is replaced with PscA-Arg638 in GsbRC. PsaB-Asp575 in PSI, which is responsible for the Em difference between A1A and A1B quinones in PSI, is absent in GsbRC. These discrepancies also contribute to the upshift in Em(A-1) and Em(A0) in GsbRC with respect to PSI. It seems likely that the upshifted Em for chlorophylls in GsbRC ultimately originates from the characteristics of the electrostatic environment that corresponds to the A1 site of PSI.
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Affiliation(s)
- Tomoki Kanda
- Department
of Applied Chemistry, The University of
Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8654, Japan
| | - Hiroshi Ishikita
- Department
of Applied Chemistry, The University of
Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8654, Japan
- Research
Center for Advanced Science and Technology, The University of Tokyo, 4-6-1 Komaba, Meguro-ku, Tokyo 153-8904, Japan
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5
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Kanda T, Saito K, Ishikita H. Mechanism of Mixed-Valence Fe 2.5+···Fe 2.5+ Formation in Fe 4S 4 Clusters in the Ferredoxin Binding Motif. J Phys Chem B 2022; 126:3059-3066. [PMID: 35435680 PMCID: PMC9059760 DOI: 10.1021/acs.jpcb.2c01320] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Most low-potential Fe4S4 clusters exist in the conserved binding sequence CxxCxxC (CnCn+3Cn+6). Fe(II) and Fe(III) at the first (Cn) and third (Cn+6) cysteine ligand sites form a mixed-valence Fe2.5+···Fe2.5+ pair in the reduced Fe(II)3Fe(III) cluster. Here, we investigate the mechanism of how the conserved protein environment induces mixed-valence pair formation in the Fe4S4 clusters, FX, FA, and FB in photosystem I, using a quantum mechanical/molecular mechanical approach. Exchange coupling between Fe sites is predominantly determined by the shape of the Fe4S4 cluster, which is stabilized by the preorganized protein electrostatic environment. The backbone NH and CO groups in the conserved CxxCxxC and adjacent helix regions orient along the FeCn···FeC(n+6) axis, generating an electric field and stabilizing the FeCn(II)FeC(n+6)(III) state in FA and FB. The overlap of the d orbitals via -S- (superexchange) is observed for the single FeCn(II)···FeC(n+6)(III) pair, leading to the formation of the mixed-valence Fe2.5+···Fe2.5+ pair. In contrast, several superexchange Fe(II)···Fe(III) pairs are observed in FX due to the highly symmetric pair of the CDGPGRGGTC sequences. This is likely the origin of FX serving as an electron acceptor in the two electron transfer branches.
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Affiliation(s)
- Tomoki Kanda
- Department of Applied Chemistry, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8654, Japan
| | - Keisuke Saito
- Department of Applied Chemistry, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8654, Japan.,Research Center for Advanced Science and Technology, The University of Tokyo, 4-6-1 Komaba, Meguro-ku, Tokyo 153-8904, Japan
| | - Hiroshi Ishikita
- Department of Applied Chemistry, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8654, Japan.,Research Center for Advanced Science and Technology, The University of Tokyo, 4-6-1 Komaba, Meguro-ku, Tokyo 153-8904, Japan
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6
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Shen JR. Structure, Function, and Variations of the Photosystem I-Antenna Supercomplex from Different Photosynthetic Organisms. Subcell Biochem 2022; 99:351-377. [PMID: 36151382 DOI: 10.1007/978-3-031-00793-4_11] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/16/2023]
Abstract
Photosystem I (PSI) is a protein complex functioning in light-induced charge separation, electron transfer, and reduction reactions of ferredoxin in photosynthesis, which finally results in the reduction of NAD(P)- to NAD(P)H required for the fixation of carbon dioxide. In eukaryotic algae, PSI is associated with light-harvesting complex I (LHCI) subunits, forming a PSI-LHCI supercomplex. LHCI harvests and transfers light energy to the PSI core, where charge separation and electron transfer reactions occur. During the course of evolution, the number and sequences of protein subunits and the pigments they bind in LHCI change dramatically depending on the species of organisms, which is a result of adaptation of organisms to various light environments. In this chapter, I will describe the structure of various PSI-LHCI supercomplexes from different organisms solved so far either by X-ray crystallography or by cryo-electron microscopy, with emphasis on the differences in the number, structures, and association patterns of LHCI subunits associated with the PSI core found in different organisms.
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Affiliation(s)
- Jian-Ren Shen
- Research Institute for Interdisciplinary Science, and Graduate School of Natural Science and Technology, Okayama University, Okayama, Japan.
- Key Laboratory of Photobiology, Institute of Botany, Chinese Academy of Sciences, Beijing, China.
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7
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Kanda T, Saito K, Ishikita H. Electron Acceptor-Donor Iron Sites in the Iron-Sulfur Cluster of Photosynthetic Electron-Transfer Pathways. J Phys Chem Lett 2021; 12:7431-7438. [PMID: 34338530 DOI: 10.1021/acs.jpclett.1c01896] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
In photosystem I, two electron-transfer pathways via quinones (A1A and A1B) are merged at the iron-sulfur Fe4S4 cluster FX into a single pathway toward the other two Fe4S4 clusters FA and FB. Using a quantum mechanical/molecular mechanical approach, we identify the redox-active Fe sites in the clusters. In FA and FB, the Fe site, which does not belong to the CxxCxxCxxxCP motif, serves as an electron acceptor/donor. FX has two independent electron acceptor Fe sites for A- and B-branch electron transfers, depending on the Asp-B575 protonation state, which causes the A1A-to-FX electron transfer to be uphill and the A1B-to-FX electron transfer to be downhill. The two asymmetric electron-transfer pathways from A1 to FX and the separation of the electron acceptor and donor Fe sites are likely associated with the specific role of FX in merging the two electron transfer pathways into the single pathway.
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Affiliation(s)
- Tomoki Kanda
- Department of Applied Chemistry, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8654, Japan
| | - Keisuke Saito
- Department of Applied Chemistry, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8654, Japan
- Research Center for Advanced Science and Technology, The University of Tokyo, 4-6-1 Komaba, Meguro-ku, Tokyo 153-8904, Japan
| | - Hiroshi Ishikita
- Department of Applied Chemistry, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8654, Japan
- Research Center for Advanced Science and Technology, The University of Tokyo, 4-6-1 Komaba, Meguro-ku, Tokyo 153-8904, Japan
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8
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Poluektov OG, Utschig LM. Quantum Sensing of Electron Transfer Pathways in Natural Photosynthesis Using Time-Resolved High-Field Electron Paramagnetic Resonance/Electron-Nuclear Double Resonance Spectroscopy. J Phys Chem B 2021; 125:4025-4030. [PMID: 33877826 DOI: 10.1021/acs.jpcb.1c00946] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Photosynthetic integral membrane reaction center (RC) proteins capture and convert sunlight into chemical energy via efficient charge separation achieved through a series of rapid, photoinitiated electron transfer steps. These fast electron transfers create an entangled spin qubit (radical) pair that contains detailed information about the weak magnetic interactions, structure, and dynamics of localized protein environments involved in charge separation events. Herein, we investigate how these entangled electron spin qubits interact with nuclear spins of the protein environment using the high spectral resolution of 130 GHz electron paramagnetic resonance (EPR) and electron-nuclear double resonance (ENDOR). Spectroscopic interrogation enabled the observation and probing of protons located in the electron transfer pathway between the membrane-spanning electron pair P+QA- (where P+ is the primary donor, a special pair of bacteriochlorophylls, and QA is the primary quinone acceptor) in the bacterial RC. Spectroscopic analysis reveals hydrogen-bonding interactions involved in regulating the route that light-induced electrons travel through the RC protein during charge separation.
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Affiliation(s)
- Oleg G Poluektov
- Chemical Sciences and Engineering Division, Argonne National Laboratory, 9700 South Cass Avenue, Lemont, Illinois 60439, United States
| | - Lisa M Utschig
- Chemical Sciences and Engineering Division, Argonne National Laboratory, 9700 South Cass Avenue, Lemont, Illinois 60439, United States
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9
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Mitsuhashi K, Tamura H, Saito K, Ishikita H. Nature of Asymmetric Electron Transfer in the Symmetric Pathways of Photosystem I. J Phys Chem B 2021; 125:2879-2885. [DOI: 10.1021/acs.jpcb.0c10885] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Affiliation(s)
- Koji Mitsuhashi
- Department of Applied Chemistry, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8654, Japan
| | - Hiroyuki Tamura
- Department of Applied Chemistry, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8654, Japan
- Research Center for Advanced Science and Technology, The University of Tokyo, 4-6-1 Komaba, Meguro-ku, Tokyo 153-8904, Japan
| | - Keisuke Saito
- Department of Applied Chemistry, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8654, Japan
- Research Center for Advanced Science and Technology, The University of Tokyo, 4-6-1 Komaba, Meguro-ku, Tokyo 153-8904, Japan
| | - Hiroshi Ishikita
- Department of Applied Chemistry, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8654, Japan
- Research Center for Advanced Science and Technology, The University of Tokyo, 4-6-1 Komaba, Meguro-ku, Tokyo 153-8904, Japan
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10
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Chestnut MM, Milikisiyants S, Chatterjee R, Kern J, Smirnov AI. Electronic Structure of the Primary Electron Donor P700+• in Photosystem I Studied by Multifrequency HYSCORE Spectroscopy at X- and Q-Band. J Phys Chem B 2021; 125:36-48. [PMID: 33356277 DOI: 10.1021/acs.jpcb.0c09000] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The primary electron donor P700 of the photosystem I (PSI) is a heterodimer consisting of two chlorophyll molecules. A series of electron-transfer events immediately following the initial light excitation leads to a stabilization of the positive charge by its cation radical form, P700+•. The electronic structure of P700+• and, in particular, its asymmetry with respect to the two chlorophyll monomers is of fundamental interest and is not fully understood up to this date. Here, we apply multifrequency X- (9 GHz) and Q-band (35 GHz) hyperfine sublevel correlation (HYSCORE) spectroscopy to investigate the electron spin density distribution in the cation radical P700+• of PSI from a thermophilic cyanobacterium Thermosynechococcus elongatus. Six 14N and two 1H distinct nuclei have been resolved in the HYSCORE spectra and parameters of the corresponding nuclear hyperfine and quadrupolar hyperfine interactions were obtained by combining the analysis of HYSCORE spectral features with direct numerical simulations. Based on a close similarity of the nuclear quadrupole tensor parameters, all of the resolved 14N nuclei were assigned to six out of total eight available pyrrole ring nitrogen atoms (i.e., four in each of the chlorophylls), providing direct evidence of spin density delocalization over the both monomers in the heterodimer. Using the obtained experimental values of the 14N electron-nuclear hyperfine interaction parameters, the upper limit of the electron spin density asymmetry parameter is estimated as RA/Bupper = 7.7 ± 0.5, while a tentative assignment of 14N observed in the HYSCORE spectra yields RB/A = 3.1 ± 0.5.
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Affiliation(s)
- Melanie M Chestnut
- Department of Chemistry, North Carolina State University, 2620 Yarbrough Drive, Raleigh, North Carolina 27695-8204, United States
| | - Sergey Milikisiyants
- Department of Chemistry, North Carolina State University, 2620 Yarbrough Drive, Raleigh, North Carolina 27695-8204, United States
| | - Ruchira Chatterjee
- Molecular Biophysics and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States
| | - Jan Kern
- Molecular Biophysics and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States
| | - Alex I Smirnov
- Department of Chemistry, North Carolina State University, 2620 Yarbrough Drive, Raleigh, North Carolina 27695-8204, United States
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11
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Poluektov OG, Niklas J, Utschig LM. Spin-Correlated Radical Pairs as Quantum Sensors of Bidirectional ET Mechanisms in Photosystem I. J Phys Chem B 2019; 123:7536-7544. [DOI: 10.1021/acs.jpcb.9b06636] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Affiliation(s)
- Oleg G. Poluektov
- Chemical Sciences and Engineering Division, Argonne National Laboratory, 9700 S. Cass Avenue, Lemont, Illinois 60439, United States
| | - Jens Niklas
- Chemical Sciences and Engineering Division, Argonne National Laboratory, 9700 S. Cass Avenue, Lemont, Illinois 60439, United States
| | - Lisa M. Utschig
- Chemical Sciences and Engineering Division, Argonne National Laboratory, 9700 S. Cass Avenue, Lemont, Illinois 60439, United States
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12
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Kurashov V, Gorka M, Milanovsky GE, Johnson TW, Cherepanov DA, Semenov AY, Golbeck JH. Critical evaluation of electron transfer kinetics in P700–FA/FB, P700–FX, and P700–A1 Photosystem I core complexes in liquid and in trehalose glass. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2018; 1859:1288-1301. [DOI: 10.1016/j.bbabio.2018.09.367] [Citation(s) in RCA: 25] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/07/2018] [Revised: 09/15/2018] [Accepted: 09/17/2018] [Indexed: 12/12/2022]
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13
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Kondo T, Matsuoka M, Azai C, Kobayashi M, Itoh S, Oh-oka H. Light-Induced Electron Spin-Polarized (ESP) EPR Signal of the P800+ Menaquinone– Radical Pair State in Oriented Membranes of Heliobacterium modesticaldum: Role/Location of Menaquinone in the Homodimeric Type I Reaction Center. J Phys Chem B 2018; 122:2536-2543. [DOI: 10.1021/acs.jpcb.7b12171] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Toru Kondo
- Division of Material Science (Physics), Graduate School of Science, Nagoya University, Furocho, Chikusa, Nagoya 464-8602, Japan
| | - Masahiro Matsuoka
- Department of Biological Sciences, Graduate School of Science, Osaka University, Osaka 560-0043, Japan
| | - Chihiro Azai
- Department of Biological Sciences, Graduate School of Science, Osaka University, Osaka 560-0043, Japan
| | - Masami Kobayashi
- Division of Materials Science, University of Tsukuba, Tsukuba, Ibaraki 305-8573, Japan
| | - Shigeru Itoh
- Division of Material Science (Physics), Graduate School of Science, Nagoya University, Furocho, Chikusa, Nagoya 464-8602, Japan
| | - Hirozo Oh-oka
- Department of Biological Sciences, Graduate School of Science, Osaka University, Osaka 560-0043, Japan
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14
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McConnell MD, Sun J, Siavashi R, Webber A, Redding KE, Golbeck JH, van der Est A. Species-dependent alteration of electron transfer in the early stages of charge stabilization in Photosystem I. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2015; 1847:429-440. [DOI: 10.1016/j.bbabio.2015.01.011] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/18/2014] [Revised: 01/21/2015] [Accepted: 01/26/2015] [Indexed: 01/05/2023]
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15
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Witwicki M, Jezierska J. DFT insight into o-semiquinone radicals and Ca2+ ion interaction: structure, g tensor, and stability. Theor Chem Acc 2013. [DOI: 10.1007/s00214-013-1383-3] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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16
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Savitsky A, Niklas J, Golbeck JH, Möbius K, Lubitz W. Orientation Resolving Dipolar High-Field EPR Spectroscopy on Disordered Solids: II. Structure of Spin-Correlated Radical Pairs in Photosystem I. J Phys Chem B 2013; 117:11184-99. [DOI: 10.1021/jp401573z] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Affiliation(s)
- A. Savitsky
- Max Planck Institute for Chemical Energy Conversion, Stiftstr. 34-36, D-45470
Mülheim an der Ruhr, Germany
| | - J. Niklas
- Max Planck Institute for Chemical Energy Conversion, Stiftstr. 34-36, D-45470
Mülheim an der Ruhr, Germany
| | - J. H. Golbeck
- Department of Biochemistry
and
Molecular Biology, Department of Chemistry, The Pennsylvania State University, University Park, Pennsylvania 16802,
United States
| | - K. Möbius
- Max Planck Institute for Chemical Energy Conversion, Stiftstr. 34-36, D-45470
Mülheim an der Ruhr, Germany
- Department of Physics, Free University Berlin, Arnimallee 14, D-14195 Berlin,
Germany
| | - W. Lubitz
- Max Planck Institute for Chemical Energy Conversion, Stiftstr. 34-36, D-45470
Mülheim an der Ruhr, Germany
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17
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Dikanov SA. Resolving protein-semiquinone interactions by two-dimensional ESEEM spectroscopy. ELECTRON PARAMAGNETIC RESONANCE 2012. [DOI: 10.1039/9781849734837-00103] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Affiliation(s)
- S. A. Dikanov
- University of Illinois at Urbana-Champaign, Department of Veterinary Clinical Medicine 190 MSB, 506 S. Mathews Ave., Urbana IL 61801 USA
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18
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Berthold T, Donner von Gromoff E, Santabarbara S, Stehle P, Link G, Poluektov OG, Heathcote P, Beck CF, Thurnauer MC, Kothe G. Exploring the Electron Transfer Pathways in Photosystem I by High-Time-Resolution Electron Paramagnetic Resonance: Observation of the B-Side Radical Pair P700+A1B– in Whole Cells of the Deuterated Green Alga Chlamydomonas reinhardtii at Cryogenic Temperatures. J Am Chem Soc 2012; 134:5563-76. [DOI: 10.1021/ja208806g] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Thomas Berthold
- Department
of Physical Chemistry, University of Freiburg, Albertstrasse 21, 79104 Freiburg,
Germany
| | | | - Stefano Santabarbara
- School of Biological
and Chemical
Sciences, Queen Mary University of London, Mile End Road, London E1 4NS, United Kingdom
| | - Patricia Stehle
- Department
of Physical Chemistry, University of Freiburg, Albertstrasse 21, 79104 Freiburg,
Germany
| | - Gerhard Link
- Department
of Physical Chemistry, University of Freiburg, Albertstrasse 21, 79104 Freiburg,
Germany
| | - Oleg G. Poluektov
- Chemical Sciences and Engineering
Division, Argonne National Laboratory,
9700 South Cass Avenue, Argonne, Illinois 60439, United States
| | - Peter Heathcote
- School of Biological
and Chemical
Sciences, Queen Mary University of London, Mile End Road, London E1 4NS, United Kingdom
| | - Christoph F. Beck
- Faculty of Biology, University of Freiburg, Schaenzlestrasse 1, 79104 Freiburg,
Germany
| | - Marion C. Thurnauer
- Chemical Sciences and Engineering
Division, Argonne National Laboratory,
9700 South Cass Avenue, Argonne, Illinois 60439, United States
| | - Gerd Kothe
- Department
of Physical Chemistry, University of Freiburg, Albertstrasse 21, 79104 Freiburg,
Germany
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19
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Witwicki M, Jezierska J. Effects of Solvents, Ligand Aromaticity, and Coordination Sphere on the g Tensor of Anionic o-Semiquinone Radicals Complexed by Mg2+ Ions: DFT Studies. J Phys Chem B 2011; 115:3172-84. [DOI: 10.1021/jp110515j] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Maciej Witwicki
- Faculty of Chemistry, Wroclaw University, 14 F. Joliot-Curie St., Wroclaw 50-283, Poland
| | - Julia Jezierska
- Faculty of Chemistry, Wroclaw University, 14 F. Joliot-Curie St., Wroclaw 50-283, Poland
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20
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MacMillan F, Kacprzak S, Hellwig P, Grimaldi S, Michel H, Kaupp M. Elucidating mechanisms in haemcopperoxidases: The high-affinity QHbinding site in quinol oxidase as studied by DONUT-HYSCOREspectroscopy and density functional theory. Faraday Discuss 2011; 148:315-44; discussion 421-41. [DOI: 10.1039/c005149g] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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21
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Witwicki M, Jezierska J. Protic and aprotic solvent effect on molecular properties and g-tensors of o-semiquinones with various aromacity and heteroatoms: A DFT study. Chem Phys Lett 2010. [DOI: 10.1016/j.cplett.2010.05.063] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
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22
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Link G, Heinen U, Berthold T, Ohmes E, Weidner JU, Kothe G. High Time Resolution Multifrequency EPR of Radical Pair Intermediates in Photosynthetic Reaction Centers: Structure Determination on a Nanosecond Time Scale. ACTA ACUST UNITED AC 2009. [DOI: 10.1524/zpch.218.1.171.25391] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
Abstract
The primary steps of photosynthesis proceed via light-induced radical pairs as short-lived intermediates. In this paper we discuss novel coherence phenomena which can be observed for these species. It is demonstrated that the analysis of quantum beat oscillations in combination with multifrequency EPR and a magnetically oriented sample represents a powerful structural tool. We expect that this is of general interest, since the detailed structure of radical pair intermediates can be determined on a nanosecond time scale.
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23
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Srinivasan N, Golbeck JH. Protein–cofactor interactions in bioenergetic complexes: The role of the A1A and A1B phylloquinones in Photosystem I. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2009; 1787:1057-88. [DOI: 10.1016/j.bbabio.2009.04.010] [Citation(s) in RCA: 97] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/26/2009] [Revised: 04/14/2009] [Accepted: 04/22/2009] [Indexed: 10/20/2022]
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24
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Niklas J, Epel B, Antonkine ML, Sinnecker S, Pandelia ME, Lubitz W. Electronic Structure of the Quinone Radical Anion A1•− of Photosystem I Investigated by Advanced Pulse EPR and ENDOR Techniques. J Phys Chem B 2009; 113:10367-79. [DOI: 10.1021/jp901890z] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Jens Niklas
- Max-Planck-Institut für Bioanorganische Chemie, Stiftstrasse 34-36, 45470 Mülheim/Ruhr, Germany, and Institut für Experimentalphysik, Freie Universität Berlin, Arnimallee 14, 14195 Berlin, Germany
| | - Boris Epel
- Max-Planck-Institut für Bioanorganische Chemie, Stiftstrasse 34-36, 45470 Mülheim/Ruhr, Germany, and Institut für Experimentalphysik, Freie Universität Berlin, Arnimallee 14, 14195 Berlin, Germany
| | - Mikhail L. Antonkine
- Max-Planck-Institut für Bioanorganische Chemie, Stiftstrasse 34-36, 45470 Mülheim/Ruhr, Germany, and Institut für Experimentalphysik, Freie Universität Berlin, Arnimallee 14, 14195 Berlin, Germany
| | - Sebastian Sinnecker
- Max-Planck-Institut für Bioanorganische Chemie, Stiftstrasse 34-36, 45470 Mülheim/Ruhr, Germany, and Institut für Experimentalphysik, Freie Universität Berlin, Arnimallee 14, 14195 Berlin, Germany
| | - Maria-Eirini Pandelia
- Max-Planck-Institut für Bioanorganische Chemie, Stiftstrasse 34-36, 45470 Mülheim/Ruhr, Germany, and Institut für Experimentalphysik, Freie Universität Berlin, Arnimallee 14, 14195 Berlin, Germany
| | - Wolfgang Lubitz
- Max-Planck-Institut für Bioanorganische Chemie, Stiftstrasse 34-36, 45470 Mülheim/Ruhr, Germany, and Institut für Experimentalphysik, Freie Universität Berlin, Arnimallee 14, 14195 Berlin, Germany
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25
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Solvent effect on EPR, molecular and electronic properties of semiquinone radical derived from 3,4-dihydroxybenzoic acid as model for humic acid transient radicals: High-field EPR and DFT studies. Chem Phys Lett 2009. [DOI: 10.1016/j.cplett.2009.03.035] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
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26
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Srinivasan N, Karyagina I, Bittl R, van der Est A, Golbeck JH. Role of the Hydrogen Bond from Leu722 to the A1A Phylloquinone in Photosystem I. Biochemistry 2009; 48:3315-24. [DOI: 10.1021/bi802340s] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Nithya Srinivasan
- Department of Biochemistry and Molecular Biology, The Pennsylvania State University, University Park, Pennsylvania 16802, Institut für Experimental Physik, Fachbereich Physik, Freie Universität Berlin, Arnimallee 14, D14195 Berlin, Germany, Department of Chemistry, Brock University, 500 Glenridge Avenue, St. Catharines, ON L2S 3A1, Canada, and Department of Chemistry, The Pennsylvania State University, University Park, Pennsylvania 16802
| | - Irina Karyagina
- Department of Biochemistry and Molecular Biology, The Pennsylvania State University, University Park, Pennsylvania 16802, Institut für Experimental Physik, Fachbereich Physik, Freie Universität Berlin, Arnimallee 14, D14195 Berlin, Germany, Department of Chemistry, Brock University, 500 Glenridge Avenue, St. Catharines, ON L2S 3A1, Canada, and Department of Chemistry, The Pennsylvania State University, University Park, Pennsylvania 16802
| | - Robert Bittl
- Department of Biochemistry and Molecular Biology, The Pennsylvania State University, University Park, Pennsylvania 16802, Institut für Experimental Physik, Fachbereich Physik, Freie Universität Berlin, Arnimallee 14, D14195 Berlin, Germany, Department of Chemistry, Brock University, 500 Glenridge Avenue, St. Catharines, ON L2S 3A1, Canada, and Department of Chemistry, The Pennsylvania State University, University Park, Pennsylvania 16802
| | - Art van der Est
- Department of Biochemistry and Molecular Biology, The Pennsylvania State University, University Park, Pennsylvania 16802, Institut für Experimental Physik, Fachbereich Physik, Freie Universität Berlin, Arnimallee 14, D14195 Berlin, Germany, Department of Chemistry, Brock University, 500 Glenridge Avenue, St. Catharines, ON L2S 3A1, Canada, and Department of Chemistry, The Pennsylvania State University, University Park, Pennsylvania 16802
| | - John H. Golbeck
- Department of Biochemistry and Molecular Biology, The Pennsylvania State University, University Park, Pennsylvania 16802, Institut für Experimental Physik, Fachbereich Physik, Freie Universität Berlin, Arnimallee 14, D14195 Berlin, Germany, Department of Chemistry, Brock University, 500 Glenridge Avenue, St. Catharines, ON L2S 3A1, Canada, and Department of Chemistry, The Pennsylvania State University, University Park, Pennsylvania 16802
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27
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Witwicki M, Jaszewski AR, Jezierska J, Jerzykiewicz M, Jezierski A. The pH-induced shift in the g-tensor components of semiquinone-type radicals in humic acids – DFT and EPR studies. Chem Phys Lett 2008. [DOI: 10.1016/j.cplett.2008.07.086] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
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28
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High-Time Resolution Electron Paramagnetic Resonance Study of Quantum Beat Oscillations Observed in Photosynthetic Reaction Center Proteins. BIOPHYSICAL TECHNIQUES IN PHOTOSYNTHESIS 2008. [DOI: 10.1007/978-1-4020-8250-4_15] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
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29
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Yulikov M, Sterrer M, Heyde M, Rust HP, Risse T, Freund HJ, Pacchioni G, Scagnelli A. Binding of single gold atoms on thin MgO(001) films. PHYSICAL REVIEW LETTERS 2006; 96:146804. [PMID: 16712109 DOI: 10.1103/physrevlett.96.146804] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/02/2005] [Indexed: 05/09/2023]
Abstract
In the present Letter the first electron paramagnetic resonance spectra of single metal atoms on a single crystalline oxide surface are presented. For Au atoms on a MgO(001) film investigated here an analysis of the angular dependent resonance positions and the hyperfine coupling to (17)O shows that the atoms are bound on top of oxygen ions on the terrace of the film. This result is in perfect agreement with scanning tunneling microscopy measurements at 5 K presented here. The measured hyperfine matrix components allow an experimental verification of the theoretically proposed binding mechanism of Au atoms on MgO. In particular, the large reduction of the isotropic hyperfine coupling constant of supported Au as compared to free atoms is not due to a charge transfer at the interface but a hybridization of orbitals and a resulting polarization of the unpaired electron.
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Affiliation(s)
- Maxim Yulikov
- Department of Chemical Physics, Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, D-14195 Berlin, Germany
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30
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Link G, Poluektov OG, Utschig LM, Lalevée J, Yago T, Weidner JU, Thurnauer MC, Kothe G. Structural organization in photosynthetic proteins as studied by high-field EPR of spin-correlated radical pair states. MAGNETIC RESONANCE IN CHEMISTRY : MRC 2005; 43 Spec no.:S103-9. [PMID: 16235208 DOI: 10.1002/mrc.1678] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
Abstract
We demonstrate the potential of high-field (HF) time-resolved electron paramagnetic resonance (EPR) spectroscopy to reveal unique information about electron transfer processes and the structure of photosynthetic systems. The lineshapes and electron spin polarization (ESP) of spin-correlated radical pair (SCRP) spectra recorded with HF-EPR are very sensitive to the magnetic parameters, interactions, and geometry of the radicals in the pair. This sensitivity facilitates an analysis of more sophisticated models and methods to reveal the important relationship between structural organization and light-induced electron transfer of the photosynthetic proteins. In this review, we report on a new time-resolved HF and multi-frequency EPR approach developed in the Freiburg laboratory in cooperation with the Argonne Photosynthesis group. The method is designed to probe the geometric structure of charge separated states in the photosynthetic membrane. First, we discuss the magneto-orientation of photosynthetic cyanobacteria as revealed by time-resolved HF-EPR of SCRPs. Then, we demonstrate how the three-dimensional structure of the SCRP P700(+)A1 from photosystem I of oxygenic photosynthesis and its arrangement in the membrane is obtained from application of multi-frequency including time-resolved HF-EPR techniques.
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Affiliation(s)
- Gerhard Link
- Department of Physical Chemistry, University of Freiburg, Albertstr. 21, D-79104 Freiburg, Germany
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31
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The influence of the structure of the radical cation dimer pair of aromatic molecules on the principal values of a g-tensor: DFT predictions. Chem Phys Lett 2005. [DOI: 10.1016/j.cplett.2005.03.012] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
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32
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Pushkar YN, Karyagina I, Stehlik D, Brown S, van der Est A. Recruitment of a Foreign Quinone into the A1 Site of Photosystem I. J Biol Chem 2005; 280:12382-90. [PMID: 15640524 DOI: 10.1074/jbc.m412940200] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
In photosystem I (PS I), phylloquinone (PhQ) acts as a low potential electron acceptor during light-induced electron transfer (ET). The origin of the very low midpoint potential of the quinone is investigated by introducing anthraquinone (AQ) into PS I in the presence and absence of the iron-sulfur clusters. Solvent extraction and reincubation is used to obtain PS I particles containing AQ and the iron-sulfur clusters, whereas incubation of the menB rubA double mutant yields PS I with AQ in the PhQ site but no iron-sulfur clusters. Transient electron paramagnetic resonance spectroscopy is used to investigate the orientation of AQ in the binding site and the ET kinetics. The low temperature spectra suggest that the orientation of AQ in all samples is the same as that of PhQ in native PS I. In PS I containing the iron sulfur clusters, (i) the rate of forward electron transfer from the AQ*- to F(X) is found to be faster than from PhQ*- to F(X), and (ii) the spin polarization patterns provide indirect evidence that the preceding ET step from A0*- to quinone is slower than in the native system. The changes in the kinetics are in accordance with the more negative reduction midpoint potential of AQ. Moreover, a comparison of the spectra in the presence and absence of the iron-sulfur clusters suggests that the midpoint potential of AQ is more negative in the presence of F(X). The electron transfer from the AQ- to F(X) is found to be thermally activated with a lower apparent activation energy than for PhQ in native PS I. The spin polarization patterns show that the triplet character in the initial state of P700)*+AQ*- increases with temperature. This behavior is rationalized in terms of a model involving a distribution of lifetimes/redox potentials for A0 and related competition between charge recombination and forward electron transfer from the radical pair P700*+A0*-.
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Affiliation(s)
- Yulia N Pushkar
- Institut für Experimentalphysik, Freie Universität Berlin, Arnimallee 14, D-14195 Berlin, Germany
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33
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Bittl R, Weber S. Transient radical pairs studied by time-resolved EPR. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2005; 1707:117-26. [PMID: 15721610 DOI: 10.1016/j.bbabio.2004.03.012] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/30/2003] [Accepted: 03/05/2004] [Indexed: 12/20/2022]
Abstract
Photogenerated short-lived radical pairs (RP) are common in biological photoprocesses such as photosynthesis and enzymatic DNA repair. They can be favorably probed by time-resolved electron paramagnetic resonance (EPR) methods with adequate time resolution. Two EPR techniques have proven to be particularly useful to extract information on the working states of photoinduced biological processes that is only difficult or sometimes even impossible to obtain by other types of spectroscopy. Firstly, transient EPR yields crucial information on the chemical nature and the geometry of the individual RP halves in a doublet-spin pair generated by a short laser pulse. This time-resolved method is applicable in all magnetic field/microwave frequency regimes that are used for continuous-wave EPR, and is nowadays routinely utilized with a time resolution reaching about 10 ns. Secondly, a pulsed EPR method named out-of-phase electron spin echo envelope modulation (OOP-ESEEM) is increasingly becoming popular. By this pulsed technique, the mutual spin-spin interaction between the RP halves in a doublet-spin pair manifests itself as an echo modulation detected as a function of the microwave-pulse spacing of a two-pulse echo sequence subsequent to a laser pulse. From the dipolar coupling, the distance between the radicals is readily derived. Since the spin-spin interaction parameters are typically not observable by transient EPR, the two techniques complement each other favorably. Both EPR methods have recently been applied to a variety of light-induced RPs in photobiology. This review summarizes the results obtained from such studies in the fields of plant and bacterial photosynthesis and DNA repair mediated by the enzyme DNA photolyase.
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Affiliation(s)
- Robert Bittl
- Institut für Experimentalphysik, Freie Universität Berlin, Arnimallee 14, 14195 Berlin, Germany.
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34
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An EPR/ENDOR study of the asymmetric hydrogen bond between the quinone electron acceptor and the protein backbone in Photosystem I. J Mol Struct 2004. [DOI: 10.1016/j.molstruc.2004.02.015] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
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35
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Heinen U, Poluektov O, Stavitski E, Berthold T, Ohmes E, Schlesselman SL, Golecki JR, Moro GJ, Levanon H, Thurnauer MC, Kothe G. Magnetic-Field-Induced Orientation of Photosynthetic Reaction Centers, As Revealed by Time-Resolved D-Band Electron Paramagnetic Resonance of Spin-Correlated Radical Pairs. II. Field Dependence of the Alignment. J Phys Chem B 2004. [DOI: 10.1021/jp036232c] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Affiliation(s)
- Ulrich Heinen
- Department of Physical Chemistry, University of Freiburg, Albertstrasse 21, D-79104, Freiburg/Germany, Chemistry Division, Argonne National Laboratory, 9700 South Cass Avenue, Argonne, Illinois 60439, Department of Physical Chemistry, The Hebrew University of Jerusalem, Jerusalem 91904, Israel, Department of Microbiology, University of Freiburg, Schänzlestrasse 1, D-79104 Freiburg/Germany, and Department of Physical Chemistry, University of Padova, Via Loredan 2, I-35131 Padova, Italy
| | - Oleg Poluektov
- Department of Physical Chemistry, University of Freiburg, Albertstrasse 21, D-79104, Freiburg/Germany, Chemistry Division, Argonne National Laboratory, 9700 South Cass Avenue, Argonne, Illinois 60439, Department of Physical Chemistry, The Hebrew University of Jerusalem, Jerusalem 91904, Israel, Department of Microbiology, University of Freiburg, Schänzlestrasse 1, D-79104 Freiburg/Germany, and Department of Physical Chemistry, University of Padova, Via Loredan 2, I-35131 Padova, Italy
| | - Eli Stavitski
- Department of Physical Chemistry, University of Freiburg, Albertstrasse 21, D-79104, Freiburg/Germany, Chemistry Division, Argonne National Laboratory, 9700 South Cass Avenue, Argonne, Illinois 60439, Department of Physical Chemistry, The Hebrew University of Jerusalem, Jerusalem 91904, Israel, Department of Microbiology, University of Freiburg, Schänzlestrasse 1, D-79104 Freiburg/Germany, and Department of Physical Chemistry, University of Padova, Via Loredan 2, I-35131 Padova, Italy
| | - Thomas Berthold
- Department of Physical Chemistry, University of Freiburg, Albertstrasse 21, D-79104, Freiburg/Germany, Chemistry Division, Argonne National Laboratory, 9700 South Cass Avenue, Argonne, Illinois 60439, Department of Physical Chemistry, The Hebrew University of Jerusalem, Jerusalem 91904, Israel, Department of Microbiology, University of Freiburg, Schänzlestrasse 1, D-79104 Freiburg/Germany, and Department of Physical Chemistry, University of Padova, Via Loredan 2, I-35131 Padova, Italy
| | - Ernst Ohmes
- Department of Physical Chemistry, University of Freiburg, Albertstrasse 21, D-79104, Freiburg/Germany, Chemistry Division, Argonne National Laboratory, 9700 South Cass Avenue, Argonne, Illinois 60439, Department of Physical Chemistry, The Hebrew University of Jerusalem, Jerusalem 91904, Israel, Department of Microbiology, University of Freiburg, Schänzlestrasse 1, D-79104 Freiburg/Germany, and Department of Physical Chemistry, University of Padova, Via Loredan 2, I-35131 Padova, Italy
| | - Sandra L. Schlesselman
- Department of Physical Chemistry, University of Freiburg, Albertstrasse 21, D-79104, Freiburg/Germany, Chemistry Division, Argonne National Laboratory, 9700 South Cass Avenue, Argonne, Illinois 60439, Department of Physical Chemistry, The Hebrew University of Jerusalem, Jerusalem 91904, Israel, Department of Microbiology, University of Freiburg, Schänzlestrasse 1, D-79104 Freiburg/Germany, and Department of Physical Chemistry, University of Padova, Via Loredan 2, I-35131 Padova, Italy
| | - Jochen R. Golecki
- Department of Physical Chemistry, University of Freiburg, Albertstrasse 21, D-79104, Freiburg/Germany, Chemistry Division, Argonne National Laboratory, 9700 South Cass Avenue, Argonne, Illinois 60439, Department of Physical Chemistry, The Hebrew University of Jerusalem, Jerusalem 91904, Israel, Department of Microbiology, University of Freiburg, Schänzlestrasse 1, D-79104 Freiburg/Germany, and Department of Physical Chemistry, University of Padova, Via Loredan 2, I-35131 Padova, Italy
| | - Giorgio J. Moro
- Department of Physical Chemistry, University of Freiburg, Albertstrasse 21, D-79104, Freiburg/Germany, Chemistry Division, Argonne National Laboratory, 9700 South Cass Avenue, Argonne, Illinois 60439, Department of Physical Chemistry, The Hebrew University of Jerusalem, Jerusalem 91904, Israel, Department of Microbiology, University of Freiburg, Schänzlestrasse 1, D-79104 Freiburg/Germany, and Department of Physical Chemistry, University of Padova, Via Loredan 2, I-35131 Padova, Italy
| | - Haim Levanon
- Department of Physical Chemistry, University of Freiburg, Albertstrasse 21, D-79104, Freiburg/Germany, Chemistry Division, Argonne National Laboratory, 9700 South Cass Avenue, Argonne, Illinois 60439, Department of Physical Chemistry, The Hebrew University of Jerusalem, Jerusalem 91904, Israel, Department of Microbiology, University of Freiburg, Schänzlestrasse 1, D-79104 Freiburg/Germany, and Department of Physical Chemistry, University of Padova, Via Loredan 2, I-35131 Padova, Italy
| | - Marion C. Thurnauer
- Department of Physical Chemistry, University of Freiburg, Albertstrasse 21, D-79104, Freiburg/Germany, Chemistry Division, Argonne National Laboratory, 9700 South Cass Avenue, Argonne, Illinois 60439, Department of Physical Chemistry, The Hebrew University of Jerusalem, Jerusalem 91904, Israel, Department of Microbiology, University of Freiburg, Schänzlestrasse 1, D-79104 Freiburg/Germany, and Department of Physical Chemistry, University of Padova, Via Loredan 2, I-35131 Padova, Italy
| | - Gerd Kothe
- Department of Physical Chemistry, University of Freiburg, Albertstrasse 21, D-79104, Freiburg/Germany, Chemistry Division, Argonne National Laboratory, 9700 South Cass Avenue, Argonne, Illinois 60439, Department of Physical Chemistry, The Hebrew University of Jerusalem, Jerusalem 91904, Israel, Department of Microbiology, University of Freiburg, Schänzlestrasse 1, D-79104 Freiburg/Germany, and Department of Physical Chemistry, University of Padova, Via Loredan 2, I-35131 Padova, Italy
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36
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Kacprzak S, Kaupp M. Electronic g-Tensors of Semiquinones in Photosynthetic Reaction Centers. A Density Functional Study. J Phys Chem B 2004. [DOI: 10.1021/jp036322h] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Sylwia Kacprzak
- Institut für Anorganische Chemie, Universität Würzburg, Am Hubland, D 97074 Würzburg, Germany
| | - Martin Kaupp
- Institut für Anorganische Chemie, Universität Würzburg, Am Hubland, D 97074 Würzburg, Germany
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37
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Time-Resolved High-Frequency and Multifrequency EPR Studies of Spin-Correlated Radical Pairs in Photosynthetic Reaction Center Proteins. ACTA ACUST UNITED AC 2004. [DOI: 10.1007/978-1-4757-4379-1_6] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/12/2023]
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38
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Ishikita H, Knapp EW. Redox potential of quinones in both electron transfer branches of photosystem I. J Biol Chem 2003; 278:52002-11. [PMID: 12972408 DOI: 10.1074/jbc.m306434200] [Citation(s) in RCA: 95] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The redox potentials of the two electron transfer (ET) active quinones in the central part of photosystem I (PSI) were determined by evaluating the electrostatic energies from the solution of the Poisson-Boltzmann equation based on the crystal structure. The calculated redox potentials are -531 mV for A1A and -686 mV for A1B. From these results we conclude the following. (i) Both branches are active with a much faster ET in the B-branch than in the A-branch. (ii) The measured lifetime of 200-290 ns of reduced quinones agrees with the estimate for the A-branch and corroborates with an uphill ET from this quinone to the iron-sulfur cluster as observed in recent kinetic measurements. (iii) The electron paramagnetic resonance spectroscopic data refer to the A-branch quinone where the corresponding ET is uphill in energy. The negative redox potential of A1 in PSI is primarily because of the influence from the negatively charged FX, in contrast to the positive shift on the quinone redox potential in bacterial reaction center and PSII that is attributed to the positively charged non-heme iron atom. The conserved residue Asp-B575 changes its protonation state after quinone reduction. The difference of 155 mV in the quinone redox potentials of the two branches were attributed to the conformation of the backbone with a large contribution from Ser-A692 and Ser-B672 and to the side chain of Asp-B575, whose protonation state couples differently with the formation of the quinone radicals.
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Affiliation(s)
- Hiroshi Ishikita
- Department of Biology, Chemistry, and Pharmacy, Institute of Chemistry, Free University of Berlin, Takustrasse 6, Berlin D-14195, Germany
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Golbeck JH. The binding of cofactors to photosystem I analyzed by spectroscopic and mutagenic methods. ANNUAL REVIEW OF BIOPHYSICS AND BIOMOLECULAR STRUCTURE 2003; 32:237-56. [PMID: 12524325 DOI: 10.1146/annurev.biophys.32.110601.142356] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
This review focuses on cofactor-ligand and protein-protein interactions within the photosystem I reaction center. The topics include a description of the electron transfer cofactors, the mode of binding of the cofactors to protein-bound ligands, and a description of intraprotein contacts that ultimately allow photosystem I to be assembled (in cyanobacteria) from 96 chlorophylls, 22 carotenoids, 2 phylloquinones, 3 [4Fe-4S] clusters, and 12 polypeptides. During the 15 years that have elapsed from the first report of crystals to the atomic-resolution X-ray crystal structure, cofactor-ligand interactions and protein-protein interactions were systematically being explored by spectroscopic and genetic methods. This article charts the interplay between these disciplines and assesses how good the early insights were in light of the current structure of photosystem I.
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Affiliation(s)
- John H Golbeck
- Department of Biochemistry and Molecular Biology, The Pennsylvania State University, University Park, Pennsylvania 16802, USA.
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Xu W, Chitnis P, Valieva A, van der Est A, Pushkar YN, Krzystyniak M, Teutloff C, Zech SG, Bittl R, Stehlik D, Zybailov B, Shen G, Golbeck JH. Electron transfer in cyanobacterial photosystem I: I. Physiological and spectroscopic characterization of site-directed mutants in a putative electron transfer pathway from A0 through A1 to FX. J Biol Chem 2003; 278:27864-75. [PMID: 12721305 DOI: 10.1074/jbc.m302962200] [Citation(s) in RCA: 72] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The Photosystem I (PS I) reaction center contains two branches of nearly symmetric cofactors bound to the PsaA and PsaB heterodimer. From the x-ray crystal structure it is known that Trp697PsaA and Trp677PsaB are pi-stacked with the head group of the phylloquinones and are H-bonded to Ser692PsaA and Ser672PsaB, whereas Arg694PsaA and Arg674PsaB are involved in a H-bonded network of side groups that connects the binding environments of the phylloquinones and FX. The mutants W697FPsaA, W677FPsaB, S692CPsaA, S672CPsaB, R694APsaA, and R674APsaB were constructed and characterized. All mutants grew photoautotrophically, yet all showed diminished growth rates compared with the wild-type, especially at higher light intensities. EPR and electron nuclear double resonance (ENDOR) studies at both room temperature and in frozen solution showed that the PsaB mutants were virtually identical to the wild-type, whereas significant effects were observed in the PsaA mutants. Spin polarized transient EPR spectra of the P700+A1- radical pair show that none of the mutations causes a significant change in the orientation of the measured phylloquinone. Pulsed ENDOR spectra reveal that the W697FPsaA mutation leads to about a 5% increase in the hyperfine coupling of the methyl group on the phylloquinone ring, whereas the S692CPsaA mutation causes a similar decrease in this coupling. The changes in the methyl hyperfine coupling are also reflected in the transient EPR spectra of P700+A1- and the CW EPR spectra of photoaccumulated A1-. We conclude that: (i) the transient EPR spectra at room temperature are predominantly from radical pairs in the PsaA branch of cofactors; (ii) at low temperature the electron cycle involving P700 and A1 similarly occurs along the PsaA branch of cofactors; and (iii) mutation of amino acids in close contact with the PsaA side quinone leads to changes in the spin density distribution of the reduced quinone observed by EPR.
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Affiliation(s)
- Wu Xu
- Department of Biochemistry, Biophysics, and Molecular Biology, Iowa State University, Ames, Iowa 50011, USA
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Andersson KK, Schmidt PP, Katterle B, Strand KR, Palmer AE, Lee SK, Solomon EI, Gräslund A, Barra AL. Examples of high-frequency EPR studies in bioinorganic chemistry. J Biol Inorg Chem 2003; 8:235-47. [PMID: 12589559 DOI: 10.1007/s00775-002-0429-0] [Citation(s) in RCA: 65] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2002] [Accepted: 11/04/2002] [Indexed: 10/18/2022]
Abstract
Low-temperature EPR spectroscopy with frequencies between 95 and 345 GHz and magnetic fields up to 12 T has been used to study metal sites in proteins or inorganic complexes and free radicals. The high-field EPR method was used to resolve g-value anisotropy by separating it from overlapping hyperfine couplings. The presence of hydrogen bonding interactions to the tyrosyl radical oxygens in ribonucleotide reductases were detected. At 285 GHz the g-value anisotropy from the rhombic type 2 Cu(II) signal in the enzyme laccase has its g-value anisotropy clearly resolved from slightly different overlapping axial species. Simple metal site systems with S>1/2 undergo a zero-field splitting, which can be described by the spin Hamiltonian. From high-frequency EPR, the D values that are small compared to the frequency (high-field limit) can be determined directly by measuring the distance of the outermost signal to the center of the spectrum, which corresponds to (2 S-1)* mid R: Dmid R: For example, D values of 0.8 and 0.3 cm(-1) are observed for S=5/2 Fe(III)-EDTA and transferrin, respectively. When D values are larger compared to the frequency and in the case of half-integer spin systems, they can be obtained from the frequency dependence of the shifts of g(eff), as observed for myoglobin in the presence ( D=5 cm(-1)) or absence ( D=9.5 cm(-1)) of fluoride. The 285 and 345 GHz spectra of the Fe(II)-NO-EDTA complex show that it is best described as a S=3/2 system with D=11.5 cm(-1), E=0.1 cm(-1), and g(x)= g(y)= g(z)=2.0. Finally, the effects of HF-EPR on X-band EPR silent states and weak magnetic interactions are demonstrated.
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Affiliation(s)
- K Kristoffer Andersson
- Department of Biochemistry, University of Oslo, Blindern, PO Box 1041, 0316, Oslo, Norway.
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Fuhs M, Schnegg A, Prisner T, Köhne I, Hanley J, Rutherford A, Möbius K. Orientation selection in photosynthetic PS I multilayers: structural investigation of the charge separated state P(700)(+z.rad;)A(1)(-z.rad;) by high-field/high-frequency time-resolved EPR at 3.4 T/95 GHz. BIOCHIMICA ET BIOPHYSICA ACTA 2002; 1556:81-8. [PMID: 12351221 DOI: 10.1016/s0005-2728(02)00338-9] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
The radical-pair state of the primary electron donor and the secondary electron acceptor (P(700)(+z.rad;)A(1)(-z.rad;)) of the photosynthetic reaction center (RC) photosystem I (PS I) of Synechocystis PCC 6803 was studied by time-resolved electron paramagnetic resonance (TREPR) at high field/high frequency (3.4 T/95 GHz) using orientation selection in multilayers. The goal of the present article is to work out the basis for future studies, in which the improved resolution of such multilayers may be used to detect mutation-induced structural changes of PS I in membrane preparations. This approach is particularly interesting for systems that cannot be prepared as single crystals. However, in order to use such multilayers for structural investigations of protein complexes, it is necessary to know their orientation distribution. PS I was chosen as a test example because the wild type was recently crystallized and its X-ray structure determined to 2.5 A resolution [Nature 411 (2001) 909]. On the basis of our experimental results we determined the orientation distribution. Furthermore, a simulation model for the general case in which the orientation distribution is not axially symmetric about the C(2) symmetry axis of the RC is developed and discussed. Spectra simulations show that changes in the TREPR spectra of PS I are much more significant for these oriented multilayers than for disordered samples. In this way the use of oriented multilayers, in conjunction with multifrequency TREPR measurements on oriented as well as on disordered samples, is a promising approach for studies of structural changes of PS I systems that are induced by point mutations.
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Affiliation(s)
- M Fuhs
- Institut für Experimentalphysik, Freie Universität Berlin, Arnimallee 14, D-14195, Berlin, Germany.
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Poluektov OG, Utschig LM, Schlesselman SL, Lakshmi KV, Brudvig GW, Kothe G, Thurnauer MC. Electronic Structure of the P700Special Pair from High-Frequency Electron Paramagnetic Resonance Spectroscopy. J Phys Chem B 2002. [DOI: 10.1021/jp021465+] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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44
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Fursman CE, Teutloff C, Bittl R. Pulsed ENDOR Studies of Short-Lived Spin-Correlated Radical Pairs in Photosynthetic Reaction Centers. J Phys Chem B 2002. [DOI: 10.1021/jp0257202] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Catherine E. Fursman
- Max-Volmer-Laboratorium, Technische Universität Berlin, Strasse des 17. Juni 135, 10623 Berlin, Germany
| | - Christian Teutloff
- Max-Volmer-Laboratorium, Technische Universität Berlin, Strasse des 17. Juni 135, 10623 Berlin, Germany
| | - Robert Bittl
- Max-Volmer-Laboratorium, Technische Universität Berlin, Strasse des 17. Juni 135, 10623 Berlin, Germany
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SALIKHOV KEVM, ZECH STEPHANG, STEHLIK DIETMAR. Light induced radical pair intermediates in photosynthetic reaction centres in contact with an observer spin label: spin dynamics and effects on transient EPR spectra. Mol Phys 2002. [DOI: 10.1080/00268970110112336] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
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46
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KANDRASHKIN YUE, VOLLMANN W, STEHLIK D, SALIKHOV K, VAN DER EST A. The magnetic field dependence of the electron spin polarization in consecutive spin correlated radical pairs in type I photosynthetic reaction centres. Mol Phys 2002. [DOI: 10.1080/00268970110118240] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
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Kaupp M, Remenyi C, Vaara J, Malkina OL, Malkin VG. Density functional calculations of electronic g-tensors for semiquinone radical anions. The role of hydrogen bonding and substituent effects. J Am Chem Soc 2002; 124:2709-22. [PMID: 11890822 DOI: 10.1021/ja0162764] [Citation(s) in RCA: 88] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
A recently developed density functional approach has been used to carry out a systematic computational study of electronic g-tensors for a series of 1,4-semiquinone radical anions. Good agreement with high-field EPR data in frozen 2-propanol is achieved only after taking into account the significant reduction of g-tensor anisotropy caused by hydrogen bonding to solvent molecules. The comparison of various model systems for the first solvation shell suggests two hydrogen bonds from 2-propanol molecules to each of the carbonyl groups of the radical anions, and one additional hydrogen bond to each of the methoxy groups in ubiquinone systems. 2-Propanol makes stronger hydrogen bonds than water and thus influences g-tensor anisotropy more strongly. Substituent effects at the semiquinone are reproduced quantitatively by the calculations. The g-tensor anisotropy is influenced significantly by the conformations of methyl and methoxy substituents, with opposite contributions. Analyses and interpretations of the interrelations between structure, bonding, and spectroscopic data are provided. The relevance of the computational results for the EPR spectroscopy of semiquinone radical anions in photosynthetic reaction centers is discussed.
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Affiliation(s)
- Martin Kaupp
- Institut für Anorganische Chemie, Universität Würzburg, Am Hubland, D-97074 Würzburg, Germany.
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Webber AN, Lubitz W. P700: the primary electron donor of photosystem I. BIOCHIMICA ET BIOPHYSICA ACTA 2001; 1507:61-79. [PMID: 11687208 DOI: 10.1016/s0005-2728(01)00198-0] [Citation(s) in RCA: 211] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The primary electron donor of photosystem I, P700, is a chlorophyll species that in its excited state has a potential of approximately -1.2 V. The precise chemical composition and electronic structure of P700 is still unknown. Recent evidence indicates that P700 is a dimer of one chlorophyll (Chl) a and one Chl a'. The Chl a' and Chl a are axially coordinated by His residues provided by protein subunits PsaA and PsaB, respectively. The Chl a', but not the Chl a, is also H-bonded to the protein. The H-bonding is likely responsible for selective insertion of Chl a' into the reaction center. EPR studies of P700(+*) in frozen solution and single crystals indicate a large asymmetry in the electron spin and charge distribution towards one Chl of the dimer. Molecular orbital calculations indicate that H-bonding will specifically stabilize the Chl a'-side of the dimer, suggesting that the unpaired electron would predominantly reside on the Chl a. This is supported by results of specific mutagenesis of the PsaA and PsaB axial His residues, which show that only mutations of the PsaB subunit significantly alter the hyperfine coupling constants associated with a single Chl molecule. The PsaB mutants also alter the microwave induced triplet-minus-singlet spectrum indicating that the triplet state is localized on the same Chl. Excitonic coupling between the two Chl a of P700 is weak due to the distance and overlap of the porphyrin planes. Evidence of excitonic coupling is found in PsaB mutants which show a new bleaching band at 665 nm that likely represents an increased intensity of the upper exciton band of P700. Additional properties of P700 that may give rise to its unusually low potential are discussed.
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Affiliation(s)
- A N Webber
- Department of Plant Biology and Center for the Study of Early Events in Photosynthesis, Arizona State University, Tempe 85287-1601, USA.
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van der Est A. Light-induced spin polarization in type I photosynthetic reaction centres. BIOCHIMICA ET BIOPHYSICA ACTA 2001; 1507:212-25. [PMID: 11687216 DOI: 10.1016/s0005-2728(01)00204-3] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The use of light-induced spin polarization to study the structure and function of type I reaction centres is reviewed. The absorption of light by these systems generates a series of sequential radical pairs, which exhibit spin polarization as a result of the correlation of the unpaired electron spins. A description of how the polarization patterns can be used to deduce the relative orientation of the radicals is given and the most important structural results from such studies on photosystem I (PS I) are summarized. Quinone exchange experiments which demonstrate the influence of protein-cofactor interactions on the polarization patterns are discussed. The results show that there are significant differences between the binding sites of the primary quinone acceptors in PS I and purple bacterial reaction centres and suggest that pi-pi interactions probably play a more important role in PS I. Studies using spin-polarized EPR transients and spectra to investigate the electron transfer pathway and kinetics are also reviewed. The results from PS I, green-sulphur bacteria and Heliobacteria are compared and the controversy surrounding the role of a quinone in the electron transfer in the latter two systems is discussed.
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Affiliation(s)
- A van der Est
- Department of Chemistry, Brock University, 500 Glenridge Avenue, L2S 3A1, St. Catharines, ON, Canada.
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Bittl R, Zech SG. Pulsed EPR spectroscopy on short-lived intermediates in Photosystem I. BIOCHIMICA ET BIOPHYSICA ACTA 2001; 1507:194-211. [PMID: 11687215 DOI: 10.1016/s0005-2728(01)00210-9] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
The application of pulsed electron paramagnetic resonance spectroscopy on short-lived intermediates in Photosystem I is reviewed. The spin polarization in light-induced radical pairs gives rise to a phase shifted 'out-of-phase' electron spin echo signal. This echo signal shows a prominent modulation of its intensity as a function of the spacing between the two microwave pulses. Its modulation frequency is determined by the electron-electron spin couplings within the radical pair. Thereby, the measurement of the dipolar coupling gives direct information about the spin-spin distance and can therefore be used to determine cofactor distances with high precision. Application of this technique to the radical pair P(*+)(700)A(*-)(1) in Photosystem I is discussed. Moreover, if oriented samples (e.g. single crystals) are used, the angular dependence of the dipolar coupling can be used to derive the orientation of the axis connecting donor and acceptor with respect to an external (crystal) axes system. Using out-of-phase electron spin echo envelope modulation spectroscopy, the localization of the secondary acceptor quinone A(1) has become possible.
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Affiliation(s)
- R Bittl
- Max-Volmer-Institut, Technische Universität Berlin, Germany.
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