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Chen H, Case DA, Dismukes GC. Reconciling Structural and Spectroscopic Fingerprints of the Oxygen-Evolving Complex of Photosystem II: A Computational Study of the S 2 State. J Phys Chem B 2018; 122:11868-11882. [PMID: 30444623 DOI: 10.1021/acs.jpcb.8b08147] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
The catalytic cycle of photosynthetic water oxidation occurs at the Mn4CaO5 oxygen-evolving complex (OEC) of photosystem II. Extensive spectroscopic data have been collected on the intermediates, especially the S2 (Kok) state, although the proton and electron inventories (Mn oxidation states) are still uncertain. The "high oxidation" paradigm assigns S2 Mn oxidation level (III, IV, IV, IV) or (IV, IV, IV, III), whereas a "low oxidation" paradigm posits two additional electrons. Here, we investigate the geometric (X-ray diffraction, extended X-ray absorption fine structure) and spectroscopic (electron paramagnetic resonance (EPR), electron nuclear double resonance (ENDOR)) properties of the S2 state using quantum chemical density functional theory calculations, focusing on the neglected low paradigm. Two interconvertible electronic spin configurations are predicted as ground states, producing multiline ( S = 1/2) and broad ( S = 5/2) EPR signals in the low paradigm oxidation state (III, IV, III, III) and with W2 as OH- and O5 as OH-. They have "open" ( S = 5/2) and "closed" ( S = 1/2) Mn3CaO4-cubane geometries. Other energetically accessible isomers with ground spin states 1/2, 7/2, 9/2, or 11/2 can be obtained through perturbations of hydrogen-bonding networks (e.g., H+ from His337 to O3 or W2), consistent with experimental observations. Conformers with the low oxidation state configuration (III, IV, IV, II) also become energetically accessible when the protonation states are O5 (OH-), W2 (H2O), and neutral His337. The configuration with (III, IV, III, III) agrees well with earlier low-temperature EPR and ENDOR interpretations, whereas the MnII-containing configuration agrees partially with recent ENDOR data. However, the low oxidation paradigm does not yield isotropic ligand hyperfine interactions in good agreement with observed values. We conclude that the low Mn oxidation state proposal for the OEC can closely fit most of the available structural and electronic data for S2 at accessible energies.
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Redox-coupled substrate water reorganization in the active site of Photosystem II-The role of calcium in substrate water delivery. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2016; 1857:740-8. [PMID: 26826591 DOI: 10.1016/j.bbabio.2016.01.015] [Citation(s) in RCA: 86] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/31/2015] [Revised: 12/10/2015] [Accepted: 01/26/2016] [Indexed: 01/08/2023]
Abstract
Photosystem II (PSII) catalyzes light-driven water splitting in nature and is the key enzyme for energy input into the biosphere. Important details of its mechanism are not well understood. In order to understand the mechanism of water splitting, we perform here large-scale density functional theory (DFT) calculations on the active site of PSII in different oxidation, spin and ligand states. Prior to formation of the O-O bond, we find that all manganese atoms are oxidized to Mn(IV) in the S3 state, consistent with earlier studies. We find here, however, that the formation of the S3 state is coupled to the movement of a calcium-bound hydroxide (W3) from the Ca to a Mn (Mn1 or Mn4) in a process that is triggered by the formation of a tyrosyl radical (Tyr-161) and its protonated base, His-190. We find that subsequent oxidation and deprotonation of this hydroxide on Mn1 result in formation of an oxyl-radical that can exergonically couple with one of the oxo-bridges (O5), forming an O-O bond. When O(2) leaves the active site, a second Ca-bound water molecule reorients to bridge the gap between the manganese ions Mn1 and Mn4, forming a new oxo-bridge for the next reaction cycle. Our findings are consistent with experimental data, and suggest that the calcium ion may control substrate water access to the water oxidation sites.
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Pantazis DA, Ames W, Cox N, Lubitz W, Neese F. Zwei ineinander umwandelbare Strukturen erklären die spektroskopischen Eigenschaften des Wasser oxidierenden Enzyms des Photosystems II im S2-Zustand. Angew Chem Int Ed Engl 2012. [DOI: 10.1002/ange.201204705] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Pantazis DA, Ames W, Cox N, Lubitz W, Neese F. Two Interconvertible Structures that Explain the Spectroscopic Properties of the Oxygen-Evolving Complex of Photosystem II in the S2State. Angew Chem Int Ed Engl 2012; 51:9935-40. [DOI: 10.1002/anie.201204705] [Citation(s) in RCA: 309] [Impact Index Per Article: 25.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2012] [Indexed: 11/06/2022]
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Haddy A. EPR spectroscopy of the manganese cluster of photosystem II. PHOTOSYNTHESIS RESEARCH 2007; 92:357-68. [PMID: 17551843 DOI: 10.1007/s11120-007-9194-9] [Citation(s) in RCA: 71] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/07/2006] [Accepted: 05/03/2007] [Indexed: 05/15/2023]
Abstract
Electron paramagnetic resonance (EPR) spectroscopy is a valuable tool for understanding the oxidation state and chemical environment of the Mn4Ca cluster of photosystem II. Since the discovery of the multiline signal from the S2 state, EPR spectroscopy has continued to reveal details about the catalytic center of oxygen evolution. At present EPR signals from nearly all of the S-states of the Mn4Ca cluster, as well as from modified and intermediate states, have been observed. This review article describes the various EPR signals obtained from the Mn4Ca cluster, including the metalloradical signals due to interaction of the cluster with a nearby organic radical.
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Affiliation(s)
- Alice Haddy
- Department of Chemistry and Biochemistry, University of North Carolina at Greensboro, Greensboro, NC 27402, USA.
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Haddy A, Lakshmi KV, Brudvig GW, Frank HA. Q-band EPR of the S2 state of photosystem II confirms an S = 5/2 origin of the X-band g = 4.1 signal. Biophys J 2004; 87:2885-96. [PMID: 15454478 PMCID: PMC1304705 DOI: 10.1529/biophysj.104.040238] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2004] [Accepted: 06/14/2004] [Indexed: 11/18/2022] Open
Abstract
Disagreement has remained about the spin state origin of the g = 4.1 EPR signal observed at X-band (9 GHz) from the S2 oxidation state of the Mn cluster of Photosystem II. In this study, the S2 state of PSII-enriched membrane fragments was examined at Q-band (34 GHz), with special interest in low-field signals. Light-induced signals at g = 3.1 and g = 4.6 were observed. The intensity of the signal at g = 3.1 was enhanced by the presence of F- and suppressed by the presence of 5% ethanol, indicating that it was from the same spin system as the X-band signal at g = 4.1. The Q-band signal at g = 4.6 was also enhanced by F-, but not suppressed by 5% ethanol, making its identity less clear. Although it can be accounted for by the same spin system, other sources for the signal are considered. The observation of the signal at g = 3.1 agrees well with a previous study at 15.5 GHz, in which the X-band g = 4.1 signal was proposed to arise from the middle Kramers doublet of a near rhombic S = 5/2 system. Zero-field splitting values of D = 0.455 cm(-1) and E/D = 0.25 are used to simulate the spectra.
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Affiliation(s)
- Alice Haddy
- Department of Chemistry and Biochemistry, University of North Carolina, Greensboro, North Carolina 27402, USA.
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Mamedov F, Smith PJ, Styring S, Pace RJ. Relaxation behaviour of the tyrosine YD radical in photosystem II: evidence for strong dipolar interaction with paramagnetic centers in the S1 and S2 states. Phys Chem Chem Phys 2004. [DOI: 10.1039/b407329k] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Mino H, Kawamori A. EPR studies of the water oxidizing complex in the S1 and the higher S states: the manganese cluster and Y(Z) radical. BIOCHIMICA ET BIOPHYSICA ACTA 2001; 1503:112-22. [PMID: 11115628 DOI: 10.1016/s0005-2728(00)00229-2] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The parallel polarization electron paramagnetic resonance (EPR) method has been applied to investigate manganese EPR signals of native S1 and S3 states of the water oxidizing complex (WOC) in photosystem (PS) II. The EPR signals in both states were assigned to thermally excited states with S=1, from which zero-field interaction parameters D and E were derived. Three kinds of signals, the doublet signal, the singlet-like signal and g=11-15 signal, were detected in Ca2+-depleted PS II. The g=11-15 signal was observed by parallel and perpendicular modes and assigned to a higher oxidation state beyond S2 in Ca2+-depleted PS II. The singlet-like signal was associated with the g=11-15 signal but not with the Y(Z) (the tyrosine residue 161 of the D1 polypeptide in PS II) radical. The doublet signal was associated with the Y(Z) radical as proved by pulsed electron nuclear double resonance (ENDOR) and ENDOR-induced EPR. The electron transfer mechanism relevant to the role of Y(Z) radical was discussed.
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Affiliation(s)
- H Mino
- Laboratory for Photo-Biology, RIKEN Photodynamics Research Center, The Institute of Physical and Chemical Research, 519-1399 Aoba, Aramaki, Sendai 980-0845, Aoba, Japan
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Dau H, Iuzzolino L, Dittmer J. The tetra-manganese complex of photosystem II during its redox cycle - X-ray absorption results and mechanistic implications. BIOCHIMICA ET BIOPHYSICA ACTA 2001; 1503:24-39. [PMID: 11115622 DOI: 10.1016/s0005-2728(00)00230-9] [Citation(s) in RCA: 180] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
Using X-ray absorption spectroscopy (XAS), relevant information on structure and oxidation state of the water-oxidizing Mn complex of photosystem II has been obtained for all four semi-stable intermediate states of its catalytic cycle. We summarize our recent XAS results and discuss their mechanistic implications. The following aspects are covered: (a) information content of X-ray spectra (pre-edge feature, edge position, extended X-ray absorption fine-structure (EXAFS), dichroism in the EXAFS of partially oriented samples); (b) S(1)-state structure; (c) X-ray edge results on oxidation state changes; (d) EXAFS results on structural changes during the S-state cycle; (e) a structural model for the Mn complex in its S(3)-state; (f) XAS-based working model for the S(2)-S(3) transition; (g) XAS-based working model for the S(0)-S(1) transition; (h) potential role of hydrogen atom abstraction by the Mn complex. Finally, we present a specific hypothesis on the mechanism of dioxygen formation during the S(3)-(S(4))-S(0) transition. According to this hypothesis, water oxidation is facilitated by manganese reduction that is coupled to proton transfer from a substrate water to bridging oxides.
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Affiliation(s)
- H Dau
- Phillips-Universität Marburg, FB Biologie, Lahnberge, D-35032, Marburg, Germany.
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Evans MC, Rich AM, Nugent JH. Evidence for the presence of a component of the Mn complex of the photosystem II reaction centre which is exposed to water in the S(2) state of the water oxidation complex. FEBS Lett 2000; 477:113-7. [PMID: 10899320 DOI: 10.1016/s0014-5793(00)01742-7] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The interaction of water oxidising photosystem II preparations with the aqueous environment has been investigated using electron spin echo envelope modulation spectroscopy in the presence of 2H(2)O. The spectra show interaction of 2H of 2H(2)O with the preparation in the S(2) state. The component interacting with water decays during 1-4 weeks storage at 77 K. No interaction of water with the classical multiline S(2) Mn signal, which is more stable on storage at 77 K, was detected. The results show that a component of the water oxidation complex, possibly involving the Mn centre, is accessible to water and may be the water binding site for photosynthetic water oxidation.
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Affiliation(s)
- M C Evans
- Department of Biology, University College London, Gower St., WC1E 6BT, London, UK.
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Boussac A, Rutherford AW. Comparative study of the g=4.1 EPR signals in the S(2) state of photosystem II. BIOCHIMICA ET BIOPHYSICA ACTA 2000; 1457:145-56. [PMID: 10773159 DOI: 10.1016/s0005-2728(00)00073-6] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
The Mn(4) complex which is involved in water oxidation in photosystem II is known to exhibit three types of EPR signals in the S(2) state, one of the five redox states of the enzyme cycle: a multiline signal (spin 1/2), signals at g5 (spin 5/2) and a signal at g=4.1 (or g=4.25). The g=4.1 signal could be generated under two distinct sets of conditions: either by illumination at room temperature or at 200 K in certain experimental conditions (g4(S) signal) or by near-infrared illumination between approximately 77 and approximately 160 K of the S(2)-multiline state (g4(IR) signal). The two g=4.1 signals arise from states which have quite different stability in terms of temperature. In the present work we have compared these two signals in order to test if they originate from the same or from different chemical origins. The microwave power saturation properties of the two signals measured at 4.2 K were found to be virtually identical. Their temperature dependencies measured at non-saturating powers were also identical. The presence of Curie law behavior for the g4(S) and g4(IR) signals indicates that the states responsible for both signals are ground states. The orientation dependence, anisotropy and resolved hyperfine structure of the two g4 signals were also found to be virtually indistinguishable. We have been unable to confirm the behavior reported earlier indicating that the g4(S) signal is an excited state, nor were we able to confirm the presence of signal from a higher excited state in samples containing the g4(S), nor a radical signal in samples containing the g4(IR). These findings are best interpreted assuming that the two signals have a common origin i.e. a spin 5/2 ground state arising from a magnetically coupled Mn-cluster of 4 Mn ions.
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Affiliation(s)
- A Boussac
- Section de Bioénergétique, URA CNRS 2096, DBCM, CEA Saclay, 91191, Gif sur Yvette, France.
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Schiller H, Dau H. Preparation protocols for high-activity photosystem II membrane particles of green algae and higher plants, pH dependence of oxygen evolution and comparison of the S2-state multiline signal by X-band EPR spectroscopy. JOURNAL OF PHOTOCHEMISTRY AND PHOTOBIOLOGY. B, BIOLOGY 2000; 55:138-44. [PMID: 10942078 DOI: 10.1016/s1011-1344(00)00036-1] [Citation(s) in RCA: 67] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
Photosystem II (PS II) membrane particles are particularly well suited for various types of spectroscopic investigations on the PS II manganese complex. Here we present: (1) a preparation protocol for PS II membrane particles of higher plants, which yields exceptionally high oxygen-evolution activity due to the use of glycinebetaine as a PS II-stabilizing agent; (2) preparation protocols for highly active PS II membrane particles for the green algae Scenedesmus obliquus and Chlamydomonas reinhardtii; (3) a determination of pH dependence of oxygen evolution for spinach and Scenedesmus; (4) a comparison of the EPR multiline signal observed in the S2-state of green algae and higher plants of PS II membrane particles. A clearly broader type of multiline EPR signal is observed in green algae.
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Affiliation(s)
- H Schiller
- FB Biologie, Philipps-Universität Marburg, Germany
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Deak Z, Peterson S, Geijer P, Ahrling KA, Styring S. Methanol modification of the electron paramagnetic resonance signals from the S(0) and S(2) states of the water-oxidizing complex of photosystem II. BIOCHIMICA ET BIOPHYSICA ACTA 1999; 1412:240-9. [PMID: 10482786 DOI: 10.1016/s0005-2728(99)00064-x] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The Mn-derived electron paramagnetic resonance (EPR) multiline signal from the S(0) state of the water-oxidizing complex is observable only in the presence methanol. In the present study, we have characterized the effect of methanol on the EPR signals from the S(0) and S(2) states as well as on the EPR Signal II(slow) originating from the Tyrosine(D)(ox) radical. The amplitudes of the S(0) and S(2) multiline signals increase with the methanol concentration in a similar way, whereas the S(2) g=4.1 excited state signal amplitude shows a concomitant decrease. The methanol concentration at which half of the spectral change has occurred is approximately 0.2% and the effect is saturating around 5%. Methanol has an effect on the microwave power saturation of the S(2) multiline signal, as well. The microwave power at half saturation (P(1/2)) is 85 mW in the presence of methanol, whereas the signal relaxes much slower (P(1/2) approximately 27 mW) without. The relaxation of Signal II(slow) in the presence of methanol has also been investigated. The P(1/2) value of Signal II(slow) oscillates with the S cycle in a similar way as without methanol, but the P(1/2) values are consistently lower in the methanol-containing samples. From the results, we conclude that methanol modifies the magnetic properties of the S(0) and S(2) states in a similar way. The possible site and nature of methanol binding is discussed.
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Affiliation(s)
- Z Deak
- Department of Biochemistry, Center for Chemistry, Lund University, P. O. Box 124, S-221 00, Lund, Sweden
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Evans MC, Gourovskaya K, Nugent JH. Investigation of the interaction of the water oxidising manganese complex of photosystem II with the aqueous solvent environment. FEBS Lett 1999; 450:285-8. [PMID: 10359090 DOI: 10.1016/s0014-5793(99)00517-7] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Interaction of the water oxidising manganese complex of photosystem II with the aqueous environment has been investigated using electron paramagnetic resonance spectroscopy and electron spin echo envelope modulation spectroscopy to detect interaction of [2H]methanol with the complex in the S2 state. The experiments show that the classical S2 multiline signal is associated with a manganese environment which is not exposed to the aqueous medium. An electron paramagnetic resonance spectroscopy signal, also induced by 200 K illumination, showing 2H modulation by methanol in the medium and a modified multiline electron paramagnetic resonance spectroscopy signal formed in parallel to it, are suggested to be associated with a second manganese environment exposed to the medium.
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Affiliation(s)
- M C Evans
- Dept. of Biology, University College London, UK.
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Mulkidjanian AY. Photosystem II of green plants: on the possible role of retarded protonic relaxation in water oxidation1. BIOCHIMICA ET BIOPHYSICA ACTA 1999; 1410:1-6. [PMID: 10076010 DOI: 10.1016/s0005-2728(98)00174-1] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Photosystem II (PSII) of green plants and cyanobacteria uses energy of light to oxidize water and to produce oxygen. The available estimates of the oxidizing potential of P680+, the primary donor of PSII, yield value of about 1.15 V. Two main factors are suggested to add up and engender this high oxidizing potential, namely: (1) the electrostatic influence dominated by Arg-181 of the D2 subunit which elevates the oxidizing potential of P680+ up to 1 V, some 0.1 V above the Em value of a hydrogen-bonded chlorophyll a; and (2) the dynamic component of 0.10-0.15 V due to the experimentally demonstrated retarded protonic relaxation at the P680 site.
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Affiliation(s)
- AY Mulkidjanian
- Division of Biophysics, Faculty of Biology/Chemistry, University of Osnabruck, Barbarastr. 11, D-49069, Osnabruck, Germany
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Spin-exchange interactions in the S2-state manganese tetramer in photosynthetic oxygen-evolving complex deduced from g=2 multiline EPR signal. Chem Phys Lett 1999. [DOI: 10.1016/s0009-2614(98)01369-4] [Citation(s) in RCA: 58] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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17
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Structural characterization of the Mn site in the photosynthetic oxygen-evolving complex. STRUCTURE & BONDING 1998. [DOI: 10.1007/3-540-62888-6_1] [Citation(s) in RCA: 45] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
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Astashkin AV, Mino H, Kawamori A, Ono TA. Pulsed EPR study of the S′3 signal in the Ca2+-depleted photosystem II. Chem Phys Lett 1997. [DOI: 10.1016/s0009-2614(97)00546-0] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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Hundelt M, Haumann M, Junge W. Cofactor X of photosynthetic water oxidation: electron transfer, proton release, and electrogenic behaviour in chloride-depleted Photosystem II. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 1997. [DOI: 10.1016/s0005-2728(97)00042-x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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