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Müh F, Madjet MEA, Renger T. Structure-based simulation of linear optical spectra of the CP43 core antenna of photosystem II. PHOTOSYNTHESIS RESEARCH 2012; 111:87-101. [PMID: 21809112 DOI: 10.1007/s11120-011-9675-8] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/30/2010] [Accepted: 07/18/2011] [Indexed: 05/31/2023]
Abstract
The linear optical spectra (absorbance, linear dichroism, circular dichroism, fluorescence) of the CP43 (PsbC) antenna of the photosystem II core complex (PSIIcc) pertaining to the S(0) → S(1) (Q(Y)) transitions of the chlorophyll (Chl) a pigments are simulated by applying a combined quantum chemical/electrostatic method to obtain excitonic couplings and local transition energies (site energies) on the basis of the 2.9 Å resolution crystal structure (Guskov et al., Nat Struct Mol Biol 16:334-342, 2009). The electrostatic calculations identify three Chls with low site energies (Chls 35, 37, and 45 in the nomenclature of Loll et al. (Nature 438:1040-1044, 2005). A refined simulation of experimental spectra of isolated CP43 suggests a modified set of site energies within 143 cm(-1) of the directly calculated values (root mean square deviation: 80 cm(-1)). In the refined set, energy sinks are at Chls 37, 43, and 45 in agreement with earlier fitting results (Raszewski and Renger, J Am Chem Soc 130:4431-4446, 2008). The present structure-based simulations reveal that a large part of the redshift of Chl 37 is due to a digalactosyldiacylglycerol lipid. This finding suggests a new role for lipids in PSIIcc, namely the tuning of optical spectra and the creation of an excitation energy funnel towards the reaction center. The analysis of electrostatic pigment-protein interactions is used to identify amino acid residues that are of potential interest for an experimental approach to an assignment of site energies and energy sinks by site-directed mutagenesis.
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Affiliation(s)
- Frank Müh
- Institut für Theoretische Physik, Johannes Kepler Universität Linz, Altenberger Str. 69, 4040, Linz, Austria.
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Abstract
This special issue is focussed on arguably the most important fundamental question in contemporary chemical research: how to efficiently and economically convert abundant and thermodynamically stable molecules, such as H2O, CO2, and N2 into useable fuel and food sources. The 3 billion year evolutionary experiment of nature has provided a blueprint for the answer: multi-electron catalysis. However, unlike one-electron transfer, we have no refined theories for multi-electron processes. This is despite its centrality to much of chemistry, particularly in catalysis and biology. In this article we highlight recent research developments relevant to this theme with emphasis on the key physical concepts and premises: (i) multi-electron processes as stepwise single-electron transfer events; (ii) proton-coupled electron transfer; (iii) stimulated, concerted, and co-operative phenomena; (iv) feedback mechanisms that may enhance electron transfer rates by minimizing activation barriers; and (v) non-linearity and far-from-equilibrium considerations. The aim of our discussion is to provide inspiration for new directions in chemical research, in the context of an urgent contemporary issue.
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Fleming GR, Schlau-Cohen GS, Amarnath K, Zaks J. Design principles of photosynthetic light-harvesting. Faraday Discuss 2012; 155:27-41; discussion 103-14. [DOI: 10.1039/c1fd00078k] [Citation(s) in RCA: 97] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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König C, Neugebauer J. Quantum chemical description of absorption properties and excited-state processes in photosynthetic systems. Chemphyschem 2011; 13:386-425. [PMID: 22287108 DOI: 10.1002/cphc.201100408] [Citation(s) in RCA: 96] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2011] [Indexed: 11/07/2022]
Abstract
The theoretical description of the initial steps in photosynthesis has gained increasing importance over the past few years. This is caused by more and more structural data becoming available for light-harvesting complexes and reaction centers which form the basis for atomistic calculations and by the progress made in the development of first-principles methods for excited electronic states of large molecules. In this Review, we discuss the advantages and pitfalls of theoretical methods applicable to photosynthetic pigments. Besides methodological aspects of excited-state electronic-structure methods, studies on chlorophyll-type and carotenoid-like molecules are discussed. We also address the concepts of exciton coupling and excitation-energy transfer (EET) and compare the different theoretical methods for the calculation of EET coupling constants. Applications to photosynthetic light-harvesting complexes and reaction centers based on such models are also analyzed.
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Affiliation(s)
- Carolin König
- Institute for Physical and Theoretical Chemistry, Technical University Braunschweig, Braunschweig, Germany
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Vassiliev S, Mahboob A, Bruce D. Calculation of chromophore excited state energy shifts in response to molecular dynamics of pigment-protein complexes. PHOTOSYNTHESIS RESEARCH 2011; 110:25-38. [PMID: 21964859 DOI: 10.1007/s11120-011-9689-2] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/14/2011] [Accepted: 09/15/2011] [Indexed: 05/26/2023]
Abstract
The absorption and energy transfer properties of photosynthetic pigments are strongly influenced by their local environment or "site." Local electrostatic fields vary in time with protein and chromophore molecular movement and thus transiently influence the excited state transition properties of individual chromophores. Site-specific information is experimentally inaccessible in many light-harvesting pigment-proteins due to multiple chromophores with overlapping spectra. Full quantum mechanical calculations of each chromophores excited state properties are too computationally demanding to efficiently calculate the changing excitation energies along a molecular dynamics trajectory in a pigment-protein complex. A simplified calculation of electrostatic interactions with each chromophores ground to excited state transition, the so-called charge density coupling (CDC) for site energy, CDC, has previously been developed to address this problem. We compared CDC to more rigorous quantum chemical calculations to determine its accuracy in computing excited state energy shifts and their fluctuations within a molecular dynamics simulation of the bacteriochlorophyll containing light-harvesting Fenna-Mathews-Olson (FMO) protein. In most cases CDC calculations differed from quantum mechanical (QM) calculations in predicting both excited state energy and its fluctuations. The discrepancies arose from the inability of CDC to account for the differing effects of charge on ground and excited state electron orbitals. Results of our study show that QM calculations are indispensible for site energy computations and the quantification of contributions from different parts of the system to the overall site energy shift. We suggest an extension of QM/MM methodology of site energy shift calculations capable of accounting for long-range electrostatic potential contributions from the whole system, including solvent and ions.
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Affiliation(s)
- Serguei Vassiliev
- Department of Biology, Brock University, 500 Glenridge Avenue, St. Catharines, ON L2S 3A1, Canada.
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Kawatsu T, Matsuda K, Hasegawa JY. Bridge-mediated excitation energy transfer pathways through protein media: a Slater determinant-based electronic coupling calculation combined with localized molecular orbitals. J Phys Chem A 2011; 115:10814-22. [PMID: 21861486 DOI: 10.1021/jp2068792] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
A computational method for calculating electronic coupling and pathway of electron transfer (ET) has been extended to that for excitation energy transfer (EET). A molecular orbital (MO)-based description has been generalized to one based on Slater determinants. This approach reduces the approximations used for the Green's function method from the perturbation of chemical-bond interactions to the perturbation of the configuration interactions. It is, therefore, reasonable to apply this method to EET, which involves the transfer of an electron-hole pair. To represent EET donor, acceptor, and bridge states, we adopted recently developed localized molecular orbitals (LMOs) for constructing locally excited determinants. The LMO approach provides a chemically meaningful interpretation of how each local excitation on the bridge contributes to the total electronic coupling of the EET. We applied the method to six model peptides and calculated their electronic couplings as well as the direct and through-peptide terms. Although the through-peptide term is usually negligibly small compared with the direct term, it can dominate the EET reaction in appropriate situations. The direct term dominates in long-range interactions because the indirect term decays in shorter distances.
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Affiliation(s)
- Tsutomu Kawatsu
- Department of Synthetic Chemistry and Biological Chemistry, Graduate School of Engineering, Kyoto University Kyoto-Daigaku-Katsura, Nishikyo-ku, Kyoto 615-8510, Japan
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58
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Neupane B, Dang NC, Kelley RF, Wasielewski MR, Jankowiak R. Low-Temperature Frequency Domain Study of Excitation Energy Transfer in Ethynyl-Linked Chlorophyll Trefoils and Aggregates. J Phys Chem B 2011; 115:10391-9. [DOI: 10.1021/jp2027252] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Bhanu Neupane
- Department of Chemistry, Kansas State University, Manhattan, Kansas 66506, United States
| | - Nhan C. Dang
- Department of Chemistry, Kansas State University, Manhattan, Kansas 66506, United States
| | - Richard F. Kelley
- Department of Chemistry and Argonne-Northwestern Solar Energy Research (ANSER) Center, Northwestern University, Evanston, Illinois 60208, United States
| | - Michael R. Wasielewski
- Department of Chemistry and Argonne-Northwestern Solar Energy Research (ANSER) Center, Northwestern University, Evanston, Illinois 60208, United States
| | - Ryszard Jankowiak
- Department of Chemistry, Kansas State University, Manhattan, Kansas 66506, United States
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59
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Theiss C, Schmitt FJ, Pieper J, Nganou C, Grehn M, Vitali M, Olliges R, Eichler HJ, Eckert HJ. Excitation energy transfer in intact cells and in the phycobiliprotein antennae of the chlorophyll d containing cyanobacterium Acaryochloris marina. JOURNAL OF PLANT PHYSIOLOGY 2011; 168:1473-1487. [PMID: 21396735 DOI: 10.1016/j.jplph.2011.02.002] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/01/2010] [Revised: 02/04/2011] [Accepted: 02/07/2011] [Indexed: 05/30/2023]
Abstract
The cyanobacterium Acaryochloris marina is unique because it mainly contains Chlorophyll d (Chl d) in the core complexes of PS I and PS II instead of the usually dominant Chl a. Furthermore, its light harvesting system has a structure also different from other cyanobacteria. It has both, a membrane-internal chlorophyll containing antenna and a membrane-external phycobiliprotein (PBP) complex. The first one binds Chl d and is structurally analogous to CP43. The latter one has a rod-like structure consisting of three phycocyanin (PC) homohexamers and one heterohexamer containing PC and allophycocyanin (APC). In this paper, we give an overview on the investigations of excitation energy transfer (EET) in this PBP-light-harvesting system and of charge separation in the photosystem II (PS II) reaction center of A. marina performed at the Technische Universität Berlin. Due to the unique structure of the PBP antenna in A. marina, this EET occurs on a much shorter overall time scale than in other cyanobacteria. We also briefly discuss the question of the pigment composition in the reaction center (RC) of PS II and the nature of the primary donor of the PS II RC.
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Affiliation(s)
- Christoph Theiss
- Institute of Optics and Atomic Physics, Technische Universität Berlin, Strasse des 17. Juni 135, Berlin, Germany.
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60
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Cardona T, Sedoud A, Cox N, Rutherford AW. Charge separation in photosystem II: a comparative and evolutionary overview. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2011; 1817:26-43. [PMID: 21835158 DOI: 10.1016/j.bbabio.2011.07.012] [Citation(s) in RCA: 245] [Impact Index Per Article: 18.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/29/2011] [Revised: 07/22/2011] [Accepted: 07/23/2011] [Indexed: 10/17/2022]
Abstract
Our current understanding of the PSII reaction centre owes a great deal to comparisons to the simpler and better understood, purple bacterial reaction centre. Here we provide an overview of the similarities with a focus on charge separation and the electron acceptors. We go on to discuss some of the main differences between the two kinds of reaction centres that have been highlighted by the improving knowledge of PSII. We attempt to relate these differences to functional requirements of water splitting. Some are directly associated with that function, e.g. high oxidation potentials, while others are associated with regulation and protection against photodamage. The protective and regulatory functions are associated with the harsh chemistry performed during its normal function but also with requirements of the enzyme while it is undergoing assembly and repair. Key aspects of PSII reaction centre evolution are also addressed. This article is part of a Special Issue entitled: Photosystem II.
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Affiliation(s)
- Tanai Cardona
- Institut de Biologie et Technologies de Saclay, URA 2096 CNRS, CEA Saclay, 91191 Gif-sur-Yvette, France
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61
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P680 (PD1PD2) and ChlD1 as alternative electron donors in photosystem II core complexes and isolated reaction centers. JOURNAL OF PHOTOCHEMISTRY AND PHOTOBIOLOGY B-BIOLOGY 2011; 104:44-50. [DOI: 10.1016/j.jphotobiol.2011.02.003] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/20/2010] [Revised: 01/25/2011] [Accepted: 02/03/2011] [Indexed: 12/13/2022]
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62
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Croce R, van Amerongen H. Light-harvesting and structural organization of Photosystem II: From individual complexes to thylakoid membrane. JOURNAL OF PHOTOCHEMISTRY AND PHOTOBIOLOGY B-BIOLOGY 2011; 104:142-53. [DOI: 10.1016/j.jphotobiol.2011.02.015] [Citation(s) in RCA: 114] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/10/2011] [Revised: 02/16/2011] [Accepted: 02/17/2011] [Indexed: 10/18/2022]
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63
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Mielke SP, Kiang NY, Blankenship RE, Gunner MR, Mauzerall D. Efficiency of photosynthesis in a Chl d-utilizing cyanobacterium is comparable to or higher than that in Chl a-utilizing oxygenic species. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2011; 1807:1231-6. [PMID: 21708123 DOI: 10.1016/j.bbabio.2011.06.007] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/06/2011] [Revised: 06/09/2011] [Accepted: 06/13/2011] [Indexed: 10/18/2022]
Abstract
The cyanobacterium Acaryochloris marina uses chlorophyll d to carry out oxygenic photosynthesis in environments depleted in visible and enhanced in lower-energy, far-red light. However, the extent to which low photon energies limit the efficiency of oxygenic photochemistry in A. marina is not known. Here, we report the first direct measurements of the energy-storage efficiency of the photosynthetic light reactions in A. marina whole cells, and find it is comparable to or higher than that in typical, chlorophyll a-utilizing oxygenic species. This finding indicates that oxygenic photosynthesis is not fundamentally limited at the photon energies employed by A. marina, and therefore is potentially viable in even longer-wavelength light environments.
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Affiliation(s)
- S P Mielke
- NASA Goddard Institute for Space Studies, Columbia University, New York, NY, USA.
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64
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Müh F, Glöckner C, Hellmich J, Zouni A. Light-induced quinone reduction in photosystem II. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2011; 1817:44-65. [PMID: 21679684 DOI: 10.1016/j.bbabio.2011.05.021] [Citation(s) in RCA: 163] [Impact Index Per Article: 12.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/14/2011] [Revised: 05/20/2011] [Accepted: 05/23/2011] [Indexed: 10/18/2022]
Abstract
The photosystem II core complex is the water:plastoquinone oxidoreductase of oxygenic photosynthesis situated in the thylakoid membrane of cyanobacteria, algae and plants. It catalyzes the light-induced transfer of electrons from water to plastoquinone accompanied by the net transport of protons from the cytoplasm (stroma) to the lumen, the production of molecular oxygen and the release of plastoquinol into the membrane phase. In this review, we outline our present knowledge about the "acceptor side" of the photosystem II core complex covering the reaction center with focus on the primary (Q(A)) and secondary (Q(B)) quinones situated around the non-heme iron with bound (bi)carbonate and a comparison with the reaction center of purple bacteria. Related topics addressed are quinone diffusion channels for plastoquinone/plastoquinol exchange, the newly discovered third quinone Q(C), the relevance of lipids, the interactions of quinones with the still enigmatic cytochrome b559 and the role of Q(A) in photoinhibition and photoprotection mechanisms. This article is part of a Special Issue entitled: Photosystem II.
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Affiliation(s)
- Frank Müh
- Max-Volmer-Laboratorium für Biophysikalische Chemie, Technische Universität Berlin, Strasse des 17. Juni 135, D-10623 Berlin, Germany
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65
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Jankowiak R, Reppert M, Zazubovich V, Pieper J, Reinot T. Site Selective and Single Complex Laser-Based Spectroscopies: A Window on Excited State Electronic Structure, Excitation Energy Transfer, and Electron–Phonon Coupling of Selected Photosynthetic Complexes. Chem Rev 2011; 111:4546-98. [DOI: 10.1021/cr100234j] [Citation(s) in RCA: 122] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Ryszard Jankowiak
- Department of Chemistry, Kansas State University, Manhattan, Kansas 66506, United States
| | - Mike Reppert
- Department of Chemistry, Kansas State University, Manhattan, Kansas 66506, United States
| | - Valter Zazubovich
- Department of Physics, Concordia University, Montreal H4B1R6 Quebec, Canada
| | - Jörg Pieper
- Max-Volmer-Laboratories for Biophysical Chemistry, Technical University of Berlin, Germany
- Institute of Physics, University of Tartu, Riia 142, 51014 Tartu, Estonia
| | - Tonu Reinot
- Department of Chemistry, Kansas State University, Manhattan, Kansas 66506, United States
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66
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Ho FM. Structural and mechanistic investigations of photosystem II through computational methods. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2011; 1817:106-20. [PMID: 21565158 DOI: 10.1016/j.bbabio.2011.04.009] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/25/2011] [Revised: 03/22/2011] [Accepted: 04/02/2011] [Indexed: 11/17/2022]
Abstract
The advent of oxygenic photosynthesis through water oxidation by photosystem II (PSII) transformed the planet, ultimately allowing the evolution of aerobic respiration and an explosion of ecological diversity. The importance of this enzyme to life on Earth has ironically been paralleled by the elusiveness of a detailed understanding of its precise catalytic mechanism. Computational investigations have in recent years provided more and more insights into the structural and mechanistic details that underlie the workings of PSII. This review will present an overview of some of these studies, focusing on those that have aimed at elucidating the mechanism of water oxidation at the CaMn₄ cluster in PSII, and those exploring the features of the structure and dynamics of this enzyme that enable it to catalyse this energetically demanding reaction. This article is part of a Special Issue entitled: Photosystem II.
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Affiliation(s)
- Felix M Ho
- Deparment of Photochemistry and Molecular Sciences, Angström Laboratory, Uppsala University, Sweden.
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67
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Renger T, Schlodder E. Optical properties, excitation energy and primary charge transfer in photosystem II: theory meets experiment. JOURNAL OF PHOTOCHEMISTRY AND PHOTOBIOLOGY B-BIOLOGY 2011; 104:126-41. [PMID: 21531572 DOI: 10.1016/j.jphotobiol.2011.03.016] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/23/2010] [Revised: 03/04/2011] [Accepted: 03/21/2011] [Indexed: 11/29/2022]
Abstract
In this review we discuss structure-function relationships of the core complex of photosystem II, as uncovered from analysis of optical spectra of the complex and its subunits. Based on descriptions of optical difference spectra including site directed mutagenesis we propose a revision of the multimer model of the symmetrically arranged reaction center pigments, described by an asymmetric exciton Hamiltonian. Evidence is provided for the location of the triplet state, the identity of the primary electron donor, the localization of the cation and the secondary electron transfer pathway in the reaction center. We also discuss the stationary and time-dependent optical properties of the CP43 and CP47 subunits and the excitation energy transfer and trapping-by-charge-transfer kinetics in the core complex.
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Affiliation(s)
- Thomas Renger
- Institut für Theoretische Physik, Johannes Kepler Universität, Abteilung Theoretische Biophysik, Austria.
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68
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van der Weij-de Wit CD, Dekker JP, van Grondelle R, van Stokkum IHM. Charge separation is virtually irreversible in photosystem II core complexes with oxidized primary quinone acceptor. J Phys Chem A 2011; 115:3947-56. [PMID: 21341818 DOI: 10.1021/jp1083746] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
X-ray structures of the Photosystem II (PSII) core revealed relatively large interpigment distances between the CP43 and CP47 antenna complexes and the reaction center (RC) with respect to the interpigment distances in a single unit. This finding questions the possibility of fast energy equilibration among the antenna and the RC, which has been the basic explanation for the measured PSII fluorescence kinetics for more than two decades. In this study, we present time-resolved fluorescence measurements obtained with a streak-camera setup on PSII core complexes from Thermosynechococcus elongatus at room temperature (RT) and at 77 K. Kinetic modeling of the RT data obtained with oxidized quinone acceptor Q(A), reveals that the kinetics are best described by fast primary charge separation at a time scale of 1.5 ps and slow energy transfer from the antenna into the RC, which results in an energy equilibration time between the antenna and the RC of about 44 ps. This model is consistent with structure-based computations. Primary radical pair formation was found to be a virtually irreversible process. Energy equilibration within the CP43 and CP47 complexes is shown to occur at a time scale of 8 ps. Kinetic modeling of the 77 K data reveals similar energy transfer time scales in the antenna units and among the antenna and the RC as at RT, respectively, 7 and 37 ps. We conclude that the energy transfer from the CP43/CP47 antenna to the RC is the dominant factor in the total charge separation kinetics in intact PSII cores.
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Affiliation(s)
- C D van der Weij-de Wit
- Department of Physics and Astronomy, Faculty of Sciences, VU University Amsterdam, De Boelelaan 1081, 1081 HV Amsterdam, The Netherlands
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69
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Novoderezhkin VI, Romero E, Dekker JP, van Grondelle R. Multiple charge-separation pathways in photosystem II: modeling of transient absorption kinetics. Chemphyschem 2011; 12:681-8. [PMID: 21322104 DOI: 10.1002/cphc.201000830] [Citation(s) in RCA: 91] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2011] [Revised: 01/17/2011] [Indexed: 11/11/2022]
Abstract
We explain the transient absorption kinetics (E. Romero, I. H. M. van Stokkum, V. I. Novoderezhkin, J. P. Dekker, R. van Grondelle, Biochemistry 2010, 49, 4300) measured for isolated reaction centers of photosystem II at 77 K upon excitation of the primary donor band (680 nm). The excited-state dynamics is modeled on the basis of the exciton states of 6 cofactors coupled to 4 charge-transfer (CT) states. One CT state (corresponding to charge separation within the special pair) is supposed to be strongly coupled with the excited states, whereas the other radical pairs are supposed to be localized. Relaxation within the strongly coupled manifold and transfer to localized CT's are described by the modified Redfield and generalized Förster theories, respectively. A simultaneous and quantitative fit of the 680, 545, and 460 nm kinetics (corresponding to respectively the Q(y) transitions of the red-most cofactors, Q(x) transition of pheophytin, and pheophytin anion absorption) enables us to define the pathways and time scales of primary electron transfer. A consistent modeling of the data is only possible with a Scheme where charge separation occurs from both the accessory chlorophyll and from the special pair, giving rise to fast and slow components of the pheophytin anion formation, respectively.
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Affiliation(s)
- Vladimir I Novoderezhkin
- Institute of Physico-Chemical Biology, Moscow State University, Leninsky Gory, 119992, Moscow, Russia
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70
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Di Donato M, Stahl AD, van Stokkum IHM, van Grondelle R, Groot ML. Cofactors Involved in Light-Driven Charge Separation in Photosystem I Identified by Subpicosecond Infrared Spectroscopy. Biochemistry 2010; 50:480-90. [DOI: 10.1021/bi101565w] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Mariangela Di Donato
- Faculty of Sciences, Department of Physics and Astronomy, VU University Amsterdam, Amsterdam, The Netherlands
| | - Andreas D. Stahl
- Faculty of Sciences, Department of Physics and Astronomy, VU University Amsterdam, Amsterdam, The Netherlands
| | - Ivo H. M. van Stokkum
- Faculty of Sciences, Department of Physics and Astronomy, VU University Amsterdam, Amsterdam, The Netherlands
| | - Rienk van Grondelle
- Faculty of Sciences, Department of Physics and Astronomy, VU University Amsterdam, Amsterdam, The Netherlands
| | - Marie-Louise Groot
- Faculty of Sciences, Department of Physics and Astronomy, VU University Amsterdam, Amsterdam, The Netherlands
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