151
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Van Brederode ME, Jones MR, Van Mourik F, Van Stokkum IH, Van Grondelle R. A new pathway for transmembrane electron transfer in photosynthetic reaction centers of Rhodobacter sphaeroides not involving the excited special pair. Biochemistry 1997; 36:6855-61. [PMID: 9188680 DOI: 10.1021/bi9703756] [Citation(s) in RCA: 86] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
It is generally accepted that electron transfer in bacterial photosynthesis is driven by the first singlet excited state of a special pair of bacteriochlorophylls (P*). We have examined the first steps of electron transfer in a mutant of the Rhodobacter sphaeroides reaction center in which charge separation from P* is dramatically slowed down. The results provide for the first time clear evidence that excitation of the monomeric bacteriochlorophyll in the active branch of the reaction center (B(A)) drives ultrafast transmembrane electron transfer without the involvement of P*, demonstrating a new and efficient mechanism for solar energy transduction in photosynthesis. The most abundant charge-separated intermediate state probably is P+B(A)-, which is formed within 200 fs from B(A)* and decays with a lifetime of 6.5 ps into P+H(A)-. We also see evidence for the involvement of a B(A)+H(A)- state in the alternative pathway.
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Affiliation(s)
- M E Van Brederode
- Department of Physics and Astronomy, Free University of Amsterdam, The Netherlands.
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152
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Hankamer B, Barber J, Boekema EJ. STRUCTURE AND MEMBRANE ORGANIZATION OF PHOTOSYSTEM II IN GREEN PLANTS. ACTA ACUST UNITED AC 1997; 48:641-671. [PMID: 15012277 DOI: 10.1146/annurev.arplant.48.1.641] [Citation(s) in RCA: 211] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Photosystem II (PSII) is the pigment protein complex embedded in the thylakoid membrane of higher plants, algae, and cyanobacteria that uses solar energy to drive the photosynthetic water-splitting reaction. This chapter reviews the primary, secondary, tertiary, and quaternary structures of PSII as well as the function of its constituent subunits. The understanding of in vivo organization of PSII is based in part on freeze-etched and freeze-fracture images of thylakoid membranes. These images show a resolution of about 40-50 A and so provide information mainly on the localization, heterogeneity, dimensions, and shapes of membrane-embedded PSII complexes. Higher resolution of about 15-40 A has been obtained from single particle images of isolated PSII complexes of defined and differing subunit composition and from electron crystallography of 2-D crystals. Observations are discussed in terms of the oligomeric state and subunit organization of PSII and its antenna components.
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Affiliation(s)
- Ben Hankamer
- Wolfson Laboratories, Department of Biochemistry, Imperial College of Science, Technology and Medicine, London SW7 2AY, United Kingdom, Biophysical Chemistry, Groningen Biomolecular Sciences and Biotechnology Institute, University of Groningen, Nijenborgh 4, Groningen, NL-9747 AG The Netherlands
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153
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Groot ML, Eijckelhoff C, Dekker JP. Charge separation in the reaction center of photosystem II studied as a function of temperature. Proc Natl Acad Sci U S A 1997; 94:4389-94. [PMID: 9113999 PMCID: PMC20732 DOI: 10.1073/pnas.94.9.4389] [Citation(s) in RCA: 59] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
In photosystem II of green plants the key photosynthetic reaction consists of the transfer of an electron from the primary donor called P680 to a nearby pheophytin molecule. We analyzed the temperature dependence of this reaction by subpicosecond transient absorption spectroscopy over the temperature range 20-240 K using isolated photosystem II reaction centers from spinach. After excitation in the red edge of the Qy absorption band, the decay of the excited state can conveniently be described by two kinetic components that both accelerate with temperature. This temperature behavior differs remarkably from that observed in purple bacterial reaction centers. We attribute the first component, which accelerates from 2.6 ps at 20 K to 0.4 ps at 240 K, to charge separation after direct excitation of P680, and explain its temperature dependence by an intermediate that lies in energy above the singlet-excited P680 and that possibly has charge-transfer character. The second component accelerates from 120 ps at 20 K to 18 ps at 240 K and is attributed to charge separation after direct excitation of the "trap" state near-degenerate with P680 and subsequent slow energy transfer from this trap state to P680. We suggest that the slow energy transfer from the trap state to P680 plays an important role in the kinetics of radical pair formation at room temperature.
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Affiliation(s)
- M L Groot
- Department of Physics and Astronomy and Institute of Molecular Biological Sciences, Vrije Universiteit, De Boelelaan 1081, 1081 HV Amsterdam, The Netherlands
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154
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Brancato-Buentello KE, Kang SJ, Scheidt WR. Metalloporphyrin Mixed-Valence π-Cation Radicals: Solution Stability and Properties. J Am Chem Soc 1997. [DOI: 10.1021/ja9616950] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
| | - Seong-Joo Kang
- Contribution from the Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, Indiana 46556
| | - W. Robert Scheidt
- Contribution from the Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, Indiana 46556
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155
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Eijckelhoff C, Vacha F, van Grondelle R, Dekker JP, Barber J. Spectroscopic characterization of a 5 Chl a photosystem II reaction center complex. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 1997. [DOI: 10.1016/s0005-2728(96)00144-2] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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156
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Levanon H, Möbius K. Advanced EPR spectroscopy on electron transfer processes in photosynthesis and biomimetic model systems. ANNUAL REVIEW OF BIOPHYSICS AND BIOMOLECULAR STRUCTURE 1997; 26:495-540. [PMID: 9241428 DOI: 10.1146/annurev.biophys.26.1.495] [Citation(s) in RCA: 76] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
This review focuses on the recent advances in EPR spectroscopy as they are applied both to photoinduced electron transfer in the photosynthetic apparatus and to biomimetic systems. The review deals with time-resolved direct-detection cw and pulsed EPR and ENDOR methods, both at conventional bands [X-(9.5 GHz), K-(24 GHz), and Q-(35 GHz)(] and at high frequency bands (W-band, 95 GHz, and even higher frequency bands). EPR studies on photosynthetic and model systems in their doublet, triplet and radical pair states are surveyed, including their static and dynamic properties. APplications of time-resolved EPR in studying photoinduced electron and energy transfer in isotropic and anisotropic environments, and the concepts of electron spin polarization and magnetic field effects in photochemical reactions are also reviewed.
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Affiliation(s)
- H Levanon
- Department of Physical Chemistry, Hebrew University of Jerusalem, Israel
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157
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Scholes GD. Energy Transfer and Spectroscopic Characterization of Multichromophoric Assemblies. ACTA ACUST UNITED AC 1996. [DOI: 10.1021/jp961784z] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Gregory D. Scholes
- Department of Chemistry, Imperial College of Science, Technology and Medicine, London SW7 2AY, United Kingdom
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158
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Xiong J, Subramaniam S. Modeling of the D1/D2 proteins and cofactors of the photosystem II reaction center: implications for herbicide and bicarbonate binding. Protein Sci 1996; 5:2054-73. [PMID: 8897606 PMCID: PMC2143261 DOI: 10.1002/pro.5560051012] [Citation(s) in RCA: 57] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
A three-dimensional model of the photosystem II (PSII) reaction center from the cyanobacterium Synechocystis sp. PCC 6803 was generated based on homology with the anoxygenic purple bacterial photosynthetic reaction centers of Rhodobacter sphaeroides and Rhodopseudomonas viridis, for which the X-ray crystallographic structures are available. The model was constructed with an alignment of D1 and D2 sequences with the L and M subunits of the bacterial reaction center, respectively, and by using as a scaffold the structurally conserved regions (SCRs) from bacterial templates. The structurally variant regions were built using a novel sequence-specific approach of searching for the best-matched protein segments in the Protein Data Bank with the "basic local alignment search tool" (Altschul SF, Gish W, Miller W, Myers EW, Lipman DJ, 1990, J Mol Biol 215:403-410), and imposing the matching conformational preference on the corresponding D1 and D2 regions. The structure thus obtained was refined by energy minimization. The modeled D1 and D2 proteins contain five transmembrane alpha-helices each, with cofactors (4 chlorophylls, 2 pheophytins, 2 plastoquinones, and a non-heme iron) essential for PSII primary photochemistry embedded in them. A beta-carotene, considered important for PSII photoprotection, was also included in the model. Four different possible conformations of the primary electron donor P680 chlorophylls were proposed, one based on the homology with the bacterial template and the other three on existing experimental suggestions in literature. The P680 conformation based on homology was preferred because it has the lowest energy. Redox active tyrosine residues important for P680+ reduction as well as residues important for PSII cofactor binding were analyzed. Residues involved in interprotein interactions in the model were also identified. Herbicide 3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU) was also modeled in the plastoquinone QB binding niche using the structural information available from a DCMU-binding bacterial reaction center. A bicarbonate anion, known to play a role in PSII, but not in anoxygenic photosynthetic bacteria, was modeled in the non-heme iron site, providing a bidentate ligand to the iron. By modifying the previous hypothesis of Blubaugh and Govindjee (1988, Photosyn Res 19:85-128), we modeled a second bicarbonate and a water molecule in the QB site and we proposed a hypothesis to explain the mechanism of QB protonation mediated by bicarbonate and water. The bicarbonate, stabilized by D1-R257, donates a proton to QB2- through the intermediate of D1-H252; and a water molecule donates another proton to QB2-. Based on the discovery of a "water transport channel" in the bacterial reaction center, an analogous channel for transporting water and bicarbonate is proposed in our PSII model. The putative channel appears to be primarily positively charged near QB and the non-heme iron, in contrast to the polarity distribution in the bacterial water transport channel. The constructed model has been found to be consistent with most existing data.
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Affiliation(s)
- J Xiong
- Department of Plant Biology, University of Illinois at Urbana-Champaign 61801, USA
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159
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Leegwater JA. Coherent versus Incoherent Energy Transfer and Trapping in Photosynthetic Antenna Complexes. ACTA ACUST UNITED AC 1996. [DOI: 10.1021/jp961448i] [Citation(s) in RCA: 156] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Jan A. Leegwater
- Department of Physics and Astronomy, Vrije Universiteit Amsterdam, De Boelelaan 1081, 1081 HV-NL Amsterdam, The Netherlands
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160
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White NTH, Beddard GS, Thorne JRG, Feehan TM, Keyes TE, Heathcote P. Primary Charge Separation and Energy Transfer in the Photosystem I Reaction Center of Higher Plants. ACTA ACUST UNITED AC 1996. [DOI: 10.1021/jp9604709] [Citation(s) in RCA: 41] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Nigel T. H. White
- Department of Chemistry, University of Manchester, Manchester M13 9PL, U.K., and School of Biological Sciences, Queen Mary and Westfield College, Mile End Road, London E1 4NS, U.K
| | - Godfrey S. Beddard
- Department of Chemistry, University of Manchester, Manchester M13 9PL, U.K., and School of Biological Sciences, Queen Mary and Westfield College, Mile End Road, London E1 4NS, U.K
| | - Jonathan R. G. Thorne
- Department of Chemistry, University of Manchester, Manchester M13 9PL, U.K., and School of Biological Sciences, Queen Mary and Westfield College, Mile End Road, London E1 4NS, U.K
| | - Tim M. Feehan
- Department of Chemistry, University of Manchester, Manchester M13 9PL, U.K., and School of Biological Sciences, Queen Mary and Westfield College, Mile End Road, London E1 4NS, U.K
| | - Tia E. Keyes
- Department of Chemistry, University of Manchester, Manchester M13 9PL, U.K., and School of Biological Sciences, Queen Mary and Westfield College, Mile End Road, London E1 4NS, U.K
| | - Peter Heathcote
- Department of Chemistry, University of Manchester, Manchester M13 9PL, U.K., and School of Biological Sciences, Queen Mary and Westfield College, Mile End Road, London E1 4NS, U.K
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161
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Groot ML, Dekker JP, van Grondelle R, den Hartog FTH, Völker S. Energy Transfer and Trapping in Isolated Photosystem II Reaction Centers of Green Plants at Low Temperature. A Study by Spectral Hole Burning. ACTA ACUST UNITED AC 1996. [DOI: 10.1021/jp960326n] [Citation(s) in RCA: 49] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- M. L. Groot
- Department of Biophysics, Faculty of Physics and Astronomy, Free University, 1081 HV Amsterdam, The Netherlands, and Center for the Study of Excited States of Molecules, Huygens and Gorlaeus Laboratories, University of Leiden, 2300 RA Leiden, The Netherlands
| | - J. P. Dekker
- Department of Biophysics, Faculty of Physics and Astronomy, Free University, 1081 HV Amsterdam, The Netherlands, and Center for the Study of Excited States of Molecules, Huygens and Gorlaeus Laboratories, University of Leiden, 2300 RA Leiden, The Netherlands
| | - R. van Grondelle
- Department of Biophysics, Faculty of Physics and Astronomy, Free University, 1081 HV Amsterdam, The Netherlands, and Center for the Study of Excited States of Molecules, Huygens and Gorlaeus Laboratories, University of Leiden, 2300 RA Leiden, The Netherlands
| | - F. T. H. den Hartog
- Department of Biophysics, Faculty of Physics and Astronomy, Free University, 1081 HV Amsterdam, The Netherlands, and Center for the Study of Excited States of Molecules, Huygens and Gorlaeus Laboratories, University of Leiden, 2300 RA Leiden, The Netherlands
| | - S. Völker
- Department of Biophysics, Faculty of Physics and Astronomy, Free University, 1081 HV Amsterdam, The Netherlands, and Center for the Study of Excited States of Molecules, Huygens and Gorlaeus Laboratories, University of Leiden, 2300 RA Leiden, The Netherlands
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162
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Merry SAP, Kumazaki S, Tachibana Y, Joseph DM, Porter G, Yoshihara K, Barber J, Durrant JR, Klug DR. Sub-picosecond Equilibration of Excitation Energy in Isolated Photosystem II Reaction Centers Revisited: Time-Dependent Anisotropy. ACTA ACUST UNITED AC 1996. [DOI: 10.1021/jp960388d] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Stephen A. P. Merry
- Molecular Dynamics and Photosynthesis Research Groups, Centre for Photomolecular Sciences, Departments of Biochemistry and Chemistry, Imperial College, London, SW7 2AY, and Institute for Molecular Science, Myodaiji, Okazaki 444, Japan
| | - Shigeichi Kumazaki
- Molecular Dynamics and Photosynthesis Research Groups, Centre for Photomolecular Sciences, Departments of Biochemistry and Chemistry, Imperial College, London, SW7 2AY, and Institute for Molecular Science, Myodaiji, Okazaki 444, Japan
| | - Yasuhiro Tachibana
- Molecular Dynamics and Photosynthesis Research Groups, Centre for Photomolecular Sciences, Departments of Biochemistry and Chemistry, Imperial College, London, SW7 2AY, and Institute for Molecular Science, Myodaiji, Okazaki 444, Japan
| | - D. Melissa Joseph
- Molecular Dynamics and Photosynthesis Research Groups, Centre for Photomolecular Sciences, Departments of Biochemistry and Chemistry, Imperial College, London, SW7 2AY, and Institute for Molecular Science, Myodaiji, Okazaki 444, Japan
| | - George Porter
- Molecular Dynamics and Photosynthesis Research Groups, Centre for Photomolecular Sciences, Departments of Biochemistry and Chemistry, Imperial College, London, SW7 2AY, and Institute for Molecular Science, Myodaiji, Okazaki 444, Japan
| | - Keitaro Yoshihara
- Molecular Dynamics and Photosynthesis Research Groups, Centre for Photomolecular Sciences, Departments of Biochemistry and Chemistry, Imperial College, London, SW7 2AY, and Institute for Molecular Science, Myodaiji, Okazaki 444, Japan
| | - James Barber
- Molecular Dynamics and Photosynthesis Research Groups, Centre for Photomolecular Sciences, Departments of Biochemistry and Chemistry, Imperial College, London, SW7 2AY, and Institute for Molecular Science, Myodaiji, Okazaki 444, Japan
| | - James R. Durrant
- Molecular Dynamics and Photosynthesis Research Groups, Centre for Photomolecular Sciences, Departments of Biochemistry and Chemistry, Imperial College, London, SW7 2AY, and Institute for Molecular Science, Myodaiji, Okazaki 444, Japan
| | - David R. Klug
- Molecular Dynamics and Photosynthesis Research Groups, Centre for Photomolecular Sciences, Departments of Biochemistry and Chemistry, Imperial College, London, SW7 2AY, and Institute for Molecular Science, Myodaiji, Okazaki 444, Japan
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163
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Müller MG, Hucke M, Reus M, Holzwarth AR. Primary Processes and Structure of the Photosystem II Reaction Center. 4. Low-Intensity Femtosecond Transient Absorption Spectra of D1-D2-cyt-b559 Reaction Centers,. ACTA ACUST UNITED AC 1996. [DOI: 10.1021/jp953714i] [Citation(s) in RCA: 43] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Marc G. Müller
- Max-Planck-Institut für Strahlenchemie, Stiftstr. 34−36, D-45470 Mülheim a.d. Ruhr, Germany
| | - Mathias Hucke
- Max-Planck-Institut für Strahlenchemie, Stiftstr. 34−36, D-45470 Mülheim a.d. Ruhr, Germany
| | - Michael Reus
- Max-Planck-Institut für Strahlenchemie, Stiftstr. 34−36, D-45470 Mülheim a.d. Ruhr, Germany
| | - Alfred R. Holzwarth
- Max-Planck-Institut für Strahlenchemie, Stiftstr. 34−36, D-45470 Mülheim a.d. Ruhr, Germany
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164
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Nugent JH. Oxygenic photosynthesis. Electron transfer in photosystem I and photosystem II. EUROPEAN JOURNAL OF BIOCHEMISTRY 1996; 237:519-31. [PMID: 8647094 DOI: 10.1111/j.1432-1033.1996.00519.x] [Citation(s) in RCA: 76] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
Photosystems I and II drive oxygenic photosynthesis. This requires biochemical systems with remarkable properties, allowing these membrane-bound pigment-protein complexes to oxidise water and produce NAD(P)H. The protein environment provides a scaffold in the membrane on which cofactors are placed at optimum distance and orientation, ensuring a rapid, efficient trapping and conversion of light energy. The polypeptide core also tunes the redox potentials of cofactors and provides for unidirectional progress of various reaction steps. The electron transfer pathways use a variety of inorganic and organic cofactors, including amino acids. This review sets out some of the current ideas and data on the cofactors and polypeptides of photosystems I and II.
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Affiliation(s)
- J H Nugent
- Department of Biology, University College London, UK
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165
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Greenfield SR, Wasielewski MR. Excitation energy transfer and charge separation in the isolated Photosystem II reaction center. PHOTOSYNTHESIS RESEARCH 1996; 48:83-97. [PMID: 24271289 DOI: 10.1007/bf00040999] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/17/1996] [Accepted: 01/22/1996] [Indexed: 06/02/2023]
Abstract
The nature of excitation energy transfer and charge separation in isolated Photosystem II reaction centers is an area of considerable interest and controversy. Excitation energy transfer from accessory chlorophyll a to the primary electron donor P680 takes place in tens of picoseconds, although there is some evidence that thermal equilibration of the excitation between P680 and a subset of the accessory chlorophyll a occurs on a 100-fs timescale. The intrinsic rate for charge separation at low temperature is accepted to be ca. (2 ps)(-1), and is based on several measurements using different experimental techniques. This rate is in good agreement with estimates based on larger sized particles, and is similar to the rate observed with bacterial reaction centers. However, near room temperature there is considerable disagreement as to the observed rate for charge separation, with several experiments pointing to a ca. (3 ps)(-1) rate, and others to a ca. (20 ps)(-1) rate. These processes and the experiments used to measure them will be reviewed.
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Affiliation(s)
- S R Greenfield
- Argonne National Laboratory, Chemistry Division, 60439-4831, Argonne, IL, USA
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166
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Konermann L, Holzwarth AR. Analysis of the absorption spectrum of photosystem II reaction centers: temperature dependence, pigment assignment, and inhomogeneous broadening. Biochemistry 1996; 35:829-42. [PMID: 8547263 DOI: 10.1021/bi9513158] [Citation(s) in RCA: 58] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
In this study a model for decomposition and pigment assignment of the low-temperature (10 K) absorption spectrum of the photosystem II reaction center (D1-D2-cytochrome b559 complex, PSII-RC) is developed. It is based on theoretical calculations of the line shapes of the inhomogeneously broadened pigment spectra, taking into account electron-phonon coupling. The analysis is performed under the hypothesis that exciton coupling is weak, except for the P680 special pair. In this way a detailed decomposition of the absorption spectrum is obtained. Within the model the temperature dependence of the spectrum can be well explained. It is mainly caused by the temperature-dependent changes of the homogeneous absorption spectra of the individual pigments in the PSII-RC. In addition, slight changes in the inhomogeneous distribution functions have to be taken into account. Two slightly different parameter sets are found. We prefer one of these parameter sets which indicates that an accessory chlorophyll (Chl) is the lowest energy pigment in the RC core and that the two antenna Chls have their spectral maxima at 667.7 and 677.9 nm, respectively. The relationship between the shape of the absorption spectrum and the pigment stoichiometry of the sample (ratio of chlorophyll a:pheophytin a), which was noticed by comparison of a variety of different independently prepared samples, can be explained by the presence of "additional" Chl molecules which are nonstoichiometrically bound to part of the PSII-RCs. These Chls can be grouped into three spectrally distinguishable pools. One of them has its absorption maximum at about 683 nm and is responsible for the prominent shoulder that is present in the 10 K absorption spectra of most PSII-RC preparations. Our results suggest that the Chl content of the samples has been underestimated in many spectroscopic studies on the PSII-RC.
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Affiliation(s)
- L Konermann
- Max-Planck-Institut für Strahlenchemie, Mülheim a.d. Ruhr, Germany
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167
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