title: Systems approach to excitation-energy and electron transfer reaction networks in photosystem II complex: model studies for chlorophyll a fluorescence induction kinetics.
abstract: Photosystem II (PS II) is a protein complex which evolves oxygen and drives charge separation for photosynthesis employing electron and excitation-energy transfer processes over a wide timescale range from picoseconds to milliseconds. While the fluorescence emitted by the antenna pigments of this complex is known as an important indicator of the activity of photosynthesis, its interpretation was difficult because of the complexity of PS II. In this study, an extensive kinetic model which describes the complex and multi-timescale characteristics of PS II is analyzed through the use of the hierarchical coarse-graining method proposed in the authors׳ earlier work. In this coarse-grained analysis, the reaction center (RC) is described by two states, open and closed RCs, both of which consist of oxidized and neutral special pairs being in quasi-equilibrium states. Besides, the PS II model at millisecond scale with three-state RC, which was studied previously, could be derived by suitably adjusting the kinetic parameters of electron transfer between tyrosine and RC. Our novel coarse-grained model of PS II can appropriately explain the light-intensity dependent change of the characteristic patterns of fluorescence induction kinetics from O-J-I-P, which shows two inflection points, J and I, between initial point O and peak point P, to O-J-D-I-P, which shows a dip D between J and I inflection points.
authors.affiliation: Graduate School of System Informatics, Department of Computational Science, Kobe University, 1-1 Rokkodai, Nada-ku, Kobe 657-8501, Japan. Electronic address: matsuoka@eniac.scitec.kobe-u.ac.jp.
authors.forename: Takeshi
authors.initials: T
authors.lastname: Matsuoka
authors.affiliation: Graduate School of System Informatics, Department of Computational Science, Kobe University, 1-1 Rokkodai, Nada-ku, Kobe 657-8501, Japan. Electronic address: tanaka2@kobe-u.ac.jp.
authors.forename: Shigenori
authors.initials: S
authors.lastname: Tanaka
authors.affiliation: Graduate School of Human Development and Environment, Kobe University, 3-11 Tsurukabuto, Nada-ku, Kobe 657-8501, Japan. Electronic address: ebina@kobe-u.ac.jp.
authors.forename: Kuniyoshi
authors.initials: K
authors.lastname: Ebina
mesh_terms: D002734:Chlorophyll / Q000378:metabolism*; D000077194:Chlorophyll A; D004579:Electron Transport; D005453:Fluorescence; D007700:Kinetics; D008954:Models, Biological; D010788:Photosynthesis; D045332:Photosystem II Protein Complex / Q000378:metabolism*; D049490:Systems Biology
chemical_list: D045332:Photosystem II Protein Complex; D002734:Chlorophyll; D000077194:Chlorophyll A
keywords: Coarse graining; Electron transfer; Excitation-energy transfer; Multi-scale simulation; Photosynthesis