title: Reduced minimum model for the photosynthetic induction processes in photosystem I.
abstract: Photosystem I (PS I) is one of the most important protein complexes for photosynthesis, which is present in plants, algae and cyanobacteria. A variety of mechanisms for environmental response in and around PS I have been elucidated experimentally and theoretically. During the photosynthetic induction time, the congestion of electron occurs in PS I and then the over-reduced PS I states are realized. This means that the degree of freedom of the redox states of PS I becomes large and thus the understanding of phenomena based on the model describing PS I in the state space becomes difficult. To understand the phenomena intuitively, we have reduced the complicated PS I model which has the multi-timescale property for electron and excitation-energy transfer processes into a simple one which has only the mono-timescale property through the use of hierarchical coarse-graining (HCG) method. The coarse-grained model describes the state of PS I by seven variable states, while the original model describes the PS I by 3×2(7)(=384) states. Based on the derived model, the I820 (820nm transmittance signal) curve in photosynthetic induction term, which indicates the accumulations of P700(+) and Pc(+), is simulated and analyzed in comparison with experiment. With respect to this signal curve, it is revealed that the initial increase up to the shoulder at 10(-3) s, the increase from that point to the peak at 2 ×10(-2) s, and the decay after that peak reflect the accumulations of P700(+), Pc(+) and P700FA(-)FB(-) (PS I state in which P700,FA(-) and FB(-) are observed.), respectively. Besides, the important role of the charge recombination processes from P700(+)A0A(-) and P700(+)A1A(-) states for the dissipation of the extra absorbed energy in photosynthetic induction period is confirmed.
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: D004583:Electrons; D004735:Energy Transfer; D008958:Models, Molecular; D010788:Photosynthesis; D045331:Photosystem I Protein Complex / Q000737:chemistry / Q000378:metabolism*
chemical_list: D045331:Photosystem I Protein Complex
keywords: Electron transfer; Excitation-energy transfer; Hierarchical coarse-graining (HCG); Photosynthesis; Photosystem I (PS I)