| Budget Amount *help |
¥2,500,000 (Direct Cost: ¥2,500,000)
Fiscal Year 2005: ¥800,000 (Direct Cost: ¥800,000)
Fiscal Year 2004: ¥800,000 (Direct Cost: ¥800,000)
Fiscal Year 2003: ¥900,000 (Direct Cost: ¥900,000)
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| Research Abstract |
In research of biological processes, it is an important step to clarify the structure of biological polymers and their arrangement in proteins. In photosynthesis, it was only recent, after 1984, that 3-d structures of protein-pigment complexes in photosystems of photosynthetic bacteria were first clarified. Since then, research of photosynthesis has greatly been developed. Photosynthesis by these bacteria, however, uses substances like H2S, but H2O, as starting materials, and hence does not evolve oxygen. Accordingly, it had been awaited to clarify 3-d structures of protein-pigment complexes participating in oxygen-evolving photosynthesis by higher plants. It was finally achieved since 2001.
However, a big issue reveals itself. Organisms participating in the initial processes of photosynthesis are the reaction center and the antenna system, in which the core antenna encloses most closely the reaction center. It was clarified that the arrangement of pigments in the core antenna is very d
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ifferent between anoxygenic and oxygenic kinds of photosynthesis, although that in the reaction center is similar between them. It has been accepted that these two kinds of photosynthesis have evolved from a common ancestor, departing from each other. Therefore, the most important processes essential in photosynthesis should be nearly common between these two kinds of photosynthesis. This cannot be understood from the structure of the reaction center ant the antenna system.
As the most important achievement of the present work, it was clarified that the mechanism for trapping of pigment excitation energies from the core antenna by the reaction center, quickly followed by the initial fixation of excitation energies into the charge-separated state in the reaction center, is conserved between the two kinds of photosynthesis. This reaction is most important in the whole of the initial photosynthetic processes, limiting it, and photosynthesis would become difficult if this reaction mechanism was changed essentially. Accordingly, it must be conserved in evolution. In other words, the present work clarified the mechanism of the most important reaction in the whole of the initial photosynthetic processes, Less
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