Chemical Analytical Approach to the Molecular Machinery of Photosynthesis
--Quest for Exotic Chlorophylls in the Reaction Centers--

Tadashi WATANABE*, Akimasa NAKAMURA and Masami KOBAYASHI

Institute of Industrial Science, The University of Tokyo, Komaba, Meguro-ku, Tokyo 153-8505 Japan
Institute of Materials Science, University of Tsukuba, Tsukuba-shi 305-8573 Japan

The molecular assemblies of photosynthetic reaction centers (RCs) driving the light-to-redox energy conversion have been studied by chemical analytical and various spectroscopic means. As a result, one molecule of chlorophyll (Chl) α', the C132-epimer of the dominant pigment Chl α, was detected for the first time as an essential component of photosystem I RC of higher plants, algae, and cyanobacteria. Further, two molecules each of bacteriochlorophyll (BChl) g' and 81-OH-Chl α in heliobacterial RCs, two molecules of BChl α' in the RC of a green sulfur bacterium Chlorobium tepidum, and one or two molecules of Chl d' in the RC of a cyanobacterium Acaryochloris marina were detected. In addition, the chemical structure of BChl 663, the primary acceptor in the RC of green sulfur bacteria, and that of Zn-BChl α found in Acidiphilium rubrum, were determined. Detection/identification of these novel minor but key pigments would contribute to the discussion on the molecular machinery of photosynthetic reaction centers.

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