Determination of the Functioning Site of Chlorophyll a' in the Photosynthetic Reaction Center I

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The present research has been conducted to draw a conclusion as to the actual number and the in vito functioning site of chloro-phyll a' (Chl a') which the researchers had detected in the vicinity of the reaction center P700 of photosystem I for a variety of oxygenic photo-synthetic organisms. After establishing HPLC conditions by which most of the chlorophylls, carotenoids/ xanthophylls and quinines can be determined in a relatively short time, we analyzed the pigment compositions of higher plants, a thermophilic cyanobacterium, regular cyanbacteria and green alga, the stoichiometry Chl a' /P700 = 1 was concluded.This, together with an X-ray crystallographic result on the system I reaction center of the thermophilic cyanobacterium, reported in 2001 by Jordan et al., finally has led to a conclusion that Chl a' is an essential component of P700 itself, forming a heterodimer with the normal Chl a molecule.In addition to these, the reaction center molecular assemblies of a green sulfur bacterium and of a marine prokaryote have been elucidated for the first time.