Time-Resolved FTIR Difference Spectroscopy of Photosynthetic Bacterial Reaction Centers
Primary photosynthetic reactions feature rapid kinetics with high quantum yield of stable charge separation occurring in basic units called reaction centers (RC). The X-ray structure of bacterial RC [1,2] suggests that the efficiency and the stability of the charge separation rely at least partly on the protein environment to optimize the orientation and the localization of the various redox components involved in electron transport. The differences in the nature and organization of the aminoacids forming the binding pocket of the two quinones, QA and QB, are thought to be responsible for their different properties in JRC. Indeed, the two quinones are unequivalent, QA (menaquinone for Rps. viridis and ubiquinone for Rb. sphaeroides) is more tightly bound to the protein than QB (ubiquinone for both RC), and they display different redox properties i.e. QA is a one-electron acceptor while QB can accept two electrons under physiological conditions.
KeywordsReaction Center Difference Spectrum Protein Environment Acceptor Quinone Bacterial Reaction Center
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