Spectroscopic resolution of the picosecond reduction kinetics of the secondary electron acceptor A(1) in photosystem I

Forward electron transfer in photosystem I from Synechocystis sp. PCC 6803 has been studied in the picosecond time range with transient absorption spe ctroscopy in the blue and near-UV spectral regions. From the direct measure ment, at 380-390 nm, of the reduction kinetics of the phylloquinone seconda ry acceptor Al and from the absence of spectral evolution between 100 ps an d 2 ns, pie conclude that electron transfer, from the chlorophyll a primary acceptor A(0), to A(1) occurs directly and completely with a time constant of about 30 ps, (C) 1999 Federation of European Biochemical Societies.