40 research outputs found
Transcriptome analysis in switchgrass discloses ecotype difference in photosynthetic efficiency
Multiple sites of retardation of electron transfer in Photosystem II after hydrolysis of phosphatidylglycerol
EPR Kinetic Studies of Oxygen Release in Thylakoids and PSII Membranes: A Kinetic Intermediate in the S 3
Proton/Hydrogen Transfer Affects the S-State-Dependent Microsecond Phases of P680+ Reduction during Water Splitting
Original article can be found at: http://pubs.acs.org/journals/bichaw/index.html Copyright American Chemical Society DOI: 10.1021/bi9713815 [Full text of this article is not available in the UHRA]To investigate a possible coupling between P680+ reduction and hydrogen transfer, we studied the effects of H2O/D2O exchange on the P680+ reduction kinetics in the nano- and microsecond domains. We concentrated on studying the period-4 oscillatory (i.e., S-state-related) part of the reduction kinetics, by analyzing the differences between the P680+ reduction curves, rather than the full kinetics. Earlier observations that P680+ reduction kinetics have microsecond components were confirmed: the longest observable lifetime whose amplitude showed period-4 oscillations was 30 μs. We found that solvent isotope exchange left the nanosecond phases of the P680+ reduction unaltered. However, a significant effect on the oscillatory microsecond components was observed. We propose that, at least in the S0/S1 and S3/S0 transitions, hydrogen (proton) transfer provides an additional decrease in the free energy of the YZ+P680 state with respect to the YZP680+ state. This implies that relaxation of the state YZ+P680 is required for complete reduction of P680+ and for efficient water splitting. The kinetics of the P680+ reduction suggest that it is intraprotein proton/hydrogen rearrangement/transfer, rather than proton release to the bulk, which is occurring on the 1−30 μs time scale.Peer reviewe