Effect of Dehydrated Trehalose Matrix on the Kinetics of Forward Electron Transfer Reactions in Photosystem I, Zeitschrift fur Physikalische Chemieстатья
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Дата последнего поиска статьи во внешних источниках: 11 марта 2017 г.
Аннотация:The effect of dehydration on the kinetics of forward electron transfer (ET) has been studied in cyanobacterial photosystem I (PS I) complexes in a trehalose glassy matrix by time-resolved optical and EPR spectroscopies in the 100 fs to 1 ms time domain. The kinetics of the flash-induced absorption changes in the subnanosecond time domain due to primary and secondary charge separation steps were monitored by pump–probe laser spectroscopy with 20-fs low-energy pump pulses centered at 720 nm. The back-reaction kinetics of P700 were measured by high-field time-resolved EPR spectroscopy and the forward kinetics of A−1A/A−1B→FX by time-resolved optical spectroscopy at 480 nm. The kinetics of the primary ET reactions to form the primary P+700A−0 and the secondary P+700A−1 ion radical pairs were not affected by dehydration in the trehalose matrix, while the yield of the P+700A−1 was decreased by ~20%. Forward ET from the phylloquinone molecules in the A−1A and A−1B sites to the iron–sulfur cluster FX slowed from ~220 ns and ~20 ns in solution to ~13 μs and ~80 ns, respectively. However, as shown by EPR spectroscopy, the ~15 μs kinetic phase also contains a small contribution from the recombination between A−1B and P+700. These data reveal that the initial ET reactions from P700 to secondary phylloquinone acceptors in the A- and B-branches of cofactors (A1A and A1B) remain unaffected whereas ET beyond A1A and A1B is slowed or prevented by constrained protein dynamics due to the dry trehalose glass matrix.