ISSN:
1573-5079
Keywords:
Photosystem II
;
core particle
;
P680
;
830 nm transient absorption
;
S-states
;
oxygen-evolving complex
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
Notes:
Abstract The kinetics of P680+ reduction in oxygen-evolving spinach Photosystem II (PS II) core particles were studied using both repetitive and single-flash 830 nm transient absorption. From measurements on samples in which PS II turnover is blocked, we estimate radical-pair lifetimes of 2 ns and 19 ns. Nanosecond single-flash measurements indicate decay times of 7 ns, 40 ns and 95 ns. Both the longer 40 ns and 95 ns components relate to the normal S-state controlled Yz → P680+ electron transfer dynamics. Our analysis indicates the existence of a 7 ns component which provides evidence for an additional process associated with modified interactions involving the water-splitting catalytic site. Corresponding microsecond measurements show decay times of 4 μs and 90 μs with the possibility of a small component with a decay time of 20–40 μs. The precise origin of the 4 μs component remains uncertain but appears to be associated with the water-splitting center or its binding site while the 90 μs component is assigned to P680+-QA − recombination. An amplitude and kinetic analysis of the flash dependence data gives results that are consistent with the current model of the oxygen-evolving complex.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00034782
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