ISSN:
1573-5079
Keywords:
H+-oscillation
;
photosystem II
;
protolytic reactions
;
Q-400(Fe2+)
;
water oxidation
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
Notes:
Abstract The protolytic reactions of PSII membrane fragments were analyzed by measurements of absorption changes of the water soluble indicator dye bromocresol purple induced by a train of 10 μs flashes in dark-adapted samples. It was found that: a) in the first flash a rapid H+-release takes place followed by a slower H+-uptake. The deprotonation is insensitive to DCMU but is completely eliminated by linolenic acid treatment of the samples; b) the extent of the H+-uptake in the first flash depends on the redox potential of the suspension. In this time domain no H+-uptake is observed in the subsequent flashes; c) the extent of the H+-release as a function of the flash number in the sequence exhibits a characteristic oscillation pattern. Multiphasic release kinetics are observed. The oscillation pattern can be satisfactorily described by a 1, 0, 1, 2 stoichiometry for the redox transitions Si → Si+1 (i=0, 1, 2, 3) in the water oxidizing enzyme system Y. The H+-uptake after the first flash is assumed to be a consequence of the very fast reduction of oxidized Q400(Fe3+) formed due to dark incubation with K3[Fe(CN)6]. The possible participation of component Z in the deprotonation reactions at the PSII donor side is discussed.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00035239
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