[Kinetics of pigment-acceptor interaction induced by steady-state illumination in Synechocystis spaeroides photosystem I preparations cooled to 160 K in the dark and on light].
The kinetics of dark reduction of chlorophyll P700 oxidized by steady-state illumination in photosystem I reaction center preparations of cyanobacterium Synechocystis sp. coolled in the dark to 160 K is greatly nonexponential. The characteristic times for the components of the reaction are from fractions of a second to minutes and more. During cooling reaction center preparations on actinic light, a great part of chlorophyll P700 is fixed at 160 K in oxidized state. The kinetics of dark reduction of P700+ in the fraction of reaction centers that retain the photochemical activity in these conditions is faster than the kinetics in samples cooled in the dark. A theoretical analysis of the substantial deceleration of the P700+ dark recovery kinetics was done for photosystem I reaction center preparations oxidized by steady-state illumination to 160 K in contrast with situation that arises after the oxidation of reaction centers by single short light pulses. The deceleration of the kinetics in samples activated by steady-state illumination can be explained by processes of microconformational relaxation, connected with proton shifts in the reaction center structure.
Noks
P P
PP
Krasil'nikov
P M
PM
Heinnickel
M
M
Rubin
A B
AB
D002734:Chlorophyll / Q000737:chemistry*; D003080:Cold Temperature; D003624:Darkness; D004579:Electron Transport; D007700:Kinetics; D008027:Light; D008029:Lighting; D010084:Oxidation-Reduction; D045331:Photosystem I Protein Complex / Q000737:chemistry* / Q000528:radiation effects*; D010860:Pigments, Biological / Q000737:chemistry; D046940:Synechococcus / Q000201:enzymology*
D045331:Photosystem I Protein Complex; D010860:Pigments, Biological; D002734:Chlorophyll; C001785:chlorophyll P 700