[Temperature independence of the rate of the rapid phase of P700+ dark reduction].
To elucidate the mechanism of interaction between P700+ and reduced primary electron acceptor in the reaction centres of photosystem I dark relaxation time course of absorption changes at 700 nm was studied at different temperatures. It is shown that in photosystem I subchloroplast fragments with partially inactivated endogenous secondary electron acceptors (treatment by ether or preliminary heating) the recombination of reduced primary acceptor and P700+ is found at -15 degrees C. In fragments with undamaged system of secondary acceptors the recovery of primary photoact in darkness is observed only at temperatures lower than -95 degrees C. At temperatures from -60 degrees to -170 degrees C the electron transfer from reduced primary acceptor to P700+ is described by the first order reaction with half time 250 ms; the rate of this process does not depend on the presence of secondary electron acceptor. The temperature independence of the rate of rapid phase P700+ dark reduction is interpreted as an indication of tunneling mechanisms from reduced primary acceptor to P700+.
D001665:Binding Sites; D002736:Chloroplasts / Q000378:metabolism*; D003624:Darkness; D004579:Electron Transport; D007700:Kinetics; D010084:Oxidation-Reduction; D010788:Photosynthesis; D010860:Pigments, Biological / Q000378:metabolism*; D013696:Temperature
D010860:Pigments, Biological
Nezavisimost' ot temperatury skorosti bystroi fazy temnovogo vosstanovleniia P700+.