EFFECT OF TRANSMEMBRANE POTENTIAL ON CHARGE PHOTOSEPARATION IN LIPOSOMES

An unexpected transmembrane potential effect on the recombination rate of the pheophytin or bacteriopheophytin anion-radicals (dissolved in membrane) and ascorbic ion-radicals (dissolved in aqueous interior) has been established in liposomes. The influence of transmembrane potential on the recombination rate of Ru3+ (dissolved in inner volume) and (C18H37)V+ or (C14H29)V+ (dissolved in membrane) was observed. The potential was created by a potassium concentration gradient between inner and outer volumes of liposomes in the presence of valinomycin. The effect of the potential was considered on the bases of: (1) it was determined by the diffusional drift of the hydrophobic radicals in a radial direction in the membrane, according to the direction of the electric field; (2) the electric field changed the rate constant of the electron transfer, owing to the effects on the free energy and electronic coupling. Our results show the first explanation to be preferable.