TRANSMEMBRANE REDUCTION OF METHYLVIOLOGEN BY ASCORBATE PHOTOSENSITIZED BY BACTERIOPHEOPHYTIN-A IN LIPOSOMES - EFFECT OF TRANSMEMBRANE POTENTIAL

Operation of a bacteriopheophytin a (BPh) reductive mechanism for elec tron transfer in liposome media has been demonstrated. The electron tr ansfer through the liposome wall can be accomplished mainly by an elec tron exchange mechanism between BPh(in)- and BPh(out) at opposing side s of the membrane. The rate of electron transfer across the bilayer an d the rate of backward recombination of BPb(in)- and ascorbate radical s on the inner liposome surface are influenced by the generation of tr ansmembrane potentials with K+ gradients in the presence of valinomyci n. The ratio of the transmembrane electron transfer rate constants was measured at positive, negative and zero transmembrane potentials by l aser photolysis.