Transmembrane reduction of methylviologen by ascorbate photosensitized by bacteriopheophytin a in liposomes. Effect of transmembrane potential

Abstract

Operation of a bacteriopheophytin a (BPh) reductive mechanism for electron transfer in liposome media has been demonstrated. The electron transfer through the liposome wall can be accomplished mainly by an electron exchange mechanism between BPh in − and BPh out at opposing sides of the membrane. The rate of electron transfer across the bilayer and the rate of backward recombination of BPh in − and ascorbate radicals on the inner liposome surface are influenced by the generation of transmembrane potentials with K + gradients in the presence of valinomycin. The ratio of the transmembrane electron transfer rate constants was measured at positive, negative and zero transmembrane potentials by laser photolysis.