ELECTRON AND PROTON PHOTOTRANSPORTS IN A BILAYER MEMBRANE. ACIDIC PORPHYRIN AND SUPEROXIDE ION AS ΔpH SENSITIVE CHARGE CARRIERS

Abstract

Abstract— Glycerolmonooleate planar bilayer membranes containing a zinc‐mesotetraphenyl l‐[3‐propionic acid] porphyrin separate two buffered aqueous phases, an oxidizing and a reducing one. Under illumination stationary photocurrents are recorded, that depend on the respective acidities of the aqueous phases. A strong enhancement is observed when the oxidizing solution is more acidic than the reducing solution. This phenomenon is attributed to the double role of the acidic porphyrin acting as an electron and a proton carrier. A second mechanism, also pH dependent, intervenes concurrently. The excited zinc‐porphyrin reduces oxygen and the resulting superoxide ion translocates through the membrane lipidic core.