Simulation of photochemical process of photosynthesis using liposome-redox dye system

Abstract

Mechanism of dye-mediated electron transport across liposomal lipid bilayers has been investigated. Water-soluble redox dyes, such as thiazines or indophenols, mediate transmembrane electron transport. Under photoirradiation electron transport via dyes in excited state was also observed. The photoinduced electron transport was remarkably asymmetric with respect to the membrane plane. The rate of the rate-limiting photoreaction in bulk phase was much higher than that in inner compartment, when the rates were compared with each other on the basis of mean total concentration in the system. The origin of the asymmetry is discussed. The reaction asymmetry originates from the difference in the local concentration of the electron donor and the non-linearity of the dependence of the rate on the donor concentration. The water-soluble dyes also mediate ‘up-hill’ transport of electron under photoirradiation. The ‘up-hill’ reaction occurs only when the system is constructed so that the rate-determining photoreaction may take place in the outside of liposomes. The asymmetry is profitable for the vectorial electron transport.