A kinetic analysis of proton transport in bacteriorhodopsin-liposomes based on bilateral pH determinations.

Simultaneous changes of pH in the inner and outer liquids of proteoliposomes, the membrane of which consisted of asolectin and bacteriorhodopsin (BR), were determined during transient states after a shift from the light to the dark and the reverse. Some mathematical equations of a model characterizing the mechanism of the proton transport through the proteoliposome membrane were developed by considering the proton pump of BR, lightdependent and light-independent proton leaks from the liposomes, and buffering capacities of the intra- and extravesicular liquids. The model equations (equations 8(A) and 8(B)) could assess the effect of concurrent change of the bilateral proton concentrations on the rate of proton transport and could simulate well the dynamic aspect of pH changes within the internal and external liquid of the proteoliposomes.