The Modification by Biliproteins of Intensity and Direction of Electron Flow Across Chlorophyll-Containing Membranes

Abstract

Photosensitive phenomena in artificial bileaflet membranes containing photosynthetic pigments are described and analyzed in terms of a potential model for the primary events in photo-synthetic energy storage. Illumination of a bilayer membrane interposed between aqueous solutions of different redox potential results in establishment of an electric current across the membrane. It is suggested that absorption of photons by the chlorophyll in the bilayer allows electron transfer across the membrane. This process differs from photosynthetic processes in two important aspects: the quantum efficiency of the process in the synthetic membrane is very low and energy is dissipated rather than stored. When biliproteins (extrinsic membrane proteins from blue-green and red algae) are introduced into the system, the resulting membranes exhibit two important properties: an increase by two- to threefold of the quantum efficiency of the electron transfer process and an abilty to direct the flow of electrons even against a pre-existing potential gradient, so that energy storage is accomplished. The observations are analyzed in terms of a model to explain the processes relevant to photosynthesis and the trivial process of degradation of the redox gradient.