A piezoelectric transducer model for phosphorylation in photosynthetic membranes

Abstract A physical model is proposed to describe a sequence of primary processes which occur in photosynthetic membranes and are involved in the synthesis of ATP. It has been recognized that, upon illumination: (i) the membrane potential is changed, and a high electric field is induced in the lipidic region of the membrane; (ii) protons are pumped from the outer into the inner phase of the membranes, leading to a pH gradient; (iii) the membranes undergo a series of mechanical modifications, the most important ones being a reversible contraction of the membrane thickness and a reduction of intermembrane spacing; (iv) ion movements occur with a net efflux of positive ions. The above mentioned electrical, electrochemical and mechanical phenomena are accommodated in a model which is based on the energy transfer through the membrane via a piezoelectric coupling. The piezoelectric effect links mutually electrical, mechanical and structural processes; it is, therefore, well suited for organizing in a single network the primary photosynthetic processes according to specific functional roles. The mathematical description of the operating characteristics of the piezoelectric energy transducer is also given, and an expression for the energy delivered at the transducer output, i.e. at the ATP synthesizing site, is calculated as a function of the electrical, mechanical and physical parameters of the layers involved in the energy transfer process.