EFFECT OF PHOSPHOLIPID-COMPOSITION OF BILAYER-LIPID MEMBRANE ON STEADY-STATE KINETICS OF PROTON-TRANSFER

When a hydrogen ion flux is induced by nigericin across a planar bilay er lipid membrane (BLM) with bulk pH values being equal at the opposit e sides of the BLM, the formation of a difference in the boundary pote ntials (Delta phi(b)) On the planar bilayer lipid membrane is observed by the method of the inner membrane field compensation. Increasing th e buffer concentration (citrate, phosphate, MES) leads to a decrease i n Delta phi(b). The latter forms only when phosphatidylserine is prese nt in the membrane-forming solution. We conclude that a steady-state d ifference in surface hydrogen ion concentration is created under condi tions of equal pH near the surfaces of the BLM. In another series of e xperiments, monensin-mediated formation of surface proton concentratio n difference leads to the formation of potassium ion gradient induced by nigericin. Thus the possibility of performing work due to the gradi ent of the surface proton concentration is demonstrated The relevance of these findings to the processes of energy transduction in membrane phosphorylation in mitochondria and chloroplasts is discussed.