Dimer machanism of the work of nigericin on the bilayer lipid membranes

The authors have studied the electrical properties of a bilayer lecithin membrane in the presence of the antibiotic nigericin. At an antibiotic concentration of the order 10^-6, m conductivity of the b.l.m. increases to 10^-7 Ω^-1cm^-2. The gradient of potassium ions causes a membrane potential of the order 40 mV, for a tenfold concentration gradient, and the negative pole is on the side with the high concentration of potassium. The membrane potential due to the gradient of hydrogen ions depends on the concentration of potassium ions present in equal amounts on both sides of the membrane. At low concentrations of potassium, the "hydrogen" potential has the usual sign with the nagative pole in solution with a high concentration of protons. At a concentration of potassium exceeding 0·03 m the "hydrogen" potential has the opposite sign. This unusual result cannot be explained on the basis of the published hypotheses of the mechanism of charge transfer across the b.l.m. by means of nigericin. To describe the experimental findings obtained the authors develop a theory based on the assumption that the charge across the membrane is carried by dimers of nigericin. Satisfactory agreement of the theory with the experimental results is achieved.