Mechanism of conductivity of artificial phospholipid membranes in presence of ion carriers

In the work we consider two mechanisms of conductivity. The first consists in the fact that uncoupling agents allow the protons to pass only through the solution-membrane boundary. Then the protons migrate through the membrane under the action of the field and at the other boundary again pass into solution by means of uncoupling agents. Formulae have been obtained for the conductivity but its dependence on pH proved to be monotonic. Thus, the main experimental finding-sharp maximum in the conductivity curve-does not find any explanation within the framework of this model. We have investigated another mechanism. The uncoupling agent is regarded as a proton carrier. At one boundary of the membrane the uncoupling agent links up with a proton, this complex diffuses to the other boundary where the proton passes into solution and the uncoupling agent again returns to the first boundary. The cycle is closed. Formulae have obtained for conductivity. They correctly describe the experimental dependence on pH of the solution. Cases both of charged and uncharged carriers are analysed.