Theoretical study on asymmetric membrane potential.

Abstract

It is well known that the asymmetry of membrane structure is closely related to the membrane function. We could obtain information on the asymmetry of membrane structure if we could analyze accurately. the asymmetric membrane potential, since the asymmetry of membrane structure should affect the membrane potential. It is considered that the origin of the asymmetric membrane potential is the difference in properties between the two membrane surfaces. In this paper, the membrane is treated by dividing it into the two sublayer (surface layer) parts adjacent to each membrane surface and the inner membrane part. The asymmetric membrane potential is investigated theoretically on the base of this model. The results show that the effects of asymmetry with respect to the surface charge density on the surface potential and on the diffusion potential within the membrane compensate for each other. The membrane potential is, therefore, scarcely affected except in the case where the diffusion potential within the membrane is negligible. It is also pointed out that, in an asymmetric membrane system with respect to the surface charge density, diffusion potential within the membrane is generated even if the mobility of a cation in equal to that of an anion. When the diffusion potential within the membrane is not negligible, only the effect of the asymmetry with respect to the standard chemical potential at the membrane surfaces is measurable experimentally. Our theory was applied to the analysis of the membrane potential of a cellulose membrane, and gave good agreement with the experimental results. Various experimental methods to confirm whether the membrane is asymmetric or symmetric are discussed.