ION-TRANSPORT THROUGH MEMBRANES WITH SOFT INTERFACES - THE INFLUENCE OF THE POLAR ZONE THICKNESS

A membrane with soft permeable interfaces in an aqueous solution has b een modelled by taking into account the spatial distribution of struct ural electric charges and dipoles in the interfaces. The model was dev eloped with special stress on its application to biological membranes. The electric potential distribution and the ion transport across the membrane are studied and the important role of the interface thickness L on ion transport and membrane selectivity is shown. An interesting result is found for certain combinations of charge and dipole densitie s: a cation selective membrane may become anion selective when L chang es. It is discussed how the results obtained can help to explain exper imental results for membrane selectivity.