pH dependence of electrostatic interaction between ion-penetrable membranes.

A theory on the electrostatic repulsion between ion-penetrable membranes proposed previously by us is extended by taking into account the degree of dissociation of the membrane-fixed ionizable groups. A system of equations which determines the pH dependence of the membrane interaction is presented. The density of membrane-fixed charges is consistently determined as a function of the electric potential so that both the membrane-fixed charge density and the potential are not constant but functions of the membrane separation. The pH at the surface of interacting membranes is also calculated as a function of the membrane separation.