Effect of pH on the interfacial tension of lipid bilayer membrane

The dependence of the interfacial tension of a lipid bilayer on the pH of t he aqueous solution has been studied. A theoretical equation is derived to describe this dependence. Interfacial tension measurements of an egg phosph atidylcholine bilayer were carried out. The experimental results agreed wit h those derived from the theoretical equation obtained close to the isoelec tric point within a range of three pH units. A maximum corresponding to the isoelectric point appears both in the theoretical equation and in the expe rimental data.