Adsorption of Monovalent Ions to Phosphatidylcholine-Cardiolipin Membranes

We examined the adsorption of Na+, Cl−, H+, and OH− ions on phosphatidylcholine-cardiolipin liposomal membrane surfaces using both experimental and theoretical approaches. The dependence of the membrane surface charge density on the pH of the electrolyte solution was determined using microelectrophoresis. A mathematical model comprising eight equilibria was formulated to describe the adsorption of the electrolyte ions. Combination of this model with experimental surface charge density values enabled the determination of association constants. From the good agreement between the experimental and theoretical data, we can conclude that the assumed model is compatible with the experimental data.