Ion equilibrium near lipid membranes: Empirical analysis of the simplest model

The distribution of ions forming the diffuse part of the electrical double layer near the surface of lipid membranes was considered within the framewo rk of the well-known Gouy-Chapman-Stern model, with allowance for multicomp onent electrolyte composition. Problems are analyzed that arise during the application of this model to the study of such membrane surface properties as the effect of traces of multivalent ions, the account for the location o f the shear plane, the possibility of independent experimental determinatio n of the parameters of ion adsorption (the binding site density and adsorpt ion constants), and the effect of the depletion of solutions of ions having a strong affinity to phospholipids. The main conclusions are illustrated b y the experimental data obtained while studying the electrophoretic mobilit y of liposomes and the boundary potentials of planar bilayer lipid membrane s.