Analysis of electrophoretic mobility data for biological cells with a new membrane model

Abstract

A new membrane model was proposed to analzye the electrophoretic mobility data of biologicall cells. The model assumes that fixed charges are uniformly distributed in a planar surface layer on the membrane lipid core and that electrolyte ions can penetrate into the layer. Based on this membrane model, an approximate analytical expression that directly relates the electrophoretic mobility of biological cells to the charge density, N, in the surface region was derived. The expression involves the Donnan potential and the surface potential in the region, both of which are a function of N and electrolyte concentration, and a parameter relating to the depth of fluid drag in the region, λ. — The best curve fitting for the experimentally obtained electrophoretic mobility values for human erythrocytes and guinea-pig polymorphonuclear leucocytes as a function of electrolyte concentration using appropriate values of N and λ gave the charge density in the surface region of both types of cells to show that the distribution of the negative charges arising from the acidic groups is fairly uniform, while the positive charges arising from the basic groups increase in the density with increasing inward distance from the boundary of the surface region and the medium.