SURFACE-POTENTIAL OF A DOUBLE-LAYER INTERACTION FORCE BETWEEN SURFACES CHARACTERIZED BY MULTIPLE IONIZABLE GROUPS

By considering that the electrostatic charge on biological surfaces arises from the presence of multiple ionizable groups, the surface potential of and double-layer force between 2 plane surfaces, separated by an electrolyte solution, were evaluated by numerically solving the non-linear Poisson-Boltzmann equation. Boundary conditions were formulated by assuming the groups of the surfaces are always in ionic equilibrium with the solution. Comparisons are made between the force numerically calculated as above and analytical expressions obtained by linearly superimposing the non-interactive electrostatic potential profiles of each surface or by solving the linearized Poisson-Boltzmann equation with fixed surface potential or with fixed surface charge density. Surface characteristics used for the comparisons were deduced from electrophoretic data on human erythrocytes or sheep leukocyte surfaces.