Electrophoretic mobility of biological cells in asymmetric electrolyte solutions

The electrophoretic mobility of a particle covered by a membrane in an a:b electrolyte solution is modeled theoretically. The membrane, which simulates the surface of a biological cell, is ion-penetrable, and carries homogeneously distributed negative fixed charges. An approximate expression for the electrophoretic mobility is derived. Based on the results of numerical simulation, we conclude the following: (1) The absolute Donnan potential increases with the concentration of the fixed charges Co, but decreases with the ionic strength 1. (2) The greater the valence of cation a, the lower the absolute potential distribution. (3) The greater the C-0, the greater the absolute mobility of a particle, \mu\, and the greater the friction coefficient of the membrane phase gamma, the smaller the \mu\. (4) A large I or a large a leads to a small \mu\. (5) The greater the ratio (permittivity of solution/permittivity of membrane phase), the smaller the \mu\. (6) For a large gamma, \mu\ decreases with the thickness of membrane d under the condition of constant amount of fixed charges. However, if gamma is sufficiently small, the variation of I lr I as a function of d exhibits a maximum. The classic result of Smoluchowski for the electrophoretic mobility of a rigid particle can be recovered as a limiting case of the present model. (C) 1996 Academic Press Limited