Realistic Model of a Fixed-charge Membrane

A realistic model of a fixed-charge membrane was constructed to elucidate the principles involved in the Teorell-Meyer-Sievers theory. Polyelectrolyte solutions (polystyrene sulfonic acid or gelatin) were used in a multicompartment cell to serve as the "membrane." The ionic concentration and potential differences between the compartments served as a finite increment approximation to a continuous membrane phase. The profiles obtained for a positively and negatively charged membrane gave striking support for the theory. The excellent papers by Teorell elucidating the essential points in the fixedcharge theory of ionic membranes are well known to investigators interested in the field of electromotive membrane systems (1, 2). Although the ideas involved in the theory are clearly expressed, it seemed helpful toward a better understanding of the theory to construct a realistic model of a fixed-charge membrane in which the over-all E.~r.l~. and the E.M.I~. and ionic profile within the membrane could be established semiquantitatively both for a negatively and a positively "charged" system. Briefly the basic arguments in the Teorell-Meyer-Sievers theory are: The membrane is looked upon as a matrix of polymers to which are attached completely ionizable groups, the so-called "fixed charge." All the properties of such a membrane are determined by the sign and concentration of the fixed-charge groups which are assumed to be at a constant concentration throughout: the membrane. Thus in the presence of the fixed charge, ion exchange occurs between ions in the bathing solutions and those of the membrane so that to a first approximation a Donnan distribution develops at each membrane-solution interface while throughout the membrane region a diffusion field develops subject to the Dorman boundary conditions of ionic concentration. Therefore so far as the total E.~.F. in the steady state is concerned the theory describes two * Work supported in part by National Science Foundation Grant (NSF G-3440). Supported by National Science Foundation Summer Stipend. 385 J. GZN. l~sYsIOX,., 1958, Vol. 42, No. 2 The Journal of General Physiology on Jne 1, 2017 D ow nladed fom Published November 20, 1958