AMINO-ACID-TRANSPORT THROUGH CATION-EXCHANGE MEMBRANES - EFFECTS OF PH ON INTERFACIAL TRANSPORT

We present a series of experiments especially designed to show the eff ects of pH on the interfacial transport of glycine through a cation ex change membrane. The experimental results are explained qualitatively by using a theoretical model which incorporates the equilibrium dissoc iation equations for the fraction of amino acid forms at different pH values, a rate equation for the membrane interfacial transport based o n the interfacial chemical reaction, and the Nernst-Planck flux equati ons for the ion transport through the bulk of the membrane. The result s appear to indicate that the rate-limiting step in the amino acid tra nsport process could be the rate at which glycine exits the membrane, and they contribute to a better understanding of amino acid permeation across charged membranes. (C) 1997 Academic Press.