LEUCINE TRANSPORT THROUGH CATION-EXCHANGE MEMBRANES, EFFECTS OF HCL CONCENTRATION ON INTERFACIAL TRANSPORT

The leucine permeability coefficients, P, through a cation exchange me mbrane were measured as a function of HCl concentration, C-HCl, from 0 to 10(-1) mol/L for three different interfacial conditions and were c ompared with the results for glycine. Leucine transport phenomena rema rkably depended on the interfacial condition between the membrane and the external solution. The lowest P (2.33 x 10(-8) cm(2)/s) was obtain ed at C-HCl = 0 for both sides of the membrane, and generally P increa ses with an increase in C-HCl. In case of the glycine, the lowest P (1 .85 x 10(-7) cm(2)/s) had been obtained if C-HCl On the glycine source side was 10(-1) mol/L and that on the opposite side was 0, The highes t P (4.34 x 10(-7) cm(2)/s) was obtained if C-HCl On the leucine sourc e side was 0 and that on the opposite side was 10(-1) mol/L as well as for glycine (4.16 x 10(-6) cm(2)/s). The P values of glycine had been explained by the transport mechanism based on the interfacial chemica l reaction (protonation, deprotonation, or ion-exchange) and the ionic transport across a charged membrane, The P values of leucine were als o explained qualitatively by the same mechanism as glycine; however, t hey are remakably affected by the physicochemical properties of the me mbrane, such as hydrophobicity and molecular size. (C) 1998 Academic P ress.