Glycine and Leucine Transport through a Cation Exchange Membrane in their Mixed Solution: Effects of HCl Concentration on Interfacial Transport.

Abstract

The glycine and leucine permeability coefficients, Pgly and Pleu, in their mixed solutions through a cation exchange membrane were measured as a function of HCl concentration, CHCl, from 0 to 10-1 mol/l for three different interfacial conditions and were compared with the results for Pgly and Pleu, in their single solutions. Generally Pgly increases with an increase in HCl concentration. However, Pgly decreased between CHCl=10-2mol/l and CHCl=10-1 mol/l for only the case when HCl was added to the amino acid feed side. Compared with Pgly in a single glycine solution, Pgly in a mixed solution was smaller than that in the single solution. However, their profile outlines are similar. Pleu, also increased with an increase in HCl concentration. Pleu, is smaller than that of Pgly, which corresponds with the result in a single solution. Pleu decreased between CHCl=10-2 mol/l and CHCl =10-1 mol/l for only the case when HCl is added to the amino acid feed side. Compared with the Pleu in the single leucine solution, Pleu in mixed solution is not very different. The transport mechanism was determined to be an interfacial transport phenomenon. However, the effect of the interfacial transport in mixed solution appears to be decreased if compared with the case in a single solution. The reduced results for glycine in mixed solutions imply that the glycine transport is affected by that of leucine. As the solutions are not idealistic, which means that there exists an interaction between glycine and leucine, the permeability coefficient ratios of glycine to leucine, Pgly /Pleu, in the mixed solution did not correspond with that of the single solution. The highest Pgly /Pleu was 6.7 at CHCl=10-4mol/l for the case when HCl was added to the amino acid-permeated side and the next one was 6.1 at CHCl=10-4 mol/l for the case when HCl was added to both sides of the membrane.