A new alternative to amino acids transport: facilitated transport of L-phenylalanine by hybrid siloxane membranes containing a fixed site macrocyclic complexant

New heteropolysiloxane (HPS) membranes containing macrocyclic or linear complexants, chemically linked in a reticulated silica matrix, were synthetized by the sol-gel process and used for the facilitated transport of L-phenylalanine. The solution-diffusion model was used to analyse experimental transport results obtained by studying the influence of the macrocyclic complexant, the pH value of the feed and the strip phases, the conditioning of the membrane, and the presence of K+ ions. This study has shed light on the role of the polytopic macrocyclic complexant. This complexant improved the partition of the amino acid into the membrane by specific macrocyclic complexation combined with non-covalent interactions (hydrogen bonding, charge interaction), leading to a dual mode transport mechanism. The transport of L-Phenylalanine increased with the pH gradient between the feed and the strip phase; this transport simulated biological amino acid transport in cell membranes. (C) 1999 Elsevier Science B.V. All rights reserved.