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

New heteropolysiloxane (HPS) membranes containing macrocyclic or linear com plexants, chemically linked in a reticulated silica matrix, were synthetize d by the sol-gel process and used for the facilitated transport of L-phenyl alanine. The solution-diffusion model was used to analyse experimental tran sport results obtained by studying the influence of the macrocyclic complex ant, 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 ro le of the polytopic macrocyclic complexant. This complexant improved the pa rtition of the amino acid into the membrane by specific macrocyclic complex ation combined with non-covalent interactions (hydrogen bonding, charge int eraction), leading to a dual mode transport mechanism. The transport of L-P henylalanine increased with the pH gradient between the feed and the strip phase; this transport simulated biological amino acid transport in cell mem branes. (C) 1999 Elsevier Science B.V. All rights reserved.