α‐Elastin coacervate as a protein liquid membrane: Effect of pH on transmembrane potential responses

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Abstract
A protein liquid membrane composed of coacervated α‐elastin, a chemical fragmentation product of the biological elastic fiber protein, functioned as an amphoteric liquid ion‐exchange membrane. Ionic permselectivities of the α‐elastin coacervate membrane to a series of metal chlorides were investigated for the concentration‐cell systems by the ordinary electrochemical measurements. Effects of pH on the transmembrane potential responses for NaCl, CaCl2, and MgCl2 systems were examined. Only in the Ca2+ ‐containing system did potential responses stay at constant levels against the pH changes, whereas in the other systems, increasing pH caused potential changes, indicating a improvement of cationic permselectivity across the α‐elastin coacervate membrane. It was suggested that the characteristic Ca2+ transport mechanisms across the α‐elastin coacervate membrane are related in some way to the polypeptide backbone interactions specific and selective to Ca2+ ions. © 1992 John Wiley & Sons, Inc.