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

Abstract

A protein liquid membrane composed of coacervated alpha-elastin, a chemical fragmentation product of the biological elastic fiber protein, functioned as an amphoteric liquid ion-exchange membrane. Ionic permselectivities of the alpha-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 Ca(2+)-containing system did potential responses stay at constant levels against the pH changes, whereas in the other systems, increasing pH caused potential changes, indicating an improvement of cationic permselectivity across the alpha-elastin coacervate membrane. It was suggested that the characteristic Ca2+ transport mechanisms across the alpha-elastin coacervate membrane are related in some way to the polypeptide backbone interactions specific and selective to Ca2+ ions.

Characteristic interaction of Ca2+ ions with elastin coacervate: Ion transport study across coacervate layers of α-elastin and elastin model polypeptide, (Val-Pro-Gly-Val-Gly)n

“…In case of the binarycharged a-elastin system, on the other hand, definite pH effects on the temperature-dependent coacervation process were observed. 6 It should be noted based on these turbidity measurements that interactions of the charged amino acid residues affect on the early onset stage of the temperature-dependent coacervation of elastin peptides. Integrated charge balance of polymeric substances is, in general, one of the ruling factors to induce the coacervation process.…”

“…6 The polypentapeptide coacervate membrane was prepared by the following procedures. 6 The polypentapeptide coacervate membrane was prepared by the following procedures.…”

A mussel-derived one component adhesive coacervate

“…The outstanding interfacial adhesive and cohesive properties of Mfp-3S over a relatively wide pH range have been demonstrated previously using a surface forces apparatus (SFA) [17], and attributed to its abundant 3, 4-dihydroxyphenylalanine (Dopa) content and unique hydrophobic sequence. The strategy of achieving efficient phase separation and surface spreading by coacervation is very appealing in its simplicity, in part, because it is only rarely observed in single protein solutions: only tropoelastin is known to undergo a simple hydrophobically driven coacervation [18, 19]. Mfp-3S provides an interesting counterpoint for understanding the molecular requirements for single component coacervation.…”

Characterizations of critical processes in liquid-liquid phase separation of the elastomeric protein-water system: Microscopic observations and light scattering measurements

“…In these systems where the hydrophobic interactions are predominant, both the d Hydro and d Micro values increased significantly as compared with the off‐critical α‐elastin–water system where the electrostatic interactions cannot be ignored. Although polar amino acid contents of elastin are extremely low such as less than 5% of the total amino acid residues,1, 2, 16 the significance of charged sites on the molecular self‐assembly process also was demonstrated in sharp pH dependence of the temperature profiles of turbidity formation 17, 18. In the present investigations, the importance of the elastin polypeptides with and without charged sites and the effects of adding metal chlorides is examined only in relation to the critical and off‐critical differences in size and distribution of primary and microcoacervate aggregates.…”