Conformational transitions of polypeptides in ternary solvent systems

Phase diagrams for conformational transitions of polypeptides in ternary organic solvent systems containing two active and one inert component are calculated for a model which takes into account possible interaction of the two active components with each other as well as with the polypeptide backbone. The results of experimental determinations of conformational transitions and isothermal phase boundaries for poly(beta-benzyl L-asparate) (PBA) in three-model solvent systems are in generally good accord with the theory. The solvent systems are: (a) 1-chloropropionic acid-dichloroacetic acid (DCA)-1,1,2,2-tetrachloroethane (TCE), (b) monochloroacetic acid-DCA-TCE, and (c) dimethyl sulfoxide-DCA-TCE.