SOLVENT-INDUCED AND SALT-INDUCED COIL HELIX TRANSITION OF POLY(L-LYSINE) SALTS IN WATER-ALCOHOL MIXTURES

Coil-helix transition has been studied for poly(L-lysine) salts, with counterion species Cl- (PLLHCl), Br- (PLLHBr) and NO3- (PLLHNO3), in a queous alcohol mixtures (water/MeOH, EtOH, 2PrOH, tBuOH) as a function of the alcohol composition and/or salt concentration. The dependence of the helix content on the solvent species and composition is interpr eted in terms of the three solvent properties i.e. dielectric constant , Gutmann-Mayer acceptor number and water activity, which have been fo und to be critical for contact ion-pair formation in the study Of poly (L-glutamic acid). The salt-induced transition is also analysed by tak ing account of the contact ion-pair formation. Comparisons are made wi th the results on the poly(L-glutamic acid) systems.