EFFECTS OF HYDROCARBON CHAIN-LENGTH OF CATIONIC SURFACTANTS ON THE INDUCTION OF THE SECONDARY STRUCTURES OF ANIONIC POLYPEPTIDES

In their fully ionized state, the alpha -helix of poly(L-glutamic acid) (PGA) and the beta -structure of poly(S-carboxymethyl-L-cysteine) (poly left bracket Cys(CH//2COOH) right bracket were induced on addition of n-alkylammonium chlorides carrying a hydrocarbon chain longer than C//6. Hexylammonium chloride (C//6) induced the alpha -helix of PGA, while it did not induce the beta -structure of poly left bracket Cys(Ch//2COOH) right bracket . Inducing power measured as the concentration corresponding to half-induced C// one-half , showed a linear dependence on chain length when plotted in a logarithmic way in the case of the alpha -helix for a range C//6-C//1//2, while a nonlinear dependence was found in the case of the beta -structure induction for a range C//6-C//1//4.