HELIX FORMATION OF POLY(L-GLUTAMIC ACID) AND POLY(L-LYSINE) IN THE POLYION COMPLEX PREPARED IN AQUEOUS ALCOHOL-SOLUTIONS

The total helix content has been estimated by circular dichroism measu rements for sodium poly(L-glutamate)/poly(L-lysine) hydrobromide (PLGN a/PLLHBr) mixed systems in aqueous alcohols. The polyion complexes wer e soluble in the mixed solvents, on account of the rather low total po lymer concentration (6.2 x 10(-4) (base) mol l-1), except when a polym er mixing ratio of 1:1 equivalents was used. It has been observed that the total helix content significantly decreases with polymer mixing, when compared to that observed in single polymer systems, while by the addition of ClO4-, or a short-chain PLGNa, both of which stabilize th e helix conformation of PLL, the respective helix conformations are al most completely retained. These experimental findings, together with t hose concerning the dependence of the helix content on the alcohol spe cies, are discussed, and possible structures for the polyion complexes are proposed.