Circular dichroism of copoly(γ‐stearyl‐L‐glutamate–γ‐methyl‐L‐glutamate)

Abstract

AbstractCopoly(γ‐stearly‐L‐glutamate‐γ‐methyl‐L‐glutamate)s with various compositions were synthesized by the ester exchange reaction of poly(γ‐methyl‐L‐glutamate). Circular dichroism studies were carried out for solution and solid film as a function of the degree of stearylation and temperature. The slight and gradual temperature dependence of molecular ellipticity was observed for solution of all the copolyglutamates studied here and for the solid film of the copolyglutamate with the degree of stearylation of 16%, indicative of no reversal in the helix sense. However the remarkable change in negative molecular ellipticity with temperature was detected for the solid film of the copolyglutamate with a low degree of stearylation, e.g., 52%, whereas the drastic change in molecular ellipticity from a negative to positive value appeared for that with a higher degree of stearylation. This is discussed in terms of the reversal in the helix sense from a right‐ to left‐handed α helix with the increase of temperature occurring at the melting temperature of the ordered side chain region.