The interaction between synthetic polypeptides and fatty acids at the air/water interface

Abstract

The interactions between synthetic polypeptides having α-helical conformation and fatty acids in monolayer on a pure water surface were studied by surface pressure measurement. Poly-γ-benzyl- l-glutamate (PBLG) and poly-γ-methyl- l-glutamate (PMLG) were used as the synthetic polypeptides, and stearic and palmitic acid as the fatty acids. At a molar ratio of PBLG to stearic or palmitic acid of more than 10 to 1, the fatty acid molecules seem to be intercalated into the side chains of PBLG. At a lower ratio, the miscibility of PBLG in the monolayer state with the fatty acid depends on whether the monolayer of fatty acid shows the liquid condensed film. PBLG in multilayer state is not miscible with the two fatty acids. The miscibility of PMLG in the monolayer state with stearic or palmitic acid also depends on the monolayer state of the fatty acid. PMLG in the multilayer state is miscible with the two fatty acids. PBLG shows better miscibility with the two fatty acids than PMLG. Palmitic acid shows better miscibility with the two peptides than stearic acid.