Etude du poly- l-γ-glutamate de methyle a l'interface air-eau

Abstract

The possibility of an α-helix-coil transition of the poly-γ-methyl- l-glutamate spread at the air-water interface has been investigated. The helical conformation of this polypeptide has been shown to exist in the solid film removed from an aqueous support. Starting from a well-defined conformation, the transition is induced by simple methods similar to those used in solution. 1. (i) Effect of the solvent: Addition to the support of dioxane-dichloroacetic acid mixtures of various relative proportions allows the inducement of a transition. 2. (ii) Effect of temperature: An increase of the substrate temperature allows the modification of the interaction forces responsible for the polypeptide structure. The transition phenomenon has been followed by the evolution of the surface pressure. The study at very low surface concentrations enables us to associate with the transition both the surface virial coefficient, which represents specifically the interaction between the spread polypeptide molecules and the molecules of the substrate, and the co-surface which is proportional to the dimension of the macromolecule at the interface.