Studies of poly-γ-methyl- l-glutamate monolayers by infrared ATR and transmission spectroscopy and electron microscopy

Abstract

Polarized infrared ATR and transmission spectra were studied of built-up films of poly-γ-methyl- l-glutamate (PMLG) transferred onto a germanium plate at 15 and 22 mN·m −1, which are below and above an apparent plateau region, respectively, in the surface pressure (π)-area ( A) isotherm. Electron photomicrographs of these films were also obtained by using the folding method, and the film thickness was measured. It was concluded from results of these experiments that the PMLG molecules were in the α-helical conformation and helix axes lay flat on the water surface as condensed ordered arrays forming a certain angle with the compressing direction. The plateau region in the π- A isotherm was ascribed to a transition process from monolayer to bilayer, the molecular conformation as well as orientation being left unchanged.