Infrared Spectra of Surface Films of Poly-gamma-Methyl-L-Glutamate

摘要

Surface pressure vs area isotherms of poly-gamma-methyl-L-glutamate spread on water from solutions of chloroform differed from those obtained when the polymer was spread from solutions of high pyridine concentration. Samples for studying infrared spectra of the material forming the monolayer were obtained by collapsing the monolayer onto a transparent plate or by depositing a monolayer by the Blodgett technique onto a multiple internal reflection prism. When solutions of the polypeptide were spread from chloroform upon water in a Langmuir-Adam film balance to form an insoluble monolayer, a plateau in the force-area isotherm and a large limiting area were observed. Spectra of these monolayers were characterized by amide I and II regions characteristic of the alpha-helical or random configuration. There was not a change in secondary structure corresponding to the plateau region detectable via the IR spectra. Spreading solutions of high pyridine concentration led to isotherms without a plateau and with a much smaller limiting area. Spectra of these monolayers showed a significant amount of beta-type material. This is the first unambiguous correlation between the infrared spectra of uncollapsed monolayers of polypeptides and their behavior at the air/water interface. (Author)