Bidimensional state conformation of poly-γ-methyl-l-glutamate: I. α, β-conformations and their mixtures with arachidic acid

Abstract

Monolayers of poly-γ-methyl- l-glutamate (PγMG) were studied in the α and β conformations, both as a function of the pH of the substrate and on substrates containing pyridine, as well as mixtures of them with arachidic acid (AA). It is shown that the polyamino acid maintains at the interface the macromolecular conformation it has in the spreading solvent (97% chloroform + 3% of dichloroacetic acid for the α conformation, and 97% pyridine + 2.5% dichloroacetic acid + 0.5% chloroform for β conformation), by MIR spectroscopy and measurement of contact angles; the spreading isotherms and MIR spectra taken as a function of substrate pH show a gradual hydrolysis of the polyamino acid, reaching complete denaturation at pH 13. Parameters deduced by applying Huggins' theory show the existence at the water-air interface of two different macromolecular forms, depending on the spreading solvent. Mixtures of both α and β forms of PγMG show incompatibility with arachidic acid, even if interactions occur between the lipid chains and the macromolecular micelles in the “bad fit” zones of the latter.