Self-Assembled Complexes of Synthetic Polypeptides and Oppositely Charged Low Molecular Weight Surfactants. Solid-State Properties

Abstract

Solid-state properties of the stoichiometric complexes formed by sodium poly(α,l-glutamate) and oppositely charged low molecular weight surfactants (alkyltrimethylammonium bromides) were examined by circular dichroism, infrared, and X-ray diffraction techniques. The polypeptide chains in the complexes were shown to be predominantly in the α-helical conformation at room temperature. At higher temperatures, weakening or disruption of intramolecular hydrogen bonds stabilizing the α-helical conformation was observed. The polypeptide−surfactant complexes were shown to adopt lamellar structures in the temperature range 20−150 °C. The lamellae consist of alternating layers of polyglutamate chains and bimolecular layers of surfactant, with the surfactant alkyl chains aligned perpendicular to the lamellar surfaces and interdigitated.