Self-assembled complexes of synthetic polypeptides and oppositely charged low molecular weight surfactants. Solid-state properties

Solid-state properties of the stoichiometric complexes formed by sodium poly(alpha,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 alpha-helical conformation at room temperature. At higher temperatures, weakening or disruption of intramolecular hydrogen bonds stabilizing the alpha-helical conformation was observed. The polypeptide-surfactant complexes were shown to adopt lamellar structures in the temperature range 20-150 degrees 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.