Polymer In A Lyotropic Lamellar Phase: Possible Model For Proteins In Membranes

We study the lamellar phase of a ternary system comprised of a non-ionic surfactant, a charged polymer and water. The polymer, a water soluble random copolymer of styrene and styrene sulfonate, can be incorporated in the system up to several weight percent and its behaviour can be varied by adjusting the proportion of hydrophobic to hydrophilic monomers. Surface tension measurements clearly indicate a surfactant-polymer interaction over a wide surfactant concentration range. Using freeze fracture electron microscopy we demonstrate that the polymer molecules are confined inside the surfactant bilayers. The system offers a simple model for the protein interactions in biological membranes.