THE INFLUENCE OF POLYMER-GRAFTED LIPIDS ON THE PHYSICAL-PROPERTIES OFLIPID BILAYERS - A THEORETICAL-STUDY

Experimental studies of bilayers containing polymer-grafted lipids hav e been underway for some time now (1-3). Modeling the physical propert ies of these bilayers, however, is not trivial because of the complexi ties in the self-assembling polymer-lipid/lipid bilayer system and the mutual influence of its two components: the lipid bilayer and the gra fted polymer. In the paper we study the influence of the grafted polym er on the structural and interactive properties of the lipid bilayer. The modeling is done in terms of some existing polymer theories (de Ge nnes' scaling theory, Flory's and Milner's mean-held theories). We pro pose a simple lateral pressure model to calculate the critical concent ration of polymer-lipid that can be incorporated into the bilayer. We study the influence of the polymer chains on the tensile strength of t he bilayer and model the dependence of the elastic coefficients K-A, k (c), and ($) over bar k(c) on the concentration and molecular weight o f the grafted polymer. For two bilayers in close proximity the interbi layer steric interactive forces are modeled for different polymer-lipi d concentrations. (C) 1994 Academic Press, Inc.