Lateral Organization in lipid-cholesterol mixed bilayers

¹ Purdue University
² Weill Medical College, Cornell University
³ University of Illinois
⁴ Illinois Institute of Technology

^* To whom correspondence should be addressed. E-mail: scotth{at}iit.edu.

Submitted on July 24, 2006
Revised on September 11, 2006
Accepted on 6 October 2006

	Abstract

Interactions between lipid and cholesterol molecules in membranes play an important role in the the structural and functional properties of cell membranes. While structural properties of lipid-cholesterol mixtures have been extensively studied, an understanding of the role of cholesterol in the lateral organization of bilayers has been elusive. In this paper we propose a simple, yet powerful model based on self-consistent mean field theory and Molecular Dynamics simulations, for lipid bilayers containing cholesterol. Properties predicted by our model are shown to be in excellent agreement with experimental data. Our model predicts that cholesterol induces structural changes in the bilayer through the formation of regions of ordered lipids surrounding each cholesterol molecule. We find that the "smooth" and "rough" sides of cholesterol play crucial roles in formation and distribution of the ordered regions. Our model is predictive in that input parameters are obtained from independent atomistic molecular dynamics simulations. The model and method are general enough to describe other heterogeneous lipid bilayers, including lipid rafts.

Key Words: cholesterol, dipalmtoylphosphatidylcholine, lipid bilayer, self-consistent mean field theory

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