BIOPHYSICAL THEORY AND MODELING |
Effect of Membrane Characteristics on Phase Separation and Domain Formation in Cholesterol-Lipid Mixtures
Veena Pata 1 and Nily Dan 1*
1 Drexel University
* To whom correspondence should be addressed. E-mail: dan{at}coe.drexel.edu.
Submitted on September 1, 2004
Revised on October 12, 2004
Accepted on 1 November 2004
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Abstract |
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We examine, using an analytical mean-field model, the distribution of cholesterol in a lipid bilayer. The model accounts for the perturbation of lipid packing induced by the embedded cholesterol, in a manner similar to that of trans-membrane proteins. We find that the membrane-induced interactions between embedded cholesterol molecules vary as a function of the cholesterol content. Thus, the effective lipid-cholesterol interaction is concentration-dependent. Moreover, it transitions from repulsive to attractive to repulsive as the cholesterol content increases. As the concentration of cholesterol in the bilayer exceeds a critical value, phase separation occurs. The coexistence between cholesterol-rich and cholesterol-poor domains is universal for any bilayer parameters, although the composition of the cholesterol-rich phase varies as a function of the lipid properties. Although we do not assume specific cholesterol-lipid interactions or the formation of a lipid-cholesterol cluster, we find that the composition of the cholesterol-rich domains is constant, independent of the cholesterol content in the bilayer.
Key Words:
cholesterol, domain, membrane, model
