Energetics of Cholesterol Transfer between Lipid Bilayers

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• 作者：Zhancheng Zhang ; Lanyuan Lu ; Max L. Berkowitz
• 刊名：Journal of Physical Chemistry B
• 出版年：2008
• 出版时间：March 27, 2008
• 年：2008
• 卷：112
• 期：12
• 页码：3807 - 3811
• 全文大小：239K
• 年卷期：v.112,no.12(March 27, 2008)
• ISSN：1520-5207

文摘

It is believed that natural biological membranes contain domains of lipid ordered phase enriched in cholesteroland sphingomyelin. Although the existence of these domains, called lipid rafts, is still not firmly establishedfor natural membranes, direct microscopic observations and phase diagrams obtained from the study of three-component mixtures containing saturated phospholipids, unsaturated phospholipids, and cholesterol demonstratethe existence of lipid rafts in synthetic membranes. The presence of the domains or rafts in these membranesis often ascribed to the preferential interactions between cholesterol and saturated phospholipids, for example,between cholesterol and sphingomyelin. In this work, we calculate, using molecular dynamics computersimulation technique, the free energy of cholesterol transfer from the bilayer containing unsaturatedphosphatidylcholine lipid molecules to the bilayer containing sphingomyelin molecules and find that the affinityof cholesterol to sphingomyelin is higher. Our calculations of the free-energy components, energy and entropy,show that cholesterol transfer is exothermic and promoted by the favorable change in the lipid-lipid interactionsnear cholesterol and not by the favorable energy of cholesterol-sphingomyelin interaction, as assumedpreviously.