Cholesterol effects on the phosphatidylcholine bilayer nonpolar region: a molecular simulation study.
A 15-ns molecular dynamics (MD) simulation of the fully hydrated dimyristoylphosphatidylcholine-cholesterol (DMPC-Chol) bilayer in the liquid-crystalline state was carried out to investigate the effect of Chol on the hydrocarbon chain region of the bilayer. The last 8-ns fragment of the generated trajectory was used for analyses. As a reference system, a pure DMPC bilayer (M. Pasenkiewicz-Gierula, Y. Takaoka, H. Miyagawa, K. Kitamura, and A. Kusumi, 1999, Biophys. J. 76:1228-1240) simulated for 14 ns was used. The study shows that a Chol-induced increase of the bulk molecular order parameter along both beta- and gamma-chain is mainly caused by a decrease of the average tilt of the chains, because the bulk average number of gauche rotamers/myristoyl chain is not significantly changed by Chol. Nevertheless, for DMPCs located near Chol molecules both the number of gauche rotamers/chain and the chain tilt are decreased. The magnitude of the Chol effect on the PC alkyl chains depends, in addition to the PC-Chol distance, on the side of the Chol molecule (alpha- or beta-face) that the chains are in contact with. This study provides some new insight into the properties of the coexistence region of the partial phase diagram for DMPC-Chol bilayers.
Róg
T
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Department of Biophysics, Institute of Molecular Biology, Jagiellonian University, 31-120 Kraków, Poland.
Pasenkiewicz-Gierula
M
M
D002784:Cholesterol / Q000737:chemistry*; D003460:Crystallization; D006838:Hydrocarbons / Q000737:chemistry*; D007536:Isomerism; D008051:Lipid Bilayers / Q000737:chemistry*; D008567:Membranes, Artificial; D008958:Models, Molecular; D018716:Molecular Mimicry; D010713:Phosphatidylcholines / Q000737:chemistry*
D006838:Hydrocarbons; D008051:Lipid Bilayers; D008567:Membranes, Artificial; D010713:Phosphatidylcholines; D002784:Cholesterol