Journal
CHEMISTRY AND PHYSICS OF LIPIDS
Volume 178, Issue -, Pages 18-26Publisher
ELSEVIER IRELAND LTD
DOI: 10.1016/j.chemphyslip.2013.12.012
Keywords
Conjugated linoleic acids; Molecular dynamic simulation; Cholesterol; POPC; Bending rigidity; Lipid splay and tilt
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Funding
- Biomedical Engineering Cross Research Fund of Shanghai Jiao Tong University [YG2012MS23]
- Natural Science Foundation Program at Shanghai Jiao Tong University School of Medicine [12XJ10078]
- HRH Prince Alwaleed Bin Talal Bin Abdulaziz Alsaud Institute of Computational Biomedicine at Weill Medical College of Cornell University
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We examine the effects of cholesterol (Chol) on the mechanical properties of membranes consisting of 16:0/18:1 POPC lipid and of lipids with conjugated linoleic acid (CIA), cis-9/trans-11 CIA (C9T11) and trans-10/cis-12 CIA (T10C12). Atomistic molecular dynamics (MD) simulations of POPC-Chol and CLA-Chol mixtures at various Chol concentrations are employed within a recently developed and validated computational methodology (Khelashvili et al., 2013) that calculates from MD trajectories the bending rigidity (K-C) for these systems. We have found that the addition of 30% Chol stiffens POPC lipid membranes much more significantly (2.3-fold) than it does C9T11 (1.5-fold) or T10C12 (1.75-fold) lipid bilayers. Extensive comparative structural analysis of the simulated mixtures supports a molecular mechanism for the differential effects of cholesterol, whereby the sterol molecules tilt more significantly in CIA membranes where they also insert deeper inside the hydrocarbon core. The observed distinct arrangement of Chol molecules in CIA and POPC bilayers, in turn, is dictated by the interplay between the specific location of the trans double bond in the two CIA lipid isomers and the preferential interaction of the rigid Chol ring with the saturated segments of the lipid tails. The simulations and analysis described in this paper provide novel insights into the specific modes of molecular interaction in bilayers composed of mixtures of Chol and unsaturated lipids that drive emergent macroscopic properties, such as the membrane's bending modulus. (C) 2013 Elsevier Ireland Ltd. All rights reserved.
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