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A variety of experimental and theoretical approaches have been employed to investigate sterol flip-flop motion in lipid bilayer membranes. However, the sterol effect on the dipole potential of lipid bilayer membranes is less well studied and the influence of dipole potential on sterol flip-flop in lipid bilayer membranes is less well understood. In our previous works, we have demonstrated the performance of our coarse-grained (CG) model in the computation of the dipole potential. In this work, five 30-μs coarse-grained (CG) simulations of dimyristoylphosphatidylcholine (DMPC) bilayers were carried out respectively at different sterol concentrations (in a range from 10% to 50% mole fraction). Then, a comparison was made between the effects of cholesterol (CHOL) and 6-ketocholestanol (6-KC) on the dipole potential of DMPC lipid bilayers as well as the sterol flip-flop motion. Our CG simulations show that membrane dipole potential is impacted more significantly by 6-KC than by CHOL. This finding is consistent with recent experimental studies. Meanwhile, our work suggests that the sterol-sterol interactions (in particular electrostatic interactions) should be critical to the formation of sterol-sterol clusters, which would hinder the sterol flip-flop motion inside lipid bilayers. This is in support of recent experimental study on the sterol transportation in lipid bilayer membranes.
PMID: 31373497 [PubMed - as supplied by publisher]