Lyu Dongyu, Zhang Lei, Zhang Yong
School of Physics, Sun Yat-Sen University No. 135 Xingang Xi Road Guangzhou 510275 China
RSC Adv. 2020 Mar 17;10(19):11088-11094. doi: 10.1039/d0ra00624f. eCollection 2020 Mar 16.
Cholesterol is one of the essential components of the cell membrane. It has a significant influence on various mechanical properties of biomembranes, such as fluidity and elasticity, which have attracted much attention. It is also well known that the concentration of cholesterol affects the mechanical strength of cell membranes. In this paper, we aim to explore the influence of the degree of unsaturation of phospholipid tails on the concentration-effect of cholesterol. Three different phospholipids (DPPC, DIPC and DAPC) were selected as the respective main components of the bilayers and several concentrations of cholesterol were also added to the systems. Our coarse-grained molecular dynamics simulations show that as the cholesterol concentration increases, the saturated phospholipid bilayer is first strengthened, by increasing the rupture tension from 68.9 to 110 mN m, and then weakened. The non-monotonic concentration-effect gradually decreases as the degree of unsaturation of the phospholipid tails increases, and in particular, the mechanical strength of the DAPC bilayer hardly changes. The results suggest that cholesterol does not influence a bilayer composed of highly unsaturated phospholipids. Furthermore, lateral density distributions reveal that the distribution of cholesterol in the bilayer is related to the carbon tail unsaturation of the phospholipids.
胆固醇是细胞膜的重要组成成分之一。它对生物膜的各种力学性质，如流动性和弹性，有着显著影响，这已引起了广泛关注。众所周知，胆固醇的浓度会影响细胞膜的机械强度。在本文中，我们旨在探究磷脂尾部不饱和度对胆固醇浓度效应的影响。选择了三种不同的磷脂（二棕榈酰磷脂酰胆碱、二油酰磷脂酰胆碱和二花生酰磷脂酰胆碱）作为各自双层膜的主要成分，并向体系中添加了几种不同浓度的胆固醇。我们的粗粒化分子动力学模拟表明，随着胆固醇浓度的增加，饱和磷脂双层首先得到强化，破裂张力从68.9 mN/m增加到110 mN/m，然后又被削弱。随着磷脂尾部不饱和度的增加，这种非单调的浓度效应逐渐减小，特别是二花生酰磷脂酰胆碱双层膜的机械强度几乎没有变化。结果表明，胆固醇对由高度不饱和磷脂组成的双层膜没有影响。此外，横向密度分布显示，双层膜中胆固醇的分布与磷脂的碳链尾部不饱和度有关。
