The Journal of Membrane Biology ( IF 2.3 ) Pub Date : 2020-11-22 , DOI: 10.1007/s00232-020-00156-9 Sagar Kamble 1 , Snehal Patil 1 , Mandar Kulkarni 2 , Venkata Ramana Murthy Appala 1
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Abstract
Artificial lipid membranes are often investigated as a replica of the cell membrane in the form of supported lipid bilayers (SLBs). In SLBs, the phase state of a lipid bilayer strongly depends on the presence of molecules such as cholesterol, ceramide, and physical parameters such as temperature. Cholesterol is a key molecule of biological membranes and it exerts condensing effect on lipid bilayers. In this paper, we demonstrate the influence of excess cholesterol content on a supported lipid bilayer of 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC) (fluid-phase) using spectroscopic ellipsometry (SE) and coarse-grained (CG) molecular dynamics (MD) simulations. The results show the condensation effect due to cholesterol addition up to 30% and interleaflet decoupling at excess cholesterol beyond 30%. SE results show the separation of individual leaflets of the bilayer and influence of cholesterol on the biophysical properties such as thickness and optical index. CG simulations were performed at different ratios of DOPC:cholesterol mixtures to explore cholesterol-driven bilayer properties and stability. The simulations displayed the accumulation of cholesterol molecules at the interface of the lower and upper leaflets of the bilayer, thus leading to undulations in the bilayer. This work reports the successful application of SE technique to study lipid–cholesterol interactions for the first time.
Graphical abstract
中文翻译：
通过光谱椭偏仪和模拟探测过量胆固醇的脂质双层中的叶间去耦
摘要
人工脂质膜通常被研究为支持脂质双层 (SLB) 形式的细胞膜的复制品。在 SLB 中，脂质双层的相态在很大程度上取决于分子（如胆固醇、神经酰胺）和物理参数（如温度）的存在。胆固醇是生物膜的关键分子，对脂质双层发挥凝聚作用。在本文中，我们使用光谱椭偏仪 (SE) 和粗粒 ( CG) 分子动力学 (MD) 模拟。结果显示了由于胆固醇添加高达 30% 和超过 30% 的过量胆固醇时的叶间去耦导致的缩合效应。SE 结果显示双层单个小叶的分离和胆固醇对生物物理特性（如厚度和光学指数）的影响。在不同比例的 DOPC: 胆固醇混合物下进行 CG 模拟，以探索胆固醇驱动的双层特性和稳定性。模拟显示胆固醇分子在双层的上下小叶的界面处积聚，从而导致双层中的波动。这项工作首次报告了 SE 技术在研究脂质 - 胆固醇相互作用方面的成功应用。胆固醇混合物来探索胆固醇驱动的双层特性和稳定性。模拟显示胆固醇分子在双层的上下小叶的界面处积聚，从而导致双层中的波动。这项工作首次报告了 SE 技术在研究脂质 - 胆固醇相互作用方面的成功应用。胆固醇混合物来探索胆固醇驱动的双层特性和稳定性。模拟显示胆固醇分子在双层的上下小叶的界面处积聚，从而导致双层中的波动。这项工作首次报告了 SE 技术在研究脂质 - 胆固醇相互作用方面的成功应用。
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