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首页> 外文期刊>Nanotechnology >The molecular-scale arrangement and mechanical strength of phospholipid/cholesterol mixed bilayers investigated by frequency modulation atomic force microscopy in liquid
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The molecular-scale arrangement and mechanical strength of phospholipid/cholesterol mixed bilayers investigated by frequency modulation atomic force microscopy in liquid

机译：调频原子力显微镜在液体中研究磷脂/胆固醇混合双层分子的分子尺度排列和机械强度

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摘要

Cholesterols play key roles in controlling molecular fluidity in a biological membrane, yet little is known about their molecular-scale arrangements in real space. In this study, we have directly imaged lipid–cholesterol complexes in a model biological membrane consisting f dipalmitoylphosphatidylcholine (DPPC) and cholesterols by frequency modulation atomic force microscopy (FM-AFM) in phosphate buffer solution. FM-AFM images of a DPPC/cholesterol bilayer in the liquid-ordered phase showed higher energy dissipation values compared to those measured on a nanoscale DPPC domain in the gel phase, reflecting the increased molecular fluidity due to the insertion of cholesterols. Molecular-resolution FM-AFM images of a DPPC/cholesterol bilayer revealed the existence of a rhombic molecular arrangement (lattice constants: a = 0.46 nm, b = 0.71 nm) consisting of alternating rows of DPPC and cholesterols as well as the increased defect density and reduced molecular ordering. The mechanical strength of a DPPC/cholesterol bilayer was quantitatively evaluated by measuring a loading force required to penetrate the membrane with an AFM tip. The result revealed the significant decrease of mechanical strength upon insertion of cholesterols. Based on the molecular-scale arrangement found in this study, we propose a model to explain the reduced mechanical strength in relation to the formation of lipid-ion networks.
机译：胆固醇在控制生物膜中的分子流动性方面起着关键作用，但是人们对其在现实空间中的分子尺度排列知之甚少。在这项研究中，我们已经通过磷酸盐缓冲溶液中的调频原子力显微镜（FM-AFM）在由f二棕榈酰磷脂酰胆碱（DPPC）和胆固醇组成的模型生物膜中直接成像了脂质-胆固醇复合物。与在凝胶相中的纳米级DPPC域上测得的能量耗散值相比，液相有序相中的DPPC /胆固醇双层的FM-AFM图像显示出更高的能量耗散值，反映出由于胆固醇的插入而增加的分子流动性。 DPPC /胆固醇双层的分子分辨率FM-AFM图像显示存在由交替排列的DPPC和胆固醇行组成的菱形分子排列（晶格常数：a = 0.46 nm，b = 0.71 nm），以及缺陷密度增加并降低了分子有序性。通过测量通过AFM尖端穿透膜所需的加载力来定量评估DPPC /胆固醇双层的机械强度。结果表明插入胆固醇后机械强度显着降低。基于本研究中发现的分子尺度排列，我们提出了一个模型来解释与脂质离子网络形成有关的降低的机械强度。

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