Department of Physics and Astronomy, Wayne State University, Detroit, MI, United States.
Department of Physics and Astronomy, Wayne State University, Detroit, MI, United States.
Biochim Biophys Acta Biomembr. 2018 Oct;1860(10):2064-2075. doi: 10.1016/j.bbamem.2018.05.009. Epub 2018 May 29.
Nanoscale membrane curvature in cells is critical for endocytosis/exocytosis and membrane trafficking. However, the biophysical ramifications of nanoscale membrane curvature on the behavior of lipids remain poorly understood. Here, we created an experimental model system of membrane curvature at a physiologically-relevant scale and obtained nanoscopic information on single-lipid distributions and dynamics. Supported lipid bilayers were created over 50 and 70 nm radius nanoparticles to create membrane buds. Single-molecule localization microscopy was performed with diverse mixtures of fluorescent and non-fluorescent lipids. Variations in lipid acyl tales length, saturation, head-group, and fluorescent labeling strategy were tested while maintaining a single fluid lipid phase throughout the membrane. Monte Carlo simulations were used to fit our experimental results and quantify the effects of curvature on the lipid diffusion and sorting. Whereas varying the composition of the non-fluorescent lipids yielded minimal changes to the curvature effects, the labeling strategy of the fluorescent lipids yielded highly varying effects of curvature. Most conditions yield single-population Brownian diffusion throughout the membrane; however, curvature-induced lipid sorting, slowing, and aggregation were observed in some conditions. Head-group labeled lipids such as DPPE-Texas Red and POPE-Rhodamine diffused >2.4× slower on the curved vs. the planar membranes; tail-labeled lipids such as NBD-PPC, TopFluor-PPC, and TopFluor-PIP2, as well as DiIC and DiIC displayed no significant changes in diffusion due to the membrane curvature. This article is part of a Special Issue entitled: Emergence of Complex Behavior in Biomembranes edited by Marjorie Longo.
细胞中的纳米尺度膜曲率对于内吞作用/外排作用和膜运输至关重要。然而，纳米尺度膜曲率对脂质行为的生物物理影响仍知之甚少。在这里，我们创建了一个在生理相关尺度下的膜曲率实验模型系统，并获得了关于单脂质分布和动力学的纳米尺度信息。在 50 和 70nm 半径纳米颗粒上创建支撑脂质双层以形成膜泡。用不同比例的荧光和非荧光脂质进行单分子定位显微镜实验。在整个膜中保持单一流体脂质相的同时，测试了脂质酰基尾部长度、饱和度、头基和荧光标记策略的变化对曲率的影响。虽然改变非荧光脂质的组成对曲率效应的影响很小，但荧光脂质的标记策略对曲率的影响则高度不同。大多数条件下，整个膜中都存在单分子布朗扩散；然而，在某些条件下观察到曲率诱导的脂质分选、减速和聚集。带头部基团标记的脂质，如 DPPE-Texas Red 和 POPE-Rhodamine，在弯曲膜上的扩散速度比在平面膜上慢>2.4 倍；带尾部基团标记的脂质，如 NBD-PPC、TopFluor-PPC 和 TopFluor-PIP2，以及 DiIC 和 DiIC，由于膜曲率，其扩散没有明显变化。本文是由 Marjorie Longo 编辑的题为“生物膜中复杂行为的出现”的特刊的一部分。
