PDF(Pubmed)
Abstract：
Biological and biomimetic membranes are based on lipid bilayers, which consist of two monolayers or leaflets. To avoid bilayer edges, which form when the hydrophobic core of such a bilayer is exposed to the surrounding aqueous solution, a single bilayer closes up into a unilamellar vesicle, thereby separating an interior from an exterior aqueous compartment. Synthetic nanovesicles with a size below 100 nanometers, traditionally called small unilamellar vesicles, have emerged as potent platforms for the delivery of drugs and vaccines. Cellular nanovesicles of a similar size are released from almost every type of living cell. The nanovesicle morphology has been studied by electron microscopy methods but these methods are limited to a single snapshot of each vesicle. Here, we review recent results of molecular dynamics simulations, by which one can monitor and elucidate the spatio-temporal remodeling of individual bilayers and nanovesicles. We emphasize the new concept of leaflet tensions, which control the bilayers\' stability and instability, the transition rates of lipid flip-flops between the two leaflets, the shape transformations of nanovesicles, the engulfment and endocytosis of condensate droplets and rigid nanoparticles, as well as nanovesicle adhesion and fusion. To actually compute the leaflet tensions, one has to determine the bilayer\'s midsurface, which represents the average position of the interface between the two leaflets. Two particularly useful methods to determine this midsurface are based on the density profile of the hydrophobic lipid chains and on the molecular volumes.
摘要：
生物和仿生膜基于脂质双层，由两个单层或小叶组成。为了避免双层边缘，当这种双层的疏水核心暴露于周围的水溶液时，一个双层封闭成单层囊泡，从而将内部与外部水性隔室分开。合成纳米囊泡，尺寸小于100纳米，传统上称为小单层囊泡，已经成为提供药物和疫苗的有效平台。相似大小的细胞纳米囊泡从几乎所有类型的活细胞中释放。已通过电子显微镜方法研究了纳米囊泡的形态，但这些方法仅限于每个囊泡的单个快照。这里,我们回顾了分子动力学模拟的最新结果，通过它可以监测和阐明单个双层和纳米囊泡的时空重塑。我们强调传单紧张的新概念,控制双层的稳定性和不稳定性，两个小叶之间的脂质触发器的转换率，纳米囊泡的形状转变，冷凝液滴和刚性纳米颗粒的吞噬和内吞作用，以及纳米囊泡的粘附和融合。为了实际计算传单的张力，必须确定双层的中间表面，其表示两个小叶之间的界面的平均位置。确定该中间表面的两种特别有用的方法是基于疏水性脂质链的密度分布和分子体积。
