Department of Biological Sciences, University of Calgary, Calgary, Alberta, Canada.
Biophys J. 2012 Apr 18;102(8):1866-71. doi: 10.1016/j.bpj.2012.03.048.
Membrane tethers are nanotubes formed by a lipid bilayer. They play important functional roles in cell biology and provide an experimental window on lipid properties. Tethers have been studied extensively in experiments and described by theoretical models, but their molecular structure remains unknown due to their small diameters and dynamic nature. We used molecular dynamics simulations to obtain molecular-level insight into tether formation. Tethers were pulled from single-component lipid bilayers by application of an external force to a lipid patch along the bilayer normal or by lateral compression of a confined bilayer. Tether development under external force proceeded by viscoelastic protrusion followed by viscous lipid flow. Weak forces below a threshold value produced only a protrusion. Larger forces led to a crossover to tether elongation, which was linear at a constant force. Under lateral compression, tethers formed from undulations of unrestrained bilayer area. We characterized in detail the tether structure and its formation process, and obtained the material properties of the membrane. To our knowledge, these results provide the first molecular view of membrane tethers.
膜栓是由脂质双层形成的纳米管。它们在细胞生物学中发挥着重要的功能作用，并为脂质性质的实验研究提供了一个窗口。由于其直径小且动态性质，栓已在实验中得到广泛研究，并通过理论模型进行了描述，但它们的分子结构仍然未知。我们使用分子动力学模拟从单组分脂质双层中获得分子水平的栓形成见解。通过沿双层法向对脂质斑块施加外力或通过限制双层的横向压缩，从脂质双层中拉出栓。在外部力的作用下，栓的发展是通过粘弹性突出物随后是粘性脂质流进行的。低于阈值的弱力只会产生突出物。更大的力导致栓延伸的交叉，在恒定力下呈线性。在横向压缩下，栓由不受约束的双层区域的波动形成。我们详细描述了栓的结构及其形成过程，并获得了膜的材料特性。据我们所知，这些结果提供了膜栓的第一个分子视图。
