几何诱导非对称扩散
Geometry-induced asymmetric diffusion
摘要：
过去的工作表明，离子可以更容易地通过膜在一个方向比其他。在这里，我们证明了在一个模型和实验中，对于小颗粒和大颗粒的混合物，这种不对称扩散可以仅仅产生于膜的孔的几何形状的不对称性。我们的确定性模拟考虑了两种尺寸的弹性圆盘通过膜扩散的二维气体，我们的实验室实验研究了两种尺寸的玻璃珠通过金属膜的扩散。在实验和模拟中，膜仅对较小的颗粒是可渗透的，并且不对称的孔导致这些颗粒的扩散速率的不对称。即使存在很小百分比的大颗粒也会堵塞膜，阻止小颗粒在一个方向上通过，同时允许小颗粒在另一个方向上自由流动。纯粹的几何动力学约束可能在常见的生物学环境中发挥作用，如膜离子通道。
英文摘要：
Past work has shown that ions can pass through a membrane more readily in one direction than the other. We demonstrate here in a model and an experiment that for a mixture of small and large particles such asymmetric diffusion can arise solely from an asymmetry in the geometry of the pores of the membrane. Our deterministic simulation considers a two-dimensional gas of elastic disks of two sizes diffusing through a membrane, and our laboratory experiment examines the diffusion of glass beads of two sizes through a metal membrane. In both experiment and simulation, the membrane is permeable only to the smaller particles, and the asymmetric pores lead to an asymmetry in the diffusion rates of these particles. The presence of even a small percentage of large particles can clog a membrane, preventing passage of the small particles in one direction while permitting free flow of the small particles in the other direction. The purely geometric kinetic constraints may play a role in common biological contexts such as membrane ion channels.
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