膜粘度在流体膜动力学中的作用
The role of membrane viscosity in the dynamics of fluid membranes
AI总结：
研究流体囊泡形态变化中膜内禀粘度与周围流体粘度的竞争机制，通过数值计算发现小囊泡中膜耗散主导且弛豫时间与尺寸平方成正比，大囊泡中体相耗散主导且弛豫时间与尺寸立方成正比。
摘要：
由脂质双分子层构成的流体膜是真核细胞中基本的分隔结构。许多生理过程依赖于流体膜系统的剧烈形状和拓扑变化（例如融合、分裂）。流动性是脂质双分子层多功能性和持续重组的关键。本文研究了膜内禀粘度（源于脂质分子在适应形状变化时重新排列产生的摩擦）在流体囊泡形态变化动力学中的作用。特别地，我们分析了膜粘度与囊泡周围流体粘度作为主导耗散机制之间的竞争。我们考虑处于非平衡状态的流体囊泡的弛豫动力学，但结论可推广至细胞中受调控形状变化的动力学或能量消耗。基于数值计算，我们发现膜粘度产生的动力学与体相粘度产生的动力学在性质上不同。当这两种耗散机制相互竞争时，我们发现对于小囊泡，膜耗散占主导，弛豫时间与囊泡尺寸的平方成正比；对于大囊泡，体相耗散占主导，弛豫时间与尺寸的关系指数为3。
英文摘要：
Fluid membranes made out of lipid bilayers are the fundamental separation structure in eukaryotic cells. Many physiological processes rely on dramatic shape and topological changes (e.g. fusion, fission) of fluid membrane systems. Fluidity is key to the versatility and constant reorganization of lipid bilayers. Here, we study the role of the membrane intrinsic viscosity, arising from the friction of the lipid molecules as they rearrange to accommodate shape changes, in the dynamics of morphological changes of fluid vesicles. In particular, we analyze the competition between the membrane viscosity and the viscosity of the bulk fluid surrounding the vesicle as the dominant dissipative mechanism. We consider the relaxation dynamics of fluid vesicles put in an out-of-equilibrium state, but conclusions can be drawn regarding the kinetics or power consumption in regulated shape changes in the cell. On the basis of numerical calculations, we find that the dynamics arising from the membrane viscosity are qualitatively different from the dynamics arising from the bulk viscosity. When these two dissipation mechanisms are put in competition, we find that for small vesicles the membrane dissipation dominates, with a relaxation time that scales as the size of the vesicle to the power 2. For large vesicles, the bulk dissipation dominates, and the exponent in the relaxation time vs. size relation is 3.
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