Saxton M J
Plant Growth Laboratory, University of California, Davis 95616.
Biophys J. 1990 Jun;57(6):1167-77. doi: 10.1016/S0006-3495(90)82636-9.
The spectrin network on the cytoplasmic surface of the erythrocyte membrane is modeled as a triangular lattice of spectrin tetramers. This network obstructs lateral diffusion of proteins and provides mechanical reinforcement to the membrane. These effects are treated in a systematic and unified manner in terms of a percolation model. The diffusion coefficient is obtained as a function of the fraction of normal spectrin tetramers for both static and fluctuating barriers. The elasticity of the network is calculated as a function of the fraction of normal spectrin and the ratio of bending to stretching energies. For static barriers, elasticity and lateral diffusion are incompatible: if a network is connected enough to be elastic, it is connected enough to block long-range lateral diffusion. The elasticity and the force required for mechanical breakdown go to zero at the percolation threshold; experimental evidence suggests the existence of a stability threshold at or near the percolation threshold. The model is qualitatively applicable to other cells with membrane skeletons, such as epithelial cells, in which localization of membrane proteins is essential to differentiation.
红细胞膜细胞质表面的血影蛋白网络被建模为血影蛋白四聚体的三角晶格。该网络阻碍蛋白质的横向扩散，并为膜提供机械强化作用。这些效应在渗流模型的框架下以系统且统一的方式进行处理。对于静态和波动屏障，扩散系数均作为正常血影蛋白四聚体分数的函数得出。网络的弹性则根据正常血影蛋白的分数以及弯曲能与拉伸能的比值来计算。对于静态屏障，弹性和横向扩散是不相容的：如果一个网络连接程度足以具有弹性，那么它也足以阻断长程横向扩散。在渗流阈值处，弹性和机械破坏所需的力均趋于零；实验证据表明在渗流阈值或其附近存在一个稳定性阈值。该模型在定性上适用于其他具有膜骨架的细胞，比如上皮细胞，其中膜蛋白的定位对于细胞分化至关重要。
