Schmidt C F, Svoboda K, Lei N, Petsche I B, Berman L E, Safinya C R, Grest G S
Department of Cellular and Developmental Biology, Harvard University, Cambridge, MA 02138.
Science. 1993 Feb 12;259(5097):952-5. doi: 10.1126/science.8438153.
Biomolecular membranes display rich statistical mechanical behavior. They are classified as liquid in the absence of shear elasticity in the plane of the membrane and tethered (solid) when the neighboring molecules or subunits are connected and the membranes exhibit solid-like elastic behavior in the plane of the membrane. The spectrin skeleton of red blood cells was studied as a model tethered membrane. The static structure factor of the skeletons, measured by small-angle x-ray and light scattering, was fitted with a structure factor predicted with a model calculation. The model describes tethered membrane sheets with free edges in a flat phase, which is a locally rough but globally flat membrane configuration. The fit was good for large scattering vectors. The membrane roughness exponent, zeta, defined through h alpha L zeta, where h is the average amplitude of out-of-plane fluctuations and L is the linear membrane dimension, was determined to be 0.65 +/- 0.10. Computer simulations of model red blood cell skeletons also showed this flat phase. The value for the roughness exponent, which was determined from the scaling properties of membranes of different sizes, was consistent with that from the experiments.
生物分子膜表现出丰富的统计力学行为。在膜平面内不存在剪切弹性时，它们被归类为液体；当相邻分子或亚基相连且膜在膜平面内表现出类固体弹性行为时，它们则被归类为束缚态（固体）。红细胞的血影蛋白骨架作为一种模型束缚膜进行了研究。通过小角X射线和光散射测量得到的骨架静态结构因子，与通过模型计算预测的结构因子进行了拟合。该模型描述了处于平相的具有自由边缘的束缚膜片，这是一种局部粗糙但整体平坦的膜构型。对于大散射矢量，拟合效果良好。通过h∝L^ζ定义的膜粗糙度指数ζ（其中h是平面外涨落的平均幅度，L是膜的线性尺寸）被确定为0.65±0.10。模型红细胞骨架的计算机模拟也显示出这种平相。根据不同尺寸膜的标度性质确定的粗糙度指数值与实验结果一致。
