Evans E A
Methods Enzymol. 1989;173:3-35. doi: 10.1016/s0076-6879(89)73003-2.
The lamellar configuration of the red cell membrane includes a (liquid) superficial bilayer of amphiphilic molecules supported by a (rigid) subsurface protein meshwork. Because of this composite structure, the red cell membrane exhibits very large resistance to changes in surface density or area with very low resistance to in-plane extension and bending deformations. The primary extrinsic factor in cell deformability is the surface area-to-volume ratio which establishes the minimum-caliber vessel into which a cell can deform (without rupture). Within the restriction provided by surface area and volume, the intrinsic properties of the membrane and cytoplasm determine the deformability characteristics of the red cell. Since the cytoplasm is liquid, the static rigidity of the cell is determined by membrane elastic constants. These include an elastic modulus for area compressibility in the range of 300-600 dyn/cm, an elastic modulus for in-plane extension or shear (at constant area) of 5-7 X 10(-3) dyn/cm, and a curvature or bending elastic modulus on the order of 10(-12) dyn.cm. Even though small, the surface rigidity of the cell membrane is sufficient to return the membrane capsule to a discoid shape after deformation by external forces. Viscous dissipation in the peripheral protein structure (cytoskeleton) dominates the dynamic response of the cell to extensional forces. Based on a time constant for recovery after extensional deformation on the order of 0.1 sec, the coefficient of surface viscosity is on the order of 10(-3) dyn.sec/cm. On the other hand, the dynamic resistance to folding of the cell appears to be limited by viscous dissipation in the cytoplasmic and external fluid phases. Dynamic rigidities for both extensional and folding deformations are important factors in the distribution of flow in the small microvessels. Although the red cell membrane normally behaves as a resilient viscoelastic shell, which recovers its conformation after deformation, structural relaxation and failure lead to break-up and fragmentation of the red cell. The levels of membrane extensional force which is two orders of magnitude less than the level of tension necessary to lyse vesicles by rapid area dilation. Each of the material properties ascribed to the red cell membrane plays an important role in the deformability and survivability of the red cell in the circulation over its several-month life span.
红细胞膜的片层结构包括一个由（刚性的）表面下蛋白质网络支撑的（液态）两亲分子表面双层。由于这种复合结构，红细胞膜对表面密度或面积变化表现出非常大的阻力，而对平面内伸展和弯曲变形的阻力非常低。细胞变形能力的主要外在因素是表面积与体积之比，它确定了细胞能够变形（而不破裂）进入的最小管径血管。在表面积和体积所提供的限制范围内，膜和细胞质的内在特性决定了红细胞的变形能力特征。由于细胞质是液态的，细胞的静态刚性由膜弹性常数决定。这些常数包括面积压缩弹性模量在300 - 600达因/厘米范围内，平面内伸展或剪切（在恒定面积下）弹性模量为5 - 7×10⁻³达因/厘米，以及曲率或弯曲弹性模量约为10⁻¹²达因·厘米。尽管细胞膜的表面刚性很小，但足以使膜囊在受到外力变形后恢复到盘状形状。外周蛋白质结构（细胞骨架）中的粘性耗散主导了细胞对伸展力的动态响应。基于伸展变形后恢复的时间常数约为0.1秒，表面粘度系数约为10⁻³达因·秒/厘米。另一方面，细胞对折叠的动态阻力似乎受细胞质和外部流体相中的粘性耗散限制。伸展和折叠变形的动态刚性都是小微血管中血流分布的重要因素。尽管红细胞膜通常表现为有弹性的粘弹性壳，在变形后能恢复其构象，但结构松弛和破坏会导致红细胞破裂和碎片化。膜伸展力的水平比通过快速面积扩张使囊泡破裂所需的张力水平低两个数量级。赋予红细胞膜的每种材料特性在红细胞在其数月寿命期间在循环中的变形能力和存活能力方面都起着重要作用。
