Dimitrov D S, Apostolova M A, Sowers A E
American Red Cross, Holland Laboratory/Cell Biology, Rockville, MD 20855.
Biochim Biophys Acta. 1990 Apr 30;1023(3):389-97. doi: 10.1016/0005-2736(90)90131-7.
The force of attraction between erythrocyte ghosts induced by low frequency electric fields (60 Hz) was measured as a function of the intermembrane separation. It varied from 10(-14) N for separation of the order of the cell diameter to 10(-12) N for close approach and contact in 20 mM sodium phosphate buffers (conductivity 260 mS/m, pH 8.5). For large separations the interaction force followed a dependence on separation as predicted for dipole-dipole interactions. For small separation an empirical formula was obtained. The membranes deformed at close approach (less than 1 microns) before making contact. The contact area increased with time until reaching the final equilibrium state. The ghosts separated reversibly after switching off the electric field. The membrane tension induced by the ghost interaction at contact was estimated to be of the order of 0.1 mN/m. These first quantitative measurements of the force/separation dependence for intermembrane interactions induced by low frequency electric fields indicate that attractive forces, membrane deformation and contact area of cells depend strongly on intermembrane separation and field strength. The quantitative relationship between them are important for measuring membrane surface and mechanical properties, intermembrane forces and understanding mechanisms of membrane adhesion, instability and fusion in electric fields and in general.
测量了低频电场（60赫兹）诱导的红细胞血影之间的吸引力与膜间间距的函数关系。在20毫摩尔磷酸钠缓冲液（电导率260毫西门子/米，pH值8.5）中，当间距为细胞直径量级时，吸引力为10⁻¹⁴牛，当接近并接触时，吸引力为10⁻¹²牛。对于较大间距，相互作用力如偶极-偶极相互作用所预测的那样，遵循与间距的依赖关系。对于小间距，得到了一个经验公式。在接触前，膜在接近时（小于1微米）会发生变形。接触面积随时间增加，直至达到最终平衡状态。关闭电场后，血影可逆地分离。接触时血影相互作用诱导的膜张力估计约为0.1毫牛/米。这些对低频电场诱导的膜间相互作用的力/间距依赖关系的首次定量测量表明，细胞的吸引力、膜变形和接触面积强烈依赖于膜间间距和场强。它们之间的定量关系对于测量膜表面和力学性质、膜间力以及理解电场中膜粘附、不稳定性和融合的机制以及总体情况都很重要。
