Allison S A, Stigter D
Department of Chemistry, Georgia State University, Atlanta, Georgia 30303, USA.
Biophys J. 2000 Jan;78(1):121-4. doi: 10.1016/S0006-3495(00)76578-7.
The use of linear theory, in particular, counterion condensation (CC) theory, in describing electrophoresis of polyelectrolyte chains, is criticized on several grounds. First, there are problems with CC theory in describing the equilibrium distribution of ions around polyelectrolytes. Second, CC theory is used to treat ion relaxation in a linear theory with respect to the polyion charge despite the fact that ion relaxation arises as a consequence of nonlinear charge effects. This nonlinearity has been well established by several investigators over the last 70 years for spherical, cylindrical, and arbitrarily shaped model polyions. Third, current use of CC theory ignores the electrophoretic hindrance as well as the ion relaxation for condensed counterions and only includes such interactions for uncondensed counterions. Because most of the condensed counterions lie outside the shear surface of the polyion (in the example of DNA), the assumption of ion condensation is artificial and unphysical. Fourth, the singular solution, based on a screened Oseen tensor, currently used in the above mentioned theories is simply wrong and fails to account for the incompressibility of the solvent. The actual singular solution, which has long been available, is discussed. In conclusion, it is pointed out that numerical alternatives based on classic electrophoresis theory (J.T.G. Overbeek, Kolloid-Beih, 1943, 54:287-364) are now available.
线性理论，特别是反离子凝聚（CC）理论，在描述聚电解质链的电泳时受到了多方面的批评。首先，CC理论在描述聚电解质周围离子的平衡分布时存在问题。其次，尽管离子弛豫是由非线性电荷效应引起的，但CC理论却被用于在线性理论中处理聚离子电荷的离子弛豫。在过去70年里，几位研究人员已经针对球形、圆柱形和任意形状的模型聚离子充分证实了这种非线性。第三，目前CC理论的应用忽略了凝聚反离子的电泳阻力以及离子弛豫，仅考虑了未凝聚反离子的此类相互作用。由于大多数凝聚反离子位于聚离子的剪切面之外（以DNA为例），离子凝聚的假设是人为的且不符合实际情况。第四，上述理论中目前使用的基于屏蔽奥森张量的奇异解是完全错误的，并且没有考虑溶剂的不可压缩性。文中讨论了早就存在的实际奇异解。总之，文中指出现在已有基于经典电泳理论（J.T.G. Overbeek，《胶体补遗》，1943年，54:287 - 364）的数值替代方法。
