Charge Inversion of a Macroion in Spherical and Rod Shapes for Different Coions and Polymer Counterions: Electrophoresis by Molecular Dynamics Simulations

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  • 25 March 2003
Abstract
By molecular dynamics simulations we show the effects of coion radius and valence, polymer counterions and monovalent salt on the electrophoretic mobility of a macroion in spherical and rod shapes. The reversed mobility increases with the ratio of coion to counterion radii, which peaks at an intermediate value of the ratio. It decreases with the ratio of coion to counterion valences, and becomes non-reversed for the coion valence larger than that of counterions. The monovalent salt suppresses the reversed mobility, except for the mobility enhancement of a strongly charged macroion at small ionic strength. There is a threshold surface charge density for charge inversion to take place. Polymers (polyelectrolyte) consisting of multivalent counterions are favorable for charge inversion of a weakly charged macroion like DNA. The reversed mobility of an elongated macroion can be enhanced by mechanical twining of polyelectrolyte counterions around the rod axis.

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