Electric and Electrophoretic Inversion of the DNA Charge in Multivalent Electrolytes.

Counterion-induced inversion of the DNA charge was characterized through extensive molecular dynamics simulations. We observed reversal of the DNA motion in an external electric field upon increasing the concentration of trivalent or quadrivalent counterions. In the case of a divalent electrolyte, inversion of the DNA's electric charge was observed at high concentrations of the electrolyte but not reversal of the DNA' electrophoretic motion. We demonstrate that inversion of the DNA's electrophoretic mobility results from a complex interplay of electrostatics and hydrodynamics.