Role of hydrodynamic interactions in the migration of polyelectrolytes driven by a pressure gradient and an electric field

Experiments have shown that DNA molecules in capillary electrophoresis migrate across field lines if a pressure gradient is applied simultaneously. We suggest that this migration results from an electrically driven flow field around the polyelectrolyte, which generates additional contributions to the center-of-mass velocity if the overall polymer conformation is asymmetric. This hypothesis leads to a coarse-grained polymer model, without explicit charges, that quantitatively explains the experimentally observed migration. The simulations contradict the widely held notion that charge neutrality eliminates the effects of hydrodynamic interactions in electrically driven flows of polyelectrolytes. We predict a measurable increase in the electrophoretic velocity of a sheared polyelectrolyte that depends on chain length.