(9d) Transverse Migration of a Polyelectrolyte Driven by a Combination of Electrophoresis and Pressure-Driven Flow

The cross-stream migration of a polyelectrolyte flowing within a confining channel under combinations of an electrophoretic driving force and pressure-driven flow is examined. When acting in conjunction, the polymer migrates to the center of the channel and when the pressure gradient and external force act in opposite directions, the polymer can migrate towards the boundaries. Producing this behavior, which agrees qualitatively with published experiments on DNA, requires including hydrodynamic interactions with only partial screening due to the action of the electric field on the counterions surrounding the polyelectrolyte; models of DNA electrophoresis that utilize an assumption of complete screening of the hydrodynamic interactions fail to predict the migration observed in the experiments. The results of the analysis suggest that models of DNA electrophoresis can be improved by including the screened hydrodynamic interactions and comparing with detailed observations from similar experiments.