Transverse Migration of Polyelectrolytes in the Presence of Pressure and Electrical Fields

Simultaneously applying an electric field and pressure gradient induces a net migration of DNA in a direction perpendicular to the fields.  We have proposed that velocity disturbances generated by the electric field acting upon the polyelectrolyte (DNA), which is distorted from its equilibrium conformation by the local shear, drives the migration.  The strength of the disturbance velocity scales quadratically with the Debye length, consequently the rate and extent of migration can be altered by changing the ionic strength of the suspending fluid according to the model.  In experiments presented here, we systematically varied the ionic concentration and measured the effect upon both the rate and extent of migration as functions of the flow and electric field strengths.  Comparisons of the measurements with Brownian dynamics simulations support the hypothesis that the electrophoretic mobility of DNA depends upon its conformation.