Simultaneous Action of Electric Fields and Nonelectric Forces on a Polyelectrolyte: Motion and Deformation

We describe the deformation and drift of a charged polymer in solution under the simultaneous action of an electric field and a nonelectric force. This should be of interest for current micromanipulation experiments on DNA fragments and for electrophoretic separation methods. Our description is qualitatively different from existing theories. The main results are (i) that the force to hold a polyelectrolyte immobile in an electric field ${\mathbf{E}}_{\infty }$ is proportional to its 3D size (and not to its curvilinear length or total charge), and (ii) that its deformation is then essentially identical to that in a purely hydrodynamic uniform flow of velocity $\mathbf{V}={\mu }_{\mathrm{el}}{\mathbf{E}}_{\infty }$ ( ${\mu }_{\mathrm{el}}$ is the electrophoretic mobility of the polyelectrolyte).