Theory of electrophoresis of polyelectrolytes through gels

We assume that the polyelectrolyte moves through a “tube” in a neutral gel under the influence of the electrical field. The tube is random except for possible bias due to the effects of the field. We also assume a frictional coefficient proportional to contour length for longitudinal motion in the tube. When the field is small, we easily recover the inverse-length dependence of the mobility found previously by de Gennes and by Doi and Edwards. At higher fields a new effect appears; the tube becomes oriented because the field biases the direction of the leading end of the chain as it moves to form an extension of the tube. This leads to an increase of the mobility with increasing field.