Magnetophoresis of tagged polymers

We present quantitative results for the drift velocity of a polymer in a gel if a force (e.g. through an electric or magnetic field) acts on a tag, attached to one of its ends. This is done by introducing a modification of the Rubinstein-Duke model for electrophoresis of DNA. We analyze this modified model with exact and Monte Carlo calculations. Tagged magnetophoresis does not show band collapse, a phenomenon that limits the applicability of traditional electrophoresis to short polymers.