Electrophoresis of polyampholytes

We consider the motion and the deformation of Gaussian polyampholytes in free flow electrophoresis, i.e., in an applied external electric field. The electrophoretic mobility and the deformation of the chains are calculated in the linear regime, as functions of the charge distribution along the backbone and of the salt concentration. The results in salt-free solutions differ from those in solutions with a high concentration of salt even at the level of scaling laws. It is shown that in solutions with a high salt concentration, the electrophoretic mobility of a given polyampholyte strongly depends not only on its total charge but also on the details of the charge distribution along the chain. The very direction of motion can also depend on it. Indeed, even ‘‘neutral” polyampholytes, i.e., chains with equal number of positive and negative charges can move in an applied electric field. To demonstrate further these effects, we systematically compare the behavior of the linear and circular chains.