  We study the electrokinetics of a single polyelectrolyte chain in salt
solution using hydrodynamic simulations. The salt-dependent chain mobility
compares well with experimental DNA data. The mobility of condensed counterions
exhibits a salt-dependent change of sign, an anomaly that is also reflected in
the counterion excess conductivity. Using Green's function techniques this
anomaly is explained by electrostatic screening of the hydrodynamic
interactions between chain and counterions.
