THE DRIFT VELOCITY IN REPTATION MODELS FOR ELECTROPHORESIS

The drift velocity (diffusion constant) in the Rubinstein-Duke model w ith per-iodic boundary condition is calculated analytically to lowest order in the applied electric field and numerically for the whole scal ing regime. The model is modified by restricting the polymer-storing c apacity of the cells and for this case again the diffusion constant is determined. The periodic boundary condition decouples the different t ube configurations. Thus, with the process of tube renewal removed, on ly the diffusion of length defects through the tube remains. The effec t of the periodic boundary condition on the value of the diffusion con stant and the behavior of the scaling function is discussed on the bas is of numerical results for both models with free endpoint motion. The results strongly suggest that to linear order in the field the drift velocity is unaffected by the process of tube renewal, i.e., is only d etermined by the transport of reptons along the tube.