  The velocity of polaron migration in the long poly-DNA chain (~40 base pairs)
in an applied electric field has been studied within a polaron model. We found
that the polaron velocity strongly depends on the polaron size. A small polaron
shows a slow propagation and strong tolerance to the electric field, while a
large polaron is much faster and less stable with increasing electric field.
Moreover, the conductance of the DNA molecule within the polaron model is found
to be sensitive to structural disorders in the DNA geometry, but that
dependence diminishes with increasing temperature.
