Anomalous electrophoresis, self-trapping and “freezing” of partially charged polyelectrolytes

According to the biased reptation model of gel electrophoresis, the alignment of the DNA molecules in the field direction is due to the presence of electric charges near the ends of the chains. This alignment limits the size of DNA molecules that can be separated, and contributes to the phenomenon of self-trapping. Here, I present a model where the biased diffusion inside the reptation tube is decoupled from the tube orientation which is produced by the end-segments. Where the ends are uncharged, self-trapping is found to dominate the dynamics : the mobility first decreases with the electric field E as 1/ln (E) before it vanishes as e-E, indicating that the molecules is “frozen” in the gel. This shows that variations in the charge distribution along a chain polyelectrolyte can have dramatic effects.