Dynamics of pulsed-field electrophoresis

The motion of a long DNA molecule in a gel is examined when an applied field is suddenly rotated 90\ifmmode^\circ\else\textdegree\fi{}. First there is a nucleation stage where kinks above a certain length will appear. Then these kinks coarsen as a result of competition between them, with the longer kinks growing at the expense of the shorter ones. A regime is reached which is self-similar in time, with the number of kinks decreasing inversely with time, analogous to droplet growth in supersaturated solution.