Reptation Theory of Pulsed Electrophoresis and Trapping Electrophoresis

In the history of the still-young technique of pulsed electrophoresis experimental, theoretical, and numerical progress are increasingly intermingled. The first key to this field can be traced to theoretical letters of Lerman and Frisch and Lumpkin and Zimm (1 ,2 ), who remarked that long flexible chains like chromosomal DNA cannot migrate in gels as random coils, and suggested a reptative-like motion in which chains thread their way among fibers like a snake among roots. They also predicted that large DNA chains orient in the field, and for the first time, made the connection between this orientation and the saturation of the mobility that causes the failure of conventional gel electrophoresis techniques. The idea of fighting this orientation by periodically changing the field appeared for the first time about two years later, in the founding experimental work of Schwartz and Cantor (3 ), giving birth to the pulsed electrophoresis technique. Detailed developments of the reptation ideas sketched in 1982 were steadily pursued in 1985 and in the following years (4 –20 ), in particular by the groups of Lumkin, Zimm, and coworkers, and Slater, Noolandi, and coworkers. These first developments, however, remained focused on migration in constant-field, and theorists got deeply involved in the understanding of pulsed electrophoresis only since