Transverse Alternating-Field Electrophoresis

Transverse alternating-field electrophoresis (TAFE) refers to a pulsed-field system that uses a vertical gel and a simple electrode geometry. A schematrc of the apparatus is shown in Fig. 1 (1 ). The electrophoresis tank is a large plexiglass box, in which the gel stands vertically, supported at each side by two thin plexiglass slots and by the buoyancy of the buffer. The electrodes, represented by dots in the figure, are wires stretched across the width of the box (in commercial designs, the electrodes are wired to removable plexiglass inserts). During electrophoresis, the DNA is alternately moved downward and to the left, when the A electrodes are activated, and downward and to the right, when the B electrodes are activated. Note that the angle between the A and B fields is not constant down the length of the gel. At the wells, it is 115�, but is much greater at increasing distances from the wells. As the angle increases, the downward component of the field decreases.