• Manual Field Switch for CHEF Pulse Field Gel Electrophoresis

    C.Lang & M. Lang, April 2004

    Pulse Field Gel Electrophoresis (PFGE) is a method for size separation of large DNA fragments for BAC cloning and many other purposes. Different electrophoresis systems are available, for example FIGE (Field Inversion Gel Electrophoresis) (1) (2) or CHEF (Clamped Homogeneous Electric Fields) (3). These methods are based on rhythmic and symmetrical oscillation of the electric field direction during gel electrophoresis. The electric field oscillates around a certain axes at a certain angle, usually 90°-120° (oscillation must occur symmetrically regarding switch angle and switch time). Over time, the field vectors result in a single "main field direction". Some electrophoresis systems are able to freely re-orientate this main axis by a free determination of the extreme angles. However, not all commercially available CHEF systems have this option.

    BAC cloning (6) sometimes requires a back and forth migration of DNA fragments inside the agarose gel (7). Here we describe a simple machine that alternatively switches the electrical connections of oppositely located electrodes of the gel tank and the CHEF power module. This results in a complete field inversion of the main electric field direction without altering any other electrophoresis conditions which are controlled by the CHEF power module. The principle of this apparatus was described previously (1). The machine was designed for a 24 electrode CHEF PFGE system (5). It enables both-, a manual and a timer dependent programmed switch.

  • Protocols: