Protocol for pulsed-field gel electrophoresis via contour-clamped homogeneous electric field gels. In CHEF gels, the electric field is generated from multiple electrodes, arranged in a square of hexagonal contour around the horizontal gel and clamped to predetermined potentials. Using a combination of low field strengths, low concentrations of aragose, long switching intervals, and extended periods of electrophoresis, DNAs up to 5000 kb can be resolved.
