Separation of large DNA by a variable-angle contour-clamped homogeneous electric field apparatus.

A device for separating large DNA molecules by pulsed field electrophoresis is described. Based on the principles of contour-clamped homogeneous electric fields (CHEF), it uses feedback to clamp voltages in a square electrode array, which is compact and inexpensive to construct, adaptable to computer control, and reorients the electric field by arbitrary angles. To illustrate its capabilities, pulsed fields with reorientation angles ranging from 90 to 140 degrees were used to separate DNAs of 4.7 and 5.7 megabases by up to four band-widths in 20 h. The combination of accessible technology and complete control of the electric field should facilitate the search for ways to resolve even larger DNA.