A simple large-scale method for separating closed circular form DNA by gel electrophoresis.

The covalently closed form of circular duplex SV40 DNA was separated from the open and linear form of SV40 DNA by agarose gel electrophoresis in a large-scale gel system. The closed circular DNA was recovered from agarose gels by re-electrophoresing the gel slices. The recovery of DNA was about 70%. Electron microscopic analysis showed that the recovered DNA did not have doube- or single-stranded breaks. The recovered DNA can be used without further purification for electron microscopy, as a substrate for experiments using restriction endonuclease and as a template for in vitro RNA synthesis.