Densitometric quantification of DNA topoisomers in ethidium bromide-stained agarose gels and chemiluminescence-detected X ray films

This study investigates the contribution of deformational strain imposed by topological interconversions of DNA in ethidium bromide-binding on agarose gels. Closed-circular plasmid DNAs were nicked using UV exposure and the DNA bands were quantified by densitometry. The results show that the closed circular DNA binds the same amount of the dye as its nicked counterpart. The relationship between the band intensity on X-ray films of chemiluminescence-detected Southern blots and DNA concentration was shown to be linear.