Dougherty, Geoffrey published the artcileThe unwinding of circular DNA by intercalating agents as determined by gel electrophoresis, SDS of cas: 518-67-2, the publication is Bioscience Reports (1983), 3(5), 453-60, database is CAplus and MEDLINE.
An accurate and precise method is described to determine the unwinding angle of the circular DNA helix of plasmid pBR322/RcβG by ethidium bromide and other intercalating agents of electrophoresis in 1.4% agarose gels containing chloroquine, followed by densitometry of the photog. negs. of the gels. Under the electrophoresis conditions used, native (form I) DNA and partially relaxed samples, running faster or slower than it, were resolved. Contaminating nicked (form II) DNA did not interfere, since it was clearly separated during electrophoresis.
Bioscience Reports published new progress about 518-67-2. 518-67-2 belongs to bromides-buliding-blocks, auxiliary class Other Aromatic Heterocyclic,Salt,Amine,Benzene, name is Dimidium bromide, and the molecular formula is C20H18BrN3, SDS of cas: 518-67-2.
Referemce:
https://en.wikipedia.org/wiki/Bromide,
bromide – Wiktionary