Peroxidase catalyzed aggregation of plasmid pBR322 DNA by benzidine metabolites in vitro

The interaction of plasmid DNA and metabolites of benzidine produced by the action of horseradish peroxidase and hydrogen peroxide was investigated by a combination of agarose gel electrophoresis and autofluorography. Benzidine becomes irreversibly bound to the DNA to form a macromolecular structure that can no longer penetrate a 0.8% agarose gel. Other carcinogens such as o-dianisidine, o-tolidine and amino-fluorene also reacted in this way but N4-tetramethylbenzidine and the non-carcinogenic 3,5,3',5',tetramethylbenzidine did not.