Photonuclease activity of Taylorʹs blue

Taylorʹs blue (1,9-dimethylmethylene blue, DMMB+) associates with DNA, at least in part, through intercalation as is evidenced from the red shift in the absorption maximum, diminution of the fluorescence, and induced circular dichroism in the presence of nucleic acid. Irradiation of DMMB+/covalently closed circular supercoiled gfX174 phage DNA complex at λ > 520 nm leads to DNA nicking in a dose-dependent manner.