The aim of this work was to study the ability of [Cr(phen)2(dppz)]3+ (Cr(III)) to associate and generate photodamage in plasmid DNA (pBS) and its capability as photobactericidal. Cr(III) was synthesized and the binding properties to DNA were investigated by absorption, fluorescence, competitive binding experiments and electrophoretic studies. A marked hypochromism in the absorption spectrum was observed with the increase in plasmid DNA concentration, the Cr(III)-DNA binding constant was calculated 1.1x105 M-1 suggesting an intercalation of Cr(III) between base pairs of DNA. Competitive binding experiments show that the emission intensity of ethidium bromide (EthBr) associated to DNA was quenched by Cr(III) complex indicating that it displaces EthBr from its binding site in the plasmid. Moreover, the Cr(III) complex, bound non-covalently to DNA, promoted the photocleavage of pBS under irradiation at 457nm. This effect was corroborated through studies of transforming ability of the photosensitized pBS. To know if the Cr(III) complex was able to induce photoinactivacion of E. Coli, a series of suspensions containing bacteria were exposed at different times of irradiation in the presence and absence of complex. The results suggest that the E. coli can be photoinactivated by irradiation in the presence of Cr(III). Light alone and Cr(III) complex alone were not able to kill bacteria.
