"DNA-[Cr(phen)2(dppz)]3+ binding and photocleavage properties by the complex having an intercalating ligand"

TONEATTO J, BOERO R, LORENZATTI G, CABANILLAS AM, ARGÜELLO, GA

JOURNAL OF INORGANIC BIOCHEMISTRY

Elseiver

Lugar: New York, USA; Año: 2008

0162-0134

A chromium(III) complex [Cr(phen)2(dppz)]3+, (dppz = dipyridophenazine, phen = 1,10-phenanthroline) was synthesized and the binding properties to DNA were investigated by UV-visible absorption spectroscopy, competitive binding experiments and electrophoretic studies. The results suggest that the complex binds with DNA by an intercalation mode. The intrinsic DNA binding constants, Kb, were 3.5x105M-1 and 1.6x105M-1 for the association complexes ([Cr(phen)2(dppz)]3+-ds-oligo) and ([Cr(phen)2(dppz)]3+-plasmid), respectively. Competitive binding experiments show that the enhancement in emission intensity of ethidium bromide (EthBr) associated to DNA was quenched by [Cr(phen)2(dppz)]3+, indicating that the Cr(III) complex displaces EthBr from its binding site in plasmid.  Moreover, [Cr(phen)2(dppz)]3+, non-covalently bounded to DNA, promotes the photocleavage of plasmid DNA under 457nm irradiation. This effect was corroborated through studies of the transforming ability of the photosensitized plasmid. These results demonstrate that *[Cr(phen)2(dppz)]3+ are responsible for damaging DNA structure. The combination of DNA, [Cr(phen)2(dppz)]3+ and light  are necessary and sufficient to induce the damage.