"Binding and photocleavage properties of [Cr(phen)2(dppz)]3+ to DNA. Implications in phototherapy"

TONEATTO J, BOERO RA, LORENZATTI G, ARGÜELLO GA & CABANILLAS AM.

San Miguel de Tucumán, Tucumán, Argentina

Congreso; XLV Reunión Anual de la SAIB; 2009

Sociedad Argentina de Investigación en Bioquímica y Biología Molecular (SAIB)

Our aim was to study the ability of [Cr(phen)2(dppz)]3+ (Cr(dppz)) to associate to DNA and to characterize it as photocleavage reagent for Photodynamic Therapy (PDT). Cr(dppz) binding to DNA was assessed by absorption and fluorescence spectroscopies, electrophoretic studies and competitive binding experiments. The Cr(dppz)-DNA binding constant was detemined as 1.1x105 M-1 and this value suggests an intercalation of Cr(dppz) between base pairs of DNA. Competitive binding experiments showed that Cr(dppz) complex displaced ethidium bromide from its binding site in the DNA. Moreover, the Cr(dppz) complex, bound non-covalently to DNA, promoted the photocleavage of DNA under irradiation at specific wavelength. These results indicated that excited state of Cr(dppz) is the responsible for the DNA structure damage. This fact was also corroborated by measuring the transformation index of E. Coli with photosensitized plasmid DNA-Cr(dppz), as well as by the same transformation index obtained by irradiation applied to E. Coli after the bacterial transformation with plasmid DNA-Cr(dppz). DNA, [Cr(phen)2(dppz)]3+ and light are the essential elements to induce the DNA damage. In sum, our results allow us to postulate the [Cr(phen)2(dppz)]3+ complex as a very attractive candidate for DNA photocleavage with potential applications in PDT.