DNA structural changes on binding and photoreaction with water-soluble tricarbonyl Re(I) complexes

F. RAGONE; J. G. YAÑUK; F. M. CABRERIZO; E. WOLCAN; G. T. RUIZ

Punta del Este

Simposio; 12th International Symposium on Metal Ions in Biology and Medicine; 2013

Metal complexes containing the fac-{ReI(CO)3} core derivatized with different diimine ligands have been known to be efficient emitters for many years and, therefore, their photophysical properties have been widely studied.1 In particular, fac-Re(CO)3L1L2 complexes, with L1 = dipyridil[3,2-a:2?3?-c]phenazine (dppz) and L2 = pyridine derivatives, have been recognized as good intercalators in double helix of DNA.2 Intercalative binding can disrupt the helical nature of DNA, causing profound effects on DNA integrity. Because of their photophysical and redox properties, many of those complexes have the capacity to cause DNA damage by photoinduced oxidative strand breakage.3 Furthermore, the binding modes to DNA for Re(I)-Pterin complexes (L1 = 2-amine-4-pteridinone) have been poorly studied. In this work we used UV-vis absorption and fluorescence spectroscopy to investigate the binding properties of a new one Re(I)-Pterin complex4with DNA (plasmid DNA, double-stranded calf thymus DNA (CT-DNA) and synthetic polynucleotides Poly[dAdT]2 and Poly[dGdC]2), in aqueous solutions. In addition, the consequences on the DNA chemical structure and the excited state reactions of these complex and super-coiled plasmid DNA were investigated by means of electrophoresis. Briefly, when solutions of the complex were incubated (30 min.) with plasmid DNA, agarose gels shown morphological changes on circular DNA changing its conformation from supercoiled to relaxed. Thermal processes show a progression of the conversion with increasing [Re(I) complex]/[DNA] ratio. Irradiation with 350 nm light reverted the changes observed in darkness and no photocleavage was observed. On the other hand, recently we have demonstrated that a Re(I)-dppz complex, (4,4'-bpy)ReI(CO)3(dppz)+, intercalates to Poly[dGdC]2 and with some selectivity to Poly[dAdT]2, Kb = 1.8 x 105 M-1 5. These studies are now complemented with binding to CT-DNA and photocleavage to plasmid DNA after intercalation. All the experimental data will be discussed in relation to the potential applications of those complexes as both luminescent and conformational probes to DNA and molecular scissors to the double helix.0