title: Direct photo-induced DNA strand scission by a ruthenium bipyridyl complex.
abstract: Irradiation of plasmid DNA in the presence of Ru(II)-2, a modified tris(2,2'-bipyridyl)Ru(II) complex, in which two hydroxamic acid groups are attached to one of the three bipyridyl ligands, results in total fragmentation of the DNA. The photo-chemical reaction products were analyzed by gel electrophoresis, which revealed complete fragmentation. Further evidence for the complete degradation of the DNA was obtained by imaging the pre- and post-treated plasmid DNA using atomic force microscopy (AFM). A mechanism for the reaction is proposed. It initially involves the photo-chemical generation of Ru(III) ions and superoxide radicals, as corroborated by absorbance difference spectroscopy and electron paramagnetic resonance (EPR). Consequently, Ru(III) preferentially oxidizes guanine, liberating superoxide radicals that yield OH radicals. The OH radicals were identified by observing the spectral change at 532 nm of a 5'-dAdG substrate forming a colored adduct with thiobarbituric acid. These radicals are associated with the major non-specific damage exerted to DNA.
authors.affiliation: Division of Chemistry and Chemical Engineering and Beckman Institute, California Institute of Technology, Pasadena, CA 91125, USA. eyavin@caltech.edu
authors.forename: Eylon
authors.initials: E
authors.lastname: Yavin
authors.forename: Eric D A
authors.initials: ED
authors.lastname: Stemp
authors.forename: Lev
authors.initials: L
authors.lastname: Weiner
authors.forename: Irit
authors.initials: I
authors.lastname: Sagi
authors.forename: Rina
authors.initials: R
authors.lastname: Arad-Yellin
authors.forename: Abraham
authors.initials: A
authors.lastname: Shanzer
mesh_terms: D015082:2,2'-Dipyridyl / Q000737:chemistry / Q000494:pharmacology*; D004578:Electron Spin Resonance Spectroscopy; D004587:Electrophoresis, Agar Gel; D007700:Kinetics; D008027:Light; D018625:Microscopy, Atomic Force; D010957:Plasmids / Q000187:drug effects / Q000528:radiation effects*; D012428:Ruthenium / Q000737:chemistry / Q000494:pharmacology*
chemical_list: D015082:2,2'-Dipyridyl; D012428:Ruthenium