Direct photo-induced DNA strand scission by a ruthenium bipyridyl complex

Eylon Yavin, Eric D.A. Stemp, Lev Weiner, Irit Sagi, Rina Arad-Yellin, Abraham Shanzer

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25 Scopus citations


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.

Original languageAmerican English
Pages (from-to)1750-1756
Number of pages7
JournalJournal of Inorganic Biochemistry
Issue number11
StatePublished - Nov 2004
Externally publishedYes

Bibliographical note

Funding Information:
We thank Prof. Jacqueline K. Barton for generously providing Ru(phen) 2 dppz, Dr. Sidney Cohen for his useful advices, Dr. Luana Scheffer for the AFM measurements, Dr. Shuping Shi for help in running the gels, Dr. Hadar Kless and Mrs. Roxana Golan for plasmid DNA preparation. This work was supported in part by the Israel Academy of Sciences and by the Helen and Martin Kimmel Center for Molecular Design. A.S. holds the Siegfried and Irma Ullman professorial chair.


  • Cage complex
  • DNA photo-cleavage
  • Nitroxyl radicals
  • Ruthenium tris(2,2′-bipyridyine) complex


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