Hydrogen peroxide and dioxygen activation by dinuclear copper complexes in aqueous solution: hydroxyl radical production initiated by internal electron transfer.
Dinuclear Cu(II) complexes, CuII2Nn (n = 4 or 5), were recently found to specifically cleave DNA in the presence of a reducing thiol and O2 or in the presence of H2O2 alone. However, CuII2N3 and a closely related mononuclear Cu(II) complex exhibited no selective reaction under either condition. Spectroscopic studies indicate an intermediate is generated from CuII2Nn (n = 4 or 5) and mononuclear Cu(II) solutions in the presence of H2O2 or from CuI2Nn (n = 4 or 5) in the presence of O2. This intermediate decays to generate OH radicals and ligand degradation products at room temperature. The lack of reactivity of the intermediate with a series of added electron donors suggests the intermediate discharges through a rate-limiting intramolecular electron transfer from the ligand to the metal peroxo center to produce an OH radical and a ligand-based radical. These results imply that DNA cleavage does not result from direct reaction with a metal-peroxo intermediate but instead arises from reaction with either OH radicals or ligand-based radicals.
Zhu
Qing
Q
Department of Chemistry and Biochemistry, University of Maryland, College Park, Maryland 20742, USA.
Lian
Yuxiang
Y
Thyagarajan
Sunita
S
Rokita
Steven E
SE
Karlin
Kenneth D
KD
Blough
Neil V
NV
D003300:Copper / Q000737:chemistry*; D004583:Electrons; D006861:Hydrogen Peroxide / Q000737:chemistry*; D017665:Hydroxyl Radical / Q000737:chemistry; D009942:Organometallic Compounds / Q000737:chemistry; D010100:Oxygen / Q000737:chemistry*; D011725:Pyridines / Q000737:chemistry; D012996:Solutions; D014867:Water / Q000737:chemistry
D009942:Organometallic Compounds; D011725:Pyridines; D012996:Solutions; D014867:Water; D017665:Hydroxyl Radical; D003300:Copper; D006861:Hydrogen Peroxide; D010100:Oxygen