title: Factors influencing the DNA nuclease activity of iron, cobalt, nickel, and copper chelates.
abstract: A library of complexes that included iron, cobalt, nickel, and copper chelates of cyclam, cyclen, DOTA, DTPA, EDTA, tripeptide GGH, tetrapeptide KGHK, NTA, and TACN was evaluated for DNA nuclease activity, ascorbate consumption, superoxide and hydroxyl radical generation, and reduction potential under physiologically relevant conditions. Plasmid DNA cleavage rates demonstrated by combinations of each complex and biological co-reactants were quantified by gel electrophoresis, yielding second-order rate constants for DNA(supercoiled) to DNA(nicked) conversion up to 2.5 × 10(6) M(-1) min(-1), and for DNA(nicked) to DNA(linear) up to 7 × 10(5) M(-1) min(-1). Relative rates of radical generation and characterization of radical species were determined by reaction with the fluorescent radical probes TEMPO-9-AC and rhodamine B. Ascorbate turnover rate constants ranging from 3 × 10(-4) to 0.13 min(-1) were determined, although many complexes demonstrated no measurable activity. Inhibition and Freifelder-Trumbo analysis of DNA cleavage supported concerted cleavage of dsDNA by a metal-associated reactive oxygen species (ROS) in the case of Cu(2+)(aq), Cu-KGHK, Co-KGHK, and Cu-NTA and stepwise cleavage for Fe(2+)(aq), Cu-cyclam, Cu-cyclen, Co-cyclen, Cu-EDTA, Ni-EDTA, Co-EDTA, Cu-GGH, and Co-NTA. Reduction potentials varied over the range from -362 to +1111 mV versus NHE, and complexes demonstrated optimal catalytic activity in the range of the physiological redox co-reactants ascorbate and peroxide (-66 to +380 mV).
authors.affiliation: Evans Laboratory of Chemistry, The Ohio State University, 100 West 18th Avenue, Columbus, Ohio 43210, United States.
authors.forename: Jeff C
authors.initials: JC
authors.lastname: Joyner
authors.forename: Jared
authors.initials: J
authors.lastname: Reichfield
authors.forename: J A
authors.initials: JA
authors.lastname: Cowan
mesh_terms: D001205:Ascorbic Acid / Q000378:metabolism; D002460:Cell Line; D002614:Chelating Agents / Q000494:pharmacology*; D003035:Cobalt / Q000378:metabolism; D003300:Copper / Q000378:metabolism; D053904:DNA Breaks, Single-Stranded / Q000187:drug effects; D053837:DNA Cleavage / Q000187:drug effects*; D003851:Deoxyribonucleases / Q000494:pharmacology*; D004121:Dimethyl Sulfoxide / Q000494:pharmacology; D005609:Free Radicals / Q000378:metabolism; D007501:Iron / Q000378:metabolism; D007700:Kinetics; D019216:Metals, Heavy / Q000494:pharmacology*; D009532:Nickel / Q000378:metabolism; D010084:Oxidation-Reduction
chemical_list: D002614:Chelating Agents; D005609:Free Radicals; D019216:Metals, Heavy; D003035:Cobalt; D003300:Copper; D009532:Nickel; D007501:Iron; D003851:Deoxyribonucleases; D001205:Ascorbic Acid; D004121:Dimethyl Sulfoxide