Sunita Thyagarajan

Publications (4)35.89 Total impact

• Article: Hydrogen peroxide and dioxygen activation by dinuclear copper complexes in aqueous solution: hydroxyl radical production initiated by internal electron transfer.

  Qing Zhu, Yuxiang Lian, Sunita Thyagarajan, Steven E Rokita, Kenneth D Karlin, Neil V Blough
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  ABSTRACT: 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.
  Journal of the American Chemical Society 06/2008; 130(20):6304-5. · 9.91 Impact Factor
• Article: Selective DNA strand scission with binuclear copper complexes: implications for an active Cu2-O2 species.

  Sunita Thyagarajan, Narasimha N Murthy, Amy A Narducci Sarjeant, Kenneth D Karlin, Steve E Rokita
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  ABSTRACT: A homologous series of binuclear copper(II) complexes [Cu(II)(2)(Nn)(Y)(2)](2+) (1-3) (n = 3-5 and Y = (ClO(4))(-) or (NO(3))(-)) were studied to investigate the intermediate(s) responsible for selective DNA strand scission in the presence of MPA/O(2) (MPA = 3-mercaptopropanoic acid). While the N3 complex does not react, the N4 and N5 analogues show comparable activity with strand scission occurring at a single-strand/double-strand junction. Identical reactivity is also observed in the alternate presence of H(2)O(2). Spectroscopic and reactivity studies with [Cu(II)(2)(N4)(Y)(2)](2+) (2) and H(2)O(2) are consistent with DNA oxidation mediated by formation of a side-on peroxodicopper(II) (Cu(2)-O(2)) complex.
  Journal of the American Chemical Society 06/2006; 128(21):7003-8. · 9.91 Impact Factor
• Article: Recognition of guanines at a double helix-coil junction in DNA by a trinuclear copper complex.

  Takeo Ito, Sunita Thyagarajan, Kenneth D Karlin, Steven E Rokita
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  ABSTRACT: Coordination between guanine N7 and a trinuclear copper complex appears critical for selective and efficient strand scission of DNA at a helix-coil junction as indicated by the lack of reactivity of comparable DNA containing 7-deazaguanine in place of guanine; both the base pair at the junction and coil flexibility also modulate the specificity of DNA oxidation.
  Chemical Communications 11/2005; · 6.17 Impact Factor
• Article: Intramolecular C-H activation by inferred terminal cobalt imido intermediates.

  Sunita Thyagarajan, Daniel T Shay, Christopher D Incarvito, Arnold L Rheingold, Klaus H Theopold
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  ABSTRACT: Reaction of TpR,MeCo(I) dinitrogen complexes (R = iPr, tBu) with trimethylsilyl azide yields structurally characterized compounds that imply the formation of reactive intermediates of the type TpR,MeCo=NSiMe3. These cobalt imido species apparently abstract hydrogen from the 3-substituent of the Tp-ligand, leading to the formation of amido complexes accompanied by either Co-C bond formation (R = tBu) or C-C bond formation (R = iPr).
  Journal of the American Chemical Society 05/2003; 125(15):4440-1. · 9.91 Impact Factor