The peroxynitrite generator, SIN-1, becomes a nitric oxide donor in the presence-of electron acceptors

Ravinder Jit Singh, Neil Hogg, Joy Joseph, Eugene Konorev, B. Kalyanaraman

Research output: Contribution to journalArticlepeer-review

112 Scopus citations


SIN-1 has been used, in vitro, to simultaneously generate nitric oxide (·NO) and superoxide (O2-). However, the pharmacological activity of SIN-1 resembles that of a ·NO donor. SIN-1 decays by a three-step mechanism. After initial isomerization to an open ring form, SIN-1A reduces oxygen by a one-electron transfer reaction to give O2- and the SIN-1 cation radical, which decomposes to form SIN-1C and ·NO. Here we report that one-electron oxidizing agents, in addition to oxygen, can oxidize SIN-1A, resulting in the release of ·NO without the concomitant formation of O2-. We demonstrate that easily reducible nitroxides, such as the nitronyl and imino nitroxides, are able to oxidize SIN-1. Biological oxidizing agents such as ferricytochrome c also stimulate ·NO production from SIN-1. In addition, decomposition of SIN-1 by human plasma or by the homogenate of rat liver, kidney, and heart tissues results in the formation of ·NO. Our findings suggest that SIN-1 may react with heme proteins and other electron acceptors in biological systems to produce ·NO. Thus, at the relatively low in vivo oxygen concentrations, SIN-1 is likely to behave more like an ·NO donor than a peroxynitrite donor. The relevance of this reaction to myocardial protection afforded by SIN-1 in ischemia/reperfusion-induced injury is discussed.

Original languageEnglish (US)
Pages (from-to)331-339
Number of pages9
JournalArchives of Biochemistry and Biophysics
Issue number2
StatePublished - Jan 15 1999


  • Cytochrome c
  • ESR
  • Nitric oxide
  • Nitroxide
  • Peroxynitrite
  • SIN-1
  • Superoxide

ASJC Scopus subject areas

  • Biophysics
  • Biochemistry
  • Molecular Biology


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