Peroxynitrite does not decompose to singlet oxygen (1ΔgO2) and nitroxyl (NO-)

Glaucia R. Martinez, Paolo Di Mascio, Marcelo G. Bonini, Ohara Augusto, Karlis Briviba, Helmut Sies, Patrick Maurer, Ursula Röthlisberger, Susanna Herold, Willem H. Koppenol*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

92 Scopus citations

Abstract

According to Khan et al. [Khan, A. U., Kovacic, D., Kolbanovskiy, A., Desai, M., Frenkel, K. & Geacintov, N. E. (2000) Proc. Natl. Acad. Sci. USA 97, 2984-2989], peroxynitrite (ONOO-) decomposes after protonation to singlet oxygen (1ΔgO2) and singlet oxonitrate (nitroxyl, 1NO-) in high yield. They claimed to have observed nitrosyl hemoglobin from the reaction of NO- with methemoglobin; however, contamination with hydrogen peroxide gave rise to ferryl hemoglobin, the spectrum of which was mistakenly assigned to nitrosyl hemoglobin. We have carried out UV-visible and EPR experiments with methemoglobin and hydrogen peroxide-free peroxynitrite and find that no NO- is formed. With this peroxynitrite preparation, no light emission from singlet oxygen at 1270 nm is observed, nor is singlet oxygen chemically trapped; however, singlet oxygen was trapped when hydrogen peroxide was also present, as previously described [Di Mascio, P., Bechara, E. J. H., Medeiros, M. H. G., Briviba, K. & Sies, H. (1994) FEBS Lett. 355, 287-289]. Quantum mechanical and thermodynamic calculations show that formation of the postulated intermediate, a cyclic form of peroxynitrous acid (trioxazetidine), and the products 1NO- and 1ΔgO2 requires Gibbs energies of ca. +415 kJ·mol-1 and ca. +180 kJ·mol-1, respectively. Our results show that the results of Khan et al. are best explained by interference from contaminating hydrogen peroxide left from the synthesis of peroxynitrite.

Original languageEnglish (US)
Pages (from-to)10307-10312
Number of pages6
JournalProceedings of the National Academy of Sciences of the United States of America
Volume97
Issue number19
DOIs
StatePublished - Sep 12 2000
Externally publishedYes

ASJC Scopus subject areas

  • General

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