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Peroxynitrite

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Peroxynitrite
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Peroxynitrite (sometimes called peroxonitrite) is an ion with the formula ONOO. It is a structural isomer of nitrate, NO
3

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Reactions of peroxynitrite leading to either apoptotic or necrotic cell death
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Preparation

Peroxynitrite can be prepared by the reaction of superoxide with nitric oxide:[1][2][3]

NO + O2 → NO(O2)

It is prepared by the reaction of hydrogen peroxide with nitrite:[4]

H2O2 + NO
2
→ ONOO + H2O

Its presence is indicated by the absorbance at 302 nm (pH 12, ε302 = 1670 M−1 cm−1).

Reactions

Peroxynitrite is weakly basic with a pKa of ~6.8.

It is reactive toward DNA and proteins.

ONOO reacts nucleophilically with carbon dioxide. In vivo, the concentration of carbon dioxide is about 1 mM, and its reaction with ONOO occurs quickly. Thus, under physiological conditions, the reaction of ONOO with carbon dioxide to form nitrosoperoxycarbonate (ONOOCO
2
) is by far the predominant pathway for ONOO. ONOOCO
2
homolyzes to form carbonate radical and nitrogen dioxide, again as a pair of caged radicals. Approximately 66% of the time, these two radicals recombine to form carbon dioxide and nitrate. The other 33% of the time, these two radicals escape the solvent cage and become free radicals. It is these radicals (carbonate radical and nitrogen dioxide) that are believed to cause peroxynitrite-related cellular damage.

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Peroxynitrous acid

Its conjugate acid peroxynitrous acid is highly reactive, although peroxynitrite is stable in basic solutions.[5][6]

See also

References

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