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Peroxynitrous acid--where is the hydroxyl radical?
Reinhard Kissner1, Thomas Nauser, Christophe Kurz
1Laboratorium für Anorganische Chemie, ETH-Hönggerberg, Zürich, Switzerland.
IUBMB Life
|January 9, 2004
Summary
Peroxynitrite, a toxic compound formed from superoxide and nitrogen monoxide, is unlikely to decompose via O-O bond homolysis. Experiments show decomposition yields do not support this mechanism, suggesting alternative pathways for peroxynitrite reactions.
Area of Science:
- Biochemistry
- Chemical Kinetics
- Toxicology
Background:
- Peroxynitrite is a reactive inorganic compound with physiological significance.
- It is formed from the rapid reaction of superoxide and nitrogen monoxide radicals.
- Understanding its decomposition pathway is crucial for biological and chemical contexts.
Purpose of the Study:
- To investigate the mechanism of peroxynitrite decomposition.
- To determine if homolysis of the O-O bond in peroxynitrous acid occurs.
- To elucidate the chemical reactivity of peroxynitrite.
Main Methods:
- Experimental analysis of peroxynitrite decomposition products.
- Isotopic labeling studies using [15N]nitrite.
- Kinetic studies involving peroxynitrite and monohydroascorbate.
- High-pressure kinetic experiments to determine activation volumes.
Main Results:
- Nitrite yield from peroxynitrite decomposition was concentration-dependent and lower than predicted by homolysis.
- [15N]nitrate yield in reactions with [15N]nitrite did not match homolysis predictions.
- Ascorbyl radicals were not detected when peroxynitrous acid reacted with monohydroascorbate.
- High-pressure kinetic studies yielded inconclusive activation volumes.
Conclusions:
- The experimental evidence strongly suggests that homolysis of the O-O bond in peroxynitrite is not the primary decomposition pathway.
- Alternative reaction mechanisms likely govern peroxynitrite's chemical behavior.
- Further studies are needed to fully characterize peroxynitrite decomposition and reactivity.