Reactions of peroxynitrite leading to either apoptotic or necrotic cell death

Peroxynitrite (sometimes called peroxonitrite) is an

ion An ion () is an atom or molecule with a net electrical charge. The charge of an electron is considered to be negative by convention and this charge is equal and opposite to the charge of a proton, which is considered to be positive by conve ...

with the formula ONOO⁻. It is a structural isomer of

nitrate Nitrate is a polyatomic ion A polyatomic ion, also known as a molecular ion, is a covalent bonded set of two or more atoms, or of a metal complex, that can be considered to behave as a single unit and that has a net charge that is not zer ...

Preparation

Peroxynitrite can be prepared by the reaction of

superoxide In chemistry, a superoxide is a compound that contains the superoxide ion, which has the chemical formula . The systematic name of the anion is dioxide(1−). The reactive oxygen ion superoxide is particularly important as the product of t ...

with

nitric oxide Nitric oxide (nitrogen oxide or nitrogen monoxide) is a colorless gas with the formula . It is one of the principal oxides of nitrogen. Nitric oxide is a free radical: it has an unpaired electron, which is sometimes denoted by a dot in its che ...

: : It is prepared by the reaction of

hydrogen peroxide Hydrogen peroxide is a chemical compound with the formula . In its pure form, it is a very pale blue liquid that is slightly more viscous than water. It is used as an oxidizer, bleaching agent, and antiseptic, usually as a dilute solution (3%� ...

with nitrite: : H₂O₂ + → ONOO⁻ + H₂O Its presence is indicated by the

absorbance Absorbance is defined as "the logarithm of the ratio of incident to transmitted radiant power through a sample (excluding the effects on cell walls)". Alternatively, for samples which scatter light, absorbance may be defined as "the negative lo ...

at 302 nm (pH 12, ''ε''₃₀₂ = 1670 M⁻¹ cm⁻¹).

Reactions

Peroxynitrite is weakly basic with a p''K''_a of ~6.8. It is reactive toward DNA and

protein Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residues. Proteins perform a vast array of functions within organisms, including catalysing metabolic reactions, DNA replication, respo ...

s. ONOO⁻ reacts nucleophilically with

carbon dioxide Carbon dioxide (chemical formula ) is a chemical compound made up of molecules that each have one carbon atom covalently double bonded to two oxygen atoms. It is found in the gas state at room temperature. In the air, carbon dioxide is transpar ...

. ''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 () is by far the predominant pathway for ONOO⁻. 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 A carbonate is a salt of carbonic acid (H2CO3), characterized by the presence of the carbonate ion, a polyatomic ion with the formula . The word ''carbonate'' may also refer to a carbonate ester, an organic compound containing the carbonate g ...

and

nitrogen dioxide Nitrogen dioxide is a chemical compound with the formula . It is one of several nitrogen oxides. is an intermediate in the industrial synthesis of nitric acid, millions of tons of which are produced each year for use primarily in the producti ...

) that are believed to cause peroxynitrite-related cellular damage.

Peroxynitrous acid

Its

conjugate acid A conjugate acid, within the Brønsted–Lowry acid–base theory, is a chemical compound formed when an acid donates a proton () to a base—in other words, it is a base with a hydrogen ion added to it, as in the reverse reaction it loses a ...

peroxynitrous acid Peroxynitrous acid (HNO3) is a reactive nitrogen species (RNS). It is the conjugate acid of peroxynitrite (ONOO−). It has a p''K''a of approximately 6.8. It is formed ''in vivo'' from the diffusion-controlled reaction of nitrogen monoxide (ON ...

is highly reactive, although peroxynitrite is stable in basic solutions.

References

{{Nitrogen compounds Oxyanions Atmospheric chemistry Toxins

Preparation

Reactions

Peroxynitrous acid

See also

References