Nitrosating agents: is peroxynitrite a likely candidate?

The reagents capable of effecting electrophilic and free radical nitrosation are briefly reviewed, together with the appropriate mechanisms, and in the light of these findings the possibilities of peroxynitrite/peroxynitrous acid acting as a nitrosating species are considered. The conclusion is that it is not to be expected that conventional direct nitrosation would occur. However, the very low yields of some nitrosation products can be accounted for in terms of nitrosation via the nitrogen oxide decomposition products of peroxynitrite. Thus NO could react with a radical substrate, or be converted to N2O3 (a well-known nitrosating species), whereas NO2 if formed can nitrosate via N2O4. A short post-script is added reviewing the Cu+-mediated reaction of S-nitrosothiols, generating (at low [thiol]) nitric oxide.