Fast and biphasic 8-nitroguanine production from guanine and peroxynitrite.

Guanine (Gua), among purines, is a preferred oxidation/nitration target because of its low one-electron redox potential. The reactive oxygen/nitrogen species peroxynitrite (ONOO), produced in vivo by the reaction between nitric oxide (NO) and superoxide radical (O), is responsible for several oxidative modifications in biomolecules, including nitration, nitrosation, oxidation, and peroxidation. In particular, the nitration of Gua, although detected, as well as its reaction kinetics have been seldom investigated.