Peroxynitrite biochemistry: formation, reactions and detection

Peroxynitrite is a powerful and cytotoxic oxidant formed by the diffusion-limited reaction between (NO)-N-. and O-2(-). Peroxynitrite reactions can be classified into a) direct reactions, including those with thiols, transition metal centers and CO2, that account for more than 95 % peroxynitrite reactivity in biology, and b) the hydroxyl radical/nitrogen dioxide pathway, which arises from homolysis of peroxynitrous acid. Different methods have been utilized to expose biochemical or cellular systems to peroxynitrite including a) addition of authentic peroxynitrite, either as a bolus or a continuous infusion, and b) generation of fluxes of the radical precursors (NO)-N-. and O-2(-). Reaction yields and product distributions are sometimes difficult to interpret, mainly due to the multiple possible and competing radical interactions, Peroxynitrite detection relies on a) the detection of footprints, and b) the modification of probes, The lack of total specificity of the methods in use makes obligatory the use of a combination of them and/or pharmacological approaches in order to unambiguously unravel peroxynitrite formation either in biochemical or biological systems.