A search for the intermediate radical, ONOO center dot, in the reaction between oxygen and nitric oxide in solution

The most probable initial reaction between (NO)-N-. and O-2 is direct addition to give the peroxyl radical ONOO.. In view of the potential importance of this radical in biology, we have searched extensively for its formation, using EPR spectroscopy and rapid freezing techniques. At best, only extremely low concentrations were detected, and in most systems, no signals were detectable. We conclude that this radical is unlikely to be of major importance per se in biological systems, in contrast with its one electron adduct, the peroxynitrite anion.