Our lab has shown that the reaction of HNO-Mb + O2 occurs over minutes at very low [O2] (>10 uM) and observed an apparent intermediate with lifetime of minutes. Low concentrations displayed a very slow second phase on the order of 30 min. The final N-based product is nitrate (NO3-), in almost quantitative yield. However results were misleading as we identified the apparent intermediate to have a Fe II oxidation state, using global analysis and CO trapping, and the second phase as simple autooxidation to FeIII and NO3-. By changing reaction conditions, it is found that at higher pH and [O2] allow for an intermediate that is observable whose lifetime increases with pH. This species has a sharp absorbance ca. 611 nm that resembles an analogous Iron adduct, definitely not a FeIV=O. The loss of this absorbance depends on both [H+] and [O2], suggesting a multistep mechanism. We hypothesizes this intermediate as an N-bound peroxynitrite-adduct of FeII myoglobin,which then further reacts with or is displaced by O2. The similarity of this intermediate we observe and those previously reported during these varied reactions is compelling, and may define some intrinsic detoxifying function for native heme proteins, converting NO/O2 (or HNO/O2) to NO3-.

Isolating the peroxynitrite intermediate

246th National Meeting (2013)

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.