The peroxynitrite-induced nitration of manganese superoxide dismutase (MnSOD) tyrosine residue, which causes enzyme inactivation, is well established. This led to suggestions that MnSOD nitration and inactivation in vivo, detected in... more
The peroxynitrite-induced nitration of manganese superoxide dismutase (MnSOD) tyrosine residue, which causes enzyme inactivation, is well established. This led to suggestions that MnSOD nitration and inactivation in vivo, detected in various diseases associated with oxidative stress and overproduction of nitric monoxide (NO), conditions which favor peroxynitrite formation, is also caused by peroxynitrite. However, our previous in vitro study demonstrated that exposure of MnSOD to NO led to NO conversion into nitrosonium (NO+) and nitroxyl (NO?) species, which caused enzyme modifications and inactivation. Here it is reported that MnSOD is tyrosine nitrated upon exposure to NO, as well as that MnSOD nitration contributes to inactivation of the enzyme. Collectively, these observations provide a compelling argument supporting the generation of nitrating species in MnSOD exposed to NO and shed a new light on MnSOD tyrosine nitration and inactivation in vivo. This may represent a novel me...
Nitration reactions are generally conducted using mixed acid. These are extremely exothermic, and tend to run away. Our study show that the reaction is more complex than it is generally believed. We have provided some preliminary evidence... more
Nitration reactions are generally conducted using mixed acid. These are extremely exothermic, and tend to run away. Our study show that the reaction is more complex than it is generally believed. We have provided some preliminary evidence to show that nitrobenzene, above a critical concentration of sulfuric acid exists forms microemulsion at ambient temperatures. This hypothesis is consent with anomalous solubility of nitro-aromatics in concentrated sulfuric acid. There is also formation of Winsor III-phases. In this work we have studied kinetics of nitration of nitrobenzene (NB) (below solubility limits) in concentrated sulfuric acid ( > 82% w/w) and found that although the reaction follows second order kinetics, the rate constant show a discontinuous decrease after a critical loading of the organic phase. Reaction is also inhibited by addition of dinitrobenzene (DNB). We have provided the explanation for this finding based on the hypothesis that the reaction between nitrobenzen...
