Free radical intermediates in the oxidation of N-methylhydroxylamine and N,N-dimethylhydroxylamine by oxyhemoglobin.
Nitroxide radicals have been detected in the methemoglobin formation reaction between oxyhemoglobin and the substituted hydroxylamine compounds, N-methylhydroxylamine and N,N-dimethylhydroxylamine, by ESR spectroscopy. The stability of these nitroxide radicals was considerably higher than that of the NH2O. radical derived from unsubstituted hydroxylamine. Only in the case of N-methylhydroxylamine the detection of the nitroxide radical required the use of a flow system, because the radical was found to undergo a rapid degradation with the concomitant formation of a secondary product, the beta-aminonitroxide CH3NO.CH2NH2. The nitroxide radical derived from N,N-dimethylhydroxylamine and oxyhemoglobin was stable for more than 1 hour. In addition, formation of low-spin iron-(III)-complexes from methemoglobin and excess substituted hydroxylamine was observed in both cases. Neither N-methylhydroxylamine nor N,N-dimethyldroxylamine formed the hemoglobin-nitric oxide complex found with unsubstituted hydroxylamine. Parallels and differences in the reaction path of un-, mono- and disubstituted hydroxylamines are discussed.
Stolze
K
K
Institute of Pharmacology, School of Veterinary Medicine, University of Vienna.
Nohl
H
H
D000818:Animals; D002417:Cattle; D055598:Chemical Phenomena; D002621:Chemistry; D004123:Dimethylamines; D004578:Electron Spin Resonance Spectroscopy; D005609:Free Radicals; D006898:Hydroxylamines; D009589:Nitrogen Oxides / Q000032:analysis*; D010084:Oxidation-Reduction; D010108:Oxyhemoglobins; D013696:Temperature
D004123:Dimethylamines; D005609:Free Radicals; D006898:Hydroxylamines; D009589:Nitrogen Oxides; D010108:Oxyhemoglobins; C063231:N,N-dimethylhydroxylamine; C039900:nitroxyl; C018338:N-methylhydroxylamine