The detection of superoxide anion from the reaction of oxyhemoglobin and phenylhydrazine using EPR spectroscopy.
The low temperature EPR spectrum of a quickly reacted mixture of oxyhemoglobin and phenylhydrazine was studied. With the use of a computer, the spectral contribution of methemoglobin in the region of g = 2 was  subtracted. The remaining spectrum was that of an axial free radical (g perpendicular = 2.00, g parallel = 2.06) having the magnetic parameters of superoxide anion. In the presence of superoxide dismutase, this axial radical was not seen, confirming that superoxide anion is indeed generated by the reaction.
D055598:Chemical Phenomena; D002621:Chemistry; D004578:Electron Spin Resonance Spectroscopy; D010100:Oxygen / Q000032:analysis*; D010108:Oxyhemoglobins; D010659:Phenylhydrazines; D013482:Superoxide Dismutase / Q000378:metabolism; D013481:Superoxides / Q000032:analysis*
D010108:Oxyhemoglobins; D010659:Phenylhydrazines; D013481:Superoxides; D013482:Superoxide Dismutase; D010100:Oxygen