The effects of myoglobin and apomyoglobin on the formation and stability of the hydroxyl radical adduct of 5,5'-dimethyl-1-pyrroline-N-oxide.
When aqueous solutions of the spin trap 5,5'-dimethyl-1-pyrroline-N-oxide (DMPO) are treated with hydrogen peroxide in the presence of either FeII or light, the hydroxyl radical adduct DMPO-OH is formed, with a characteristic 4 line ESR spectrum. When oxy- or metmyoglobin is added to such a system the initial yield and the halife of DMPO-OH are reduced, and at high myoglobin concentrations (about 0.1 mmol dm-3) DMPO-OH becomes undetectable. Using the stable nitroxide 2,2,6,6-tetramethyl-1-piperidinyloxy-N-oxyl (TMPO) for comparison it was found that neither hydrogen peroxide nor myoglobin alone caused a loss of signal, but together a marked loss of signal was induced. From the evidence of these and other experiments it was concluded that the DMPO-OH adduct reacts with hydrogen peroxide and myoglobin to give non-paramagnetic products, and hence that the use of the DMPO spin trap to detect hydroxyl or other active radicals in systems containing physiological concentrations of myoglobin may give misleading results.
Department of Cardiology, University of Leicester.
W D
WD
Yang
D
D
De Bono
M C
MC
Symons
D001059:Apoproteins / Q000494:pharmacology*; D003497:Cyclic N-Oxides / Q000737:chemistry*; D004578:Electron Spin Resonance Spectroscopy; D006861:Hydrogen Peroxide / Q000494:pharmacology; D006878:Hydroxides / Q000737:chemistry*; D017665:Hydroxyl Radical; D009211:Myoglobin / Q000494:pharmacology*; D013113:Spin Labels
D001059:Apoproteins; D003497:Cyclic N-Oxides; D006878:Hydroxides; D009211:Myoglobin; D013113:Spin Labels; C010857:apomyoglobin; C051831:3,3,5,5-tetramethyl-1-pyrroline N-oxide; D017665:Hydroxyl Radical; C017245:5,5-dimethyl-1-pyrroline-1-oxide; D006861:Hydrogen Peroxide