title: Electron-paramagnetic-resonance studies on a photochemically produced species of horseradish peroxidase compound I.
abstract: Strong electron-paramagnetic-resonance signals in the g = 2.00 region were detected after irradiation of horseradish peroxidase Compound I at temperatures of 10 and 100 K. These signals establish the presence of new free-radical species in the peroxidase system. The new species are interpreted in terms of a haem-photosensitized oxidation of the protein's peptide groups close to the Compound I radical site. On warming to room temperature, the radicals decayed irreversibly to a species having a weak asymmetric electron-paramagnetic-resonance signal at 100 K, which could still be observed after incubation at room temperature for more than 1 h.
mesh_terms: D003080:Cold Temperature; D004578:Electron Spin Resonance Spectroscopy; D005609:Free Radicals; D006735:Horseradish Peroxidase; D008027:Light; D010544:Peroxidases; D010777:Photochemistry; D013696:Temperature
chemical_list: D005609:Free Radicals; D006735:Horseradish Peroxidase; D010544:Peroxidases