title: Low-level chemiluminescence of hydroperoxide-supplemented cytochrome c.
abstract: Ferricytochrome c showed low-level chemiluminescence, with a light-emission measured of about 1x10(3)-3x10(3) counts/s, when supplemented with organic hydroperoxides. Tertiary hydroperoxides (cumene hydroperoxide and t-butyl hydroperoxide) showed a saturation behaviour at about 5mm-hydroperoxide, whereas primary hydroperoxides showed a quadratic dependence on the hydroperoxide concentration. Chemiluminescence depended linearly on cytochrome c concentration, and optimal light-emission was observed at [t-butyl hydroperoxide]/[ferricytochrome c] ratios of 160-500. Hydroperoxide-supplemented ferricytochrome c consumed O(2) at a rate of 1.0mumol/min per mumol of cytochrome c; the rate of O(2) uptake was linearly related to the concentration of cytochrome c. The Soret absorption band of ferricytochrome c decreased about 64% after incubation with t-butyl hydroperoxide, whereas the 530nm band was almost totally abolished. Light-emission was (a) inhibited competitively by cyanide. (b) inhibited by singlet-oxygen quenchers (e.g. beta-carotene), scavengers (e.g. dimethylfuran) and traps (e.g. histidine and tryptophan) and (c) increased by singlet-oxygen-chemiluminescence enhancer 1,4-diazabicyclo[2.2.2]-octane. Superoxide dismutase had no effect on the present system. The participation of free radicals is suggested by the effect of the radical trap 2,5-di-t-butylquinol. Singlet-oxygen dimol emission seems to be mainly responsible for the observed light-emission; a mechanism that can account for the major part of the present experimental observations is proposed.
mesh_terms: D001555:Benzene Derivatives; D001643:Bridged Bicyclo Compounds; D002338:Carotenoids; D055598:Chemical Phenomena; D002621:Chemistry; D003486:Cyanides; D003574:Cytochrome c Group / Q000037:antagonists & inhibitors; D005609:Free Radicals; D006873:Hydroquinones; D008163:Luminescent Measurements; D010545:Peroxides; D010879:Piperazines; D013053:Spectrophotometry; D020122:tert-Butylhydroperoxide
chemical_list: D001555:Benzene Derivatives; D001643:Bridged Bicyclo Compounds; D003486:Cyanides; D003574:Cytochrome c Group; D005609:Free Radicals; D006873:Hydroquinones; D010545:Peroxides; D010879:Piperazines; C019359:2,5-di-tert-butylhydroquinone; D002338:Carotenoids; D020122:tert-Butylhydroperoxide; C007164:cumene hydroperoxide; C007306:triethylenediamine