title: Relation between redox potentials and rate constants in reactions coupled with the system oxygen-superoxide.
abstract: Univalent oxidation-reduction reactions coupled with the oxygen-superoxide system were investigated in the reactions shown in eq 3 and 8, where Q and Q.- stand for p-benzoquinone and p-benzosemiquinone, respectively. From kinetic experiments the following rate constants were obtained at pH 7.0:k3 = 4.5 x 10(4) M-1 sec-1 and k8 = 3 x 10(-2) M-1 sec-1. With known values of k-3 and k-8, and of E0' for the systems Q-Q.- (0.10 V) and Cyt c3+ - Cyt c2+ (0.255 V), the calculated values of E0(O2-O2.-) were found to lie in the range between -0.27 and -0.33 V.
mesh_terms: D001665:Binding Sites; D003574:Cytochrome c Group / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008433:Mathematics; D010084:Oxidation-Reduction; D010100:Oxygen; D010544:Peroxidases / Q000378:metabolism; D011199:Potentiometry; D011485:Protein Binding; D011809:Quinones / Q000494:pharmacology; D013482:Superoxide Dismutase / Q000378:metabolism
chemical_list: D003574:Cytochrome c Group; D011809:Quinones; D010544:Peroxidases; D013482:Superoxide Dismutase; D010100:Oxygen