| Abstract: | Using the direct method of pulse radiolysis to determine the superoxide dismutase like activity of copper(II) cimetidine complexes, it was found that the reaction rate constant with O?2, kcat, was (8.5 ± 0.5) × 108 M?1s?1 independent of the cimetidine concentrations present in excess of 50–200 μM over the metal. The results suggest that either the 1:1 ligand to metal complex does not catalyze O?2 dismutation at a comparable rate to that of the 2:1 complex, or that the stability constant of the last species is much higher than that determined earlier by Kimura el al.,1 and only the 2:1 species is present in the solutions. With the indirect methods of cytochrome c and NBT for determining the ability of these complexes to catalyze O?2 dismutation, these compounds exhibited a much lower SOD activity. and kcat was determined to be (5.0 ± 0.3) × 106 and (7.± 0.4) × 101 M?1s?1. respectively using the two assays. |
