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.
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