Interaction between copper(II)−arginine complexes and HO2/O2− radicals, a pulse radiolysis study

Superoxide radicals were shown to react with all four Cu(II)-arginine complexes that exist between pH 1.5 and 12.5; k/sub 10/(O/sub 2//sup -/ + CuArgH/sup 2 +/) = 3.3 x 10/sup 9/ M/sup -1/ s/sup -1/, k/sub 12/(O/sub 2//sup -/ + Cu(ArgH)/sub 2//sup 2 +/) = 1.3 x 10/sup 7/ M/sup -1/ s/sup -1/, k/sub 13/(O/sub 2//sup -/ + CuArg/sub 2/H/sup +/) = 1 x 10/sup 6/ M/sup -1/ s/sup -1/, k/sub 14/(O/sub 2//sup -/ + CuArg/sup +/) = 1 x 10/sup 8/ M/sup -1/ s/sup -1/. The system was studied in detail at pH 2.0 and pH greater than or equal to7. At low pH the mechanism was shown to proceed via a CuO/sub 2/H/sup 2 +/ complex while at higher pH a superoxide complex of the Cu(II)-arginine complexes was formed. The results are discussed in terms of the currently accepted mechanism by which SOD-Cu/sup 2 +/ dismutates O/sub 2//sup -/ radicals.