Figure 1. EPR analysis of O₂^•−-scavenging activity of intact mitochondria.

The reaction mixtures consisted of: (A) 20 m-units/ml of xanthine oxidase, 7 μM xanthine and 160 mM DMPO; (B) as (A) in the presence of 0.8 μM Cu,Zn-superoxide dismutase; (C) as (B) plus 5 mM KCN; (D) computer simulation of spectrum in (C); (E) as (A) in the presence of intact mitochondria (100 μg of protein/ml); (F) as (A) in the presence of mitochondrial intermembrane space preparation (25 μg of protein/ml); and (G) as (F) plus 5 mM KCN. All reactions were carried out in sucrose/Tris buffer, pH 7.4. The DMPO–OH spin adduct was detected by EPR as described in the Experimental section.