Singlet oxygen generation in the superoxide reaction

ESR spin trapping was utilized to study the singlet oxygen (¹O₂) generation in the reaction of superoxide (O₂^-) with H₂O₂. The spin trap used was 2,2,6,6-tetramethyl-4-piperdone. Incubation of xanthine, xanthine oxidase and H₂O₂ generated ¹O₂ spin adduct signal. Omission of xanthine, xanthine oxidase or H₂O₂ caused a sharp decrease in ¹O₂ generation. ¹O₂ scavenger, sodium azide, inhibited ¹O₂ generation while ^.OH scavenger, ethanol, only slightly decreased the signal intensity. Potassium superoxide (KO₂) decomposition generated ¹O₂. Catalase and sodium azide inhibited ¹O_2- generation and H₂O₂ enhanced it. The results demonstrate that O₂ is capable of generating ¹O₂ upon reaction with H₂O₂.