Superoxide and Hydroperoxyl Radical Spin Trapping Using 5,5- Dimethyl-1-Pyrroline N-Oxide in Dehydrated N,N-Dimethylformamide

Abstract

Herein, superoxide radical (O2•−) spin trapping using 5,5-dimethyl-1-pyrroline N-oxide (DMPO) in dehydrated N,N-dimethylformamide (DMF) solution is investigated via electrochemistry and electron spin resonance (ESR) measurements supported by theoretical calculations. In aprotic environments, DMPO gradually reacts with electrogenerated O2•−; however, the trapping kinetics are considerably slow and cannot enable successful radical trapping in aqueous biological experiments. Alternatively, adding a proton source changes the voltammetric behavior, rendering the detection of the spin adduct easy with ESR. These results suggest that the proton addition to O2•−, which forms a hydroperoxyl radical (HO2•), accelerates the kinetics of radical trapping. Accordingly, we propose that the actual target of DMPO spin trapping is HO2• rather than O2•−.