5, 5-Dimethylpyrroline N-oxide (DMPO) 1 has become the most commonly used spin trap in biological systems to date. This is because the hydroxyl radical spin adduct gives a simple and distinctive EPR spectrum2 consisting of four peaks with relative intensity 1: 2: 2: 1, and the superoxide/hydroperoxyl radical spin adduct gives a different but also distinctive multiline EPR spectrum2 composed of 6 major peaks plus additional partially resolved ...