Fig. 1.

Room temperature EPR spectra of the sulfite radical adduct of DMPO, DMPO-${\mathrm{SO}}_3^{-}$. All the reactions were performed in 50 mM phosphate buffer (pH=7.4) containing 0.1 mM DTPA. Spectrum A: DMPO (0.1 M), Fe³⁺cyt c (0.1 mM), and sulfite (1 mM). Spectrum B: DMPO (0.1 M) and sulfite (1 mM). Spectrum C: DMPO (0.1 M) and Fe³⁺cyt c (0.1 mM). EPR instrument parameters used were as described in the Materials and Methods section. EPR spectra are sum of 10 scans.