Figure 2.

Representative low-temperature EPR spectra obtained from mixtures of 1 mM MetHb and ONOO⁻ or HN₂O₃⁻ under reduced oxygen tensions. A, MetHb; B, MetHb + 1 mM ONOO⁻; C, MetHb + 0.1 mM HN₂O₃⁻; and D, MetHb + 1 mM HN₂O₃⁻. The incubation mixtures were prepared and EPR analyses were performed as described in Materials and Methods. Instrumental conditions: power, 20 mW; modulation amplitude, 5 G; scan rate, 7.4 G/s; gain, 1.42 × 10⁴, except for D, where the gain was 2.83 × 10³.