Figure 1.

EPR spectra of Fe–MGD in the absence and presence of NO or NO⁻. Control, 1 mM Fe–MGD in 50 mM Tris⋅HCl buffer (pH 7.4); NO, Fe–MGD with the NO (¹⁴N) donor N-SNAP (10 μM); ¹⁵NO, with 10 μM ¹⁵N-SNAP; NO⁻, with 10 μM NO⁻ donor Na₂N₂O₃. In the presence of the trap Fe–MGD, natural abundance ¹⁴NO gives rise to the characteristic triplet spectrum whereas ¹⁵NO gives rise to a characteristic doublet. NO⁻ did not produce any significant signal. Spectra were recorded at room temperature with a microwave frequency of 9.77 GHz by using 80 mW of microwave power and 3.9 G modulation amplitude.