Figure 2.

¹H NMR (600 MHz) (A) and photo-CIDNP (B) spectra of the purified native state (N) and of the MFI (0.3 mM protein/0.2 mM flavin mononucleotide, pH* 7, in ²H₂O at 25°C). NMR and photo-CIDNP spectra were recorded with 512 and 16 scans, respectively. The assignments of the N-state tyrosine resonances are taken from Lu et al. (8). The tyrosine resonances of the MFI species, labeled Y_A, Y_B, and Y_C, have not been assigned to specific residues. Attempts to measure the spectra of the fully reduced protein at pH 7 were thwarted by the rapid formation of disulfide species (Fig. 1A). (pH* is the measured pH of a ²H₂O solution, uncorrected for the deuterium isotope effect.)