TABLE 1.

Frequencies (cm⁻¹) and tentative assignment of the CO stretching vibrations according to B3LYP/6-31G(d) calculations in harmonic approximation with scaling factor 0.96

	Model
Tentative assignment
C2=O2 in flavin	1742	1748
C4=O4 in flavin	1705	1662
C=O in Asn45	1685	1700
C=O in Gln63 or C=N in Gln*63	1655	1685

^*Shown in Fig. 3 A.

^†Shown in Fig. 3 B.