Normalized time course absorbance plots of catalytic reaction of metal-substituted QDOs, as followed by loss of quercetin absorbance at 380 nm in IP buffer pH 6.5. (Upper) Dioxygenase assays in aerobic solutions (130 μM O2): Co-QDO (2.85 μM, [Q]: 14.25 μM, dashed), Fe-QDO (2.48 μM, [Q]: 12.42 μM, dotted), and Mn-QDO (2.31 μM, [Q]: 11.55 μM, solid). (Lower) Nitroxygenase assays in anaerobic solutions: Co-QDO (2.98 μM, [Q]: 14.90 μM, [AS]: 148 μM, dashed), Fe-QDO (2.85 μM, [Q]: 14.2 μM, [AS]: 140 μM, dotted), and Mn-QDO (3.73 μM, [Q]: 18.63 μM, [AS]: 184 μM, solid).