Fig. 3.

Reaction rate and amount of F₄₂₀ produced at various dissolved oxygen concentrations and at fixed levels of DEA-NONOate and F₄₂₀H₂. The assay mixture contained 1 mL of anaerobic 100 mM potassium phosphate buffer (pH 7.0), with 20 μM F₄₂₀H₂ and varied volumes of O₂ added to the nitrogen headspace. Before the assay, the mixture was held at room temperature for 15 min to ensure equilibration with the added oxygen. The reaction was initiated by the addition of DEA-NONOate (final concentration, 320 μM) and was followed spectrophotometrically at 420 nm. The dissolved oxygen concentration was calculated by using a value of 43,800 atm/mol fraction for the Henry's constant for oxygen (40).