Fig. 4.

Oxidation of F₄₂₀H₂ under anaerobic condition by nitrogen dioxide generated from an in situ reaction between carboxy-PTIO and NO (from DEA-NONOate). Into 1 mL of anaerobic 50 mM potassium phosphate buffer (pH 7.0) in a stoppered cuvette with N₂ in the headspace, the following were added: 25 μM F₄₂₀H₂, 100 μM C-PTIO, and 250 μM DEA-NONOate. The point of each addition is shown by an arrow and the name of the compound. Oxidation of F₄₂₀H₂ was monitored spectrophotometrically at 420 nm. Carboxy-PTIO or C-PTIO, 2-(4-carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide potassium salt. Other abbreviations are shown in the legend for Fig. 2.