FIGURE 1.

Reductive nitrosylation of methemoglobin (HbFe³⁺). HbFe³⁺ (≈25 μm) was mixed with variable amounts of ProliNONOate to achieve the indicated NO concentrations. Reactions were performed at 37 °C in 100 mm sodium phosphate (pH 7.4), except reactions in panels D and F, which were performed at 25 °C. A, 24 μm HbFe³⁺ and reacted with the NO donor ProliNONOate (final [NO] = 21 μm). B, concentration of different species following spectral deconvolution for the reaction shown in panel A (HbFe³⁺, red; HbFe²⁺-NO, black; HbFe³⁺-NO, green). C, observed rate constants of HbFe²⁺-NO formation from experiments where HbFe³⁺ (≈25 μm) was mixed with increasing amounts of ProliNONOate. The red line shows the calculated rates from a simulation with the model in Equations 1–8 (see text for details). D, observed rate constants of HbFe²⁺-NO formation from experiments where ≈20 μm ProliNONOate was mixed with increasing concentrations of HbFe³⁺. E, observed initial rates of HbFe²⁺-NO formation for the experiments in panel C. F, observed initial rates of HbFe²⁺-NO formation for the experiments in panel D.