FIGURE 6.

pH effects on reductive nitrosylation observed rate constants. Ferric Hb chains (HbFe³⁺) were mixed with NO from ProliNONOate. Reactions were performed at 37 °C in 100 mm sodium phosphate (pH 6.5 or 7.4) or in 100 mm Tris-HCl buffer (pH 9.0). The observed rate constants increase at higher pH but the dependence is smaller than what would be expected if the reaction were completely base-catalyzed (expectation is a 10-fold increase in rate per pH unit increase). The inset shows the observed rate constants in the high NO range.