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. 2003 Sep 26;100(21):12087–12092. doi: 10.1073/pnas.2032603100

Fig. 1.

Fig. 1.

Apparent anion-dependent departure from stoichiometric formation of NO–Hb at low NO to Hb ratios. Data show fractional saturation of Hb with NO after NO injection into 0.7 mM (heme) deoxy Hb samples in 0.05 M Bis-Tris, pH 7.5, containing 0.5 mM EDTA. The MetHb reductase system was calculated after 1 h equilibrium at 20°C by using set I spectral standards (pure deoxy Hb, NO–Hb, and MetHb generated as described in Materials and Methods). Representative data are shown for NO injections that should have formed 25% NO–Hb (A) and 42% NO–Hb (B). The dotted line shows the stoichiometric levels of NO–Hb expected. The bars show the apparently sub-stoichiometric levels of NO–Hb obtained for stripped (cofactor-free) Hb samples and in the presence of DPG and IHP.