Fig. 4.

Hb–O₂ equilibrium curves of big cats. Hb–O₂ equilibrium curves of African lion (A) and snow leopard (B) HbA and HbB are insensitive to 2,3-diphosphoglycerate (DPG) and are right-shifted compared with those of human adult Hb (open symbols, dotted lines). Data were obtained at a heme concentration of 0.3 mmol l⁻¹, 37°C, in 0.1 mol l⁻¹ Hepes buffer, pH 7.4, in the absence (circles) and presence of DPG (triangles), at a 2-fold molar excess of DPG over tetrameric Hb. Non-linear regression of the O₂-saturation data according to the sigmoidal Hill equation is shown for each of the conditions used. 1 Torr≈133 Pa.