Biochemical properties of human embryonic and semi-embryonic hemoglobins.

(A) Effect of pH on O₂ binding (Bohr effect). The P₅₀ of each hemoglobin was determined in standard buffers adjusted to defined pH levels. Bohr effect values (included in Table 1) were calculated from best-fit curves of values from the alkaline range. ζ₂ε₂ (⧫), α₂ε₂ (●), ζ₂β₂ (■), α₂β₂ (○). (B) Effect of allosteric modifiers on O₂ binding. The P₅₀ values of human hemoglobins were determined in standard buffers containing defined concentrations of 2,3-BPG. The affinity of each Hb for 2,3-BPG (indicated in Table 1) was derived from the half-saturation point of each curve. ζ₂ε₂ (⧫), α₂ε₂ (●), ζ₂β₂ (■), α₂β₂ (○).