Dioxygen binding to hemoglobin

A note on cooperativity You see that such processes - and the math used to describe them - can get rather complicated. There is more to it after the first O2 molecule binds to hemoglobin, to form the HbA 02 complex, the hemoglobin changes shape and other properties to accommodate binding of the second O2. This is even more true in the case of third and fourth O2 molecule the more saturated the hemoglobin molecule is, the more likely it is to bind the next dioxygen ligand. 

Dioxygen binding in hemoglobins occurs at the monomeric Fe(II) center in an rj manner - a similar binding mode as described for P450s. There is overwhelming biochemical and physical data to support that in most hemoglobins... 

Spin-pairing model of dioxygen binding and its application to various transition metal systems as well as hemoglobin cooperativity. R. S. Drago and B. B. Corden, Acc. Chem. Res., 1980, 13, 353-360 (39). 

The thermodynamic association (or dissociation) constants used in the Adair equation for a ligand binding at sites in a multisite protein. The term Adair constants originally referred only to the four constants for the reversible binding of dioxygen to hemoglobin. See Adair Equation... 

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