Oxygen affinity of hemoglobin

Astrup, P. and Rorth, M., eds. Oxygen Affinity of Hemoglobin and Red Cell Acid Base Status. Academic Press, New York (1972). 

Shirasawa T, Izumizaki M, Suzuki Y, et al. Oxygen affinity of hemoglobin regulates O2 consumption, metabolism, and physical activity. J Biol Chem 2003 278 5035. 

Decrease in pH results in decreased 1 oxygen affinity of hemoglobin and,... 

Effect of carbon monoxide on the oxygen affinity of hemoglobin. CO-Hb = carbon monoxyhemoglobin. 

The oxygen affinity of hemoglobin varies with the pH of the medium. This is the Bohr effect, and arises from the effect of pH on the interaction between the heme and the ionizable groups of the protein. It appears that the Bohr effect is linked to the presence of a second imidazole group (the distal imidazole group), which is involved in uptake of dioxygen in some indirect way. 

The oxygen affinity of hemoglobin is lowered by the chloride ion strengthening the salt link. Thus, in the presence of chloride, more oxygen would be released. 

Tuning the Oxygen Affinity of Hemoglobin The Effect of 2,3-Bisphosphoglycerate... 

Figure 10.25. Effect of pH and CO2 concentration on the oxygen affinity of hemoglobin. Lowering the pH from 7.4 (red curve) to 7.2 (blue curve) results in the release of O2 from oxyhemoglobin. Raising the CO2 partial pressure from 0 to 40 torr (purple curve) also favors the release of O2 from oxyhemoglobin.

M. F. Perutz Regulation of oxygen affinity of hemoglobin Influence of structure of the globin on the heme iron. Annual Review of Biochemistry 48,327(1979). 

Bisphosphoglycerate in Red Cells Is Crucial in Determining the Oxygen Affinity of Hemoglobin... 

The most important and universal type of chemical equilibria to which a heme protein is subjected in natural environments is pH equilibria, involving the protein aminoacid residues and the ionizable groups of the porphyrin, the propionate side chains. Beside the effects on the overall protein structure, which are outside the scope of this review, the major consequences of proton equilibria may be the changes of the heme reduction potential (electron affinity), called the redox-Bohr effect (see Sect. 3.2), by analogy to the pH effect on the oxygen affinity of hemoglobin (Bohr effect). 

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