Bohr effect, in hemoglobin

The Bohr effect in hemoglobin physiology is associated with... 

KIO. Kilmartin, J. V., and Rossi-Bemardi, L., Inhibition of CO2 combination and reduction of the Bohr effect in hemoglobin chemically modified at its a-amino groups. Nature London) 222, 1243-1246 (1969). 

When such an amino acid is incorporated into a protein, the local chemical environment in the protein may affect the pK of a group and thus alter its charge. Such changes can be very important in the function of proteins (e.g., the Bohr effect in hemoglobin depends on structural changes that affect the pK of histidine... 

S.3.3 Equivalence of the Reduction/Oxidation (Redox) Bohr Effect in Complex IV and the Original Deoxygenation/Oxygenation Bohr Effect in Hemoglobin... 

Manz, B Stilbs, P Jonsson, B Soderman, O Callaghan, PT, NMR Imaging of the Time Evolution of Electroosmotic Flow in a Capillary, Journal of Physical Chemistry 99, 11297, 1995. Matthew, JB Hanania, GIH Gurd, FRN, Electrostatic Effects in Hemoglobin Bohr Effect and Ionic Strength Dependence of Individual Groups, Biochemistry 18, 1928, 1979. 

Figure 4. The calculated values of the equilibrium constant (%) in units of k = zlFs/RT, the surface free energy change due to the conformational change, superimposed upon the dashed curve of the Bohr effect in units of log P0 5, the oxygen pressure for half saturation of hemoglobin. The sets of values are made to coincide at pH 6.3 and are in the same units over the same pH range. (Reproduced with permission from reference 8. Copyright 1975.)...

Implications of oxygen Bohr effect in terms of respiratory quotient and CO2 transport. Its significance for chloride shift and related phenomena. Speculations concerning physiological role of interactions in hemoglobin. 

The transition between the T and R states of hemoglobin is also deeply involved in the Bohr effect and cooperativity. Therefore stabilization of either of the two stmctures should diminish these effects, which have important physiologic consequences. The clinical consequences of stabilization are not known. 

In 1982 a study of the usefulness of DBBF in the production of a blood substitute was reported (99). A single modification achieved the dual goals of reduced oxygen affinity and restricted tetramer—dimer dissociation. This work was confirmed in 1987 (98). The product, called aa-hemoglobin, was formulated in Ringer s lactate. P q under physiologic conditions is 3.7 kPa (28.0 torr). Hill s parameter is 2.2, and the Bohr effect was reduced (100). Plasma retention was increased, and the product appeared to be less heterogeneous than some of the other derivatives under study. Its production was scaled up by Baxter Healthcare Corp., under contract to the U.S. Army. 

Figure 6-9. The Bohr effect. Carbon dioxide generated in peripheral tissues combines with water to form carbonic acid, which dissociates into protons and bicarbonate ions. Deoxyhemoglobin acts as a buffer by binding protons and delivering them to the lungs. In the lungs, the uptake of oxygen by hemoglobin releases protons that combine with bicarbonate ion, forming carbonic acid, which when dehydrated by carbonic anhydrase becomes carbon dioxide, which then is exhaled.

In hemoglobin M, histidine F8 (His F8) has been replaced by tyrosine. The iron of HbM forms a tight ionic complex with the phenolate anion of tyrosine that stabilizes the Fc3 form. In a-chain hemoglobin M variants, the R-T equilibrium favors the T state. Oxygen affinity is reduced, and the Bohr effect is absent. P Ghain hemoglobin M variants exhibit R-T switching, and the Bohr effect is therefore present. 

Hemoglobin s dioxygen binding is regulated by local concentrations of H+ (known as the Bohr effect), CO2 concentration, and organic phosphates such as diphosphoglycerate (DPG), whose structure is shown in Figure 4.2.17... 

In another aquatic f rog, Amphiuma, the adult hemoglobin has an acid Bohr effect at physiological pH, converted in vivo to a weak alkaline one... 

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