Hemoglobin oxygenation curves

To the best of my knowledge, the hemoglobin oxygenation curve is historically the first example of a biologically essential positive cooperativity. Because of this, it becomes an important objective to explore the phenomenology of hemoglobin s positive cooperativity and compare it with that of the consilient mechanism due to an apolar-polar repulsive free energy of hydration (as is done in Chapter 7) and, in fact, to do so for a number of protein-based machines that exhibit positive cooperativity. 

We can determine quantitatively the physiological significance of the sigmoid nature of the hemoglobin oxygen-binding curve, or, in other words, the biological importance of cooperativity. The equation... 

Oxygenation curves of hemoglobin are often fitted with the Adair equation (Eq. 7-12). Thus, at pH 7.4 under the conditions given in Table 7-2, Imai125 found for the successive formation constants Kj = 0.004, K2 = 0.009, K3 = 0.002 and fQ = 0.95 in units of mm Hg 1. From the definition of a formation constant the oxygen... 

Two quite different models were proposed about 25 years ago to explain the unusual nature of the hemoglobin oxygen-binding curve (fig. 5.14). These models can also be used as a starting point for discussing other allosteric proteins. The first model, introduced by Jacque Monod, Jeffery Wyman, and Pierre Changeux in 1965, is called the symme-... 

Fig. 4. Oxygenation curves for myoglobin and hemoglobin. The average number of oxygen molecules bound per protein molecule, n, is plotted vs. the partial pressure of O2. For hemoglobin the oxygenation curve is given at three different partial pressures of carbon dioxide...

F. C. Mills, M. L. Johnson, and J. K. Akers, Oxygenation-linked subunit interactions in human hemoglobin Experimental studies on the concentration dependence of oxygenation curves, Biochemistry 15, 5350 (1976). 

A 72-year-old woman with emphysema presents to the emergency room with fatigue and respiratory distress. Which set of arterial blood gas values below would represent her condition and reflect a shift of the hemoglobin oxygen dissociation curve to the right ... 

The oxygen contents and partial pressures are related by the hemoglobin dissociation curves for maternal and fetal bloods. We used a modified Hill equation (17, 18) ... 

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