Hemoglobin fractional saturation

In the absence of experimental methods for distinguishing experimentally between the five forms of the tetramer, the fractional saturation of hemoglobin is measured. The fractional saturation of tetramer Y, is defined by... 

Calculate the fractional saturation YT of the tetramer of human hemoglobin with molecular oxygen using the equilibrium constants determined by Mills, Johnson, and Akers (1976) at 21.5 °C, 1 bar, pH 7.4, [Cl"] = 0.2 M and 0.2 M ionic strength. Make the calculation with the Adair equation and also by using the binding polymomial YT. 

The fractional saturation Y at the highest possible hemoglobin concentration is given by yhigh=y/.heme->5 10 -3 ... 

The fractional saturation at the lowest currently possible hemoglobin concentration is given by ylow=y/.heme->4 10A-8 ... 

At specified concentration of molecular oxygen, the five forms of hemoglobin are pseudoisomers, and they have the same further transformed Gibbs energy of formation at equilibrium. The further transformed thermodynamic properties of the tetramer can be calculated from experimental measurements of the fractional saturation, but in order to interpret experimental data, it is necessary to provide for the partial dissociation of tetramer 02 Bz into dimers a/3 (3). Seven apparent equilibrium constants are required to describe experimental data, and it is shown that all seven can be determined using limiting forms (4). 

R. A. Alberty, Determination of the seven apparent equilibrium constants for the binding of oxygen by hemoglobin from measured fractional saturations, Biophys. Chem. 63,119-132 (1997). 

The fractional saturation of all the hemoglobin binding sites Y is given by... 

Fig. 4.9 The variation of the fractional saturation of myoglobin and hemoglobin molecules with the partial pressure of oxygen. The different shapes of the curves account for the different biological functions of the two proteins.

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