Page 337 - Thermodynamics of Biochemical Reactions

Chapter 7 Thermodynamics of Binding of Ligands by Proteins

7.1 Use the equilibrium constants in equations 7.1-3 to 7.1-6 to calculate the further transformed Gibbs energies of formation
of the forms of the tetramer of hemoglobin and of the pseudoisomer group at O,] = 5 x~O-~, lo-', and 2 x~O-~M. (a)
Make a table with the last three columns like Table 7.1. (b) Calculate the equilibrium mole fractions of forms of the tetramer
at 21.4 OC, 1 bar, pH 7.4, (21-1 = 0.2 M, and 0.2 M ionic strength and make a table like Table 7.2.

7.2 Use the equilibrium constants in equations 7.3-2 and 7.3-3 to calculate the further transformed Gibbs energies of forma-
tion of the forms of the dimer of hemoglobin and of the pseudoisomer group at O,] = 5 x~O-~, and 2 x~O-~M.
Make a table with the last three columns and first four rows of Table 7.3.

7.3 Calculate the fractional saturation Y, 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 Y, .

7.4 Calculate the fractional saturation Y, of the dimer 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 P, .

7.5 (a) Calculate the oxygen binding curve Y for human hemoglobin when the dimer and tetramer are in equilibrium 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. This plot depends on the heme concentration. The currently accessible range of heme concentrations is
about 0.04 pM to 5 mM. Plot logK" versus [O,]. (b) Use the equation for Y to extrapolate to values of Y, at high heme
concentrations. (c) Use the equation for Y to extrapolate to values of Y, at low heme concentrations.

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