Calculation of thermodynamic properties of species from binding of a ligand by a macromolecule

Abstract

In the absence of experimental methods for determining concentrations of species in protein-ligand binding, it is not possible to determine the thermodynamic properties of species directly. However, this article on a simple reaction system shows that measurements of the average number of oxygen molecules bound at various T, pH and concentrations of molecular oxygen can be used to calculate thermodynamic properties of species. The simple system considered has some of the characteristics of the binding of oxygen by hemoglobin, but it has been simplified so that the method for obtaining thermodynamic information can be clarified. A table of standard thermodynamic properties of species is the most efficient way to store thermodynamic information on a reaction system. All the standard further transformed thermodynamic properties at specified T, pH and concentrations of molecular oxygen, all the standard transformed thermodynamic properties at specified T and pH, and all the standard thermodynamic properties of species at a specified temperature can be calculated. These calculations are based on the fact that the mathematical function for the standard further transformed Gibbs energy of the system contains all the thermodynamic information on the system. These properties are all interrelated by Maxwell equations.