Chemical and biochemical thermodynamics reunification (IUPAC Technical Report)

According to the 1994 IUBMB-IUPAC Joint Commission on Biochemical Nomenclature (JCBN) on chemical and biochemical reactions, two categories of thermodynamics, based on different concepts and different formalisms, are established: (i) chemical thermodynamics, which employ conventional thermodynamic potentials to deal with chemical reactions [1], [2], [3]; and (ii) biochemical thermodynamics, which employ transformed thermodynamic quantities to deal with biochemical reactions based on the formalism proposed by Alberty [4], [5], [6], [7]. We showed that the two worlds of chemical and biochemical thermodynamics, which so far have been treated separately, can be reunified within the same thermodynamic framework. The thermodynamics of chemical reactions, in which all species are explicitly considered with their atoms and charge balanced, are compared with the transformed thermodynamics generally used to treat biochemical reactions where atoms and charges are not balanced. The transformed thermodynamic quantities suggested by Alberty are obtained by a mathematical transformation of the usual thermodynamic quantities. The present analysis demonstrates that the transformed values for Δr G′0 and Δr H′0 can be obtained directly, without performing any transformation, by simply writing the chemical reactions with all the pseudoisomers explicitly included and the elements and charges balanced. The appropriate procedures for computing the stoichiometric coefficients for the pseudoisomers are fully explained by means of an example calculation for the biochemical ATP hydrolysis reaction. It is concluded that the analysis reunifies the "two separate worlds"of conventional thermodynamics and transformed thermodynamics.