Calculation of Standard Transformed Formation Properties of Biochemical Reactants and Standard Apparent Reduction Potentials of Half Reactions

Abstract

The standard Gibbs energies of formation and standard enthalpies of formation of species involved in biochemical reactions are used to calculate standard transformed Gibbs energies of formation and standard transformed enthalpies of formation of 62 biochemical reactants (sums of species) at 298.15 K, pH 7, and ionic strengths of 0, 0.10, and 0.25 M. It has been possible to put the oxidized and reduced forms of some reactants in this table because their standard apparent reduction potentials are known at pH 7. This paper emphasizes redox reactions. Two applications have been made of these 62 new values of standard transformed Gibbs energies of formation at pH 7: (1) They have been used to calculate standard transformed Gibbs energies of formation of 16 more biochemical reactants from measurements of apparent equilibrium constants of redox reactions.(2) They have been used to calculate standard apparent reduction potentials at pH 7 for half reactions involving reactants discussed in this article and the previous one. This table of standard apparent reduction potentials can be extended considerably from known apparent equilibrium constants for enzyme-catalyzed redox reactions. This brings the total number of reactants for which the standard transformed Gibbs energy of formation at 298K, pH 7, and ionic strengths of 0, 0.10, and 0.25 M have been calculated to 142.