The objective of this project is to extend the current tables of standard thermodynamic properties of species and standard transformed thermodynamic properties, which I have just put on the web, and to develop ne ways to study the energetics of systems of enzyme-catalyzed reactions. Apparent equilibrium constants are available in the literature for about 500 enzyme-catalyzed reactions, involving about 1000 reactants, but there are over 3500 named biochemical reactions, involving on the order of 10,000 reactants, and more reactions are being identified at a rapid rate. The answer to the question as to whether a reaction will go forward or backward in a living cell depends on the ambient concentrations of the reactants involved, as well as the apparent equilibrium constant at the pH and ionic strength of interest. Our implicit knowledge of apparent equilibrium constants is greater than indicated above because the apparent equ8ilibrium constant can be calculated for any biochemical reaction involving the 100 reactants mentioned above. The efficient way to store this thermodynamic information is construct of a table of standard transformed Gibbs energies of formation deltafG'o of biochemical reactants (sums of species) at 298.15 K, pH 7, and ionic strengths of 0, 0.10, and 0.25 M. The advantage of this table is that the reactants can be looked up and the apparent equilibrium constant K' calculated by taking sums and differences. The process of constructing this table and using it has already been demonstrated with a table of 116n reactants. This table can also be used to calculate the apparent equilibrium constant for the net reaction for a pathway and to answer the question as to whether this net reaction can occur spontaneously at the ambient concentrations of the reactants it involves. Net reactions are of special interest because they show the utilization of storage of chemical energy in the pathway. An even more useful way to store thermodynamic information on biochemical reactants is to construct functions of pH and ionic strength that give the values of these properties at 298.15 K. That has been done in the web site. The new aspect of this project is the inclusion of temperature as an independent variable. That can be done when enthalpies of reaction have been determined calorimetrically or by determining the temperature dependence of the apparent equilibrium constant. Since systems of biochemical reactions are complicated, it is important to develop methods to obtain a more global overview. When concentrations of co-enzymes like ATP, ADP, NAD/Ox, and NAD/red are in steady states, a Legendre transform can be used to define a further transformed Gibbs energy """"""""G"""""""" that provides the criterion for spontaneous reaction and equilibrium under these conditions. This has the effect of reducing the number of concentrations involved in the calculation of the equilibrium concentration, but no thermodynamic information is lost. The table of deltafG'0 values for reactants will also be used to calculate standard transformed reduction potentials for half reactions at pH 7 and be used in Haldane relations between kinetic parameters. This quantitative treatment of the literature data on biochemical reactions will uncover errors because deltafG'0 values can be determined by use of two or more biochemical reactions, which should give the same answer.
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