Biochemical reactions thermodynamic data

This is referred to as the extended Debye-Huckel equation. It is an approximation that gives a good fit of data at low ionic strengths (Goldberg and Tewari, 1991) when B= 1.6 L1/2 mol 1/2. Better fits can be obtained with more complicated equations with more parameters, but these parameters are not known for solutions involved in studying biochemical reactions. The way that thermodynamic properties vary with the ionic strength is discussed in more detail in Section 3.6. 

A long time ago chemists realized that the most efficient way to store thermodynamic data on chemical reactions is by making tables of standard thermodynamic properties of species. The NBS Tables of Chemical Thermodynamic Properties (4) gives AfG°, Af// and Sm° for species at 298.15 K at xero ionic strength. Since the standard molar entropy is not available for many species of biochemical interest, the standard entropies of formation Af S" are used. This property of a species is calculated by using... 

R. A. Alberty, Standard apparent reduction potentials of biochemical half reactions and thermodynamic data on the species involved, Biophys. Chem., 111,115-122 (2004). 

The calculation of Af G° and Af H° of species from experimental data on apparent equilibrium constants and transformed enthalpies of reaction is described in R. A. Alberty, Thermodynamics of Biochemical Reactions, Wiley, Hoboken, NJ (2003) and a number of places in the literature. That is not discussed here because this package is oriented toward the derivation of mathematical functions to calculate thermodynamic properties at specified T, pH, and ionic strength. There are two types of biochemical reactants in the database ... 

Note that there is considerable scatter in the results, which is an indication of the difficulty in obtaining accurate thermodynamic data for some biochemical reactions. It is also interesting to notice that the results for the equilibrium constants, Gibbs energies of reaction, and heats of reaction are all affected by pH. This is typical of reactions involving compounds that can ionize, as discussed earlier and will be considered in greater detail in Chapter 15. ... 

As the apparent equilibrium constant is more easily measured in the laboratory than the thermodynamic equilibrium constant, most reported data on biochemical reactions are apparent equilibrium constants. Since the thermodynamic equilibrium constant here is based on ideal 1-molal standard states, so that the activity coefficients are unity at infinite dilution, we have... 

Two volumes edited by Lax include thermodynamic data on the ideal gas state properties of a wide range of elements and compounds, including organic compounds. Other publications in 1967 giving thermodynamic data include the work by Rudman et on phases in metals and alloys, by Klotz on biochemical reactions, by Mueller on metallurgical phenomena, and by Wendlandt and Smith on the thermal properties of metal ammine complexes. 

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