Errors in the evaluation of Arrhenius and van't Hoff plots.

Area of Science:

• Biophysical Chemistry
• Chemical Kinetics
• Biochemistry

Background:

• Thermodynamic parameters like activation enthalpy and entropy are crucial for understanding reaction mechanisms.
• Arrhenius and van't Hoff plots are commonly used to determine these parameters.
• Previous studies have highlighted potential inaccuracies in these calculations.

Purpose of the Study:

• To identify and explain the sources of error in calculating thermodynamic parameters from Arrhenius and van't Hoff plots.
• To provide guidelines for accurate thermodynamic analysis of chemical and enzymatic reactions.
• To clarify the appropriate application of these plots in biochemical contexts.

Main Methods:

• Analysis of the mathematical and dimensional consistency of thermodynamic equations.
• Evaluation of approximations commonly used in the derivation of kinetic parameters.
• Comparison of the application of Arrhenius and van't Hoff plots to theoretical and experimental reaction data.

Main Results:

• Errors often arise from neglecting equidimensionality or using inappropriate approximations in calculations.
• Logarithmizing dimensioned quantities is a significant source of error, necessitating the use of relative concentrations.
• The application of Arrhenius plots to enzyme kinetics (using Vmax/ET) is valid only for simple Michaelis-Menten mechanisms, while van't Hoff plots using Km are questionable.

Conclusions:

• Strict adherence to dimensional consistency and avoiding logarithmization of dimensioned quantities are essential for accurate thermodynamic calculations.
• The interpretation of thermodynamic parameters derived from kinetic data requires careful consideration of the underlying reaction mechanism and the validity of approximations used.
• Guidelines are provided for the correct application of Arrhenius and van't Hoff plots in chemical and biochemical research to ensure reliable results.