Determination of Thermodynamic and Kinetic Parameters from Calorimetric Data

2 Determination of Thermodynamic and Kinetic Parameters from Calorimetric Data 

The form of the flow calorimetric equations described earlier can also be manipulated to incorporate Michaelis-Menten parameters such as the Michaelis constant, as well as yielding the first order rate constant and enthalpy for the overall reaction, Equation (6). 

Note that it is trivial to calculate the first-order rate constant from the calorimetric data from Equation (6), it is simply the slope of the line for a plot of In dq/dt vs. f. However second-order rate constants require a more complicated approach and are accessible through a new calculational approach of data pairing, this is not considered further and more details can be found in refs. 11 and 26. 

Once the rate constant for reaction is known, it then becomes possible to calculate the enthalpy for the reaction for all time points of the reaction and obtain an average for the lifetime of the first-order reaction. Once the enthalpy is found, it is possible to calculate the value of from a consideration of the zero-order output and hence the Michaelis constant is now accessible from the slope of the first-order In dq/dt vs. t plot (the slope of this plot is equal to 

It must be emphasized that this analysis is not possible without prior knowledge of the thermal volume of the calorimetric cell and therefore the validation routine described above must be conducted if accurate values for the enthalpy in particular are to be obtained. 

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