HypCal, a general-purpose computer program for the determination of standard reaction enthalpy and binding constant values by means of calorimetry

The program HypCal has been developed to provide a means for the simultaneous determination, from dataobtained by isothermal titration calorimetry, of both standard enthalpy of reaction and binding constant values. The chemical system is defined in terms of species of given stoichiometryrather than in terms of binding models (e.g., independent or cooperative). The program does not impose any limits on the complexity of the chemical systems that can be treated, including competing ligand systems. Many titration curves may be treated simultaneously. HypCal can also be used as asimulation program when designing experiments. The use of the program is illustrated with data obtained with nicotinicacid (niacin, pyridine-3 carboxylic acid). Preliminary experiments were used to establish the rather different titration conditionsfor the two sets of titration curves that are needed todetermine the parameters for protonation of the carboxylateand amine groups.