Isothermal Titration Calorimeter (nanoITC)
Essentially all studies of biomolecular interactions involve measurements of dissociation constants or free energies of association (∆G = RT ln Kd). However, a detailed understanding of the physicochemical basis of the interactions often requires more detailed measurements of the thermodynamic components of the free energy change (the enthalpy change, ∆H, and the entropy change, ∆S) and the dependence of these parameters on perturbing conditions such as temperature (i.e. the heat capacity change ∆Cp). Isothermal titration calorimetry has emerged as a convenient and reliable method for obtaining these parameters in a model-independent way. In a single titration, the method gives ∆G, ∆H, and the stoichiometry allowing ∆S to be readily calculated. Repeated titrations at several temperatures give a robust measurement of ∆Cp (∆Cp = d(∆H)/dT, if ∆Cp is independent of temperature) and possibly also the temperature dependence of ∆Cp (if the data are sufficiently sensitive). The Facility currently houses a newly acquired nanoITC instrument with an experimental operating range of 2° - 80° C and a low-volume sample cell interfaced with Origin software for data analysis in a convenient automated package.