A unified framework based on the binding polynomial for characterizing biological systems by isothermal titration calorimetry

• A unified framework for data analysis in isothermal titration calorimetry based on the binding polynomial is described.
• The formalism is based on a finite-differences scheme and the Newton–Raphson algorithm to solve the binding equations.
• The methodology is valid for any system (homotropic and heterotropic chemical linkage, allosteric and polysteric linkage).

Isothermal titration calorimetry (ITC) has become the gold-standard technique for studying binding processes due to its high precision and sensitivity, as well as its capability for the simultaneous determination of the association equilibrium constant, the binding enthalpy and the binding stoichiometry. The current widespread use of ITC for biological systems has been facilitated by technical advances and the availability of commercial calorimeters. However, the complexity of data analysis for non-standard models is one of the most significant drawbacks in ITC. Many models for studying macromolecular interactions can be found in the literature, but it looks like each biological system requires specific modeling and data analysis approaches. The aim of this article is to solve this lack of unity and provide a unified methodological framework for studying binding interactions by ITC that can be applied to any experimental system. The apparent complexity of this methodology, based on the binding polynomial, is overcome by its easy generalization to complex systems.