High-Precision Isothermal Titration Calorimetry with Automated Peak-Shape Analysis

TLDR

Isothermal titration calorimetry measures the heat of molecular interactions by recording power changes during reagent injections, but baseline noise limits the precision of the resulting isotherms. The authors present an automated peak‑assignment method that uses singular value decomposition of peak shapes combined with least‑squares baseline modeling. This technique filters short‑term noise and sporadic events from the power trace, enabling cleaner peak integration. The method yields statistical error estimates for each isotherm point, improving detection limits for high‑affinity or low‑enthalpy bindings and enhancing the precision of derived thermodynamic parameters.

Abstract

Isothermal titration calorimetry (ITC) is a powerful classical method that enables researchers in many fields to study the thermodynamics of molecular interactions. Primary ITC data comprise the temporal evolution of differential power reporting the heat of reaction during a series of injections of aliquots of a reactant into a sample cell. By integration of each injection peak, an isotherm can be constructed of total changes in enthalpy as a function of changes in solution composition, which is rich in thermodynamic information on the reaction. However, the signals from the injection peaks are superimposed by the stochastically varying time-course of the instrumental baseline power, limiting the precision of ITC isotherms. Here, we describe a method for automated peak assignment based on peak-shape analysis via singular value decomposition in combination with detailed least-squares modeling of local pre- and postinjection baselines. This approach can effectively filter out contributions of short-term noise and adventitious events in the power trace. This method also provides, for the first time, statistical error estimates for the individual isotherm data points. In turn, this results in improved detection limits for high-affinity or low-enthalpy binding reactions and significantly higher precision of the derived thermodynamic parameters.