kinITC: A New Method for Obtaining Joint Thermodynamic and Kinetic Data by Isothermal Titration Calorimetry

TLDR

Isothermal titration calorimetry (ITC) is the preferred method for obtaining thermodynamic data across diverse systems. This study demonstrates that modern ITC instruments and advanced data processing enable a complete kinetic description of systems ranging from simple ligand binding to complex RNA folding. The kinITC approach, illustrated with HIV‑1 reverse transcriptase/inhibitor binding and riboswitch folding, dissects both thermodynamic and kinetic components—primary ligand binding and subsequent RNA folding—using the same experiment. KinITC uniquely provides deep insight into composite processes and explains common observations from routine ITC experiments.

Abstract

Isothermal titration calorimetry (ITC) is the method of choice for obtaining thermodynamic data on a great variety of systems. Here we show that modern ITC apparatus and new processing methods allow researchers to obtain a complete kinetic description of systems more diverse than previously thought, ranging from simple ligand binding to complex RNA folding. We illustrate these new features with a simple case (HIV-1 reverse transcriptase/inhibitor interaction) and with the more complex case of the folding of a riboswitch triggered by the binding of its ligand. The originality of the new kinITC method lies in its ability to dissect, both thermodynamically and kinetically, the two components: primary ligand binding and subsequent RNA folding. We are not aware of another single method that can yield, in a simple way, such deep insight into a composite process. Our study also rationalizes common observations from daily ITC use.