Related Experiment Video
Updated: Jul 10, 2026

Isothermal Titration Calorimetry for Measuring Macromolecule-Ligand Affinity
Published on: September 7, 2011
Direct determination of thiol pKa by isothermal titration microcalorimetry
Stephen G Tajc1, Blanton S Tolbert, Ravi Basavappa
1Department of Biochemistry and Biophysics, University of Rochester, Rochester, New York 14642, USA.
Abstract:
Knowledge of the acid dissociation constant (pKa) of a molecule is a critical step toward understanding its structure and reactivity. Current methods for pKa measurement, including electrochemical, spectroscopic, and spectrophotometric titrations, have proven to be useful but also have significant limitations. To overcome these limitations, we report the use of isothermal titration calorimetry (ITC) as a new method for pKa determination. We demonstrate by the measurement of the pKa values for free cysteine, glutathione, and a cysteine residue in a protein that this method is rapid and accurate.
Related Concept Videos
Weak Base Solutions
Determining the pH of Salt Solutions
Indicators
Acid and Bases: Ka, pKa, and Relative Strengths
Basicity of Aliphatic Amines
To measure the basicity of amines, two conventions are generally used. The first defines Kb as the basicity constant for the deprotonation reaction of water by the amine, as presented in Figure 1. Conventionally, lower Kb indicates higher...
Gas Chromatography: Types of Detectors-II

