6 Inhibitor Binding to Carbonic Anhydrases by Isothermal Titration Calorimetry Vaida Paketuryt˙ e, Asta Zubrien ˙ e, Wen-Yih Chen, Sandro Keller, Margarida Bastos, Matthew J. Todd, John E. Ladbury, and Daumantas Matulis Abstract Small-molecule drug-candidate compounds are ranked by their capability, pri- marily described as affinity, to bind a target protein, for example, human carbonic anhydrase (CA), a subject of this book. One of the methods of choice to determine the affinity is isothermal titration calorimetry (ITC), a biophysical technique that enables the determination of the thermodynamic parameters of binding between a protein and a small molecule, both unmodified V. Paketuryt˙ e · A. Zubrien˙ e · D. Matulis () Department of Biothermodynamics and Drug Design, Institute of Biotechnology, Life Sciences Center, Vilnius University, Vilnius, Lithuania e-mail: vaida.paketuryte@gmc.vu.lt; astzu@ibt.lt; daumantas.matulis@bti.vu.lt W.-Y. Chen Department of Chemical and Materials Engineering, National Central University, Taoyuan City, Taiwan e-mail: wychen@ncu.edu.tw S. Keller Molecular Biophysics, Technische Universität Kaiserslautern (TUK), Kaiserslautern, Germany e-mail: mail@sandrokeller.com M. Bastos CIQUP, Department of Chemistry and Biochemistry, Faculty of Sciences, University of Porto, Porto, Portugal e-mail: mbastos@fc.up.pt M. J. Todd Biophysical Solutions, Inc., Ambler, PA, USA e-mail: matthew.todd@biophysical-solutions.com J. E. Ladbury Department of Molecular and Cell Biology and Astbury Center for Structural Biology, University of Leeds, Leeds, UK e-mail: J.E.Ladbury@leeds.ac.uk © Springer Nature Switzerland AG 2019 D. Matulis (ed.), Carbonic Anhydrase as Drug Target, https://doi.org/10.1007/978-3-030-12780-0_6 79