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Updated: Aug 11, 2026
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Isothermal Titration Calorimetry for Measuring Macromolecule-Ligand Affinity
Published on: September 7, 2011
Significant discrepancies between van't Hoff and calorimetric enthalpies. II
1Department of Chemistry, Yale University, New Haven, Connecticut 06520, USA.
Protein Science : a Publication of the Protein Society
|December 1, 1995
Summary
Precise binding constants for 18-crown-6 ether and BaCl2 were determined using isothermal titration calorimetry. A significant discrepancy was observed between calorimetric and van
Area of Science:
- Supramolecular chemistry
- Thermodynamics
- Solution chemistry
Background:
- 18-crown-6 ether is a well-studied macrocycle.
- BaCl2 is a common salt used in chemical studies.
- Calorimetric titration is a standard method for studying binding interactions.
Purpose of the Study:
- To precisely determine binding constants and enthalpy changes for 18-crown-6 ether with BaCl2.
- To investigate the thermodynamic parameters of this interaction over a range of temperatures.
- To identify and analyze discrepancies between experimental calorimetric data and theoretical van't Hoff analysis.
Main Methods:
- Isothermal titration calorimetry (ITC) was employed.
- Binding constants and enthalpy changes were measured at temperatures ranging from 7 to 40 degrees C.
- Nonlinear least-squares fitting was used to analyze the binding data.
Main Results:
- Precise binding constants and enthalpy changes were obtained.
- A significant discrepancy was found between the van't Hoff enthalpies and the observed calorimetric enthalpies.
- This discrepancy was observed even when accounting for a temperature-independent change in heat capacity.
Conclusions:
- The study highlights a perplexing and widely occurring discrepancy in thermodynamic analysis of macrocycle-metal ion interactions.
- Standard van't Hoff analysis may not accurately represent the thermodynamics of 18-crown-6 ether-BaCl2 binding.
- Further investigation is needed to understand the origin of this thermodynamic inconsistency.
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