Experimental support for a desolvation energy term in governing equations for binding equilibria
Brian M Castellano1, Daryl K Eggers
1Department of Chemistry, San José State University, San José, CA 95192-0101, USA.
The Journal of Physical Chemistry. B
|June 19, 2013
Summary
This study presents a new thermodynamic framework for aqueous reactions, treating water as a coreactant. It defines binding energy by including desolvation effects, offering insights into solution thermodynamics and calorimetry discrepancies.
Area of Science:
- Physical Chemistry
- Solution Thermodynamics
- Biophysical Chemistry
Background:
- Aqueous reaction equilibria are fundamental to many chemical and biological processes.
- Traditional thermodynamic models often overlook the role of water and hydration changes.
- Discrepancies exist between calorimetric and van't Hoff methods for enthalpy determination.
Purpose of the Study:
- To develop a general binding equation by treating water as a coreactant.
- To explicitly account for hydration changes during surface interactions.
- To redefine standard-state free energy of binding to include desolvation effects.
Main Methods:
- Introduction of a novel thermodynamic framework for aqueous equilibria.
- Development of a general binding equation incorporating water as a coreactant.
- Experimental validation using isothermal titration calorimetry (ITC).
Main Results:
- The standard-state free energy of binding is defined as a sum of traditional and desolvation terms.
- The equilibrium ratio (Ki) is shown to be concentration-dependent.
- Molar desolvation energy and standard-state free energy at infinite dilution can be determined from Ki dependence.
Conclusions:
- The new framework provides a more comprehensive understanding of binding equilibria in solution.
- It reconciles enthalpy discrepancies between ITC and van't Hoff methods.
- This approach has significant implications for solution thermodynamics and molecular interactions.
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