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Cooperativity, partially bound states, and enthalpy-entropy compensation
Christopher A Hunter1, Salvador Tomas
1Centre for Chemical Biology, Krebs Institute for Biomolecular Science, Department of Chemistry, University of Sheffield, S3 7HF, Sheffield, United Kingdom. c.hunter@sheffield.ac.uk
Chemistry & Biology
|December 4, 2003
Summary
Molecular recognition studies often assume additive interactions. This research experimentally shows that interactions within synthetic H-bonded complexes are additive, challenging the concept of cooperativity in some systems.
Area of Science:
- Chemical thermodynamics
- Molecular interactions
- Supramolecular chemistry
Background:
- Quantitative understanding of molecular recognition is crucial.
- Cooperativity in intermolecular interactions poses a challenge to additivity principles.
- Experimental validation of interaction additivity is needed.
Purpose of the Study:
- To experimentally measure cooperativity between functional group interactions.
- To assess the additivity of intermolecular interactions in synthetic H-bonded complexes.
- To propose alternative explanations for observed cooperative phenomena.
Main Methods:
- Utilized a chemical double-mutant cycle technique.
- Synthesized H-bonded complexes with varying stability.
- Experimentally measured free energies of intermolecular interactions.
Main Results:
- The interaction between two aromatic groups showed minimal variation (0.2 +/- 0.4 kJ mol(-1)).
- The overall stability of the synthetic complexes differed significantly (8-13 kJ mol(-1)).
- Free energies of individual intermolecular interactions were reliably additive in these systems.
Conclusions:
- Intermolecular interactions in the studied synthetic complexes can be treated additively.
- The findings suggest that cooperativity in other systems may require alternative explanations.
- A model involving partially bound states in flexible molecules is proposed to explain enthalpic effects.