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Stability of a model beta-sheet in water
D J Tobias1, S F Sneddon, C L Brooks
1Department of Chemistry, Carnegie Mellon University, Pittsburgh, PA 15213.
Journal of Molecular Biology
|October 20, 1992
Summary
A model beta-sheet formed by two alanine dipeptides is significantly more stable in water than a single amide hydrogen bond. This enhanced stability arises from specific solute-solute and solute-water interactions, highlighting the importance of structure in molecular interactions.
Area of Science:
- Computational Chemistry
- Biophysical Chemistry
- Molecular Dynamics
Background:
- Beta-sheets are crucial secondary structures in proteins.
- Understanding the stability of hydrogen bonds in aqueous environments is fundamental to molecular biology.
Purpose of the Study:
- To determine the stability of a model beta-sheet in water using molecular dynamics simulations.
- To compare the stability of a two-hydrogen-bond beta-sheet with a single amide hydrogen bond.
Main Methods:
- Molecular dynamics simulations were employed to calculate binding free energy.
- Free energy surfaces were computed as a function of a reaction coordinate for sheet formation.
- Decomposition of free energy differences into energetic and entropic contributions was performed.
Main Results:
- The model beta-sheet exhibited a binding free energy of -5.5 kcal/mol, indicating significant stability.
- A formamide dimer model (single amide hydrogen bond) showed a binding free energy of -0.34 kcal/mol, indicating marginal stability.
- Differences in solute-solute and solute-water interactions explained the stability discrepancy.
Conclusions:
- A model beta-sheet with two hydrogen bonds is substantially more stable in water than a single amide hydrogen bond.
- Solute-water interactions, influenced by side-chains or blocking groups, play a critical role in the enhanced stability of the beta-sheet.
- The findings provide insights into the factors governing the stability of peptide structures in solution.