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Size dependence of cavity volume: a molecular dynamics study
Nisha Patel1, David N Dubins, Régis Pomès
1Department of Pharmaceutical Sciences, University of Toronto, Toronto, Ontario, Canada.
Biophysical Chemistry
|December 3, 2011
Summary
Partial molar volume analysis reveals that the thickness of the thermal volume around solutes increases with solute size. This finding offers insights into solute hydration and water compressibility for large nonpolar molecules.
Area of Science:
- Physical Chemistry
- Computational Chemistry
- Solution Chemistry
Background:
- Partial molar volume (V°) is a key metric for studying solute hydration.
- Accurately distinguishing between cavity (V(C)) and interaction (V(I)) contributions to V° is crucial for hydration studies.
- Cavity volume (V(C)) comprises intrinsic molecular volume (V(M)) and thermal volume (V(T)).
Purpose of the Study:
- To compute partial molar volumes for organic solutes in water using molecular dynamics simulations and Kirkwood-Buff theory.
- To investigate the contributions of cavity and thermal volumes to the partial molar volume.
- To analyze the relationship between solute size and the thickness of the thermal volume.
Main Methods:
- Employed molecular dynamics simulations with Lennard-Jones and Coulombic pair potentials.
- Utilized Kirkwood-Buff theory to calculate partial molar volumes.
- Applied spherical approximation to determine thermal volume thickness (δ).
Main Results:
- Partial molar volume computed using Lennard-Jones potentials without Coulombic terms closely matched cavity volume (V(C)).
- Thermal volume (V(T)) was determined by subtracting van der Waals volume (V(W)) from V(C).
- An increasing trend in thermal volume thickness (δ) was observed with increasing solute size.
Conclusions:
- The thickness of the thermal volume around a solute increases with its size.
- This phenomenon may be linked to the dewetting of large nonpolar solutes.
- Increased solute size correlates with enhanced compressibility of hydration water.
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