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Amine hydration: a united-atom force-field solution
Chris Oostenbrink1, Daniel Juchli, Wilfred F van Gunsteren
1Division of Molecular Toxicology, Faculty of Sciences, Vrije Universiteit, Amsterdam De Boelelaan 1083, 1081 HV Amsterdam, The Netherlands.
Summary
Computational methods can now accurately predict the hydration free energies of methylated amines. A simple united-atom force field resolves the long-standing amine hydration problem.
Area of Science:
- Computational chemistry
- Molecular modeling
- Physical chemistry
Background:
- Experimental hydration free energies for ammonia and methylated amines exhibit an unexpected trend.
- Previous computational methods struggled to accurately reproduce this trend.
Purpose of the Study:
- To computationally reproduce the experimentally observed hydration free energy trend for amines.
- To evaluate the performance of different molecular mechanics force fields for this task.
Main Methods:
- Calculated absolute and relative free energies of hydration using OPLS all-atom and GROMOS united-atom force fields.
- Utilized the GROMOS 53A6 parameter set for enhanced accuracy.
Main Results:
- Both force fields reproduced relative free energies of hydration.
- Absolute free energies were accurately reproduced only with the GROMOS 53A6 parameter set.
- Relative solvation free energies in chloroform were also reproduced, indicating correct partitioning behavior.
Conclusions:
- The GROMOS 53A6 united-atom force field successfully resolves the amine hydration problem.
- Simple united-atom force fields are capable of accurately modeling amine solvation properties.