Molecular simulation of absolute hydration Gibbs energies of polar compounds

In this work, we present simulation-based predictions of the absolute hydration energy for several simple polar molecules with different functional groups, as well as for more complex multifunctional molecules. Our calculations were performed using the thermodynamic integration methodology where electrostatic and non-polar interactions were treated separately, allowing for a stable transition path between the end-points of the integration. An appropriate methodology for the analytical integration of the simulation data was applied. We compare the performance of three popular molecular mechanics force fields: TraPPE, Gromos and OPLS-AA for the description of solute atoms in MSPC/E water. It is observed that these force fields generally perform well for the simpler molecules, but are less accurate when multifunctional molecules are considered.