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Are Mixed Explicit/Implicit Solvation Models Reliable for Studying Phosphate Hydrolysis? A Comparative Study of Continuum, Explicit and Mixed Solvation Models
Author(s) -
Kamerlin Shina C. L.,
Haranczyk Maciej,
Warshel Arieh
Publication year - 2009
Publication title -
chemphyschem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.016
H-Index - 140
eISSN - 1439-7641
pISSN - 1439-4235
DOI - 10.1002/cphc.200800753
Subject(s) - solvation , implicit solvation , chemistry , free energy perturbation , ab initio , molecule , computational chemistry , hydrolysis , water model , solvent models , thermodynamics , solvation shell , perturbation theory (quantum mechanics) , solvent , molecular dynamics , statistical physics , organic chemistry , quantum mechanics , physics
Abstract Are all solvation models equal? An in‐depth comparison of mixed implicit/explicit solvation models shows that while both the implicit and explicit (QM/MM–FEP) solvation models can reproduce activation free energies for phosphate diester hydrolysis in solution with high accuracy, the use of a mixed solvation model tends to be unreliable for modelling phosphate hydrolysis in solution.Phosphate hydrolysis is ubiquitous in biology. However, despite intensive research on this class of reactions, the precise nature of the reaction mechanism remains controversial. Herein, we have examined the hydrolysis of three homologous phosphate diesters. The solvation free energy was simulated by means of either an implicit solvation model (COSMO), hybrid quantum mechanical/molecular mechanical free energy perturbation (QM/MM–FEP) or a mixed solvation model in which N water molecules were explicitly included in the ab initio description of the reacting system (where N =1–3), with the remainder of the solvent being implicitly modelled as a continuum. Here, both COSMO and QM/MM–FEP reproduce Δ G obs within an error of about 1 kcal mol −1 . However, we demonstrate that in order to obtain any kind of reliable results from a mixed model, it is essential to carefully select the explicit water molecules from short QM/MM runs that act as a model for the true infinite system. Additionally, the mixed models tend to be increasingly unstable and miss larger entropic contributions as more explicit water molecules are placed into the system. Thus, our analysis indicates that this approach provides an unreliable way for modelling phosphate hydrolysis in solution.

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