Solvation of the Guanidinium Ion in Pure Aqueous Environments: A Theoretical Study from an "Ab Initio"-Based Polarizable Force Field - Archive ouverte HAL Accéder directement au contenu
Article Dans Une Revue Journal of Physical Chemistry B Année : 2017

Solvation of the Guanidinium Ion in Pure Aqueous Environments: A Theoretical Study from an "Ab Initio"-Based Polarizable Force Field

Résumé

We report simulation results regarding the hydration process of the guanidinium cation in water droplets and in bulk liquid water, at a low concentration of 0.03 M, performed using a polarizable approach to model both water/water and ion/water interactions. In line with earlier theoretical studies, our simulations show a preferential orientation of guanidinium at water-vacuum interfaces, i.e., a parallel orientation of the guanidinium plane to the aqueous surface. In an apparent contradiction with earlier simulation studies, we show also that guanidinium has a stronger propensity for the cores of aqueous systems than the ammonium cation. However, our bulk simulation conditions correspond to weaker cation concentrations than in earlier studies, by 2 orders of magnitude, and that the same simulations performed using a standard nonpolarizable force field leads to the same conclusion. From droplet data, we extrapolate the guanidinium single hydration enthalpy value to be -82.9 ± 2.2 kcal mol-1. That is about half as large as the sole experimental estimate reported to date, about -144 kcal mol-1. Our result yields a guanidinium absolute bulk hydration free energy at ambiant conditions to be -78.4 ± 2.6 kcal mol-1, a value smaller by 3 kcal mol-1 compared to ammonium. The relatively large magnitude of our guanidinium hydration free energy estimate suggests the Gdm+ protein denaturing properties to result from a competition between the cation hydration effects and the cation/protein interactions, a competition that can be modulated by weak differences in the protein or in the cation chemical environment.
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Dates et versions

hal-02281954 , version 1 (09-09-2019)

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Celine Houriez, Michael Meot-Ner Mautner, Michel Masella. Solvation of the Guanidinium Ion in Pure Aqueous Environments: A Theoretical Study from an "Ab Initio"-Based Polarizable Force Field. Journal of Physical Chemistry B, 2017, 121 (50), pp.11219--11228. ⟨10.1021/acs.jpcb.7b07874⟩. ⟨hal-02281954⟩
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