The imidazole motif is widely encountered in biomolecules, and its biological role, for instance, as a proton relay, is often linked to its ability to form hydrogen bonds with water molecules. The detailed characterization of the hydration pattern of imidazole and of its changes upon protonation is thus of high interest. Here, we combine neutron scattering experiments with force field simulations to provide an unprecedented characterization of the neutral and protonated imidazole solvation at the atomistic level. We show that neutron diffraction data can be used to assess the quality of the imidazole force field in molecular simulations. Simulations using the CHARMM general force field for imidazole are in excellent agreement with the experimental neutron scattering data and we use them to provide an atomic scale interpretation of the neutron scattering patterns. Upon protonation, we clearly identify the signature of the reorganization in the hydration pattern caused by the change from one H-bond donor and one H-bond acceptor group for imidazole to two H-bond donor groups for imidazolium. We also point the limits of the experiment, which are rather insensitive to details of the H-bond geometry at the deprotonated nitrogen of imidazole and further complement the description of the hydration structure with ab initio molecular dynamics simulations.
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14 May 2017
Research Article|
May 11 2017
Changes in the hydration structure of imidazole upon protonation: Neutron scattering and molecular simulations
Elise Duboué-Dijon
;
Elise Duboué-Dijon
a)
1Institute of Organic Chemistry and Biochemistry,
Czech Academy of Sciences
, Flemingovo nam. 2, 16610 Prague 6, Czech Republic
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Philip E. Mason;
Philip E. Mason
a)
1Institute of Organic Chemistry and Biochemistry,
Czech Academy of Sciences
, Flemingovo nam. 2, 16610 Prague 6, Czech Republic
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Henry E. Fischer
;
Henry E. Fischer
2
Institut Laue-Langevin
, 71 Avenue des Martyrs, CS 20156, 38042 Grenoble Cedex 9, France
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Pavel Jungwirth
Pavel Jungwirth
1Institute of Organic Chemistry and Biochemistry,
Czech Academy of Sciences
, Flemingovo nam. 2, 16610 Prague 6, Czech Republic
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a)
Authors to whom correspondence should be addressed. Electronic addresses: [email protected] and [email protected]
J. Chem. Phys. 146, 185102 (2017)
Article history
Received:
January 12 2017
Accepted:
April 10 2017
Citation
Elise Duboué-Dijon, Philip E. Mason, Henry E. Fischer, Pavel Jungwirth; Changes in the hydration structure of imidazole upon protonation: Neutron scattering and molecular simulations. J. Chem. Phys. 14 May 2017; 146 (18): 185102. https://doi.org/10.1063/1.4982937
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