Changes in the hydration structure of imidazole upon protonation: Neutron scattering and molecular simulations

0475774 - ÚOCHB 2018 RIV US eng J - Journal Article
Duboué-Dijon, Elise - Mason, Philip E. - Fischer, H. E. - Jungwirth, Pavel
Changes in the hydration structure of imidazole upon protonation: Neutron scattering and molecular simulations.
Journal of Chemical Physics. Roč. 146, č. 18 (2017), č. článku 185102. ISSN 0021-9606. E-ISSN 1089-7690
R&D Projects: GA ČR(CZ) GBP208/12/G016
Institutional support: RVO:61388963
Keywords : imidazole protonation * molecular dynamics * neutron scattering
OECD category: Physical chemistry
Impact factor: 2.843, year: 2017

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.
Permanent Link: http://hdl.handle.net/11104/0272404