Abstract
Neutron diffraction with isotopic H/D substitution on water, augmented by Empirical Potential Structure Refinement has been applied to extract the hydration properties of the osmolyte zwitterionic ectoine at 1.5 M concentration. This has evidenced differences between the hydration of COO− and NH groups, both in terms of number of water molecules involved in the hydration shell and of three-dimensional symmetry. Signatures of ectoine–ectoine contacts, due to hydrogen bonds, have been found, as possible precursors of ectoine aggregation at higher concentrations. The influence of ectoine on the water structure is ascribed to the dipolar electric field generated by the exposed charges of ectoine.
GRAPHICAL ABSTRACT
Acknowledgments
Beamtime awarded by ISIS under RB number 1710038 is gratefully acknowledged. The data that support the findings of this study are openly available (The release date is: Fri Oct 02 10:00:00 BST 2020) in ISIS Data Journal at http://doi.org/10.5286/ISIS.E.87768521, reference number RB1710038. The authors thank Prof. Alan Soper for the availability of the room temperature water data and acknowledge useful discussions with P. Corsi, L. Ruggiero and M. Sbroscia.
Disclosure statement
No potential conflict of interest was reported by the authors.
ORCID
Michael Di Gioacchino http://orcid.org/0000-0001-7465-2456
Silvia Imberti http://orcid.org/0000-0001-7037-6829
Maria Antonietta Ricci http://orcid.org/0000-0002-6904-6686