Hydration in aqueous osmolyte solutions: the case of TMAO and urea

The hydration and hydrogen-bond topology of small water solvated molecules such as the naturally occurring organic osmolytes trimethylamine N-oxide (TMAO) and urea are under intense investigation. We aim at furthering the understanding of this complex hydration by combining experimental oxygen K-edg...

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Bibliographic Details
Published in:Physical chemistry chemical physics : PCCP 2020-05, Vol.22 (2), p.11614-11624
Main Authors: Sahle, Christoph J, Schroer, Martin A, Niskanen, Johannes, Elbers, Mirko, Jeffries, Cy M, Sternemann, Christian
Format: Article
Language:English
Subjects:
Excitation spectra
Hydration
Hydrogen bonds
Mathematical analysis
Molecular dynamics
Topology
Trimethylamine
Ureas
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Summary:The hydration and hydrogen-bond topology of small water solvated molecules such as the naturally occurring organic osmolytes trimethylamine N-oxide (TMAO) and urea are under intense investigation. We aim at furthering the understanding of this complex hydration by combining experimental oxygen K-edge excitation spectra with results from spectra calculated via the Bethe-Salpeter equation based on structures obtained from ab initio molecular dynamics simulations. Comparison of experimental and calculated spectra allows us to extract detailed information about the immediate surrounding of the solute molecules in the solvated state. We quantify and localize the influence of the solute on the hydrogen bond network of the water solvent and find spectroscopic fingerprints of a clear directional asymmetry around TMAO with strong and local kosmotropic influence around TMAO's NO head group and slight chaotropic influence around the hydrophobic methyl groups. The influence of urea on the local water network is qualitatively similar to that of TMAO but weaker in magnitude. The strongest influence of both molecules on the shape of the oxygen K-edge spectra is found in the first hydration shells. X-ray Raman scattering spectroscopy and first principles simulations reveal details of the hydration and hydrogen-bond topology of trimethylamine N-oxide (TMAO) and urea in aqueous solutions.
ISSN:1463-9076
1463-9084
DOI:10.1039/c9cp06785j