Wrapping up hydrophobic hydration
Solvent chemistry

Date:
June 29, 2020
Source:
Ruhr-University Bochum
Summary:
Studied in detail, the embedding of hydrophobic molecules in water
looks quite different than previously assumed.



FULL STORY ==========================================================================
In water, hydrophobic molecules are surrounded by a two different water populations: the inner shell forms a two-dimensional network of water molecules. The next layer is formed by a second water population that is
almost bulk like but forms slightly stronger hydrogen bonds to the bulk
water. The assumption to date was that tetrahedral, "ice-like" water
dominate in the innermost hydration shell of hydrophobic molecules. The opposite is the case.

These new findings were published by the team headed by Professor Martina Havenith, Chair of Physical Chemistry II and Speaker of the Ruhr Explores Solvation Cluster of Excellence at Ruhr-Universita"t Bochum (RUB) in
The Journal of Physical Chemistry Letters on 18 June 2020.


========================================================================== Insights by THz spectroscopy and simulations In their study, the
researchers investigated the hydrogen bond network around the hydrophobic solvated alcohol tert-butanol, as researchers use alcohols as a prototype models for hydrophobic molecules. The team combined results from terahertz (THz) spectroscopy and simulations.

In THz spectroscopy, researchers measure the absorption of THz radiation
in a sample. The absorption spectrum provides a fingerprint of the
water network.

A thin layer In their study they obtained a detailed picture of the
water layers surrounding the molecule. "We refer to the innermost
layer as 'HB-wrap', where HB stands for water hydrogen bond," explains
Martina Havenith. The top layer is called 'HB-hydration2bulk' as it
described the interface to the bulk water. Combined, both layers of
the coating are sometimes no thicker than a single layer of water
molecules. "Occasionally, a single water molecule may be part of both
layers," says Havenith.

Inner layer is longer stable When the temperature is increased, the
outer layer melts first, the HP-wrap layer remains longer intact. "The
inner layer has also less freedom to form distinct configurations due
to the hydrophobicity of the solute," elaborates the researcher. "As
individual water molecules must always turn away from the alcohol, they
form a two-dimensional, loose network." Water molecules in the outer
layer have more freedom to move and therefore also more possibilities to connect with other water molecules; researchers refer to this phenomenon
as greater entropy.

This type of interaction is relevant for the folding processes of
proteins as well as biomolecular recognition between a drug and its
target molecule.

Understanding the role of water plays a crucial role in the process.

Funding The study was funded by the German Research Foundation (DFG)
as part of the Ruhr Explores Solvation Cluster of Excellence, funding
code EXC 2033-390677874- Resolv, by the German-French Dynawin-Grant 14-CE35-0011-01 by Agence national de la recherche and DFG, and by Genci-France-Grant 072484 (Cines/Idris/TGCC).

Martina Havenith is funded by an Advanced Grant des European Research
Council, grant number 695437.


========================================================================== Story Source: Materials provided by Ruhr-University_Bochum. Note:
Content may be edited for style and length.


========================================================================== Journal Reference:
1. V. Conti Nibali, S. Pezzotti, F. Sebastiani, D. R. Galimberti, G.

Schwaab, M. Heyden, M.-P. Gaigeot, M. Havenith. Wrapping
Up Hydrophobic Hydration: Locality Matters. The Journal
of Physical Chemistry Letters, 2020; 11 (12): 4809 DOI:
10.1021/acs.jpclett.0c00846 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2020/06/200629120147.htm

--- up 22 weeks, 6 days, 2 hours, 38 minutes
* Origin: -=> Castle Rock BBS <=- Now Husky HPT Powered! (1337:3/111)