Wrapping up hydrophobic hydration

June 29, 2020

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-Universität 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.
-end-
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.

Original publication

Valeria Conti Nibali, Simone Pezzotti, Federico Sebastiani, Daria Ruth Galimberti, Gerhard Schwaab, Matthias Heyden, Marie-Pierre Gaigeot, Martina Havenith: Wrapping up hydrophobic hydration: locality matters, in Physical Chemistry Letters, 2020, DOI: 10.1021/acs.jpclett.0c00846

Press contact

Prof. Dr. Martina Havenith
Physical Chemistry II
Faculty of Chemistry and Biochemistry
Ruhr-Universität Bochum
Germany
Phone: +49 234 32 28249
Email: pc2office@rub.de

Ruhr-University Bochum

Related Spectroscopy Articles from Brightsurf:

Perspectives of infrared spectroscopy in quantitative estimation of proteins
The present review describes the basic principle and the instrumentation of IR spectroscopy along with its advancements.

A new method to measure optical absorption in semiconductor crystals
Tohoku University researchers have revealed more details about omnidirectional photoluminescence (ODPL) spectroscopy - a method for probing semiconducting crystals with light to detect defects and impurities.

Properties of catalysts studied with gamma ray resonance
Steam-assisted oil extraction methods for heavy deposits have long been the focus of attention at Kazan Federal University.

Researchers demonstrate record speed with advanced spectroscopy technique
Researchers have developed an advanced spectrometer that can acquire data with exceptionally high speed.

Spectroscopy approach poised to improve treatment for serious heart arrhythmia
Researchers have demonstrated that a new mapping approach based on near infrared spectroscopy can distinguish between fat and muscle tissue in the heart.

Late blight research pairs spectroscopy with classic plant pathology diagnostics
Gold and colleagues at the University of Wisconsin-Madison recently published research showing how they used contact spectroscopy to non-destructively sense how plant pathogens differentially damage, impair, and alter plant traits during the course of infection.

Doing more with terahertz: Simplifying near-infrared spectroscopy systems
Researchers from Beihang University, China, and Tokushima University, Japan, have developed a terahertz spectroscopy scheme that offers outstanding resolution using a single laser.

A new horizon for vibrational circular dichroism spectroscopy
(1) The development of solid state and time-step VCD methods opened a new horizon to reveal the mechanism of chirality amplification from microscopic to supramolecular scales.

Unraveling the optical parameters: New method to optimize plasmon enhanced spectroscopy
Plasmon enhanced spectroscopies allow to reach single molecule sensitivity and a lateral resolution even down to sub-molecular resolution.

Nanoscale spectroscopy review showcases a bright future
A new review authored by international leaders in their field, and published in Nature, focuses on the luminescent nanoparticles at the heart of many advances and the opportunities and challenges for these technologies to reach their full potential.

Read More: Spectroscopy News and Spectroscopy Current Events
Brightsurf.com is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.