How two water molecules dance together-Although water is omnipresent, the interaction between individual water molecules is not yet fully understood

Water drop splash (stock image).Credit: © Romolo Tavani / Adobe Stock

https://www.sciencedaily.com/releases/2019/08/190813102348.htm

An international research team has gained new insights into how water molecules interact. For the first time, the researchers were able to completely observe all of the movements between the water molecules, known as intermolecular vibrations. A certain movement of individual water molecules against each other, called hindered rotations, is particularly important. Among other things, the findings help to better determine the intermolecular energy landscape between water molecules and thus to better understand the strange properties of water.

The team led by Professor Martina Havenith from Ruhr-Universität Bochum and Professor Joel Bowman from Emory University in Atlanta, together with colleagues from Radboud University in Nijmegen and Université de Montpellier, describe the work in the journal Angewandte Chemie International Edition on 27 July 2019.

Unknown interactions

Water is the most important solvent in chemistry and biology and possesses an array of strange properties -- for instance, it reaches its highest density at four degrees Celsius. This is due to the special interactions between the water molecules. "Describing these interactions has posed a challenge for research for decades," says Martina Havenith, head of the Bochum-based Chair of Physical Chemistry II and spokesperson for the Ruhr Explores Solvation (Resolv) Cluster of Excellence.

Experiments at extremely low temperatures

The team investigated the simplest conceivable interaction, namely between precisely two individual water molecules, using terahertz spectroscopy. The researchers send short pulses of radiation in the terahertz range through the sample, which absorbs part of the radiation. The absorption pattern reveals information about the attractive interactions between the molecules. A laser with especially high brightness, as is available in Nijmegen, was needed for the experiments. The researchers analysed the water molecules at extremely low temperatures. To do this, they successively stored individual water molecules in a tiny droplet of superfluid helium, which is as cold as 0.4 Kelvin. The droplets work like a vacuum cleaner that captures individual water molecules. Due to the low temperature, a stable bond occurs between two water molecules, which would not be stable at room temperature.

This experimental setup allowed the group to record a spectrum of the hindered rotations of two water molecules for the first time. "Water molecules are moving constantly," explains Martina Havenith. "They rotate, open and close." However, a water molecule that has a second water molecule in its vicinity cannot rotate freely -- this is why it is referred to as a hindered rotation.

A multidimensional energy map

The interaction of the water molecules can also be represented in the form of what is known as water potential. "This is a kind of multidimensional map that notes how the energy of the water molecules changes when the distances or angles between the molecules change," explains Martina Havenith. All the properties, such as density, conductivity or evaporation temperature, can be derived from the water potential. "Our measurements now allow the best possible test of all potentials developed to date," summarises the researcher.

Quantum cascade lasers assist rapid cancer diagnosis

The RUB team applied a QCL source and bespoke algorithms

http://optics.org/news/9/6/3

Infrared microscopy, in particular a Fourier transform infrared (FTIR) technique, has been an attractive method for the identification of cancer tissues for several years, thanks to the potential for label-free and automated classification procedures.

However the technique has yet to realize its full clinical potential as a diagnostic tool, partly because of the complex instrumental set-ups involved, and the length of time required to produce results.

A team at Ruhr-University Bochum (RUB) has now developed a new approach to the problem, demonstrating that an infrared microscope based on a quantum cascade laser (QCL) source was able to reduce the time needed to characterize colorectal cancer tissues from one day to a few minutes. The findings were published in Scientific Reports.

"The results of the study give rise to hope that highly precise therapy is within reach, which can be personalized for each individual patient and ultimately prove more successful than traditional approaches," commented Klaus Gerwert of RUB.

The project's fundamental advance was the use of a QCL, a form of semiconductor laser characterized by relatively narrow line width and good wavelength tunability, as the high-power light source, rather than the silicon carbide rod termed a globar that is conventionally employed for FTIR.

In trials using a source from QCL-specialists DRS Daylight Solutions, the new method imaged 120 tissue samples taken from patients suffering from colorectal cancer, using analysis algorithms developed in-house. The results corresponded with traditional histopathology analyses in 97 per cent of cases, according to the project.

New avenues for tissue classification

In its published paper, the team noted that the change to a QCL from a classical black body light source altered the nature of the coherence effects observed during the imaging operation, which had proven a significant hurdle to rapid characterization of tissues in previous scenarios.

Partly thanks to the increased stability of modern laser sources, coherence effects in the QCL set-up were minimized, with a significant improvement in signal noise. Sample-based coherence effects are still present and must be addressed in pre-processing and classification, but these can be adequately tackled when the instrument's coherence effects are minimized, according to the authors.

"A remarkable advantage of the QCL IR imaging is the gain of speed," noted the team. "Acquiring the conventional FTIR image required 5,400 minutes. In this case the QCL-based IR analyses were approximately 160 times faster for the same measured area. This allows us to analyze a much larger number of patients in a much shorter time period."

The paper calculates that it would previously have taken more than one year to gather the data for the RUB study using conventional FTIR methods, but using QCL imaging allowed all the necessary spectral data sets to be collected in about 100 hours.

The new project was also able to exploit previous work at RUB on an automated and label-free approach to detecting tumor tissue in a biopsy or tissue sample, a combination of modified workflows and bespoke algorithms which had already proved able to identify the five biomarkers used to diagnose subtypes of mesothelioma in patients.

“The method is now very fast, reliable, and does not depend on a specific device or a specific user,” said Angela Kallenbach-Thieltges of RUB. “This opens up new avenues for automated classification of tissue samples taken directly from the patient.”

Fingerprint of dissolved glycine in the Terahertz range explained

http://www.sciencecodex.com/fingerprint_of_dissolved_glycine_in_the_terahertz_range_explained-130677

Chemists at the Ruhr-Universität Bochum (RUB) have, for the first time, completely analysed the fingerprint region of the Terahertz spectrum of a biologically relevant molecule in water, in this case, an amino acid. By combining spectroscopy and molecular-dynamics simulations, they rendered the motion of the most basic amino acid, glycine, visible in an aqueous solution. Their results have disproved the long-standing theory that frequencies in the Terahertz range provide no information regarding the amino acid's motion. The team led by Prof Dr Martina Havenith-Newen and Prof Dr Dominik Marx published their report in the "Journal of the American Chemical Society" (JACS).

Representing molecular motion by means of Terahertz spectroscopy

Researchers use Terahertz (THz) spectroscopy to send short radiation pulses into a sample of interest. The Terahertz range covers wavelengths of one to ten THz (0.3 millimetres to 30 micrometres) and extends between the infrared and the microwave range. The sample, in this case a mixture of water and glycine, partially absorbs the radiation, forming an absorption pattern, which is represented by chemists in the form of a spectrum. Certain areas of the spectrum, so-called bands, describe the motions of molecular bonds. Individual atoms in a molecule are not bonded rigidly; rather, they are permanently in motion. Complex computer simulations contribute significantly to analysing the spectra, as it is not always easy to decipher which individual bands of a spectrum correlate with which molecular motions.

THz analysis renders glycine motion in water visible

The RUB team has proved that THz analysis may be used to represent both the motion inside the glycine molecule and the motion of the glycine molecule together with its bound water molecules. The bands in the Terahertz spectrum, moreover, reflected the glycine's opening and closing motion. The spectrum also incorporated the motion of hydrogen bridges between the glycine and its bound water molecules. "The interaction between ab initio molecular-dynamics simulations and Terahertz spectroscopy provides us with an excellent instrument for tracking and understanding solvation processes on the molecular level," says Martina Havenith-Newen, Head of the Department of Physical Chemistry II.

The molecular motion of the amino acid glycine and its surrounding water molecules result in the formation of characteristic bands in the Terahertz spectrum.

(Photo Credit: RUB, illustration: Decka, Havenith)

Terahertz spectroscopy used to record the motion of water molecules and antifreeze proteins (AFP)

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Story from LabNews Pages
http://www.labnews.co.uk/laboratory_article.php/5810/2/deep-sea-freeze

Why don’t fish freeze in the ocean?
They have an antifreeze protein in their blood, and scientists have just uncovered the mechanism of how this protein works.

Macropteris maculates and the antifreeze protein structure
Ocean temperatures of -1.8°C should be enough to freeze any fish – especially since the freezing point of their blood is around -0.9°C – but Antarctic fish are still able to keep moving and until recently, scientists were puzzled at how.

Scientists from the Ruhr Universität Bochum used terahertz spectroscopy to record the motion of water molecules and antifreeze proteins (AFP) in the blood of the Antarctic toothfish. They discovered that AFP in the blood affects water molecules in its vicinity preventing ice crystallisation. However, the AFP doesn’t bind to water – just its presence is enough to stop freezing.

“We could see that the protein has an especially long-range effect on the water molecules around it,” said co-author Konrad Meister, “We speak of an extended dynamical hydration shell.”

“This effect, which prevents ice crystallisation, is even more pronounced at low temperatures than at room temperature,” said Professor Martina Havenith.
Using terahertz radiation, the researchers showed that water molecules – which usually perform a permanent dance in liquid water, constantly forming new bonds – perform a more ordered dance in the presence of proteins.

Researchers found that when in a complex with borate, the antifreeze activity of the AFP was strongly reduced and that there was no change in the terahertz dance.
The results provide evidence of a new model of how AFP prevents water from freezing. It suggests activity is not achieved by a single molecular bonding between the water and protein but that the protein disturbs the aqueous solvent over long distances.

The investigation – funded by the Volkswagen Foundation – showed for the first time a direct link between a protein and its signature in the terahertz range.