Chemical Science Blog

A sensor that can discriminate between different tannins and be used to fingerprint a wide variety of red wines to confirm their authenticity has been developed by US scientists. 

Eric Anslyn and colleagues at the University of Texas at Austin and University of California Davis have developed a sensor made with colour-changing indicators. They used the sensor to test wine samples from different vintners and managed to distinguish between specific flavonoids – chemicals found in fruit and vegetables, tea and red wine – in particular looking at tannins, which are responsible for colour, aging ability and texture. 

When wine is added to the sensor, the indicators are displaced, which results in a colour change that can be monitored and recorded. The team found that patterns emerged for different wine varietals. They tested Pinot Noir, Zinfandel, Beaujolais, Cabernet Sauvignon, Shiraz and Merlot and assigned signatures to each wine type. The team could also classify wines from the same varietal. They tested different brands of Shiraz (and Zinfandel in a separate study) and they were able to link the tannins to the genome of the specific grape. 

The sensor can assign signatures to different wine types and to wines within types

 

‘The ability to fingerprint mixtures of metabolic origin, without knowing their exact compositions, has huge potential for applications in medical diagnostics, environmental science and the food industry,’ says Anslyn. 

Kim Janda, a detection expert at the Scripps Research Institute in the US, has visions of the sensor being used for ‘biodefense purposes where rapid and accurate identification is at a premium.’ Janda adds: ‘if Anslyn improved the method further he could put sommeliers out of business!’ 

‘Product authenticity is an important issue with food and beverages, particularly with high value products such as wine,’ says Bob Dambergs, a senior research scientist at the Australian Wine Research Institute, Glen Osmond. ‘Flavonoid compounds define red wines and this study makes clever use of specific interactions of flavonoids with peptides to produce a sensor array with high discriminatory power. Most wine producing countries have strict label-integrity regulations to protect consumers – the availability of rapid analysis methods utilising chemical sensors will facilitate compliance monitoring.’

Fancy reading more? Then why not download and read the Chemical Science Edge Article for yourself, details can be found below:-

Discrimination of flavonoids and red wine varietals by arrays of differential peptidic sensors
Alona P. Umali, Sarah E. LeBoeuf, Robert W. Newberry, Siwon Kim, Lee Tran, Whitney A. Rome, Tian Tian, David Taing, Jane Hong, Melissa Kwan, Hildegarde Heymann and Eric V. Anslyn, Chem. Sci., 2011
DOI: 10.1039/c0sc00487a

  

Scientists have converted a protein from a pathogenic bacterium into a FRET-based fluorescent probe to help find out why bismuth therapeutics can treat gastric illnesses.

Helicobacter pylori is a bacterium that colonises the digestive track and causes chronic gastritis, ulcers and even some gastric cancers. Bismuth-containing medicines are known treatments for H. pylori. It is thought that bismuth ions bind to metal binding sites in H. pylori’s metalloproteins but their exact mechanism of action is unknown.

Chuan He and colleagues at the University of Chicago investigated the metal binding properties of their FRET probe, made from the Hpn protein found in H. pylori, with different biometals in vitro. They showed that the sensor has a high affinity for Ni²⁺ and Zn²⁺ and moderate affinity for Bi³⁺. They then used the sensor in E. coli cells, which act as a model system for H. pylori, to measure uptake of these three ions. To their surprise, E. coli concentrated significant amounts of Bi³⁺, but not Ni²⁺ or Zn²⁺.

If Bi³⁺ accumulates to similarly high levels in H. pylori, says He, it may target Hpn, eventually killing the bacteria.

Read the Edge article online today and let us know what you think of this work by leaving your comments below.

Confining enzymes in a small container increases overall reaction rates but the increase is independent of the number of enzymes encapsulated, claim scientists in the Netherlands. 

Jeroen Cornelissen, at the University of Twente, and colleagues used the capsid of the Cowpea Chlorotic Mottle virus to encapsulate enzymes, mimicking the crowded environment enzymes experience in a cell. They found that encapsulated enzymes have a higher activity than free enzymes, which they say is caused by the high confinement molarity of the enzyme and the increased collision rate with its substrate. 

But increasing the number of enzymes inside the capsid does not increase the reaction rate, says Cornelissen. A capsid rarely contains more than one substrate molecule so one enzyme is sufficient to convert the substrate, he explains.

Want to learn more about the art of confinement? Read the Edge article for free online.

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The Ruddlesden-Popper structure is an archetypal structure in solid state chemistry, consisting of slabs of perovskite units separated by rock salt layers. But conventional high temperature oxide synthesis methods can’t be used to make these structures when the perovskite blocks are greater than three octahedral thick.

Now Matthew Rosseinsky, at the University of Liverpool, UK, and colleagues have exploited the capabilities of modern thin film deposition to grow an artificial metastable oxide where the perovskite block is six octahedral thick and is made of two distinct perovskite units.

Find out more in their Chemical Science Edge article and let us know your comments on the work below.

Scientists from Switzerland have created a system that mimics the way the human nose recognises scents.

Stefan Matile and colleagues from the University of Geneva made an artificial membrane that can distinguish between a range of odour molecules. Their ‘nose’ uses differential sensing, a form of molecular recognition, to recognise subtle structural differences between the molecules. ‘Our nose works by differential sensing in the membrane and differential sensing has been done almost everywhere except in the membrane,’ says Matile.

The human nose can distinguish over 10,000 different smells using 350 receptors. Smell molecules, known as an odorants, interact with the receptors to create an overall ‘fingerprint’ that is recognised by the brain. Matile’s system works by moving odorants across a lipid bilayer, an artificial cell membrane, using electrostatic interactions. Once across the membrane, this creates a fluorescent response, which is then measured to build up an electronic fingerprint of the smell. The team say they can distinguish a range of commercial perfumes using their nose.

The artificial nose builds up a fingerprint of odour molecules

‘This highlights just how closely related this system is to the human system,’ says Jon Steed, an expert in supramolecular sensing at the University of Durham, Durham, UK, who adds: ‘You can adapt the chemistry to sense whatever you want.’

‘The applications are broad and very promising,’ says Matile. Steed adds that detection of low levels of molecules is important in many areas, for example in the detection of explosives or pollutants. Matile is now studying different forms of membrane transport in the system and how this affects its sensing capability.

Will Dennis

Read the full Edge article for free in Chemical Science.