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Porous organic polymers filter toxins from the air

25 Mar 2013

In a search for the next generation of filtration materials, for use in devices such as gas masks, a group of US scientists has synthesised a series of porous organic polymers (POPs) bearing metal-catecholate groups. By changing the molecular building blocks the researchers were able to tailor the materials to hydrogen bond to, and consequently remove, different toxins, such as ammonia.

POPs are very similar in nature to metal-organic frameworks (MOFs) but do not suffer from such instability, particularly towards water, making them ideal for use as filters in real-word environments.

Read this ‘HOT’ Communication now:

Removal of airborne toxic chemicals by porous organic polymers containing metal–catecholates
Mitchell H. Weston , Gregory W. Peterson , Matthew A. Browe , Paulette Jones , Omar K. Farha , Joseph T. Hupp and SonBinh T. Nguyen
Chem. Commun., 2013,49, 2995-2997

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Making Bispirin: A new drug to fight both indigestion and pain

25 Mar 2013

Until now, drugs which fight gastrointestinal infections and those which treat acute inflammation have been found to interfere with each other. For instance, people infected with the Helicobacter pylori bacterium have needed to deal with the additional risk of gastrointestinal bleeding associated with the use of aspirin and other inflammatory drugs.

Australian research chemists, led by Philip C. Andrews of Monash University, have designed a new drug which treats gastrointestinal infections and acute inflammation at the same time. They have successfully synthesized bispirin, a bismuth acetylsalicylate complex which combines the effectiveness of bismuth carboxylate compounds as anti-infection agents with that of acetylsalicylic acid (aspirin) as an anti-inflammatory drug. Their initial tests have shown that bispirin’s antibacterial effects are comparable or better than those of current bismuth drugs, and investigations of bispirin’s anti-inflammatory activity are currently in progress.

Making Bispirin_graphical abstract

This journal article has also been recently featured on C&EN – read it here.

Read this ‘HOT’ ChemComm article in full:

Making Bispirin: synthesis, structure and activity against Helicobacter pylori of bismuth (III) acetylsalicylate

Philip C. Andrews, Victoria L. Blair, Richard L. Ferrero, Peter C. Junk and Ish Kumar

Chem. Commun., 2013, 49, 2870-2872

DOI: 10.1039/C3CC40645H

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If you like it, then you should put two rings on it

19 Mar 2013

Microring resonators are pretty amazing things, offering label-free biosensing by coupling with light and then circulating the photons inside the cavity of the ring, enhancing the interaction between the light and the analytes.

However, I like to think of traditional microring resonators as tents: difficult to construct. They require a submicrometer gap between the input waveguide and the resonator ring structure to allow the coupling of light and before you can even get to that stage, you need to make the microring resonator, which requires a series of complex fabrication steps (FIG 1a). In this Communication, which is part of ChemComm‘s Microfluidics themed web collection, Professor Jonathan Cooper and his colleagues at Glasgow University and at the International Islamic University Malaysia’s CTS Department have made (what I think of as) the double pop-up tent equivalent– or as they call it, the dual disk resonator (DDR). Made from SU8, an epoxy-based polymer used in microfluidics chips, it can be patterned in a single lithographic step. Not only that, but the DDR uses a gapless design and two rings, increasing the sensitivity of the device (FIG 1b).

FIG 1: The hard way or the easy way (a) the traditional microring resonator with submicrometer gap (b) gapless dual disk resonator

Once they had constructed the DDR, the team characterised the optical sensitivity of the device using sucrose solutions to vary the refractive index of the sample above the waveguide. They then went on to show that the sensor could be used to evaluate the dynamics of antibody interactions on surfaces, exploring avidin-biotin-based immobilisations; sharp resonance shifts confirmed the assembly and disassembly of constructs.

The simpler fabrication shows great promise, as the authors suggest that the sensitivity of the device could be greatly improved by coupling more disks to it– in which case Beyoncé might soon be singing ‘if you like it, then you should put a chain on it.’

Read this ‘HOT’ ChemComm article today:

Polymer dual ring resonators for label-free optical biosensing using microfluidics

Muhammad H. M. Salleh, Andrew Glidle, Marc Sorel, Julien Reboud and Jonathan M. Cooper

Chem. Commun., 2013, Advance Article

DOI: 10.1039/C3CC38228A

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Harnessing enzyme-substrate specificity for gel-based sensors

16 Mar 2013

Gels that are held together by non-covalent interactions are a hot topic in supramolecular chemistry. In this Communication, Itaru Hamachi’s research group from Kyoto University report a series of glycolipids that form yellow hydrogels from orange suspensions when heated. The gelation and hence the colour change is reversible, and the authors hoped to use this response to create a sensor system.

Hamachi's gelator molecules

Once the gel has formed, adding a glycosidase enzyme which can selectively cleave the β-glucosidic bond leads to breakup of the gel and a colour change from yellow to orange. This response is only observed with an enzyme that is complimentary to the saccharide used as a “substrate unit” in the gelator. Hence, the authors have harnessed natural enzyme-substrate selectivity to yield a highly selective sensing system. The combination of a number of these gels into a sensor array chip yields a system that can simply and rapidly detect and distinguish a range of glycosidase enzymes. The ability to selectively sense these enzymes could have significant application for diagnosing disease and identifying bacterial contamination of drinking water.

Hamichi's sensor array

Read this ‘HOT’ ChemComm article today:

Supramolecular hydrogels based on bola-amphiphilic glycolipids showing color change in response to glycosidases

Rika Ochi, Kazuya Kurotani, Masato Ikeda, Shigeki Kiyonaka and Itaru Hamachi

Chem. Commun., 2013, 49, 2115-2117

DOI: 10.1039/C2CC37908B

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Removing toxic chemicals with POPs

14 Mar 2013

The filters used in gas masks, which give protection against toxic industrial chemicals, are often large and cumbersome, being made from activated carbon that is impregnated with metal salts. In a search for alternatives, SonBinh Nguyen and colleagues at Northwestern University, Evanston, Illinois, have joined forces with scientists at the Edgewood Chemical Biological Center, Maryland, to investigate a series of porous organic polymers (POPs) bearing metal-catecholate groups. By changing the molecular components used in their synthesis, the materials have been tailored to hydrogen bond to, and consequently eliminate, specific toxic industrial chemicals, like ammonia.

‘Metal-organic frameworks (MOFs) have the same customisable characteristics as POPs, and have been investigated for their ability to remove toxic chemicals,’ says Nguyen. ‘Yet many of the MOFs known today are not very stable, owing to the prevalence of metal-oxygen bonds, and will degrade in the presence of atmospheric moisture. POPs, on the other hand, contain carbon-carbon bonds, which are less susceptible to moisture attack,’ he explains.

Chemical reaction

Read the full article in Chemistry World

Read the original journal article in ChemComm:
Removal of airborne toxic chemicals by porous organic polymers containing metal–catecholate
Mitchell H. Weston, Gregory W. Peterson, Matthew A. Browe, Paulette Jones, Omar K. Farha, Joseph T. Hupp and SonBinh T. Nguyen
Chem. Commun., 2013, Advance Article
DOI: 10.1039/C3CC40475G

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Combating Influenza: Anthraquinone–Sialic Acid Hybrids for the Inhibition of Viral Neuraminidase

17 Feb 2013

In the fight against influenza, viral neuraminidase (NA) represents an important target. This enzyme is essential for the replication of the virus, and its inhibition can prevent the spread of the disease. Scientists at Keio University have now identified a set of novel anthraquinone–sialic acid hybrids which can inhibit influenza virus neuraminidase with photo-irradiation under neutral conditions.

Anthraquinone derivatives were found to degrade proteins when subjected to photo-irradiation; this degradation is likely caused by hydroxy radicals which are produced from the photolysis of anthraquinone and oxygen. Crucially, researchers led by Prof. Kazunobu Toshima proposed that NA-inhibition could be obtained if such an anthraquinone derivative could be tethered to an NA-binding moiety. Sialic acid is a native ligand for NA— both “normal” NA and drug-resistant NA— and so researchers prepared and investigated a number of anthraquinone–sialic acid hybrids (1–3).

These hybrids were found to be effective for the inhibition of NA under photo-irradiation, and interestingly, showed comparable or superior results compared to the leading anti-NA drug, especially in the inhibition of drug-resistant NA. While further tests are ongoing, this research represents an important advance in influenza treatment, and offers great potential for the inhibition of other disease targets.

For more, read this ‘HOT’ ChemComm article in full:

Photodegradation and inhibition of drug-resistant influenza virus neuraminidase using anthraquinone–sialic acid hybrids

Yusuke Aoki, Shuho Tanimoto, Daisuke Takahashi and Kazunobu Toshima

Chem. Commun., 2013, 49, 1169–1171

DOI: 10.1039/C2CC38742E

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A new system for cancer detection

14 Feb 2013

While current cancer-diagnosis methods rely on an invasive biopsy or the detection of cancer-specific biomarkers, South Korean scientists have developed a simple and non-invasive detector for cancer cells that could speed up the early diagnosis of the condition, leading to a greater chance of survival for cancer patients.

Daunomycin interacting cancer cells viewed with fluorescene microscopy

Cancer cells have been found to differ from normal cells in several ways, including the make up of their cell membranes. Cancer-cell membranes have been found to contain more anionic lipids than normal cells, leading to an overall negatively charged cell surface. Yoon-Bo Shim and co-workers from Pusan National University, have exploited this negative surface charge to develop a probe based on daunomycin, an anti-cancer drug that is known to interact strongly with anionic lipids.

Read the full article in Chemistry World.

Read the original journal article:
Cancer cell detection based on the interaction between an anticancer drug and cell membrane components
Chem. Commun., 2013, 49, 1900-1902
DOI: 10.1039/C2CC38235K

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Novel silicon-mediated transannular cyclopropanation

23 Jan 2013

An intriguing new method of transannular cyclopropanation has been reported by Prof. James Dowden‘s group at the University of Nottingham. This cyclopropanation, mediated by the presence of a trimethylsilyl group, allows the rapid formation of 4-azabicyclo(5.1.0)octenones (3) from simple starting materials. Divinyl beta-lactam (1) was elegantly formed via a Staudinger cycloaddition reaction beginning from 3-trimethylsilylpropenal, 4-methoxyaniline and crotonyl chloride. Next, researchers were able to transform 1 into dihydroazocinone (2) using a thermal Cope rearrangement.

The Dowden group discovered that if 2 was treated with TBAF or aqueous sodium hydroxide, 4-azabicyclo(5.1.0)octenone (3) could be formed. Interestingly, the reaction was dependent on the presence of the silicon group; when the trimethylsilyl group was replaced with an ester, no cyclopropanation occurred. The researchers proposed that the transannular cyclopropanation could be viewed as a Lewis-base–promoted Hosomi–Sakurai reaction proceeding via intramolecular 1,4-conjugate addition. 4-azabicyclo(5.1.0)octenones (3) are an unusual structural motif and it is hoped that this facile method for their construction may facilitate further examination of chemical space interactions.

Read this ‘HOT’ Chem Comm article today:

An unusual silicon mediated transannular cyclopropanation

Bing You, Kate Hamer, William Lewis and James Dowden

Chem. Commun., 2013, 49, 795-797

DOI: 10.1039/C2CC37739J

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Liquid crystal relaxation controlled by dopant kinetics

20 Jan 2013

Liquid crystals are an area of intense interest due to their potential use in smart materials such as displays. Cholesteric liquid crystals are of particular interest due to their helical nature and their ability to selectively reflect light over a narrow range of wavelengths. This range can be modified by the inclusion of photo-responsive dopants.

Dopants include overcrowded alkenes which undergo a stable to unstable (cis–trans) transition upon irradiation with UV light. This results in an unwinding and eventual inversion of the cholesteric helix. This is accompanied by a red-shift of the reflection band which then returns close to the original position. However, the handedness of the helix has changed, and therefore the polarization of the light has also changed.

Helix inversion of a cholesteric liquid crystal.

An important parameter with all liquid crystals is their relaxation step which needs to be suitable for the envisioned application. Nathalie Katsonis and her team have studied cholesteric liquid crystals doped with overcrowded alkenes in an effort to find a general paradigm correlating relaxation kinetics with the rate of helix inversion.

In their recent Communication, Katsonis’ group shows that the helix relaxation kinetics are fully determined by the kinetics of the light-sensitive dopants. The relaxation of the dopants from unstable to stable is unperturbed by the liquid crystalline environment.

On the other hand, the presence of the dopants can dramatically accelerate helix inversion. Therefore the inversion can be time-programmed by judicious choice of the dopant. This opens up the great potential of fine tuning cholesteric liquid crystals for smart materials with sophisticated functions.

For more, read this ‘HOT’ Chem Comm article in full:

Time-programmed helix inversion in phototunable liquid crystals

Sarah J. Aßhoff, Supitchaya Iamsaard, Alessandro Bosco, Jeroen J. L. M. Cornelissen, Ben L. Feringa and Nathalie Katsonis

Chem. Commun., 2013, Advance Article

DOI: 10.1039/C2CC37161H

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True racemic crystals: Surprising new insights on preparation and structure

16 Jan 2013

Isopropyl 3,3,3-trifluoro-2-hydroxypropanoate (1) is an important compound for the study of self-disproportionation of enantiomers (SDE), in which an enantiomerically enriched mixture can be separated into enantiopure and racemic portions under achiral conditions. This remarkable separation is made possible by the differences in physicochemical properties of enantiopure and racemic substances. Research led by Professor Vadim A. Soloshonok at the University of the Basque Country has now shed light on the unusual properties of racemic crystals of 1.

True racemic crystals were obtained by sublimation of a mixture of (S)- and (R)- crystal conglomerates at ambient temperature and atmospheric pressure. Surprisingly, when these racemic crystals were analysed, the unit cell was not dimeric in nature as previously thought, but rather contained two distinct (S)- and (R)- enantiomers with no heterochiral H-bonding. The preference of 1 for homochiral intermolecular interactions may explain its extraordinary ability for SDE. Indeed, Soloshonok and co-workers showed that achiral chromatography could be used to obtain enantiopure 1 from an original sample with just 75% ee (see above).

For more, read this ‘HOT’ Chem Comm article today:

Unconventional preparation of racemic crystals of isopropyl 3,3,3-trifluoro-2-hydroxypropanoate and their unusual crystallographic structure: the ultimate preference for homochiral intermolecular interactions

José Luis Aceña, Alexander E. Sorochinsky, Toshimasa Katagiri and Vadim A. Soloshonok

Chem. Commun., 2013, 49, 373–375

DOI: 10.1039/c2cc37491a

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