Author Archive

New micro-dendrites separate themselves from the field

Bioanalysis and biosensors represent a current area of wide interest in the chemical sciences. Much work is being put into methods that allow easy separation and detection of biological targets. Erkang Wang and coworkers at the Chinese Academy of Sciences in Changchun have presented a new way of doing just that.

The group synthesised a new type of silver micro-dendrite (SMD) that has a silver surface perfect for tethering biomolecules. The SMDs could also be reversibly separated and dispersed in water merely by oscillation and then settling under gravity for 30 seconds.

 

The team used the SMDs to successfully detect DNA from sickle cell disease, human T-lymphotropic virus and anthrax. Probe DNA was attached to the SMDs and then the target strands were selectively bound with a second, fluorophore-containing probe. The target DNA could then be detected using laser scanning confocal microscopy. They found that this technique was so sensitive it could even detect DNA with a one nucleotide mismatch.

Wang hopes that this type of separation system can be expanded to more targets and other types of sensing system.

Interested in finding out more? Then download the ChemComm article for free today and leave a comment below.

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The first use of organometallic hosts in crystalline organic frameworks

Chemists working at Ruhr-University Bochum in Germany have for the first time studied the host–guest chemistry of organometallic complexes with covalent organic frameworks (COVs).

COVs are the organic analogues of metal–organic frameworks (MOFs) and are made up of strong organic covalent bonds to form large organic polymers. They have a crystalline  structure and have attracted a lot of attention due to their possible applications in gas storage, sensing and catalysis. To date, only the  host–guest chemistry of small gas molecules such as CO2 and H2 have been studied in COVs. The team in Germany, led by Roland A. Fischer, set about changing this and demonstrated the use of organometallic molecules as guests.

Using COF-102 as the host, the team looked at the adsorption of FeCp2 , CoCp2 and [Ru(cod)(cot)] within the framework. They found that FeCp2 remained intact within the framework and that it assumed a structure reminscent of the host via π–π interactions.  Overall, the work displayed the similarity between COVs and MOFS as hosts for metal complexes.

If you are interested in finding out more on this hot area then why not download the full ChemComm article for free today?

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New copper complex offers easy access to complex structures

Chemists working at the University of Cambridge in the UK have discovered a new dicopper complex capable of forming diverse supramolecular structures.

The creation of supramolecular structures for a wide variety of uses has been something that chemists have pursued for years and, as such, new methods to access these structures are constantly sought.  Jonathan Nitschke and colleagues are prominent figures in this field and have just reported a new copper complex that self assembles into larger architectures.

The team first assembled the copper complex and then showed they could modified it at two points. This is done either by substitution of solvent molecules with ligands capable of linking multiple complexes or by modifying the imine bonds. Using both these approaches and varying the ligands, it was possible to achieve the templated synthesis of 26- and 52-membered macrocycles. More complex assemblies that utilise this approach are currently being investigated.

Interested in finding out more? Then download Nitschke’s ChemComm article for free today. Also why not check out Dr Nitschke’s mini review and edge article form our sister journal Chemical Science?

Reactivity modulation in container molecules
Boris Breiner, Jack K. Clegg and Jonathan R. Nitschke
Chem. Sci., 2011, 2, 51-56
DOI: 10.1039/C0SC00329H, Minireview

Selective anion binding by a “Chameleon” capsule with a dynamically reconfigurable exterior
Yana R. Hristova, Maarten M. J. Smulders, Jack K. Clegg, Boris Breiner and Jonathan R. Nitschke
Chem. Sci., 2011, 2, 638-641
DOI: 10.1039/C0SC00495B, Edge Article

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A new and simple polymer synthesis for polymer solar cells

A team of Swedish chemists have presented a novel and straightforward method for synthesising polymers for use in polymer solar cells (PSC) with a wide absorption spectrum.

The researchers, led by Mats R. Andersson from the Chalmers University of Technology in Sweden, synthesised the polymer from a widely available stannyl thiophene and an easily synthesised bromoisoindigo monomer. These were then coupled together using a Stille coupling reaction. Overall this represents just 3 steps and was achieved with a high overall yield of 68%.

 

The polymer itself is a low band-gap polymer with a donor–acceptor structure, which is important for harvesting photons from sunlight. The team found that the polymer exhibited promising performance when used in a PSC device and expect to be able to further improve this by varying the indigo groups.

If you would like to read more about this topic then download the ChemComm article for free today. Also, why not check out these other great ChemComm articles on PCSs?

Synthesis of annulated thiophene perylene bisimide analogues: their applications to bulk heterojunction organic solar cells
Hyunbong Choi, Sanghyun Paek, Juman Song, Chulwoo Kim, Nara Cho and Jaejung Ko
Chem. Commun., 2011, DOI: 10.1039/C0CC05448H

Crystalline conjugated polymer containing fused 2,5-di(thiophen-2-yl)thieno[2,3-b]thiophene and thieno[3,4-c]pyrrole-4,6-dione units for bulk heterojunction solar cells
Guan-Yu Chen, Yu-Hsin Cheng, Yi-Jen Chou, Ming-Shin Su, Chia-Min Chen and Kung-Hwa Wei
Chem. Commun., 2011, DOI: 10.1039/C1CC10585J

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A rare example of synthon polymorphism

Scientists in India have reported a rare example of synthon polymorphism in co-crystals of 4,4′-bipyridine and 4-hydroxybenzoic acid.

Graphical abstract: Synthon polymorphism and pseudopolymorphism in co-crystals. The 4,4′-bipyridine–4-hydroxybenzoic acid structural landscape

Polymorphism is defined as the ability of a material to exist in more than one form or crystal structure. It has important implications for the properties of such materials; for example in pharmaceuticals, the dissolution rate of a drug can be dependent on the polymorphic form. While this is a common phenomenon in single crystals it is much less common in co-crystals, systems where the structure has at least two distinct components.

Gautam Desiraju from the Indian Institute of Science, found that when 4,4′-bipyridine and 4-hydroxybenzoic acid were dissolved together in a solvent such as methanol they would co-crystallise to form two different polymorphs. They noticed that a third form, a pseudopolymorph, was also present.

If you would like to read more about Desiraju’s discovery then why not download his ChemComm article for free today? This article is also part the ChemComm web themed issue on Supramolecular Chemistry to mark the International Year of Chemistry 2011.

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Meet our author… Barbara Zajc

Barbara Zajc is an organic chemist working at The City College and The City University of New York. Her research interests cover, among other things, the regioselective fluorination of bioactive molecules, the synthesis and study of fluorinated carcinogen analogues, polycyclic aromatic hydrocarbons and modified nucleosides.

Zajc’s recent communication, published in ChemComm, utilises ‘Click’ chemistry and Julia-
Kocienski olefination to synthesise vinyl and fluorovinyl triazoles: Facile synthesis of 4-vinyl- and 4-fluorovinyl-1,2,3-triazoles via bifunctional “click-olefination” reagents

Below, Barbara takes some time away from her research to talk to us…

What initially inspired you to become a scientist?

Anything related with nature and life has always interested me, and chemistry is one of the basic sciences for understanding how things work.  When I was an undergraduate at the University of Ljubljana (Slovenia), I became involved with research and I enjoyed it.  So when the opportunity arose to join a research group and pursue a Ph.D. , this became a natural choice.

What was your motivation behind the work described in your ChemComm article?

One focus of our research is the development of methods for the regiospecific introduction of fluorine into organic molecules. We are exploring the synthesis and reactivity of specific fluorinated building blocks, leading to diverse fluorinated molecules via a modular assembly approach.  We are also interested in the role fluorine has on the reactivity of various reagents, compared to a hydrogen atom.  We have previously developed a series of novel Julia-Kocienski reagents for the synthesis of various functionalised vinyl fluorides.  In this particular work we were interested in developing “multifunctionalisable” Julia-Kocienski reagents that would allow quick and facile introduction of different substituents at N– and vinyl moieties, during assembly of the vinyl or fluorovinyl triazole scaffold.

Why did you choose ChemComm to publish your work?

For many years now, ChemComm has remained a prestigious journal, with broad readership and high-impact.  I am impressed with the Editorial department’s speed of review, the publication process, and the “error-free” reproduction of our submitted material.

Where do you see your research heading next?

We are planning on using this particular method we have developed for the synthesis of new classes of vinyl and fluorovinyl triazoles of potential biological importance.

What do enjoy doing in your spare time?

Hiking in nature, watching wildlife, occasionally visiting an art gallery, going to the opera or a classical music concert, reading a good novel and skiing when I find the time.

If you could not be a scientist, but could be anything else, what would you be?

I was always fascinated with nature and in particular with the animal world.  If I was not a chemist, I would have loved to be an animal behaviour observer.

Other organic chemistry articles recently published in our sister journal Chemical Science that might interest you include:-

Catalytic asymmetric allylic alkylation employing heteroatom nucleophiles: a powerful method for C–X bond formation
Barry M. Trost, Ting Zhang and Joshua D. Sieber
Chem. Sci., 2010, 1, 427-440
DOI: 10.1039/C0SC00234H, Perspective

Continuous flow multi-step organic synthesis
Damien Webb and Timothy F. Jamison
Chem. Sci., 2010, 1, 675-680
DOI: 10.1039/C0SC00381F, Minireview

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A new class of molecular propellers

Scientist based in Italy have recently demonstrated a new class of molecular propellers based upon polyoxometalates (POMs).

POMs consist of a cluster of transition metal oxides that are water soluble and are used for a wide range of applications. In particular, Andrea Sartorel and Marcella Bonchio, from the Univerity of Padova, are interested in their use as photosynthetic oxygen-evolving catalysts. The team studied a series of POMs with different metal centres and their catalytic performance in the disproportionation of hydrogen peroxide (H2O2) to water and oxygen.

They found that of all the POMS studied, Ru4(SiW10)2 performed the best in terms of oxygen evolution. This production of oxygen could then be used to create movement of the POM;  in effect using H2O2as fuel to create oxygen that then propels the POM material in aqueous solution. A video of this can be seen here. This represents a step towards the use of light-driven molecular machines based on POMs.

If you are interested in finding out more, then why not download Sartorel and Bonchio’s ChemComm article for free today? Also, don’t forget to leave a comment below!

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Paper spray ionisation of polar analytes using non-polar solvents

US analytical scientists have used non-polar solvents for the paper spray ionisation of polar compounds.

Polar compounds are normally ionised in mass spectrometry using a desorption ionisation method, such as MALDI, or from solution in a polar solvent using electrospray ionisation (ESI). However, ESI does not usually tolerate non-polar solvents and, as many reactions or purifications of compounds occur in non-polar solvents, this can present some difficulties.

Graham Cooks and co-workers from Purdue University have extended the scope of the recently developed paper spray ionisation technique to allow the use of non-polar solvents. When a low voltage is exposed to a triangle of paper wetted with a solvent such as hexane or toluene, droplets of that solvent are produced.  Polar compounds that are deposited on the paper are transported by the non-polar solvent compounds despite being sparingly soluble in them.

This technique can be applied to biological compounds, such as nucleotides, phospholipids and peptides, and avoids a typical problem associated with ESI where there capillary may clog when a non-ideal solvent is used. Furthermore, compounds may be analysed simply by ionising spots separated via TLC.

If you want to find out more then download the ChemComm article today. For wider look at analytical chemistry, why not check out these papers in our sister journal Chemical Science?

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Novel chemical tag illuminates protein cholesterylation in cells

UK chemists have for the first time used a chemical probe to study the post- translational cholesterylation of proteins in living cells.

Post-translational modification (PTM) in cells plays an important role in the function of proteins in vivo. One example is the mammalian Hedgehog (Hh) protein family: the post-translational cholesterylation of Sonic hedgehog (shh) protein regulates its secretion. However, mis-regulation of this protein can promote different types of cancers. Therefore a simple way of studying this type of modification is important.

Graphical abstract: Bioorthogonal chemical tagging of protein cholesterylation in living cells

Edward Tate and colleagues at Imperial College, London have done just this. They first modified cholesterol molecules to bear an azide group and then gave this to their target cells, where it was used in PTM. They next managed to attach, via ‘click’ chemistry, a dye molecule called TAMRA to the modified proteins that carried the synthetic cholesterol. The team used this dye for ‘fluorescence visualisation’ of the target protein.

When compared to traditional techniques for studying cholesterylated proteins, this new method stacks up well. It makes significant savings in both time and expense, as well as avoiding the use of potentially harmful radiation. Furthermore, Tate suspects that in the future an optimised version of this process might be used to search for new cholesterylated proteins.

Want to find out more? Then download the ChemComm article for free today. You can also check out coverage of this article in C&EN.

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New polymer hydrogels offer step forward in desalination

Chemists working in Australia have used polymer hydrogels as a ‘draw’ agent in a desalination process.

Forward osmosis (FO) desalination is an emerging area of interest for chemists as it provides a low energy method of obtaining salt free water from the sea. Typically in FO, saline water is separated by a membrane from a ‘draw’ solute. Water passes through the membrane from the saline side to the ‘draw’ solute via osmosis. The water is then recovered from the ‘draw’ agent using distillation.

Now Huanting Wang and colleagues at Monash University have investigated the use of polymer hydrogels as the draw agent for FO desalination. Polymer hydrogels can reversibly change their volume when exposed to certain stimuli such as temperature and pressure. This gives them an advantage over traditional draw agents as they can potentially be recycled and release the water at lower energy and therefore cost.

Graphical abstract: Stimuli-responsive polymer hydrogels as a new class of draw agent for forward osmosis desalination

The team found that it is indeed possible to release significant amounts of water from the polymer hydrogels tested and are investigating other stimuli, such as light, to further increase the efficiency of this process.

Read more about this exciting advance by downloading  the full ChemComm communication today and let us know what you think below.

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