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A model for the single chirality of life

14 Nov 2011

The boiling solutions in prebiotic hot springs could shed light on the emergence of a single chiral form of biomolecules in nature, say Spanish scientists.

Amino acids and sugars exist in living organisms exclusively in one of their two molecular chiral forms, which are mirror images of one another. The reason for this specificity has long puzzled scientists. Conditions on Earth when life first evolved in prebiotic times presumably favoured one form over the other, but the mechanism is so far unresolved.

‘We will most likely be unable to solve this fascinating conundrum, but experiments carried out under environmentally credible conditions may be important signposts to this end,’ says Cristóbal Viedma at the Universidad Complutense, Madrid. With this in mind, he and colleague Pedro Cintas have investigated crystallisation processes that lead to single chiral forms.

Read the full news story in Chemistry World and download Viedma’s ChemComm communication to find out the exact details.

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50 days until 100 issues…

11 Nov 2011

….and did you know….?

Graphical abstract: Percent buried volume for phosphine and N-heterocyclic carbene ligands: steric properties in organometallic chemistry Steven Nolan’s Feature article from 2010 has received 50 citations to date according to Web of Science^SM (Thomson Reuters, 2011).

Read it: Percent buried volume for phosphine and N-heterocyclic carbene ligands: steric properties in organometallic chemistry

Are you interested in writing a Feature article? Contact the Editorial Office with your suggestion.

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Once, twice, three times a potential life saver – electrochemical immunoassay of cancer biomarkers

09 Nov 2011

Early detection and diagnosis of cancer is essential to give sufferers an increased chance of overcoming the disease. The symptoms of liver cancer, in particular, are fairly innocuous – tumours are difficult to detect by physical examination and therefore the disease is not usually discovered until the later stages of development.

Dong Wang and co-workers have developed an electrochemical immunoassay which has the potential to improve the early detection rates of liver cancer by simultaneous detection of not one, not two, but three tumour markers. This simultaneous multianalyte immunoassay (SMIA) has a number of advantages over single-analyte immunoassay methods such as reduced overall cost per assay; improved efficiency; the potential to quantitatively measure the concentrations of proteins detected; as well as having a panel of biomarkers to confirm the diagnosis, lowering the likelihood of false-positive or false-negative results.

The team selected three electrochemical redox species with distinct voltammetric peaks to label three different antibodies as signal tags. These were then loaded onto carbon nanotubes coated with gold nanoparticles to improve the signal response.

Binding of the redox species labelled nanotube-antibody conjugates to the cancer biomarkers enables their electrochemical detection

By deciphering the voltammetric read-out, the team were able to establish successful binding events between the probes and the protein biomarkers, allowing simultaneous identification of the three analytes. Wang and his team then increased the sophistication of the immunoassay further by proving quantitative detection.

Dong Wang and co-workers appeared to have produced a robust SMIA with low detection limits that has the potential to save many lives. This efficient, gold nanoparticle-based technology could also be applied to other types of cancer or diseases – an immunoassay with a Midas touch.

To find out more, download the ChemComm article.

Posted on behalf of Sarah Brown, ChemComm web science writer.

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55 days until 100 issues…

06 Nov 2011

….and did you know….?

Picture of Professor Jonathan L. Sessler 55 is the age of ChemComm Associate Editor Jonathan Sessler (although don’t tell him I told you!).

Jonathan handles North American submissions in the areas of supramolecular and macrocyclic chemistry. He was one of the guest editors of this year’s Supramolecular Chemistry web theme, which is a superb collection of cutting edge contributions by international leaders in the field.

You can submit to Jonathan’s editorial office via our online submission system.

Read Jonathan’s latest ChemComm communication >

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Overcoming obstacles in labelling RNA

02 Nov 2011

If you can’t beat them, join them… or rather incorporate, and then join them together. This is the approach adopted by Srivatsan and colleagues for conjugating labels to RNA, which they achieve by incorporating azide functionality into RNA nucleotides.

DNA oligonucleotides are routinely labelled by incorporating modified nucleosides into the desired DNA sequence and introducing the label post-synthesis; however, these standard methods offer low yields of the desired conjugate. Furthermore, modification of RNA is more challenging than DNA modification due to its inherent instability.

Copper catalysed alkyne–azide cycloadditions (CuAAC) and Staudinger ligations are the conjugation reactions du jour due to their high chemoselectivity and reported high yield. So, with this in mind, were Srivatsan and his team able to incorporate the required moieties into RNA oligonucleotides?

Yes! Using some extremely nice chemistry, they synthesised an azide-modified nucleotide and incorporated it into an oligoribonucleotide using in vivo transcription reactions in the presence of a series of promoter-template oligonucleotides. After rigorous testing and analysis of their modified nucleic acid sequence, click reactions were performed to yield biotinylated and fluorescent-labelled click products. They also showed that amine functionality can be introduced through Staudinger ligation.

Although azides are not usually found in nature, they are becoming more useful and versatile in the design of diagnostic and therapeutic biological probes as has been very elegantly demonstrated here.

Read more in Srivatsan’s ChemComm article…

Also of interest: Synthetic DNA synthesises RNA by transcription: ‘click’ here for more

Posted on behalf of Sarah Brown, web science writer for ChemComm.

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Green hydrogenation of cyclic di-esters to diols

02 Nov 2011

Hydrogenation of esters under mild conditions is difficult at best, however David Milstein and his team push the boundaries by hydrogenating biomass products, glycolide and lactide, to afford the corresponding 1,2-diols. Their synthesis, which utilises ruthenium pincer complex catalysts, offers an atom-economical, green alternative to existing methods for producing 1,2-diols, which currently rely on petroleum-derived ethylene and propylene feedstocks.

The team say that the cyclic di-esters can be selectively and efficiently hydrogenated under very mild conditions, whilst producing no waste, and even discovered that optically pure diols could be produced from chiral lactide.

Download the ChemComm article today to find out how Milstein and his team did this.

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Aromaticity web theme issue – welcoming submissions

02 Nov 2011

We are delighted to announce a high-profile web themed issue on Aromaticity.

Guest editors: Nazario Martín (University Complutense of Madrid), Michael Hayley (University of Oregon) and Rik Tykwinski (University of Erlangen-Nuremberg)

This themed issue will consist of a series of invited Communications and Feature Articles covering work on all aspects of chemistry related with aromaticity – from new fundamental knowledge about aromaticity and theoretically interesting new arene structures to novel applications of aromatics and heteroaromatics which take advantage of their unique optical and electronic attributes.

The level of quality of this issue will be extremely high, and all manuscripts will undergo strict peer review. You are therefore encouraged to report work that you consider to be very important and conceptually significant. Please note that inclusion in the issue is subject to the discretion of the guest editors.

Publication of the peer-reviewed articles will occur without delay to ensure the timely dissemination of the work. The articles will then be assembled on the ChemComm website as a web-based thematic issue.

Submit your work before 31^st May 2012. Please add “aromaticity” in the comments to the editor section.

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Further insight into aromatic borylation chemistry

31 Oct 2011

Thorough characterisation of arene–borane Lewis acid contacts is essential for understanding the mechanistic pathway for aromatic borylation chemistry and by extension, electrophilic aromatic substitution. However, until now, structural determination of such arene–borane compounds has been somewhat ambiguous.

Simon Aldridge and his team have set out to fill this knowledge gap by reacting a sterically encumbered pyridine donor with BBr₃ to yield a cationic tri-coordinate borane–arene complex. Employing crystallography and computational studies, the team found that a weak electrostatic interaction is responsible for the short contacts between the positively charged boron centre and the arene π system.

Read the ChemComm article to find out more…

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Metal evasion still leads to nitration

31 Oct 2011

Researchers from Germany and China have designed a simple method for forming nitroarenes.

Aromatics substituted with nitro groups are ubiquitous motifs in important molecules required by the textiles, materials and pharmaceutical industries.

However, installing nitro groups can be tricky because it requires the use of strong acids or dinitrogen peroxide. These harsh conditions are not commonly tolerated by sensitive functionality present in molecules, and problems of selectivity or over-nitration commonly arise. Alternate methods use large quantities of silver salts or expensive palladium catalysts.

Now Xiao-Feng Wu (Zhejiang Sci-Tech University, China), Matthias Beller (Leibniz Institute for Catalysis, Germany) and colleagues have designed a metal-free method for nitrating aryl boronic acids.

The team used an alkyl nitrite at 80 ˚C to convert the boronic acid group to a nitro group. The reaction works in moderate to good yields for electron-rich and electron-neutral aryl boronic acids. Electron-poor aromatics are more challenging substrates, as the boronic acid are less reactive.

While this method is not yet suitable for vinyl or hydroxy substituted aryl boronic acids, it offers an economically and operationally attractive method for synthesising nitro compounds.

Researcher’s perspective:Our initial investigations started with the use of a rhodium catalyst, because of rhodium’s known ability to transmetalate with arylboronic acid. Our target product, nitrobenzene, was formed but we found that the rhodium catalyst is not necessary for this transformation.

On one hand, we were disappointed, as our aim is to develop catalytic reactions; on the other hand, we are happy, because this reaction works so nicely.

Xiao-Feng Wu

Using this method, nitroarenes can be easily prepared from arylboronic acids without using catalyst and hazardous reagents.

More information can be found in the ChemComm communication, free to download for a limited period.

Posted on behalf of Alice E. Williamson, ChemComm web writer.

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Supramolecular assembly of polyoxometalate triangles

31 Oct 2011

Polyoxometalates (POMs) are a diverse class of inorganic materials that are of great interest due to their exciting range of redox, conducting, magnetic and catalytic properties. Recent collaborative work from Professor Garry Hanan in Montreal and Professor Bernold Hasenknopf in Paris reports the inclusion of a Lindqvist-type hexavanadate POM as a component of a self-assembling supramolecular framework.

They designed ligand 1 utilising a triol motif to complex the POM in combination with pyridyl groups to serve as binding sites for a transition metal. The reaction of 1 with a suitable decavanadate yielded complex 2, a hexavanadate POM complex that is itself a structurally rigid and spatially well-defined bi-pyridyl ligand. The 60° angle between the coordination vectors of the pyridyl groups led the authors to predict that the coordination of a trans-PdCl₂ unit by 2 would result in a supramolecular triangle.

Initially the reaction of 2 with [PdCl₂(CH₃CN)₂] in DMAc yielded a complex mixture of products; however, heating to 80 °C for 48 hours led to just a single assembly. This was shown by a number of analytical techniques to be the predicted triangular assembly 3.

This work elegantly uses a classical motif for self-assembly to create a multi-component supramolecular architecture. It is a great step towards the goal of creating functional supramolecular arrays, integrating the desirable properties of POMs into a new framework and bridging the gap between solid state oxides and coordination chemistry.

Researcher’s perspective:

The obtention of discrete coordination-driven POM-based arrays had so far eluded the community, with only a few well characterised coordination polymers. We started this challenging project of a molecular triangle by a simple drawing based on geometrical considerations. A range of conditions were explored, but most lead to complex mixtures except one. This identification of optimal conditions was our first satisfaction. However, we needed solid evidence of the triangular nature of the obtained array to validate our approach as a rational design: a combination of techniques confirmed the successful and selective synthesis of the triangle. As a student, I learnt a lot from the complementary competencies provided by the two groups on a project at the interface of inorganic, organic, supramolecular and coordination chemistry. Dealing with the specific difficulties of each domain has been an exciting challenge that has re-confirmed my choice in academic research. Marie-Pierre Santoni, a student in the research collaboration

To read more about Hanan and Hasenknopf’s work, download their ChemComm article.

Posted on behalf of Cally Haynes, ChemComm web writer.

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Chemical Communications Blog

Archive for the ‘Subject Areas’ Category

A model for the single chirality of life

50 days until 100 issues…

Once, twice, three times a potential life saver – electrochemical immunoassay of cancer biomarkers

55 days until 100 issues…

Overcoming obstacles in labelling RNA

Green hydrogenation of cyclic di-esters to diols

Aromaticity web theme issue – welcoming submissions

Further insight into aromatic borylation chemistry

Metal evasion still leads to nitration

Supramolecular assembly of polyoxometalate triangles

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