2011/03/31

Amino acid synthesis hints at how the genetic code expanded

30 March 2011

The detailed pathway for the biosynthesis of pyrrolysine - the 22nd and latest amino acid to be discovered - has been outlined by US researchers. The results show that each pyrrolysine is made from two lysine precursors, pointing towards a route by which new amino acids could have been introduced into the genetic code during evolution.

There are 20 common amino acids that are widely recognised as making up all proteins. These are known as the canonical amino acids. But protein synthesis is more flexible than we once thought. And while synthetic biologists have realised it is possible to expand the language of the genetic code by introducing amino acids of their own design, we are still - albeit infrequently - coming across rare but completely natural amino acids beyond the canonical 20. Pyrrolysine is the latest, discovered a decade ago in methane-producing archaea (ancient lifeforms related to bacteria).

Until now, pyrrolysine remained the only natural amino acid for which there was no established biosynthetic pathway. But Joseph Krzycki and colleagues at Ohio State University in Ohio have revealed that pyrrolysine is made by combining two molecules of the canonical amino acid lysine - a result Krzycki didn't expect. 'We had a discussion about a week before we actually observed it that theoretically it would be possible,' he says. 'But we never predicted it in any papers. So that was a bit of a surprise. I stared at that for about an hour before I realised it was actually what I'd said the week before.'

One molecule of lysine is converted to an ornithine derivative then combines with a second lysine to make pyrrolysine

Krzycki's team transferred genes for pyrrolysine production from archaea into Escherichia coli bacteria and then used stable isotope labelling and mass spectrometry to trace the path of 'heavy' lysine precursors. They saw that the bacteria incorporated the heavier carbon (13C) and nitrogen (15N) isotopes to form heavy pyrrolysine. Their results also indicated that lysine was most likely converted to pyrrolysine via an ornithine derivative, in reactions catalysed by enzymes encoded in the gene cluster they had introduced.

According to Krzycki, the pathway his team uncovered fits with the so-called coevolutionary theory for how the genetic code evolved. Under this theory, there were only a few amino acids to begin with, but new amino acids could be synthesised from existing ones. 'This would kind of fit with that - that pyrrolysine is now coming from lysine and lysine is derived from aspartate,' he says.

The real significance of the work, says Dieter Söll, a molecular biochemist at Yale University in Connecticut, is that it shows in detail what is required to add a new amino acid to the genetic code - as pyrrolysine's biosynthetic pathway likely represents its origin. 'It is exciting to learn from nature such a simple and elegant scheme for introduction of new amino acids into the genetic code,' Söll says. He also thinks the pyrrolysine scheme for introducing new amino acids into the genetic code is one that scientists could imitate using their own designs - and he is 'convinced' they will try.

Hayley Birch

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Nanotubes spot damage

30 March 2011

Researchers in the US have created a new system for monitoring structural damage in real time. Based on a carbon nanotube composite, the system uses thermal imaging to reveal areas of unsafe cracks and stresses.

Damage detection systems are already used in some civil structures and aircraft. In helicopters, for instance, systems monitor the vibration of gearboxes and bearings to spot dangerous behaviour before anything fails. Other systems use strain gauges with computer models to predict when structures are close to fracture.

One upcoming method to spot damage is thermography. Here, a structure is heated and simultaneously monitored with an infrared camera. The transmitted heat is forced to detour and concentrate around areas where the structure is stressed, or where small cracks are developing, and these patterns reveal themselves on camera. But existing thermography techniques all require a heating element that is separate to the structure itself, and this baggage prevents the systems from being used in real time.

A thermal image of a strip of the material shows where holes have been cut to make the MIT logo
© R Guzmán de Villoria, MIT

Brian Wardle, with colleagues at the Massachusetts Institute of Technology in Cambridge, have got around this problem using a thermographic system that contains its own means of heating: a composite of carbon nanotubes. The composite can be incorporated into a structure, and heats up once a voltage is applied across both ends. 'The temperature is able to penetrate much deeper into parts than an external supply, and the heaters and sensors are actually structural and improve mechanical properties,' says Seth Kessler, who heads Metis Design, a consultation firm also based in Cambridge that is furthering the design.

Wardle's group made the composites by growing nanotubes on alumina fibres that had been woven into a cloth, and then surrounding them with epoxy resin. In a test, they drilled a hole into the centre of a long piece of the composite and then, while applying power of two watts, applied tension to either end of the sample until it broke. Using an infrared camera, the researchers were able to see 'hot regions' around the hole where stresses concentrated, and finally a bright crack appear just before the sample failed completely.

'Because of the [short] length scale of these nanofibers, there is an inherent advantage in using them for this purpose because the defects are often relatively small compared to the component we are inspecting,' says Douglas Adams, mechanical engineer at Purdue University in Illinois, US.

Jon Cartwright

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2011/03/30

A single scale tells more than a whole wing

29 March 2011

Scientists in China have made zinc oxide replicas of single scales from butterfly wings to understand and exploit their optical properties for sensor and solar cell applications.

Butterfly wings are made up of chitin scales and their iridescent blue and green colours are generated by light and air travelling through the chitin. The way the scales are arranged dictates which colour is seen. Studying the wings' properties to replicate the process could lead to the design of new photonic crystal structures for optical devices.

Until now, researchers have focused on making devices based on whole butterfly wings, but Jiajun Gu and Di Zhang from Shanghai Jiao Tong University and their team, believe that this misses important mechanisms and phenomena. This is because whole wings are covered by redundant parts, such as wing membranes, which could alter the optical properties of the wings' scales.

Photonic crystal structures can control light reflectance, so have the potential to be applied in optical computers, as well as sensors and solar cells. But they are hundreds of times smaller than the diameter of a human hair and are difficult to fabricate. This creates a bottleneck in the process of understanding them and their applications. 'If the structures can be made similar to photonic crystal structures borrowed from natural species, novel photonic crystals that are unavailable through traditional artificial methods can be fabricated,' say Gu and Zhang.

The Morpho menelaus butterfly with a magnified image of a wing scale (left) and zinc oxide scale replicas with a magnified image (right)

The team used individual butterfly scales as templates to create the zinc oxide replicas. 'It's like a natural fossilisation process, but by doing it in the lab, we can make it faster,' say Gu and Zhang. They studied the way the replicas reflect light. Changing the angle that the light hits the scale reduces the reflectance intensity by a factor of ten, and the replicas' optical properties matched those of the original scales.

'The angle-dependent investigation of isolated, single butterfly wing scales and their zinc oxide replicas provides interesting new details and will help us to better understand nature's strategies to manipulate light,' says Michael Bartl, an expert on functional nanostructured materials for energy and information technology applications from the University of Utah, US. 'However, the exact impact of these complex architectures on the behavior of light is still not completely resolved.'

Gu and Zhang hope to explore novel uses for the structures in light manipulation and colour display.

Jennifer Newton

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Precursor boost for uranium chemistry

28 March 2011

The study of uranium chemistry should become significantly easier thanks to researchers in the US who have discovered a simple way to make key precursors to a wide range of low valency uranium compounds.

A deep understanding of uranium chemistry is important not only for developing improved nuclear fuel cycles, but because the element has also shown promise in materials such as superconductors and catalysts. Uranium complexes are highly sensitive to water and air, but the only viable syntheses started from aqueous reactions of uranium oxides with harsh chlorinating reagents at high temperatures.

The 1,4-dioxane derivatives of uranium iodides are easy to make and can be converted into a range of other compounds
© J Kiplinger

'Uranium's aqueous chemistry has been studied for a long time, but getting into non-aqueous chemistry has been limited to a very few stable compounds,' says Jaqueline Kiplinger of the Los Alamos National Laboratory in New Mexico, who led the research. Currently the most popular starting materials for synthetic uranium(III) and -(IV) chemistry are UI3(tetrahydrofuran)4 and UCl4. Synthesis of both of these compounds requires exacting or toxic reaction and storage conditions and produces low yields.

Kiplinger's team has borrowed a technique they demonstrated for thorium chemistry and applied it successfully to uranium. Simply incubating uranium metal turnings with iodine in a solvent of 1,4-dioxane, the researchers synthesised the dioxane derivatives of UI3 and UI4. 'We could not believe how easy it was in a glove box, obtaining 90 per cent yields in a very clean synthesis,' Kiplinger says. The key, she believes, is the 1,4-dioxane - which is highly resistant to degradation by ring-opening, unlike tetrahydrofuran.

The dioxane complexes in turn were used to make a wide range of other uranium compounds, including alkoxides, halides, amides, nitrides and carbides.

'The time required and yields we obtained were far better than existing pathways to these types of compounds,' says Kiplinger. 'I believe this will open the door to a whole lot of new uranium chemistry.'

Stephen Liddle, who researches uranium chemistry at the University of Nottingham in the UK, agrees. 'Historically this area has lagged behind many others, and one reason is the lack of suitable precursor materials,' he says. 'Hopefully these alternative uranium halides will help open up the area in general by leading to new compounds.'

Simon Hadlington

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2011/03/28

Nanotubes make 'exceptional' strain sensor

27 March 2011

New strain sensor from Japan uses carbon nanotube network that separates and folds back together in the same way each time.

A sensor that can measure the movements of a human body has several requirements: it must report the movement quickly and consistently; hug curves; and survive considerable and repeated stretching. A material that ticks all the boxes is hard to come by, but researchers in Japan say their new carbon nanotube strain sensor can do it all.

The sensor measures strain through electrical resistance, which increases as the sensor is stretched. Unlike similar sensors, the sensor made by Kenji Hata and his colleagues at the National Institute of Advanced Industrial Science and Technology in Tsukuba can withstand and measure huge strains repeatedly.

Hata has shown that the sensor can be extended to 280 per cent beyond its normal size, survive 10,000 repeated stretches to 2.5 times its length, and report stretching after just a 14 millisecond delay - the shortest known for a material that can measure such large strains.

'The performance and strains reported are exceptional,' says Gordon Wallace director of the Intelligent Polymer Research Institute at the University of Wollongong in Australia, adding that the sensors 'far exceed anything previously reported in the scientific literature.' John Rogers who works on flexible circuits and sensors at the University of Illinois at Urbana-Champagne in the US is also 'very impressed' and describes as the design as 'clever'.

When the sensor is stretched, the network pulls apart like latticework
© Nature Publishing Group

Hata and his colleagues grew thin films of single-walled carbon nanotubes and set the films onto a piece of silicon rubber with the length of the tubes running broadside to the direction of the strain. A drop of isopropyl alcohol pushed out the air between the film and the substrate, creating strong adhesion.

The first pull on the dense network of carbon nanotubes generates cracks between them, turning the network into a series of thick islands and filamentous bridges. The bridges create bottlenecks in electron traffic and this showed up as resistance in the sensor's electrical conductivity.

When strain is released, the bridges and islands fold back into a network of parallel carbon nanotubes like an accordion, but next time the sensor is stretched, they reappeare in the same configuration. The material does not repeatedly break in new places and according to Hata this is the key to the sensor's durability. Hata has even shown that the sensor has outlasted the silicon rubber it's attached to.

In addition to testing the properties of the sensor, Hata and his colleagues have also attached it to bandages, stockings and gloves to test how well it detected the motion of a human body. 'Any large motion can be detected, and it can be used for millions of times,' explains Hata.

Affixed to the chest as a respiration monitor, the team suggest it might help prevent sudden infant death syndrome (SIDS) but Hata's favourite application is the "data glove", which senses the movement of each finger. The group's glove sensed the motions of typing, but they say a version could be used to guide robots which perform surgery. Hata also has more fun applications in mind, such as game controllers and virtual reality systems.

Kate McAlpine

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2011/03/27

New synthesis for chiral anticancer compound

25 March 2011

The promising anticancer compound nutlin-3 is likely to become more widely available to researchers thanks to a new synthetic protocol developed by US chemists.

Nutlins, a group of compounds centred on a nitrogen-containing heterocycle, were discovered by scientists working for Hoffman-La Roche in 2004 and were found to inhibit a key interaction between two proteins involved in cancer pathways, with nutlin-3 the most potent of these.

The compound has attracted widespread interest but details of its synthesis are difficult to glean from the available literature - no full protocol has been published. The molecule has multiple chiral centres and synthesising the required stereoisomer is difficult.

Tyler Davis and Jeffrey Johnston at Vanderbilt University in Tennessee have used catalysts they developed to devise a straightforward synthesis of nutlin-3 that is highly selective for the required stereoisomer.

The key step in the synthesis is an aza-Henry, or nitro-Mannich, reaction involving the addition of a nitroalkane to an imine. Uncontrolled addition of the two substrates for the nutlin-3 reaction produces a total of four stereoisomers, whereas only one is effective.

Davis and Johnston had previously demonstrated that high stereoselectivity for aza-Henry reactions can be achieved by using electron-rich chiral bis(amidine) (BAM) catalysts. They screened a range of these compounds and identified one that promoted the reaction to give only the required nutlin stereoisomer.

Synthesis of nutlin-3

'We are not sure of the precise mechanism, but believe that the nitroalkane substrate forms a salt with the BAM catalyst by donating a proton,' says Johnston. 'This complex in turn binds to the imine substrate, promoting the addition reaction.'

The chirality of the catalyst ensures that only certain faces of the substrates can come into contact. This geometrical constraint results in one stereoisomer product being favoured over the others.

'We think this is a chance to substantially increase access not only to nutlin-3 but also its derivatives,' Johnston says. 'It is a relatively straightforward synthesis using standard techniques.'

Commenting on the work, Jim Anderson, an expert in stereoselective organic synthesis at University College London in the UK, says, 'The beauty of this synthesis lies in the recognition that the beta-nitro amine product from the nitro-Mannich or aza-Henry reaction has each amine essentially orthogonally protected. Asymmetry is efficiently provided by the development of the Johnston group's bis-amidine catalysts. It's a nice example of a very underused classic reaction that should be used more in synthesis now stereochemistry can be efficiently controlled.'

Simon Hadlington

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Flights from Japan trip US airport radiation detectors

24 March 2011

Low levels of radiation have been detected on planes arriving at US airports from Japan, but experts say that overly sensitive detectors are culpable and the public should not be concerned.

The US Department of Homeland Security (DHS) is monitoring maritime and air traffic from Japan closely in response to the ongoing nuclear crisis. On 16 March, two American Airlines planes arriving from Tokyo tested positive for low-level radiation - one in Dallas, Texas, and another in Chicago, Illinois. But in both cases commonplace explanations were found: a routine medical shipment in a cargo compartment and medical equipment inside an empty cargo container. Both planes were quickly put back into service.

American Airlines spokesperson Tim Smith says the radiation detected on its flights was 300 times lower than levels emitted during one chest x-ray. According to the US Department of Energy (DOE), a typical chest x-ray produces 0.1 millisievert (mSv) per image. US federal guidelines call for public health action for exposure exceeding 10 mSv over four days.

DHS Customs and Border Protection (CBP) says that no aircraft entering the US from Japan has tested positive for radiation at harmful levels. The monitoring represents 'an abundance of caution', it adds.

Frontline personnel at airports are equipped with personal radiation detectors (PRDs), and all airports have radiation isotope identification devices (RIIDs), which are more sensitive and detect radiation as well as determining its type. The agency would not give details of how the detectors work, however, or the composition of the materials that they detect, citing reasons of national security.

CBP points out that radiation is all around us - from commodities including marble, granite, bananas and medical isotopes. The agency had 580,000 radiation alerts in 2010, and all were deemed harmless.

Radiation experts also dismiss the recent alerts, claiming that the detectors are overly sensitive. 'If you look you will find, but that's a testament to the sensitivity of the radiation detectors, and not to any public health concern,' says David Brenner, who directs the Columbia University Center for Radiological Research.

Nuclear expert Jay Lehr, science director of the Chicago-based Heartland Institute, agrees. 'In many ways the instrumentation has worked against us in creating fear where there should be no fear,' he tells Chemistry World. There is 'absolutely zero possibility of health risk' from any radiation carried on a plane from Japan, he adds.

Brenner points out that iodine-131 has a half life of 8 days, and within a few weeks the levels emitted from the damaged Fukushima Daiichi nuclear plant will have decayed away.

Rebecca Trager, US correspondent for Research Europe

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2011/03/24

Antibacterial clays kill with iron

23 March 2011

US researchers have made a step towards understanding why some natural clays are antibacterial, boosting the chances that they could one day be used as alternatives to antibiotic drugs. According to the researchers, the clays supply iron that kills bacteria by generating radicals that attack cell components.

People have used clays throughout history for healing. More recently, patients in Ivory Coast suffering from a flesh-eating disease known as Buruli ulcer were treated with French green clays. The clays appeared to ease the swelling of the lesions like an antibiotic, but no-one knew how they did it.

Lynda Williams and colleagues at Arizona State University in Tempe came to this mystery in 2002. They found that in fact just one of the French clays was antibacterial, and that even then the clay's antibacterial properties were not consistent from batch to batch. 'Because of this we have been studying what makes a natural clay antibacterial,' says Williams.

Buruli ulcer, a flesh-eating bacterial infection, can be treated with certain iron-rich clays. The iron infiltrates the cells and generates lethal radicals
© Environ. Sci. Technol.

Williams and colleagues have now made a crucial step in that direction. They have analysed clay supplied by an open-pit mine in the volcanic Cascade mountains in Oregon, US, which is the most effective antibacterial clay the researchers have come across. Using x-ray spectroscopy and inductively coupled plasma mass spectrometry, the researchers studied the clay's mineralogy, its composition, and the chemistry of both the clay and nearby E. coli bacteria in water.

Compared with control experiments, in which non-antibacterial clay was dispersed in water with E. coli, the concentration of iron inside the bacteria near to the antibacterial clay was eight times higher. Williams's group therefore says that iron is the 'primary reactant' in the antibacterial process. They believe that Fe2+ ions overwhelm the bacteria's outer membranes, oxidising inside the cells to produce lethal hydroxyl (OH) radicals.

'I think the results should contribute to the understanding of antimicrobial behaviour of nanoparticles,' says Yulong Ding, a bioengineer at the University of Leeds who studies naturally antibacterial nanoparticles. However, Ding adds that scientists should probably interpret the finding 'as one of several possible mechanisms.'

Jon Cartwright

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Battery turns entropy into electricity

23 March 2011

When fresh water rivers flow into the sea the concentration difference leads to a change in entropy. US researchers have developed a battery that generates power from that entropy difference.

Yi Cui's team at Stanford University, California, extract energy with 74 per cent efficiency using manganese dioxide nanorods and silver electrodes1. 'What we have really demonstrated that this idea can work,' says Cui.

Cui's team estimate that if the technology was used on all world's rivers this renewable energy technology would hypothetically generate 2 TW, or approximately 13 per cent of current global consumption.

Entropy based power generation has been done before but is most reliably done today by separating fresh and seawater with membranes and as ions travel through the membranes they generate currents. The Stanford method extracts energy from the difference in concentration between two solutions by storing it chemically in batteries.

'The big pro is that they need no membranes, but they need a lot of surface area of electrodes' observes Bert Hamelers, head of the renewable energy group at Wageningen University in the Netherlands. Cui says that his nanorod electrode helps deliver that surface area.

The battery that electrochemically extracts energy that would be otherwise released as entropy
© ACS/Nano Letters

The battery extracts energy through sodium and chlorine ions' movements into and out of the crystal lattice of the electrodes. The battery discharges in seawater as chlorine is taken up by the silver electrode and sodium is taken up by the manganese dioxide electrode. The ions are released when the battery charges in freshwater.

Because of the higher ion concentration in seawater, the electrical energy discharged is greater than that needed for the battery to charge in freshwater. 'The reason we can gain this energy is we change the electrolyte,' Cui says.

Hamelers, whose membrane based approach for turning marine mixing entropy into electricity is 76 per cent efficient, welcomes the latest approach. 'As we cannot foresee all problems that might arise in future when developing these technologies, it is important to have more techniques available to harness this energy,' he says. Cui is excited by the battery's efficiency and hopes to further optimise its electrode materials and design. 'If we put the two electrodes closer I think we can get up to about 85 per cent,' he predicts.

Andy Extance
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2011/03/23

Microfluidics to diagnose sleeping sickness

22 March 2011

A simple and cheap device to diagnose sleeping sickness is a step closer according to scientists in Sweden.

Human African trypanosomiasis, or sleeping sickness, is caused by parasites in the blood called trypanosomes. The disease is transmitted by tsetse flies and is fatal is left untreated. Standard diagnosis is done by looking for the parasites in blood samples using a microscope. However, the concentration of parasites is often very low, so they need to be separated from the red blood cells before analysis. Many separation methods have been developed, but they are expensive and too complex to use in remote areas where the disease is common.

Jonas Tegenfeldt from the University of Lund, and his colleagues, have developed a microfluidic device that separates the parasites from the blood cells using their shape, because parasites and red blood cells are very difficult to separate by size.

Tegenfeldt and his team 'attacked the problem of separating parasite from blood by first determining a robust difference in intrinsic properties between trypanosomes and red blood cells, namely shape, and then they figured out how to adapt a nominally size-dependent separation device into one that can separate by shape,' explains Joel Voldman, an expert in microtechnology at the Massachussetts Institute of Technology, US.

Parasites (green) are separated from red blood cells in the device according to shape, not size

The researchers modified and tailored the depth of microfluidic devices known to separate particles according to size, making them able to discriminate particles by shape instead. In conventional size-separating devices, the particles flow through an array of posts that create narrow streams of different sizes. The particles that are too big to go through the smaller streams are filtered to bigger streams. The problem comes when trying to separate non-spherical particles (like parasites), as these can show different sizes depending on their orientation. Building these devices with a shallow depth (tailored to the size of the parasites), forces the particles to adopt a fixed orientation as they cannot rotate freely in the fluid, accentuating their different morphologies.

'The change in the device is minor, but it comes about through understanding the physics of separation,' adds Voldman.

The principle, says Tegenfeldt, could be applied to other diseases. He adds that 'there are many other neglected diseases identified by, for example, the Bill and Melinda Gates Foundation, in which simple microfluidics may make a difference'.

Amaya Camara-Campos
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2011/03/22

Origin of life experiments revisited

21 March 2011

Modern analysis of forgotten samples has given chemists in the US additional insights the origins of life on Earth.

Stanley Miller became famous with a single experiment carried out during his PhD thesis with Harold Urey. The experiment simulated conditions in a sealed apparatus, which according to Urey's previous work were believed to have predominated on the primeval Earth, including an ocean, a reducing atmosphere, and a spark discharge meant to simulate lightning. After only a few days, this experiment produced a rich mixture of organic molecules including some of the amino acids found in proteins today.

Miller's apparatus mimicked primeval earth

Over the next half-century, Miller continued to study prebiotic chemistry and possible origins of life in many variations but he never reached a definitive explanation of the origin of life.

Following Miller's death in May 2007, his former student Jeffrey Bada, a geochemist at the University of California at San Diego, inherited the contents of Miller's lab and office and discovered samples from 1958. The samples were clearly labelled and referenced in Miller's lab notebook but never reported. Bada's group has now analysed these samples using modern HPLC and mass spectrometry to gain two independent descriptions of their chemical composition.

The unreported (until now) 1958 experiment again involved a spark but the gas mixture included both reduced and oxidised substances and was the first experiment to contain hydrogen sulphide (H2S). Bada's team found that the unreported samples contained a greater abundance and variety of biologically relevant molecules than Miller had reported in his 1950s studies. The samples also contained oxidation products of the sulfur-containing amino acids cysteine and methionine, which Miller didn't report making until the 1970s.

While a gas mixture like the one Miller used in 1958 may not be representative of the Earth's early atmosphere overall, Bada and coworkers believe that it may well mimic the complex chemical conditions near volcanic sites.

The study 'demonstrates how the addition of hydrogen sulphide may have been important in producing a richer assortment of key building block such as amino acids,' says Bada. 'It seems increasingly apparent that volcanic plume chemistry may have played an important role in the synthesis of organic compounds on the early Earth.'

Bemused by the new findings from old samples, biochemist Kevin Plaxco from the University of California at Santa Barbara comments: 'Miller was such a pioneer that even now, four years after his death and more than 50 years after the experiments in question, his work is still yielding surprises.'

Michael Gross

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Seeing clearly with silicone

21 March 2011

School children in developing countries who have poor vision could soon see clearly thanks to cheap self-adjustable glasses that use silicone fluid to control the lens power. The glasses are being developed as part of an initiative called Child ViSion, a collaboration between the Centre of Vision for the Developing World (CVDW) in Oxford, UK, and Dow Corning - a global leader in silicone technology.

Improving the design of the self-adjustable glasses will allow manufacturing to be scaled up, while keeping costs down
© CVDW

The first fluid-filled adjustable eyeglasses were invented in the 1990s by Josh Silver, a physicist at the University of Oxford, and now director of CVDW. To date, over 30,000 pairs of the glasses, have been distributed to adults in several developing nations.

Around 100 million children require corrective eyewear in order to fully benefit from classroom education, but the developing world suffers from a lack of eye specialists needed to prescribe glasses. The CVDW, with the help of $3 million (£1.8 million) and support from Dow Corning, is now trying to address this problem.

'We haven't got the child specific device yet. That's something we're working on now,' says Silver. Currently, the glasses cost around $20 a pair, but Silver explains: 'The aim is to get the cost of this eyewear down to around a dollar in order to really make them accessible to large numbers of people.' The partnership reckons that improving the design will allow the manufacturing process to be scaled up while keeping costs down.

The glasses comprise tough polycarbonate lenses which each contain a silicone filled membrane. Each membrane is connected to a small syringe on each arm of the eyewear. All the user has to do to create their own prescription glasses is control a dial on each syringe which increases or reduces the amount of silicone fluid in the membranes, altering the power of each lens. Once the wearer is satisfied with the settings, the membrane can be sealed and the syringes removed.

'It's a very strong concept,' comments Bruce Moore at the New England College of Optometry in Boston, US. 'A large segment of the eye care professions believe that the only approach we ought to be utilising to provide universal care, for example in Africa, would be to produce a vast numbers of highly trained professionals,' he says. 'I have no problem with that, but somehow I don't think that's going to happen next year. I see this [adaptable eyewear] as at least a possibility of an interim solution.'

'This project is very much in its infancy and a lot of what we need to work out and move through is still to be developed,' says James Stevenson, Dow Corning's global healthcare marketing manager. 'A key part of this initiative is to create a business plan which will allow all the parties involved to understand both the technical and economic hurdles of scaling this to the hundred million pairs level.'

The initial goal is to design, manufacture and distribute 50,000 pairs of self-adjustable glasses to teenagers aged 12-18 in the developing world, primarily through and in support of education programmes.

James Urquhart

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2011/03/21

Amino acids flag risk of diabetes

20 March 2011

Raised levels of certain amino acids in the blood could flag up the possibility of someone developing diabetes later in life, researchers in the US have discovered. The finding provides another potential predictor for the risk of developing diabetes - along with obesity and abnormal blood sugar levels - and opens new avenues to investigating the fundamental biochemistry of how diabetes develops.

A team from Harvard University in Boston, led by Robert Gerszten and Thomas Wang, screened blood samples from people who had enrolled in a major medical project, called the Framingham Heart Study, in the early 1990s. Of 2,400 participants, around 200 developed type 2 diabetes during the following 12 years. The research team used mass spectrometry to analyse metabolites in the blood of the people who went on to develop diabetes, compared with a control population in the study, with similar characteristics but who did not develop the condition.
"We now need to figure out what is the cart and what is the horse"
- Robert Gerstzen
The scientists discovered that five amino acids - isoleucine, leucine, valine, tyrosine and phenylalanine - were likely to be at increased levels in the people who went on to develop diabetes, up to 12 years later, even though they had no other signs at the time. In particular, elevated levels of isoleucine, phenylalanine and tyrosine pointed to greater risk. Individuals with the highest level of these three metabolites had a four- to five-times greater risk of developing diabetes than those with the lowest levels.

The findings were confirmed by screening blood samples of participants in another long-term study in Sweden, some of whom also developed diabetes later in life.

Gerszten says that identifying people with higher risk of developing diabetes would allow intervention at an early stage to prevent or delay the condition, such as radical changes in lifestyle or the use of drugs.

'We now need to figure out what is the cart and what is the horse,' Gerszten says. 'In other words, are these early markers of the disease, or do they participate in the causal pathway that leads to the condition? We are currently investigating this.'

'This is some way off being considered a routine diagnostic test,' says Iain Frame, director of research at the charity Diabetes UK. 'But it nicely highlights the potential use of surrogate biomarkers in helping us to not only identify those at high risk of developing type 2 diabetes, but also to help shed light on the role of certain metabolites in promoting development of the disease.'

Simon Hadlington

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Simple salt removal to get fresh water

18 March 2011

Scientists in the US have developed a membrane-free, solvent extraction method to remove salt from seawater that works at low temperatures.

Access to clean, fresh water is a necessity. Unfortunately, supply is becoming over-stretched and there is a struggle to meet demand. As a result, the development of desalination technology (the conversion of salt water to fresh water) has become increasingly important.

Current desalination techniques require large amounts of energy or membranes that need to be changed constantly as they become blocked. Although significant advances have been made in these areas, Gang Chen and colleagues from the Massachusetts Institute of Technology, Cambridge, have gone a step further and removed the need for a membrane entirely.

The extraction method is membrane-free and needs less energy than current techniques

The team used decanoic acid as a solvent to mix with the water. 'Upon slight heating, our solvent dissolves the water out, leaving salts and impurities behind. Then, upon cooling, the mixture separates into two layers by gravity, releasing pure water. Unlike reverse osmosis, this method does not use expensive membranes and unlike evaporation processes, does not need heating to high temperatures,' explains Chen. The process was shown to be effective at temperatures as low as 40 degrees Celsius and the recovered water met the salinity standards set by the World Health Organisation and the US Environmental Protection Agency.

Adel Sharif, an expert in water engineering and director of the Centre for Osmosis Research and Applications at the University of Surrey, UK, believes that further research is needed in areas such as scalability and practicality, but believes that the concept has promise. 'The proposed desalination process has the potential for low environmental impact, since it uses low grade heat, and for low capital and operating costs,' he says.

Chen believes that the work opens up a new field of research in desalination. 'Being a simple, inexpensive process, directional solvent extraction also bears tremendous commercial potential in the desalination of seawater, clean-up of industrial waste water, treatment of water produced from oil and gas wells and other such uses,' he concludes.

Rebecca Brodie
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Digging deeper into bone fossils

18 March 2011

The accuracy of studies on ancient bones of interest to archaeologists and paleontologists can be improved thanks to a new procedure designed by scientists in France.

Ancient human and animal bones give us an idea of what the climate and environment were like throughout geological history. They can also give us information on past diets and lifestyles. Unfortunately, the changes that occur to bone once it has been buried in the ground, called diagenesis, can modify bone fossils and limit their use as proxies.

Matthieu Lebon, from the National Museum of Natural History in Paris, and colleagues, have applied a method currently used in modern biomedical applications called synchrotron radiation Fourier transform infrared (SR-FTIR) microspectroscopy, to understand the fossilisation process of ancient bone.

The team prepared samples for analysis by impregnating the bone with a resin and then cutting off very thin sections. This allowed them to sample sites within the bone, irrespective of the preservation state, without affecting the structure.

A thin section of fossil bone was analysed by SR-FTIR microspectroscopy

They then applied SR-FTIR microspectroscopy and found that they could determine the molecular composition and structural properties of the bone at the microscale, a resolution not possible with other techniques. They observed different patterns of collagen-phosphate ratios and crystallinity levels in the bone, which could help in understanding the different effects that diagenesis has on ancient bone, and also in selecting the best sections for carbon dating and palaeo-diet analysis.

'The information provided by fossil bone composition plays an increasing role in current archaeological and paleontological research. Understanding fossilisation processes and evaluating preservation state are crucial when selecting the sample or the part of the sample that can provide the more reliable information, particularly in the framework of palaeo-isotopic studies,' says Lebon.

Matthew Collins, from the University of York, UK, who studies the decay of archaeological materials comments: 'The team's work elegantly highlights the heterogeneous nature of bone decomposition and opens up the possibility to investigate patterns of bone diagenesis and molecular survival.'

Lebon hopes to apply the procedure to more varied fossil samples. The team's goal is to be able to model diagenesis according to specific climate and sediment in archaeological sites.

Rebecca Brodie

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Carbon capture with sawdust

18 March 2011

Plants may help to reduce carbon dioxide in the atmosphere when dead as well as alive, say scientists from Spain.

Carbon capture - the removal of CO2 from waste gases (such as from power plants) - is an important method for reducing CO2 emissions. One such strategy is the use of porous solids, such as zeolites and porous carbons, to absorb CO2 into their pores. However, these materials exhibit poor uptake capacities (about 3mmol CO2/g) and have complex and costly syntheses.

Now, Antonio Fuertes and his group at the National Institute of Carbon, Oviedo, have made a porous carbon material that performs better than other currently available ones, using a simple and inexpensive process. The major difference in this work, however, is that the raw material is sawdust.

The two step synthesis involves hydrothermal carbonisation of the sawdust, creating a hydrochar, which is then activated using potassium hydroxide. The KOH treatment creates pores in the sawdust structure by oxidation of carbon and carbon gasification from K2CO3 decomposition. These pores are responsible for the material's uptake capabilities, bestowing it with a capacity as high as 4.8mmol CO2/g. In addition, Fuertes' material has good selectivity for CO2 over N2, fast adsorption rates and can be easily regenerated.

Magnified image of sawdust before (left) and after (right) being heated and activated, showing the pores

'This type of carbonaceous material gives rise to an activated carbon that possesses textural properties that are appropriate for CO2 capture,' says Fuertes. 'What's more, the fabrication process is not complex and the raw material is abundant and widely available.'

Peter Styring, an expert in carbon capture technologies at the University of Sheffield says that the material has advantages over the currently most popular class of materials. 'They're comparable in terms of performance [to alkanolamines], but in terms of their engineering capabilities, these are superior,' he explains. 'With the alkanolamines, you get problems with corrosion, evaporation and degradation.'

Fuertes says that there is more work to be done before this technology can be commercialised, including investigations into scaling up. For now, he is focusing on other materials, such as nitrogen-doped carbons.

Yuandi Li
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Cool roof coating inspired by the poplar leaf

18 March 2011

Scientists in China have made a reflective coating with a structure that mimics the underside of a poplar tree leaf. The coating could be used on the outside of buildings to counteract the heating effect of carbon dioxide emissions, reducing the energy needed to cool the building from the inside.

Yanlin Song and colleagues from the Chinese Academy of Sciences, Beijing, mimicked the structure of the leaf's lower surface using polymers spun into reflective films consisting of long, hollow uniform fibres.

The underside of the poplar leaf is better at reflecting light than the top. This is because of the 'cool roof' effect, in which a layer of hairs on the underside reflects the light, so that less heat penetrates the leaf. The leaf turns over in strong sunlight to reveal the underside and as the light is being reflected rather than absorbed, the leaf appears white. 'Normally, the poplar tree looks green, but sometimes in the summer, the tree shows a white cast,' says Song.

The poplar leaf's hair structure (left) and the reflective coating with a magnified image showing one of the hollow fibres (right

The team discovered that controlling the film thickness and making the cross section of the fibres as similar to the leaf hair as possible is the key to high reflectivity. They tested their films by coating them onto the compound diarylethene, which changes from red to colourless in the presence of visible light - the structure changes from a closed ring to an open ring. They found that the coating stopped the diarylethene changing colour, and had the additional benefit of being hydrophobic.

'The reflectance and waterproof nature of the coatings make them ideal candidates for a number of building situations,' says Robert Lamb, an expert on surface science. 'Improving the durability of such delicate interfaces with the environment will be the major hurdle, but the alternative of sticking poplar leaves to our roofs to achieve the same effect is really not an option!'

Song says that his team will continue to develop highly reflective materials, widening the wavelength at which they function, to eventually be used to improve the efficiency of lighting.

Holly Sheahan
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The way to pain-free uterine disease detection

18 March 2011

A potential non-invasive method to detect endometriosis by acquiring a spectral signature of the uterus has been developed by scientists from the UK.

Francis Martin from Lancaster University and colleagues used infrared spectroscopy together with computational analysis to analyse the difference between uterine tissue affected by endometriosis and normal tissue in the uterus.

'Endometriosis [the growth of endometrial tissue outside the uterus] affects about 10 per cent of young women and can be associated with severe abdominal pain and could result in cancer,' says Martin. 'Currently, there is no non-invasive means of diagnosis; it is done by laparoscopic surgery,' Martin adds.

An image showing endometriosis of the ovary

Martin and his team analysed uterine samples from hysterectomy patients. They compared endometrial tissue growing outside the uterus with the endometrial tissue within the uterus using infrared spectroscopy to give a biochemical-cell fingerprint for each sample. They also compared the samples to tissue from endometriosis-free women. 'These IR spectra can then be processed using computational algorithms that allow one to quickly visualise the data to determine which spectra are similar or dissimilar to each other. Consequently, one can determine the normal tissue IR spectra and those outside this range may be determined as atypical,' explains Martin.

The team found that endometriotic tissue possesses a unique spectral signature and, more importantly, that the uterus of women with endometriosis express a signature distinct from that of the non-endometriotic uterus.

Martin hopes that the technique can be used on samples that can be obtained directly from patients in a non-invasive way. 'Screening cytology from the cervix is already well established. It is also possible to obtain cytology in a similar fashion from the uterus, or even small biopsies,' he says. He adds that cases of endometrial cancer are on the rise and this approach could be used as a cancer screening tool.

'Over the last few years, a great amount of work has been carried out to study cancer with Fourier Transform infrared (FTIR) spectroscopy. However, it is also important to apply this technique to the study of non-malignant diseases such as in this work,' says Josep Sulé-Suso, an expert in oncology from Keele University. 'The combination of FTIR spectroscopy with available diagnostic procedures for endometriosis should help in understanding the causes of this disease, leading to the development of effective therapies,' he adds.

Elinor Richards

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Hydrazine fuels hydrogen power hopes

17 March 2011

Renowned as a rocket propellant, hydrazine could also push forward the development of hydrogen fuel cells for powering vehicles say US-based researchers. Andrew Sutton from Los Alamos National Laboratory (LANL), New Mexico, and colleagues use the chemical to improve the regeneration of spent ammonia borane (AB) hydrogen storage material. 'It definitely makes the regeneration easier' explains Sutton, whose technique uses a few simple reagents to convert the spent material back to ammonia borane with high efficiency. 'That's a significant advance'

Ammonia borane (left) releases hydrogen and becomes polyborazylene (right), hydrazine and ammonia can regenerate the AB. credit= Josh Smith, Los Alamos National Laboratory

AB contains about 20 per cent hydrogen by weight and can release over two equivalents of molecular hydrogen per molecule. As it does this it forms a polyborazylene (PB) polymer residue. According to Sutton, AB is a good potential hydrogen storage material because it is stable at ambient temperature and doesn't require external cooling to keep hydrogen in or high temperatures to evolve hydrogen. But for AB to controllably deliver hydrogen and be used commercially it must be regenerated from PB. The University of Oxford's Martin Jones calls this the 'the most significant problem associated with using ammonia borane as a hydrogen storage material'.

LANL had previously used ortho-benzenedithiol and tin hydride to regenerate AB. However Dow Chemical, LANL's industrial partners in the US Department of Energy's Chemical Hydrogen Storage Center of Excellence, found a practical flaw in this approach. 'Pushing large amounts of tin around was going to be quite expensive, because it's got considerable mass,' Sutton says. 'That got me thinking about a lighter reducing agent.'

Now, the LANL team and researchers from the University of Alabama show that hydrazine in liquid ammonia can almost quantitatively regenerate AB. The idea is that this regeneration would be centralized and at an industrial scale, not aboard individual vehicles, notes Sutton.

Jones, who has worked with the International Partnership for the Hydrogen Economy, notes that AB is just one of several materials that show 'high promise' for hydrogen storage. 'Other issues remain, but this certainly places it high on the list of materials that might, in time, find commercial applications,' he says.

But Sutton is convinced. 'As an initial hydrogen storage material, AB is good,' Sutton underlines. 'Once you throw in this one-step efficient regeneration, that just adds to its value.'

Andy Extance

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Uncertainty for nuclear power

17 March 2011

Ned Stafford/Hamburg, Germany

As workers battle to cool down damaged Fukushima Daiichi nuclear power plant reactors after the devastating earthquake and tsunami that struck Japan on 11 March, the potential environmental impact from the release of radioactive material remains uncertain. Already political fallout from the disaster has spread to Europe and will no doubt have a lasting impact on nuclear power policy and research funding.

Four days after the earthquake, German chancellor Angela Merkel announced that seven nuclear power plants, that began operating before 1980, will be shut down for safety review until at least June. The closures reverse a controversial decision made last year by Merkel's coalition government to extend the life of older nuclear power plants. And France, where nuclear power provides 80 per cent of total electricity supply, announced safety tests on its 58 reactors.

Francis Livens, research director at Dalton Nuclear Institute at the University of Manchester, UK, told Chemistry World that the global impact of the damaged Fukushima Daiichi power plant depends on how the situation develops. 'If the situation gets no worse and everything is brought back under control over the next few days, then there will be an argument that the reactors did their job,' he says. 'If the situation deteriorates further, then it will depend on just what the end result is, so one can't say at this point. However, I would be astonished if public perception of nuclear power as a risky technology hasn't increased.'

Radioactive contamination by the nuclear reactor problems at Fukushima Daiichi nuclear power plant are not as serious as Chernobyl
© DigitalGlobe / Getty Images

Mats Jonsson, head of nuclear chemistry at the Royal Institute of Technology in Stockholm, says: 'From what we have seen so far, this situation will initiate discussions and debates concerning the safety of nuclear power in Europe and in the rest of the world. My guess is that chemistry, as well as related research fields, could switch from chemical problems in new reactor types and reprocessing, to issues more related to safety and the environmental impact of nuclear energy.'

Some experts fear the severity of the Fukushima Daiichi accident could approach the level of the Chernobyl nuclear plant disaster in the Ukraine. In April 1986 during a routine systems test a power surge followed by an attempted emergency shutdown triggered a series of explosions and the release of radioactive fallout over a large area. Yoshihito Watanabe, a chemist and vice president at Nagoya University in Japan, tells Chemistry World that, thus far, 'radioactive contamination by the nuclear reactor problems are not so serious.'

Depending on the outcome of the attempts to cool down Fukushima Daiichi nuclear power plant, the major problem now is the physical damage from the earthquake and tsunami, he says. Toyota, Honda, and other automotive manufacturers have had to stop production due to automotive part shortages and Tohoku University in Sendai suffered major damage to research facilities. It is far too early to speculate what the effect might be on Japanese research, he says, adding: 'The first priority for the government to consider right now is how to support the recovery of the earthquake area, including the lifeline, construction of houses, reconstruction of factories, offices and so on.'

The future for nuclear power policy in Japan also remains uncertain, he says. 'Currently, people even who are against the nuclear power policy are quiet on this issue, because so many people are working hard to stop the current troubles at Fukushima Daiichi nuclear power plant under very dangerous and risky conditions.'

The Japanese people are highly appreciative of the global outpouring of support and sympathy in the wake of the earthquake, he says, adding that the embattled nation will persevere.

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Cleaning up nuclear storage ponds

17 March 2011

UK scientists have analysed the chemistry taking place in storage ponds at nuclear power sites, such as Sellafield, to come up with a way to remove radioactive waste as nuclear regulatory bodies are pressing on the nuclear industry to clean up the ponds.

Storage ponds are used to store spent Magnox rods, which are uranium fuel rods covered by a magnesium-aluminium alloy cladding. The rods contain large amounts of fission products, which are highly reactive. The ponds are maintained to minimise corrosion of the rods, but the cladding corrodes in water, creating fine particle sludge. 'The sludge in one of these ponds is estimated to contain tonnes of fuel debris including considerable quantities of plutonium,' says Stephen Parry from the University of Manchester.

Parry, together with his colleagues, made a model of Magnox storage pond liquor to study how plutonium interacts with the corroded Magnox sludge to find a way of removing the plutonium before the ponds are emptied.

Their pond consisted of plutonium, a sludge simulant, sodium carbonate, polyelectrolyte and silica to replicate real conditions. One component of the sludge is brucite (magnesium hydroxide), which sequesters plutonium, forming a colloid. This is soluble at neutral and acidic pH, meaning that the plutonium's mobility in the ponds is enhanced.

A magnified image of nuclear storage pond sludge showing brucite crystals, which sequester plutonium, making it difficult to remove from the mixture

'One potential problem is the risk that disturbing the sludge will release fine, plutonium-containing particles in the effluent from the ponds. Pond effluents are treated before discharge into the sea under authorisation, but we need to be sure that the treatment process will effectively remove plutonium from the effluents before we can start to empty them,' explains Parry.

The team found that a low carbonate concentration, high CMS concentration and high polyelectrolyte concentration resulted in almost all of the plutonium being filtered.

'The work we have done, supported by the site operators and the EPSRC, shows that it is possible to optimise effluent treatment and also which steps in the treatment process are the most important in ensuring efficient plutonium removal, helping to open the way to removal of the sludge,' concludes Parry.

Nick Evans, an expert in radiochemistry from the University of Loughborough, UK, says that the study contributes to the body of knowledge about how sludge should be treated. 'A lot of research is being done now and the nuclear decommissioning authority is being more proactive, as at Sellafield [nuclear decommissioning, reprocessing and waste management site], but there hasn't been much work on this in the past, particularly with regards to difficult materials like plutonium,' he says. 'The work should be useful for Sellafield for dealing with these problematic sludges.'

Parry and his team are working on immobilising the sludges so that they can be stored safely before disposal.

Elinor Richards

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International recognition helps Chinese vaccine industry

17 March 2011

Hepeng Jia/Beijing, China

Vaccines made in China will now be supplied through United Nations (UN) agencies to developing countries, after recognition from the World Health Organisation (WHO) that China's State Food and Drug Administration (SFDA) has complied with international standards for vaccine regulation.

'It is a validation of the capability of the Chinese regulatory authority to ensure that vaccines released onto the market are of assured quality,' says Michael O'Leary, a WHO China representative.

According to the SFDA, China has 36 vaccine producers that collectively produce 49 vaccines for 27 diseases, with an annual output capacity for up to one billion doses, most of which are cheaper than their domestic counterparts. For example, the price approved by China's National Development and Reform Commission for the combined measles, mumps and rubella (MMR) vaccine, is Yuan20.8 (US$3.2) per dose. This is only one fifth of the price approved by the US Centre for Disease Control and Prevention (CDC).

'The WHO's approval does not mean that previously China did not have a well regulated vaccine industry. It is mainly a precondition to enter the international market,' says Liang Xiaofeng, director of the national vaccination office at the China CDC.

The WHO's vaccine approval is a precondition to enter the international market

To Liang and his colleagues, the acknowledgement may reduce public mistrust of domestic vaccines after widespread reports of several vaccine related scandals and accidents, which have posed a serious challenge to China's national vaccination campaign.

In March 2010, the problematic vaccine logistic system in Shanxi Province was blamed for causing the sickness and deaths of more than 100 children. Though the government denied the link, public confidence has been seriously eroded, and together with reports of sub-standard rabies vaccines in May 2010, there was less compliance from the public in a nationwide vaccination campaign to eliminate measles in September 2010.

'The WHO approval will help domestic vaccines to regain public trust, benefiting the industry,' says Liu Peicheng, a spokesperson of Beijing Sinovac, which has developed the world's first vaccines for SARS (Severe Acute Respiratory Syndrome) and the H1N1 strain of influenza. The acknowledgement on China's regulatory system is a precondition that could lead to the UN purchasing individual vaccines from Chinese vaccine makers. For this to occur, the manufacturers have to pass the approval for China's new version of GMP (Good Manufacturing Practice) for the Chinese pharmaceutical industry that was released at the end of February.

'As well as the new GMP, the acknowledgement and the subsequent approval of individual vaccines will certainly help strengthen our industry,' Liu tells Chemistry World.

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Monitoring oil sand toxicity

16 March 2011

Researchers in the UK and Canada have identified for the first time some of the individual components of toxic naphthenic acid mixtures present in waste water from oil sands.

Oil sands are large natural deposits that contain sand, clay, water and bitumen - an extremely viscous form of petroleum. Separating the bitumen from the sand requires an extraction process that uses large amounts of water - between two and four barrels of water for each barrel of bitumen - producing large volumes of toxic waste water.

These latest findings could help understand the toxic naphthenic acid (NA) mixtures in that waste water. The findings boost the prospect of improving much sought after environmental monitoring programmes.

Athabasca oil sands Nasa Earth Observatory image by Jesse Allen and Robert Simmon using EO-1 ALI data courtesy of the Nasa EO-1 team

The Athabasca oil sands in the Canadian province of Alberta are the world's largest oil sands and represent some 174 billion barrels of bitumen that can be turned into synthetic oil. The waste water generated is either recycled back into the processing or stored under a 'zero-discharge' policy in large lagoons called tailings ponds.

'Identifying individual components within this mixture has proven quite difficult because of the similarities between structural conformations, as well as the sheer number of compounds contained within the acidic fraction of oil sands process-affected water,' says Richard Frank at the Aquatic Ecosystems Protection Research Division of Environment Canada, Burlington, Ontario, who conducted the research with Steven Rowland's lab at the University of Plymouth, UK.

Using two dimensional gas chromatography and time of flight mass spectometry, the team studied methyl ester derivatives of oil sands process water (OSPW) acid-extractable matter. The chromatographic method gave a high enough resolution of hundreds of the components, enabling the mass spectral identification of numerous tricyclic diamondoid acids, which the team suggests is indicative of significant biodegredation.

Since toxic action is frequently determined by structure, identifying the NA structures in the OSPW is crucial. Not knowing the structures has made it difficult to monitor the potential leaching of NA from tailing ponds into surface waters. Furthermore, the oil sands are known to leak naturally into the environment, so there is a need to differentiate between industrial and natural contaminates.

'The advancement of naphthenic acid analysis presented in this study will allow for a better understanding of the complexity of this poorly understood mixture,' says Frank.

Mark Barrow, who investigates petroleum-related and environmental samples at the University of Warwick, UK, says the work makes a valuable contribution to environmental monitoring of oil sands. 'Just as establishing the sizes and molecular formulas of the organic acids has been vital, there is a need for greater insight into the structures of these compounds,' says Barrow, 'the structures will be important in determining toxicity towards aquatic organisms.'

James Urquhart
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The explosive potential of nitrogen compounds

16 March 2011

Two separate groups have looked at the explosive potential of nitrogen compounds but while one group made an incredibly explosive compound, the others have developed a safer synthetic route for tetrazoles.

In Germany, Thomas Klapötke and Davin Piercey of the University of Munich hoped to make a green alternative primary explosive using a chain of 10 nitrogens. However, the new compound is much more explosive than anticipated and can only really be of interest for refining models.

Currently, lead azide is used to initiate large amounts of secondary explosives like dynamite but it has the unfortunate side effect of being toxic. Klapötke and Piercey have been trying to find green/non-toxic replacements for lead azide and were inspired to investigate long-chain nitrogen compounds by a surprisingly stable eight-nitrogen compound.

The pair hoped that a 10-nitrogen chain compound would be slightly more sensitive. However, the bis tetrazole joined by an azo linkage proved to be so explosive that the dry compound easily exploded, destroying glassware and setting off further explosions as glass shrapnel hit other samples of the compound around the lab.


The new compound shattered glassware around the lab

'It was a bit of a surprise to see how sensitive it was,' says Piercey, quickly adding that the compound was always handled carefully so that the accidental explosions 'were only an inconvenience.'

Timothy Jamison at the Massachusetts Institute of Technology, Cambridge, US, describes the molecule as 'really impressive'. Jamison has recently developed a flow reactor that makes the manufacture of tetrazoles (the precoursors of Klapötke and Piercey's compound) safer and thinks that he could in theory make the 10-nitrogen compound using a modified system although given the compound's sensitivity 'we probably won't'.

As well as being used to make explosives, tetrazoles are used in many industrial applications, from catalysis to medicinal chemistry. The problem is that tetrazole manufacture can itself be explosive as hydrazoic acid is produced.

Jamison has bypassed this problem by using flow so that there is no place for any hydrazoic acid to collect. With this approach, Jamison can use high temperatures and pressures to produce high yields of tetrazoles using chemistry that would otherwise not be viable.

As Jamison investigated the process further he found that it could be made simpler to run and scaled up to an industrial scale. He has shown that scaling up the process by a factor of 10 should yield around 40 kilos of product annually, which he suggests would be enough for a global supply of some products.

This is Jamison's first bit of tetrazole chemistry, but his interest in tetrazoles grew out of a collaboration with Novartis. Now that he has developed an interest in azide chemistry in general, Jamison's group is looking to develop some other azide reactions using flow.

Jamison's flow method would not necessarily help Klapötke and Piercey's work, since their compound is mainly dangerous when dry. But Pierecy does suggest that the flow reactor would be 'very useful' for the manufacture of tetrazole precursors.

Despite the reactor's usefulness, Piercey and Klapötke have no desire to keep making longer and longer nitrogen chain compounds. Instead, Piercey concludes: 'as always, the focus is on practical compounds to replace currently used secondary and primary explosives with focus on safer, cheaper, greener, higher performing materials.'

Laura Howes
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2011/03/16

Benlysta breaks 50 year Lupus drug drought

15 March 2011

The first new treatment for lupus erythematosus in half a century has been approved by the US Food and Drug Administration (FDA).

Benlysta (benlimumab) is a monoclonal antibody that was developed by US biotech Human Genome Sciences from antibodies provided by Cambridge Antibody Technology in the UK, and commercialised in collaboration with GlaxoSmithKline. It acts against B-lymphocyte stimulator, a protein that is thought to increase production of white blood cells that attack healthy tissue, and which is present in elevated levels in lupus patients.

Lupus is often characterised by skin lesions
© Scott Camazine / Science Photo Library

The cause of the autoimmune disease is unknown, which has made it difficult to find a target for drug treatment. Current therapy relies on preventing flare-ups of the disease occurring, and reducing their severity and duration when they do. Many patients rely on steroids, and also take drugs designed to treat rheumatoid arthritis, another autoimmune disease, and even antimalarial drugs - the last drug to be licensed for lupus, in 1955, was the antimalarial plaquenil (hydroxychloroquine).

Analysts are predicting blockbuster status for the drug - annual sales of anywhere between $3 million and $7 million (£1.9-4.4 million) have been estimated, with the annual price per patient expected to be around $35,000. But it is not the solution for all lupus sufferers. It does not work in all forms of the disease, and while Phase III trials showed an improvement in patients given the antibody on top of standard therapy, it remains unclear whether it actually reduces the number of severe flare-ups. It also appeared to be less effective in black patients, in whom the incidence of lupus is higher, and further trials will be carried out in this group.

Despite these limitations, its approval has been welcomed. 'It is the first drug ever to be specifically developed to treat lupus,' said Sandra Raymond, president and chief executive of the Lupus Foundation of America. 'It is a significant first step toward reaching our goal of developing an arsenal of new, safe, effective, and tolerable treatments.'

Sarah Houlton
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2011/03/15

China bans whitening additives in flour

14 March 2011

By Hepeng Jia/Beijing, China

After strong public pressure, China will ban the use of wheat flour whiteners in May. Although analysts say the ban will not affect other food additives in the short term, the policy may hamper research and development (R&D) in the field.

Whiteners to be banned include benzoyl peroxide and calcium peroxide, which whiten flour through oxidation. When ingested in large amounts, the chemicals are harmful to the respiratory system and can cause sensitisation.

On 1 March, the Chinese Ministry of Health, together with six other ministries, released a notice to withdraw food additive licenses for benzoyl peroxide and calcium peroxide and ban their production and application as food additives. 'The debate on four whiteners has lasted for more than 10 years. Although at the current maximum level there is no clear evidence to prove their harm, the government takes a low-risk principle to ban its uses,' says Dong Jinshi, director of the Beijing Kaifa Environment Protection Technology Centre.

Benzoyl peroxide and calcium peroxide are seen as unnecessary food additives in flour

In China, the legal level of benzoyl peroxide or calcium peroxide as additives is no more than 60mg/kg, which is much lower than international levels - for example in Canada the legal level is 150mg/kg. But despite the low maximum level in China, the rule is often broken by flour manufacturers because it doesn't whiten the flour effectively. 'Actually, the additives are seriously abused. Chinese producers and consumers like the white colour too much,' says Yu Jianping, a manager of Shanghai Yiyuan Company, a leading food additive developer.

In December 2010, 90 per cent of the Chinese public opposed the use of additives, in a nationwide poll on flour whiteners. 'We will stop adopting any unnecessary food additives,' Health Minister Chen Zhu told a press conference, held during the ongoing plenary meeting of China's parliament, the National People's Congress.

Chinese media outlets have widely interpreted the ban of the whiteners as a signal to abolish more additives. 'The ban is more like a move to appease the public,' Yu tells Chemistry World. 'Chinese manufacturers have pursued the appearance, the low costs, the long preservation and the early maturity of food too much, which are impossible without food additives.'

'The research into food additives will be halted because developers will worry about the government's reluctance to approve new additives,' says Dong. Although food additive levels are being abused, Dong still suggested that any ban should be made cautiously and with more evidence. When there is no clear evidence, the best option is to highlight the use of controversial additives in food and let consumers make their own choices, he says.

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2011/03/13

Drawing batteries

11 March 2011

Scientists in Japan have made an electrode for a lithium-air battery using a pencil. The advance could bring efficient, environmentally friendly and safe batteries for electric vehicles a step closer.

Lithium-air batteries have the potential to produce enough energy to power an electric vehicle, but the amount of energy is a safety concern. Contamination in lithium batteries can result in unstable and high energy reactions, and the current lithium-air batteries are vulnerable to decomposition and burn-out.

Haoshen Zhou and Yonggang Wang at the National Institute of Advanced Industrial Science and Technology in Tsukuba, have designed a battery in which the lithium is encapsulated by an organic electrolyte topped with a ceramic protection layer. The ceramic layer acts as a solid-state electrolyte upon which the team simply drew a 2D cathode using a graphite pencil. Zhou says that 'removing and redrawing the novel air electrode is simple.'

Safer batteries for electric vehicles could be down to the graphite in a pencil

During the discharge process, lithium at the anode surface is converted into lithium ions. Simultaneously, lithium ions in the electrolyte solution pass across the ceramic layer and combine with oxygen in the air to form LixOy within the pencil trace. The battery was able to go through 15 charge-discharge cycles without losing its capacity. This is a lower number of cycles than current batteries, but the design promises a much higher potential energy and can be recharged simply by redrawing the cathode with the pencil.

'Using a solid state electrolyte suppresses detrimental side reactions encountered when using liquid organic electrolytes, improving cyclic stability,' explains Leela Mohana Reddy Arava, an expert in lithium battery technology at Rice University, US. He adds that 'drawing electrode materials onto the surface of a solid electrolyte is an innovative approach'.

Zhou and Wang intend to improve their battery's recyclability, making recharging more efficient.

Harriet Brewerton

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Making baby food safer

11 March 2011

Scientists from Spain have used a lab on a chip device to quickly analyse levels of zearalenone, a contaminant, in infant foods with a detection limit below legislative requirements.

Alberto Escarpa and his team from Alcala University, in Madrid, have made a microfluidic device that can detect zearalenone levels to 0.4ug/l-1, well below the maximum legal amount of 20ug/kg-1.

Zearalenone is a metabolite from fungi found in cereal crops, such as maize, barley, oats, wheat and rice. It can be a risk to humans because it causes infertility and has been linked to cervical cancer. Current methods used to detect the compound involve two separate steps - an immunoassay followed by detection using techniques such as thin-layer chromatography or mass spectrometry.

Escarpa's team designed a microdevice that combines the two stages in two separate chambers on a glass microchip. They injected a food sample into an immunological reaction chamber where zearalenone, in the sample, competes with an enzyme-bound zearalenone in the system to bind to antibodies attached to protein-coated magnetic beads. The beads were then guided towards an enzymatic reaction chamber using a magnet. Here, the enzymes catalyse an oxidation reaction. The response current produced is proportional to the enzymes' activity and also to the amount of zearalenone in the sample.

The food sample passes through two separate chambers in the device, an immunological reaction chamber and an enzyme reaction chamber

'Such lab on a chip devices are important from the standpoint of saving time, money and expensive reagents and don't need a skilled operator,' says Escarpa. This highly sensitive and selective chip, he adds 'avoids the laborious and time-consuming procedures associated with conventional immunoassays'.

'This is useful for a problem that is otherwise quite expensive to solve. Usually, the food has to be taken away to be analysed, which takes a long time, but this device can do it in a few minutes,' says Martin Pumera, an expert in electrochemistry and biological chemistry at Nanyang Technological University in Singapore. He adds that as the detector has been miniaturised, it could be integrated into a mobile phone sized device, increasing its applicability.

In the future, Escarpa hopes to automate the sampling and sample pretreatment steps too.

Elinor Richards

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Out of the blue - a new phosphor for flat screen displays

11 March 2011

Materials chemists in China have developed a compound that they believe should improve the quality of field emission displays (FEDs), bringing applications a step closer. FEDs have, for a number of years, been a promising technology for flat panel displays, but progress has been hampered by the display quality.

Jun Lin at the Chinese Academy of Sciences, Changchun, and colleagues developed a phosphor with promising colour properties for FED applications. Phosphors are materials that emit light of a particular wavelength when struck by an electron. They have long been used in cathode ray tubes, and have more recently found application in FEDs. These work by a very similar principle to cathode ray tubes, but instead of a single electron source, a grid of tiny electron sources is used, making flat-panel displays possible.

FEDs have numerous advantages over other flat panel technologies, such as the plasma and liquid crystal displays commonly used in TVs and computer monitors. These advantages include lower energy consumption, wide viewing angle, good contrast ratio and wide working temperature range. However, the phosphors for FEDs need to work at lower voltages than those in cathode ray tubes, and developing low voltage phosphors with suitable colour characteristics has hindered uptake of the technology.

The triangle and quadrangle show the typical and enlarged colour range for FED phosphors, respectively

The phosphor developed by Lin's team is based on Mg2SnO4, previously known as a good base material for phosphors. By doping it with Mn2+ and Ti4+, they created a phosphor with a pure blue colour that works at low voltages. Lin says that the colour emitted is out of the range of the FED phosphors developed so far, giving it 'potential to increase the display quality of full-colour FEDs'. Importantly, he adds, the colour could be adjusted from green to blue simply by changing the concentrations of the two dopants.

Lin concludes that 'FEDs have been recognised as one of the most promising technologies in the flat panel display market,' and that improvements such as theirs will 'make the technology more viable in the future'.

Markku Leskelä, an inorganic chemist at the University of Helsinki, Finland, says that 'blue colour is one of the limiting factors in fabrication of full-color field emission displays, and this is an interesting new material, which has potential.' However, he also notes that the stability would need to be improved for practical applications. 'The 8 per cent decrease in intensity observed over one hour would be a problem in real devices,' he says.

David Barden

RSC

Aerosol data from BP spill

10 March 2011

The oil slick in the Gulf of Mexico last summer provided a unique opportunity to study, in the field, the air quality effects of two widespread types of pollutants. Analysis of atmospheric data suggests that emissions of intermediate volatile organic compounds (IVOCs) and semi-volatile organic compounds (SVOCs) were low compared with those of volatile organic compounds (VOCs). But crucially those emissions led to the formation of microscopic aerosol droplets, a finding that could affect how these pollutants are managed in urban settings.

Checking the instruments onboard the NOAA 'hurricane hunter', diverted from a mission in California to collect data above the oil
© Morgan Heim

The Deepwater Horizon drilling unit, owned by oil super major BP, blew out on 20 April 2010, and by mid-June, the gushing well had generated an oil slick over 100 miles wide. On 8 June, and then again on 10 June, five scientists from the National Oceanic and Atmospheric Administration (NOAA) shared a plane with over 20 chemical instruments on a looping tour of the slick, collecting air quality data. A few of these instruments measured organic compounds and organic aerosol concentrations.

Commenting on the research, Hugh Coe from the University of Manchester says 'it's been very difficult to unpick the roles of these intermediate volatility compounds from those of higher volatility compounds.' IVOCs tend to be produced together with VOCs and SVOCs in, for example, the combustion of fossil fuels. They are also naturally produced by forests. According to Joost de Gouw of the NOAA, by the time IVOCs condense into microscopic droplets, they have typically acquired functional groups, or otherwise combined, until only about ten per cent of the original compounds are identifiable.

However, computer simulations of aerosol formation have shown that 'IVOCs may be one of the most important sources of organic particles during summertime air pollution episodes,' says Spyros Pandis of Carnegie Mellon University in Pittsburgh, US. Pandis modelled this phenomenon in European cities, and he says that the work by de Gouw's team provides the first strong evidence from atmospheric observation that IVOCs create significant amounts of particulate matter

The Deepwater Horizon slick separated the volatile compounds as it spread, creating an ideal study site. VOCs are relatively small molecules, typically containing fewer than 10 carbon atoms, and the ones from the slick evaporated within ten hours. With between 10 and 20 carbon atoms, the IVOCS required between 10 hours and four days to get airborne, and the SVOCs, with over 20 carbon atoms, took even longer.

The separation of compounds at the water surface enabled the researchers pin down the source of the aerosol
© Science/AAAS

In the atmosphere, however, the IVOCs and SVOCs condensed into droplets. The data taken on the plane suggests that, downwind of the spill site, the amount of organic aerosol increased, as did the typical droplet mass - indicating that the freshly-evaporated hydrocarbons formed an aerosol. Matching their data to a simulation of hydrocarbons evaporating from the oil slick, the team found that alkane chains containing 14 to 16 carbon atoms were probably the greatest contributors.

These molecules have higher weights than most environmental laws address, and de Gouw says that the IVOCs particularly merit further investigation. 'What we need to do next is focus on these species and determine how this chemistry works in urban air,' he says.

Kate McAlpine

RSC