Monday, September 5, 2011

Screens set to go green

Fitting the screens of electronic devices, such as televisions and smartphones, with a new display technology called 'organic light-emitting diodes' (OLEDs) will reduce their energy consumption, but such screens currently require rare and expensive metal components. Now, Masahisa Osawa and his colleagues at the RIKEN Innovation Center in Wako, along with researchers from electronics company Canon, have found a way to replace these costly metals with copper.


In addition to offering significant energy savings over conventional LCD-based displays, OLED screens improve picture quality by producing richer blacks; they also offer a wider viewing angle. In an LCD screen, each pixel is effectively a little filter, selectively blocking light produced by a large backlight. In an , however, each pixel is a tiny light emitter such that no backlight is needed. This means that pixels in dark areas of the image consume no power, reducing energy use.


To maximize the energy-saving benefit, screen makers select OLED materials that most efficiently convert electrical current into light, a property known as high external (EQE). Some of the best materials are phosphorescent , but these are typically composed of rare and expensive metals such as iridium.


Copper complexes have long been known as potential alternatives, and would cost 1/2,000th that of iridium phosphors, according to Osawa. Until the work of Osawa and his colleagues, however, these copper complexes had a low EQE. Such complexes can be readily excited into a high-energy state, but they tend to physically distort, which dissipates their extra energy rather than emitting it as light.


The researchers resolved this problem by altering the molecular environment in which the copper sits. They wrapped each copper ion inside a newly designed bulky organic ligand. They then conducted X-ray diffraction studies, which revealed that the ligand had forced the copper to become three-coordinate—it had formed three bonds to the ligand, rather than the usual four (Fig. 1).


Osawa and colleagues also demonstrated that the EQE of their green-light-emitting copper complex increased dramatically and matched that of iridium complexes. “The three-coordinate structure is a crucial factor for high EQE, because it hardly distorts in the excited state,” Osawa explains.


The team’s next step will be to deploy the complex in a working device. Copper might not be limited to producing green light, Osawa adds. “Our goal is to make red-, green-, and blue-colored phosphorescent three-coordinate materials.”


More information: Hashimoto, M., Igawa, S., Yashima, M., Kawata, I., Hoshino, M. & Osawa, M. Highly efficient green organic light-emitting diodes containing luminescent three-coordinate copper(I) complexes. Journal of the American Chemical Society 133, 10348–10351 (2011). http://pubs.acs.or … 21/ja202965y


Provided by RIKEN (news : web)

Improved method for capturing proteins holds promise for biomedical research

Antibodies are the backbone of the immune system—capable of targeting proteins associated with infection and disease. They are also vital tools for biomedical research, the development of diagnostic tests and for new therapeutic remedies.


Producing antibodies suitable for research however, has often been a difficult, costly and laborious undertaking.


Now, John Chaput and his colleagues at the Biodesign Institute at Arizona State University have developed a new way of producing antibody-like binding agents and rapidly optimizing their affinity for their target proteins. Such capture reagents are vital for revealing the subtleties of function, and may pave the way for improved methods of detecting and treating a broad range of diseases.


The team's results appear in today's issue of the journal ChemBioChem.


Antibodies are Y-shaped structures, capable of binding in two or more places with specific target proteins. Synthetic antibodies are much simpler forms that attempt to mimic this behavior. As Chaput explains, creating affinity reagents with strong binding properties can be accomplished by combining two weak affinity segments on a synthetic scaffold. The resulting affinity reagent, if properly constructed, can amplify the binding properties of the individual segments by two or three orders of magnitude.


"This dramatic change in affinity has the ability to transform ordinary molecules into a high affinity synthetic antibody," Chaput says. "Unfortunately, the chemistry used to make these reagents can be quite challenging and often requires a lot of trial-and-error. With NIH funding, my group has reduced the complexity of this problem to simple chemistry that is user friendly and easily amenable to high throughput automation. Such technology is absolutely necessary if we want to compete with traditional monoclonal antibody technology. "


Traditionally, antibodies for research have been extracted from animals induced to produce them in response to various protein antigens. While the technique has been invaluable to medical science, obtaining antibodies in this way is a cumbersome and costly endeavor. Instead, Chaput and his team produce synthetic antibodies that do not require cell culture, in vitro selection or the application of complex chemistry. They call their reagents DNA synbodies.


The new strategy—referred to as LINC (for Ligand Interaction by Nucleotide Conjugates) uses DNA as a programmable scaffold to determine the optimal distance needed to transform two weak affinity binding segments or ligands into a single high affinity protein capture reagent. The result is an artificial antibody, capable of binding to its antigen target with both high affinity and high specificity. The process is rapid and inexpensive. It also offers considerable flexibility, as the distance between the two ligand components bonded to the short, double-stranded DNA scaffold can be fine-tuned for optimum affinity.


In earlier work, the group identified ligand candidates by producing thousands of random sequence peptide chains—strings of amino acids, connected like pearls on a necklace. The peptide sequences were affixed to a glass microarray slide and screened against a target protein to pinpoint those that were capable of recognizing distinct protein binding sites. Two promising ligand candidates could then be combined to form a DNA synbody.


In the current study, the group instead makes use of pre-existing ligands with documented affinity for various disease-related proteins. The method involves the use of well-characterized ligands as building components for high quality DNA synbodies, eliminating the initial screening procedure and expanding the potential to tinker with the two-piece synbody in order to optimize affinity.


The peptides of choice for the study were those with high affinity for something called growth factor receptor bound protein 2 (Grb2). Grb2 has many cell-signaling functions and is an important focus of research due to its association with cellular pathways involved in tumor growth and metastasis.


By scouring the scientific literature, the group identified two peptides that recognize distinct sites on the surface of Grb2. Chaput points out, "this is a nice example where a few hours in the library can save you weeks in the lab."


The next step was to create an assortment of synbody constructs based on these peptides. To do this, one peptide was attached to the end of a short DNA strand, while the other peptide was attached to the complementary DNA strand further along its length (see figure 1).


The two peptide strands could be attached to the scaffold in either a forward or reverse direction and could be interchanged, with either occupying the terminal end of the first DNA strand. Further, the distance between peptide segments along the DNA strands could be adjusted to yield the best target affinity.


Experiments examined binding affinity for peptide chains separated by 3, 6, 9, 12, 15 and 18 base pairs along the DNA strand, (a distance range of 1.0-6.1 nm). Inspection revealed the best results for a synbody constructed of peptides separated by 12 base pairs at a distance of 4.1 nm, compared with the other 5 constructs.


The results for the best synbody in the study were impressive, demonstrating a binding affinity five- to ten-fold stronger than commercially available for Grb2, despite the synbody's comparatively primitive architecture. In further tests, the synbody was shown to exhibit high specificity—isolating Grb2 from other proteins in a complex biological mixture and selectively binding with its target.


The technique offers a new approach to producing high qualityaffinity reagents for disease research, diagnostic testing and the development of effective therapeutics.


Provided by Arizona State University (news : web)

Are those liquids explosive?

A team of researchers from the University of the Basque Country (Spain) has developed a method to determine the chemical composition of liquids seized by police and suspected to be explosive. Some of the samples analysed contained substances hazardous to health, such as methanol and boric acid.


Each year seize tonnes of pyrotechnic substances which, in principle, are for indoor firework manufacturing (i.e. or those used in artistic or sporting events), but which also may end up in the hands of violent groups and hooligans.


A group of from the University of the Basque Country (UPV/EHU, Spain) has developed a method that offers judges conclusive scientific tests on the nature of these . Until now, many resources have been allocated to detecting high explosives such as TNT, but very few for less powerful ones which can also be dangerous.


"We have found a relatively simple way to detect explosive or flammable compounds in suspicious liquids, by combining four techniques commonly used in laboratories," stated Kepa Castro, UPV/EHU researcher and the study's lead author.


On one hand, the of the substances is obtained using two spectroscopy techniques (Raman and infrared) that can be performed with mobile devices in airports, customs or ports offices.


On the other hand, energy-dispersive spectroscopy (EDS) combined with (SEM) images is used to determine which elements are in the sample.


"With the SEM-EDS technique we are able to observe how the sample's elements are distributed and grouped (for example, calcium with sulphur suggests that calcium sulphate is present)" explains Castro, "and by crossing data from four different techniques, we are able to check and confirm the results."


Samples with dangerous compounds


To check the method, the scientists applied it to five seized liquid samples. Four of the samples presented substances used in indoor fireworks. Alcohols, such as isopropyl and methanol, are used to solubilise compounds and the scientists managed to produce coloured flames with them.


The team was surprised to find being used as a main solvent, given that this compound is very toxic for human beings, causing acidosis and blindness, and it is restricted in many countries.


Boric acid was also detected in one of the other sample liquids. This substance has recently been added to the list of Substances of Very High Concern (SVHC) as part of the European Union's REACH Regulation (Registration, Evaluation, Authorisation and Restriction of Chemical substances). These acids can have a negative effect on the human reproduction system.


Strangely, no flammable or explosive substances were found in the fifth sample. "It is probably a flame retardant, which is precisely used in fire prevention," suggested the researcher.


More information: Kepa Castro, Silvia Fdez-Ortiz de Vallejuelo, Izaskun Astondoa, Félix M. Goni, Juan Manuel Madariaga. "Are these liquids explosive? Forensic analysis of confiscated indoor fireworks". Analytical and Bioanalytical Chemistry 400:3065, 2011. DOI:10.1007/s00216-011-5013-4


Provided by FECYT - Spanish Foundation for Science and Technology

How soft corals defy their environment

Many marine organisms, including corals, build skeletons from calcium carbonate -- in the form of calcite or aragonite. The current composition of seawater favors the formation of aragonite -- but soft corals have a specific protein that allows them to form calcite skeletons instead.

Calcium carbonate is a salt for all seasons. It turns up not only in marble, but also in biogenic sediments such as limestone and – and even in pearls. The compound exists in two major crystalline forms, as calcite or aragonite. However, it is not clear what determines which variant an organism will exploit under conditions in which both forms can precipitate.

A team of researchers led by LMU geobiologist Dr. Azizur Rahman, who is also a Research Fellow of the Alexander von Humboldt Foundation, has now answered this question, in collaboration with colleagues based at the University of the Ryukyu Islands in Japan. Together, the scientists have shown that, in the soft coral species Lobophytum crissum, a secreted, extracellular protein known as ECMP-67 is the decisive factor that results in the precipitation of calcite, irrespective of the chemical conditions prevailing in the surrounding seawater.

"Over the course of Earth's history, and most probably depending on the relative amounts of dissolved magnesium and calcium ions, either calcite or aragonite has dominated in the world's oceans," says Professor Gert Wörheide, one of the authors of the new study. Current conditions favor the formation of aragonite, and many stony corals build their skeletons exclusively from this material. However, thanks to ECMP-67, Lobophytum crassum can still produce calcite in an aragonite sea.

"We have also been able to show how the extracellular ECMP-67 contributes to the production of calcite at the molecular level," says Rahman. "These findings should also allow us to elucidate the crystal structure of in natural environments." The study was funded by the Alexander von Humboldt Foundation and the Japanese Society for the Promotion of Sciences.

More information: Calcite formation in soft coral sclerites is determined by a single reactive extracellular protein, Azizur Rahman, Tamotsu Oomori and Gert Wörheide, Journal of Biological Chemistry 286: 31638-31649, 2. September 2011. Doi 10.1074/jbc.M109.070185

Provided by Ludwig-Maximilians-Universitat Munchen