Tuesday, August 30, 2011

Researchers improve performance of iron-based catalysts

Having pioneered the development of the first high-performance iron-based catalyst for fuel cells, researchers at INRS recently achieved a second major advance. They developed a new and improved iron-based catalyst capable of generating even more electric power in fuel cells for transportation applications. Previously, only platinum-based catalysts could produce similar performance.

The new research findings from the team of Professor Jean-Pol Dodelet were published in Nature Communications, a prestigious scientific journal part of the Nature Publishing Group. With these new and promising results, we bolster the prospect of iron-based catalysts replacing platinum ones in the electrochemical reduction of , one of two reactions needed to activate the electric power generator we call a . Platinum is rare and very costly, whereas iron is the second most abundant metal on earth and is inexpensive.

"Thanks to this breakthrough we are nearing the day when we will be able to drive electric-electric —i.e. battery and fuel cell powered—, which can potentially free us from our current dependence on oil to power our cars," said Professor Dodelet.

Working at the Énergie Matériaux Télécommunications Research Centre in Varennes (Québec), INRS scientists are now focusing on the improvement of the long-term stability (at least 5,000 hours) of these promising new catalysts. "The next step is the most important because it will automatically lead to a high value commercial product, not only for car manufacturers but also for all industrial sectors that use electric power generators or manufacture their components," explained Mr. Dodelet.

Provided by INRS

Steering a beam of 'virtual particles' to manipulate ultra-small-scale particles in real time

The steady improvement in speed and power of modern electronics may soon hit the brakes unless new ways are found to pack more structures into microscopic spaces. Unfortunately, engineers are already approaching the limit of what light -- the choice tool for "tweezing" tiny features -- can achieve. But there may be a way of reaching beyond this so-called "diffraction limit" by precisely steering, in real time, a curve-shaped beam of weird "virtual particles" known as surface plasmons.

This technique, described in the Optical Society's (OSA) journal Optics Letters, opens the possibility of even smaller, faster communications systems and optoelectronic devices. Examples of optoelectronic devices used today include photodiodes such as solar cells, integrated optical circuits used in communications, and charged coupled imaging devices at the heart of cell phone cameras and receivers on the world's most advanced telescopes. This method also may yield new, important tools for research in chemistry, biology, and medicine.

The key to this innovation is the ability -- for the first time -- to actively manipulate a blended stream of light and plasma, known as a plasmonic Airy beam. The beam, owing to the laws of electromagnetism, travels, not in a straight line like the beams of light to which we are accustomed, but rather in an arc. "It's an odd thing for sure, as light is supposed to travel in a straight line," says Peng Zhang a member of the research team with the National Science Foundation (NSF) Nanoscale Science and Engineering Center of the University of California, Berkeley and Department of Physics and Astronomy at San Francisco State University (SFSU). "That's why people are so crazy about these kinds of interesting beams."

As the beam first strikes a metal surface (typically at an irregular feature called a grating structure), it stirs up small waves of electrons at the metal-insulator interface. These waves, which can be thought of as "virtual particles" known as surface plasmon polaritons (SPPs), then follow the curved trajectory of the Airy beams. And, just as ocean waves move objects on the surface of the water, the SPPs can be directed to manipulate ultrafine-scale features on the surface of a metal.

SPPs are already essential elements in the design and manufacture of optoelectronic devices. The reason they're so critical is that they can affect extremely small-scale objects, smaller than the diffraction limit, or half of the wavelength of light used to create SPPs.

The current systems, however, have a significant drawback: they required fixed, permanent nanostructures to direct the SPPs. This lack of flexibility severely limits their uses in nano-system design and manufacture. But by being able to manipulate the Airy beam, and therefore the SPPs, in real time, the new design gives scientists on-the-fly control.

"We have demonstrated a new way of routing the flow of surface plasmons without any guiding structures," says Xiang Zhang, who led this research and is the director of the NSF Nanoscale Science and Engineering Center at Berkeley and a faculty scientist with the Materials Sciences Division of the Lawrence Berkeley National Laboratory.

The lack of guiding structures, according to Xiang Zhang, is the critical innovation in their design. Currently, to manipulate surface plasmons over two-dimensional metal surfaces, different elements such as waveguides, lenses, beam splitters, and reflectors need to be created. This is done by either structuring metal surfaces (fabricating some permanent nanostructures) or placing insulators on metals. These permanent guiding structures cannot be reconfigured; once the structure is fabricated it cannot be changed in real time.

By using computer-controlled optics, however, the research team has developed a way to steer and manipulate the beams, precisely directing their trajectories to specific spots on an optical surface and adjusting them as needed. Due to their unique arc-shaped paths, the beams have the added ability to bypass surface roughness and defects, or even vault over obstacles.

"These on-the-fly adjustments are extremely desirable," says Zhigang Chen, a principal investigator with the Department of Physics and Astronomy at SFSU. "They enable reconfigurable optical interconnections in ultra-compact integrated photonic circuits, which are at the core of many high-speed computing technologies. They also would enable on-chip nanoparticle manipulations for chemical, medical, or biological research purposes."

The Airy beams used to direct the flow of plasmons also remain coherent, not fanning out or distorting as they travel along their curved trajectories, much in the same way that laser light remains coherent even after traveling great distances.

To create the Airy beams, the researchers used a laser beam and modulated its phase, or wave front, with a spatial light modulator (a device similar to a miniature liquid crystal display) controlled by a personal computer. By continuously changing the specially designed patterns in the computer, they were able to dynamically control the trajectories of the beam in real time.

"These results point out a new direction for dynamically routing surface energies without any permanent guiding structures," says Peng Zhang, "which could inspire researchers from different areas to develop new technologies or tools for a variety of applications." For example, in nano-photonics, researchers may design practical reconfigurable plasmonic devices for ultra-compact integrated photonic circuits. In biology and chemistry, researchers may establish new tools for dynamically manipulating nanoparticles or molecules, and improving the performance of sensors.

"The ultrafine wavelength nature of surface plasmons makes them a promising tool for future nanolithography or nanoimaging applications," says research team member Sheng Wang, also of the NSF Nanoscale Science and Engineering Center. "Now, with the dynamic tunable plasmonic Airy beams, researchers may also shed new light on ultrahigh resolution bioimaging. For example, by bypassing obstacles and directly shining a beam on a target sample, background noise can be greatly reduced, which would enable more accurate imaging."

"This method may also encourage researchers in other fields to manipulate the surface waves in other low-dimensional systems, including graphenes, topological insulators, and magnetic thin films," says fellow team member Yongmin Liu of the NSF Nanoscale Science and Engineering Center.

This research was supported by the U.S. Army Research Office, the Air Force Office of Scientific Research, and the National Science Foundation.

Story Source:

The above story is reprinted (with editorial adaptations) from materials provided by Optical Society of America, via EurekAlert!, a service of AAAS.

Journal Reference:

Peng Zhang, Sheng Wang, Yongmin Liu, Xiaobo Yin, Changgui Lu, Zhigang Chen, Xiang Zhang. Plasmonic Airy beams with dynamically controlled trajectories. Optics Letters, 2011; 36 (16): 3191 DOI: 10.1364/OL.36.003191

Study builds on plausible scenario for origin of life on Earth

A relatively simple combination of naturally occurring sugars and amino acids offers a plausible route to the building blocks of life, according to a paper published in Nature Chemistry co-authored by a professor at the University of California, Merced.

The study, "A Route to Enantiopure RNA Precursors from Nearly Racemic Starting Materials," shows how the precursors to RNA could have formed on Earth before any life existed. It was authored by Jason E. Hein, Eric Tse and Donna G. Blackmond, a team of researchers with the Scripps Research Institute. Hein is now a chemistry professor with UC Merced. The paper was published online Sunday.

, such as RNA and proteins, can exist in either a natural or unnatural form, called enantiomers. By studying the chemical reactions carefully, the research team found that it was possible to generate only the natural form of the necessary RNA precursors by including simple .

"These amino acids changed how the reactions work and allowed only the naturally occurring RNA precursors to be generated in a stable form," said Hein. "In the end, we showed that an amazingly simple result emerged from some very complex and interconnected chemistry."

The natural enantiomer of the RNA precursor molecules formed a visible to the naked eye. The crystals are stable and avoid normal chemical breakdown. They can exist until the conditions are right for them to change into .

More information: DOI: 10.1038/NCHEM.110

Provided by University of California - Merced

Genetically engineered spider silk for gene therapy

 Genetically engineered spider silk could help overcome a major barrier to the use of gene therapy in everyday medicine, according to a new study that reported development and successful initial laboratory tests of such a material. It appears in ACS' journal Bioconjugate Chemistry.

David Kaplan and colleagues note that — the use of beneficial to prevent or treat disease — requires safe and efficient carriers or "vectors." Those carriers are the counterparts to pills and capsules, transporting therapeutic genes into in the body. Safety and other concerns surround the experimental use of viruses to insert genes. The lack of good gene delivery systems is a main reason why there are no FDA-approved gene therapies, despite almost 1,500 clinical trials since 1989. The new study focused on one promising prospect, silk proteins, which are biocompatible and have been used in everyday medicine and medical research for decades.

The scientists describe modifying proteins so that they attach to diseased cells and not healthy cells. They also engineered the spider silk to contain a gene that codes for the that makes fireflies glow in order to provide a visual signal (seen using special equipment) that the gene has reached its intended target. In lab studies using mice containing human breast cancer cells, the spider-silk proteins attached to the cancer cells and injected the DNA material into the cells without harming the mice. The results suggest that the genetically-engineered spider-silk proteins represent "a versatile and useful new platform polymer for nonviral gene delivery," the article notes.

More information: “Spider Silk-Based Gene Carriers for Tumor Cell-Specific Delivery” Bioconjugate Chem., Article ASAP. DOI: 10.1021/bc200170u

The present study demonstrates pDNA complexes of recombinant silk proteins containing poly(l-lysine) and tumor-homing peptides (THPs), which are globular and approximately 150–250 nm in diameter, show significant enhancement of target specificity to tumor cells by additions of F3 and CGKRK THPs. We report herein the preparation and study of novel nanoscale silk-based ionic complexes containing pDNA able to home specifically to tumor cells. Particular focus was on how the THP, F3 (KDEPQRRSARLSAKPAPPKPEPKPKKAPAKK), and CGKRK, enhanced transfection specificity to tumor cells. Genetically engineered silk proteins containing both poly(l-lysine) domains to interact with pDNA and the THP to bind to specific tumor cells for target-specific pDNA delivery were prepared using Escherichia coli, followed by in vitro and in vivo transfection experiments into MDA-MB-435 melanoma cells and highly metastatic human breast tumor MDA-MB-231 cells. Non-tumorigenic MCF-10A breast epithelial cells were used as a control cell line for in vitro tumor-specific delivery studies. These results demonstrate that combination of the bioengineered silk delivery systems and THP can serve as a versatile and useful new platform for nonviral gene delivery.

Provided by American Chemical Society (news : web)

Student brings home new expertise to answer question in antibiotic resistance

Working out the structure of a complex formed when a protein binds to DNA has proved to be key in understanding how an antibiotic-producing organism controls resistance to its own antibiotic, and may be an example of how other antibiotic producers regulate export to prevent self-toxicity.

The natural production of antibiotics by certain is a complex and highly regulated process, not least because the organism making these compounds must protect itself from their . Researchers at the John Innes Centre, which is strategically funded by the Biotechnology and Biological Sciences Research Council (BBSRC), have been studying the production of simocyclinone, produced by Streptomyces antibioticus, and in particular how the production of this potent antibiotic triggers an efficient pumping mechanism that exports the antibiotic from the cell.

Much of the work elucidating this protection mechanism has been carried out by Tung Le, a Vietnamese PhD student enrolled in the JIC's four-year rotation PhD programme. Tung, working under the supervision of Mark Buttner and David Lawson, showed that SimR, the protein Streptomyces antibioticus uses to regulate antibiotic export, can bind either to DNA or to the antibiotic itself, but crucially cannot bind to both. This means that when the antibiotic is around, SimR releases the DNA, which allows the expression of a gene that encodes a pump responsible for removing simocyclinone from the cell.

"This provides a mechanism that couples the potentially lethal biosynthesis of the antibiotic to its export, which has wider implications for resistance to clinically important antibiotics," commented Prof. Buttner. "However, we needed to know more detail about the interaction between SimR and DNA."

In this latest research, published in the journal , they show that the SimR protein has a novel 'arm' and that cutting off this arm unexpectedly weakened SimR binding to DNA. To determine the function of this arm, the researchers needed to work out the crystal structure of the protein bound to DNA, something which hadn't been achieved in Norwich before.

To overcome this skills gap, Tung won both a Korner Travelling Fellowship and an EMBO Short-Term Travel Fellowship to visit the University of Texas M.D. Anderson Cancer Center, home to one of the leading laboratories specialising in this technique. Tung spent three months working in the labs of Richard Brennan and Maria Schumacher, learning how to solve the structures of protein-DNA complexes. He was then able to apply this to his own project.

"I learned a lot and it was a great experience," said Tung. "The knowledge I brought back was not only useful for my project but will also be beneficial for others, and I feel very proud about that."

Usually, the SimR arm is unstructured, but in the presence of DNA they saw that it becomes ordered and binds into the minor groove of the DNA molecule. The crystal structure also shows how other parts of the SimR protein form sequence-specific interactions with a binding site in front of the export pump gene.

SimR is a member of a large family of regulatory proteins found in bacteria, and is the fifth one to have its structure solved when bound to DNA. The way these proteins recognise their target sequences differs. This new example has wider implications, as a bioinformatic search of this family of regulators showed that many of them also have arms similar to the one characterised in this study.

Tung submitted his PhD thesis in early August, and his research has already produced four first-author papers. He is due to take up a post-doctoral position at the Massachusetts Institute of Technology in January.

"It can be very difficult for non-EU students to find the funding to study for a PhD in the UK, and so I was delighted to be offered a place on the JIC rotation programme. I am keen to encourage and help build relations between JIC and Vietnam. I was very happy to see the JIC is involved in joint work with Vietnam to sequence the genomes of different varieties of rice" said Tung, who left Vietnam at the age of seventeen for a bioscience career in the UK.

The researchers have also recently received a grant from the BBSRC to continue investigating the complexities of the regulation of antibiotic biosynthetic pathways, focussing on SimR and two other antibiotic-responsive transcription factors encoded in the simocyclinone biosynthetic cluster. This will establish the roles that the antibiotic plays in regulating self-resistance and its own . With the ever-growing problem of resistance, this kind of fundamental research is vital.

Provided by Norwich BioScience Institutes