Quantum plasmons demonstrated in atomic-scale nanoparticles

 Addressing a half-decade-old debate, engineers at Stanford have positively identified the presence of plasmons, the collective oscillations of electrons, in individual metal particles as small as one nanometer in diameter. The discovery could impact nanotechnology.

The physical phenomenon of plasmon resonances in small metal particles has been apparent for centuries. They are visible in the vibrant hues of the great stained-glass windows of the world. More recently, plasmon resonances have been used by engineers to develop new, light-activated cancer treatments and to enhance light absorption in photovoltaics and photocatalysis.

"The stained-glass windows of Notre Dame Cathedral and Stanford Chapel derive their color from metal nanoparticles embedded in the glass. When the windows are illuminated, the nanoparticles scatter specific colors depending on the particle's size and geometry " said Jennifer Dionne, an assistant professor of materials science and engineering at Stanford and the senior author of a new paper on plasmon resonances to be published in the journal Nature.

In the study, the team of engineers report the direct observation of plasmon resonances in individual metal particles measuring down to one nanometer in diameter, just a few atoms across.

"Plasmon resonances at these scales are poorly understood," said Jonathan Scholl, a doctoral candidate in Dionne's lab and first author of the paper. "So, this class of quantum-sized metal nanoparticles has gone largely under-utilized. Exploring their size-dependent nature could open up some interesting applications at the nanoscale."

The research could lead to novel electronic or photonic devices based on excitation and detection of plasmons in these extremely small particles, the engineers said.

"Alternatively, there could be opportunities in catalysis, quantum optics, and bio-imaging and therapeutics," added Dionne.

Longstanding debate

The science of tiny metal particles has perplexed physicists and engineers for decades. As metallic particles near about 10 nanometers in diameter, classical physics breaks down. The particles begin to demonstrate unique physical and chemical properties that bulk counterparts of the very same materials do not. A nanoparticle of silver measuring a few atoms across, for instance, will respond to photons and electrons in ways profoundly different from a larger particle or slab of silver.

By clearly illustrating the details of this classical-to-quantum transition, Scholl and Dionne have pushed the field of plasmonics into a new realm that could have lasting consequences for catalytic processes such as artificial photosynthesis, for cancer research and treatment, and even quantum computing.

"Particles at this scale are more sensitive and more reactive than bulk materials," said Dionne. "But we haven't been able to take full advantage of their optical and electronic properties without a complete picture of the science. This paper provides the foundation for new avenues of nanotechnology entering the 100-to-10,000 atom regime."

Noble metals

In recent years, engineers have paid particular attention to nanoparticles of the noble metals: silver, gold, palladium, platinum and so forth. These metals are well known to support localized surface plasmon resonances in larger particles. Plasmons are the collective oscillation of electrons at the metal surface in response to light or an electric field.

Additionally, other important physical properties can be driven when plasmons are constrained in extremely small spaces, like the nanoparticles Dionne and Scholl studied, a phenomenon known as quantum confinement.

Depending on the shape and size of the particle, therefore, quantum confinement can dominate a particle's electronic and optical response. This research allows scientists, for the first time, to directly correlate a quantum-sized plasmonic particle's geometry -- its shape and size -- with its plasmon resonances.

Standing to benefit

Nanotechnology stands to benefit from this new understanding. Medical science, for instance, has devised a way to use nanoparticles excited by light to burn away cancer cells, a process known as photothermal ablation. Metal nanoparticles are affixed with molecular appendages called ligands that attach exclusively to chemical receptors on cancerous cells. When irradiated with infrared light, the plasmons begin to resonate and the metal nanoparticles heat up, burning away the cancerous cells while leaving the surrounding healthy tissue unaffected. The use of smaller nanoparticles in these therapies might improve their accuracy and the effectiveness, particularly since they can be more easily integrated into cells.

There is great promise for such small nanoparticles in catalysis, as well. The greater surface-area-to-volume ratios offered by atomic-scale nanoparticles could could significantly improve catalyic rates and efficiencies and provide advances in water-splitting and artificial photosynthesis, yielding clean and renewable energy sources from artificial fuels.

Aiding and abetting

The researchers' ability to observe plasmons in particles of such small size was abetted by the powerful, multi-million dollar environmental scanning transmission electron microscope (E-STEM) installed recently at Stanford's Center for Nanoscale Science and Engineering, one of just a handful of such microscopes in the world.

E-STEM imaging was used in conjunction with electron energy-loss spectroscopy (EELS) -- a research technique that measures the change in an electron's energy as it passes through a material -- to determine the shape and behavior of individual nanoparticles. Combined, STEM and EELS allowed the team to address many of the ambiguities of previous investigations.

"With this new microscope, we can resolve individual atoms within the nanoparticle," said Dionne, "and we can directly observe these particles' quantum plasmon resonances."

Ai Leen Koh, a research scientist at the Stanford Nanocharacterization Laboratory, and co-author of the paper, noted: "Even though plasmons can be probed using both light and electrons, electron excitation is advantageous in that it allows us to image the nanoparticle down to the atomic level and study its plasmon resonances at the same time."

Scholl added, "Someday, we might use this microscope to watch reactions in progress to better understand and optimize them."

Elegant and versatile

The researchers concluded by explaining the physics of their discovery through an elegant and versatile analytical model based on well-known quantum mechanical principles.

"Technically speaking, we've created a relatively simple, computationally light model that describes plasmonic systems where classical theories have failed," said Scholl.

"This paper represents fundamental research. We have clarified what was an ambiguous scientific understanding and, for the first time, directly correlated a particle's geometry with its plasmonic resonance for quantum-sized particles," summarized Dionne. "And this could have some very interesting, and very promising, implications and applications."

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The above story is reprinted from materials provided by Stanford School of Engineering. The original article was written by Andrew Myers.

Note: Materials may be edited for content and length. For further information, please contact the source cited above.

Journal Reference:

Jonathan A. Scholl, Ai Leen Koh, Jennifer A. Dionne. Quantum plasmon resonances of individual metallic nanoparticles. Nature, 2012; 483 (7390): 421 DOI: 10.1038/nature10904

New plastics 'bleed' when cut or scratched — and then heal like human skin

"Mother Nature has endowed all kinds of biological systems with the ability to repair themselves," explained Professor Marek W. Urban, Ph.D., who reported on the research. "Some we can see, like the skin healing and new bark forming in cuts on a tree trunk. Some are invisible, but help keep us alive and healthy, like the self-repair system that DNA uses to fix genetic damage to genes. Our new plastic tries to mimic nature, issuing a red signal when damaged and then renewing itself when exposed to visible light, temperature or pH changes."

Urban, who is with the University of Southern Mississippi in Hattiesburg foresees a wide range of potential applications for plastic with warn-and-self-repair capabilities. Scratches in automobile fenders, for instance, might be repaired by simply exposing the fender to intense light. Critical structural parts in aircraft might warn of damage by turning red along cracks so that engineers could decide whether to shine the light and heal the damage or undertake a complete replacement of the component. And there could be a range of applications in battlefield weapons systems.

Plastics have become so common, replacing steel, aluminum, glass, paper and other traditional materials because they combine desirable properties such as strength, light weight and corrosion resistance. Hundreds of scientists around the world have been working, however, to remedy one of the downsides of these ubiquitous materials: Once many plastics get scratched or cracked, repairs can be difficult or impossible.

Self-healing plastics have become a Holy Grail of materials science. One approach to that goal involves seeding plastics with capsules that break open when cracked or scratched and release repairing compounds that heal scratches or cuts. Another is to make plastics that respond to an outside stimulus — like light, heat or a chemical agent — by repairing themselves.

Urban's group developed plastics with small molecular links or "bridges" that span the long chains of chemicals that compose plastic. When plastic is scratched or cracked, these links break and change shape. Urban tweaked them so that changes in shape produce a visible color change — a red splotch that forms around the defect. In the presence of ordinary sunlight or visible light from a light bulb, pH changes or temperature, the bridges reform, healing the damage and erasing the red mark.

Urban cited other advantages of the new plastic. Unlike self-healing plastics that rely on embedded healing compounds that can self-repair only once, this plastic can heal itself over and over again. The material also is more environmentally friendly than many other plastics, with the process for producing the plastic water-based, rather than relying on potentially toxic ingredients. And his team now is working on incorporating the technology into plastics that can withstand high temperatures.

More information:
Abstract
Although the last decade has brought self-healing materials on the forefront of scientific interests, combining repair and sensing attributes into one material entity have not been addressed. These studies report the development of poly(methyl methacrylate/n-butylacrylate/2-[(1,3,3-trimethyl-1,3-dihydrospiro[indole-2,3'-naphtho[2,1-b][1,4]oxazin]-5-yl)amino]ethyl-2-methylacrylate) [p(MMA/nBA/SNO)] copolymer films that upon mechanical scratch undergo color changes from clear to red in the damaged area, but upon exposure to sunlight, temperature and/or acidic vapors, the damaged area is self-repaired and the initial colorless appearance is recovered. The process is reversible and driven by the ring-opening-closure of spironapthoxazine (SNO) segments to form merocyanine (MC), which are recovered back to the SNO form. Upon mechanical damage, SNO segments of the neighboring copolymer segments form inter-molecular H-bonding that stabilizes copolymer backbone, that remains in an extended conformation. External stimuli, such as light, temperature, or acidic environments cause a dissociation of the H-bonded MC pairs, which are converted back to SNO. This process is associated with the p(MMA/nBA/SNO) backbone collapse, thus pulling entangled neighboring copolymers to fill removed mass and repair a scratch. Mechanical nano-indentation analysis combined with molecular modeling and spectroscopic measurements confirm this behavior. The enclosed video clip illustrates molecular repair processes induced by visible light monitored by in-situ Raman imaging spectroscopy. These materials may find numerous future applications, where coupling of simultaneous color changes and reversible self-repair responses may lead to new technological paradigms.

Provided by American Chemical Society (news : web)

Brown liquor and solar cells to provide sustainable electricity

 A breakthrough for inexpensive electricity from solar cells, and a massive investment in wind power, will mean a need to store energy in an intelligent way. According to research at Linköping University, published in Science, batteries of biological waste products from pulp mills could provide the solution.

Organic solar cells based on conductive plastic is a low cost alternative that has achieved high enough performance to be upscaled and, in turn, become competitive. However, solar electricity must be able to be stored from day to night, as well as electricity from wind turbines from windy to calm days.

In conventional batteries metal oxides conduct the charge. Materials, such as cobalt, are expensive and a limited resource, therefore, low cost solutions are sought preferably with renewable materials.

"Nature solved the problem long ago," says Olle Inganäs, professor of biomolecular and organic electronics at Linköping University (LiU) and lead author of the article in a recent edition of Science.

He drew inspiration from the process of photosynthesis, where electrons charged by solar energy are transported by quinones; electrochemically active molecules based on benzene rings composed of six carbon atoms. Inganäs chose the raw material brown liquor that is a by-product from the manufacture of paper pulp. The brown liquor is largely composed of lignin, a biological polymer in the plant cell walls.

To utilise the quinones as charge carriers in batteries, Inganäs and his Polish colleague Grzegorz Milczarek devised a thin film from a mixture of pyrrole and lignin derivatives from the brown liquor. The film, 0.5 microns in thickness, is used as a cathode in the battery.

The goal is to offer ways to store renewable electricity where it is produced, without constructing up large grids. In several countries, major wind power investments are planned. Meanwhile, the performance of cheap organic solar cells has now reached a critical level. A research team at the University of California, Los Angeles, has recently reported efficiency of more than 10 percent of the energy of the captured sunlight.

According to Inganäs who for many years conducted research on organic solar cells, the efficiency is sufficient to initiate an industrial scale up of the technology.

"Now we need more research into new energy storage based on cheap and renewable raw materials. Lignin constitutes 20-30 percent of the biomass of a tree, so it's a source that never ends."

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The above story is reprinted from materials provided by Linköping University.

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Journal Reference:

Grzegorz Milczarek and Olle Inganäs. Renewable Cathode Materials from Biopolymer/Conjugated Polymer Interpenetrating Networks. Science, 2012 DOI: 10.1126/science.1215159]

Researchers create living human gut-on-a-chip

Building on the Wyss Institute's breakthrough "Organ-on-Chip" technology that uses microfabrication techniques to build living organ mimics, the gut-on-a-chip is a silicon polymer device about the size of a computer memory stick. Wyss Founding Director, Donald Ingber, M.D., Ph.D., led the research team, which included Postdoctoral Fellow, Hyun Jung Kim, Ph.D; Technology Development Fellow, Dan Huh, Ph.D.; and Senior Staff Scientist, Geraldine Hamilton, Ph.D. Ingber is also the Judah Folkman Professor of Vascular Biology at Harvard Medical School and the Vascular Biology Program at Children's Hospital Boston, and Professor of Bioengineering at Harvard's School of Engineering and Applied Sciences.

The new device mimics complex 3D features of the intestine in a miniaturized form. Inside a central chamber, a single layer of human intestinal epithelial cells grows on a flexible, porous membrane, recreating the intestinal barrier. The membrane attaches to side walls that stretch and recoil with the aid of an attached vacuum controller. This cyclic mechanical deformation mimics the wave-like peristaltic motions that move food along the digestive tract. The design also recapitulates the intestinal tissue-tissue interface, which allows fluids to flow above and below the intestinal cell layer, mimicking the luminal microenvironment on one side of the device and the flow of blood through capillary vessels on the other.

In addition, the researchers were able to grow and sustain common intestinal microbes on the surface of the cultured intestinal cells, thereby simulating some of the physiological features important to understanding many diseases. These combined capabilities suggest that gut-on-a-chip has the potential to become a valuable in vitro diagnostic tool to better understand the cause and progression of a variety of intestinal disorders and to help develop safe and effective new therapeutics, as well as probiotics. The gut-on-a-chip could also be used to test the metabolism and oral absorption of drugs and nutrients.

"Because the models most often available to us today do not recapitulate human disease, we can't fully understand the mechanisms behind many intestinal disorders, which means that the drugs and therapies we validate in animal models often fail to be effective when tested in humans," said Ingber. "Having better, more accurate in vitro disease models, such as the gut-on-a-chip, can therefore significantly accelerate our ability to develop effective new drugs that will help people who suffer from these disorders."

Gut-on-a-chip represents the most recent advance in the Wyss Institute's portfolio of engineered organ models. The platform technology was first reported on in Science in June 2010, where a living, breathing, human lung-on-a-chip was described. That same year, the Wyss received funding from the National Institutes of Health and the U.S. Food and Drug Administration to develop a heart-lung micromachine to test the safety and efficacy of inhaled drugs on the integrated heart and lung function. In September 2011, the Wyss was awarded a four-year grant from the Defense Advanced Research Projects Agency to develop a spleen-on-a-chip to treat sepsis, a commonly fatal bloodstream infection.

Provided by Harvard University (news : web)

New inhibitors of a cancer-causing protein may lead to targeted therapeutics

The activity of protein kinases, a large class of signaling molecules, must be closely regulated or signaling chaos arises within cells. Signaling chaos sets off a process that is implicated in the development of cancers, including solid tumors. Because protein kinases have a central role in cell signaling, researchers have devoted decades of investigation to developing protein kinase inhibitors.

One kinase inhibitor, a drug called Imatinib (or Gleevec), illustrates the profound potential of kinase inhibitors in cancer treatment. The hyperactivity of the Abl kinase is the most common cause of chronic myelogenic leukemia (CML). Imatinab is routinely used to treat CML. Since Imatinib’s Food and Drug Administration-approval in 2001, deaths related to CML have dropped significantly.

Src kinase inhibitors have been used in clinical trials as experimental treatments for many types of solid tumors. However, in contrast to the success of Imatinib for treating CML, a drug based on inhibiting the Src kinase has not been effective in treating solid tumors.

“Think of kinases as a traffic light system that is regulated to keep traffic flowing properly,” says Dr. Seeliger. “But if all lights on a road system are green, chaos occurs. The Src kinase is a dangerous ‘traffic light’ when it stays green. The challenge is to inhibit Src kinase, in other words make it a ‘red light,’ without stopping other Src family of kinases from staying ‘green’ to keep the traffic moving safely.”

In “Highly specific, bisubstrate-competitive Src inhibitors from DNA-templated macrocycles,” the researchers successfully completed two steps that are necessary for the development of new Src kinase-targeted drugs.

First, under the direction of David Liu, Ph.D., Professor, Department of Chemistry, Harvard University, the team developed chemical inhibitors of Src kinase. Dr. Seeliger’s laboratory at Stony Brook then determined the three-dimensional structure of these inhibitors bound to the Src kinase. This second step enabled the team to explain why the inhibitors work to stop the Src kinase but not the other kinases in cultured mammalian cells.

“Using this method, the precise molecular basis of the inhibitory mechanism and Src kinase are revealed,” says Dr. Seeliger. “These results provide new insights into the development of Src-specific inhibitors with potential therapeutic relevance.”

Provided by Stony Brook University (news : web)

How electrons outrun vibrating nuclei -- the X-ray movie

 Researchers at the Max-Born-Institute, Berlin, Germany, resolved spatial oscillations of electrons in a crystal by taking a real-time 'movie' with ultrashort x-ray flashes. Outer electrons move forth and back over the length of a chemical bond and modulate the electric properties while the tiny elongation of the inner electrons and the atomic nuclei is less than 1% of this distance.

A crystal represents a regular array of atoms in space, a so-called lattice, which is held together by interactions between the electron clouds of neighboring atoms. While most electrons are tightly bound to the positively charged nuclei, the outermost valence electrons form chemical bonds to the next neighbors. Such bonds determine the distance between atoms in the crystal as well as basic properties such as mechanical stability or the electrical behavior.

In the crystal lattice, atoms are not at rest but perform vibrational motions around their equilibrium positions. The spatial elongation of the vibrating nuclei together with their core electrons is a tiny fraction -- typically less than 1 percent -- of the distance between neighboring atoms. With respect to the outer valence electrons, the situation is much less clear and their elongations have remained unknown in many cases. Measuring the motions of valence electrons in space and time is important for understanding their fundamental role for the crystal's static and dynamic electric properties.

To address this issue, Flavio Zamponi, Philip Rothhardt, Johannes Stingl, Michael Woerner, and Thomas Elsaesser built an x-ray "reaction microscope" which allows for an in situ imaging of moving electrons and atoms in crystalline materials. As they report in PNAS (doi/10.1073/pnas.1108206109) vibrations in the ionic crystal potassium dihydrogen phosphate (KDP) are kicked off by excitation with an optical pulse of 50 femtosecond duration (1 fs = 10-15 seconds). The momentary position of atoms and electrons is measured with high spatial resolution by 100 fs hard x-ray pulses which are diffracted from the vibrating atoms. Measuring simultaneously many different x-ray diffraction peaks allows for reconstructing the momentary distances of atoms and in turn the three-dimensional distribution of electrons within the crystal. Taking x-ray snap shots at various delay times after initiating the vibrations creates a molecular movie according to the well known stroboscope effect.

It was a big surprise for the researchers that for a special kind of lattice vibrations (the so called soft mode of KDP) the involved valence electrons move a 30 times larger distance than the involved atoms (i.e. nuclei plus core electrons) when performing their oscillatory motion. Such a scenario is sketched in the electron density maps shown in Fig. 1. During the soft mode oscillation an electron initially residing on the phosphorus (P) atom moves to one of the neighboring oxygen (O) atoms (P-O bond length: 160 picometers (10-12 m)) and returns to the P-atom after half the oscillation period. However, when measuring the positions of the involved atoms one finds that the latter move just a few picometers. This is very surprising, because according to textbook knowledge one expects the same motion as that of the nucleus for all electrons of an atom. To understand this unexpected large-amplitude motion of valence electrons, one has to consider the electric forces the oscillating ionic lattice exerts on the electrons during the soft mode vibration. Theories developed in the 1960's predicted such a behaviour which is now experimentally proven for the first time and determines the ultrahigh-frequency electric behavior of the material. In the attached movie, we show the iso-electron density surface of the phosphate ion during the soft mode oscillation in a KDP crystal.

The femtosecond x-ray powder diffraction method demonstrated here can be applied to many other systems in order to map ultrafast structure changes in physical and chemical processes.

Movie: http://www.fv-berlin.de/news/videos/x-ray-movie/view

Story Source:

The above story is reprinted from materials provided by Forschungsverbund Berlin e.V. (FVB), via AlphaGalileo.

Note: Materials may be edited for content and length. For further information, please contact the source cited above.

Journal Reference:

F. Zamponi, P. Rothhardt, J. Stingl, M. Woerner, T. Elsaesser. Ultrafast large-amplitude relocation of electronic charge in ionic crystals. Proceedings of the National Academy of Sciences, 2012; DOI: 10.1073/pnas.1108206109

New twist on 1930s technology may become a 21st century weapon against global warming

 Far from being a pipe dream years away from reality, practical technology for capturing carbon dioxide -- the main greenhouse gas -- from smokestacks is aiming for deployment at coal-fired electric power generating stations and other sources, scientists saidin San Diego March 27. Their presentation at the 243rd National Meeting of the American Chemical Society was on a potential advance toward dealing with the 30 billion tons of carbon dioxide released into the air each year through human activity.

"With little fanfare or publicity and a decade of hard work, we have made many improvements in this important new technology for carbon capture," said James H. Davis, Jr., Ph.D., who headed the research. "In 2002, we became the first research group to disclose discovery of the technology, and we have now positioned it as a viable means for carbon dioxide capture. Our research indicates that its capacity for carbon dioxide capture is greater than current technology, and the process is shaping up to be both more affordable and durable as well."

The new approach has a back-to-the-future glint, leveraging technology that the petroleum industry has used since the 1930s to remove carbon dioxide and other impurities from natural gas. Davis, who is with the University of South Alabama (USA) in Mobile, explained that despite its reputation as a clean fuel, natural gas is usually contaminated with a variety of undesirable materials, especially carbon dioxide and hydrogen sulfide. Natural gas from certain underground formations, so-called "sweet" gas, has only small amounts of these other gases, while "sour" gas has larger amounts. Natural gas companies traditionally have used a thick, colorless liquid called aqueous monoethanolamine (MEA) to remove that carbon dioxide.

Several problems, however, would prevent use of MEA to capture carbon dioxide on the massive basis envisioned in some proposed campaigns to slow global warming. These involve, for instance, capturing or "scrubbing" the carbon dioxide from smokestacks before it enters the atmosphere and socking it away permanently in underground storage chambers. Vast amounts of MEA would be needed, and its loss into the atmosphere could create health and environmental problems, and it would be very costly.

Davis and his group believe that their new approach avoids those pitfalls. It makes use of a nitrogen-based substance termed an "ionic liquid" that binds to carbon dioxide very effectively. Unlike MEA, it is odorless, does not evaporate easily and can be easily recycled and reused.

Davis also described one important advantage the technology has over many other ionic liquid carbon-capture systems. He explained that the presence of water, like moisture in the atmosphere, reduces the effectiveness of many nitrogen-based ionic liquids, complicating their use. Water is always present in exhaust gases because it is a byproduct of combustion. Davis noted that the liquids prefer to interact with carbon dioxide over water, and thus are not hampered by the latter in real-world applications.

Although cautioning that the final application in power plants or factories may look different, Davis envisioned a possible set-up for power plants that would be similar to the one used in his laboratory. He described bubbling exhaust gas through a tank full of the nitrogen-based liquid, which the system could cycle out and replace with fresh liquid. Removing the carbon dioxide would create a new supply of ionic liquid. Once removed, companies could sequester the carbon dioxide by burying it or finding another way to keep it permanently out of the atmosphere. Others have suggested using captured carbon dioxide in place of petroleum products to make plastics and other products.

Davis suggested that in the future, people might also use the technology on a smaller scale in cars or homes, although he cautioned that these applications were likely a long way away. While his group has not fully explored the possible dangers of the chemicals his technology uses, Davis noted that his compounds are quite similar to certain compounds which are known to be safe for consumer use.

His presentation was part of a symposium on research advances involving "ionic liquids," strange liquids that consist only of atoms stripped of some of their electrons, with applications ranging from food processing to energy production.

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The above story is reprinted from materials provided by American Chemical Society (ACS), via Newswise.

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Analyzing food quality with an artificial intestine: the NutriChip

What happens in our bodies when we have eaten something? Are “healthy” food products actually good for us, once they have been digested and absorbed? Supported by Nano-Tera and Nestlé, the NutriChip project developed by Martin Gijs’s team at the Laboratory of Microsystems 2 (LMIS2) provides new insights to these questions. The NutriChip is a miniature artificial intestinal wall that can be used to identify foods that cause inflammation in the human body.

Preventing chronic inflammatory illness

“Generally, once a given food has been digested and absorbed by the intestine, it carries certain molecules into the body, such as Palmitic acid,” says Guy Vergeres, a member of the Agroscope Liebefeld-Posieux (ALP) Research Center, which is collaborating on the project. These molecules set off an immune response, in the form of slight, temporary inflammation. Biomarkers for inflammation, notably cytokines, can then be found in the blood. This is a normal phenomenon, but it must be monitored. “If this happens over and over for a long period of time, it can set the stage for inflammatory chronic illnesses,” warns Vergeres.

The NutriChip platform makes it possible to compare different foods in terms of their ability to lower the concentrations of those biomarkers – and thus possibly their ability to reduce inflammation itself. The research team began its tests with milk, a food that is widely consumed in Switzerland. “Some studies have shown that dairy products can reduce the concentration of inflammatory biomarkers in the blood, while others did not find any significant reduction in concentrations. With the NutriChip, we will be able to make a contribution to this debate,” says Martin Gijs.

The complexities of artificial digestion

The human body is complex, and designing a miniature artificial gastrointestinal system proved to be extremely exacting. The solution provided by researchers at EPFL ultimately took the shape of a two-level chip, whose levels are connected via a porous membrane.

The upper level, which represents the intestinal wall, is made of a homogeneous layer of cultured epithelial cells. The lower level represents the circulatory system and is made up of immune system cells, and in particular macrophages. The macrophages’ job within the human body is to keep it clean: when they encounter any potentially dangerous agents they release molecules such as cytokines that activate other immune-system cells. The NutriChip platform uses CMOS high-resolution optical sensors developed by Sandro Carrara’s team in the EPFL’s Integrated Sytems Lab in order to precisely detect and measure cytokine production by the immune cells that are on the other side of the layer of intestinal wall cells. These measurements, which are performed using fluorescence, show exactly how much inflammation is caused by a given food.

“We have to reproduce every stage in the digestive process before food hits the intestine,” says Professor Gijs. Milk, for instance, is successively digested by the enzymes and chemical components from the saliva, gastric juices, pancreatic juices and bile. The mixture that emerges from this process is then applied to the upper level of the NutriChip.

Is milk an anti-inflammatory?

Some studies have found that milk can reduce the concentration of inflammatory biomarkers in humans. However, these results need to be confirmed. “On another front, studies are being done on volunteers at the Bern University Hospital to find links between body mass, diet, and pro-inflammatory cytokine production,” says Martin Gijs. “The study participants eat various types of meals, and then afterwards their cytokine levels are measured via a blood test. Blood tests could tell us whether we obtain the same results with the NutriChip artificial intestine.” If the project team does obtain the same results, this will pave the way for in vitro screening of various types of foods to determine their pro- or anti-inflammatory potentials. The most promising foods could then be tested more intensely, via nutritional studies.

Provided by Ecole Polytechnique Federale de Lausanne

Forces among molecules: Tiny but important

 Forces are not only associated with machines or muscles. You can also find them elsewhere, for instance between molecules. Theoretical chemists like Dr. Łukasz Tomasz Rajchel (University of Warsaw) are familiar with that. However, they -- or rather their computers -- are not capable of calculating them with high accuracy and efficiency at the same time.

The scholarship holder of the Alexander von Humboldt Foundation wants to get to the bottom of the computational problem while working in Prof. Dr. Georg Jansen's Theoretical Organic Chemistry team at the University Duisburg-Essen (UDE).

Since intermolecular forces are very small, the computational technique must be very precise. Furthermore, getting significant results by experiment is difficult. For solving the task Łukasz Rajchel refers to various approximations of quantum chemistry. "They form my theoretical basis and shall help me develop new approaches for calculating intermolecular energies." The 30-year-old chemist solves the underlying equations with the help of self-developed computer codes.

The more Łukasz Rajchel and his colleagues get to know about the interactions between chemical compounds, the better they can understand matter and predict its characteristics. The significance of those tiny forces cannot be stressed enough. "They are substantial in nature," says Dr. Rajchel. For example: they are responsible for DNA and RNA's stability in genetic information or for the existence of molecular crystals and the proteins' structure. Interestingly, they also let the gecko walk on vertical glass surfaces.

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New process converts polyethylene into carbon fiber

(PhysOrg.com) -- In a paper published in Advanced Materials, a team led by Amit Naskar of the Materials Science and Technology Division outlined a method that allows not only for production of carbon fiber but also the ability to tailor the final product to specific applications.

"Our results represent what we believe will one day provide industry with a flexible technique for producing technologically innovative fibers in myriad configurations such as fiber bundle or non-woven mat assemblies," Naskar said.

Using a combination of multi-component fiber spinning and their sulfonation technique, Naskar and colleagues demonstrated that they can make polyethylene-base fibers with a customized surface contour and manipulate filament diameter down to the submicron scale. The patent-pending process also allows them to tune the porosity, making the material potentially useful for filtration, catalysis and electrochemical energy harvesting.

Naskar noted that the sulfonation process allows for great flexibility as the carbon fibers exhibit properties that are dictated by processing conditions. For this project, the researchers produced carbon fibers with unique cross-sectional geometry, from hollow circular to gear-shaped by using a multi-component melt extrusion-based fiber spinning method.

The possibilities are virtually endless, according to Naskar, who described the process.

"We dip the fiber bundle into an acid containing a chemical bath where it reacts and forms a black fiber that no longer will melt," Naskar said. "It is this sulfonation reaction that transforms the plastic fiber into an infusible form.

"At this stage, the plastic molecules bond, and with further heating cannot melt or flow. At very high temperatures, this fiber retains mostly carbon and all other elements volatize off in different gas or compound forms."

The researchers also noted that their discovery represents a success for DOE, which seeks advances in lightweight materials that can, among other things, help the U.S. auto industry design cars able to achieve more miles per gallon with no compromise in safety or comfort. And the raw material, which could come from grocery store plastic bags, carpet backing scraps and salvage, is abundant and inexpensive.

More information: "Patterned functional carbon fibers from polyethylene," http://onlinelibra … 01104551/pdf

Provided by Oak Ridge National Laboratory (news : web)

Some flame retardants make fires more deadly

Anna A. Stec, Ph.D., led the research, which focused on the most widely-used category of flame retardants, which contain the chemical element bromine. Scientists term these "halogen-based" flame retardants because bromine is in a group of elements called halogens.

"Halogen-based flame retardants are effective in reducing the ignitability of materials," Stec said. "We found, however, that flame retardants have the undesirable effect of increasing the amounts of carbon monoxide and hydrogen cyanide released during combustion. These gases, not the thermal effects of burns on the body, are the No. 1 cause of fire deaths." Stec, who is with the University of Central Lancashire, Centre for Fire and Hazards Science, Lancashire, U.K., spoke at an ACS symposium on "Fire and Polymers," which included 60 presentations.

Almost 10,000 deaths from fires occur in industrialized countries worldwide each year, including about 3,500 in the U.S. Contrary to popular belief, inhalation of toxic gases released by burning materials –– not burns –– causes the most deaths and most of the serious injuries. Stec's team set out to determine the effects of flame retardants on the production of those gases. The scientists tested brominated flame retardants with antimony synergists, mineral-based flame retardants and so-called intumescent agents, which swell when heated, forming a barrier that flames cannot penetrate.

Unlike the halogen-based retardants, mineral-based fire retardants have little effect on fire toxicity. Most intumescent fire retardants reduce the amount of potentially toxic gases released in a fire.

Provided by American Chemical Society (news : web)

Images capture split personality of dense suspensions

 Stir lots of small particles into water, and the resulting thick mixture appears highly viscous. When this dense suspension slips through a nozzle and forms a droplet, however, its behavior momentarily reveals a decidedly non-viscous side. University of Chicago physicists recorded this surprising behavior in laboratory experiments using high-speed photography, which can capture action taking place in one hundred-thousandths of a second or less.

UChicago graduate student Marc Miskin and Heinrich Jaeger, the William J. Friedman and Alicia Townsend Friedman Professor in Physics, expected that the dense suspensions in their experiments would behave strictly like viscous liquids, which tend to flow less freely than non-viscous liquids. Viscosity certainly does matter as the particle-laden liquid begins to exit the nozzle, but not at the moment where the drop's thinning neck breaks in two.

New behavior appears to arise from feedback between the tendencies of the liquid and what the particles within the liquid can allow. "While the liquid deforms and becomes thinner and thinner at a certain spot, the particles also have to move with that liquid. They are trapped inside the liquid," Jaeger explained. As deformation continues, the particles get in each other's way.

"Oil, honey, also would form a long thread, and this thread would become thinner and break in a way characteristic of a viscous liquid," Jaeger said. "The particles in a dense suspension conspire to interact with the liquid in a way that, when it's all said and done, a neck forms that shows signs of a split personality: It thins in a non-viscous fashion, like water, all the while exhibiting a shape more resembling that of its viscous cousins."

It took Miskin and Jaeger six months to become convinced that the viscosity of the suspending liquid was a minor player in their experiments. "It is a somewhat heretical view that this viscosity should not matter," Jaeger said. "Who would have thought that?"

Miskin and Jaeger presented their results in the March 5 online early edition and the March 20 print edition of the Proceedings of the National Academy of Sciences.

In their experiments, Miskin and Jaeger compared a variety of pure liquids to mixtures in which particles occupy more than half the volume.

"The results indicate that what we know about drop breakup from pure liquids does not allow us to predict phenomena observed in their experiments," said Jeffrey Morris, professor of chemical engineering at City College of New York. "The most striking and interesting result is the fact that, despite these being very viscous mixtures, the viscosity plays little role in the way a drop forms."

Few studies have examined droplet formation in dense suspensions. As Morris noted, such work could greatly impact applications such as inkjet printing, combustion of slurries involving coal in oil, and the drop-by-drop deposition of cells in DNA microarrays.

Scientific defiance

In these applications particles often are so densely packed that their behavior defies a simple scientific description, one that might only take into account average particle size and the fraction of the liquid that the particles occupy, Morris explained. The UChicago study showed that particles cause deformations and often protrude through the liquid, rendering any such description incomplete until fundamental questions about the interface between a liquid mixture and its surroundings are properly addressed.

"Miskin and Jaeger provide arguments for the importance of these protrusions in their work and suggest that the issue is of broader relevance to any flow where a particle-laden liquid has an interface with another fluid," Morris said.

Miskin and Jaeger verified their results by systematically evaluating different viscosities, particle sizes and suspending liquids, and developed a mathematical model to explain how the droplet necks evolve over time until they break apart.

One initially counter-intuitive prediction of this model was that larger particles should produce behavior resembling that in pure water without any particles. "If you want to make it behave more like a pure non-viscous liquid, you want to make the particles large," said Jaeger, who finds himself intrigued by nature's seemingly endless store of surprises.

Miskin and Jaeger indeed observed this when the particle size approached a significant fraction of the nozzle diameter, making the particles visible to the naked eye.

"You think you have a pretty good idea of what should happen, and instead there's a surprise at every corner. Honestly, finding surprises is what I love about this work," Jaeger said.

Story Source:

The above story is reprinted from materials provided by University of Chicago, via Newswise.

Note: Materials may be edited for content and length. For further information, please contact the source cited above.

Journal Reference:

M. Z. Miskin, H. M. Jaeger. Droplet formation and scaling in dense suspensions. Proceedings of the National Academy of Sciences, 2012; 109 (12): 4389 DOI: 10.1073/pnas.1111060109

Novel filter metal-organic framework material could cut natural gas refining costs

Today, to separate hydrocarbon gas mixtures into the pure chemicals needed to make plastics, refineries "crack" crude oil at high temperatures – 500 to 600 degrees Celsius – to break complex hydrocarbons into lighter, short-chain molecules. They then chill the gaseous mixture to 100 degrees below zero Celsius to liquefy and divide the gases into those destined for plastics and those used as fuel for home heating and cooking.

"Cryogenic distillation at low temperatures and high pressures is among the most energy-intensive separations carried out at large scale in the chemical industry, and an environmental problem because of its contributions to global climate change," said Jeffrey Long, a professor of chemistry at the UC Berkeley and a faculty researcher at Lawrence Berkeley National Laboratory.

Long and his UC Berkeley colleagues now have created an iron-based material – a metal-organic framework, or MOF – that can be used at high temperatures to efficiently separate these gases while eliminating the chilling.

"You need a very pure feedstock of propylene and ethylene for making some of the most important polymers, such as polypropylene, for consumer products, but refineries dump a lot of energy into bringing the high temperature gases down to cryogenic temperatures," Long said. "If you can do the separation at higher temperatures, you can save that energy. This material is really good at doing these particular separations."

"The research conducted by the Long group exemplifies the potential of MOF-based materials relative to olefin/paraffin separations," said chemist Peter Nickias, a Dow Fellow at Dow Chemical Company in Michigan who was not involved in the research. "More specifically, the ability of the reported iron-based MOF to separate a variety of unsaturated hydrocarbons from saturated species not only shows the versatility of the iron-MOF system, but also clearly reveals the potential of MOFs as alternative adsorbents."

In the chemical industry, ethylene and propylene are called olefins, while methane, ethane and propane are called paraffins.

Long and his colleagues at UC Berkeley and the National Institute of Standards and Technology (NIST) in Gaithersburg, Md., report their findings in the March 30 issue of Science.

MOFs for natural gas purification

The iron-MOF is also good at purifying natural gas, which is a mixture of methane and various types of hydrocarbon impurities that have to be removed before the gas can be used by consumers. These impurities can then be sold for other uses, Long said.

"MOF compounds have a very high surface area, which provides lots of area a gas mixture can interact with, and that surface contains iron atoms that can bind the unsaturated hydrocarbons," Long said. "Acetylene, ethylene and propylene will stick to those iron sites much more strongly than will ethane, propane or methane. That is the basis for the separation."

Nickias noted that increased supplies of natural gas from shale have provided more opportunity to extract and use ethylene and propylene from natural gas, and a variety of materials and approaches are being examined to cut energy use during the refining and purification of olefins.

"Significant energy savings could be achieved if a non-distillation separation could be implemented, or more realistically, the load on a cryogenic distillation unit can be reduced via upstream modifications to the process," Nickias said.

Petroleum refined for the chemical industry is typically a mix of hydrocarbons, primarily two-carbon molecules – ethane, ethylene and acetylene – and three-carbon chains – propane and propylene. Cryogenic distillation separates these compounds – all of them gases at room temperature – by liquefying them at low temperatures and high pressure, which causes them to separate by density. Ethylene and propylene go into plastic polymers, while ethane and propane are typically used for fuel.

The researchers found that when pumping a gas mixture through the iron-based MOF (Fe-MOF-74), the propylene and ethylene bind to the iron embedded in the matrix, letting pure propane and ethane through. In their trials, the ethane coming out was 99.0 to 99.5 percent pure. The propane output was close to 100 percent pure, since no propylene could be detected.

After the ethane and propane emerge, the MOF can be heated or depressurized to release ethylene and propylene pure enough for making polymers.

"Once you saturate the material with ethylene, for example – you shut off the valve, stop the feed gas, warm up the absorber unit and the ethylene would come out in pure form as a gas," Long said.

MOFs like packed soda straws

Through a microscope, Fe-MOF-74 looks like a collection of narrow tubes packed together like drinking straws in a box. Each tube is made of organic materials and six long strips of iron, which run lengthwise along the tube. Analysis by Long's colleagues at the NIST Center for Neutron Research showed that different light hydrocarbons have varied levels of attraction to the tubes' iron. By passing a mixed-hydrocarbon gas through a series of filters made of the tubes, the hydrocarbon with the strongest affinity can be removed in the first filter layer, the next strongest in the second layer, and so forth.

"It works well at 45 degrees Celsius, which is closer to the temperature of hydrocarbons at some points in the distillation process," said Wendy Queen, a postdoctoral fellow at NIST who worked for six months in Long's UC Berkeley lab. "The upshot is that if we can bring the MOF to market as a filtration device, the energy-intensive cooling step potentially can be eliminated. We are now trying out metals other than iron in the MOF in case we can find one that works even better."

Long and his laboratory colleagues are developing iron-based MOFs to capture carbon from smokestack emissions and sequester it to prevent its release into the atmosphere as a greenhouse gas. Similar MOFs, which can be made with different pore sizes and metals, turn out to be ideal for separating different types of hydrocarbons and for storing hydrogen and methane for use as fuel.

More information: E.D. Bloch, W.L. Queen, R.Krishna, J.M. Zadrozny, C.M. Brown and J.R. Long. Hydrocarbon separations in a metal-organic framework with open Iron(II) coordination sites. Science, March 30, 2012.

Provided by National Institute of Standards and Technology (news : web)

New method for cleaning up nuclear waste

While the costs associated with storing nuclear waste and the possibility of it leaching into the environment remain legitimate concerns, they may no longer be obstacles on the road to cleaner energy.

A new paper by researchers at the University of Notre Dame, led by Thomas E. Albrecht-Schmitt, professor of civil engineering and geological sciences and concurrent professor of chemistry and biochemistry, showcases Notre Dame Thorium Borate-1 (NDTB-1) as a crystalline compound that can be tailored to safely absorb radioactive ions from nuclear waste streams. Once captured, the radioactive ions can then be exchanged for higher-charged species of a similar size, recycling the material for re-use.

If one considers that the radionuclide technetium (99Tc) is present in the nuclear waste at most storage sites around the world, the math becomes simple. There are more than 436 nuclear power plants operating in 30 countries; that is a lot of nuclear waste. In fact, approximately 305 metric tons of 99Tc were generated from nuclear reactors and weapons testing from 1943 through 2010. Its safe storage has been an issue for decades.

"The framework of the NDTB-1 is key," says Albrecht-Schmitt. "Each crystal contains a framework of channels and cages featuring billions of tiny pores, which allow for the interchange of anions with a variety of environmental contaminants, especially those used in the nuclear industry, such as chromate and pertechnetate."

Albrecht-Schmitt's team has concluded successful laboratory studies using the NDTB-1 crystals, during which they removed approximately 96 percent of 99Tc. Additional field tests conducted at the Savannah River National Laboratory in Aiken, S.C., and discussed in the paper have shown that the Notre Dame compound successfully removes 99Tc from nuclear waste and also exhibits positive exchange selectivity for greater efficiency.

Story Source:

The above story is reprinted from materials provided by University of Notre Dame. The original article was written by William G. Gilroy.

Note: Materials may be edited for content and length. For further information, please contact the source cited above.

Journal Reference:

Shuao Wang, Ping Yu, Bryant A. Purse, Matthew J. Orta, Juan Diwu, William H. Casey, Brian L. Phillips, Evgeny V. Alekseev, Wulf Depmeier, David T. Hobbs, Thomas E. Albrecht-Schmitt. Selectivity, Kinetics, and Efficiency of Reversible Anion Exchange with TcO4- in a Supertetrahedral Cationic Framework. Advanced Functional Materials, 2012; DOI: 10.1002/adfm.201103081

Shiny new tool for imaging biomolecules

 At the heart of the immune system that protects our bodies from disease and foreign invaders is a vast and complex communications network involving millions of cells, sending and receiving chemical signals that can mean life or death. At the heart of this vast cellular signaling network are interactions between billions of proteins and other biomolecules. These interactions, in turn, are greatly influenced by the spatial patterning of signaling and receptor molecules. The ability to observe signaling spatial patterns in the immune and other cellular systems as they evolve, and to study the impact on molecular interactions and, ultimately, cellular communication, would be a critical tool in the fight against immunological and other disorders that lead to a broad range of health problems including cancer. Such a tool is now at hand.

Researchers with the U.S. Department of Energy (DOE)'s Lawrence Berkeley National Laboratory (Berkeley Lab) and the University of California (UC) Berkeley, have developed the first practical application of optical nanoantennas in cell membrane biology. A scientific team led by chemist Jay Groves has developed a technique for lacing artificial lipid membranes with billions of gold "bowtie" nanoantennas. Through the phenomenon known as "plasmonics," these nanoantennas can boost the intensity of a fluorescent or Raman optical signal from a protein passing through a plasmonic "hot-spot" tens of thousands of times without the protein ever being touched.

"Our technique is minimally invasive since enhancement of optical signals is achieved without requiring the molecules to directly interact with the nanoantenna," Groves says. "This is an important improvement over methods that rely on adsorption of molecules directly onto antennas where their structure, orientation, and behavior can all be altered."

Groves holds joint appointments with Berkeley Lab's Physical Biosciences Division and UC Berkeley's Chemistry Department, and is also a Howard Hughes Medical Institute investigator. He is the corresponding author of a paper that reports these results in the journal NanoLetters. The paper is titled "Single Molecule Tracking on Supported Membranes with Arrays of Optical Nanoantennas." Co-authoring the paper were Theo Lohmuller, Lars Iversen, Mark Schmidt, Christopher Rhodes, Hsiung-Lin Tu and Wan-Chen Lin.

Fluorescent emissions, in which biomolecules of interest are tagged with dyes that fluoresce when stimulated by light, and Raman spectroscopy, in which the scattering of light by molecular vibrations is used to identify and locate biomolecules, are work-horse optical imaging techniques whose value has been further enhanced by the emergence of plasmonics. In plasmonics, light waves are squeezed into areas with dimensions smaller than half-the-wavelength of the incident photons, making it possible to apply optical imaging techniques to nanoscale objects such as biomolecules. Nano-sized gold particles in the shape of triangles that are paired in a tip-to-tip formation, like a bow-tie, can serve as optical antennas, capturing and concentrating light waves into well-defined hot spots, where the plasmonic effect is greatly amplified. Although the concept is well-established, applying it to biomolecular studies has been a challenge because gold particle arrays must be fabricated with well-defined nanometer spacing, and molecules of interest must be delivered to plasmonic hot-spots.

"We're able to fabricate billions of gold nanoantennas in an artificial membrane through a combination of colloid lithography and plasma processing," Groves says. "Controlled spacing of the nanoantenna gaps is achieved by taking advantage of the fact that polystyrene particles melt together at their contact point during plasma processing. The result is well-defined spacing between each pair of gold triangles in the final array with a tip-to-tip distance between neighboring gold nanotriangles measuring in the 5-to-100 nanometer range."

Until now, Groves says, it has not been possible to decouple the size of the gold nanotriangles, which determines their surface plasmon resonance frequency, from the tip-to-tip distance between the individual nanoparticle features, which is responsible for enhancing the plasmonic effect. With their colloidal lithography approach, a self-assembling hexagonal monolayer of polymer spheres is used to shadow mask a substrate for subsequent deposition of the gold nanoparticles. When the colloidal mask is removed, what remains are large arrays of gold nanoparticles and triangles over which the artificial membrane can be formed.

The unique artificial membranes, which Groves and his research group developed earlier, are another key to the success of this latest achievement. Made from a fluid bilayer of lipid molecules, these membranes are the first biological platforms that can combine fixed nanopatterning with the mobility of fluid bilayers. They provide an unprecedented capability for the study of how the spatial patterns of chemical and physical properties on membrane surfaces influence the behavior of cells.

"When we embed our artificial membranes with gold nanoantennas we can trace the trajectories of freely diffusing individual proteins as they sequentially pass through and are enhanced by the multiple gaps between the triangles," Groves says. "This allows us to study a realistic system, like a cell, which can involve billions of molecules, without the static entrapment of the molecules."

As molecules in living cells are generally in a state of perpetual motion, it is often their movement and interactions with other molecules rather than static positions that determine their functions within the cell. Groves says that any technique requiring direct adsorption of a molecule of interest onto a nanoantenna intrinsically removes that molecule from the functioning ensemble that is the essence of its natural behavior. The technique he and his co-authors have developed allows them to look at individual biomolecules but within the context of their surrounding community.

"The idea that optical nanoantennas can produce the kinds of enhanced signals we are observing has been known for years but this is the first time that nanoantennas have been fabricated into a fluid membrane so that we can observe every molecule in the system as it passes through the antenna array," Groves says. "This is more than a proof-of-concept we've shown that we now have a useful new tool to add to our repertoire."

This research was primarily supported by the DOE Office of Science.

The above story is reprinted from materials provided by DOE/Lawrence Berkeley National Laboratory.

Note: Materials may be edited for content and length. For further information, please contact the source cited above.

Journal Reference:

T. Lohmüller, L. Iversen, M. Schmidt, C. Rhodes, H.-L. Tu, W.-C. Lin, J. T. Groves. Single Molecule Tracking on Supported Membranes with Arrays of Optical Nanoantennas. Nano Letters, 2012; 12 (3): 1717 DOI: 10.1021/nl300294b

Protein 'jailbreak' helps breast cancer cells live

All four proteins were already under suspicion. Researchers, for example, have already tried to assess what levels of HDAC6 in patients with estrogen-receptor positive breast cancer may mean for their prognosis. The results have been inconclusive. The new research suggests that measuring overall levels may not be enough, said the study's senior author Dr. Rachel Altura, associate professor of pediatrics in The Warren Alpert Medical School of Brown University and a pediatric oncologist at Hasbro Children's Hospital.

"We need to look not only at the levels, but also where is it in the cell," she said.

Altura's emphasis on location comes from what her research team found as they tracked and tweaked the comings and goings of survivin in cells. Inside the nucleus, survivin is no problem. Outside the nucleus, but within the cell, it can prevent normal cell death, allowing cancer cells to persist.

In previous work, Altura and her collaborators established that under normal circumstances, CBP chemically regulates survivin, a process called acetylation, and keeps it in the nucleus. The question in the new work was how survivin gets out.

In a series of experiments, what they observed was that in human and mouse breast cancer cells, HDAC6 gathers at the boundary between the nucleus and the rest of the cell, becomes activated by CBP, then binds survivin and undoes its acetylation. This deacetylation allows survivin to then be shuttled out of the nucleus by CRM1.

In the classic jailbreak, CBP is a corrupt guard who looks the other way as HDAC6, the shovel, is smuggled in. The final accomplice, CRM1, is the tunnel with a getaway car on the other end.

Working the new leads

Altura said the research suggests a clear strategy — to keep survivin in the nucleus — and two leads to pursue it, both of which she has already begun working on with collaborators in academia and in the pharmaceutical industry.

One idea is to inhibit HDAC6 in an attempt to prevent it from misregulating the acetylation of survivin. While general HDAC inhibitors are in clinical trials, Altura is optimistic that blocking just HDAC6, using specific inhibitors developed by a colleague in Japan, would have fewer complications.

"You always have to worry about all the things you don't know that you are targeting," she said. "If we can target HDAC6, we can maybe block survivin from coming out of the nucleus and maintain it in its good state."

The other strategy is to block CRM1, Altura said, an idea she is pursuing with a pharmaceutical company in breast cancer cells in the lab. She said preliminary experiments look promising in keeping survivin inside the nucleus and making cancer cells more susceptible to dying.

Provided by Brown University (news : web)

Unexpected behaviour of microdroplets

Physicists agree that laminar flow of liquids has been well understood and described in detail from the theoretical point of view. Researchers at the Institute of Physical Chemistry of the Polish Academy of Sciences in Warsaw have, however, observed that droplets of chemical substances flowing in a carrier liquid inside microchannels -- although presenting laminar flow inside them -- present ultiple mysteries.

Researchers from the Institute of Physical Chemistry of the Polish Academy of Sciences (IPC PAS) in Warsaw discovered a new phenomenon related to the fluid dynamics. It occurs when minute droplets translate through microfluidic channels. "The effect observed by our group is related to changes in swirls inside microdroplets and as yet has not been predicted by existing theoretical models," says Dr Sławomir Jakieła from the IPC PAS. The results of the research pursued thanks to a TEAM grant from the Foundation for Polish Science, have just been published in the journal Physical Review Letters.

Microfluidic systems are miniature chemical reactors of a credit card in size, or even less. Inside these systems, microchannels with diameters of tenths or hundredths of a milimeter provide a path for laminar flow of a carrier fluid (commonly oil) with floating microdroplets of appropriate chemical compounds.

"Using a single microfluidic system, even today one can carry out as much as a few tens of thousands of different chemical reactions a day. In future, these systems will become for chemistry what integrated circuits turned out to be for electronics. Yet before we build chemical devices as revolutionary as silicon microprocessors, we have to reach a comprehensive understanding of all physical phenomena occurring in flows of microdroplets," continues Dr Jakieła.

The flows that we experience at the macroscale are often dominated by inertia and turbulences. With small volumes that are typical for microfluidic systems, the flow of a liquid is laminar and subject to viscosity-related effects.

The speed of oil flowing in microchannels is not uniform. The layers close to the walls move with the lowest speed, whereas those near the middle of a channel -- with the highest speed. "If a microdroplet is distinctly smaller than the channel diameter, it can find a place in the middle part of the flow, reaching the speed even twice as high as the average oil speed. This is nothing surprising. Similar effect can be observed for instance in rivers: the current near the banks is much slower than in the middle of the river," explains Sylwia Makulska, a PhD student at the IPC PAS.

If a sufficiently large droplet flows in a circular channel, it occupies almost the entire lumen of the channel. The droplet speed is then almost identical as that of the oil flow. The situation gets much more interesting when the droplet translates in rectangular channels that are typical to microfluidic systems. Due to interfacial tension the cross-section of a microdroplet remains rounded leaving the corners of the channel free for the flow of oil.

The team from the IPC PAS produced microdroplets from aqueous solutions of glycerine of different concentrations, and therefore of different viscosities. They translated in oil (hexadecane) through a 10 cm long rectangular channel. The researchers measured the speed of microdroplets relative to the oil as a function of their volume (length in a microchannel), droplet and oil viscosities and the flow speed of the carrier liquid.

When the viscosity of microdroplets was less than or comparable to that of the carrier liquid, their speed relative to the oil turned out to decrease with increasing droplet length, but in a certain range only. The droplets were translating with the lowest speed when their length was two, three times greater than the channel width. "Every time we observed the minimum speed relative to oil. Everything seemed to be in line with what the theoreticians would expect," says Jakieła.

But what was really interesting were things that happened when the researchers started to change the rate of oil flow. It turned out that the minimum of the droplet speed relative to oil was disappearing with increasing flow rate. Further increase in the oil flow rate resulted, however, in reappearance of the minimum -- but this time deeper and wider. "To make the long story short: we discovered that, depending on the oil flow rate, a droplet of specific length can translate under some conditions faster and under other conditions slower relative to oil," concludes Jakieła.

To find out what is the reason for the surprising behaviour of the droplets, the researchers from the IPC PAS introduced to microdroplets fluorescent markers of a few micrometers in size. When the droplets were moving along the microchannel, they were irradiated with laser light to excite fluorescence of the markers, which allowed for observation of fluid movements inside the droplets.

The measurements revealed that the distribution of swirls inside a droplet changes with increasing flow rate of the carrier liquid. "We expected changes, but the existing theories suggested that the number of swirls in microdroplets decreases with increasing oil flow rate. We observed, meanwhile, an opposite phenomenon: the faster was the oil flow, the more swirls were in a droplet. The Nature played again a trick on theoreticians," sums up Prof. Piotr Garstecki (IPC PAS).

At the Institute of Physical Chemistry PAS a work has started to make use of the new phenomenon in processes related to mixing the contents of microdroplets in microfluidic systems.

Story Source:

The above story is reprinted from materials provided by Institute of Physical Chemistry of the Polish Academy of Sciences, via AlphaGalileo.

Note: Materials may be edited for content and length. For further information, please contact the source cited above.

Journal Reference:

Slawomir Jakiela, Piotr Korczyk, Sylwia Makulska, Olgierd Cybulski, Piotr Garstecki. Discontinuous Transition in a Laminar Fluid Flow: A Change of Flow Topology inside a Droplet Moving in a Micron-Size Channel. Physical Review Letters, 2012; 108 (13) DOI: 10.1103/PhysRevLett.108.134501

Sweet success in hunt for honey's healing factor

The ground-breaking research, carried out at Industrial Research Ltd (IRL), Plant & Food Research and Massey University, found that different varieties of New Zealand honey appear to trigger different immune responses.
IRL's role was to provide its world-class expertise in the extraction, analysis, and purification of complex molecules that play an important role in biological systems.

Comvita’s Chief Technology Officer Dr. Ralf Schlothauer says the research provides the tools for understanding why honey stimulates healing of stalled wounds.

“We know a lot about the anti-microbial properties of manuka honey but had much less scientific information about the immune system-related effects of honey in wound healing.

“The findings suggest there could be a number of honeys to consider if you want to stimulate the immune system. Ultimately, it might mean we produce medical honey products that are specifically tailored for certain treatments or that we select a range of honeys for their particular properties to include in a specific blend.”

Headquartered in Paengaroa in the Bay of Plenty, Comvita is the world’s largest manufacturer and marketer of Manuka honey and produces natural health products for the wound care, health care, personal care and functional foods markets. It also produces Medihoney™ wound care products that are sold through a global licensing deal with US-based Derma Sciences.

Prior to the latest work, Dr. Schlothauer says published research had shown there were big carbohydrate molecules in honey that stimulated immune cells but their structure had not been analysed.

Comvita put two students, Swapna Gannabathula and Gregor Steinhorn, onto the task and their discoveries eventually led the company to Crown Research Institute IRL.

“We started separating the molecule but were puzzled about what it was. Initially we thought it was a glycan and sought appropriate analysis but they put us on to Dr. Ian Sims in the Carbohydrate Chemistry group at IRL, who is a leading expert in analysing complex molecules that play an important role in biological systems,” says Dr. Schlothauer.

IRL has one of only three laboratories world-wide with the capability and expertise required to carry out complex research into the extraction, purification and analysis of oligo- and poly-saccharides, and glycoconjugates.

Dr. Sims began his work with small-scale analyses that were conducted on Manuka, Kanuka and Clover honeys. Starting with five grams of honey, separation of high molecular weight polymers from small sugars yielded just a few milligrams of sample for analysis. 

After Dr Sims completed an initial, detailed analysis of the sugars Gregor Steinhorn, who now works full-time for Comvita, spent many hours purifying buckets of honey and identified its exact nature under the supervision of Dr. Sims and Dr. Alistair Carr (Massey University).

Comvita is determining the commercial value of this discovery and has a range of new products under development.

The findings from the research have been published in Food Chemistry, an international, peer-reviewed publication that reports on the chemistry and biochemistry of foods and raw materials.

Dr. Schlothauer says the next challenge is to better understand how and why honey promotes healing, with Comvita planning to do more research with the University of Auckland and IRL.

“The work is helping us ensure there is much better information about natural medicines,” says Dr. Schlothauer. "We need to be able to talk about the immune relevance of honey and have proof of its scientific efficacy to ensure natural medicines can sit alongside conventional health products.”

Provided by Industrial Research

Getting to the moon on drops of fuel

 Imagine reaching the Moon using just a fraction of a liter of fuel. With their ionic motor, MicroThrust, EPFL scientists and their European partners are making this a reality and ushering in a new era of low-cost space exploration. The complete thruster weighs just a few hundred grams and is specifically designed to propel small (1-100 kg) satellites, which it enables to change orbit around Earth and even voyage to more distant destinations -- functions typically possible only for large, expensive spacecraft. The just-released prototype is to be employed on CleanSpace One, a satellite under development at EPFL that is designed to clean up space debris, and on OLFAR, a swarm of Dutch nanosatellites that will record ultra-low radio-frequency signals on the far side of the Moon.

The motor, designed to be mounted on satellites as small as 10x10x10 cm3, is extremely compact but highly efficient. The prototype weighs only about 200 grams, including the fuel and control electronics.

"At the moment, nanosatellites are stuck in their orbits. Our goal is to set them free," explains Herbert Shea, coordinator of the European MicroThrust project and director of EPFL's Microsystems for Space Technologies Laboratory.

Small satellites are all the rage right now because their manufacturing and launch costs are relatively low -- about half a million dollars, compared to conventional satellites that run into the hundreds of millions. But nanosatellites currently lack an efficient propulsion system that would render them truly autonomous and thus able to carry out exploration or observation missions.

A motor that doesn't burn fuel

Instead of a combustible fuel, the new mini motor runs on an "ionic" liquid, in this case the chemical compound EMI-BF4, which is used as a solvent and an electrolyte. It is composed of electrically charged molecules (like ordinary table salt) called ions, except that this compound is liquid at room temperature. The ions are extracted from the liquid and then ejected by means of an electric field to generate thrust. This is the principle behind the ionic motor: fuel is not burned, it is expelled.

In the motor developed at EPFL, the flow of ions is emitted from an array of tiny silicon nozzles -- over 1,000 per square centimeter. The fuel is first guided by capillary action from a reservoir to the extremity of the micro-nozzles, where the ions are then extracted by an electrode held at 1,000 volts, accelerated, and finally emitted out the back of the satellite. The polarity of the electric field is reversed every second, so that all the ions -- positive and negative -- are ejected.

SystematIC Design, a MicroThrust project partner, designed the motor's electrical system. The ion ejection system requires a high electrical voltage, but the available energy aboard a 1-liter nanosatellite is limited to a few small solar cells -- in practice, about four watts of power. The Dutch company was able to develop a system that overcame this difficulty.

Cruising speed: 40,000 km per hour

After six months of acceleration, the microsatellite's speed increases from 24,000 km/h, its launch speed, to 42,000 km/h. The acceleration is only about a tenth of a millimeter per square second, which translates into 0-100 km/h in 77 hours. But in space, where there is no friction to impede motion, gentle but steady acceleration is the way to go.

The ionic motor will power CleanSpace One -- a nanosatellite whose mission is to tidy up space by grabbing space debris and pulling it into Earth's atmosphere to be safely incinerated. According to the Swiss Space Center, CleanSpace One will take two to three months and more than 1,000 terrestrial revolutions to reach one of its targets, the decommissioned Swisscube cubesat or Tlsat-1 cubesat. Scientists have just over a year to finalize their system.

Researchers have a bit more than a year to finalize the ionic motor. The prototype was developed in the context of a European project coordinated by EPFL and involved Queen Mary and Westfield College in the UK, the Dutch companies TNO and SystematIC Design B.V., and Nanospace AB in Sweden.

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The above story is reprinted from materials provided by Ecole Polytechnique Fédérale de Lausanne.

Note: Materials may be edited for content and length. For further information, please contact the source cited above.

Scientists unlock key to cancer cell death mystery

A group led by the University of Leicester has shown that particular cancer cells are especially sensitive to a protein called p21. This protein usually forces normal and cancer cells to stop dividing but it was recently shown that in some cases it can also kill cancer cells.

However, scientists have been unclear about how this happens.

Researcher Salvador Macip, from the University of Leicester Department of Biochemistry, said: "If we could harness this 'killing power' that p21 has, we could think of designing new therapies aimed at increasing its levels in tumours. This is what motivated us to look into it".

Now the team from the universities of Leicester and Cardiff in the UK, University of South Carolina, USA and Karolinska Institutet, Sweden has discovered that cells from sarcomas tend to die in response to p21 and that this is determined by the sensitivity of their mitochondria to oxidants.

They have published their findings in The Journal of Biological Chemistry. The research was funded by the MRC, the NIH, CONACYT and the Swedish Cancer Society

Dr Macip added: "Our research also showed that p21 can kill cells even in the absence of p53, a protein that is in the main responsible for cell death but is inactivated in most cancers.

"This shows that certain types of cancer, sarcomas for instance, but maybe also others, should respond well to drugs that increase the levels of p21, even if they don't have an active p53. The side effects of these therapies should be minimal, since our experiments show that normal cells would arrest but not die in response to p21.

"There are already drugs available that selectively increase p21. Our results provide a rationale for testing them in certain types of cancers, which could be identified using the experiments we describe."

More information: Reactive oxygen species and mitochondrial sensitivity to oxidative stress determine induction of cancer cell death by p21. Masgras I, Carrera S, de Verdier PJ, Brennan P, Majid A, Makhtar W, Tulchinksy E, Jones GD, Roninson IB, Macip S. J Biol Chem. 2012 Feb 6. [Epub ahead of print]

The Journal of Biological Chemistry, Vol. 287, Issue 13, 9845-9854, MARCH 23, 2012

Provided by University of Leicester (news : web)

Modified microbes turn carbon dioxide to liquid fuel

Today, electrical energy generated by various methods is still difficult to store efficiently. Chemical batteries, hydraulic pumping and water splitting suffer from low energy-density storage or incompatibility with current transportation infrastructure.

In a study published March 30 in the journal Science, James Liao, UCLA's Ralph M. Parsons Foundation Chair in Chemical Engineering, and his team report a method for storing electrical energy as chemical energy in higher alcohols, which can be used as liquid transportation fuels.

"The current way to store electricity is with lithium ion batteries, in which the density is low, but when you store it in liquid fuel, the density could actually be very high," Liao said. "In addition, we have the potential to use electricity as transportation fuel without needing to change current infrastructure."

Liao and his team genetically engineered a lithoautotrophic microorganism known as Ralstonia eutropha H16 to produce isobutanol and 3-methyl-1-butanol in an electro-bioreactor using carbon dioxide as the sole carbon source and electricity as the sole energy input.

Photosynthesis is the process of converting light energy to chemical energy and storing it in the bonds of sugar. There are two parts to photosynthesis — a light reaction and a dark reaction. The light reaction converts light energy to chemical energy and must take place in the light. The dark reaction, which converts CO2 to sugar, doesn't directly need light to occur.

"We've been able to separate the light reaction from the dark reaction and instead of using biological photosynthesis, we are using solar panels to convert the sunlight to electrical energy, then to a chemical intermediate, and using that to power carbon dioxide fixation to produce the fuel," Liao said. "This method could be more efficient than the biological system."

Liao explained that with biological systems, the plants used require large areas of agricultural land. However, because Liao's method does not require the light and dark reactions to take place together, solar panels, for example, can be built in the desert or on rooftops.

Theoretically, the hydrogen generated by solar electricity can drive CO2 conversion in lithoautotrophic microorganisms engineered to synthesize high-energy density liquid fuels. But the low solubility, low mass-transfer rate and the safety issues surrounding hydrogen limit the efficiency and scalability of such processes. Instead Liao's team found formic acid to be a favorable substitute and efficient energy carrier.

"Instead of using hydrogen, we use formic acid as the intermediary," Liao said. "We use electricity to generate formic acid and then use the formic acid to power the CO2 fixation in bacteria in the dark to produce isobutanol and higher alcohols."

The electrochemical formate production and the biological CO2 fixation and higher alcohol synthesis now open up the possibility of electricity-driven bioconversion of CO2 to a variety of chemicals. In addition, the transformation of formate into liquid fuel will also play an important role in the biomass refinery process, according to Liao.

"We've demonstrated the principle, and now we think we can scale up," he said. "That's our next step."

More information: "Integrated Electromicrobial Conversion of CO2 to Higher Alcohols," by H. Li; D.G. Wernick, Science.

Provided by University of California Los Angeles (news : web)

New process converts polyethylene into carbon fiber

Common material such as polyethylene used in plastic bags could be turned into something far more valuable through a process being developed at the Department of Energy's Oak Ridge National Laboratory.

In a paper published in Advanced Materials, a team led by Amit Naskar of the Materials Science and Technology Division outlined a method that allows not only for production of carbon fiber but also the ability to tailor the final product to specific applications.

"Our results represent what we believe will one day provide industry with a flexible technique for producing technologically innovative fibers in myriad configurations such as fiber bundle or non-woven mat assemblies," Naskar said.

Using a combination of multi-component fiber spinning and their sulfonation technique, Naskar and colleagues demonstrated that they can make polyethylene-base fibers with a customized surface contour and manipulate filament diameter down to the submicron scale. The patent-pending process also allows them to tune the porosity, making the material potentially useful for filtration, catalysis and electrochemical energy harvesting.

Naskar noted that the sulfonation process allows for great flexibility as the carbon fibers exhibit properties that are dictated by processing conditions. For this project, the researchers produced carbon fibers with unique cross-sectional geometry, from hollow circular to gear-shaped by using a multi-component melt extrusion-based fiber spinning method.

The possibilities are virtually endless, according to Naskar, who described the process.

"We dip the fiber bundle into an acid containing a chemical bath where it reacts and forms a black fiber that no longer will melt," Naskar said. "It is this sulfonation reaction that transforms the plastic fiber into an infusible form.

"At this stage, the plastic molecules bond, and with further heating cannot melt or flow. At very high temperatures, this fiber retains mostly carbon and all other elements volatize off in different gas or compound forms."

The researchers also noted that their discovery represents a success for DOE, which seeks advances in lightweight materials that can, among other things, help the U.S. auto industry design cars able to achieve more miles per gallon with no compromise in safety or comfort. And the raw material, which could come from grocery store plastic bags, carpet backing scraps and salvage, is abundant and inexpensive.

Story Source:

The above story is reprinted from materials provided by DOE/Oak Ridge National Laboratory.

Note: Materials may be edited for content and length. For further information, please contact the source cited above.

Journal Reference:

Marcus Hunt, Tomonori Saito, Rebecca Brown and Amar Kumbhar. Patterned functional carbon fibers from polyethylene. Advanced Materials, 2012 DOI: 10.1002/adma.201104551

New nano-measurements add spark to centuries-old theory of friction

 The phenomenon of friction, when studied on a nanoscale, is more complex than previously thought. When friction occurs, an object does not simply slide its surface over that of another, it also makes a slight up-and-down movement. This finding completes a centuries-old theory of friction dating to 1699 and uncovers a gap in contemporary thinking on friction. The phenomenon -- termed lift-up hysteresis -- was described in a recent study by researchers Farid Al-Bender, Kris De Moerlooze and Paul Vanherck of the Production Engineering, Machine Design and Automation Division at KU Leuven's Department of Mechanical Engineering.

Friction is the force that occurs when one surface slides over another, or when an object moves through a liquid or a gas. Until now, the theory explaining the phenomenon of friction was fragmented. French physicists Guillaume Amontons and Charles August Coulomb, working in the late-17th and mid-18th centuries, respectively, strove to find an explanation for frictional resistance. Frictional resistance explains, for instance, why gliding a heavy cabinet across a floor is much more difficult than gliding a chair. As the weight of an object increases, so too does the resistance. The floor and the bottom of the cabinet move against one another from left to right or vice versa. But at the same time the weight of the cabinet bears perpendicularly upon the bottom of the cabinet and the floor. This normal load -- 'normal' in the sense of being perpendicular to the direction of shifting -- pushes the two surfaces together and produces resistance as friction occurs. If we put the chair and the cabinet on wheels and push them uphill, more force is needed to move the cabinet than to move the chair.

Using this reasoning, Amontons and Coulomb explained friction by the roughness of both surfaces: the (sometimes microscopically small) nooks and crannies of one surface -- asperities -- which settle upon those of another when one object rests upon another. When friction occurs, these asperities play the role of slopes. They are made to climb, descend and deform so that movement can continue, similar to what happens when the bristles of two brushes rub together. This theory is sometimes called the 'bump hypothesis' because one surface grinds over the bumps of another with an up-and-down movement.

In the 20th century it became clear that the existing theory did not fully correspond with the laws of thermodynamics, the science that studies the conversion of heat into mechanical energy or vice versa. Specifically, Amontons and Coulomb's bump hypothesis failed to explain energy lost as a result of friction. In their theory, the sum of the energy needed to go 'uphill' and then 'downhill' is zero. At the same time, we know that pure surfaces have an electro-chemical tendency to stick to each other. This is caused by asperities being stuck to one another in a phenomenon called adhesion. A typical example is Scotch tape. When movement occurs, all the bonds between the asperities of the two surfaces are broken and reformed elsewhere. Consequently, factors such as speed and acceleration influence friction. With the rise of the newer adhesion theory, Amontons and Coulomb's theory gradually faded into oblivion. But the modern adhesion theory of friction was shown to have inconsistencies of its own.

Normal motion, nano-scale Micro- and nano-scale measurement techniques now allow researchers to study friction at an atomic level. Professor Farid Al-Bender and his team conducted an experiment with extremely precise friction and displacement sensors and tested various materials (paper, plastic and brass) at different speeds of movement. The results map out frictional force measurements consistent with those predicted by adhesion theory. But until now, 'normal motion' -- movement perpendicular to the rubbing movement -- had not yet been measured. While normal motion amounts to a mere 5 -- 50 nanometers -- billionths of a meter -- this systematic up-and-down motion had previously been overlooked. Measurements of this normal motion, say the KU Leuven researchers, confirms the centuries-old hypothesis of asperity deformation and slope pioneered by Amontons and Coulomb and paints a more complex picture of the phenomenon of friction because normal motion must now be taken into account when developing a comprehensive theory of friction. Al-Bender and his team's results suggest that friction is caused by an interaction of both adhesion on the one hand and asperity deformation and slope on the other.

Tribology Tribology -- the science of friction, lubrication and wear -- is an important area of mechanical engineering. Tribology research can help lower economic and environmental costs of production and usage. If the interaction between moving surfaces can be controlled, time and energy inputs can be optimised and wear-and-tear, malfunctions and waste can be reduced. Tribology research can also contribute to the miniaturisation of products, such as computer components. At KU Leuven, research in tribology is closely linked with research in mechanical engineering, machine design, materials science and robotics.

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The above story is reprinted from materials provided by Katholieke Universiteit Leuven, via AlphaGalileo.

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Journal Reference:

Farid Al-Bender, Kris Moerlooze, Paul Vanherck. Lift-up Hysteresis Butterflies in Friction. Tribology Letters, 2012; 46 (1): 23 DOI: 10.1007/s11249-012-9914-y