Tuesday, June 14, 2011

'Biological circuit' components developed; New microscope technique for measuring them

Electrical engineers have long been toying with the idea of designing biological molecules that can be directly integrated into electronic circuits. University of Pennsylvania researchers have developed a way to form these structures so they can operate in open-air environments, and, more important, have developed a new microscope technique that can measure the electrical properties of these and similar devices.

The research was conducted by Dawn Bonnell, Trustee Chair Professor and director of the Nano/Bio Interface Center, graduate students Kendra Kathan-Galipeau and Maxim Nikiforov and postdoctoral fellow Sanjini Nanayakkara, all of the Department of Materials Science and Engineering in Penn's School of Engineering and Applied Science. They collaborated with assistant professor Bohdana Discher of the Department of Biophysics and Biochemistry at Penn's Perelman School of Medicine and Paul A. O'Brien, a graduate student in Penn's Biotechnology Masters Program.

Their work was published in the journal ACS Nano.

The development involves artificial proteins, bundles of peptide helices with a photoactive molecule inside. These proteins are arranged on electrodes, which are common feature of circuits that transmit electrical charges between metallic and non-metallic elements. When light is shined on the proteins, they convert photons into electrons and pass them to the electrode.

"It's a similar mechanism to what happens when plants absorb light, except in that case the electron is used for some chemistry that creates energy for the plant," Bonnell said. "In this case, we want to use the electron in electrical circuits."

Similar peptide assemblies had been studied in solution before by several groups and had been tested to show that they indeed react to light. But there was no way to quantify their ambient electrical properties, particularly capacitance, the amount of electrical charge the assembly holds.

"It's necessary to understand these kinds of properties in the molecules in order to make devices out of them. We've been studying silicon for 40 years, so we know what happens to electrons there," Bonnell said. "We didn't know what happens to electrons on dry electrodes with these proteins; we didn't even know if they would remain photoactive when attached to an electrode."

Designing circuits and devices with silicon is inherently easier than with proteins. The electrical properties of a large chunk of a single element can be measured and then scaled down, but complex molecules like these proteins cannot be scaled up. Diagnostic systems that could measure their properties with nanometer sensitivity simply did not exist.

The researchers therefore needed to invent both a new way of a measuring these properties and a controlled way of making the photovoltaic proteins that would resemble how they might eventually be incorporated into devices in open-air, everyday environments, rather than swimming in a chemical solution.

To solve the first problem, the team developed a new kind of atomic force microscope technique, known as torsional resonance nanoimpedance microscopy. Atomic force microscopes operate by bringing an extremely narrow silicon tip very close to a surface and measuring how the tip reacts, providing a spatial sensitivity of a few nanometers down to individual atoms.

"What we've done in our version is to use a metallic tip and put an oscillating electric field on it. By seeing how electrons react to the field, we're able to measure more complex interactions and more complex properties, such as capacitance," Bonnell said.

Bohdana Discher's group designed the self-assembling proteins much as they had done before but took the additional step of stamping them onto sheets of graphite electrodes. This manufacturing principle and the ability to measure the resulting devices could have a variety of applications.

"Photovoltaics -- solar cells -- are perhaps the easiest to imagine, but where this work is going in the shorter term is biochemical sensors," Bonnell said.

Instead of reacting to photons, proteins could be designed to produce a charge when in the presence of a certain toxins, either changing color or acting as a circuit element in a human-scale gadget.

This research was supported by the Nano/Bio Interface Center and the National Science Foundation.

Story Source:

The above story is reprinted (with editorial adaptations) from materials provided by University of Pennsylvania.

Journal Reference:

Kendra Kathan-Galipeau, Sanjini Nanayakkara, Paul A. O’Brian, Maxim Nikiforov, Bohdana M. Discher, Dawn A. Bonnell. Direct Probe of Molecular Polarization inDe NovoProtein–Electrode Interfaces. ACS Nano, 2011; 110603081000090 DOI: 10.1021/nn200887n

Univar creates dedicated EMEA Energy team

Univar Inc has expanded its operations in the energy sector with the establishment of an Energy team for Europe, the Middle East and Africa (EMEA), focusing exclusively on the oil and gas industry. The move is part of Univar’s strategy to significantly expand its energy business in EMEA within the next three years and become a key supplier to the oil and gas industry in the region.

The new energy team will promote Univar’s range of commodity and specialty chemicals to the upstream oilfield industry, in addition to offering unique filtration systems, new generation purification guards and hydrotreating catalysts to refineries, natural gas and petrochemical plants in the downstream industry. These products take out unwanted elements, including mercury, sulphur and chlorine, from the feed-stocks such as crude-oil or naptha, thus increasing product sustainability.

The team is beginning its sales push within Europe, where the energy sector is worth an estimated €600 million in chemical sales annually. By 2012, the energy team will expand operations further into the Middle East and Africa.

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SGL Group: Carbon Fiber Pilot Plant Inaugurated at Group’s Research Facility in Meitingen

SGL Group officially inaugurated a state-of-the-art carbon fiber pilot plant at the Group’s central research facility in Meitingen. The new plant forms the core of the “AirCarbon” project funded by the German Federal Ministry of Economics and Technology (BMWi), in which European industrial partners led by SGL Group are for the first time developing high strength carbon fibers for use in aerospace.

Addressing almost 100 economists, scientists and politicians, Robert Koehler, CEO of the SGL Group, underlined the company’s commitment to the further development of carbon fiber technology: “Carbon fiber technology has become a key technology for Germany as an economic location. Over the past ten years in Germany alone, we have invested some €200 million in new technologies as well as research and development. These investments, combined with the bundling of our global research and development activities in the central “Technology & Innovation” research facility in Meitingen, mean that we chose the right path at the right time.”

Dr. Gerd Wingefeld, member of the Board of Management responsible for Technology and Innovation, highlighted the importance of the new carbon fiber pilot plant for product and process development: “We will develop the next generation of high performance carbon fibers in this carbon fiber pilot plant, which is the most advanced of its kind in the world.”

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Researchers discover superatoms with magnetic shells

A team of Virginia Commonwealth University scientists has discovered a new class of 'superatoms' -- a stable cluster of atoms that can mimic different elements of the periodic table -- with unusual magnetic characteristics.

The superatom contains magnetized magnesium atoms, an element traditionally considered as non-magnetic. The metallic character of magnesium along with infused magnetism may one day be used to create molecular electronic devices for the next generation of faster processors, larger memory storage and quantum computers.

In a study published online in the Early Edition of the Proceedings of the National Academy of Sciences, the team reports that the newly discovered cluster consisting of one iron and eight magnesium atoms acts like a tiny magnet that derives its magnetic strength from the iron and magnesium atoms. The combined unit matches the magnetic strength of a single iron atom while preferentially allowing electrons of specific spin orientation to be distributed throughout the cluster.

Through an elaborate series of theoretical studies, Shiv N. Khanna, Ph.D., a Commonwealth professor in the VCU Department of Physics, and his team examined the electronic and magnetic properties of clusters having one iron atom surrounded by multiple magnesium atoms. The team included instructor J. Ulises Reveles and Victor M. Medel, a post-doctoral associate, both from VCU; A. W. Castleman Jr., Ph.D., the Evan Pugh Professor of Chemistry and Physics, and Eberly Distinguished chair in Science in the Department of Chemistry at Penn State University; and Prasenjit Sen and Vikas Chauhan from the Harish-Chandra Research Institute in Allahabad, India.

"Our research opens a new way of infusing magnetic character in otherwise non-magnetic elements through controlled association with a single magnetic atom. An important objective was to discover what combination of atoms would lead to a species that is stable as we put multiple units together," said Khanna.

"The combination of magnetic and conducting attributes was also desirable. Magnesium is a good conductor of electricity and, hence, the superatom combines the benefit of magnetic character along with ease of conduction through its outer skin," he said.

The team found that when the cluster had eight magnesium atoms it acquired extra stability due to filled electronic shells that were far separated from the unfilled shells. An atom is in a stable configuration when its outermost shell is full and far separated from unfilled shells, as found in inert gas atoms. Khanna said that such phenomena commonly occur with paired electrons which are non-magnetic, but in this study the magnetic electronic shell showed stability.

According to Khanna, the new cluster had a magnetic moment of four Bohr magnetons, which is almost twice that of an iron atom in solid iron magnets. A magnetic moment is a measure of the magnetic strength of the cluster. Although the periodic table has more than one hundred elements, there are only nine elements that exhibit magnetic character in solid form.

"A combination such as the one we have created here can lead to significant developments in the area of "molecular electronics" where such devices allow the flow of electrons with particular spin orientation desired for applications such as quantum computers. These molecular devices are also expected to help make denser integrated devices, higher data processing, and other benefits," said Reveles.

Khanna and his team are conducting preliminary studies on the assemblies of the new superatoms and have made some promising observations that may have applications in spintronics. Spintronics is a process using electron spin to synthesize new devices for memory and data processing.

This research was supported by the U.S. Department of Energy.

Story Source:

The above story is reprinted (with editorial adaptations) from materials provided by Virginia Commonwealth University.

Journal Reference:

Victor M. Medel, Jose Ulises Reveles, Shiv N. Khanna, Vikas Chauhan, Prasenjit Sen, A. Welford Castleman. Hund's rule in superatoms with transition metal impurities. Proceedings of the National Academy of Sciences, 2011; DOI: 10.1073/pnas.1100129108

New driving force for chemical reactions

New research just published in the journal Science by a team of chemists at the University of Georgia and colleagues in Germany shows for the first time that a mechanism called tunneling control may drive chemical reactions in directions unexpected from traditional theories.

The finding has the potential to change how scientists understand and devise reactions in everything from materials science to biochemistry.

The discovery was a complete surprise and came following the first successful isolation of a long-elusive molecule called methylhydroxycarbene by the research team. While the team was pleased that it had "trapped" the prized compound in solid argon through an extremely low-temperature experiment, they were surprised when it vanished within a few hours. That prompted UGA theoretical chemistry professor Wesley Allen to conduct large scale, state-of-the-art computations to solve the mystery.

"What we found was that the change was being controlled by a process called quantum mechanical tunneling," said Allen, "and we found that tunneling can supersede the traditional chemical reactivity processes of kinetic and thermodynamic control. We weren't expecting this at all."

What had happened? Clearly, a chemical reaction had taken place, but only inert argon atoms surrounded the compound, and essentially no thermal energy was available to create new molecular arrangements. Moreover, said Allen, "the observed product of the reaction, acetaldehyde, is the least likely outcome among conceivable possibilities."

Other authors of the paper include Professor Peter Schreiner and his group members Hans Peter Reisenauer, David Ley and Dennis Gerbig of the Justus-Liebig University in Giessen, Germany. Graduate student Chia-Hua Wu at UGA undertook the theoretical work with Allen.

Quantum tunneling isn't new. It was first recognized as a physical process decades ago in early studies of radioactivity. In classical mechanics, molecular motions can be understood in terms of particles roaming on a potential energy surface. Energy barriers, visualized as mountain passes on the surface, separate one chemical compound from another.

For a chemical reaction to occur, a molecular system must have enough energy to "get over the top of the hill," or it will come back down and fail to react. In quantum mechanics, particles can get to the other side of the barrier by tunneling through it, a process that seemingly requires imaginary velocities. In chemistry, tunneling is generally understood to provide secondary correction factors for the rates of chemical reactions but not to provide the predominant driving force.

(The strange world of quantum mechanics has been subject to considerable interest and controversy over the last century, and Austrian physicist Erwin Schrödinger's thought-experiment called "Schrödinger's Cat" illustrates how perplexing it is to apply the rules and laws of quantum mechanics to everyday life.)

"We knew that the rate of a reaction can be significantly affected by quantum mechanical tunneling," said Allen. "It becomes especially important at low temperatures and for reactions involving light atoms. What we discovered here is that tunneling can dominate a reaction mechanism sufficiently to redirect the outcome away from traditional kinetic control. Tunneling can cause a reaction that does not have the lowest activation barriers to occur exclusively."

Allen suggests a vivid analogy between the behavior of methylhydroxycarbene and Schrödinger's iconic cat.

"The cat cannot jump out of its box of deadly confinement because the walls are too high, so it conjures a Houdini-like escape by bursting through the thinnest wall," he said.

The fact that new ideas about tunneling came from the isolation of methylhydroxycarbene was the kind of serendipity that runs through the history of science. Schreiner and his team had snagged the elusive compound, and that was reason enough to celebrate, Allen said. But the surprising observation that it vanished within a few hours raised new questions that led to even more interesting scientific discoveries.

"The initiative to doggedly follow up on a 'lucky observation' was the key to success," said Allen. "Thus, a combination of persistent experimentation and exacting theoretical analysis on methylhydroxycarbene and its reactivity led to the concept I dubbed tunneling control, which may be characterized as `a type of nonclassical kinetic control wherein the decisive factor is not the lowest activation barrier'."

While the process was unearthed for the specific case of methylhydroxycarbene at extremely low temperatures, Allen said that tunneling control "can be a general phenomenon, especially if hydrogen transfer is involved, and such processes need not be restricted to cryogenic temperatures."

Allen's research was funded by the U.S. Department of Energy.

Story Source:

The above story is reprinted (with editorial adaptations) from materials provided by University of Georgia.

Journal Reference:

Peter R. Schreiner, Hans Peter Reisenauer, David Ley, Dennis Gerbig, Chia-Hua Wu, Wesley D. Allen. Methylhydroxycarbene: Tunneling Control of a Chemical Reaction. Science, 10 June 2011: Vol. 332 no. 6035 pp. 1300-1303 DOI: 10.1126/science.1203761

INEOS and BASF sign joint venture contract for Styrolution

BASF SE and INEOS Industries Holdings Limited have made an important step towards the establishment of the joint venture company Styrolution. On May 27, 2011 the companies signed a joint venture contract, which regulates the formation of the joint venture company Styrolution. The establishment of the joint venture is subject to approval by the appropriate antitrust authorities.

BASF and INEOS plan to combine their global business activities in styrene monomers (SM), polystyrene (PS), acrylonitrile butadiene styrene (ABS), styrene-butadiene block copolymers (SBC) and other styrene-based copolymers (SAN, AMSAN, ASA, MABS) as well as copolymer blends into the new joint venture called Styrolution. The business with expandable polystyrene is not part of the transaction. BASF and INEOS will retain their respective businesses.

The company headquarters will be located in Frankfurt/Main, Germany. In the joint venture 50% of the shares will be owned by BASF and 50% by INEOS. BASF will receive cash consideration following the completion of the transaction.

Dr. Martin Brudermüller, Vice Chairman of the Board of Executive Directors of BASF SE and responsible for the Plastics segment said: “The signing of the joint venture contract is an important milestone. With the signing we have built a strong foundation to establish Syrolution, the leading global company for styrenics, before the end of the year, subject to regulatory approval. Styrolution will deliver to its customers around the globe even better service, a fast and secure supply as well as excellent product quality.”

“The Joint Venture agreement paves the way for a globally competitive business that will provide significant benefit to its customers,” said Jim Ratcliffe, Chairman, INEOS Capital. “Styrolution will be capable of meeting the long-term needs of a rapidly changing market as it competes effectively with large-scale producers from Asia and the Middle East.”

BASF intends to contribute its SM, PS, ABS, SBC and styrene-based copolymers businesses in the joint venture. This includes production plants located in Germany (Ludwigshafen, Schwarzheide), Belgium (Antwerp), Korea (Ulsan), India (Dahej) and Mexico (Altamira). BASF employs approximately 1,460 people in its styrenics business and generated sales of about €3.9 billion in 2010.

INEOS intends to contribute ABS production plants at sites in Germany (Cologne), Spain (Tarragona), India (Vadodara) and Thailand (Map Ta Phut) to the joint venture. In addition INEOS will contribute its SM and PS businesses to the joint venture, which includes INEOS and INEOS Styrenics sites in Canada (Sarnia), the United States (Indian Orchard, Joliet, Decatur, Texas City, Bayport), Germany (Marl), France (Wingles) and Sweden (Trelleborg). INEOS employs approximately 2,200 people in its styrenics activities and generated sales of about €2.8 billion in 2010.

BASF and INEOS will continue to operate as strictly independent companies until the completion of the deal, which is anticipated in 2011, subject to the approval by the appropriate antitrust authorities.

Tuning 'metasurface' with fluid in new concept for sensing and chemistry

Like an opera singer hitting a note that shatters a glass, a signal at a particular resonant frequency can concentrate energy in a material and change its properties. And as with 18th century "musical glasses," adding a little water can change the critical pitch. Echoing both phenomena, researchers at the National Institute of Standards and Technology (NIST) have demonstrated a unique fluid-tuned "metasurface," a concept that may be useful in biomedical sensors and microwave-assisted chemistry.

A metasurface or metafilm is a two-dimensional version of a metamaterial, popularized recently in technologies with seemingly unnatural properties, such as the illusion of invisibility. Metamaterials have special properties not found in nature, often because of a novel structure. NIST's metasurface is a small piece of composite circuit board studded with metal patches in specific geometries and arrangements to create a structure that can reflect, store, or transmit energy (that is, allow it to pass right through).

As described in a new paper,  NIST researchers used purified water to tune the metasurface's resonant frequency -- the specific microwave frequency at which the surface can accumulate or store energy. They also calculated that the metasurface could concentrate electric field strength in localized areas, and thus might be used to heat fluids and promote microwave-assisted chemical or biochemical reactions.

The metasurface's behavior is due to interactions of 18 square copper frame structures, each 10 millimeters on a side (see photo). Computer simulations help design the copper squares to respond to a specific frequency. They are easily excited by microwaves, and each one can store energy in a T-shaped gap in its midsection when the metasurface is in a resonant condition. Fluid channels made of plastic tubing are bonded across the gaps. The sample is placed in a waveguide, which directs the microwaves and acts like a kaleidoscope, with walls that serve as mirrors and create the electrical illusion that the metasurface extends to infinity.

Researchers tested the metasurface properties with and without purified water in the fluid channels. The presence of water shifted the resonant frequency from 3.75 to 3.60 gigahertz. At other frequencies, the metasurface reflects or transmits energy. Researchers also calculated that the metasurface, when in the resonant condition, could concentrate energy in the gaps at least 100 times more than the waveguide alone.

Metasurface/fluid interactions might be useful in tunable surfaces, sensing and process monitoring linked to changes in fluid flow, and catalysis of chemical or biochemical reactions in fluid channels controlled by changes in microwave frequency and power as well as fluid flow rates. NIST researchers are also looking into the possibility of making metamaterial chips or circuits to use for biomedical applications such as counting cells.

Story Source:

The above story is reprinted (with editorial adaptations) from materials provided by National Institute of Standards and Technology (NIST).

Journal Reference:

J. Gordon, C. Holloway, J.C. Booth, J.R. Baker-Jarvis, D. Novotny, S. Kim and Y. Wang. Fluid interactions with metafilm/metasurfaces for tuning, sensing, and microwave assisted chemical processes. Physical Review B, 83, 205130 (2011) DOI: 10.1103/PhysRevB.83.205130

Researchers solve decades-old molecular mystery linked to blood clotting

Blood clotting is a complicated business, particularly for those trying to understand how the body responds to injury. In a new study, researchers report that they are the first to describe in atomic detail a chemical interaction that is vital to blood clotting. This interaction – between a clotting factor and a cell membrane – has baffled scientists for decades.

The study appears online in the .

"For decades, people have known that blood-clotting proteins have to bind to a cell membrane in order for the clotting reaction to happen," said University of Illinois biochemistry professor James Morrissey, who led the study with chemistry professor Chad Rienstra and biochemistry, biophysics and pharmacology professor Emad Tajkhorshid. "If you take clotting factors off the membrane, they're thousands of times less active."

The researchers combined laboratory detective work with supercomputer simulations and solid-state nuclear magnetic resonance (SSNMR) to get at the problem from every angle. They also made use of tiny rafts of lipid membranes called nanodiscs, using an approach developed at Illinois by biochemistry professor Stephen Sligar.

Previous studies had shown that each clotting factor contains a region, called the GLA domain, which interacts with specific lipids in cell membranes to start the cascade of chemical reactions that drive blood clotting.

One study, published in 2003 in the journal Nature Structural Biology, indicated that the GLA domain binds to a special phospholipid, phosphatidylserine (PS), which is embedded in the membrane. Other studies had shown that PS binds weakly to the clotting factor on its own, but in the presence of another phospholipid, phosphatidylethanolamine (PE), the interaction is much stronger.

Both PS and PE are abundant in the inner – but not the outer – leaflets of the double-layered membranes of cells. This keeps these lipids from coming into contact with clotting factors in the blood. But any injury that ruptures the cells brings PS and PE together with the clotting factors, initiating a chain of events that leads to blood clotting.

Researchers have developed many hypotheses to explain why clotting factors bind most readily to PS when PE is present. But none of these could fully explain the data.

In the new study, Morrissey's lab engineered nanodiscs with high concentrations of PS and PE, and conducted functional tests to determine if they responded like normal membranes.

"We found that the nanodisc actually is very representative of what really happens in the cell in terms of the reaction of the lipids and the role that they play," Morrissey said.

Then Tajkhorshid's lab used advanced modeling and simulation methods to position every atom in the system and simulated the molecular interactions on a supercomputer. The simulations indicated that one PS molecule was linking directly to the GLA domain of the clotting factor via an amino acid (serine) on its head-group (the non-oily region of a phospholipid that orients toward the membrane surface).

More surprisingly, the simulations indicated that six other phospholipids also were drawing close to the GLA domain. These lipids, however, were bending their head-groups out of the way so that their phosphates, which are negatively charged, could interact with positively charged calcium ions associated with the GLA domain.

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Computer simulation of how a blood clotting protein interacts with a membrane surface.

"The simulations were a breakthrough for us," Morrissey said. "They provided a detailed view of how things might come together during membrane binding of coagulation factors. But these predictions had to be tested experimentally."

Rienstra's lab then analyzed the samples using SSNMR, a technique that allows researchers to precisely measure the distances and angles between individual atoms in large molecules or groups of interacting molecules. His group found that one of every six or seven PS molecules was binding directly to the clotting factor, providing strong experimental support for the model derived from the simulations.

"That turned out to be a key insight that we contributed to this study," Rienstra said.

The team reasoned that if the PE head-groups were simply bending out of the way, then any phospholipid with a sufficiently small head-group should work as well as PE in the presence of PS. This also explained why only one PS molecule was actually binding to a GLA domain. The other phospholipids nearby were also interacting with the clotting factor, but more weakly.

The finding explained another mystery that had long daunted researchers. A different type of membrane lipid, phosphatidylcholine (PC), which has a very large
head-group and is most abundant on the outer surface of cells, was known to block any association between the membrane and the clotting factor, even in the presence of PS.

Follow-up experiments showed that any phospholipid but PC enhanced the binding of PS to the GLA domain. This led to the "ABC" hypothesis: when PS is present, the GLA domain will interact with "Anything But Choline."

"This is the first real insight at an atomic level of how most of the blood-clotting proteins interact with membranes, an interaction that's known to be essential to blood clotting," Morrissey said. The findings offer new targets for the development of drugs to regulate , he said.

More information: "Molecular Determinants of Phospholipid Synergy in Blood Clotting," http://www.jbc.org … .M111.251769

Provided by University of Illinois at Urbana-Champaign (news : web)