Writing nanostructures: Heated AFM tip allows direct fabrication of ferroelectric nanostructures on plastic

Using a technique known as thermochemical nanolithography (TCNL), researchers have developed a new way to fabricate nanometer-scale ferroelectric structures directly on flexible plastic substrates that would be unable to withstand the processing temperatures normally required to create such nanostructures.

The technique, which uses a heated atomic force microscope (AFM) tip to produce patterns, could facilitate high-density, low-cost production of complex ferroelectric structures for energy harvesting arrays, sensors and actuators in nano-electromechanical systems (NEMS) and micro-electromechanical systems (MEMS). The research was reported July 15 in the journal Advanced Materials.

"We can directly create piezoelectric materials of the shape we want, where we want them, on flexible substrates for use in energy harvesting and other applications," said Nazanin Bassiri-Gharb, co-author of the paper and an assistant professor in the School of Mechanical Engineering at the Georgia Institute of Technology. "This is the first time that structures like these have been directly grown with a CMOS-compatible process at such a small resolution. Not only have we been able to grow these ferroelectric structures at low substrate temperatures, but we have also been able to pattern them at very small scales."

The research was sponsored by the National Science Foundation and the U.S. Department of Energy. In addition to the Georgia Tech researchers, the work also involved scientists from the University of Illinois Urbana-Champaign and the University of Nebraska Lincoln.

The researchers have produced wires approximately 30 nanometers wide and spheres with diameters of approximately 10 nanometers using the patterning technique. Spheres with potential application as ferroelectric memory were fabricated at densities exceeding 200 gigabytes per square inch -- currently the record for this perovskite-type ferroelectric material, said Suenne Kim, the paper's first author and a postdoctoral fellow in laboratory of Professor Elisa Riedo in Georgia Tech's School of Physics.

Ferroelectric materials are attractive because they exhibit charge-generating piezoelectric responses an order of magnitude larger than those of materials such as aluminum nitride or zinc oxide. The polarization of the materials can be easily and rapidly changed, giving them potential application as random access memory elements.

But the materials can be difficult to fabricate, requiring temperatures greater than 600 degrees Celsius for crystallization. Chemical etching techniques produce grain sizes as large as the nanoscale features researchers would like to produce, while physical etching processes damage the structures and reduce their attractive properties. Until now, these challenges required that ferroelectric structures be grown on a single-crystal substrate compatible with high temperatures, then transferred to a flexible substrate for use in energy-harvesting.

The thermochemical nanolithography process, which was developed at Georgia Tech in 2007, addresses those challenges by using extremely localized heating to form structures only where the resistively-heated AFM tip contacts a precursor material. A computer controls the AFM writing, allowing the researchers to create patterns of crystallized material where desired. To create energy-harvesting structures, for example, lines corresponding to ferroelectric nanowires can be drawn along the direction in which strain would be applied.

"The heat from the AFM tip crystallizes the amorphous precursor to make the structure," Bassiri-Gharb explained. "The patterns are formed only where the crystallization occurs."

To begin the fabrication, the sol-gel precursor material is first applied to a substrate with a standard spin-coating method, then briefly heated to approximately 250 degrees Celsius to drive off the organic solvents. The researchers have used polyimide, glass and silicon substrates, but in principle, any material able to withstand the 250-degree heating step could be used. Structures have been made from Pb(ZrTi)O3 -- known as PZT, and PbTiO3 -- known as PTO.

"We still heat the precursor at the temperatures required to crystallize the structure, but the heating is so localized that it does not affect the substrate," explained Riedo, a co-author of the paper and an associate professor in the Georgia Tech School of Physics.

The heated AFM tips were provided by William King, a professor in the Department of Mechanical Science and Engineering at the University of Illinois at Urbana-Champaign.

As a next step, the researchers plan to use arrays of AFM tips to produce larger patterned areas, and improve the heated AFM tips to operate for longer periods of time. The researchers also hope to understand the basic science behind ferroelectric materials, including properties at the nanoscale.

"We need to look at the growth thermodynamics of these ferroelectric materials," said Bassiri-Gharb. "We also need to see how the properties change when you move from the bulk to the micron scale and then to the nanometer scale. We need to understand what really happens to the extrinsic and intrinsic responses of the materials at these small scales."

Ultimately, arrays of AFM tips under computer control could produce complete devices, providing an alternative to current fabrication techniques.

"Thermochemical nanolithography is a very powerful nanofabrication technique that, through heating, is like a nanoscale pen that can create nanostructures useful in a variety of applications, including protein arrays, DNA arrays, and graphene-like nanowires," Riedo explained. "We are really addressing the problem caused by the existing limitations of photolithography at these size scales. We can envision creating a full device based on the same fabrication technique without the requirements of costly clean rooms and vacuum-based equipment. We are moving toward a process in which multiple steps are done using the same tool to pattern at the small scale."

In addition to those already mentioned, the research team included Yaser Bastani from the G.W. Woodruff School of Mechanical Engineering at Georgia Tech, Seth Marder and Kenneth Sandhage, both from Georgia Tech's School of Chemistry and Biochemistry and School of Materials Science and Engineering, and Alexei Gruverman and Haidong Lu from the Department of Physics and Astronomy at the University of Nebraska-Lincoln.

Story Source:

The above story is reprinted (with editorial adaptations ) from materials provided by Georgia Institute of Technology Research News. The original article was written by John Toon.

Journal Reference:

Suenne Kim, Yaser Bastani, Haidong Lu, William P. King, Seth Marder, Kenneth H. Sandhage, Alexei Gruverman, Elisa Riedo, Nazanin Bassiri-Gharb. Direct Fabrication of Arbitrary-Shaped Ferroelectric Nanostructures on Plastic, Glass, and Silicon Substrates. Advanced Materials, 2011; DOI: 10.1002/adma.201101991

Modified metals change color in the presence of particular gases

 Modified metals that change colour in the presence of particular gases could warn consumers if packaged food has been exposed to air or if there's a carbon monoxide leak at home. This finding could potentially influence the production of both industrial and commercial air quality sensors.

"We initially found out by accident that modified rhodium reacts in a colourful way to different gases," says Cathleen Crudden, a professor in the Department of Chemistry. "That happy accident has become a driving force in our work with rhodium."

Rhodium that is modified using carbon, nitrogen or hydrogen-based complexes changes to yellow in the presence of nitrogen, deep blue in the presence of oxygen, and brown in the presence of carbon monoxide. This colour change occurs because of the way that the gases bind to the compound's central metal, according to the researchers.

Another remarkable aspect of this discovery is that the chemical changes take place without disrupting the exact placement of each individual atom in the compound's crystalline lattice. Dr. Crudden notes that this type of transformation is virtually unprecedented.

Rhodium is the main metal used in the production of catalytic convertors to reduce the toxicity of car exhaust emissions. Dr. Crudden's team, including graduate student Eric Keske and postdoctoral fellow Dr. Olena Zenkina, is currently investigating whether cobalt, a significantly cheaper metal than rhodium, reacts similarly.

Story Source:

The above story is reprinted (with editorial adaptations) from materials provided by Queen's University.

Note: If no author is given, the source is cited instead.

Disclaimer: Views expressed in this article do not necessarily reflect those of ScienceDaily or its staff.

Chemists create molecular polyhedron -- and potential to enhance industrial and consumer products

Chemists have created a molecular polyhedron, a ground-breaking assembly that has the potential to impact a range of industrial and consumer products, including magnetic and optical materials.

The work, reported in the latest issue of the journal Science, was conducted by researchers at New York University's Department of Chemistry and its Molecular Design Institute and the University of Milan's Department of Materials Science.

Researchers have sought to coerce molecules to form regular polyhedra -- three-dimensional objects in which each side, or face, is a polygon -- but without sustained success. Archimedean solids, discovered by the ancient Greek mathematician Archimedes, have attracted considerable attention in this regard. These 13 solids are those in which each face is a regular polygon and in which around every vertex -- the corner at which its geometric shapes meet -- the same polygons appear in the same sequences. For instance, in a truncated tetrahedron, the pattern forming at every vertex is hexagon-hexagon-triangle. The synthesis of such structures from molecules is an intellectual challenge.

The work by the NYU and University of Milan chemists forms a quasi-truncated octahedron, which also constitutes one of the 13 Archimedean solids. Moreover, as a polyhedron, the structure has the potential to serve as a cage-like framework to trap other molecular species, which can jointly serve as building blocks for new and enhanced materials.

"We've demonstrated how to coerce molecules to assemble into a polyhedron by design," explained Michael Ward, chair of NYU's Department of Chemistry and one of the study's co-authors. "The next step will be to expand on the work by making other polyhedra using similar design principles, which can lead to new materials with unusual properties."

The research team's creation relies on a remarkably high number of hydrogen bonds -- 72 -- to assemble two kinds of hexagonal molecular tiles, four each, into a truncated octahedron, which consists of eight molecular tiles. Although chemists often use hydrogen bonds because of their versatility in building complex structures, these bonds are weaker than those holding atoms together within the molecules themselves, which often makes larger scale structures constructed with hydrogen bonds less predictable and less sustainable. The truncated octahedron discovered by the NYU team proved to be remarkably stable, however, because the hydrogen bonds are stabilized by the ionic nature of the molecules and because no other outcomes are possible. In fact, the truncated octahedra assemble further into crystals that have nanoscale pores, resembling a class of well-known compounds called zeolites, which are made from inorganic components.

Because the structure also serves as a molecular cage, it can house, or encapsulate, other molecular components, giving future chemists a vehicle for developing a range of new compounds.

The study's other co-authors were Yuzhou Liu, a graduate student, and Chunhua Hu, a researcher professor, in NYU's Department of Chemistry and Molecular Design Institute and Professor Angiolina Comotti of the University of Milan's Department of Materials Science.

Story Source:

The above story is reprinted (with editorial adaptations) from materials provided by New York University, via EurekAlert!, a service of AAAS.

Journal Reference:

Yuzhou Liu, Chunhua Hu, Angiolina Comotti, Michael D. Ward. Supramolecular Archimedean Cages Assembled with 72 Hydrogen Bonds. Science, 2011; 333 (6041): 436-440 DOI: 10.1126/science.1204369

Cadmium selenide quantum dots degrade in soil, releasing their toxic guts, study finds

Quantum dots made from cadmium and selenium degrade in soil, unleashing toxic cadmium and selenium ions into their surroundings, a University at Buffalo study has found.

The research, accepted for publication in the journal Environmental Science and Technology, demonstrates the importance of learning more about how quantum dots -- and other nanomaterials -- interact with the environment after disposal, said Diana Aga, the chemistry professor who led the study.

Quantum dots are semiconductor nanocrystals with diameters of about 2 to 100 nanometers. Though quantum dots are not yet commonly used in consumer products, scientists are exploring the particles' applications in technologies ranging from solar panels to biomedical imaging.

"Quantum dots are not yet used widely, but they have a lot of potential and we can anticipate that the use of this nanomaterial will increase," said Aga, who presented the findings in late June at a National Science Foundation-funded workshop on nanomaterials in the environment. "We can also anticipate that their occurrence in the environment will also increase, and we need to be proactive and learn more about whether these materials will be a problem when they enter the environment."

"We can conclude from our research that there is potential for some negative impacts, since the quantum dots biodegrade. But there is also a possibility to modify the chemistry, the surface of the nanomaterials, to prevent degradation in the future," she said.

Aga's research into the afterlife of quantum dots is funded by a $400,000 Environmental Protection Agency grant to investigate the environmental transport, biodegradation and bioaccumulation of quantum dots and oxide nanoparticles.

Her collaborators on the new study in Environmental Science and Technology include PhD student Divina Navarro, Assistant Professor Sarbajit Banerjee and Associate Professor David Watson, all of the UB Department of Chemistry.

Working in the laboratory, the team tested two kinds of quantum dots: Cadmium selenide quantum dots, and cadmium-selenide quantum dots with a protective, zinc-sulfide shell. Though the shelled quantum dots are known in scientific literature to be more stable, Aga's team found that both varieties of quantum dot leaked toxic elements within 15 days of entering soil.

In a related experiment designed to predict the likelihood that discarded quantum dots would leach into groundwater, the scientists placed a sample of each type of quantum dot at the top of a narrow soil column. The researchers then added calcium chloride solution to mimic rain.

What they observed: Almost all the cadmium and selenium detected in each of the two columns -- more than 90 percent of that in the column holding unshelled quantum dots, and more than 70 percent of that in the column holding shelled quantum dots -- -remained in the top 1.5 centimeters of the soil.

But how the nanomaterials moved depended on what else was in the soil. When the team added ethylenediaminetetraacetic acid (EDTA) to test columns instead of calcium chloride, the quantum dots traveled through the soil more quickly. EDTA is a chelating agent, similar to the citric acid often found in soaps and laundry detergents.

The data suggest that under normal circumstances, quantum dots resting in top soil are unlikely to burrow their way down into underground water tables, unless chelating agents such as EDTA are introduced on purpose, or naturally-occurring organic acids (such as plant exudates) are present.

Aga said that even if the quantum dots remain in top soil, without contaminating underground aquifers, the particles' degradation still poses a risk to the environment.

In a separate study submitted for publication in a different journal, she and her colleagues tested the reaction of Arabidopsis plants to quantum dots with zinc sulfide shells. The team found that while the plants did not absorb the nanocrystals into their root systems, the plants still displayed a typical phytotoxic reaction upon coming into contact with the foreign matter; in other words, the plants treated the quantum dots as a poison.

Story Source:

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

Discovery may overcome obstacle for quantum computing: Researchers find a way to quash decoherence

 Researchers have made a major advance in predicting and quashing environmental decoherence, a phenomenon that has proven to be one of the most formidable obstacles standing in the way of quantum computing.

The findings -- based on theoretical work conducted at the University of British Columbia and confirmed by experiments at the University of California Santa Barbara -- are published online in the July 20 issue of the journal Nature.

Quantum mechanics states that matter can be in more than one physical state at the same time -- like a coin simultaneously showing heads and tails. In small objects like electrons, physicists have had success in observing and controlling these simultaneous states, called "state superposition."

Larger, more complex physical systems appear to be in one consistent physical state because they interact and "entangle" with other objects in their environment. This entanglement makes these complex objects "decay" into a single state -- a process called decoherence.

Quantum computing's potential to be exponentially faster and more powerful than any conventional computer technology depends on switches that are capable of state superposition -- that is, being in the "on" and "off" positions at the same time. Until now, all efforts to achieve such superposition with many molecules at once were blocked by decoherence.

"For the first time we've been able to predict and control all the environmental decoherence mechanisms in a very complex system, in this case a large magnetic molecule called the 'Iron-8 molecule,'" said Phil Stamp, UBC professor of physics and astronomy and director of the Pacific Institute of Theoretical Physics. "Our theory also predicted that we could suppress the decoherence, and push the decoherence rate in the experiment to levels far below the threshold necessary for quantum information processing, by applying high magnetic fields."

In the experiment, the California researchers prepared a crystalline array of Iron-8 molecules in a quantum superposition, where the net magnetization of each molecule was simultaneously oriented up and down. The decay of this superposition by decoherence was then observed in time -- and the decay was spectacularly slow, behaving exactly as the UBC researchers predicted.

"Magnetic molecules now suddenly appear to have serious potential as candidates for quantum computing hardware," said Susumu Takahashi, assistant professor of chemistry and physics at the University of Southern California. "This opens up a whole new area of experimental investigation with sizeable potential in applications, as well as for fundamental work."

Takahashi conducted the experiments while at UC Santa Barbara and analyzed the data while at UC Santa Barbara and the University of Southern California.

"Decoherence helps bridge the quantum universe of the atom and the classical universe of the everyday objects we interact with," Stamp said. "Our ability to understand everything from the atom to the Big Bang depends on understanding decoherence, and advances in quantum computing depend on our ability to control it."

The research was supported by the Pacific Institute of Theoretical Physics at UBC, the Natural Sciences and Engineering Research Council of Canada, the Canadian Institute for Advanced Research, the Keck Foundation, and the National Science Foundation.

Story Source:

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

Journal Reference:

S. Takahashi, I. S. Tupitsyn, J. van Tol, C. C. Beedle, D. N. Hendrickson, P. C. E. Stamp. Decoherence in crystals of quantum molecular magnets. Nature, 2011; DOI: 10.1038/nature10314

New photonic crystals have both electronic and optical properties

 In an advance that could open new avenues for solar cells, lasers, metamaterials and more, researchers at the University of Illinois have demonstrated the first optoelectronically active 3-D photonic crystal.

"We've discovered a way to change the three-dimensional structure of a well-established semiconductor material to enable new optical properties while maintaining its very attractive electrical properties," said Paul Braun, a professor of materials science and engineering and of chemistry who led the research effort.

The team published its advance in the journal Nature Materials.

Photonic crystals are materials that can control or manipulate light in unexpected ways thanks to their unique physical structures. Photonic crystals can induce unusual phenomena and affect photon behavior in ways that traditional optical materials and devices can't. They are popular materials of study for applications in lasers, solar energy, LEDs, metamaterials and more.

However, previous attempts at making 3-D photonic crystals have resulted in devices that are only optically active that is, they can direct light but not electronically active, so they can't turn electricity to light or vice versa.

The Illinois team's photonic crystal has both properties.

"With our approach to fabricating photonic crystals, there's a lot of potential to optimize electronic and optical properties simultaneously," said Erik Nelson, a former graduate student in Braun's lab who now is a postdoctoral researcher at Harvard University. "It gives you the opportunity to control light in ways that are very unique to control the way it's emitted and absorbed or how it propagates."

To create a 3-D photonic crystal that is both electronically and optically active, the researchers started with a template of tiny spheres packed together. Then, they deposit gallium arsenide (GaAs), a widely used semiconductor, through the template, filling in the gaps between the spheres.

The GaAs grows as a single crystal from the bottom up, a process called epitaxy. Epitaxy is common in industry to create flat, two-dimensional films of single-crystal semiconductors, but Braun's group developed a way to apply it to an intricate three-dimensional structure.

"The key discovery here was that we grew single-crystal semiconductor through this complex template," said Braun, who also is affiliated with the Beckman Institute for Advanced Science and Technology and with the Frederick Seitz Materials Research Laboratory at Illinois. "Gallium arsenide wants to grow as a film on the substrate from the bottom up, but it runs into the template and goes around it. It's almost as though the template is filling up with water. As long as you keep growing GaAs, it keeps filling the template from the bottom up until you reach the top surface."

The epitaxial approach eliminates many of the defects introduced by top-down fabrication methods, a popular pathway for creating 3-D photonic structures. Another advantage is the ease of creating layered heterostructures. For example, a quantum well layer could be introduced into the photonic crystal by partially filling the template with GaAs and then briefly switching the vapor stream to another material.

Once the template is full, the researchers remove the spheres, leaving a complex, porous 3-D structure of single-crystal semiconductor. Then they coat the entire structure with a very thin layer of a semiconductor with a wider bandgap to improve performance and prevent surface recombination.

To test their technique, the group built a 3-D photonic crystal LED the first such working device.

Now, Braun's group is working to optimize the structure for specific applications. The LED demonstrates that the concept produces functional devices, but by tweaking the structure or using other semiconductor materials, researchers can improve solar collection or target specific wavelengths for metamaterials applications or low-threshold lasers.

"From this point on, it's a matter of changing the device geometry to achieve whatever properties you want," Nelson said. It really opens up a whole new area of research into extremely efficient or novel energy devices.

Story Source:

The above story is reprinted (with editorial adaptations) from materials provided by University of Illinois at Urbana-Champaign, via EurekAlert!, a service of AAAS.

Journal Reference:

Erik C. Nelson, Neville L. Dias, Kevin P. Bassett, Simon N. Dunham, Varun Verma, Masao Miyake, Pierre Wiltzius, John A. Rogers, James J. Coleman, Xiuling Li, Paul V. Braun. Epitaxial growth of three-dimensionally architectured optoelectronic devices. Nature Materials, 2011; DOI: 10.1038/nmat3071

Chemists create molecular flasks: Researchers design a self-assembling material that can house other molecules

Chemical reactions happen all of the time: some things burn or rust, others react to light exposure--even batteries use chemical reactions to supply electricity. One of the big challenges chemists continually face is finding new ways to control these reactions or create conditions that promote desirable reactions and limit undesirable ones.

Recently, researchers at New York University demonstrated an ability to make new materials with empty space on the inside, which could potentially control desired and unwanted chemical reactions.

Mike Ward, of NYU's Department of Chemistry and a team of researchers, essentially created a "molecular flask," self-assembling cages capable of housing other compounds inside of them. These "flasks" may eventually allow researchers to isolate certain chemical reactions within or outside the cage.

The research is published in the July 22, 2011 issue of the journal Science.

"We wanted to create frameworks to serve as the 'hotel' for 'guest' molecules, which can deliver the function independent of framework design," said Ward. "This makes it possible to separate chemicals based on size or perform reactions inside well-defined cages, which could potentially give you more control over chemical reactivity and reaction products. Moreover, these frameworks may prove ideal for encapsulating a wide range of guest molecules, producing materials with new optical or magnetic properties."

The molecular "hotels" described by Ward and his collaborators take the shape of a truncated octahedron, one of 13 shapes described as an Archimedean solid, discovered by the Greek mathematician Archimedes. Archimedean solids are characterized by a specific number of sides that meet at corners which are all identical. The regularity of these shapes often means they are of particular interest to chemists and materials researchers looking to create complex materials that assemble themselves.

The extraordinary aspect of this work, supported by the National Science Foundation (NSF), is the self-assembly of the molecular tiles into a polyhedron, a well-defined, three-dimensional, geometric solid. The individual polyhedra assemble themselves using the attractive interactions associated with hydrogen bonds. They then further organize into a crystal lattice that resembles a porous structure called zeolite, an absorbent material with many industrial uses.

The new material differs from zeolite because it is constructed from organic building blocks rather than inorganic ones, which make it more versatile and easier to engineer. In general, inorganic compounds are considered mineral in origin, while organic compounds are considered biological in origin.

This discovery paves the way towards development of a new class of solids with properties that may prove useful for a range of industrial and consumer products.

"By using geometric design principles and very simple chemical precursors, the Ward group has been able to construct relatively sturdy materials which contain many identically sized and shaped cavities," explained Michael Scott, program director in the Division of Materials Research at NSF. "The hollow space inside these materials offers many exciting opportunities for chemists to do things such as isolate unstable molecules, catalyze unknown reactions and separate important chemical compounds."

Future research projects will try to create other types of Archimedean solids or use the truncated octahedron to house different types of functional molecules.

Story Source:

The above story is reprinted (with editorial adaptations) from materials provided by National Science Foundation.

Journal Reference:

Yuzhou Liu, Chunhua Hu, Angiolina Comotti, Michael D. Ward. Supramolecular Archimedean Cages Assembled with 72 Hydrogen Bonds. Science, 2011; 333 (6041): 436-440 DOI: 10.1126/science.1204369

New graphene discovery boosts oil exploration efforts, could enable self-powered microsensors

Researchers at Rensselaer Polytechnic Institute have developed a new method to harvest energy from flowing water. This discovery aims to hasten the creation of self-powered microsensors for more accurate and cost-efficient oil exploration.

Led by Rensselaer Professor Nikhil Koratkar, the researchers investigated how the flow of water over surfaces coated with the nanomaterial graphene could generate small amounts of electricity. The research team demonstrated the creation of 85 nanowatts of power from a sheet of graphene measuring .03 millimeters by .015 millimeters.

This amount of energy should be sufficient to power tiny sensors that are introduced into water or other fluids and pumped down into a potential oil well, Koratkar said. As the injected water moves through naturally occurring cracks and crevices deep in the earth, the devices detect the presence of hydrocarbons and can help uncover hidden pockets of oil and natural gas. As long as water is flowing over the graphene-coated devices, they should be able to provide a reliable source of power. This power is necessary for the sensors to relay collected data and information back to the surface.

"It's impossible to power these microsensors with conventional batteries, as the sensors are just too small. So we created a graphene coating that allows us to capture energy from the movement of water over the sensors," said Koratkar, professor in the Department of Mechanical, Aerospace, and Nuclear Engineering and the Department of Materials Science and Engineering in the Rensselaer School of Engineering. "While a similar effect has been observed for carbon nanotubes, this is the first such study with graphene. The energy-harvesting capability of graphene was at least an order of magnitude superior to nanotubes. Moreover, the advantage of the flexible graphene sheets is that they can be wrapped around almost any geometry or shape."

Details of the study were published online last week by the journal Nano Letters. The study also will appear in a future print edition of the journal.

It is the first research paper to result from the $1 million grant awarded to Koratkar's group in March 2010 by the Advanced Energy Consortium.

Hydrocarbon exploration is an expensive process that involves drilling deep down in the earth to detect the presence of oil or natural gas. Koratkar said oil and gas companies would like to augment this process by sending out large numbers of microscale or nanoscale sensors into new and existing drill wells. These sensors would travel laterally through the earth, carried by pressurized water pumped into these wells, and into the network of cracks that exist underneath Earth's surface. Oil companies would no longer be limited to vertical exploration, and the data collected from the sensors would arm these firms with more information for deciding the best locations to drill.

The team's discovery is a potential solution for a key challenge to realizing these autonomous microsensors, which will need to be self-powered. By covering the microsensors with a graphene coating, the sensors can harvest energy as water flows over the coating.

"We'll wrap the graphene coating around the sensor, and it will act as a 'smart skin' that serves as a nanofluidic power generator," Koratkar said.

Graphene is a single-atom-thick sheet of carbon atoms, which are arranged like a chain-link fence. For this study, Koratkar's team used graphene that was grown by chemical vapor deposition on a copper substrate and transferred onto silicon dioxide. The researchers created an experimental water tunnel apparatus to test the generation of power as water flows over the graphene at different velocities.

Along with physically demonstrating the ability to generate 85 nanowatts of power from a small fragment of graphene, the researchers used molecular dynamics simulations to better understand the physics of this phenomenon. They discovered that chloride ions present in the water stick to the surface of graphene. As water flows over the graphene, the friction force between the water flow and the layer of adsorbed chloride ions causes the ions to drift along the flow direction. The motion of these ions drags the free charges present in graphene along the flow direction -- creating an internal current.

This means the graphene coating requires ions to be present in water to function properly. Therefore, oil exploration companies would need to add chemicals to the water that is injected into the well. Koratkar said this is an easy, inexpensive solution.

For the study, Koratkar's team also tested the energy harvested from water flowing over a film of carbon nanotubes. However, the energy generation and performance was far inferior to those attained using graphene, he said.

Looking at potential future applications of this new technology, Koratkar said he could envision self-powered microrobots or microsubmarines. Another possibility is harvesting power from a graphene coating on the underside of a boat.

Story Source:

The above story is reprinted (with editorial adaptations) from materials provided by Rensselaer Polytechnic Institute.

Journal Reference:

Prashant Dhiman, Fazel Yavari, Xi Mi, Hemtej Gullapalli, Yunfeng Shi, Pulickel M. Ajayan, Nikhil Koratkar. Harvesting Energy from Water Flow over Graphene. Nano Letters, 2011; 110714113416089 DOI: 10.1021/nl2011559

Wiedemann-Franz Law: Physicists break 150-year-old empirical laws of physics

A violation of one of the oldest empirical laws of physics has been observed by scientists at the University of Bristol. Their experiments on purple bronze, a metal with unique one-dimensional electronic properties, indicate that it breaks the Wiedemann-Franz Law. This historic discovery is described in a paper published July 20 in Nature Communications.

In 1853, two German physicists, Gustav Wiedemann and Rudolf Franz, studied the thermal conductivity (a measure of a system's ability to transfer heat) of a number of elemental metals and found that the ratio of the thermal to electrical conductivities was approximately the same for different metals at the same temperature.

The origin of this empirical observation did not become clear however until the discovery of the electron and the advent of quantum physics in the early twentieth century. Electrons have a spin and a charge. When they move through a metal they cause an electrical current because of the moving charge. In addition, the moving electrons also carry heat through the metal but now it is via both the charge and the spin. So a moving electron must carry both heat and charge: that is why the ratio does not vary from metal to metal.

For the past 150-plus years, the Wiedemann-Franz law has proved to be remarkably robust, the ratio varying at most by around 50 per cent amongst the thousands of metallic systems studied.

In 1996, American physicists C. L. Kane and Matthew Fisher made a theoretical prediction that if you confine electrons to individual atomic chains, the Wiedemann-Franz law could be strongly violated. In this one-dimensional world, the electrons split into two distinct components or excitations, one carrying spin but not charge (the spinon), the other carrying charge but not spin (the holon). When the holon encounters an impurity in the chain of atoms it has no choice but for its motion to be reflected. The spinon, on the other hand, has the ability to tunnel through the impurity and then continue along the chain. This means that heat is conducted easily along the chain but charge is not. This gives rise to a violation of the Wiedemann-Franz law that grows with decreasing temperature.

The experimental group, led by Professor Nigel Hussey of the Correlated Electron Systems Group at the University of Bristol, tested this prediction on a purple bronze material comprising atomic chains along which the electrons prefer to travel.

Remarkably, the researchers found that the material conducted heat 100,000 times better than would have been expected if it had obeyed the Wiedemann-Franz law like other metals. Not only does this remarkable capability of this compound to conduct heat have potential from a technological perspective, such unprecedented violation of the Wiedemann-Franz law provides striking evidence for this unusual separation of the spin and charge of an electron in the one-dimensional world.

Professor Hussey said: "One can create purely one-dimensional atomic chains on substrates, or free-standing two-dimensional sheets, like graphene, but in a three-dimensional complex solid, there will always be some residual coupling between individual chains of atoms within the complex that allow the electrons to move in three-dimensional space.

"In this purple bronze, however, nature has conspired to limit this coupling to such an extent that the electrons are effectively confined to individual chains and thus creating a one-dimensional world inside the three-dimensional complex. The goal now is to find a way, for example, using pressure or chemical substitution, to increase the ability of the electrons to hop between adjacent chains and to study the evolution of the spin and charge states as the three-dimensional world is restored within the material."

Story Source:

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

Journal Reference:

Nicholas Wakeham, Alimamy F. Bangura, Xiaofeng Xu, Jean-Francois Mercure, Martha Greenblatt, Nigel E. Hussey. Gross violation of the Wiedemann–Franz law in a quasi-one-dimensional conductor. Nature Communications, 2011; 2: 396 DOI: 10.1038/ncomms1406

Hydrogen may be key to growth of high-quality graphene

 A new approach to growing graphene greatly reduces problems that have plagued researchers in the past and clears a path to the crystalline form of graphite's use in sophisticated electronic devices of tomorrow.

Findings of researchers at the Department of Energy's Oak Ridge National Laboratory demonstrate that hydrogen rather than carbon dictates the graphene grain shape and size, according to a team led by ORNL's Ivan Vlassiouk, a Eugene Wigner Fellow, and Sergei Smirnov, a professor of chemistry at New Mexico State University. This research is published in ACS Nano.

"Hydrogen not only initiates the graphene growth, but controls the graphene shape and size," Vlassiouk said. "In our paper, we have described a method to grow well-defined graphene grains that have perfect hexagonal shapes pointing to the faultless single crystal structure."

In the past two years, graphene growth has involved the decomposition of carbon-containing gases such as methane on a copper foil under high temperatures, the so-called chemical vapor deposition method. Little was known about the exact process, but researchers knew they would have to gain a better understanding of the growth mechanism before they could produce high-quality graphene films.

Until now, grown graphene films have consisted of irregular- shaped graphene grains of different sizes, which were usually not single crystals.

"We have shown that, surprisingly, it is not only the carbon source and the substrate that dictate the growth rate, the shape and size of the graphene grain," Vlassiouk said. "We found that hydrogen, which was thought to play a rather passive role, is crucial for graphene growth as well. It contributes to both the activation of adsorbed molecules that initiate the growth of graphene and to the elimination of weak bonds at the grain edges that control the quality of the graphene."

Using their new recipe, Vlassiouk and colleagues have created a way to reliably synthesize graphene on a large scale. The fact that their technique allows them to control grain size and boundaries may result in improved functionality of the material in transistors, semiconductors and potentially hundreds of electronic devices.

Implications of this research are significant, according to Vlassiouk, who said, "Our findings are crucial for developing a method for growing ultra-large-scale single domain graphene that will constitute a major breakthrough toward graphene implementation in real-world devices."

Other authors of the paper, "Role of Hydrogen in Chemical Vapor Deposition Growth of Large Single-Crystal Graphene," are Murari Regmi, Pasquale Fulvio, Sheng Dai, Panos Datskos and Gyula Eres of ORNL.

The research was supported by the Department of Energy's Office of Science, in part through the Fluid Interface Reactions, Structures and Transport Center, a DOE Energy Frontier Research Center led by ORNL.

A portion of the work was performed at the Center for Nanophase Materials Sciences, one of the five DOE Nanoscale Science Research Centers supported by the DOE Office of Science, premier national user facilities for interdisciplinary research at the nanoscale. Together the NSRCs comprise a suite of complementary facilities that provide researchers with state-of-the-art capabilities to fabricate, process, characterize and model nanoscale materials, and constitute the largest infrastructure investment of the National Nanotechnology Initiative.

Story Source:

The above story is reprinted (with editorial adaptations ) from materials provided by DOE/Oak Ridge National Laboratory.

Journal Reference:

Ivan Vlassiouk, Murari Regmi, Pasquale Fulvio, Sheng Dai, Panos Datskos, Gyula Eres, Sergei Smirnov. Role of Hydrogen in Chemical Vapor Deposition Growth of Large Single-Crystal Graphene. ACS Nano, 2011; 110701132829005 DOI: 10.1021/nn201978y

Bacteria use Batman-like grappling hooks to 'slingshot' on surfaces, study shows

Bacteria use various appendages to move across surfaces prior to forming multicellular bacterial biofilms. Some species display a particularly jerky form of movement known as "twitching" motility, which is made possible by hairlike structures on their surface called type IV pili, or TFP.

"TFP act like Batman's grappling hooks," said Gerard Wong, a professor of bioengineering and of chemistry and biochemistry at the UCLA Henry Samueli School of Engineering and Applied Science and the California NanoSystems Institute (CNSI) at UCLA. "These grappling hooks can extend and bind to a surface and retract and pull the cell along."

In a study to be published online this week in Proceedings of the National Academy of Sciences, Wong and his colleagues at UCLA Engineering identify the complex sequence of movements that make up this twitching motility in Pseudomonas aeruginosa, a biofilm-forming pathogen partly responsible for the deadly infections seen in cystic fibrosis.

During their observations, Wong and his team made a surprising discovery. Using a high-speed camera and a novel two-point tracking algorithm, they noticed that the bacteria had the unique ability to "slingshot" on surfaces.

The team found that linear translational pulls of constant velocity alternated with velocity spikes that were 20 times faster but lasted only milliseconds. This action would repeat over and over again.

"The constant velocity is due to the pulling by multiple TFP; the velocity spike is due to the release of a single TFP," Wong said. "The release action leads to a fast slingshot motion that actually turns the bacteria efficiently by allowing it to over-steer."

The ability to turn and change direction is essential for bacteria to adapt to continually changing surface conditions as they form biofilms. The researchers found that the slingshot motion helped P. aeruginosa move much more efficiently through the polysaccharides they secrete on surfaces during biofilm formation, a phenomenon known as shear-thinning.

"If you look at the surfaces the bacteria have to move on, they are usually covered in goop. Bacterial cells secrete polysaccharides on surfaces, which are kind of like molasses," Wong said. "Because these polysaccharides are long polymer molecules that can get entangled, these are very viscous and can potentially impede movement. However, if you move very fast in these polymer fluids, the viscosity becomes much lower compared to when you're moving slowly. The fluid will then seem more like water than molasses. This kind of phenomenon is well known to chemical engineers and physicists."

Since the twitching motion of bacteria with TFP depends of the physical distributions of TFP on the surface of individual cells, Wong hopes that the analysis of motility patterns may in the future enable new methods for biometric "fingerprinting" of individual cells for single-cell diagnostics.

"It gives us the possibility of not just identifying species of bacteria but the possibility of also identifying individual cells. Perhaps in the future, we can look at a cell and try to find the same cell later on the basis of how it moves," he said.

The study was funded by the National Institutes of Health and the National Science Foundation. The lead authors are Fan Jin from the UCLA Department of Bioengineering, the UCLA Department Chemistry and Biochemistry, and the CNSI, and Jacinta C. Conrad of the department of chemical and biomolecular engineering at the University of Houston.

Story Source:

The above story is reprinted (with editorial adaptations) from materials provided by University of California - Los Angeles. The original article was written by Wileen Wong Kromhout.

Journal Reference:

Fan Jin, Jacinta C. Conrad, Maxsim L. Gibiansky, Gerard C. L. Wong. Bacteria use type-IV pili to slingshot on surfaces. Proceedings of the National Academy of Sciences, 2011; DOI: 10.1073/pnas.1105073108

Deep below the Deepwater Horizon oil spill: New molecular model better explains diffusion of spill under water

 For the first time, scientists gathered oil and gas directly as it escaped from a deep ocean wellhead -- that of the damaged Deepwater Horizon oil rig. What they found allows a better understanding of how pollution is partitioned and transported in the depths of the Gulf of Mexico and permits superior estimation of the environmental impact of escaping oil, allowing for a more precise evaluation of previously estimated repercussions on seafloor life in the future.

The explosion of the Deepwater Horizon rig in April 2010 was both a human and an environmental catastrophe. Getting the spill under control was an enormous challenge. The main problem was the depth of the well, nearly 1,500 meters below the sea surface. It was a configuration that had never been tried before, and the pollution it unleashed after methane gas shot to the surface and ignited in a fiery explosion is also unequalled. Much research has been done since the spill on the effects on marine life at the ocean's surface and in coastal regions. Now, École Polytechnique Fédérale de Lausanne (EPFL) professor Samuel Arey and the Woods Hole Oceanographic Institute reveal in the advance online edition of Proceedings of the National Academy of Sciences how escaped crude oil and gas behave in the deep water environment.

Into the deep

In June 2010, with the help of a remotely operated vehicle (ROV), Woods Hole scientists reached the base of the rig and gathered samples directly from the wellhead using a robotic arm. The oceanographers also made more than 200 other measurements at various water depths over a 30-kilometer area. These samples were then analyzed with the help of the US National Oceanic and Atmospheric Administration and the dissolution of hydrocarbons was modeled at EPFL. This model showed how the properties of hydrocarbons are important in understanding the wellhead structure and pollution diffusion -- how pollution spreads out -- in the depths.

From the ROV to the lab

Lab analysis led the scientists to describe for the first time the physical basis for the deep sea trajectories of light-weight, water-soluble hydrocarbons such as methane, benzene, and naphthalene released from the base of the rig. The researchers observed, for example, that at a little more than 1,000 meters below the surface, a large plume spread out from the original gusher, moving horizontally in a southwest direction with prevailing currents. Unlike a surface spill, from which these volatile compounds evaporate into the atmosphere, in the deep water under pressure, light hydrocarbon components predominantly dissolve or form hydrates, compounds containing water molecules. And depending on its properties, the resulting complex mixture can rise, sink, or even remain suspended in the water, and possibly go on to cause damage to seafloor life far from the original spill.

By comparing the oil and gas escaping from the well with the mixture at the surface, EPFL's Samuel Arey, head of Environmental Chemistry Modeling Laboratory, and colleagues were able to show that the composition of the deep sea plumes could be explained by significant dissolution of light hydrocarbons at 1 kilometer depth. In other words, an important part of the oil spreads out in underwater plumes, so we need a more precise evaluation of previously estimated repercussions on seafloor life in the future. Arey's methodology offers a better estimation of how pollution travels and the potential deep sea consequences of spills.

"Modeling the environmental fate of hydrocarbons in deep water ecosystems required a new approach, with a global view, in order to correctly understand the impact of the pollution," explains Arey. This research will have a significant impact on assessments of the environmental impact of deep water oil spills.

Story Source:

The above story is reprinted (with editorial adaptations) from materials provided by Ecole Polytechnique Fédérale de Lausanne, via EurekAlert!, a service of AAAS.

Journal Reference:

Christopher M. Reddy, J. Samuel Arey, Jeffrey S. Seewald, Sean P. Sylva, Karin L. Lemkau, Robert K. Nelson, Catherine A. Carmichael, Cameron P. McIntyre, Judith Fenwick, G. Todd Ventura, Benjamin A. S. Van Mooy, Richard Camilli. Science Applications in the Deepwater Horizon Oil Spill Special Feature: Composition and fate of gas and oil released to the water column during the Deepwater Horizon oil spill. Proceedings of the National Academy of Sciences, 2011; DOI: 10.1073/pnas.1101242108

Click chemistry with copper: A biocompatible version

Biomolecular imaging can reveal a great deal of information about the inner workings of cells and one of the most attractive targets for imaging are glycans -- sugars that are ubiquitous to living organisms and abundant on cell surfaces. Imaging a glycan requires that it be tagged or labeled. One of the best techniques for doing this is a technique called click chemistry. The original version of click chemistry could only be used on cells in vitro, not in living organisms, because the technique involved catalysis with copper, which is toxic at high micromolar concentrations.

A copper-free version of click chemistry that can safely be used in living organisms is available, but it is not always optimal in terms of reaction kinetics and target specificity. Now, a variation of click chemistry has been introduced that retains the copper catalyst of the original reaction -- along with its speed and specificity -- but is safe for cells in vivo.

Researchers with the Lawrence Berkeley National Laboratory (Berkeley Lab), in collaboration with researchers at the Albert Einstein College of Medicine at Yeshiva University in New York, have found a way to make copper-catalyzed click chemistry biocompatible. By adding a ligand that minimizes the toxicity of copper but still allows it to catalyze the click chemistry reaction, the researchers can safely use their reaction in living organisms. Compared to the copper-free click chemistry reaction, which can take up to an hour, the ligand-accelerated copper-catalyzed click chemistry reaction can achieve effective labeling within 3-5 minutes. The presence of the copper catalyst also enables this new formulation of click chemistry to be more target-specific with fewer background side reactions.

"The discovery of this new accelerating ligand for copper-catalyzed click chemistry should provide an effective complimentary tool to copper-free click chemistry," says Yi Liu, a chemist with Berkeley Lab's Molecular Foundry and the co-leader of this research with Peng Wu, of the Albert Einstein College of Medicine.

"While copper-free click chemistry may have advantages for whole animal imaging experiments such as imaging in mice," Liu says, "our ligand-accelerated copper reaction is better suited for enriching glycoproteins for their identification."

The ligand-accelerated copper-catalyzed reaction was used to label glycans in recombinant glycoproteins, glycoproteins in cell lysates, glycoproteins on live cell surfaces, and glycoconjugates in live zebrafish embryos. Because a zebrafish embryo is transparent in the first 24 hours of its development, it allows labeled glycans to be detected via molecular imaging techniques, making it a highly useful model for developmental biology studies.

"Based on our results," says Peng Wu, "we believe that ligand-accelerated copper-catalyzed click chemistry represents a powerful and highly adaptive bioconjugation tool that holds great promise for further improvement with the discovery of more versatile catalyst systems."

Click chemistry, which was introduced in 2002 by the Nobel laureate chemist Barry Sharpless of the Scripps Research Institute, utilizes a copper-catalyzed azide-alkyne cycloaddition (CuAAC) reaction that makes it possible for certain chemical building blocks to "click" together in an irreversible linkage, analogous to the snapping together of Lego blocks. While the technique immediately proved valuable for attaching small molecular probes to various biomolecules in a test tube or on fixed cells, it could not be used for biomolecule labeling in live cells or organisms because of the copper catalyst.

In 2007, Carolyn Bertozzi, a chemist who holds joint appointments with Berkeley Lab, the University of California (UC) Berkeley, and the Howard Hughes Medical Institute, led a research effort that produced a copper-free version of click chemistry. In this version, glycans were metabolically labeled with azides -- a functional group featuring three nitrogen atoms -- via reactions that were carried out through the use of cyclooctyne reagents that required no copper catalyst. With their latest reagent, biarylazacyclooctynone (BARAC), Bertozzi and her group have provided a copper-free click chemistry technique that delivers relatively fast reaction kinetics and the bioorthogonality needed for biomolecule labeling. However, the technique can only be used on biomolecules that can be tagged with azides.

"Our bio-benign ligand-accelerated copper-catalyzed click chemistry reaction liberates bioconjugation from the limitation where ligations could only be accomplished with azide-tagged biomolecules," Liu says. "Now terminal alkyne residues can also be incorporated into biomolecules and detected in vivo."

This work was supported by a grant from the National Institutes of Health, and in part as a User Project at the Molecular Foundry, which is funded through DOE's Office of Science.

Story Source:

The above story is reprinted (with editorial adaptations ) from materials provided by DOE/Lawrence Berkeley National Laboratory.

Journal Reference:

Christen Besanceney-Webler, Hao Jiang, Tianqing Zheng, Lei Feng, David Soriano del Amo, Wei Wang, Liana M. Klivansky, Florence L. Marlow, Yi Liu, Peng Wu. Increasing the Efficacy of Bioorthogonal Click Reactions for Bioconjugation: A Comparative Study. Angewandte Chemie International Edition, 2011; DOI: 10.1002/anie.201101817

Environmental pollutants lurk long after they 'disappear'

The health implications of polluting the environment weigh increasingly on our public consciousness, and pharmaceutical wastes continue to be a main culprit. Now a Tel Aviv University researcher says that current testing for these dangerous contaminants isn't going far enough.

Dr. Dror Avisar, head of the Hydro-Chemistry Laboratory at TAU's Department of Geography and the Human Environment, says that, when our environment doesn't test positive for the presence of a specific drug, we assume it's not there. But through biological or chemical processes such as sun exposure or oxidization, drugs break down, or degrade, into different forms -- and could still be lurking in our water or soil.

In his lab, Dr. Avisar is doing extensive testing to determine how drugs degrade and identify the many forms they take in the environment. He has published his findings in Environmental Chemistry and the Journal of Environmental Science and Health.

Replicating nature

Drug products have been in our environment for years, whether they derive from domestic wastewater, hospitals, industry or agriculture. But those who are searching for these drugs in the environment are typically looking for known compounds -- parent drugs -- such as antibiotics, pain killers, lipid controllers, anti-psychotic medications and many more.

"If we don't find a particular compound, we don't see contamination -- but that's not true," Dr. Avisar explains. "We may have several degradation products with even higher levels of bioactivity." Not only do environmental scientists need to identify the degraded products, but they must also understand the biological-chemical processes that produce them in natural environments. When they degrade, compounds form new chemicals entirely, he cautions.

For the first time, Dr. Avisar and his research group have been working to simulate environmental conditions identical to our natural environment, down to the last molecule, in order to identify the conditions under which compounds degrade, how they degrade, and the resulting chemical products. Among the factors they consider are sun exposure, water composition, temperatures, pH levels and organic content.

Currently using amoxicillin, a common antibiotic prescribed for bacterial infections such as strep throat, as a test case, Dr. Avisar has successfully identified nine degradation products with different levels of stability. Two may even be toxic, he notes.

Classifying compounds with a fine-tooth comb

According to Dr. Avisar, who will soon expand his research to include the degraded products of chemotherapy drugs, his research is breaking new ground, extending past research. And while the attempt to catalogue the degraded products of common compounds in our environment may feel like looking for needles in haystacks, it's research that the world can't afford to ignore.

"It's important to talk about the new chemicals in our environment, derived from parent drugs. They are part of the mixture," Dr. Avisar warns. "Chemicals do not simply disappear -- we must understand what they've turned into. We are dealing with a whole new range of contaminants."

Story Source:

The above story is reprinted (with editorial adaptations ) from materials provided by American Friends of Tel Aviv University.

Journal Reference:

Igal Gozlan, Adi Rotstein, Dror Avisar. Investigation of an amoxicillin oxidative degradation product formed under controlled environmental conditions. Environmental Chemistry, 2010; 7 (5): 435 DOI: 10.1071/EN10037

Pocket chemistry: DNA helps glucose meters measure more than sugar

 Glucose meters aren't just for diabetics anymore. Thanks to University of Illinois chemists, they can be used as simple, portable, inexpensive meters for a number of target molecules in blood, serum, water or food.

Chemistry professor Yi Lu and postdoctoral researcher Yu Xiang published their findings in the journal Nature Chemistry.

"The advantages of our method are high portability, low cost, wide availability and quantitative detection of a broad range of targets in medical diagnostics and environmental monitoring," Lu said. "Anyone could use it for a wide range of detections at home and in the field for targets they may care about, such as vital metabolites for a healthy living, contaminants in their drinking water or food, or potential disease markers."

A glucose meter is one of the few widely available devices that can quantitatively detect target molecules in a solution, a necessity for diagnosis and detection, but only responds to one chemical: glucose. To use them to detect another target, the researchers coupled them with a class of molecular sensors called functional DNA sensors.

Functional DNA sensors use short segments of DNA that bind to specific targets. A number of functional DNAs and RNAs are available to recognize a wide variety of targets.

They have been used in the laboratory in conjunction with complex and more expensive equipment, but Lu and Xiang saw the potential for partnering them with pocket glucose meters.

The DNA segments, immobilized on magnetic particles, are bound to the enzyme invertase, which can catalyze conversion of sucrose (table sugar) to glucose. The user adds a sample of blood, serum or water to the functional DNA sensor to test for drugs, disease markers, contaminants or other molecules. When the target molecule binds to the DNA, invertase is released into the solution. After removing the magnetic particle by a magnet, the glucose level of the sample rises in proportion to the amount of invertase released, so the user then can employ a glucose meter to quantify the target molecule in the original sample.

"Our method significantly expands the range of targets the glucose monitor can detect," said Lu, who also is affiliated with the Beckman Institute for Advanced Science and Technology and with the Frederick Seitz Materials Research Lab at U. of I. "It is simple enough for someone to use at home, without the high costs and long waiting period of going to the clinics or sending samples to professional labs."

The researchers demonstrated using functional DNA with glucose meters to detect cocaine, the disease marker interferon, adenosine and uranium. The two-step method could be used to detect any kind of molecule that a functional DNA or RNA can bind.

Next, the researchers plan to further simplify their method, which now requires users to first apply the sample to the functional DNA sensor and then to the glucose meter.

"We are working on integrating the procedures into one step to make it even simpler," Lu said. "Our technology is new and, given time, it will be developed into an even more user-friendly format."

The U.S. Department of Energy, the National Institutes of Health and the National Science Foundation supported this work.

Story Source:

The above story is reprinted (with editorial adaptations) from materials provided by University of Illinois at Urbana-Champaign, via EurekAlert!, a service of AAAS.

Journal Reference:

Yu Xiang, Yi Lu. Using personal glucose meters and functional DNA sensors to quantify a variety of analytical targets. Nature Chemistry, 2011; DOI: 10.1038/nchem.1092

Shining a light on the elusive 'blackbody' of energy research: Designer material has potential applications for thermophotovoltaics

 A designer metamaterial has shown it can engineer emitted "blackbody" radiation with an efficiency beyond the natural limits imposed by the material's temperature, a team of researchers led by Boston College physicist Willie Padilla report in the current edition of Physical Review Letters.

A "blackbody" object represents a theorized ideal of performance for a material that perfectly absorbs all radiation to strike it and also emits energy based on the material's temperature. According to this blackbody law, the energy absorbed is equal to the energy emitted in equilibrium.

The breakthrough reported by Padilla and colleagues from Duke University and SensorMetrix, Inc., could lead to innovative technologies used to cull energy from waste heat produced by numerous industrial processes. Furthermore, the human-made metamaterial offers the ability to control emissivity, which could further enhance energy conversion efficiency.

"For the first time, metamaterials are shown to be able to engineer blackbody radiation and that opens the door for a number of energy harvesting applications," said Padilla. "The energy a natural surface emits is based on its temperature and nothing more. You don't have a lot of choice. Metamaterials, on the other hand, allow you to tailor that radiation coming off in any desirable manner, so you have great control over the emitted energy."

Researchers have long sought to find the ideal "blackbody" material for use in solar or thermoelectric energy generation. So far, the hunt for such a class of thermal emitters has proved elusive. Certain rare earth oxides are in limited supply and expensive, in addition to being almost impossible to control. Photonic crystals proved to be inferior emitters that failed to yield significant efficiencies.

Constructed from artificial composites, metamaterials are designed to give them new properties that exceed the performance limits of their actual physical components and allow them to produce "tailored" responses to radiation. Metamaterials have exhibited effects such as a negative index of refraction and researchers have combined metamaterials with artificial optical devices to demonstrate the "invisibility cloak" effect, essentially directing light around a space and masking its existence.

Three years ago, the team developed a "perfect" metamaterial absorber capable of absorbing all of the light that strikes it thanks to its nano-scale geometric surface features. Knowing that, the researches sought to exploit Kirchoffs's law of thermal radiation, which holds that the ability of a material to emit radiation equals its ability to absorb radiation.

Working in the mid-infrared range, the thermal emitter achieved experimental emissivity of 98 percent. A dual-band emitter delivered emission peaks of 85 percent and 89 percent. The results confirmed achieving performance consistent with Kirchoff's law, the researchers report.

"We also show by performing both emissivity and absorptivity measurements that emissivity and absorptivity agree very well," said Padilla. "Even though the agreement is predicted by Kirchoff's law, this is the first time that Kirchoff's law has been demonstrated for metamaterials."

The researchers said altering the composition of the metamaterial can results in single-, dual-band and broadband metamaterials, which could allow greater control of emitted photons in order to improve energy conversion efficiency.

"Potential applications could lie in energy harvesting area such as using this metamaterial as the selective thermal emitter for thermophotovoltaic (TPV) cells," said Padilla. "Since this metamaterial has the ability to engineer the thermal radiation so that the emitted photons match the band gap of the semiconductor -- part of the TPV cell -- the converting efficiency could be greatly enhanced.

In addition to Padilla, the research team included BC graduate student Xianliang Liu, Duke University's Nan Marie Jokerst and Talmage Tyler and SensorMetrix, Inc., researchers Tatiana Starr and Anthony F. Starr.

Story Source:

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

Journal Reference:

Xianliang Liu, Talmage Tyler, Tatiana Starr, Anthony Starr, Nan Jokerst, Willie Padilla. Taming the Blackbody with Infrared Metamaterials as Selective Thermal Emitters. Physical Review Letters, 2011; 107 (4) DOI: 10.1103/PhysRevLett.107.045901

Molecules 'light up' Alzheimer's roots: Light-switching complex attaches itself to amyloid proteins

 A breakthrough in sensing at Rice University could make finding signs of Alzheimer's disease nearly as simple as switching on a light.

The technique reported in the Journal of the American Chemical Society should help researchers design better medications to treat the devastating disease.

The lab of Rice bioengineer Angel Martí is testing metallic molecules that naturally attach themselves to a collection of beta amyloid proteins called fibrils, which form plaques in the brains of Alzheimer's sufferers. When the molecules, complexes of dipyridophenazine ruthenium, latch onto amyloid fibrils, their photoluminescence increases 50-fold.

The large increase in fluorescence may be an alternative to molecules currently used to study amyloid fibrils, which researchers believe form when misfolded proteins begin to aggregate. Researchers use changes in fluorescence to characterize the protein transition from disordered monomers to aggregated structures.

Nathan Cook, a former Houston high school teacher and now a Rice graduate student and lead author of the new paper, began studying beta amyloids when he joined Martí's lab after taking a Nanotechnology for Teachers course taught by Rice Dean of Undergraduates and Professor of Chemistry John Hutchinson. Cook's goal was to find a way to dissolve amyloid fibrils in Alzheimer's patients.

But the Colorado native's research led him down a different path when he realized the ruthenium complexes, the subject of much study in Martí's group, had a distinctive ability to luminesce when combined in a solution with amyloid fibrils.

Such fibrils are simple to make in the lab, he said. Molecules of beta amyloid naturally aggregate in a solution, as they appear to do in the brain. Ruthenium-based molecules added to the amyloid monomers do not fluoresce, Cook said. But once the amyloids begin to aggregate into fibrils that resemble "microscopic strands of spaghetti," hydrophobic parts of the metal complex are naturally drawn to them. "The microenvironment around the aggregated peptide changes and flips the switch" that allows the metallic complexes to light up when excited by a spectroscope, he said.

Thioflavin T (ThT) dyes are the standard sensors for detecting amyloid fibrils and work much the same way, Marti said. But ThT has a disadvantage because it fluoresces when excited at 440 nanometers and emits light at 480 nanometers -- a 40-nanometer window.

That gap between excitation and emission wavelengths is known as the Stokes shift. "In the case of our metal complexes, the Stokes is 180 nanometers," said Martí, an assistant professor of chemistry and bioengineering. "We excite at 440 and detect in almost the near-infrared range, at 620 nanometers.

"That's an advantage when we want to screen drugs to retard the growth of amyloid fibrils," he said. "Some of these drugs are also fluorescent and can obscure the fluorescence of ThT, making assays unreliable."

Cook also exploited the metallic's long-lived fluorescence by "time gating" spectroscopic assays. "We specifically took the values only from 300 to 700 nanoseconds after excitation," he said. "At that point, all of the fluorescent media have pretty much disappeared, except for ours. The exciting part of this experiment is that traditional probes primarily measure fluorescence in two dimensions: intensity and wavelength. We have demonstrated that we can add a third dimension -- time -- to enhance the resolution of a fluorescent assay."

The researchers said their complexes could be fitting partners in a new technique called fluorescence lifetime imaging microscopy, which discriminates microenvironments based on the length of a particle's fluorescence rather than its wavelength.

Cook's goal remains the same: to treat Alzheimer's -- and possibly such other diseases as Parkinson's -- through the technique. He sees a path forward that may combine the ruthenium complex's ability to target fibrils and other molecules' potential to dissolve them in the brain.

"That's something we are actively trying to target," Martí said.

More information: http://pubs.acs.or … 21/ja204656r

Provided by Rice University (news : web)

New material could offer hope to those with no voice

In 1997, the actress and singer Julie Andrews lost her singing voice following surgery to remove noncancerous lesions from her vocal cords. She came to Steven Zeitels, a professor of laryngeal surgery at Harvard Medical School, for help.

Zeitels was already starting to develop a new type of material that could be implanted into scarred vocal cords to restore their normal function. In 2002, he enlisted the help of MIT’s Robert Langer, the David H. Koch Institute Professor in the Department of Chemical Engineering, an expert in developing polymers for biomedical applications.

The team led by Langer and Zeitels has now developed a polymer gel that they hope to start testing in a small clinical trial next year. The gel, which mimics key traits of human vocal cords, could help millions of people with voice disorders — not just singers such as Andrews and Steven Tyler, another patient of Zeitels’.

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Video: Watch how the gel mimics human vocal cords

About 6 percent of the U.S. population has some kind of voice disorder, and the majority of those cases involve scarring of the vocal cords, says Sandeep Karajanagi, a former MIT researcher who developed the gel while working as a postdoc in the Langer lab. Many of those are children whose cords are scarred from intubation during surgery, while others are victims of laryngeal cancer.

Other people who could benefit are those with voices strained from overuse, such as teachers. “This would be so valuable to society, because every time a person loses their voice, say, a teacher or a politician, all of their contributions get lost to society, because they can’t communicate their ideas,” Zeitels says.

‘A mechanical problem’

When Langer and his lab joined the effort in 2002, they considered two different approaches: creating a synthetic material that would mimic the properties of vocal cords, or engineering artificial vocal-cord tissue. Both approaches have potential, Langer says, but the team decided to pursue a synthetic material because it would likely take less time to reach patients. “Making a totally natural vocal cord is a more long-term project,” he says.

Some doctors treat vocal-fold scars with materials normally used in dermatology or plastic surgery, in hopes of softening the vocal cords, but those don’t work for everyone, and the effects don’t last long, says Nathan Welham, assistant professor of otolaryngology at the University of Wisconsin School of Medicine.

“Scarred vocal cords are really hard to fix,” says Welham, who is not involved in this project. “People have tried this and that, but there’s really no commonly used, available approach that treats the inherent problem of scarring in the vocal folds.”

Other researchers have tried developing drugs that would dissolve the scar tissue, but the MIT/Harvard team decided on a different approach.

“What we did differently is we looked at this as a mechanical problem that we need to solve. We said, ‘Let’s not look at the scar itself as a problem, let’s think of how we can improve the voice despite the presence of the scar tissue,’” says Karajanagi, who is now an instructor of surgery at Harvard Medical School and a researcher at the Center for Laryngeal Surgery and Voice Rehabilitation at Massachusetts General Hospital.

The team chose polyethylene glycol (PEG) as its starting material, in part because it is already used in many FDA-approved drugs and medical devices.

By altering the structure and linkage of PEG molecules, the researchers can control the material’s viscoelasticity. In this case, they wanted to make a substance with the same viscoelasticity as human vocal cords. Viscoelasticity is critical to voice production because it allows the vocal cords to vibrate when air is expelled through the lungs.

For use in vocal cords, the researchers created and screened many variations of PEG and selected one with the right viscoelasticity, which they called PEG30. In laboratory tests, they showed that the vibration that results from blowing air on a vocal-fold model of PEG30 is very similar to that seen in human vocal folds. Also, tests showed that PEG30 can restore vibration to stiff, non-vibrating vocal folds such as those seen in human patients suffering from vocal-fold scarring.

Under FDA guidelines, the gel would be classified as an injectable medical device, rather than a drug. The researchers, who have published more than a dozen papers on their voice-restoration efforts, have applied for a patent on the material and are working toward FDA approval. If approved for human use, the gel would likely have to be injected at least once every six months, because it eventually breaks down.

The project is funded by the Institute of Laryngology and Voice Restoration, which consists of patients whose mission is to support and fund research and education in treating and restoring voice. Julie Andrews is the foundation’s honorary chairwoman.

Safety tests

In a study recently published in the Annals of Otology, Rhinology & Laryngology, the researchers tested the biocompatibility of the gel by injecting it into the healthy vocal folds of dogs. After four months, the treated dogs showed no damage to their vocal cords.

“That gives us exciting data that this has a real good chance of working in people without creating damage,” Karajanagi says, adding that clinical trials will be needed to confirm this.

The researchers are now working on developing a manufacturing process that will generate enough of the material, in high quality, for human trials. They hope to run a trial of about 10 patients next year. They are also working on developing methods for injecting the material at the right location to treat human vocal cords.

Such gels could find other medical applications, by varying the chemical properties of the PEG, Langer says. “We think of what we do as ‘designer polymers,’” he says. “We can modify them depending on the problem we’re trying to solve.”
This story is republished courtesy of MIT News (http://web.mit.edu/newsoffice/), a popular site that covers news about MIT research, innovation and teaching.

Provided by Massachusetts Institute of Technology (news : web)

Roman Baths algae could fuel the future (w/ video)

Algae growing in Bath’s Roman Baths could one day be used to make fuel for our cars.

The Roman Baths are currently at the centre of a Department of Biology & Biochemistry study aimed at producing renewable biofuels from algae.

The race is on for a renewable liquid fuel as oil prices skyrocket and global resources deplete rapidly. Biodiesel can be produced by extracting the oil from the algae cell, with certain types of algae having a higher oil content.

Researchers from the University are looking for ways to make the production of biodiesel from algae commercially viable.
Studying the unique algae growing in the high temperature waters of the baths might make the wide-scale production of biofuels a real possibility for future transportation energy.

Research has been carried out into creating biodiesel from algae over the past 20 years; however limitations currently prevent the technology being used on a large scale.

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PhD student Holly Smith-Baedorf is working on the research project. She explains: “Algae are usually happiest growing at temperatures around 25 degrees celsius and that can limit the places in which it can be cultivated on a large scale.

“Areas where these ideal conditions are available also usually make good arable areas and are therefore needed for food production.

“In an ideal world we would like to grow algae in desert areas where there are huge expanses of land that don’t have other uses, but the temperatures in these zones are too high for algae to flourish.”

But the algae growing in the hot water of the Roman Baths is perfect for the research.

Algae cells are very versatile and can change many of their characteristics in response to their environment. The protected environment in the baths gives an ideal environment in which adaptation can take place.

There are two different baths, and both maintain a steady temperature. The King’s Bath is 46 degrees celsius and the Great Bath is 39 degrees celsius; both have remained constant for many years.

The temperature of the Roman Baths is created by rain falling in the Mendip Hills, and running down through limestone at 10,000 – 14,000 feet below ground where thermal temperatures can reach nearly 100 degrees celsius.

Pressure builds up and pushes the water up through faults in the limestone, surfacing at approximately 250,000 gallons a day in the Roman Baths.

Holly said: “We have identified seven different types of algae in the baths. There are many more but they are in such low cell densities that we have difficulty isolating them, for now”.

The research team, which also includes collaborators from the Department of Chemistry, led by Professor Matt Davidson, and scientists at the University of the West of England, headed by Dr Heather Macdonald, is growing each of the seven types of algae from the Roman Baths over a range of temperatures and comparing them to ‘control’ algae known for being good for producing biodiesel at normal temperatures.

Algae project researcher, Professor Rod Scott, said: “The results of this study will help us identify whether there is a particular algae species among the seven identified in the Roman Baths that is well adapted to growing at higher temperatures and also suitable for producing sufficient amounts of biodiesel to make wide-scale production viable.”

However, while the ability to grow at high temperatures is one limitation on large-scale biodiesel production, it is not the only restraint.

Algae cell walls are particularly difficult to break making extraction of the oil inside an energy intensive process. Some algae cells are also easier to filter than others, greatly reducing the energy and economic cost of ‘harvesting’ the algae from cultures.

The research team are therefore also looking for a species of algae with a weaker cell wall, high oil content and the possibility to use cheap filtration techniques, keeping production costs low.

Professor Scott said: “There are a lot of variables that need to be right in order for the wide-scale production of biodiesel from algae to be viable, which is why it is important for us to classify and test as many species from the Roman Baths as possible.

“One species might produce a lot of oil, but if we can’t harvest the algae or break the cell walls easily then the production costs of the biodiesel will rise and it will no longer be a suitable alternative to other fuels.”

The research team is now carrying out tests on the species of algae identified to determine which most suits potential future mass growth for biodiesel production.

Provided by University of Bath (news : web)

New finding shows a research area to expand in EMSL Radiochemistry Annex

Scientists from Pacific Northwest National Laboratory and Rai Enviro-Chem, LLC, recently published first-ever results that illustrate the importance of determining hard-to-find oxidized Fe(III) reaction products in the reduction of Pu(IV) to Pu(III) by the reductant Fe(II). The shift from the insoluble Pu(IV)—the current state of plutonium contaminants within sediments at the Department of Energy’s Hanford Site—to the lower oxidation state Pu(III) is a very important reaction to study because Pu(III) is soluble, and therefore potentially more mobile in the groundwater.

However, this particular reduction reaction is far less studied than other contaminant-related reactions because of the radioactivity of the samples and the need for specialized facilities and equipment. The research team’s overall strategy was to move beyond bulk studies of Pu(IV) /Fe(II) interactions  to explore the microscopic and molecular processes involved in forming the tiny amounts of Fe(III) oxidization products that the reaction generates—a challenge that had never been attempted.

In this case, the team coupled solution-phase measurements of Pu concentrations and oxidation state determinations with SEM/TEM analysis of the reaction products, which demonstrated the enhancing role that Fe(III) reaction products play in the formation of Pu(III), and led to development of the first thermodynamic theory of such an effect. This outcome is a considerable step toward understanding the molecular mechanisms that govern the reduction from Pu(IV) to Pu(III), while also arming engineers with new information on how to inhibit the reaction in contaminated subsurface environments around the nation. Studies like these will be greatly enhanced by the addition of EMSL’s new Radiochemistry Annex, which is set to fully open to the global user community in Fall 2012. Until then, selected new radiological capabilities will become available to users beginning in August 2011.

More information: Felmy AR, et al. 2011. "Heterogeneous Reduction of PuO2 with Fe(II): Importance of the Fe(III) Reaction Product." Environmental Science & Technology 45:3952-3958. DOI: 10.1021/es104212g

 

Research shows 'BPA-free' bottles live up to manufacturers' claims

The alarm caused by bisphenol A (BPA) presence in reusable plastic bottles resulted in a recent industry change, producing products made with supposed BPA-free materials.

Prompted by requests and concern from consumers, University of Cincinnati (UC) researchers wanted to see if these alternatives--including products made with stainless steel and coated aluminum--were truly giving the consumer an option free of BPA.

In a study reported in the July 8, 2011 advance online edition of the journal Chemosphere, Scott Belcher, PhD, associate professor in the pharmacology and cell biophysics department, and colleagues found that stainless steel- and/or co-polyester lined-aluminum bottles did not release BPA; however, aluminum bottles lined with epoxy-based resins still resulted in BPA contamination of liquids.

"BPA is an ever-present, high-volume industrial chemical that is an estrogen and an environmental endocrine disrupting chemical," explains Belcher, adding that it has been shown in experimental models to negatively impact the heart and reproductive system and enhance the growth of certain tumors.

"It is used extensively in the production of consumer goods, polycarbonate plastics, in epoxy resins that are used to coat metallic food and beverage cans and in other products," he continues. "There is great concern regarding the possible harmful effects from exposures that result from BPA leaching into foods and beverages from packaging or storage containers.

"The objective of this study was to independently assess whether BPA contamination of water was occurring from different types of reusable drinking bottles marketed as alternatives to BPA-containing polycarbonate plastics."

Belcher says that all reusable bottles used in the study were obtained from retail sources and were constructed from polycarbonate, co-polyester, stainless steel, aluminum with co-polyester lining or aluminum with epoxy resin lining.

The bottles, divided into test groups based on their material or lining, and collection vials were washed and rinsed using a standardized protocol to ensure that they were free of non-experimental contaminants. The interior of each bottle was scrubbed with a soft nylon bristle brush for approximately 30 seconds with a cleaner.

Belcher says bottles were then rinsed six times with BPA-free water, two of those times with high-performance liquid chromatography (HPLT)-grade water used to identify, quantify and purify the individual components of the water, and then air dried.

"Briefly, 100 milliliters of HPLC-grade water was added to each bottle on the first day and was kept in the bottle for five days at room temperature," he says.

Three replicate experiments were performed for each bottle. The water was then rotated using a cell culture roller bottle system to ensure even contact of the water and the bottles' surface.

The effect of hot water on BPA leaching from the epoxy resin-lined bottles was measured by the addition of 100 milliliters of HPLC-grade water heated to 100 degrees on the first day.

Following the transfer of boiling water, the bottles were kept at room temperature with rotation for 24 hours during which water samples cooled to room temperature.

"Results once again showed that, at room temperature, detectable concentrations of BPA migrated from polycarbonate bottles. This confirmed our lab's previous study," says Belcher. "However, under the same conditions, BPA migration from aluminum bottles lined with epoxy-based resins was variable depending on the manufacturer. The discount store branded bottles tested released much more BPA."

He says boiling water significantly increased BPA migration from the epoxy-lined bottles. No detectable contamination was observed in water stored in bottles made from co-polyester plastic, uncoated stainless steel or aluminum lined with EcoCare™.

"The results from this study show that when used according to manufacturers' recommendations, reusable water bottles constructed from 'BPA-free' alternative materials are suitable for consumption of beverages without the fear of BPA contamination," Belcher says. "BPA does, however, migrate into water stored in polycarbonate plastic and metal bottles coated with epoxy-resins, especially when heated to high temperatures.

"Consumers should not think that just because a bottle isn't polycarbonate plastic that it is safe from the dangers of BPA, but while there are no standards for claims of 'BPA-free,' it appears that 'BPA-free' labels used to market co-polyester-based water bottle alternatives actually reflect a lack of BPA contamination in liquids stored in those containers," he continues.

"While consumers have been skeptical of manufacturers' claims, these studies confirm that these specific products do offer a BPA-free alternative to polycarbonate or epoxy lined bottles and that companies have responded to their consumers' desires for BPA-free products."

Provided by University of Cincinnati (news : web)

New method for making human-based gelatin

Scientists are reporting development of a new approach for producing large quantities of human-derived gelatin that could become a substitute for some of the 300,000 tons of animal-based gelatin produced annually for gelatin-type desserts, marshmallows, candy and innumerable other products. Their study appears in ACS's Journal of Agriculture and Food Chemistry.

Jinchun Chen and colleagues explain that animal-based gelatin, which is made most often from the bones and skin of cows and pigs, may carry a risk of infectious diseases such as "Mad Cow" disease and could provoke immune system responses in some people. Animal-based gelatin has other draw-backs, with variability from batch to batch, for instance, creating difficulties for manufacturers. Scientists thus have sought alternatives, including development of a human-recombinant gelatin for potential use in drug capsules and other medical applications.

To get around these difficulties, the scientists developed and demonstrated a method where human gelatin genes are inserted into a strain of yeast, which can produce gelatin with controllable features. The researchers are still testing the human-yeast gelatin to see how well it compares to other gelatins in terms of its viscosity and other attributes. Chen and colleagues suggest that their method could be scaled up to produce large amounts of gelatin for commercial use.

More information: “New Strategy for Expression of Recombinant Hydroxylated Human-Derived Gelatin in Pichia pastoris KM71” J. Agric. Food Chem., 2011, 59 (13), pp 7127–7134 DOI: 10.1021/jf200778r

Abstract
Gelatin is a well-known biopolymer, and it has a long history of use mainly as a gelling agent in the food industry. This paper reports a new method for producing recombinant hydroxylated human-derived gelatin in Pichia pastoris KM71. Three independent expression cassettes encoding for specific length of gelatin, prolyl 4-hydroxylase (P4H, EC 1.14.11.2), ?-subunit (?P4H), and protein-disulfide isomerase (PDI) were individually cloned in one expression vector, pPIC9K. The modified gelatin gene and two subunit genes of P4H were under the control of two different inducible promoters, namely, alcohol oxidase 1 promoter (PAOX1) and formaldehyde dehydrogenase 1 promoter (PFLD1), respectively. The results of sodium dodecylsulfate-polyacrylamide gel electrophoresis show that a recombinant gelatin was successfully expressed in P. pastoris KM71 by methanol induction. Liquid chromatography coupled with tandem mass spectrometry analysis indicates that the expressed gelatin was hydroxylated with approximately 66.7% of proline residues in the Y positions of Gly-X-Y triplets. The results of nuclear magnetic resonance spectroscopy of recombinant gelatin test show that the 1H and 13C spectra have many corresponding characteristic displacement peaks, and amino acids composition analysis shows that it contains hydroxyproline and its UV absorption is consistent with the characteristics of gelatin.

Provided by American Chemical Society (news : web)