Chemists reveal the force within you: New method for visualizing mechanical forces on cell surface

ScienceDaily (Nov. 9, 2011) — A new method for visualizing mechanical forces on the surface of a cell, reported in Nature Methods, provides the first detailed view of those forces, as they occur in real-time.

"Now we're able to measure something that's never been measured before: The force that one molecule applies to another molecule across the entire surface of a living cell, and as this cell moves and goes about its normal processes," says Khalid Salaita, assistant professor of biomolecular chemistry at Emory University. "And we can visualize these forces in a time-lapsed movie."

Salaita developed the florescent-sensor technique with chemistry graduate students Daniel Stabley and Carol Jurchenko, and undergraduate senior Stephen Marshall.

"Cells are constantly tugging and pushing on their surroundings, and they can even communicate with one another using mechanics," Salaita says. "One way that cells use forces is evident from the characteristic architecture of tissue, like a lung or a heart. If we want to really understand cells and how they work, we have to understand cell mechanics at a molecular level. The first step is to measure the tension applied to specific receptors on the cell surface."

The researchers demonstrated their technique on the epidermal growth factor receptor (EGFR), one of the most studied cellular signaling pathways. They mapped the mechanical strain exerted by EGFR during the early stages of endocytosis, when the protein receptor of a cell takes in a ligand, or binding molecule. The results showed that the cell does not passively absorb the ligand, but physically pulls it inside during the process. Their experiments provide the first direct evidence that force is exerted during endocytosis.

Mapping such forces may help to diagnose and treat diseases related to cellular mechanics. Cancer cells, for instance, move differently from normal cells, and it is unclear whether that difference is a cause or an effect of the disease.

"It's known that if EGFR is over-active, that can lead to cancer," Salaita says. "And one of the ways that EGFR is activated is by binding its ligand and taking it in. So if we can understand how tugging on EGFR force changes the pathway, and whether it plays a role in cancer, it might be possible to design drugs that target this pulling process."

Several methods have been developed in recent years to try to study the mechanics of cellular forces, but they have major limitations.

One genetic engineering approach requires splitting open and modifying proteins of a cell. This invasive technique may change the behavior of the cell, skewing the results.

The technique developed at Emory is non-invasive, does not modify the cell, and can be done with a standard fluorescence microscope. A flexible polymer is chemically modified at both ends. One end gets a fluorescence-based turn-on sensor that will bind to a receptor on the cell surface. The other end is chemically anchored to a microscope slide and a molecule that quenches fluorescence.

"Once a force is applied to the polymer, it stretches out," Salaita explains. "And as it extends, the distance from the quencher increases and the fluorescent signal turns on and grows brighter. We can determine the force being exerted by measuring the amount of fluorescent light emitted."

The forces of any individual protein or molecule on the cell surface can be measured using the technique, at far higher spatial and temporal resolutions than was previously possible.

Many mysteries beyond the biology and chemistry of cells may be explained through measuring cellular forces. How does a cancer cell crawl when a tumor spreads? What are the forces involved in cell division and immune response? What are the mechanics that allow groups of cardiac cells to beat in unison?

"Our method can be applied to nearly any receptor, opening the door to rapidly studying chemical and mechanical interactions across the thousands of membrane-bound receptors on the surface of virtually any cell type," Salaita says. "We hope that measuring cellular forces could then become part of the standard repertoire of biochemical techniques that scientists use to study living systems."

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The above story is reprinted from materials provided by Emory University. The original article was written by Carol Clark.

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

Journal Reference:

Daniel R Stabley, Carol Jurchenko, Stephen S Marshall, Khalid S Salaita. Visualizing mechanical tension across membrane receptors with a fluorescent sensor. Nature Methods, 2011; DOI: 10.1038/nmeth.1747

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Chemists reveal the force within you: New method for visualizing mechanical forces on cell surface

ScienceDaily (Nov. 9, 2011) — A new method for visualizing mechanical forces on the surface of a cell, reported in Nature Methods, provides the first detailed view of those forces, as they occur in real-time.

"Now we're able to measure something that's never been measured before: The force that one molecule applies to another molecule across the entire surface of a living cell, and as this cell moves and goes about its normal processes," says Khalid Salaita, assistant professor of biomolecular chemistry at Emory University. "And we can visualize these forces in a time-lapsed movie."

Salaita developed the florescent-sensor technique with chemistry graduate students Daniel Stabley and Carol Jurchenko, and undergraduate senior Stephen Marshall.

"Cells are constantly tugging and pushing on their surroundings, and they can even communicate with one another using mechanics," Salaita says. "One way that cells use forces is evident from the characteristic architecture of tissue, like a lung or a heart. If we want to really understand cells and how they work, we have to understand cell mechanics at a molecular level. The first step is to measure the tension applied to specific receptors on the cell surface."

The researchers demonstrated their technique on the epidermal growth factor receptor (EGFR), one of the most studied cellular signaling pathways. They mapped the mechanical strain exerted by EGFR during the early stages of endocytosis, when the protein receptor of a cell takes in a ligand, or binding molecule. The results showed that the cell does not passively absorb the ligand, but physically pulls it inside during the process. Their experiments provide the first direct evidence that force is exerted during endocytosis.

Mapping such forces may help to diagnose and treat diseases related to cellular mechanics. Cancer cells, for instance, move differently from normal cells, and it is unclear whether that difference is a cause or an effect of the disease.

"It's known that if EGFR is over-active, that can lead to cancer," Salaita says. "And one of the ways that EGFR is activated is by binding its ligand and taking it in. So if we can understand how tugging on EGFR force changes the pathway, and whether it plays a role in cancer, it might be possible to design drugs that target this pulling process."

Several methods have been developed in recent years to try to study the mechanics of cellular forces, but they have major limitations.

One genetic engineering approach requires splitting open and modifying proteins of a cell. This invasive technique may change the behavior of the cell, skewing the results.

The technique developed at Emory is non-invasive, does not modify the cell, and can be done with a standard fluorescence microscope. A flexible polymer is chemically modified at both ends. One end gets a fluorescence-based turn-on sensor that will bind to a receptor on the cell surface. The other end is chemically anchored to a microscope slide and a molecule that quenches fluorescence.

"Once a force is applied to the polymer, it stretches out," Salaita explains. "And as it extends, the distance from the quencher increases and the fluorescent signal turns on and grows brighter. We can determine the force being exerted by measuring the amount of fluorescent light emitted."

The forces of any individual protein or molecule on the cell surface can be measured using the technique, at far higher spatial and temporal resolutions than was previously possible.

Many mysteries beyond the biology and chemistry of cells may be explained through measuring cellular forces. How does a cancer cell crawl when a tumor spreads? What are the forces involved in cell division and immune response? What are the mechanics that allow groups of cardiac cells to beat in unison?

"Our method can be applied to nearly any receptor, opening the door to rapidly studying chemical and mechanical interactions across the thousands of membrane-bound receptors on the surface of virtually any cell type," Salaita says. "We hope that measuring cellular forces could then become part of the standard repertoire of biochemical techniques that scientists use to study living systems."

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The above story is reprinted from materials provided by Emory University. The original article was written by Carol Clark.

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

Journal Reference:

Daniel R Stabley, Carol Jurchenko, Stephen S Marshall, Khalid S Salaita. Visualizing mechanical tension across membrane receptors with a fluorescent sensor. Nature Methods, 2011; DOI: 10.1038/nmeth.1747

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New benchtop polymer characterization method developed

ScienceDaily (Oct. 20, 2011) — Researchers at UC Santa Barbara have developed a new and highly efficient way to characterize the structure of polymers at the nanoscale -- effectively designing a routine analytical tool that could be used by industries that rely on polymer science to innovate new products, from drug delivery gels to renewable bio-materials.

Professor Omar Saleh and graduate student Andrew Dittmore of the UCSB Materials department have successfully measured the structure and other critical parameters of a long, string-like polymer molecule -- polyethylene glycol, or PEG -- by stretching it with an instrument called magnetic tweezers.

"We attach one end of the PEG molecule to a surface, and the other to a tiny magnetic bead, then pull on the bead by applying a magnetic field," explained Saleh. "The significance is that we're able to perform the elastic measurements -- force vs. length measurement -- to see aspects of polymer structure that are hard to see in any other way, and we can do it within minutes on a benchtop apparatus."

Their research to characterize this particular polymer will lay the groundwork for developing a screening tool that could be used by a number of industries, according to Saleh's research team.

"Our measurements of PEG can be used as a baseline for comparison to other polymers, including biomolecules such as DNA, RNA and proteins, which display more complex physics," said Dittmore. "We chose to study PEG because it is an inert polymer that is biocompatible, soluble in water, and used for many technological purposes. The protocols we developed will be useful for future work with a variety of polymers, greatly expanding the versatility of the magnetic tweezers technique."

PEG is one of the most frequently used polymers in creams, cosmetics, adhesives and medicines, but its application goes beyond everyday household products. As a coating, PEG can shield against an unwanted immune response to give a medicine a stealth-like quality. To this end, it is used to enhance the effectiveness of anticancer drugs by increasing the circulation time in the body. PEG repels other molecules and is often used as a nonfouling coating for biomedical implants and biosensors that detect the presence of drugs or antibodies in blood.

In 1974, Paul Flory won the Nobel Prize in Chemistry for his theories regarding polymer structure in a solvent. Inspired by the work of Flory, and theories put forth decades earlier by UCSB materials and physics professor Philip Pincus, Saleh and Dittmore set out to develop an experiment that would validate their theories.

"Flory and de Gennes taught us that the structure of a polymer in solution depends on both the quality of solvent and also the length of the chain. Pincus extended upon this theory, and brought force into the picture as an important experimental variable," said Dittmore. "Now we have a method to directly test these ideas at the single-molecule level, using a powerful and quantitative technique."

"Until now, the most general method to obtain comparable data is to use neutron or x-ray diffraction which involves expensive national facilities such as nuclear reactors or particle accelerators. Thus, this research opens up a broad area of research that can be carried out at academic and industrial laboratories with modest resources," commented Professor Philip Pincus, Chair of Biomolecular Science and Engineering at UCSB.

The findings of Dittmore et al. were published in the journal Physical Review Letters in September. The paper establishes a framework for comparing biomolecules and synthetic polymers based on chain structure that could be further refined and translated into a laboratory tool for industry.

"Many companies are looking to replace the petroleum-based polymers they use in consumer products with polymers made from biomass, such as sugar cane or cellulose," said Professor Glenn Fredrickson, Chair of Functional Materials and Founding Director of the Mitsubishi Chemical Center for Advanced Materials at UCSB. "If their methods could be made into a compact and inexpensive screening tool for polymer properties in an industrial setting, it could be important in affecting industry transformation to producing polymers from renewable resources.

Their research was made possible by support from the National Science Foundation and was carried out at the Materials Research Laboratory: an NSF MRSEC facility at UC Santa Barbara.

"This is an excellent example of high-risk, transformative research that breaks down conventional wisdom," said Craig Hawker, Director of the Materials Research Laboratory at UCSB. "The MRL is proud to have contributed to the success of this project through a Seed program designed to fund research that will revolutionize existing fields. By establishing this technique as a powerful, new strategy for characterizing synthetic polymers, countless future studies are now possible."

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Journal Reference:

Andrew Dittmore, Dustin McIntosh, Sam Halliday, Omar Saleh. Single-Molecule Elasticity Measurements of the Onset of Excluded Volume in Poly(Ethylene Glycol). Physical Review Letters, 2011; 107 (14) DOI: 10.1103/PhysRevLett.107.148301

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Method for creating tiny diamond machines improved

ScienceDaily (Sep. 28, 2011) — Diamonds may be best known as a symbol of long-lasting love. But semiconductor makers are also hoping they'll pan out as key components of long-lasting micromachines if a new method developed at the National Institute of Standards and Technology (NIST) for carving these tough, capable crystals proves its worth.* The method offers a precise way to engineer microscopic cuts in a diamond surface, yielding potential benefits in both measurement and technological fields.

By combining their own observations with background gleaned from materials science, NIST semiconductor researchers have found a way to create unique features in diamond -- potentially leading to improvements in nanometrology in short order, as it has allowed the team to make holes of precise shape in one of the hardest known substances. But beyond the creation of virtually indestructible nanorulers, the method could one day lead to the improvement of a class of electronic devices useful in cell phones, gyroscopes and medical implants.

Well known for making the hugely complex electronic microchips that run our laptops, the semiconductor industry has expanded its portfolio by fabricating tiny devices with moving parts. Constructed with substantially the same techniques as the electronic chips, these "micro-electromechanical systems," or MEMS, are just a few micrometers in size. They can detect environmental changes such as heat, pressure and acceleration, potentially enabling them to form the basis of tiny sensors and actuators for a host of new devices. But designers must take care that tiny moving parts do not grind to a disastrous halt. One way to make the sliding parts last longer without breaking down is to make them from a tougher material than silicon.

"Diamond may be the ideal substance for MEMS devices," says NIST's Craig McGray. "It can withstand extreme conditions, plus it's able to vibrate at the very high frequencies that new consumer electronics demand. But it's very hard, of course, and there hasn't been a way to engineer it very precisely at small scales. We think our method can accomplish that."

The method uses a chemical etching process to create cavities in the diamond surface. The cubic shape of a diamond crystal can be sliced in several ways -- a fact jewelers take advantage of when creating facets on gemstones. The speed of the etching process depends on the orientation of the slice, occurring at a far slower rate in the direction of the cube's "faces" -- think of chopping the cube into smaller cubes -- and these face planes can be used as a sort of boundary where etching can be made to stop when desired. In their initial experiments, the team created cavities ranging in width from 1 to 72 micrometers, each with smooth vertical sidewalls and a flat bottom.

"We'd like to figure out how to optimize control of this process next," McGray says, "but some of the ways diamond behaved under the conditions we used were unexpected. We plan to explore some of these mysteries while we develop a prototype diamond MEMS device."

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

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Craig D. McGray, Richard A. Allen, Marc Cangemi, Jon Geist. Rectangular scale-similar etch pits in monocrystalline diamond. Diamond and Related Materials, 2011; DOI: 10.1016/j.diamond.2011.08.007

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Method for creating tiny diamond machines improved

ScienceDaily (Sep. 28, 2011) — Diamonds may be best known as a symbol of long-lasting love. But semiconductor makers are also hoping they'll pan out as key components of long-lasting micromachines if a new method developed at the National Institute of Standards and Technology (NIST) for carving these tough, capable crystals proves its worth.* The method offers a precise way to engineer microscopic cuts in a diamond surface, yielding potential benefits in both measurement and technological fields.

By combining their own observations with background gleaned from materials science, NIST semiconductor researchers have found a way to create unique features in diamond -- potentially leading to improvements in nanometrology in short order, as it has allowed the team to make holes of precise shape in one of the hardest known substances. But beyond the creation of virtually indestructible nanorulers, the method could one day lead to the improvement of a class of electronic devices useful in cell phones, gyroscopes and medical implants.

Well known for making the hugely complex electronic microchips that run our laptops, the semiconductor industry has expanded its portfolio by fabricating tiny devices with moving parts. Constructed with substantially the same techniques as the electronic chips, these "micro-electromechanical systems," or MEMS, are just a few micrometers in size. They can detect environmental changes such as heat, pressure and acceleration, potentially enabling them to form the basis of tiny sensors and actuators for a host of new devices. But designers must take care that tiny moving parts do not grind to a disastrous halt. One way to make the sliding parts last longer without breaking down is to make them from a tougher material than silicon.

"Diamond may be the ideal substance for MEMS devices," says NIST's Craig McGray. "It can withstand extreme conditions, plus it's able to vibrate at the very high frequencies that new consumer electronics demand. But it's very hard, of course, and there hasn't been a way to engineer it very precisely at small scales. We think our method can accomplish that."

The method uses a chemical etching process to create cavities in the diamond surface. The cubic shape of a diamond crystal can be sliced in several ways -- a fact jewelers take advantage of when creating facets on gemstones. The speed of the etching process depends on the orientation of the slice, occurring at a far slower rate in the direction of the cube's "faces" -- think of chopping the cube into smaller cubes -- and these face planes can be used as a sort of boundary where etching can be made to stop when desired. In their initial experiments, the team created cavities ranging in width from 1 to 72 micrometers, each with smooth vertical sidewalls and a flat bottom.

"We'd like to figure out how to optimize control of this process next," McGray says, "but some of the ways diamond behaved under the conditions we used were unexpected. We plan to explore some of these mysteries while we develop a prototype diamond MEMS device."

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

Journal Reference:

Craig D. McGray, Richard A. Allen, Marc Cangemi, Jon Geist. Rectangular scale-similar etch pits in monocrystalline diamond. Diamond and Related Materials, 2011; DOI: 10.1016/j.diamond.2011.08.007

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.

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New method for imaging molecules inside cells

ScienceDaily (June 29, 2011) — Using a new sample holder, researchers at the University of Gothenburg have further developed a new method for imaging individual cells. This makes it possible to produce snapshots that not only show the outline of the cell's contours but also the various molecules inside or on the surface of the cell, and exactly where they are located, something which is impossible with a normal microscope.

Individual human cells are small, just one or two hundredths of a millimeter in diameter. As such, special measuring equipment is needed to distinguish the various parts inside the cell. Researchers generally use a microscope that magnifies the cell and shows its contours outline, but does not provide any information on the molecules inside the cell and on its surface.

"The new sample holder is filled with holds cells in solution," says Ingela Lanekoff, one of the researchers who developed the new method at the University of Gothenburg's Department of Chemistry. "We then rapidly freeze the sample down to -196°C, which enables us to get a snapshot of where the various molecules are at the moment of freezing. Using this technique we can produce images that show not only the outline of the cell's contours, but also the molecules that are there, and where they are located."

Important to measure chemical processes in the body

So why do the researchers want to know which molecules are to be found in a single cell? Because the cell is the smallest living component there is, and the chemical processes that take place here play a major role in how the cell functions in our body. For example, our brain has special cells that can communicate with each other through chemical signals. This vital communication has been shown to be dependent on the molecules in the cell's membrane.

Imaging the molecules in the membrane of single individual cells's membrane enables researchers to measure changes. Together with previous results, Lanekoff's findings show that the rate of communication in the studied cells studied is affected by a change of less than one per cent in the quantities abundance of a specific molecule in the membrane. This would suggest that communication between the cells in the brain is heavily dependent on the chemical composition of the membrane of each individual cell,. This could be an important part of the puzzle which could go some way towards explaining the mechanisms behind learning and memory.

The thesis, Analysis of phospholipids in cellular membranes with LC and imaging mass spectrometry, has been successfully defended at the University of Gothenburg. Supervisors: Andrew Ewing and Roger Karlsson. Download the thesis at: hdl.handle.net/2077/25279

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Chirality: New method to consistently make left-handed or right-handed molecules

ScienceDaily (June 18, 2011) — Many organic molecules are non-superimposable with their mirror image. The two forms of such a molecule are called enantiomers and can have different properties in biological systems. The problem is to control which enantiomer you want to produce -- a problem that has proved to be important in the pharmaceutical industry. Researchers at the University of Gothenburg have now come up with a new method to control the process.

"Organic chemists think that it's impossible to create only one of the enantiomers without introducing some kind of optical activity into the reaction, but I've succeeded," says Theonitsa Kokoli at the University of Gothenburg's Department of Chemistry. "My method will allow the industry to produce the version they want without the use of a catalyst."

The phenomenon of non-superimposable mirror-image molecular structures is known as chirality. The two enantiomers can be compared to a pair of hands; they are non-superimposable mirror images of each other. A consequence of the different properties in biological systems is that a molecule can behave either as Dr Jekyll or Mr Hyde. The different characteristics in the enantiomers can be harmless, like in the limonene molecule. One enantiomer smells like orange and the other like lemon.

Thalidomide is a good example of how different forms of the same molecule can have disastrous consequences. One of the enantiomers was calming and eased nausea in pregnant women, while the other caused serious damage to the fetus. The thalidomide catastrophe is one of the reasons that a lot of research is devoted to chirality, as it is absolutely vital to be able to control which form of the molecule that is produced. Research on chirality has resulted in several Nobel Prizes over the years.

In biomolecules like DNA and proteins only one of the enantiomers exists in nature. In contrast to biomolecules, the same does not apply when chiral compounds are created synthetically in the lab. Generally an equal amount of both enantiomers is produced. One way of creating an excess of one enantiomer is to use a chiral catalyst, but this only transfers the properties that are already present in the catalyst.

"I've been working with absolute asymmetric synthesis instead, where optical activity is created," says Kokoli. "This is considered impossible by many organic chemists. I've used crystals in my reactions, where the two forms have crystallised as separate crystals, which in itself is fairly unusual. The product that was formed after the reactions comprised just one enantiomer."

While the results of Kokoli's research are particularly significant for the pharmaceuticals industry, they can also be used in the production of flavourings and aromas.

The thesis has been successfully defended on May 6, 2011.

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

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.

View the original article here

Chirality: New method to consistently make left-handed or right-handed molecules

ScienceDaily (June 18, 2011) — Many organic molecules are non-superimposable with their mirror image. The two forms of such a molecule are called enantiomers and can have different properties in biological systems. The problem is to control which enantiomer you want to produce -- a problem that has proved to be important in the pharmaceutical industry. Researchers at the University of Gothenburg have now come up with a new method to control the process.

"Organic chemists think that it's impossible to create only one of the enantiomers without introducing some kind of optical activity into the reaction, but I've succeeded," says Theonitsa Kokoli at the University of Gothenburg's Department of Chemistry. "My method will allow the industry to produce the version they want without the use of a catalyst."

The phenomenon of non-superimposable mirror-image molecular structures is known as chirality. The two enantiomers can be compared to a pair of hands; they are non-superimposable mirror images of each other. A consequence of the different properties in biological systems is that a molecule can behave either as Dr Jekyll or Mr Hyde. The different characteristics in the enantiomers can be harmless, like in the limonene molecule. One enantiomer smells like orange and the other like lemon.

Thalidomide is a good example of how different forms of the same molecule can have disastrous consequences. One of the enantiomers was calming and eased nausea in pregnant women, while the other caused serious damage to the fetus. The thalidomide catastrophe is one of the reasons that a lot of research is devoted to chirality, as it is absolutely vital to be able to control which form of the molecule that is produced. Research on chirality has resulted in several Nobel Prizes over the years.

In biomolecules like DNA and proteins only one of the enantiomers exists in nature. In contrast to biomolecules, the same does not apply when chiral compounds are created synthetically in the lab. Generally an equal amount of both enantiomers is produced. One way of creating an excess of one enantiomer is to use a chiral catalyst, but this only transfers the properties that are already present in the catalyst.

"I've been working with absolute asymmetric synthesis instead, where optical activity is created," says Kokoli. "This is considered impossible by many organic chemists. I've used crystals in my reactions, where the two forms have crystallised as separate crystals, which in itself is fairly unusual. The product that was formed after the reactions comprised just one enantiomer."

While the results of Kokoli's research are particularly significant for the pharmaceuticals industry, they can also be used in the production of flavourings and aromas.

The thesis has been successfully defended on May 6, 2011.

Story Source:

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

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.

View the original article here

New method to make sodium ion-based battery cells could lead to better, cheaper batteries for the electrical grid

ScienceDaily (June 8, 2011) — By adding the right amount of heat, researchers have developed a method that improves the electrical capacity and recharging lifetime of sodium ion rechargeable batteries, which could be a cheaper alternative for large-scale uses such as storing energy on the electrical grid.

To connect solar and wind energy sources to the electrical grid, grid managers require batteries that can store large amounts of energy created at the source. Lithium ion rechargeable batteries -- common in consumer electronics and electric vehicles -- perform well, but are too expensive for widespread use on the grid because many batteries will be needed, and they will likely need to be large. Sodium is the next best choice, but the sodium-sulfur batteries currently in use run at temperatures above 300 degrees Celsius, or three times the temperature of boiling water, making them less energy efficient and safe than batteries that run at ambient temperatures.

Battery developers want the best of both worlds -- to use both inexpensive sodium and use the type of electrodes found in lithium rechargeables. A team of scientists at the Department of Energy's Pacific Northwest National Laboratory and visiting researchers from Wuhan University in Wuhan, China used nanomaterials to make electrodes that can work with sodium, they reported June 3 online in the journal Advanced Materials.

"The sodium-ion battery works at room temperature and uses sodium ions, an ingredient in cooking salt. So it will be much cheaper and safer," said PNNL chemist Jun Liu, who co-led the study with Wuhan University chemist Yuliang Cao.

The electrodes in lithium rechargeables that interest researchers are made of manganese oxide. The atoms in this metal oxide form many holes and tunnels that lithium ions travel through when batteries are being charged or are in use. The free movement of lithium ions allows the battery to hold electricity or release it in a current. But simply replacing the lithium ions with sodium ions is problematic -- sodium ions are 70 percent bigger than lithium ions and don't fit in the crevices as well.

To find a way to make bigger holes in the manganese oxide, PNNL researchers went much much smaller. They turned to nanomaterials -- materials made on the nanometer-sized scale, or about a million times thinner than a dime -- that have surprising properties due to their smallness. For example, the short distances that sodium ions have to travel in nanowires might make the manganese oxide a better electrode in ways unrelated to the size of the tunnels.

To explore, the team mixed two different kinds of manganese oxide atomic building blocks -- one whose atoms arrange themselves in pyramids, and another one whose atoms form an octahedron, a diamond-like structure from two pyramids stuck together at their bases. They expected the final material to have large S-shaped tunnels and smaller five-sided tunnels through which the ions could flow.

After mixing, the team treated the materials with temperatures ranging from 450 to 900 degrees Celsius, then examined the materials and tested which treatment worked best. Using a scanning electron microscope, the team found that different temperatures created material of different quality. Treating the manganese oxide at 750 degrees Celsius created the best crystals: too low and the crystals appeared flakey, too high and the crystals turned into larger flat plates.

Zooming in even more using a transmission electron microscope at EMSL, DOE's Environmental Molecular Sciences Laboratory on PNNL's campus, the team saw that manganese oxide heated to 600 degrees had pockmarks in the nanowires that could impede the sodium ions, but the 750 degree-treated wires looked uniform and very crystalline.

But even the best-looking material is just window-dressing if it doesn't perform well. To find out if it lived up to its good looks, the PNNL-Wuhan team dipped the electrode material in electrolyte, the liquid containing sodium ions that will help the manganese oxide electrodes form a current. Then they charged and discharged the experimental battery cells repeatedly.

The team measured peak capacity at 128 milliAmp hours per gram of electrode material as the experimental battery cell discharged. This result surpassed earlier ones taken by other researchers, one of which achieved peak capacity of 80 milliAmp hours per gram for electrodes made from manganese oxide but with a different production method. The researchers think the lower capacity is due to sodium ions causing structural changes in that manganese oxide that do not occur or occur less frequently in the heat-treated nano-sized material.

In addition to high capacity, the material held up well to cycles of charging and discharging, as would occur in consumer use. Again, the material treated at 750 Celsius performed the best: after 100 cycles of charging-discharging, it lost only 7 percent of its capacity. Material treated at 600 Celsius or 900 Celsius lost about 37 percent and 25 percent, respectively.

Even after 1,000 cycles, the capacity of the 750 Celsius-treated electrodes only dropped about 23 percent. The researchers thought the material performed very well, retaining 77 percent of its initial capacity.

Last, the team charged the experimental cell at different speeds to determine how quickly it could take up electricity. The team found that the faster they charged it, the less electricity it could hold. This suggested to the team that the speed with which sodium ions could diffuse into the manganese oxide limited the battery cell's capacity -- when charged fast, the sodium ions couldn't enter the tunnels fast enough to fill them up.

To compensate for the slow sodium ions, the researchers suggest in the future they make even smaller nanowires to speed up charging and discharging. Grid batteries need fast charging so they can collect as much newly made energy coming from renewable sources as possible. And they need to discharge fast when demands shoots up as consumers turn on their air conditioners and television sets, and plug in their electric vehicles at home.

Such high performing batteries could take the heat off an already taxed electrical power grid.

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The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by DOE/Pacific Northwest National Laboratory.

Journal Reference:

Yuliang Cao, Lifen Xiao, Wei Wang, Daiwon Choi, Zimin Nie, Jianguo Yu, Laxmikant V. Saraf, Zhenguo Yang, Jun Liu. Reversible Sodium Ion Insertion in Single Crystalline Manganese Oxide Nanowires with Long Cycle Life. Advanced Materials, 2011; DOI: 10.1002/adma.201100904

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.

View the original article here

New method to make sodium ion-based battery cells could lead to better, cheaper batteries for the electrical grid

ScienceDaily (June 8, 2011) — By adding the right amount of heat, researchers have developed a method that improves the electrical capacity and recharging lifetime of sodium ion rechargeable batteries, which could be a cheaper alternative for large-scale uses such as storing energy on the electrical grid.

To connect solar and wind energy sources to the electrical grid, grid managers require batteries that can store large amounts of energy created at the source. Lithium ion rechargeable batteries -- common in consumer electronics and electric vehicles -- perform well, but are too expensive for widespread use on the grid because many batteries will be needed, and they will likely need to be large. Sodium is the next best choice, but the sodium-sulfur batteries currently in use run at temperatures above 300 degrees Celsius, or three times the temperature of boiling water, making them less energy efficient and safe than batteries that run at ambient temperatures.

Battery developers want the best of both worlds -- to use both inexpensive sodium and use the type of electrodes found in lithium rechargeables. A team of scientists at the Department of Energy's Pacific Northwest National Laboratory and visiting researchers from Wuhan University in Wuhan, China used nanomaterials to make electrodes that can work with sodium, they reported June 3 online in the journal Advanced Materials.

"The sodium-ion battery works at room temperature and uses sodium ions, an ingredient in cooking salt. So it will be much cheaper and safer," said PNNL chemist Jun Liu, who co-led the study with Wuhan University chemist Yuliang Cao.

The electrodes in lithium rechargeables that interest researchers are made of manganese oxide. The atoms in this metal oxide form many holes and tunnels that lithium ions travel through when batteries are being charged or are in use. The free movement of lithium ions allows the battery to hold electricity or release it in a current. But simply replacing the lithium ions with sodium ions is problematic -- sodium ions are 70 percent bigger than lithium ions and don't fit in the crevices as well.

To find a way to make bigger holes in the manganese oxide, PNNL researchers went much much smaller. They turned to nanomaterials -- materials made on the nanometer-sized scale, or about a million times thinner than a dime -- that have surprising properties due to their smallness. For example, the short distances that sodium ions have to travel in nanowires might make the manganese oxide a better electrode in ways unrelated to the size of the tunnels.

To explore, the team mixed two different kinds of manganese oxide atomic building blocks -- one whose atoms arrange themselves in pyramids, and another one whose atoms form an octahedron, a diamond-like structure from two pyramids stuck together at their bases. They expected the final material to have large S-shaped tunnels and smaller five-sided tunnels through which the ions could flow.

After mixing, the team treated the materials with temperatures ranging from 450 to 900 degrees Celsius, then examined the materials and tested which treatment worked best. Using a scanning electron microscope, the team found that different temperatures created material of different quality. Treating the manganese oxide at 750 degrees Celsius created the best crystals: too low and the crystals appeared flakey, too high and the crystals turned into larger flat plates.

Zooming in even more using a transmission electron microscope at EMSL, DOE's Environmental Molecular Sciences Laboratory on PNNL's campus, the team saw that manganese oxide heated to 600 degrees had pockmarks in the nanowires that could impede the sodium ions, but the 750 degree-treated wires looked uniform and very crystalline.

But even the best-looking material is just window-dressing if it doesn't perform well. To find out if it lived up to its good looks, the PNNL-Wuhan team dipped the electrode material in electrolyte, the liquid containing sodium ions that will help the manganese oxide electrodes form a current. Then they charged and discharged the experimental battery cells repeatedly.

The team measured peak capacity at 128 milliAmp hours per gram of electrode material as the experimental battery cell discharged. This result surpassed earlier ones taken by other researchers, one of which achieved peak capacity of 80 milliAmp hours per gram for electrodes made from manganese oxide but with a different production method. The researchers think the lower capacity is due to sodium ions causing structural changes in that manganese oxide that do not occur or occur less frequently in the heat-treated nano-sized material.

In addition to high capacity, the material held up well to cycles of charging and discharging, as would occur in consumer use. Again, the material treated at 750 Celsius performed the best: after 100 cycles of charging-discharging, it lost only 7 percent of its capacity. Material treated at 600 Celsius or 900 Celsius lost about 37 percent and 25 percent, respectively.

Even after 1,000 cycles, the capacity of the 750 Celsius-treated electrodes only dropped about 23 percent. The researchers thought the material performed very well, retaining 77 percent of its initial capacity.

Last, the team charged the experimental cell at different speeds to determine how quickly it could take up electricity. The team found that the faster they charged it, the less electricity it could hold. This suggested to the team that the speed with which sodium ions could diffuse into the manganese oxide limited the battery cell's capacity -- when charged fast, the sodium ions couldn't enter the tunnels fast enough to fill them up.

To compensate for the slow sodium ions, the researchers suggest in the future they make even smaller nanowires to speed up charging and discharging. Grid batteries need fast charging so they can collect as much newly made energy coming from renewable sources as possible. And they need to discharge fast when demands shoots up as consumers turn on their air conditioners and television sets, and plug in their electric vehicles at home.

Such high performing batteries could take the heat off an already taxed electrical power grid.

Story Source:

The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by DOE/Pacific Northwest National Laboratory.

Journal Reference:

Yuliang Cao, Lifen Xiao, Wei Wang, Daiwon Choi, Zimin Nie, Jianguo Yu, Laxmikant V. Saraf, Zhenguo Yang, Jun Liu. Reversible Sodium Ion Insertion in Single Crystalline Manganese Oxide Nanowires with Long Cycle Life. Advanced Materials, 2011; DOI: 10.1002/adma.201100904

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.

View the original article here

Simple method of dealing with harmful radioactive iodine discovered

ScienceDaily (May 24, 2011) — A novel way to immobilise radioactive forms of iodine using a microwave, has been discovered by an expert at the University of Sheffield. Iodine radioisotopes are produced by fission of uranium fuel in a nuclear reactor. Radioactive iodine is of concern because it is highly mobile in the environment and selective uptake by the thyroid gland can pose a significant cancer risk following long term exposure. Furthermore, iodine-129, which is a type of radioactive iodine, has an extremely long half life of 15.7 million years, so is one of the most significant long term hazards faced by the population due to its emission during the geological disposal of nuclear waste.

Professor Neil Hyatt, from the University´s Department of Materials Science and Engineering, has now found a way of locking up iodine radioisotopes in a durable, solid material suitable for ultimate disposal, like lead iodovanadinite(Pb5(VO4)3I). The research, which was published in the Journal of Nuclear Materials, demonstrates how his simple, inexpensive and rapid method can be done at atmospheric pressure.

Professor Hyatt and his team created a solid material for immobilisation of iodine with the formula Pb5(VO4)3I, by heating a mixture of lead iodide, lead oxide and vanadium oxide.

Previously, this has only been achieved using high pressure and a sealed container, because iodine is volatilised at high temperature. However, using the knowledge that vanadium is a good absorber of microwaves at 2.45 GHz -- the frequency used in domestic microwave ovens -- the team were able to heat the mixture of chemicals in a microwave oven to produce Pb5(VO4)3I in about three minutes.

The key to the method´s success is that Pb5(VO4)3I is a poor absorber of 2.45 GHz microwaves, so once this is formed, the sample cannot absorb microwaves, so the temperature does not get high enough for the iodine to volatilise.

Iodine-131 was the harmful gas emitted from the Fukushima power plant in Japan following the earthquake and tsunami last month, and was a significant contributor to the health effects from open-air atomic bomb testing in the 1950s, and was also emitted during the Chernobyl disaster. It is hoped the new research will reduce the public health impact associated with the release of radioactive iodine to the environment by providing a simple and inexpensive method of immobilisation in a solid material, which could be rapidly deployed in an accident scenario.

Professor Neil Hyatt, said: "In spent nuclear fuel, the iodine is not immobilised, so once the containment is breached it simply gets dispersed. At present, iodine-129 released by nuclear fuel reprocessing is discharged direct to the Irish Sea off the coast of Sellafield. Substantial quantities of this radioisotope were also released into the sea off the coast of Japan in the Fukushima incident. Our new method offers a way of safely and rapidly containing this radionuclide, reducing the potential long term impact on human health from discharge to the environment."

Story Source:

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

Journal Reference:

M.C. Stennett, I.J. Pinnock, N.C. Hyatt. Rapid synthesis of Pb5(VO4)3I, for the immobilisation of iodine radioisotopes, by microwave dielectric heating. Journal of Nuclear Materials, 2011; DOI: 10.1016/j.jnucmat.2011.04.041

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

Disclaimer: This article is not intended to provide medical advice, diagnosis or treatment. Views expressed here do not necessarily reflect those of ScienceDaily or its staff.

View the original article here

Simple method of dealing with harmful radioactive iodine discovered

ScienceDaily (May 24, 2011) — A novel way to immobilise radioactive forms of iodine using a microwave, has been discovered by an expert at the University of Sheffield. Iodine radioisotopes are produced by fission of uranium fuel in a nuclear reactor. Radioactive iodine is of concern because it is highly mobile in the environment and selective uptake by the thyroid gland can pose a significant cancer risk following long term exposure. Furthermore, iodine-129, which is a type of radioactive iodine, has an extremely long half life of 15.7 million years, so is one of the most significant long term hazards faced by the population due to its emission during the geological disposal of nuclear waste.

Professor Neil Hyatt, from the University´s Department of Materials Science and Engineering, has now found a way of locking up iodine radioisotopes in a durable, solid material suitable for ultimate disposal, like lead iodovanadinite(Pb5(VO4)3I). The research, which was published in the Journal of Nuclear Materials, demonstrates how his simple, inexpensive and rapid method can be done at atmospheric pressure.

Professor Hyatt and his team created a solid material for immobilisation of iodine with the formula Pb5(VO4)3I, by heating a mixture of lead iodide, lead oxide and vanadium oxide.

Previously, this has only been achieved using high pressure and a sealed container, because iodine is volatilised at high temperature. However, using the knowledge that vanadium is a good absorber of microwaves at 2.45 GHz -- the frequency used in domestic microwave ovens -- the team were able to heat the mixture of chemicals in a microwave oven to produce Pb5(VO4)3I in about three minutes.

The key to the method´s success is that Pb5(VO4)3I is a poor absorber of 2.45 GHz microwaves, so once this is formed, the sample cannot absorb microwaves, so the temperature does not get high enough for the iodine to volatilise.

Iodine-131 was the harmful gas emitted from the Fukushima power plant in Japan following the earthquake and tsunami last month, and was a significant contributor to the health effects from open-air atomic bomb testing in the 1950s, and was also emitted during the Chernobyl disaster. It is hoped the new research will reduce the public health impact associated with the release of radioactive iodine to the environment by providing a simple and inexpensive method of immobilisation in a solid material, which could be rapidly deployed in an accident scenario.

Professor Neil Hyatt, said: "In spent nuclear fuel, the iodine is not immobilised, so once the containment is breached it simply gets dispersed. At present, iodine-129 released by nuclear fuel reprocessing is discharged direct to the Irish Sea off the coast of Sellafield. Substantial quantities of this radioisotope were also released into the sea off the coast of Japan in the Fukushima incident. Our new method offers a way of safely and rapidly containing this radionuclide, reducing the potential long term impact on human health from discharge to the environment."

Story Source:

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

Journal Reference:

M.C. Stennett, I.J. Pinnock, N.C. Hyatt. Rapid synthesis of Pb5(VO4)3I, for the immobilisation of iodine radioisotopes, by microwave dielectric heating. Journal of Nuclear Materials, 2011; DOI: 10.1016/j.jnucmat.2011.04.041

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

Disclaimer: This article is not intended to provide medical advice, diagnosis or treatment. Views expressed here do not necessarily reflect those of ScienceDaily or its staff.

View the original article here

New method for engineering human tissue regeneration

ScienceDaily (May 13, 2011) — If pending clinical trials prove successful, a new discovery published in The FASEB Journal could represent a major scientific leap toward human tissue regeneration and engineering. In a research report appearing online, Yale scientists provide evidence to support a major paradigm shift in this specialty area from the idea that cells added to a graft before implantation are the building blocks of tissue, to a new belief that engineered tissue constructs can actually induce or augment the body's own reparative mechanisms, including complex tissue regeneration.

"With the constant growing clinical demand for alternative vessels used for vascular reconstructive surgeries, a significant development for alternative grafts is currently the primary focus of many investigators worldwide," said Christopher K. Breuer, M.D., a researcher involved in the work from Yale University School of Medicine/Yale-New Haven Hospital in New Haven, CT. "We believe that through an understanding of human vascular biology, coupled with technologies such as tissue engineering, we can introduce biological grafts that mimic the functional properties of native vessels and that are capable of growing with the patients." Breuer also says that patients are currently being enrolled in a first-of-its-kind clinical trial at Yale University to evaluate the safety and growth potential of tissue-engineered vascular grafts in children undergoing surgery for congenital heart disease.

To make this discovery, Breuer and colleagues conducted a three-part study, starting with two groups of mice. The first group expressed a gene that made all of its cells fluorescent green and the second group was normal. Researchers extracted bone marrow cells from the "green" mice, added them to previously designed scaffolds, and implanted the grafts into the normal mice. The seeded bone marrow cells improved the performance of the graft; however, a rapid loss of green cells was noted and the cells that developed in the new vessel wall were not green, suggesting that the seeded cells promoted vessel development, but did not turn into vessel wall cells themselves.

These findings led to the second part of the study, which tested whether cells produced in the host's bone marrow might be a source for new cells. Scientists replaced the bone marrow cells of a female mouse with those of a male mouse before implanting the graft into female mice. The researchers found that the cells forming the new vessel were female, meaning they did not come from the male bone marrow cells. In the final experiment, researchers implanted a segment of male vessel attached to the scaffold into a female host. After analysis, the researchers found that the side of the graft next to the male segment developed with male vessel wall cells while the side of the graft attached to the female host's vessel formed from female cells, proving that the cells in the new vessel must have migrated from the adjacent normal vessel.

"There's a very good chance that this study will eventually have a major impact on many disorders that afflict humankind," said Gerald Weissmann, M.D., Editor-in-Chief of The FASEB Journal. "These scientists have basically used the body's repair mechanisms to make new tissues through bioengineering. In years to come, starfish and salamanders will have nothing on us!"

Story Source:

The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by Federation of American Societies for Experimental Biology, via EurekAlert!, a service of AAAS.

Journal Reference:

Narutoshi Hibino, Gustavo Villalona, Nicholas Pietris, Daniel R. Duncan, Adam Schoffner, Jason D. Roh, Tai Yi, Lawrence W. Dobrucki, Dane Mejias, Rajendra Sawh-Martinez, Jamie K. Harrington, Albert Sinusas, Diane S. Krause, Themis Kyriakides, W. Mark Saltzman, Jordan S. Pober, Toshiharu Shin'oka, Christopher K. Breuer. Tissue-engineered vascular grafts form neovessels that arise from regeneration of the adjacent blood vessel. FASEB Journal, 2011; DOI: 10.1096/fj.11-182246

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

Disclaimer: This article is not intended to provide medical advice, diagnosis or treatment. Views expressed here do not necessarily reflect those of ScienceDaily or its staff.

View the original article here

New method for engineering human tissue regeneration

ScienceDaily (May 13, 2011) — If pending clinical trials prove successful, a new discovery published in The FASEB Journal could represent a major scientific leap toward human tissue regeneration and engineering. In a research report appearing online, Yale scientists provide evidence to support a major paradigm shift in this specialty area from the idea that cells added to a graft before implantation are the building blocks of tissue, to a new belief that engineered tissue constructs can actually induce or augment the body's own reparative mechanisms, including complex tissue regeneration.

"With the constant growing clinical demand for alternative vessels used for vascular reconstructive surgeries, a significant development for alternative grafts is currently the primary focus of many investigators worldwide," said Christopher K. Breuer, M.D., a researcher involved in the work from Yale University School of Medicine/Yale-New Haven Hospital in New Haven, CT. "We believe that through an understanding of human vascular biology, coupled with technologies such as tissue engineering, we can introduce biological grafts that mimic the functional properties of native vessels and that are capable of growing with the patients." Breuer also says that patients are currently being enrolled in a first-of-its-kind clinical trial at Yale University to evaluate the safety and growth potential of tissue-engineered vascular grafts in children undergoing surgery for congenital heart disease.

To make this discovery, Breuer and colleagues conducted a three-part study, starting with two groups of mice. The first group expressed a gene that made all of its cells fluorescent green and the second group was normal. Researchers extracted bone marrow cells from the "green" mice, added them to previously designed scaffolds, and implanted the grafts into the normal mice. The seeded bone marrow cells improved the performance of the graft; however, a rapid loss of green cells was noted and the cells that developed in the new vessel wall were not green, suggesting that the seeded cells promoted vessel development, but did not turn into vessel wall cells themselves.

These findings led to the second part of the study, which tested whether cells produced in the host's bone marrow might be a source for new cells. Scientists replaced the bone marrow cells of a female mouse with those of a male mouse before implanting the graft into female mice. The researchers found that the cells forming the new vessel were female, meaning they did not come from the male bone marrow cells. In the final experiment, researchers implanted a segment of male vessel attached to the scaffold into a female host. After analysis, the researchers found that the side of the graft next to the male segment developed with male vessel wall cells while the side of the graft attached to the female host's vessel formed from female cells, proving that the cells in the new vessel must have migrated from the adjacent normal vessel.

"There's a very good chance that this study will eventually have a major impact on many disorders that afflict humankind," said Gerald Weissmann, M.D., Editor-in-Chief of The FASEB Journal. "These scientists have basically used the body's repair mechanisms to make new tissues through bioengineering. In years to come, starfish and salamanders will have nothing on us!"

Story Source:

The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by Federation of American Societies for Experimental Biology, via EurekAlert!, a service of AAAS.

Journal Reference:

Narutoshi Hibino, Gustavo Villalona, Nicholas Pietris, Daniel R. Duncan, Adam Schoffner, Jason D. Roh, Tai Yi, Lawrence W. Dobrucki, Dane Mejias, Rajendra Sawh-Martinez, Jamie K. Harrington, Albert Sinusas, Diane S. Krause, Themis Kyriakides, W. Mark Saltzman, Jordan S. Pober, Toshiharu Shin'oka, Christopher K. Breuer. Tissue-engineered vascular grafts form neovessels that arise from regeneration of the adjacent blood vessel. FASEB Journal, 2011; DOI: 10.1096/fj.11-182246

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

Disclaimer: This article is not intended to provide medical advice, diagnosis or treatment. Views expressed here do not necessarily reflect those of ScienceDaily or its staff.

View the original article here