Friday, July 1, 2011

Stretching old material yields new results for energy- and environment-related devices

 Researchers at Virginia Tech in Blacksburg, Va. recently found a way to improve electricity generating fuel cells, potentially making them more efficient, powerful and less expensive. Specifically, they discovered a way to speed up the flow and filtering of water or ions, which are necessary for fuel cells to operate.

Simply put, the researchers stretched Nafion, a polymer electrolyte membrane, or PEM, commonly used in fuel cells and increased the speed at which it selectively filters substances from ions and water.

The resulting process could be important to a number of energy and environment-related applications such as any of several industrial processes that involve filtering, including improving batteries in cars, water desalination and even the production of artificial muscles for robots.

The journal Nature Materials published the results in its June 19 issue in the article, "Linear coupling of alignment with transport in a polymer electrolyte membrane," by Jing Li, Jong Keun Park, Robert B. Moore and Louis A. Madsen, all with the chemistry department in the College of Science and the Macromolecules and Interfaces Institute at Virginia Tech.

"I got the idea for some of these experiments after I saw Bob Moore give a talk at the University of North Carolina about Nafion when I was a post-doc there working with liquid crystals," said Madsen, an assistant professor of physical, polymer and materials chemistry who led the study.

In order to improve PEMs, Madsen and Virginia Tech Chemistry Professor Robert Moore studied exactly how water moves through Nafion at the molecular level and measured how changes in the structure of the material affected water flow. They found stretching it caused channels in the PEM material to align in the direction of the stretch, allowing water to flow through faster.

"Stretching drastically influences the degree of alignment," said Madsen. "So the molecules move faster along the direction of the stretch, and in a very predictable way. These materials actually share some properties with liquid crystals--molecules that line up with each other and are used in every LCD television, projector and screen."

"This is a very clever approach which demonstrates the advantages of interdisciplinary materials research and which may offer important benefits to both energy technologies and sustainability of our natural resources," said Andy Lovinger, polymers program director in the National Science Foundation's Division of Materials Research, which funded the study.

Nafion was discovered in the 1960's and is made up of molecules that combine the non-stick and tough nature of Teflon with the conductive properties of an acid. It is one of many PEMs used to filter water and ions that the researchers say could benefit from the stretching process.

Story Source:

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

Journal Reference:

Jing Li, Jong Keun Park, Robert B. Moore, Louis A. Madsen. Linear coupling of alignment with transport in a polymer electrolyte membrane. Nature Materials, 2011; DOI: 10.1038/NMAT3048

Scientists find simple way to produce graphene

Scientists at Northern Illinois University say they have discovered a simple method for producing high yields of graphene, a highly touted carbon nanostructure that some believe could replace silicon as the technological fabric of the future.

The focus of intense scientific research in recent years, graphene is a two-dimensional material, composed of a single layer of carbon atoms arranged in a hexagonal lattice. It is the strongest material ever measured and has other remarkable qualities, including high electron mobility, a property that elevates its potential for use in high-speed nano-scale devices of the future.

In a June communication to the Journal of Materials Chemistry, the NIU researchers report on a new method that converts carbon dioxide directly into few-layer graphene (less than 10 atoms in thickness) by burning pure magnesium metal in dry ice.

"It is scientifically proven that burning magnesium metal in carbon dioxide produces carbon, but the formation of this carbon with few-layer graphene as the major product has neither been identified nor proven as such until our current report," said Narayan Hosmane, a professor of chemistry and biochemistry who leads the NIU research group.

"The synthetic process can be used to potentially produce few-layer graphene in large quantities," he said. "Up until now, graphene has been synthesized by various methods utilizing hazardous chemicals and tedious techniques. This new method is simple, green and cost-effective."

Hosmane said his research group initially set out to produce single-wall carbon nanotubes. "Instead, we isolated few-layer graphene," he said. "It surprised us all."

"It's a very simple technique that's been done by scientists before," added Amartya Chakrabarti, first author of the communication to the Journal of Materials Chemistry and an NIU post-doctoral research associate in chemistry and biochemistry. "But nobody actually closely examined the structure of the carbon that had been produced."

Other members of the research group publishing in the Journal of Materials Chemistry include former NIU physics postdoctoral research associate Jun Lu, NIU undergraduate student Jennifer Skrabutenas, NIU Chemistry and Biochemistry Professor Tao Xu, NIU Physics Professor Zhili Xiao and John A. Maguire, a chemistry professor at Southern Methodist University.

The work was supported by grants from the National Science Foundation, Petroleum Research Fund administered by the American Chemical Society, the Department of Energy and Robert A. Welch Foundation.

Story Source:

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

Journal Reference:

Amartya Chakrabarti, Jun Lu, Jennifer C. Skrabutenas, Tao Xu, Zhili Xiao, John A. Maguire, Narayan S. Hosmane. Conversion of carbon dioxide to few-layer graphene. Journal of Materials Chemistry, 2011; DOI: 10.1039/C1JM11227A

Hitting moving RNA drug targets: New way to search for novel drugs

By accounting for the floppy, fickle nature of RNA, researchers at the University of Michigan and the University of California, Irvine have developed a new way to search for drugs that target this important molecule. Their work appears in the June 26 issue of Nature Chemical Biology.

Once thought to be a passive carrier of genetic information, RNA now is understood to perform a number of other vital roles in the cell, and its malfunction can lead to disease. The versatile molecule also is essential to retroviruses such as HIV, which have no DNA and instead rely on RNA to both transport and execute genetic instructions for everything the virus needs to invade and hijack its host. As more and more links to disease are discovered, the quest for drugs that target RNA is intensifying.

Searching for such drugs is not a simple matter, however. Most of today's drug-hunting tools are designed to find small molecules that bind to protein targets, but RNA is not a protein, and it differs from proteins in many key features. "So there's a growing need for high-throughput technologies that can identify compounds that bind RNA," said Hashim M. Al-Hashimi, the Robert L. Kuczkowski Professor of Chemistry and Professor of Biophysics at U-M.

Al-Hashimi and coworkers adapted an existing computational technique for virtually screening libraries of small molecules to determine their RNA-binding abilities. In this approach, the shape of a target molecule is first determined by X-ray crystallography or NMR spectroscopy; next, researchers run computer simulations to compute how well various small molecules -- potential drugs, for example -- nestle into and bind to the target structure. RNA presents a major challenge to this methodology because it doesn't have just one configuration; it's a floppy molecule, and depending on which small molecule it binds, it can assume vastly different shapes.

It once was thought that encounters with drug molecules actually caused RNA's shape changes, and that it was impossible to predict what shape an RNA would adopt upon binding to a given small molecule. However, in earlier research, Al-Hashimi's team challenged this conventional "induced-fit" concept by showing that the RNA, on its own, can dance through the various shapes that it adopts when bound to different drugs. The team discovered that each drug molecule simply "waits" for the RNA to morph into its preferred shape and then latches onto it.

The researchers' previous work involved creating "nano-movies" of RNA that capture this dance of shape changes. In this new study, the researchers froze individual "frames" from the nano-movies, each showing the RNA in a different conformation, and subjected each of them to virtual screening. To test the method in the "real world," they first tried it on compounds already known to bind a particular RNA molecule from HIV called TAR.

"We showed that by virtually screening multiple snapshots of TAR, we could predict at a useful level of accuracy how tightly these different compounds bind to TAR," Al-Hashimi said. "But if we used the conventional method and virtually screened a single TAR structure determined by X-ray crystallography or NMR spectroscopy, we failed to predict binding of these drugs that we know can bind TAR."

Next, the researchers tried using the method to discover new TAR-targeting drugs. They screened about 51,000 compounds from the U-M Life Sciences Institute's Center for Chemical Genomics. "From this relatively small compound library, we ended up identifying six new small molecules that bind TAR and block its interaction with other essential viral molecules," Al-Hashimi said.

What's more, one of the six compounds, netilmicin, showed a strong preference for TAR.

"Netilmicin specifically binds TAR but not other related RNAs," said former graduate student Andrew Stelzer. "We were very pleased with these results because one of the biggest challenges in RNA-targeted drug discovery is to be able to identify compounds that bind a specific RNA target without binding other RNAs. The ability of netilmicin to specifically bind TAR provides proof of concept for this new technology," said Stelzer.

Further experiments showed that, for the six potential drug molecules, the method not only successfully predicted that they would bind to TAR, it also showed -- with atomic-level accuracy -- where on the RNA molecule each drug would bind.

Al-Hashimi then turned the six drug candidates over to David Markovitz, a professor of infectious diseases at the U-M Medical School, who tested them in cultured human T cells infected with HIV. The point of this experiment was to see if the drugs would prevent HIV from making copies of itself, an essential step in the disease process.

"Netilmicin did in fact inhibit HIV replication," Markovitz said. "This result demonstrates that using an NMR spectrometer and some computers we can discover drugs that target RNA and are active in human cells."

In addition to testing compounds in existing molecular libraries, the virtual screening technique can be used to explore the potential of new compounds that have not yet been synthesized, Al-Hashimi said. "This opens up a whole new frontier for exploring RNA as a drug target and finding new compounds that specifically target it."

In addition to Al-Hashimi, Stelzer and Markowitz, study authors are U-M graduate students Mike Swanson, Marta Gonzales-Hernandez and Janghyun Lee; U-M undergraduate student Jeremy Kratz; U-C Irvine graduate student Aaron Frank; and U-C Irvine associate professor Ioan Andricioaei.

Funding was provided by the National Institutes of Health, the Michigan Economic Development Corporation and Michigan's Technology Tri-Corridor.

The enabling technology has been exclusively licensed to Nymirum, a drug discovery company that has partnerships with Fortune 500 pharmaceutical and medical companies.

Story Source:

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

Journal Reference:

Andrew C Stelzer, Aaron T Frank, Jeremy D Kratz, Michael D Swanson, Marta J Gonzalez-Hernandez, Janghyun Lee, Ioan Andricioaei, David M Markovitz, Hashim M Al-Hashimi. Discovery of selective bioactive small molecules by targeting an RNA dynamic ensemble. Nature Chemical Biology, 2011; DOI: 10.1038/nchembio.596

Generating 'green' electricity: Waste heat converted to electricity using new alloy

University of Minnesota engineering researchers in the College of Science and Engineering have recently discovered a new alloy material that converts heat directly into electricity. This revolutionary energy conversion method is in the early stages of development, but it could have wide-sweeping impact on creating environmentally friendly electricity from waste heat sources.

Researchers say the material could potentially be used to capture waste heat from a car's exhaust that would heat the material and produce electricity for charging the battery in a hybrid car. Other possible future uses include capturing rejected heat from industrial and power plants or temperature differences in the ocean to create electricity. The research team is looking into possible commercialization of the technology.

"This research is very promising because it presents an entirely new method for energy conversion that's never been done before," said University of Minnesota aerospace engineering and mechanics professor Richard James, who led the research team."It's also the ultimate 'green' way to create electricity because it uses waste heat to create electricity with no carbon dioxide."

To create the material, the research team combined elements at the atomic level to create a new multiferroic alloy, Ni45Co5Mn40Sn10. Multiferroic materials combine unusual elastic, magnetic and electric properties. The alloy Ni45Co5Mn40Sn10 achieves multiferroism by undergoing a highly reversible phase transformation where one solid turns into another solid. During this phase transformation the alloy undergoes changes in its magnetic properties that are exploited in the energy conversion device.

During a small-scale demonstration in a University of Minnesota lab, the new material created by the researchers begins as a non-magnetic material, then suddenly becomes strongly magnetic when the temperature is raised a small amount. When this happens, the material absorbs heat and spontaneously produces electricity in a surrounding coil. Some of this heat energy is lost in a process called hysteresis. A critical discovery of the team is a systematic way to minimize hysteresis in phase transformations. The team's research was recently published in the first issue of the new scientific journal Advanced Energy Materials.

Watch a short research video of the new material suddenly become magnetic when heated:

In addition to Professor James, other members of the research team include University of Minnesota aerospace engineering and mechanics post-doctoral researchers Vijay Srivastava and Kanwal Bhatti, and Ph.D. student Yintao Song. The team is also working with University of Minnesota chemical engineering and materials science professor Christopher Leighton to create a thin film of the material that could be used, for example, to convert some of the waste heat from computers into electricity.

"This research crosses all boundaries of science and engineering," James said. "It includes engineering, physics, materials, chemistry, mathematics and more. It has required all of us within the university's College of Science and Engineering to work together to think in new ways."

Funding for early research on the alloy came from a Multidisciplinary University Research Initiative (MURI) grant from the U.S. Office of Naval Research (involving other universities including the California Institute of Technology, Rutgers University, University of Washington and University of Maryland), and research grants from the U.S. Air Force and the National Science Foundation. The research is also tentatively funded by a small seed grant from the University of Minnesota's Initiative for Renewable Energy and the Environment.

Story Source:

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

Journal Reference:

Vijay Srivastava, Yintao Song, Kanwal Bhatti, R. D. James. The Direct Conversion of Heat to Electricity Using Multiferroic Alloys. Advanced Energy Materials, 2011; 1 (1): 97 DOI: 10.1002/aenm.201000048