Thursday, April 5, 2012

Oscillating gel acts like artificial skin, giving robots potential ability to 'feel'

A team of researchers at Pitt made predictions regarding the behavior of Belousov-Zhabotinsky (BZ) gel, a material that was first fabricated in the late 1990s and shown to pulsate in the absence of any external stimuli. In fact, under certain conditions, the gel sitting in a petri dish resembles a beating heart.

Along with her colleagues, Anna Balazs, Distinguished Professor of Chemical and Petroleum Engineering in Pitt's Swanson School of Engineering, predicted that BZ gel not previously oscillating could be re-excited by mechanical pressure. The prediction was actualized by MIT researchers, who proved that chemical oscillations can be triggered by mechanically compressing the BZ gel beyond a critical stress.

"Think of it like human skin, which can provide signals to the brain that something on the body is deformed or hurt," says Balazs. "This gel has numerous far-reaching applications, such as artificial skin that could be sensory—a holy grail in robotics."

Balazs says the gel could serve as a small-scale pressure sensor for different vehicles or instruments to see whether they'd been bumped, providing diagnostics for the impact on surfaces. This sort of development—and materials like BZ —are things Balazs has been interested in since childhood.

"My mother would often tease me when I was young, saying I was like a mimosa plant— shy and bashful," says Balazs. "As a result, I became fascinated with the plant and its unique hide-and-seek qualities—the plant leaves fold inward and droop when touched or shaken, reopening just minutes later. I knew there had to be a scientific application regarding touch, which led me to studies like this in mechanical and chemical energy."

Also on Balazs's research team were Olga Kuksenok, research associate professor, and Victor Yashin, visiting research assistant professor, both in Pitt's Swanson School of Engineering. At MIT, the work was performed by Krystyn Van Vliet, Paul M. Cook Career Development Associate Professor of Material Sciences and Engineering, and graduate student Irene Chen.

Provided by University of Pittsburgh

Vitamins doing gymnastics: Scientists capture first full image of vitamin B12 in action

But when it gets inside your body, new research suggests, B12 turns into a gymnast.

In a paper published recently in the journal Nature, scientists from the University of Michigan Health System and the Massachusetts Institute of Technology report they have created the first full 3-D images of B12 and its partner molecules twisting and contorting as part of a crucial reaction called methyltransfer.

That reaction is vital both in the cells of the human body and, in a slightly different way, in the cells of that consume and . That includes bacteria that live in the guts of humans, cows and other animals, and help with digestion. The new research was done using B12 complexes from another type of carbon dioxide-munching bacteria found in the murky bottoms of ponds.

The 3-D images produced by the team show for the first time the intricate molecular juggling needed for B12 to serve its biologically essential function. They reveal a multi-stage process involving what the researchers call an elaborate protein framework – a surprisingly complicated mechanism for such a critical reaction.

U-M Medical School professor and co-author Stephen Ragsdale, Ph.D., notes that this transfer reaction is important to understand because of its importance to human health. It also has potential implications for the development of new fuels that might become alternative renewable energy sources.

"Without this transfer of single carbon units involving B12, and its partner B9 (otherwise known as folic acid), heart disease and birth defects might be far more common," explains Ragsdale, a professor of biological chemistry. "Similarly, the bacteria that rely on this reaction would be unable to consume carbon dioxide or carbon monoxide to stay alive – and to remove gas from our guts or our atmosphere. So it's important on many levels."

In such bacteria, called anaerobes, the reaction is part of a larger process called the Wood-Ljungdahl pathway. It's what enables the organisms to live off of carbon monoxide, a gas that is toxic to other living things, and carbon dioxide, which is a greenhouse gas directly linked to climate change. Ragsdale notes that industry is currently looking at harnessing the Wood-Ljungdahl pathway to help generate liquid fuels and chemicals.

In addition to his Medical School post, Ragsdale is a member of the faculty of the U-M Energy Institute.

In the images created by the team, the scientists show how the complex of molecules contorts into multiple conformations -- first to activate, then to protect, and then to perform catalysis on the B12 molecule. They had isolated the complex from Moorella thermoacetica bacteria, which are used as models for studying this type of reaction.

The images were produced by aiming intense beams of X-rays at crystallized forms of the protein complex and painstakingly determining the position of every atom inside.

"This paper provides an understanding of the remarkable conformational movements that occur during one of the key steps in this microbial process, the step that involves the generation of the first in a series of organometallic intermediates that lead to the production of the key metabolic intermediate, acetyl-CoA," the authors note.

Senior author Catherine L. Drennan from MIT and the Howard Hughes Medical Institute, who received her Ph.D. at the U-M Medical School, adds, "We expected that this methyl-handoff between B vitamins must involve some type of conformational change, but the dramatic rearrangements that we have observed surprised even us."

More information: Nature, doi:10.1038/nature10916

Provided by University of Michigan (news : web)

Electricity and carbon dioxide used to generate alternative fuel

 Imagine being able to use electricity to power your car -- even if it's not an electric vehicle. Researchers at the UCLA Henry Samueli School of Engineering and Applied Science have for the first time demonstrated a method for converting carbon dioxide into liquid fuel isobutanol using electricity.

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

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

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

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

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

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

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

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

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

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

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

The study was funded by a grant from the U.S. Department of Energy's Advanced Research Projects Agency-Energy (ARPA-E).

Story Source:

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

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

Journal Reference:

H. Li, P. H. Opgenorth, D. G. Wernick, S. Rogers, T.-Y. Wu, W. Higashide, P. Malati, Y.-X. Huo, K. M. Cho, J. C. Liao. Integrated Electromicrobial Conversion of CO2 to Higher Alcohols. Science, 2012; 335 (6076): 1596 DOI: 10.1126/science.1217643

Writing graphene circuitry with ion 'pens'

The unique electrical properties of graphene have enticed researchers to envision a future of fast integrated circuits made with the one-carbon-atom-thick sheets, but many challenges remain on the path to commercialization. Scientists from the University of Florida have recently tackled one of these challenges -- how to reliably manufacture graphene on a large scale.

The team has developed a promising new technique for creating graphene patterns on top of silicon carbide (SiC). SiC comprises both silicon and carbon, but at high temperatures (around 1300 degrees Celsius) silicon atoms will vaporize off the surface, leaving the carbon atoms to grow into sheets of pure graphene. Researchers had previously used this thermal decomposition technique to create large sheets of graphene, which were then etched to make the patterns required for devices.

The etching process, however, can introduce defects or chemical contaminants that reduce graphene's prized electron mobility. In contrast, the Florida team's technique allowed the researchers to confine the growth of graphene to a defined pattern as small as 20 nanometers. The team found that implanting silicon or gold ions in SiC lowered the temperature at which graphene formed by approximately 100 degrees Celsius. The team implanted ions only where graphene layers were desired, and then heated the SiC to 1200 degrees Celcius.

At this temperature the pure SiC did not form graphene, but the implanted areas did. Using this technique, the team successfully created graphene nanoribbons, thin lines of graphene with nanoscale dimensions. With further refining, the process, described in the American Institute of Physics' journal Applied Physics Letters, may be able to encourage selective graphene growth at even lower temperatures, the researchers write.

Story Source:

The above story is reprinted from materials provided by American Institute of Physics, via Newswise.

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

Journal Reference:

S. Tongay, M. Lemaitre, J. Fridmann, A. F. Hebard, B. P. Gila, B. R. Appleton. Drawing graphene nanoribbons on SiC by ion implantation. Applied Physics Letters, 2012; 100 (7): 073501 DOI: 10.1063/1.3682479