Friday, October 7, 2011

Argonne patents technology that increases safety of Li-ion batteries

Scientists at the U.S. Department of Energy's (DOE) Argonne National Laboratory have patented a new, extremely stable, 4-volt redox shuttle molecule that provides overcharge protection for lithium-ion batteries containing lithium-iron-phosphate based cathodes across hundreds of charging cycles.

Overcharge is a major safety concern for Li-ion batteries because it could cause thermal runaway. Thermal runaway is a concern for large batteries—such as those used for transportation, satellite and storage applications—because they contain a large amount of active material.

"When a pack is being charged, each cell in the pack may have varying levels of charge," said Argonne materials scientist Khalil Amine, who leads the research group that developed the shuttle. "Overcharge generally occurs when a current is forced through a battery and the charge that is delivered exceeds the charge-storing capacity of the battery, which can damage the entire battery.” Modern, well-designed batteries prevent overcharge from occurring through the use of external battery monitoring and control systems that function both at the cell and battery level. This new material offers a tool for addressing some of the concerns associated with overcharge using an approach that functions inside each cell.

"The new redox shuttle, known as 2,5-di-tert-butyl-1,4-bis(2-methoxyethoxy)benzene or DBBB, works by halting the charging process of individual cells as they come to a full state of charge," Amine said. "Being able to discontinue the charging process on a cell-by-cell basis protects the entire battery pack by preventing individual cells from overcharging."

DBBB, which dissolves in the electrolyte, works by moving back and forth from the anode and cathode in place of the Li-ion, Amine explained. The shuttle technology achieved up to 300 cycled overcharges in the lab.

The shuttle is currently undergoing validation test by industry, and the results to date are very encouraging, he said.

Researchers in Argonne's Advanced Battery Materials Synthesis and Manufacturing Research & Development Program have already scaled up production of DBBB to 1.5 kilograms from the sub-gram amounts Amine's group required for bench-scale research and development (See related story). The larger amount of the redox shuttle material is needed by companies that want to test the material for possible commercialization.

The stability and repeated long-term overcharge cycling capability of this new shuttle molecule was demonstrated by Amine and his Argonne colleagues Zhengcheng Zhang, Lu Zhang and Wei Weng.

The redox shuttle is part of a suite of advanced battery materials developed by scientists at Argonne. This research was funded by the DOE Office of Energy Efficiency and Renewable Energy.

Provided by Argonne National Laboratory (news : web)

Physicist detects movement of macromolecules engineered into our food

Toxin proteins are genetically engineered into our food because they kill insects by perforating body cell walls, and Professor Rikard Blunck of the University of Montreal's Group for the study of membrane proteins (GEPROM) has detected the molecular mechanism involved. In recognition of his breakthrough, he received the Traditional Paul F. Cranefield Award of the Society of General Physiologists yesterday evening. "This study is about gaining a better understanding of the basic functioning of the toxin proteins in order to judge the risks of using them as pesticides for our nutrition," Dr. Blunck explained.

The Cry1Aa toxin of B. thuringiensis that was investigated is a member of the class of proteins which are called "pore-forming toxins" because they perforate the walls, or membranes, of cells. Cry toxins kill if ingested by them and are, therefore, genetically engineered into a number of transgenic crops, including those for , to make them resistant against these insects.

The pores in the membranes cause minerals necessary for the cell to live to break out and collapse the energy household of the cell. While these toxins could be studied outside of cell membranes through existing techniques that provide images of the 3D structure, the toxins rapidly change their architecture once in contact with the membrane, where the traditional approaches cannot be applied.

Dr. Blunck and his co-workers found a way of using fluorescent light to analyze the architecture and mechanism of the proteins in an artificial environment. Planar (PLB) are artificial 0.1 mm-wide systems that mimic the cell membrane. The researchers developed a chip to investigate proteins introduced into these artificial cell walls with fluorescent . Molecular fluorescent probes are coupled to the toxin proteins. If the proteins now enter the artificial membranes and change their structure, their architecture and movement and even their distribution can be followed – thanks to the developed technique - by the fluorescent light they are emitting.

"By watching the toxin in both its active and inactive state, and by measuring the dynamic changes of the light emitted by the molecular probes, we were able to determine which parts of it were interacting with the membrane to cause the pores." Dr. Blunck explained. "We expect the technique to be applied to a wide range of disease-causing toxins in future."

More information: "Rapid topology probing using fluorescence spectroscopy in planar lipid bilayer: the pore-forming mechanism of the toxin Cry1Aa of Bacillus thuringiensis" was published in the Journal of General Physiology by Rikard Bunck, Nicolas Groulx and Marc Juteau of the University of Montreal.

Provided by University of Montreal (news : web)

Decoding the proteins behind drug-resistant superbugs

Penicillin and its descendants once ruled supreme over bacteria. Then the bugs got stronger, and hospitals have reported bacterial infections so virulent that even powerful antibiotics held in reserve for these cases don't work.

To create the next line of defense against the most drug-resistant pathogens, scientists at the U.S. Department of Energy's Argonne National Laboratory and Texas A&M University have decoded the structure of a that confers drug resistance against our best antibiotics. The work could provide the foundation for new treatments to fight emerging drug-resistant .

ß-lactam antibiotics are the most widely used antibacterials in the world because they effectively kill bacteria, but are minimally toxic to human cells—which means they have few side effects. But 1999 sounded the end of the reign of ß-lactams. That year, a patient died in a Swedish from an infection that didn't respond to antibiotics.

Penicillin was the original ß-lactam, but as bugs evolved to fight it, scientists developed an entire family of related antibiotics, including amoxicillin, cephalexin and imipenem. The drugs work by blocking the bacteria's cell walls from growing normally. The latest class, called carbapenems, is generally held as the last line of defense against the toughest drug-resistant infections, like MRSA.

But resistant even to carbapenems have begun spreading across the world, and they can trade this ability not only among each other but to other species of bacteria as well.

Scientists tracked down a gene that allows bacteria to resist these antibiotics, called NDM-1. The gene codes for a protein that latches onto part of the antibiotic molecule: the ß-lactam ring that gives the family its name. The rings are rigid, and once they break apart, the antibiotic is useless. "That's why with NDM-1 genes are so deadly,” explained Andrzej Joachimiak, an Argonne Distinguished Fellow who co-authored the study.

But NDM-1's greatest trick is that it can disable the entire spectrum of ß-lactam antibiotics. Each different antibiotic has a different molecular structure. Argonne researchers needed to know how one protein could break the rings in a dozen different configurations.

Joachimiak, who has a joint appointment with Argonne and the University of Chicago, took up the challenge with colleagues at the Midwest Center for Structural Genomics and Texas A&M University.

One of the most powerful tools in a biologist's kit is protein crystallography, which zooms down to the molecular level to get a picture of what the protein looks like. Protein crystals are tiny things: a thousand of them could sit side by side in a human hair. But intense X-rays from large synchrotrons like Argonne's Advanced Photon Source can be used as a "camera”: detectors collect the data from X-rays bouncing off the crystallized protein and use it to reconstruct the enzyme's structure, atom by atom.

The team managed to capture the NDM-1 enzyme in three different states. They found that NDM-1's active site, where it latches onto the antibiotic, is abnormally enormous, and flexible—like a mouth that is so large that it can capture the rings from a dozen different , no matter their shape.

Decoding the structure allows scientists and companies to study the molecule for weaknesses: places where the structure could be attacked to disrupt its function. Joachimiak and the team are already beginning another study to test one way to neutralize the enzyme.

The study, "Structure of Apo- and Monometalated Forms of NDM-1—A Highly Potent Carbapenem-Hydrolyzing Metallo-ß-Lactamase”, was funded by the National Institutes of Health and has been published online in the journal PLoS ONE</i>.

Provided by Argonne National Laboratory (news : web)

From protein to planes and pigskin

Scientists may soon be able to make pest insects buzz off for good or even turn them into models for new technologies, all thanks to a tiny finding with enormous potential.

Sujata Chaudhari, a Kansas State University doctoral candidate in biochemistry, Pune, India, is the senior author of a study that was published this week in the . Her work includes a discovery that could expand the possibilities for selective pest control and new biomaterials like football padding or lightweight aircraft components -- and all by debunking a more than 50-year-old belief about the protective shell of insects.

The study looks at the red flour beetle and examines the dynamic the insect uses to replace the protective coating on its skin while shedding its old skin. This coating is called the cuticle and is the main structural and protective part of an insect's , creating a stiff but lightweight outer shell or flexible wings and joints.

"As an insect develops, it outgrows its rigid skin and must periodically get rid of its old cuticle and synthesize a new, larger one," Chaudhari said. "This process of shedding the old cuticle is called molting."

In order to molt, the insect's body secretes a fluid loaded with an enzyme called chitinase, which is pronounced ky-tin-ayes. Chitinase breaks down chitin, the main component of the cuticle, and consequently aids in dissolving the insect's old cuticle. For decades it has been assumed that chitinase does not come into contact with and dissolve the insect's newly formed cuticle because of an impenetrable envelope between the old and new cuticles, Chaudhari said.

But Chaudhari and her colleagues found that's not actually the case.

Instead, their research shows that chitinase is present in the new cuticle as well as in the old cuticle. Moreover, they found that the enveloping layer that separates the two cuticles is not responsible for protecting the new cuticle from being dissolved by chitinase. Rather it is the protein called Knickkopf -- pronounced kuh-NICK-kaw-pff.

"Think of Knickkopf as a fire retardant, chitinase as a fire, and the insect's cuticle as the wall of a house," said Subbaratnam Muthukrishnan, a university distinguished professor of biochemistry at Kansas State University, Chaudhari's adviser and a collaborator on the study. "During molting, it's like the house is on fire, but the fire is only burning things on the outside. Everything inside is safe because there's a fire retardant wall."

Although this discovery that chitinase is stopped by a protein and not a physical barrier was made in the red flour beetle, Tribolium castaneum, the same protein is found in all other insect species examined, and probably has the same chitin-protective function, Chaudhari said. Most likely the same holds true for all arthropods: , arachnids, crustaceans, nematodes and other organisms. That's a game-changer for scientists and inventors.

In the future, agricultural crop pests like the red could find themselves the targets of insecticides or interfering RNAs that shut down the Knickkopf protein, leaving the insect's body open to disease or to molting defects, said Richard Beeman, a Kansas State University entomology adjunct professor, researcher with the U.S. Department of Agriculture and collaborator on the project. Additionally, the beetle's cuticle could be replicated into new lightweight body armor, prosthetics or materials for flight.

"The cuticle is a gigantic puzzle, and we're slowly finding what the pieces are in the puzzle and how they interact to make the cuticle, organize it and digest it," said Karl Kramer, a Kansas State University emeritus biochemistry adjunct professor and collaborator with the USDA, who also worked on the project. "In solving the puzzle, we could target these composition materials for improved insect control. We could also develop biomaterial that could be used in agriculture or medicine -- or even make K-State football coach Bill Snyder some new protective padding for the Wildcats."

More information: "Knickkopf protein protects and organizes chitin in the newly synthesized insect exoskeleton," Proceedings of the National Academy of Sciences.

Provided by Kansas State University (news : web)