Sunday, October 9, 2011

Self-cleaning cotton breaks down pesticides, bacteria

 UC Davis scientists have developed a self-cleaning cotton fabric that can kill bacteria and break down toxic chemicals such as pesticide residues when exposed to light.

"The new fabric has potential applications in biological and chemical protective clothing for health care, food processing and farmworkers, as well as military personnel," said Ning Liu, who conducted the work as a doctoral student in Professor Gang Sun's group in the UC Davis Division of Textiles of Clothing.

A paper describing the work was published Sept. 1 in the Journal of Materials Chemistry.

Liu developed a method to incorporate a compound known as 2-anthraquinone carboxylic acid, or 2-AQC, into cotton fabrics. This chemical bonds strongly to the cellulose in cotton, making it difficult to wash off, unlike current self-cleaning agents. Unlike some other experimental agents that have been applied to cotton, it does not affect the properties of the fabric.

When exposed to light, 2-AQC produces so-called reactive oxygen species, such as hydroxyl radicals and hydrogen peroxide, which kill bacteria and break down organic compounds such as pesticides and other toxins.

Although 2-AQC is more expensive than other compounds, the researchers say that cheaper equivalents are available.

The work was funded by the National Science Foundation, the U.S. Defense Threat Reduction Agency and the Jastro Shields Graduate Research Fellowship from the UC Davis College of Agricultural and Environmental Sciences.

Story Source:

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

Journal Reference:

Ning Liu, Gang Sun, Jing Zhu. Photo-induced self-cleaning functions on 2-anthraquinone carboxylic acid treated cotton fabrics. Journal of Materials Chemistry, 2011; 21 (39): 15383 DOI: 10.1039/C1JM12805A

New materials engineering labs see early success

After only a few months of work, a small group of researchers at the U.S. Department of Energy's (DOE) Argonne National Laboratory has successfully scaled up the production of a new molecule that protects advanced lithium-ion batteries from thermal overcharge.

When Argonne materials scientist Khalil Amine and Zhengcheng Zhang and Lu Zhang invented a redox shuttle additive material known as 2,5-di-tert-butyl-1,4-bis(2-methoxyethoxy) or DBBB, the amount of the molecule they produced was sufficient for scientific testing and validation at the laboratory bench scale. But their process yielded too little material—less than 1 gram—for a company that may be interested in licensing and manufacturing the material to validate and test.

Applied researchers in Argonne’s Advanced Battery Materials Synthesis and Manufacturing Research & Development Program took the formula and developed an improved, scalable process that created 1,576 grams in a single batch—enough to study and validate in a real battery cell, said Argonne's Greg Krumdick, a systems engineer whose team developed the scale-up process.

Scientists typically do not need large amounts of materials to work with, but companies that want to manufacture a new material do. And therein lay the challenge—it is critical for companies to test the viability of a new material they are looking to mass produce.

However, the scale-up of a specialty material like DBBB is no small feat. Unlike the doubling or tripling of a cake recipe, it is not a matter of multiplying the amount of a chemical formulation by 1,000 or 10,000 or more to make larger quantities of a molecule.

Other considerations—like time, temperature, concentration, mixing speeds and even the chemical ingredients themselves—that do not come up when making very small amounts of a material arise when attempting to make vastly larger volumes for commercial testing and mass market production.

"Unless you have a process to make a material in sufficient quantities, you simply can't get enough of the material," Krumdick said. "It is often wrongly assumed that industry will do the scale-up work, but most companies don't want to make the significant financial investment required to develop the scale-up process. It's too risky, especially if you don’t know if it will be economical to make the material at scale."

That is where the process engineering and scale-up expertise and facilities of Argonne’s federally funded Advanced Battery Materials Synthesis and Manufacturing Research & Development Program are brought to bear.

The goal of process scale up is to find economical ways to make a material. The bench scale process used to discover DBBB would have cost 20 times more and generated 50 times as much waste as the scaled up process to make 1 kilogram. The new process also is 3 times faster.

However, it was never intended to use the bench scale process to make commercial quantities of materials, Krumdick said. "When discovering new materials, it’s not your objective to be sure it is made economical; it’s to make it quickly. Once a new material has been discovered and is shown to have promise, it’s my group’s job to scale it up, meaning find economical ways to make large volumes of the materials.

"After finishing work on DBBB, we had made a kilogram scale batch that was chemically analyzed and its electrochemical performance characterized and was found to be identical to the initial material synthesized. The new process is also highly reproducible in yield and purity from batch to batch."

Krumdick worked with Krzystof Pupek and Trevor Dzwiniel—both of who came from the pharmaceutical industry, which routinely develops scale-up processes—to scale-up DBBB at the Material Engineering Facility (MEF), where the scale-up work was done.

DOE invested $5.8 million from the American Recovery and Reinvestment Act to help fund MEF's construction to help close the lag time between innovation and commercialization. The U.S. Department of Defense (DoD) provided another $4 million toward MEF construction.

DoD is also interested in Argonne’s battery research. According to the assistant secretary of defense, Sharon Burk, the average U.S. soldier on a 72 hour patrol carries between 10 and 20 pounds of batteries.”You can follow a U.S. infantry patrol by the disposable batteries that it trails behind it,” Army Chief of Staff General Martin Dempsey told an Institute of Land Warfare breakfast in May. "At the highest levels, there appears to be recognition of the inadequacy of disposable batteries”.

The military uses batteries in a wide range of electronics, including the electronics systems in tanks, which would be able to remain in the field longer and without detection if some of its systems were run on batteries.

The MEF is not yet fully constructed. The facility is expected to be completed in January and will contain three pilot labs and high-bays for continuous batch production of large volumes—up to 100 kilograms—of specialty materials for industry validation, said Krumdick, who oversees MEF construction.

Argonne plans make the MEF a quasi-user facility that will be accessible to other R&D organizations and companies, said Jeff Chamberlain, who leads Argonne's energy storage research initiative. The facility and the close teaming of scientists and engineers are part of a full-circle approach that Argonne employs to help industry move U.S. energy innovations into the marketplace more quickly.

“There are at least two battery manufacturers interested in the DBBB redox shuttle,” Chamberlain said. “I believe that the success that Greg and his team have had in scaling up production of the material will allow Argonne to significantly shrink the time between product innovation and commercial licensing and manufacturing. Not only will the payback to the taxpayer’s investment in R&D be shortened, but innovation’s contribution to the growth of the U.S. economy will be realized that much sooner.”

Provided by Argonne National Laboratory (news : web)

Long-standing plant biochemistry mystery solved

Scientists at the U.S. Department of Energy's (DOE) Brookhaven National Laboratory and collaborators at the Karolinska Institute in Sweden have discovered how an enzyme "knows" where to insert a double bond when desaturating plant fatty acids. Understanding the mechanism -- which relies on a single amino acid far from the enzyme's active site -- solves a 40-year mystery of how these enzymes exert such location-specific control. The work, published in the Proceedings of the National Academy of Sciences the week of September 19, 2011, may lead to new ways to engineer plant oils as a renewable replacement for petrochemicals.

"Plant are an approximately $150-billion-dollar-a-year market," said Brookhaven John Shanklin, lead author on the paper. "Their properties, and therefore their potential uses and values, are determined by the position of double bonds in the hydrocarbon chains that make up their backbones. Thus the ability to control double bond positions would enable us to make new designer fatty acids that would be useful as industrial raw materials."

The enzymes responsible for double-bond placement, called desaturases, remove and insert between adjacent at specific locations on the hydrocarbon chains. But how one enzyme knows to insert the double bond at one location while a different but closely related enzyme inserts a double bond at a different site has been a mystery.

"Most enzymes recognize features in the molecules they act on that are very close to the site where the enzyme's action takes place. But all the carbon-hydrogen groups that make up fatty-acid backbones are very similar with no distinguishing features — it's like a greasy rope with nothing to hold onto," said Shanklin.

In describing his group's long-standing quest to solve the desaturation puzzle, Shanklin quotes Nobel laureate Konrad Bloch, who observed more than 40 years ago that such site-specific removal of hydrogen "would seem to approach the limits of the discriminatory power of enzymes."

Shanklin and his collaborators approached the problem by studying two genetically similar desaturases that act at different locations: a castor desaturase that inserts a double bond between carbon atoms 9 and 10 in the chain (a 'delta-9' desaturase); and an ivy desaturase that inserts a double bond between carbon atoms 4 and 5 (delta-4). They reasoned that any differences would be easy to spot in such extreme examples.

But early attempts to find a telltale explanation — which included detailed analyses of the two enzymes' atomic-level crystal structures — turned up few clues. "The crystal structures are almost identical," Shanklin said.

The next step was to look at how the two enzymes bind to their substrates — fatty acid chains attached to a small . First the scientists analyzed the crystal structure of the castor desaturase bound to the substrate. Then they used computer modeling to further explore how the carrier protein "docked" with the enzyme.

"Results of the computational docking model exactly matched that of the real crystal structure, which allows carbon atoms 9 and 10 to be positioned right at the enzyme's active site," Shanklin said.

Next the scientists modeled how the carrier protein docked with the ivy desaturase. This time it docked in a different orientation that positioned carbon atoms 4 and 5 at the desaturation active site. "So the docking model predicted a different orientation that exactly accounted for the specificity," Shanklin said.

To identify exactly what was responsible for the difference in binding, the scientists then looked at the amino acid sequence — the series of 360 building blocks that makes up each enzyme. They identified amino acid locations that differ between delta-9 and delta-4 desaturases, and focused on those locations that would be able to interact with the substrate, based on their positions in the structural models.

The scientists identified one position, far from the active site, where the computer model indicated that switching a single amino acid would change the orientation of the bound fatty acid with respect to the active site. Could this distant amino-acid location remotely control the site of double bond placement?

To test this hypothesis, the scientists engineered a new desaturase, swapping out the aspartic acid normally found at that location in the delta-9 castor desaturase for the lysine found in the delta-4 ivy desaturase. The result: an enzyme that was castor-like in every way, except that it now seemed able to desaturate the fatty acid at the delta-4 carbon location. "It's quite remarkable to see that changing just one amino acid could have such a striking effect," Shanklin said.

The computational modeling helped explain why: It showed that the negatively charged aspartic acid in the castor desaturase ordinarily repels a negatively charged region on the carrier protein, which leads to a binding orientation that favors delta-9 desaturation; substitution with positively charged lysine results in attraction between the desaturase and carrier protein, leading to an orientation that favors delta-4 desaturation.

Understanding this mechanism led Ed Whittle, a research associate in Shanklin's lab, to add a second positive charge to the castor desaturase in an attempt to further strengthen the attraction. The result was a nearly complete switch in the castor enzyme from delta-9 to delta-4 desaturation, adding compelling support for the remote control hypothesis.

"I really admire Ed's persistence and insight in taking what was already a striking result and pushing it even further to completely change the way this enzyme functions," Shanklin said.

"It's very rewarding to have finally solved this mystery, which would not have been possible without a team effort drawing on our diverse expertise in biochemistry, genetics, computational modeling, and x-ray crystallography.

"Using what we've now learned, I am optimistic we can redesign enzymes to achieve new desirable specificities to produce novel fatty acids in plants. These novel fatty acids would be a renewable resource to replace raw materials now derived from petroleum for making industrial products like plastics," Shanklin said.

Provided by Brookhaven National Laboratory (news : web)

Breakthrough technology in identification of prostate cancer cells

A team of researchers at UC Santa Barbara has developed a breakthrough technology that can be used to discriminate cancerous prostate cells in bodily fluids from those that are healthy. The findings are published this week in the Proceedings of the National Academy of Sciences.

While the new technology is years away from use in a clinical setting, the researchers are nonetheless confident that it will be useful in developing a microdevice that will help in understanding when will metastasize, or spread to other parts of the body.

"There have been studies to find the relationship between the number of cancer cells in the blood, and the outcome of the disease," said first author Alessia Pallaoro, postdoctoral fellow in UCSB's Department of Chemistry and Biochemistry. "The higher the number of cancer cells there are in the patient's blood, the worse the prognosis.

"The cancer cells that are found in the blood are thought to be the initiators of metastasis," Pallaoro added. "It would be really important to be able to find them and recognize them within blood or other bodily fluids. This could be helpful for diagnosis and follow-ups during treatment."

The researchers explained that although the primary tumor does not kill prostate cancer patients, metastasis does. "The delay is not well understood," said Gary Braun, second author and postdoctoral fellow in the Department of Molecular, Cellular, and Developmental Biology. "There is a big focus on understanding what causes the tumor to shed cells into the blood. If you could catch them all, then you could stop metastasis. The first thing is to monitor their appearance."

The team developed a novel technique to discriminate between cancerous and non-cancerous cells using a type of laser spectroscopy called surface enhanced Raman spectroscopy (SERS) and silver nanoparticles, which are biotags.

"Silver nanoparticles emit a rich set of colors when they absorb the laser light," said Braun. "This is different than fluorescence. This new technology could be more powerful than fluorescence."

The breakthrough is in being able to include more markers in order to identify and study unique tumor cells that are different from the main tumor cells, explained Pallaoro. "These different cells must be strong enough to start a new tumor, or they must develop changes that allow them to colonize in other areas of the body," she said. "Some changes must be on the surface, which is what we are trying to detect."

The team is working to translate the technology into a diagnostic microdevice for studying cancer cells in the blood. Cells would be mixed with nanoparticles and passed through a laser, then discriminated by the ratio of two signals.

The two types of biotags used in this research have a particular affinity that is dictated by the peptide they carry on their surface. One type attaches to a cell receptor called neuropilin-1, a recently described biomarker found on the surface membrane of certain . The other biotag binds many cell types (both cancerous and non-cancerous) and serves as a standard measure as the cells are analyzed.

In this study, the team mixed the two biotags and added them to the healthy and tumor cell cultures. The average SERS signal over a given cell image yielded a ratio of the two signals consistent with the cells' known identity.

Pallaoro said she believes the most important part of the new technique is the fact that it could be expanded by adding more colors –– different particles of different colors –– as more biomarkers are found. The team used a new biomarker discovered by scientists at UCSB and the Sanford Burnham Medical Research Institute.

Provided by University of California - Santa Barbara (news : web)

A model could guide the design of artificial composites

Many biomaterials such as bone, shell and mineralized tendon have a hierarchical structure that provides the material with exceptional mechanical and load-bearing properties, even though the building blocks of such structures may themselves have very poor mechanical properties. One type of structural hierarchy known as ‘self-similarity’ is ubiquitous in nature and is based on the repetition of units that are composed of biominerals and proteins, creating multi-level structures that provide enhanced strength and durability.

The number of hierarchical levels in such structures is dependent on the mineral content. Bone, for example, combines soft organic collagen material and hard crystal phases in an organized seven-level structure (see image), whereas shell is typically organized into two- or three-level structures. Little has been known, however, about what determines the number of levels in natural systems. Zuoqi Zhang at the A*STAR Institute of High Performance Computing and co-workers have now developed a theoretical, quasi-self-similar model to demonstrate why these natural biomaterials typically exhibit two to seven levels of structural hierarchy.

Previous experiments at different size scales have shown that the cooperative deformation of load-bearing biomaterials depends on their underlying hierarchical structures. The model developed by Zhang’s team, however, is the first to match these measurements of mineral and collagen deformation in bone and mineralized tendon. In the new model, each hierarchical level consists of hard, slender inclusions that form a staggered pattern within a soft matrix. These staggered microstructures then serve as inclusions in the next level. “The aspect ratio of the inclusions varies from level to level,” says Zhang.

The model showed that depending on mineral concentration, maximum toughness is obtained at a certain number of hierarchical levels and a certain . Zhang notes that within the optimal structure, characteristic sizes range from tens of nanometers to hundreds of micrometers. The model also confirmed the predicted trend that the number of hierarchical levels would be highest for bone, lower for mineralized tendon, and lowest for shell. “These predictions are in agreement with experimental observations,” says Zhang.

The researchers are currently planning to use their to guide the design and fabrication of artificial hierarchical composites in the laboratory. In addition, they are investigating the ability of hierarchical biomaterials to resist impact load. “We are trying to reveal the underlying mechanisms that may lead to acoustic cloaking composites—materials with the ability to make an object ‘invisible’ to sound,” says Zhang.

More information: Zhang, Z., et al. On optimal hierarchy of load-bearing biological materials. Proceedings of the Royal Society B 278, 519–525 (2011). http://rspb.royals … 278/1705/519

Provided by Agency for Science, Technology and Research (A*STAR)