Wednesday, March 30, 2011

Debut of the first practical 'artificial leaf'

Scientists today claimed one of the milestones in the drive for sustainable energy — development of the first practical artificial leaf. Speaking here at the 241st National Meeting of the American Chemical Society, they described an advanced solar cell the size of a poker card that mimics the process, called photosynthesis, that green plants use to convert sunlight and water into energy.

"A practical artificial leaf has been one of the Holy Grails of science for decades," said Daniel Nocera, Ph.D., who led the research team. "We believe we have done it. The artificial leaf shows particular promise as an inexpensive source of electricity for homes of the poor in developing countries. Our goal is to make each home its own power station," he said. "One can envision villages in India and Africa not long from now purchasing an affordable basic power system based on this technology."

The device bears no resemblance to Mother Nature's counterparts on oaks, maples and other green plants, which scientists have used as the model for their efforts to develop this new genre of solar cells. About the shape of a poker card but thinner, the device is fashioned from silicon, electronics and catalysts, substances that accelerate chemical reactions that otherwise would not occur, or would run slowly. Placed in a single gallon of water in a bright sunlight, the device could produce enough electricity to supply a house in a developing country with electricity for a day, Nocera said. It does so by splitting water into its two components, hydrogen and oxygen.

The hydrogen and oxygen gases would be stored in a fuel cell, which uses those two materials to produce electricity, located either on top of the house or beside it.

Nocera, who is with the Massachusetts Institute of Technology, points out that the "artificial leaf" is not a new concept. The first artificial leaf was developed more than a decade ago by John Turner of the U.S. National Renewable Energy Laboratory in Boulder, Colorado. Although highly efficient at carrying out photosynthesis, Turner's device was impractical for wider use, as it was composed of rare, expensive metals and was highly unstable — with a lifespan of barely one day.

Nocera's new leaf overcomes these problems. It is made of inexpensive materials that are widely available, works under simple conditions and is highly stable. In laboratory studies, he showed that an artificial leaf prototype could operate continuously for at least 45 hours without a drop in activity.

The key to this breakthrough is Nocera's recent discovery of several powerful new, inexpensive catalysts, made of nickel and cobalt, that are capable of efficiently splitting water into its two components, hydrogen and oxygen, under simple conditions. Right now, Nocera's leaf is about 10 times more efficient at carrying out photosynthesis than a natural leaf. However, he is optimistic that he can boost the efficiency of the artificial leaf much higher in the future.

"Nature is powered by photosynthesis, and I think that the future world will be powered by as well in the form of this artificial leaf," said Nocera, a chemist at Massachusetts Institute of Technology in Cambridge, Mass.

Provided by American Chemical Society (news : web)

Protein biologists find new chink in staph's armor

The battle against deadly staph infections is closer to victory as Illinois researchers have uncovered secrets of how the bacterium protects itself from human immune attacks, which could lead to more effective anti-staph therapies.

Using powerful X-ray beams from the (APS) at the U.S. Department of Energy's Argonne National Laboratory, scientists from the University of Illinois at Urbana-Champaign documented how a key enzyme enables staph to make a coating that protects the bacteria from human . Armed with details about how the chemistry works, researchers hope to find drugs that can interfere with the process, leaving the bacteria vulnerable to immune system attacks.

"More people in the United States die of staph infections each year than from HIV/AIDS," said Eric Oldfield, the Illinois chemistry professor who co-led the team of researchers from the University of Illinois and from Taiwan who made the discovery. "We need to come up with new antibiotics."

Using X-ray diffraction available at the APS, the researchers were able to watch how a key drug target, the staph enzyme dehydrosqualene synthase (CrtM), functions. They discovered the uses a two-step reaction involving two active sites on the enzyme, so finding a way to block both sites would stop the reaction and kill an infection.

"The leads that people have been developing for inhibiting these sorts of enzymes really haven't had any structural basis," said Oldfield, who also is a professor of biophysics. "Now that we can see how the proteins work, we're in a much better position to design molecules that will be more effective against staph infections." Inhibitors used in the project have been licensed to AuricX Pharmaceuticals, a start-up company that has a grant from the Texas Emerging Technology Fund to do preclinical testing in .

The knowledge might also be applied to fight some parasitic diseases and even lower cholesterol levels because the same sorts of enzymes are involved in those processes as well.

Helping researchers reveal the structures of proteins and how they interact dynamically with one another is an ongoing function of the APS, and progress has accelerated as APS researchers and their academic collaborators have automated the process of refining proteins and crystallizing them so they can be studied with .

Seven years ago, scientists using the APS characterized 162 protein structures in a year, said Andrzej Joachimiak, director of the Structural Biology Center and Midwest Center for Structural Genomics at Argonne. In 2009, that number was up to 1,493.

Such increased efficiency stems from installing robotic systems that now quickly handle tedious operations once done by hand. Joachimiak said that further automation, such as a system that could quickly locate tiny crystals in droplets of liquid, will further reduce time and expense required to tease out nature's secrets of protein structure and function.

An advanced protein crystallization facility to be built adjacent to the APS is in the design phase now, and Joachimiak said that construction may begin late this year or early in 2012. The state of Illinois is helping to fund the facility, which is intended to further boost the output of information about proteins.

Many drug companies as well as academic researchers use APS beamlines to characterize proteins, and as more information becomes available, the industry moves closer to its goal of designing drugs based on knowledge of the structure of biological targets.

Since 2006, researchers of the Argonne's Midwest Center for Structural Genomics (MCSG) and Northwestern University Center for Structural Genomics of Infectious Diseases (CSGID), funded by the National Institutes of Health, have mapped out over 1,300 3-D protein structures from bacterial and protozoan pathogens, making the information available to scientists designing therapies and diagnostics. By the end of next year, these consortia are on track to have 2,000 such structures mapped.

"In addition to the aim of providing a starting point for structure-based drug discovery, we can also use this research as a way to learn more about these pathogens and how they cause diseases, how they get around the immune system, how we defend ourselves against them and how they interact with their host," said Wayne Anderson, a Northwestern University professor of molecular pharmacology and biological chemistry and principal investigator of the CSGID project.

Provided by Argonne National Laboratory (news : web)

Taming the flame: Electrical wave 'blaster' could provide new way to extinguish fires

A curtain of flame halts firefighters trying to rescue a family inside a burning home. One with a special backpack steps to the front, points a wand at the flame, and shoots a beam of electricity that opens a path through the flame for the others to pass and lead the family to safety.

Scientists today described a discovery that could underpin a new genre of fire-fighting devices, including sprinkler systems that suppress fires not with water, but with zaps of electric current, without soaking and irreparably damaging the contents of a home, business, or other structure. Reporting at the 241st National Meeting & Exposition of the American Chemical Society (ACS), Ludovico Cademartiri, Ph.D., and his colleagues in the group of George M. Whitesides, Ph.D., at Harvard University, picked up on a 200-year-old observation that can affect the shape of flames, making flames bend, twist, turn, flicker, and even snuffing them out. However, precious little research had been done over the years on the phenomenon.

"Controlling fires is an enormously difficult challenge," said Cademartiri, who reported on the research. "Our research has shown that by applying large electric fields we can suppress flames very rapidly. We're very excited about the results of this relatively unexplored area of research."

currently use water, foam, powder and other substances to extinguish flames. The new technology could allow them to put out fires remotely — without delivering material to the — and suppress fires from a distance. The technology could also save water and avoid the use of fire-fighting materials that could potentially harm the environment, the scientists suggest.

In the new study, they connected a powerful electrical amplifier to a wand-like probe and used the device to shoot beams of electricity at an open flame more than a foot high. Almost instantly, the flame was snuffed out. Much to their fascination, it worked time and again.

The device consisted of a 600-watt amplifier, or about the same power as a high-end car stereo system. However, Cademartiri believes that a power source with only a tenth of this wattage could have similar flame-suppressing effect. That could be a boon to firefighters, since it would enable use of portable flame-tamer devices, which perhaps could be hand-carried or fit into a backpack.

But how does it work? Cademartiri acknowledged that the phenomenon is complex with several effects occurring simultaneously. Among these effects, it appears that carbon particles, or soot, generated in the flame are key for its response to electric fields. Soot particles can easily become charged. The charged particles respond to the electric field, affecting the stability of flames, he said.

"Combustion is first and foremost a chemical reaction – arguably one of the most important – but it's been somewhat neglected by most of the chemical community," said Cademartiri. "We're trying to get a more complete picture of this very complex interaction."

Cademartiri envisions that futuristic electrical devices based on the phenomenon could be fixed on the ceilings of buildings or ships, similar to stationary water sprinklers now in use. Alternatively, firefighters might carry the flame-tamer in the form of a backpack and distribute the electricity to fires using a handheld wand. Such a device could be used, for instance, to make a path for firefighters to enter a or create an escape path for people to exit, he said.

The system shows particular promise for fighting fires in enclosed quarters, such as armored trucks, planes, and submarines. Large forest fires, which spread over much larger areas, are not as suitable for the technique, he noted.

Cademartiri also reported how he and his colleagues found that electrical waves can control the heat and distribution of flames. As a result, the technology could potentially improve the efficiency of a wide variety of technologies that involve controlled combustion, including automobile engines, power plants, and welding and cutting torches, he said.

Provided by American Chemical Society (news : web)

New insight into how 'tidying up' enzymes work

A new discovery about how molecules are broken down by the body, which will help pharmaceutical chemists design better drugs, has been made by researchers at the University of Bristol.

Working with Professor Jeremy Harvey and Professor Adrian Mulholland of Bristol's School of Chemistry, Dr Julianna Olah, an EU Marie Curie Fellow in Bristol at the time, studied a class of enzymes – cytochromes P450 – which play an important role in removing molecules from the body.

When a tablet of medicine is taken, the active molecules get absorbed into the bloodstream through the gut and make their way around the body, including to the cells in which they are intended to act; however, it's important they don't stay in the body forever. Enzymes (biological catalysts) help break them down to facilitate excretion.

The cytochromes P450 are a very important class of these 'tidying up' enzymes which have evolved to deal with all 'foreign' compounds that do not get broken down as part of normal metabolism (that is, any compounds which are not proteins, carbohydrates or lipids).

Mainly situated in the liver, the P450 enzymes help remove drug molecules by adding oxygen to them. This process usually works smoothly, but for some molecules, it can lead to oxygenated variants that are toxic. Other molecules are also able to interfere with the normal function of the P450 enzymes.

For these reasons, it is important to be able to understand how a given new molecule, considered for use as a medicine, will react with these enzymes. The Bristol researchers aimed to provide this understanding by modeling the reaction mechanism for interaction between one specific drug (dextromethorphan, a component of some cough syrups) and one P450 variant.

Professor Jeremy Harvey said: "Our calculations showed that the outcome of the oxygen transfer process (that is, which part of dextromethorphan oxygen gets added to) is affected by three factors.

"The first is the way in which the molecule fits into the ('docking'). The second is the intrinsic ability of each part of the molecule to accept . The third is how much each competing oxygen-delivery process is compatible with the shape of the enzyme pocket where the reaction occurs.

"While these first two factors were already known, the third was not. This discovery can help pharmaceutical chemists design new with a better understanding of how they will be broken down in the body."

Provided by University of Bristol (news : web)

Molecular muscle: Small parts of a big protein play key roles in building tissues


We all know the adage: A little bit of a good thing can go a long way. Now researchers in London are reporting that might also be true for a large protein associated with wound healing.

The team at the Kennedy Institute of Rheumatology at Imperial College reports in the that a protein generated when the body is under stress, such as in cases of physical trauma or disease, can affect how the protective housing that surrounds each cell develops. What's more, they say, tiny pieces of that protein may one day prove useful in preventing the spread of tumors or .

At just 174 in diameter, tenascin-C is pretty big in the world of proteins, and it looks a lot like a spider with six legs, which are about 10 times longer than its body. Thanks to those long legs, tenascin-C can do real heavy lifting when it comes to wound healing.

"Tenascin-C plays many roles in the response to tissue injury, including, first of all, initiating an and, later, ensuring proper tissue rebuilding," explains Kim Midwood, who oversaw the project.

When the injury alarm is rung, tenascin-C shows up on the scene and attaches to another protein, fibronectin. Together, tenascin-C and fibronectin help to construct the housing, or extracellular matrix, that surrounds each cell.

"The extracellular matrix is the home in which the cells of your body reside: It provides shelter and and also sends signals to the cell to tell it how to behave," says Midwood. "To make a finished tissue, the matrix must be carefully built."

Tenascin-C's job is a temporary one. When your hand is cut, for example, it appears at the edges of the wound and then goes away when develops, says postdoctoral research associate Wing To: "Tenascin-C is thought to play a major role during the rebuilding phase of by promoting of tissue that has been damaged."

If the extracellular matrix were a construction site, tenascin-C could be seen as the scaffold upon which the weaving of fibronectin threads, or fibrils, is done. "Tenascin-C has multiple arms, and we have shown that it has multiple binding sites for fibronectin," Midwood says. "In this way, it can bind to many fibronectin fibrils at once and help to form the whole tissue by linking the fibrils together. Then, when the repair is done, the scaffolding is taken down."

Midwood and To systematically determined where tenascin-C and fibronectin bind together. They also identified small parts of tenascin-C, known as domains, that can bind to only one fibronectin fibril apiece.

"The small domains act as caps of the scaffold. No more fibronectin fibrils can bind once these caps are in place," Midwood says. So, in essence, they found that certain pieces of tenascin-C determine when fibril building should stop once enough, but not too much, tissue is made.

The findings could be especially useful for creating therapies for conditions in which there is aberrant extracellular matrix deposition, such as in cancers, fibrotic conditions or chronic non-healing wounds, adds To.

In abnormal conditions, such as in the case of a tumor cell, "the home that's made of fibronectin helps it to survive, shelters it and provides signals that enable it to proliferate," says Midwood. "As the tumor thrives, the home keeps on growing, expanding to destroy the existing neighborhood."

Similarly, in fibrotic diseases, tissue rebuilding rages out of control – with too much fibronectin assembly – so that it takes over the whole affected organ, Midwood says.

"In the end, we found that tenascin-C has both stop and go functions cleverly concealed in the same molecule," Midwood says. "The large spiderlike protein may provide a scaffold for building, and the small domains of the protein block excess building. Small domains may be therapeutically useful in situations where too much fibronectin drives disease."

If certain domains can stop uncontrolled matrix deposition in conditions where there is an increase in unwanted , such as in fibrosis, then they could be useful tools for controlling such diseases.

Meanwhile, To says, in conditions with high levels of tenascin-C degradation by enzymes, for example in nonhealing chronic wounds, that may expose active tenascin-C domains, "if we can stop the production of these domains during disease progression with specific inhibitors, maybe we could help ameliorate the condition.

Similarly we could try and get the cells to make tenascin-C variants that are not as easily broken down by enzymes to help facilitate wound healing."

More information: Midwood and To's paper was named a "Paper of the Week" by the Journal of Biological Chemistry.

Provided by American Society for Biochemistry and Molecular Biology

UConn reactor uses more efficient process to make biodiesel fuel

Deep inside the University of Connecticut’s chemical engineering building in Storrs, Professor Richard Parnas and a team of students quietly monitor a murky brown emulsion bubbling inside an enormous 6-inch diameter glass tube like doctors carefully observing a patient undergoing surgery.

Moving among an array of flexible tubing and metal rods surrounding the nearly floor-to-ceiling device, Parnas keeps a watchful eye on a series of multicolored charts blinking on a nearby laptop. The display represents the real-time readings of a high-tech fiber-optic probe monitoring the chemical reactions taking place inside the tube. It helps Parnas, a UConn professor of chemical, materials, and biomolecular engineering, maintain the precise recipe he needs to turn a mixture of methanol, potassium hydroxide, and waste vegetable oil into nearly pure, cheap, environmentally-friendly biodiesel fuel.

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Parnas’ patented biodiesel reactor is unique in both its simplicity and efficiency. In conventional biodiesel production, vegetable oil is converted into biodiesel fuel and glycerol, a byproduct of the conversion process. Then, the glycerol must be mechanically separated from the diesel fuel, as part of a two-step process. Parnas’ reactor is different in that it uses gravity, heat, and natural chemical reactions to make the biodiesel and separate the glycerol in one step.

As the chemical reactions take place inside the giant tube, temperatures reach more than 100 degrees Fahrenheit. The glycerol starts to coagulate in opaque swirls inside the tube. Because the glycerol droplets are heavier than the biodiesel fuel, they gradually sink to the bottom, where they are siphoned off. At the same time, the biodiesel fuel floats to the top of the tube and is pumped into a holding tank, where it undergoes refinement before being mixed with petroleum-based diesel fuel and used in the University’s bus fleet.

“What is unique about our reactor and why we have a patent on it, is that it gives a much better performance for the separation of the glycerol, and we don’t need a special separate step as is used in most other processes,” says Parnas, who also serves as chairman of UConn’s biodiesel consortium research group.

“That motion and those swirls you are seeing when you look at the reactor are the result of both a chemical reaction and phase separation in real time,” Parnas says. “Phase separation is like what happens when you have an oil and vinegar salad dressing … In other biodiesel processes out there, the reactants are very highly mixed and come out of the reactor together.”

The first UConn biodiesel reactor was built by Greg Magoon, a UConn chemical engineering undergraduate student, in 2004. In 2006, a larger continuous flow biodiesel reactor was designed by UConn graduate student Cliff Weed, under Parnas’ tutelage. The reactor in place today was constructed by students Matthew Boucher and Ryan Couture. Undergraduate and graduate students from chemical engineering, chemistry, economics, and natural resources and the environment have been involved with the project over the years. Every chemical engineering student at UConn learns how to make biodiesel as part of the academic program.

Igor Anisimov, a third-semester chemical engineering student, was one of the students helping Parnas with the reactor during a recent production run.

“The biodiesel reactor is exploiting the molecular differences of the elements,” says Anisimov. “By exploiting the natural properties of these chemicals, we can separate the biodiesel from the glycerol. It’s very cool seeing it happening here, compared to seeing it in the classroom on pen and paper.”

The existing facility produces about 2,000 gallons of biodiesel fuel a year. Parnas and colleagues Yi Li of the plant science department, Steven Suib of the chemistry department, Fred Carstensen of the economics department, and Harrison Yang of the Department of Natural Resources and the Environment are preparing to build a larger pilot biodiesel production facility using part of a two-year, $1.8 million grant from the Department of Energy. The will be capable of producing up to 200,000 gallons of biodiesel a year. Parnas says the pilot plant’s production can easily be magnified for larger-scale commercial production.

In an era of rising gasoline prices and increasing worry about global warming and the emission of greenhouse gases, biodiesel is proving to be a valuable and important substitute for traditional petroleum-based fuels.

Biodiesel releases more energy than is consumed during its production, making it four times more efficient than traditional diesel fuels. It is a renewable fuel source that can be produced locally, cutting down on transportation costs, greenhouse gas emissions, and the nation’s reliance on foreign oil reserves. And, since it is made from plant materials, biodiesel is 100 percent biodegradable.

Provided by University of Connecticut (news : web)