Dr. Mom Was Right — and Wrong — About Washing Fruits and Vegetables



Washing fresh fruits and vegetables before eating may reduce the risk of food poisoning and those awful episodes of vomiting and diarrhea. But according to new research, described today at the 235th national meeting of the American Chemical Society, washing alone — even with chlorine disinfectants — may not be enough.

Studies show that certain disease-causing microbes are masters at playing hide-and-go seek with such chemical sanitizers. These bacteria can make their way inside the leaves of lettuce, spinach and other vegetables and fruit, where surface treatments cannot reach. In addition, microbes can organize themselves into tightly knit communities called biofilms that coat fruits and vegetables and protect the bacteria from harm. This kind of bacterial community can harbor multiple versions of infectious, disease-causing bacteria, such as Salmonella and E. coli.

Now, new findings from scientists at the U.S. Department of Agriculture suggest that irradiation, a food treatment currently being reviewed by the FDA, can effectively kill internalized pathogens that are beyond the reach of conventional chemical sanitizers.

Irradiation exposes food to a source of electron beams, creating positive and negative charges. It disrupts the genetic material of living cells, inactivating parasites and destroying pathogens and insects in food, including E. coli and Salmonella.

Using this technique on fresh and fresh-cut fruits and vegetables could provide a reliable way to reduce the numbers of foodborne illnesses reported each year in the United States, says Brendan A. Niemira, Ph.D., a microbiologist with the USDA's Agricultural Research Service in Wyndmoor, Pa., who directed the study.

“When bacteria are protected — whether they’re inside a leaf or inside a biofilm — they’re not going to be as easy to kill,” Niemira says. “This is the first study to look at the use of irradiation on bacteria that reside inside the inner spaces of a leaf or buried within a biofilm.”

The quantity of fresh fruits and vegetables in the United States has increased every year in the last decade. Unfortunately, the increase in consumption has been accompanied with an increase in the number of outbreaks and recalls due to contamination with human pathogens such as E. coli. Fresh fruits and vegetables carry the potential risk of contamination because they are generally grown in open fields with potential exposure to pathogens from soil, irrigation water, manure, wildlife or other sources.

“The spinach outbreak in the fall of 2006, in particular, raised questions about how these organisms survived the various treatments that are applied – the rinses and the washes and things,” Niemira says.

At the time, research had already demonstrated that pathogens like Salmonella and E. coli can be drawn into fruits after they've formed, and can migrate into them during fruit growth and maturation if the plant is exposed to them during pollination or in the irrigation water. But questions remained as to whether a penetrating process such as irradiation could kill a pest located inside a leaf.

To see how internalized sources of bacteria responded to various treatments, Niemira and his colleagues devised a way to pull bacteria into the leaves of leafy green vegetables. The scientists cut leaves of romaine lettuce and baby spinach into pieces and submerged them in a cocktail mixture of E. coli. The bacteria was pushed inside the leaves with a vacuum perfusion process. The leaves were then treated with either a three-minute water wash, a three-minute chemical treatment or irradiation.

After treatment, the leaves were suspended in a neutral buffer solution and crushed to recover and count the internalized bacteria. The study showed that washing with plain water was not effective at reducing the levels of the pathogen on either spinach or lettuce. The chemical treatment, a sodium hypochlorite solution, did not result in significant reductions of E. coli cells in spinach leaves, and an gave less than 90 percent reduction of E. coli in the romaine lettuce samples.

Ionizing radiation, in contrast, significantly reduced the pathogen population in both the spinach and the lettuce leaves. The level of kill was dependent on the dose applied, with reductions of 99.99 percent on romaine lettuce and 99.9 percent on spinach at the highest dose tested.

The researchers then conducted lab tests with biofilms to see how well different strains of Salmonella and E. coli, which were buried inside the biofilms, stood up to irradiation.

The biofilms that contained Salmonella tended to die more easily with irradiation, while those that were infected with E. coli were a bit more resistant, Niemira says.

“In the most resistant cases, we saw a difference of a few percent, but it was nothing at all compared to the resistance you might see if you were using a chemical treatment,” he says.

The scientists now are conducting studies of biofilms on leafy green vegetables to better gauge how irradiation might work on plants in the field.

Niemira says it’s still not clear if human pathogens can actually increase in population within plant tissues, or if they merely persist.

“This is an important question, because if the pathogens don't reproduce effectively within these protected spaces and stay below minimally infective population sizes, then the risk they pose to consumers is less,” he says. “If they are able to reproduce inside, then they may increase to more dangerous levels.”

Though some activist groups continue to speak against irradiation, consumer confidence in the application has grown steadily through the years as studies have shown its effectiveness in reducing pathogens that cause foodborne illnesses, says Christine Bruhn, Ph.D., who focuses on consumer issues in food safety and quality at the University of California at Davis.

“Sixty to 90 percent of consumers indicate that they would buy irradiated food when told of the benefits of the process and the endorsement of health authorities,” Bruhn says.

She and Niemira have submitted a proposal to the USDA to further explore the applications of irradiation in leafy greens and to gauge consumer acceptance of this application.

Note for reporters’ use only: For full information about the New Orleans meeting, including access to abstracts of more than 9,000 scientific papers and hundreds of non-technical summaries, visit http://www.eurekalert.org/acsmeet.php.
The paper on this research, AGFD 136, will be presented at 9:00 a.m., Thursday, April 10, 2008, in the Marriott Convention Center, Blaine Kern E, during the symposium, "Intentional and Unintentional Contaminants of Food and Feed."
Brendan A Niemira, Ph.D., is a microbiologist with the USDA's Agricultural Research Service in Wyndmoor, Pa.

ALL PAPERS ARE EMBARGOED UNTIL DATE AND TIME OF PRESENTATION, UNLESS OTHERWISE NOTED
AGFD 136
Inactivation of microbial contaminants in fresh produce
Program Selection: Division of Agricultural & Food Chemistry
Topic Selection: Intentional and Unintentional Contaminants of Food and Feed: Potential Strategies to Prevent Contamination of Food

Abstract
With the microbial safety of fresh produce of increasing concern, conventional sanitizing treatments need to be supplemented with effective new interventions to inactivate human pathogens. Our research group investigates physical and chemical treatments such as hot water pasteurization, gaseous chlorine dioxide, cold plasma and irradiation. Research in biological controls deals with the use of single or multiple isolates of antagonistic bacteria for inhibiting the outgrowth of bacterial human pathogens. Related research in microbial ecology determines how pathogen biofilm formation and interactions with native microflora may alter the efficacy of applied treatments and interventions. This presentation will summarize the advances made in these areas, as well as research results on the process of scaling up effective interventions from laboratory scale to pilot plant scale, including the critical process of evaluating the effects of the various interventions on sensory and nutritional quality attributes, yield, physiology, and shelf-life.

New Method Rapidly Produces Low-Cost Biofuels from Wood, Grass

George Huber of the University of Massachusetts Amherst has received a $400,000 CAREER grant from the National Science Foundation to pursue his revolutionary new method for making biofuels, or “green gasoline,” from wood or grasses, a process that would be much less expensive than conventional gasoline or ethanol made from corn.

Results of Huber’s research were published in the April 2008 issue of ChemSusChem, a publication devoted to environmentally-sound chemistry.

“We’ve proven this method on a small scale in the lab,” says Huber, a professor of chemical engineering. “But we need to make further improvements and prove it on a large scale before it’s going to be economically viable.”

Huber is a nationally recognized expert on biofuels, which are sustainable fuels made from plant materials. In June 2007, he chaired a workshop in Washington, D.C., for the National Science Foundation and the U. S. Department of Energy titled “Breaking the Chemical & Engineering Barriers to Lignocellulosic Biofuels,” which was attended by 71 top experts from academia, industry and governmental agencies.

Huber’s method is for making biofuels from cellulose, the non-edible portion of plant biomass and a major component of grasses and wood. At $10 to $30 per barrel of oil energy equivalent, cellulosic biomass is significantly cheaper than crude oil. The U.S. could potentially produce 1.3 billion dry tons of cellulosic biomass per year, which has the energy content of four billion barrels of crude oil. That’s more than half of the seven billion barrels of crude oil consumed in our country each year. What’s more, biomass as an energy crop could increase the national farm income by $3 to $6 billion per year.

Huber is addressing the lack of an economical process for converting cellulose into liquid biofuels, which is the main roadblock for their mass production. Every conventional conversion method takes several steps, with each step making the whole process more expensive and less feasible. For example, ethanol production from cellulosic biomass currently involves multiple steps, including pretreatment, enzymatic or acid hydrolysis, fermentation, and distillation. Other processes for making biofuels have been hamstrung by similar multi-step methods.

Huber has come up with a technique for producing his “green gasoline” from biomass in one simple step by placing solid biomass feedstocks such as wood in a reactor, which is basically a high-tech still for thermal conversion of feedstock to gasoline. He heats the feedstock by a technique known as catalytic fast pyrolysis, which means the rapid heating of the biomass to between 400 and 600 degrees centigrade, followed by quick cooling. By adding zeolite catalysts to this process, gasoline range hydrocarbons can be directly produced from cellulose within sixty seconds.

“This is a big improvement because it’s all done in one single step, instead of several stages,” explains Huber. “Also, because of the high temperatures we use in the process, the residence time in our reactor is two to 60 seconds. With cellulosic ethanol, your residence time is five to ten days, which means you have to have a huge reactor costing much more money. So we estimate that building a facility to use our process would be much less expensive.”

Using the current cost of wood in Massachusetts, which is $40 per dry ton, as an example of the feedstock he can use in this process, Huber estimates that a gallon of green gasoline can be produced with his method for between $1 and $1.70, depending on how much he can improve the catalytic conversion in his process through standard engineering techniques.

Huber has already demonstrated that this process will work on a small scale in his lab. Now he has to design a reactor and catalysts that are specifically geared for his process. Huber just received a $30,000 grant from the UMass Amherst Office of Commercial Ventures and Intellectual Property, as funded by the UMass president’s office, to develop a prototype reactor to demonstrate green gasoline production on a large scale.

Huber has been working with three other professors at UMass Amherst including Phillip R. Westmoreland, a chemical engineer and expert on fast pyrolisis who has been helping to design the reactor, and William C. Conner, a chemical engineer with expertise in zeolite catalysts. The third researcher is Scott Auerbach, a theoretical chemist from the UMass Amherst chemistry department.

Scientists, Collaborators Create First Superinsulator



Superinsulation may sound like a marketing gimmick for a drafty attic or winter coat. But it is actually a newly-discovered fundamental state of matter created by scientists at the U.S. Department of Energy's (DOE) Argonne National Laboratory in collaboration with several European institutions. This discovery both opens new directions of inquiry in condensed matter physics and breaks ground for a new generation of microelectronics.

Led by Argonne senior scientist Valerii Vinokur and Russian scientist Tatyana Baturina, an international team of scientists from Argonne, Germany, Russia and Belgium fashioned a thin film of titanium nitride with they then chilled to near absolute zero. When they tried to pass a current through the material, the researchers noticed that its resistance suddenly increased by a factor of 100,000 once the temperature dropped below a certain threshold. The same sudden change also occurred when the researchers decreased the external magnetic field.

"Titanium nitride films as well as films prepared from some other materials can be either superconductors or insulators depending on the thickness of the film. If you take the film which is just on the insulating side of the transition and decrease the temperature or magnetic field, then the film all of a sudden becomes a superinsulator," Vinokur said.

Like superconductors, which have applications in many different areas of physics, from accelerators to magnetic levitation (maglev) trains to MRI machines, superinsulators could eventually find their way into a number of products, including circuits, sensors and battery shields.

If, for example, a battery is left exposed to the air, the charge will eventually drain from it in a matter of days or weeks because the air is not a perfect insulator, according to Vinokur. "If you pass a current through a superconductor, then it will carry the current forever; conversely, if you have a superinsulator, then it will hold a charge forever," he said.

Additionally, scientists could eventually form superinsulators that would encapsulate superconducting wires, creating an optimally efficient electrical pathway with almost no energy lost as heat. A miniature version of these superinsulated superconducting wires could find their way into more efficient electrical circuits.

Titanium nitride's sudden transition to a superinsulator occurs because the electrons in the material join together in twosomes called Cooper pairs. When these Cooper pairs of electrons join together in long chains, they enable the unrestricted motion of electrons and the easy flow of current, creating a superconductor. In superinsulators, however, the Cooper pairs stay separate from each other, forming self-locking roadblocks. "In superinsulators, Cooper pairs avoid each other, creating enormous electric forces that oppose penetration of the current into the material,” Vinokur said. "It's exactly the opposite of the superconductor," he added.

The theory behind the experiment stemmed from Argonne's Materials Theory Institute, which Vinokur organized six years ago in the laboratory's Materials Science Division. The MTI hosts a handful of visiting scholars from around the world who then perform cutting-edge research on the most pressing questions in condensed matter physics. Upon completion of their tenure at Argonne, these scientists return to their home institutions but continue to collaborate on the joint projects. The MTI attracts the world's best condensed matter scientists, including Russian "experimental star" Tatyana Baturina, who, according to Vinokur, "became a driving force in our work on superinsulators."

Scientists from the Institute of Semiconductor Physics in Novosibirsk, Russia, Regensburg and Bochum Universities in Germany and IMEC in Leuven, Belgium also participated in the research.


About Argonne
Argonne National Laboratory brings the world’s brightest scientists and engineers together to find exciting and creative new solutions to pressing national problems in science and technology. The nation’s first national laboratory, Argonne conducts leading-edge basic and applied scientific research in virtually every scientific discipline. Argonne researchers work closely with researchers from hundreds of companies, universities, and federal, state and municipal agencies to help them solve their specific problems, advance America’s scientific leadership and prepare the nation for a better future. With employees from more than 60 nations, Argonne is managed by UChicago Argonne, LLC for the U.S. Department of Energy’s Office of Science. (NewsWise)

p53 hampers energy metabolism in cancer cells


The tumour suppressor p53 can limit tumour development by inhibiting aerobic glycolysis reports a paper.

Cancer cells normally shift their metabolism to aerobic glycolysis - the conversion of glucose to lactic acid in the presence of oxygen - which confers an advantage in sustaining tumour growth.

p53 activity is lost in over half of human tumours; its primary role is to eliminate cells that have undergone oncogenic transformation by inducing cell growth arrest or programmed cell death. Nobuyuki Tanaka and colleagues found, by looking at p53-deficient primary fibroblasts, that loss of p53 leads to higher glucose metabolism, and demonstrated that this requires de-repression of the transcription factor NF-kB and one of its target genes called GLUT3.

This work reveals an additional function of p53 in restricting cell proliferation through suppression of NF-kB, which is important for maintaining normal levels of glucose metabolism and cell growth.

Author contact:
Nobuyuki Tanaka (Nippon Medical School, Kawasaki-shi, Japan)
Tel: +81 44 733 1860; E-mail: nobuta@nms.ac.jp

Common genetic variants influencing adult height

Scientists have discovered dozens of common genetic variants influencing adult human height.

Recently, two independent studies reported that common variants near two genes, HMGA2 and GDF5, are associated with variation in human height in the general population. Using substantially larger sample sizes, three groups now report the discovery of dozens of additional variants influencing adult height.

The newly discovered variants explain up to 4% of normal height variation in populations of European ancestry. Individuals carrying predominantly ‘tall’ versions of these variants are, on average, 5 cm taller than individuals carrying only a few of the ‘tall’ variants.

Many of the height-associated variants reside near genes known or suspected to have a role in skeletal development. Others reside near genes that control how cells grow and divide.

Height is considered a classic complex trait with a strong heritable component. Therefore, understanding the genetic basis of this model trait may shed light on the genetic architecture of other traits, including those influencing risk of common diseases.

Author contacts:

Timothy Frayling (Peninsula Medical School, Exeter, UK)
Tel: +44 1392 262935; E-mail: tim.frayling@pms.ac.uk

Kari Stefansson (deCODE Genetics, Reykjavik, Iceland)
Tel: +354 570 1900; E-mail: kstefans@decode.is

Joel Hirschhorn (Broad Institute of Harvard and MIT, Cambridge, MA, USA)
Tel: +1 617 919 2129; E-mail: joelh@broad.mit.edu

Host-to-graft disease spread in Parkinson disease?

Cell transplants have long been proposed as a possible therapy for Parkinson disease, but a series of reports suggest that the pathology may spread from the host to the transplants.

Parkinson disease results from the abnormal aggregation of a protein known as alpha-synuclein and the degeneration of the substantia nigra, a dopamine-releasing region of the midbrain. Therapies for the disease aiming at replacing the lost cells have given hope and, in the 1990s, clinical trials transplanting dopaminergic fetal brain tissue into the brains of patients with Parkinson took place.

Two independent groups led by Patrik Brundin and by Jeffrey Kordower report that the transplanted tissue in some subjects shows evidence of alpha-synuclein aggregates. This observation is striking because the grafts were too young to develop this on their own, and the fetal tissue had been placed into the striatum, a brain region that receives input from the substantia nigra but does not develop alpha-synuclein aggregates in Parkinson disease. So, in these subjects, the disease seems to have spread from the host to the graft.

But not all studies agree. A third study, led by Ole Isacson, failed to show Parkinson-like pathology in the transplants from a different set of similar subjects, finding instead a large proportion of serotonergic, and not only dopaminergic, neurons within the grafts.

As current efforts to develop cell-replacement therapies focus on the use of stem cells to generate substantia nigra-like dopaminergic neurons, the findings of these three groups on long-term transplant recipients add a level of complexity to the idea of curing Parkinson disease with grafted tissue.

Author contacts:

Patrik Brundin (Wallenberg Neuroscience Center, Lund, Sweden)
Tel: +46 46 222 05 63; E-mail: patrik.brundin@med.lu.se

Jeffrey Kordower (Rush University Medical Center, Chicago, IL, USA)
Tel.: +1 312 563 3570; E-mail: jkordowe@rush.edu

Ole Isacson (Harvard Medical School/McLean Hospital, Belmont, MA, USA)
Tel: +1 617 855 3283; E-mail: isacson@hms.harvard.edu

Coastal pollution could produce an unhealthy chemical cocktail

The reaction of chemical compounds in the pollution from cities and ships with sea salt aerosols from the ocean could affect air quality in coastal areas where the two meet, according to a research. A team measured high levels of nitryl chloride, an active halogen implicated in ground-level ozone production, in industrially polluted air along the southeast coast of the US, implying that ozone pollution could be particularly high where industrial combustion products meet the ocean, as in many megacities around the world.

James Roberts and colleagues measured unexpectedly high levels of nitryl chloride in ship exhaust plumes along the southeast coast of the US. They show that this chemical compound is produced during the night by the reaction of the nitrogen oxides in polluted air from ships or cities with the chlorine from sea salt. With the help of the morning sunlight, nitryl oxide is rapidly split into a reactive radical that can produce ozone in combination with suitable atmospheric compounds, and nitrogen oxides. (researchsea)
Author contact:

James Roberts (National Oceanic and Atmospheric Administration, Boulder, CO, USA)
Tel: +1 303 497 3982, E-mail: James.M.Roberts@noaa.gov

Algae Could One Day be Major Hydrogen Fuel Source
As gas prices continue to soar to record highs, motorists are crying out for an alternative that won’t cramp their pocketbooks.

Scientists at U.S. Department of Energy’s Argonne National Laboratory are answering that call by working to chemically manipulate algae for production of the next generation of renewable fuels – hydrogen gas.

“We believe there is a fundamental advantage in looking at the production of hydrogen by photosynthesis as a renewable fuel,” senior chemist David Tiede said. “Right now, ethanol is being produced from corn, but generating ethanol from corn is a thermodynamically much more inefficient process.”

Some varieties of algae, a kind of unicellular plant, contain an enzyme called hydrogenase that can create small amounts of hydrogen gas. Tiede said many believe this is used by Nature as a way to get rid of excess reducing equivalents that are produced under high light conditions, but there is little benefit to the plant.
Tiede and his group are trying to find a way to take the part of the enzyme that creates the gas and introduce it into the photosynthesis process.

The result would be a large amount of hydrogen gas, possibly on par with the amount of oxygen created.

“Biology can do it, but it’s making it do it at 5-10 percent yield that’s the problem,” Tiede said. “What we would like to do is take that catalyst out of hydrogenase and put into the photosynthetic protein framework. We are fortunate to have Professor Thomas Rauchfuss as a collaborator from the University of Illinois at Champaign-Urbana who is an expert on the synthesis of hydrogenase active site mimics.”

Algae has several benefits over corn in fuel production. It can be grown in a closed system almost anywhere including deserts or even rooftops, and there is no competition for food or fertile soil. Algae is also easier to harvest because it has no roots or fruit and grows dispersed in water.

“If you have terrestrial plants like corn, you are restricted to where you could grow them,” Tiede said. “There is a problem now with biofuel crops competing with food crops because they are both using the same space. Algae provides an alternative, which can be grown in a closed photobioreactor analogous to a microbial fermentor that you could move any place.”

Tiede admitted the research is its beginning phases, but he is confident in his team and their research goals. The next step is to create a way to attach the catalytic enzyme to the molecule.

Funding for the research was provided by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences.

Argonne National Laboratory brings the world's brightest scientists and engineers together to find exciting and creative new solutions to pressing national problems in science and technology. The nation's first national laboratory, Argonne conducts leading-edge basic and applied scientific research in virtually every scientific discipline. Argonne researchers work closely with researchers from hundreds of companies, universities, and federal, state and municipal agencies to help them solve their specific problems, advance America’s scientific leadership and prepare the nation for a better future. With employees from more than 60 nations, Argonne is managed by UChicago Argonne, LLC for the U.S. Department of Energy's Office of Science.

Astronomers Find Suspected Medium-Size Black Hole in Omega Centauri


A well-known star cluster that glitters with the light of millions of stars may have a mysterious dark object tugging at its core. Astronomers have found evidence for a medium-size black hole at the core of Omega Centauri, one of the largest and most massive globular star clusters orbiting our Milky Way Galaxy.

The intermediate-mass black hole is estimated to be roughly 40,000 times the mass of the Sun. The black hole was discovered with NASA's Hubble Space Telescope and Gemini Observatory on Cerro Pachon in Chile. The ancient cluster is located 17,000 light-years from Earth.

Globular clusters are gravitationally bound swarms of typically up to a million stars. There are more than 200 globular clusters in our Milky Way Galaxy.

"This result shows that there is a continuous range of masses for black holes, from supermassive, to intermediate, to small, stellar types," explained astronomer Eva Noyola of the Max-Planck Institute for Extraterrestrial Physics in Garching, Germany, and leader of the team that made the discovery.

"This finding also is important because the theory of formation for supermassive black holes requires seed black holes that are exactly in the mass range of the one we found. Such seeds have not been identified so far. If these types of intermediate-mass black holes happen to be common in star clusters, then they can provide numerous seeds for the formation of the supermassive black holes."

Astronomers have debated the existence of moderately sized black holes because they have not found strong evidence for them, and there is no widely accepted mechanism for how they could form. They have ample evidence that small black holes of a few solar masses are produced when giant stars die. There is similar evidence that supermassive black holes weighing the equivalent of millions to billions of solar masses sit at the heart of many galaxies, including our Milky Way.

"Before this observation, we had only one example of an intermediate-mass black hole in the globular cluster G1, in the nearby Andromeda Galaxy," said astronomer Karl Gebhardt of the University of Texas at Austin and a member of the team that made the discovery.

Noyola and Gebhardt used Hubble and Gemini to gather evidence for the black hole. Hubble's Advanced Camera for Surveys showed how the stars are bunching up near the center of Omega Centauri, as seen in the gradual increase in starlight near the center. Measuring the speed of the stars swirling near the cluster's center with the Gemini Observatory, the astronomers found that the stars closer to the core are moving faster than the stars farther away. The measurement implies that some unseen matter at the core is tugging on stars near it.

By comparing these results with standard models, the astronomers determined that the most likely cause of this accelerating stellar traffic jam is the gravitational pull of a massive, dense object, the astronomers explained. They also used models to calculate the black hole's mass.

Although the presence of an intermediate-mass black hole is the most likely reason for the stellar speedway near the cluster's center, the astronomers said they have considered a couple of other possible causes.

In the first scenario, the traffic jam of stars near the center is due to a collection of burned-out stars such as white dwarfs or neutron stars. Another possibility is that stars in the center of Omega Centauri have elongated orbits that would make the stars closest to the center appear to speed up.

"For both alternative scenarios it is very hard to get stars to behave that way, either the burned-out stars really bunched up in the center or many stars with very elongated orbits," Noyola explained. "The normal evolution of a star cluster like Omega Centauri should not end up with stars behaving in those ways. But even if we assume that either scenario did happen somehow, both configurations are expected to be very short lived. A clump of burned-out stars, for example, are expected to move farther away from the center quickly. The stars with elongated orbits are expected to become circular very quickly."

Many astronomers regard Omega Centauri as an unusual globular cluster because of its enormous size and mass. In fact, the 12 billion year old cluster has long been suspected of being the stripped-down core of a dwarf galaxy that had been shredded of most of its stars long ago. A previous Hubble survey of supermassive black holes and their host galaxies showed a correlation between the mass of a black hole and that of its host. Astronomers estimated that the mass of the suspected Omega Centauri dwarf galaxy was roughly 10 million solar masses. If lower-mass galaxies obey the same rule, then the mass of Omega Centauri does match that of its black hole.

Noyola and Gebhardt will use the European Southern Observatory's Very Large Telescope in Paranal, Chile to conduct follow-up observations of the velocity of the stars near the cluster's center to confirm the discovery.

The finding will appear in the April 10 issue of The Astrophysical Journal.

Black Carbon Pollution Emerges as Major Player in Global Warming


Black carbon, a form of particulate air pollution most often produced from biomass burning, cooking with solid fuels and diesel exhaust, has a warming effect in the atmosphere three to four times greater than prevailing estimates, according to scientists in an upcoming review article in the journal Nature Geoscience.

Scripps Institution of Oceanography at UC San Diego atmospheric scientist V. Ramanathan and University of Iowa chemical engineer Greg Carmichael, said that soot and other forms of black carbon could have as much as 60 percent of the current global warming effect of carbon dioxide, more than that of any greenhouse gas besides CO2. The researchers also noted, however, that mitigation would have immediate societal benefits in addition to the long term effect of reducing greenhouse gas emissions.

The article, “Global and regional climate changes due to black carbon,” will be posted in the online version of Nature Geoscience on Sunday, March 23.

“Observationally based studies such as ours are converging on the same large magnitude of black carbon heating as modeling studies from Stanford, Caltech and NASA,” said Ramanathan. “We now have to examine if black carbon is also having a large role in the retreat of arctic sea ice and Himalayan glaciers as suggested by recent studies.”

In the paper, Ramanathan and Carmichael integrated observed data from satellites, aircraft and surface instruments about the warming effect of black carbon and found that its forcing, or warming effect in the atmosphere, is about 0.9 watts per meter squared. That compares to estimates of between 0.2 watts per meter squared and 0.4 watts per meter squared that were agreed upon as a consensus estimate in a report released last year by the Intergovernmental Panel on Climate Change (IPCC), a U.N.-sponsored agency that periodically synthesizes the body of climate change research.

Ramanathan and Carmichael said the conservative estimates are based on widely used computer model simulations that do not take into account the amplification of black carbon’s warming effect when mixed with other aerosols such as sulfates. The models also do not adequately represent the full range of altitudes at which the warming effect occurs. The most recent observations, in contrast, have found significant black carbon warming effects at altitudes in the range of 2 kilometers (6,500 feet), levels at which black carbon particles absorb not only sunlight but also solar energy reflected by clouds at lower altitudes.

Between 25 and 35 percent of black carbon in the global atmosphere comes from China and India, emitted from the burning of wood and cow dung in household cooking and through the use of coal to heat homes. Countries in Europe and elsewhere that rely heavily on diesel fuel for transportation also contribute large amounts.

“Per capita emissions of black carbon from the United States and some European countries are still comparable to those from south Asia and east Asia,” Ramanathan said.

In south Asia, pollution often forms a prevalent brownish haze that has been termed the “atmospheric brown cloud.” Ramanathan’s previous research has indicated that the warming effects of this smog appear to be accelerating the melt of Himalayan glaciers that provide billions of people throughout Asia with drinking water. In addition, the inhalation of smoke during indoor cooking has been linked to the deaths of an estimated 400,000 women and children in south and east Asia.

Elimination of black carbon, a contributor to global warming and a public health hazard, offers a nearly instant return on investment, the researchers said. Black carbon particles only remain airborne for weeks at most compared to carbon dioxide, which remains in the atmosphere for more than a century. In addition, technology that could substantially reduce black carbon emissions already exists in the form of commercially available products.

Ramanathan said that an observation program for which he is currently seeking corporate sponsorship could dramatically illustrate the benefits. Known as Project Surya, the proposed venture would provide some 20,000 rural Indian households with smoke-free cookers and equipped to transmit data. At the same time, a team of researchers led by Ramanathan would observe air pollution levels in the region to measure the effect of the cookers.

Carmichael said he hopes that the paper’s presentation of the immediacy of the benefits will make it easier to generate political and regulatory momentum toward reduction of black carbon emissions.

“It offers a chance to get better traction for implementing strategies for reducing black carbon,” he said. (Newswise)

Seeking schizophrenia genes

Researchers map genetic alterations associated with human schizophrenia


Japanese scientists have linked atypical expression patterns of the gene FABP7, which encodes the brain fatty acid binding protein 7, with human schizophrenia. Although initially attributed to environmental abnormalities, this debilitating disease is now accepted as being influenced by a strong, yet likely multifactorial, genetic component.

The phenotypic, or behavioral, outcomes of schizophrenia are perhaps just as complicated as the genotypic alterations underlying the disease. Fortunately, suppression of a particular startle response—known as prepulse inhibition (PPI)—provides an easily measurable biological readout of the sensory motor gating mechanisms that are often impaired in schizophrenia.

In an effort to identify genes associated with schizophrenia, a team led by Takeo Yoshikawa at the RIKEN Brain Science Institute in Wako, mapped genetic alterations associated with PPI in mice1.

After tracking the PPI responses of a panel of distinct inbred mouse strains for over one year, the researchers intercrossed the strains having the lowest and highest PPI scores. Next, the team scanned the genomes of the progeny for sets of microsatellite markers, or genetic ‘tags’, and compared the presence of these tags with the PPI scores.

Using progressively rigorous sets of tags, the researchers linked impaired PPI to a region of chromosome 10 containing approximately 30 genes. The team honed in on Fabp7 (Fig. 1), one gene within this region, because of its influence over the metabolism of the polyunsaturated fatty acid DHA (docosahexaenoic acid), a process often impaired in schizophrenia.

Encouragingly, although stronger in males than in females, human schizophrenia patients exhibit abnormally high expression of FABP7 similar to mice exhibiting defective PPI responses. Notably, mice rendered genetically deficient in Fabp7 also score low in PPI measurements and display stronger behavioral responses to chronic NMDA receptor antagonist treatment, another feature of schizophrenia.

Although the team detected defects in the maintenance of neural progenitor cells in Fabp7-deficient mice, future work is needed to elucidate the precise molecular mechanism through which alterations in Fabp7 expression promote schizophrenia-like behavior in mice and humans.

Similarly, why males seem to be more strongly affected by Fabp7 over-expression remains unclear. However, sex hormone-responsive elements in the DNA regions controlling Fabp7 expression might play a role.

“It is well known that malnutrition in utero increases the probability of future schizophrenia. Our results raise the importance of cohort studies to examine whether replenishment of DHA in pregnant mothers can be beneficial in reducing the chance of schizophrenia development in offspring,” says Yoshikawa.
Reference

1. Watanabe, A., Toyota, T., Owada, Y., Hayashi, T., Iwayama, Y., Matsumata, M., Ishitsuka, Y., Nakaya, A., Maekawa, M., Ohnishi, T., et al. Fabp7 maps to a quantitative trait locus for a schizophrenia endophenotype. PLoS Biology 5, 2469–2483 (2007).

Quantum corkscrews from twisting electron waves



RIKEN researchers have shown that electron beams, like light, can be twisted into vortices that have useful functions

Recently scientists discovered that light can be twisted like a corkscrew around its direction of travel. This unusual quantum feature allows photons to whirl around in a vortex, even when no external force is applied to the beam. Now researchers from the RIKEN Frontier Research System in Wako have shown that the same kind of vortices can be produced in beams of electrons1, promising novel applications.

“When a light or electron beam is twisted, waves at the central axis cancel each other out forming a dark core, like at the eye of a storm (Fig. 1),” says RIKEN scientist Franco Nori, also with the University of Michigan in the USA. His RIKEN collaborator Sergey Savel’ev, also at Loughborough University in the UK, adds: “As the photons or electrons spin around the axis, they carry orbital angular momentum that can rotate an electric dipole.”

To explain these properties, the researchers solved the Schrödinger equation of quantum mechanics for a twisting beam of electrons. This produced new dynamical equations that are highly analogous to those found for light. The similarities arise because the twisting angular momentum of the electrons interacts with their forward motion in the same way that intrinsic angular momentum (spin) interacts with the motion of photons, which is known as spin-orbit coupling.

The theory implies that vortices in electron beams have all the features of optical vortices. This reinforces the famous concept of wave-particle duality, which states that all particles have a wave associated with them. More importantly, it means that the useful applications of optical vortices could be replicated at much shorter wavelengths.

In practice, optical vortices can be made by passing a laser beam through a fork-shaped computer generated hologram. Electron-beam vortices could be produced in a similar fashion, using a thin crystal plate with a dislocation. Such vortices could power tiny nanomotors and nano-engines, or could be used in telecommunications by storing information in the optical vorticity, or the intensity of twisting. The vorticity is robust against perturbations, so this potential future technology could reduce the loss of information during optical communications.

Furthermore, electron vortices are predicted to cause a shift of the electron beam at right angles to an electric field. “The unique electron microscope developed by Akira Tonomura's group, also at RIKEN, could observe this unusual effect,” says Nori. “Such work would considerably expand the textbook analogy between matter and waves which Tonomura helped to establish in pioneering experiments.”

1. Bliokh, K. Y., Bliokh, Y. P., Savel’ev, S. & Nori, F. Semiclassical dynamics of electron wave packet states with phase vortices. Physical Review Letters 99, 190404 (2007).

Magnetic flux quanta get a dance lesson


Alternating electric current can be used to precisely control tiny vortices of magnetism

Swirling cyclones of magnetism at the sub-micron scale that can trouble superconducting devices have been tamed by RIKEN scientists. Their technique could help to minimize magnetic noise in sensitive superconducting detectors, and could even help to build a new generation of devices for supercomputers.

When cooled below a critical temperature, superconductors carry electricity with no resistance. But magnetic fields can disrupt this behavior by introducing magnetic flux quanta into the material. These quanta, also known as vortices, are the basic units of magnetism, just as the charge of an electron is the fundamental unit of electricity.

Scientists can control how these vortices move by introducing tiny traps, or nano-holes, into the structure of the superconducting material. But since the pattern of these tiny traps is fixed once the device is made, it’s a relatively inflexible approach that restricts the way the vortices can be moved around.

Now, a team including Franco Nori and Sergey Savel’ev of RIKEN’s Frontier Research System in Wako, have shown how to precisely control the movement of magnetic flux quanta with an alternating electric current (AC)1.

The scientists tested the method on a high-temperature superconductor made from bismuth, strontium, calcium and copper (Bi2Sr2CaCu2O8 + δ). When the electrical current oscillates back and forth, the vortices obediently follow their rhythm.

Nori, also based at University of Michigan, US, says that the technique is like leading the magnetic flux quanta through a series of dance steps (Fig. 1). “The applied current acts as the leading dance partner and the vortices follow the steps imposed by the current,” he says.

More complicated rhythms are created by adding more overlapping alternating currents, allowing the scientists to steer their magnetic flux quanta through the material. “The two ‘control knobs’ we use are the ratio of the AC frequencies, and the relative phase difference between them,” explains Nori.

Savel’ev, also at Loughborough University, UK, adds: “By slowly varying either one of these two control knobs, vortices are pushed either in one direction or the opposite.”

Nori says that the technique could also be used to manipulate trapped ions, moving electrons around in certain types of crystal, or even separating different types of very tiny particles.

In the longer term, the scientists hope that the technique could contribute to the burgeoning field of ‘fluxtronics’—moving magnetic quanta around to manipulate computer data. This would potentially be much faster that conventional methods relying on shuttling electrons between transistors.

1. Ooi, S., Savel'ev, S., Gaifullin, M. B., Mochiku, T., Hirata, K. & Nori, F. Nonlinear nanodevices using magnetic flux quanta. Physical Review Letters 99, 207003 (2007).

Two-protein Complex Protects Nerve Cells


Since its discovery as a protein that gets specifically released in response to brain injury, ciliary neurotrophic factor (CNTF) has prompted much interest as a potential therapeutic agent. However, numerous experiments have met with limited success, until now; a research team shows that co-administrating CNTF with its receptor promotes the growth and survival of neurons.

While the receptor for CNTF is normally tied to the surface of neurons, this tether is frequently chopped off during trauma, which led Mark Ozog, Christian Naus and colleagues to suspect that CNTF and the free-floating receptor might act in a complex. Their study appears in JBC online February 29.

They treated mouse neurons with CNTF, its receptor (CNTFR), or both and then exposed the cells to massive amounts of the neurotransmitter glutamate, enough to kill the neurons by over-stimulating them. CNTF or CNTFR alone did not protect the neurons, but the two complexed together could. In addition, the complex could foster increased growth of nerve cells.

Ozog, Naus and colleagues next ran a microarray analysis of the CNTF complex and found that it altered the expression of 47 genes associated with nerve growth and survival, suggesting it protects neurons through multiple direct and indirect mechanisms and thus making it a strong therapeutic candidate.

Researchers Find Key Step in Programmed Cell Death

Investigators at St. Jude Children’s Research Hospital have discovered a dance of proteins that protects certain cells from undergoing apoptosis, also known as programmed cell death. Understanding the fine points of apoptosis is important to researchers seeking ways to control this process.

In a series of experiments, St. Jude researchers found that if any one of three molecules is missing, certain cells lose the ability to protect themselves from apoptosis. A report on this work appears in the advance online publication of Nature.

“This is probably the first description of what is happening mechanistically that contributes to the ability of cells to delay apoptosis,” said James Ihle, Ph.D., the paper’s senior author and chair of the St. Jude Department of Biochemistry. “It provides incredible insights into how three proteins work and how they can control apoptosis.”

The molecular interactions that St. Jude researchers describe in Nature play out in nerve cells and blood cells that develop from hematopoietic (blood-forming) stem cells.

A research team elsewhere recently reported that Kostmann’s syndrome, a potentially fatal inherited deficiency of granulocytes in children, caused by excessive apoptosis of granulocytes, results from a deficiency in one of the three proteins, called Hax1.

“This suggests that the protein is playing basically the same role in humans as we described in mice,” Ihle said.

Apoptosis rids the body of faulty or unneeded cells. However, molecular malfunctions that trigger apoptosis may cause some diseases, including Parkinson’s disease. Understanding the biochemical interactions that control the extent of programmed cell death could lead to new treatments.

St. Jude biochemists have long studied how cytokines—small proteins used by neurons and blood-borne cells to communicate messages—contribute to keeping cells alive. For example, they demonstrated earlier that most cytokines controlling hematopoietic cells require an enzyme called Jak2, or Jak3 in lymphocytes, at the receptors where cytokines attached to the cell.

In screening for components that are regulated by the Jak enzymes, the St. Jude team found the Hax1 protein.

“That was intriguing because several studies suggested that Hax1 was controlled by cytokine signaling,” Ihle said. “Also, studies have suggested that if you overexpressed Hax1 in cells, the cells were protected from undergoing apoptosis.”

To pursue this lead, the researchers genetically engineered mice that lacked the gene for Hax1. The results showed that apoptosis in the animals’ brain caused extensive nerve cell degeneration that killed the mice within 10 to 12 weeks.

Second, apoptosis in immune-system lymphocytes occurred in the altered mice eight hours sooner than in those with the Hax1 gene, when limited amounts of cytokines were available.

“That additional window of survival is extremely important because in the body, cytokines are limiting.” Ihle said. “The key observation was that Hax1 was important in helping cells to survive. Importantly, what happened to the mice we generated was remarkably similar to what happens if you remove the mitochondrial enzymes called HtrA2 or Parl.”

Exploring the similarities, the investigators found that Hax1 and Parl pair up in the inner membrane of the mitochondria—tiny chemical packets that serve as the main energy source for cells. HtrA2 is made in the cell’s cytoplasm and is transported into the mitochondria, where the enzyme must have a region removed for it to be active. This requires snipping away 133 amino acids, the building blocks of proteins. The St. Jude researchers demonstrated that it is the Hax1/Parl pair that positions HtrA2 to allow the precise snipping that is required. Without Hax1, the snipping does not occur and HtrA2 remains inert.

In lymphocytes, members of the Bcl-2 family of proteins both protect and initiate apoptosis. For this reason, Ihle and the researchers explored this family of proteins to understand why lymphocytes needed an active HtrA2 mitochondrial enzyme. This led them to discover that if active HtrA2 were present, the incorporation of a protein called Bax into the mitochondrial outer membrane did not occur. This was significant since accumulation of Bax in the outer mitochondrial membrane allows the release of proteins that set off a chain of biochemical reactions, including the activation of enzymes that are responsible for cell death.

Other authors of this study include Jyh-Rong Chao, Kelli Boyd, Evan Parganas, Cheol Yi Hong and Joseph T. Opferman (all St. Jude).

This work was supported in part by grants from the National Institutes of Health and ALSAC.

Researchers Discover Novel Way to Develop Tumor Vaccines


Researchers at the University of Southern California (USC) have uncovered a new way to develop more effective tumor vaccines by turning off the suppression function of regulatory T cells. The results of the study, titled “A20 is an antigen presentation attenuator, and its inhibition overcomes regulatory T cell-mediated suppression,” will be published in Nature Medicine on March 2, 2008.

“Under normal circumstances, regulatory T cells inhibit the immune system to attack its own cells and tissues to prevent autoimmune diseases. Cancer cells take advantage of regulatory T cells' suppressor ability, recruiting them to keep the immune system at bay or disabling the immune system’s attack provoked by tumor vaccines.” says Si-Yi Chen, M.D., Ph.D., professor of immunology and molecular microbiology at the USC/Norris Comprehensive Cancer Center and the Keck School of Medicine of USC. “Our study provides a new vaccination strategy to overcome the regulatory T cells’ immune suppression while avoiding non-specific overactivation of autoreactive T cells and pathological autoimmune toxicities.”

The study identified a new molecular player called A20, an enzyme that restricts inflammatory signal transduction in dendritic cells. When it is inhibited, the dendritic cells overproduce an array of cytokines and co-stimulatory molecules that triggers unusually strong immune responses that cannot be suppressed by regulatory T cells. The resulting hyperactivated immune responses triggered by A20-deficient dendritic cells are capable of destroying various types of tumors that are resistant to current tumor vaccines in mice.

“Through a series of immunological studies, we have identified A20 as an essential antigen presentation attenuator that prevents the overactivation and excessive inflammation of the dendritic cells, which, in turn, restricts the potency of tumor vaccines,” says Chen.

The immune system’s dendritic cells are the guardian cells of the immune systems and play an important role in activating immune responses to recognize and destroy tumor cells. Tumor vaccines have been designed and developed to incite the immune response to cancer cells so that the immune system can attack and destroy cancer cells. However, discovering A20’s role in restricting immune responses has led to a method for blocking tumors from using regulatory T cells for protection.

“Despite intensive efforts, tumor vaccines have been largely ineffective in causing tumor regression in the clinic,” says Chen. “The vaccination approach we developed inhibits the key inhibitor in tumor antigen-loaded dendritic cells to selectively hyperactivate immune responses and to tip the balance from immune suppression in tumor-bearing hosts or cancer patients to effective antitumor immunity.”

This approach is capable of overcoming the regulatory T cells’ suppression mechanism and will allow for a new generation of tumor vaccines to be developed. The next step is to translate these findings into a human clinical trial, says Chen.

The National Institutes of Health and the Leukemia and Lymphoma Society funded the study.

Xiao-Tong Song, Kevin E. Kabler, Lei Shen, Lisa Rollins, Xue F. Huang, Si-Yi Chen. “A20 is an antigen presentation attenuator, and its inhibition overcomes regulatory T cell-mediated suppression.” Nature Medicine, Mar. 2, 2008. Digital object identifier number 10.1038/nm1721.
(NewsWise)

Inventor Develops an Electrical Apparatus That Produces FREE Energy


TAMPA, Fla., Feb. 5, 2008 -- Alternative energy researcher and inventor O'Keefe Natheniel Douglas has recently developed an apparatus for duplicating electrical power as it flows through a bypass circuit whereas the primary power remains unaltered and the duplicated induced energy increases the sum of the output power to become greater than the input power.

Unlike a transformer, the Duplicator is connected in a series with the load. The Duplicator harnesses the changing magnetic flux of the passing current to generate additional current into an independent circuit. Electron drift is comprised of electromotive force in random directions. The Duplicator's inductive line of force simply navigates a portion of this drift into a selected direction, thus, generating an electric current, preferably described as duplicated current. Duplication requires no energy transfer or energy depletion, therefore, there is no electrical energy lost within the main circuit.

Power Duplicator will amplify electrical energy on both small and large scale, without limitation to the number of duplications. The duplicated energy can also be connected in parallel with the passing energy - and in series with another Duplicator. The interconnection between Duplicators, series and parallel, are infinite. A relatively small electrical energy source is required to initiate the duplicating reaction. The technology will diminish and undermine the need for nuclear energy conversion plants and long-distance power plants. Because the Duplicator converts and duplicates all forms of electrical energy (alternating and direct), the technological implementations are quite versatile, thus allowing the adaptation for integration and mobility.

It is impelling to discuss in brief its ancestor - the transformer. Transformers may be used to manipulate current and voltage, a very unique trait. Electrical transformers have the potential to multiply current indefinitely within its primary circuit, and voltage indefinitely within its secondary circuit - limited only to engineering. Transformers, similar to the Duplicator, amplify power. Without this amplification, modern transformers would never exceed 45 percent efficiency. For any type of induction, the inducing power has to be twice the induced power in order to cancel opposing force of the induced and to sustain induction. Transformers held the key to power amplification, yet mutual induction retards their full potential. Power Duplicator provides the necessary modifications transformer technology lacks for efficient power amplification.

The challenge started around seven years ago. The inventor was driving through rural Georgia and could not help but notice the miles and miles stretch of high-tension power lines along the highway. He wondered to himself, "What if I could tap into the varying magnetic field these wires produced to obtain free energy?" He later started the research project "In Search of FREE Energy." Advance research into transformer technology provided assurance that fuels his determination - yet still there was a missing link. On September 19th, 2007 he found it.

Sleep onset and duration uncoupled



Receptors producing synaptic inhibition regulate the time it takes to get to sleep. This work begins to dissect the biological mechanisms underlying the differences between various types of insomnia.

Drosophila are used as a model for understanding sleep because flies replicate many of the behavioral characteristics of mammalian sleep. This research has not yet produced evidence that the pathways targeted by insomnia drugs in humans are necessary for sleep in flies, however, casting doubt of the relevance of fly sleep as a model for human sleep.

Using genetics and pharmacology, Leslie Griffith and colleagues demonstrate that the biophysical properties of a particular inhibitory receptor influenced both falling and staying asleep in flies, but in different ways. Manipulating receptor desensitization only affected sleep onset, uncoupling the control of sleep initiation and maintenance.

This work further confirms the validity of Drosophila as a model of mammalian sleep and provides a biological explanation for a specific type of insomnia. Future studies exploring other aspects of sleep regulation involving inhibitory receptors may assist in better targeting of drugs designed to specifically influence one particular aspect of sleep without unnecessarily affecting other aspects.

Author contact:
Leslie Griffith (Brandeis University, Waltham, MA, USA)
Tel: +1 781 736 3125; E-mail: griffith@brandeis.edu

Mother knows best



Breast feeding may help protect babies against allergic asthma reports a paper in this week’s Nature Medicine. Airborne allergen is able to pass from mother to child through breast milk, which creates a tolerance to the allergen.

Allergic asthma affects 300 million people worldwide and is characterized by obstruction of the respiratory pathways in response to allergen exposure. Its prevalence has increased in recent decades, probably due to changes in environmental factors. Indeed, exposure to environmental antigens during infancy reduces the likelihood of developing asthma.

Valerie Julia and her colleagues investigated whether exposing lactating mice to an airborne allergen—ovalbumin—affected asthma development in the offspring. They found that ovalbumin was efficiently transferred from the mother to the neonate through the milk, leading to the development of immunological tolerance. Tolerance induction relied on the presence of transforming growth factor-beta and was mediated by regulatory CD4+ T lymphocytes, but did not require the transfer of immunoglobulins through the milk.

Breast milk-mediated transfer of an antigen to the neonate can result in oral tolerance induction, leading to antigen-specific protection from allergic asthma. These observations may pave the way for the design of new strategies to prevent the development of allergic diseases.

Author contact:
Valerie Julia (INSERM-UNSA, Valbonne, France)
Tel. +33 4 93 95 77 85;E-mail: vjulia@unice.fr

An amicable separation



Graphene — a carbon-based nanomaterial known for its unique electronic, thermal and mechanical properties — can form stable dispersions in water without the need for additional chemical stabilizers. The research has practical implications for the development of coatings to reduce static build-up on materials.

Graphene is the name given to the individual sheets of carbon, just one atom thick, that stack together to form graphite. Keeping graphene sheets separate from one another is a difficult task because they tend to stick together, forming larger structures that are not particularly useful. Now, however, using a sequence of chemical reactions, a team led by Gordon Wallace and Dan Li have shown how aqueous dispersions of well-separated graphene sheets can be made from graphite — an abundant and inexpensive starting material.

Rather than relying on either polymer or surfactant stabilizers, their approach maximizes the electrostatic charge on the graphene sheets, ensuring that they repel one another instead of clumping together. This low-cost approach offers the potential for large-scale production of stable graphene colloids that can be processed using well-established solution-based techniques — such as filtration or spraying — to make conductive films. In addition to antistatic coatings, these materials are expected to have applications in flexible transparent electronics, high-performance composites and nanomedicine.

Author contact:
Gordon Wallace (University of Wollongong, New South Wales, Australia)
Tel: +61 2 4221 3127; E-mail: gwallace@uow.edu.au

Dan Li (University of Wollongong, New South Wales, Australia)
Tel: +61 2 4221 3319; E-mail: danli@uow.edu.au