DNA wires' could help physicians diagnose disease

Credit: Comstock/Thinkstock

Scientists have found that Mother Nature uses DNA as a wire to detect the constantly occurring genetic damage and mistakes that can result in diseases like cancer. DNA wires are potentially useful in identifying people at risk for certain diseases. 

That topic ― DNA wires and their potential use in identifying people at risk for certain diseases ― is the focus of a plenary talk on August 19 during the 244th National Meeting & Exposition of the American Chemical Society in Philadelphia, Pennsylvania.

"DNA is a very fragile and special wire," said Jacqueline K. Barton, Ph.D., who delivered the talk. "You're never going to wire a house with it, and it isn't sturdy enough to use in popular electronic devices. But that fragile state is exactly what makes DNA so good as an electrical biosensor to identify DNA damage."

Barton won the U.S. National Medal of Science, the nation's highest honor for scientific achievement, for discovering that cells use the double strands of the DNA helix like a wire for signaling, which is critical to detecting and repairing genetic damage. She is a professor of chemistry and is chair of the division of chemistry and chemical engineering at the California Institute of Technology in Pasadena.

Damage is constantly occurring to DNA, Barton explained ― damage that skin cells, for instance, receive from excessive exposure to sunlight or that lung cells get hit with from carcinogens in cigarette smoke. Cells have a natural repair system in which special proteins constantly patrol the spiral-staircase architecture of DNA. They monitor the 3 billion units, or "base pairs," in DNA, looking for and mending damage from carcinogens and other sources.

Barton and other scientists noticed years ago that the DNA architecture chemically resembles the solid-state materials used in transistors and other electronic components. And DNA's bases, or units, are stacked on top of each other in an arrangement that seemed capable of conducting electricity.

"It's like a stack of copper pennies," said Barton. "And when in good condition and properly aligned, that stack of copper pennies can be conductive. But if one of the pennies is a little bit awry ― if it's not stacked so well ― then you're not going to be able to get good conductivity in it. But if those bases are mismatched or if there is any other damage to the DNA, as can happen with damage that leads to cancer, the wire is interrupted and electricity will not flow properly."

Barton's team established that the electrons that comprise a flow of electricity can move from one end of a DNA strand to the other, just as they do through an electrical wire. In one recent advance, the team was able to send electricity down a 34-nanometer-long piece of DNA. That might not sound like much -- a nanometer is one-tenth the width of a human hair. But that is just the right scale for use in medical diagnostic devices and biosensors to pick up on mutations, or changes, in DNA that could lead to cancer and other diseases.

Barton's research suggested that DNA uses its electrical properties to signal repair proteins that fix DNA damage. If the DNA is no longer conducting electricity properly, that would be a signal for repair proteins to do their thing. Barton's team is applying that knowledge in developing "DNA chips," devices that take advantage of DNA's natural electrical conductivity and its ability to bind to other strands of DNA that have a complementary sequence of base units, and thus probe that sequence for damage. Such a DNA chip would help diagnose disease risk by changes in electrical conductivity resulting from mutations or some other damage.

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Full color images at 100,000 dots-per-inch resolution, using metal-laced nano-structures

Inspired by colorful stained-glass windows, researchers from Singapore have demonstrated an innovative method for producing sharp, full-spectrum color images at 100,000 dpi which can be applicable in reflective color displays, anti-counterfeiting, and high-density optical data recording.

This novel breakthrough allows colouring to be treated not as an inking matter but as a lithographic matter, which can potentially revolutionise the way images are printed and be further developed for use in high-resolution reflective colour displays as well as high density optical data storage.

The inspiration for the research was derived from stained glass, which is traditionally made by mixing tiny fragments of metal into the glass. It was found that nanoparticles from these metal fragments scattered light passing through the glass to give stained glass its colours. Using a similar concept with the help of modern nanotechnology tools, the researchers precisely patterned metal nanostructures, and designed the surface to reflect the light to achieve the colour images.

"The resolution of printed colour images very much depends on the size and spacing between individual 'nanodots' of colour," explained Dr Karthik Kumar, one of the key researchers involved. "The closer the dots are together and because of their small size, the higher the resolution of the image. With the ability to accurately position these extremely small colour dots, we were able to demonstrate the highest theoretical print colour resolution of 100,000 dpi."

"Instead of using different dyes for different colours, we encoded colour information into the size and position of tiny metal disks. These disks then interacted with light through the phenomenon of plasmon resonances," said Dr Joel Yang, the project leader of the research. "The team built a database of colour that corresponded to a specific nanostructure pattern, size and spacing. These nanostructures were then positioned accordingly. Similar to a child's 'colouring-by-numbers' image, the sizes and positions of these nanostructures defined the 'numbers'. But instead of sequentially colouring each area with a different ink, an ultrathin and uniform metal film was deposited across the entire image causing the 'encoded' colours to appear all at once, almost like magic!" added Dr Joel Yang.

The researchers from IMRE had also collaborated with A*STAR's Institute of High Performance Computing (IHPC) to design the pattern using computer simulation and modelling. Dr Ravi Hegde of IHPC said, "The computer simulations were vital in understanding how the structures gave rise to such rich colours. This knowledge is currently being used to predict the behaviour of more complicated nanostructure arrays."

The researchers are currently working with Exploit Technologies Pte Ltd (ETPL), A*STAR's technology transfer arm, to engage potential collaborators and to explore licensing the technology. The research was published online on August 12, 2012 in Nature Nanotechnology.

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What sets allergies in motion?

Allergies, or hypersensitivities of the immune system, are more common than ever before. According to the Asthma and Allergies Foundation of America, one in five Americans suffers from an allergy -- from milder forms like hay fever to more severe instances, like peanut allergies which can lead to anaphylactic shock.

While medications like antihistamines can treat the symptoms of an allergic reaction, the treatment is too limited, says Prof. Ronit Sagi-Eisenberg, a cell biologist at Tel Aviv University's Sackler Faculty of Medicine. Cells release dozens of molecules during an allergic reaction, and available medications address only a small subset. Now she and her fellow researchers are working to identify what triggers allergic reactions in the body, with the goal of stopping an allergic reaction before it starts.

The answer may lie within the Rab family, a group of 60 proteins that are known to regulate the distribution of proteins throughout the body. Along with her Ph.D. student Nurit Pereg-Azouz, Prof. Sagi-Eisenberg found that 30 of these proteins determined how cells react to an allergen, and two of these have been identified for further research as instruments of preventative medication. When the chain of events leading up to an allergic reaction can be understood, drugs can be developed to inhibit the initial reaction, explains Prof. Sagi-Eisenberg. This research has been published in The Journal of Immunology.

Getting to the root

Allergic reactions can appear as rashes, respiratory difficulties, or swelling, but they're all caused by the same mechanism. When exposed to an allergen, the body activates the immune system. But mast cells, located throughout the body, sense that the immune system has mistakenly been activated against something that is not bacterial or viral, and they release biologically active molecules to create an inflammatory response.

So what causes mast cells to react? Prof. Sagi-Eisenberg and her team work to identify the exact chain of events in an allergic reaction. They looked to the Rab family of proteins as a potential source for answers, screening for the proteins' involvement in initiating allergic reaction.

"We genetically manipulated mast cells so that they contained mutated versions of these proteins, which were already active without an allergen," explains Prof. Sagi-Eisenberg. If a protein was relevant, it would cause an allergic reaction. "This new methodology allowed us to screen for the functional impact of each member of this family, determining if they either inhibited or activated the allergic process."

In the end, the researchers flagged 30 proteins that were relevant to the process of creating an allergic reaction in the body, and have identified two that appear to be the most involved. Further research will use these two proteins as tools to gain more understanding of allergic reactions.

Targeted drugs could prevent allergic reaction

An allergic reaction is not only a function of two proteins interacting -- it's the result of a chain of events. By identifying crucial links in such a chain, researchers can create targeted drugs that break the chain. New medications that target tumor cells, for example, are directed at halting the tumor's ability to function and grow, starving it of crucial blood and oxygen supplies. Prof. Sagi-Eisenberg envisions similar medications for allergies, with medications that address the source of the allergic reaction instead of the symptoms.

The need for such medications is pressing. Steroids, the only available type of drug that effectively prevents mast cells from secreting biologically active agents, also cause harm to kidneys, bones, and the immune system. Patients may suffer more from the treatment than they do from the allergy itself. Alternative medications that are as effective as steroids but will be devoid of their adverse side effects are desperately needed. Prof. Sagi-Eisenberg's work will help to identify proteins that can be targeted by medications without impacting the function of other cells, she hopes.

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High dietary antioxidant intake might cut pancreatic cancer risk

Increasing dietary intake of the antioxidant vitamins C, E, and selenium could help cut the risk of developing pancreatic cancer by up to two thirds, suggests new research. 

If the association turns out to be causal, one in 12 of these cancers might be prevented, suggest the researchers, who are leading the Norfolk arm of the European Prospective Investigation of Cancer (EPIC) study. Cancer of the pancreas kills more than a quarter of a million people every year around the world. And 7500 people are diagnosed with the disease every year in the UK, where it is the six commonest cause of cancer death.

The disease has the worst prognosis of any cancer, with just 3% of people surviving beyond five years. Genes, smoking, and type 2 diabetes are all risk factors, but diet is also thought to have a role, and may explain why rates vary so much from country to country, say the authors. The researchers tracked the health of more than 23,500 40 to 74 year olds, who had entered the Norfolk arm of the EPIC study between 1993 and 1997.

Each participant filled in a comprehensive food diary, detailing the types and amount of every food they ate for 7 days, as well as the methods they used to prepare it. Each entry in the food diary was matched to one of 11,000 food items, and the nutrient values calculated using a specially designed computer program (DINER). Forty nine people (55% men) developed pancreatic cancer within 10 years of entering the study. This increased to 86 (44% men) by 2010. On average, they survived 6 months after diagnosis.

The nutrient intakes of those diagnosed with the disease within 10 years of entering EPIC were compared with those of almost 4000 healthy people to see if there were any differences. The analysis showed that a weekly intake of selenium in the top 25% of consumption roughly halved their risk of developing pancreatic cancer compared with those whose intake was in the bottom 25%. And those whose vitamins C, E, and selenium intake was in the top 25% of consumption were 67% less likely to develop pancreatic cancer than those who were in the bottom 25%. If the link turns out to be causal, that would add up to the prevention of more than one in 12 (8%) of pancreatic cancers, calculate the authors.

Antioxidants may neutralize the harmful by-products of metabolism and normal cell activity -- free radicals -- and curb genetically programmed influences, as well as stimulating the immune system response, explain the authors.

Other trials using antioxidant supplements have not produced such encouraging results, but this may be because food sources of these nutrients may behave differently from those found in supplements, they say. "If a causal association is confirmed by reporting consistent findings from other epidemiological studies, then population based dietary recommendations may help to prevent pancreatic cancer," they conclude.

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New Study Suggests Moderate Alcohol Consumption May Help Prevent Bone Loss

Drinking a moderate amount of alcohol as part of a healthy lifestyle may benefit women's bone health, lowering their risk of developing osteoporosis. A new study assessed the effects of alcohol withdrawal on bone turnover in postmenopausal women who drank one or two drinks per day several times a week. Researchers at Oregon State University measured a significant increase in blood markers of bone turnover in women after they stopped drinking for just two weeks.

Low power scanning electron microscope image,
showing osteoporotic architecture in the fourth
 lumbar vertebra of an 89 year old woman.
The bone is heavily eroded in places by
 the action of osteoclasts and
 consists mainly of thin, fragile struts

Bones are in a constant state of remodeling with old bone being removed and replaced. In people with osteoporosis, more bone is lost than reformed resulting in porous, weak bones. About 80 percent of all people with osteoporosis are women, and postmenopausal women face an even greater risk because estrogen, a hormone that helps keep bone remodeling in balance, decreases after menopause.


Past studies have shown that moderate drinkers have a higher bone density than non-drinkers or heavy drinkers, but these studies have provided no explanation for the differences in bone density. Alcohol appears to behave similarly to estrogen in that it reduces bone turnover, the researchers said.


In the current study, published online July 11 in the journalMenopause, researchers in OSU’s Skeletal Biology Laboratory studied 40 early postmenopausal women who regularly had one or two drinks a day, were not on any hormone replacement therapies, and had no history of osteoporosis-related fractures.


The researchers found evidence for increased bone turnover – a risk factor for osteoporotic fractures – during the two week period when the participants stopped drinking. Even more surprising: the researchers found that less than a day after the women resumed their normal drinking, their bone turnover rates returned to previous levels.


“Drinking moderately as part of a healthy lifestyle that includes a good diet and exercise may be beneficial for bone health, especially in postmenopausal women,” said Urszula Iwaniec, associate professor in the College of Public Health and Human Sciences at OSU and one of the study’s authors. “After less than 24 hours to see such a measurable effect was really unexpected.”


Iwaniec, OSU’s Skeletal Biology Laboratory director Russell Turner, and researcher Gianni Maddalozzo assisted OSU alumna Jill Marrone with the study, which was Marrone’s master’s thesis.


This study is important because it suggests a cellular mechanism for the increased bone density often observed in postmenopausal women who are moderate drinkers, Turner said.
The researchers said many of the medications to help prevent bone loss are not only expensive, but can have unwanted side effects. While excessive drinking has a negative impact on health, drinking a glass of wine or beer regularly as part of a healthy lifestyle may be helpful for postmenopausal women.


“Everyone loses bone as they age, but not everyone develops osteoporosis,” Turner said. “Being able to identify factors, such as moderate alcohol intake, that influence bone health will help people make informed lifestyle choices.”


The study was funded by grants from the National Institutes of Health and the John C. Erkkila, M.D. Endowment for Health and Human Performance.


Karin Hardin, Adam Branscum, Kenneth Philbrick and Lynn Cialdella-Kam of OSU co-authored the study, along with Anne Breggia and Clifford Rosen of the Maine Medical Center Research Institute.


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Naturally adhesive: New glues from renewable raw materials

Until now most adhesives have been manufactured from petroleum-based materials. However, they can also be obtained from renewable raw materials -- for example from proteins, natural rubber, starch, or cellulose. Researchers are working on new formulas for industrial applications.

Glues can be obtained from renewable raw materials –
for example from proteins, natural rubber, starch, or cellulose.
(Credit: Image courtesy of Fraunhofer-Gesellschaft)

Shoes, cars, airplanes, rotor blades for wind turbines, self-adhesive notes, plasters -- this is just a sample of the many products featuring adhesives. More than 820,000 tons of adhesive were produced in Germany in 2010, according to the German Adhesives Association -- Industrieverband Klebstoffe. To this day the majority of adhesives are manufactured from petroleum-based materials. Only gradually is the industry also offering adhesives made from renewable raw materials such as starch, cellulose, dextrins, and proteins. Pioneering products featuring these new adhesives include wallpaper pastes and glue sticks.

Adhesive based on polylactic acid

In two projects, researchers at the Fraunhofer Institute for Environmental, Safety and Energy Technology UMSICHT are working on further new adhesive formulas based on renewable raw materials. In cooperation with the Recklinghausen site of the Westfälische Hochschule, University of Applied Sciences, and the companies Jowat, Logo tape, and Novamelt, and with support from Germany's Federal Ministry of Food, Agriculture and Consumer Protection, researchers at UMSICHT in Oberhausen are developing a pressure-sensitive adhesive for industrial applications. Products using pressure-sensitive adhesives include adhesive bandages, self-adhesive labels, and adhesive tapes. They are subject to particularly demanding requirements: They have to remain permanently adhesive at room temperature. Gentle pressure should suffice for them to adhere to almost all substrates, and yet it must be possible to remove them without leaving behind any residue. To achieve this, the adhesive force must precisely match the respective use.

Pressure-sensitive adhesives are based on backbone polymers, which give the adhesives their inner strength (cohesion). The challenge for the UMSICHT researchers is to develop a backbone polymer from the raw material polylactic acid. What makes this biological material particularly attractive is its low production cost; since lactic acid is produced on an industrial scale, costs are in the region of prices for fossil-based backbone polymers. "However, the properties of polylactic acid are completely different from those of the polymers used to date, such as polyacrylates and styrene-based block copolymers," explains Dr. Stephan Kabasci, who heads the UMSICHT renewable resources business unit. This means that the researchers have to develop a completely new formula.

Packaging using compostable films

However, adhesives are also found in many types of packaging, for example where laminating films protect foodstuffs from dirt, moisture, and chemicals. This involves covering printed packaging and printed paper products on one or both sides with a transparent, shiny, matt, or embossed plastic film. In a collaborative project, UMSICHT scientists are working with the companies Achilles Papierveredelung Bielefeld, Jowat, and Deckert Management Consultants to develop innovative adhesive systems that meet the exacting quality requirements of laminated products as well as being compostable. In pursuit of this objective, the researchers are focusing primarily on water-based dispersion adhesives, in which the adhesive components are dispersed very finely in water. They are applied to one side of the product and joined while wet.

Nature shows us another path to developing biological adhesives. The buoy barnacle (Dosima fascicularis) produces a special adhesive which it uses to attach itself tightly to flotsam. This super-adhesive is so strong that it is almost impossible to break down into its constituent parts using ordinary solvents. Another special property it has is its ability to cure under water. Researchers at the Fraunhofer Institute for Manufacturing Technology and Advanced Materials IFAM in Bremen are now trying to find out which amino acid components make up the relevant proteins. "Once we've done that, the next step will be to recreate the adhesive proteins in the laboratory," says Dr. Ingo Grunwald, expert for biological adhesives at the IFAM. Such bioadhesives are primarily of interest for medical applications, for example to close incisions or to replace or support the pins and screws used to treat bone fractures.

Injecting life-saving oxygen into a vein

Patients unable to breathe because of acute lung failure or an obstructed airway need another way to get oxygen to their blood -- and fast -- to avoid cardiac arrest and brain injury. Medical researchers have designed tiny, gas-filled microparticles that can be injected directly into the bloodstream to quickly oxygenate the blood.

The microparticles consist of a single layer of lipids (fatty molecules) that surround a tiny pocket of oxygen gas, and are delivered in a liquid solution. In a cover article in the June 27 issue of Science Translational Medicine, John Kheir, MD, of the Department of Cardiology at Boston Children's Hospital, and colleagues report that an infusion of these microparticles into animals with low blood oxygen levels restored blood oxygen saturation to near-normal levels, within seconds.

When the trachea was completely blocked -- a more dangerous "real world" scenario -- the infusion kept the animals alive for 15 minutes without a single breath, and reduced the incidence of cardiac arrest and organ injury.

The microparticle solutions are portable and could stabilize patients in emergency situations, buying time for paramedics, emergency clinicians or intensive care clinicians to more safely place a breathing tube or perform other life-saving therapies, says Kheir.

"This is a short-term oxygen substitute -- a way to safely inject oxygen gas to support patients during a critical few minutes," he says. "Eventually, this could be stored in syringes on every code cart in a hospital, ambulance or transport helicopter to help stabilize patients who are having difficulty breathing."

The microparticles would likely only be administered for a short time, between 15 and 30 minutes, because they are carried in fluid that would overload the blood if used for longer periods, Kheir says.

Kheir also notes that the particles are different from blood substitutes, which carry oxygen but are not useful when the lungs are unable to oxygenate them. Instead, the microparticles are designed for situations in which the lungs are completely incapacitated.

Kheir began investigating the idea of injectable oxygen in 2006, after caring for a little girl who sustained a severe brain injury resulting from a severe pneumonia that caused bleeding into her lungs and severely low oxygen levels. Despite the team's best efforts, she died before they could place her on a heart-lung machine. Frustrated by this, Kheir formed a team to search for another way to deliver oxygen.

"Some of the most convincing experiments were the early ones," he says. "We drew each other's blood, mixed it in a test tube with the microparticles, and watched blue blood turn immediately red, right before our eyes."

Over the years, Kheir and his team have tested various concentrations and sizes of the microparticles to optimize their effectiveness and to make them safe for injection. "The effort was truly multidisciplinary," says Kheir. "It took chemical engineers, particle scientists and medical doctors to get the mix just right."

In the studies reported in the paper, they used a device called a sonicator, which uses high-intensity sound waves to mix the oxygen and lipids together. The process traps oxygen gas inside particles averaging 2 to 4 micrometers in size (not visible without a microscope). The resulting solution, with oxygen gas making up 70 percent of the volume, mixed efficiently with human blood.

"One of the keys to the success of the project was the ability to administer a concentrated amount of oxygen gas in a small amount of liquid," Kheir says. "The suspension carries three to four times the oxygen content of our own red blood cells." Intravenous administration of oxygen gas was tried in the early 1900s, but these attempts failed to oxygenate the blood and often caused dangerous gas embolisms.

"We have engineered around this problem by packaging the gas into small, deformable particles," Kheir explains. "They dramatically increase the surface area for gas exchange and are able to squeeze through capillaries where free gas would get stuck."

The study was funded by three awards from the Technology Development Fund at Boston Children's Hospital Boston and a U.S. Department of Defense Basic Research Award to Kheir.

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Dieting? Study challenges notion that a calorie is just a calorie

A new study challenges the notion that "a calorie is a calorie." The study finds diets that reduce the surge in blood sugar after a meal -- either low-glycemic index or very-low carbohydrate -- may be preferable to a low-fat diet for those trying to achieve lasting weight loss.

Weight re-gain is often attributed to a decline in motivation or adherence to diet and exercise, but biology also plays an important role. After weight loss, the rate at which people burn calories (known as energy expenditure) decreases, reflecting slower metabolism. Lower energy expenditure adds to the difficulty of weight maintenance and helps explain why people tend to re-gain lost weight.

Prior research by Ebbeling and Ludwig has shown the advantages of a low glycemic load diet for weight loss and diabetes prevention, but the effects of these diets during weight loss maintenance has not been well studied. Research shows that only one in six overweight people will maintain even 10 percent of their weight loss long-term.

The study suggests that a low-glycemic load diet is more effective than conventional approaches at burning calories (and keeping energy expenditure) at a higher rate after weight loss. "We've found that, contrary to nutritional dogma, all calories are not created equal," says Ludwig, also director of the Optimal Weight for Life Clinic at Boston Children's Hospital. "Total calories burned plummeted by 300 calories on the low fat diet compared to the low carbohydrate diet, which would equal the number of calories typically burned in an hour of moderate-intensity physical activity," he says.

Each of the study's 21 adult participants (ages 18-40) first had to lose 10 to 15 percent of their body weight, and after weight stabilization, completed all three of the following diets in random order, each for four weeks at a time. The randomized crossover design allowed for rigorous observation of how each diet affected all participants, regardless of the order in which they were consumed:

          A low-fat diet,which reduces dietary fat and emphasizes whole grain products and a variety of fruits and vegetables, composed of 60 percent of daily calories from carbohydrates, 20 percent from fat and 20 percent from protein.

          A low-glycemic index diet made up of minimally processed grains, vegetables, healthy fats, legumes and fruits, with 40 percent of daily calories from carbohydrates, 40 percent from fat and 20 percent from protein. Low glycemic index carbohydrates digest slowly, helping to keep blood sugar and hormones stable after the meal.

         A low-carbohydrate diet, modeled after the Atkins diet, composed of 10 percent of daily calories from carbohydrates, 60 percent from fat and 30 percent from protein.

The study used state-of-the-art methods, such as stable isotopes to measure participants' total energy expenditure, as they followed each diet.

Each of the three diets fell within the normal healthy range of 10 to 35 percent of daily calories from protein. The very low-carbohydrate diet produced the greatest improvements in metabolism, but with an important caveat: This diet increased participants' cortisol levels, which can lead to insulin resistance and cardiovascular disease. The very low carbohydrate diet also raised C-reactive protein levels, which may also increase risk of cardiovascular disease.

Though a low-fat diet is traditionally recommended by the U.S. Government and Heart Association, it caused the greatest decrease in energy expenditure, an unhealthy lipid pattern and insulin resistance. "In addition to the benefits noted in this study, we believe that low-glycemic-index diets are easier to stick to on a day-to-day basis, compared to low-carb and low-fat diets, which many people find limiting," says Ebbeling. "Unlike low-fat and very- low carbohydrate diets, a low-glycemic-index diet doesn't eliminate entire classes of food, likely making it easier to follow and more sustainable."

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Reversible doping: Hydrogen flips switch on vanadium oxide

If you are not a condensed matter physicist, vanadium oxide (VO2) may be the coolest material you've never heard of. It's a metal. It's an insulator. It's a window coating and an optical switch. And thanks to a new study by physicists at Rice University, scientists have a new way to reversibly alter VO2's electronic properties by treating it with one of the simplest substances -- hydrogen.

So what is VO2? It's an oxidized form of the metal vanadium, an ingredient in hardened steel. When oxygen reacts with vanadium to form VO2, the atoms form crystals that look like long rectangular boxes. The vanadium atoms line up along the four edges of the box in regularly spaced rows. A single crystal of VO2 can have many of these boxes lined up side by side, and the crystals conduct electricity like wire as long as they are kept warm.

"The weird thing about this material is that if you cool it, when you get to 67 degrees Celsius, it goes through a phase transition that is both electronic and structural," said Rice's Douglas Natelson, lead co-author of the study in this week's Nature Nanotechnology. "Structurally, the vanadium atoms pair up and each pair is slightly canted, so you no longer have these long chains. When the phase changes, and these pairings take place, the material changes from being a electrical conductor to an electrical insulator."

While other materials exhibit a similar electronic about-face, VO2 is unique in that the change occurs at a relatively modest temperature -- around 153 degrees Fahrenheit -- and sometimes at incredible speed -- less than a trillionth of second. In recent years, scientists have put these quirky properties to work. In 2004, a group in London used VO2 to design a temperature-sensitive window coating that could absorb sunlight on cold days and turn reflective on hot days. And electronics researchers are also working to create optical switches from VO2.

"As an experimental physicist, VO2 is intriguing because the detailed physics of the material are still not well understood, and theoretical models alone cannot give us the answers," said Natelson, professor of physics and astronomy and of electrical and computer engineering at Rice. "Experiments are key to understanding this."

In 2010, Natelson and postdoctoral research associate Jiang Wei began to systematically study the phase changes in VO2. Wei and graduate student Heng Ji began by using a process called vapor deposition to grow VO2 wires that were about 1,000 times smaller than a human hair. One set of experiments on wires that had been baked in the presence of hydrogen gas returned particularly odd readings. Wei, Ji and Natelson determined that the hydrogen was apparently modifying the VO2 nanowires, but only those in contact with metal electrodes.

"The gold electrodes we were using to supply current to the experiment were acting as a catalyst that split the hydrogen gas molecules into atomic hydrogen, which could then diffuse into channels in the VO2," Natelson said. "It appears that the hydrogen is taken up into the VO2 crystals, and this changes their electronic properties. If a little hydrogen is added, the phase transition happens at a slightly lower temperature, and the insulating phase becomes more conductive. If enough hydrogen is added, the transition to the insulating phase disappears altogether."

To gain insight into just how the hydrogen is able to alter the transition, the experimenters consulted with theoretical physicist Andriy Nevidomskyy, assistant professor of physics and astronomy at Rice. Nevidomskyy's calculations showed that the hydrogen changes the amount of charge in the VO2 material and also forces the crystal to expand slightly. Both of these effects favor the metallic state.

This is not the first time physicists have lowered the transition temperature of VO2 by adding other materials -- a technique known as "doping." But Natelson said Rice's hydrogen doping is unique in that it is completely reversible: To remove the hydrogen, the material simply has to be baked in an oven at moderate temperature.

"On the applied side, there may be a number of applications for this, like ultrasensitive hydrogen sensors," Natelson said. "But the more immediate payoff will likely be in helping us to better understand the physics involved in the VO2 phase transition. If we can find out exactly how much hydrogen is required to shut down the transition, then we will have a knob that we can turn to systematically raise or lower the temperature in future experiments.

Apple peel compound boosts brown fat, reduces obesity in mice

Obesity and its associated problems such as diabetes and fatty liver disease are increasingly common global health concerns. A new study shows that a natural substance found in apple peel can partially protect mice from obesity and some of its harmful effects. The findings suggest that the substance known as ursolic acid reduces obesity and its associated health problems by increasing the amount of muscle and brown fat, two tissues recognized for their calorie-burning properties. The study, which was published June 20 in the journal PLoS ONE, was led by Christopher Adams, M.D., Ph.D., UI associate professor of internal medicine and a Faculty Scholar at the Fraternal Order of Eagles Diabetes Research Center at the UI. In mice fed a high fat diet, ursolic acid increases skeletal muscle Akt signaling,  anabolic mRNA expression, grip strength,  skeletal muscle mass, and fast and slow skeletal muscle fiber size. "From previous work, we knew that ursolic acid increases muscle mass and strength in healthy mice, which is important because it might suggest a potential therapy for muscle wasting," Adams says. "In this study, we tested ursolic acid in mice on a high-fat diet -- a mouse model of obesity and metabolic syndrome. Once again, ursolic acid increased skeletal muscle. Interestingly, it also reduced obesity, pre-diabetes and fatty liver disease. "Since muscle is very good at burning calories, the increased muscle in ursolic acid-treated mice may be sufficient to explain how ursolic acid reduces obesity. However, we were surprised to find that ursolic acid also increased brown fat, a fantastic calorie burner. This increase in brown fat may also help protect against obesity." Until quite recently, researchers believed that only infants had brown fat, which then disappeared during childhood. However, improved imaging techniques have shown that adults do retain a very small amount of the substance mostly in the neck and between the shoulder blades. Some studies have linked increased levels of brown fat with lower levels of obesity and healthier levels of blood sugar and blood lipid, leading to the suggestion that brown fat may be helpful in preventing obesity and diabetes. The UI team, which also included Steven Kunkel, Christopher Elmore, Kale Bongers, Scott Ebert, Daniel Fox, Michael Dyle, and Steven Bullard, studied mice on a high-fat diet over a period of several weeks. Half of the animals also received ursolic acid in their high-fat food. Interestingly, mice whose diet included ursolic acid actually ate more food than mice not getting the supplement, and there was no difference in activity between the two groups. Despite this, the ursolic acid-treated mice gained less weight and their blood sugar level remained near normal. Ursolic acid-treated mice also failed to develop obesity-related fatty liver disease, a common and currently untreatable condition that affects about one in five American adults. Further study showed that ursolic acid consumption increased skeletal muscle, increasing the animals' strength and endurance, and also boosted the amount of brown fat. Because both muscle and brown fat burn calories, the researchers investigated energy expenditure in the mice and showed that ursolic acid-fed mice burned more calories than mice that didn't get the supplement. "Our study suggests that ursolic acid increases skeletal muscle and brown fat leading to increased calorie burning, which in turn protects against diet-induced obesity, pre-diabetes and fatty liver disease," Adams says. "Brown fat is beneficial and people are trying to figure out ways to increase it. At this point, we don't know how ursolic acid increases brown fat, or if it increases brown fat in healthy mice. And, most importantly, we don't know if ursolic acid will benefit people. Our next step is to determine if ursolic acid can help patients." The research was supported by funding from the Fraternal Order of Eagles Diabetes Research Center at the University of Iowa, the National Institute of Arthritis and Musculoskeletal and Skin Diseases of the National Institutes of Health (grant 5R01AR059115-03), the Department of Veterans Affairs, and the University of Iowa Research Foundation. Story Source: The above abstract is republished from materials provided by Newswise. Note: please contact the source cited above