Sunday, February 12, 2012

New standard for vitamin D testing to ensure accurate test results

Karen Phinney and colleagues explain that medical research suggests or insufficiency may be even more common than previously thought and a risk factor for more than just bone diseases. An estimated 50-75 percent of people in the U.S. may not have enough vitamin D in their bodies. Low levels of vitamin D have been linked to the development of several conditions, including rickets (soft and deformed bones), osteoporosis, some cancers, multiple sclerosis and Parkinson's disease. People can make their own vitamin D simply by rolling up their shirt sleeves and exposing their skin to sunlight. But for those cooped up in offices all day long, food and also can provide vitamin D. With this renewed interest in vitamin D, scientists need an accurate way to measure its levels in the blood. Measuring vitamin D itself doesn't work because it is rapidly changed into another form in the liver. That's why current methods detect levels of a vitamin D metabolite called 25(OH)D. However, the test methods don't always agree and produce different results. To help laboratories come up with consistent and accurate methods, the researchers developed a Standard Reference Material called SRM 972, the first certified reference material for the determination of the metabolite in human serum (a component of blood).

The researchers developed four versions of the standard, with different levels of the vitamin D metabolites 25(OH)D2 and 25(OH)D3 in human serum. They also determined the levels of 3-epi-25(OH)D in the adult human serum samples. Surprisingly, they found that this — previously thought to only exist in the blood of infants — was present in adult serum. "This reference material provides a mechanism to ensure measurement accuracy and comparability and represents a first step toward standardization of 25(OH)D measurements," say the researchers.

More information: Development and Certification of a Standard Reference Material for Vitamin D Metabolites in Human Serum, Anal. Chem., 2012, 84 (2), pp 956–962. DOI: 10.1021/ac202047n

The National Institute of Standards and Technology (NIST), in collaboration with the National Institutes of Health’s Office of Dietary Supplements (NIH-ODS), has developed a Standard Reference Material (SRM) for the determination of 25-hydroxyvitamin D [25(OH)D] in serum. SRM 972 Vitamin D in Human Serum consists of four serum pools with different levels of vitamin D metabolites and has certified and reference values for 25(OH)D2, 25(OH)D3, and 3-epi-25(OH)D3. Value assignment of this SRM was accomplished using a combination of three isotope-dilution mass spectrometry approaches, with measurements performed at NIST and at the Centers for Disease Control and Prevention (CDC). Chromatographic resolution of the 3-epimer of 25(OH)D3 proved to be essential for accurate determination of the metabolites.

Provided by American Chemical Society (news : web)

From cancer research to energy storage, Berkeley Lab scientist takes on big challenges

It’s fair to say that what she does is difficult to grasp. Why she does it is easy: “I want to help solve big problems. That’s why I’m here,” she says.

In this case, the big problem is energy—or how you can drive to work without consuming fossil fuel or emitting CO2. Bardhan’s research is part of a Department of Energy goal to develop an on-board hydrogen-storage system that will enable a fuel cell powered car to go 300 miles without refueling, with water as the only by-product.

Getting there requires synthesizing new materials that can safely store a lot of hydrogen in a small package without costing too much. The work is part fundamental science and part real-world know-how. It’s also the perfect challenge for Bardhan, who recently earned a spot on Forbes’ list of 30 people under 30 who are rising stars in science.

Science seems to surround the 29-year-old chemist. Her husband, a researcher at Intel Corporation, also made the Forbes’ 30-under-30 list for work on nanotube supercapacitors for high-energy batteries. She grew up in India, where her father and several uncles are engineers. She came to the U.S. ten years ago, studied chemistry at a small liberal arts college in Missouri, and then received a PhD in chemistry from Rice University. Her graduate work focused on developing plasmonic structures for cancer therapy and diagnosis.

In 2010, she was offered a postdoctoral position in Jeff Urban’s lab at the Molecular Foundry. The research focused on clean energy, not cancer research, but she jumped at the opportunity. It was a natural transition.

“When I think of science, I think of major problems that I can help solve,” she says. “There’s human health. There’s also human sustainability, and for me, that means clean energy production and storage. We need to find renewable energy sources that have very little impact on the environment.”

Vehicles powered by hydrogen fuel cells could be one such solution, but there are significant hurdles to overcome. Chief among them is storing enough hydrogen in a car to provide a driving range that competes with a tank of gas. The most common way to store hydrogen is in a pressurized tank that contains gaseous or liquefied hydrogen. But this approach has safety issues. And the volumetric density of a tank of gaseous or liquefied hydrogen—or how much energy it holds—is very low.

Instead, Bardhan and her colleagues in Jeff Urban’s lab at the Molecular Foundry are developing storage materials composed of hydrides, a compound in which hydrogen is bound to a metal. Metal hydrides have the potential to store a lot of hydrogen in a small volume, and release it at low temperatures and pressures.

Recently, they designed a new composite consisting of nanoparticles of magnesium metal uniformly embedded through a matrix of a hydrogen-selective polymer, which is related to Plexiglas. Bardhan says the material is very close to the Department of Energy’s goal of six weight percent, meaning six percent by weight of the metal hydride is . They’re now optimizing the material even more, with the goal of edging toward the material’s theoretical limit of 7.6 weight percent.

Part of this optimization involves gaining a better understanding of how a metal transitions to a metal hydride, such as how Mg becomes MgH2. To do this, Bardhan is developing optical spectroscopy techniques that will enable scientists to watch this transformation in real time as it happens.

“Without understanding these very fundamental processes, we cannot improve the properties of the materials,” says Bardhan.

Provided by Lawrence Berkeley National Laboratory (news : web)

Scientists X-ray key enzyme of common pathogen crystallized in living cells

The three-dimensional structure of a biomolecule gives biologists clues about its function, and in the case of a pathogen it also offers the perspective to block a harmful protein with a tailor-made artificial molecule. For example, if the enzyme cathepsin B of Trypanosoma brucei is blocked, the parasite will die. However, the structure analysis of biomolecules is a difficult and time-consuming process. Normally, a sufficiently large crystal of the protein in question has to be grown in the lab before it can be investigated with X-ray light of a synchrotron radiation source.

Crystal growing is complicated and often takes weeks or even months. Therefore, the team of scientists – among them scientists from the universities of Tübingen, Hamburg and Lübeck, and from Deutsches Elektronen-Synchrotron DESY in Hamburg – chose another approach. With the help of a virus, they inserted the genetic blueprint for cathepsin B into living insect cells. The infected cells started to produce the enzyme incessantly, and with the steadily increasing concentration, the enzyme eventually crystallised. After about 70 hours, the micrometre-small crystals became visible in the microscope, some of them even sticking out of the cells.

At the US accelerator centre SLAC in California, the scientists bombarded these crystals with the world’s strongest X-ray free-electron laser LCLS. Although its intensive X-ray flash completely vaporises the crystals in less than a billionth of a second, it is bright enough to previously take a detailed diffraction image of the crystal, making it possible to calculate the structure of the crystallised enzyme. However, to gain the complete structural information the experiment must be repeated very often with a large number of crystals, which was not part of the study.

But the result shows that with the new technology it is possible to generate high-quality data of the protein structure of nanocrystals. "Our experiments have shown that the promise of X-ray lasers to revolutionize structural biology is indeed becoming true," said DESY scientist Prof. Henry Chapman from the Center for Free-Electron Laser Science (CFEL). "We have shown that previous limitations to protein crystallography can be overcome by using pulses of X-rays so intense, that they transform the proteins into a dense plasma similar to the conditions inside the sun. Yet the pulses are so short that fine details are seen before destroying the sample," Dr. Anton Barty from CFEL added.

Apart from the Federal Ministry of Education and Research-funded young investigators group "Structural Infection Biology Using new Radiation Sources (SIAS)" of the universities of Hamburg and Lübeck, and the Hamburg School for Structure and Dynamics in Infection (SDI) of the State of Hamburg Excellence Initiative, the research was done with the participation of a team of scientists headed by professor Michael Duszenko from the University of Tübingen, a CFEL-group headed by professor Henry Chapman as well as other DESY scientists and international collaboraters. CFEL is a cooperation of DESY, the Max Planck Society and the University of Hamburg.

“Our result shows that the super lasers offer completely new possibilities for the structure determination of biological macromolecules, and perhaps the days will be over soon when we needed months or even years to grow crystals of certain proteins being large enough for X-ray radiation sources at synchrotrons” said SIAS leader Dr. Lars Redecke, one of the main authors of this study.

As from 2010, SIAS - an initiative of the structural research scientists professor Christian Betzel, University of Hamburg, and professor Rolf Hilgenfeld, University of Lübeck - investigates the use of innovative radiation sources for structural determination of proteins and other biological molecules.

The European European XFEL, currently being built in Hamburg, will open a unique opportunity for biomolecule investigation. Already today, DESY operates the free-electron laser FLASH for soft X-ray radiation.

More information: "In vivo protein crystallization opens new routes in structural biology"; Michael Duszenko et al.; "Nature Methods", Advance Online Publication; DOI: 10.1038/nmeth.1859

Provided by DESY

Scientists rediscover self-healing silicone mechanism from the 1950s

The researchers, grad student Peiwen Zheng and Professor Thomas J. McCarthy from the University of Massachusetts, have published a paper on the rediscovery of siloxane equilibration in a recent issue of the .

“We have been working on materials from a couple of different perspectives,” Zheng told “When we rediscovered the forgotten unusual properties of silicones and combined them with today’s research interests, we found that the silicone material with the siloxane equilibration was an obvious candidate for a self-healing material.”

The researchers performed several experiments to test the theoretical predictions from papers published in the early 1950s, as well as to extend some of the experiments performed at that time. In one experiment, Zheng and McCarthy prepared a siloxane-based mixture containing a cross-linking agent and a catalyst. Then they poured the solution into molds of various shapes, such as cylinders, disks, and dog bones. After heating the molds at 90 °C (194 °F) for four hours, the researchers removed clear, rubbery silicone shapes from the molds. The scientists described these silicone samples as “living networks.”

“The silicone network is at a chemically anionic equilibrium,” Zheng explained of the term, “where the reactive center will cleave and reform a covalent siloxane bond.” These bonds are reversible, which enables the two sides of a crack to reconnect under the right conditions.

To demonstrate the self-healing ability, the researchers cut a 1-cm-long cylindrical sample in half using a razor blade. Then they rejoined the two pieces by wrapping them together with Teflon plumbing tape and heating them in an oven at 90 °C (194 °F) for 24 hours. When the researchers retrieved the sample and removed the tape, they found that the silicone cylinder had completely healed. Then they bent the cylinder by hand until it broke again - significantly, it broke in a different location than where it had been cut. The scientists repeated this experiment on different shaped objects with the same results.

In another experiment, the researchers molded a silicone dog bone, which they cut into multiple pieces. Then they rearranged the pieces to fit into a mold of a dog. Heating the sample resulted in a silicone dog with no visible fractures or weak spots where the pieces had been fitted together.

The researchers also quantified the strength of the healed samples in comparison with the original samples using fracture toughness measurements. The data for the two types of samples was indistinguishable, indicating exceptional self-healing.

The researchers explained that, in principle, any cross-linked dimethylsilicone elastomer (only one type was used here) can be converted into a living elastomer by the addition of basic catalysts. This possibility opens up many different routes for synthesizing a variety of self-healing silicione-based materials. While the samples used here required applied heating to self-heal, the researchers predict that samples in a sealed, high-temperature environment would self-heal “autonomically,” or automatically. Zheng explained that self-healing materials, with some improvements, could lead to a variety of applications.

“It can be developed into self-healing coatings on auto vehicles or countertops,” she said. “It is also a ‘plastic’ elastomer which can be used in molding to form desired shapes and patterns. The concept of a self-healing silicone can be used to guide the preparation of elastomers with gradient modulus, Janus elastomers, reversible surface patterns when filled with magnetic particles, and super tough materials which can chemically relax stress.”

More information: Peiwen Zheng and Thomas J. McCarthy. “A Surprise from 1954: Siloxane Equilibration Is a Simple, Robust, and Obvious Polymer Self-Healing Mechanism.” Journal of the American Chemical Society. DOI: 10.1021/ja2113257

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