Producing clean water in an emergency

Disasters such as floods, tsunamis, and earthquakes often result in the spread of diseases like gastroenteritis, giardiasis and even cholera because of an immediate shortage of clean drinking water. Now, chemistry researchers at McGill University have taken a key step towards making a cheap, portable, paper-based filter coated with silver nanoparticles to be used in these emergency settings.

"Silver has been used to clean water for a very long time. The Greeks and Romans kept their water in silver jugs," says Prof. Derek Gray, from McGill's Department of Chemistry. But though silver is used to get rid of bacteria in a variety of settings, from bandages to antibacterial socks, no one has used it systematically to clean water before. "It's because it seems too simple," affirms Gray.

Prof. Gray's team, which included graduate student Theresa Dankovich, coated thick (0.5mm) hand-sized sheets of an absorbent porous paper with silver nanoparticles and then poured live bacteria through it. "Viewed in an electron microscope, the paper looks as though there are silver polka dots all over," says Dankovich, "and the neat thing is that the silver nanoparticles stay on the paper even when the contaminated water goes through." The results were definitive. Even when the paper contains a small quantity of silver (5.9 mg of silver per dry gram of paper), the filter is able to kill nearly all the bacteria and produce water that meets the standards set by the American Environmental Protection Agency (EPA).

The filter is not envisaged as a routine water purification system, but as a way of providing rapid small-scale assistance in emergency settings. "It works well in the lab," says Gray, "now we need to improve it and test it in the field."

The research was funded by the National Sciences and Engineering Council of Canada (NSERC) and the work is part of the NSERC Sentinel Bioactive Paper Network.

Story Source:

The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by McGill University.

Journal Reference:

Theresa A. Dankovich, Derek G. Gray. Bactericidal Paper Impregnated with Silver Nanoparticles for Point-of-Use Water Treatment. Environmental Science & Technology, 2011; : 110211114613010 DOI: 10.1021/es103302t

Metallic molecules to nanotubes: Ruthenium complexes dissolve nanotubes, add functionality

A lab at Rice University has stepped forward with an efficient method to disperse nanotubes in a way that preserves their unique properties -- and adds more.

The new technique allows inorganic metal complexes with different functionalities to remain in close contact with single-walled carbon nanotubes while keeping them separated in a solution.

That separation is critical to manufacturers who want to spin fiber from nanotubes, or mix them into composite materials for strength or to take advantage of their electrical properties. For starters, the ability to functionalize the nanotubes at the same time may advance imaging sensors, catalysis and solar-activated hydrogen fuel cells.

Better yet, a batch of nanotubes can apparently stay dispersed in water for weeks on end.

Keeping carbon nanotubes from clumping in aqueous solutions and combining them with molecules that add novel abilities have been flies in the ointment for scientists exploring the use of these highly versatile materials.

They've tried attaching organic molecules to the nanotubes' surfaces to add functionality as well as solubility. But while these techniques can separate nanotubes from one another, they take a toll on the nanotubes' electronic, thermal and mechanical properties.

Angel Marti, a Rice assistant professor of chemistry and bioengineering and a Norman Hackerman-Welch Young Investigator, and his students reported this month in the Royal Society of Chemistry journal Chemical Communications that ruthenium polypyridyl complexes are highly effective at dispersing nanotubes in water efficiently and for long periods. Ruthenium is a rare metallic element.

One key is having just the right molecule for the job. Marti and his team created ruthenium complexes by combining the element with ligands, stable molecules that bind to metal ions. The resulting molecular complex is part hydrophobic (the ligands) and part hydrophilic (the ruthenium). The ligands strongly bind to nanotubes while the attached ruthenium molecules interact with water to maintain the tubes in solution and keep them apart from one another.

Another key turned out to be moderation.

Originally, Marti said, he and co-authors Disha Jain and Avishek Saha weren't out to solve a problem that has boggled chemists for decades, but their willingness to "do something crazy" paid off big-time. Jain is a former postdoctoral researcher in Marti's lab, and Saha is a graduate student.

The researchers were eyeing ruthenium complexes as part of a study to track amyloid deposits associated with Alzheimer's disease. "We started to wonder what would happen if we modified the metal complex so it could bind to a nanotube," Marti said. "That would provide solubility, individualization, dispersion and functionality."

It did, but not at first. "Avishek put this together with purified single-walled carbon nanotubes (created via Rice's HiPco process) and sonicated. Absolutely nothing happened. The nanotubes didn't get into solution -- they just clumped at the bottom.

"That was very weird, but that's how science works -- some things you think are good ideas never work."

Saha removed the liquid and left the clumped nanotubes at the bottom of the centrifuge tube. "So I said, 'Well, why don't you do something crazy. Just add water to that, and with the little bit of ruthenium that might remain there, try to do the reaction.' He did that, and the solution turned black."

A low concentration of ruthenium did the trick. "We found out that 0.05 percent of the ruthenium complex is the optimum concentration to dissolve nanotubes," Marti said. Further experimentation showed that simple ruthenium complexes alone did not work. The molecule requires its hydrophobic ligand tail, which seeks to minimize its exposure to water by binding with nanotubes. "That's the same thing nanotubes want to do, so it's a favorable relationship," he said.

Marti also found the nanotubes' natural fluorescence unaffected by the ruthenium complexes. "Even though they've been purified, which can introduce defects, they still exhibit very good fluorescence," he said.

He said that certain ruthenium complexes have the ability to stay in an excited state for a long time -- about 600 nanoseconds, or 100 times longer than normal organic molecules. "It means the probability that it will transfer an electron is high. That's convenient for energy transfer applications, which are important for imaging," he said.

That nanotubes stay suspended for a long time should catch the eye of manufacturers who use them in bulk. "They should stay separated for weeks without problems," Marti said. "We have solutions that have been sitting for months without any signs of crashing."

The Welch Foundation supported the research.

Story Source:

The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by Rice University.

Journal Reference:

Disha Jain, Avishek Saha, Angel A. Mart. Non-covalent ruthenium polypyridyl complexes–carbon nanotubes composites: an alternative for functional dissolution of carbon nanotubes in solution. Chemical Communications, 2011; 47 (8): 2246 DOI: 10.1039/C0CC05295G

Structure, dynamics of a chemical signal that triggers metastatic cancer revealed

 By Warren Froelich  Molecular Dynamics simulation shows that oxygen molecules reach the active site of Lysine Specific Demethylase 1 although substrate peptides (black, H3 histone tail & orange, SNAIL1 protein) are bound Credit: Riccardo Baron et al., UC San Diego

In cancer and other pathological diseases, researchers are discovering that packaging is important: specifically, how DNA – about two meters long when unwound and stretched – coils up and compacts neatly inside the nucleus of a cell.

What they’ve learned is that molecular signals that control the packaging of DNA are critical to the activation and silencing of genes in the human body – a process generally described as epigenetics.

Now, a team of researchers from UC San Diego and the University of Pavia in Italy, with the help of high-performance computers housed at the San Diego Supercomputer Center (SDSC), have captured the chemical structure of one such signal – in static crystal form and in motion – which is at the heart of a variety of morphological events including the rapid movement of cells during embryonic development, wound healing, and cancer.

The results offer a potentially new path to combat metastatic cancer by blocking the activity of this epigenetic signal, which, among other things, has been shown to silence a gene responsible for cell-to-cell adhesion, a “molecular glue,” thus allowing cancer cells to spread.

“Our study opens the understanding of the molecular interaction and dynamics to be targeted to develop epigenetic drugs which hopefully will lead in the future to potent drugs against cancer,” said J. Andrew McCammon, Joseph Mayer Chair of Theoretical Chemistry and Professor of Pharmacology at UC San Diego and a Howard Hughes Medical Institute Investigator.

Historically, cancer researchers have generally focused on genetic mutations, specific changes in DNA which alter the function of the proteins they encode; studies ultimately have yielded several targeted drugs based on this approach. But treatments for many forms of cancer remain limited, prompting the search for other novel approaches. In particular, some have turned to epigenetics and processes that activate or silence genes by altering the physical structure of DNA -- how it’s packaged -- leaving its message or sequence intact.

“The full potential of epigenetic therapy is far from being exploited,” said Riccardo Baron, a postdoctoral researcher in McCammon’s lab and first author of the study, published in the February issue of the journal Structure. “Very little has been done in terms of pharmacological manipulation and studies such as this are a start down that road. Computer applications in chemistry hold great promises for designing new experiments and future drug development.”

Briefly, to compact an otherwise lengthy strand of DNA neatly inside the nucleus, cells rely on proteins called histones. DNA tightly loops around histones to form nucleosomes, the so-called “beads- on-a-string” that coil up to make up chromatin, the basic unit of chromosomes. Here, the DNA remains sequestered until it’s silenced or activated by enzymes responsible for gene expression.

One such enzyme coming under increasing scrutiny lately is lysine-specific demethylase 1, or LSD1 (no relation to the hallucinogen). Specifically, in 2004 researchers at Harvard University and University of Pavia found that LSD1 – particularly when bound to another protein called CoREST – removes one or more methyl groups from the amino acid lysine on histone H3, in a region that protrudes from the globular core known as the N-terminal tail. The result: DNA closes up shop, shutting down gene expression.

In a study published last year by a team at the University of Kentucky, it was discovered that the LSD1-CoRest complex worked in tandem with an enzyme called SNAIL1 to silence the activity of a gene responsible for E-cadherin, considered a type of “molecular glue” that keeps cells together. When this gene is repressed, cancer cells are allowed to spread – a hallmark of metastasis.

SNAIL1, a master regulator of the epithelial-mesenchymal transition (EMT) process that’s at the heart of many morphological events, has been found in high quantities in the sera of patients with several cancers, including breast and certain forms of leukemia.

Based partly on this work, the UCSD-University of Pavia team sought to find out precisely how and where the enzyme complex bound to and interacted with SNAIL1, and why LSD1-CoREST is selectively drawn to, and recruited by, SNAIL1 in the first place.

Their research included analysis of the crystal structure of the LSD1-CoREST complex bound to SNAIL1 as determined from X-ray diffraction experiments. This snapshot demonstrated that the LSD1-CoRest complex tightly binds to a region of the SNAIL1 molecule that closely resembles the N-terminal tail of histone effectively mimicking the active site on this histone. The structure has been made publicly available in the Protein Data Bank.

“What this shows is how LSD1 recognizes and discriminates specific proteins in a crowded cell environment, and why the LSD1 complex is drawn to SNAIL 1,” said Andrea Mattevi, a researcher from the Department of Genetics and Microbiology at the University of Pavia, and the study’s principal investigator.

Though insightful, X-ray structures offer only a static view of molecular activity at a given moment. To learn more about the interaction of the enzyme complex and its target over time, scientists work with molecular dynamics software that simulate how proteins wiggle, weave and gyrate over time. Such is the complexity of the calculations needed for these simulations that researchers often turn to supercomputers.

“Experiments captured a key molecular-level photograph of this process from which computer simulations were initiated providing a movie on the nanosecond timescale,” added Baron. “For example, molecular films like these allow us to predict the routes of individual oxygen molecules to the reactive site of LSD1.”

Of particular note, the UCSD-University of Pavia researchers examined picosecond-by-picosecond movement of the LSD1-CoREST complex as it binds to SNAIL1, and changes – at the atomic level -- resulting from this activity. The “movies” show that oxygen can continue to reach the enzyme’s active site even when it’s bound to the histone tail, allowing the enzyme to perform its de-methylating task without needing to detach from its target.

“Overall, these observations and data are of crucial importance to understand which of these processes is the most promising target for future drugs,” said Mattevi. “Potent drugs could be developed targeting both the binding cleft of LSD1, as well as the active site access by oxygen molecules.”

Mattevi’s group in Pavia recently demonstrated that inhibitors to LSD1, and a close relative known as LSD2, strongly increased the potency of a chemotherapeutic agent called retinoic acid in the treatment of acute promyelocytic leukemia. Further, they recently discovered that known antidepressant drug inhibitors of enzymes with similar active sites (monoamine oxidase A and B) are promising candidates to develop highly specific inhibitors of LSD1 and LSD2.

Baron added he is in the process of establishing an independent research group focused on epigenetic drug discovery and design of LSD1 and LSD2 inhibitors using computational methodologies developed by the McCammon lab.

Swimming microbes monitor water quality

 By Peter Gwynne  Scott Gallager works on the swimming behavioral spectrophotometer to analyze the safety of a water sample. Credit: Tom Kleindinst Copyright Woods Hole Oceanographic Institution (WHOI)

Miners used to rely on canaries to alert them to dangerous build-ups of gases. Now much smaller animals -- the smallest of all -- can warn of toxins in water supplies.

Single-celled creatures called protozoa provide the warning when they change the way they swim. If efforts to develop the patent-pending technology succeed, the "swimming behavioral spectrophotometer", or SBS, could be coming to a water supply near you.

The SBS, said inventor Scott Gallager, an associate scientist at the Woods Hole Oceanographic Institution in Mass., can potentially "monitor all the drinking water in the world."

To facilitate that goal, local start-up company Petrel Biosensors, Inc., has licensed the technology.

"Once we have financing, it will take between 12-15 months to get to a commercial product," said CEO Robert Curtis.

Visible only through a microscope, protozoa are covered in hair-like projections called cilia. In clean water, cilia propel the protozoa forward by working together like the oars of a rowing team. Pollutants in water can interfere with the movement of calcium through the microbes' bodies to the cilia. That alters their owners' swimming styles. The protozoa might spiral out of control or careen erratically around their tanks.

Different pollutants impact the swimming styles in identifiable ways. And various types of protozoa react to specific pollutants and other toxins in different ways. By using just a few types of protozoa in the SBS, scientists can trace a wide range of impurities, including pesticides, heavy metals, and biological warfare agents.

Between 50-250 protozoa are placed in the water to be tested, in a chamber about the size of a container for emergency gasoline. A camera records their movements for any time between 10 seconds and a minute.

The camera then feeds the images to software that evaluates about 50 characteristics of the microbes' swimming. The software determines the purity of the water sample by comparing the characteristics with those of protozoa in distilled water.

The SBS uses a colored light system to reveal the water's quality. Green indicates that the water is safe, yellow calls for further testing, and red indicates danger, meaning, don't drink the water.

Gallager and his colleague Wade McGillis, now at Columbia University's Lamont-Doherty Earth Observatory in Palisades, N.Y., developed the SBS with a grant from the Defense Department.

"The technology is very quick; it monitors in real time," said Curtis. "It's got a great ability to detect a broad range of contaminants."

The SBS remains in a pilot stage. Eventually, Curtis expects to miniaturize the device and that each test will cost $1-2, in contrast to the $50-250 per test for existing methods. He also claimed the test will reduce the response time and the number of false positives and negatives.

One reason for the high cost of current methods is that they are very labor-intensive, said Andrew Gottlieb, executive director of the Cape Cod Water Protection Collaborative.

"So anything that can give us a line on less expensive water quality monitoring is good," Gottlieb said.

Initially, Petrel Biosensors plans to use the technology to test discharges of industrial waste water and runoff from storm drains. "Then we'll target municipal drinking water and military installations," Curtis said.

Another potential application: rapid testing of water that engineers use in hydraulic fracturing of rocks in the search for oil and gas.

 

Sleeping Trojan horse to aid imaging of diseased cells

February 17, 2011 A unique strategy developed by researchers at Cardiff University is opening up new possibilities for improving medical imaging.

Medical imaging often requires getting unnatural materials such as metal ions into cells, a process which is a major challenge across a range of biomedical disciplines. One technique currently used is called the 'Trojan Horse' in which the drug or imaging agent is attached to something naturally taken up by cells.

The Cardiff team, made of researchers from the Schools of Chemistry and Biosciences, has taken the technique one step further with the development of a 'sleeping Trojan horse'. The first example of its kind, this is delivery system resolves some of the current difficulties involved in transporting metal ions into cells.

It is not itself taken up by cells so does not interfere with natural functions until it is 'woken' by the addition of the metal ions. This minimises the unwanted uptake and need for time-consuming purification associated with the common 'Trojan Horse' technique.

The research was led by Dr Mike Coogan, Senior Lecturer in Synthetic Chemistry, along with the paper's first author, Flora Thorp-Greenwood.

Dr Coogan said: "The sleeping Trojan horse process happens rapidly, and the vessel is capable of carrying metals which have positron-emitting isotopes, so it has potential for use in bimodal fluorescence and PET imaging. Combined agents for these types of imaging are known but rare, so this is a significant development in the field.

"There is also additional potential for use in radiotherapy as the metal-bearing form not only enters cells but also localises in the nucleolus. In principle, the concept could also be used to improve delivery of a huge range of drugs and imaging agents into cells or the body."

The study A 'Sleeping Trojan Horse' which transports metal ions into cells, localises in nucleoli, and has potential for bimodal fluorescence/PET imaging is published in the advanced article section of Chemical Communications. Published by the Royal Society of Chemistry, this is the leading weekly journal for the publication of important developments in the chemical sciences.

Provided by Cardiff University (news : web)

Rate this story - not rated yet

The hidden danger of oxygen

 

Birch pollen with allergenic potential. The colouring of the fluorescence microscopic picture shows the difference in the chemical composition of the pollen which can contain allergy-triggering protein in the cell and on its surface. Credit: Manabu Shiraiwa/MPI for Chemistry

(PhysOrg.com) -- New findings from German researchers at the Max Planck Institute for Chemistry and the Paul Scherrer Institute in Switzerland help to explain how toxic and allergy-causing substances in our air are formed. The scientists have for the first time detected long lived reactive oxygen intermediates on the surface of aerosol particles. These forms of oxygen survive here for more than 100 seconds and in that time react with other air pollutants such as nitrogen oxides. Chemically speaking, the dust particles are oxidized and nitrated. This is what makes soot particles more toxic and increases the potential of pollen to cause allergies.

Although scientists have suspected for years that these intermediate forms exist, it was believed that they disappeared within a fraction of a second, and therefore had little impact on chemical processes in the atmosphere. The intermediate forms of oxygen develop when ozone reacts with particulate matter such as soot, polycyclic aromatic hydrocarbons or pollen proteins.

"Not only does our research resolve earlier contradictions between theoretical calculations and measurements, it also shows that intermediates are also responsible for many atmospheric and physiological reactions," said Manabu Shiraiwa, lead author of the study.

Ulrich Pöschl, head of the aerosol research group at the Max Planck Institute in Mainz, goes one step further: "We suspect that the increase in allergies in industrialized countries is linked to these reactions. The more ozone and nitrogen oxides that are emitted by industry and traffic, the more frequently organic molecules such as birch pollen proteins are being nitrated and this is what irritates our immune system.” Pöschl and his colleagues have obtained evidence that these nitrated proteins can indeed cause more severe allergic reactions than the native protein form. If this hypothesis is confirmed, human health would be at even greater risk from combustion-related emissions than previously thought.

The reactive oxygen intermediates may also explain some of the direct adverse health effects of diesel soot and tobacco smoke particles. The polycyclic aromatic hydrocarbons found on the surface of these particles again readily react with ozone and form long-lived reactive oxygen intermediates. If the particles are inhaled, they interact directly with physiological processes in the human lung and other organs.

The scientists assume also that the oxygen intermediates may have an indirect effect on our climate. Presumably they are involved in the formation and growth of fine organic particles from volatile organic compounds emitted from both natural and manufactured sources such as vegetation and industrial activities. These particles scatter sunlight and influence the formation of clouds and precipitation, thus affecting the Earth’s energy balance and the hydrological cycle.

To quantify the atmospheric abundance and climatic effects of reactive oxygen intermediates, the Mainz-based Max Planck researchers will perform further kinetic experiments and extensive, numerical simulations. In collaboration with biomedical partners, they are also investigating the physiological effects of nitrated proteins formed by the oxygen intermediates reacting with nitrogen oxides.

More information: Manabu Shiraiwa, et al. The role of long-lived reactive oxygen intermediates in the reaction of ozone with aerosol particles. Nature Chemistry, 20. Februar 2011; doi: 10.1038/NCHEM.988

Provided by Max-Planck-Gesellschaft (news : web)

Manipulating molecules for a new breed of electronics

ScienceDaily (Feb. 21, 2011) — In research recently appearing in the journal Nature Nanotechnology, Nongjian "NJ" Tao, a researcher at the Biodesign Institute at Arizona State University, has demonstrated a clever way of controlling electrical conductance of a single molecule, by exploiting the molecule's mechanical properties.

Such control may eventually play a role in the design of ultra-tiny electrical gadgets, created to perform myriad useful tasks, from biological and chemical sensing to improving telecommunications and computer memory.

Tao leads a research team used to dealing with the challenges entailed in creating electrical devices of this size, where quirky effects of the quantum world often dominate device behavior. As Tao explains, one such issue is defining and controlling the electrical conductance of a single molecule, attached to a pair of gold electrodes.

"Some molecules have unusual electromechanical properties, which are unlike silicon-based materials. A molecule can also recognize other molecules via specific interactions." These unique properties can offer tremendous functional flexibility to designers of nanoscale devices.

In the current research, Tao examines the electromechanical properties of single molecules sandwiched between conducting electrodes. When a voltage is applied, a resulting flow of current can be measured. A particular type of molecule, known as pentaphenylene, was used and its electrical conductance examined.

Tao's group was able to vary the conductance by as much as an order of magnitude, simply by changing the orientation of the molecule with respect to the electrode surfaces. Specifically, the molecule's tilt angle was altered, with conductance rising as the distance separating the electrodes decreased, and reaching a maximum when the molecule was poised between the electrodes at 90 degrees.

The reason for the dramatic fluctuation in conductance has to do with the so-called pi orbitals of the electrons making up the molecules, and their interaction with electron orbitals in the attached electrodes. As Tao notes, pi orbitals may be thought of as electron clouds, protruding perpendicularly from either side of the plane of the molecule. When the tilt angle of a molecule trapped between two electrodes is altered, these pi orbitals can come in contact and blend with electron orbitals contained in the gold electrode -- a process known as lateral coupling. This lateral coupling of orbitals has the effect of increasing conductance.

In the case of the pentaphenylene molecule, the lateral coupling effect was pronounced, with conductance levels increasing up to 10 times as the lateral coupling of orbitals came into greater play. In contrast, the tetraphenyl molecule used as a control for the experiments did not exhibit lateral coupling and conductance values remained constant, regardless of the tilt angle applied to the molecule. Tao says that molecules can now be designed to either exploit or minimize lateral coupling effects of orbitals, thereby permitting the fine-tuning of conductance properties, based on an application's specific requirements.

A further self-check on the conductance results was carried out using a modulation method. Here, the molecule's position was jiggled in 3 spatial directions and the conductance values observed. Only when these rapid perturbations specifically changed the tilt angle of the molecule relative to the electrode were conductance values altered, indicating that lateral coupling of electron orbitals was indeed responsible for the effect. Tao also suggests that this modulation technique may be broadly applied as a new method for evaluating conductance changes in molecular-scale systems.

The research was supported by the Department of Energy -- Basic Energy Science program.

In addition to directing the Biodesign Institute's Center for Bioelectronics and Biosensors, Tao is a professor in the School of Electrical, Computer, and Energy Engineering, at ASU's Ira A. Fulton Schools of Engineering, and an affiliated professor of chemistry and biochemistry, physics and material engineering.

Story Source:

The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by Arizona State University. The original article was written by Richard Harth, Science Writer at The Biodesign Institute.

Journal Reference:

Ismael Diez-Perez, Joshua Hihath, Thomas Hines, Zhong-Sheng Wang, Gang Zhou, Klaus Müllen & Nongjian Tao. Controlling single-molecule conductance through lateral coupling of ? orbitals. Nature Nanotechnology, 20 February 2011 DOI: 10.1038/nnano.2011.20

Note: If no author is given, the source is cited instead.

Disclaimer: Views expressed in this article do not necessarily reflect those of ScienceDaily or its staff.

Greener chemical reaction for pharmaceutical production awarded $50,000 in development funding from GreenCentre Canada

A key chemical process used by the pharmaceutical industry has the potential to become less expensive and more energy efficient, thanks to a green chemistry discovery at the University of British Columbia.

Dr. Laurel Schafer, a professor of chemistry at UBC, has created a method and a compound that affects a crucial chemical reaction in drug production. Current methods of producing this reaction are costly because they are energy-intensive and require multiple steps that generate waste. 

Dr. Schafer's technology reduces extra steps, is energy-efficient and reduces waste byproducts. It also uses less expensive reagents, substances that react with other substances to produce chemical products.

Recognizing the green promise in Dr. Schafer's work, GreenCentre Canada has awarded Dr. Schafer $50,000 in Proof of Principle funding to pursue further development of her technology.

Here you can receive further information concerning the news opposite directly from the publisher:

This is where you can add this news to your personal favourites

The lock shapes the key: Mystery about recognition of unfolded proteins solved

Proteins normally recognize each other by their specific 3-D structure. If the key fits in the lock, a reaction can take place. However there are reactions at the onset of which the key does not really have a shape. German chemists at the Technische Universitaet Muenchen and the Max Planck Research Unit for Enzymology of Protein Folding (Halle/Saale) have now shown how this might work. Their results will appear in PNAS this week.

Interactions between proteins are of fundamental importance for a number of processes in virtually every living cell. However, in order for the proteins to carry out any biological function, they must first assume their specific three-dimensional shape. A number of reactions have been described in recent years, where one of the interaction partners does not assume its active structure until the actual binding process commences. It was still a great mystery, though, how the binding partners could actually recognize such unstructured proteins.

Scientists led by Professor Thomas Kiefhaber (TUM) posed the question of whether local properties are sufficient for the recognition to take place or whether the unstructured binding partner first had to assume a specific spatial structure. Possible candidates were regularly structural elements such as coiled ?-helices or ß-pleated sheets, in which internal hydrogen bonds are formed.

In collaboration with Professor Gunter Fischer's research group at the Max Planck Research Unit for Enzymology of Protein Folding Halle/Saale, the scientists developed a novel method for observing the formation of individual hydrogen bonds in the course of a binding process.

The model system was the enzyme ribonuclease S, which in its active form comprises the S-protein and an ?-helical S-peptide. While the S-protein has a defined three-dimensional shape, the S-peptide on its own is initially unfolded. The scientists attempted to determine whether the S-protein recognizes the unstructured S-peptide or a small fraction of peptide molecules in their helical conformation. To this end, the oxygen atoms in the peptide bonds were replaced by sulfur atoms via chemical protein synthesis, causing individual hydrogen bonds to become destabilized.

Time-based measurements of the binding process of the altered peptide have now shown that the hydrogen bonds in the S-peptide, and as such in the ?-helical structure, do not form until after the bonding to the S-protein. Thus, they cannot play a role in the recognition process. Protein-protein recognition in this case takes place via hydrophobic interaction of the S-protein with two spatially clearly defined areas of the unstructured S-peptide.

These results are of fundamental importance for understanding the mechanism of protein-protein interactions. In the future, this method can be used to examine in detail the structure formation in proteins in other systems, as well.

More information: Mapping backbone and side-chain interactions in the transition state of a coupled protein folding and binding reaction, Annett Bachmann, Dirk Wildemann, Florian Praetorius, Gunter Fischer, and Thomas Kiefhaber PNAS, Early Edition, Publikation Online in der Woche vom 14.02.2011, http://www.pnas.or … s.1012668108

Provided by Technische Universitaet Muenchen

Warring molecules keep the colon cancer-free

 By Jill Jess A molecular battle is going on inside your colon, and University of Kansas researchers want neither side to win.

KU associate professor of molecular biosciences Kristi Neufeld and her graduate student Erick Spears study how a molecule, a protein called APC, suppresses colon cancer. In a recent article in the Journal of Biological Chemistry, they explain how a drug might someday treat the disease by blocking the action of one of APC’s molecular opponents.

Currently, no drug specifically treats colon cancer. The vast majority of cases derive from a faulty gene in intestinal cells that produces a defective APC protein. APC — whose hefty full name is Adenomatous Polyposis Coli — is named after the intestinal polyps it helps prevent. Polyps can turn malignant if not removed by surgery.

“Many researchers are trying to figure out now why this protein is so critical for preventing polyp formation,” Neufeld said. “Mine has been one of those labs.”

Neufeld’s work concerns the health of an astonishingly sophisticated organ. The last part of the digestive system, the colon absorbs water, salt, some nutrients, and keeps symbiotic bacteria in check. Key to its success are stem cells in its lining. These cells reproduce or mature to take different jobs, and then shed when they wear out.

Inside the cells, a governing board of proteins decides whether more cells should reproduce — divide — or take on different jobs — differentiate. Scientists have previously determined that APC always advises differentiation. At the same time, another protein board member pushes for division. It is named Musashi after a renowned samurai swordsman.

APC and Musashi not only have opposite agendas in the colon, Neufeld and Spears now find, but also actively sabotage each other: behind the scenes, APC controls how many Musashi proteins get made and vice versa. When APC is absent, Musashi in a sense shouts louder, causing cells to proliferate out of control and form polyps and tumors.

The health of the colon requires both Musashi and APC. Restoring APC to people who lack a proper copy of its gene is still out of reach. But a designer drug may be able to subdue Musashi.

“Eighty percent of colon cancers will have a nonfunctioning APC protein. Technology doesn’t allow us to fix that,” Neufeld said. “Keeping Musashi controlled — we can try to do that in another way.”

Next, the team will look for a drug that will inhibit Musashi and will test their hypothesis in mice. The current work was done in cultures of human colon cells.

“Talking to different people, I am struck by how prevalent the disease is,” Neufeld said. “The research that I do is still years away from something that would benefit patients directly. But we’re getting closer. And I do think about how great it would be if something we found in the lab could be translated into a real therapy.”

Provided by University of Kansas

 

X-rays show why van Gogh paintings lose their shine

 

This illustration shows how X-Rays were used to study why van Gogh paintings lose their shine. Top: a photo of the painting "Bank of the River Seine" on display at the van Gogh Museum, divided in three and artificially colored to simulate a possible state in 1887 and 2050. Bottom left: microscopic samples from art masterpieces moulded in plexiglass blocks. The tube with yellow chrome paint is from the personal collection of M. Cotte. Bottom right: X-ray microscope set-up at the ESRF with a sample block ready for a scan. Centre: an image made using a high-resolution, analytical electron microscope to show affected pigment grains from the van Gogh painting, and how the color at their surface has changed due to reduction of chromium. The scale bar indicates the size of these pigments. Credit: ESRF/Antwerp University/Van Gogh Museum

Scientists using synchrotron X-rays have identified the chemical reaction in two van Gogh paintings that alters originally bright yellow colors into brown shades.

Scientists have identified a complex chemical reaction responsible for the degradation of two paintings by Vincent van Gogh and other artists of the late 19th century. This discovery is a first step to understanding how to stop the bright yellow colours of van Gogh's most famous paintings from being covered by a brown shade, and fading over time. In the meantime, the results suggest shielding affected paintings as much as possible from UV and sunlight. The results are published in the 15 February 2011 issue of Analytical Chemistry.

You need Flash installed to watch this video

A microsample is taken from the van Gogh painting "Bank of river Seine" on display at the van Gogh Museum in Amsterdam (Netherlands), and then analyzed at the X-rays microscope at the European Synchrotron Radiation Facility in Grenoble (France). Credit: ESRF/van Gogh Museum

The work was carried out by an international team of scientists from four countries led by Koen Janssens of Antwerp University (Belgium), with Letizia Monico, an Italian chemist preparing a Ph.D. at Perugia University (Italy), taking the centre stage in the experiments. As an Erasmus student, she worked for one year in Janssens' research group in Antwerp, and is also the lead author of the two papers. Scientists from the CNR Institute of Molecular Science and Technologies (Perugia, Italy), the CNRS C2RMF (Paris, France), TU Delft (Netherlands) and the van Gogh Museum (Amsterdam, Netherlands) were also part of the team.

Uncovering the secrets of the chemical reaction needed deployment of an impressive arsenal of analytical tools, with synchrotron X-rays at the ESRF in Grenoble (France) providing the final answers. "For every Italian, conservation of masterpieces has always mattered. I am pleased that science has now added a piece to a puzzle that is a big headache for so many museums" says Letizia Monico from University of Perugia.

The experiment reads like a crime scene investigation. The scientists employed an X-ray beam of microscopic dimensions to reveal a complex chemical reaction taking place in the incredibly thin layer where the paint meets the varnish. Sunlight can penetrate only a few micrometers into the paint, but over this short distance, it will trigger a hitherto unknown chemical reaction turning chrome yellow into brown pigments, altering the original composition.

Van Gogh's decision to use novel bright colours in his paintings is a major milestone in the history of art. He deliberately chose colours that conveyed mood and emotion, rather than employing them realistically. At the time, this was completely unheard of and, without major innovations in pigment manufacturing made in the 19th century, would also have been impossible.

It was the vibrancy of new industrial pigments such as chrome yellow which allowed van Gogh to achieve the intensity of, for example, his series of Sunflowers paintings. He started to paint in these bright colours after leaving his native Holland for France where he became friends with artists who shared his new ideas about the use of colours. For one of them, Paul Gauguin, he started painting yellow sunflower motifs as a decoration for his bedroom.

The fact that yellow chrome paint darkens under sunlight has been known since the early 19th Century. However, not all period paintings are affected, nor does it always happen at the same speed. As chrome yellow is toxic, artists quickly switched to new alternatives in the 1950s. However, Vincent van Gogh did not have this choice, and to preserve his work and that of many comtemporaries, interest in the darkening of chrome yellow is now rising again.

To solve a chemical puzzle nearly 200 years old, the team around Janssens used a two-step approach: first, they collected samples from three left-over historic paint tubes. After these samples had been artificially aged for 500 hours using an UV-lamp, only one sample, from a paint tube belonging to the Flemish Fauvist Rik Wouters (1882-1913), showed significant darkening. Within 3 weeks, its surface of originally bright yellow had become chocolate brown. This sample was taken as the best candidate for having undergone the fatal chemical reaction, and sophisticated X-ray analysis identified the darkening of the top layer as linked to a reduction of the chromium in the chrome yellow from Cr(VI) to Cr(III). The scientists also reproduced Wouters' chrome yellow paint and found that the darkening effect could be provoked by UV light.

Enlarge

This is an image, made using an optical microscope, of the sample taken from ?Bank of the Seine? studied with synchrotron X-rays. The brown layer on top of the paint is varnish, it appears opaque but in reality it lets light through. The brown pigments are invisible to the optical microscope. They are located at the interface between varnish and paint, in a layer less than three micrometers thick. The scale bar at the bottom indicates the size of the sample. Credit: University of Antwerp, Department of Chemistry.

In the second step, the scientists used the same methods to examine samples from affected areas of two van Gogh paintings, View of Arles with Irises (1888) and Bank of the Seine (1887), both on display in the Van Gogh Museum in Amsterdam.

"This type of cutting edge research is crucial to advance our understanding of how paintings age and should be conserved for future generations", says Ella Hendriks of the van Gogh Museum Amsterdam.

Because the affected areas in these multicoloured samples were even more difficult to locate than in the artificially aged ones, an impressive array of analytical tools had to be deployed which required the samples travelling to laboratories across Europe. The results indicate that the reduction reaction from Cr(VI) to Cr(III) is likely to also have taken place in the two van Gogh paintings.

The microscopic X-ray beam also showed that Cr(III) was especially prominent in the presence of chemical compounds which contained barium and sulphur. Based on this observation, the scientists speculate that van Gogh's technique of blending white and yellow paint might be the cause of the darkening of his yellow paint.

"Our next experiments are already in the pipeline. Obviously, we want to understand which conditions favour the reduction of chromium, and whether there is any hope to revert pigments to the original state in paintings where it is already taking place.", summarises Koen Janssens from University of Antwerp.

Note to Editors: the crime scene investigation

The techniques used by the scientists included X-ray diffraction along with various spectroscopies employing infrared radiation, electrons and X-rays at the universities of Antwerp and Perugia, and at two synchrotrons (ESRF and DESY).

"I am not aware of a similarly big effort ever having been made for the chemistry of an oil painting", says Joris Dik, Professor at Delft Technical University.

In the decisive step, two techniques were combined using a single X-ray beam at the ESRF: X-Ray fluorescence (XRF) and X-Ray absorption near-edge spectroscopy (XANES). For the XRF, the microscopic beam size (0.9 x 0.25 µm2) made possible to separate the study of degraded and unaffected areas, and the XANES technique proved the speciation of chromium, i.e. the reduction from Cr(VI) to Cr(III).

"Our X-ray beam is one hundred times thinner than a human hair, and it reveals subtle chemical processes over equally minuscule areas. Making this possible has opened the door to a whole new world of discovery for art historians and conservators," says Marine Cotte, an ESRF scientist also working at CNRS/Musée du Louvre.

The reduction of chromium that had been observed in the artificially aged sample from the atelier of Rik Wouters was finally confirmed in both microsamples from the van Gogh paintings.

The study was completed with a nanoscopic investigation of the discoloured paint using electron energy loss spectroscopy at the University of Antwerp, which confirmed the results and showed that the newly formed Cr(III) compounds were formed as a nanometer-thin coating of the pigment particles that constitute the paint.

More information: L. Monico et al., Degradation Process of Lead Chromate in Paintings by Vincent van Gogh Studied by Means of Synchrotron X-ray Spectromicroscopy and Related Methods. 1. Artificially Aged Model Samples and 2. Original Paint Layer Samples, Analytical Chemistry 15 February 2011.

Provided by European Synchrotron Radiation Facility

Venom of marine snails provide new drugs

 Baldomero Olivera studies chemical compounds found in the venoms of marine cone snails, a potential source of powerful, yet safe and effective drugs. He will discuss the development of Prialt - an FDA-approved drug for intractable, chronic pain - and the potential for new drugs during a free public lecture at the University of Utah.

The conventional picture of a snail is a slow-moving, plant-eating, shelled animal found in gardens. However, in the marine environment, there are more than 100,000 species of snails. About 100 different species have evolved to become venomous predators that specialize in hunting fish. These fish-hunting Conus snails harpoon fish with a hypodermic needle-like tooth that injects paralyzing venom made up of 100 chemical components.

"The long-range goal is to use these toxins as an entrée for studying key molecules in the central nervous system," Olivera says.

The fact that the poisons can be synthesized and categorized easily will enable researchers to learn more about parts of the nervous system affected by the Conus toxins.

The precise mechanism that accounts for the biological activity of most peptides present in cone snail venoms has not yet been determined. A major challenge in the next few years is to clarify the molecular mechanisms through which the different peptides in Conus venom elicit their profound behavioral effects.

The natural form of Prialt - a drug for severe pain approved in 2004 by the U.S. Food and Drug Administration - was discovered in Olivera's lab in 1979 by J. Michael McIntosh, then an incoming freshman at the University of Utah and now a professor of psychiatry and research professor of biology. The drug was isolated from the fish-hunting cone snail Conus magus, or magician's cone, which is only 1.5 inches long.

Prialt is injected into the fluid surrounding the spinal cord to treat chronic, intractable pain suffered by people with cancer, AIDS, injury, failed back surgery or certain nervous system disorders.

Olivera was named a distinguished professor of biology at the University of Utah in 1992. He is the author of more than 250 scientific publications. In 2006, he was appointed a Howard Hughes Medical Institute Professor. He was elected to the Institute of Medicine in 2007 and to the National Academy of Sciences in 2009.

Valentine's Day can be scientific, romantic

Who said there is no romance in science? Well there is, and it comes in many different chemical compounds!
In celebration of Valentine’s Day the team behind the Periodic Table of Videos at The University of Nottingham has created a special perfume called ‘Mendeleev’s Dream’.

The perfume has been named after Dmitri Mendeleev the 19th century Russian scientist who created the Periodic Table – which has made this group of 21st century scientists into award winning YouTube hit.
Created in the labs of the School of Chemistry, the perfume is laced with Vanillin for the essence of ice cream, Cinnamaldehyde with its warmth and colour of cinnamon, Hexachloroplatinic Acid for some platinum bling, Citronellol to produce the classic scent of lemons and Theobromine, an extract of cocoa - to tempt the lady in your life with the irresistible aroma of chocolate!
Professor Martyn Poliakoff is one of the ‘noses’ involved in the creation of this perfume. He said: "The video was really fun to make and a great opportunity to blend light hearted banter with some serious points about the role of chemicals in various aspects of our lives."
Because everything they make is created in a scientific research laboratory nothing they produce can be consumed or used by humans. So Mendeleev’s Dream is what it says – just a dream! Even the special birthday cake they made to celebrate their first anniversary had to be exploded – under strict safety conditions.
To find out more about the Periodic Table of Videos and how it is making science more accessible follow the scent: http://www.periodicvideos.com
Professor Poliakoff said: “Mendeleev was one of the first great science communicators. Crowds of students filled lecture halls to hear him speak and he never lost touch with the classroom. We are delighted that his Periodic Table is now enabling us to communicate with new generations of young scientists. If a little fun on Valentine’s Day teaches people something about chemistry and science then we have had some success.”

Same rules apply to some experimental systems regardless of scale

New experiments show that common scientific rules can apply to significantly different phenomena operating on vastly different scales.

The results raise the possibility of making discoveries pertaining to phenomena that would be too large or impractical to recreate in the laboratory, said Cheng Chin, associate professor in physics and the James Franck Institute at the University of Chicago. Chin and associates Chen-Lung Hung, Xibo Zhang and Nathan Gemelke will publish their results in the Feb. 10, 2011 issue of the journal Nature.

Chin aspires to simulate the impossibly hot conditions that followed the big bang, during the earliest moments of the universe, by using an ultracold vacuum chamber in his laboratory. "It's fascinating to think about all these connections," he said.

The UChicago experiments demonstrate the validity of two widely discussed topics in the physics community today: scale invariance and universality.

Theoretical physicist Lev Pitaevskii had predicted that scale invariance would apply to a two-dimensional, cold-atom gas in 1997. Scale invariance means that the properties of a given phenomenon will remain the same, no matter how much its size is expanded or contracted. This contrasts sharply the three-dimensional world of everyday life, where dynamics change dramatically.

In the biological world, for example, scale invariance does not apply to complex organisms like humans, but exists in simple biological structures like nautilus shells, ferns and even broccoli. In physics, special cases also exist that exhibit scale invariance. Fractal structures have been observed in nature, which manifest similar structures whether magnified 10, 1,000 or a million times.

"There are only a few systems in nature that can display this kind of scale invariance, and we have shown that our two-dimensional system belongs to this very special class," Chin explained. "Once you identify these special cases and see how they are all linked together, then you can bring all these physical phenomena under the same umbrella," Chin said. "Now they can be fully described using the same language."

Exotic transformation

The universality concept applies to matter that undergoes smooth phase transitions. In the physics of everyday life, a phase transition occurs when water freezes to ice on a cold winter day. The phase transition in the UChicago experiment is more exotic: In the experiment, cesium atoms transform from a gas to a superfluid, a form of matter that exists only at temperatures of hundreds of degrees below zero.

Theoretical physicists in the early 1970s predicted that weakly interacting two-dimensional gases would exhibit similar behaviors under a variety of conditions as they neared the critical point of phase transition. Their prediction has remained unverified until now.

In their experiment, the UChicago researchers super-cooled thousands of cesium atoms to 10 nano-Kelvin, billionths of a degree above absolute zero (-459.67 degrees Fahrenheit), then loaded them into a pancake-like laser trap. The trap simulated a two-dimensional system by restricting the atoms' motion vertically but allowed a significant degree of horizontal freedom.

Chin's team was able to control the properties of this cold-atom gas system to make it non-interacting, weakly interacting or strongly interacting and then compared the results.

"At the same time, we can prepare the two-dimensional system at different sizes and also at different temperatures," Chin said. They could adjust the size parameters from 10 to 100 microns (a human hair is approximately 50 microns in diameter), and the temperature parameters from 10 to 100 nano-Kelvin.

Their experiment showed that no matter how they changed these three parameters, just one general description could characterize the resulting dynamics.

"There's a strong reason to believe that this kind of scale invariance can be extrapolated and on a more fundamental level can be mapped to other types of two-dimensional systems," Chin said. "The bigger question is whether our observation can shed light on other complex phenomena in nature. So our next step will be to explore going beyond two-dimensional systems."

Story Source:

The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by University of Chicago.

Journal Reference:

Chen-Lung Hung, Xibo Zhang, Nathan Gemelke, Cheng Chin. Observation of scale invariance and universality in two-dimensional Bose gases. Nature, 2011; DOI: 10.1038/nature09722

Note: If no author is given, the source is cited instead.

Disclaimer: Views expressed in this article do not necessarily reflect those of ScienceDaily or its staff.

World's first programmable nanoprocessor: Nanowire tiles can perform arithmetic and logical functions

 Engineers and scientists collaborating at Harvard University and the MITRE Corporation have developed and demonstrated the world's first programmable nanoprocessor.

The groundbreaking prototype computer system, described in a paper appearing in the journal Nature, represents a significant step forward in the complexity of computer circuits that can be assembled from synthesized nanometer-scale components.

It also represents an advance because these ultra-tiny nanocircuits can be programmed electronically to perform a number of basic arithmetic and logical functions.

"This work represents a quantum jump forward in the complexity and function of circuits built from the bottom up, and thus demonstrates that this bottom-up paradigm, which is distinct from the way commercial circuits are built today, can yield nanoprocessors and other integrated systems of the future," says principal investigator Charles M. Lieber, who holds a joint appointment at Harvard's Department of Chemistry and Chemical Biology and School of Engineering and Applied Sciences.

The work was enabled by advances in the design and synthesis of nanowire building blocks. These nanowire components now demonstrate the reproducibility needed to build functional electronic circuits, and also do so at a size and material complexity difficult to achieve by traditional top-down approaches.

Moreover, the tiled architecture is fully scalable, allowing the assembly of much larger and ever more functional nanoprocessors.

"For the past 10 to 15 years, researchers working with nanowires, carbon nanotubes, and other nanostructures have struggled to build all but the most basic circuits, in large part due to variations in properties of individual nanostructures," says Lieber, the Mark Hyman Professor of Chemistry. "We have shown that this limitation can now be overcome and are excited about prospects of exploiting the bottom-up paradigm of biology in building future electronics."

An additional feature of the advance is that the circuits in the nanoprocessor operate using very little power, even allowing for their miniscule size, because their component nanowires contain transistor switches that are "nonvolatile."

This means that unlike transistors in conventional microcomputer circuits, once the nanowire transistors are programmed, they do not require any additional expenditure of electrical power for maintaining memory.

"Because of their very small size and very low power requirements, these new nanoprocessor circuits are building blocks that can control and enable an entirely new class of much smaller, lighter weight electronic sensors and consumer electronics," says co-author Shamik Das, the lead engineer in MITRE's Nanosystems Group.

"This new nanoprocessor represents a major milestone toward realizing the vision of a nanocomputer that was first articulated more than 50 years ago by physicist Richard Feynman," says James Ellenbogen, a chief scientist at MITRE.

Co-authors on the paper included four members of Lieber's lab at Harvard: Hao Yan (Ph.D. '10), SungWoo Nam (Ph.D. '10), Yongjie Hu (Ph.D. '10), and doctoral candidate Hwan Sung Choe, as well as collaborators at MITRE.

The research team at MITRE comprised Das, Ellenbogen, and nanotechnology laboratory director Jim Klemic. The MITRE Corporation is a not-for-profit company that provides systems engineering, research and development, and information technology support to the government. MITRE's principal locations are in Bedford, Mass., and McLean, Va.

The research was supported by a Department of Defense National Security Science and Engineering Faculty Fellowship, the National Nanotechnology Initiative, and the MITRE Innovation Program.

Story Source:

The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by Harvard University, via EurekAlert!, a service of AAAS.

Journal Reference:

Hao Yan, Hwan Sung Choe, SungWoo Nam, Yongjie Hu, Shamik Das, James F. Klemic, James C. Ellenbogen, Charles M. Lieber. Programmable nanowire circuits for nanoprocessors. Nature, 2011; 470 (7333): 240 DOI: 10.1038/nature09749

Note: If no author is given, the source is cited instead.

Disclaimer: Views expressed in this article do not necessarily reflect those of ScienceDaily or its staff.

Scientists customize a magnet's performance by strategically replacing key atoms

Scientists have given us a plethora of new materials -- all created by combining individual elements under varying temperatures and other conditions. But to tweak an intermetallic compound even more, in order to give it the attributes you desire, you have to go deeper and re-arrange individual atoms.

It's a process similar to what bioengineers employ when they add and delete genes to create synthetic organisms, and it was the focus of a group of researchers at the U.S. Department of Energy's Ames Laboratory, when they replaced key atoms in a gadolinium-germanium magnetic compound with lutetium and lanthanum atoms.

The group was led by Vitalij Pecharsky, Ames Lab senior scientist and Distinguished Professor of Materials Science and Engineering at Iowa State University, and included his Lab colleagues, Karl Gschneidner Jr., Ames Lab senior metallurgist and Distinguished Professor of MS&E at ISU, and Gordon Miller, Ames Lab senior scientist and ISU professor of chemistry, along with assistant scientists Yaroslav Mudryk and Durga Paudyal. Also participating was Sumohan Misra, research associate at the DOE's SLAC National Accelerator in Menlo Park, Calif., formerly a Ph.D. student of Miller's.

Creating materials by design is no easy task, especially in the case of the complex gadolinium-germanium -- Gd5Ge4 -- compound. Making things even more difficult, the compound's structure is highly symmetrical, which is common in intermetallics, so predicting which atoms are key to changing the material's characteristics would be difficult if not impossible unless some methodology was available to help in the selection process.

The Gd5Ge4 compound's uniformity results from the fact that like nearly all metallic solids' atoms are arranged in a highly symmetrical crystal structure called a lattice. The more complex the material, the more intricate its lattice. And while the individual elements making up the lattice influence its characteristics, in some cases the location of specific atoms within the lattice can also have a profound influence on such things as its melting point, mechanical strength or -- in the case of magnets -- ferromagnetic properties.

"Individuality doesn't happen often among the atoms of metallic crystals," Pecharsky explained, "But atoms still are able to 'cooperate' with one another in areas such as magnetic ordering and superconductivity."

By discovering these cooperative relationships, scientists can determine what will happen if they replace one or more of the atoms with those of another element, which is precisely what the team accomplished.

"We revealed that a single site occupied by the Gd atoms is much more active than all of the other Gd sites when it comes to bringing the ferromagnetic order in a complex crystal structure of gadolinium germanide," Pecharsky said.

Pecharsky, Gschneidner and other researchers at the Ames Lab have spent years working with gadolinium alloys, because of the magnetic compound's use in the green, energy-saving field of magnetic refrigeration. However, that was not the main reason the Ames Lab researchers chose Gd5Ge4 for their work.

As it turns out, "the metal exhibits an impressive combination of intriguing and potentially important properties, the researchers explained in their paper, "Controlling Magnetism of a Complex Metallic System Using Atomic Individualism," published in the August 10, 2010 Physical Review Letters. "The extraordinary responsiveness to relatively weak external stimuli makes Gd5Ge4 and related compounds a phenomenal playground for condensed matter science."

Besides being unusually responsive, Gd5Ge4 was an ideal alloy for the work, because any changes in its magnetic properties resulting from the group's manipulations could be easily measured.

In 2008, Pecharsky and members of the same research team had already discovered that adding silicon to the alloy resulted in a magnetostructural transition that occurred without the application of a magnetic field. Chemical pressure alone was able to enhance the material's ferromagnetism.

That earlier finding led the team to experiment with other additions to the alloy. To ferret out precisely which atoms in the lattice were the best candidates for manipulation, the researchers called upon density functional theory, which is a means of studying the electronic structure of solids developed by Nobel Prize winning physicist Walter Kohn.

Kohn's methodology enabled the group to model the effects substituting small amounts of gadolinium atoms within the Gd5Ge4 solid with the elements lutetium and lanthanum. With the modeled results in hand, the group's next step was to create the actual alloys in the lab, in order to test the accuracy of their computer-based predictions.

In fact, the complex fabrication process confirmed the modeling results. The researchers found if they replaced just a few gadolinium atoms with lutetium, the result would be a severe loss in the alloy's ferromagnetism. By contrast, substituting an equal number of lanthanum atoms had no significant effect; though substituting greater amounts of lanthanum might have a more pronounced impact on the resulting alloy's ferromagnetism, the researchers speculated.

Going forward, the lessons learned in this experiment could have important far-reaching implications, as materials scientists search for new exotic substances to be used in this and future generations of high-tech products. "Knowing how to identify key atomic positions is similar to understanding the roles specific genes play in an organism's DNA sequence," Pecharsky said. "And that knowledge could ultimately lead to materials by design."

This research was funded by the DOE Office of Science.

Story Source:

The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by DOE/Ames Laboratory.

Note: If no author is given, the source is cited instead.

Disclaimer: Views expressed in this article do not necessarily reflect those of ScienceDaily or its staff.

X-rays show why van Gogh paintings lose their shine

 Scientists have identified a complex chemical reaction responsible for the degradation of two paintings by Vincent van Gogh and other artists of the late 19th century. This discovery is a first step to understanding how to stop the bright yellow colours of van Gogh's most famous paintings from being covered by a brown shade, and fading over time. In the meantime, the results suggest shielding affected paintings as much as possible from UV and sunlight.

The results are published in the 15 February 2011 issue of Analytical Chemistry.

The work was carried out by an international team of scientists from four countries led by Koen Janssens of Antwerp University (Belgium), with Letizia Monico, an Italian chemist preparing a Ph.D. at Perugia University (Italy), taking the centre stage in the experiments. As an Erasmus student, she worked for one year in Janssens' research group in Antwerp, and is also the lead author of the two papers. Scientists from the CNR Institute of Molecular Science and Technologies (Perugia, Italy), the CNRS C2RMF (Paris, France), TU Delft (Netherlands) and the van Gogh Museum (Amsterdam, Netherlands) were also part of the team.

Uncovering the secrets of the chemical reaction needed deployment of an impressive arsenal of analytical tools, with synchrotron X-rays at the ESRF in Grenoble (France) providing the final answers. "For every Italian, conservation of masterpieces has always mattered. I am pleased that science has now added a piece to a puzzle that is a big headache for so many museums" says Letizia Monico from University of Perugia.

The experiment reads like a crime scene investigation. The scientists employed an X-ray beam of microscopic dimensions to reveal a complex chemical reaction taking place in the incredibly thin layer where the paint meets the varnish. Sunlight can penetrate only a few micrometers into the paint, but over this short distance, it will trigger a hitherto unknown chemical reaction turning chrome yellow into brown pigments, altering the original composition.

Van Gogh's decision to use novel bright colours in his paintings is a major milestone in the history of art. He deliberately chose colours that conveyed mood and emotion, rather than employing them realistically. At the time, this was completely unheard of and, without major innovations in pigment manufacturing made in the 19th century, would also have been impossible.

It was the vibrancy of new industrial pigments such as chrome yellow which allowed van Gogh to achieve the intensity of, for example, his series of Sunflowers paintings. He started to paint in these bright colours after leaving his native Holland for France where he became friends with artists who shared his new ideas about the use of colours. For one of them, Paul Gauguin, he started painting yellow sunflower motifs as a decoration for his bedroom.

The fact that yellow chrome paint darkens under sunlight has been known since the early 19th Century. However, not all period paintings are affected, nor does it always happen at the same speed. As chrome yellow is toxic, artists quickly switched to new alternatives in the 1950s. However, Vincent van Gogh did not have this choice, and to preserve his work and that of many comtemporaries, interest in the darkening of chrome yellow is now rising again.

To solve a chemical puzzle nearly 200 years old, the team around Janssens used a two-step approach: first, they collected samples from three left-over historic paint tubes. After these samples had been artificially aged for 500 hours using an UV-lamp, only one sample, from a paint tube belonging to the Flemish Fauvist Rik Wouters (1882-1913), showed significant darkening. Within 3 weeks, its surface of originally bright yellow had become chocolate brown. This sample was taken as the best candidate for having undergone the fatal chemical reaction, and sophisticated X-ray analysis identified the darkening of the top layer as linked to a reduction of the chromium in the chrome yellow from Cr(VI) to Cr(III). The scientists also reproduced Wouters' chrome yellow paint and found that the darkening effect could be provoked by UV light.

In the second step, the scientists used the same methods to examine samples from affected areas of two van Gogh paintings, View of Arles with Irises (1888) and Bank of the Seine (1887), both on display in the Van Gogh Museum in Amsterdam.

"This type of cutting edge research is crucial to advance our understanding of how paintings age and should be conserved for future generations," says Ella Hendriks of the van Gogh Museum Amsterdam.

Because the affected areas in these multicoloured samples were even more difficult to locate than in the artificially aged ones, an impressive array of analytical tools had to be deployed which required the samples travelling to laboratories across Europe. The results indicate that the reduction reaction from Cr(VI) to Cr(III) is likely to also have taken place in the two van Gogh paintings.

The microscopic X-ray beam also showed that Cr(III) was especially prominent in the presence of chemical compounds which contained barium and sulphur. Based on this observation, the scientists speculate that van Gogh's technique of blending white and yellow paint might be the cause of the darkening of his yellow paint.

"Our next experiments are already in the pipeline. Obviously, we want to understand which conditions favour the reduction of chromium, and whether there is any hope to revert pigments to the original state in paintings where it is already taking place.," summarises Koen Janssens from University of Antwerp.

The techniques used by the scientists included X-ray diffraction along with various spectroscopies employing infrared radiation, electrons and X-rays at the universities of Antwerp and Perugia, and at two synchrotrons (ESRF and DESY).

"I am not aware of a similarly big effort ever having been made for the chemistry of an oil painting," says Joris Dik, Professor at Delft Technical University.

In the decisive step, two techniques were combined using a single X-ray beam at the ESRF: X-Ray fluorescence (XRF) and X-Ray absorption near-edge spectroscopy (XANES). For the XRF, the microscopic beam size (0.9 x 0.25 µm2) made possible to separate the study of degraded and unaffected areas, and the XANES technique proved the speciation of chromium, i.e. the reduction from Cr(VI) to Cr(III).

"Our X-ray beam is one hundred times thinner than a human hair, and it reveals subtle chemical processes over equally minuscule areas. Making this possible has opened the door to a whole new world of discovery for art historians and conservators," says Marine Cotte, an ESRF scientist also working at CNRS/Musée du Louvre.

The reduction of chromium that had been observed in the artificially aged sample from the atelier of Rik Wouters was finally confirmed in both microsamples from the van Gogh paintings.

The study was completed with a nanoscopic investigation of the discoloured paint using electron energy loss spectroscopy at the University of Antwerp, which confirmed the results and showed that the newly formed Cr(III) compounds were formed as a nanometer-thin coating of the pigment particles that constitute the paint.

Story Source:

The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by European Synchrotron Radiation Facility.

Journal Reference:

Letizia Monico, Geert Van der Snickt, Koen Janssens, Wout De Nolf, Costanza Miliani, Joris Dik, Marie Radepont, Ella Hendriks, Muriel Geldof, Marine Cotte. Degradation Process of Lead Chromate in Paintings by Vincent van Gogh Studied by Means of Synchrotron X-ray Spectromicroscopy and Related Methods. 2. Original Paint Layer Samples. Analytical Chemistry, 2011; 83 (4): 1224 DOI: 10.1021/ac1025122

Note: If no author is given, the source is cited instead.

Disclaimer: Views expressed in this article do not necessarily reflect those of ScienceDaily or its staff.

New transistor for plastic electronics exhibits the best of both worlds

In the quest to develop flexible plastic electronics, one of the stumbling blocks has been creating transistors with enough stability for them to function in a variety of environments while still maintaining the current needed to power the devices. Online in the journal Advanced Materials, researchers from the Georgia Institute of Technology describe a new method of combining top-gate organic field-effect transistors with a bilayer gate insulator. This allows the transistor to perform with incredible stability while exhibiting good current performance. In addition, the transistor can be mass produced in a regular atmosphere and can be created using lower temperatures, making it compatible with the plastic devices it will power.

The research team used an existing semiconductor and changed the gate dielectric because transistor performance depends not only on the semiconductor itself, but also on the interface between the semiconductor and the gate dielectric.

"Rather than using a single dielectric material, as many have done in the past, we developed a bilayer gate dielectric," said Bernard Kippelen, director of the Center for Organic Photonics and Electronics and professor in Georgia Tech's School of Electrical and Computer Engineering.

The bilayer dielectric is made of a fluorinated polymer known as CYTOP and a high-k metal-oxide layer created by atomic layer deposition. Used alone, each substance has its benefits and its drawbacks.

CYTOP is known to form few defects at the interface of the organic semiconductor, but it also has a very low dielectric constant, which requires an increase in drive voltage. The high-k metal-oxide uses low voltage, but doesn't have good stability because of a high number of defects on the interface.

So, Kippelen and his team wondered what would happen if they combined the two substances in a bilayer. Would the drawbacks cancel each other out?

"When we started to do the test experiments, the results were stunning. We were expecting good stability, but not to the point of having no degradation in mobility for more than a year," said Kippelen.

The team performed a battery of tests to see just how stable the bilayer was. They cycled the transistors 20,000 times. There was no degradation. They tested it under a continuous biostress where they ran the highest possible current through it. There was no degradation. They even stuck it in a plasma chamber for five minutes. There was still no degradation.

The only time they saw any degradation was when they dropped it into acetone for an hour. There was some degradation, but the transistor was still operational.

No one was more surprised than Kippelen.

"I had always questioned the concept of having air-stable field-effect transistors, because I thought you would always have to combine the transistors with some barrier coating to protect them from oxygen and moisture. We've proven ourselves wrong through this work," said Kippelen.

"By having the bilayer gate insulator we have two different degradation mechanisms that happen at the same time, but the effects are such that they compenstate for one another," explains Kippelen. "So if you use one it leads to a decrease of the current, if you use the other it leads to a shift of the thereshold voltage and over time to an increase of the current. But if you combine them, their effects cancel out."

"This is an elegant way of solving the problem. So, rather than trying to remove an effect, we took two processes that compliment one another and as a result you have a result that's rock stable."

The transistor conducts current and runs at a voltage comparable to amorphous silicon, the current industry standard used on glass substrates, but can be manufactured at temperatures below 150°C, in line with the capabilities of plastic substrates. It can also be created in a regular atmosphere, making it easier to fabricate than other transistors.

Applications for these transistors include smart bandages, RFID tags, plastic solar cells, light emitters for smart cards -- virtually any application where stable power and a flexible surface are needed.

In this paper the tests were performed on glass substrates. Next, the team plans on demonstrating the transistors on flexible plastic substrates. Then they will test the ability to manufacture the bilayer transistors with ink jet printing technologies.

Story Source:

The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by Georgia Institute of Technology.

Journal Reference:

Do Kyung Hwang, Canek Fuentes-Hernandez, Jungbae Kim, William J. Potscavage, Sung-Jin Kim, Bernard Kippelen. Top-Gate Organic Field-Effect Transistors with High Environmental and Operational Stability. Advanced Materials, 2011; DOI: 10.1002/adma.201004278

Note: If no author is given, the source is cited instead.

Disclaimer: Views expressed in this article do not necessarily reflect those of ScienceDaily or its staff.

Nanowires exhibit giant piezoelectricity

Gallium nitride (GaN) and zinc oxide (ZnO) are among the most technologically relevant semiconducting materials. Gallium nitride is ubiquitous today in optoelectronic elements such as blue lasers (hence the blue-ray disc) and light-emitting-diodes (LEDs); zinc oxide also finds many uses in optoelectronics and sensors.

In the past few years, though, nanostructures made of these materials have shown a plethora of potential functionalities, ranging from single-nanowire lasers and LEDs to more complex devices such as resonators and, more recently, nanogenerators that convert mechanical energy from the environment (body movements, for example) to power electronic devices. The latter application relies on the fact that GaN and ZnO are also piezoelectric materials, meaning that they produce electric charges as they are deformed.

In a paper published online in the journal Nano Letters, Horacio Espinosa, the James N. and Nancy J. Farley Professor in Manufacturing and Entrepreneurship at the McCormick School of Engineering and Applied Science at Northwestern University, and Ravi Agrawal, a graduate student in Espinosa's lab, reported that piezoelectricity in GaN and ZnO nanowires is in fact enhanced by as much as two orders of magnitude as the diameter of the nanowires decrease.

"This finding is very exciting because it suggests that constructing nanogenerators, sensors and other devices from smaller nanowires will greatly improve their output and sensitivity," Espinosa said.

"We used a computational method called Density Functional Theory (DFT) to model GaN and ZnO nanowires of diameters ranging from 0.6 nanometers to 2.4 nanometers," Agrawal said. The computational method is able to predict the electronic distribution of the nanowires as they are deformed and, therefore, allows calculating their piezoelectric coefficients.

The researchers' results show that the piezoelectric coefficient in 2.4 nanometer-diameter nanowires is about 20 times larger and about 100 times larger for ZnO and GaN nanowires, respectively, when compared to the coefficient of the materials at the macroscale. This confirms previous computational findings on ZnO nanostructures that showed a similar increase in piezoelectric properties. However, calculations for piezoelectricity of GaN nanowires as a function of size were carried out in this work for the first time, and the results are clearly more promising as GaN shows a more prominent increase.

"Our calculations reveal that the increase in piezoelectric coefficient is a result of the redistribution of electrons in the nanowire surface, which leads to an increase in the strain-dependent polarization with respect to the bulk materials," Espinosa said.

The findings by Espinosa and Agrawal may have important implications for the field of energy harvesting as well as for fundamental science. For energy harvesting, where piezoelectric elements are used to convert mechanical to electrical energy in order to power electronic devices, these results point to an advantage in reducing the size of the piezoelectric elements down to the nanometer scale. Energy harvesting devices built from small-diameter nanowires should in principle be able to produce more electrical energy from the same amount of mechanical energy than their bulk counterparts.

In terms of fundamental science, these results further previous conclusions that matter at the nanoscale has different properties. It is clear now that by tailoring the size of nanostructures, their mechanical, electrical and thermal properties can be tuned as well.

"Our focus remains on understanding the fundamental principles governing the behavior of nanostructures as a function of their size," Espinosa and Agrawal say. "One of the most important issues that needs to be addressed is to obtain experimental confirmation of these results, and establish up to what size the giant piezoelectric effects remain significant."

Espinosa and Agrawal hope their work will spur new interest in the electromechanical properties of nanostructures, both from theoretical and experimental standpoints, in order to clear the path for the design and optimization of future nanoscale devices.

Story Source:

The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by Northwestern University.

Journal Reference:

Ravi Agrawal, Horacio D. Espinosa. Giant Piezoelectric Size Effects in Zinc Oxide and Gallium Nitride Nanowires. A First Principles Investigation. Nano Letters, 2011; : 110111090244079 DOI: 10.1021/nl104004d

Note: If no author is given, the source is cited instead.

Disclaimer: Views expressed in this article do not necessarily reflect those of ScienceDaily or its staff.

Scientists model tiny rotors, key to future nanomachines

"This is no cartoon. It's a real molecule, with all the interactions taking place correctly," said Anatoly Kolomeisky as he showed an animation of atoms twisting and turning about a central hub like a carnival ride gone mad.

Kolomeisky, a Rice University associate professor of chemistry, was offering a peek into a molecular midway where atoms dip, dive and soar according to a set of rules he is determined to decode.

Kolomeisky and Rice graduate student Alexey Akimov have taken a large step toward defining the behavior of these molecular whirligigs with a new paper in the American Chemical Society's Journal of Physical Chemistry C. Through molecular dynamics simulations, they defined the ground rules for the rotor motion of molecules attached to a gold surface.

It's an extension of their work on Rice's famed nanocars, developed primarily in the lab of James Tour, Rice's T.T. and W.F. Chao Chair in Chemistry as well as a professor of mechanical engineering and materials science and of computer science, but for which Kolomeisky has also constructed molecular models.

Striking out in a different direction, the team has decoded several key characteristics of these tiny rotors, which could harbor clues to the ways in which molecular motors in human bodies work.

The motion they described is found everywhere in nature, Kolomeisky said. The most visible example is in the flagella of bacteria, which use a simple rotor motion to move. "When the flagella turn clockwise, the bacteria move forward. When they turn counterclockwise, they tumble." On an even smaller level, ATP-synthase, which is an enzyme important to the transfer of energy in the cells of all living things, exhibits similar rotor behavior -- a Nobel Prize-winning discovery.

Understanding how to build and control molecular rotors, especially in multiples, could lead to some interesting new materials in the continuing development of machines able to work at the nanoscale, he said. Kolomeisky foresees, for instance, radio filters that would let only a very finely tuned signal pass, depending on the nanorotors' frequency.

"It would be an extremely important, though expensive, material to make," he said. "But if I can create hundreds of rotors that move simultaneously under my control, I will be very happy."

The professor and his student cut the number of parameters in their computer simulation to a subset of those that most interested them, Kolomeisky said. The basic-model molecule had a sulfur atom in the middle, tightly bound to a pair of alkyl chains, like wings, that were able to spin freely when heated. The sulfur anchored the molecule to the gold surface.

While working on a previous paper with researchers at Tufts University, Kolomeisky and Akimov saw photographic evidence of rotor motion by scanning tunneling microscope images of sulfur/alkyl molecules heated on a gold surface. As the heat rose, the image went from linear to rectangular to hexagonal, indicating motion. What the pictures didn't indicate was why.

That's where computer modeling was invaluable, both on the Kolomeisky lab's own systems and through Rice's SUG@R platform, a shared supercomputer cluster. By testing various theoretical configurations -- some with two symmetrical chains, some asymmetrical, some with only one chain -- they were able to determine a set of interlocking characteristics that control the behavior of single-molecule rotors.

First, he said, the symmetry and structure of the gold surface material (of which several types were tested) has a lot of influence on a rotor's ability to overcome the energy barrier that keeps it from spinning all the time. When both arms are close to surface molecules (which repel), the barrier is large. But if one arm is over a space -- or hollow -- between gold atoms, the barrier is significantly smaller.

Second, symmetric rotors spin faster than asymmetric ones. The longer chain in an asymmetric pair takes more energy to get moving, and this causes an imbalance. In symmetric rotors, the chains, like rigid wings, compensate for each other as one wing dips into a hollow while the other rises over a surface molecule.

Third, Kolomeisky said, the nature of the chemical bond between the anchor and the chains determines the rotor's freedom to spin.

Finally, the chemical nature of rotating groups is also an important factor.

Kolomeisky said the research opens a path for simulating more complex rotor molecules. The chains in ATP-synthase are far too large for a simulation to wrangle, "but as computers get more powerful and our methods improve, we may someday be able to analyze such long molecules," he said.

The Welch Foundation, the National Science Foundation and the National Institutes of Health funded the research.

An animation of a rotor simulation: http://www.youtube.com/watch?v=GJJxSs6AkeM

Story Source:

The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by Rice University.

Journal Reference:

Alexey Akimov, Anatoly B. Kolomeisky. Dynamics of Single-Molecule Rotations on Surfaces that Depend on Symmetry, Interactions, and Molecular Sizes. The Journal of Physical Chemistry C, 2011; 115 (1): 125 DOI: 10.1021/jp108062p

Note: If no author is given, the source is cited instead.

Disclaimer: Views expressed in this article do not necessarily reflect those of ScienceDaily or its staff.

Scientists synthesize long-sought-after anticancer agent

A team of Yale University scientists has synthesized for the first time a chemical compound called lomaiviticin aglycon, leading to the development of a new class of molecules that appear to target and destroy cancer stem cells.

Chemists worldwide have been interested in lomaiviticin's potential anticancer properties since its discovery in 2001. But so far, they have been unable to obtain significant quantities of the compound, which is produced by a rare marine bacterium that cannot be easily coaxed into creating the molecule. For the past decade, different groups around the world have been trying instead to synthesize the natural compound in the lab, but without success.

Now a team at Yale, led by chemist Seth Herzon, has managed to create lomaiviticin aglycon for the first time, opening up new avenues of exploration into novel chemotherapies that could target cancer stem cells, thought to be the precursors to tumors in a number of different cancers including ovarian, brain, lung, prostate and leukemia. Their discovery appears online in the Journal of the American Chemical Society.

"About three quarters of anticancer agents are derived from natural products, so there's been lots of work in this area," Herzon said. "But this compound is structurally very different from other natural products, which made it extremely difficult to synthesize in the lab."

In addition to lomaiviticin aglycon, Herzon's team also created smaller, similar molecules that have proven extremely effective in killing ovarian stem cells, said Gil Mor, M.D., a researcher at the Yale School of Medicine who is collaborating with Herzon to test the new class of molecules' potential as a cancer therapeutic.

The scientists are particularly excited about lomaiviticin aglycon's potential to kill ovarian cancer stem cells because the disease is notoriously resistant to Taxol and Carboplatin, two of the most common chemotherapy drugs. "Ovarian cancer has a high rate of recurrence, and after using chemotherapy to fight the tumor the first time, you're left with resistant tumor cells that tend to keep coming back," Mor explained. "If you can kill the stem cells before they have the chance to form a tumor, the patient will have a much better chance of survival -- and there aren't many potential therapies out there that target cancer stem cells right now."

Herzon's team, which managed to synthesize the molecule in just 11 steps starting from basic chemical building blocks, has been working on the problem since 2008 and spent more than a year on just one step of the process involving the creation of a carbon-carbon bond. It was an achievement that many researchers deemed impossible, but while others tried to work around having to create that bond by using other techniques, the team's persistence paid off.

"A lot of blood, sweat and tears went into creating that bond," Herzon said. "After that, the rest of the process was relatively easy."

Next, the team will continue to analyze the compound to better understand what's happening to the stem cells at the molecular level. The team hopes to begin testing the compounds in animals shortly.

"This is a great example of the synergy between basic chemistry and the applied sciences," Herzon said. "Our original goal of synthesizing this natural product has led us into entirely new directions that could have broad impacts in human medicine."

Other authors of the paper include Liang Lu, Christina M. Woo and Shivajirao L. Gholap, all of Yale University.

Story Source:

The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by Yale University, via EurekAlert!, a service of AAAS.

Journal Reference:

Seth B. Herzon, Liang Lu, Christina M. Woo, Shivajirao L. Gholap. 11-Step Enantioselective Synthesis of (-)-Lomaiviticin Aglycon. Journal of the American Chemical Society, 2011; 110131110847001 DOI: 10.1021/ja200034b

Note: If no author is given, the source is cited instead.

Disclaimer: This article is not intended to provide medical advice, diagnosis or treatment. Views expressed here do not necessarily reflect those of ScienceDaily or its staff.