ChemWeb Newsletter

Not a subscriber? Join now.August 22, 2006


Once again, The Alchemist has plundered the chemical sciences news to bring you the latest discoveries. This week, we learn that oscillating carbon fibers could supplant silicon in the world of microscopic video and find out how a sugar molecule found only on anthrax spores could help defeat the bacterium in the event of a bioterrorism attack. The US government reports that dioxin levels are down in meat and poultry and we discover how to make see-through silver. Finally, a new surfactant allows oil and water to be mixed and unmixed on demand and could mitigate oil spill disasters.

Microelectromechanical systems (MEMS) using carbon fibers rather than silicon could allow high frequency oscillations and perhaps pave the way to video and other devices that are not possible with silicon MEMS. Shahyaan Desai and colleagues at Cornell University have shown that micrometer-scale carbon fibers can bend through more than 90 degrees without snapping and can vibrate in the gigahertz range without degrading. "This is, to our knowledge, the first material to even approach such large deformation at high frequencies without observable fatigue," the researchers say. For decades, researchers have been trying to make video displays using tiny mirrors mounted on silicon oscillators. But silicon is just too slow for this application. Carbon fiber could be the answer.

Researchers in Switzerland have developed a detector for anthrax spores based on a monoclonal antibody that recognizes a specific sugar on the bacterium. Once inhaled, spores of Bacillus anthracis almost always kill, unless victims are treated within a day or two. According to Peter Seeberger of the Swiss Federal Institute of Technology (ETH) in Zurich and colleagues there and at the Swiss Tropical Institute, and the University of Bern accurate and rapid diagnosis is therefore vital. The researchers have now developed a novel immunological approach to anthrax detection that promises to be just as accurate but far simpler to carry out than current detection methods. Their detector is based on detecting anthrose, a sugar unique to anthrax spore surface carbohydrates. Antibodies raised against anthrose respond only to anthrax spores and not to bacteria closely related to B. anthracis. "Our results demonstrate that small differences in the carbohydrates on cell surfaces can be used to obtain specific immune reagents," says Seeberger, "Our new antibodies will be used as the basis for highly sensitive anthrax diagnosis and will contribute to the development of new therapeutic approaches."

Levels of the infamous dioxin-like compounds, including dioxins, furans, and dioxin-like polychlorinated biphenyls, have fallen in chickens, hogs, and turkeys, according to the US Department of Agriculture. DLCs are ubiquitous in the environment, arising from forest fires and volcanic activity as well as industrial processes, such as chemical manufacturing and waste incineration. They can persist for decades and accumulate in body fat of food animals leading to human exposure and consequent health concerns. USDA scientist Cynthia Deyrup and colleagues surveyed DLC levels in the four slaughter classes that represent about 90% of meat and poultry production in the US and found levels for 2002-2003 to be between 20 and 80 percent lower than those reported in less extensive tests carried out in 1994-1996. Her report points out that all the meat products tested had levels of DLCs below those recommended as acceptable in the European Union.

A sliver of silver, which is totally opaque, when sandwiched between two transparent layers of another material becomes transparent, according to US researchers. Thin silver films are normally completely opaque but can be made to transmit light with 35% efficiency through an effect analogous to quantum tunneling. If a light ray passing from glass to air strikes the interface at a sufficiently shallow angle, it is reflected internally. However, some of the electromagnetic field strays across the boundary between the two materials as a so-called evanescent wave. If this wave encounters another block of glass a short distance away, a true light wave with reduced intensity appears in the second block. Normally, complete transmission does not occur, but Ian Hooper and colleagues at the University of Exeter, UK, have devised a system in which two glass prisms coated with a thin layer of zinc sulfide sandwich a 40 nanometer layer of silver between them. The effect demonstrates the quantum nature of light but could also have applications in opto-electronics.

Philip Jessop and colleagues at Queen's University in Kingston Ontario have created a new surfactant that allows oil and water to be mixed and de-mixed on demand. The compound, a long-chain alkyl amidine, could help mitigate the kind of oil spills that are currently threatening the coasts of Lebanon and Syria as well as offering new opportunities for oil extraction from otherwise intractable sources. Carbon dioxide and air are the on and off switches for the new reversible surfactant. Bubble carbon dioxide through a solution and the surfactant switches on, forming an oil-water emulsion. Bubble air through this emulsion and the oil and water separate again, explains Jessop. The researchers explain that ongoing research will help them improve the speed of switching and to optimize their surfactants for particular applications.