ChemWeb Newsletter

Not a subscriber? Join now.December 14, 2004

contents
overview

In this week's Alchemist: electrons flowing in single file reveal clues about the mechanism of superconductivity, while monomers too that also fall into rank on metal surfaces can form a new chemical type known as a proto-polymer. Researchers also reveal how computational techniques on a new enzyme from the malaria parasite could offer an inroad into novel drugs against the disease and we discover why safety limits on the archetypal aromatic compound, benzene, might have to be revised. Finally, chemists are well advised to be skeptical of results reporting magnetic effects on diamagnetic materials, but Japanese work extends earlier observations and could have implications for our understanding of hydrogen bonding in water and the properties of benzene and other diamagnetic materials.




Observations of electrons moving in single file along channels on a metal are providing Austrian scientists with new insights into how to make novel superconductors. Erminald Bertel of the Institute of Physical Chemistry, University of Innsbruck and his colleagues have used nanoscale channels in a metal single crystal to control the movement of electrons. They used photoelectron spectroscopy and other techniques to observe the movement of the electronic rank and file and showed that above a critical temperature the electrons move from this coherent state to an incoherent one. Such a transition could be related to the break down of superconductivity above a critical temperature and might help in the design of higher temperature superconductors.





Paul Weiss and Gregory McCarty of Pennsylvania State University have discovered a new chemical state they dub a protopolymer. They laid out chains of phenylene monomers on a crystalline copper surface at low temperature and found that the monomers begin to align and link together. Pairing of molecules has been reported before, but this is the first time extended chains of molecules have been found to interact on a surface in this way. Inevitably, the discovery will have implications for controlling the growth of structures on surfaces with potential applications in nanoscience.





Scientists in Sweden have laid bare the structure and function of a new enzyme from the malaria parasite, Plasmodium falciparum. Johan Åqvist and doctoral student Sinisa Bjelic working under the umbrella of the RAPID project at the Uppsala University Center for Structural Biology, Medical Chemistry, and Computer Chemistry, studied the previously unknown enzyme, which is of a new class. Knowing its structure and function will lead to a new target for drug discovery against this killer disease at a time when new drug leads against malaria are desperately needed because of emerging parasite resistance.





Benzene is dangerous even at low levels according to a study from China and the US. The study reveals that benzene is harmful to human blood cells even when inhaled at levels below the US exposure limits for the workplace of 1 part per million over eight hours. The findings by Qing Lan and Nathaniel Rothman at the National Cancer Institute and Martyn Smith at the University of California Berkeley suggest that regulatory authorities must re-evaluate the occupational safety limits on this and related compounds. It also raises new concerns regarding environmental exposure from cigarette smoke, gasoline, and vehicle exhausts.





Japanese researchers have discovered that a strong magnetic field can raise the melting point of ice. The effect is minute but not insignificant say Hideaki Inaba and colleagues at Chiba University. They found that a 6 Tesla field is enough to raise the melting point of ice by 5.6 millikelvin for ordinary water and 21.8 millikelvin for heavy water. Other researchers previously demonstrated that a magnetic field affects water's infra-red spectrum and suggested that it somehow "tightens" the hydrogen bonds. Water is diamagnetic so should not be affected by a magnetic field at all. Inaba's findings add to a growing list of anomalies for water and hint at a magnetic effect on other diamagnetic materials, such as gallium, indium, mercury, and benzene.