The Alchemist Newsletter: June 24, 2008

Since tetrachloromethane is banned as an industrial solvent avoiding its formation as a byproduct of other chlorocarbons is important, this week, The Alchemist learns that a lanthanum chloride catalyst could help with the cleanup. A paradigm shift in drug discovery could be approaching as researchers working with proteins involved in Alzheimer's disease have discovered an apparently novel approach to inhibiting disease. In organic chemistry, the Alchemist hears that molecules are not quite as diverse as we first thought, while an Olympic analysis could help sports officials spot dopey athletes. Princeton scientists are focusing on a new approach to making microchips and, finally, an astronomer with a chemical bent has had a cometary mineral named for him.

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Part exchange reaction

Tetrachloromethane is no longer used as a laboratory or industrial solvent, but the production of other chlorinated hydrocarbons, such as chloroform, produces tetrachloromethane as a byproduct. So, Bert Weckhuysen at the University of Utrecht in The Netherlands and his colleagues have now found a way to recycle the byproduct using a lanthanum(III) chloride deposited carbon nanofibers. Writing in Angewandte Chemie, they explain how this catalyst induces tetrachloromethane and its reaction partner dichloromethane to exchange one chlorine atom for a hydrogen atom, which results in almost 100% conversion to chloroform. "We are reporting for the first time a lanthanum-based catalyst material that can activate both C-H and C-Cl bonds in the absence of oxygen," explains Weckhuysen.

Fair trade

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Pharmaceutical protection racket

Designing new drugs usually involves finding a target protein - receptor or enzyme - involved in a disease and then identifying a small molecule that slots into the protein's active site and block its activity. Alzheimer's researchers have been taking this approach for years looking for inhibitors of the enzymes involved in producing the harmful amyloid compounds that cause the proteinaceous plaques in the brain. However, recent surprising work published in Nature reveals an alternative design paradigm. A study of putative enzyme inhibitors for AD show, for the first time, that one putative drug may work, not be inhibiting any enzyme involved, but by blocking the substrate for that enzyme instead. The substrate itself is a protein (the imaginatively named amyloid precursor protein, or APP). By protecting APP the small molecule precludes the cleavage of APP to form amyloids. This finding could represent a paradigm shift in drug discovery.

Protecting Amyloid's Parent?

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Molecular extinction

That's perhaps a slightly misleading headline, this is not about species extinction but the fact that there is a lack of molecular diversity to begin with. Alan Lipkus and colleagues at the Chemical Abstracts Service have shown that there are far fewer chemical shapes among the many millions of organic molecules in the CAS Registry than one might think. "We found more than 800,000 different framework shapes among the 24 million compounds we studied," explains Lipkus, "and yet half of the compounds can be described by only 143 of those shapes." The authors pared down molecules to their fundamental ring structure, so that both cyclohexane and aniline are essentially hexagons, the most common framework shape in the Registry. The finding supports the results of previous, smaller studies. The authors suggest that keeping costs down is the underlying reason in that chemists return to familiar structures, but this could be stifling exploration of lesser-known regions of chemical space.

Exploring Chemical Space

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Olympic analysis

A new test for testosterone and epitestosterone based on mass spectrometry could help anti-doping officials at sports events such as the Olympic Games. The test will reveal whether athletes have used drugs to boost levels of their body's natural steroidal hormones. Testosterone levels vary considerably between people, so testing just this one compound does not reveal illicit doping. However, epitestosterone is usually present at equal concentration as testosterone regardless of absolute levels. Comparing the ratio of testosterone to epitestosterone, as revealed by mass spectrometry, can indicate whether testosterone or one of its precursors has been taken as this will not raise epitestosterone levels.

New Test Makes Cheating With Drugs in Sports Easier to Detect

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It's a zap trap

An affordable technique for patterning a new generation of microchips using lasers and plastic beads has been developed by researchers at Princeton University. Craig Arnold and Euan McLeod explain that their approach is akin to using magnifying lens to focus sunlight to scorch a scrap of paper, but the lens is a microscopic plastic bead floating in water and a powerful laser is the light source for burning designs on to a blank microchip. Their technique allows them to create nano-scale patterns on uneven surfaces and without relying on a vibrationless and oxygen-free environment.

Trap And Zap

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Rocky tribute

A new mineral, the first to be discovered in a particle from a comet, has been named brownleeite in honor of Donald Brownlee. The International Mineralogical Association named the manganese silicide mineral for the University of Washington astronomer who has revolutionized research on interplanetary dust entering Earth's atmosphere, adding it to a growing list of more than 4300 minerals. "I've always been very intrigued by minerals, so it's great to be one," Brownlee said, "I never dreamed I'd have a mineral named after me. I guess maybe being a vitamin is next."

Like a rock

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-- David Bradley, Science Journalist

To Our Readers: In our last Alchemist, one of the links in the Nature Chemistry Sponsorship ad was incorrect. The correct link should have been: www.nature.com/naturechemistry. We apologize for this oversight.