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Science & Technology

July 14, 2008
Volume 86, Number 28
pp. 34-35

Science & Technology Concentrates

Moon Glass Contains Water

Water and other volatile chemicals have been found inside these spherules of lunar glass.

In a finding that counters the prevailing wisdom that the moon has always been dry as a bone, a new study shows that small spheres of lunar volcanic glass contain water. Alberto E. Saal of Brown University and colleagues studied small glass spherules retrieved from the moon's surface by Apollo astronauts in the 1960s and '70s. Although scientists have analyzed the beads numerous times over the past 40 years, they've never found any trace of volatile elements. But now, using secondary ion mass spectrometry—an ultrasensitive technique that improves detection limits by over an order of magnitude—Saal's group identified water and other volatiles, such as fluorine, inside the spherules (Nature 2008, 454, 192). They ruled out contamination from other sources. The beads most likely were formed during volcanic eruptions that occurred during the moon's early history, 3.5 billion years ago. The finding is all the more intriguing, the scientists say, given that recent orbiting spacecrafts have spotted possible water ice inside craters at the moon's poles.

Side Effects Help Teach Old Drugs New Tricks

The seemingly endless list of possible side effects that accompanies each dispensed prescription medication may now hold the clue to identifying new uses for existing drugs. Unlike traditional drug discovery methods, which use molecular structure and binding assays, a team led by Peer Bork at Germany's Max Delbrück Center for Molecular Medicine, instead examined a drug's side effects (Science 2008, 321, 263). To identify chemically dissimilar drugs that bind the same protein, the team compiled listings of the side effects of more than 700 different drugs. Bork's team created a mathematical model to predict the likelihood that two different drugs would interact with the same protein. Of the 2,903 pairs of drugs predicted to target the same protein on the basis of their shared side effects, 754 pairs were from drugs used to treat entirely different clinical conditions. The group tested their predictions on 20 of these pairings through in vitro binding assays and found that in 13 of these, the drugs indeed bound to the same target. The researchers say this type of analysis shows that side effects can identify additional targets for an existing drug in unrelated disease categories.

Fast Route To Radiolabeled Formaldehyde

Scientists and doctors may soon have access to a greater number of radiotracer compounds for positron emission tomography (PET), thanks to a new method for making radiolabeled formaldehyde. Compounds containing carbon-11 are popular radiotracers for PET scans, but the radionuclide's 20-minute half-life presents a challenge to chemists: The process of generating a 11C labeling reagent, synthesizing a tracer molecule, and then purifying that compound so that it can be injected into a patient waiting for a PET scan must all take place before the radioactive signal decays. Methylation with [11C]methyl iodide is the most common radiolabeling reaction, but this restricts radiotracers to compounds with pendant methyl groups. A team led by Jacob M. Hooker of Brookhaven National Laboratory now has developed a simple and rapid route to [11C] formaldehyde, thereby expanding the types of radiolabeling reactions (Angew. Chem. Int. Ed., DOI: 10.1002/anie.200800991). The synthesis uses [11C] methyl iodide to methylate trimethylamine N-oxide. [11C] formaldehyde is subsequently generated via elimination of trimethylamine. Hooker's group was able to make the reaction work with radiolabeled reagents in a matter of minutes under mild conditions.

Scans Expose Violins' Density Differences

Image Title Terry M. Borman
A violin crafted by 18th-century master Guarneri.

Consistent wood density is the latest theory that researchers are floating to help explain the superior sound of Stradivarius and other classical Italian violins (PLoS ONE, DOI: 10.1371/journal.pone.0002554). For decades, researchers have scrutinized the antique violins' craftsmanship, including wood treatments and varnishes, to find the secrets behind their rich, resonant tone. Now, Fayetteville, Ark., violinmaker Terry M. Borman and computer scientist Berend C. Stoel of Leiden University Medical Center, in the Netherlands, have examined the wood grains in violins made by Antonio Stradivari and his contemporary, Giuseppe Guarneri del Gesu. Using a computed tomography (CT) scanner, a nondestructive instrument used in medical settings, they compared modern violins to some made by the two masters. The scans revealed that classical violins' wood had less variation in density than that of modern violins. Although differences in wood density do affect sound production, "it would be a mistake to think that it would be enough to reduce the density differential" to recreate the Stradivarius sound, says retired Texas A&M University biochemist and violin aficionado Joseph Nagyvary.

Laser-Cooled Molecules

Two teams of researchers have demonstrated that laser methods can be used to cool molecules to near absolute zero. Ensembles of molecules with nearly zero energy provide opportunities to explore quantum phenomena that cannot be observed in energetic systems. Ultracold molecules may also be useful for high-resolution spectroscopy and quantum computing. Laser-based methods for stripping energy from atoms have been used for 20 years to produce nearly motionless collections of atoms in a state of matter known as a Bose-Einstein condensate. Efforts to apply those types of methods to molecules, however, have generally yielded molecules with little translational energy but considerable rotational and vibrational energy. Scientists have now figured out ways to reduce much of the internal molecular energy. At the University of Paris-Sud, in France, Pierre Pillet and colleagues have devised a laser method for downshifting cold Cs2 molecules that occupy a distribution of vibrational states into the ground vibrational state (Science 2008, 321, 232). And Johann G. Danzl at the University of Innsbruck, in Austria, and colleagues have shown that a different laser scheme can reduce Cs2's rotational energy (Science, DOI: 10.1126/science.1159909).

Detecting Fingerprints with Lawsone

© 2008 Chem. Commun.
Fingerprints treated with lawsone as viewed through red filter.

The law enforcement community is constantly looking for more sensitive techniques to sleuth out fingerprint evidence for criminal investigations. Simon W. Lewis of Curtin University of Technology, in Australia, and colleagues report that lawsone can reveal fingerprints left on paper, opening up a new class of potential detection analogs (Chem. Commun., DOI: 10.1039/b808424f). Lawsone gives henna its characteristic property for dying hair and skin reddish brown. The compound reacts with amino acids in fingerprint residues, leaving colored ridges that fluoresce at longer wavelengths than established reagents, so lawsone might help reveal details not visible to the naked eye or on surfaces where other reagents fail. Ninhydrin, the classic fingerprint reagent sensitive to amino acid residues, is still widely used on porous surfaces, but it does not fluoresce without special treatments. Jan Zonjee, a research chemist at forensic supplier BVDA International, says lawsone is not ready to replace ninhydrin, but a derivative or analog might become the reagent of choice in the future or especially good for a niche application, such as developing fingerprints on colored papers.

Adorning with Alkenes

Two new ways to selectively modify proteins using alkene chemistry can now be added to chemical biology's toolbox. Benjamin G. Davis and colleagues at Oxford University are reporting the first example of applying olefin cross metathesis to a protein, a milestone they achieved in aqueous conditions. First the researchers modified cysteine residues of a bacterial protease protein, converting these amino acids into ones with an allyl sulfide sidechain. "The allyl group turned out to be the key motif for the metathesis," Davis notes. Then polyethylene glycol and sugars with allyl functional groups were placed on the modified cysteines by using a ruthenium-based Hoveyda-Grubbs catalyst to push the metathesis (J. Am. Chem. Soc., DOI: 10.1021/ja8026168). In a second report, Qing Lin and colleagues at the State University of New York, Buffalo, adorn modified tyrosine residues on proteins by using "photoclick chemistry," a photoactivated, nitrile imine-mediated 1,3-dipolar cycloaddition reaction. The researchers genetically encode O-allyl-tyrosine into proteins and then attach diaryltetrazoles to the modified amino acids to produce fluorescent pyrazoline cycloadducts, which they can observe in live bacterial cells (J. Am. Chem. Soc., DOI: 10.1021/ja803598e).

Structure of Ebola Virus Surface Glycoprotein

Lee & Ollmann Saphire
View Enlarged Image
Ebola virus surface glycoprotein bound to an antibody.

After a five-year effort, researchers have determined the structure of the Ebola virus surface glycoprotein, which enables the virus to enter cells. They analyzed the glycoprotein bound to an antibody from a rare survivor of a 1995 Ebola outbreak in Congo (Nature 2008, 454, 177). The work aids in understanding the mechanism by which Ebola virus enters cells and could help lead to immunotherapeutics. Ebola virus kills more than half of those infected by causing hemorrhagic fever—dehydration, bleeding, and shock. There's no effective treatment. The new structure, obtained by Erica Ollmann Saphire, Jeffrey E. Lee, Dennis R. Burton, and coworkers at Scripps Research Institute in La Jolla, Calif., shows how the survivor's antibody (yellow) bridges the trimeric glycoprotein's GP1 host-attachment subunits (light blue, dark blue, and teal) and GP2 membrane fusion-inducing subunits (white). It reveals how the subunits might mediate cell attachment and membrane fusion while masking themselves from immune surveillance. The new structural data also help explain why anti-Ebola antibodies are so rare, identify the few surface sites to which antibodies might bind, and provide a template for vaccine and antibody design, Ollmann Saphire notes.

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