SCIENCE CONCENTRATES

Ozone hole smaller than usual

The ozone hole over the Antarctic is now the smallest it has been since 1988, according to scientists at NASA and the National Oceanic & Atmospheric Administration (NOAA). During the past two weeks, the ozone hole covered about 6 million square miles, in contrast to the more than 9 million square miles it covered during the same period in 1999, 2000, and 2001. The diminished area of ozone depletion is due to unusual stratospheric weather patterns and does not necessarily indicate a long-term trend, the researchers explain. Warmer than normal temperatures around the polar vortex that forms annually over Antarctica are responsible for the reduced loss of ozone, says Paul Newman, an ozone researcher at NASA's Goddard Space Flight Center in Greenbelt, Md. This is also the first time the ozone hole (shown in blue) has split into pieces in September, says Craig Long, a meteorologist at NOAA's Climate Prediction Center. In the primary area of ozone loss--7 to 14 miles above the Southern Polar region--depletion is similar to what it has been in recent years. But at 15 miles and higher, ozone concentrations are unusually high.

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Vitamin D-3 analog induces bone formation

A modified form of vitamin D-3 has been found to stimulate bone growth in rats, providing hope that a better treatment might be developed for osteoporosis and other bone diseases. Vitamin D-3, added to milk to help prevent rickets in children, is converted in the body to its 1,25-dihydroxy analog [1,25(OH)₂], which serves as a regulator of calcium and phosphate metabolism. 1,25(OH)₂ isn't thought to play a direct role in bone formation, but several analogs synthesized a few years ago by biochemistry professor Hector F. DeLuca and coworkers of the University of Wisconsin, Madison, were found to be more active in controlling calcium mobilization. DeLuca and colleagues now report that one of those analogs, called 2MD, is effective even at picomolar levels in promoting osteoblast cell growth to form bone in lab cultures. In treated rats, 2MD stimulated a 9% increase in total bone mass during a 23-week period [Proc. Natl. Acad. Sci. USA, published on-line, http://www.pnas.org/cgi/doi/10.1073/pnas.202471299]. To change 1,25(OH)₂ into 2MD, one needs to add the methylene group shown in black, remove the red methylene group, and change the stereochemistry of the orange methyl group from (R) to (S).

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Benzenium ion dispute settled

complex is most stable," and this view is in agreement with calculations on the isolated benzenium ion (C₆H₇⁺) and with its NMR and IR spectra in the condensed phase, says physicist Otto Dopfer of the University of Basel, in Switzerland. However, a 1995 mass spectrometric study of C₆H₇⁺ in the gas phase--that is, in the absence of counterions and solvent molecules--concluded that the face-centered

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Smart silica nanotubes for bioseparations

Nanotubes of nearly any dimensions and composition can be prepared by the template synthesis devised several years ago by University of Florida chemistry professor Charles R. Martin and his colleagues. In this method, nanotubes are synthesized in an alumina membrane that can be dissolved to release the nanotubes. During the synthesis, the nanotubes' inner and outer surfaces can be functionalized as desired. Martin's group and colleagues at VTT Biotechnology, Espoo, Finland, have now used this technology to prepare silica nanotubes that can be used in bioseparations [J. Am. Chem. Soc., 124, 11864 (2002)]. For one batch of nanotubes, a dansylamide was attached to the inner surface and a hydrophobic C₁₈ silane was attached to the outer surface, while for a second batch a quinineurethane was attached to the inner surface and the outer surface was left unmodified. The researchers show that a mixture of the two batches can be separated into different phases in a cyclohexane/water system. They also show that the inner voids of these "smart" nanotubes can be used to extract lipophilic compounds from aqueous solution and that biochemically functionalized nanotubes can be used to separate racemic mixtures.

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Watery cocoon affects HBr dissolution

How many water molecules does it take to dissolve a molecule of hydrogen bromide? To investigate this question, A. Welford Castleman Jr., professor of chemistry and physics, and his coworkers at Pennsylvania State University, University Park, used a combination of femtosecond spectroscopy and time-of-flight mass spectrometry to study the dynamics of mixed clusters of HBr and water [Science, 298, 202 (2002)]. Theory predicts that complete dissolution of HBr into the solvated ion pair H⁺Br^– occurs when HBr is surrounded by four water molecules. Castleman and coworkers, however, find that complete dissolution actually occurs when HBr is surrounded by five water molecules. The team's detailed picture of how HBr dissolves in water could prove useful in atmospheric and biological chemistry.

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