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BUILDING A JELLYFISH
To help regulators spot contaminated vials of the blood thinner heparin, researchers have developed a nuclear magnetic resonance method that exposes any additive in a sample of the drug (Anal. Chem., DOI: 10.1021/ac301428d). In each batch of heparin, the polysaccharide’s structure varies slightly because manufacturers extract it from pig intestines, says Timothy R. Rudd of the Ronzoni Institute, in Milan. As a result, regulators can’t monitor the drug’s purity on the basis of a single structure. Instead they rely on its anticoagulant activity. To devise a more precise test, Rudd created an NMR-based description of heparin, which would include signals unique to pig heparin and would delineate how those signals change from batch to batch. He and his colleagues defined heparin’s unique NMR signals as those whose intensities varied together from sample to sample. By comparing the chemical shifts and intensities of signals between sets of heparin spectra, the researchers established how much heparin’s signals vary naturally. In heparin samples spiked with sheep and cow heparin, which differ only slightly from pig heparin, the researchers used the definition to detect contaminant levels as low as 1%.—JNC
SPINNING SUGAR INTO HYDROCARBONS In some sweet synthetic work, chemists at the University of California, Berkeley, have found a mild method for converting sugars and sugar alcohols into aromatic compounds and polyenes, respectively (Angew. Chem. Int. Ed., DOI: 10.1002/ anie.201203877). The deoxydehydration reaction, developed by F. Dean Toste and Mika Shiramizu, could be used to convert saccharides, the major component of cellulosic biomass, into commodity chemicals and fuels. Although the deoxydehydration reaction has been used to pluck oxygen
The list of creatures that have inspired scientists to build synthetic, or biomimetic, devices just got longer, according to a report in Nature Biotechnology (DOI: 10.1038/nbt.2269). John O. Dabiri of Caltech, Kevin Kit Parker of Harvard University, and coworkers have engineered a thin, eight-armed polymeric sheet to swim like a jellyfish. To accomplish the feat, the team
mapped the pumping motions of a juvenile jellyfish while it was swimming. Then the researchers used the collected information to build a mimic from three simple components, says Janna C. Nawroth, a graduate student at Caltech and lead author of the report. The first of these parts is a spin-coated 22-µm-thick polydimethylsiloxane film. Onto that layer, the team printed the protein fibronectin in a pattern simulating jellyfish muscle-fiber alignment. Finally, the researchers seeded rat heart cells onto the structure and incubated them until they formed electrically conductive tissue. The resulting mimic, called a medusoid, swims like VIDEO ONLINE a jellyfish when exposed to a pulsed electrical field. Aside from being a model system to inspire the development of future tissue-engineered organs that pump, Nawroth says, these medusoids might eventually be used to test drugs for cardiac disease.—LKW Tissue-engineered jellyfish (right) are stripped-down, polymeric versions of the real thing (left).
atoms off of diols and epoxides, getting the reaction to strip down polyols had been problematic. Toste and Shiramizu discovered that a methyltrioxorhenium catalyst could do the job efficiently when an alcohol, such as 3-pentanol, was used as a reductant. For example, using this protocol, they transformed the six-carbon sugar alcohol d-sorbitol into hexatriene—a possible feedstock for polymers. And when the chemists used sugars in the reaction, followed by dehydration, they were able to generate aromatic compounds, such as furan, benzene, and phenol. Future plans include boosting the reaction’s efficiency, applying the transformation to polysaccharides, and immobilizing and recycling the catalyst.—BH
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FISHING FOR GLYCOSYLTRANSFERASES Cells use glycosyltransferases biosynthetically to form glycosidic linkages between sugar “donor” and “acceptor” molecules, and chemists use them to synthesize new sugar-based biomolecules in the laboratory. To better understand sugar-based biosynthetic processes and to be able to make a wider variety of oligosaccharides in the lab, it is useful to know about as many glycosyltransferases as possible. But finding previously unknown glycosyltransferases in complex cell media has been a challenging task.Now,anarray-basedmethod—devised by Peng George Wang of Nankai University, in China; Milan Mrksich of Northwestern University; and coworkers—could make it easier to identify and characterize glycosyltransferases (Nat. Chem. Biol., DOI: 10.1038/nchembio.1022). In the technique, solutions of sugar donors and putative
NAT. BIOTECHNOL.(LEFT)/HARVAR D U & CALT ECH (R IGHT )
NMR DETECTS CONTAMINANTS IN HEPARIN
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SCIENCE & TECHNOLOGY CONCENTRATES
glycosyltransferases (produced by bacterial gene expression) are applied to selfassembled monolayers of sugar acceptors. Then linkage products, if any, are analyzed by mass spectrometry to detect new glycosyltransferases and their activity. The system enabled the researchers to identify and characterize four new glycosyltransferases. The researchers believe a similar array/MS strategy can be extended to the identification of other types of enzymes as well.—SB An ascomycete fungus in coal mine drainage treatment systems oxidizes manganese, precipitating manganese oxides at the base of its reproductive structures.
DETONATION PUSHES LIMITS OF CHEMISTRY The detonation of a nitrogen-based primary explosive occurs so quickly that it approaches the fundamental limits of chemistry, scientists report (Phys. Rev. Lett., DOI: 10.1103/physrevlett.109.038301). Detonations are difficult to study in the lab because the extreme sensitivity of these compounds carries a high risk of accidental explosions. Now, Evan J. Reed of Stanford University and colleagues have performed the first molecular dynamics simulation of a detonation of an azide, the primary explosive hydrazoic acid, which is sensitive to friction and heat. Previously, scientists have simulated the detonation of secondary explosives, which require a detonator to set them off. Such explosions occur on the order of a nanosecond. But the detonation of hydrazoic acid, from start to decomposition, occurs in only 10 picoseconds, which is on the order of vibrational timescales. “This reaction is likely one of the fastest naturally occurring chemical reactions,” write the researchers, and is surpassed only by ultrafast, photon-induced reactions. The researchers posit that this ultrafast chemistry may also be generalized to the detonation of other nitrogen-rich, high-energy-density materials such as N4, N5 ions, and polynitrogen.—EKW
SUPEROXIDE-PRODUCING FUNGUS SPONGES UP MINE METALS Manganese oxides are environmental sponges that scavenge and sequester toxic metals such as lead, copper, and zinc, making them effective in cleaning up coal mine drainage. In their efforts to improve mine drainage treatment, researchers have struggled to understand how microorganisms, generally thought to be bacteria, oxidize soluble Mn(II) to precipitate
manganese oxides in these systems. Now Colleen M. Hansel, a microbial geochemist at Harvard University and Woods Hole Oceanographic Institution, and colleagues have found that the key to some successful treatment systems is not bacteria but a fungus (Proc. Natl. Acad. Sci. USA, DOI: 10.1073/pnas.1203885109).Combininglight microscopy with synchrotron-based X-ray absorption spectroscopy and fluorescence microscopy, the researchers showed that a common ascomycete fungus found in mine drainage treatment systems oxidizes Mn(II) by producing superoxide extracellularly during reproduction. This superoxide reacts with Mn(II), causing precipitation of brown Mn(III) and Mn(IV) oxides on the base of the fungus’ reproductive structures. The work could help in bioremediating acid mine drainage, says Bradley M. Tebo, a microbiologist at Oregon Health & Science University.—DL
DENTAL AMALGAM ENABLES MERCURY CHEMISTRY Laser ablation reactions combining vaporized dental amalgam and oxygen difluoride (OF2) yield the oxyfluoride compounds OHgF and FOHgF, according to a new report (Angew. Chem. Int. Ed., DOI: 10.1002/anie.201204331). The compounds are the first oxyfluorides observed to incorporate a group 12 metal atom. University of Virginia chemistry professor Lester S. Andrews, who led the work, had previously tried using other sources
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of mercury to no avail. Then he asked his dentist for samples of standard dental amalgam, 46.5% Hg and 53.5% Permite silver-tin alloy. “We used exactly the same filling material he’s been putting in my mouth,” Andrews says, although Andrews later added more mercury. Theoretical analysis of the products by Sebastian Riedel and Tobias Schlöder of Germany’s University of Freiburg shows that OHgF is a radical Hg(II) compound, with the radical electron located on the oxygen. The mercury in FOHgF is also Hg(II). Other group 12 oxyfluoride compounds might be possible, Andrews says, if researchers can find the right experimental conditions.—JK
EN ROUTE TO POLYMER THAT HEALS WHEN SQUEEZED Researchers at the University of Illinois, Urbana-Champaign, have taken a first step toward making a material that responds directly to being damaged (J. Am. Chem. Soc., DOI: 10.1021/ja305645x).
Self-healing polymers have been synthesized in the past, but many of those materials use encapsulated reagents or require external stimuli, such as light or heat, to initiate repair. To make the material, the Illinois researchers generated what they call a “mechanophore” from a gem-dichlorocyclopropanated indene flanked by two methacrylate groups. The team then polymerized this mechanophore with methyl acrylate. When squeezed hard enough to simulate pressures above what a roadway bridge might withstand, the mechanophores in the resulting polymeric material rearrange and release protons (shown). Team leader Jeffrey S. Moore says that the next step will be to couple these mechanophores with a polymer that can also undergo acid-catalyzed crosslinking. That way, he adds, the protons generated will initiate localized healing of the material “only in regions of highstress concentration, where cross-linking is needed most.”—LKW
