SCIENCE & TECHNOLOGY CONCENTRATES
When male fruit flies find a bounty of food, they mark the territory with a pheromone called 9-tricosene. The pheromone entices females to lay their eggs nearby, presumably to give the offspring a full meal and a chance to survive, according to a team of researchers led by Christopher J. Potter of Johns Hopkins University (eLife 2015, DOI: 10.7554/elife.08688). The chemical mark also acts as a dinner-is-ready beacon to other Drosophila melanogaster that aggregate in response to the scent ( )7 ( )12 in search of the promised buffet. The team found that 9-tricosene activates 9-Tricosene a family of odor receptors known as Or7a. These receptors are also activated by several alcohols, aldehydes, and E2-hexenal, a volatile compound that wafts from damaged plants—another food source for the tiny insects—and that in turn also guides egg-laying behavior. The research suggests that a variety of chemically distinct signals activate Or7a receptors triggering a common behavioral response—laying eggs near a promising food source.—SE
OZONE-DEPLETING COMPOUNDS ON DECLINE Chlorofluorocarbons and hydrochlorofluorocarbons (HCFCs) are valued as refrigerants and propellants. When they are released to the atmosphere, however, they destroy Earth’s protective ozone layer. Although an international treaty controls the use of such compounds, a study last year indicated that concentrations of some of them continued to increase through 2012. Follow-up measurements now indicate that concentrations of two HCFCs, CH2ClF and CF3CH2Cl, peaked around 2012 and have since steeply declined, with emissions dropping by as much as 50% in three years (Geophys. Res. Lett. 2015, DOI: 10.1002/2015gl064709 and 10.1002/2015gl065846). The compounds were studied by international teams led by Fabian Schoenenberger and Martin K. Vollmer of the Swiss Federal Laboratories for Materials Science & Technology. CH2ClF has been used to a limited extent in refrigerant blends, and CF3CH2Cl has no known industrial use. The researchers propose that the compounds are most likely produced and emitted as intermediates or by-prod-
COBALT-BORON MOLECULAR DRUM BEATS BONDING RECORD A multinational research team has created a drum-shaped cobalt-boron species in the gas phase, CoB16–, which sets a record for highest coordination number in a molecule. The sandwich complex created by Alexander I. Boldyrev of Utah State University, Lai-Sheng Wang of Brown University, and their colleagues consists of two B8 rings connected to the central cobalt atom via 16 bonds, the theoretical maximum based on the number of available atomic orbitals. A top view (top) and side view Boron is particularly useful in such ef(bottom) of the forts because the electron-deficient cobalt-boron element tends to share electron pairs molecular with multiple other atoms to form drum, CoB16–. The connections strongly bonded network structures. between atoms The researchers made CoB16– by help visualize the pressing cobalt and boron into a pelstructure but do let and then vaporizing it with a laser not necessarily beam. They used a mass spectromindicate bonds. eter to select CoB16– clusters from the product mixture and analyzed them with photoelectron spectroscopy. The team correlated the experimental results with computational analysis (Nat. Commun. 2015, DOI: 10.1038/ncomms9654). The previous record stood with a 15-coordinate thorium complex, Th[(H3B)2N(CH3)2]4, which remains the most-coordinated molecule that has been isolated in a condensed state. Boldyrev and Wang believe their work on CoB16– could inspire synthetic chemists to find a way to produce isolable clusters for use as nanomaterial building blocks.—SR
ucts of manufacturing HCFCs and that the decrease is probably due to a change in the processes that make those HCFCs. Emissions from other sources would be unlikely to show the observed steep decline.—JK
BETTER BRAIN IMAGING FOR EPILEPSY For many patients with epilepsy, a single spot, or lesion, in their brain is the source of their seizures. When patients don’t find relief with standard antiseizure medication—about one-third of all epilepsy cases—surgically removing the lesion can help. But standard magnetic resonance imaging can’t always identify these seizure focal points. A new study suggests that an MRI method that looks for the neurotransmitter glutamate can detect epileptic lesions when standard MRI fails (Sci. Transl. Med. 2015, DOI: 10.1126/scitranslmed. aaa7095). Kathryn Adamiak Davis, RavinCEN.ACS.ORG
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der Reddy, and colleagues at the University of Pennsylvania investigated glutamate imaging because the neurotransmitter excites neurons to fire and epilepsy is thought to result when neuronal circuits become overexcited. The MRI technique, called glutamate chemical exchange saturation transfer (GluCEST), senses the neurotransmitter through a characteristic signal arising from the proton exchange between glutamate’s amine group and bulk water in the brain. By using GluCEST, the researchers could find epileptic lesions in the brains of four patients who had lesions that were undetectable with standard MRI. One patient later underwent surgery, and the lesion’s location was confirmed.—MT
MAKING GLUCOSEPANE IN EIGHT STEPS Some proteins are known to react with the open-chain forms of carbohydrates,
ALEXANDER BOLDYREV
NEW FRUIT FLY PHEROMONE
SCIENCE & TECHNOLOGY CONCENTRATES
HO
N
O
N
H N
N+ H
HO H
OH NH2
CF3CO2–
HO Glucosepane
and glucose, the moiety formed is called glucosepane. Scientists think there’s a direct relationship between glucosepane and symptoms of diabetes. But studying glucosepane has proven problematic because it’s difficult to isolate the adduct from biological samples and the glucosepane exists naturally as a mix of eight diastereomers. Thanks to a concise enantioselective synthesis devised by Yale University chemists David A. Spiegel, Cristian Draghici, and Tina Wang, scientists can now make and study all of these glucosepane isomers (Science 2015, DOI: 10.1126/science. aac9655). The key step in the eight-step synthesis is a onepot procedure for making the nonaromatic 4H-imidazole tautomer. Because the synthesis is short and modular, the Yale chemists believe it will find many applications. For example, the synthesis could be used to incorporate glucosepane into synthetic oligopeptides, or it could help identify novel therapies for breaking glucosepane cross-links.—BH
XENON EXPANDS ITS MOLECULAR PORTFOLIO The noble gases, which occupy the last column of the periodic table, were once thought to be inert and not capable of forming molecules. It has now been more than 50 years since that thinking has been debunked, and in that time an array of noble-gas compounds have been reported. Even so, when new versions are announced they are still considered noteworthy. In the latest examples, Gary J. Schrobilgen and his group at McMaster University, in Ontario, have reported two new types of xenon molecules. In one case, the researchers ran a reaction of XeF2 with ReO3F in anhydrous HF to prepare the bridging
figuration, essentially filling superatomic valence shells. In the new structures, tetrahedrons of gold atoms act as the primary, electron-donating units, with gold-thiolate staples holding the polyhedrons together. Rather than superatoms, Jin says, these new structures are supermolecules.—MD
MOFs SEPARATE PARAFFINS BY SIZE
SUPERMOLECULAR WIZARDRY An international research team has wrapped thiolate-protected groups of gold atoms into benzene-like rings and DNA-like he-
Gold tetrahedrons twist into a double helical kernel to form the core of a new metal structure, which is about 0.3 nm wide.
lices that are too small to be considered nanoparticles, but too big to be thought of as molecules (Sci. Adv. 2015, DOI: 10.1126/ sciadv.1500425). These structures, which are stable in solution, could be useful for catalysis, biosensing, and drug delivery, says team leader Rongchao Jin of Carnegie Mellon University. And if that weren’t enchanting enough, the newly synthesized superstructures are also known as magic-sized clusters because they are made from an especially stable “magic number” of gold atoms—40 for the rings and 52 for the helices. Magic-sized gold clusters first bewitched researchers years ago, Jin tells C&EN, but the previously synthesized structures are best described as superatoms. In those structures, gold atoms contribute electrons to build a cluster with a stable electronic conCEN.ACS.ORG
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SCI. ADV.
O
H2N
complex [XeOXeOXe][µ-F(ReO2F3)2]2. The cation is an unprecedented example of a xenon(II) oxide and noble-gas oxocation, as well as a rare example of a noble-gas dication (J. Am. Chem. Soc. 2015, DOI: 10.1021/jacs.5b08765). In a second case, the researchers treated the potent oxidant XeF6 with acetonitrile in a chlorofluorocarbon solvent to make the shock-sensitive compounds F6XeNCCH3 and F6Xe(NCCH3)2·CH3CN. These are the first examples of molecules with Xe(VI)–N bonds (Angew. Chem. Int. Ed. 2015, DOI: 10.1002/anie.201507635). With X-ray crystal structures and computational analysis, the researchers provide additional insight into xenon’s electronic structure and bonding abilities.—SR
MOHAMED EDDAOUDI/KAUST
forming adducts that have been linked to diabetes, inflammation, and aging. When this reaction happens between proteins
By finely tuning the sizes of pores in metalorganic framework (MOF) compounds, chemists have designed solid sorbents that thoroughly separate branched paraffins from their linear analogs (Angew. Chem. Int. Ed. 2015, DOI: 10.1002/anie.201506345). Sorbents that completely discriminate between compounds on the basis of small differences in molecular size could potentially lower the cost of separating light hydrocarbons for fuel production. That separation is typically done via fractional distillation, an energy-intensive process. Mohamed Eddaoudi of King Abdullah University of Science & Technology and colleagues had previously synthesized rare-earth-based MOFs that showed potential for separating branched alkanes from linear ones. Now, by shortening the organic linkers that join the metal clusters, the team has tuned the pore size and improved the separation efficiency. Specifically, by joining yttrium- and terbium-based building blocks with fumarate linkers, the team synthesized MOFs with 4.7-Å-wide pores. On the basis of various sorption tests, they showed that the new MOFs completely separate butane Coupling rare-earthbased building blocks (green polyhedrons) with fumarate linkers (red lines) yields MOFs with pores (blue) of just the right size to separate branched paraffins from their linear analogs. Colored spheres indicate the volume of internal cages. from isobutane and pentane from isopentane and predict similar results for isomers of longer paraffins.—MJ
