SCIENCE & TECHNOLOGY CONCENTRATES
ION CHANNEL LINKED TO BINGE DRINKING Neuroscientists don’t fully understand the mechanisms in the brain that drive people to drink alcohol compulsively. But researchers have now learned that reducing expression of one protein, an ion channel subunit, can increase binge drinking in mice (Proc. Natl. Acad. Sci. USA 2015, DOI: 10.1073/ pnas.1416146112). Candice Contet of Scripps Research Institute California and colleagues studied mice genetically engineered to not produce GIRK3, one member of a family of potassium ion channels. The team set up what Contet calls a mouse happy hour: For two hours every day, the researchers added a bottle filled with an ethanol solution to the animals’ cages. Over several days, the mice started to binge drink from the ethanol bottle and get tipsy, with GIRK3-free mice drinking 30% more than unmodified mice. The scientists could curb the modified mice’s drinking by injecting a virus containing the GIRK3 gene into the ventral tegmental area (VTA) of the brain. This region is part of the brain circuitry that controls reward-seeking behavior. How the loss of GIRK3 leads to increased bingeing is still unknown, but Contet’s team showed that, unlike in unmodified mice, GIRK3-free VTA neurons do not respond to ethanol.—MT
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UNWELCOME FAT BLOOMS ON CHOCOLATE Chocolate lovers worldwide are all too familiar with the profound misery experienced when they unwrap a piece of their favorite treat and see it covered in a white haze. These so-called chocolate fat blooms—when fats migrate to the surface of chocolate and recrystallize there—are also a bane of the chocolate industry, which would like to increase the shelf life of its products. A research team led by Svenja K. Reinke of the Technical University of Hamburg, in Germany, has used smallangle X-ray scattering to track the structural changes in chocolate when this blooming By the time fat migrates to the surface of a chocolate bar and crystallizes there, the tasty treat is stale.
GLOBAL CO2 BREACHES 400 PPM Scientists who operate the NaUPWARD NOAA scientists have tracked tional Oceanic & Atmospheric Adatmospheric CO2 concentrations since 1980. ministration’s Global Greenhouse Gas Reference Network report that Global average CO2 concentration, ppm 425 Earth’s global average atmospheric carbon dioxide level surpassed 400 400 ppm in March. NOAA bases the global CO2 average on air samples 375 taken at 40 remote sites around the globe and analyzed at its Earth 350 System Research Laboratory in 325 Boulder, Colo. The NOAA team first 1980 1985 1990 1995 2000 2005 2010 2015 recorded levels above 400 ppm SOURCE: NOAA at some sites in 2012, but now the average for all reporting stations is above the mark. The last time Earth’s atmospheric CO2 level reached 400 ppm is thought to have been during a peak warm period roughly 4.5 million years ago, which scientists have deduced from a combination of analytical instrument readings since the 1950s and proxy data from ice cores and other sources. The CO2 level was hovering around 280 ppm prior to the Industrial Revolution in the mid-1800s, but the level has been creeping up because of the increased burning of fossil fuels. The data show that half of the 120-ppm increase since 1850 has occurred after 1980 and that the growth rate is increasing and now stands at 2.25 ppm per year. The scientists note that the global average fluctuates seasonally as vegetation and soil organisms wax and wane, but the overall trend continues upward.—SR
occurs (ACS Appl. Mater. Interfaces 2015, DOI: 10.1021/acsami.5b02092). The team showed that when fats begin to migrate to the surface through pores in the chocolate, they dissolve cocoa butter (a mixture of triglycerides). This dissolution destroys the crystalline structure of cocoa butter, which is responsible for the delightful texture of chocolate. Thus, the tasty treat turns into a stale disappointment. The new study may help thwart this travesty by revealing how chocolatiers can better control porosity and migration pathways in chocolate.—SE
A NEW SPIN ON NANOCELLULOSE Scientists in Switzerland have developed an approach for producing cellulose nanofibers starting from vegetable food waste such as pomace left over from carrot juice production. But along the way, the team led by Roland Hischier of the Swiss Federal Laboratories for Materials Science & Technology (Empa) performed a life-cycle assessment to compare environmental impact, perforCEN.ACS.ORG
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mance, and economic data against those for other nanocellulose preparation methods. The assessment helped the team select the processes in the new method to ensure it will be commercially competitive (ACS Sustainable Chem. Eng. 2015, DOI: 10.1021/ acssuschemeng.5b00209). Cellulose nanofibers are biodegradable materials derived from renewable resources such as cotton, coconuts, and wood pulp that are being developed as alternatives to carbon or glass fibers for food packaging, medical applications, and organic-based displays. Because nanocellulose is only just beginning to be commercialized, the production methods are still being worked out. Hischier and his colleagues looked at energy use, choice of starting material, water and solvent use, and waste trade-offs. They selected enzymes over chemical acid hydrolysis to depolymerize and isolate the cellulose, identified an approach to functionalize the fiber surface with a polymer coating, and chose a wetspinning method over commonly used electrospinning to orient the fibers and spin them into yarn. The team also looked at other details, such as whether carrot
SCIENCE & TECHNOLOGY CONCENTRATES
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Chemists can of 75% poly(ethylene now pencil in glycol) methyl ether reagents to make and 25% graphite powpaper-based der. The researchers assay devices. then press the mixture into pellets, which they load into mechanical pencils. They use the pencils to draw the reagents on premarked channels on paper microfluidic devices. During an assay, water in the sample wicks reagents into a test zone. The researchers ran colorimetric glucose assays using the enzymes glucose oxidase and horseradish peroxidase. They found that the assays performed with pencil-deposited reagents had comparable accuracy and precision as ones performed with solvent-deposited reagents. The enzymes remain stable in the reagent pencils for weeks to months.—CHA
CHEMICAL SIGNALS ACTIVATE TOXIC ALGAE BLOOMS Single-celled marine algae called Alexandrium minutum, which are responsible for nearly half of the photosynthesis on Earth, sometimes grow with abandon, producing neurotoxic alkaloid compounds that ac-
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PENCILING IN REAGENTS Researchers have developed a simple method for loading chemical reagents onto paper-based microfluidic devices: Just draw them on. Andres W. Martinez and coworkers at California Polytechnic State University, San Luis Obispo, developed reagent pencils as a solvent-free way to deposit the chemicals needed for paper assays (Lab Chip 2015, DOI: 10.1039/ c5lc00297d). The Cal Poly team makes the pencils by dispersing reagents in a matrix
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Copepodamides are cumulate in food a family of polar chains and harm lipids in which R1 is commercial fishertypically a methyl ies. What motivates or methylene group these phytoplankton and R2 ranges to produce the poifrom a hydrogen sons has been a long- atom to 22-carbon docosahexaenoic standing question. acid. According to a team of researchers led by Erik Selander of the University of Gothenburg, in Sweden, the algae’s zooplankton predators are to blame (Proc. Natl. Acad. Sci. USA 2015, DOI: 10.1073/pnas.1420154112). The researchers discovered that phytoplankton-eating zooplankton produce a family of polar lipids called copepodamides that likely help them digest their algae prey. However, when the algae detect the copepodamides, they start producing the alkaloids, such as saxitoxin, as a defense strategy. Just pico- to nanomolar levels of copepodamides can increase production of the neurotoxic alkaloids by a factor of 20, the researchers say.—SE
ACHIRAL SURFACE PROMOTES CHIRAL AMPLIFICATION The curious observation that certain biochemical building blocks found in living organisms come almost exclusively in just one enantiomeric form—l for amino acids and d for sugars—has led scientists to propose mechanisms explaining its origins. Researchers at Carnegie Mellon University have now added another piece to this homochirality-of-life puzzle. Yongju Yun and Andrew J. Gellman determined that adsorption of gas-phase chiral molecules on an achiral surface can amplify the enantiomeric excess of the mixture (Nat. Chem. 2015, DOI: 10.1038/nchem.2250). For years, scientists have studied the role that adsorption processes may play in enantioselectivity. But until now the focus has been on chiral surfaces, including naturally occurring chiral minerals such as quartz. Surprisingly, Yun and Gellman found that a chiral surface is not required for adsorptionbased enantiomeric enrichment. The team CEN.ACS.ORG
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exposed an achiral copper surface to a 13C-labeled gas-phase mixture of d- and l-aspartic acid that was slightly enriched in the d isomer. On the basis of mass spectrometry analysis of adsorbed enantiomers and numerous control experiments, the team showed that adsorption on the achiral surface increased the d isomer’s enantiomeric excess from roughly 30% to nearly 90%.—MJ
FREE-RADICAL ENZYME CHEMISTRY THRIVES IN CONFINED SPACES To safely catalyze radical chemistry, a large group of enzymes positions their target substrates immediately adjacent to a radical-generating cofactor, a spectroscopic study indicates (J. Am. Chem. Soc. 2015, DOI: 10.1021/jacs.5b00498). By locating the substrate next to the cofactor, the enzymes help ensure that the radical acts as desired and doesn’t stray to engage in proteindamaging side reactions. The enzymes in question combine a [4Fe-4S] cluster and Sadenosyl-l-methionine (SAM) to generate 5´-deoxyadenosyl radical, which then reacts with a bound substrate. More than 100,000 such enzymes have been identified across all kingdoms of life. A team led by Joan B. Broderick of Montana State University and Brian M. Hoffman of Northwestern University used electron nuclear double resonance spectroscopy to study lysine 2,3-aminomutase, which isomerizes l-α-lysine to l-β-lysine. The researchers used a SAM analog to investigate the interactions The active site of lysine 2,3-aminomutase, in which the yellow arrow points from the C5´ position of SAM to the hydrogen abstraction site on l-α-lysine.
between the cofactor radical and lysine substrate. They found that once the radical forms it needs to shift less than 1 Å to abstract a hydrogen from lysine. Comparison of other structurally characterized SAM radical enzymes suggests that they operate similarly. Enzymes that use coenzyme B12 to generate 5´-deoxyadenosyl radicals require greater movement, which may help explain why they are relatively scarce.—JK
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pomace was best burned for energy production, used as a fertilizer, or as a source of nanocellulose.—SR
