PROTEOMICS
C R E D I T: CL E ME N S R I CH E RT ( CRYSTA L STRU CT UR E ) ; JU LI E RUS S EL L/L LN L (H A I R SA M P L E )
▸ ‘Hairprints’ could aid forensic profiling Human hair is a classic piece of crime scene evidence. But proving whom the hair belongs to can be, well, a bit hairy. Traditionally, an expert visually compares hairs under a microscope, although this method lacks quantitative validation. Researchers at Lawrence Livermore National Laboratory are aiming to change that. The human hair shaft contains more than 300 different proteins, which gave the scientists an idea to create a system for turning hair samples into molecular fingerprints by examining single amino acid variations between individuals. “It is a method that goes beyond the ambiguities of appearance,” says team member Deon S. Anex. By using mass spectrometry to study hair proteins from 66 European-American subjects, Anex and his colleagues show that “hairprints” have only a onein-12,500 chance of being shared by two individuals, making it a good method to rule out the innocent in criminal investigations (PLOS One 2016, DOI: 10.1371/journal.pone.0160653). Parker holds The approach origa hair sample inated with study for proteomic coauthor Glendon analysis. J. Parker, who holds a patent for conducting genetic analysis on human hair and is the founder and CEO of Protein-Based Identification Technologies, a company aiming to commercialize the technique.—RYAN CROSS
2-D MATERIALS
▸ MXenes shield against electromagnetic interference Cell phones and other electronic gadgets emit electromagnetic radiation that can cause the annoying buzzing often heard through television, radio, and computer speakers. Device manufacturers try to protect their products from this stray electromagnetic interference, referred to as EMI, and reduce the interference their gadgets
REAGENTS
Crystalline coating tames rambunctious reagents Chemistry has always been a smelly and potentially hazardous business. To safely handle useful but highly sensitive, toxic, and malodorous compounds, chemists have developed methods involving vacuum lines, glove boxes, and fume hoods. But those approaches can be costly and are often inconvenient to use. Researchers have thus come up with some clever
An X-ray crystal structure depicts TDA with benzoyl chloride inclusions— benzoyl chloride normally fumes in air and has an irritating odor, but crystallization tames it for safe handling. work-arounds, such as encapsulating air- and moisture-sensitive reagents in paraffin capsules, protecting enzymes in cross-linked aggregates, and storing reactive metals in silica or alumina powders. But for organic reagents, a general-use crystalline material that acts as an inert delivery system has been missing. Alexander Schwenger, Wolfgang Frey, and Clemens Richert of the University of Stuttgart have now found one in the form of a bulkily substituted adamantane that creates inclusion compounds to tame rambunctious reagents such as benzoyl chloride, cyclohexyl isocyanide, and phosphorus trichloride (Angew. Chem. Int. Ed. 2016, DOI: 10.1002/anie.201605507). The researchers mix tetrakis(dimethoxyphenyl)adamantane (TDA) with the reagents to generate crystalline materials that mask the reactivity and odor of the reagents and make them easy to handle and dispense on the benchtop. When the crystal-coated materials are dissolved in an appropriate solvent, the reagents are able to react as normal, and TDA precipitates and can be recovered by filtration for reuse.—STEVE RITTER
cause by using a shielding material such as a layer of copper or aluminum. Electronics makers may soon be able to use less expensive, thinner, and lighter EMI shielding thanks to a newly discovered property of a family of two-dimensional metal carbides and nitrides (Science 2016, DOI: 10.1126/ science.aag2421). Referred to as MXenes (pronounced “max-eens”), these strong, flexible, and electrically conducting materials are being studied for use in batteries and flexible electronics. A team led by Drexel University’s Yury Gogotsi now finds that, on a weight and thickness basis, films of Ti3C2Tx, Mo2TiC2Tx, and Mo2Ti2C3Tx (T represents OH and F surface terminations) provide EMI protection nearly as effectively as or better than pure metals and far better than carbon fibers, nanotubes, and other synthetic materials that have been studied for this application. In addition, MXenes, which can be incorporated into polymer composites, are easily processed in solution and can be sprayed onto irregularly shaped devices.—MITCH JACOBY
ENVIRONMENT
▸ Better screen for lowdose drug pollution Researchers are increasingly concerned about the impact on microorganisms and wildlife from the long-term exposure to low-dose mixtures of antibiotics, lipid regulators, psychiatric drugs, and other medicines that end up in aquatic environments. A new study suggests that existing approaches to studying these environmental risks—which typically measure the risk of individual chemicals separately and then add them together—may not provide a realistic assessment of the harm being done, particularly for low-dose mixtures containing antibiotics. Seeking a better alternative, a team led by Francisca Fernández-Piñas of the Autonomous University of Madrid, Rafael Muñoz-Carpena of the University of Florida, and their collaborators has developed a combined computational and SEPTEMBER 12, 2016 | CEN.ACS.ORG | C&EN
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Science Concentrates FOOD experimental high-throughput screening method that involves studying the effects of chemical mixtures on cyanobacteria, a group of microorganisms found abundantly in water systems (Sci. Adv. 2016, DOI: 10.1126/sciadv.1601272). The team created 180 mixtures of 16 pharmaceutical and personal care product chemicals at nanogram to microgram levels. The researchers modified the cyanobacteria so that they would be bioluminescent and then tracked the toxicity impact of the mixtures by measuring light intensity. For example, the bacteria produce fewer bioluminescent proteins, and thus emit less light, when they are struggling with the toxicity of specific drug mixtures.—SARAH EVERTS
Beer yeast adapted to life with humans
MICROBIOME
▸ Microbial communities thrive in fracking wells Some hardy microorganisms can survive the harsh underground conditions created by the oil and natural gas extraction method known as hydraulic fracturing. New revelations about the microbes come from a team led by microbiologist Kelly C. Wrighton of Ohio State University, which has used metagenomics CH3 and metabolite analyses O +N CH3 to characterize microbial –O CH3 communities deep inside the Marcellus and Utica Glycine betaine shale formations of the northeastern U.S. (Nat. Microbiol. 2016, DOI: 10.1038/nmicrobiol.2016.146). The researchers collected samples from a week to months after initial fracking when oil and gas were flowing from the wells. From metagenomics data, they reconstructed 31 microbial genomes, finding one organism that seems to be unique to shale formations, which they have named Candidatus Frackibacter. Overall, the microbes have interdependent metabolisms. For example, some microbes make glycine betaine, a compound that protects cells against osmotic stress that results from the high salt content of the shale. Other organisms take up that glycine betaine and metabolize it to form trimethylamine, which can be used by still other organisms to produce methane. The researchers also identified microbes that are likely culprits in producing sulfides that can lead to equipment corrosion and oil and gas reservoir souring. They further
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C&EN | CEN.ACS.ORG | SEPTEMBER 12, 2016
observed that the microbes persisted and even thrived despite added biocides and the high temperatures of fracking wells.—CELIA ARNAUD
SYNTHESIS
▸ Flow reaction reduces aryl diazonium safety risk The Balz-Schiemann reaction is a versatile means for synthesizing aryl fluorides from anilines. But there’s a catch: The procedure involves preparing and isolating intermediate aryl diazonium salts or generating them in situ under batch conditions. Both routes present a safety hazard because diazonium salts have the potential to spontaneously undergo violent decomposition,
R
NH2 Anilines
CF3CO2H, (CH3)3CONO, LiBF4, H3C(CH2)3CO2CH3
which has limited the scalability and utility of the reaction. Nathaniel H. Park, Timothy J. Senter, and Stephen L. Buchwald of Massachusetts Institute of Technology have addressed this problem by devising a continuous-flow process to prepare aryl diazonium salts that eliminates the need to handle them directly (Angew. Chem. Int. Ed. 2016, DOI: 10.1002/anie.201606601). The researchers were challenged to find reagents and conditions for their flow reactor that avoid side reactions that sometimes plague the Balz-Schiemann reaction and still lead to the desired aryl diazonium salts. Using the streamlined diazonium preparation shown, they fed the intermediate into a stirred batch reactor for the final dediazotization step to prevent precipitated salt from clogging the reactor channel. The approach enabled the MIT team to quickly and safely produce gram amounts of aryl and heteroaryl fluorides.—STEVE
RITTER R
Continuous-flow generation of aryl diazonium salts
N2+X–
F
R Aryl fluorides
C R E D I T: S H UT T E RSTO C K ( BE E R )
Long before scientists discovered the existence of microorganisms, humans domesticated yeast, coaxing the organism to make palatable beer in exchange for a reliable supply of food and a stable existence. A comprehensive genetic and phenotypic analysis of 157 Saccharomyces cerevisiae yeast strains used in fermentation industries Beer-making yeast has reveals that beer-making yeasts originate from a cozy life with humans. a few common ancestors that quickly evolved ways to satisfy their brewmasters (Cell 2016, DOI: 10.1016/j.cell.2016.08.020). A team led by Kevin J. Verstrepen and Steven Maere of the Flemish Institute for Biotechnology found that, compared with wild yeast, beer yeast has duplicated genes that help the organism break down maltotriose, a sugar found in beer mash. Many beer yeast strains have also evolved CH3O mutations that prevent production of 4-vinylguaiacol, an off-flavor in many beers. Meanwhile, because beer yeast HO is used continuously from one batch to another, it has lost the ability to reproduce sexually, the researchers found, a 4-Vinylguaiacol skill the organisms would need to survive and to adapt to stressful environments in the wild. By comparison, the team found that wine yeast still retains the ability to reproduce sexually, probably because wine making occurs only in autumn, leaving the yeast to fend for themselves during the rest of the year.—SARAH EVERTS
