SCIENCE & TECHNOLOGY CONCENTRATES
BUYER BEWARE OF 3-D PRINTER EMISSIONS
TAPESTRY WOVEN FROM ORGANIC THREADS
SCIENCE /COURTESY OF ENRIQUE GUTIÉRREZ-PUEBLA
As costs of three-dimensional printers drop and the devices increasingly make their way into offices, schools, and homes, users should consider how to limit exposure to emissions of particles and gases in the space where the printer is located. This caution stems from research by a team led by Brent Stephens of Illinois Institute of Technology and Neil E. Crain of the University of Texas, Austin (Environ. Sci. Technol. 2016, DOI: 10.1021/acs.est.5b04983). The researchers tested the emissions of five commercially available desktop 3-D polymer-extrusion printers for ultrafine particles, which have a diameter less than 100 nm, and volatile organic compounds, including caprolactam and styrene. They used the printers to make a standard part from nine different polymer filament starting materials. The emissions varied more by the type of material than they did by the type of printer. Modeling the emissions in a 45 m3 air-conditioned office, the team predicts that caprolactam and styrene would reach concentrations that could be harmful to health.—JK
CRAFTY COBALT POLYBORYLATIONS Precious-metal catalysts such as iridium and rhodium are widely used to promote C–H borylation reactions, in which a boronate group is installed in place of a hydrogen atom. The aryl boronate product is a useful intermediate that can in turn be used in cross-coupling and BPin other reactions to complete functionalization of the C–H bond. Although functionalizing aryl ring carbons with BPin groups such as boron pinacolate is well-known, less common is BPin + B2Pin2 achieving addition of the boronate to benzylic carbons in BPin molecules such as toluene. W. BPin Pin = pinacolate Neil Palmer, Paul J. Chirik, and BPin New cobalt catalysts enable colleagues of Princeton Univerlevels of selective polyborylation sity have now devised a method for adding not just one boronate that have not been achieved before. group to toluene’s methyl group but an unprecedented two or three, depending on the ratio of reactants, amount of catalyst, and reaction time. In addition, their approach works on branched alkylarenes, which has not been accomplished before (J. Am. Chem. Soc. 2015, DOI: 10.1021/jacs.5b12249). The chemistry is made possible by new α-diimine cobalt dialkyl and bis(carboxylate) catalysts the Princeton team has created.—SR
bisphenanthroline complex in which the two organic groups adopt an interlaced inverted-U orientation. They then added In an extension of chemical domesticity, benzidines to the ends of the organic groups researchers have shown that organic chemand linked the benzidines by forming imine istry is good not only for cooking but for bonds, creating a woven material they call weaving as well. Several types of supramoCOF-505. The copper ions can be removed and reinserted reversibly. The demetalation increases the material’s elasticity 10-fold because the threads can move around more easily without copper present. The material could be used for Benzidines (black) are added to the ends of copper preparing controllably bisphenanthrolines. A condensation reaction then links the flexible thin films and bisphenanthrolines to form a woven material (right). electronic devices. “Interlecular structures—catenanes, rotaxanes, weaving organic threads in the solid state is molecular knots, and molecular Borromean totally new and will lead to unexplored marings—have interwoven two- and threeterials with unexpected properties,” comdimensional parts. Now, Osamu Terasaki ments Jean-Pierre Sauvage of the University of Stockholm University; Omar M. Yaghi of of Strasbourg.—SB the University of California, Berkeley; and coworkers have designed and constructed FLAME-RETARDANT the first structures in which 1-D molecular “threads” are interwoven, forming a crystalGRAPHENE FOAM line covalent organic framework (Science Halogenated flame-retardant materials have 2016, DOI: 10.1126/science.aad4011). The come under fire in recent years because researchers first synthesized a copper(I) CEN.ACS.ORG
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of concerns they have negative health and environmental impacts. Knowing that graphene has worked well as a flame-retardant additive for polymers, researchers in China and the U.S. wondered if they could make a fire-resistant material composed primarily of the carbon allotrope. A team led by Liangti Qu of Beijing Institute of Technology and Liming Dai of Case Western Reserve University prepared an ultralight foam made of graphene and phosphorus oxide and phosphorus nitride nanoparticles (ACS Nano 2016, DOI: 10.1021/acsnano.5b06710). The scientists prepare the flame-retardant material by mixing a graphene oxide solution with hexachlorocyclotriphosphazene and turning the blend into foam via a freezedrying process. This method, they note, has the advantages of being simple, scalable, and environmentally friendly. They then expose this material to a flame, which transforms the graphene oxide into graphene and eliminates chlorine from the material. The resulting foam outperformed flameretardant polymers, metallic oxides, and metal hydroxides in tests. What’s more, the foam is a lightweight absorber of microwave radiation, which makes it promising as a radar-shielding material in commercial or military aircraft.—BH
ACS NANO
SCIENCE & TECHNOLOGY CONCENTRATES
MASS SPEC SINGLE-CELL PROTEOMIC ANALYSIS
and Chu’s team created a “mechanical chameleon” covered with “scales” represented by the nanodome-based cells. The scales are connected to cameras that analyze color and transmit the appropriate electric voltage to generate colors that match the color of the mechanical chameleon’s background to keep it camouflaged. At the moment, the mechanical chameleon only works with backgrounds of red, green, and blue, but the engineers hope to combine it with more sophisticated color-sensing systems.—BH
A SPIFFY WAY TO CLEAN NMR TUBES Life in a chemistry lab isn’t always fun and games—chemists must also do their chores, including cleaning out used NMR tubes. Although commercial devices are available for the task, they are expensive glassware and typically only clean one tube
CHAMELEON-INSPIRED CAMOUFLAGE Chameleons are nature’s masters of disguise, blending into their surroundings by changing the spacing between guanine nanocrystals in their skin. This trick alters the wavelengths of light their skin absorbs and reflects. Inspired by the chameleon’s clever camouflage, engineers in China have developed an artificial camouflage system that takes advantage of the lightreflecting and light-absorbing properties of nanoparticles (ACS Nano 2016, DOI: 10.1021/acsnano.5b07472). Researchers led by Guoping Wang of Wuhan University and Sheng Chu of Sun Yat-sen University created arrays of gold “nanodomes” roughly 50 nm across and packaged them into cells filled with a gel electrolyte containing silver ions. By electrodepositing or stripping silver from the surface of the gold nanodomes, the researchers change the nanoparticles’ plasmonic characteristics and therefore the color of the cells. Wang
es and falls with each vacuum cycle, cleaning out the tubes. A final rinse with fresh acetone completes the cleaning. Nguyen says he came up with the idea when his research funds were short. “I had to optimize everything—time, chemicals, human power—and here is one of my solutions.” Early responses on Twitter to Nguyen’s OPR&D paper were mixed: Some commenters questioned publishing the work in an industrial process chemistry journal, noting that industrial chemists often consider NMR tubes as a onetime consumable and toss them out. Plus cleaning them creates more lab waste. But most admit it’s a clever idea.—SR
A mechanical chameleon changes color as it rolls past different colored backgrounds.
A simple strategy for cleaning many NMR tubes at once involves a little solvent and a vacuum desiccator.
or a few at a time. To remedy that problem, Thanh Binh Nguyen of the CNRS Institute of Natural Product Chemistry has devised an NMR tube cleaning system that can handle dozens of tubes at once and only requires a small amount of solvent and equipment already at hand in most labs (Org. Process Res. Dev. 2016, DOI: 10.1021/ acs.oprd.6b00001). First, Nguyen empties NMR tubes and places them upside down in a beaker containing solvent or cleaning solution. Nguyen then puts the beaker in a vacuum desiccator, which he evacuates and vents with air several times. The liquid risCEN.ACS.ORG
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ORG. PROCESS RES. DEV.
Most proteomic analyses are averages of many cells. But as the sensitivity of mass spectrometry improves, comprehensive analysis of individual cells is becoming possible. By combining single-cell capillary electrophoresis, microflow electrospray ionization, and high-resolution mass spectrometry, Peter Nemes, Sally A. Moody, and Camille Lombard-Banek of George Washington University have performed proteomic analyses of individual cells dissected from a 16-cell frog embryo (Angew. Chem. Int. Ed. 2016, DOI: 10.1002/ anie.201510411). The researchers extracted and identified a total of 1,709 different proteins from three types of cells destined to develop into different parts of the frog’s body. To quantify proteins with high sensitivity, they used different mass tags to label each cell’s proteome, allowing them to detect even trace-level proteins at a low nanomolar concentration. Nearly a quarter of the proteins were common to all three cell types, but each cell type also had several hundred proteins unique to it. With the more direct measurements, the researchers were able to observe differences in protein expression that indicate dorsal-ventral asymmetry is already established, even at this early stage of development.—CHA
BOOSTING IMMUNITY TO TREAT ALZHEIMER’S A study in mice suggests that loosening the reins on the body’s immune system could help repair damage in the brain caused by Alzheimer’s disease. Inhibiting a protein that restrains immune responses cleared out characteristic protein plaques in the animals’ brains and improved their memory (Nat. Med. 2016, DOI: 10.1038/ nm.4022). Michal Schwartz of Weizmann Institute of Science and colleagues last year showed that stimulating an immune response in mouse brains reversed symptoms of Alzheimer’s. They concluded that boosting immunity could be a strategy for treating the disease. In the new study, they looked for inspiration from cancer therapies that manipulate so-called immune checkpoint proteins to push the immune system to attack tumors. These signaling proteins encourage or discourage immune cells from springing into action. Schwartz’s team decided to test an antibody that inhibits PD-1, one of the checkpoint proteins. In mice genetically engineered to carry known Alzheimer’s mutations, the antibody led to recruitment of immune cells called macrophages to the brain. The mice later exhibited fewer plaques of amyloid-β—one peptide associated with the disease—and had improved performance in a test of learning and memory.—MT
