Science Concentrates GEOCHEMISTRY
▸ Nuked zinc isotopes hint at the moon’s formation A study of glass formed by sand that was fused during the first nuclear bomb test not only demonstrates that high temperatures fractionate zinc isotopes, but also strengthens the giant-impact theory of the moon’s formation (Sci. Adv. 2017, DOI: 10.1126/ sciadv.1602668). The moon is highly depleted in volatile elements such as zinc compared with Earth. Scientists have suggested that the volatiles likely evaporated when a planet-sized object hit the nascent Earth billions of years ago, and the moon formed from the detritus. But in lunar samples, the zinc isotope fractionation patterns—the distribution of isotope abundances relative to each other—have been difficult to interpret in the context of the giant-impact scenario. A group led by James Day of Scripps Institution of Oceanography turned to the site of the 1945 Trinity nuclear bomb test in New Mexico, which is a rare ready-made laboratory. The tremendous heat and pressures created by the nuclear blast were similar to those believed to be involved in planetary formation and can’t otherwise be simulated on Earth. The explosion melted silica on the desert floor, producing a green glass called trinitite. The researchers found that the closer the trinitite samples were to the original blast site, the more fractionated the zinc isotopes, supporting the moon-formation hypothesis.—ELIZABETH WILSON
Insulin Trehalose glycopolymer
BIOLOGICS
New polymer protects insulin Attaching a biocompatible polymer such as polyethylene glycol (PEG) to therapeutic proteins can prolong their lifetime in the bloodstream. But many of these polymers don’t stabilize protein drugs outside the body. The medicines often require refrigeration and careful handling during storage and transport, otherwise they can become inactive—with life-threatening consequences for patients. Heather D. Maynard of the University of California, Los Angeles, and colleagues have now developed a glycopolymer that, when attached to insulin, not only prolongs the protein’s lifetime in mice without toxic effects but also prevents insulin from aggregating in a test tube (Bioconjugate Chem. 2017, DOI: acs.bioconjchem.6b00659). The researchers attached a glycopolymer with side chains containing the disaccharide trehalose to insulin at two different sites. Injected into mice, the insulin-glycopolymer conjugate had about the same lifetime as an insulin-PEG conjugate, which is a combination known to increase the lifetime of insulin in the body. The insulin-glycopolymer conjugate also remained stable in a test tube when heated at 90 °C for 30 minutes and agitated with a laboratory shaker for three hours.—MELISSA PANDIKA, special to C&EN
SYNTHESIS
▸ Click chemistry reaches a new dimension In 2014, K. Barry Sharpless and coworkers at Scripps Research Institute California developed sulfur fluoride exchange (SuFEx), a simple and rapid click chemistry reac-
F F O S F F SOF4
R R NH2 Primary amine
N
R S
Aryl alcohol
F F
TBS = tert-butyldimethylsilyl
10
N
O ArOTBS
C&EN | CEN.ACS.ORG | FEBRUARY 13, 2017
O S F OAr
H R N R Alkyl amine
R
N O
R
N
S
OAr R Multidimensional tetrahedral product
dles.” One fluoride or both can then react with aryl alcohols or alkyl amines to create products that are doubly or triply substituted along the sulfur hub’s tetrahedral axes. Potential applications include the synthesis of functional polymers and small-molecule enzyme inhibitors.—STU BORMAN
TOXICOLOGY
▸ Glyphosate linked to liver troubles in rodents Glyphosate, the plant-killing molecule in the widely used herbicide Roundup, is under perpetual scrutiny for its potential toxicity in mammals. Harm could derive from the chemical’s metabolites, such as glyoxylate, that are hypothesized to react with a protein’s functionally important amino acids, including cysteine. To test that idea, Daniel K. Nomura’s group at the
CREDIT: BIOCONJUGATE CHEM.
tion that uses sulfuryl fluoride (SO2F2) to make carbon-sulfate links. They used the technique to synthesize disulfates, polysulfate polymers, and other linear products. Suhua Li, Sharpless, and coworkers have now devised a variation that kicks SuFEx click chemistry into another dimension. Using thionyl tetrafluoride (SOF4) instead of SO2F2 as a SuFEx reagent enables them to make up to three tetrahedrally oriented connections to each sulfur hub molecule instead of two linear linkages (Angew. Chem. Int. Ed. 2017, DOI: 10.1002/anie.201611048). Thionyl tetrafluoride reacts initially with a primary amino group, forming a tetrahedral iminosulfur product with two fluoride “han-
University of California, Berkeley, charted differences in the proteomes of mice exposed to glyphosate compared with those of untreated mice (Cell Chem. Biol. 2017, DOI: 10.1016/j.chembiol.2016.12.013). Nomura’s team found that glyoxylate attached to several liver enzymes that are important for lipid metabolism and measured significant increases in liver fat deposits. They also conducted the experiment with acetochlor, another common herbicide, and found similar results (ACS Chem. Biol. 2017, DOI: 10.1021/acschembio.6b01001). “We don’t want to raise too much concern,” Nomura says, emphasizing that his study exposed mice to unnaturally high levels of herbicides. But the results are corroborated by another study recently published by Michael N. Antoniou of King’s College London and coworkers. That group exposed rats to extremely low doses of glyphosate in drinking water for two years and found disturbances in fat metabolism reminiscent of nonalcoholic fatty liver disease (Sci. Rep. 2017, DOI: 10.1038/srep39328). Nomura says that study “nicely reinforces” his group’s paper.—RYAN CROSS
NATURAL PRODUCTS
CREDIT: SCIENCE
▸ Mining for new cancer fighters Whether it’s on the isolated shores of Easter Island or on the more well-traversed terrain of a Japanese golf course, drug-producing bacteria have a penchant for popping up in some peculiar places. One of the latest locations is the acid drainage from an abandoned underground eastern Kentucky coal mine. Researchers led by the University of Kentucky’s Jon S. Thorson and Khaled A. Shaaban have found a strain of Streptomyces that produces 10 novel metabolites. Six of the compounds are new geldanamycins, and four of them are new cyclopentenone-containing ansamycin polyketides, dubbed mccrearamycins for McCreary County, where the bacterium was found (Angew. Chem. Int. Ed. 2017, DOI: 10.1002/anie.201612447). Previous examples of geldanamycins are known to have anticancer activity via inhibition of heat shock protein 90 (Hsp90). When Thorson and Shaaban’s team tested the new geldanamycins in assays with Hsp90 and in cell tests, they found some of the new compounds also had anticancer activity. The chemists believe the mccrearamycins arise from benzylic acid rearrangement of the geldanamycins, suggesting a unique biosynthetic pathway.—BETHANY HALFORD
Produced via roll-to-roll manufacturing, this low-cost film made of silica spheres embedded in a polymer matrix efficiently cools sunlit surfaces.
MATERIALS
Glass-hybrid plastic plays it cool If the temperature of buildings could be controlled by simply covering them with a plastic wrap that dissipates daytime heat without consuming electricity, owners could save a bundle on energy costs. Researchers at the University of Colorado, Boulder, have taken a key step in that direction by developing an inexpensive glass-polymer hybrid material that excels in this type of passive cooling (Science 2017, DOI: 10.1126/science.aai7899). Scientists have identified a number of materials for efficient nighttime radiative cooling. But daytime cooling remains a challenge because solar absorbance of just a few percent exceeds many materials’ cooling capacities, causing buildings and other surfaces to become hot. So Colorado mechanical engineers Ronggui Yang, Xiaobo Yin, and coworkers devised a material that strongly emits thermal energy in the form of infrared light and hardly absorbs sunlight. The material, which the team makes via low-cost roll-to-roll manufacturing methods, consists of randomly distributed micrometer-sized SiO2 spheres embedded in a poly(methylpentene) matrix. A 50-µm-thick film of the transparent material containing 6% microspheres by volume emits intensely throughout the IR region and reflects approximately 96% of solar radiation when backed with a 200-nm-thick silver coating. Having conducted initial lab tests, the team now plans to evaluate the technology this summer in the form of a 20 m2 roof cover on Colorado’s engineering building.—MITCH JACOBY
CHEMICAL BONDING
had the good fortune to do so, until now. A team led by Xinliang Feng of Dresden University of Technology and Klaus Müllen of the Max Planck Institute for Polymer Research has succeeded in preparing what it considers the next generation of sulflower: It’s a good day for a chemist when you persulfurated coronene. It’s the first fully synthesize a new compound, it has a cute sulfur-substituted polycyclic aromatic structure, and you get to pick a name for it. hydrocarbon (J. Am. Chem. Soc. 2017, DOI: That was the case for a team of chemists in 10.1021/jacs.6b12630). The researchers grew Russia a decade ago when they synthetheir sulflower in a multistep chlorinasized octathio[8]circulene, a new tion/sulfurization process starting S S form of carbon sulfide. The rewith coronene. The sulfur-rich S S character of the new compound searchers called the molecule S S renders it a promising cathode a “sulflower”—a mash-up of sulfur and flower—for its hetmaterial for lithium-sulfur baterocyclic structure resembling teries, the researchers say, and S it could pave the way to preparS a sunflower blossom. ChemS S ists have been eager to create ing graphene with persulfurated other members of this class of edges, which would be useful in S S compounds, including the electronic and superconductsimplest one, persulfurated Persulfurated coronene, a ing applications.—STEVE second-generation sulflower RITTER benzene. But no one has
▸ A new ‘sulflower’ has bloomed
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