2-D MATERIALS
▸ Tuning up microscale resonators with graphene A range of sensing and communications technologies, such as satellites, already rely on tiny devices called resonators. These resonators operate like the skin of a drum, vibrating at certain frequencies when struck by stimuli, such as molecules or photons. But engineers have faced limits in the temperatures these components can withstand and the range of frequencies that they can pick up. Now, scientists at Case Western University have constructed resonators out
C RE D I T: A NG EW. C HE M. I N T. E D. ( S U N FLOWE RS ) ; A DA PTE D F RO M N A NO L ET T. (G RA P H E N E ); WI K I ME D I A CO MMO N S / T IM V I C KE RS ( PYT H O N )
A resonator is made of a sheet of graphene on top of a silicon substrate. of a single layer of graphene that can withstand high temperatures and operate across a broad range of frequencies (Nano Lett. 2018, DOI: 10.1021/acs.nanolett.7b04685). Philip Feng and colleagues carved circular drumheads 3–5 µm in diameter out of silicon and then placed flakes of graphene across the openings. Their devices have an unprecedentedly broad tuning range of 300%, Feng says. Also, they can function at temperatures that exceed 900 °C, opening up myriad additional applications for resonators that can operate in harsh environments or in space.—DEXTER JOHNSON,
special to C&EN
DRUG DISCOVERY
▸ Snake peptide bites bacteria Biomolecules from snakes don’t often fight bacterial infections in mice, but a peptide called cathelicidin from a Burmese python (Python bivittatus) does just that. Cathelicidins are immune system peptides that help protect animals from microbial infections. Isolated mostly from humans and other mammals, they are being tested as possible
ART & ARTIFACTS
X-rays locate Van Gogh’s vulnerable yellows With X-ray powder diffraction, Frederik Vanmeert of the University of Antwerp and coworkers have analyzed the number and distribution of chrome yellow pigments, known for their tendency to discolor, in three regions of “Sunflowers,” painted by Vincent van Gogh in 1889 (Angew. Chem. Int. Ed. 2018, DOI: 10.1002/anie.201713293). Chrome yellows are a class of inorganic pigments. Lightfast chrome yellow, which is fade-resistant, contains PbCrO4. In light-sensitive chrome yellow, which is prone to darkening under the influence of light, some of the CrO42– is replaced by SO42–. Different light-sensitive subtypes have different amounts of X-ray mapping depicts the distribution of chrome yellow sulfate. The researchers found (left) in the portion of Van Gogh’s chrome yellow in darker yellow “Sunflowers” shown (right). The map flowers, lighter ones, and in the size is 92 × 182 mm. background, as well as mixed with other pigments. In addition to lightfast chrome yellow, they found one light-sensitive subtype. Each subtype was present on about one-third of the examined painting surface. The researchers found lightfast chrome yellow mainly in orange-yellow regions, whereas light-sensitive chrome yellow was in the bright yellow regions. They also visualized overlapping layers of the two subtypes and more complicated mixtures of the yellows with other pigments. The findings will allow conservators to identify regions of the painting at higher risk of degradation and will also aid art historians with digital reconstructions of the original colors used by Van Gogh, the researchers note.—CELIA ARNAUD
synthesizer and tested them, they found antibacterial drugs, but their stability and longevity of action have been limited. In an that one called CATHPb1 is indeed more effort to find better drug prospects, Yipeng stable in blood serum and works longer in mice than its mammalian peptide relaWang of Soochow University, Haining Yu of Dalian University of Technology, and co- tives (J. Med. Chem. 2018, DOI: 10.1021/acs. jmedchem.8b00036). CATHPb1 protected workers found six novel cathelicidins from mice from methicillin- and a new animal source, P. bivittavancomycin-resistant Staphytus, in a biomedical and genomic The Burmese lococcus aureus infections when database. When they made python, Python injected one day before or four the cathelicidins in a peptide bivittatus hours after the mice were infected. It didn’t show significant toxicity, and it resists protease breakdown, suggesting that oral administration may be possible. The researchers believe the peptide’s favorable properties give it good prospects for development as an antibiotic to treat multi-drug-resistant Staph infections.—STU BORMAN MARCH 12, 2018 | CEN.ACS.ORG | C&EN
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