ANTIBIOTICS
MASS SPECTROMETRY
▸ Probes track vancomycin-induced cell wall changes The antibiotic vancomycin works by interfering with bacterial cell wall synthesis. Some bacteria evade this drug by altering their cell wall precursors so they’re insensitive to it. These adaptations affect the substrates of key enzymes—a dipeptidase that degrades drug-sensitive building blocks and a ligase that stitches together drug-resistant ones. Marcos M. Pires and Sean E. Pidgeon of Lehigh University have now developed a pair of probes for monitoring in live bacteria the changes that lead to vancomycin resistance. Both probes include alkyne handles for attaching fluorescent labels via click chemistry. One
O +
H3N
H N
O
HO
OH
O–
O Dipeptide probe
D-Lactate analog
probe is a synthetic dipeptide analog of the dipeptidase substrate (Angew. Chem. Int. Ed. 2017, DOI: 10.1002/anie.201704851). Decreasing fluorescence levels of that probe are associated with development of drug resistance. The other probe is an alkyne-containing analog of the d-lactate that is a substrate of the ligase (ACS Chem. Biol. 2017, DOI: 10.1021/acschembio.7b00412). That probe signals development of drug resistance via increasing fluorescence levels. The researchers used the probes to monitor changes in the cell wall composition associated with drug resistance in response to increasing vancomycin concentrations. In addition, the researchers distinguished between subtypes of vancomycin-resistant bacteria.—CELIA CREDIT: PNAS (TISSUE SAMPLE); SCI. ADV. (BATTERY)
ARNAUD
ENERGY STORAGE
▸ Helical, serpentine batteries stretch repeatedly An advance in making flexible, stretchable batteries may help push these compliant energy storage devices closer to production. Researchers are making rapid progress with flexible electronics for wearable ap-
Mass spec identifies tumor margins during brain surgery Glioma—a type of brain cancer that infiltrates surrounding tissue—is hard to distinguish visually and texturally from the surrounding healthy tissue. Surgeons need to remove as much of the cancer as possible while minimizing removal of healthy tissue. A team led by R. Graham Cooks of Purdue University and pathologist Eyas M. Hattab and neurosurgeon Aaron A. Cohen-Gadol of Indiana University School of Medicine have now used desorption electrospray ionization mass spectrometry The sampling locations of in the operating room to assess tumor borsix tissue smears (blue = der during surgery to remove glioma (Proc. white matter; red = glioma) Natl. Acad. Sci. USA 2017, DOI: 10.1073/ are superimposed on a pnas.1706459114). The researchers obtained magnetic resonance imaging mass spectra of biopsied tissue smears in reconstruction of the tumor the operating room within three minutes, region. This image represents which is fast enough to be useful for making an area 8 cm by 8 cm. decisions during surgery. By using mass spec signals associated with membrane-derived lipids and N-acetylaspartate, the researchers were able to distinguish among glioma, white matter, and gray matter in the brain. In addition, they were able to detect a previously known glioma prognostic marker and determine the percentage of tumor cells in the biopsies. They followed the mass spectrometry determinations with conventional histopathological evaluations.—CELIA ARNAUD
plications and body implants, but progress developing the required power sources lags behind. Numerous research teams have demonstrated approaches to making flexible batteries, for example, ones based on stretchable or coiled interconnects and various wire-battery designs. But those devices have not proved durable enough to withstand thousands of simultane-
ous multidirectional flexing motions, as needed to commercialize products with long lifetimes. So Ana Claudia Arias of the University of California, Berkeley, and coworkers designed batteries in which current collectors with helical springs or serpentine shapes support all battery components, which are deposited sequentially onto the support (Sci. Adv. 2017, DOI: 10.1126/sciadv.1602051). Helical (top) and serpentine (bottom) batteries During testing, the helical continue to function properly even after repeated batteries withstood more than stretches. 17,000 small-radius flexing and bending cycles with no loss in electrochemical performance. And serpentine batteries also continued to function properly after repeated multidirectional flexing and stretching motions. The team stresses that their durable stretchy batteries, which are based on silver-zinc chemistry, are inherently safe and nonflammable, unlike lithium-ion batteries.—MITCH
JACOBY JUNE 19, 2017 | CEN.ACS.ORG | C&EN
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