SCIENCE & TECHNOLOGY CONCENTRATES
SUGAR HELPS PROTEINS LIVE LONG AND PROSPER
A BETTER PERYLENE SUNCATCHER
O-GlcNAcylation, which is the modification of protein serine or threonine residues with the sugar N-acetylglucosamine (GlcNAc), plays a key role in cell 5 physiology. But the mechanisms by which it acts are not completely understood. Yan7 ping Zhu, David J. Vocadlo, and coworkers at Canada’s O 5 Simon Fraser University now report that O-GlcNAcylation occurs at higher levels cotranslationally—that is, while proteins are being synthesized on the ribosome—than posttranslationally (Nat. Chem. Biol. 2015, DOI: 10.1038/nchembio.1774). They also find that O-GlcNAcylation inhibits ubiquitination of nascent proteins, a modification that would otherwise mark them for disposal. Inhibiting ubiquitination thus stabilizes proteins and aids proteostasis, the maintenance of proper levels of functional proteins in cells. Vocadlo notes that his group hopes to learn more about the molecular mechanism by which O-GlcNAc decreases ubiquitination on the nascent chains.—SB
Researchers in China have decorated the polycyclic aromatic hydrocarbon perylene with auxiliary groups to create the most efficient metal-free lightharvesting molecule reported to date for making dye-sensitized solar cells (J. Am. Chem. Soc. 2015, DOI: 10.1021/jacs.5b01537). 5 Perylene derivatives have been used extensively as photocata7 lysts and in organic light-emitting diodes, but they S 5 have not been very competitive against N N N OH ruthenium and zinc organometallic complexes when it comes to solar O cells. Perylene does hold an advantage in being less expensive than the metal complexes, and therefore researchers Indenoperylene-based dye have been tweaking the molecule to improve its efficiency. Peng Wang of Changchun Institute of Applied Chemistry of the Chinese Academy of Sciences and coworkers tailored their N-annulated indenoperylene (red) with an ethynylbenzothiadiazolylbenzoic acid group (black) from scratch by using a combination of alkylation, cross-coupling, and other steps. Through a series of electrochemical and spectroscopy tests, the team determined that the new dye achieves a power conversion efficiency of 12.5%, which is on par with the best metal complexes. Both metal-containing and metal-free organic dyes are now being challenged by upstart perovskite light-harvesting materials.—SR
NOT SO DYE-FAST Many of the colorful textile products we use—think clothing, sofas, and carpeting— come courtesy of reactive dye molecules that are designed to adsorb onto and covalently bond to fabric fibers. But during a typical dyeing treatment, up to 40% of the dye molecules hydrolyze and remain only loosely associated with the fibers via electrostatic interactions such as hydrogen bonding. Manufacturers must repeatedly wash and rinse the fabric to get the unsecured dye out, which requires a lot of water, time, and energy. Motivated to make the dye wash-off process more efficient, Richard S. Blackburn of the University of Leeds, in England, introduced vinylpyridine-based polymers into the process to electrostatically attract and shepherd away errant dye (ACS Sustainable Chem. Eng. 2015, DOI: 10.1021/ acssuschemeng.5b00034). ( )n These polymers, such as poly(vinylpyridine-N-oxide), are already used as additives in laundry detergent to maintain N+ colorfastness. Blackburn and O– research assistant NaPoly(vinylpyridine-N-oxide) beel Amin found that
using the polymers during dyeing cuts water use in half, reduces processing time by 75%, and consumes 90% less energy.—SR
MELANIN SKINS PROVIDE UV PROTECTION Melanin is a biopolymer responsible for the color of human eyes, skin, and hair. It also protects us from harmful ultraviolet radiation and oxidative stress. Researchers want to take advantage of these properties by using melanin in protective coatings for electronics and other engineered materials. But natural melanin is tough to work with because of its poor solubility. Chemists have recently developed a synthetic version of melanin that mimics the behavior of the real thing and dissolves in basic aqueous solutions. A team led by Christopher J. Ellison of the University of Texas, Austin, and Jaime C. Grunlan of Texas A&M University has now developed a method that uses solutions of the melanin substitute to deposit protective thin films (ACS Macro Lett. 2015, DOI: 10.1021/acsmacrolett.5b00080). The researchers alternately dipped glass slides into solutions of cationic poly(allylamine hydrochloride), or PAH, and anionic synthetic melanin. They thus built up multiple UV-absorbent PAH-melanin bilayers.—MD CEN.ACS.ORG
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NMR MICROSANDWICHES FOR CELL SENSING Understanding biomolecular processes, especially within living cells, typically requires a probe to illuminate whatever it is researchers are interested in studying. A new addition to the sensor toolbox is a probe consisting of a micrometer-sized hydrogel layer sandwiched between metallic disks, report Stephen J. Dodd and Alan P. Koretsky of NIH and Gary Zabow of NIH and NIST (Nature 2015, DOI: 10.1038/ nature14294). The hydrogel reversibly shrinks or swells in response to its surrounding conditions, such as pH or ion concentration, changing the sandwich geometry. Add an applied magnetic field and the proton NMR signal of water molecules in and around the hydrogel also becomes sensitive to the sandwich geometry. The conditions around the sandwich can therefore be tracked by NMR. Zabow and colleagues used disks made of nickel or iron that were 10 to 60 nm thick and 1,800 to 2,000 nm in diameter. The polyethylene glycol-based hydrogel filling was 800 to 1,000 nm tall and 300 to 400 nm wide. Different disk shapes and materials combined with hydrogels sensitive to different conditions provide a means for simultaneous sensing of multiple parameters.—JK
