phobic porous organic polymers, according to a study (Chem 2016, DOI: 10.1016/j. chempr.2016.09.008). Enveloping the catalytic sites in a water-excluding polymeric framework can extend catalyst lifetime as well as broaden the range of reactions for which they can be used. Shengqian Ma of the University of South Florida and coworkers demonstrated the strategy by synthesizing rhodium-infused phosphite-based materials and testing how well they catalyze conversion of olefins to aldehydes, a commercially important reaction. Rhodium phosphite catalysts generally are very active but are prone to decomposition via hydrolysis of P–O bonds. To make a superhydrophobic version of the phosphite-based material, the team prepared a substituted triphenyl phosphite monomer and polymerized it. The researchers treated the water-repellent porous polymer with a rhodium precatalyst, resulting in the rhodium binding to the phosphite sites within the material. Catalysis tests showed that the superhydrophobic material was highly active, even in the presence of water, retaining its activity throughout 14 runs over a weeklong period. In contrast, the activity of traditional heterogeneous and homogeneous rhodium catalysts tested began falling after just a few runs.—MITCH JACOBY
ANTIBIOTICS
▸ Bioinformatics approach finds new drug candidates
FOOD
Chilling messes with tomato flavor Tomato lovers commonly rant about the suboptimal taste of supermarket varieties. Part of the problem is that most store-bought tomatoes have been bred to slow down softening of the fruit, which makes the tomatoes travel-hardy but also less flavorful. Now researchers are pointing to cold storage—another common feature of the global produce market—as an additional culprit for poor tomato flavor (Proc. Natl. Acad. Sci. USA 2016, DOI: 10.1073/ pnas.1613910113). A team led by Harry J. Klee of the University of Florida explored the expression of tomato enzymes that convert lycopene into flavor-imparting volatile compounds. The team found that when tomatoes were stored at temperatures below 12 °C, genes involved in ripening flavor development were methylated, leading to reduced expression of those genes. In parallel, the researchers found that levels of messenger RNA coding for enzymes involved in producing flavor, including those responsible for several consumer-favorite volatiles such as isovaleraldehyde, 3-methyl-1-butanol, and 2-methyl-1-butanol, dropped when tomatoes were chilled.—SARAH EVERTS
Biol. 2016, DOI: 10.1038/nchembio.2207). “This was just the first step of building complex molecules guided by bioinformatics,” Brady says. Next, his group plans to explore beyond the human microbiome to other microorganism habitats.—RYAN CROSS
CREDIT: SHUTTERSTOCK (TOMATO); STRUCT. HEALTH MONIT. (CONCRETE)
COATINGS Microbes are full of undiscovered molecules, including antibiotics. But many species remain difficult to culture or simply contain large swaths of genes that remain inactive under laboratory conditions. Hoping to harvest untapped molecules without growing a single cell, Sean F. Brady of Rockefeller University and colleagues looked to genomic data from the human microbiome for inspiration. “Genomic sequences are coming at us fast, and we need tools to turn that information into molecules,” Brady says. So the researchers mined previously reported DNA sequences for nonribosomal peptide gene clusters. With those data, they synthesized the predicted structures of 25 peptides and tested them for antibiotic activity. Two peptides, dubbed humimycin A and humimycin B, are effective against several pathogenic bacteria. Humimycin A drastically improved survival in mice infected with methicillin-resistant Staphylococcus aureus (MRSA) when given in conjunction with the antibiotic dicloxacillin (Nat. Chem.
▸ Concrete skin detects cracking, chemical leaks
Just say no to cold storage— researchers find chilling tomatoes alters production of key flavor compounds, including those shown. H O Isovaleraldehyde OH 3-Methyl-1-butanol OH 2-Methyl-1-butanol
impedance of a multilayer coating applied to the structure’s surface (Struct. Health Monit. 2016, DOI: 10.1177/1475921716670574). Researchers led by Aku Seppänen of the University of Eastern Finland and Mohammad Pour-Ghaz of North Carolina State University made the sensing skin from silver, latex, and copper. Silver paint’s impedance is sensitive to cracking, whereas copper paint’s impedance is sensitive to both cracking and chloride ions, which can corrode the reinforcing steel placed in concrete. The latex layer separates and insulates the two metal layers. The team showed that imaging the skin’s two conductive layers using electrical impedance tomography signaled the presence of chloride from a salt solution as well as cracks in a concrete specimen after force was applied.—SARAH EVERTS
When concrete chemical and nuclear containment structures begin to crack or corrode, facility engineers need an instant warning. One way to monitor structural integrity of concrete is to measure its electrical impedance, which changes when the material cracks. However, this strategy suffers sensitivity issues. An international team instead is proposing to monitor both cracking and chemical Using electrical impedance tomography, concrete exposed to leakage of concrete chloride ions (top row) is sensed by the copper layer but not the structures by measilver one. Both layers sense cracking in the concrete (bottom suring the electrical row) after a force is applied. OCTOBER 24, 2016 | CEN.ACS.ORG | C&EN
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