Date: 12.19.2012

resistant bacteria from labs enter rivers in china

bacteria

In China, resistant bacteria from molecular biology experiments are turning up in rivers and streams. Molecular biologists use different resistant strains in order to clone bacteria and produce different proteins. In the US, academic and industrial labs have implemented steps to prevent these resistant genes from being introduced into our environment. China, it appears, still has a ways to go before they get a handle on this. From C&EN:

But because this technique is still commonly used in molecular biology labs, some researchers have been concerned that these experiments could release resistance genes into the environment. To search for antibiotic-resistance genes introduced by synthetic plasmids, Jun-Wen Li at the Institute of Health and Environmental Medicine, in Tianjin, China, and his colleagues took water samples from six Chinese rivers downstream of densely populated cities. They extracted plasmids from the samples and transferred the DNA into Escherichia coli. Then they screened the bacteria for a gene commonly used in academic and industrial labs that confers resistance to the antibiotic ampicillin. To determine if a gene in a sample came from a manmade source, they used polymerase chain reaction to look for sequences unique to several synthetic plasmids.

The researchers found synthetic resistance genes in all six rivers. Of all of the ampicillin-resistance plasmids they found in the rivers, about 27% had the synthetic vector-sourced gene.

More here.

brighter OLED screens

From C&EN, via nature.com

A new set of organic molecules might be able to bring us brighter screens for the many technologies we use today. From C&EN:

Researchers in Japan have designed and synthesized low-cost compounds based on carbazolyl dicyano­benzene (CDCB) and show they efficiently emit light in response to an electric current (Nature, DOI:10.1038/nature11687). The family members, which differ in the number of carbazolyl units and the presence of other organic substituents, emit a wide spectrum of colors ranging from sky blue to orange.

The earliest OLED displays, introduced roughly 25 years ago, were based on all-organic fluorescent materials that inherently convert just a small fraction of electrical energy input to light. OLEDs featuring phosphorescent metal-organic compounds proved to be more efficient emitters, and they are now the standard in this area. Yet they are costly because they include rare metals such as iridium and depend on exotic metal catalysts for their synthesis.

By tailoring the structure of compounds that include electron-donating carbazole groups and electron-accepting dicyanobenzene units, Kyushu University chemists Chihaya Adachi and Hiroki Uoyama and coworkers have now designed metal-free compounds with a tiny energy gap between the molecules’ excited singlet and triplet electronic states. The low-cost, all-organic compounds were made in one step from commercially available starting materials. Because of their electronic structures, the compounds exhibit electroluminescent efficiencies comparable to today’s best phosphorescent OLEDs.

 

More here and at nature.com

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