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Insects inspire super rubber
A flea can jump hundreds of times its height, and a cicada can make noise all night, thanks to the elastic protein resilin. Resilin can be found in the cuticles of most insects and in the sound-producing organs of cicadas. The materials randomly coiled, cross-linked polypeptide chains provide low stiffness, high strain, and efficient energy storage for locomotion and repetitive movements. Now, researchers in Australia have created a synthetic polymer based on resilin (Nature 2005, 437, 999). Christopher M. Elvin of Commonwealth Scientific & Industrial Research Organization Livestock Industries, in St. Lucia, and colleagues took a gene known to produce a resilin-like protein in fruit flies and inserted it into Escherichia coli. The bacteria worked like factories, churning out large quantities of the protein. Elvins group introduced resilins characteristic dityrosine cross-links (shown) via Ru(II)-mediated photochemistry. The resulting polymer was rubbery and resilient, as evidenced by its ability to stretch to three times its original length without breaking.
When mice with chronic kidney infections are inoculated with prions, they shed prions in their urine, a team led by Adriano Aguzzi of the University Hospital of Zurich reports (Science 2005, 310, 324). Prions are the infectious agents for a variety of transmissible spongiform encephalopathies (TSEs), such as mad cow disease, scrapie in sheep, Creutzfeldt-Jakob disease in humans, and chronic wasting disease (CWD) in deer and elk. After mice with kidney disease were inoculated with prions from scrapie-infected sheep, they excreted prions in their urine. But when healthy mice were inoculated with prions, no prions were found in their urine. This research has several implications, the authors write. It shows that prions are not always confined to the central nervous and lymphatic systems of TSE-infected animals. It may explain the long-standing mystery of how deer and elk transmit CWD to other animals in the herd and how sheep transmit scrapie. Prion-infected animals with kidney inflammation may be responsible for transmission. Also, the study implies that it may be important to test biopharmaceuticals derived from urine for prions, Aguzzi says.
A small molecule thatinhibits the virulence and colonization of Vibrio cholerae, the bacterium that causes cholera, has been discovered by microbiologists at Harvard Medical School (Science, published online Oct. 13, dx.doi.org/10.1126/science.1116739). The team members, led by Deborah T. Hung and John J. Mekalanos, screened a 50,000-compound library to find compounds that inhibit expression of the bacterial virulence factors known as cholera toxin (CT) and toxin coregulated pilus, which is a hairlike structure on the surface of the bacterium. From a group of 109 compounds that inhibited the expression of CT, they selected the one shown at right, also known as virstatin, for further study. Virstatin did not inhibit bacterial growth, but it did prevent the production of CT and the assembly of a functional pilus. Virstatin protected infant mice from intestinal colonization by V. cholerae. Administration of the drug even after infection reduced the amount of bacteria in the mices intestines.
The structure shown—a fragment of the thiopeptide antibiotic thiostrepton—exhibits biological activity comparable with, and sometimes even better than, that of the complex natural product, a new study shows (J. Am. Chem. Soc. 2005, 127, 15042). Thiostrepton also has promising antimalarial and anticancer activity. Its total synthesis last year, by K. C. Nicolaou and coworkers at Scripps Research Institute and the University of California, San Diego, allowed access to various fragments and structural motifs. Now, Nicolaou and coworkers report that the fragment, called the dehydropiperidine core, possesses significant activity against antibiotic-resistant bacteria and is 30 times more active against bacterial cells than against human red blood cells. Furthermore, the fragments potency against various cancer cell lines is higher than that of thiostrepton.
Chemists claim to have answered a long-standing question about the reactive intermediate in the Fenton reaction, an oxidation reaction that plays a key role in catalysis, environmental and atmospheric processes, and biology. In the Fenton reaction, hydrogen peroxide oxidizes iron(II), generating a reactive intermediate that carries out the oxidation of various organic substrates. The nature of this reactive intermediate—thought by many to be hydroxyl radical and by others to be an Fe(IV)-oxo species—has been subject to a long-simmering debate, according to Andreja Bakac of Iowa State Universitys Ames Laboratory. Now, a team led by Bakac has succeeded in generating an aqueous Fe(IV)-oxo species independently and has ruled it out as the Fenton intermediate (Angew. Chem., published online Oct. 5, dx.doi.org/10.1002/anie.200502686). This achievement also may guide the development of new catalytic reactions based on Fe(IV), Bakac says.
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