Saturday, January 7, 2012

Chemists find new way to break amide bonds

The work, published in Angewandte Chemie, features as the lead highlight in the American Chemical Society's C&ENews this week.

An amide is an organic compound containing a carbonyl group (R-C=O) linked to a nitrogen atom (N).  The bonds in an amide are notoriously difficult to break: reaction times under mild, neutral-pH conditions are over 100 years.  The only way to make amide bonds break down faster without resorting to acids, bases, and catalysts is to twist them physically.

Now, Professor Guy Lloyd-Jones and Professor Kevin Booker-Milburn and colleagues have demonstrated that amide bonds (–CO–NH–) can be broken down much more easily by attaching an electron-withdrawing group (R) to an ? carbon and bulky substituents (R') to the nitrogen.  The groups induce the ? carbon to lose a proton and the nitrogen to gain one.  This results in R–HC––CO–HN+–R'2 which expels the bulky group HN–R'2, thus breaking the amide bond.

The method may help explain how some cellular enzymes break amide bonds and will make it easier to carry out amide-based reactions.

Professor Tim Gallagher, Head of the School of Chemistry said: “This is an intriguing reaction, all the more so because we think of amides as such stable entities.  Achieving this process under mild conditions has defied some of the best brains for years and this paper presents and explains the solution against an elegant background of observation and understanding.”

More information: ‘Switching Pathways: Room-Temperature Neutral Solvolysis and Substitution of Amides’ by Marc Hutchby, Chris E. Houlden, Mairi F. Haddow, Simon N. G. Tyler, Guy C. Lloyd-Jones and Kevin I. Booker-Milburn in Angew. Chem. Int. Ed DOI: 10.1002/anie.201107117

Provided by University of Bristol (news : web)

Success in synthesis of new high performance functional material mesoporous prussian blue

This research result was achieved by a team headed by Dr. Yusuke Yamauchi, a MANA Scientist at the NIMS International Center for Materials Nanoarchitectonics, and Dr. Hu Ming, who is a Postdoctoral Researcher at MANA.

Prussian blue has a high cesium adsorption capacity, on the same level as natural minerals such as . To date, various attempts have been made to increase the adsorption capacity of Prussian blue by increasing its surface area by refinement/fabrication of . However, with the conventional synthesis process for mesoporous material, the of Prussian blue was greatly reduced by refinement, and the expected increase in surface area was not obtained. Therefore, the development of a new which increases the area of Prussian blue while maintaining its crystallinity, and thereby maximizes its adsorption capacity, was indispensable.

In this work, the NIMS researchers succeeded in fabricating nanoporous Prussian blue using a new etching type synthesis method. As illustrated in the accompanying figure, it was possible to induce of an extremely large number of nanopores in particles of Prussian blue by adding water-soluble macromolecules to a solution in which of Prussian blue had been dispersed and stirring the resulting solution under an acidic condition.

The surface area showed a high value of more than 330m2/g, which is the largest area reported for Prussian blue until now and is also more than 10 times larger than the area of commercial Prussian blue particles. In a cesium adsorption experiment using this mesoporous Prussian blue, cesium adsorption was more than 8 times greater than that with the commercial Prussian blue. It is thought that a similar adsorption capacity can be expected in seawater. In order to further increase the adsorption capacity of Prussian blue by metal replacement, the research team is attempting to apply this technique to Co-Fe Prussian blue analogues, etc. In the future, tests of these materials as adsorbents will be conducted, and development will be carried out with the aim of simplifying the process. As a result, development approaching practical applications, beginning with application to mass production, is expected.

The results were on December 19, 2011 in the online edition of the Angewandte Chemie International Edition (published by the German Chemical Society).

Provided by National Institute for Materials Science

Researchers discover secret of weevil diamond-like coat

Researchers and various other people have been puzzled for years as to how the diamond weevil manages to produce a coat that sparkles as well as any real diamond, but until recently, lacked the technology necessary to uncover the secret.

Now, using electron microscopy, this team discovered that the diamond-like material is actually made of nothing more than , a long polymer derivative of glucose. Its most commonly found in anthropoids, mollusks and crustaceans as well as in a variety of insects. In this case, the diamond weevil.

Scanning electron microscopy of single scales of E. imperialis. (a) A single, intact scale. The upper side of the scale consists of a set of more or less parallel furrows (scale bar: 20 ?m). (b) SEM image of a cross-section showing tilted sheets with hexagonal symmetry (scale bar: 2 ?m). Image (c) J. R. Soc. Interface, doi:10.1098/?rsif.2011.0730

In most other animals, chitin appears as a dull whitish material, and is used by those higher up the evolutionary chain as an ingredient in medical and industrial products. In diamond weevils, it’s the way the material that is arranged that is different. For some as yet to be discovered reason, the gems in their coats are crystal structured in the same way as real , i.e. as photonic crystals.

Turns out, each little “gem” has crystal scales on it, each of which reflect a different wavelength of light at a different angle, producing the sparkling effect.

Now that the little bug’s secret has been revealed, other researchers will no doubt be looking into whether such gems might be made artificially and if so, if there might be any good use for them.

More information: Hemispherical Brillouin zone imaging of a diamond-type biological photonic crystal, J. R. Soc. Interface, Published online before print December 21, 2011, doi: 10.1098/?rsif.2011.0730

The brilliant structural body colours of many animals are created by three-dimensional biological photonic crystals that act as wavelength-specific reflectors. Here, we report a study on the vividly coloured scales of the diamond weevil, Entimus imperialis. Electron microscopy identified the chitin and air assemblies inside the scales as domains of a single-network diamond (Fd3m) photonic crystal. We visualized the topology of the first Brillouin zone (FBZ) by imaging scatterometry, and we reconstructed the complete photonic band structure diagram (PBSD) of the chitinous photonic crystal from reflectance spectra. Comparison with calculated PBSDs indeed showed a perfect overlap. The unique method of non-invasive hemispherical imaging of the FBZ provides key insights for the investigation of photonic crystals in the visible wavelength range. The characterized extremely large biophotonic nanostructures of E. imperialis are structurally optimized for high reflectance and may thus be well suited for use as a template for producing novel photonic devices, e.g. through biomimicry or direct infiltration from dielectric material.

via Wired

? 2011