Intramolecular pyridone/enyne photocycloaddition: partitioning of the [4 + 4] and [2 + 2] pathways

Intramolecular photocycloaddition (>290 nm) between a 1,3-enyne and a 2-pyridone is far more selective than the intermolecular version; a three-atom linkage both controls regiochemistry and separates the [2 + 2] and [4 + 4] pathways. All four head-to-head, head-to-tail, tail-to-head, and tail-to-tail tetherings have been investigated. Linkage via the ene of the enyne leads to [2 + 2] products regardless of alkene geometry, whereas linkage through the yne results in [4 + 4] cycloadducts. The bridged 1,2,5-cyclooctatriene products of [4 + 4] cycloaddition are unstable and undergo a subsequent [2 + 2] dimerization reaction.     

Fabrication of bovine serum albumin nanotubes through template-assisted layer by layer assembly

One-dimensional protein nanostructures have many potential applications in the biomedical field. In this article, protein nanotubes have been fabricated via sequential filtration of bovine serum albumin (BSA) solution at pH 3.8 and 7.0 through the nanochannels of anodic aluminum oxide templates. The morphology of the nanostructures has been examined using scanning electron microscopy and transmission electron microscopy. Circular dichroism and UV/Vis spectroscopy have been used to select experimental conditions such as the pH values and the etching solution to release the fabricated protein nanotubes to minimize potential damage to the bioactivity of BSA. These results indicate that much more study needs to be done to strengthen the mechanical stability of the protein nanotubes and to better control their morphology.     

Preliminary limits on the WIMP-nucleon cross section from the cryogenic dark matter search (CDMS)

We are conducting an experiment to search for WIMPs, or weakly-interacting massive particles, in the galactic halo using terrestrial detectors. This generic class of hypothetical particles, whose properties are similar to those predicted by extensions of the standard model of particle physics, could comprise the cold component of nonbaryonic dark matter. We described our experiment, which is based on cooled germanium and silicon detectors in a shielded low-background cryostat. The detectors achieve a high degree of background rejection through the simultaneous measurement of the energy in phonons and ionization. Using exposures on the order of one kilogram-day from initial runs of our experiment, we have achieved (preliminary) upper limits on the WIMP-nucleon cross section that are comparable to much longer runs of other experiments.