Structure of the cross-beta spine of amyloid-like fibrils

Numerous soluble proteins convert to insoluble amyloid-like fibrils that have common properties. Amyloid fibrils are associated with fatal diseases such as Alzheimer's, and amyloid-like fibrils can be formed in vitro. For the yeast protein Sup35, conversion to amyloid-like fibrils is associated with a transmissible infection akin to that caused by mammalian prions. A seven-residue peptide segment from Sup35 forms amyloid-like fibrils and closely related microcrystals, from which we have determined the atomic structure of the cross-beta spine. It is a double beta-sheet, with each sheet formed from parallel segments stacked in register. Side chains protruding from the two sheets form a dry, tightly self-complementing steric zipper, bonding the sheets. Within each sheet, every segment is bound to its two neighbouring segments through stacks of both backbone and side-chain hydrogen bonds. The structure illuminates the stability of amyloid fibrils, their self-seeding characteristic and their tendency to form polymorphic structures.     

Terahertz-field-induced insulator-to-metal transition in vanadium dioxide metamaterial

Electron-electron interactions can render an otherwise conducting material insulating, with the insulator-metal phase transition in correlated-electron materials being the canonical macroscopic manifestation of the competition between charge-carrier itinerancy and localization. The transition can arise from underlying microscopic interactions among the charge, lattice, orbital and spin degrees of freedom, the complexity of which leads to multiple phase-transition pathways. For example, in many transition metal oxides, the insulator-metal transition has been achieved with external stimuli, including temperature, light, electric field, mechanical strain or magnetic field. Vanadium dioxide is particularly intriguing because both the lattice and on-site Coulomb repulsion contribute to the insulator-to-metal transition at 340?K (ref. 8). Thus, although the precise microscopic origin of the phase transition remains elusive, vanadium dioxide serves as a testbed for correlated-electron phase-transition dynamics. Here we report the observation of an insulator-metal transition in vanadium dioxide induced by a terahertz electric field. This is achieved using metamaterial-enhanced picosecond, high-field terahertz pulses to reduce the Coulomb-induced potential barrier for carrier transport. A nonlinear metamaterial response is observed through the phase transition, demonstrating that high-field terahertz pulses provide alternative pathways to induce collective electronic and structural rearrangements. The metamaterial resonators play a dual role, providing sub-wavelength field enhancement that locally drives the nonlinear response, and global sensitivity to the local changes, thereby enabling macroscopic observation of the dynamics. This methodology provides a powerful platform to investigate low-energy dynamics in condensed matter and, further, demonstrates that integration of metamaterials with complex matter is a viable pathway to realize functional nonlinear electromagnetic composites.     

ORGANIZATIONAL LEARNING AND VENDOR SUPPORT QUALITY BY THE USAGE OF APPLICATION SOFTWARE PACKAGES： A STUDY OF ASIAN ENTREPRENEURS

In this paper we study how organizational learning impacts organizational behavior, and howvendor support quality enhances product adoption and usage behavior.These constructs were verifiedusing Application Software Packages(ASP)-a prewritten, precoded, commercially available set ofprograms that eliminates the need for individuals or organizations to write their own softwareprograms for certain functions. The relationship between ASP usage, usage outcomes and useprocesses were also investigated. Two hundred and ninety-five Chinese, Indian, and Malayentrepreneurships were studied. It was found that usage outcome strongly determines usage, while useprocess has only an indirect relationship (via outcome) on usage. The impact of organizational learningand vendor service quality on usage, usage outcome, and use process were robust. Theoretical andpractical implications of the research are discussed.     

Semi-annual oscillations in Saturn's low-latitude stratospheric temperatures

Observations of oscillations of temperature and wind in planetary atmospheres provide a means of generalizing models for atmospheric dynamics in a diverse set of planets in the Solar System and elsewhere. An equatorial oscillation similar to one in the Earth's atmosphere has been discovered in Jupiter. Here we report the existence of similar oscillations in Saturn's atmosphere, from an analysis of over two decades of spatially resolved observations of its 7.8-microm methane and 12.2-microm ethane stratospheric emissions, where we compare zonal-mean stratospheric brightness temperatures at planetographic latitudes of 3.6 degrees and 15.5 degrees in both the northern and the southern hemispheres. These results support the interpretation of vertical and meridional variability of temperatures in Saturn's stratosphere as a manifestation of a wave phenomenon similar to that on the Earth and in Jupiter. The period of this oscillation is 14.8 +/- 1.2 terrestrial years, roughly half of Saturn's year, suggesting the influence of seasonal forcing, as is the case with the Earth's semi-annual oscillation.     

Occurence and effect of Chrysomyxa pirolata cone rust on Picea pungens in Utah

In a rare 1969 epidemic, spruce cone rust caused by Chrysomyxa pirolata infected 40 – 100 percent of trees and 20 – 67 percent of cones on riparian Colorado blue spruce on plots located in a 2200 – 2400 m elevational zone in Huntington Canyon of central Utah. Uredinial and telial sporulation on Pyrola spp. began in mid - June, a time closely correlated with opening of pistillate spruce cones. Come phenology and host habitat, as influenced by elevation, are apparently important factors in the restricted niche of the cone rust fungus in Utah. Several preceding consecutive years with extended periods of spring and fall moisture were associated with occurrence of the epidemic, although no cause - and - effect relationship was established. Weather records indicate that these events are infrequent in this climatic zone, and there was no detectable recurrence of cone rust for at least 9 years following 1969. Outwardly normal seeds developed in diseased cones, but seed germinability was reduced by 25 percent. Aecial spore masses between cone scales, cone resinosis, and distortion of cone scales prevented seed dispersal to the extent that the seed crop was effectually destroyed.     

Evidence for lateral gene transfer between Archaea and bacteria from genome sequence of Thermotoga maritima.

The 1,860,725-base-pair genome of Thermotoga maritima MSB8 contains 1,877 predicted coding regions, 1,014 (54%) of which have functional assignments and 863 (46%) of which are of unknown function. Genome analysis reveals numerous pathways involved in degradation of sugars and plant polysaccharides, and 108 genes that have orthologues only in the genomes of other thermophilic Eubacteria and Archaea. Of the Eubacteria sequenced to date, T. maritima has the highest percentage (24%) of genes that are most similar to archaeal genes. Eighty-one archaeal-like genes are clustered in 15 regions of the T. maritima genome that range in size from 4 to 20 kilobases. Conservation of gene order between T. maritima and Archaea in many of the clustered regions suggests that lateral gene transfer may have occurred between thermophilic Eubacteria and Archaea.     

Cloning of adiponectin receptors that mediate antidiabetic metabolic effects

Adiponectin (also known as 30-kDa adipocyte complement-related protein; Acrp30) is a hormone secreted by adipocytes that acts as an antidiabetic and anti-atherogenic adipokine. Levels of adiponectin in the blood are decreased under conditions of obesity, insulin resistance and type 2 diabetes. Administration of adiponectin causes glucose-lowering effects and ameliorates insulin resistance in mice. Conversely, adiponectin-deficient mice exhibit insulin resistance and diabetes. This insulin-sensitizing effect of adiponectin seems to be mediated by an increase in fatty-acid oxidation through activation of AMP kinase and PPAR-alpha. Here we report the cloning of complementary DNAs encoding adiponectin receptors 1 and 2 (AdipoR1 and AdipoR2) by expression cloning. AdipoR1 is abundantly expressed in skeletal muscle, whereas AdipoR2 is predominantly expressed in the liver. These two adiponectin receptors are predicted to contain seven transmembrane domains, but to be structurally and functionally distinct from G-protein-coupled receptors. Expression of AdipoR1/R2 or suppression of AdipoR1/R2 expression by small-interfering RNA supports our conclusion that they serve as receptors for globular and full-length adiponectin, and that they mediate increased AMP kinase and PPAR-alpha ligand activities, as well as fatty-acid oxidation and glucose uptake by adiponectin.