Bitter taste is sensed by bitter taste receptors (TAS2Rs) that belong to the G protein-coupled receptor (GPCR) superfamily. In addition to bitter taste perception, TAS2Rs have been reported recently to be expressed in many extraoral tissues and are now known to be involved in health and disease. Despite important roles of TAS2Rs in biological functions and diseases, no crystal structure is available to help understand the signal transduction mechanism or to help develop selective ligands as new therapeutic targets. We report here the three-dimensional structure of the fully activated TAS2R4 human bitter taste receptor predicted using the GEnSeMBLE complete sampling method. This TAS2R4 structure is coupled to the gustducin G protein and to each of several agonists. We find that the G protein couples to TAS2R4 by forming strong salt bridges to each of the three intracellular loops, orienting the activated Gα5 helix of the Gα subunit to interact extensively with the cytoplasmic region of the activated receptor. We find that the TAS2Rs exhibit unique motifs distinct from typical Class A GPCRs, leading to a distinct activation mechanism and a less stable inactive state. This fully activated bitter taste receptor complex structure provides insight into the signal transduction mechanism and into ligand binding to TAS2Rs.

The preparation of transmission electron microscopy (TEM) samples from powders is quite difficult and challenging. For powders with particles in the 1–5 μm size range, it is especially difficult to select an adequate sample preparation technique. Epoxy is commonly used to bind powder, but drawbacks, such as differential milling originating from unequal milling rates between the epoxy and powder, remain. We propose a new, simple method for preparing TEM samples. This method is especially useful for powders with particles in the 1–5 μm size range that are vulnerable to oxidation. The method uses solder as an embedding agent together with focused ion beam (FIB) milling. The powder was embedded in low-temperature solder using a conventional hot-mounting instrument. Subsequently, FIB was used to fabricate thin TEM samples via the lift-out technique. The solder proved to be more effective than epoxy in producing thin TEM samples with large areas. The problem of differential milling was mitigated, and the solder binder was more stable than epoxy under an electron beam. This methodology can be applied for preparing TEM samples from various powders that are either vulnerable to oxidation or composed of high atomic number elements.

In this study, we synthesized ZnO nanowires using Au catalytic particles formed on a ZnO seed layer. We modulated the microstructure of the ZnO seed layer by changing the sputtering power to investigate how the underlying ZnO film microstructure affects the distribution of ZnO nanowires. Examining the samples after each of the three key steps of the growth process (ZnO seed layer deposition, Au catalytic particle formation, and nanowire growth) using various characterization methods such as scanning electron microscopy, transmission electron microscopy, and x-ray diffraction helped us illuminate the profound impacts of the grain size of the seed layer on the nanowire density.

The activation of PPARγ by ligands, including conjugated linoleic acid (CLA) isomers, plays an important role in the immune response. Among CLA isomers, trans-10, cis-12 (t10c12)-CLA is known to participate in the modulation of pro-inflammatory cytokine secretion. The aim of the present study was to assess the effect of t10c12-CLA on PPARγ activation, NF-κB activation and TNF-α expression in lipopolysaccharide (LPS)-naive and LPS-stimulated porcine peripheral blood mononuclear cells (PBMC). In addition, the effect of PPARγ inhibition on NF-κB activation and TNF-α expression in porcine PBMC was examined. t10c12-CLA was found to increase TNF-α expression and NF-κB activity in LPS-naive porcine PBMC. In contrast, t10c12-CLA decreased TNF-α expression and NF-κB activity in LPS-stimulated porcine PBMC. t10c12-CLA up-regulated PPARγ activity and mRNA expression in both LPS-naive and LPS-stimulated porcine PBMC. GW9662, a PPARγ antagonist, completely negated the modulating effects of t10c12-CLA on TNF-α expression and NF-κB activity in both LPS-naive and LPS-stimulated porcine PBMC. These results suggest that t10c12-CLA can modulate TNF-α production and NF-κB activation by a PPARγ-dependent pathway in porcine PBMC.

SiC nanowire was grown by APCVD using single precursors. Grown SiC nanowires had 10∼60nm diameters and lengths of several micrometers. Nanowire's diameters and lengths were varied with kind of catalysts. Nanowire's growth scheme was divided by two regions with diameter of nanowire. At first region, nanowire was grown by VLS (vapor-liquid-solid) mechanism, but at the second region, nanowire growth was made by VS (vapor-solid) reaction. These differences were made from limitations of growth rate and deactivation effects. Growth temperature, time and flow rates of source gases were affected nanowire's diametesr and its lengths. And kind of catalysts, coating methods and precursors were affected growth direction and microstructures too.

SiOx nanowire were synthesized using VLS (vapor-liquid-solid) and SLS (ssolid-liquid-solid) growth mechanism. Grown nanowires had a different shapes by the kind of substrates and kind of catalysts. Diameters and lengths of grown nanowires were varied with growth conditions. By vapor evaporation method, used substrates effected growth scheme and density of nanowires because of differences of catalyst nucleation characteristics. Grown nanowires showed different microstructures and optical properties. By catalyst evaporation method, various shapes of SiOx nanowires were grown. These shapes of nanowire were formed by the typical reaction of catalyst and Si source. Measured optical properties show blue luminescence about 430nm because of oxygen defects in the nannowire.

Bulk-quantity single crystalline wurtzite gallium nitride nanowires with a mean diameter of 25 nm were synthesized on silicon substrate using a catalyst-assisted reaction of gallium and gallium nitride mixture with ammonia. They exhibit a strong and broad photoluminescence in the energy range of 2.9-3.6 eV with no yellow band. X-ray diffraction and Raman scattering data suggest that the nanowires would experience biaxial compressive stresses in the inward radial direction and the induced tensile uniaxial stresses in the wire axis. The blue photoluminescence would originate from the recombination of the bound excitons under the compressive and tensile stresses.

Interfacial reactions between an Al thin film and a single-crystal (001) 6H–SiC substrate were investigated using x-ray diffraction and cross-sectional transmission electron microscopy. Aluminum thin films were prepared by radio-frequency magnetron sputtering method on 6H–SiC substrates at room temperature and then annealed at various temperatures from 500 to 900 °C. A columnar-type polycrystalline Al thin film was formed on a 6H–SiC substrate in the as-deposited sample. No remarkable microstructural change, compared to the as-deposited sample, was observed in the sample annealed at 500 °C for 1 h. However, it was found that the Al layer reacted with the SiC substrate at 700 °C and formed an Al–Si–C ternary compound at the Al/SiC interface. Samples annealed at 900 °C showed a double-layer structure with an Al–Si mixed surface layer and an Al–Si–C compound layer below in contact with the substrate.

High quality ZnS epilayers were grown on GaAs and GaP substrates by hot wall epitaxy. The optimum temperature conditions for high quality ZnS epilayer were found. The photoluminescence(PL) spectrum of high quality ZnS epilayers showed sharp and narrow exciton peaks and no self-activated peaks. The room temperature energy gap of ZnS/GaAs was found to be 3.729 eV from the experimentally observed free exciton PL peaks. The temperature dependence of the PL intensity showed a two step quenching process and the temperature dependence of the PL linewidth broadening was tried to analyze in terms of exciton scattering process. From the splitting of the heavy hole and the light hole exciton peaks, the strain was identified.

A gradual change in thermal oxide surface state from hydrophilic to hydrophobic was observed with time -delay in a clean room environment. Surface quality and reflectivity for the Al/Ti metal layers showed a strong dependency on the oxide surface state. From the hydrophilic oxide substrate, a lower (002) Ti preferred orientation was obtained than from hydrophobic ones. This resulted in a degraded (111) Al preferred orientation and rough metal surface. The RF-etch process increased the smoothness and hydrophobic surface property for the inter -metal dielectric (IMD) oxides, and therefore greatly improved Al/Ti surface quality. When conventional CMOS double layer metal interconnection process is performed, metal inter-line bridge yield was strongly affected by the surface state of substrate oxides.