A Generic Platform for Cellular Screening Against Ubiquitin Ligases

Ubiquitin signalling regulates most aspects of cellular life, thus deregulation of ubiquitylation has been linked with a number of diseases. E3 ubiquitin ligases provide substrate selectivity in ubiquitylation cascades and are therefore considered to be attractive targets for developing therapeutic molecules. In contrast to established drug target classes, such as protein kinases, GPCRs, hormone receptors and ion channels, ubiquitin drug discovery is in its early stages. This is, in part, due to the complexity of the ubiquitylation pathways and the lack of robust quantitative technologies that allow high-throughput screening of inhibitors. Here we report the development of a Ubiquitin Ligase Profiling system, which is a novel and generic cellular technology designed to facilitate identification of selective inhibitors against RING type E3 ubiquitin ligases. Utilization of this system requires a single co-transfection of cells with assay vectors, thereby enabling readout of E3 ubiquitin ligase catalytic activity within the cellular environment. Therefore, our robust high-throughput screening platform offers novel opportunities for the development of inhibitors against this difficult-to-target E3 ligase enzyme class

Growth of single crystals in the (Na1/2Bi1/2)TiO3-(Sr1-xCax)TiO3 system by solid state crystal growth

Ceramics based on (Na1/2B1/2)TiO3 are promising candidates for actuator applications because of large strains generated by an electric field-induced phase transition. For example, the (1-x)(Na1/2Bi1/2)TiO3-xSrTiO(3) system exhibits a morphotropic phase boundary at x = 0.2-0.3, leading to high values of inverse piezoelectric constant d*(33), which can be further improved by the use of single crystals. In our previous work, single crystals of (Na1/2B1/2)TiO3-SrTiO3 and (Na1/2B1/2)TiO3-CaTiO3 were grown by the solid state crystal growth technique. Growth in the (Na1/2B1/2)TiO3-SrTiO3 system was sluggish whereas the (Na1/2B1/2)TiO3-CaTiO3 single crystals grew well. In the present work, 0.8(Na1/2Bi1/2)TiO3-0.2(Sr1-xCax)TiO3 single crystals (with x = 0.0, 0.1, 0.2, 0.3, 0.4) were produced by the solid state crystal growth technique in an attempt to improve crystal growth rate. The dependence of mean matrix grain size, single crystal growth distance, and electrical properties on the Ca concentration was investigated in detail. These investigations indicated that at x = 0.3 the matrix grain growth was suppressed and the driving force for single crystal growth was enhanced. Replacing Sr with Ca increased the shoulder temperature T-s and temperature of maximum relative permittivity T-max, causing a decrease in inverse piezoelectric properties and a change from normal to incipient ferroelectric behavior

Coarsening of polyhedral grains in a liquid matrix

The coarsening of polyhedral grains in a liquid matrix was calculated using crystal growth and dissolution equations used in crystal growth theories for faceted crystals. The coarsening behavior was principally governed by the relative value of the maximum driving force for growth (Delta g(max)), which is determined by the average size and size distribution, to the critical driving force for appreciable growth (Delta g(c)). When Delta g(max) was much larger than Delta g(c), pseudonormal grain coarsening occurred. With a reduction of Delta g(max) relative to Delta g(c), abnormal grain coarsening (AGC, when Delta g(max) >= Delta g(c)) and stagnant grain coarsening (SGC, when Delta g(max) < Delta g(c)) were predicted. The observed cyclic AGC and incubation for AGC in real systems with faceted grains were explained in terms of the relative value between Delta g(max) and Delta g(c). The effects of various processing and physical parameters, such as the initial grain size and distribution, the liquid volume fraction, step free energy, and temperature, were also evaluated. The calculated results were in good agreement with previous experimental observations.

Effect of surface carburization on dynamic deformation and fracture of tungsten heavy alloys

Effects of surface carburization on dynamic deformation and fracture behavior of tungsten heavy alloys were investigated in order to improve the penetration performance. Dynamic torsional tests using a torsional Kolsky bar were conducted on four specimens, three of which were carburized by the case carburization process. The test data were then compared with hardness, Charpy impact energy, adiabatic shear banding, deformation and fracture mode, and penetration performance, With increasing carburization temperature and time, surface hardness increased, but impact energy decreased. The dynamic torsional test results indicated that for the carburized tungsten specimens, cleavage fracture occurred in the center of the gage section with little shear deformation, whereas shear deformation was concentrated at the center of the gage section for the conventionally processed specimen without carburization. The deformation and fracture behavior of the carburized specimens correlated well with the observation of the impacted penetrator specimens, i.e,, microcrack initiation at tungsten particles and cleavage crack propagation. Since the cleavage fracture mode is thought to be beneficial for self-sharpening, these findings suggest the beneficial effect of the surface carburization on the penetration performance.open1112sciescopu

Control of surface carburization and improvement of dynamic fracture behavior in tungsten heavy alloys

A carburization technique using a Cr powder layer has been developed to control the diffusion depth of carbon in W-Ni-Fe heavy alloys. The aged heavy alloy samples were covered with a Cr powder layer of about 1-mm thickness and then packed with carbon black powder. The packed samples were heat-treated at 1150 C for 10 minutes in H-2 and then for 50 minutes in N-2. The carburization treatment resulted in the formation of Cr7C3 and Fe3W3C around the tungsten grains from the sample surface with a thickness of 40 to 50 mum. This carburized layer was much thinner than that formed without a Cr powder layer under the same experimental conditions. With the surface carburization, the surface hardness increased by similar to75 pct, from 508 to 888 VHN, and the impact energy decreased by similar to31 pct, from 123 to 85 J. After the carburization treatment, the main fracture behavior in a dynamic torsional test changed from smearing of the matrix to cleavage of the tungsten grains. A high-speed impact test showed that the surface carburization of penetrators induced the formation of many cracks around the penetrator surface, enhanced the self-sharpening, and improved the penetration performance. It appears that the developed technique provides an easy method of carburization without serious deterioration of the toughness of the material.open114sciescopu