Overexpression, purification, and characterization of SHPTP1, a Src homology 2-containing protein-tyrosine-phosphatase

A protein-tyrosine-phosphatase (PTPase; EC 3.1.3.48) containing two Src homology 2 (SH2) domains, SHPTP1, was previously identified in hematopoietic and epithelial cells. By placing the coding sequence of the PTPase behind a bacteriophage T7 promoter, we have overexpressed both the full-length enzyme and a truncated PTPase domain in Escherichia coli. In each case, the soluble enzyme was expressed at levels of 3-4% of total soluble E. coli protein. The recombinant proteins had molecular weights of 63,000 and 45,000 for the full-length protein and the truncated PTPase domain, respectively, as determined by SDS/PAGE. The recombinant enzymes dephosphorylated p-nitrophenyl phosphate, phosphotyrosine, and phosphotyrosyl peptides but not phosphoserine, phosphothreonine, or phosphoseryl peptides. The enzymes showed a strong dependence on pH and ionic strength for their activity, with pH optima of 5.5 and 6.3 for the full-length enzyme and the catalytic domain, respectively, and an optimal NaCl concentration of 250-300 mM. The recombinant PTPases had high Km values for p-nitrophenyl phosphate and exhibited non-Michaelis-Menten kinetics for phosphotyrosyl peptides.     

Calibrated,Registered Images of an Extended Urban Area

We describe a dataset of several thousand calibrated, time-stamped, geo-referenced, high dynamic range color images, acquired under uncontrolled, variable illumination conditions in an outdoor region spanning several hundred meters. The image data is grouped into several regions which have little mutual inter-visibility. For each group, the calibration data is globally consistent on average to roughly five centimeters and 0 1°, or about four pixels of epipolar registration. All image, feature and calibration data is available for interactive inspection and downloading at http://city.lcs.mit.edu/data.Calibrated imagery is of fundamental interest in a variety of applications. We have made this data available in the belief that researchers in computer graphics, computer vision, photogrammetry and digital cartography will find it of value as a test set for their own image registration algorithms, as a calibrated image set for applications such as image-based rendering, metric 3D reconstruction, and appearance recovery, and as input for existing GIS applications.     

Solvent and Extraction Conditions Control the Assayable Phenolic Content and Antioxidant Activities of Seeds of Black Beans,Canola and Millet

The effects of extraction solvent and conditions on the total phenolic content (TPC) and antioxidant activity of black beans, canola and foxtail millet were investigated. The antioxidant activity was assayed using 2,2‐diphenyl‐1‐picrylhydrazyl radical scavenging activity (DRSA) and oxygen radical absorbance capacity (ORAC). Four solvent systems, namely 70 % acetone, 80 % ethanol, 80 % methanol and a mixture of acetone/methanol/water (7:7:6, v/v/v) were used. The extraction methods adopted in this study included refluxing, homogenization, cold extraction and sonication. The TPC as measured using the Folin Ciocalteu's method were 12.35–28.39, 2.43–16.73, and 1.78–5.06 µmol catechin equivalents/g dry matter (dm) for canola, black beans and foxtail millet, respectively. Aqueous acetone afforded the highest TPC for black beans and canola. Within the same solvent system used, the TPC, DRSA and ORAC obtained from different extraction techniques differed for black beans, canola and foxtail millet. The results demonstrated that the solvent system as well as method influenced the extraction of phenolic compounds and their antioxidant activities, depending on the type of matrix in which phenolics were embedded.     

Concentration of cupric and nickel ions by complexation-ultrafiltration. Synergic effect of succinic acid

In ultrafiltration, high rejection of small ion species can be achieved by complexing these species with a suitable macroligand.We have studied the concentration of cupric or/and nickel ions by ultrafiltration, through the DDS GR8 membrane, using polyethylenimine as a basic macroligand. The rejections of the metallic ions increased with the pH and the concentration of the polymeric ligand as expected. The addition of succinic acid (a molecular acidic chelating) to the mixtures allowed an improvement of the retentions of these ions at all pHs studied. This indicates that positive synergic effect was obtained by the formation of a mixed complex base-metal-acid.     

Liquid transport through membranes prepared by grafting of polar monomers onto poly(tetrafluoroethylene) films. II. Some factors determining pervaporation rate and selectivity

The effect of some factors including temperature, pressure, film thickness, and grafting ratio on the fractionation of binary liquid mixtures has been investigated by pervaporation through poly(tetrafluoroethylene) films grafted with N-vinylpyrrolidone or 4-vinylpyridine. The purpose was to estimate the best conditions in which the pervaporation process must be carried out. It was concluded that the pervaporation rate is increased at roughly constant selectivity when the temperature of the liquid charge is higher or when the downstream vapor pressure or the film thickness are decreased. A pressure higher than 1 atmosphere above the liquid does not increase the rate. When the grafting ratio is increased, the rate shows a maximum, and for particular conditions, the selectivity becomes much higher.     

Liquid transport through membranes prepared by grafting of polar monomers onto poly(tetrafluoroethylene) films. III. Steady-state distribution in membrane during pervaporation

Steady-state concentration and composition gradients of pervaporating liquids inside the membranes were measured using stacks of membranes. The experimental results on pure components agree well with a simple mechanism of diffusion down a chemical potential gradient in a nonporous membrane. For mixtures, concentration gradients are similar to those obtained for pure liquids, and composition distribution shows that the selection between the two species does not take place at a given interface in the membrane but is progressive along the diffusional paths through the membrane. Data are also listed to show that solubility and diffusivity enhancements occur for components which are hydrogen bonded with the basic groups of the membrance.     

Hydroxyapatite, fluor-hydroxyapatite and fluorapatite produced via the sol–gel method: dissolution behaviour and biological properties after crystallisation

Hydroxyapatite (HA), fluor-hydroxyapatite (FHA) with varying levels of fluoride ion substitution and fluorapatite (FA) were synthesised by the sol–gel method as possible implant coating or bone-grafting materials. Calcium nitrate and triethyl phosphite were used as precursors under an ethanol–water based solution. Different amounts of ammonium fluoride were incorporated for the preparation of the FHA and FA sol–gels. After heating and powdering the sol–gels, dissolution behaviour was assessed using ion chromatography to measure Ca²⁺ and PO₄ ^3? ion release. Biological behaviour was assessed using cellular proliferation with human osteosarcoma cells and alamarBlue? assay. Statistical analysis was performed with a two way analysis of variance and post hoc testing with a Bonferroni correction. Increasing fluoride substitution into an apatite structure decreased the dissolution rate. Increasing the firing temperature of the HA, FHA and FA sol–gels up to 1,000 °C decreased the dissolution rate. There was significantly higher cellular proliferation on highly substituted FHA and FA than on HA or Titanium. The properties of an implant coating or bone grafting material can be tailored to meet specific requirements by altering the amount of fluoride that is incorporated into the original apatite structure. The dissolution behaviour can further be altered by the temperature at which the sol–gel is fired.