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.     

Thermal and crystallization behavior of engineering polyblends. I. Glass reinforced polyphenylene sulfide with polyethylene terephthalate

The thermal and crystallization behavior of blends of glass fiber reinforced polyphenylene sulfide (PPS) with polyethylene terephthalate (PET) has been reported. The blends showed two overlapping melting peaks and two separate crystallization peaks. The heat of crystallization of PPS was found to decrease continuously with increasing PET content, whereas the heat of crystallization of PET was found to increase with increasing PPS content. This indicates that the degree of crystallinity of PPS is reduced whereas that of PET is increased as a result of blending. It is interesting to note that the combined heats of fusion of the blends were marginally higher than those calculated by proportional additivity rule in spite of the drop in the heat of crystallization of PPS. The temperature onset of crystallization of PET in the blends shifted to higher temperature whereas there was no significant change in the crystallization temperature of PPS. The increase in the temperature of crystallization of PET indicates enhanced nucleation. The isothermal crystallization studies of the component polymers revealed that both the component polymers crystallized at a relatively faster rate in the blend. The crystallization rate of PPS was found to increase significantly with increasing PET content. A significant increase in the rate of crystallization of PET was also observed in the blends. The acceleration of crystallization rate of PET in the blends was more pronounced as compared to that of PPS. The acceleration in the PET crystallization rate was attributed to the presence of glass fibers and crystallized PPS.     

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.     

Mathematics for reasoning about loop functions

The criticality of modern software applications, the pervasiveness of malicious code concerns, the emergence of third-party software development, and the preponderance of program inspection as a quality assurance method all place a great premium on the ability to analyze programs and derive their function in all circumstances of use and all its functional detail. For C-like programming languages, one of the most challenging tasks in this endeavor is the derivation of loop functions. In this paper, we outline the premises of our approach to this problem, present some mathematical results, and discuss how these results can be used as a basis for building an automated tool that derives the function of while loops under some conditions.     

Rheology of nylon 6 containing metal halides

Addition of metal halides to nylons has been shown to be advantageous in a number of ways. The decrease in melting temperature, increase in glass transition temperature and melt viscosity by such additions have allowed more convenient processing of low molecular weight polymers and thermally unstable polymers. Rheological data depicting the variation of melt viscosity with shear rate at temperatures relevant to processing are necessary in optimizing and trouble-shooting plastics processing operations. In the present paper, a method has been proposed to estimate, complete flow curves or rheograms of nylon—metal halide systems with the use of a master curve knowing the melt flow index and glass transition temperature of the system. The validity of the approach has been verified for the nylon 6—lithium chloride system and shown to hold good for any nylon—metal halide combination.