Effect of high-pressure torsion on microstructure, mechanical properties and corrosion resistance of cast pure Mg

© 2018, The Author(s). High-pressure torsion (HPT) processing was applied to cast pure magnesium, and the effects of the deformation on the microstructure, hardness, tensile properties and corrosion resistance were evaluated. The microstructures of the processed samples were examined by electron backscatter diffraction, and the mechanical properties were determined by Vickers hardness and tensile testing. The corrosion resistance was studied using electrochemical impedance spectroscopy in a 3.5% NaCl solution. The results show that HPT processing effectively refines the grain size of Mg from millimeters in the cast structure to a few micrometers after processing and also creates a basal texture on the surface. It was found that one or five turns of HPT produced no significant difference in the grain size of the processed Mg and the hardness was a maximum after one turn due to recovery in some grains. Measurements showed that the yield strength of the cast Mg increased by about seven times whereas the corrosion resistance was not significantly affected by the HPT processing

Structural characterization and low-resolution model of BJ-48, a thrombin-like enzyme from Bothrops jararacussu venom

Thrombin-like enzymes (TLEs) are important components of snake venoms due to their involvement in coagulopathies occurring on envenoming. Structural characterization of this group of serine proteases is of utmost importance for better understanding their unique properties. However, the high carbohydrate content of some members of this group prevents successful crystallization for structural determination. Circumventing this difficulty, the structure of BJ-48, a highly glycosylated TLE from Bothrops jararacussu venom, was studied in solution. At pH 8.0, where the enzyme displays maximum activity, BJ-48 has a radius of gyration (Rg) of 37 angstrom and a maximum dimension (D-max) of 130 angstrom as measured by small-angle X-ray scattering (SAXS) and a Stokes radius (SR) of 50 angstrom according to dynamic light scattering (DLS) data. At the naturally more acidic pH (6.0) of the B. jararacussu venom BJ-48 behaves as a more compact particle as evidenced by SAXS (R-g= 27.9 angstrom and D-max = 82 angstrom) and DLS (SR=30 angstrom) data. In addition, Kratky plot analysis indicates a rigid shape at pH 8.0 and a flexible shape at pH 6.0. On the other hand, the center of mass of intrinsic fluorescence was not changed while varying pH, possibly indicating the absence of fluorescent amino acids in the regions affected by pH variation. Circular dichroisin experiments carried out with BJ-48 indicate a substantially random coiled secondary structure that is not affected by pH. Low-resolution model of BJ-48 presented a prolate elongated shape at pH 8.0 and a U-shape at 6.0. BJ-48 tertiary structure at pH 6.0 was maintained on heating up to 52 degrees C and was completely lost at 75 degrees C. The possible existence of two pH-induced folding states for BJ-48 and its importance for the biological role and stability of this enzyme was discussed. (C) 2007 Elsevier B.V. All rights reserved.1324170015916

A new case of translocation t(14;14)(q11;q32) in B lineage ALL

Case report of a translocation : A new case of translocation t(14;14)(q11;q32) in B lineage ALL

Structural insights into the interaction between prion protein and nucleic acid

The infectious agent of transmissible spongiform encephalopathies (TSE) is believed to comprise, at least in part, the prion protein (PrP). Other molecules can modulate the conversion of the normal PrPC into the pathological conformer ( PrPSc), but the identity and mechanisms of action of the key physiological factors remain unclear. PrP can bind to nucleic acids with relatively high affinity. Here, we report small-angle X-ray scattering (SAXS) and nuclear magnetic resonance spectroscopy measurements of the tight complex of PrP with an 18 bp DNA sequence. This double-stranded DNA sequence (E2DBS) binds with nanomolar affinity to the full-length recombinant mouse PrP. The SAXS data show that formation of the rPrP-DNA complex leads to larger values of the maximum dimension and radius of gyration. In addition, the SAXS studies reveal that the globular domain of PrP participates importantly in the formation of the complex. The changes in NMR HSQC spectra were clustered in two major regions: one in the disordered portion of the PrP and the other in the globular domain. Although interaction is mediated mainly through the PrP globular domain, the unstructured region is also recruited to the complex. This visualization of the complex provides insight into how oligonucleotides bind to PrP and opens new avenues to the design of compounds against prion diseases.45309180918