Assembly of physalis mottle virus capsid protein in Escherichia coli and the role of amino and carboxy termini in the formation of the icosahedral particles

The coat protein gene of physalis mottle tymovirus (PhMV) was over expressed in Escherichia coli using pET-3d vector. The recombinant protein was found to self assemble into capsids in vivo. The purified recombinant capsids had an apparent s value of 56.5 S and a diameter of 29(+/-2) nm. In order to establish the role of amino and carboxy-terminal regions in capsid assembly, two amino-terminal deletions clones lacking the first 11 and 26 amino acid residues and two carboxy-terminal deletions lacking the last five and ten amino acid residues were constructed and overexpressed. The proteins lacking N-terminal 11 (PhCPN1) and 26 (PhCPN2) amino acid residues self assembled into T=3 capsids in vivo, as evident from electron microscopy, ultracentrifugation and agarose gel electrophoresis. The recombinant, PhCPN1 and PhCPN2 capsids were as stable as the empty capsids formed in vivo and encapsidated a small amount of mRNA. The monoclonal antibody PA3B2, which recognizes the epitope within region 22 to 36, failed to react with PhCPN2 capsids while it recognized the recombinant and PhCPN1 capsids. Disassembly of the capsids upon treatment with urea showed that PhCPN2 capsids were most stable. These results demonstrate that the N-terminal 26 amino acid residues are not essential for T=3 capsid assembly in PhMV. In contrast, both the proteins lacking the C-terminal five and ten amino acid residues were present only in the insoluble fraction and could not assemble into capsids, suggesting that these residues are crucial for folding and assembly of the particles.     

Preparation,structural, and electrical studies of polyaniline/ZnFe2O4 nanocomposites

Polyaniline/ZnFe₂O₄ nanocomposites were synthesized by a simple and inexpensive one‐step in situ polymerization method in the presence of ZnFe₂O₄ nanoparticles. The structural, morphological, and electrical properties of the samples were characterized by wide angle X‐ray diffraction (WAXD), Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), and thermogravimetric analysis (TGA). WAXD and SEM revealed the formation of polyaniline/ZnFe₂O₄ nanocomposites. Infrared spectroscopy indicated that there was some interaction between the ZnFe₂O₄ nanoparticles and polyaniline. The dc electrical conductivity measurements were carried in the temperature range of 80 to 300 K. With increase in the doping concentration of ZnFe₂O₄, the conductivity of the nanocomposites found to be decreasing from 5.15 to 0.92 Scm⁻¹ and the temperature dependent resistivity follows ln ρ(T) ∼ T^−1/2 behavior. The nanocomposites (80 wt % of ZnFe₂O₄) show a more negative magnetoresistance compared with that of pure polyaniline (PANI). These results suggest that the interaction between the polymer matrix PANI and zinc nanoparticles take place in these nanocomposites. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Structural and phase dependent thermo and photoluminescent properties of Dy(OH)3 and Dy2O3 nanorods

Hexagonal Dy(OH)₃ and cubic Dy₂O₃ nanorods were prepared by hydrothermal method. Dy(OH)₃ nanorods was directly obtained at 180 °C for 20 h after hydrothermal treatment whereas subsequently heat treatment at 750 °C for 2 h gives pure cubic Dy₂O₃. SEM micrographs reveal that needle shaped rods with different sizes were observed in both the phases. TEM results also confirm this. The TL response of hexagonal Dy(OH)₃ and cubic Dy₂O₃ nanorods have been analyzed for γ-irradiation over a wide range of exposures (1–5 kGy). TL glow peak intensity increases with γ dose in both the phases. The activation energy (E), order of kinetics (b), and frequency factor (s) for both the phases have been determined using Chen's peak shape method. The simple glow curve shape, structure and linear response to γ-irradiation over a large span of exposures makes the cubic Dy₂O₃ as a useful dosimetric material to estimate high exposures of γ-rays.     

Finite element analysis of the three-dimensional transient temperature field in steam turbine casings

One of the important considerations going into the process of optimization of start-up schedules for steam turbines is the estimation of thermal stresses during the transients. This in turn requires prediction of the transient temperature fields. In the case of the turbine casing, the procedures are complex in view of the irregular geometrical shape. Finite element analysis offers better scope in this regard and has been employed in the present work to compute the 3-D transient temperature distribution in the casing metal. The results obtained by a code developed for a specific type of turbine casing have been compared with the values measured by experiment and have been found to validate the code. Time-temperature histories for two typical locations inside the casing metals are presented. Isotherm surfaces across the metal at a given instant are shown.     

Synthesis and characterization of gold-conjugated <Emphasis Type="Italic">Backhousia citriodora</Emphasis> nanoparticles and their anticancer activity against MCF-7 breast and HepG2 liver cancer cell lines

Environmentally benign-synthesized gold nanoparticles (Au-NPs) have received substantial attention owing to their biomedical applications, particularly in cancer therapy. In the current study, Backhousia citriodora (B. citriodora) leaf extract was applied as a reducing agent for one-pot synthesis of controlled size Au-NPs. The effect of various parameters such as reaction time, pH, and B. citriodora leaf boiling time on the synthesis of Au-NPs was studied. The characterization of the Au-NPs synthesized at 15.0-min incubation time showed colour change because of the surface plasma resonance band around 530.0 nm. TEM photographs showed spherical morphologies with an average size of 8.40 ± 0.084 nm and zeta potential value was ? 29.74 mV, indicating stability of the nanoparticles. The biomedical properties of Au-NPs and B. citriodora leaf extract showed strong DPPH radical scavenging. The in vitro anticancer activity determined using MTT assay exhibited that Au-NPs showed a significant dose-dependent reduction in the viability of the MCF-7 breast cancer cell line and the HepG2 liver cancer cell line with IC₅₀ values of 116.65 and 108.21 µg, respectively.     

Photoluminescence properties of Eu3+-activated CaMoO4 phosphors for WLEDs applications and its Judd–Ofelt analysis

A series of scheelite-type Eu³⁺-activated CaMoO₄ phosphors were synthesized by the nitrate–citrate gel combustion method. All the compounds crystallized in the tetragonal structure with space group I4 ₁ /a (No. 88). FESEM results reveal the spherical-like morphology. The CaMoO₄ phosphor exhibited broad emission centered at 500 nm under the excitation of 298 nm wavelength, while Eu³⁺-activated CaMoO₄ shows an intense characteristic red emission peak at 615 nm at different excitation wavelengths, due to ⁵D₀ → ⁷F₂ transition of Eu³⁺ ions. The intensities of transitions between different J levels depend on the symmetry of the local environment of Eu³⁺ ions and were estimated using the Judd–Ofelt analysis. The high asymmetric ratio revealed that Eu³⁺ occupies sites with a low symmetry and without an inversion center. The CIE chromaticity co-ordinates (x, y) were calculated from emission spectra, and the values were close to the NTSC standard. Therefore, the present phosphor is highly useful for LEDs applications.     

Sm mediated structural properties for MO dye degradation on the titania surface

In the present investigation, titania thin films doped with varying concentrations of Samarium (Sm) were synthesized by spin coating method on glass substrate. The obtained films were annealed at two different temperatures (350 and 450 ?C) to induce crystallinity. The structural property of these samples was characterized by using X-ray Diffraction (XRD) and Raman spectrometer. The surface morphology of the films was analysed by Field Emission Scanning Electron Microscopy (FESEM) and Atomic Force Microscopy (AFM). The presence of pure anatase phase with enhanced polycrystalline nature was evident for the films annealed at 350 and 450 ?C. Due to the addition of Sm, the titania thin films exhibited increased crystallinity. The Raman analysis also support the presence of crystalline anatase phase and the existence of defects in the deposited films. The prepared samples were also subjected to photocatalytic activity studies by using methyl orange (MO) dye and the results are discussed herein. The rate constant increased and half life time decreased considerably for 0.4 at% doped samples. The current work provides new ideas for monitoring the structural properties by adding low concentration rare earth dopant into metal oxides (titania) suitable for various applications.