The stability of invertase was studied under various conditions, including at 75°C, in presence of stabilizers (sorbitol and
glycerol) at 75°C, and in the presence of denaturants (urea and trichloroacetic acid) at 37°C in reverse micelles. Stability
of the invertase in reverse micelles was found to be improved over that of the enzyme in bulk aqueous solution. Sorbitol could
enhance enzyme stability as it does in the bulk aqueous system. The stabilizing effect of glycerol was reduced in reverse
micelles. The denaturation pattern of urea remains unaltered. However, the denaturation effect of trichloroacetic acid has
been reduced in reverse micelles. 相似文献
89Sr was produced via 89Y(n, p) 89Sr using yttria as target in Fast Breeder Test Reactor (FBTR), Kalpakkam, India. A radiochemical procedure has been developed for the separation of bulk yttrium using TBP by solvent extraction followed by purification of 89Sr source by ion exchange chromatography using the cation exchange resin Dowex 50WX8 (100–200 mesh) and nitric acid of variable molarity as eluant. The present study establishes the purification of 89Sr source from the other radionuclidic impurities like 88Y, 65Zn, 54Mn, 60Co, 86Rb, 192Ir, 103Ru, 113Sn, 139Ce, 160Tb, 154Eu etc. produced during the irradiation of yttria by using the complexing agent tri-sodium tri-meta phosphate (SMP) in nitric acid medium instead of nitric acid alone as an eluant. The purification was achieved by using 0.1 M SMP as complexing agent which was optimized based on the distribution ratio data and final elution of Sr fraction was obtained in nitric acid medium. This resulted into a faster purification of 89Sr source in a smaller volume of eluant. Purity of Sr source from the cross contamination of the complexing agent SMP was also ensured. 相似文献
89Sr was produced using the 89Y(n, p) 89Sr reaction by irradiating yttria target in the fast breeder test reactor (FBTR). An analytical scale procedure was standardized for the removal of the bulk target yttrium by solvent extraction using the tri-n-butyl phosphate (TBP). The final purification of 89Sr source was carried out by ion exchange chromatography. However, extraction chromatography is preferred to solvent extraction due to its low waste generation and ease of operation. This paper reports the separation of Sr from bulk Y and other radioactive impurities produced during irradiation by extraction chromatography using TBP coated XAD-4 resin. Initially the separation procedure was standardized using 85Sr and 88Y tracers. The 89Sr in the dissolver solution of the irradiated yttria target was separated under the same standardized conditions. The study established the separation of Sr from Y in the dissolver solution of the irradiated target yttria by the TBP coated XAD-4 column. However the evaluation of the column after every use for about three separation studies exhibited the reduction in its breakthrough capacity for yttrium. 相似文献
The authors describe an inexpensive electrode for the sensitive amperometric determination of the pesticide methyl parathion. A glassy carbon electrode was modified with a nanocomposite consisting of molybdenum disulfide nanosheets (MoS2) and graphene that was prepared via a hydrothermal process. Its morphology, elemental composition, diffraction, impedance and voltammetric characteristics were studied. The modified electrode displays excellent electrocatalytic ability towards methyl parathion, and the reduction peak current, measured typically at ?0.60 V (vs. Ag/AgCl) is related to the concentration of methyl parathion. The effect of concentration, scan rate and solution pH value were optimized. The calibration plot is linear in the 10 nM to 1.9 mM concentration range, with a 3.2 nM detection limit (at a signal-to-noise ratio of 3). The electrode is selective, stable, adequately repeatable and reproducible. The method was successfully applied to the determination of methyl parathion in spiked samples of homogenized apple, kiwi, tomato and cabbage.
Graphical Abstract A reliable and robust methyl parathion sensor has been developed using heterostructured MoS2/graphene. The linear range is 10 nM–1.9 nM and detection limit is 3.2 (±0.8) nM. The method was successful in real sample determination of spiked methyl parathion in food samples such as apple, kiwi, tomato and cabbage.
Multibranched gold (Au) nanocomposite materials encapsulated by poly(o-phenylenediamine) (PoPD) (Au@PoPD) were synthesized in a Nafion polymer film through the electroless synthetic route. The micro-heterogeneous structured Nafion film acted as a reaction vessel and as the template for the formation of Au@PoPD nanocomposite materials leading to the formation of highly uniform distribution of high density of the polymer-gold nanocomposite material. The formation of Au@PoPD nanomaterials at the GP/Nf surface was scrutinized by recording in situ absorption spectra and was characterized. The formation of the (111) plane of gold was dominant at the Au@PoPD nanocomposite. The ratio of the benzenoid and quinoid units of the PoPD (ca. 1.65) observed for the Au@PoPD confirmed that the micro-heterogeneous structure of Nf film acted as a reaction vessel and as template for the formation of Au@PoPD nanocomposite material. Both PoPD and Au at the Au@PoPD nanocomposite showed electrochemical activities at the GC/Nf-Au@PoPD modified electrode. The electrocatalytic activity of the GC/Nf-Au@PoPD modified electrode was studied for oxygen reduction reaction (ORR). 相似文献
By using the layer-by-layer deposition method, we build three dimensional (3D) supramolecular nanostructures by stacking small molecular species on top of the first buffer layer, which can be utilized to fabricate novel 3D supramolecular functional nanostructures. 相似文献
A process to prepare microparticles of narrow size distribution having a particle size in the range of approximately 1–8 μm was developed. The primary objective of this work was to study the formation and morphology of copolyester microparticles prepared using a sulfonated copolyester emulsion by an emulsion–aggregation process. Molecular weight of the copolyesters was measured by gel permeation chromatography. The glass transition temperature (Tg) of the copolyesters was found to be in the range of 40–70 °C. Aggregating agents used in this study were 1–5% (wt.%) solutions of divalent ions of zinc acetate and magnesium chloride salts. Emulsion–aggregation experiments were performed at various temperatures: 40, 50, 60, and 80 °C. Particle morphologies studied by field emission-scanning electron microscopy measurements provided an understanding of the conditions and mechanism leading to formation of microparticles by the emulsion–aggregation process. Molecular weight and Tg of the copolyester, the concentration of aggregating agent, and the temperature were determined to be the most important parameters influencing the preparation of microparticles. This process illustrates the preparation of microparticles of uniform size with morphology of controlled shape from a nanometer-sized emulsion by ionic crosslinking. 相似文献