A kinetic study of the aqueous polymerisation of methacrylamide initiated by hydrogen peroxide has shown that the polymerisation proceeds in two stages. The rate of polymerisation up to about 16% conversion is represented by the equation Within this period, the hydrogen peroxide is completely consumed and a hydroperoxide of methacrylamide is formed. Subsequently this hydroperoxide initiates polymerisation. 相似文献
A practical synthetic route to various 2-alkylpropane-1,3-sultones, the key intermediates for the preparation of 2-substituted homotaurines as analogs of tramiprosate, was developed. 相似文献
Summary A simple and rapid systematic optimization scheme was described for the micellar electrokinetic chromatographic separation of a group of flavonoids. The scheme employed an interpretative optimization approach to predict the optimum conditions for the separation of a group of flavonoids by micellar electrokinetic chromatography. By performing a set of nine pre-planned experiments conducted over the maximum working range for the system, global optimum separation conditions could be determined. To validate the optimization procedure, additional experiments were performed using the optimum experimental conditions derived from the optimization scheme. The results showed that satisfactory separation of all the peaks could be obtained. In addition, the application of the method in micropreparative micellar electrokinetic chromatography of the flavonoids was demonstrated. 相似文献
The refolding of the reduced-denatured insulin from bovine pancreas was investigated with the size exclusion chromatography (SEC). It was shown that the reduced-denatured insulin originally denatured with 7.0 mol L?1 guanidine hydrochloride (GuHCI) or 8.0 mol L?1 urea could not be refolded with a non-oxidized mobile phase. Although the oxidized and reduced glutathione (GSSG and GSH) were employed in the oxidized mobile phase, the reduced-denatured insulin still could not be renatured. However, in the presence of 2.0 mol Lt-1 urea in the oxidized mobile phase employed, the reduced-denatured insulin can be refolded with SEC, and the aggregation of denatured insulin can be diminished by urea. In addition, the disulfide exchange of reduced-denatured insulin also can be accelerated with GSSG/GSH in the oxidized mobile phase. The three disulfide bridges of insulin were formed correctly and the reduced-unfolded insulin can be renatured completely. The results were further tested with reversed-phase liquid chromatography (RPLC) and hydrophobic interaction chromatography (HIC). 相似文献
A nickel-catalyzed method for the three-component coupling of alkenes (ethylene and alpha olefins), aldehydes, and silyl triflates is described, and this process represents the first catalytic method for coupling aldehydes and alkenes to give allylic alcohol derivatives. Conceptually, the alkene functions as a replacement for an alkenylmetal reagent. 相似文献
A new analytical procedure was developed for the extraction of degradation products of chemical warfare agents from water and for in-situ derivatisation prior to analysis by gas chromatography-mass spectrometry (GC-MS). With this new procedure, degradation products of the chemical warfare agents can be analysed and identified without going through laborious sample preparation. Parameters such as fiber selection, pH, salt content, derivatisation temperature, extraction and derivatisation periods, and sequence of adsorption/derivatisation were experimented with, to optimise the efficiency of this method. The detection limit is in the ppb to sub-ppb range with GC-MS in the full scan mode. Based on six injections of the devised procedure, a relative standard deviation from 10-35% can be achieved, depending on the compound. This method was demonstrated during the 4th International Interlaboratory Proficiency Test organised by the Organisation for the Prohibition of Chemical Weapons to be comparable to existing recommended operating procedures for verification of degradation products of chemical warfare agents. 相似文献
An efficient and feasible synthetic approach was developed for the synthesis of an array of new flavane derivafives from the substituted benzaldehyde with the reduction of chalcones and subsequent cyclization as the key steps. The purity and structure of the products were confirmed by the elemental analysis and a combination of its IR, ^1H and ^13C NMR, and mass spectra. These synthetic compounds were tested for xanthine oxidase (XO) inhibitions and antifungal actions against Candida albicans, Cryptococcus neoformans, Aspergillus sp. and Trichophyton rubrum. 7-Hydrazinocarbonylmethoxy-4'-methoxyflavane (9) was found to be the most XO inhibitory with IC50=76.4 μmol/L, and the most potent antifungal compound was 4'-hydrazinocarbonylmethoxyflavane (12) with minimal inhibition concentration MIC=8 μg/mL against Trichophyton rubrum. 相似文献
In order to increase the biocompatibility and bioactivity of chitosan, hydroxyapatite had been in situ combined into chitosan scaffolds. The bioactivity of the composite scaffolds was studied by examining the apatite formed on the scaffolds by incubating in simulated body fluid and the activity of preosteoblasts cultured on them. The apatite layer was assessed using scanning electronic microscope (SEM), X-ray diffraction (XRD), Fourier-Transformed Infrared spectroscopy (FTIR) and weight measurement. Composite analysis showed that after incubation in simulated body fluid on both of the scaffolds carbonate hydroxyapatite was formed. With increasing nano-hydroxyapatite content in the composite, the quantity of the apatite formed on the scaffolds increased. Compared with pure chitosan, the composite with nano-hydroxyapatite could form apatite more readily during the biomimetic process, which suggests that the composite possessed better mineralization activity. Furthermore, preosteoblast cells cultured on the apatite-coated scaffolds showed different behavior. On the apatite-coated composite scaffolds cells presented better proliferation than on apatite-coated chitosan scaffolds. In addition, alkaline phosphatase activities of cells cultured on the scaffolds in conditioned medium were assessed. The cells on composite scaffolds showed a higher alkaline phosphatase activity which suggested a higher differentiation level. The results indicated that the addition of nano-hydroxyapatite improved the bioactivity of chitosan/nano-hydroxyapatite composite scaffolds. On the other hand, that is to say composition of substrates could affect the apatite formation on them, and pre-loaded hydroxyapatite can enhance the apatite-coating. It will also be significant in preparation of apatite-coating polymer scaffolds for bone tissue engineering. 相似文献
A new liquid crystalline polyacetylene containing a phenyl benzoate mesogen (5) is synthesized,whose mesomorphic properties are found to be easily "tunab1e" by simple mechanical perturbation. Thepolymerization of 10- [ 4 - (4' -methoxyphenoxycarbonyl )phenoxycarbonyl] - 1 -decyne (4 ) in itiated by theWCl_6-Ph_4Sn/dioxane complex yields polymer 5 with a M_w of 28400. The molecular structure of 5 ischaracterized by NMR, IR, and UV spectroscopy and its liquid crystalline behavior is investigated by DSC,POM, and XRD analysis. Upon mechanical perturbation, 5 exhibits unusual agitation-induced high-strengthdisclinations, shear-induced inversion walls, and solidification-induced banded textures. Such phenomenahave been observed in the main-chain liquid crystalline polymers with rigid backbones, but have seldom beenreported for the side-chain liquid crystalline polymers with flexible backbones, suggesting that the rigidpolyacetylene backbone of 5 plays a constructive role in inducing the novel molecular alignments. 相似文献