不同P负载量对Co-Mo/γ-Al_2O_3煤焦油加氢脱硫性能影响的研究

以分步浸渍法在固定MoO_3、CoO含量(质量分数)为13.50%、2.11%的条件下,通过改变磷酸浓度,制备了不同P负载量的Co-Mo/γ-Al_2O_3催化剂。考察了不同的P负载量催化剂对内蒙古赤峰中温煤焦油加氢脱硫性能的影响。并以NH3程序升温脱附(NH_3-TPD)、X射线衍射(XRD)、X射线光电子能谱(XPS)等手段对催化剂的结构性质进行了表征。结果表明,适宜的P负载量可减弱活性组分与载体间的相互作用,利于活性组分均匀分散在载体表面,改善了催化剂的还原、硫化性能和酸性分布,从而提高了催化剂的加氢脱硫活性。当磷酸质量分数为4%时,催化剂表现出最佳的加氢脱硫性能,硫脱除率达到96.98%。不同P负载量Co-Mo/γ-Al_2O_3催化剂加氢脱硫活性对应的磷酸浓度顺序为:4%2%6%1%08%。     

Coagulant Activity of Water-Soluble <Emphasis Type="Italic">Moringa oleifera</Emphasis> Lectin Is Linked to Lowering of Electrical Resistance and Inhibited by Monosaccharides and Magnesium Ions

Moringa oleifera seeds contain a water-soluble lectin [water-soluble M. oleifera lectin (WSMoL)] that has shown coagulant activity. Magnesium ions are able to interfere with the ability of this lectin to bind carbohydrates. In this study, we performed structural characterization of WSMoL and analyzed its effect on the electrical resistance of a kaolin clay suspension in both presence and absence of monosaccharides (N-acetylglucosamine, glucose, or fructose) and magnesium ions. The coagulant activity of WSMoL was monitored by measuring optical density and electrical resistance over a period of 60 min. Native WSMoL had a molecular mass of 60 kDa and exhibited anionic nature (pI 5.5). In sodium dodecyl sulfate–polyacrylamide gel electrophoresis (SDS-PAGE), it appeared as three polypeptide bands of 30, 20, and 10 kDa. WSMoL reduced the optical density and electrical resistance of the kaolin suspension, which suggests that suspended particles are destabilized and that this is followed by formation of complexes. The coagulant activity of lectin decreased in the presence of Mg²⁺ ions and carbohydrates at concentrations that also inhibited hemagglutinating activity. This was most likely due to conformational changes in lectin structure. Our findings suggest that the coagulant activity of WSMoL is enhanced by lowering of electrical resistance of the medium and is impaired by lectin–carbohydrate and lectin–Mg²⁺ interactions.     

M?ssbauer characterization of the iron-sulfur clusters in Desulfovibrio vulgaris hydrogenase.

The periplasmic hydrogenase of Desulfovibrio vulgaris (Hildenbourough) is an all Fe-containing hydrogenase. It contains two ferredoxin type [4Fe-4S] clusters, termed the F clusters, and a catalytic H cluster. Recent X-ray crystallographic studies on two Fe hydrogenases revealed that the H cluster is composed of two sub-clusters, a [4Fe-4S] cluster ([4Fe-4S](H)) and a binuclear Fe cluster ([2Fe](H)), bridged by a cysteine sulfur. The aerobically purified D. vulgaris hydrogenase is stable in air. It is inactive and requires reductive activation. Upon reduction, the enzyme becomes sensitive to O(2), indicating that the reductive activation process is irreversible. Previous EPR investigations showed that upon reoxidation (under argon) the H cluster exhibits a rhombic EPR signal that is not seen in the as-purified enzyme, suggesting a conformational change in association with the reductive activation. For the purpose of gaining more information on the electronic properties of this unique H cluster and to understand further the reductive activation process, variable-temperature and variable-field M?ssbauer spectroscopy has been used to characterize the Fe-S clusters in D. vulgaris hydrogenase poised at different redox states generated during a reductive titration, and in the CO-reacted enzyme. The data were successfully decomposed into spectral components corresponding to the F and H clusters, and characteristic parameters describing the electronic and magnetic properties of the F and H clusters were obtained. Consistent with the X-ray crystallographic results, the spectra of the H cluster can be understood as originating from an exchange coupled [4Fe-4S]-[2Fe] system. In particular, detailed analysis of the data reveals that the reductive activation begins with reduction of the [4Fe-4S](H) cluster from the 2+ to the 1+ state, followed by transfer of the reducing equivalent from the [4Fe-4S](H) subcluster to the binuclear [2Fe](H) subcluster. The results also reveal that binding of exogenous CO to the H cluster affects significantly the exchange coupling between the [4Fe-4S](H) and the [2Fe](H) subclusters. Implication of such a CO binding effect is discussed.     

Specific Proteins in the Indirect Somatic Embryogenesis of Freesia Refracta

IntroductionHaberlandt[1]proposed the conception of plantso-matic embryo in 1902, which states that plant cellsexhibit totipotency; each cell could divide ceaselesslyand eventually develops into a mature plantlet. Allthese provide a theoretical evidence for somatic embryo-genesis. The related researches reveal thatplantembry-ogenesis occurs as a result of the selective expression ofsets of genes that allowthe synthesis of special proteinsin a temporal and spatial sequential manner under themut…     

Revisitation of the molecular mobility of the amorphous solid 4,4′-methylenebis(N,N-diglycidylaniline) (MBDA): New contributions from the TSDC technique

In the present work we revisit the previously published study by Thermally Stimulated Depolarisation Currents (TSDC) of the slow molecular mobility in the amorphous solid state of 4,4′-methylenebis(N,N-diglycidylaniline), MBDA (H. P. Diogo, J. J. Moura Ramos, J. Mol. Liq. 129(2006)138–146) in order to add two important points dealing with recent uses of the TSDC technique. One of them concerns a new method to account for nonexponentiality in Thermally Stimulated Depolarisation Currents (TSDC) data treatment which affects the analysis of the alpha relaxation peak and the determination of the fragility index of the glass-forming system. The other point concerns the analysis of the secondary relaxations in MBDA. It is shown that two kinds of secondary relaxations are differently influenced by aging. The faster components of the secondary relaxation are negligibly dependent on aging and may be ascribed to intramolecular modes of motion, while the slower motional modes show a significant dependence on aging and correspond to the genuine Johari-Goldstein β-relaxation.     

Specific Proteins in the Indirect Somatic Embryogenesis of Freesia

Using the young inflorescence segments of Freesia refracta as explants, indirect somatic embryogenesis of somatic cells was induced in a N6 medium supplemented with some exogenous hormones. SDS-polyacrylamide gel electrophoresis（SDS-PAGE） was used for the analysis of soluble proteins produced during the somatic embryogenesis of this plant. There are six polypeptides, which might play some roles in the process of somatic embryo development. Tltree polypeptides（45, 53 and 55 kD） were detected in the stages of embryogenic callus, globular embryoid, and embryoid with coleoptiles, except the embryoid with leaf. One polypeptide（ 83 kD） was specific for the stages of embryoid with eoleoptiles and embryoid with leaf. One polypeptide（37 kD） was detected in the first two stages, namely, embryogenic callus and globular embryoid. One polypeptide（35 kD） was regularly synthesized in each stage, from embryogenic callus to embryoid with leaf.     

Thermal studies of isoniazid and mixtures with rifampicin

Rifampicin–Isoniazid mixture is a frequently used product in the treatment of tuberculosis. Rifampicin exhibits polymorphism and exists in two polymorphic forms: the stable form I and the metastable form II. The aim of this work was to evaluate the thermal behavior of the binary mixtures of polymorphs I and II of rifampicin and isoniazid by using DSC. Mixtures of different forms (rifampicin form I and II) showed interaction with isoniazid indicating that the mixtures are less stable compared to the drug alone. Interaction was observed in case of both polymorphs of rifampicin.     

New Imatinib Derivatives with Antiproliferative Activity against A549 and K562 Cancer Cells

Tyrosine kinase enzymes are among the primary molecular targets for the treatment of some human neoplasms, such as those in lung cancer and chronic myeloid leukemia. Mutations in the enzyme domain can cause resistance and new inhibitors capable of circumventing these mutations are highly desired. The objective of this work was to synthesize and evaluate the antiproliferative ability of ten new analogs that contain isatins and the phenylamino-pyrimidine pyridine (PAPP) skeleton, the main pharmacophore group of imatinib. The 1,2,3-triazole core was used as a spacer in the derivatives through a click chemistry reaction and gave good yields. All the analogs were tested against A549 and K562 cells, lung cancer and chronic myeloid leukemia (CML) cell lines, respectively. In A549 cells, the 3,3-difluorinated compound (3a), the 5-chloro-3,3-difluorinated compound (3c) and the 5-bromo-3,3-difluorinated compound (3d) showed IC₅₀ values of 7.2, 6.4, and 7.3 μM, respectively, and were all more potent than imatinib (IC₅₀ of 65.4 μM). In K562 cells, the 3,3-difluoro-5-methylated compound (3b) decreased cell viability to 57.5% and, at 10 µM, showed an IC₅₀ value of 35.8 μM (imatinib, IC₅₀ = 0.08 μM). The results suggest that 3a, 3c, and 3d can be used as prototypes for the development of more potent and selective derivatives against lung cancer.     

Dipolar relaxations in the glass transition region and in the liquid crystalline phase of two side-chain liquid crystalline polysiloxanes

The molecular relaxation mechanisms in the glass transition region and in the liquid crystalline phase exhibited by two side-chain liquid crystalline polysiloxanes have been studied by Thermally Stimulated Discharge Currents. These results were compared with those previously obtained by dielectric relaxation spectroscopy. It was observed that two relaxation mechanisms were present in the liquid crystalline phase, and we suggest that these might correspond to the motions of the mesogenic moieties in the liquid crystalline phase. © 1996 John Wiley & Sons, Inc.     

A Special Two-Soliton Solution of sine-Gordon Equation

A special two-soliton solution of sine-Gordon equation is obtained by using the Hirota direct method. It is shown in a mass-centre system how two kinks move and interact with each other.