玉米须化学成分研究

将干燥玉米须水煮提取,提取液依次用乙酸乙酯和正丁醇萃取,制得乙酸乙酯和正丁醇提取物,用硅胶柱层析进行分别分离两种提取物得到4个化合物,依据理化性质及波普数据分析,分别鉴定它们的结构为：香草醛（1）、硬脂酸（2）、尿囊素（3）和邻苯二甲酸二异辛酯（4）。其中,化合物1和3为首次从该植物中分离得到。     

Acrylic Homo- and Co-polymers Based on 2, 4-dichlorophenyl Methacrylate and 8-quinolinyl Methacrylate

The monomer 2, 4-dichlorophenyl methacrylate (2,4-DMA) was synthesized from 2, 4-dichlorophenol and characterized by conventional methods. The homopolymers of 2,4-dichlorophenyl methacrylate and its copolymers with 8-quinolinyl methacrylate (8-QMA) in different feed ratio were prepared by free radical polymerization using dimethyl formamide (DMF) as a solvent and 2,2-azobis iso butyronitrile (AIBN) as an initiator. The resulting polymers were characterized by using IR spectroscopy. Reactivity ratios of monomer were evaluated using UV-spectroscopy. Average molecular weights and polydispersity were determined by gel permeation chromatography (GPC). Solution viscosity was also obtained. The thermal analysis was carried out using TGA and DSC. The homo- and co-polymers were also tested for their antimicrobial properties against selected microorganism. The metal ion uptake capacity of synthesized copolymers was estimated by batch equilibration method using different metal ion solution under different experimental conditions. It is observed that due to the presence of pendant ester bound quinoline group, the copolymers are capable of adsorbing cations from their aqueous solution.     

Influence of Distributed Particle Size on the Determination of the Parabolic Rate Constant for Oxidation by the Powder Method

The established analysis for the study of oxidation using powder specimens is based on the assumption of monosized particles. The experiments, however, are conducted on powders with a distributed particle size. Here we present a statistical approach for the calculation of the rate constant for oxidation. The results of the analysis are applied to new data on oxidation studies of dense powders of silicon carbonitride amorphous ceramics. The monosized model requires a wide range of values for the rate constant to fit the short term and the long-term data, leading to considerable ambiguity in the estimate of the parabolic rate constant, k _p, for oxidation. In contrast the statistical model fits over the entire range of data, yielding a much more reliable value for k _p. For example, the monosized approach gave a value in the range 19.7 × 10⁻¹⁸ < k _p < 2.7 × 10⁻¹⁸ m²/s. In contrast, the statistical model yields a specific value of 4.5 × 10⁻¹⁸ m²/s.     

Efficient Chemical and Enzymatic Syntheses of FAD Nucleobase Analogues and Their Analysis as Enzyme Cofactors**

Flavin adenine dinucleotide (FAD) is an essential redox cofactor in cellular metabolism. The organic synthesis of FAD typically involves coupling flavin mononucleotide (FMN) with adenosine monophosphate, however, existing synthesis routes present limitations such as multiple steps, low yields, and/or difficult-to-obtain starting materials. In this study, we report the synthesis of FAD nucleobase analogues with guanine/cytosine/uracil in place of adenine and deoxyadenosine in place of adenosine using chemical and enzymatic approaches with readily available starting materials, achieved in 1–3 steps with moderate yields (10–57 %). We find that the enzymatic route using Methanocaldococcus jannaschii FMN adenylyltransferase (MjFMNAT) is versatile and can produce these FAD analogues in high yields. Further, we demonstrate that Escherichia coli glutathione reductase is capable of binding and using these analogues as cofactors. Finally, we show that FAD nucleobase analogues can be synthesized inside a cell from cellular substrates FMN and nucleoside triphosphates by the heterologous expression of MjFMNAT. This lays the foundation for their use in studying the molecular role of FAD in cellular metabolism and as biorthogonal reagents in biotechnology and synthetic biology.     

Study of cation distribution for Cu–Co nanoferrites synthesized by the sol–gel method

Nano sized polycrystalline soft ferrite particles with composition Cu_1−xCo_xFe₂O₄ (x =0.1, 0.3, 0.5, 0.7, 0.9) were synthesized by the sol–gel technique. The existence of well-defined single cubic spinel structure was confirmed in all the samples by X-ray diffraction. The crystallite size found by XRD varied from 14.8 to 34.0 nm. The microstructure was also characterized by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Slight expansion of the unit cell was detected with the increase of Cobalt concentration, which may be attributed due to larger ionic radius of Co²⁺. Lattice parameter ranged from 8.34 Å to 8.37 Å for Co²⁺ from 0.1–0.9. The distribution of cations amongst A- and B-sites of the lattice was estimated by X-ray diffraction by using the R-factor technique. The results showed that both Cu²⁺ and Co²⁺ ions occupy mainly the B-site while Fe³⁺ ions were equally distributed among A- and B-sites. The data obtained from cation distribution analysis was used to determine the magnetic moment for each sample and VSM studies were also carried out to validate these calculations. Magnetic measurements showed that the saturation magnetization (Ms) and coercivity (Hc) increased with increasing cobalt content.     

Determining the mechanical properties of epoxy resin (DGEBA) composites by ultrasonic velocity measurement

In this study, the composites of diglycidyl ether of bisphenol A (DGEBA) epoxy resin that have been formed by mixing epoxy resin with allyl glycidyl ether (AGE) and 2,3‐epoxypropyl methacrylate [glycidyl methacrylate (GMA)] were prepared in weight % ratios of 90 : 10, 80 : 20, and 70 : 30. A computer controlled analyzer with 35 MHz and a digital oscilloscope with 60 MHz were used for measuring the velocities of ultrasonic wave. The measurement of ultrasonic velocity carried out by pulse echo method at frequencies of 2.25 and 3.5 MHz at room temperature. The values of acoustic impedance (Z), Poisson ratio (μ), and coefficients of elasticity (L, G, K, E) of composites were calculated by values of densities and velocities that obtained. Thus, the effect of modificating epoxy resin (DGEBA) by AGE and GMA on mechanical properties of DGEBA was investigated using the ultrasonic method. Atomic force microscopy has been used for determining the microstructure of composites. By the results obtained from the investigation, it have been established that the longitudinal and shear ultrasonic wave velocities, and the values of all the elasticity constants of DGEBA were increased by modification with AGE and GMA. Also the most suitable combination ratio for the compound of DGEBA : AGE and DGEBA : GMA has been found as 80 : 20. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Effect of Absolute Configuration on the Optical and NMR Properties of Oligonucleotides Containing Benzo[a]Pyrene Adducts at N 6 of Deoxyadenosine

For oligonucleotide duplexes derived from trans opening of benzo[a]pyrene diol epoxides (BaP DEs) by the exocyclic N⁶-amino group of deoxyadenosine (dA), the hydrocarbon is intercalated toward the 5′-end of the modified strand when the configuration at the site of attachment of the base to the hydrocarbon (C-10) is R, and toward the 3′-end when this configuration is S. In oligonucleotide 11-mer duplexes modified by BaP DE-1 (benzylic 7-OH and epoxide oxygen cis) and DE-2 (7-OH and epoxide oxygen trans), as well as 7,8,9,10-tetrahydro BaP 9,10-epoxide, 10R adducts had consistently higher (5–9d°C) T_m values than the corresponding 10S adducts. Dodecamer duplexes from the HPRT gene with trans opened 10S (but not those with 10R) BaP DE-2 adducts at either of two adjacent dA residues exhibited blue shifts at ～350 nm at temperatures well below the T_m. We propose that these blue shifts result from a conformation in which the hydrocarbon is not stacked with the DNA bases.     

Oxygen,Nitrogen, and Sulfur Removal Reactions in Donor Solvent Coal Liquefaction

There are a number of ways coal can be converted to liquid fuel. It can be pyrolyzed to produce gas, liquid, and char. It can be first converted to carbon monoxide and hydrogen which can then be converted to liquid fuel via Fischer-Tropsch synthesis. It can be hy-dropyrolyzed to produce gases, naphtha range liquids, and heavy residues. Finally, it can be liquefied in the presence of a hydrogen donor solvent to produce liquid and gaseous products. This review is concerned with the last method for conversion of coal to liquid fuel.     

Studies on the formation of yttrium iron garnet (YIG) through stoichiometry modification prepared by conventional solid-state method

Y₃Fe₅O₁₂ (YIG) prepared by conventional solid-state method can rarely be of high purity. However, this study suggests that high purity YIG can be produced via conventional solid-state methods, through stoichiometry modification. This is achieved by adding various amounts of excess Fe₂O₃ to control the YIG stoichiometric ratios. In this work, ferrite and yttria were calcined at 1100 °C (for 8 h) and sintered at 1420 °C (6 h). In most samples, the formation of YIG, with YFeO₃ (YIP) and/or Fe₂O₃ as associated phases were detected. Uniform microstructures of YIG are also observed. YIP phase in YIG is found to be inversely related to the addition of excess Fe₂O₃, up to 8 wt%. At above 8 wt% Fe₂O₃ addition, YIP disappears, leaving unreacted excess Fe₂O₃ as a new associated phase. From the investigation, it is safe to conclude that the purity of YIG can be increased with the addition of excess Fe₂O₃.     

Characterization of purified fungal endoxylanase and its application for production of value added food ingredient from agroresidues

Xylanase from Aspergillus foetidus MTCC 4898 was purified using ammonium sulphate fractionation followed by ion exchange and gel permeation chromatography with 12.26-fold purity and 29.9% recovery. Purified xylanase was found to be 29.9 kDa. Optimum temperature and pH for xylanase activity of purified xylanase were found to be 50 °C and 5.3 respectively. Presence of additives like polyethylene glycol, sodium azide, Tween 80, KCl and NaCl increased the stability of purified xylanase by 35, 29, 28, 32 and 43% respectively at 50 °C after 180 min. Kinetic parameters like K_m and V_max were found to be 4 mg/ml and 7288 μmol/mg/min respectively. The purified xylanase was found to be an endoxylanase as it produced only xylooligosaccharides (XOS) from birchwood xylan. Production of XOS was carried out from xylan extracted from agro-residues using β-xylosidase free xylanase. Maximum yield of XOS was 7.28 ± 0.14 mg/ml and 4.52 ± 0.21 mg/ml from wheat straw xylan and rice straw xylan respectively. XOS mixture was suitable for food industry looking at its high thermal stability at low pH. Prebiotic effect of XOS was evaluated by in vitro fermentation of XOS using known probiotic strains of Bifidobacterium spp.