DNA-modified electrodes; part 4: optimization of covalent immobilization of DNA on self-assembled monolayers

The covalent immobilization of DNA onto self-assembled monolayer (SAM) modified gold electrodes (SAM/Au) was studied by X-ray photoelectron spectrometry and electrochemical method so as to optimize its covalent immobilization on SAMs. Three types of SAMs with hydroxyl, amino, and carboxyl terminal groups, respectively, were examined. Results obtained by both X-ray photoelectron spectrometry and cyclic voltammetry show that the largest covalent immobilization amount of dsDNA could be gained on hydroxyl-terminated SAM/Au. The ratio of amount of dsDNA immobilized on hydroxyl-terminated SAMs to that on carboxyl-terminated SAMs and to that on amino-terminated SAMs is (3-3.5): (1-1.5): 1. The dsDNA immobilized covalently on hydroxyl-terminated SAMs accounts for 82.8-87.6% of its total surface amount (including small amount of dsDNA adsorbed). So the hydroxyl-terminated SAM is a good substrate for the covalent immobilization of dsDNA on gold surfaces.     

氯代十六烷基吡啶存在下钯与1，4－双肼酞嗪新显色反应的研究

本文研究了１，４－双肼酞嗪（ＤＨＰＨ）与钯的配合显色反应，在阳离子型表面活性剂氯代十六烷基吡啶存在下，在０．１～０．２ｍｏｌ／ＬＨＣｌ溶液中，试剂与钯形成１：１的稳定的黄绿色配合物，最大吸收峰在４００ｎｍ处，表观摩尔吸光系数为２．６×１０￣４，钯量在０～５０μｇ／２５ｍＬ范围内股从比尔定律，方法简便快速，选择性好，已用于催化剂中钯的测定，结果满意。     

Modification of polybenzimidazole: Synthesis and thermal stability of poly(N1-methylbenzimidazole) and poly(N1,N3-dimethylbenzimidazolium) salt

Poly(N₁,N₃-dimethylbenzimidazolium) (PDMBI) salt and poly(N₁-methylbenzimidazole) (PMMBI) were synthesized by methylation of commercial polybenzimidazole [poly-2,2′-(m-phenylene)-5,5′-bibenzimidazole (PBI)]. First, the N-lithium salt of polybenzimidazole was formed by treating polybenzimidazole solution of 1-methyl-2-pyrolidinone (NMP) with lithium hydride at 80°C for 18 h. Ninety percent substitution of PMMBI was obtained by treating the N-lithium salt of PBI with equimolar ratio of iodomethane at room temperature. Upon addition of excess iodomethane to the lithium salt of PBI at 80°C, a polymer was formed that showed 100% substitution on the N₁ nitrogen and about 30% substitution of the methyl group on the N₃ nitrogen in the form of N₁,N₃-dimethylbenzimidazolium iodide salt [PDMBI (30%)]. The content of the benzimidazolium iodide salt was increased to about 90% by dissolving PDMBI (30%) in dimethyl sulfoxide (DMSO) and re-treating with excess iodomethane at 80°C overnight. The modified PBI polymers were characterized by NMR and FTIR. The modified PBI differed in solubility from PBI. PMMBI could be easily dissolved in NMP and PDMBI in DMSO at room temperature. The solution of PDMBI could be mixed with water in all proportions without precipitation. PDMBI could be also dissolved directly in a mixture of DMSO and water (1 : 1). Typical polyelectrolyte behavior of viscosity was found in solution of PDMBI (30%) and PDMBI (90%) when DMSO and a mixture of DMSO and water were used as solvents. A salt effect on viscosity was also found in the mixed solvent solution. Thermogravimetric analysis (TGA) showed that the methyl group on the imidazole ring was unstable above 180°C under nitrogen. When PDMBI was heated under nitrogen, one of the methyl groups was lost with the counterion to result in a neutral PMMBI. © 1993 John Wiley & Sons, Inc.     

A novel definition of the overall hyper-wiener index for unsaturated hydrocarbons

By replacing the distances between pairs of vertices with the relative distances, we define a novel overall hyper-Wiener index (NOR); the novel overall hyper-Wiener index extends the usefulness of the hyper-Wiener index and the overall hyper-Wiener index to unsaturated hydrocarbons.     

Structure and antiferroelectric properties of cesium niobate, Cs2Nb4O11

The compound cesium niobate, Cs₂Nb₄O₁₁, is an antiferroelectric, as demonstrated by double hysteresis loops in the electric field versus polarization plot. The crystal structure refinement by X-ray diffraction at both 100 and 297 K shows it to have a centrosymmetric structure in point group mmm and orthorhombic space group Pnna, which is consistent with its antiferroelectric behavior. The 100-K structure data is reported herein. The lattice is comprised of niobium-centered tetrahedra and octahedra connected through shared vertices and edges; cesium atoms occupy channels afforded by the three-dimensional polyhedral network. Antiferroelectricity is produced by antiparallel displacements of niobium atoms along the c-axis at the phase transition temperature of 165 °C. The critical field for onset of ferroelectric behavior in a single-crystal sample is 9.5 kV/cm at room temperature.     

New supports for enzyme immobilization based on copolymers of vinylene carbonate and acrylamide

In this study, a series of beadlike and hydrophilic supports containing reactive cyclic carbonate groups for enzyme immobilization were prepared via reverse-phase suspension copolymerization of the aqueous solutions of vinylene carbonate (VCA), acrylamide (AA), and N,N′-methylene bisacrylamide in paraffin oil. The supports were used as a matrix for immobilization of trypsin and showed a considerable capacity to couple with trypsin and reasonable retention of activity for the immobilized trypsin, depending on the immobilization conditions, such as the content of VCA structural units, reaction time, and pH of the medium.     

稀土金属硼氢化物的研究(Ⅸ)——N,N''''-双(邻羟基苯叉)-1,3-丙二胺合稀土(Ⅲ)十氢十硼酸盐的合成

我们曾报道过含闭式氢硼駿根的二齿配体的稀土螯合物的合成及性质。为了解不同配体的稀土配合物在结构及性质上的差异,又合成了四齿(ONNO)配体N,N′-双(邻羟基苯叉)-1,3-丙二胺(salpr),并通过两种方法(模板合成法及配体合成法)合成了稀土配合物的闭式十氢十硼酸盐。化合物均为黄色粉末固体,室温下它们对光、空气、潮汽均稳定。     

平菇多糖稀溶液行为的研究

平菇多糖属生物高分子, 文章对平菇多糖稀溶液性质进行了研究。实验系采用Elias浊点滴定法测定平菇多糖溶液的θ组成, 用快速动态膜渗透计和粘度法测定平菇多糖的数均分子量、维利系数与分子链的构型参数。探讨其在θ条件下的分子形态及用Tung函数法等处理分级数据, 从而获得平菇多糖的分子量分布。     

Selective ordering of surfactant modified gold nanoparticles in a diblock copolymer

Ordered aggregation of thiol-passivated Au nanoparticles in a diblock copolymer polystyrene-b-poly(methyl methacrylate) has been observed. The morphology of the diblock copolymer/Au-nanocomposite was dependent on the composition of the thiol modifier. For the thiol modifier that does not preferentially interact with one of the blocks, a perpendicular (relative to the substrate) lamellar morphology is maintained. However, for a thiol with a surfactant structure similar to one of the blocks, we observed a parallel lamellar morphology and speculate that the nanoparticles have localized at the microdomain interface. These conclusions are based on transmission electron microscopy, angle-dependent X-ray photoelectron microscopy and tensiometry. These results are consistent with theoretical predictions on the hybrid systems composed of block copolymers and nanoparticles.     

A copper- and amine-free sonogashira reaction employing aminophosphines as ligands

An efficient Pd-catalyzed Sonogashira coupling reaction was achieved in the absence of a copper salt or amine with an inorganic base and easily prepared, air-stable aminophosphine ligands in commonly used organic solvents; good to excellent yields were obtained. Under optimized reaction conditions, the Sonogashira coupling reaction occurred selectively when an enyne substrate was employed and no Heck reaction product was detected; acetone-masked acetylene and trimethylsilylacetylene can also be efficiently coupled, providing a method to make terminal alkynes.