CeO2对低氟连铸保护渣转折温度和结晶性能的影响

研究了低氟条件下,稀土氧化物CeO2对连铸保护渣转折温度和结晶性能的影响,同时与常规的高氟连铸保护渣性能进行了对比分析。结果表明：在碱度R较低的条件下,随着CeO2含量的升高,转折温度和结晶温度均有先下降后上升的趋势;在碱度较高的情况下,CeO2的加入将明显提高连铸保护渣的转折温度和凝固温度。     

Preparation of a monolith functionalized with zinc oxide nanoparticles and its application in the enrichment of fluoroquinolone antibiotics

This study describes the enrichment ability of ZnO‐modified methacrylic acid‐co‐ethylene dimethacrylate polymer monoliths as stationary phases for the simultaneous determination of antibiotics (ofloxacin, ciprofloxacin, enoxacin, and pefloxacin) combined with high‐performance liquid chromatography. The prepared monolith was characterized by scanning electron microscopy, X‐ray photoelectron spectroscopy, Fourier‐transformed infrared spectroscopy, and thermogravimetric analysis. The polymer monolith microextraction method has been applied to the enrichment of fluoroquinolone antibiotics and satisfactory results were obtained in the analysis of water samples. Compared with the conventional methacrylic acid based monolith, the developed monolith exhibited a higher enrichment capacity because of the introduction of zinc oxide into the preparation process.     

An Improved Method for the Separation and Quantification of Major Phospholipid Classes by LC-ELSD

An improved HPLC procedure for the separation of phospholipids is described. The method described utilizes a solvent mixture of acetonitrile-methanol–water-trifluoroacetic acid (100:25:1.7:2.5, v/v) as the mobile phase, which is more compatible with the pump than mobile phases containing inorganic acids. Separation was by isocratic elution on a Hypersil silica column coupled to an evaporative light scattering detector. Complete separation of phosphatidylserine (PS), phosphatidylethanolamine (PE), phosphatidylcholine (PC) and sphingomyelin (SM) was achieved in less than 20 min. The detection limits for PS, PE, PC and SM were 50, 50, 80 and 150 ng (S/N = 3), respectively. Human, bovine and porcine erythrocyte ghost membranes and animal tissues have been successfully analyzed for their phospholipid contents.     

The Effect of Backbone Stereochemistry on the Folding of Acyclic β2, 3‐Aminoxy Peptides

As a new type of foldamer, β‐aminoxy peptides have the ability to adopt novel β N? O turns or β N? O helices in solution. Herein, we describe a new subclass of β‐aminoxy peptide, that is, peptides of acyclic β^{2, 3}‐aminoxy acids (NH₂OCHR₁CHR₂COOH), in which the presence of two chiral centers provides insight into the effect of backbone stereochemistry on the folding of β‐aminoxy peptides. Acyclic β^{2, 3}‐aminoxy peptides with syn and anti configurations have been synthesized and their conformations investigated by NMR, IR, and circular dichroism (CD) spectroscopic, and X‐ray crystallographic analysis. The β N? O turns or β N? O helices, which feature nine‐membered rings with intramolecular hydrogen bonds and have been identified previously in peptides of β³‐ and β^{2, 2}‐aminoxy acids, are also predominantly present in the acyclic β^{2, 3}‐aminoxy peptides with a syn configuration and N? O bonds gauche to the C_α? C_β bonds in both solution and the solid state. In the acyclic β^{2, 3}‐aminoxy peptides with an anti configuration, an extended strand (i.e., non‐hydrogen‐bonded state) is found in the solid state, and several conformations including non‐hydrogen‐bonded and intramolecular hydrogen‐bonded states are present simultaneously in nonpolar solvents. These results suggest that the backbone stereochemistry does affect the folding of the acyclic β^{2, 3}‐aminoxy peptides. Theoretical calculations on the conformations of model acyclic β^{2, 3}‐aminoxy peptides with different backbone stereochemistry were also conducted to elucidate structural characteristics. Our present work may provide useful guidelines for the design and construction of new foldamers with predicable structures.     

Bioelectrochemical response of a choline biosensor fabricated by using polyaniline

On the basis of the isoelectric point of an enzyme and the doping principle of conducting polymers, choline oxidase was doped in a polyaniline film to form a biosensor. The amperometric detection of choline is based on the oxidation of the H₂O₂ enzymatically produced on the choline biosensor. The response current of the biosensor as a function of temperature was determined from 3 to 40°C. An apparent activation energy of 22.8 kJ·mol⁻¹ was obtained. The biosensor had a wide linear response range from 5 × 10⁻⁷ to 1 × 10⁻⁴ M choline with a correlation coefficient of 0.9999 and a detection limit of 0.2 μM, and had a high sensitivity of 61.9 mA·M⁻¹·cm⁻² at 0.50 V and at pH 8.0. The apparent Michaelis constant and the optimum pH for the immobilized enzyme are 1.4 mM choline and 8.4, respectively, which are very close to those of choline oxidase in solution. The effect of selected organic compounds on the response of the choline biosensor was studied.     

聚噻吩/多壁碳纳米管复合材料的导电性能

通过共混多壁碳纳米管(MWNTs)和聚噻吩(PTh), 制备了PTh/MWNTs复合材料, 复合材料表现出良好的导电性能(电导率达16.1 S/m). 通过Raman, TG, XPS, UV-Vis等对复合材料进行了分析, 结果表明, MWNTs和 PTh之间存在强的相互作用, MWNTs上的离域电子与噻吩共轭主链上的π电子之间形成π-π共轭, 电子从MWNTs转移到聚噻吩, 增加了噻吩主链的有效共轭长度, 提高了复合材料的导电性能. FESEM分析表明, MWNTs和它周围被掺杂的聚噻吩通过π-π共轭作用结合在一起, 形成相对独立的导电单元, 在复合材料的导电体系中起到主要作用.     

微乳凝胶中小分子传质研究

微乳凝胶中小分子传质研究对于拓宽胶束酶学研究内涵、加速酶在生物合成与转化领域中的应用、研制高性能生物传感器等具有重要理论意义和潜在应用价值.以微乳液中二价金属离子与紫脲酸胺之间的配位反应为指示反应,采用分光光度技术,研究了金属离子在由阳离子表面活性剂十六烷基三甲基溴化胺构建的微乳凝胶中的传质问题.结果表明,在由含紫脲酸胺微乳液及含金属离子微乳凝胶构成的体系中,金属离子在微乳凝胶中的传质是金属离子与紫脲酸胺配位反应的限速步骤.为进一步证实上述结论,还对影响金属离子在微乳凝胶中传质的各种因素(如微乳液中水与表面活性剂的摩尔比值、分散相中甘油与水的配比等)进行了研究,结果也证实了上述结论.     

One‐Step Synthesis of Folic Acid Protected Gold Nanoparticles and Their Receptor‐Mediated Intracellular Uptake

We report here a facile method to obtain folic acid (FA)‐protected gold nanoparticles (Au NPs) by heating an aqueous solution of HAuCl₄/FA in which FA acts as both the reducing and stabilizing agent. The successful formation of FA‐protected Au NPs is demonstrated by UV/Vis spectroscopy, transmission electron microscopy (TEM), selected‐area electron diffraction (SAED), X‐ray photoelectron spectroscopy (XPS), and Fourier transform infrared spectroscopy (FTIR). The intracellular uptake of these nanoparticles is facilitated by HeLa cells overexpressing the folate reporter, which itself is significantly inhibited by free FA in a competitive assay as quantified by inductively coupled plasma mass spectroscopy (ICP‐MS). This simple one‐step approach affords a new perspective for creating functional nanomaterials, and the resulting biocompatible, functional Au NPs may find some prospective applications in various biomedical fields.     

Enhanced indirect fluorescence detection of p-nitrophenol, 2,4-dinitrophenol and trinitrophenol by micellar electrokinetic capillary chromatography with in-column optical-fiber LED-induced fluorescence detection

Enhanced indirect fluorescence detection with in-column optical-fiber LED-induced fluorescence (LED-IF) detection has been developed for the simultaneous separation and determination of p-nitrophenol, 2,4-dinitrophenol and trinitrophenol. The instrumental set-up is simple, cost-effective and the detection method is stable. Different experimental parameters have been studied. The optimum conditions were determined as: running buffer (pH 9.1) composed of 10 mM borate, 80 mM sodium dodecylsulfate and 0.18 μM fluorescein (as a background reagent); applied voltage of 15 kV; working temperature of 25.0 °C. The limits of detection (S/N = 3) were 11, 18 and 16 μM for p-nitrophenol, 2,4-dinitrophenol and trinitrophenol, respectively. The nitrophenols were completely separated in 13 min and the number of theoretical plates for p-nitrophenol, 2,4-dinitrophenol and trinitrophenol were 8.1 × 10(6), 6.5 × 10(6) and 8.4 × 10(6), respectively. The RSDs (n = 6) for the migration time and the peak area were better than 0.85 and 0.91%, respectively. Our proposed method possesses the advantages of rapidness and good separation efficiency.     

Effect of colloidal particle size on adsorbed monodisperse and bidisperse monolayers

Coating hydrogel films or microspheres by an adsorbed colloidal shell is one synthesis method for forming colloidosomes. The colloidal shell allows control of the release rate of encapsulated materials, as well as selective transport. Previous studies found that the packing density of self-assembled, adsorbed colloidal monolayers is independent of the colloidal particle size. In this paper we develop an equilibrium model that correlates the packing density of charged colloidal particles in an adsorbed shell to the particle dimensions in monodisperse and bidisperse systems. In systems where the molar concentration in solution is fixed, the increase in adsorption energy with increasing particle size leads to a monotonic increase in the monolayer packing density with particle radius. However, in systems where the mass fraction of the particles in the adsorbing solutions is fixed, increasing particle size also reduces the molar concentration of particles in solution, thereby reducing the probability of adsorption. The result is a nonmonotonic dependence of the packing density in the adsorbed layer on the particle radius. In bidisperse monolayers composed of two particle sizes, the packing density in the layer increases significantly with size asymmetry. These results may be utilized to design the properties of colloidal shells and coatings to achieve specific properties such as transport rate and selectivity.