Microcalorimetry as a possible tool for phylogenetic studies of Tetrahymena

Using isothermal microcalorimetry, the growth power-time curves of three strains of Tetrahymena were determined at 28°C. Their Euclidean distances and cluster analysis diagram were obtained by using two thermokinetic parameters (r and Q_log), which showed that T. thermophila BF₁ and T. thermophila BF₅ had a closer relationship. Compared with the single molecular biomarker (ITS1) method, microcalorimetry wasmaybe a simpler, more sensitive andmore economic technique in the phylogenetic studies of Tetrahymena species.     

Screening for protease substrate by polyvalent phage display

Proteases are key regulators of many physiological and pathological processes [1,2], and are recognized as important and tractable drug candidates. Consequently, knowledge of protease substrate recognition and specificity promotes identification of biologically relevant substrates, helps elucidating a protease's biological function, and the design of specific inhibitors. Traditional methods for establishing substrate recognition profiles involve the identification of the scissile bond within a given protein substrate by proteomic methods such as Edman degradation. Then, synthetic peptide variants of this sequence can be screened in an iterative fashion to arrive at more optimized substrates. Even though it can be fruitful, this iterative strategy is biased toward the original substrate sequence and it is also tremendously cumbersome. Furthermore, it is not amenable to high throughput analysis. In 1993, Matthew & Wells presented a method for the use of monovalent "substrate phage" libraries for discovering peptide substrates for proteases, in which more than 10(7) potential substrates can be tested concurrently [3]. A library of fusion proteins was constructed containing randomized substrate sequences placed between a binding domain and the gene III coat protein of the filamentous phage, M13, which displays the fusion protein and packages the gene coding for it inside. Each fusion protein was displayed as a single copy on filamentous phagemid particles (substrate phage). This method allows one to rapidly survey the substrate recognition and specificity of individual or closely related members of proteases. Over the past decade, substrate phage screening has shown terrific utility in rapidly determining protease specificity and characterization of substrate recognition profile of proteases. In some cases, the structural insights of the catalytic domain were obtained from comparison of substrate specificity among closely related family of proteases [4-6]. The number of proteases (from various classes) characterized by this approach testifies to its power. Since the initial development of substrate phage library, different versions of the substrate phage cloning vectors have been constructed to further improve the utility of substrate phage display. This review will provide an overview of the construction of substrate phage display libraries, screening of substrate phage libraries, examples of application, summary and future directions.     

水中痕量镉的准液膜富集

准液膜法是在液膜法基础上提出的新分离方法，它保持了液膜法分离富集的高效能，但省去了液膜法的制乳与破乳过程，使操作更为简便易行。本文用此法富集了水及废水中痕量镉，富集倍数可达２３０倍，镉的回收率在９７％以上。     

Recent progress in nanomaterial-enhanced fluorescence polarization/anisotropy sensors

In this review, we summarize the number of scientific publications in the field of FP/FA sensor in recent five years, and introduce the recent progress of FP/FA sensor based on nanomaterial. The various analytical applications of FP/FA sensor based on nanomaterial are discussed. We also provide perspectives on the current challenges and future prospects in the promising field.     

Determination of trace silver by solid substrate room temperature phosphorescence quenching method based on lead carboxymethyl cellulose particles (Pb(CMC)2) containing luminescent salicyl fluorenes molecules

Luminescent particles of lead carboxymethyl cellulose (Pb(CMC)2) containing salicyl fluorones (THBF), Pb(CMC)2-THBF were synthesized by the sol-gel method, using sodium carboxymethyl cellulose (NaCMC) as precursor and Pb2+ as precipitant. Pb(CMC)2-THBF can emit the intense and stable solid substrate room temperature phosphorescence (SS-RTP) on filter paper. And EDTA can chelate Pb2+ in Pb(CMC)2-THBF, causing it to decompose into aqueous soluble components PbY2-, CMC- and THBF, which can react with Ag+ to form Ag(CMC)2-THBF, causing the decrease of phosphorescence intensity. Based on the facts above, a new method for the determination of trace silver by SS-RTP quenching method was established. The linear range of this method is 8.0-40.0 fg spot(-1) (20.0-100.0 pg ml(-1)), with a detection limit (LD) of 2.2 fg spot(-1) (corresponding to a concentration range of 5.5 x 10(-13) g ml(-1)), and the regression equation of working curve is DeltaI(p) = 12.56 + 0.5527C(Ag+) (fg spot(-1), 0.4 microl spot(-1)), n = 8, r = 0.9992. This method has been applied to the determination of trace silver in human hair and tea sample with satisfactory results. The mechanism of SS-RTP emission is also discussed.     

萃取分光光度法测定废烟末中的尼古丁

本文在ｐＨ４．５的乙酸－乙酸钠缓冲溶液中，使烟碱与甲基橙生成稳定的黄色络合物，然后用二氯甲烷萃取。于λｍａｘ＝４３５ｎｍ处测定有机相的吸光度，烟碱浓度在０－６５μｇ／５ｍＬ范围内符合比尔定律，摩尔吸光系数为９．８％１０＾３Ｌ．ｍｏｌ＾－＾１．ｃｍ＾－＾１。方法快速，简便，应用于烟草中烟碱的定量分析，其加标回收率在８１－１０９％之间，相对标准偏差小于４．１％。     

Fe/Zn double metal cyanide catalyzed ring-opening polymerization of propylene oxide: 2. Characterization of active structure of double metal cyanide catalysts

Double metal cyanide (DMC) complexes based on Zn₃[Fe(CN)₆]₂ were synthesized using different molar ratios of ZnCl₂ to K₃[Fe(CN)₆] and special complexing agents. IR spectroscopy, electron spectroscopy for chemical analysis, X-ray diffraction, scanning electron microscopy, X-ray photoelectron spectroscopy, and other analytical techniques were employed to characterize these catalysts. The morphology and structure of these DMC catalysts were attributed to the different complexing agents as well as to the different molar ratios of ZnCl₂ to K₃[Fe(CN)₆]. In addition, the catalytic activity was strongly correlated with the morphology and noncrystalline content of DMC catalysts. High-activity catalysts could be prepared by controlling the structure of DMC catalysts by incorporating complexing agents. The active species of DMC catalysts for ring-opening polymerization are Zn²⁺, [Fe(CN)₆]^3–, Cl^–, and the compound of their ligands.     

Morin applied in speciation of aluminium in natural waters and biological samples by reversed-phase high-performance liquid chromatography with fluorescence detection

A reversed-phase high-performance liquid chromatographic method with fluorescence detection for the determination of labile monomeric aluminium has been developed through pre-column complexation using morin as the analytical reagent. The highly fluorescent aluminium-morin complex (excitation wavelength 418 nm, emission wavelength 490 nm) was separated on a Spherisorb ODS 2 column with an eluent consisting of 30% methanol and 70% water (pH 1.0 with perchloric acid). The most remarkable point of this protocol was that only the most toxic aluminium species, that is, free aqua-aluminium ion and its monomeric hydroxo complex ions, selectively respond among various aluminium complexes. This strategy has been successfully applied to direct fractionation of the toxic aluminium in natural waters and biological samples without any pretreatment.     

Processing and error analysis of signals in flow-injection analysis

The processing and error analysis of signals in flow-injection systems were systematically studied by simulation and experimental measurements. The content includes an error analysis for peak-height and peak-area signal, a least-squares filtering procedure applied to the flow-injection curve and a peak recognition to remove interferences from air bubbles. Simulation results were obtained by statistical processing of peak-height and peak-area values from Gaussian curves to which noise had been added. The experimental measurements were done by an automatic flow-injection device to obtain detailed information for each individual point of a peak. 2-(2-Arsenophenylazo)-7-(2,6-dichlorophenylazo-4-sulphonic acid)-1,8-dihydroxynaphthalene-3,6-disulphonic acid (DCSA) was used for measuring physical dispersion alone, and Fe(II)-o-phenanthroline for the measurement of both physical dispersion and chemical reaction. The results from computer simulation and experiments agreed well.