Bienzymatic analytical microreactors for glucose, lactate, ethanol, galactose and l-amino acid monitoring in cell culture media

A new alternative method for bioprocess monitoring based on bienzymatic analytical microreactors integrated in a flow injection analysis (FIA) system is described. Glucose-, alcohol-, lactate-, galactose- and l-amino acid oxidases (GO, AO, LacO, GalO and LAAO) and horseradish peroxidase (HRP) are immobilized on controlled pore glass (CPG) and used for the development of glucose, ethanol, lactate, galactose and amino acid sensors. The analytical methodology is based on HRP catalysed reaction of hydrogen peroxide produced by oxidases with phenol-4-sulfonic acid and 4-aminoantipyrine. The immobilized enzymes are characterized and used for preparation of the packed bed analytical microreactors. Shelf life and operational stability of the microeactors are determined. GO/HRP, AO/HRP and LAAO/HRP microreactors showed excellent shelf life, they could be stored and reused for more than 6 months with no or very little activity loss, while GalO/HRP and LacO/HRP could be stored for shorter periods of time (10-20 days). Operational stability of GO and LacO microreactors was very good: an equivalent to 16,900 FIA injections of 25 μl to a LacO microreactor resulted in loss of half of its activity, immobilized GO was so stable that it was impossible to evaluate enzyme halflife. Immobilized GalO and LAAO lose their operational activity much faster: approximately 1400 and 8000 FIA injections of the respective substrate solution in a FIA set-up resulted in 50% activity loss. The methods with all the described microreactors were successfully validated using off-line samples from S. cerevisiae, E. coli and mesenchymal stem cell cultures with HPLC as the reference method.     

Novel synthesis of a strained para-cyclophane derivative

A [P. Rajakumar, A.M.A. Rasheed, Tetrahedron 61（22） （2005） 5351] para-cyclophane derivative was synthesized via intramolecular esterification of a dipeptide surrogate containing asparagine to form tetrahydropyrimidinone ring. The structures of the product and intermediates were characterized by 1H NMR, 13C NMR and mass spectrum.     

铽与邻氨基苯基苯甲酸配合物的合成、表征及荧光性质

选择不同的pH值,在乙醇-水溶液中合成了铽与邻氨基苯基苯甲酸固体配合物.通过元素分析、摩尔电导、热分析、红外光谱、紫外光谱,表征并确定了配合物的化学组成为TbL4K·nH2O(n=1,2).同时,在不同pH值下合成得到的配合物的荧光性质也得到了测试和讨论,表明pH=10.0时配合物TbL4K·2H2O在544 nm处5D4→7F5跃迁的发射峰为最强.     

Molecular mass distribution of sodium alginate by high-performance size-exclusion chromatography

A sensitive high-performance size-exclusion chromatography (HPSEC) method with simple UV detection was developed for the molecular mass analysis of sodium alginate. It was used to evaluate alginates of varying molecular mass and the results were compared with the viscosity measurements. This HPSEC method was sensitive to serve as the stability indicating method for alginate after storage under different conditions. The information of relative molecular mass distribution of alginate was provided with reference to pullulan molecular mass standards. The comparison of the HPSEC chromatograms of alginate, pullulan and dextran revealed the effect of chemical composition of a polysaccharide and its effect on apparent molecular mass distribution.     

NMR频率综合器的微机控制

为实现ＰＴＳ系列频率综合器的微机控制，设计了一种简单的控制电路。在微机的控制下，通过该电路与微机的并行通讯口，用Ｃ语言编写的控制程序可以很方便的控制频率综合器的输出频率。控制程序采用菜单操作，电路所需的＋５Ｖ电源由微机提供，整个控制系统简单实用，值得推广。     

缝管原子捕集原子吸收光谱法测定维生素B12

本文研究了Ａｌ２Ｏ２涂层的开缝石英管原子捕集法测定ＣＯ的条件并通过测ＣＯ间接测定维生素Ｂ（１２）。结果表明，在优化条件下Ｃｏ的特征浓度为８×１０（－３）μｇ·ｍＬ（－１），比常规火焰原子吸收法的灵敏度提高８倍。采用本法测定腺苷辅酶维生素Ｂ（１２）中ＶＢ（１２）的含量，相对标准偏差１．１％，加标回收率９８．２～１００．４％。     

A New Diterpene Acid from the Flowers of Heteropappus altaicus

A new compound, named heteraltaic acid was isolated from the flowers of Heteropappus altaicus (willd) Novopokr. The compound was elucidated as (5R, 6S, 8aS) -5-[2-(3-furyl) ethyl-5, 6, 8a-trimethyl-4a, 5, 6, 7, 8, 8a -hexahydro-l-naphthalenecarboxylic acid] by the combination of 1D and 2D NMR techniques (HSQC, HMBC) and X-ray analysis.     

In-situ probing of the biotic-abiotic boundary of plants by laser desorption/ionization time-of-flight mass spectrometry

Laser desorption/ionization time-of-flight (LDI-TOF) mass spectrometry was applied for the direct analysis of cuticular waxes on intact plant tissues. Cuticular wax compounds were ionized by laser desorption in the presence of colloidal silver. Silver-adduct ions were detected on samples from Arabidopsis thaliana and from maize. Good spot-to-spot reproducibility indicated homogeneous coverage of the sample by the fine colloidal material. The results were consistent with GC-MS analyses of cuticular extracts, thus confirming the feasibility of direct analysis based on this protocol. Molecular masses of the adduct ions correspond well with the known composition of cuticular waxes. Moreover, LDI-TOF gave good estimates of the relative local abundances of a given compound. However, bias was found in cases where compounds with different ionization efficiencies were analyzed.     

Hydrogen adsorption on zigzag (8,0) boron nitride nanotubes

The chemical adsorption of H atoms on an (8,0) zigzag boron nitride nanotube is studied using the density functional theory with the supercell method. One to four H atoms per 32 B and 32 N are considered. The results show that H atoms prefer to adsorb on the top sites of adjacent B and N atoms to form an armchair chain along the tube axis. An even-odd oscillation behavior of the adsorption energy of H atoms on the tube is found, and the average adsorption energy of even H atoms is obviously bigger than that of odd H atoms. The results can be understood with the frontier orbital theory. Based on this adsorption behavior, several high-symmetric structures of H adsorbed boron nitride nanotubes with 50% and 100% coverages are studied. The pairs of lines' pattern with 50% coverage has the biggest average adsorption energy per H(2) among the chosen configurations, corresponding to approximately 4 wt % hydrogen storage.     

Evaluating formation and growth mechanisms of silica particles using fluorescence anisotropy decay analysis

At present, there is no direct experimental evidence that primary silica particles, which exist only transiently for a few seconds during the St?ber silica synthesis, can be stable in aqueous solutions. In the present work, we show that primary silica particles are formed spontaneously after the dissolution of diglycerylsilane (DGS) in aqueous solutions and remain stable for prolonged periods of time. By using time-resolved fluorescence anisotropy (TRFA), we demonstrate that this unique property of DGS is ascribed to the slow kinetics of silica particle growth in diluted sols at pH approximately 9.0. The anisotropy decay of the cationic dye rhodamine 6G (R6G), which strongly adsorbs to silica oligomers and nanoparticles in DGS sols, could be fit to three components: a fast (picosecond) scale component associated with free R6G, a slower (nanosecond) rotational component associated with R6G bound to primary silica particles, and a residual (nondecaying) anisotropy component associated with R6G that was bound to secondary or larger particles that were unable to rotate on the time scale of the R6G emission lifetime (4 ns). The data show that, under conditions where fast hydrolysis is obtained, the initial size of the nuclei depends on the silica concentration, with larger nuclei being present in more concentrated sols, while the rate of growth of primary particles depends on both silica concentration and solution pH. At low silica concentrations and high pHs, it was possible to observe the growth of stable, nonaggregating primary silica particles by a mechanism involving rapid nucleation followed by monomer addition. The presence of stable primary particles was confirmed by atomic force microscopy (AFM) imaging. At higher silica concentrations and lower pHs, there was an increase in the initial size of the nuclei formed, which subsequently grew to a larger radius (> 4.5 nm) or aggregated with time, and in such cases, nucleation and aggregation occurred simultaneously in the early stage of silica formation. The data clearly show the power of time-resolved fluorescence anisotropy decay measurements for probing the growth of silica colloids and show that this method is useful for elucidating the mechanism of particle formation and growth in situ.