Quantification of Tin and Lead in Binary Alloys Using Voltammetry of Immobilized Microparticles

Voltammetry of immobilized microparticles (VMP) has been used in this work for the quantitative determination of tin and lead particles in their binary alloys. Carbon paste electrodes, which contained small amounts of tin and lead or their mixtures, were used as working electrodes and square wave voltammograms of each electrode were recorded. Quantification was performed using optimum experimental conditions, obtained by an experimental design technique. The calibration was made by measuring the percentage peak height of each metal taking the sum of peak currents of the both metals as 100 %. The results were compared with quantitative results of X‐ray fluorescence (XRF) technique to evaluate the capability of VMP method in its quantitative determination of solid samples.     

人神经母细胞瘤的磷酸化膜蛋白质组分析

针对人神经母细胞瘤SH-SY5Y细胞系的磷酸化膜蛋白质组,发展了基于多酶酶解法结合杂化硅胶基质固定化钛离子亲和色谱(Ti4+-IMAC)整体柱富集的分析策略。该方法通过对细胞裂解液进行超速离心,以及1 mol/L NaCl和0.1 mol/L Na2CO3顺序清洗,获得膜蛋白质组分。所提取的蛋白质分别经胰蛋白酶、胰凝乳蛋白酶和胃蛋白酶平行酶解,产生的肽段经Ti4+-IMAC整体柱选择性富集磷酸肽后,采用纳升级反相液相色谱分离和质谱鉴定,成功鉴定到43个磷酸化蛋白质,其中有14个定位于膜上。研究结果表明,采用该策略开展SH-SY5Y细胞系磷酸化膜蛋白质组学分析有望加速对该肿瘤的研究和相关潜在标记物的筛选。     

微柱高效液相色谱法测定大鼠脑微透析液中 的乙酰胆碱和胆碱

用所建立的微柱高效液相色谱分离、柱后固定化酶反应器酶解、电化学检测器检测的方法, 对用不同浓度异氟醚麻醉前后的大鼠脑微透析液中的乙酰胆碱和胆碱的浓度进行了测定。在 乙酰胆碱和胆碱的浓度为10～ 2 000 nmol/L 时,其浓度分别与各自相应峰高的线性 关系良好,两者的检测限(以信噪比为3计)均可达5 nmol/L 。微透析液中乙酰胆碱和胆碱的含量在大鼠清醒时最高,随着异氟醚吸入浓度的增加,乙酰胆碱和胆碱含量明显降低。在大鼠海马和脑皮层中乙酰胆碱浓度的降低与大鼠吸入异氟醚的浓度相关( P ＜     

负载型纳米TiO2光催化降解活性艳红X-3B染料

光催化氧化;负载型纳米光催化剂;负载型纳米TiO2光催化降解活性艳红X-3B染料     

交联酶聚集体与仿生硅化技术结合制备固定化脂肪酶

将交联酶聚集体(CLEAs)与仿生硅化技术相结合,制备了交联脂肪酶Candidasp.99-125杂化生物催化剂.以京尼平为交联剂,在最佳条件下制得的脂肪酶CLEAs的酶活达771U/g,回收率达75%;保护剂聚乙烯亚胺(PEI)与Candidasp.99-125脂肪酶共沉淀制备P/CLEAs,其酶活达897U/g,回收率约88%;利用PEI的诱导作用,在P/CLEAs表面形成氧化硅涂层,制得的脂肪酶CLEAs(Coated-CLEAs)显示出良好的稳定性,特别是其抗蛋白酶水解能力、有机溶剂耐受能力、重复使用性能等方面明显提高.     

Oxidation of Hydrogen by Metal Complexes of Platinum and Palladium Immobilized on Silica

The thermal stability of metal complexes immobilized on the surface of silica and its connection with the catalytic activity in the oxidation of hydrogen were investigated. High catalytic activity was exhibited by heterogenized platinum and palladium acetylacetonate near room temperatures in the initial state and by γ-aminopropylsilicas treated with platinum and palladium complexes. The catalytic activity of the metal complexes correlates with their thermal stability and with the ability to undergo oxidation to a metal state with high valence. This revised version was published online in August 2006 with corrections to the Cover Date.     

Thermal stability and energy of deactivation of free and immobilized amyloglucosidase in the saccharification of liquefied cassava starch

Amyloglucosidase from Novo (Copenhagen, Denmark) was immobilized in controlled pore silica particles with the silane-glutaraldehyde covalent method. Thermal stability of the free and immobilized enzyme (IE) was determined with 30% (w/v) α-amylase liquefied cassava starch, pH 4.5, temperatures from 35 to 75°C. Free amyloglucosidase maintained its activity practically constant for 240 min and temperatures up to 50°C. The IE has shown higher stability retaining its activity for the same period up to 60°C. Half-life for free enzyme was 20.6, 6.44, 2.07, 0.69, and 0.24 h for 55, 60, 65, 70, and 75°C, respectively, whereas the IE at the same temperatures had half-lives of 116.4, 30.88, 8.52, 2.44, and 0.73 h. The energy of thermal deactivation was thus 50.6 and 57.6 kcal/mol, respectively for the free and IE, confirming stabilization by immobilization.     

Synthesis and Silica‐Based Immobilization of Monofunctionalized Heptakis(2,6‐di‐O‐methyl‐3‐O‐pentyl)‐β‐cyclodextrin for Enantioselective Capillary‐HPLC

Heptakis(2,6‐di‐O‐methyl‐3‐O‐pentyl)‐β‐cyclodextrin was monofunctionalized by the regioselective introduction of exactly one ω‐epoxyoctyl group at the primary site of the cyclodextrin. The site‐specifically substituted cyclodextrin was immobilized to commercially available aminopropyl silica by nucleophilic opening of the epoxy function of the spacer substituent resulting in a lipophilic chiral stationary phase with broad applicability for enantiomer separations in capillary‐HPLC under reversed‐phase conditions.     

Enzymatic synthesis of medium chain monoglycerides in a solvent-free system

The synthesis of monocaprin, monolaurin, and monomyristin in a solvent-free system was conducted by mixing a commercial immobilized lipase with the organic reactants (glycerol and fatty acids) in a 20-mL batch reactor with constant stirring. The effects of temperature, fatty acid/glycerol molar ratio, and enzyme concentration on the reaction conversion were determined. The addition of molecular sieves in the assays of monomyristin synthesis was also evaluated. The reactions were carried out for 5 to 6 h and the nonpolar phase was analyzed by gas chromatography. The best results in terms of selectivity and conversion (defined as the percentage of fatty acid consumed) were achieved when the stoichiometric amount of reagents (molar ratio=1) and 9% (w/w) commercial enzyme were used and the reaction was performed at 60°C. The addition of molecular sieves did not improve the synthesis of monomyristin. Conversions as high as 80%, with monoglycerides being the major products, were attained. After 5 h of reaction, the concentration of monoglyceride was about twice that of diglyceride, and only trace amounts of triglyceride were found. The results illustrate the technical possibility of producing medium chain monoglycerides in a solvent-free medium using a simple batch reactor.     

Development and application of an integrated system for monitoring ethanol content of fuels

An automated flow injection analysis (FIA) system for quantifying ethanol was developed using alcohol oxidase, horseradish peroxidase, 4-aminophenazone, and phenol. A colorimetric detection method was developed using two different methods of analysis, with free and immobilized enzymes. The system with free enzymes permitted analysis of standard ethanol solution in a range of 0.05–1.0 g of ethanol/L without external dilution, a sampling frequency of 15 analyses/h, and relative SD of 3.5%. A new system was designed consisting of a microreactor with a 0.91-mL internal volume filled with alcohol oxidase immobilized on glass beads and an addition of free peroxidase, adapted in an FIA line, for continued reuse. This integrated biosensor-FIA system is being used for quality control of biofuels, gasohol, and hydrated ethanol. The FIA system integrated with the microreactor showed a calibration curve in the range of 0.05–1.5 g of ethanol/L, and good results were obtained compared with the ethanol content measured by high-performance liquid chromatography and gas chromatography standard methods.