Kinetic behaviour and stability of Escherichia coli ATCC27257 alkaline phosphatase immobilised in soil humates

Alkaline phosphatase (EC 3.1.3.1) extracted from Escherichia coli ATCC27257 was immobilised by co‐flocculation with soil humates in the presence of Ca²⁺. The effects of time, temperature, pH and concentration of enzyme and support on immobilisation were studied. Between 58 and 92% of the added phosphatase was strongly bound to the humates, depending on the conditions of immobilisation used. Some characteristics of the humate–phosphatase complexes and of the free enzyme were compared. The enzymatic complexes showed values of K_m (2.22 mM ) and activation energy (33.4 kJ mol^?1) similar to those of the free enzyme (2.00 mM and 27.6 kJ mol^?1). The pH/activity profiles revealed no change in terms of shape or optimum pH (10.5) upon immobilisation of alkaline phosphatase. However, the immobilised enzyme showed maximal activity in the range of 80–100 °C, while the free enzyme had its highest activity at 60 °C. The thermal stability of alkaline phosphatase was enhanced by complexation to the soil humates. © 2003 Society of Chemical Industry     

Fe(Ⅱ)-磺基荧光酮-CTMAB三元络合物间接分光光度法测定织物的甲醛含量

在碱性条件下，甲醛与水合氧化银发生氧化还原反应，生成的银定量还原Fe(Ⅱ)为Fe(Ⅱ)，Fe(Ⅱ)与磺基荧光酮在CTMAB存在下形成三元络合物、利用分光光度法测定该络合物以间接测量织物的甲醛含量，该法是测定织物中甲醛量的一种简便、灵敏的新方法。     

Base-catalyzed oxidation of poly (ethylene glycol) by alkaline permanganate: Part I. Kinetics and mechanism of formation of coordination intermediate complex

A spectrophotometric investigation has been applied to study the kinetics of oxidation of poly (ethylene glycol) (PEG) as a synthetic polymer by alkaline permanganate at a constant ionic strength of 1.0 mol.dm^?3. The reaction was found to proceed through two distinct measurable stages. The first stage was relatively fast and corresponding to the formation of coordination polymer intermediate complexes involving blue hypomanganate (V) and/or green manganate (VI) transient species. The influence of variable factors on the oxidation rates such as the concentration of permanganate ion and PEG substrate concentrations as well as the pH and ionic strength have been examined. Under the pseudo-first-order reaction conditions of [PEG] ? [MnO₄^?], the experimental results showed a first-order dependence in [MnO₄^?] and fractional first-order kinetics in each of [PEG] and alkali concentration. The oxidation process was of base-catalyzed nature where the oxidation rates were increased with increasing the alkali concentration. The observed first-order rate constant was found to be 1.1 ×10^?3 s^?1 with deprotonation constant of 0.72 dm³ mol^?1 at 45 °C. Blue hypomanganate (V) was detected for the first time by using a conventional spectrophotometer. The oxidation process has proceeded without the intervention of a free-radical mechanism. Colloidal manganese (IV) and the acid derivatives of PEG were identified as final oxidation products. The activation parameters of the second-order reaction have been calculated and found to be ΔH^≠ = 40.66 kJmol^?1; ΔS^≠ = ? 145.41 Jmo^l?K^?1 and ΔG^≠ = 83.99 kJmol^?1. A plausible reaction mechanism for oxidation based on the evaluated activation parameters and in good consistent with the observed kinetic data was suggested and discussed.     

Formation of Supramolecular Structures of Aroma Compounds with Polysaccharides of Corn Starch Cryotextures

The binding absorption of individual alcohols, ketones, alkyl acetates and their mixtures — used as aroma compounds — from aqueous solutions by corn starch cryotextures was studied by capillary gas chromatography at different starting concentrations of the odourants (1—25 mmol/L). The amount of compound sorbed by the cryotextures increases with concentration of this compound in the initial sol and increasing length of the alkyl chain in the corresponding compound. Linear equations describing the concentration dependence were proposed. The presence of octanol in the mixture increases the binding of hexanol as compared to hexanol alone. The methods of scanning electron microscopy (SEM), X‐ray photoelectron spectroscopy, differential scanning microcalorimetry (DSC) and scanning tunneling microscopy (STM) were used for estimation of the microstructure of sols, and cryotextures, and for the determination of supramolecular complex formation in the systems odourant/cryotexture and odourant/sol. It was shown that waxy corn cryotextures do not form supramolecular complexes with aroma compounds.     

聚二烯丙基二甲基氯化铵与木素磺酸钠的复合作用

利用电荷滴定、透光度和粒度测定研究了聚二烯丙基二甲基氯化铵与木素磺酸钠在水介质中的复合作用。发现,两种分子量的聚二烯丙基二甲基氯化铵与木素磺酸钠的等电点复合物具有相同的阴阳离子聚电解质比例,而且加入顺序对等电点的影响不大。此外,聚二烯丙基二甲基氯化铵与木素磺酸钠的加入顺序对复合物的透光度影响很大,同时对粒度也有一定的影响。     

丙三醇和丙二醇热裂解生成羰基化合物研究

为了解保润剂对卷烟感官质量和有害性的影响,采用正交试验方案研究了热解温度、氮气流量和氧气浓度对丙三醇和丙二醇裂解生成的8种挥发性羰基化合物的影响。结果表明:①氮气流量是丙三醇和丙二醇裂解生成甲醛的主要影响因素,除丙二醇裂解生成丙烯醛和巴豆醛外,其他7种挥发性羰基化合物的主要影响因素都是裂解温度;②相同条件下丙三醇的甲醛、丙烯醛和巴豆醛产生量显著高于丙二醇,800℃下丙二醇裂解产生的丙酮、丙醛和甲乙酮量显著高于丙三醇;③丙二醇和丙三醇热裂解产物甲醛、乙醛、丙烯醛、丙醛和丙酮产生量的不同可能是其分子中的C-O和C-C键能的差别造成的;④就危害性和感官质量而言,丙二醇作卷烟保润剂的效果应好于丙三醇。     

酒精诱导氧化应激小鼠模型建立及姜黄素抗氧化活性的初步研究

目的建立酒精诱导的氧化应激小鼠模型,对姜黄素的抗氧化活性进行初步评价,探讨补充生物活性因子的抗氧化功能评价方法。方法8周龄,昆明小鼠60只,动物房适应1周,按体重随机分为5组。实验周期内,每日按0.2ml/10g·BW给予各组实验小鼠连续灌服相应剂量受试物。实验结束时,处死全部小鼠,取血,测定肝脏相关生化指标。结果酒精模型组血浆和肝脏谷胱甘肽过氧化酶GPx的酶活性均显著低于正常对照组(P0.05);肝脏蛋白质羰基含量(PCO)显著高于正常对照组(P0.05)。结论长期摄入低浓度酒精,可以诱导建立氧化应激小鼠模型;实验中姜黄素的抗氧化活性得到初步证实;蛋白质羰基含量的测定显示,其可有效补充生物活性因子抗氧化功能评价方法。     

PVAm/淀粉复合物在再生浆中的应用

通过聚丙烯酰胺（PAM）的霍夫曼反应得到的聚乙烯胺（PVAm）与淀粉共混制备PVAm/淀粉复合物。在中性造纸条件下,PVAm/淀粉复合物对再生浆具有显著的助滤和纸张增强作用。当添加量为0.5%（对绝干浆）时,样品SF-1502的纸张干抗张强度增加33.3%,湿抗张强度提高2倍,打浆度降低41.3%。     

矿物元素蛋白盐的生物利用率

经SD品系的大白鼠试验证明 ,钙锌蛋白盐的生物利用率显著高于氨基酸配合物和无机盐 .蛋白盐能显著地提高股骨密度 (p <0 .0 5)以及股骨钙和血清钙含量 ,并能显著地提高血清锌含量 (p <0 .0 1 )以及股骨锌和脑锌含量 ,但氨基酸锌和无机锌的利用率差异不显著 ,说明小肽是一种比游离氨基酸更好的蛋白盐配体 .     

测定羰基化合物阶自动电位滴定法

本文介绍了自动电位滴定法测定羰基化合物的具体方法及其依据。实验结果证明该方法简便可行。