重铬酸钾自动电位滴定法测定茶多酚的研究

[目的]建立茶叶中茶多酚含量测定的新方法.[方法]根据茶多酚与重铬酸钾的定量反应,设计重铬酸钾电位滴定法测定茶多酚的检测方法.[结果]该方法的相对标准偏差为0.1％～0.8％(n=6),标准样品回收率为99.4％～100.6％,适用于任意茶多酚含量的茶叶样品检测.[结论]采用该方法测定茶多酚含量所需仪器设备简单,操作简便,重现性好,准确度高,试剂稳定性好,适合各种茶叶中茶多酚含量的测定.     

基于等温滴定微量热技术的植物脱落酸受体鉴定的方法

等温滴定微量热技术(ITC)是一种新发展的研究生物分子互作的方法,可获得生物分子相互作用的完整的热力学和动力参数等。为了探明ITC在植物激素受体筛选和鉴定方面的应用可靠性,以植物激素脱落酸(ABA)受体为例,通过等温滴定试验获得ABA受体PYR1和ABA结合的热力学信息,包括结合常数(Kd),反应的化学计量数(N)和焓(ΔH)等,开发植物激素受体筛选和鉴定的技术体系。ITC试验显示,受体蛋白PYR1和ABA结合Kd为67μmol/L,N为0.92,ΔH为19.78kJ/mol,表明他们结合具有特异性、饱和性和高亲和性等特征。等温滴定微量热技术可以应用于激素受体的筛选和鉴定。     

Thermal degradation and cyclodepolymerization of poly(ethylene terephthalate-co-isophthalate)s

The thermal degradation of poly(ethylene terephthalate-co-isophthalate)s (PETIs) is investigated by using isothermal thermogravimetric analysis at the temperature range of 280–310°C. The degradation rate of PETIs is increased as the mole ratio of ethylene isophthaloyl (EI) units in PETIs increases. The activation energies for the thermal degradation of poly(ethylene terephthalate), PETI(5/5), and poly(ethylene isophthalate) are 33.4, 16.6, and 8.9 kcal/mole, respectively. The degradation rate of PETIs is influenced by their volatile cyclic oligomer components formed during the polymerization and the thermal degradation. It is simulated by the rotational isomeric state model that the content of cyclic dimer in PETIs, which is the most volatile cyclic oligomer component, increases with the EI units in PETIs.     

刨花楠木聚戊糖的含量分析

刨花楠木中含有大量聚戊糖,具有很高的经济利用价值。该文建立了用硫代硫酸钠滴定法测定刨花楠木粉中戊糖含量的方法。主要对木材原木粉、经苯乙醇抽提后的木粉、经1%盐酸加热提取后的木粉、经热水抽提后的木粉等样品进行戊糖测定,对各种方法处理的木粉原料中的戊糖含量进行了比较。该方法操作简单,对于粗测刨花楠木粉中戊糖含量有重要意义。     

Starch properties, in vitro digestibility and sensory evaluation of fresh egg pasta produced from oat,teff and wheat flour

Specific dietary requirements, e.g. celiac disease, as well as increased consumer demand for products of high nutritional value, makes the production of pasta from alternative cereals interesting. Raw material characterisation showed that the utilisation of oat and teff flour is beneficial as these ingredients contain higher levels of fibre and mineral composition is superior to that of wheat. Starch properties significantly influence pasta quality and therefore damaged starch levels, amylase activity, pasting properties and gelatinisation temperatures of the flours were investigated. Fresh egg pasta based on wheat, oat and teff flour was produced. Sensory properties of oat spaghetti were found to be very close to that of wheat pasta but improvement of smoothness and aroma is necessary, while teff spaghetti showed reduced sensory quality. An in vitro enzymatic digestion was performed using a dialysis system to mimic the behaviour of pasta as eaten and make predictions on the glycemic index (GI). The predicted GI was highest for wheat pasta, followed by teff and oat. Ultra structure was studied using confocal laser scanning microscopy, allowing the visualisation of differences in starch granule size and shape as well as gelatinisation occurring during the cooking process.     

Variation in physicochemical properties and nutritional quality in chalky mutants derived from an indica rice

The physicochemical and nutritional quality of four chalky mutants (JM1-4) rice and their parent 93-11 were investigated. JM1 and JM4 are white-belly mutants, and JM2 is white-core mutant, while JM3 is floury mutant. JM2 is also a high amylose mutant with AAC of 29%. JM3 had the lipid content nearly three times of the parent, so it is also a high lipid mutant. JM1 had similar pasting viscosities with the parent, while JM2 and JM3 had smaller breakdown and setback than 93-11. JM2 had lower enthalpy of gelatinization, but higher enthalpy of retrogradation, so it had highest retrogradation percentage. JM3 had the highest accumulation of amino acids, fatty acids, and some major mineral elements such as P, K, Mg and Ca. The amino acids and fatty acids had negative correlation with PV, HPV and CPV. The pleiotropic effects caused by the mutations on starch and lipid metabolism deserve further investigation.     

软儿梨中氨基酸的提取及总氨基酸的定量分析

以青海产软儿梨为原料,以70%乙醇回流提取总氨基酸2h,采用甲醛滴定法测定总氨基酸的含量。结果表明:软儿梨中总氨基酸的含量为1.84%,标准偏差为0.244。     

Stability of 0.5% cidofovir stored under various conditions for up to 6 months

Objective To evaluate the effect of time, temperature and storage vial material on the antiviral activity of 0.5% cidofovir solution. Procedures Commercial 7.5% cidofovir solution for injection was diluted with normal saline to a 0.5% concentration. Aliquots were stored in plastic and glass vials at 4, ?20, and ?80 °C for 30, 60, 120, and 180 days. Antiviral activity against feline herpesvirus was evaluated in a virus titration assay at time zero (baseline) and at each subsequent time point. Results Cidofovir caused a fourfold log reduction in virus titer at baseline and at each time point and for each storage condition (P < 0.001). Conclusion 0.5% cidofovir demonstrated stable antiviral activity when stored for up to 6 months in glass or plastic, at 4, ?20, and ?80 °C.     

纳米无机物对MF树脂耐磨性能的影响

用单一和复合的纳米无机物直接加入三聚氰胺甲醛(MF)树脂中,探讨其种类、用量、复合比例等对MF树脂耐磨性的影响。结果表明,纳米二氧化硅HTSi-03和纳米三氧化二铝HTAl-06以1:2的质量比复合,总用量为30g·m-2时,能显著提高MF树脂浸渍装饰纸层压板的耐磨性能,耐磨转数可达4300r,达到浸渍纸层压木质地板国家标准家用Ⅱ级的要求。用红外光谱和差示扫描量热法进一步分析了纳米无机物对提高MF树脂耐磨性的改性机理。     

敌草隆原药中二甲胺分析方法研究

本文建立了敌草隆原药中游离二甲胺的分析方法,先萃取后蒸馏的方法将二甲胺从敌草隆原药中分离出来,再采用酸碱返滴定的方法进行测定,该方法线性相关系数为0.999 1,标准偏差为0.007 5,变异系数为4.75%。回收率为97.86%~102.5%。该方法精密度高,准确度好,可以满足分析要求。