核磁共振磷谱法测定乳制品中的酪蛋白含量

基于插值法建立乳制品中酪蛋白的核磁共振磷谱定量检测方法。结果表明，该方法的检出限为0.38 g/L（信噪比（RSN）=3），定量限为1.25 g/L（RSN=10）；在5.00～35.00 g/L质量浓度范围内线性良好，相关系数R2大于0.999；加标回收率在91.94%～105.10%范围区间；日内精密度在0.65%～1.40%范围区间；日间精密度在1.40%～1.80%范围区间。对市售不同乳制品中酪蛋白含量进行检测，该方法与GB 31638—2016《酪蛋白》测定结果误差在±5%以内，满足方法可行性对比分析验证要求。该方法相比常规方法样品前处理简单、定量准确性高，大大缩短了检测时间，且有更广泛的适用性，满足乳制品中酪蛋白快速定量检测的要求。     

~(137)Csγ射线累积照射SD大鼠后肝脏蛋白质组的分析

采用相对和绝对定量的同位素标签技术(Isobaric tags for relative and absolute quantitation,i TRAQ)分析累积受137Csγ射线照射大鼠肝脏组织的蛋白质表达,筛选出差异蛋白质,对差异表达的蛋白质进行GO注释分析及相互作用网络分析,探讨137Csγ射线累积照射对SD大鼠肝脏蛋白质的影响。结果显示,质谱数据经蛋白质数据库搜索,在3组样品中有定量信息的蛋白质有2 220个;0.2 Gy照射组与对照组相比,差异蛋白有149种,52种蛋白上调,97种蛋白下调;2 Gy照射组有243种差异蛋白,123种上调,120种下调;两组共同表达差异的蛋白有122种,其中,52种蛋白表达上调,70种蛋白表达下调;利用GO注释对122个共同差异蛋白质功能进行聚类分析,结果表明:根据分子功能注释,差异蛋白以酶催化、蛋白质结合、核酸结合等功能为主,另外少数蛋白还有翻译调控活性;根据细胞组成注释,多数蛋白参与细胞胞浆、细胞核、细胞膜的组成;根据生物学过程注释,多数蛋白参与代谢调节和生物过程调节。利用PAJEK软件对两个剂量组共同差异表达的蛋白进行相互作用网络分析。结果显示SF3B1、ATP6V1C1是蛋白相互作用网络的重要节点,这两个蛋白直接或间接地与其它差异蛋白存在相互作用。上述研究结果表明,137Csγ射线累积照射可诱导SD大鼠肝脏组织蛋白质组的改变,SF3B1、ATP6V1C1蛋白可能在累积照射的肝脏损伤机制中发挥作用。     

硫酸铵存在下的改良福林-酚试剂法

研究了样品中的硫酸铵对福林-酚法(Lowry法)测定蛋白质含量的影响程度,初步确定了减小硫酸铵干扰的技术参数.结果显示,当样品中的硫酸铵大于0.13%时就开始引起样品蛋白质含量测定值的降低;当样品蛋白质浓度为100~200μg.mL-1时,随着样品硫酸铵浓度的增加,蛋白质含量测定值的偏差逐渐增加;当样品中的蛋白含量为100~200μg.mL-1,硫酸铵浓度为0.3%~1%时,适当增大反应体系中的试剂甲A液的浓度(约在1.4倍左右),可以将硫酸铵干扰引起的测定偏差消除或降低到3%以下.     

30种白酒中乳酸丙酯的发现与研究

本文研究了首次在中国白酒中发现的乳酸丙酯。在对茅台、五粮液、汾酒、古井、扳倒井、今世缘、泰山、景芝、红星、兰陵、趵突泉、衡水老白干、四特、湘山、石湾、玉林泉、玉泉、西凤、北京顺鑫19个著名白酒生产厂商的30种白酒的分析中发现,乳酸丙酯含量在0.151~3.346 mg/L范围。对乳酸丙酯的香气特征进行评价,其香气特征为酯香、似葡萄的清甜果香和奶香。采用直接进样法结合标准品定性,建立了气相色谱-质谱/选择离子扫描法分析白酒中乳酸丙酯的方法。色谱条件是:DB-FFAP毛细管柱,程序升温;内标法定量,选择乳酸甲酯作内标;乳酸丙酯,选择质荷比为m/z 45,75和117的离子进行SIM扫描;乳酸甲酯,选择质荷比为m/z 45,75,89和105的离子进行SIM扫描。结果表明:在乳酸丙酯质量浓度0.005~5.000 mg/L范围,线性回归方程y=2.6032x-0.1984,线性相关系数0.9958;检测限0.025 mg/L;定量限0.050 mg/L。     

HPLC analysis of quaternary ammonium surfactants with the evaporative light scattering detector

A normal-phase high-pressure liquid chromatography technique has been elaborated for the separation of quaternary ammonium surfactants. The separation was achieved on a bonded polyphenol silica gel column with gradient elution and evaporative light-scattering (ELS) detection. The proposed method has been applied to the quantitative determination of low levels of monoalkyltrimethylammonium and trialkylmethylammonium chlorides in dialkyldimethylammonium chloride.     

Quantitating Fluorescence Intensity from Fluorophore: The Definition of MESF Assignment

The quantitation of fluorescence radiance may at first suggest the need to obtain the number of fluorophore that are responsible for the measured fluorescence radiance. This goal is beset by many difficulties since the fluorescence radiance depends on three parameters 1) the probability of absorbing a photon (molar extinction), 2) the number of fluorophores, and 3) the probability of radiative decay of the excited state (quantum yield). If we use the same fluorophore in the reference solution and the analyte then, to a good approximation, the molar extinction drops out from the comparison of fluorescence radiance and we are left with the comparison of fluorescence yield which is defined as the product of fluorophore concentration and the molecular quantum yield. The equality of fluorescence yields from two solutions leads to the notion of equivalent number of fluorophores in the two solutions that is the basis for assignment of MESF (Molecules of Equivalent Soluble Fluorophore) values. We discuss how MESF values are assigned to labeled microbeads and by extension to labeled antibodies, and how these assignments can lead to the estimate of the number of bound antibodies in flow cytometer measurements.