Preparation of 17β‐estradiol‐imprinted material by surface‐initiated atom transfer radical polymerization and its application

A novel 17β‐estradiol molecularly imprinted polymer was grafted onto the surface of initiator‐immobilized silica by surface‐initiated atom transfer radical polymerization. The resulting molecularly imprinted polymer was characterized by elemental analysis and thermogravimetric analysis. The binding property of molecularly imprinted polymer for 17β‐estradiol was also studied with both static and dynamic methods. The results showed that the molecularly imprinted polymer possessed excellent recognition capacity for 17β‐estradiol (180.65 mg/g at 298 K), and also exhibited outstanding selectivity for 17β‐estradiol over the other competitive compounds (such as testosterone and progesterone). Then, the determination of trace 17β‐estradiol in beef samples was successfully developed by using molecularly imprinted polymer solid‐phase extraction coupled with high‐performance liquid chromatography. The limit of detection was 0.25 ng/mL, and the amount of 17β‐estradiol in beef samples was detected at 2.83 ng/g. This work proposed a sensitive, rapid, reliable, and convenient approach for the determination of trace 17β‐estradiol in complicated beef samples.     

氯化钙/水-醇溶液稀释热

电解质溶液稀释热是溶液的重要热性质之一．由它可计算不同浓度下电解质的溶解热、表现相对摩尔焓、溶液中反应热和化合物生成热等．在电解质溶液理论研究中，稀释热也是重要的基础数据．由稀释热可推算溶液中组分的活度系数、渗透系数、相对偏摩尔焓及表观摩尔热容等[1-3]．在化工生产中，稀释热是化工过程能量计算不可缺少的数据．电解质水溶液稀释热已有不少研究[2，4]．但电解质混合溶剂体系稀释热报导甚少．随着加盐精馏技术、海水淡化技术等研究的进展，急需这方面数据．本文作者已报告了CaCl2／C2H5OH－H2O体系[5]和CaCl2／n－C…     

Micellization of dissymmetric cationic gemini surfactants and their interaction with dimyristoylphosphatidylcholine vesicles

The micellization process of a series of dissymmetric cationic gemini surfactants [CmH2m+1(CH3)2N(CH2)6N(CH3)2C6H13]Br2 (designated as m-6-6 with m = 12, 14, and 16) and their interaction with dimyristoylphosphatidylcholine (DMPC) vesicles have been investigated. In the micellization process of these gemini surfactants themselves, critical micelle concentration (cmc), micelle ionization degree, and enthalpies of micellization (DeltaHmic) were determined, from which Gibbs free energies of micellization (DeltaGmic) and entropy of micellization (DeltaSmic) were derived. These properties were found to be influenced significantly by the dissymmetry in the surfactant structures. The phase diagrams for the solubilization of DMPC vesicles by the gemini surfactants were constructed from calorimetric results combining with the results of turbidity and dynamic light scattering. The effective surfactant to lipid ratios in the mixed aggregates at saturation (Resat) and solubilization (Resol) were derived. For the solubilization of DMPC vesicles, symmetric 12-6-12 is more effective than corresponding single-chain surfactant DTAB, whereas the dissymmetric m-6-6 series are more effective than symmetric 12-6-12, and 16-6-6 is the most effective. The chain length mismatch between DMPC and the gemini surfactants may be responsible for the different Re values. The transfer enthalpy per mole of surfactant within the coexistence range may be associated with the total hydrophobicity of the alkyl chains of gemini surfactants. The transfer enthalpies of surfactant from micelles to bilayers are always endothermic due to the dehydration of headgroups and the disordering of lipid acyl chain packing during the vesicle solubilization.     

Solubilization of phosphatidylcholine vesicles by hydrophobically modified poly(acrylamide)-co-(acrylic acid): effects of acrylic acid fraction and polymer concentration

The interaction of hydrophobically modified copolymers of acrylamide and acrylic acid, designated as PAM-C12-AA (X%) (X% indicates the percentage of acrylic acid unit and X = 5, 10, 20), with dimyristoylphosphatidylcholine (DMPC) vesicles has been studied. Complementary techniques including isothermal titration microcalorimetry (ITC), differential scanning calorimetry (DSC), turbidity measurement, calcein leakage measurement, dynamic light scattering (DLS), and transmission electron microscopy (TEM) were used to get comprehensive information. The results show that PAM-C12-AA leads to solubilization of DMPC vesicles. There is a critical concentration (C(s)) for PAM-C12-AA to induce obvious vesicle disruption. This concentration is very close to the critical aggregation concentration (CAC) for the polymer self-aggregation. The Cs values are found to be similar for the three polymers. However, the disruption of DMPC vesicles induced by the polymers increases to a greater degree at higher AA fraction, owing to the increasing strength of interaction between the polymer and the lipid bilayer.     

Simultaneous measurement of methyl tert‐butyl ether and tert‐butyl alcohol in human serum by headspace solid‐phase microextraction gas chromatography–mass spectrometry

The abundant production of methyl tert‐butyl ether (MTBE) and its widespread use have led to an increase in the potential for human exposure. This work described a simple, fast, sensitive, reliable and low‐cost method for the simultaneous measurement of MTBE and its metabolite, tert‐butyl alcohol (TBA) in human serum by headspace solid‐phase microextraction gas chromatography–mass spectrometry. Extraction conditions were optimized and 40 °C, 10 min, 250 rpm and 0.3 g NaCl for a 1 mL sample were the optimal conditions. This method showed good analytical performance in terms of sensitivity with limits of detection in serum (1 mL) of 0.03 µg/L for MTBE and 0.05 µg/L for TBA, accuracy (mean recovery values) from 75.8% to 85.8%, precision (relative standard deviations) <10% and sample stability (biodegradation) <10% after 28 days. A verification experiment proved the reproducibility and stability of this method as well. Finally the method was used to detect 212 specimens, and the internal dose levels for MTBE in human serum were presented in China. Copyright © 2015 John Wiley & Sons, Ltd.     

部份互溶体系4-甲基-2-戊醇和水的过量焓研究

使用LKB-2107型流动式微量量热计测定了4-甲基-2-戊醇和水这一部份互溶体系在293.15 K、298.15 K和303.15 K的常压过量焓。测量结果用Redlich-Kister方程作了关联。另外,还用该体系富醇区的过量焓数据拟合NRTL模型的参数与温度关系,推算较高温度下该体系的常压汽液平衡(VLE)组成及泡点。推算值与文献值是接近的。实验试剂4-甲基-2-戊醇由粗品经三次蒸馏提纯,沸点为404.95 K,折光率n_D~(20)1.4113,密度d~(20)0.8067 g cm~(-3),与文献值一致。无水乙醇、尿素均为分析纯。液体试剂在使用前均     

Genetically Engineered Epidermal Growth Factor Conjugate Crosses Cell Membrane

Epidermal growth factor (EGF) is a well-known pleiotropic growth factor in mammal, and has been attempted to be used in many different fields. However, the application of EGF is limited because of its poor cell permeation. In order to increase membrane permeation ability of EGF, a genetically modified recombinant EGF (GST-TAT-EGF) was prepared through conjugation of EGF with two protein transduction domains, glutathione-S-transferase and TAT47-57. The results showed that the GST-TAT-EGF fusion protein exhibited higher ability in biomembrane penetration than that of the EGF alone. The results also implied that two different mechanisms (EGF receptor-mediated endocytosis and direct penetration) might be involved in GST-TAT-EGF transmembrane delivery.     

末端带有溴甲基基团的柱状树枝化聚酰胺的合成与表征

采用大分子单体的方法合成了一种含大量溴甲基官能团端基,主链和侧链均为聚酰胺的功能化柱状树枝化聚酰胺.氯化亚砜的新活化工艺使整个合成过程不需要保护和去保护的步骤且减少了副反应的产生,从而使得合成和纯化更加简单.产物的结构通过红外和核磁得到了证实.由分子量测试知,聚酰胺的重均分子量(Mw)为5.01×104,分子量分布为2.74.由溶解性测试知,该聚合物能溶解于N,N′-二甲基甲酰胺、N,N′-二甲基乙酰胺、二甲亚砜、1-甲基-2-吡咯烷酮和硫酸等溶剂,溶解性能得到了大大的提高,主要是由于侧链树枝化单元和末端溴甲基存在的缘故.由粘度测试知,该聚酰胺的粘度低,主要是由于侧链树枝化单元的屏蔽效应.该聚合物的热性能也由TGA测试得到了表征,结果表明该聚酰胺具有良好的热性能.由于该聚酰胺外端具有大量的溴甲基基团,它可以作为原子转移自由基聚合反应的引发剂来合成大型的梳形聚合物,另外通过把它外围的溴甲基转化为其它的功能化基团,可以使它应用于其它更广的领域.     

Determination of activity coefficients using a flow EMF method. 1. HCl in methanol-water mixtures at 25, 35 and 45°C

A method to determine activity coefficients of electrolytes in mixed solvent is described which makes use of ion-selective electrode(s) (ISE) and in which a concentrated electrolyte solution is continuously added. Activity coefficients for HCl in methanol-water mixtures containing 0, 10, 20, 30, 50, 70, and 90 weight percent methanol at 25, 35 and 45°C were calculated using the Pitzer equation, and the electromotive force (emf) data of the cell: The experimental results agree well with literature values indicating that the proposed method is procise and reliable.