Reaction of Acenaphthylene with the Benzoyloxy Radical

Acenaphthylene (ACN) has been polymerized at 60° C using benzoyl peroxide labeled with carbon-14 and tritium as the Lnitiator. End-group analyses show a very high proportion of benzoate groups among the incorporated initiator fragments. It is deduced that ACN is much more reactive than most other monomers toward the benzoyloxy radical. There is evidence that transfer to benzoyl peroxide is significant during the polymerization of ACN.     

New Grafted Copolymers Carrying Betaine Units Based on Gellan and N-Vinylimidazole as Precursors for Design of Drug Delivery Systems

New grafted copolymers possessing structural units of 1-vinyl-3-(1-carboxymethyl) imidazolium betaine were obtained by graft copolymerization of N-vinylimidazole onto gellan gum followed by the polymer-analogous reactions on grafted polymer with the highest grafting percentage using sodium chloroacetate as the betainization agent. The grafted copolymers were prepared using ammonium persulfate/N,N,N′,N′ tetramethylethylenediamine in a nitrogen atmosphere. The grafting reaction conditions were optimized by changing one of the following reaction parameters: initiator concentration, monomer concentration, polymer concentration, reaction time or temperature, while the other parameters remained constant. The highest grafting yield was obtained under the following reaction conditions: c_i = 0.08 mol/L, c_m = 0.8 mol/L, c_p = 8 g/L, t_r = 4 h and T = 50 °C. The kinetics of the graft copolymerization of N-vinylimidazole onto gellan was discussed and a suitable reaction mechanism was proposed. The evidence of the grafting reaction was confirmed through FTIR spectroscopy, X-ray diffraction, ¹H-NMR spectroscopy and scanning electron microscopy. The grafted copolymer with betaine structure was obtained by a nucleophilic substitution reaction where the betainization agent was sodium chloroacetate. Preliminary results prove the ability of the grafted copolymers to bind amphoteric drugs (cefotaxime) and, therefore, the possibility of developing the new sustained drug release systems.     

Investigational Studies on Highly Purified Fenugreek Gum as Emulsifying Agent

In this study, highly purified galactomannan containing fenugreek gum was isolated by newly reported method and investigated for its surface and emulsification property. Comparative studies were carried out with other galactomannan containing natural emulsifiers like locust bean gum, guar gum, and non-galactomannan anionic xanthan gum. The results revealed that highly purified fenugreek gum has better surface and interfacial tension reducing property among all gums used in this study. Emulsion prepared with 0.6% highly purified fenugreek gum showed greater reduction in droplets size with greater surface area compared to guar gum, locust bean gum, and xanthan gum emulsion. Zeta potential values indicated that highly purified fenugreek gum emulsion showed greater repulsive forces and was able to form more stable emulsion compared to other gums. No coalescence or phase separation was observed during storage.      

Alumina supported synthesis of Cassia marginata gum‐g‐poly(acrylonitrile) under microwave irradiation

In view of the known advantages of the microwave promoted reactions done in dry medium, the seed gum sourced from Cassia marginata has been graft copolymerized with acrylonitrile in dry medium at neutral alumina support under microwave irradiation. Grafting conditions were optimized and the representative graft copolymer was characterized by Fourier transform‐infrared, Thermo gravimetric analysis, Scanning electron microscopy, and X‐Ray Diffraction (XRD) measurement, taking Cassia marginata gum (CM) as reference. Much higher % grafting and % efficiency could be obtained in the microwave promoted alumina supported grafting as compared to grafting done in aqueous medium (microwave promoted and conventional). Properties of the microwave synthesized Cassia marginata gum‐graft‐poly(acrylonitrile) (CM‐g‐PAN) were studied and compared with the parent seed gum. © 2007 John Wiley & Sons, Ltd.     

Entrapment of plant invertase within novel composite of agarose-guar gum biopolymer membrane

Invertase or β-d-Fructofuranosidase (E.C.3.2.1.26) was extracted from Cucumis melo. L. fruit (Family-Cucurbitaceae). Soluble, plant invertase enzyme was immobilized in novel composite of agarose-guar gum biopolymer matrix in the form of hydrophilic, porous membranes. The immobilized invertase was characterized for sucrose hydrolytic activity and leakage from the matrix support. The efficiency of immobilization was found to be 91% with negligible leaching. The kinetic parameters K_m and V_max for free and immobilized invertase were also determined. Immobilized invertase was optimally active in the wide pH range of 4.5-6.5. The immobilization process also enhanced the thermal stability of enzyme up to 65 °C. Immobilized invertase membranes showed excellent storage stability with shelf life of 110 days. Entrapped invertase showed better operational stability and reusability up to 12 cycles. The fluorescence spectra of the composite membranes were studied and compared with that of soluble enzyme. All these characteristics of the immobilized invertase membranes make them suitable for the fabrication of biosensors.     

The role of shear and elongation in the flow of solutions of semi-flexible polymers through porous media

The rheological behavior of hydrophobically modified hydroxyethyl cellulose (HMHEC) and xanthan gum solutions has been characterized in simple shear flow, opposed-jets flow, and flow through porous media. Both polymers exhibit shear thinning in simple shear flow and apparent shear thinning in flow through porous media. Analysis of the results shows there is a direct correspondence between shear viscosities determined in simple shear experiments and apparent viscosities in porous media flow at relatively low shear rates. At high shear rates the extensional component of the flow in porous media appreciably increases the apparent viscosity over the simple shear values. This increase is shown to correlate with results obtained in opposed-jets experiments, and is attributed to formation of transient entanglements.     

对GB5889-86苎麻残胶率测试方法的修正意见

本文根据对苎麻碱煮过程中胶质转移动态属性的分析,讨论了GB5889-86试验方法在测定高残胶率精干麻时所存在的主要问题,探讨了多级碱煮测定的设想,通过分析和实验,对GB5889-86试验方法提出了修正意见,并给出了修正值,使之能够适用于高残胶率精干麻的测定,减少了系统误差,提高了测定精度。     

原子吸收分光光度法测定杜仲茶中无机元素含量

原子吸收分光光度法测定杜仲茶中无机元素含量王彩兰ａ孙瑞霞ｂ吕文英ｂ王太霞ｃａ（河南师范大学化学系新乡４５３００２）ｂ（河南师范大学分析测试中心新乡４５３００２）ｃ（河南师范大学生物系新乡４５３００２）关键词原子吸收杜仲叶制茶无机元素中图分类号Ｏ６５７...     

绿原酸的分离纯化工艺研究

研究从杜仲提取物中分离纯化绿原酸的工艺,确定其分离纯化参数.采用料液比1∶20水超声提取,上聚酰胺柱分离,4BV15％乙醇洗脱,洗脱浓缩液调pH为1-2静置结晶,可得85％以上的绿原酸粗晶,再甲醇重结晶,可得97％绿原酸白色针状晶体.采用此工艺可以将杜仲提取物中绿原酸由20％分离纯化至97％,工艺适合工业化生产.     

杜仲内生真菌抗氧化活性

应用TBA反应法对从杜仲(Eucommia ulmoides Olive．)叶片中分离到的内生真菌刺孢壳Chaetomella sp．培养液提取物进行的抗氧化活性的测定表明该菌能够产生抗氧化活性成分，通过TLC和HPLC对抗氧化活性成分的分析表明其活性成分为黄酮类化合物。