Synthesis of novel poly(ethylene glycol) supported benzazepines: the crucial role of PEG on the selectivity of an intramolecular Heck reaction

Poly(ethylene glycol) (PEG 3400) was used as a soluble polymeric support for the synthesis of a series of novel benzazepines. The key step for the preparation of these heterocycles was a phosphine-free palladium-catalyzed Heck reaction. Palladium nanoparticles formed during the course of the reaction were characterized. The presence of PEG 3400 influenced the outcome of the reaction in terms of selectivity.     

A photodimerization approach to crosslink and functionalize microgels

Microgels were prepared within reverse micelles via photocrosslinking. Gelation resulted from the [2 + 2] photodimerization reaction of nitrocinnamoyl (NC) groups on multi-arm polyethylene glycol (PEG) or gelatin. Because of the potential for biomedical and chemical applications, immobilization capacity within the microgels was investigated. Quantum dots (QDs), for example, share a similar size scale with proteins and can be physically trapped within the microgels. In addition, the optoelectronic properties of QDs could be utilized for analytical, imaging, and therapeutic purposes. Small molecules and recognition sequences (e.g. biotin) can also be covalently immobilized within the microgel networks through the photodimerization reaction. In the presence of biotin-PEG-NC, the resulting microgels added to streptavidin-coated plates. The microgel properties such as biodegradability and degree of swelling may be engineered for particular applications including targeted monitoring and controlled drug delivery systems.     

Immobilization of invertase and glucose oxidase in poly 2-methylbutyl-2-(3-thienyl) acetate/polypyrrole matrices

Immobilization of invertase and glucose oxidase in conducting polypyrrole and copolymers of poly 2-methylbutyl-2-(3-thienyl) acetate with pyrrole were achieved via electrochemical method. Sodium dodecyl sulphate was found to be the most suitable supporting electrolyte. Maximum reaction rate, Michaelis-Menten constant and optimum temperatures were determined for native and immobilized enzymes. Storage and operational stabilities of enzyme electrodes were also investigated.     

基于脱乙酰基魔芋葡甘聚糖固定酶的葡萄糖传感器

制备了脱乙酰基魔芋葡甘聚糖(d-KGM)的溶胶-凝胶,用红外光谱表征了其脱乙酰基前后的结构转化.探讨了d-KGM溶胶-凝胶的制备条件对其成膜性能及酶固定化的影响.在此基础上将d-KGM用于电极表面葡萄糖氧化酶的固定,制备了相应的葡萄糖传感器,并对传感器的工作条件进行了优化.所制备的传感器灵敏度为240 nA/mmol/L,线性范围为0.1～8 mmol/L,表观米氏常数KM为19.6 mmol/L,稳定性好,寿命长.实验结果表明d-KGM是一种可用于生物传感器中酶固定化的优良材料.     

Hydrolysis of cellobiose by immobilized β-glucosidase entrapped in maintenance-free gel spheres

A crude preparation of Aspergillus niger β-glucosidase (27.5 cello-biase U/mg protein at 40°C, pH 5.0) was immobilized on concanavalin A-Sepharose (CAS). The cellobiase activity of the immobilized enzyme was 1334 U/mg dried CAS or 108 U/mL CAS gel. The β-glucosidase-CAS complex was entrapped within crosslinked propylene glycol alginate/bone-geletin gel spheres that possessed between 0.67 and 2.35 cellobiase U/mL spheres, depending on their size. The effect of cellobiose concentration (10–300 mM) on the activity of native, immobilized, and gel-entrapped enzyme was determined. It was shown that concentrations of cellobiose between 10 and 180 mM were not inhibitory to the entrapped enzyme, although inhibition was found to occur with the native and immobilized enzyme. Exogenous ion addition was not necessary to maintain the structural integrity of the spheres, which were stable for 4 d at 40°C.     

聚苯胺尿酸酶电极性能的研究

依据pH对聚苯胺尿酸酶电极最大响应电流的影响, logim～pH图表明尿酸酶电极的催化活性只与其电离基团的碱性形式有关. 扫描电镜的结果表明, 聚苯胺尿酸酶电极的稳定性与其制备方法有关. 电化学法固定的尿酸酶电极具有高的稳定性.     

Simultaneous purification and reversible immobilization of d-amino acid oxidase from Trigonopsis variabilis on a hydrophobic support

Purification and reversible immobilization of d-amino acid oxidase from Trigonopsis variabilis could be simultaneously accomplished by hydrophobic interaction on Phenyl Sepharose CL-4B in the presence of 50 mM pyrophosphate buffer (pH 8.5). The presence of a high salt concentration of 2M, which is generally required for the hydrophobic interactions, was not essential for the hydrophobic immobilization. The enzyme in free as well as immobilized form was optimally active between pH 7.0 and 9.0. The immobilized preparation could be reused in a batch process for the conversion of d-amino acids to α-keto acids. When the activity of the preparation dropped below practical limits, the gel could be regenerated by water wash and recharged with fresh crude extract from yeast.     

Physical immobilization of Rhizopus oryzae lipase onto cellulose substrate: activity and stability studies

Rhizopus oryzae lipase (ROL) was immobilized by adsorption onto oxidized cellulose fibers and regenerated films. The maximum adsorption level increases with the raise in the amount of carboxylic groups on cellulose surface confirming that adsorption is being governed mainly by electrostatic interaction between the enzyme and the substrate. This hypothesis was further confirmed by zeta-potential measurements showing a decrease in the zeta-potential of the fibers after enzyme adsorption. XPS analysis showed an intensification of the N 1s peak attesting the presence of the enzyme on the surface. The effect of temperature, pH and solvent polarity on the immobilized enzyme activity and stability was investigated. The catalytic esterification of oleic acid with n-butanol has been carried on using hexane as an organic solvent. A high conversion yield was obtained (about 80%) at 37 degrees C with a molar ratio of oleic acid to butanol 1:1 and 150IU immobilized lipase. The adsorption achieved two successive cycles with the same efficiency, and started to lose its activity during the third cycle.     

Chemical modification of silica surface by immobilization of functional groups for extractive concentration of metal ions

Increased utilization of mechanically stable synthetic matrices particularly silica gel as a solid support and its surface modification either by impregnation of organic ligands directly or covalent grafting through spacer unit for extractive concentration of trace elements are highlighted in the present article. Experimental evidences for existence of surface silanol and its chemical nature have explored the idea of silica surface modification. Recent methods of development in functionalized silica synthesis by attachment of various ligands or organic reagents to the silica surface and techniques of characterization of the modified surface have been reported. Analytical applications of various modified silica surfaces, in particular, adsorption of trace elements taking separation and preconcentration into account from complex synthetic mixture as well as natural water is presented.     

Immobilization of copper in organic-inorganic hybrid materials: a highly efficient and reusable catalyst for the Ullmann diaryl etherification

The immobilization of copper in organic-inorganic hybrid materials catalyzing the Ullmann reaction has been described. Phenols reacted with aryl iodides, aryl bromides and aryl chlorides smoothly in the presence of a 3-(2-aminoethylamino)propyl functionalized silica gel immobilized copper catalyst. The protocol involved the use of DMSO as the solvent, and potassium fluoride as the base. The reactions generated the corresponding cross-coupling products in good to excellent yields. Furthermore, the silica-supported copper could be recovered and recycled by a simple filtration of the reaction solution and used for 10 consecutive trials without loss of its reactivity.