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Qian Rong LI* Ting Hu ZHANG Robert S.WARD Structure Research Laboratory University of Science Technology of China Hefei Chemistry Department University of Wales Swansea Singleton Park Swansea SA PP UK 《中国化学快报》2001,(12)
Introduction 2, 3-Dichloro-5, 6-dicyanobenzoquinone (DDQ) can react with lignans of the mono- arylidene-butyrolactone1, aryltetralin2, dibenzylbutane3 and aryltetralin-butyrolactone4,5 series. We have studied the reactions of this reagent with podophyllotoxin 1, which is a well-known natural product on account of its long history of use in folk medicine and the biological activity of its many derivatives6. In particular, derivatives of 4-demethyl epipodophyllotoxin are used in cancer chemo… 相似文献
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Glucose 2-oxidase (pyranose oxidase, pyranose:oxygen-2-oxidoreductase, EC 1.1.3.10) from Coriolus versicolor catalyses the oxidation of d-glucose at carbon 2 in the presence of molecular O2 producing d-glucosone (2-keto-glucose and d-arabino-2-hexosulose) and H2O2. It was used to convert d-glucose into d-glucosone at moderate pressures (i.e. up to 150 bar) with compressed air in a modified commercial batch reactor. Several
parameters affecting biocatalysis at moderate pressures were investigated as follows: pressure, [enzyme], [glucose], pH, temperature,
nature of fluid and the presence of catalase. Glucose 2-oxidase was purified by immobilized metal affinity chromatography
on epoxy-activated Sepharose 6B-IDA-Cu(II) column at pH 6.0. The rate of bioconversion of d-glucose increased with the pressure since an increase in the pressure with compressed air resulted in higher rates of conversion.
On the other hand, the presence of catalase increased the rate of reaction which strongly suggests that H2O2 acted as inhibitor for this reaction. The rate of bioconversion of d-glucose by glucose 2-oxidase in the presence of either nitrogen or supercritical CO2 at 110 bar was very low compared with the use of compressed air at the same pressure. The optimum temperature (55°C) and
pH (5.0) of d-glucose bioconversion as well as kinetic parameters for this enzyme were determined under moderate pressure. The activation
energy (E
a) was 32.08 kJ mol−1 and kinetic parameters (V
max, K
m, K
cat and K
cat/K
m) for this bioconversion were 8.8 U mg−1 protein, 2.95 mM, 30.81 s−1 and 10,444.06 s−1 M−1, respectively. The biomass of C. versicolor as well as the cell-free extract containing glucose 2-oxidase activity were also useful for bioconversion of d-glucose at moderate pressures. The enzyme was apparently stable at moderate pressures since such pressures did not affect
significantly the enzyme activity. 相似文献
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Mejri Faiza Karmali Amin Jaoued Najeh Casabianca Hervé Hosni Karim 《Applied biochemistry and biotechnology》2019,189(2):576-588
Applied Biochemistry and Biotechnology - In this study, peroxidases (PODs) from three waste by-products: broad bean pods (BBP), pea pods (PP), and artichoke stems (ARS) were purified and their... 相似文献
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The aim of this work was to devise a one‐step purification procedure for monoclonal antibodies (MAbs) of IgG class by immobilized metal affinity chromatography (IMAC). Therefore, several stationary phases were prepared containing immobilized metal chelates in order to study the chromatographic behaviour of MAbs against wild‐type amidase from Pseudomonas aeruginosa. Such MAbs adsorbed to Cu(II), Ni(II), Zn(II) and Co(II)–IDA agarose columns. The increase in ligand concentration and the use of longer spacer arms and higher pH values resulted in higher adsorption of MAbs into immobilized metal chelates. The dynamic binding capacity and the maximum binding capacity were 1.33 ± 0.015 and 3.214 ± 0.021 mg IgG/mL of sedimented commercial matrix, respectively. A KD of 4.53 × 10−7 m was obtained from batch isotherm measurements. The combination of tailor‐made stationary phases of IMAC and the correct selection of adsorption conditions permitted a one‐step purification procedure to be devised for MAbs of IgG class. Culture supernatants containing MAbs were purified by IMAC on commercial‐Zn(II) and EPI‐30–IDA–Zn(II) Sepharose 6B columns and by affinity chromatography on Protein A‐Sepharose CL‐4B. This MAb preparation revealed on SDS–PAGE two protein bands with Mr of 50 and 22 kDa corresponding to the heavy and light chains, respectively. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
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