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排序方式: 共有162条查询结果,搜索用时 15 毫秒
91.
You M Zhu Z Liu H Gulbakan B Han D Wang R Williams KR Tan W 《ACS applied materials & interfaces》2010,2(12):3601-3605
An efficient pyrene-assisted method has been developed for the photolysis of disulfide bonds, with 77% of disulfides cleaved after only 20 min of irradiation (0.3W) at 350 nm. By employing a DNA framework, it was possible to observe both a distance-dependent cleavage pathway and a radical-forming photoreaction mechanism. To demonstrate the biomedical applications of such pyrene disulfide molecular assemblies, a DNA micelle structure and DNAzyme analog were further studied. Rapid photodriven disassembly of DNA micelles was achieved, allowing the further design of controlled pharmaceutical release at the target region and at a specific time. The DNAzyme analog can carry out multiple turnover reactions that follow the Michaelis-Menten equation, with a kcat of 10.2 min(-1) and a KM of 46.3 μM (0.3W 350 nm light source), comparable to that of common DNAzymes, e.g., 8-17 DNAzyme. 相似文献
92.
Mahiran Basri Kamaruzaman Ampon Wan Md. Zin Wan Yunus Che Nyonya A. Razak A. Bakar Salleh 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》1995,64(1):10-16
Monomethoxypolyethylene glycols (PEG) of molecular masses 1900 and 5000 were activated using p-nitrophenyl chloroformate to form PEG–nitrophenyl carbonates (activated PEG) with high yield (96–98%). The activated PEG was covalently attached to Candida rugosa lipase. Increasing the molar ratio of activated PEG to the enzyme increased the degree of lipase modification. These modified lipases exhibited specific ester synthesis activities on organic solvents compared with native lipase. The degree of activity enhancement depended on the size of activated PEG used and the degree of modification of the enzyme. Maximal activity was attained after exhaustive of modification. The effects of different solvents, reaction temperature, and fatty acids on the esterification activity and the stability of the modified enzyme were investigated. The optimum esterification temperature (40° C) and preference of fatty acids as acyl donors of the modified lipase were very similar to those of the native enzyme. The modified lipase exhibited higher activity non-polar solvents than in polar solvents, and showed higher temperature, solvent and storage stability then the native lipase. 相似文献
93.
Taha Ahmed Bazil Calvo Ramón Miguel de Haro Ariet Leandro 《International Journal of Wireless Information Networks》2003,10(2):101-104
The downlink power control problem in W-CDMA is studied using a new near optimum power control scheme (model). The downlink cell capacity is given for both the old given by Gejji and our new model. A capacity increase of 7.5% for the special case = 0 (no orthogonality between users) and a generalization of the old model are obtained using the new model. 相似文献
94.
Senturk HB Gundogdu A Bulut VN Duran C Soylak M Elci L Tufekci M 《Journal of hazardous materials》2007,149(2):317-323
A simple and accurate method was developed for separation and enrichment of trace levels of gold in environmental samples. The method is based on the adsorption of Au(III)-diethyldithiocarbamate complex on Amberlite XAD-2000 resin prior to the analysis of gold by flame atomic absorption spectrometry after elution with 1 molL(-1) HNO3 in acetone. Some parameters including nitric acid concentration, eluent type, matrix ions, sample volume, sample flow rate and adsorption capacity were investigated on the recovery of gold(III). The recovery values for gold(III) and detection limit of gold were greater than 95% and 16.6 microgL(-1), respectively. The preconcentration factor was 200. The relative standard deviation of the method was <6%. The adsorption capacity of the resin was 12.3 mg g(-1). The validation of the presented procedure was checked by the analysis of CRM-SA-C Sandy Soil certified reference material. The presented procedure was applied to the determination of gold in some environmental samples. 相似文献
95.
Emilia Abdulmalek Mahashanon Arumugam Mahiran Basri Mohd Basyaruddin Abdul Rahman 《International journal of molecular sciences》2012,13(10):13140-13149
Herein, an efficient epoxidation of 1-nonene is described. In a simple epoxidation system, commercially available Novozym 435, an immobilized Candida antarctica lipase B, and hydrogen peroxide (H2O2) were utilized to facilitate the in situ oxidation of phenylacetic acid to the corresponding peroxy acid which then reacted with 1-nonene to give 1-nonene oxide with high yield and selectivity. The aliphatic terminal alkene was epoxidised efficiently in chloroform to give an excellent yield (97%–99%) under the optimum reaction conditions, including temperature (35 °C), initial H2O2 concentration (30%), H2O2 amount (4.4 mmol), H2O2 addition rate (one step), acid amount (8.8 mmol), and stirring speed (250 rpm). Interestingly, the enzyme was stable under the single-step addition of H2O2 with a catalytic activity of 190.0 Ug−1. The entire epoxidation process was carried out within 12 h using a conventional water bath shaker. 相似文献
96.
Characterization of membrane-bound lipase from a thermophilic Rhizopus oryzae isolated from palm oil mill effluent 总被引:1,自引:0,他引:1
C. N. A. Razak R. Musani M. Basri A. B. Salleh 《Journal of the American Oil Chemists' Society》1999,76(2):171-174
The characteristics of the membrane-bound lipase from a thermophilic Rhizopus oryzae were studied. The pH and temperature optima for lipase activity were at 7.0 and 37°C, respectively. The enzyme was stable
and acidic conditions, retaining more than 80% of its initial activity at pH 4.0 after 30 min incubation. It was stable up
to 50°C with 70% of initial activity retained after 3 h incubation. The enzyme is 1,3 specific and exhibits substrate preference.
Monoacid triglyceride substrates were hydrolyzed better than methyl esters, polyoxysorbitan and sorbitan substrates. 相似文献
97.
98.
99.
Lariyah Mohd Sidek Hidayah Basri Mohamed Roseli Zainal Abidin Lira Chow Hock Md Nasir Md Nor Nor Azazi Zakaria 《土木工程与建筑:英文版》2014,(1):107-114
Gross pollutants are the primary targeted pollutants in urban catchment management for urban water quality improvement as well as mitigation of flood. Apart from aesthetically unattractive because of its visibility, gross pollutants also contributes to degradation of river water quality and loss of aquatic habitat as it carries harmful pollutants such as oxygen demanding material, hydrocarbons and heavy metals. This study analyzed trend of gross pollutant generated from two urban residential areas located in Selangor, Malaysia. The median value of gross pollutant load obtained fi'om the Amanah Apartment and Bandar Botanic are 347.41 kg/ha/year and 32.46 kg/ha/year, respectively. Relationship between gross pollutant wet load with rainfall depths was derived using regression equation. A significant trend of increasing gross pollutant wet load into drainage system with increasing rainfall depth was observed. The behavior of pollutant load is related to the one observed in Australia. 相似文献
100.
Uswatun Hasanah Zaidan Mohd Basyaruddin Abdul Rahman Siti Salhah OthmanMahiran Basri Emilia AbdulmalekRaja Noor Zaliha Raja Abdul Rahman Abu Bakar Salleh 《Food chemistry》2012,131(1):199-205
Enzyme immobilisation technology is an effective means to improve sugar ester production through the employment of biocatalysts. In the present study, immobilisation of Candida rugosa (CRL) lipase onto amino-activated mica is performed via covalent bonding (namely Amino-CRL) and the cross-linking of lipases into nano-reactors through physical adsorption (namely NER-CRL). Free and immobilised lipases were tested for their esterification activities. Specific activities for Amino-CRL and NER-CRL increased by 2.4 and 2.6-fold, respectively, upon immobilisation. Extending this work, immobilised lipases have novel capabilities in the synthesis of sugar esters. The optimised conditions for sugar fatty acid ester syntheses are 48 h at 2:1 of molar ratio of lactose sugar to capric acid at 55 °C. Furthermore, a high operational stability with half-lives of over 13 and 10 runs was achieved for NER-CRL and Amino-CRL, respectively, indicating the efficiency of the immobilisation process. 相似文献