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W. Laiwattanapaisal J. Yakovleva M. Bengtsson T. Laurell S. Wiyakrutta V. Meevootisom O. Chailapakul J. Emn��us 《Biomicrofluidics》2009,3(1)
Two microfluidic systems have been developed for specific analysis of L-glutamate in food based on substrate recycling fluorescence detection. L-glutamate dehydrogenase and a novel enzyme, D-phenylglycine aminotransferase, were covalently immobilized on (i) the surface of silicon microchips containing 32 porous flow channels of 235 μm depth and 25 μm width and (ii) polystyrene Poros™ beads with a particle size of 20 μm. The immobilized enzymes recycle L-glutamate by oxidation to 2-oxoglutarate followed by the transfer of an amino group from D-4-hydroxyphenylglycine to 2-oxoglutarate. The reaction was accompanied by reduction of nicotinamide adenine dinucleotide (NAD+) to NADH, which was monitored by fluorescence detection (εex=340 nm, εem=460 nm). First, the microchip-based system, L-glutamate was detected within a range of 3.1–50.0 mM. Second, to be automatically determined, sequential injection analysis (SIA) with the bead-based system was investigated. The bead-based system was evaluated by both flow injection analysis and SIA modes, where good reproducibility for L-glutamate calibrations was obtained (relative standard deviation of 3.3% and 6.6%, respectively). In the case of SIA, the beads were introduced and removed from the microchip automatically. The immobilized beads could be stored in a 20% glycerol and 0.5 mM ethylenediaminetetraacetic acid solution maintained at a pH of 7.0 using a phosphate buffer for at least 15 days with 72% of the activity remaining. The bead-based system demonstrated high selectivity, where L-glutamate recoveries were between 91% and 108% in the presence of six other L-amino acids tested. 相似文献
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M. A. Fallah V. M. Myles T. Kr��ger K. Sritharan A. Wixforth F. Varnik S. W. Schneider M. F. Schneider 《Biomicrofluidics》2010,4(2)
Accurately mimicking the complexity of microvascular systems calls for a technology which can accommodate particularly small sample volumes while retaining a large degree of freedom in channel geometry and keeping the price considerably low to allow for high throughput experiments. Here, we demonstrate that the use of surface acoustic wave driven microfluidics systems successfully allows the study of the interrelation between melanoma cell adhesion, the matrix protein collagen type I, the blood clotting factor von Willebrand factor (vWF), and microfluidic channel geometry. The versatility of the tool presented enables us to examine cell adhesion under flow in straight and bifurcated microfluidic channels in the presence of different protein coatings. We show that the addition of vWF tremendously increases (up to tenfold) the adhesion of melanoma cells even under fairly low shear flow conditions. This effect is altered in the presence of bifurcated channels demonstrating the importance of an elaborate hydrodynamic analysis to differentiate between physical and biological effects. Therefore, computer simulations have been performed along with the experiments to reveal the entire flow profile in the channel. We conclude that a combination of theory and experiment will lead to a consistent explanation of cell adhesion, and will optimize the potential of microfluidic experiments to further unravel the relation between blood clotting factors, cell adhesion molecules, cancer cell spreading, and the hydrodynamic conditions in our microcirculatory system. 相似文献
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在对传统情报服务模式进行反思的基础上 ,分析了过渡时期情报服务模式的演变特征 ,探讨了在社会主义市场经济条件下 ,构建情报社会化服务模式的原则 ,并提出了培育信息市场、建立以竞争情报为主体的情报经营服务体系和大力发展信息技术、加速手段现代化等模式优化对策 相似文献
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从社会与经济的关系出发 ,对“既取得经济效益 ,又产生社会效益”的提法提出质疑 ,分析了这一提法对不能直接产生经济效益的事业部门乃至我国市场经济体制的建立可能产生的不良影响 相似文献
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通过检索、统计、分析我国图书馆学１３种核心期刊１９９１～１９９５年论文在各个类目上的分布数据,得出每个类目下的主要期刊,以此分析、比较每种核心期刊的专业倾向性,并由此了解我国图书馆学当前研究的重点 相似文献
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�ҹ���Ϣ��ѯҵ�ķ�չ�Բ��о� 总被引：10，自引：0，他引：10
对我国信息咨询业的发展现状做了概要总结,分析了我国信息咨询业发展中存在的主要问题,并针对这些问题提出了具体对策 相似文献
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论述科技文献中缩略语,尤其是刊名缩写和机构名称缩写的查找方法,并概要介绍几种常用的检索工具 相似文献
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针对信息社会对人才培养的需要,从四个方面论述高等院校图书馆学情报学教育的内容与方法,认为分层次、分阶段、多种方法并举的系统性、连续性教育是目前的最佳选择 相似文献
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̸ͼ����������� 总被引：4，自引：1，他引：3
阐述文献收藏部门在立法问题上制定文献资源保护法的必要性、理论依据、基本内容和立法原则 相似文献