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关键词： 基因工程   链霉菌   发酵液脂溶性成分   结构鉴定  

摘要： 该文报道对基因工程链霉菌K3发酵液脂溶性成分的研究.K3发酵液调节PH3,然后用乙酸乙酯提取;再经过Sephadex LH-20柱层析、制备性薄层层析及反相中压液相层析等一系列分离方法进行分离.最后得到四个单一化合物K3-D3、K3-D4、K3-D5和K3-D6.

关键词： 心钠素   包涵体   凝血酶   FPLC  

摘要： 以高效表达的基因工程菌为材料,对以包涵体形式存在的目的产物--心钠素(ANF)融合蛋白进行了酶切及分离纯化。先用Trition X-100和低浓度尿素、盐酸胍洗涤,提高包涵体的纯度。再用高浓度的尿素处理,使蛋白变性溶解,脱氧胆酸钠对蛋白有明显的促溶作用。在非变性条件下进行Sephadex G-75凝胶过滤,FPLC系统纯化,得到目的融合蛋白。用凝血酶对融合蛋白作特异性切割,释放出ANF小肽,经FPLC分离鉴定,与标准ANF有相同的T_(R)值,说明其纯度已达均一。生物活性检测表明:有明显的放免活性和舒张血管、利尿的生理活性。

关键词： 膜分离   生物工程   膜过滤流速   膜过滤阻力  

摘要： 分析了膜分离在生物工程应用中存在的问题和解决上述问题的方法。

关键词： X-rays   TOMOGRAPHY   INDUSTRIAL applications   IMAGING systems   MANUFACTURING industries   INDUSTRIAL radiography  

摘要： X-ray computed tomography (CT) is an important and powerful tool in industrial imaging for obtaining shape and dimensional information of industrial parts. It also serves to provide digital models of parts for inputs to new and emerging technologies in the manufacturing industry which have begun to embrace CT-assisted engineering and design. Since a large number of objects encountered in industrial CT are made of either a single homogenous material or a few homogenous materials, algorithms for discrete tomography should, in principle, yield CT images whose resolution and dimensional accuracy are superior to CT images obtained by conventional algorithms. This in turn should result in significant improvements in the accuracy of boundaries extracted from CT images for digital models of a large class of parts of interest in CT-assisted manufacturing. In this article, we look at some important applications in CT-assisted manufacturing that can benefit from the techniques of discrete tomography, and discuss some of the technical challenges faced in extracting boundaries with the degree of accuracy demanded for engineering and manufacturing applications. (C) 1998 John Wiley & Sons, Inc.

关键词： 大豆Kunitz型胰蛋白酶抑制剂   RT-PCR   DNA序列   抗虫   转基因烟草  

摘要： 从未成熟的大豆子叶中提取总RNA,然后反转录成单链cDNA,以此为模板,用PCR方法扩增出大豆Kunitz型胰蛋白酶抑制剂基因,并克隆到pBluescript KS(+)的 SmaI位点上。序列分析表明:克隆片段大小为663bp,包含了基因完整的编码序列。编码多肽由217个氨基酸组成,其中包括N端25个氨基酸组成的信号肽序列,181个氨基酸组成的成熟蛋白序列和C端11个氨基酸组成的液泡定位信号序列。构建了此基因的一系列植物表达载体,用于烟草、水稻、棉花等作物的转化。

关键词： 香菇   原生质体   再生   分离  

摘要： 本研究通过电镜观察与酶解分析确定香菇(Lentinula edodes)菌丝细胞壁组成.并进行了双核菌丝原生质体的分离和培养.研究发现:酶解过程中,菌丝原生质体一般只从菌丝顶端等新生部位释放出来.合适的渗透剂、菌龄和酶解温度是原生质体得率的重要保证;原生质体再生菌丝过程是一个间歇性的依赖于原生质团涌动流向的过程,再生菌丝的形成经历了原生质体形成突起-哑铃状-分枝状等不同形态类型的再生阶段;再生菌丝体在形态上没有观察到锁状联合,栽培后未能结实,初步判断为单核菌株.

关键词： separation   equipment   residue   water   separation   filter   plate  

摘要： 本文通过对某引进工程渣水分离设备的剖析,提出改进后的新结构。

关键词： Disjunctive Logic Programming   semantics   non-monotonic reasoning  

摘要： This paper gives a brief high-level description of what has been done in the Disjunctive Logic Programming-project (funded by Deutsche Forschungs-Gemeinschaft), undertaken by the University of Koblenz, Germany since July 1995. Presented are the main ideas, the implemented systems and how to access them, and the relevant papers are cited. This paper also serves as a brief survey of the current status of disjunctive logic programming by highlighting important developments and provides enough pointers for further reading.

关键词： central gray   ventrolateral medulla   preganglionic parasympathetic neurons   vagus nerve   autonomic regulation   vocalization  

摘要： We investigated the organization of projections from the rat midbrain periaqueductal gray to nucleus ambiguus and the periambigual region using retrograde and anterograde tract tracing techniques. Retrograde tracing results revealed that neurons that project to nucleus ambiguus arise from three discrete, longitudinally organized columns of neurons located in the supraoculomotor central gray, lateral and ventrolateral periaqueductal gray. Anterograde tracing studies demonstrated that projections from these three columns of periaqueductal gray neurons terminate with topographic specificity in nucleus ambiguus and the periambigual region. Double-labelling studies demonstrated that periaqueductal gray neurons terminate in close contiguity to cholinergic neurons in the compact, semicompact, loose and external formations of nucleus ambiguus. The present results suggest that projections from periaqueductal gray to nucleus ambiguus may mediate, in part, certain cardiovascular adjustments and vocalizations produced by stimulation of periaqueductal gray. (C) 1997 IBRO. Published by Elsevier Science Ltd.

关键词： Blacks   Demography   Economically Disadvantaged   Educationally Disadvantaged   Ethnic Groups   Hispanic Americans   Low Income Groups   Minority Groups   Public Schools   Racial Distribution   Racial Relations   School DesegregationSupreme Court  

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