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201.
用柱层析和TLC分离小麦PGIP和植保素 总被引:1,自引:0,他引:1
植物抗病能力大小的测定需要比较准确可靠且相对简便的办法。采用接种病菌于植物上观察染菌情况虽然直观,但受病菌本身的生理状态及外界环境影响很大,且不便于定量的表述。因此,选择合适的生理生化指标作为植物抗性大小的衡量标准,对于植物病理的研究具有重要的意义。选择了小麦体系的两种抗性物质- 小麦植保素和 P G I P作为小麦的抗性指标来分离分析 相似文献
202.
水蓄冷空调系统蓄冷槽中斜温层厚度的数值计算 总被引:2,自引:0,他引:2
介绍了水蓄冷空调系统蓄冷槽中温度场与斜温层厚度的数值求解及影响斜温层厚度的因素。 相似文献
203.
用中腔胞壁比值法测定棉纤维成熟度系数有明确的标准规定,但这些规定有些令人费解.为此作者用折射率跟棉纤维折射率相近的厚壁玻璃管模拟棉纤维在放大镜和高倍显微镜下观察,证实了标准规定的合理和必要性.中腔胞壁比值的理论计算值与实验值准确地符合. 相似文献
204.
U. Mrwa K. Güth J. C. Rüegg R. J. Paul S. Boström R. Barsotti D. Hartshorne 《Cellular and molecular life sciences : CMLS》1985,41(8):1002-1006
Summary The contraction induced by a Ca2+-independent myosin light chain kinase (MLCK-) was characterized in terms of isometric force (Fo), immediate elastic recoil (SE), unloaded shortening velocity (Vus), shortening under a constant load and ATPase activity of chemically skinned smooth muscle preparations. These parameters were compared to those measured in a Ca2+-induced contraction to assess the nature of cross bridge interaction in the MLCK-induced contraction. Fo developed in chicken gizzard fibers as well as SE were similar in contractions elicited by either agent. Vus in the contraction induced by MLCK-(0.36 mg/ml) was similar though averaged 39.3±8.9% less than Vus induced by Ca2+ (1.6x10–6M) in the control fibers. Addition of Ca2+ (1.6x10–6M) to a contraction induced by MLCK-resulted in small increases in both Fo and Vus. Shortening under a constant load was similar for both types of contractions. The contraction induced by MLCK-was accompanied by an increased rate of ATP hydrolysis. The MLCK-induced contraction is thus kinetically similar though not identical to a contraction induced by Ca2+. We conclude that with respect to actin-myosin interaction, MLCK- and Ca2+-induced contractions are similar. 相似文献
205.
Hybrid antibodies can target sites for attack by T cells 总被引:10,自引:0,他引:10
It would be advantageous in the case of certain diseases to be able to focus a strong T-cell response at a chosen target, for example, in treating cancer or infections that have escaped the normal host response. At present, it seems inconceivable that we could use antigen-specific lines or clones of effector T cells for this purpose because of complications due to the major histocompatibility restriction of T-cell specificity and the problem of rejection of transplanted effector cells. Here we describe a novel technology which combines the power of T lymphocytes in eliminating unwanted cells and causing beneficial inflammatory reactions with the great advantages of monoclonal antibodies (their specificity and availability). We show that heteroconjugates of monoclonal antibodies (referred to hereafter as hybrid antibodies), in which one of the component binding sites is anti-T-cell receptor and the other component binding site is directed against any chosen target antigen, can focus T cells to act at the targeted site. Monoclonal antibodies directed against the T-cell receptor, such as the anti-allotype used here, are mitogenic for resting T cells and can be used to induce effector T cells carrying the T-cell receptor determinant which can then be directed against the target by a hybrid antibody. 相似文献
206.
路英娟 《科技情报开发与经济》2004,14(6):220-221
TCP/IP(Transmission Control Protocol/Internet Protocol)即传输控制协议/网间协议是计算机网络之间的一套通用的标准协议,是实现互联网连接和操作的关键。简要介绍了数据传送的一般过程以及TCP/IP协议通信所包括的3个基本要素(IP地址、子网掩码、网关地址)。 相似文献
207.
208.
209.
A model for interfacial activation in lipases from the structure of a fungal lipase-inhibitor complex 总被引:37,自引:0,他引:37
A M Brzozowski U Derewenda Z S Derewenda G G Dodson D M Lawson J P Turkenburg F Bjorkling B Huge-Jensen S A Patkar L Thim 《Nature》1991,351(6326):491-494
Lipases are hydrolytic enzymes which break down triacylglycerides into free fatty acids and glycerols. They have been classified as serine hydrolases owing to their inhibition by diethyl p-nitrophenyl phosphate. Lipase activity is greatly increased at the lipid-water interface, a phenomenon known as interfacial activation. X-ray analysis has revealed the atomic structures of two triacylglycerol lipases, unrelated in sequence: the human pancreatic lipase (hPL)4, and an enzyme isolated from the fungus Rhizomucor (formerly Mucor) miehei (RmL). In both enzymes the active centres contain structurally analogous Asp-His-Ser triads (characteristic of serine proteinases), which are buried completely beneath a short helical segment, or 'lid'. Here we present the crystal structure (at 3 A resolution) of a complex of R. miehei lipase with n-hexylphosphonate ethyl ester in which the enzyme's active site is exposed by the movement of the helical lid. This movement also increases the nonpolarity of the surface surrounding the catalytic site. We propose that the structure of the enzyme in this complex is equivalent to the activated state generated by the oil-water interface. 相似文献
210.
Selective immortalization of murine macrophages from fresh bone marrow by a raf/myc recombinant murine retrovirus 总被引:4,自引:0,他引:4
Myeloid precursors can be grown in vitro in the presence of specific growth factors; however, their expansion is limited by a competing process of terminal differentiation. Proto-oncogenes seem to be involved in cellular proliferation and/or differentiation and may also play a role in the myelopoietic process. Murine myeloid precursors which are grown in vitro with growth factors respond with augmented self-renewal upon infection with recombinant retroviruses carrying the v-myc or v-src oncogenes, suggesting a synergism or complementation between some viral oncogenes (v-onc) and certain growth factors. We now show that the combination of two v-onc genes (raf and myc) induces the selective proliferation of monocytic cells from fresh murine bone marrow (BM) in the absence of a specific growth factor supplement. Depending on the culture conditions these cells can either differentiate and cease to proliferate or grow continuously, thus mimicking the alternative pathways that can be followed by committed BM stem cells in vivo. 相似文献