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81.
采用光谱法和胰酯酶分解法对大果木姜子油酯中分得的结晶C—I组成进行了分析,结果表明C—I是由11种甘油三酯组成。其中2-位为月硅酸的甘油三酯占91.80%,1,3-位脂肪酸主要为癸酸和月桂酸,甘油三酯的组成中,CLC占62.24%,LLC占24.50%。 相似文献
82.
青龙河底栖无脊椎动物群落结构及其水质评价 总被引:17,自引:3,他引:14
本文论述了青龙河底栖生物种类、数量、分布和结构等特点及其与环境因子间的关系。应用Beck、Gleason、Shannon、Simpson等生物指数对水质状况进行评价。结果表明青龙河除个别断面受污染外,大部分河段属尚清洁水。 相似文献
83.
84.
René Roy François D. Tropper Anna Romanowska Marie Letellier Luc Cousineau Serge J. Meunier Janusz Boratyński 《Glycoconjugate journal》1991,8(2):75-81
Starting from peracetylated chloro- or bromo-glycosyl donors ofN-acetylneurmainic acid,N-acetylglucosamine, glucose and lactose, the correspondingp-formylphenyl glycosides were synthesized stereospecifically under phase transfer catalysed conditions at room temperature in yields of 38–67%. After Zemplén de-O-acetylation, the formyl groups were directly and chemoselectively coupled to the lysine residues of bovine serum albumin by reductive amination using sodium cyanoborohydride. The conjugation reactions were followed as a function of time and under a series of different molar ratios of the reactants to provide glycoconjugates of varying degree of antigenicities. Thus, carbohydrate protein conjugates were made readily available using essentially two key reactions.Presented in part at the 15th International Carbohydrate Symposium, Yokohama, Japan, August 12–17, 1990. 相似文献
85.
86.
The refined 2.3 A crystal structure of human leukocyte elastase in a complex with a valine chloromethyl ketone inhibitor 总被引:4,自引:0,他引:4
The stoichiometric complex formed between human leukocyte elastase and a synthetic MeO-Suc-Ala-Ala-Pro-Val chloromethyl ketone inhibitor was co-crystallized and its X-ray structure determined, using Patterson search methods. Its structure has been crystallographically refined to a final R value of 0.145 (8.0 and 2.3 A). The enzyme structure is very similar to that recently observed in a complex formed with the ovomucoid third domain from turkey [(1986) EMBO J. 5,2453-2458]. The rms deviation of all alpha-carbon atoms is 0.32 A. The peptidic inhibitor is bound in a similar overall conformation as the ovomucoid binding segment. Covalent bonds are formed between Val-P1 of the inhibitor and His-57 NE2 and Ser-195 OG of the enzyme. The carbonyl carbon is tetrahedrally deformed to a hemiketal. The valine side chain is arranged in the S1 pocket in the g-conformation. 相似文献
87.
The effects of eluent composition, pH, and chaotropic agents on the recovery of T2, MS2, and indigenous coliphages from various foods were investigated. Additionally, methods of sample suspension and clarification were evaluated for coliphage recovery and application to various foods. Clarified sample suspensions were assayed for coliphages with a modified agar layer technique and appropriate Escherichia coli hosts. Centrifugation and polypropylene mesh filtration were more rapid and effective than glass wool filtration for clarification of sample suspensions and subsequent recovery of coliphages. Blending, stomaching, and shaking procedures were generally comparable for sample liquefaction and release of coliphages from foods. Complex basal eluents, EC medium and 1% casein, were generally more effective than a less complex eluent, phosphate buffer, for elution of coliphages from foods. For most foods, incorporation of sodium chloride or chaotropic agents, i.e., sodium trichloroacetate, urea, Tween 80, Triton X-100, and sodium nitrate, into basal eluents did not enhance recovery of coliphages. Indigenous coliphage recovery was not affected by sample suspension pH over a range of 6.0 to 9.0. With an optimal procedure, i.e., EC medium eluent, blending, and centrifugation, the recovery of T2 and MS2 ranged from 48 to 81% and from 58 to 100%, respectively, depending on the food type. 相似文献
88.
Y F Wei K Heghinian R L Bell B A Jakschik 《Journal of immunology (Baltimore, Md. : 1950)》1986,137(6):1993-2000
The interaction of mast cells with other leukocytes during immediate hypersensitivity reactions was tested by in vivo and in vitro experiments. Intraperitoneal challenge of passively sensitized rats with antigen caused the production of peptidoleukotrienes, leukotriene (LT)B4, thromboxane (TX)B2, and 6-keto-prostaglandin (PG) F1 alpha in the peritoneal cavity. Pretreatment of the rats with thioglycollate i.p. markedly changed the amount of eicosanoids formed. When polymorphonuclear leukocytes were the predominant cell type in the peritoneal exudate, both LTC4 and 6-keto-PGF1 alpha were decreased by 75% each and TXB2 by 50%. When elicited macrophages were predominant, there was an additional reduction in LTC4 by 68% as compared with 18 hr after thioglycollate treatment, but no additional change in the other arachidonic acid metabolites. In vitro antigen challenge of passively sensitized mouse bone marrow-derived mast cells caused the release of LTC4, LTB4, 6-trans-LTB4, 5-hydroxyeicosatetraenoic (5-HETE), and TXB2. Exposure to antigen of these mast cells in the presence of resident peritoneal macrophages markedly altered eicosanoid formation. Early in the time course (2 to 15 min), macrophages markedly enhanced all 5-lipoxygenase products. However, later in the time course (30 to 120 min), these products were decreased. This decrease was reversed by catalase and superoxide dismutase, which suggests the involvement of oxygen radicals. These active oxygen species also seemed to be generated by mast cells, because these enzymes caused an increase in 5-lipoxygenase products when mast cells were challenged alone. RIA of cyclooxygenase products showed that mast cells released only TXB2 when stimulated with antigen. When they were stimulated in the presence of macrophages, TXB2 and also PGE2 and 6-keto-PGF1 alpha were synthesized. Therefore, macrophages probably contribute the PGE2 and 6-keto-PGF1 alpha. Because the same amount of TXB2 was generated whether macrophages were present or not, the mast cells seem to be the major source of this compound. These data indicate that macrophages and possibly polymorphonuclear leukocytes participate in immediate hypersensitivity reactions. 相似文献
89.
本文研究了北京东郊污灌区重金属在作物—土壤中的迁移、分布、积累规律,证实本区蔬菜中汞含量比粮食作物约大3—15倍,比水果约大6—200倍。麦粒、糙米中的Cu、Hg、Cd、Pb、Ni的含量与土壤含量相关性不显著。架豆中重金属含量与土壤中重金属含量的相关性,只有Zn,Pb达显著水平。白菜土有机质含量与重金属含量相关性达显著水平,而白菜的重金属含量与土壤的重金属含量相关性却不显著。说明除了土壤中重金属的总量外,有效态含量的多少,是影响本区作物吸收积累重金属的主要因素。 本区施污泥的土壤和生长的作物Cd/Zn大部小于1%、盆栽试验证明:施用本区污泥污水对水稻生长发育的影响比施污泥灌清水的影响大些,因此,施用含重金属污泥时,最好不要超过5000斤/亩。大田和室内模拟试验证明:重金属从土壤中迁移到植物,由植物带走输出的量极少,其中以带走输出的Hg、Cd,As相对较多,带走输出的Pb、Cr相对的少些。 相似文献
90.