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排序方式: 共有197条查询结果,搜索用时 15 毫秒
1.
研究了疏水柱吸附分离工业酵母(S.Cerevisiae)中的L-天门冬氨酸酶.考察了三种疏水吸附剂TskgelButy_Toyopearl,TskgelPhenyl_Toyopearl和TsKgelEther_Toyopearl650C的吸附性能.研究表明,通过选择控制流动相的pH值和离子强度,一次吸附过程中L-天门冬氨酸酶的分离纯化纯度可提高14倍并保持较高的活性。实验还考察了吸附等温线类型和温度等因素的影响.结果表明,酵母中分子的电荷和疏水性是疏水柱吸附的重要影响因素. 相似文献
2.
Summary The leaf of the bitter oliveOlea europaea (Oleaceae) is heavily coated by almost pure oleanolic acid, which forms part of a multichemical defense against fungal attack.We thank Mr K. A. Hoelmer for taking the electron micrographs and also Professor T. Kamikawa for NMR measurements. 相似文献
3.
H. Takeuchi T. Morimasa M. Matsumoto 《Cellular and molecular life sciences : CMLS》1977,33(7):938-939
Summary Several peptides were separated from-chymotrypsin-treated physalaemin by high voltage paper electrophoresis, and inhibition of the excitability of a molluscan giant neurone (tonically autoactive neurone) by the tripeptide, Lys-Phe-Tyr, was demonstrated.We thank Dr Sadaaki Iwanaga of Osaka University and Dr Atsuo Inoue of Daiichi Pharmaceutical CO for their helpful advice and the donation of the tripeptide (Lys-Phe-Tyr). 相似文献
4.
Structure,biosynthesis and functions of glycoprotein glycans 总被引:14,自引:0,他引:14
Eric G. Berger Eckhart Buddecke Johannis P. Kamerling Akira Kobata James C. Paulson Johannes F. G. Vliegenthart 《Cellular and molecular life sciences : CMLS》1982,38(10):1129-1162
Since the pioneering work on structure and function of heteroglycans compiled in the classical books edited by A. Gottschalk in 19721, there have been several promising developments in glycoconjugate research, as reviewed in this article.In Part 1, contributed by A. Kobata, current knowledge on heteroglycan structures is presented and representative examples taken from higher organisms are given. Part 2, written by J. F. G. Vliegenthart and J. P. Kamerling, covers the most important achievements in methodology: procedures to obtain pure glycans and to analyze their structures. Part 3, contributed by J. Paulson, is devoted to biosynthesis of glycans now describable as pathways since several of the glycosyltransferases have been isolated and analyzed for specificity. In Part 4, contributed by E. Buddecke, current knowledge on functional roles of glycans is presented. It will become apparent that the prerequisite for valid work either in biosynthetic or functional context depends on solid structural information. This is particularly true whenever glycosyltransferase reaction products are being analyzed, or glycans involved in biological functions are investigated. Although in past years, a great deal of important knowledge has been gathered by use of crude glycosidase or glycosyltransferase activities (a notable example is found in reference 2), one may now postulate that glycans implicated in biological reactions should be thoroughly analyzed.This review may familiarize newcomers with the field of glycoconjugate research with special emphasis on glycoprotein glycans. Glycolipids are not included in this article as they have recently been reviewed by S. I. Hakomori3. The reader is also referred to several excellent monographs4,5 and the Proceedings of the Glycoconjugate Symposia held biannually6–8. 相似文献
5.
Influence of the Gulf Stream on the troposphere 总被引:13,自引:0,他引:13
The Gulf Stream transports large amounts of heat from the tropics to middle and high latitudes, and thereby affects weather phenomena such as cyclogenesis and low cloud formation. But its climatic influence, on monthly and longer timescales, remains poorly understood. In particular, it is unclear how the warm current affects the free atmosphere above the marine atmospheric boundary layer. Here we consider the Gulf Stream's influence on the troposphere, using a combination of operational weather analyses, satellite observations and an atmospheric general circulation model. Our results reveal that the Gulf Stream affects the entire troposphere. In the marine boundary layer, atmospheric pressure adjustments to sharp sea surface temperature gradients lead to surface wind convergence, which anchors a narrow band of precipitation along the Gulf Stream. In this rain band, upward motion and cloud formation extend into the upper troposphere, as corroborated by the frequent occurrence of very low cloud-top temperatures. These mechanisms provide a pathway by which the Gulf Stream can affect the atmosphere locally, and possibly also in remote regions by forcing planetary waves. The identification of this pathway may have implications for our understanding of the processes involved in climate change, because the Gulf Stream is the upper limb of the Atlantic meridional overturning circulation, which has varied in strength in the past and is predicted to weaken in response to human-induced global warming in the future. 相似文献
6.
A comparative view of insect circadian clock systems 总被引:1,自引:0,他引:1
7.
In some butterfly species males attach a large external mating plug termed a sphragis to the female abdomen during mating. This is derived from male accessory secretions and covers the female ostium bursae and surrounding areas, thus preventing or delaying remating. Specimens of all 12 species of the genera Zerynthia, Allancastria and Bhutanitis (Lepidoptera: papilionidae), which form a natural clade within the Zerynthiini, were examined for presence or absence of a sphragis and their male and female genitalia were studied. In all three genera female genitalia lack a typical sinus vaginalis and the sterigma is modified to form an exposed, shiny, well-sclerotized genital plate, derived from the fusion and expansion of the lamellae ante- and postvaginales. The exposed ostium bursae is situated near the posterior end of the genital plate in Zerynthia, whereas in Allancastria and Bhutanitis it is near the anterior end. A crude irregularly formed sphragis was found at least facultatively in all species. The sphragides of Zerynthia and Bhutanitis were generally poorly developed, in most cases only partially covering the female genital plate. In Allancastria the sphragis mostly covered the genital plate entirely, and generally incorporated numerous long scales derived from the male’s 8th abdominal segment; scales were sometimes sparse or absent, probably due to depletion from repeated matings by males. In Zerynthia, males lacked the dense terminal abdominal tuft of elongated scales found in Allancastria, and their sphragis lacked scales. The sphragis of Bhutanitis thaidina incorporated scales from the male valves, whereas in the B. lidderdalii sphragis (and probably B. ludlowi) the scales derived from the male’s 8th abdominal segment. The role of the scales and possible reasons for the difference in the development of the sphragis among these genera are discussed. 相似文献
8.
9.
10.
Tezuka H Abe Y Iwata M Takeuchi H Ishikawa H Matsushita M Shiohara T Akira S Ohteki T 《Nature》2007,448(7156):929-933
Immunoglobulin-A has an irreplaceable role in the mucosal defence against infectious microbes. In human and mouse, IgA-producing plasma cells comprise approximately 20% of total plasma cells of peripheral lymphoid tissues, whereas more than 80% of plasma cells produce IgA in mucosa-associated lymphoid tissues (MALT). One of the most biologically important and long-standing questions in immunology is why this 'biased' IgA synthesis takes place in the MALT but not other lymphoid organs. Here we show that IgA class-switch recombination (CSR) is impaired in inducible-nitric-oxide-synthase-deficient (iNOS-/-; gene also called Nos2) mice. iNOS regulates the T-cell-dependent IgA CSR through expression of transforming growth factor-beta receptor, and the T-cell-independent IgA CSR through production of a proliferation-inducing ligand (APRIL, also called Tnfsf13) and a B-cell-activating factor of the tumour necrosis factor (TNF) family (BAFF, also called Tnfsf13b). Notably, iNOS is preferentially expressed in MALT dendritic cells in response to the recognition of commensal bacteria by toll-like receptor. Furthermore, adoptive transfer of iNOS+ dendritic cells rescues IgA production in iNOS-/- mice. Further analysis revealed that the MALT dendritic cells are a TNF-alpha/iNOS-producing dendritic-cell subset, originally identified in mice infected with Listeria monocytogenes. The presence of a naturally occurring TNF-alpha/iNOS-producing dendritic-cell subset may explain the predominance of IgA production in the MALT, critical for gut homeostasis. 相似文献