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881.
Insights into the local residual entropy of proteins provided by NMR relaxation. 总被引:4,自引:3,他引:1 下载免费PDF全文
Z. Li S. Raychaudhuri A. J. Wand 《Protein science : a publication of the Protein Society》1996,5(12):2647-2650
A simple model is used to illustrate the relationship between the dynamics measured by NMR relaxation methods and the local residual entropy of proteins. The expected local dynamic behavior of well-packed extended amino acid side chains are described by employing a one-dimensional vibrator that encapsulates both the spatial and temporal character of the motion. This model is then related to entropy and to the generalized order parameter of the popular "model-free" treatment often used in the analysis of NMR relaxation data. Simulations indicate that order parameters observed for the methyl symmetry axes in, for example, human ubiquitin correspond to significant local entropies. These observations have obvious significance for the issue of the physical basis of protein structure, dynamics, and stability. 相似文献
882.
883.
双水相电泳分离蛋白质的研究 总被引:2,自引:0,他引:2
近几年来,随着生物技术的迅速发展,制备型电泳技术的研究得到了重视。然而由于技术上的原因,大规模的制备型电泳技术的研究还未能取得突破。阻碍电泳放大的一个主要问题是由于电加热作用而导致的热对流对电泳分离的破坏。为解决这一问题,人们提出了许多方法。例如,在太空的微重力环境下进行电泳,应力稳定自由流动电泳,循环等电聚焦和区带电泳,色谱电泳和等电膜等电聚焦等。这些方法在电泳放大上都取得了一定的进展,但各有其局限性。最近,Clark提出利用双水相的液液界面阻止热对流的设想,为开发大规模的制备型电泳技术开辟了一条新途径、Raghava Rao等在两种双水相体系上施加电场后成倍地缩短了分相时间。Levine和Bier采用U型管电泳装置研究了双水相体系中血红蛋白的电泳迁移率,观测到界面有阻滞作用。Clark在柱型电泳装置中进行了一组双水相萃取肌红蛋白的简单实验。在10mA的恒电流下电泳40min之后,肌红蛋白的分配系数为7.5,而当电场反向后,分配系数变为0.04,界面阻力并不显著,两者结论并不一致。 相似文献
884.
885.
DISCOVERY OF VERTEBRATE FOSSILS AND PALEOLITHIC ARTIFACTS IN DANJIANG SUBMERGING AREA AND ITS IMPLICATIONS 总被引:1,自引:1,他引:0
IntheareatobefloodedinthesecondengineeringstagefortheDanjiangreservoir,wediscovered16vertebratefossillocalitiesand52Paleolithicsitesin1994,andcollected603artifactsandmanyfossils.Ofthel6new1yfoundvertebratefossillocalities,threearereptilesitesrepresentedbydinosaureggsandlimbbones,andl3producemamma1s,including4Pale0gene,2Ne0geneand7Quaternarysites'ThemammalianlocalitiesareofPale0cene,Eocene,EarlyMiocene,andPli0ceneorEarlyPleistocene,MiddleandIntePleistocene,respectively.Theyfillinsomestrat… 相似文献
886.
887.
David A. Rouse Joseph A. DeVito Zhongming Li Heather Byer & Sheldon L. Morris 《Molecular microbiology》1996,22(3):583-592
Recent studies examining the molecular mechanisms of isoniazid (INH) resistance in Mycobacterium tuberculosis have demonstrated that a significant percentage of drug-resistant strains are mutated in the katG gene which encodes a catalase–peroxidase, and the majority of these alterations are missense mutations which result in the substitution of a single amino acid. In previous reports, residues which may be critical for enzymatic activity and the drug-resistant phenotype have been identified by evaluating INH-resistant clinical isolates and in vitro mutants. In this study, site-directed mutagenesis techniques were utilized to alter the wild-type katG gene from M. tuberculosis at 13 of these codons. The effects of these mutations were determined using complementation assays in katG -defective, INH-resistant strains of Mycobacterium smegmatis and Mycobacterium bovis BCG. This mutational analysis revealed that point mutations in the katG gene at nine of the 13 codons can cause drug resistance, and that enzymatic activity and resistance to INH are inversely related. In addition, mutations in the mycobacterial catalase–peroxidase which reduce catalase activity also decrease peroxidase activity. 相似文献
888.
889.
Further progress towards a catalogue of all Arabidopsis genes: analysis of a set of 5000 non-redundant ESTs 总被引:9,自引:1,他引:8
Richard Cooke Monique Raynal Michele Laudi Franoise Grellet Michel Delseny Peter-Christian Morris Danile Guerrier Jrme Giraudat Franoise Quigley Grard Clabault You-Fang Li Rgis Mache Micheline Krivitzky Isabelle Jean-Jacques Gy Martin Kreis Alain Lecharny Yves Parmentier Jacqueline Marbach Jacqueline Fleck Bernadette Clment Gabriel Philipps Christine Herv Claude Bardet Dominique Tremousaygue Bernard Lescure Christophe Lacomme Dominique Roby Marie-Franoise Jourjon Patrick Chabrier Jean-Louis Charpenteau Thierry Desprez Joelle Amselem Helen Chiapello Herman Hfte 《The Plant journal : for cell and molecular biology》1996,9(1):101-124
Nearly 7000 Arabidopsis thaliana -expressed sequence tags (ESTs) from 10 cDNA libraries have been sequenced, of which almost 5000 non-redundant tags have been submitted to the EMBL data bank. The quality of the cDNA libraries used is analysed. Similarity searches in international protein data banks have allowed the detection of significant similarities to a wide range of proteins from many organisms. Alignment with ESTs from the rice systematic sequencing project has allowed the detection of amino acid motifs which are conserved between the two organisms, thus identifying tags to genes encoding highly conserved proteins. These genes are candidates for a common framework in genome mapping projects in different plants. 相似文献
890.
Gejiao Wang Stefano Castiglione Ying Chen Ling Li Yifan Han Yingchuan Tian Dean W. Gabriel Yinong Han Kequiang Mang Francesco Sala 《Transgenic research》1996,5(5):289-301
Insect-resistant poplar (Populus nigra L.) plants have been produced by infecting leaves withAgrobacterium tumefaciens strains carrying a binary vector containing different truncated forms of aBacillus thuringiensis (B.t.) toxin gene under a duplicated CaMV 35S promoter. Putative transgenic plants were propagated by cuttings at two experimental farms (in Beijing and Xinjiang, China). At 2–3 years after transformation, 17 of them were selected on the bases of insect-tolerance and good silvicultural traits, and evaluated for insect resistance, for the presence of theB.t. toxin DNA fragment (Southern blots and PCR) and for the expression of the transgene (western and northern blots). Somaclonal variation, as suggested by the appearance of permanent changes in the shape of the leaves, was also investigated with molecular tools (RFLP (restriction fragment length polymorphism), RAPD (random amplified polymorphic DNA) and microsatellite DNA).Bioassays withApochemia cineraius andLymantria dispar on the leaves of the selected clones showed different and, in some cases, high levels of insecticidal activity. The molecular analysis demonstrated integration and expression of the foreign gene. Somatic changes were correlated to extensive genomic changes and were quantified in dendrograms, in terms of genomic similarity. The analysis of control plants suggested that genomic changes were correlated to thein vitro culture step necessary forA. tumefaciens-mediated gene transfer, rather than to the integration of the foreign genes.Three transgenic clones (12, 153 and 192), selected for insect resistance, reduced morphological changes and promising silvicultural traits, are now under large-scale field evaluation in six different provinces in China. 相似文献