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81.
Insight into the kinetics and the mode of the interaction between smooth muscle calponin and F-actin
Kinetics of the smooth muscle calponin-F-actin interaction was studied by stopped-flow measurements of light scattering and fluorescence intensity of pyrene-labelled F-actin. The intensity and character of the changes in light scattering, and thus the mode of calponin binding to actin filaments leading to changes in their shape and bundling, depend on the molar ratio of the two proteins. Parallel measurements of pyrene-fluorescence quenching upon calponin binding revealed that intrinsic conformational changes in actin filaments are delayed relative to the binding process and are not markedly influenced by the mode of calponin binding. Bundling of actin filaments by calponin was not correlated with fluorescence changes and thus with alterations in the structure of actin filaments. 相似文献
82.
Vladimir B Arion Victor Ch KravtsovJulieta I Gradinaru Yuri A SimonovNicolai V Gerbeleu Janusz LipkowskiJean-Pierre Wignacourt Hervé VezinOlivier Mentré 《Inorganica chimica acta》2002,328(1):123-133
The macrocyclisation reaction of 3,3′-(3,6-dioxaoctane-1,8-diyldioxy)-bis(2-hydroxybenzaldehyde) (1) with S-methylisothiosemicarbazide hydroiodide (H2NNC(SCH3)NH2·HI) in the presence of potassium triflate, followed by addition of M(CH3COO)2·nH2O, where M=Ni, Cu, Zn, afforded [NiLKI3] (2), [NiLK(CF3SO3)] (3), [CuLK(CF3SO3)(CH3OH)] (4) and [(ZnILK)2CH3OH] (5), respectively. Compounds 2-5 have been characterised by X-ray crystallography. IR, electronic, mass, 1H, 13C{1H} and 19F{1H} NMR spectra are reported. Magnetic susceptibility measurements and ESR spectra of 4 indicate weak intermolecular spin-spin interactions, which are mostly dipolar in origin. 相似文献
83.
Kubrakiewicz J 《Arthropod Structure & Development》2002,31(1):23-31
The ovary of Polystoechotes punctatus consists of several ovarioles of meroistic-polytrophic type. Histological, histochemical and ultrastructural studies revealed that the extrachromosomal amplification of rDNA takes place in the oocyte nucleus. Prior to previtellogenic growth the oocyte nucleus contains the chromosomes of meiotic prophase and a condensed extra DNA body. Initial split of extrachromosomal DNA material into several fragments coincides with the appearance of a spherical, fine granular body (referred to as primary nucleolus). Its gradual fragmentation accompanied by further dispersion of amplified DNA results in the formation of a growing number of multiple nucleoli. Until mid previtellogenesis each multiple nucleolus contains detectable amount of rDNA. In the advanced stages of previtellogenesis rDNA can hardly be visualized within the multiple nucleoli, while chromosomes form a few dense aggregates randomly disposed in the karyoplasm. At the onset of vitellogenesis the chromosomes assemble to form a karyosome. In its close vicinity DNA-positive material reaggregates. Multiple nucleoli are either found on the periphery of this aggregation or merge within it. At the final stages of vitellogenesis the number of multiple nucleoli significantly decreases. 相似文献
84.
Background
Escherichia coli guanine-N2 (m2G) methyltransferases (MTases) RsmC and RsmD modify nucleosides G1207 and G966 of 16S rRNA. They possess a common MTase domain in the C-terminus and a variable region in the N-terminus. Their C-terminal domain is related to the YbiN family of hypothetical MTases, but nothing is known about the structure or function of the N-terminal domain. 相似文献85.
Swiatkowska M Szemraj J Al-Nedawi KN Pawłowska Z 《Cellular & molecular biology letters》2002,7(4):1065-1071
Second messengers involved in the signal transduction pathway leading to induction of the plasminogen activator inhibitor (PAI-1) have not yet been well characterized. This study focuses on the mechanisms of regulation of PAI-1 expression by reactive oxygen species (ROS) in human endothelial cells. Inhibition of the tumor necrosis factor alpha (TNFalpha?-induced expression of PAI-1 by antioxidant N-acetyl-L-cysteine (NAC) indicated redox-sensitive mechanisms involved in the signaling pathway. Because TNFalpha induces PAI-1 production in endothelial cells, and NAC attenuated this response, we attempted to investigate the possible involvement of ROS in the activation of PAI-1 by TNFalpha. Upregulation of PAI-1 expression in endothelial cells by the stimulation with TNFalpha (50 ng/ml) or H2O2 (10-200 micro M), observed by measurement of the antigen and mRNA levels, was reversed in the presence of NAC (20mM). The stimulatory effect of ROS was detected also at the level of the PAI-1 promoter in endothelial cells transfected with plasmid p800 LUC containing a PAI-1 promoter fragment (+71 to -800). The PAI-1 promoter activity was increased in the presence of ROS, and was suppressed by up to 75% in the presence of antioxidants. On the basis of this study we can conclude that reactive oxygen species play an important role in a cytokine-induced activation of PAI-1 expression, and may act as a signal transduction messenger. 相似文献
86.
Salmain M Fischer-Durand N Cavalier L Rudolf B Zakrzewski J Jaouen G 《Bioconjugate chemistry》2002,13(3):693-698
The preparation of several transition metal-carbonyl tracers of biotin and avidin is described. Multiple labeling of avidin was achieved by acylation of some of its amine-bearing residues with N-succinimidyl 4-pentynoate (dicobalt hexacarbonyl). By varying the initial amount of this complex, protein conjugates with the extent of derivatization of up to 13 were obtained. Biotin was labeled with one (eta5-cyclopentadienyl)manganese tricarbonyl moiety by reaction of biotin hydrazide, whereas multiple labeling was reached by successive conjugation of biotin and N-succinimidyl 4-pentynoate (dicobalt hexacarbonyl) or (eta5-cyclopentadienyl)iron dicarbonyl (eta1-N-maleimidato) to poly-L-lysine or fourth generation Starburst dendrimer. All the conjugates displayed a good to excellent bioaffinity toward their respective counterparts, as measured by competitive enzymatic assays. 相似文献
87.
Bujnicki JM Leach RA Debski J Rychlewski L 《Journal of molecular microbiology and biotechnology》2002,4(4):405-415
Functional analyses of the tRNA:(guanine 26, N2,N2)-dimethyltransferase (Trm1) have been hampered by a lack of structural information about the enzyme and by low sequence similarity to better studied methyltransferases. Here we used computational methods to detect novel homologs of Trm1, infer the evolutionary relationships of the family, and predict the structure of the Trm1 methyltransferase. The N-terminal region of the protein is predicted to form an S-adenosylmethionine-binding domain, which harbors the active site. The C-terminal region is rich in predicted alpha-helices and, in analogy to other nucleic acid methyltransferases, may constitute the target recognition domain of the enzyme. Interposing these two domains, most Trm1 homologs possess a highly variable inserted sequence that is delimited by a Cys4 cluster, likely forming a Zn-finger structure. The residues of Trm1 predicted to participate in cofactor binding, target recognition, and catalysis, were mapped onto a preliminary structural model, providing a platform for designing new experiments to better understand the molecular functions of this protein family. In addition, identification of novel, atypical Trm1 homologs suggests candidates for cloning and biochemical characterization. 相似文献
88.
Schlegel-Zawadzka M Kopański Z Piekoszewski W Tabak J Puto T Engel B 《Biological trace element research》2002,88(2):139-144
A study was carried out on 92 patients (58 males and 34 females) aged 42–76 treated for malignant neoplasm of the gastrointestinal
tract (54 patients with colorectal carcinoma, 38 with gastric carcinoma). In all patients, the zinc serum concentration was
measured and the results obtained were referred to some epidemiological-clinical factors (sex, age, primary cause of cancer,
the stage of clinical progression, and histological type). The results showed that the most pronounced hypozincemia occurred
in male patients with mucous membrane carcinoma of the stomach. 相似文献
89.
90.
Michael C. Klein Andrea Spence Janusz Kaczorowski Ann Kelly Stefan Grzybowski 《CMAJ》2002,166(10):1257-1263