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排序方式: 共有237条查询结果,搜索用时 46 毫秒
1.
Eliahu Heldman Ayala Balan Ora Horowitz Sarit Ben-Zion Michael Torten 《FEBS letters》1985,180(2):243-248
Antiparaoxon immune sera were employed in a new immunoassay based on competition between acetylcholinesterase and antibodies for the binding ofparaoxon. Unlike radioimmunoassay, the new assay described herein can be extended to predict the feasibility of antibodies to confer in vivo protection of acetylcholinesterase against organophosphate poisoning. The toxicity of paraoxon was reduced in mice which were pre-injected with the immune sera. 相似文献
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3.
Membrane particle changes attending the acrosome reaction in guinea pig spermatozoa 总被引:15,自引:11,他引:4
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To examine the freeze-fracture appearance of membrane alterations accompanying the preparation of sperm membranes for fusions-the first preparatory stage occurring before physiological release of the acrosomal content, the second afterward-we induced the acrosome reaction in capacitated guinea pig spermatozoa by adding calcium to the mixture. The most common features observed before fusion of the acrosomal and plasma membranes were the deletion of fibrillar intramembranous particles from the E-fracture faces of both membranes, and the clearance of globular particles from the P face of the plasma membrane-events taking place near the terminus of the equatorial segment. Large particles, >12nm, remained not far from the cleared E-face patches. The P face of the outer acrosomal membrane is virtually clear from the outset. In addition, when fusion was completed, occasional double lines of large particles transiently embossed the P face of the plasma membrane (postacrosomal) side of the fusion zone. Behind the line of fusion, another series of particle-cleared foci emerged. We interpreted these postfusion membrane clearances as a second adaptation for sperm-egg interaction. Induction of the acrosome reaction in media containing phosphatidylcholine liposomes resulted in their apparent attachment, incorporation, or exchange in both the originally and secondarily cleared regions. Our observations support the concepts that membranes become receptive to union at particle- deficient interfaces, and that the physiologically created barren areas in freeze-fracture replicas may herald incipient membrane fusion. 相似文献
4.
Modifications of anionic-lipid domains preceding membrane fusion in guinea pig sperm 总被引:19,自引:15,他引:4
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The relationship between anionic-lipid concentration and the functional properties of plasma-membrane domains was explored using the guinea-pig sperm membrane as a model, with polymyxin B (PXB) as a probe. Areas of plasmalemma specialized for fusion during the acrosome reaction had a higher affinity for the probe than adjacent nonfusigenic regions. In addition, capacitation--a process preceding acrosome:plasma-membrane fusion--markedly enlarged the area susceptible to PXB binding over the acrosomal cap. Protease treatment mimicked capacitation by increasing the acrosome-reaction incidence as well as PXB binding, at enzyme concentrations not affecting the surface coat nor altering filipin/sterol localization. Both proteolytic digestion and capacitation failed to augment PXB- or filipin-affinity in nonfusigenic zones, such as the post-acrosomal segment, including its particle-free maculae. Incubation of sperm in capacitating medium supplemented with 32P-labeled phosphate, followed by lipid extraction, thin-layer chromatography, and autoradiography, revealed a radioactive band comigrating with cardiolipin and phosphatidic acid. Vermiform protrusions elicited by PXB in the outer lamellae of cardiolipin- phosphatidylcholine liposomes resembled those seen in fusional regions of sperm membrane. We conclude that (a) differing concentrations of anionic lipids are found in adjacent domains of the sperm plasma membrane; (b) these domains mirror the functional regions of the membrane, with higher anionic-lipid concentrations localized over fusional zones; (c) the surface coat does not participate in the maintenance of such domains; (d) anionic-lipid synthesis may contribute to their formation; and (e) anionic-lipid concentrations increase as the membrane becomes fusionally competent, indicating that cellular modulation of lipid domains accompanies regulation of membrane function. 相似文献
5.
Leon V. Backinowsky Nikolay F. Balan Vitali I. Betaneli Nikolay K. Kochetkov 《Carbohydrate research》1982,99(2):189-193
The capsular polysaccharide from Klebsiella type K54, containing both O-formyl and O-acetyl groups, has been investigated by using the techniques of methylation analysis (by gas-liquid chromatography), periodate oxidation-Smith degradation, and both 1H- and 13C-n.m.r. spectroscopy. Degradation of the native polysaccharide with a bacteriophage-induced glucosidase generated a formylated, as well as a formylated and acetylated, tetrasaccharide, whereas similar depolymerization of the deacetylated polysaccharide yielded a single tetrasaccharide; the corresponding, O-acylated octasaccharides were also isolated and characterized. These oligosaccharides, utilized in chemical and spectroscopic studies in order to determine the location of the O-acyl substituents in the repeating sequence, indicated formylation at O-4 of each lateral d-glucosyl group and acetylation at O-2 of alternate l-fucosyl residues. A new structure for the repeating unit in the polysaccharide is proposed. 相似文献
6.
Cytochrome P-448 (mol wt 55,000 Daltons) from rabbit liver was purified to a specific content of 16.6 nmol/mg. Mice were immunised with this preparation, their spleens removed and dissociated lymphocytes hybridised with myeloma cells. Four monoclonal antibodies against cytochrome P-448 were raised and partially characterised. All four antibodies interacted with cytochrome P-448 in intact microsomal fractions and selectively immunoadsorbed cytochrome P-448 from solubilised microsomal preparations. One of the antibodies inhibited benzo[a] pyrene hydroxylase activity in a reconstituted system, one had no effect on activity and two increased activity. The possible applications of such antibodies are discussed. 相似文献
7.
Balan Biji Dhaulaniya Amit S. Varma Diksha A. Sodhi Kushneet K. Kumar Mohit Tiwari Manisha Singh Dileep Kumar 《Archives of microbiology》2021,203(1):13-30
Archives of Microbiology - Biofilms are structured microbial communities of single or multiple populations in which microbial cells adhere to a surface and get embedded in extracellular polymeric... 相似文献
8.
Samantha J. Emery-Corbin Joshua J. Hamey Balu Balan Laura Rojas-López Staffan G. Svärd Aaron R. Jex 《International journal for parasitology》2021,51(4):225-239
Diarrheal disease caused by Giardia duodenalis is highly prevalent, causing over 200 million cases globally each year. The processes that drive parasite virulence, host immune evasion and transmission involve coordinated gene expression and have been linked to epigenetic regulation. Epigenetic regulatory systems are eukaryote-conserved, including in deep branching excavates such as Giardia, with several studies already implicating histone post-translational modifications in regulation of its pathogenesis and life cycle. However, further insights into Giardia chromatin dynamics have been hindered by a lack of site-specific knowledge of histone modifications. Using mass spectrometry, we have provided the first known molecular map of histone methylation, acetylation and phosphorylation modifications in Giardia core histones. We have identified over 50 previously unreported histone modifications including sites with established roles in epigenetic regulation, and co-occurring modifications indicative of post-translational modification crosstalk. These demonstrate conserved histone modifications in Giardia which are equivalent to many other eukaryotes, and suggest that similar epigenetic mechanisms are in place in this parasite. Further, we used sequence, domain and structural homology to annotate putative histone enzyme networks in Giardia, highlighting representative chromatin modifiers which appear sufficient for identified sites, particularly those from H3 and H4 variants. This study is to our knowledge the first and most comprehensive, complete and accurate view of Giardia histone post-translational modifications to date, and a substantial step towards understanding their associations in parasite development and virulence. 相似文献
9.
Aline Sampaio Cremonesi Lilia I. De la Torre Maximillia Frazão de Souza Gabriel S. Vignoli Muniz M. Teresa Lamy Cristiano Luis Pinto Oliveira Andrea Balan 《Biochemistry and Biophysics Reports》2021
ATP-Binding Cassette transporters (ABC transporters) are protein complexes involved in the import and export of different molecules, including ions, sugars, peptides, drugs, and others. Due to the diversity of substrates, they have large relevance in physiological processes such as virulence, pathogenesis, and antimicrobial resistance. In Xanthomonas citri subsp. citri, the phytopathogen responsible for the citrus canker disease, 20% of ABC transporters components are expressed under infection conditions, including the putative putrescine/polyamine ABC transporter, PotFGHI. Polyamines are ubiquitous molecules that mediate cell growth and proliferation and play important role in bacterial infections. In this work, we characterized the X. citri periplasmic-binding protein PotF (XAC2476) using bioinformatics, biophysical and structural methods. PotF is highly conserved in Xanthomonas sp. genus, and we showed it is part of a set of proteins related to the import and assimilation of polyamines in X. citri. The interaction of PotF with putrescine and spermidine was direct and indirectly shown through fluorescence spectroscopy analyses, and experiments of circular dichroism (CD) and small-angle X-ray scattering (SAXS), respectively. The protein showed higher affinity for spermidine than putrescine, but both ligands induced structural changes that coincided with the closing of the domains and increasing of thermal stability. 相似文献
10.
Fabiano Tófoli de Araújo Victor M. Bolanos-Garcia Cristiane T. Pereira Mario Sanches Elisa E. Oshiro Rita C. C. Ferreira Dimitri Y. Chigardze Jo?o Alexandre Gon?alves Barbosa Luís Carlos de Souza Ferreira Celso E. Benedetti Tom L. Blundell Andrea Balan 《PloS one》2013,8(11)