Academic literature on the topic 'Membrance domains'
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Journal articles on the topic "Membrance domains"
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Dale, B., E. Tosti, and M. Iaccarino. "Is the plasma membrane of the human oocyte reorganised following fertilisation and early cleavage?" Zygote 3, no. 1 (February 1995): 31–36. http://dx.doi.org/10.1017/s0967199400002355.
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SummaryThe purpose of the present study was to determine whether the plasma membrance of the human oocyte is reorganised following fertlisation and during early cleavage. In order to characterise and localise the major sugar moieties on surface glycoporteins, oocytes and embroys were labelled with a range of flourescent lectins. Regional organisation of plasma membrane microvilli in oocytes and embryos was also studied using scanning electron microscopy (SEM). The plasma membrance of human oocytes, zygotes and early blastomeres stained strongly and homogeneously with concanavalin A and Triticum vulgaris lectin (WGA), indicationg the presence of plasma membrance glycoconjugates with α-D-mannosyl residues, sialic acid and β-NAc-glucosaminyl groups. We did not observe regional domains in oocytes and zygotes, suggesting that the plasma membrane is not topographically reorganised following fertilisation. SEM shows the surface of the human zygote to be organised into short microvilli 0.2–3.0 μm in length and at a density of 5–20/μm2. In early cleavage stages the microvilli are shorter and less frequent (0.2–1.0 μm; 1–5/μm2); however, there is no evidence of polarisation at this level of organisation, at either stage of development. The surface of cell fragments, common in the human embryo in vitro, differs in having few microvilli and numerous cytoplasmic blebs. In conclusion, there are no obvious morphological signs of regionalisation in the plasma membrane of the human embryo before the 8-cell stage.
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Snead, Wilton T., Wade F. Zeno, Grace Kago, Ryan W. Perkins, J. Blair Richter, Chi Zhao, Eileen M. Lafer, and Jeanne C. Stachowiak. "BAR scaffolds drive membrane fission by crowding disordered domains." Journal of Cell Biology 218, no. 2 (November 30, 2018): 664–82. http://dx.doi.org/10.1083/jcb.201807119.
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Cellular membranes are continuously remodeled. The crescent-shaped bin-amphiphysin-rvs (BAR) domains remodel membranes in multiple cellular pathways. Based on studies of isolated BAR domains in vitro, the current paradigm is that BAR domain–containing proteins polymerize into cylindrical scaffolds that stabilize lipid tubules. But in nature, proteins that contain BAR domains often also contain large intrinsically disordered regions. Using in vitro and live cell assays, here we show that full-length BAR domain–containing proteins, rather than stabilizing membrane tubules, are instead surprisingly potent drivers of membrane fission. Specifically, when BAR scaffolds assemble at membrane surfaces, their bulky disordered domains become crowded, generating steric pressure that destabilizes lipid tubules. More broadly, we observe this behavior with BAR domains that have a range of curvatures. These data suggest that the ability to concentrate disordered domains is a key driver of membrane remodeling and fission by BAR domain–containing proteins.
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Gallop, Jennifer L., and Harvey T. McMahon. "BAR domains and membrane curvature: bringing your curves to the BAR." Biochemical Society Symposia 72 (January 1, 2005): 223–31. http://dx.doi.org/10.1042/bss0720223.
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BAR (bin, amphiphysin and Rvs161/167) domains are a unique class of dimerization domains, whose dimerization interface is edged by a membrane-binding surface. In its dimeric form, the membrane-binding interface is concave, and this gives the ability to bind better to curved membranes, i.e. to sense membrane curvature. When present at higher concentrations, the domain can stabilize membrane curvature, generating lipid tubules. This domain is found in many contexts in a wide variety of proteins, where the dimerization and membrane-binding function of this domain is likely to have a profound effect on protein activity. If these proteins function as predicted, then there will be membrane subdomains based on curvature, and thus there is an additional layer of compartmentalization on membranes. These and other possible functions of the BAR domain are discussed.
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Golantsova, Nina E., Elena E. Gorbunova, and Erich R. Mackow. "Discrete Domains within the Rotavirus VP5* Direct Peripheral Membrane Association and Membrane Permeability." Journal of Virology 78, no. 4 (February 15, 2004): 2037–44. http://dx.doi.org/10.1128/jvi.78.4.2037-2044.2004.
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ABSTRACT Cleavage of the rotavirus spike protein, VP4, is required for rotavirus-induced membrane permeability and viral entry into cells. The VP5* cleavage product selectively permeabilizes membranes and liposomes and contains an internal hydrophobic domain that is required for membrane permeability. Here we investigate VP5* domains (residues 248 to 474) that direct membrane binding. We determined that expressed VP5 fragments containing residues 248 to 474 or 265 to 474, including the internal hydrophobic domain, bind to cellular membranes but are not present in Triton X-100-resistant membrane rafts. Expressed VP5 partitions into aqueous but not detergent phases of Triton X-114, suggesting that VP5 is not integrally inserted into membranes. Since high-salt or alkaline conditions eluted VP5 from membranes, our findings demonstrate that VP5 is peripherally associated with membranes. Interestingly, mutagenesis of residue 394 (W→R) within the VP5 hydrophobic domain, which abolishes VP5-directed permeability, had no effect on VP5's peripheral membrane association. In contrast, deletion of N-terminal VP5 residues (residues 265 to 279) abolished VP5 binding to membranes. Alanine mutagenesis of two positively charged residues within this domain (residues 274R and 276K) dramatically reduced (>95%) binding of VP5 to membranes and suggested their potential interaction with polar head groups of the lipid bilayer. Mutations in either the VP5 hydrophobic or basic domain blocked VP5-directed permeability of cells. These findings indicate that there are at least two discrete domains within VP5* required for pore formation: an N-terminal basic domain that permits VP5* to peripherally associate with membranes and an internal hydrophobic domain that is essential for altering membrane permeability. These results provide a fundamental understanding of interactions between VP5* and the membrane, which are required for rotavirus entry.
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Chowdary, Tirumala Kumar, and Ekaterina E. Heldwein. "Syncytial Phenotype of C-Terminally Truncated Herpes Simplex Virus Type 1 gB Is Associated with Diminished Membrane Interactions." Journal of Virology 84, no. 10 (March 3, 2010): 4923–35. http://dx.doi.org/10.1128/jvi.00206-10.
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ABSTRACT The cytoplasmic domain of glycoprotein B (gB) from herpes simplex virus type 1 (HSV-1) is an important regulator of membrane fusion. C-terminal truncations of the cytoplasmic domain lead to either hyperfusion or fusion-null phenotypes. Currently, neither the structure of the cytoplasmic domain nor its mechanism of fusion regulation is known. Here we show, for the first time, that the full-length cytoplasmic domain of HSV-1 gB associates stably with lipid membranes, preferentially binding to membranes containing anionic head groups. This interaction involves a large increase in helical content. However, the truncated cytoplasmic domains associated with the hyperfusion phenotype show a small increase in helical structure and a diminished association with lipid membranes, whereas the one associated with the fusion-null phenotype shows no increase in helical structure and only a minimal association with lipid membranes. We hypothesize that stable binding to lipid membranes is an important part of the mechanism by which the cytoplasmic domain negatively regulates membrane fusion. Moreover, our experiments with truncated cytoplasmic domains point to two specific regions that are critical for membrane interactions. Taken together, our work provides several important new insights into the architecture of the cytoplasmic domain of HSV-1 gB and its interaction with lipid membranes.
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Yamamoto, Eiji, Jan Domański, Fiona B. Naughton, Robert B. Best, Antreas C. Kalli, Phillip J. Stansfeld, and Mark S. P. Sansom. "Multiple lipid binding sites determine the affinity of PH domains for phosphoinositide-containing membranes." Science Advances 6, no. 8 (February 2020): eaay5736. http://dx.doi.org/10.1126/sciadv.aay5736.
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Association of peripheral proteins with lipid bilayers regulates membrane signaling and dynamics. Pleckstrin homology (PH) domains bind to phosphatidylinositol phosphate (PIP) molecules in membranes. The effects of local PIP enrichment on the interaction of PH domains with membranes is unclear. Molecular dynamics simulations allow estimation of the binding energy of GRP1 PH domain to PIP3-containing membranes. The free energy of interaction of the PH domain with more than two PIP3 molecules is comparable to experimental values, suggesting that PH domain binding involves local clustering of PIP molecules within membranes. We describe a mechanism of PH binding proceeding via an encounter state to two bound states which differ in the orientation of the protein relative to the membrane, these orientations depending on the local PIP concentration. These results suggest that nanoscale clustering of PIP molecules can control the strength and orientation of PH domain interaction in a concentration-dependent manner.
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Karotki, Lena, Juha T. Huiskonen, Christopher J. Stefan, Natasza E. Ziółkowska, Robyn Roth, Michal A. Surma, Nevan J. Krogan, et al. "Eisosome proteins assemble into a membrane scaffold." Journal of Cell Biology 195, no. 5 (November 28, 2011): 889–902. http://dx.doi.org/10.1083/jcb.201104040.
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Spatial organization of membranes into domains of distinct protein and lipid composition is a fundamental feature of biological systems. The plasma membrane is organized in such domains to efficiently orchestrate the many reactions occurring there simultaneously. Despite the almost universal presence of membrane domains, mechanisms of their formation are often unclear. Yeast cells feature prominent plasma membrane domain organization, which is at least partially mediated by eisosomes. Eisosomes are large protein complexes that are primarily composed of many subunits of two Bin–Amphiphysin–Rvs domain–containing proteins, Pil1 and Lsp1. In this paper, we show that these proteins self-assemble into higher-order structures and bind preferentially to phosphoinositide-containing membranes. Using a combination of electron microscopy approaches, we generate structural models of Pil1 and Lsp1 assemblies, which resemble eisosomes in cells. Our data suggest that the mechanism of membrane organization by eisosomes is mediated by self-assembly of its core components into a membrane-bound protein scaffold with lipid-binding specificity.
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Pennington, Edward Ross, E. Madison Sullivan, Amy Fix, Sahil Dadoo, Tonya N. Zeczycki, Anita DeSantis, Uwe Schlattner, et al. "Proteolipid domains form in biomimetic and cardiac mitochondrial vesicles and are regulated by cardiolipin concentration but not monolyso-cardiolipin." Journal of Biological Chemistry 293, no. 41 (August 29, 2018): 15933–46. http://dx.doi.org/10.1074/jbc.ra118.004948.
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Cardiolipin (CL) is an anionic phospholipid mainly located in the inner mitochondrial membrane, where it helps regulate bioenergetics, membrane structure, and apoptosis. Localized, phase-segregated domains of CL are hypothesized to control mitochondrial inner membrane organization. However, the existence and underlying mechanisms regulating these mitochondrial domains are unclear. Here, we first isolated detergent-resistant cardiac mitochondrial membranes that have been reported to be CL-enriched domains. Experiments with different detergents yielded only nonspecific solubilization of mitochondrial phospholipids, suggesting that CL domains are not recoverable with detergents. Next, domain formation was investigated in biomimetic giant unilamellar vesicles (GUVs) and newly synthesized giant mitochondrial vesicles (GMVs) from mouse hearts. Confocal fluorescent imaging revealed that introduction of cytochrome c into membranes promotes macroscopic proteolipid domain formation associated with membrane morphological changes in both GUVs and GMVs. Domain organization was also investigated after lowering tetralinoleoyl-CL concentration and substitution with monolyso-CL, two common modifications observed in cardiac pathologies. Loss of tetralinoleoyl-CL decreased proteolipid domain formation in GUVs, because of a favorable Gibbs-free energy of lipid mixing, whereas addition of monolyso-CL had no effect on lipid mixing. Moreover, murine GMVs generated from cardiac acyl-CoA synthetase-1 knockouts, which have remodeled CL acyl chains, did not perturb proteolipid domains. Finally, lowering the tetralinoleoyl-CL content had a stronger influence on the oxidation status of cytochrome c than did incorporation of monolyso-CL. These results indicate that proteolipid domain formation in the cardiac mitochondrial inner membrane depends on tetralinoleoyl-CL concentration, driven by underlying lipid-mixing properties, but not the presence of monolyso-CL.
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Ma, Alice D., Lawrence F. Brass, and Charles S. Abrams. "Pleckstrin Associates with Plasma Membranes and Induces the Formation of Membrane Projections: Requirements for Phosphorylation and the NH2-terminal PH Domain." Journal of Cell Biology 136, no. 5 (March 10, 1997): 1071–79. http://dx.doi.org/10.1083/jcb.136.5.1071.
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Pleckstrin homology (PH) domains are sequences of ∼100 amino acids that form “modules” that have been proposed to facilitate protein/protein or protein/lipid interactions. Pleckstrin, first described as a substrate for protein kinase C in platelets and leukocytes, is composed of two PH domains, one at each end of the molecule, flanking an intervening sequence of 147 residues. Evidence is accumulating to support the hypothesis that PH domains are structural motifs that target molecules to membranes, perhaps through interactions with Gβγ or phosphatidylinositol 4,5-bisphosphate (PIP2), two putative PH domain ligands. In the present studies, we show that pleckstrin associates with membranes in human platelets. We further demonstrate that, in transfected Cos-1 cells, pleckstrin associates with peripheral membrane ruffles and dorsal membrane projections. This association depends on phosphorylation of pleckstrin and requires the presence of its NH2-terminal, but not its COOH-terminal, PH domain. Moreover, PH domains from other molecules cannot effectively substitute for pleckstrin's NH2terminal PH domain in directing membrane localization. Lastly, we show that wild-type pleckstrin actually promotes the formation of membrane projections from the dorsal surface of transfected cells, and that this morphologic change is similarly PH domain dependent. Since we have shown previously that pleckstrin-mediated inhibition of PIP2 metabolism by phospholipase C or phosphatidylinositol 3-kinase also requires pleckstrin phosphorylation and an intact NH2-terminal PH domain, these results suggest that: (a) pleckstrin's NH2terminal PH domain may regulate pleckstrin's activity by targeting it to specific areas within the cell membrane; and (b) pleckstrin may affect membrane structure, perhaps via interactions with PIP2 and/or other membrane-bound ligands.
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GILLOOLY, David J., Anne SIMONSEN, and Harald STENMARK. "Cellular functions of phosphatidylinositol 3-phosphate and FYVE domain proteins." Biochemical Journal 355, no. 2 (April 6, 2001): 249–58. http://dx.doi.org/10.1042/bj3550249.
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PtdIns3P is a phosphoinositide 3-kinase product that has been strongly implicated in regulating membrane trafficking in both mammalian and yeast cells. PtdIns3P has been shown to be specifically located on membranes associated with the endocytic pathway. Proteins that contain FYVE zinc-finger domains are recruited to PtdIns3P-containing membranes. Structural information is now available concerning the interaction between FYVE domains and PtdIns3P. A number of proteins have been identified which contain a FYVE domain, and in this review we discuss the functions of PtdIns3P and its FYVE-domain-containing effector proteins in membrane trafficking, cytoskeletal regulation and receptor signalling.
Dissertations / Theses on the topic "Membrance domains"
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Gutlederer, Erwin Johann. "On the morphology of vesicles. - [überarb. Diss.]." Universität Potsdam, 2007. http://opus.kobv.de/ubp/volltexte/2007/1506/.
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This dissertation contains theoretical investigations on the morphology and statistical mechanics of vesicles. The shapes of homogeneous fluid vesicles and inhomogeneous vesicles with fluid and solid membrane domains are calculated. The influence of thermal fluctuations is investigated. The obtained results are valid on mesoscopic length scales and are based on a geometrical membrane model, where the vesicle membrane is described as either a static or a thermal fluctuating surface. The thesis consists of three parts.
In the first part, homogeneous vesicles are considered. The focus in this part is on the thermally induced morphological transition between vesicles with prolate and oblate shape. With the help of Monte Carlo simulations, the free energy profile of these vesicles is determined. It can be shown that the shape transformation between prolate and oblate vesicles proceeds continuously and is not hampered by a free energy barrier.
The second and third part deal with inhomogeneous vesicles which contain intramembrane domains. These investigations are motivated by experimental results on domain formation in single or multicomponent vesicles, where phase separation occurs and different membrane phases coexist. The resulting domains differ with regard to their membrane structure (solid, fluid). The membrane structure has a distinct effect on the form of the domain and the morphology of the vesicle. In the second part, vesicles with coexisting solid and fluid membrane domains are studied, while the third part addresses vesicles with coexisting fluid domains. The equilibrium morphology of vesicles with simple and complex domain forms, derived through minimisation of the membrane energy, is determined as a function of material parameters. The results are summarised in morphology diagrams. These diagrams show previously unknown morphological transitions between vesicles with different domain shapes. The impact of thermal fluctuations on the vesicle and the form of the domains is investigated by means of Monte Carlo simulations.Die vorliegende Arbeit enthält theoretische Untersuchungen zur Morphologie und statistischen Mechanik von Vesikeln. Es wird die Gestalt homogener fluider Vesikel und inhomogener Vesikel mit fluiden und festen Membrandomänen berechnet. Der Einfluss thermischer Fluktuationen wird untersucht. Die erzielten Ergebnisse beziehen sich auf mesoskopische Längenskalen und basieren auf einem geometrischen Membranmodell, in welchem die Vesikelmembran als statische, beziehungsweise thermisch fluktuierende Fläche beschrieben wird. Die Arbeit besteht aus drei Teilen. Im ersten Teil werden homogene fluide Vesikel betrachtet. Das Interesse gilt dem thermisch induzierten Morphologieübergang zwischen prolaten und oblaten Vesikelformen. Mit Hilfe von Monte-Carlo-Simulationen wird ein freies Energieprofil für diese Vesikel ermittelt. Es kann gezeigt werden, dass die Formumwandlung zwischen prolaten und oblaten Formen kontinuierlich verläuft und mit keiner freien Energiebarriere verbunden ist. Der zweite und dritte Teil beschäftigt sich mit inhomogenen Vesikeln, die intramembrane Domänen enthalten. Ausgangspunkt und Motivation der Berechnungen sind experimentelle Studien über Domänbildung in ein- oder mehrkomponentigen Vesikelmembranen, bei denen Phasentrennung stattfindet und unterschiedliche Membranphasen koexistieren. Die dabei auftretenden Domänen unterscheiden sich hinsichtlich ihrer Membranstruktur (fest, fluid). Diese beeinflusst die Form der Domäne und des gesamten Vesikels auf entscheidende Weise. Im zweiten Teil werden Vesikel untersucht, bei denen feste und fluide Membrandomänen koexistieren, Teil drei widmet sich Vesikeln mit zwei koexistierenden fluiden Membranphasen. In Abhängigkeit von Materialparametern werden durch Minimierung der Membranenergie die Grundzustandsformen von Vesikeln mit einfachen und komplexen Domänenformen bestimmt. Die Ergebnisse werden in Morphologiediagrammen zusammengefasst. Dabei werden bisher unbekannte Morphologieübergänge zwischen Vesikeln mit unterschiedlichen Domänformen beobachtet. Die Auswirkungen thermischer Fluktuationen auf die Vesikel und die Form ihrer Domänen werden mittels Monte-Carlo-Simulationen untersucht.
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Oldham, Alexis Jean. "Modulation of lipid domain formation in mixed model systems by proteins and peptides." View electronic thesis, 2008. http://dl.uncw.edu/etd/2008-1/r1/oldhama/alexisoldham.pdf.
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Wilkinson, Debbie Isabelle. "Visualisation of osteoclast membrane domains." Thesis, University of Aberdeen, 2010. http://digitool.abdn.ac.uk:80/webclient/DeliveryManager?pid=158808.
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Osteoclasts polarise upon activation and form four distinct membrane domains; the basolateral domain, the sealing zone, the functional secretory domain and the ruffled border. The ruffled border is the resorptive organelle of the cell and provides a large surface area for the release of protons and enzymes into the space beneath the osteoclast. Defects in osteoclast formation or function can lead to diseases such as osteopetrosis. Ruffled border formation is a critical event in osteoclast function but the process by which it and other membrane domains form is only partially understood. Vesicular trafficking is essential for the tight regulation of the osteoclast membrane domains and it has been shown previously that treatment with pharmacological inhibitors causes disruption of trafficking. The aims of this PhD were to increase our understanding of vesicular trafficking in osteoclasts and to optimise ways of visualising osteoclast membrane domains. My studies of patients with osteoclast-poor osteopetrosis identified defects in RANKL as a cause of the defect. This in turn has identified a potential therapy of recombinant RANKL for patients with this form of the disease. Although purification of wild type or mutant RANKL was not completely successful, it did suggest that the mutant forms of RANKL were not functional. I have used pharmacological inhibitors to study osteoclast membrane domains, and found that transmission electron microscopy is an essential tool for studying membrane changes following pharmacological inhibition at the ultrastructural level. I also established that the study of vesicular trafficking to analyse formation of membrane domains can make excellent use of immuno-electron methods. Furthermore, genetic diseases associated with defective ruffled border formation such as XLA and osteopetrosis provide useful tools to further analyse the dynamics involved in the formation and maintenance of the ruffled border, as well as revealing more about the diseases themselves.
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Daste, Frédéric. "Function and regulation of coiled‐coil domains in intracellular membrane fusion." Thesis, Sorbonne Paris Cité, 2015. http://www.theses.fr/2015PA05T001.
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Les mécanismes moléculaires impliqués dans la fusion membranaire ont été amplement étudiés au cours des trente dernières années. Notre compréhension actuelle de ce phénomène est principalement basée sur des résultats obtenus par (1) le développement de modèles physiques décrivant la fusion des membranes biologiques, (2) l’étude mécanistique et structurale des protéines de fusion membranaire des virus à enveloppe et (3) l’étude des évènements de fusion intracellulaire médiés par les protéines SNARES dans les cellules eucaryotes. La découverte du complexe SNARE fut l’aboutissement de travaux interdisciplinaires qui ont exigés un large éventail de techniques tel que la génétique de la levure, l’électrophysiologie, la biologie moléculaire, la biochimie cellulaire, la biophysique expérimentale et l’imagerie. Tirant parti des paradigmes et techniques biophysiques qui ont émergés de ces études, nous avons examiné les fonctions et mécanismes de régulation des domaines « coiled-coil » dans les processus de fusion intracellulaire impliquant des protéines de la famille des Longin-SNAREs ou des Mitofusines, deux machineries protéiques de fusion dont le mode d’action exact reste encore peu clair. La conception exacte des mécanismes moléculaires de la fusion membranaire requiert la reconstitution in vitro des protéines de fusion dans un large spectre d’environnement membranaire avec des propriétés biophysiques définies et facilement modulables. Idéalement, ces systèmes membranaires devraient permettre à l’expérimentateur de contrôler la composition lipidique et protéique, ainsi que la topologie membranaire, afin de rendre compte de l’importante variabilité observée entre les différents compartiments de fusion cellulaire. La reconstitution dans des liposomes offre une incroyable flexibilité avec la possibilité de faire varier la plupart des paramètres clefs et de créer un environnement minimal dans lequel les facteurs solubles et/ou membranaires peuvent être ajoutés, seuls ou en combinaison, pour dévoiler leur rôle avec clarté. Nous avons mis au point des systèmes in vitro de reconstitution de protéines dans des plateformes membranaires artificielles pour nos deux systèmes d’études (les deux protéines Longin-SNAREs TI-VAMP et Sec 22b, ainsi que les domaines « coiled-coil » des Mitofusines) et nous avons réalisé des expériences biochimiques pour caractériser le mode d’action de ces protéines. L’objectif à long-terme de ce projet est de comparer les mécanismes moléculaires des machineries de fusion associés aux protéines SNAREs et Mitofusines, et ainsi de dévoiler des similitudes structurelles et fonctionnelles entre (1) leur protéines de fusion principales et (2) leur facteurs régulateursThe molecular mechanisms involved in membrane fusion have been extensively studied for the past thirty years. Our current understanding of this phenomenon is mainly based on results obtained by (i) the development of physical models describing the fusion of membranes, (ii) structural and mechanistic investigations on fusion proteins of enveloped viruses and (iii) studies of SNARE protein-mediated intracellular fusion events of eukaryotic cells. Discovery of the SNARE complex was the outcome of interdisciplinary works which involved a wide range of techniques including yeast genetics, electrophysiology, molecular biology, cell-free biochemistry, adhesion/fusion biophysics and imaging. Taking advantage of the paradigms and biophysical techniques that emerged from these studies, we investigated the function and regulation of coiled-coil domains in intracellular fusion processes involving Longin-SNAREs or Mitofusins, two fusion protein machineries whose exact mode of action still remains unclear. A comprehensive understanding of the molecular mechanisms of membrane fusion requires the in vitro reconstitution of fusion proteins into a wide variety of membrane environments with defined and tunable biophysical properties. Ideally, these membrane systems should allow the experimentalists to control the lipid and protein composition as well as the membrane topology, to account for the variability observed across cellular fusing compartments. Reconstitution into liposomes offers amazing flexibility with the capacity to vary most of these relevant parameters, and to create a minimal environment in which membrane and/or soluble factors can be added, one at a time or in combination, to reveal their role with clarity. We have set up the in vitro reconstitution of proteins into various artificial membrane platforms for both systems (the Longin-SNAREs TI-VAMP and Sec22b and the coiled-coil domains of Mitofusins) and performed biochemical assays to gain insight into how these proteins execute their functions. The long-term goal of this project is to compare the molecular mechanisms of SNARE and Mitofusin fusion machineries and thus reveal structural and functional similitudes between (i) their core fusion proteins, and (ii) their regulatory factors
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Jean-François, Frantz. "Vers un nouveau mode d’action de peptides antimicrobiens structurés en feuillets ß : formation de domaines membranaires par la cateslytine." Thesis, Bordeaux 1, 2008. http://www.theses.fr/2008BOR13638/document.
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Le peptide antimicrobien Cateslytine (bCGA RSMRLSFRARGYGFR ) inhibe la libération des catécholamines des cellules chromaffines. Des études biologiques ont montré que ce peptide est capable d’inhiber aussi la croissance de nombreux microorganismes notamment des bactéries, des levures ainsi que le parasite Plasmodium falciparum responsable de la malaria. Cependant, le mode d’action moléculaire demeurait inconnu. Afin de mieux comprendre le ciblage et la sélectivité de ce peptide sur les membranes de mammifères ou de microorganismes, nous avons donc envisagé la reconstitution du système biologique composé initialement de peptides en contact avec des cellules, en le substituant par des modèles de membrane, de composition mimant celle des différents microorganismes. Des études structurales ont été menées en utilisant la technique d’ATR-FTIR polarisé, le dichroïsme circulaire et la RMN à haute résolution. La dynamique membranaire a été étudiée en utilisant la RMN des solides du phosphore et du deutérium. Des expériences de patch-clamp ont été effectuées afin de mesurer des flux d’ions au travers de la membrane. Enfin, de la simulation par ordinateur a permis de comprendre cette interaction au niveau moléculaire. Trois résultats principaux sont ressortis de cette approche pluridisciplinaire : i) Des flux ioniques au travers de la membrane attestent de la présence de cannaux. ii) La formation de domaines membranaires rigides constitués de lipides chargés négativement est démontrée. iii) Une structuration des peptides en feuillets ß antiparallèles est observée sur des membranes chargées négativement mimant les microorganismes. L’ensemble de ces résultats conduit à la proposition d’un mode d’action dans lequel la déstabilisation membranaire est induite par les domaines rigides stabilisés par les agrégats de peptides structurés en feuillets ßThe antimicrobial peptide Cateslytin (bCGA RSMRLSFRARGYGFR ) is a five positively charged arginin rich peptide known to inhibit the release of catecholamine in chromaffin granules. Although biological data showed that it is able to inhibit the growth of several microorganisms such as bacteria, yeast and Plasmodium falciparum parasite involved in malaria, the mechanism of action has not been yet studied. In order to better understand both targeting and selectivity of this peptide towards microorganisms, model membranes of variable compositions have been chosen to respectively mimic microorganisms or mammalian membranes. Structural studies have been performed using polarised ATR-FTIR, circular dichroïsm and high resolution NMR Membrane dynamics has been followed using deuterium labelled lipids and solid state NMR Patch clamp experiments were also performed on lipid vesicles to measure channe conductivity. All-atom molecular dynamics on hydrated peptide-lipid membrane systems was also used to assess the interaction from the atomic level. Main results from this interdisciplinary approach are three-fold. i) Electric current passages through membranes demonstrate permeation akin to pore formation. ii) Peptide-induced formation of rigid domains mainly made of negatively charged lipids is found. iii) Peptide antiparallel ß-sheets are observed preferentially with negatively charged lipids mimicking microorganism membranes. The general picture leads to the proposal that membrane destabilization/permeation is promoted by rigid domains stabilised by peptide ß-sheets
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Goulding, Rebecca Ellen. "Membrane localization of RasGRPs by C1 domains." Thesis, University of British Columbia, 2008. http://hdl.handle.net/2429/24211.
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Ras and Rap GTPases are membrane-bound activators of signal transduction pathways that regulate several cell processes including proliferation, apoptosis and adhesion. Guanine nucleotide exchange factors (GEF5) positively regulate Ras and Rap GTPases by exchanging guanosine diphosphate (GDP) for guanosine triphosphate (GTP). In order to activate Ras and Rap GTPases, GEFs must be at the same membrane compartments where their target GTPases are located. The Ras guanine nucleotide releasing protein (RasGRP)
family of four GEFs regulate both Ras and Rap GTPases, with differential specificities. All
RasGRPs contain Cl domains, which have the potential to bind the lipid second messenger
diacylglycerol (DAG) that is generated at membranes in response to the ligation of many cell
surface receptors. Binding of their Cl domains to DAG could serve to co-localize RasGRPs
with membrane bound Ras and Rap GTPases. While some evidence exists for each member of the RasGRP family being potentially regulated by their Cl domains binding to DAG, there is contradictory evidence for RasGRP2. My thesis research focused on Cl domain-mediated mechanisms of RasGRP membrane localization, with special focus on RasGRP2. I found that the Cl domains of RasGRP2 and the β splice variant of RasGRP4 do not bind either DAG or phorbol ester, a DAG analog. However, all RasGRP Cl domains were shown to
bind anionic phospholipids. I determined that the Cl domain of RasGRP2 is required for
constitutive plasma membrane localization in NIH 3T3 fibroblasts and T-cells, and also for
translocation to the plasma membrane in SDF-1α-stimulated T-cells. I also identified a putative PDZ protein binding site which is required for RasGRP2 localization at the Golgi. My experiments showed that while RasGRP2 localization can occur at the plasma membrane and Golgi of NIH 3T3s, RasGRP2 mediated Rapi activation at the plasma membrane via its Cl domain is required for changes in cell morphology that are induced by RasGRP2
expression. My thesis research has demonstrated that all four members of the RasGRP family utilize their Cl domains to localize to membranes, although in the case of RasGRP2 this occurs via a DAG-independent mechanism, which targets RasGRP2 to the plasma membrane.
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Headlam, Madeleine Joyce. "Cytochrome P450scc (CYP11A1) : effects of glycerol and identification of the membrane binding domain." University of Western Australia. School of Biomedical and Chemical Sciences, 2004. http://theses.library.uwa.edu.au/adt-WU2004.0065.
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The first step in the synthesis of steroid hormones occurs in the mitochondria where cholesterol is converted to pregnenolone by cytochrome P450scc (CYP11A1). Cholesterol is insoluble in water and is supplied to the CYP11A1 directly from the inner mitochondrial membrane to which the enzyme is bound. The aim of this study was to characterise the interaction of bovine CYP11A1 with the phospholipid membrane. The effect of osmotic stress provided by glycerol on the spin-state, activity and degree of hydration of CYP11A1 was also investigated. Multiple sequence alignment of mitochondrial P450s revealed that there are 46 absolutely conserved residues, with the highest conservation in the heme-binding region at the C-terminal. The greatest variablility between subfamilies is in the regions believed to be involved in substrate binding (SRSs), as defined for the CYP2B family. The secondary structure prediction for CYP11A1 suggests that there is strong similarity in secondary structure to P450s of known structure. A model structure of CYP11A1 was built from primary sequence alignment to template P450 structures using the SwissModel automated server. From the model and other bioinformatic analyses, the distal face of the P450 which includes the A’ helix, F-G loop and beta sheet 1 regions, were predicted to interact with the membrane. Tryptic digests of CYP11A1 were performed with the aim of identifying membrane bound peptides that may be protected from protease activity. HPLC tryptic maps were similar in profile between soluble and vesicle-bound P450 which suggests that there is not a large region of CYP11A1 protected from protease digestion when the enzyme is attached to a membrane. Mass spectrometric analysis of peptides resulting from tryptic digestion revealed a number of peptides in the soluble digest that were not present in the digest of vesicle-bound P450. These peptides were located at the N-terminal and the J to J’ helix and interestingly, there was an absence of C-terminal peptides for both digests. This C-terminal peptide could be detected in digests of vesicle-bound P450 but not in digests of soluble P450 by tricine SDS polyacrylamide gel electrophoresis, Western transfer and N-terminal sequence analysis. Based upon the bioinfomatic and tryptic digestion data, a set of N- and C-terminal deletion mutants of CYP11A1 were expressed in E. coli and fractionated based on their association with the soluble or membrane fraction of the cells. The N-terminal deletion of the A’ helix resulted in an increase in the proportion of CYP11A1 in the soluble fraction while the C-terminal deletion did not alter membrane localisation. There are eight tryptophan residues in mature CYP11A1. The accessibility of these tryptophans to a water-soluble fluorescence quencher was determined for soluble and vesicle-bound enzyme. When CYP11A1 was associated with the vesicle membrane an average of 2 tryptophan residues were protected from quenching compared to soluble CYP11A1. This suggests that these tryptophan residues become buried within the membrane following association of CYP11A1 with the vesicles and are no longer accessible to quencher. The only free cysteine (C265S) of bovine CYP11A1 was removed by site directed mutagenesis and new cysteine residues introduced at selected sites based upon earlier results and the modelled CYP11A1 structure. The cysteine mutants were expressed, purified and labelled with the environmentally sensitive fluorescent probe, N-(7-nitrobenz-2-oxal-3-diazol-4-yl)ethylenediamine (NBD). There was an increase in the hydrophobicity of the NBD environment following the association of CYP11A1 with vesicles for the labeled mutants V212C and L219C. This indicates that these residues which are in the F-G loop, become localized to a more hydrophobic environment following membrane binding. Labeled cysteine residues introduced into the A’, B’ and G helices and β4-2 did not show major changes in hydrophobicity following membrane integration of CYP11A1. Osmotic stress of CYP11A1 induced by glycerol resulted in a low-spin spectral response and inhibition of activity. The change to low spin correlated with the dissociation of five or six water molecules from CYP11A1 and the inhibition of activity with cholesterol as substrate correlated with the dissociation of two molecules of water. In conclusion, this study shows that CYP11A1 is held to the membrane, at least in part, by the F-G loop region, and that the removal of water from the active site of CYP11A1 by osmotic stress causes a low spin spectral response and inhibition of activity.
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Salkhordeh, Mahmoud. "Localization of membrane binding domains in synapsin I." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2001. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/MQ57790.pdf.
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Salkhordeh, Mahmoud Carleton University Dissertation Biology. "Localization of membrane binding domains in synapsin I." Ottawa, 2000.
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Brechin, C. "14-3-3 proteins and cholesterol-dependent membrane domains." Thesis, University of Edinburgh, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.641914.
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In this thesis I set out to characterise the interaction of 14-3-3 with lipid raft-like membrane domains. 14-3-3 associated with DRMs isolated from rate brain extract in a 14-3-3 isoform specific manner. Inhibition of 14-3-3 target protein interactions suggested that this association was reliant on binding of 14-3-3 to a membrane protein. The interaction of 14-3-3 with DRMs was further investigated in N2a and PC12 cells and also be detergent-free method. There are, however, some concerns over whether DRMs represent physiological membrane domains. Therefore I also investigated quantitatively the colocalisation of 14-3-3 with membrane domains in intact cells by confocal microscopy, using the lipid raft marker cholera toxin B subunit (CTXB). For comparison, other DRM-resident proteins, Thy-1, syntaxin-1a and SNAP-25, were also examined. SNAP-25 and Thy-1 showed a high degree of coincidence with CTXB in PC12 cells, 14-3-3 also colocalised with CTXB but to a much lower extent. As lipid rafts have been implicated in the control of regulated exocytosis the high coincidence of SNAP-25 and lack of coincidence of syntaxin-1 with CTXB is of interest. Cholesterol depletion, which affects the integrity of lipid raft-like domains, revealed some discrepancies between the association of 14-3-3., Thy-1, SNAP-25 and syntaxin-1a with DRMs and CTXB domains imaged in intact PC12 and N2a cells. CTXB clusters were partially disrupted in N2a cells and the coincidence of SNAP-25, but not 14-3-3, with CTXB was reduced. These findings indicate a role for lipid raft-like domains in controlling the spatial distribution of SNAP-25 on the plasma membrane. However, the lack of cholesterol dependent 14-3-3 localisation indicates that other membrane compartmentalisation mechanism may affect 14-3-3 distribution.
Books on the topic "Membrance domains"
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J, Quinn P., ed. Membrane dynamics and domains. Dordrecht: Kluwer Academic/Plenum, 2004.
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Cellular domains. Hoboken, N.J: Wiley-Blackwell, 2011.
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Quinn, Peter J., ed. Membrane Dynamics and Domains. Boston, MA: Springer US, 2004. http://dx.doi.org/10.1007/978-1-4757-5806-1.
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K, Tamm Lukas, ed. Protein-lipid interactions: From membrane domains to cellular networks. Weinheim: Wiley-VCH, 2005.
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Saleh, Mazen T. Identifying domains of Shiga-like toxin I that are responsible for its membrane translocation. Ottawa: National Library of Canada = Bibliothèque nationale du Canada, 1997.
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Karlsson, Jenny. Functional and structural analysis of the membrane domain of proton-translocating Escherichia coli Transhydrogenase. Göteborg: Department of Chemistry, Biochemistry and Physices, Göteborg University, 2006.
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C, Aloia Roland, Curtain Cyril C, and Gordon Larry M, eds. Lipid domains and the relationship to membrane function. New York: Liss, 1988.
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Kusumi, Akihiro, and Takahiro Fujiwara. Plasma Membrane Domains. Morgan & Claypool Life Science Publishers, 2012.
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Nabi, Ivan R. Cellular Domains. Wiley & Sons, Incorporated, John, 2011.
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Nabi, Ivan R. Cellular Domains. Wiley & Sons, Incorporated, John, 2011.
Find full textBook chapters on the topic "Membrance domains"
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Coombs, Daniel, Raibatak Das, and Jennifer S. Morrison. "Modeling Membrane Domains." In Cellular Domains, 71–84. Hoboken, NJ, USA: John Wiley & Sons, Inc., 2011. http://dx.doi.org/10.1002/9781118015759.ch5.
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Wolf, Claude, and Peter J. Quinn. "Membrane Lipid Homeostasis." In Membrane Dynamics and Domains, 317–57. Boston, MA: Springer US, 2004. http://dx.doi.org/10.1007/978-1-4757-5806-1_10.
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Meiri, Karina F. "Membrane/Cytoskeleton Communication." In Membrane Dynamics and Domains, 247–82. Boston, MA: Springer US, 2004. http://dx.doi.org/10.1007/978-1-4757-5806-1_8.
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Oliver, Janet M., Janet R. Pfeiffer, Zurab Surviladze, Stanly L. Steinberg, Karin Leiderman, Margaret L. Sanders, Carla Wofsy, et al. "Membrane Receptor Mapping: The Membrane Topography of FcεRI Signaling." In Membrane Dynamics and Domains, 3–34. Boston, MA: Springer US, 2004. http://dx.doi.org/10.1007/978-1-4757-5806-1_1.
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Veldhuizen, Ruud, and Fred Possmayer. "Phospholipid Metabolism in Lung Surfactant." In Membrane Dynamics and Domains, 359–88. Boston, MA: Springer US, 2004. http://dx.doi.org/10.1007/978-1-4757-5806-1_11.
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Schrader, Michael. "Membrane Targeting in Secretion." In Membrane Dynamics and Domains, 391–421. Boston, MA: Springer US, 2004. http://dx.doi.org/10.1007/978-1-4757-5806-1_12.
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Parat, Marie-Odile, and Paul L. Fox. "Oxidative Stress, Caveolae and Caveolin-1." In Membrane Dynamics and Domains, 425–41. Boston, MA: Springer US, 2004. http://dx.doi.org/10.1007/978-1-4757-5806-1_13.
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Nayak, Debi P., and Eric K. W. Hui. "The Role of Lipid Microdomains in Virus Biology." In Membrane Dynamics and Domains, 443–91. Boston, MA: Springer US, 2004. http://dx.doi.org/10.1007/978-1-4757-5806-1_14.
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Morris, Roger, Helen Cox, Enrico Mombelli, and Peter J. Quinn. "Rafts, Little Caves and Large Potholes: How Lipid Structure Interacts with Membrane Proteins to Create Functionally Diverse Membrane Environments." In Membrane Dynamics and Domains, 35–118. Boston, MA: Springer US, 2004. http://dx.doi.org/10.1007/978-1-4757-5806-1_2.
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Wollscheid, Bernd, Priska D. von Haller, Eugene Yi, Samuel Donohoe, Kelly Vaughn, Andrew Keller, Alexey I. Nesvizhskii, et al. "Lipid Raft Proteins and Their Identification in T Lymphocytes." In Membrane Dynamics and Domains, 121–52. Boston, MA: Springer US, 2004. http://dx.doi.org/10.1007/978-1-4757-5806-1_3.
Full textConference papers on the topic "Membrance domains"
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Shao, Jianwang, Xian Wu, and Bruno Cochelin. "Study of Targeted Energy Transfer Inside 3D Acoustic Cavity by Two Nonlinear Membrane Absorbers." In ASME 2015 International Design Engineering Technical Conferences and Computers and Information in Engineering Conference. American Society of Mechanical Engineers, 2015. http://dx.doi.org/10.1115/detc2015-46227.
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The targeted energy transfer (TET) phenomenon has been observed in the field of acoustics, which provides a new approach to passive sound control in low frequency domain. The TET phenomenon has been investigated firstly inside one tube (1D acoustic system) with a membrane nonlinear energy sink (NES) or a loudspeaker nonlinear absorber, then inside an acoustic cavity (3D acoustic system) with a membrane NES. 3D acoustic cavities have been considered as more general geometry for the acoustic medium in view of applications in the acoustic field and the membrane NES is mounted directly on the wall of the acoustic cavity. The placement of a membrane NES on the wall involves a weak coupling between the membrane NES and a considered acoustic mode, which constitute the two degrees-of-freedom (DOF) system. The beginning of TET phenomenon of the two DOFs system has been analyzed and the desired working zone for the membrane NES has also been defined. The two thresholds of the zone have been determined by an analytical formula and semi-analytically, respectively. The parametric analysis of the membrane NES by using the two DOFs system has been investigated to design the membrane NES. In order to enhance the robustness and the effective TET range in acoustic cavities, a three DOFs system with two membranes and one acoustic mode is studied in this paper. We consider two different membranes and two almost identical membranes to analyze the TET phenomenon, respectively. The desired working zone for the membrane NES and the value of the plateau which are obtained by the two DOFs system are applied to analyze the three DOFs system. We observe that two membranes can enlarge the desired working zone of the NES.
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Tabouillot, Tristan, Hari S. Muddana, and Peter J. Butler. "Shear Stress Induces Time- and Domain-Dependent Changes in Lipid Dynamics of Endothelial Cell Membranes." In ASME 2009 Summer Bioengineering Conference. American Society of Mechanical Engineers, 2009. http://dx.doi.org/10.1115/sbc2009-206882.
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Endothelial cells (ECs) form the inner lining of the blood vasculature and are exposed to shear stress (τ), the tangential component of hemodynamic forces. ECs transduce τ into biochemical signals possibly via EC-membrane perturbations. We have previously used confocal-FRAP on the DiI-stained plasma membranes of confluent cultured bovine aortic ECs (BAECs) to show that τ induces a rapid, spatially heterogeneous, and time-dependent increase in the lateral diffusion of the fluorescent lipoid probe in the BAEC membrane [1]. We now present evidence at the single molecule level that shear stress differentially perturbs membrane domains that are defined by their selective staining by lipoid dyes (DiI) of differing alkyl chain lengths. This study is the first to directly measure perturbation by shear stress of endothelial cell membrane microdomains.
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Lee, Chi-Hung, Jia-Ru Chen, Hung-Wei Shiu, Ko-Shan Ho, Shinn-Dar Wu, Kuo-Huang Hsieh, and Yen-Zen Wang. "Effect of Bridging Groups on Sulfonated Poly(Imide-Siloxane) for Application in Proton Exchange Membrane of Fuel Cells." In ASME 2008 6th International Conference on Fuel Cell Science, Engineering and Technology. ASMEDC, 2008. http://dx.doi.org/10.1115/fuelcell2008-65155.
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A series of six-membered sulfonated poly(imide-siloxane)s were synthesized using 1,4,5,8-naphthalenetetracarboxylic dianhydride (NTDA), aminopropyl-terminated polydimethylsiloxane (PDMS) 2,2-benzidinedisulfonic acid (BDSA), as the sulfonation target diamine groups, and various non-sulfonated diamine monomers behaving as bridging groups. The structure-property relationship of SPI-SXx membranes is discussed in details according to the chemical structure of the nvarious non-sulfonated diamines of SPI-SXx membranes from the viewpoints of proton conductivity, ion exchange capacity (IEC) and membranes properties (water uptake, membrane swelling) at equal PDMS content SPI-SXx. They showed good solubility and high thermal stability up to 300 °C. The PDMS was introduced to enhance the proton conductivity and water uptake attributed from the highly flexibility of the siloxane segments. They showed a comparable or even higher proton conductivity than that of Nafion 117 in water at 60 °C. The conductivity and water uptake of angled, SPI-SXm and ODA-based SPI-SX membranes (SPI-SXO) are greater than those prepared from DDM-based SPI-SX membranes (SPI-SXD) at a given IEC. These differences resulted from the increased numbers of entanglements of the flexibility membrane. The SPI-SXD showed alomost isotropically dimensional changes with the increases of water uptake and the volume were slightly smaller than those estimated from the additivity rule. Microscopic analyses revealed that these smaller (<10 nm) and well-dispersed hydrophilic domains contribute to the better proton conducting properties. The new sulfonated poly(imide-siloxane)s have proved to be a possible candidate as the polymer electrolyte membrane for PEFCs and DMFCs.
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Kalyan, N. K., S. G. Lee, W.-T. Hum, R. Hartzell, M. Levner, and P. P. Hung. "IN VITRO STUDIES ON THE BINDING OF TISSUE-TYPE PLASMINOGEN ACTIVATOR (t-PA) AND UROKINASE (u-PA) TO LIVER MEMBRANES." In XIth International Congress on Thrombosis and Haemostasis. Schattauer GmbH, 1987. http://dx.doi.org/10.1055/s-0038-1643603.
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The plasminogen activators, t-PA and u-PA, are glycoproteins known to be involved in homeostasis of the blood clotting system, and thus are of potential clinical use in the treatment of thrombosis. Several in vivo studies have shown that both t-PA and u-PA are quickly removed from the blood circulation, predominantly by the liver. The mechanism by which the liver removes these proteins is not understood. To delineate this, we conducted in vitro studies of binding of PAs or their derivatives to isolated mouse liver membranes utilizing a functional assay developed in our laboratory. The assay consisted of initial binding of t-PA to liver membranes followed by centrifugation to pellet the membranes and the assay of the activity of the membrane-bound t-PA by a fibrin-agar plate method. The bound t-PA, which retained complete enzymic activity, could be dissociated by SDS treatment in an undegraded form as shown by SDS-PAGE. The binding of t-PA as well as u-PA was very fast and did not compete with glycoproteins or sugars containing the terminal galactose, mannose and N-acetylglucosamine residues. Furthermore, the treatment of t-PA with neuraminidase and/or periodate oxidation did not affect its binding characteristics. These data suggest that the carbohydrate moieties of t-PA and u-PA, unlike many glycoproteins, do not mediate their binding to the liver. This raised the possibility of the liver binding sequence being located in the protein backbone, especially the non-protease domains which are known to determine the biological specificities of PAs. The relative binding of u-PA and its low molecular weight (LMW) derivative containing only the protease domain, to the liver membranes was studied. Unlike u-PA and t-PA, LMW-urokinase did not bind significantly. This suggests that the protein sequence containing the non-protease domains, rather than the carbohydrate moieties of PAs contain the information necessary for binding to the liver and possibly their clearance from the blood circulation.
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Gurau, Vladimir, Sadik Kakaç, and Hongtan Liu. "Mathematical Model for Proton Exchange Membrane Fuel Cells." In ASME 1998 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 1998. http://dx.doi.org/10.1115/imece1998-0845.
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Abstract A two dimensional, non-isothermal mathematical model for the entire sandwich of a proton exchange membrane (PEM) fuel cell including the gas channels is developed. To take into consideration the real concentration distributions along the interface between the gas diffuser and catalyst layer, transport equations are solved simultaneously for the domain consisting of the coupled gas channel, gas diffuser, catalyst layer and membrane. The selfconsistent schematical model for porous media is used for the equations describing transport phenomena in the membrane, catalyst layers and gas diffusers, while standard Navier-Stokes, energy transport, continuity and species concentration equations are solved in the gas channels. A special handling of the transport equations enabled us to use the same numerical method to solve them, and therefore to treat the gas channel-gas diffuser-catalyst layer domains as an entirety, avoiding arbitrary boundary conditions at their interfaces. The oxygen mole fraction distribution in the coupled cathode gas channel-gas diffuser is studied for different values of the operating current density. Influences of the inlet conditions at the gas channel entries and of the gas diffuser porosity on the cell performance are also analyzed.
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Usta, Mustafa, Ali E. Anqi, Michael Morabito, Alaa Hakim, Mohammed Alrehili, and Alparslan Oztekin. "Computational Study of Reverse Osmosis Desalination Process: Hollow Fiber Module." In ASME 2017 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2017. http://dx.doi.org/10.1115/imece2017-70884.
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Reverse Osmosis (RO) is a process whereby solutes are removed from a solution by means of a semipermeable membrane. Providing access to clean water is one of our generation’s grand engineering challenges, and RO processes are taking center stage in the global implementation of water purification technologies. In this work, computational fluid dynamics simulations are performed to elucidate the steady state phenomena associated with the mass transport of solution through cylindrical hollow fiber membranes in hopes of optimizing RO technologies. The Navier-Stokes and mass transport equations are solved numerically to determine the flow field and solute concentration distribution in the hollow fiber membrane bank, which is a portion of the three-dimensional feed channel containing a small collection of fibers. The k-ω Shear Stress Transport turbulence model is employed to characterize the flow field. Special attention is given to the prediction of water passage through hollow fiber membranes by the use of the solution-diffusion model, which couples the salt gradient, water flux, and local pressure at the membrane surface. This work probes hollow fiber membrane arrangement in the feed channel by considering inline and staggered alignments. Feed flow rates for Reynolds number values ranging between 400 and 1000 are considered. Increased momentum mixing within the feed channel solution can substantially enhance the system efficiency, and hollow fiber membrane arrangements and feed flow rates dictate the momentum mixing intensity. Velocity and vorticity iso-surfaces of the flow domain are presented in order to assess the momentum mixing achieved with various hollow fiber membrane arrangements and flow rates. The total water permeation rate per hour is calculated to compare system efficiencies, and the coefficient of performance is calculated to compare membrane performance relative to the necessary power input, both for the various hollow fiber membrane arrangements and feed flow rates.
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Jiang, Yanfei, Guy M. Genin, Srikanth Singamaneni, and Elliot L. Elson. "Interfacial Phases on Giant Unilamellar Vesicles." In ASME 2012 Summer Bioengineering Conference. American Society of Mechanical Engineers, 2012. http://dx.doi.org/10.1115/sbc2012-80942.
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Lipid nanodomains in cell membranes are believed to play a significant role in a number of critical cellular processes (Elson, et al., 2010). These include, for example, replication processes in enveloped viruses such as bird flu and HIV and signaling mechanisms underlying pathological conditions such as cancer. Due to the potential for developing new disease treatments through the control of these membrane rafts, the biophysics underlying their formation has been the subject of intense study, much of this focused on domain formation in giant unilamellar lipid vesicles (GUVs), a simplified model system.
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Romero, T., and W. Me´rida. "Transient Water Transport in Nafion Membranes Under Activity Gradients." In ASME 2010 8th International Conference on Fuel Cell Science, Engineering and Technology. ASMEDC, 2010. http://dx.doi.org/10.1115/fuelcell2010-33317.
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Transient water transport experiments on Nafion of different thicknesses were carried out in the temperature range of 30 to 70 °C. These experiments report on water transport measurements under activity gradients in the time domain for liquid and vapour equilibrated Nafion membranes. Using a permeability test rig with a gated valve, the water crossover was measured as a function of time. The typical response is shown as a time dependent flux, and it shows the dynamic transport from an initially dry condition up to the final steady state. Contrarily to previous reports from dynamic water transport measurements, where the activity gradient across the membrane is absent; in this work, the membrane was subjected to an activity gradient acting as the driving force to transport water from an environment with higher water activity to an environment with lower water activity through the membrane’s structure. Measurements explored temperature and membrane thickness variation effect on the transient response. Results showed dependency on temperature and a slower water transport rate across the vapour-membrane interface than for the liquid-membrane interface. These measurements showed the transport dependency on water content at the beginning of the experiment when the membrane was in a close-to-dry condition suggesting a transport phenomenon transition due to a reached critical water content value. The new protocol for transient measurements proposed here will allow the characterization of water transport dependency on membrane water content with a more rational representation of the membrane-environment interface.
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Jahangiri Mamouri, Sina, Volodymyr V. Tarabara, and André Bénard. "Numerical Simulation of Filtration of Charged Oil Particles in Stationary and Rotating Tubular Membranes." In ASME 2015 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2015. http://dx.doi.org/10.1115/imece2015-52038.
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Cross flow filtration (CFF) is a common membrane separation process with applications in food, biochemical and petroleum industries. In particular, membranes can be used for liquid-liquid separation processes such as needed in oil-water separation. A major challenge in cross flow filtration is membrane fouling. It can decrease significantly the permeate flux and a membrane’s efficiency. Membrane fouling can be mitigated by inducing shear on the membrane’s surface and this can be enhanced by inducing a swirl in the flow. In addition, a possible approach to improve membrane efficiency consists of repelling droplets/particles from the porous surface toward the centerline using a repulsive electric force. For this purpose, the surface of the membrane can be exposed to electric potential and droplets/particles are also induced to have the same electric charge. In this work, numerical simulations of charged non-deformable droplets moving within an axially rotating charged tubular membrane are performed. The results show that by increasing the electric potential on the membrane surface, the repelling force increases which obviously improves the grade efficiency of the membrane. However, the electric field gradients found in the flow field require large potentials on the membrane surface to observe a noticeable effect. Hence, a smaller solid cylinder is located in the centerline of the flow channel with zero potential. This solid cylinder enhances the electric field gradient in the domain which results in higher repelling forces and larger grade efficiency of the membrane at small potentials. The addition of a small cylinder in the flow field also improves the grade efficiency increases due to the higher shear stress near the membrane surface.
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Swickrath, Michael J., Kevin Dorfman, Yoav Segal, and Victor H. Barocas. "The Effect of Composition and Inter- and Intrafibrillar Interactions on the Structure of Collagen IV Networks in the Computer-Simulated Glomerular Basement Membrane." In ASME 2009 Summer Bioengineering Conference. American Society of Mechanical Engineers, 2009. http://dx.doi.org/10.1115/sbc2009-205518.
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The glomerular basement membrane of the kidney, responsible for performing ultrafiltration blood plasma, is largely comprised of type-IV collagen and laminin. Type-IV collagen self-assembles into a heterotrimer composed of three distinct domains (fig. 1A): (1) the globular non-collagenous NCl domain of ∼10 nm in diameter, (2) the non-collagenous 7S domain ∼30 nm in length and ∼3nm in diameter, and (3) the collagenous triple helix of ∼370 nm in length and ∼3 nm in diameter composed of a repeating Gly-X-Y subunit [1]. The heterotrimers associate with remarkable specificity from six genetically distinct α-chains, α1(IV) to α6(IV) forming α1α1α2, α3α4α5, and α5α5α6 heterotrimers [2]. In the healthy glomerulus, α1α1α2 ([α1]2α2) is the predominate collagen while significant α3α4α5 is present; α5α5α6 exists only in negligible quantities [2].
Reports on the topic "Membrance domains"
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Shai, Yechiel, Arthur Aronson, Aviah Zilberstein, and Baruch Sneh. Study of the Basis for Toxicity and Specificity of Bacillus thuringiensis d-Endotoxins. United States Department of Agriculture, January 1996. http://dx.doi.org/10.32747/1996.7573995.bard.
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The report contains three parts which summarizes the three years achievements of the three participating research groups; The Weizmann group, Tel-Aviv group and Purdue group. The firs part describes the achievements obtained by Shai's group toward the elucidation of the mechanism of membrane insertion and the structural organization of the pores formed by the Cry3A and Cry1Ac B. thuringiensis d-endotoxins. For that purpose Shai's group synthesized, fluorescently labeled and structurally and functionally characterized peptides corresponding to the seven helices that compose the pore-forming domain of Cry3A toxin, including mutants peptides and the hairpin a4G-a5 of both Cry3A and Cry 1Ac toxins composed of a4, a5 and the loop connecting a4-a5. Among the synthesized peptides were three mutated a4 helices based on site directed mutagenesis done at Aronson's group that decreased or increased Cry 1Ac toxicity. The results of these studies are consistent with a situation in which only helices a4 anda5 insert into the membrane as a helical hairpin in an antiparallel manner, while the other helices lie on the membrane surface like ribs of an umbrella (the "umbrella model"). In order to test this model Shai's group synthesized the helical hairpin a4<-->a5 of both Cry3A and Cry 1 Ac toxins, as well. Initial functional and structural studies showed direct correlation between the properties of the mutated helices and the mutated Cry1Ac. Based on Shai's findings that a4 is the second helix besides a5 that insert into the membrane, Aronson and colleagues performed extensive mutation on this helix in the CrylAc toxin, as well as in the loop connecting helices 4 and 5, and helix 3 (part two of the report). In addition, Aronson performed studies on the effect of mutations or type of insect which influence the oligomerization either the Cry 1Ab or Cry 1Ac toxins with vesicles prepared from BBMV. In the third part of the report Zilberstein's and Sneh's groups describe their studies on the three domains of Cry 1C, Cry 1E and crylAc and their interaction with the epithelial membrane of the larval midgut. In these studies they cloned all three domains and combinations of two domains, as well as cloning of the pore forming domain alone and studying its interaction with BBMV. In addition they investigated binding of Cry1E toxin and Cry1E domains to BBMV prepared from resistant (R) or sensitive larvae. Finally they initiated expression of the loop a4G<-->a5 Cry3A in E. coli to be compared with the synthetic one done by Shai's group as a basis to develop a system to express all possible pairs for structural and functional studies by Shai's group (together with Y. Shai).
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Wisniewski, Michael, Samir Droby, John Norelli, Dov Prusky, and Vera Hershkovitz. Genetic and transcriptomic analysis of postharvest decay resistance in Malus sieversii and the identification of pathogenicity effectors in Penicillium expansum. United States Department of Agriculture, January 2012. http://dx.doi.org/10.32747/2012.7597928.bard.
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Use of Lqh2 mutants (produced at TAU) and rNav1.2a mutants (produced at the US side) for identifying receptor site-3: Based on the fact that binding of scorpion alpha-toxins is voltage-dependent, which suggests toxin binding at the mobile voltage-sensing region, we analyzed which of the toxin bioactive domains (Core-domain or NC-domain) interacts with the DIV Gating-module of rNav1.2a. This analysis was based on the assumption that the dissociation of toxin mutants upon depolarization would vary from that of the unmodified toxin should the substitutions affect a site of interaction with the channel Gating-module. Using a series of toxin mutants (mutations at both domains) and two channel mutants that were shown to reduce the sensitivity to scorpion alpha-toxins, and by comparison of depolarization-driven dissociation of Lqh2 derivatives off their binding site at rNav1.2a mutant channels we found that the toxin Core-domain interacts with the Gating-module of DIV. Details of the experiments and results appear in Guret al (2011). Mapping receptor site 3 at Nav1.2a by extensive channel mutagenesis (Seattle): Since previous studies with photoaffinity labeling and antibody mapping implicated domains I and IV in scorpion alpha-toxin binding, Nav1.2 channel mutants containing substitutions at these extracellular regions were expressed and tested for receptor function by whole-cell voltage clamp. Of a large number of channel mutants, T1560A, F1610A, and E1613A in domain IV had ~5.9-, ~10.7-, and ~3.9-fold lower affinities for the scorpion toxin Lqh2, respectively, and mutant E1613R had 73-fold lower affinity. Toxin dissociation was accelerated by depolarization for both wild-type and mutants, and the rates of dissociation were also increased by mutations T1560A, F1610A and E1613A. In contrast, association rates for these three mutant channels at negative membrane potentials were not significantly changed and were not voltage-dependent. These results indicated that Thr1560 in the S1-S2 loop, Phe1610 in the S3 segment, and Glu1613 in the S3-S4 loop in domain IV participate in toxin binding. T393A in the SS2-S6 loop in domain I also showed a ~3.4-fold lower affinity for Lqh2, indicating that this extracellular loop may form a secondary component of the toxin binding site. Analysis with the Rosetta-Membrane algorithm revealed a three-dimensional model of Lqh2 binding to the voltage sensor in a resting state. In this model, amino acid residues in an extracellular cleft formed by the S1-S2 and S3-S4 loops in domain IV that are important for toxin binding interact with amino acid residues on two faces of the wedge-shaped Lqh2 molecule that are important for toxin action. The conserved gating charges in the S4 transmembrane segment are in an inward position and likely form ion pairs with negatively charged amino acid residues in the S2 and S3 segments (Wang et al 2011; Gurevitz 2012; Gurevitzet al 2013).
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Mevarech, Moshe, Jeremy Bruenn, and Yigal Koltin. Virus Encoded Toxin of the Corn Smut Ustilago Maydis - Isolation of Receptors and Mapping Functional Domains. United States Department of Agriculture, September 1995. http://dx.doi.org/10.32747/1995.7613022.bard.
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Ustilago maydis is a fungal pathogen of maize. Some strains of U. maydis encode secreted polypeptide toxins capable of killing other susceptible strains of U. maydis. Resistance to the toxins is conferred by recessive nuclear genes. The toxins are encoded by genomic segments of resident double-strande RNA viruses. The best characterized toxin, KP6, is composed of two polypeptides, a and b, which are not covalently linked. It is encoded by P6M2 dsRNA, which has been cloned, sequenced and expressed in a variety of systems. In this study we have shown that the toxin acts on the membranes of sensitive cells and that both polypeptides are required for toxin activity. The toxin has been shown to function by creating new pores in the cell membrane and disrupting ion fluxes. The experiments performed on artificial phospholipid bilayers indicated that KP6 forms large voltage-independent, cation-selective channels. Experiments leading to the resolution of structure-function relationship of the toxin by in vitro analysis have been initiated. During the course of this research the collaboration also yielded X-ray diffracion data of the crystallized a polypeptide. The effect of the toxin on the pathogen has been shown to be receptor-mediated. A potential receptor protein, identified in membrane fractions of sensitive cells, was subjected to tryptic hydrolysis followed by amino-acid analysis. The peptides obtained were used to isolate a cDNA fragment by reverse PCR, which showed 30% sequence homology to the human HLA protein. Analysis of other toxins secreted by U. maydis, KP1 and KP4, have demonstrated that, unlike KP6, they are composed of a single polypeptide. Finally, KP6 has been expressed in transgenic tobacco plants, indicating that accurate processing by Kex2p-like activity occurs in plants as well. Using tobacco as a model system, we determined that active antifungal toxins can be synthesized and targeted to the outside of transgenic plant cells. If this methodology can be applied to other agronomically crop species, then U. maydis toxins may provide a novel means for biological control of pathogenic fungi.
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Brown, Deborah A. The Role of Spingolipid- and Cholesterol-Rich Membrane Domains in Pathophysiology of Cultured Human Breast Cancer. Fort Belvoir, VA: Defense Technical Information Center, June 2001. http://dx.doi.org/10.21236/ada395838.
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Brown, Deborah A. The Role of Sphingolipid-and Cholesterol-Rich Membrane Domains in Pathophysiology and Cultured Human Breast Cancer. Fort Belvoir, VA: Defense Technical Information Center, June 2004. http://dx.doi.org/10.21236/ada431301.
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Brown, Deborah A. The Role of Sphingolipid- and Cholesterol-Rich Membrane Domains in Pathophsiology of Cultured Human Breast Cancer. Fort Belvoir, VA: Defense Technical Information Center, June 2003. http://dx.doi.org/10.21236/ada421916.
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Oliver, Janet, Janet Pfeiffer, Bridget Wilson, and Alan Richard Burns. Studies of signaling domains in model and biological membranes through advanced imaging techniques: final report. US: Sandia National Laboratories, October 2006. http://dx.doi.org/10.2172/894746.
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Yordanova, Vesela, Galya Staneva, Miglena Angelova, Victoria Vitkova, Aneliya Kostadinova, Dayana Benkova, Ralitsa Veleva, and Rusina Hazarosova. Modelling of Molecular Mechanisms of Membrane Domain Formation during the Oxidative Stress: Effect of Palmitoyl-oxovaleroyl-phosphatidylcholine. "Prof. Marin Drinov" Publishing House of Bulgarian Academy of Sciences, January 2021. http://dx.doi.org/10.7546/crabs.2021.01.10.
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Zilberstein, Aviah, Bo Liu, and Einat Sadot. Studying the Involvement of the Linker Protein CWLP and its Homologue in Cytoskeleton-plasma Membrane-cell Wall Continuum and in Drought Tolerance. United States Department of Agriculture, June 2012. http://dx.doi.org/10.32747/2012.7593387.bard.
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The study has been focused on proline-rich proteins from the HyPRP family. Three proline-rich proteins have been characterized with the CWLP as the main objective. We showed that this unique protein is assembled in the plasma membrane (PM) and forms a continuum between the cell wall (CW) and cytosol via the PM. While spanning the PM, it is arranged in lipid rafts as CWLP-aquaporin complexes that recruit PP2A-β”, as a part of PP2A enzyme, close to the aquaporin moiety where it dephosphorylates two crucial Ser residues and induces closure of the aquaporin water channels. The closure of water channels renders cells more tolerant to plasmolysis and plants to dehydration. This unique effect was observed not only in Arabidopsis, but also in potato plants over expressing the CWLP, suggesting a possible usage in crop plants as a valve that reduces loss of water or/and elevates cold resistance. The CWLP is a member of the HyPRP protein family that all possess structurally similar 8CM domain, predicted to localize to PM lipid rafts. In this study, two additional highly homologous HyPRP proteins were also studied. The GPRP showed the same localization and it’s over expression increased tolerance to lack of water. However, the third one, PRP940, despite sharing high homology in the 8CM domain, is completely different and is assembled in parallel to cortical microtubules in the cell. Moreover, our data suggest that this protein is not involved in rendering plants resistant to lack of water. We suggest implying CWLP as a tool for better regulation of water maintenance in crop plants.
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McElwain, Terry, Eugene Pipano, Guy Palmer, Varda Shkap, Stephen Hines, and Douglas Jasmer. Protection of Cattle Against Babesiosis: Immunization with Recombinant DNA Derived Apical Complex Antigens of Babesia bovis. United States Department of Agriculture, June 1995. http://dx.doi.org/10.32747/1995.7612835.bard.
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Bovine babesiosis caused by Babesia bovis continues to be a significant deterrent to global livestock production. Current control methods have both biological and technical drawbacks that have stimulated research on improved methods of vaccination. This BARD project has focused on characterization of candidate Babesia bovis vaccine antigens located in the apical complex, a unique group of subcellular organelles - including rhoptries, micronemes, and spherical bodies - involved in the invation of erythrocytes. Spherical bodies and rhoptries were partially purified and their contents characterized using monoclonal antibodies. Existing and newly developed monoclonal antibodies bound to antigens in the spherical body, rhoptry, merozoite membrane, and infected erythrocyte membrane. In an initial immunization study using biologically cloned strains, it was demonstrated that strain-common epitopes are important for inducing immune protection against heterologous challenge. Rhoptry-associated antigen 1 (RAP-1) had been demonstrated previously to induce partial immune protection, fulfilled criteria of broad interstrain B and T cell epitope conservation, and thus was further characterized. The RAP-1 gene family consists of at least two gene copies, is homologous to the RAP-1 gene family in B. bigemina, and contains significant sequence similarity to other erythroparasitic protozoan candidate vaccine antigens, including the apical membrane antigen of Plasmodium falciparum. A new RAP-1 monoclonal antibody was developed that inhibits merozoite growth in vitro, demonstrating the presence of a RAP-1 neutralization sensitive domain. Based on these observations, cattle were immunized with Mo7 (Mexico) strain recombinant RAP-1 representing one of the two gene copies. All cattle responded with variable levels of serum antibodies inhibitory to heterologous Israel strain merozoite growth in vitro, and RAP-1 specific T lymphocytes that proliferated when stimulated with either homologous or heterologous native parasite antigen. Minimal protection from clinical disease was present after virulent Israel (heterologous) strain B. bovis challenge. In total, the results support the continued development of RAP-1 as a vaccine antigen, but indicate that additional information about the native structure and function of both RAP-1 gene copies, including the relationship of conserved and polymorphic sequences to B and T cell lepitopes relevant for protection, is necessary for optimization of RAP-1 as a vaccine component.