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Sample records for raft aggregates enriched

  1. Lipid Rafts: Linking Alzheimer's Amyloid-β Production, Aggregation, and Toxicity at Neuronal Membranes

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    Jo V. Rushworth

    2011-01-01

    Full Text Available Lipid rafts are membrane microdomains, enriched in cholesterol and sphingolipids, into which specific subsets of proteins and lipids partition, creating cell-signalling platforms that are vital for neuronal functions. Lipid rafts play at least three crucial roles in Alzheimer's Disease (AD, namely, in promoting the generation of the amyloid-β (Aβ peptide, facilitating its aggregation upon neuronal membranes to form toxic oligomers and hosting specific neuronal receptors through which the AD-related neurotoxicity and memory impairments of the Aβ oligomers are transduced. Recent evidence suggests that Aβ oligomers may exert their deleterious effects through binding to, and causing the aberrant clustering of, lipid raft proteins including the cellular prion protein and glutamate receptors. The formation of these pathogenic lipid raft-based platforms may be critical for the toxic signalling mechanisms that underlie synaptic dysfunction and neuropathology in AD.

  2. Involvement of glycosphingolipid-enriched lipid rafts in inflammatory responses.

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    Iwabuchi, Kazuhisa

    2015-01-01

    Glycosphingolipids (GSLs) are membrane components consisting of hydrophobic ceramide and hydrophilic sugar moieties. GSLs cluster with cholesterol in cell membranes to form GSL-enriched lipid rafts. Biochemical analyses have demonstrated that GSL-enriched lipid rafts contain several kinds of transducer molecules, including Src family kinases. Among the GSLs, lactosylceramide (LacCer, CDw17) can bind to various microorganisms, is highly expressed on the plasma membranes of human phagocytes, and forms lipid rafts containing the Src family tyrosine kinase Lyn. LacCer-enriched lipid rafts mediate immunological and inflammatory reactions, including superoxide generation, chemotaxis, and non-opsonic phagocytosis. Therefore, LacCer-enriched membrane microdomains are thought to function as pattern recognition receptors (PRRs), which recognize pathogen-associated molecular patterns (PAMPs) expressed on microorganisms. LacCer also serves as a signal transduction molecule for functions mediated by CD11b/CD18-integrin (αM/β2-integrin, CR3, Mac-1), as well as being associated with several key cellular processes. LacCer recruits PCKα/ε and phospholipase A2 to stimulate PECAM-1 expression in human monocytes and their adhesion to endothelial cells, as well as regulating β1-integrin clustering and endocytosis on cell surfaces. This review describes the organizational and inflammation-related functions of LacCer-enriched lipid rafts.

  3. Properties of glycolipid-enriched membrane rafts in antigen presentation.

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    Rodgers, William; Smith, Kenneth

    2005-01-01

    Presentation of antigen to T cells represents one of the central events in the engagement of the immune system toward the defense of the host against pathogens. Accordingly, understanding the mechanisms by which antigen presentation occurs is critical toward our understanding the properties of host defense against foreign antigen, as well as insight into other features of the immune system, such as autoimmune disease. The entire antigen-presentation event is complex, and many features of it remain poorly understood. However, recent studies have provided evidence showing that glycolipid-enriched membrane rafts are important for efficient antigen presentation; the studies suggest that one such function of rafts is trafficking of antigen-MHC II complexes to the presentation site on the surface of the antigen-presenting cell. Here, we present a critical discussion of rafts and their proposed functions in antigen presentation. Emerging topics of rafts and antigen presentation that warrant further investigation are also highlighted.

  4. Dynamic changes in the mobility of LAT in aggregated lipid rafts upon T cell activation.

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    Tanimura, Natsuko; Nagafuku, Masakazu; Minaki, Yasuko; Umeda, Yukio; Hayashi, Fumie; Sakakura, Junko; Kato, Akiko; Liddicoat, Douglas R; Ogata, Masato; Hamaoka, Toshiyuki; Kosugi, Atsushi

    2003-01-06

    Lipid rafts are known to aggregate in response to various stimuli. By way of raft aggregation after stimulation, signaling molecules in rafts accumulate and interact so that the signal received at a given membrane receptor is amplified efficiently from the site of aggregation. To elucidate the process of lipid raft aggregation during T cell activation, we analyzed the dynamic changes of a raft-associated protein, linker for activation of T cells (LAT), on T cell receptor stimulation using LAT fused to GFP (LAT-GFP). When transfectants expressing LAT-GFP were stimulated with anti-CD3-coated beads, LAT-GFP aggregated and formed patches at the area of bead contact. Photobleaching experiments using live cells revealed that LAT-GFP in patches was markedly less mobile than that in nonpatched regions. The decreased mobility in patches was dependent on raft organization supported by membrane cholesterol and signaling molecule binding sites, especially the phospholipase C gamma 1 binding site in the cytoplasmic domain of LAT. Thus, although LAT normally moves rapidly at the plasma membrane, it loses its mobility and becomes stably associated with aggregated rafts to ensure organized and sustained signal transduction required for T cell activation.

  5. Tumor exosomes induce tunneling nanotubes in lipid raft-enriched regions of human mesothelioma cells

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    Thayanithy, Venugopal [Department of Medicine, Division of Hematology, Oncology and Transplantation, University of Minnesota, Minneapolis, MN 55455 (United States); Babatunde, Victor [Moore Laboratory, Department of Cell Biology, Sloan-Kettering Institute, Memorial Sloan-Kettering Cancer Center, New York, NY 10021 (United States); Dickson, Elizabeth L. [Department of Obstetrics and Gynecology, Division of Gynecologic Oncology, University of Minnesota, Minneapolis, MN 55455 (United States); Wong, Phillip [Department of Medicine, Division of Hematology, Oncology and Transplantation, University of Minnesota, Minneapolis, MN 55455 (United States); Oh, Sanghoon; Ke, Xu; Barlas, Afsar; Fujisawa, Sho; Romin, Yevgeniy [Molecular Cytology, Memorial Sloan-Kettering Cancer Center, New York, NY 10021 (United States); Moreira, André L. [Department of Pathology, Memorial Sloan-Kettering Cancer Center, New York, NY 10021 (United States); Downey, Robert J. [Department of Surgery, Memorial Sloan-Kettering Cancer Center, New York, NY 10021 (United States); Steer, Clifford J. [Departments of Medicine and Genetics, Cell Biology and Development, University of Minnesota, Minneapolis, MN 55455 (United States); Subramanian, Subbaya [Department of Surgery, University of Minnesota, Minneapolis, MN 55455 (United States); Manova-Todorova, Katia [Molecular Cytology, Memorial Sloan-Kettering Cancer Center, New York, NY 10021 (United States); Moore, Malcolm A.S. [Moore Laboratory, Department of Cell Biology, Sloan-Kettering Institute, Memorial Sloan-Kettering Cancer Center, New York, NY 10021 (United States); Lou, Emil, E-mail: emil-lou@umn.edu [Department of Medicine, Division of Hematology, Oncology and Transplantation, University of Minnesota, Minneapolis, MN 55455 (United States)

    2014-04-15

    Tunneling nanotubes (TnTs) are long, non-adherent, actin-based cellular extensions that act as conduits for transport of cellular cargo between connected cells. The mechanisms of nanotube formation and the effects of the tumor microenvironment and cellular signals on TnT formation are unknown. In the present study, we explored exosomes as potential mediators of TnT formation in mesothelioma and the potential relationship of lipid rafts to TnT formation. Mesothelioma cells co-cultured with exogenous mesothelioma-derived exosomes formed more TnTs than cells cultured without exosomes within 24–48 h; and this effect was most prominent in media conditions (low-serum, hyperglycemic medium) that support TnT formation (1.3–1.9-fold difference). Fluorescence and electron microscopy confirmed the purity of isolated exosomes and revealed that they localized predominantly at the base of and within TnTs, in addition to the extracellular environment. Time-lapse microscopic imaging demonstrated uptake of tumor exosomes by TnTs, which facilitated intercellular transfer of these exosomes between connected cells. Mesothelioma cells connected via TnTs were also significantly enriched for lipid rafts at nearly a 2-fold higher number compared with cells not connected by TnTs. Our findings provide supportive evidence of exosomes as potential chemotactic stimuli for TnT formation, and also lipid raft formation as a potential biomarker for TnT-forming cells. - Highlights: • Exosomes derived from malignant cells can stimulate an increased rate in the formation of tunneling nanotubes. • Tunneling nanotubes can serve as conduits for intercellular transfer of these exosomes. • Most notably, exosomes derived from benign mesothelial cells had no effect on nanotube formation. • Cells forming nanotubes were enriched in lipid rafts at a greater number compared with cells not forming nanotubes. • Our findings suggest causal and potentially synergistic association of exosomes and

  6. y Human herpesvirus 6 envelope components enriched in lipid rafts: evidence for virion-associated lipid rafts

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    Yamanishi Koichi

    2009-08-01

    Full Text Available Abstract In general, enveloped viruses are highly dependent on their lipid envelope for entry into host cells. Here, we demonstrated that during the course of virus maturation, a significant proportion of human herpesvirus 6 (HHV-6 envelope proteins were selectively concentrated in the detergent-resistant glycosphingolipid- and cholesterol-rich membranes (rafts in HHV-6-infected cells. In addition, the ganglioside GM1, which is known to partition preferentially into lipid rafts, was detected in purified virions, along with viral envelope glycoproteins, gH, gL, gB, gQ1, gQ2 and gO indicating that at least one raft component was included in the viral particle during the assembly process.

  7. Proteomic identification of VEGF-dependent protein enrichment to membrane caveolar-raft microdomains in endothelial progenitor cells.

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    Chillà, Anastasia; Magherini, Francesca; Margheri, Francesca; Laurenzana, Anna; Gamberi, Tania; Bini, Luca; Bianchi, Laura; Danza, Giovanna; Mazzanti, Benedetta; Serratì, Simona; Modesti, Alessandra; Del Rosso, Mario; Fibbi, Gabriella

    2013-07-01

    Endothelial cell caveolar-rafts are considered functional platforms that recruit several pro-angiogenic molecules to realize an efficient angiogenic program. Here we studied the differential caveolar-raft protein composition of endothelial colony-forming cells following stimulation with VEGF, which localizes in caveolae on interaction with its type-2 receptor. Endothelial colony-forming cells are a cell population identified in human umbilical blood that show all the properties of an endothelial progenitor cell and a high proliferative rate. Two-dimensional gel electrophoresis analysis was coupled with mass spectrometry to identify candidate proteins. The twenty-eight differentially expressed protein spots were grouped according to their function using Gene Ontology classification. In particular, functional categories relative to cell death inhibition and hydrogen peroxide metabolic processes resulted enriched. In these categories, Peroxiredoxin-2 and 6, that control hydrogen peroxide metabolic processes, are the main enriched molecules together with the anti-apoptotic 78 kDa glucose regulated protein. Some of the proteins we identified had never before identified as caveolar-raft components. Other identified proteins include calpain small subunit-1, known to mediates angiogenic response to VEGF, gelsolin, which regulates stress fiber assembly, and annexin A3, an angiogenic mediator that induces VEGF production. We validated the functional activity of the above proteins, showing that the siRNA silencing of these resulted in the inhibition of capillary morphogenesis. Overall, our data show that VEGF stimulation triggers the caveolar-raft recruitment of proteins that warrant a physiological amount of reactive oxygen species to maintain a proper angiogenic function of endothelial colony-forming cells and preserve the integrity of the actin cytoskeleton.

  8. SDF-1α/CXCR4 Signaling in Lipid Rafts Induces Platelet Aggregation via PI3 Kinase-Dependent Akt Phosphorylation.

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    Ohtsuka, Hiroko; Iguchi, Tomohiro; Hayashi, Moyuru; Kaneda, Mizuho; Iida, Kazuko; Shimonaka, Motoyuki; Hara, Takahiko; Arai, Morio; Koike, Yuichi; Yamamoto, Naomasa; Kasahara, Kohji

    2017-01-01

    Stromal cell-derived factor-1α (SDF-1α)-induced platelet aggregation is mediated through its G protein-coupled receptor CXCR4 and phosphatidylinositol 3 kinase (PI3K). Here, we demonstrate that SDF-1α induces phosphorylation of Akt at Thr308 and Ser473 in human platelets. SDF-1α-induced platelet aggregation and Akt phosphorylation are inhibited by pretreatment with the CXCR4 antagonist AMD3100 or the PI3K inhibitor LY294002. SDF-1α also induces the phosphorylation of PDK1 at Ser241 (an upstream activator of Akt), GSK3β at Ser9 (a downstream substrate of Akt), and myosin light chain at Ser19 (a downstream element of the Akt signaling pathway). SDF-1α-induced platelet aggregation is inhibited by pretreatment with the Akt inhibitor MK-2206 in a dose-dependent manner. Furthermore, SDF-1α-induced platelet aggregation and Akt phosphorylation are inhibited by pretreatment with the raft-disrupting agent methyl-β-cyclodextrin. Sucrose density gradient analysis shows that 35% of CXCR4, 93% of the heterotrimeric G proteins Gαi-1, 91% of Gαi-2, 50% of Gβ and 4.0% of PI3Kβ, and 4.5% of Akt2 are localized in the detergent-resistant membrane raft fraction. These findings suggest that SDF-1α/CXCR4 signaling in lipid rafts induces platelet aggregation via PI3K-dependent Akt phosphorylation.

  9. SDF-1α/CXCR4 Signaling in Lipid Rafts Induces Platelet Aggregation via PI3 Kinase-Dependent Akt Phosphorylation

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    Hayashi, Moyuru; Kaneda, Mizuho; Iida, Kazuko; Shimonaka, Motoyuki; Hara, Takahiko; Arai, Morio; Koike, Yuichi; Yamamoto, Naomasa; Kasahara, Kohji

    2017-01-01

    Stromal cell-derived factor-1α (SDF-1α)-induced platelet aggregation is mediated through its G protein-coupled receptor CXCR4 and phosphatidylinositol 3 kinase (PI3K). Here, we demonstrate that SDF-1α induces phosphorylation of Akt at Thr308 and Ser473 in human platelets. SDF-1α-induced platelet aggregation and Akt phosphorylation are inhibited by pretreatment with the CXCR4 antagonist AMD3100 or the PI3K inhibitor LY294002. SDF-1α also induces the phosphorylation of PDK1 at Ser241 (an upstream activator of Akt), GSK3β at Ser9 (a downstream substrate of Akt), and myosin light chain at Ser19 (a downstream element of the Akt signaling pathway). SDF-1α-induced platelet aggregation is inhibited by pretreatment with the Akt inhibitor MK-2206 in a dose-dependent manner. Furthermore, SDF-1α-induced platelet aggregation and Akt phosphorylation are inhibited by pretreatment with the raft-disrupting agent methyl-β-cyclodextrin. Sucrose density gradient analysis shows that 35% of CXCR4, 93% of the heterotrimeric G proteins Gαi-1, 91% of Gαi-2, 50% of Gβ and 4.0% of PI3Kβ, and 4.5% of Akt2 are localized in the detergent-resistant membrane raft fraction. These findings suggest that SDF-1α/CXCR4 signaling in lipid rafts induces platelet aggregation via PI3K-dependent Akt phosphorylation. PMID:28072855

  10. Amyloid beta-protein and lipid rafts: focused on biogenesis and catabolism.

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    Araki, Wataru; Tamaoka, Akira

    2015-01-01

    Cerebral accumulation of amyloid β-protein (Aβ) is thought to play a key role in the molecular pathology of Alzheimer's disease (AD). Three secretases (β-, γ-, and α-secretase) are proteases that control the production of Aβ from amyloid precursor protein. Increasing evidence suggests that cholesterol-rich membrane microdomains termed 'lipid rafts' are involved in the biogenesis and accumulation of Aβ as well as Aβ-mediated neurotoxicity. γ-Secretase is enriched in lipid rafts, which are considered an important site for Aβ generation. Additionally, Aβ-degrading peptidases located in lipid rafts, such as neprilysin, appear to play a role in Aβ catabolism. This mini-review focuses on the roles of lipid rafts in the biogenesis and catabolism of Aβ, covering recent research on the relationship between lipid rafts and the three secretases or Aβ-degrading peptidases. Furthermore, the significance of lipid rafts in Aβ aggregation and neurotoxicity is briefly summarized.

  11. Lipid Raft Alterations in Aged-Associated Neuropathologies.

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    Marin, Raquel; Fabelo, Noemí; Fernández-Echevarría, Cecilia; Canerina-Amaro, Ana; Rodríguez-Barreto, Deiene; Quinto-Alemany, David; Mesa-Herrera, Fátima; Díaz, Mario

    2016-01-01

    Lipid rafts are membrane microdomains particularly enriched in cholesterol, sphingolipids and saturated fatty acids. These microstructures play a key role in a plethora of mechanisms involved in cell signaling, synapsis, cell-cell communication and cell survival. In the last years, increasing evidence indicate that lipid rafts may be altered in age-related neuropathologies, such as Alzheimer's disease and Parkinson disease even at asymptomatic stages. In particular, important changes in raft lipid composition are observed with the progression of these diseases, then inducing alterations in their physicochemical properties. Furthermore, these phenomena contribute to neuropathological events related to amyloidogenesis, aberrant protein aggregation and toxic cell signalling. In this review, we discuss some relevant data on the age-related molecular changes occurring in lipid rafts since the first stages of these neurodegenerative diseases. Further characterization of specific parameters associated with alterations of these microdomains may provide potential tools of diagnosis and prediction of these neuropathologies.

  12. Size-dependent enrichment of waste slag aggregate fragments abraded from asphalt concrete.

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    Takahashi, Fumitake; Shimaoka, Takayuki; Gardner, Kevin; Kida, Akiko

    2011-10-30

    Authors consider the environmental prospects of using melted waste slag as the aggregate for asphalt pavement. In particular, the enrichment of slag-derived fragments in fine abrasion dust particles originated from slag asphalt concrete and its size dependency were concerned. A series of surface abrasion tests for asphalt concrete specimens, containing only natural aggregates as reference or 30 wt% of substituted slag aggregates, were performed. Although two of three slag-asphalt concretes generated 1.5-3.0 times larger amount of abrasion dust than the reference asphalt concrete did, it could not be explained only by abrasion resistance of slag. The enrichment of slag-derived fragments in abrasion dust, estimated on the basis of the peak intensity of quartz and heavy metal concentrations, had size dependency for all slag-asphalt concretes. Slag-derived fragments were enriched in abrasion dust particles with diameters of 150-1000 μm. Enrichment factors were 1.4-2.1. In contrast, there was no enrichment in abrasion dust particles with diameter less than 75 μm. This suggests that prior airborne-size fragmentation of substituted slag aggregates does not need to be considered for tested slag aggregates when environmental risks of abrasion dust of slag-asphalt pavement are assessed.

  13. Dlgh1 coordinates actin polymerization, synaptic T cell receptor and lipid raft aggregation, and effector function in T cells.

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    Round, June L; Tomassian, Tamar; Zhang, Min; Patel, Viresh; Schoenberger, Stephen P; Miceli, M Carrie

    2005-02-07

    Lipid raft membrane compartmentalization and membrane-associated guanylate kinase (MAGUK) family molecular scaffolds function in establishing cell polarity and organizing signal transducers within epithelial cell junctions and neuronal synapses. Here, we elucidate a role for the MAGUK protein, Dlgh1, in polarized T cell synapse assembly and T cell function. We find that Dlgh1 translocates to the immune synapse and lipid rafts in response to T cell receptor (TCR)/CD28 engagement and that LckSH3-mediated interactions with Dlgh1 control its membrane targeting. TCR/CD28 engagement induces the formation of endogenous Lck-Dlgh1-Zap70-Wiskott-Aldrich syndrome protein (WASp) complexes in which Dlgh1 acts to facilitate interactions of Lck with Zap70 and WASp. Using small interfering RNA and overexpression approaches, we show that Dlgh1 promotes antigen-induced actin polymerization, synaptic raft and TCR clustering, nuclear factor of activated T cell activity, and cytokine production. We propose that Dlgh1 coordinates TCR/CD28-induced actin-driven T cell synapse assembly, signal transduction, and effector function. These findings highlight common molecular strategies used to regulate cell polarity, synapse assembly, and transducer organization in diverse cellular systems.

  14. RaftProt: mammalian lipid raft proteome database.

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    Shah, Anup; Chen, David; Boda, Akash R; Foster, Leonard J; Davis, Melissa J; Hill, Michelle M

    2015-01-01

    RaftProt (http://lipid-raft-database.di.uq.edu.au/) is a database of mammalian lipid raft-associated proteins as reported in high-throughput mass spectrometry studies. Lipid rafts are specialized membrane microdomains enriched in cholesterol and sphingolipids thought to act as dynamic signalling and sorting platforms. Given their fundamental roles in cellular regulation, there is a plethora of information on the size, composition and regulation of these membrane microdomains, including a large number of proteomics studies. To facilitate the mining and analysis of published lipid raft proteomics studies, we have developed a searchable database RaftProt. In addition to browsing the studies, performing basic queries by protein and gene names, searching experiments by cell, tissue and organisms; we have implemented several advanced features to facilitate data mining. To address the issue of potential bias due to biochemical preparation procedures used, we have captured the lipid raft preparation methods and implemented advanced search option for methodology and sample treatment conditions, such as cholesterol depletion. Furthermore, we have identified a list of high confidence proteins, and enabled searching only from this list of likely bona fide lipid raft proteins. Given the apparent biological importance of lipid raft and their associated proteins, this database would constitute a key resource for the scientific community.

  15. Organic Matter Enrichment and Aggregate Stabilization in a Severely Degraded Ultisol After Reforestation

    Institute of Scientific and Technical Information of China (English)

    ZHANG Bin; PENG Xin-Hua

    2006-01-01

    Three types of soils: an eroded barren soil under continuous fallow, an eroded soil transplanted with Lespedeza shrubs(Lespedeza bicolor), and an eroded soil transplanted with camphor tree (Cinnamomum camphora) were investigated to quantify organic matter pools and aggregates in reforested soils using physical fractionation techniques and to determine aggregate stability in relation to the enrichment of soil organic carbon (SOC). Soil organic matter (SOM) was physically fractionalized into free particulate organic matter (fPOM), occluded particulate organic matter (oPOM), and mineralassociated organic matter (mOM). The SOM was concentrated on the surface soil (0-5 cm), with an average C sequestration rate of 20-25 g C m-2 year-1 over 14 years. As compared to the eroded barren land, organic C content of fPOM, oPOM,and mOM fractions of the soil under Lespedeza and under camphor tree increased 12-15, 45-54, and 3.1-3.5 times,respectively. A linear relationship was found between aggregate stability and organic C (r2 = 0.45, P < 0.01), oPOM(r2 = 0.34, P < 0.05), and mOM (r2 = 0.46, P < 0.01) of aggregates. The enrichment of organic C improved aggregate stability of the soil under Lespedeza but not that under camphor tree. However, further research is needed on the physical and biological processes involved in the interaction of soil aggregation and SOC sequestration in ecosystem.

  16. Uptake of long chain fatty acids is regulated by dynamic interaction of FAT/CD36 with cholesterol/sphingolipid enriched microdomains (lipid rafts

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    Herrmann Thomas

    2008-08-01

    Full Text Available Abstract Background Mechanisms of long chain fatty acid uptake across the plasma membrane are important targets in treatment of many human diseases like obesity or hepatic steatosis. Long chain fatty acid translocation is achieved by a concert of co-existing mechanisms. These lipids can passively diffuse, but certain membrane proteins can also accelerate the transport. However, we now can provide further evidence that not only proteins but also lipid microdomains play an important part in the regulation of the facilitated uptake process. Methods Dynamic association of FAT/CD36 a candidate fatty acid transporter with lipid rafts was analysed by isolation of detergent resistant membranes (DRMs and by clustering of lipid rafts with antibodies on living cells. Lipid raft integrity was modulated by cholesterol depletion using methyl-β-cyclodextrin and sphingolipid depletion using myriocin and sphingomyelinase. Functional analyses were performed using an [3H]-oleate uptake assay. Results Overexpression of FAT/CD36 and FATP4 increased long chain fatty acid uptake. The uptake of long chain fatty acids was cholesterol and sphingolipid dependent. Floating experiments showed that there are two pools of FAT/CD36, one found in DRMs and another outside of these domains. FAT/CD36 co-localized with the lipid raft marker PLAP in antibody-clustered domains at the plasma membrane and segregated away from the non-raft marker GFP-TMD. Antibody cross-linking increased DRM association of FAT/CD36 and accelerated the overall fatty acid uptake in a cholesterol dependent manner. Another candidate transporter, FATP4, was neither present in DRMs nor co-localized with FAT/CD36 at the plasma membrane. Conclusion Our observations suggest the existence of two pools of FAT/CD36 within cellular membranes. As increased raft association of FAT/CD36 leads to an increased fatty acid uptake, dynamic association of FAT/CD36 with lipid rafts might regulate the process. There is no

  17. Cytotoxicity of calcium enriched mixture cement compared with mineral trioxide aggregate and intermediate restorative material.

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    Mozayeni, Mohammad A; Milani, Amin S; Marvasti, Laleh A; Asgary, Saeed

    2012-08-01

    Calcium enriched mixture (CEM) cement has been recently invented by the last author. It is composed of calcium oxide, calcium phosphate, calcium silicate and calcium sulphate; however, it has a different chemical composition to mineral trioxide aggregate (MTA). The purpose of this ex vivo study was to investigate the cytotoxicity of CEM cement, and compare it with intermediate restorative material (IRM) and MTA. The materials were tested in fresh and set states on L929 fibroblasts to assess their cytotoxicity. The cell viability responses were evaluated with methyl-tetrazolium bromide assay and Elisa reader at 1, 24 and 168 h (7 days). The tested materials were eluted with L929 culture medium according to international standard organisation 109935 standard. Distilled water and culture medium served as positive and negative controls, respectively. Differences in cytotoxicity were evaluated by one-way anova and t-tests. The cytotoxicity of the materials was statistically different at the three time intervals (P IRM subgroups were the most cytotoxic root-end/dental material (P IRM because of lower cytotoxicity. CEM cement also has good biocompatibility as well as lower estimated cost to MTA and seems to be a promising dental material.

  18. Designing the lipid raft marker protein for synaptic vesicles

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    Lv Jihua; Sui Senfang

    2009-01-01

    Lipid rafts are cholesterol-enriched microdomains and implicated in many essential physiological activities such as the neurotransmitter release. Many studies have been carried out on the function of rafts in the plasma membranes, whereas little is known about the information of such microdomains in subcellular compartments especially synaptic vesicles (SVs). In the well-studied plasma membranes, several proteins have been recognized as raft markers, which are used to label or trace rafts. But the raft marker protein on SVs has not been identified yet. Although some SV proteins, including VAMP and CPE, have been found in raft fractions, they cannot be used as markers due to their low abundance in rafts. In this work, we designed several chimera proteins and tested their characteristics for using as SV raft makers. First, we detected whether they located in SVs, and then the chimeras exhibiting the better localization in SVs were further examined for their enrichment in raft using detergent treatment and gradient density floatation analysis. Our results indicate that one of the chimeric proteins is primarily located in SVs and distributed in raft microdomains, which strongly suggests that it could be served as a raft marker for SVs.

  19. The lipid raft proteome of Borrelia burgdorferi.

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    Toledo, Alvaro; Pérez, Alberto; Coleman, James L; Benach, Jorge L

    2015-11-01

    Eukaryotic lipid rafts are membrane microdomains that have significant amounts of cholesterol and a selective set of proteins that have been associated with multiple biological functions. The Lyme disease agent, Borrelia burgdorferi, is one of an increasing number of bacterial pathogens that incorporates cholesterol onto its membrane, and form cholesterol glycolipid domains that possess all the hallmarks of eukaryotic lipid rafts. In this study, we isolated lipid rafts from cultured B. burgdorferi as a detergent resistant membrane (DRM) fraction on density gradients, and characterized those molecules that partitioned exclusively or are highly enriched in these domains. Cholesterol glycolipids, the previously known raft-associated lipoproteins OspA and OpsB, and cholera toxin partitioned into the lipid rafts fraction indicating compatibility with components of the DRM. The proteome of lipid rafts was analyzed by a combination of LC-MS/MS or MudPIT. Identified proteins were analyzed in silico for parameters that included localization, isoelectric point, molecular mass and biological function. The proteome provided a consistent pattern of lipoproteins, proteases and their substrates, sensing molecules and prokaryotic homologs of eukaryotic lipid rafts. This study provides the first analysis of a prokaryotic lipid raft and has relevance for the biology of Borrelia, other pathogenic bacteria, as well as for the evolution of these structures. All MS data have been deposited in the ProteomeXchange with identifier PXD002365 (http://proteomecentral.proteomexchange.org/dataset/PXD002365).

  20. Comparison of Tooth Discoloration Induced by Calcium-Enriched Mixture and Mineral Trioxide Aggregate

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    Rouhani, Armita; Akbari, Majid; Farhadi-faz, Aida

    2016-01-01

    Introduction: The aim of this in vitro study was to evaluate the tooth discoloration induced by calcium-enriched mixture (CEM) cement and mineral trioxide aggregate (MTA). Methods and Materials: Forty five endodontically treated human maxillary central incisors were selected and divided into three groups (n=15) after removing the coronal 3 mm of the obturating materials. In the MTA group, white MTA plug was placed in pulp chamber and coronal zone of the root canal. In CEM cement group, CEM plug was placed in the tooth in the same manner. In both groups, a wet cotton pellet was placed in the access cavity and the teeth were temporarily sealed. After 24 h the teeth were restored with resin composite. In the negative control group the teeth were also restored with resin composite. The color change in the cervical third of teeth was measured with a colorimeter and was repeated 3 times for each specimen. The teeth were kept in artificial saliva for 6 months. After this period, the color change was measured again. Data were collected by Commission International de I'Eclairage's L*a*b color values, and corresponding ΔE values were calculated. The results were analyzed using the one-way ANOVA and post-hoc Tukey’s test with the significance level defined as 0.05. Results: There was no significant differences between CEM group and control group in mean discoloration. The mean tooth discoloration in MTA group was significantly greater than CEM and control groups (P<0.05). Conclusion: According to the result of the present study CEM cement did not induce tooth discoloration after six months. Therefore it can be used in vital pulp therapy of esthetically sensitive teeth. PMID:27471526

  1. Lipid raft: A floating island of death or survival

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    George, Kimberly S. [Edison Biotechnology Institute and Department of Chemistry and Biochemistry, Ohio University, Athens, Ohio 45701 (United States); Department of Chemistry, Marietta College, Marietta, OH 45750 (United States); Wu, Shiyong, E-mail: wus1@ohio.edu [Edison Biotechnology Institute and Department of Chemistry and Biochemistry, Ohio University, Athens, Ohio 45701 (United States)

    2012-03-15

    Lipid rafts are microdomains of the plasma membrane enriched in cholesterol and sphingolipids, and play an important role in the initiation of many pharmacological agent-induced signaling pathways and toxicological effects. The structure of lipid rafts is dynamic, resulting in an ever-changing content of both lipids and proteins. Cholesterol, as a major component of lipid rafts, is critical for the formation and configuration of lipid raft microdomains, which provide signaling platforms capable of activating both pro-apoptotic and anti-apoptotic signaling pathways. A change of cholesterol level can result in lipid raft disruption and activate or deactivate raft-associated proteins, such as death receptor proteins, protein kinases, and calcium channels. Several anti-cancer drugs are able to suppress growth and induce apoptosis of tumor cells through alteration of lipid raft contents via disrupting lipid raft integrity. -- Highlights: ► The role of lipid rafts in apoptosis ► The pro- and anti-apoptotic effects of lipid raft disruption ► Cancer treatments targeting lipid rafts.

  2. Intra-aggregate CO2 enrichment: a modelling approach for aerobic soils

    Directory of Open Access Journals (Sweden)

    H. Schack-Kirchner

    2012-10-01

    Full Text Available CO2 concentration gradients inside soil aggregates, caused by the respiration of soil microorganisms and fungal hyphae, might lead to variations in the soil solution chemistry on a mm-scale, and to an underestimation of the CO2 storage. But, up to now, there seems to be no feasible method for measuring CO2 inside natural aggregates with sufficient spatial resolution. We combined a one-dimensional model for gas diffusion in the inter-aggregate pore-space with a cylinder diffusion model, simulating the consumption/production and diffusion of O2 and CO2 inside soil aggregates with air- and water-filled pores. Our model predicts that for aerobic respiration (respiratory quotient = 1 the intra-aggregate increase in the CO2 partial pressure can never be higher than 0.9 kPa for siliceous, and 0.08 kPa for calcaric aggregates, independent of the level of water-saturation. This suggests that only for siliceous aggregates CO2 produced by aerobic respiration might cause a high small-scale spatial variability in the soil solution chemistry. In calcaric aggregates, however, the contribution of carbonate species to the CO2 transport should lead to secondary carbonates on the aggregate surfaces. As regards the total CO2 storage in aerobic soils, both siliceous and calcaric, the effect of intra-aggregate CO2 gradients seems to be negligible. To assess the effect of anaerobic respiration on the intra-aggregate CO2 gradients, the development of a device for measuring CO2 on a mm-scale in soils is indispensable.

  3. 脂筏在阿尔茨海默症中的作用%Emerging Roles of Lipid Rafts in Alzheimer's Disease

    Institute of Scientific and Technical Information of China (English)

    郑毅; 马芙蓉; 吉尚戎

    2012-01-01

    Lipid rafts are cholesterol-enriched micro-domains in cell membranes with critical functions in cellular signaling and transportation. Accumulating evidence indicates lipid rafts are intimately associated with the pathogenesis of Alzheimer's disease (AD). Because the abnormal metabolism and aggregation of amyloid p-peptide (Ap) is causally involved in the initiation and development of AD, lipid rafts regulate the production, aggregation and toxicity of A3, thus pinpointing a critical role of lipid rafts in AD.%脂筏(lipid raft)是细胞膜中富含胆固醇的功能性微区,在信号转导、物质运输等方面发挥着重要作用.大量证据显示脂筏与阿尔茨海默症(Alzheimer's disease,AD)的致病机理密切相关.β-淀粉样肽(amyloid β-peptide,Aβ)的异常代谢和聚集可能是AD的致病主因,而脂筏不但是Aβ产生的主要场所,还能调节Aβ的聚集行为及神经毒性,因而在AD的病理过程中扮演着关键角色.

  4. Paradoxical Condensation of Copper with Elevated β-Amyloid in Lipid Rafts under Cellular Copper Deficiency Conditions: IMPLICATIONS FOR ALZHEIMER DISEASE*

    OpenAIRE

    Hung, Ya Hui; Robb, Elysia L.; Volitakis, Irene; Ho, Michael; Evin, Genevieve; Li, Qiao-Xin; Janetta G Culvenor; Masters, Colin L.; Cherny, Robert A.; Bush, Ashley I.

    2009-01-01

    Redox-active copper is implicated in the pathogenesis of Alzheimer disease (AD), β-amyloid peptide (Aβ) aggregation, and amyloid formation. Aβ·copper complexes have been identified in AD and catalytically oxidize cholesterol and lipid to generate H2O2 and lipid peroxides. The site and mechanism of this abnormality is not known. Growing evidence suggests that amyloidogenic processing of the β-amyloid precursor protein (APP) occurs in lipid rafts, membrane microdomains enriched in cholesterol. ...

  5. Lipid rafts, caveolae and GPI-linked proteins.

    NARCIS (Netherlands)

    Reeves, V.L.; Thomas, C.M.G.; Smart, E.J.

    2012-01-01

    Lipid rafts and caveolae are specialized membrane microdomains enriched in sphingolipids and cholesterol. They function in a variety of cellular processes including but not limited to endocytosis, transcytosis, signal transduction and receptor recycling. Here, we outline the similarities and differe

  6. Erythropoietin receptor signaling is membrane raft dependent.

    Directory of Open Access Journals (Sweden)

    Kathy L McGraw

    Full Text Available Upon erythropoietin (Epo engagement, Epo-receptor (R homodimerizes to activate JAK2 and Lyn, which phosphorylate STAT5. Although recent investigations have identified key negative regulators of Epo-R signaling, little is known about the role of membrane localization in controlling receptor signal fidelity. Here we show a critical role for membrane raft (MR microdomains in creation of discrete signaling platforms essential for Epo-R signaling. Treatment of UT7 cells with Epo induced MR assembly and coalescence. Confocal microscopy showed that raft aggregates significantly increased after Epo stimulation (mean, 4.3±1.4(SE vs. 25.6±3.2 aggregates/cell; p≤0.001, accompanied by a >3-fold increase in cluster size (p≤0.001. Raft fraction immunoblotting showed Epo-R translocation to MR after Epo stimulation and was confirmed by fluorescence microscopy in Epo stimulated UT7 cells and primary erythroid bursts. Receptor recruitment into MR was accompanied by incorporation of JAK2, Lyn, and STAT5 and their activated forms. Raft disruption by cholesterol depletion extinguished Epo induced Jak2, STAT5, Akt and MAPK phosphorylation in UT7 cells and erythroid progenitors. Furthermore, inhibition of the Rho GTPases Rac1 or RhoA blocked receptor recruitment into raft fractions, indicating a role for these GTPases in receptor trafficking. These data establish a critical role for MR in recruitment and assembly of Epo-R and signal intermediates into discrete membrane signaling units.

  7. Rafts - the current picture

    Directory of Open Access Journals (Sweden)

    Aleksander F. Sikorski

    2011-08-01

    Full Text Available Although evidences that cell membrane contains microdomains are accumulating, the exact properties, diversity and levels of organization of small lipid patches built mainly of cholesterol and sphingomyelin, termed rafts, remain to be elucidated. Our understanding of the cell membrane is increasing with each new raft feature discovered. Nowadays rafts are suggested to act as sites of cell signaling events, to be a part of protein sorting machinery but also they are used by several pathogens as gates into the cells. It is still unclear how rafts are connected to the membrane skeleton and cytoskeleton and with how many different types of rafts are we actually dealing with. This review summarizes some of the most recent discoveries trying to make a view of the complex raft properties.

  8. Life raft stabilizer

    Science.gov (United States)

    Radnofsky, M. I.; Barnett, J. H., Jr.; Harrison, F. L.; Marak, R. J. (Inventor)

    1973-01-01

    An improved life raft stabilizer for reducing rocking and substantially precluding capsizing is discussed. The stabilizer may be removably attached to the raft and is defined by flexible side walls which extend a considerable depth downwardly to one another in the water. The side walls, in conjunction with the floor of the raft, form a ballast enclosure. A weight is placed in the bottom of the enclosure and water port means are provided in the walls. Placement of the stabilizer in the water allows the weighted bottom to sink, producing submerged deployment thereof and permitting water to enter the enclosure through the port means, thus forming a ballast for the raft.

  9. Synaptic membrane rafts: traffic lights for local neurotrophin signalling?

    Directory of Open Access Journals (Sweden)

    Barbara eZonta

    2013-10-01

    Full Text Available Lipid rafts, cholesterol and lipid rich microdomains, are believed to play important roles as platforms for the partitioning of transmembrane and synaptic proteins involved in synaptic signalling, plasticity and maintenance. There is increasing evidence of a physical interaction between post-synaptic densities and post-synaptic lipid rafts. Localization of proteins within lipid rafts is highly regulated, and therefore lipid rafts may function as traffic lights modulating and fine-tuning neuronal signalling. The tyrosine kinase neurotrophin receptors (Trk and the low-affinity p75 neurotrophin receptor (p75NTR are enriched in neuronal lipid rafts together with the intermediates of downstream signalling pathways, suggesting a possible role of rafts in neurotrophin signalling. Moreover, neurotrophins and their receptors are involved in the regulation of cholesterol metabolism. Cholesterol is an important component of lipid rafts and its depletion leads to gradual loss of synapses, underscoring the importance of lipid rafts for proper neuronal function. Here, we review and discuss the idea that translocation of neurotrophin receptors in synaptic rafts may account for the selectivity of their transduced signals.

  10. Modeling Signal Transduction and Lipid Rafts in Immune Cells

    Science.gov (United States)

    Prasad, Ashok

    2011-03-01

    Experimental evidence increasingly suggests that lipid rafts are nanometer sized cholesterol dependent dynamic assemblies enriched in sphingolipids and associated proteins. Lipid rafts are dynamic structures that break-up and reform on a relatively short time-scale, and are believed to facilitate the interactions of raft-associated proteins. The role of these rafts in signaling has been controversial, partly due to controversies regarding the existence and nature of the rafts themselves. Experimental evidence has indicated that in several cell types, especially T cells, rafts do influence signal transduction and T cell activation. Given the emerging consensus on the biophysical character of lipid rafts, the question can be asked as to what roles they possibly play in signal transduction. Here we carry out simulations of minimal models of the signal transduction network that regulates Src-family kinase dynamics in T cells and other cell types. By separately treating raft-based biochemical interactions, we find that rafts can indeed putatively play an important role in signal transduction, and in particular may affect the sensitivity of signal transduction. This illuminates possible functional consequences of membrane heterogeneities on signal transduction and points towards mechanisms for spatial control of signaling by cells.

  11. IMPACT OF BRACHIARIA, ARBUSCULAR MYCORRHIZA, AND POTASSIUM ENRICHED RICE STRAW COMPOST ON ALUMINIUM, POTASSIUM AND STABILITY OF ACID SOIL AGGREGATES

    Directory of Open Access Journals (Sweden)

    Bariot Hafif

    2013-04-01

    Full Text Available Acid soil is commonly grown with cassava, which in general, tolerate low soil  fertility and aluminum (Al toxicity. However, without any improvement efforts such soil will become worse. Intercropping cassava with Brachiaria decumbens (BD which adapts to acid soil and tolerates low fertility soils as well as application of arbuscular mycorrhiza (AM and organic matters are among the important efforts to rehabilitate this soil. The experiment was conducted to  examine the impact of BD, AM, and potassium (K enriched rice straw compost on exchangeable Al, available K, and stability of soil aggregates. Experiment was arranged in a completely randomized design with three factors and three replications. The first factor was BD as cassava intercropping, the second factor was AM, and the third factor was 2 t ha-1 rice straw compost enriched with 0 kg, 50 kg, 100 kg, and 200 kg KCl ha-1. Brick pots (1 m length x 1 m width x 0.45 m depth filled with Kanhapludult soil was used for growing cassava in which row of BD was planted at 60 cm from cassava stem. K-enriched rice straw compost and AM (10 g per stem were applied around cassava stem at 2 and 12 days after planting, respectively. BD was cut every 30 days and the cutting was returned to the soil. Soil exchangeable Al was analyzed at 0, 3, 6 and 9 months after planting (MAP, while Al and K contents as well as aggregate stability were measured at 6 MAP. The results showed that planting BD decreased 33% exchangeable Al, which means that the root exudates of this grass was effective in detoxifying Al3+. Treatment of BD and/or in combination with AM was effective in preserving K added to the soil, increasing total polysaccharides, and improving soil aggregate stability. This indicated that planting BD and applying AM and Kenriched rice straw compost improved acid soil fertility, and therefore can be recommended in cassava cultivation.

  12. Lipid raft involvement in yeast cell growth and death.

    Science.gov (United States)

    Mollinedo, Faustino

    2012-01-01

    The notion that cellular membranes contain distinct microdomains, acting as scaffolds for signal transduction processes, has gained considerable momentum. In particular, a class of such domains that is rich in sphingolipids and cholesterol, termed as lipid rafts, is thought to compartmentalize the plasma membrane, and to have important roles in survival and cell death signaling in mammalian cells. Likewise, yeast lipid rafts are membrane domains enriched in sphingolipids and ergosterol, the yeast counterpart of mammalian cholesterol. Sterol-rich membrane domains have been identified in several fungal species, including the budding yeast Saccharomyces cerevisiae, the fission yeast Schizosaccharomyces pombe as well as the pathogens Candida albicans and Cryptococcus neoformans. Yeast rafts have been mainly involved in membrane trafficking, but increasing evidence implicates rafts in a wide range of additional cellular processes. Yeast lipid rafts house biologically important proteins involved in the proper function of yeast, such as proteins that control Na(+), K(+), and pH homeostasis, which influence many cellular processes, including cell growth and death. Membrane raft constituents affect drug susceptibility, and drugs interacting with sterols alter raft composition and membrane integrity, leading to yeast cell death. Because of the genetic tractability of yeast, analysis of yeast rafts could be an excellent model to approach unanswered questions of mammalian raft biology, and to understand the role of lipid rafts in the regulation of cell death and survival in human cells. A better insight in raft biology might lead to envisage new raft-mediated approaches to the treatment of human diseases where regulation of cell death and survival is critical, such as cancer and neurodegenerative diseases.

  13. Lipid raft involvement in yeast cell growth and death

    Directory of Open Access Journals (Sweden)

    Faustino eMollinedo

    2012-10-01

    Full Text Available The notion that cellular membranes contain distinct microdomains, acting as scaffolds for signal transduction processes, has gained considerable momentum. In particular, a class of such domains that is rich in sphingolipids and cholesterol, termed as lipid rafts, is thought to compartmentalize the plasma membrane, and to have important roles in survival and cell death signaling in mammalian cells. Likewise, yeast lipid rafts are membrane domains enriched in sphingolipids and ergosterol, the yeast counterpart of mammalian cholesterol. Sterol-rich membrane domains have been identified in several fungal species, including the budding yeast Saccharomyces cerevisiae, the fission yeast Schizosaccharomyces pombe as well as the pathogens Candida albicans and Crytococcus neoformans. Yeast rafts have been mainly involved in membrane trafficking, but increasing evidence implicates rafts in a wide range of additional cellular processes. Yeast lipid rafts house biologically important proteins involved in the proper function of yeast, such as proteins that control Na+, K+ and pH homeostasis, which influence many cellular processes, including cell growth and death. Membrane raft constituents affect drug susceptibility, and drugs interacting with sterols alter raft composition and membrane integrity, leading to yeast cell death. Because of the genetic tractability of yeast, analysis of yeast rafts could be an excellent model to approach unanswered questions of mammalian raft biology, and to understand the role of lipid rafts in the regulation of cell death and survival in human cells. A better insight in raft biology might lead to envisage new raft-mediated approaches to the treatment of human diseases where regulation of cell death and survival is critical, such as cancer and neurodegenerative diseases.

  14. Lipid rafts as major platforms for signaling regulation in cancer.

    Science.gov (United States)

    Mollinedo, Faustino; Gajate, Consuelo

    2015-01-01

    Cell signaling does not apparently occur randomly over the cell surface, but it seems to be integrated very often into cholesterol-rich membrane domains, termed lipid rafts. Membrane lipid rafts are highly ordered membrane domains that are enriched in cholesterol, sphingolipids and gangliosides, and behave as major modulators of membrane geometry, lateral movement of molecules, traffic and signal transduction. Because the lipid and protein composition of membrane rafts differs from that of the surrounding membrane, they provide an additional level of compartmentalization, serving as sorting platforms and hubs for signal transduction proteins. A wide number of signal transduction processes related to cell adhesion, migration, as well as to cell survival and proliferation, which play major roles in cancer development and progression, are dependent on lipid rafts. Despite lipid rafts harbor mainly critical survival signaling pathways, including insulin-like growth factor I (IGF-I)/phosphatidylinositol 3-kinase (PI3K)/Akt signaling, recent evidence suggests that these membrane domains can also house death receptor-mediated apoptotic signaling. Recruitment of this death receptor signaling pathway in membrane rafts can be pharmacologically modulated, thus opening up the possibility to regulate cell demise with a therapeutic use. The synthetic ether phospholipid edelfosine shows a high affinity for cholesterol and accumulates in lipid rafts in a number of malignant hematological cells, leading to an efficient in vitro and in vivo antitumor activity by inducing translocation of death receptors and downstream signaling molecules to these membrane domains. Additional antitumor drugs have also been shown to act, at least in part, by recruiting death receptors in lipid rafts. The partition of death receptors together with downstream apoptotic signaling molecules in membrane rafts has led us to postulate the concept of a special liquid-ordered membrane platform coined as

  15. Lipid Raft, Regulator of Plasmodesmal Callose Homeostasis

    Directory of Open Access Journals (Sweden)

    Arya Bagus Boedi Iswanto

    2017-04-01

    Full Text Available Abstract: The specialized plasma membrane microdomains known as lipid rafts are enriched by sterols and sphingolipids. Lipid rafts facilitate cellular signal transduction by controlling the assembly of signaling molecules and membrane protein trafficking. Another specialized compartment of plant cells, the plasmodesmata (PD, which regulates the symplasmic intercellular movement of certain molecules between adjacent cells, also contains a phospholipid bilayer membrane. The dynamic permeability of plasmodesmata (PDs is highly controlled by plasmodesmata callose (PDC, which is synthesized by callose synthases (CalS and degraded by β-1,3-glucanases (BGs. In recent studies, remarkable observations regarding the correlation between lipid raft formation and symplasmic intracellular trafficking have been reported, and the PDC has been suggested to be the regulator of the size exclusion limit of PDs. It has been suggested that the alteration of lipid raft substances impairs PDC homeostasis, subsequently affecting PD functions. In this review, we discuss the substantial role of membrane lipid rafts in PDC homeostasis and provide avenues for understanding the fundamental behavior of the lipid raft–processed PDC.

  16. Lipid rafts and detergent-resistant membranes in epithelial keratinocytes.

    Science.gov (United States)

    McGuinn, Kathleen P; Mahoney, Mỹ G

    2014-01-01

    Our understanding of the plasma membrane has markedly increased since Singer and Nicolson proposed the fluid mosaic model in 1972. While their revolutionary theory of the lipid bilayer remains largely valid, it is now known that lipids and proteins are not randomly dispersed throughout the plasma membrane but instead may be organized within membrane microdomains, commonly referred to as lipid rafts. Lipid rafts are highly dynamic, detergent resistant, and enriched with both cholesterol and glycosphingolipids. The two main types are flotillin-rich planar lipid rafts and caveolin-rich caveolae. It is proposed that flotillin and caveolin proteins regulate cell communication by compartmentalizing and interacting with signal transduction proteins within their respective lipid microdomains. Consequently, membrane rafts play an important role in vital cellular functions including migration, invasion, and signaling; thus, alterations in their microenvironment can initiate signaling pathways that affect cellular function and behavior. Therefore, the identification of lipid rafts and their associated proteins is integral to the study of transmembrane signaling. Here, we review the current standard protocols and biochemical approaches used to isolate and define raft proteins from epithelial cells and tissues. Furthermore, in Section 3 of this chapter, detailed protocols are offered for isolating lipid rafts by subjection to detergent and sucrose density centrifugation, as well as an approach for selectively isolating caveolae. Methods to manipulate rafts with treatments such as methyl-β-cyclodextrin and flotillin III are also described.

  17. Lipid rafts prepared by different methods contain different connexin channels, but gap junctions are not lipid rafts.

    Science.gov (United States)

    Locke, Darren; Liu, Jade; Harris, Andrew L

    2005-10-04

    Cell extraction with cold nonionic detergents or alkaline carbonate prepares an insoluble membrane fraction whose buoyant density permits its flotation in discontinuous sucrose gradients. These lipid "rafts" are implicated in protein sorting and are attractive candidates as platforms that coordinate signal transduction pathways with intracellular substrates. Gap junctions form a direct molecular signaling pathway by end-to-end apposition of hemichannels containing one (homomeric) or more (heteromeric) connexin isoforms. Residency of channels composed of Cx26 and/or Cx32 in lipid rafts was assessed by membrane insolubility in alkaline carbonate or different concentrations of Triton X100, Nonidet P40 and Brij-58 nonionic detergents. Using Triton X100, insoluble raft membranes contained homomeric Cx32 channels, but Cx26-containing channels only when low detergent concentrations were used. Results were similar using Nonidet P40, except that Cx26-containing channels were excluded from raft membranes at all detergent concentrations. In contrast, homomeric Cx26 channels were enriched within Brij-58-insoluble rafts, whereas Cx32-containing channels partitioned between raft and nonraft membranes. Immunofluorescence microscopy showed prominent colocalization only of nonjunctional connexin channels with raft plasma membrane; junctional plaques were not lipid rafts. Rafts prepared by different extraction methods had considerable quantitative and qualitative differences in their lipid compositions. That functionally different nonjunctional connexin channels partition among rafts with distinct lipid compositions suggests that unpaired Cx26 and/or Cx32 channels exist in membrane domains of slightly different physicochemical character. Rafts may be involved in trafficking of plasma membrane connexin channels to gap junctions.

  18. Functional Proteomic Analysis of Lipid Raft Kinase Complexes

    Science.gov (United States)

    2009-08-01

    distinct modes. J Cell Sci 2006;119:3833–44. Supplemental Data Proteome-scale Characterization of Human S-acylated Proteins in Lipid Raft...enriched and Non-raft Membrane Domains Wei Yang, Dolores Di Vizio, Marc Kirchner, Hanno Steen, and Michael R. Freeman Supplemental Tables include: 1...Carboxypeptidase M precursor Raft 2 18/443 – 0.5 0.5 1.0 1 1 1.0 0 0 0.0 181 + + IPI00032038 CPT1A Isoform 1 of Carnitine O-palmitoyltransferase I, liver isoform

  19. How Capillary Rafts Sink

    CERN Document Server

    Protiere, S; Aristoff, J; Stone, H

    2010-01-01

    We present a fluid dynamics video showing how capillary rafts sink. Small objects trapped at an interface are very common in Nature (insects walking on water, ant rafts, bubbles or pollen at the water-air interface, membranes...) and are found in many multiphase industrial processes. Thanks to Archimedes principle we can easily predict whether an object sinks or floats. But what happens when several small particles are placed at an interface between two fluids. In this case surface tension also plays an important role. These particles self-assemble by capillarity and thus form what we call a "capillary raft". We show how such capillary rafts sink for varying sizes of particles and define how this parameter affects the sinking process.

  20. Lipid rafts and raft-mediated supramolecular entities in the regulation of CD95 death receptor apoptotic signaling.

    Science.gov (United States)

    Gajate, Consuelo; Mollinedo, Faustino

    2015-05-01

    Membrane lipid rafts are highly ordered membrane domains enriched in cholesterol, sphingolipids and gangliosides that have the property to segregate and concentrate proteins. Lipid and protein composition of lipid rafts differs from that of the surrounding membrane, thus providing sorting platforms and hubs for signal transduction molecules, including CD95 death receptor-mediated signaling. CD95 can be recruited to rafts in a reversible way through S-palmitoylation following activation of cells with its physiological cognate ligand as well as with a wide variety of inducers, including several antitumor drugs through ligand-independent intracellular mechanisms. CD95 translocation to rafts can be modulated pharmacologically, thus becoming a target for the treatment of apoptosis-defective diseases, such as cancer. CD95-mediated signaling largely depends on protein-protein interactions, and the recruitment and concentration of CD95 and distinct downstream apoptotic molecules in membrane raft domains, forming raft-based supramolecular entities that act as hubs for apoptotic signaling molecules, favors the generation and amplification of apoptotic signals. Efficient CD95-mediated apoptosis involves CD95 and raft internalization, as well as the involvement of different subcellular organelles. In this review, we briefly summarize and discuss the involvement of lipid rafts in the regulation of CD95-mediated apoptosis that may provide a new avenue for cancer therapy.

  1. Generation of stable lipid raft microdomains in the enterocyte brush border by selective endocytic removal of non-raft membrane.

    Science.gov (United States)

    Danielsen, E Michael; Hansen, Gert H

    2013-01-01

    The small intestinal brush border has an unusually high proportion of glycolipids which promote the formation of lipid raft microdomains, stabilized by various cross-linking lectins. This unique membrane organization acts to provide physical and chemical stability to the membrane that faces multiple deleterious agents present in the gut lumen, such as bile salts, digestive enzymes of the pancreas, and a plethora of pathogens. In the present work, we studied the constitutive endocytosis from the brush border of cultured jejunal explants of the pig, and the results indicate that this process functions to enrich the contents of lipid raft components in the brush border. The lipophilic fluorescent marker FM, taken up into early endosomes in the terminal web region (TWEEs), was absent from detergent resistant membranes (DRMs), implying an association with non-raft membrane. Furthermore, neither major lipid raft-associated brush border enzymes nor glycolipids were detected by immunofluorescence microscopy in subapical punctae resembling TWEEs. Finally, two model raft lipids, BODIPY-lactosylceramide and BODIPY-GM1, were not endocytosed except when cholera toxin subunit B (CTB) was present. In conclusion, we propose that constitutive, selective endocytic removal of non-raft membrane acts as a sorting mechanism to enrich the brush border contents of lipid raft components, such as glycolipids and the major digestive enzymes. This sorting may be energetically driven by changes in membrane curvature when molecules move from a microvillar surface to an endocytic invagination.

  2. Generation of stable lipid raft microdomains in the enterocyte brush border by selective endocytic removal of non-raft membrane.

    Directory of Open Access Journals (Sweden)

    E Michael Danielsen

    Full Text Available The small intestinal brush border has an unusually high proportion of glycolipids which promote the formation of lipid raft microdomains, stabilized by various cross-linking lectins. This unique membrane organization acts to provide physical and chemical stability to the membrane that faces multiple deleterious agents present in the gut lumen, such as bile salts, digestive enzymes of the pancreas, and a plethora of pathogens. In the present work, we studied the constitutive endocytosis from the brush border of cultured jejunal explants of the pig, and the results indicate that this process functions to enrich the contents of lipid raft components in the brush border. The lipophilic fluorescent marker FM, taken up into early endosomes in the terminal web region (TWEEs, was absent from detergent resistant membranes (DRMs, implying an association with non-raft membrane. Furthermore, neither major lipid raft-associated brush border enzymes nor glycolipids were detected by immunofluorescence microscopy in subapical punctae resembling TWEEs. Finally, two model raft lipids, BODIPY-lactosylceramide and BODIPY-GM1, were not endocytosed except when cholera toxin subunit B (CTB was present. In conclusion, we propose that constitutive, selective endocytic removal of non-raft membrane acts as a sorting mechanism to enrich the brush border contents of lipid raft components, such as glycolipids and the major digestive enzymes. This sorting may be energetically driven by changes in membrane curvature when molecules move from a microvillar surface to an endocytic invagination.

  3. Cytotoxic effects of mineral trioxide aggregate, calcium enriched mixture cement, Biodentine and octacalcium pohosphate on human gingival fibroblasts

    Directory of Open Access Journals (Sweden)

    Eshagh

    2016-06-01

    Full Text Available Background. This in vitro study compared the effects of mineral trioxide aggregate (MTA, calcium enriched mixture (CEM cement, Biodentine (BD and octacalcium phosphate (OCP on the viability of human gingival fibroblasts (HGFs. Methods. After completion of the setting time of the materials under study, fibroblasts were placed in 24-well insert plates and 1 mg of each material was added to the respective wells. The plates were then incubated at 37°C. The inserts were removed at 24, 48 and 168 hours and 2,5-diphenyltetrazolium bromide was added to assess cytotoxicity via the MTT colorimetric assay. Data were analyzed at different time intervals using repeated-measures ANOVA, followed by the Bonferroni test at three levels of significance of P < 0.05, P < 0.01 and P < 0.001. Results. Cytotoxicity of the materials under study was not significantly different at 24 and 48 hours compared to the control group. However, at 168 hours, a significant difference was noted between MTA (P< 0.05 and Biodentine (P < 0.01 and the control group. Conclusion. Cytotoxicity of MTA, CEM, Biodentine and OCP against HGFs was similar to that of the control group at 24 and 48 hours. Over time, MTA and Biodentine exhibited less cytotoxicity than other materials.

  4. Bacterial Leakage of Mineral Trioxide Aggregate, Calcium-Enriched Mixture and Biodentine as Furcation Perforation Repair Materials in Primary Molars

    Science.gov (United States)

    Ramazani, Nahid; Sadeghi, Parisa

    2016-01-01

    Introduction: Adequate seal of iatrogenically perforated area within the root canal system can improve the long term treatment prognosis. This in vitro study evaluated the sealing ability of mineral trioxide aggregate (MTA), calcium-enriched mixture (CEM) cement and Biodentine in repair of furcation perforation in primary molars. Methods and Materials: A total of 61 freshly extracted primary mandibular second molars were randomly divided into three groups (n=17) and 10 teeth were put in negative (without perforation, n=5) and positive (perforated without repair, n=5) control groups. Turbidity was used as the criteria of bacterial leakage, when detected in the model of dual-chamber leakage. Data were analyzed using the Chi-Square and Kaplan-Meier survival analysis in SPSS software. The level of significance was set at 0.05. Results: All positive samples showed turbidity, whereas none of the negative samples allowed bacterial leakage. There was no significant difference between the number of turbidity samples in repaired teeth with all test materials (P=0.13). No significant difference was also detected in the mean survival time (P>0.05). Conclusion: CEM cement and Biodentine showed promising results as perforation repair materials and can be recommended as suitable alternatives of MTA for repair of furcation perforation of primary molars. PMID:27471534

  5. Native low density lipoprotein promotes lipid raft formation in macrophages.

    Science.gov (United States)

    Song, Jian; Ping, Ling-Yan; Duong, Duc M; Gao, Xiao-Yan; He, Chun-Yan; Wei, Lei; Wu, Jun-Zhu

    2016-03-01

    Oxidized low‑density lipoprotein (LDL) has an important role in atherogenesis; however, the mechanisms underlying cell‑mediated LDL oxidation remain to be elucidated. The present study investigated whether native‑LDL induced lipid raft formation, in order to gain further insight into LDL oxidation. Confocal microscopic analysis revealed that lipid rafts were aggregated or clustered in the membrane, which were colocalized with myeloperoxidase (MPO) upon native LDL stimulation; however, in the presence of methyl‑β‑cyclodextrin (MβCD), LDL‑stimulated aggregation, translocation, and colocalization of lipid rafts components was abolished.. In addition, lipid raft disruptors MβCD and filipin decreased malondialdehyde expression levels. Density gradient centrifugation coupled to label‑free quantitative proteomic analysis identified 1,449 individual proteins, of which 203 were significantly upregulated following native‑LDL stimulation. Functional classification of the proteins identified in the lipid rafts revealed that the expression levels of translocation proteins were upregulated. In conclusion, the results of the present study indicated that native‑LDL induced lipid raft clustering in macrophages, and the expression levels of several proteins were altered in the stimulated macrophages, which provided novel insights into the mechanism underlying LDL oxidation.

  6. C-type lectin like receptor 2 (CLEC-2) signals independently of lipid raft microdomains in platelets.

    Science.gov (United States)

    Manne, Bhanu Kanth; Badolia, Rachit; Dangelmaier, Carol A; Kunapuli, Satya P

    2015-01-15

    C-type lectin like receptor 2 (CLEC-2) has been reported to activate platelets through a lipid raft-dependent manner. Secreted ADP potentiates CLEC-2-mediated platelet aggregation. We have investigated whether the decrease in CLEC-2-mediated platelet aggregation, previously reported in platelets with disrupted rafts, is a result of the loss of agonist potentiation by ADP. We disrupted platelet lipid rafts with methyl-β-cyclodextrin (MβCD) and measured signaling events downstream of CLEC-2 activation. Lipid raft disruption decreases platelet aggregation induced by CLEC-2 agonists. The inhibition of platelet aggregation by the disruption of lipid rafts was rescued by the exogenous addition of epinephrine but not 2-methylthioadenosine diphosphate (2MeSADP), which suggests that lipid raft disruption effects P2Y12-mediated Gi activation but not Gz. Phosphorylation of Syk (Y525/526) and PLCγ2 (Y759), were not affected by raft disruption in CLEC-2 agonist-stimulated platelets. Furthermore, tyrosine phosphorylation of the CLEC-2 hemi-ITAM was not effected when MβCD disrupts lipid rafts. Lipid rafts do not directly contribute to CLEC-2 receptor activation in platelets. The effects of disruption of lipid rafts in in vitro assays can be attributed to inhibition of ADP feedback that potentiates CLEC-2 signaling.

  7. Interactive protein network of FXIII-A1 in lipid rafts of activated and non-activated platelets.

    Science.gov (United States)

    Rabani, Vahideh; Montange, Damien; Davani, Siamak

    2016-09-01

    Lipid-rafts are defined as membrane microdomains enriched in cholesterol and glycosphingolipids within platelet plasma membrane. Lipid raft-mediated clot retraction requires factor XIII and other interacting proteins. The aim of this study was to investigate the proteins that interact with factor XIII in raft and non-raft domains of activated and non-activated platelet plasma membrane. By lipidomics analysis, we identified cholesterol- and sphingomyelin-enriched areas as lipid rafts. Platelets were activated by thrombin. Proteomics analysis provided an overview of the pathways in which proteins of rafts and non-rafts participated in the interaction network of FXIII-A1, a catalytic subunit of FXIII. "Platelet activation" was the principal pathway among KEGG pathways for proteins of rafts, both before and after activation. Network analysis showed four types of interactions (activation, binding, reaction, and catalysis) in raft and non-raft domains in interactive network of FXIII-A1. FXIII-A1 interactions with other proteins in raft domains and their role in homeostasis highlight the specialization of the raft domain in clot retraction via the Factor XIII protein network.

  8. Apical Sealing Ability of Mineral Trioxide Aggregate, Intermediate Restorative Material and Calcium Enriched Mixture Cement: A Bacterial Leakage Study

    Science.gov (United States)

    Shahriari, Shahriar; Faramarzi, Farhad; Alikhani, Mohammad-Yousef; Farhadian, Maryam; Hendi, Seyedeh Sareh

    2016-01-01

    Introduction: This in vitro study compared the apical sealing ability of three common root end filling materials namely mineral trioxide aggregate (MTA), intermediate restorative material (IRM) and calcium-enriched mixture (CEM) cement using a bacterial leakage model. Methods and Materials: The study was conducted on 83 single-rooted human teeth. Tooth crowns were cut and root canals were prepared using the step-back technique. Apical 3 mm of the roots were cut and a three-mm-deep cavity was prepared using an ultrasonic instrument. The samples were divided into three groups (n=25) according to the root-end filling material including MTA, IRM and CEM cement. The roots were inserted into cut-end microtubes. After sterilization with ethylene oxide, microtubes were placed in sterile vials containing 10 mL of Brain Heart Infusion (BHI) broth and incubated at 37°C and 0.1 mL of Enterococcus faecalis suspension compatible with 0.5 McFarland standard (1.5×108 cell/ ml), which was refreshed daily. This procedure was continued for 70 days. The data were analyzed using the chi-square, Kruskal-Wallis and log rank tests. The level of significance was set at 0.05. Results: No significant difference was found in bacterial microleakage among three groups; MTA showed slightly (but not significantly) less microleakage than IRM and CEM. However, the difference in the mean time of microleakage was significant among the groups (P<0.04) and in MTA samples leakage occurred in a longer time than CEM (P<0.012). Conclusion: The three tested root end filling materials had equal sealing efficacy for preventing bacterial leakage. PMID:27790267

  9. The Effects of Alkaline pH on Microleakage of Mineral Trioxide Aggregate and Calcium-Enriched Mixture Apical Plugs

    Directory of Open Access Journals (Sweden)

    Hossein Mirhadi

    2016-03-01

    Full Text Available Statement of the Problem: Alkaline pH can affect the physical and chemical properties and sealing ability of apical plug material. Calcium hydroxide is used in non-vital teeth as an intracanal medication to complete disinfection of root canals. It raises the pH of environment to alkaline value. Purpose: The aim of this in vitro study was to evaluate and compare the effect of alkaline pH on the sealing ability of calcium-enriched mixture (CEM cement and mineral trioxide aggregate (MTA apical plugs. Materials and Method: Seventy single-rooted human maxillary anterior teeth were randomly divided to two experimental groups for Angelus MTA and CEM cement (n=30 and two control groups (n=5. Each group was divided into two subgroups of 15 for neutral and alkaline pH, and 1 negative and 1 positive control groups of 5. The root canals were cleaned and shaped by using ProTaper rotary system (Dentsply Maillefer; Ballaigues, Switzerland and the terminal 3mm of the roots were resected. Then, MTA and CEM cement were condensed in apical region with 3mm thickness. The samples were exposed to two environments with different pH values of 13 and 7.4. The leakage was assessed by using the fluid filtration technique at 1, 7, 14, 30 days intervals. Data were analyzed by the repeated measures MANOVA. Results: There was no statistically significant difference in the rate of microleakage between neutral and alkaline pH of CEM cement and MTA (p> 0.05. The sealing ability of MTA in an alkaline pH of 13 was significantly less than CEM cement in this pH (p< 0.05. Conclusion: An environment with alkaline pH had no adverse effect on the sealing ability of MTA and CEM cement used as apical plugs. CEM cement had better sealing ability in alkaline pH.

  10. Plasma membrane organization and function: moving past lipid rafts.

    Science.gov (United States)

    Kraft, Mary L

    2013-09-01

    "Lipid raft" is the name given to the tiny, dynamic, and ordered domains of cholesterol and sphingolipids that are hypothesized to exist in the plasma membranes of eukaryotic cells. According to the lipid raft hypothesis, these cholesterol- and sphingolipid-enriched domains modulate the protein-protein interactions that are essential for cellular function. Indeed, many studies have shown that cellular levels of cholesterol and sphingolipids influence plasma membrane organization, cell signaling, and other important biological processes. Despite 15 years of research and the application of highly advanced imaging techniques, data that unambiguously demonstrate the existence of lipid rafts in mammalian cells are still lacking. This Perspective summarizes the results that challenge the lipid raft hypothesis and discusses alternative hypothetical models of plasma membrane organization and lipid-mediated cellular function.

  11. Generation of stable lipid raft microdomains in the enterocyte brush border by selective endocytic removal of non-raft membrane

    DEFF Research Database (Denmark)

    Danielsen, E Michael; Hansen, Gert H

    2013-01-01

    multiple deleterious agents present in the gut lumen, such as bile salts, digestive enzymes of the pancreas, and a plethora of pathogens. In the present work, we studied the constitutive endocytosis from the brush border of cultured jejunal explants of the pig, and the results indicate that this process...... major lipid raft-associated brush border enzymes nor glycolipids were detected by immunofluorescence microscopy in subapical punctae resembling TWEEs. Finally, two model raft lipids, BODIPY-lactosylceramide and BODIPY-GM1, were not endocytosed except when cholera toxin subunit B (CTB) was present....... In conclusion, we propose that constitutive, selective endocytic removal of non-raft membrane acts as a sorting mechanism to enrich the brush border contents of lipid raft components, such as glycolipids and the major digestive enzymes. This sorting may be energetically driven by changes in membrane curvature...

  12. Abnormal lipid rafts related ganglioside expression and signaling in T lymphocytes in immune thrombocytopenia patients.

    Science.gov (United States)

    Zhang, Xian; Zhang, Donglei; Liu, Wenjie; Li, Huiyuan; Fu, Rongfeng; Liu, Xiaofan; Xue, Feng; Yang, Renchi

    2016-01-01

    Aberrant T lymphocytes signaling is considered to play a crucial role in the abnormal immune state of primary immune thrombocytopenia (ITP). Lipid raft has been verified to engage in the T cell receptor (TCR)-mediated T lymphocytes signal transduction. Whether lipid raft-associated T cells signal transduction has impact on the pathogenesis of ITP is still unconfirmed. In this study, we aimed to reveal the abnormality in structure and function of lipid rafts (LRs) in CD4(+) and CD8(+) T lymphocytes of patients with ITP. Our results showed that there was an increased lipid raft aggregation in ITP patients, while this kind of increase would not be influenced by platelet counts or therapeutic regimes. Stimulation by anti-CD3/CD28 monoclonal antibodies promoted enhanced lipid raft clustering in T lymphocytes of ITP patients compared with negative controls. Methyl-β-cyclodextrin (MβCD) could block the abnormal lipid raft aggregation and disrupt the TCR-mediated T cells proliferation and cytokines secretion, including both proinflammatory cytokines and anti-inflammatory cytokines. The spontaneous activation of T lymphocytes from ITP patients might be due to the elevated co-localization of protein tyrosine phosphatase (PTP) CD45 and lipid rafts in patients' CD4(+) and CD8(+) T lymphocytes. These findings suggest that the autoactivation of T lymphocytes from ITP patients may lead to the abnormality in lipid raft structure and raft-anchored proteins, and the changes conversely promote the TCR-mediated T cells activation of ITP patients.

  13. Lipid raft association restricts CD44-ezrin interaction and promotion of breast cancer cell migration.

    LENUS (Irish Health Repository)

    Donatello, Simona

    2012-12-01

    Cancer cell migration is an early event in metastasis, the main cause of breast cancer-related deaths. Cholesterol-enriched membrane domains called lipid rafts influence the function of many molecules, including the raft-associated protein CD44. We describe a novel mechanism whereby rafts regulate interactions between CD44 and its binding partner ezrin in migrating breast cancer cells. Specifically, in nonmigrating cells, CD44 and ezrin localized to different membranous compartments: CD44 predominantly in rafts, and ezrin in nonraft compartments. After the induction of migration (either nonspecific or CD44-driven), CD44 affiliation with lipid rafts was decreased. This was accompanied by increased coprecipitation of CD44 and active (threonine-phosphorylated) ezrin-radixin-moesin (ERM) proteins in nonraft compartments and increased colocalization of CD44 with the nonraft protein, transferrin receptor. Pharmacological raft disruption using methyl-β-cyclodextrin also increased CD44-ezrin coprecipitation and colocalization, further suggesting that CD44 interacts with ezrin outside rafts during migration. Conversely, promoting CD44 retention inside lipid rafts by pharmacological inhibition of depalmitoylation virtually abolished CD44-ezrin interactions. However, transient single or double knockdown of flotillin-1 or caveolin-1 was not sufficient to increase cell migration over a short time course, suggesting complex crosstalk mechanisms. We propose a new model for CD44-dependent breast cancer cell migration, where CD44 must relocalize outside lipid rafts to drive cell migration. This could have implications for rafts as pharmacological targets to down-regulate cancer cell migration.

  14. Dynamics of putative raft-associated proteins at the cell surface.

    Science.gov (United States)

    Kenworthy, Anne K; Nichols, Benjamin J; Remmert, Catha L; Hendrix, Glenn M; Kumar, Mukesh; Zimmerberg, Joshua; Lippincott-Schwartz, Jennifer

    2004-06-07

    Lipid rafts are conceptualized as membrane microdomains enriched in cholesterol and glycosphingolipid that serve as platforms for protein segregation and signaling. The properties of these domains in vivo are unclear. Here, we use fluorescence recovery after photobleaching to test if raft association affects a protein's ability to laterally diffuse large distances across the cell surface. The diffusion coefficients (D) of several types of putative raft and nonraft proteins were systematically measured under steady-state conditions and in response to raft perturbations. Raft proteins diffused freely over large distances (> 4 microm), exhibiting Ds that varied 10-fold. This finding indicates that raft proteins do not undergo long-range diffusion as part of discrete, stable raft domains. Perturbations reported to affect lipid rafts in model membrane systems or by biochemical fractionation (cholesterol depletion, decreased temperature, and cholesterol loading) had similar effects on the diffusional mobility of raft and nonraft proteins. Thus, raft association is not the dominant factor in determining long-range protein mobility at the cell surface.

  15. Lenalidomide induces lipid raft assembly to enhance erythropoietin receptor signaling in myelodysplastic syndrome progenitors.

    Science.gov (United States)

    McGraw, Kathy L; Basiorka, Ashley A; Johnson, Joseph O; Clark, Justine; Caceres, Gisela; Padron, Eric; Heaton, Ruth; Ozawa, Yukiyasu; Wei, Sheng; Sokol, Lubomir; List, Alan F

    2014-01-01

    Anemia remains the principal management challenge for patients with lower risk Myelodysplastic Syndromes (MDS). Despite appropriate cytokine production and cellular receptor display, erythropoietin receptor (EpoR) signaling is impaired. We reported that EpoR signaling is dependent upon receptor localization within lipid raft microdomains, and that disruption of raft integrity abolishes signaling capacity. Here, we show that MDS erythroid progenitors display markedly diminished raft assembly and smaller raft aggregates compared to normal controls (p = 0.005, raft number; p = 0.023, raft size). Because lenalidomide triggers raft coalescence in T-lymphocytes promoting immune synapse formation, we assessed effects of lenalidomide on raft assembly in MDS erythroid precursors and UT7 cells. Lenalidomide treatment rapidly induced lipid raft formation accompanied by EpoR recruitment into raft fractions together with STAT5, JAK2, and Lyn kinase. The JAK2 phosphatase, CD45, a key negative regulator of EpoR signaling, was displaced from raft fractions. Lenalidomide treatment prior to Epo stimulation enhanced both JAK2 and STAT5 phosphorylation in UT7 and primary MDS erythroid progenitors, accompanied by increased STAT5 DNA binding in UT7 cells, and increased erythroid colony forming capacity in both UT7 and primary cells. Raft induction was associated with F-actin polymerization, which was blocked by Rho kinase inhibition. These data indicate that deficient raft integrity impairs EpoR signaling, and provides a novel strategy to enhance EpoR signal fidelity in non-del(5q) MDS.

  16. Lenalidomide induces lipid raft assembly to enhance erythropoietin receptor signaling in myelodysplastic syndrome progenitors.

    Directory of Open Access Journals (Sweden)

    Kathy L McGraw

    Full Text Available Anemia remains the principal management challenge for patients with lower risk Myelodysplastic Syndromes (MDS. Despite appropriate cytokine production and cellular receptor display, erythropoietin receptor (EpoR signaling is impaired. We reported that EpoR signaling is dependent upon receptor localization within lipid raft microdomains, and that disruption of raft integrity abolishes signaling capacity. Here, we show that MDS erythroid progenitors display markedly diminished raft assembly and smaller raft aggregates compared to normal controls (p = 0.005, raft number; p = 0.023, raft size. Because lenalidomide triggers raft coalescence in T-lymphocytes promoting immune synapse formation, we assessed effects of lenalidomide on raft assembly in MDS erythroid precursors and UT7 cells. Lenalidomide treatment rapidly induced lipid raft formation accompanied by EpoR recruitment into raft fractions together with STAT5, JAK2, and Lyn kinase. The JAK2 phosphatase, CD45, a key negative regulator of EpoR signaling, was displaced from raft fractions. Lenalidomide treatment prior to Epo stimulation enhanced both JAK2 and STAT5 phosphorylation in UT7 and primary MDS erythroid progenitors, accompanied by increased STAT5 DNA binding in UT7 cells, and increased erythroid colony forming capacity in both UT7 and primary cells. Raft induction was associated with F-actin polymerization, which was blocked by Rho kinase inhibition. These data indicate that deficient raft integrity impairs EpoR signaling, and provides a novel strategy to enhance EpoR signal fidelity in non-del(5q MDS.

  17. Generic sorting of raft lipids into secretory vesicles in yeast

    DEFF Research Database (Denmark)

    Surma, Michal A; Klose, Christian; Klemm, Robin W;

    2011-01-01

    a complete lipid overview of the yeast late secretory pathway. We could show that vesicles captured with different baits carry the same cargo and have almost identical lipid compositions; being highly enriched in ergosterol and sphingolipids. This finding indicates that lipid raft sorting is a generic...... feature of vesicles carrying PM cargo and suggests a common lipid-based mechanism for their formation....

  18. Cholesterol depletion disorganizes oocyte membrane rafts altering mouse fertilization.

    Directory of Open Access Journals (Sweden)

    Jorgelina Buschiazzo

    Full Text Available Drastic membrane reorganization occurs when mammalian sperm binds to and fuses with the oocyte membrane. Two oocyte protein families are essential for fertilization, tetraspanins and glycosylphosphatidylinositol-anchored proteins. The firsts are associated to tetraspanin-enriched microdomains and the seconds to lipid rafts. Here we report membrane raft involvement in mouse fertilization assessed by cholesterol modulation using methyl-β-cyclodextrin. Cholesterol removal induced: (1 a decrease of the fertilization rate and index; and (2 a delay in the extrusion of the second polar body. Cholesterol repletion recovered the fertilization ability of cholesterol-depleted oocytes, indicating reversibility of these effects. In vivo time-lapse analyses using fluorescent cholesterol permitted to identify the time-point at which the probe is mainly located at the plasma membrane enabling the estimation of the extent of the cholesterol depletion. We confirmed that the mouse oocyte is rich in rafts according to the presence of the raft marker lipid, ganglioside GM1 on the membrane of living oocytes and we identified the coexistence of two types of microdomains, planar rafts and caveolae-like structures, by terms of two differential rafts markers, flotillin-2 and caveolin-1, respectively. Moreover, this is the first report that shows characteristic caveolae-like invaginations in the mouse oocyte identified by electron microscopy. Raft disruption by cholesterol depletion disturbed the subcellular localization of the signal molecule c-Src and the inhibition of Src kinase proteins prevented second polar body extrusion, consistent with a role of Src-related kinases in fertilization via signaling complexes. Our data highlight the functional importance of intact membrane rafts for mouse fertilization and its dependence on cholesterol.

  19. Mini-Raft Backpack Development.

    Science.gov (United States)

    1983-01-01

    AD-R14i 301 MINI-RAFT BACKPACK DEVELOPMENT(U) NAVAL AIRil IIIDEVELOPMENT CENTER WARMINSTER PA AIRCRAFT AND CREW SYSTEMS TECHNOLOGY DIRECTORATE G P...GOVT ACCESSION NO. 3. RECIPIENT’S CATALOG NUMBER NADC-83097-60 4. TITLE (and Sublitle) S. TYPE OF REPORT & PERIOD COVERED MINI-RAFT BACKPACK ...number) Mini-Raft, Backpack , Mini-Boat, Life Raft, One !-an, Vee Bottom RW" 24. ABSTRACT (Contnue on revere eld* i necessary and Identify by block number

  20. Surface chemistry of lipid raft and amyloid Aβ (1-40) Langmuir monolayer.

    Science.gov (United States)

    Thakur, Garima; Pao, Christine; Micic, Miodrag; Johnson, Sheba; Leblanc, Roger M

    2011-10-15

    Lipid rafts being rich in cholesterol and sphingolipids are considered to provide ordered lipid environment in the neuronal membranes, where it is hypothesized that the cleavage of amyloid precursor protein (APP) to Aβ (1-40) and Aβ (1-42) takes place. It is highly likely that the interaction of lipid raft components like cholesterol, sphingomylein or GM1 leads to nucleation of Aβ and results in aggregation or accumulation of amyloid plaques. One has investigated surface pressure-area isotherms of the lipid raft and Aβ (1-40) Langmuir monolayer. The compression-decompression cycles and the stability of the lipid raft Langmuir monolayer are crucial parameters for the investigation of interaction of Aβ (1-40) with the lipid raft Langmuir monolayer. It was revealed that GM1 provides instability to the lipid raft Langmuir monolayer. Adsorption of Aβ (1-40) onto the lipid raft Langmuir monolayer containing neutral (POPC) or negatively charged phospholipid (DPPG) was examined. The adsorption isotherms revealed that the concentration of cholesterol was important for adsorption of Aβ (1-40) onto the lipid raft Langmuir monolayer containing POPC whereas for the lipid raft Langmuir monolayer containing DPPG:cholesterol or GM1 did not play any role. In situ UV-vis absorption spectroscopy supported the interpretation of results for the adsorption isotherms.

  1. Milk protein suspensions enriched with three essential minerals: Physicochemical characterization and aggregation induced by a novel enzymatic pool.

    Science.gov (United States)

    Lombardi, Julia; Spelzini, Darío; Corrêa, Ana Paula Folmer; Brandelli, Adriano; Risso, Patricia; Boeris, Valeria

    2016-04-01

    Structural changes of casein micelles and their aggregation induced by a novel enzymatic pool isolated from Bacillus spp. in the presence of calcium, magnesium or zinc were investigated. The effect of cations on milk protein structure was studied using fluorescence and dynamic light scattering. In the presence of cations, milk protein structure rearrangements and larger casein micelle size were observed. The interaction of milk proteins with zinc appears to be of a different nature than that with calcium or magnesium. Under the experimental conditions assayed, the affinity of each cation for some groups present in milk proteins seems to play an important role, besides electrostatic interaction. On the other hand, the lowest aggregation times were achieved at the highest calcium and zinc concentrations (15 mM and 0.25 mM, respectively). The study found that the faster the aggregation of casein micelles, the less compact the gel matrix obtained. Cation concentrations affected milk protein aggregation kinetics and the structure of the aggregates formed.

  2. Microdomains Associated to Lipid Rafts.

    Science.gov (United States)

    Pacheco, Jonathan; Ramírez-Jarquín, Josué O; Vaca, Luis

    2016-01-01

    Store Operated Ca(2+) Entry (SOCE), the main Ca(2+) influx mechanism in non-excitable cells, is implicated in the immune response and has been reported to be affected in several pathologies including cancer. The basic molecular constituents of SOCE are Orai, the pore forming unit, and STIM, a multidomain protein with at least two principal functions: one is to sense the Ca(2+) content inside the lumen of the endoplasmic reticulum(ER) and the second is to activate Orai channels upon depletion of the ER. The link between Ca(2+) depletion inside the ER and Ca(2+) influx from extracellular media is through a direct association of STIM and Orai, but for this to occur, both molecules have to interact and form clusters where ER and plasma membrane (PM) are intimately apposed. In recent years a great number of components have been identified as participants in SOCE regulation, including regions of plasma membrane enriched in cholesterol and sphingolipids, the so called lipid rafts, which recruit a complex platform of specialized microdomains, which cells use to regulate spatiotemporal Ca(2+) signals.

  3. Improving stability and activity of cross-linked enzyme aggregates based on polyethylenimine in hydrolysis of fish oil for enrichment of polyunsaturated fatty acids.

    Science.gov (United States)

    Yan, Jinyong; Gui, Xiaohua; Wang, Guilong; Yan, Yunjun

    2012-02-01

    Cross-linking of enzyme aggregates from recombinant Geotrichum sp. lipase based on polyethylenimine (PEI) was applied to hydrolyze fish oil for enrichment of polyunsaturated fatty acids successfully. Through acetone precipitation and cross-linking of physical aggregates using glutaraldehyde in the presence of PEI, firmly cross-linked enzyme aggregates (PEI-CLEAs) were prepared. They could maintain more than 65% of relative hydrolysis degree after incubation in the range of 50-55 °C for 4 h and maintain more than 85% of relative hydrolysis degree after being treated by acetone, tert-butyl alcohol and octane for 4 h. PEI-CLEAs increased hydrolysis degree to 42% from 12% by free lipase. After five batch reactions, PEI-CLEAs still maintained 72% of relative hydrolysis degree. Hydrolysis of fish oil by PEI-CLEAs produced glycerides containing concentrated EPA and DHA in good yield. PEI-CLEAs had advantages over general CLEAs and free lipase in initial reaction rate, hydrolysis degree, thermostability, organic solvent tolerance and reusability.

  4. Function of MRP1/ABCC1 is not dependent on cholesterol or cholesterol-stabilized lipid rafts

    NARCIS (Netherlands)

    Meszaros, Peter; Klappe, Karin; Hummel, Ina; Hoekstra, Dick; Kok, Jan Willem

    2011-01-01

    MRP1 (multidrug-resistance-related protein 1)/ABCC1 (ATP-binding cassette transporter C1) has been localized in cholesterol-enriched lipid rafts, which suggests a role for these lipid rafts and/or cholesterol in MRP1 function. In the present study, we have shown for the first time that nearly comple

  5. Cholesterol, sphingolipids, and glycolipids: What do we know about their role in raft-like membranes?

    DEFF Research Database (Denmark)

    Rog, T.; Vattulainen, I.

    2014-01-01

    Lipids rafts are considered to be functional nanoscale membrane domains enriched in cholesterol and sphingolipids, characteristic in particular of the external leaflet of cell membranes. Lipids, together with membrane-associated proteins, are therefore considered to form nanoscale units...... emerged based on recent atomistic and coarse-grained molecular dynamics simulation studies on the key lipid raft components, which include cholesterol, sphingolipids, glycolipids, and the proteins interacting with these classes of lipids. The simulation results are compared to experiments when possible...... with potential specific functions. Although the understanding of the structure of rafts in living cells is quite limited, the possible functions of rafts are widely discussed in the literature, highlighting their importance in cellular functions. In this review, we discuss the understanding of rafts that has...

  6. Lipid rafts and Alzheimer’s disease: protein-lipid interactions and perturbation of signalling

    Directory of Open Access Journals (Sweden)

    David A. Hicks

    2012-06-01

    Full Text Available Lipid rafts are membrane domains, more ordered than the bulk membrane and enriched in cholesterol and sphingolipids. They represent a platform for protein-lipid and protein-protein interactions and for cellular signalling events. In addition to their normal functions, including membrane trafficking, ligand binding (including viruses, axonal development and maintenance of synaptic integrity, rafts have also been implicated in the pathogenesis of several neurodegenerative diseases including Alzheimer’s disease (AD. Lipid rafts promote interaction of the amyloid precursor protein (APP with the secretase (BACE-1 responsible for generation of the amyloid β peptide, Aβ. Rafts also regulate cholinergic signalling as well as acetylcholinesterase and Aβ interaction. In addition, such major lipid raft components as cholesterol and GM1 ganglioside have been directly implicated in pathogenesis of the disease. Perturbation of lipid raft integrity can also affect various signalling pathways leading to cellular death and AD. In this review, we discuss modulation of APP cleavage by lipid rafts and their components, while also looking at more recent findings on the role of lipid rafts in signalling events.

  7. Role of lipid rafts in neuronal differentiation of dental pulp-derived stem cells.

    Science.gov (United States)

    Mattei, Vincenzo; Santacroce, Costantino; Tasciotti, Vincenzo; Martellucci, Stefano; Santilli, Francesca; Manganelli, Valeria; Piccoli, Luca; Misasi, Roberta; Sorice, Maurizio; Garofalo, Tina

    2015-12-10

    Human dental pulp-derived stem cells (hDPSCs) are characterized by a typical fibroblast-like morphology. They express specific markers for mesenchymal stem cells and are capable of differentiation into osteoblasts, adipoblasts and neurons in vitro. Previous studies showed that gangliosides are involved in the induction of early neuronal differentiation of hDPSCs. This study was undertaken to investigate the role of lipid rafts in this process. Lipid rafts are signaling microdomains enriched in glycosphingolipids, cholesterol, tyrosine kinase receptors, mono- or heterotrimeric G proteins and GPI-anchored proteins. We preliminary showed that established cells expressed multipotent mesenchymal stromal-specific surface antigens. Then, we analyzed the distribution of lipid rafts, revealing plasma membrane microdomains with GM2 and EGF-R enrichment. Following stimulation with EGF/bFGF, neuronal differentiation was observed. To analyze the functional role of lipid rafts in EGF/bFGF-induced hDPSCs differentiation, cells were preincubated with lipid raft affecting agents, i.e. [D]-PDMP or methyl-β-cyclodextrin. These compounds significantly prevented neuronal-specific antigen expression, as well as Akt and ERK 1/2 phosphorylation, induced by EGF/bFGF, indicating that lipid raft integrity is essential for EGF/bFGF-induced hDPSCs differentiation. These results suggest that lipid rafts may represent specific chambers, where multimolecular signaling complexes, including lipids (gangliosides, cholesterol) and proteins (EGF-R), play a role in hDPSCs differentiation.

  8. Isolation and use of rafts.

    Science.gov (United States)

    Brown, Deborah A

    2002-11-01

    This unit describes methods for isolating and analyzing rafts by detergent insolubility. To distinguish these rafts from raft-like membranes isolated by other methods, they are referred to here as detergent-resistant membranes (DRMs). DRMs can be isolated by flotation on sucrose density gradients or by pelleting after detergent extraction. DRM proteins can be analyzed by SDS-PAGE and immunoblotting. Additionally, radiolabeled DRM proteins can be analyzed, and lipids can be quantitated by high-performance thin layer chromatography. Support protocols needed for the lipid analysis are also provided. Finally, protocols for raft disruption by cholesterol removal and measuring the kinetics of such removal are included together with a method that reverses the cholesterol removal (cholesterol repletion).

  9. Vacuum Packed Mini-Raft.

    Science.gov (United States)

    1974-12-16

    the cloth, seam tapes, and attachments to shrink or pucker at any point on the life raft. —4— The life raft shall be free from any congealed mass of...be cut in strict accordance with the patterns, developed by the Engineering Department, which show seam allowance , size , shape and location of the...to the flow of the carbon dioxide gas or bir restriction by any component . The carbon dioxide shall enter the main tubes only. All the seams

  10. O-glycans direct selectin ligands to lipid rafts on leukocytes.

    Science.gov (United States)

    Shao, Bojing; Yago, Tadayuki; Setiadi, Hendra; Wang, Ying; Mehta-D'souza, Padmaja; Fu, Jianxin; Crocker, Paul R; Rodgers, William; Xia, Lijun; McEver, Rodger P

    2015-07-14

    Palmitoylated cysteines typically target transmembrane proteins to domains enriched in cholesterol and sphingolipids (lipid rafts). P-selectin glycoprotein ligand-1 (PSGL-1), CD43, and CD44 are O-glycosylated proteins on leukocytes that associate with lipid rafts. During inflammation, they transduce signals by engaging selectins as leukocytes roll in venules, and they move to the raft-enriched uropods of polarized cells upon chemokine stimulation. It is not known how these glycoproteins associate with lipid rafts or whether this association is required for signaling or for translocation to uropods. Here, we found that loss of core 1-derived O-glycans in murine C1galt1(-/-) neutrophils blocked raft targeting of PSGL-1, CD43, and CD44, but not of other glycosylated proteins, as measured by resistance to solubilization in nonionic detergent and by copatching with a raft-resident sphingolipid on intact cells. Neuraminidase removal of sialic acids from wild-type neutrophils also blocked raft targeting. C1galt1(-/-) neutrophils or neuraminidase-treated neutrophils failed to activate tyrosine kinases when plated on immobilized anti-PSGL-1 or anti-CD44 F(ab')2. Furthermore, C1galt1(-/-) neutrophils incubated with anti-PSGL-1 F(ab')2 did not generate microparticles. In marked contrast, PSGL-1, CD43, and CD44 moved normally to the uropods of chemokine-stimulated C1galt1(-/-) neutrophils. These data define a role for core 1-derived O-glycans and terminal sialic acids in targeting glycoprotein ligands for selectins to lipid rafts of leukocytes. Preassociation of these glycoproteins with rafts is required for signaling but not for movement to uropods.

  11. Targeting Cell Membrane Lipid Rafts by Stoichiometric Functionalization of Gold Nanoparticles With a Sphingolipid-Binding Domain Peptide.

    Science.gov (United States)

    Paramelle, David; Nieves, Daniel; Brun, Benjamin; Kraut, Rachel S; Fernig, David G

    2015-04-22

    A non-membrane protein-based nanoparticle agent for the tracking of lipid rafts on live cells is produced by stoichiometric functionalization of gold nanoparticles with a previously characterized sphingolipid- and cell membrane microdomain-binding domain peptide (SBD). The SBD peptide is inserted in a self-assembled monolayer of peptidol and alkane thiol ethylene glycol, on gold nanoparticles surface. The stoichiometric functionalization of nanoparticles with the SBD peptide, essential for single molecule tracking, is achieved by means of non-affinity nanoparticle purification. The SBD-nanoparticles have remarkable long-term resistance to electrolyte-induced aggregation and ligand-exchange and have no detectable non-specific binding to live cells. Binding and diffusion of SBD-nanoparticles bound to the membrane of live cells is measured by real-time photothermal microscopy and shows the dynamics of sphingolipid-enriched microdomains on cells membrane, with evidence for clustering, splitting, and diffusion over time of the SBD-nanoparticle labeled membrane domains. The monofunctionalized SBD-nanoparticle is a promising targeting agent for the tracking of lipid rafts independently of their protein composition and the labelling requires no prior modification of the cells. This approach has potential for further functionalization of the particles to manipulate the organization of, or targeting to microdomains that control signaling events and thereby lead to novel diagnostics and therapeutics.

  12. Caveolin interaction governs Kv1.3 lipid raft targeting.

    Science.gov (United States)

    Pérez-Verdaguer, Mireia; Capera, Jesusa; Martínez-Mármol, Ramón; Camps, Marta; Comes, Núria; Tamkun, Michael M; Felipe, Antonio

    2016-03-02

    The spatial localization of ion channels at the cell surface is crucial for their functional role. Many channels localize in lipid raft microdomains, which are enriched in cholesterol and sphingolipids. Caveolae, specific lipid rafts which concentrate caveolins, harbor signaling molecules and their targets becoming signaling platforms crucial in cell physiology. However, the molecular mechanisms involved in such spatial localization are under debate. Kv1.3 localizes in lipid rafts and participates in the immunological response. We sought to elucidate the mechanisms of Kv1.3 surface targeting, which govern leukocyte physiology. Kv1 channels share a putative caveolin-binding domain located at the intracellular N-terminal of the channel. This motif, lying close to the S1 transmembrane segment, is situated near the T1 tetramerization domain and the determinants involved in the Kvβ subunit association. The highly hydrophobic domain (FQRQVWLLF) interacts with caveolin 1 targeting Kv1.3 to caveolar rafts. However, subtle variations of this cluster, putative ancillary associations and different structural conformations can impair the caveolin recognition, thereby altering channel's spatial localization. Our results identify a caveolin-binding domain in Kv1 channels and highlight the mechanisms that govern the regulation of channel surface localization during cellular processes.

  13. Isolation and analysis of membrane lipids and lipid rafts in common carp (Cyprinus carpio L.).

    Science.gov (United States)

    Brogden, Graham; Propsting, Marcus; Adamek, Mikolaj; Naim, Hassan Y; Steinhagen, Dieter

    2014-03-01

    Cell membranes act as an interface between the interior of the cell and the exterior environment and facilitate a range of essential functions including cell signalling, cell structure, nutrient uptake and protection. It is composed of a lipid bilayer with integrated proteins, and the inner leaflet of the lipid bilayer comprises of liquid ordered (Lo) and liquid disordered (Ld) domains. Lo microdomains, also named as lipid rafts are enriched in cholesterol, sphingomyelin and certain types of proteins, which facilitate cell signalling and nutrient uptake. Lipid rafts have been extensively researched in mammals and the presence of functional lipid rafts was recently demonstrated in goldfish, but there is currently very little knowledge about their composition and function in fish. Therefore a protocol was established for the analysis of lipid rafts and membranous lipids in common carp (Cyprinus carpio L.) tissues. Twelve lipids were identified and analysed in the Ld domain of the membrane with the most predominant lipids found in all tissues being; triglycerides, cholesterol, phosphoethanolamine and phosphatidylcholine. Four lipids were identified in lipid rafts in all tissues analysed, triglycerides (33-62%) always found in the highest concentration followed by cholesterol (24-32%), phosphatidylcholine and sphingomyelin. Isolation of lipid rafts was confirmed by identifying the presence of the lipid raft associated protein flotillin, present at higher concentrations in the detergent resistant fraction. The data provided here build a lipid library of important carp tissues as a baseline for further studies into virus entry, protein trafficking or environmental stress analysis.

  14. Mature N-linked glycans facilitate UT-A1 urea transporter lipid raft compartmentalization.

    Science.gov (United States)

    Chen, Guangping; Howe, Ashley G; Xu, Gang; Fröhlich, Otto; Klein, Janet D; Sands, Jeff M

    2011-12-01

    The UT-A1 urea transporter is a glycoprotein with two different glycosylated forms of 97 and 117 kDa. In this study, we found the 117-kDa UT-A1 preferentially resides in lipid rafts, suggesting that the glycosylation status may interfere with UT-A1 lipid raft trafficking. This was confirmed by a site-directed mutagenesis study in MDCK cells. The nonglycosylated UT-A1 showed reduced localization in lipid rafts. By using sugar-specific binding lectins, we further found that the UT-A1 in nonlipid rafts contained a high amount of mannose, as detected by concanavalin A, while the UT-A1 in lipid rafts was the mature N-acetylglucosamine-containing form, as detected by wheat germ agglutinin. In the inner medulla (IM) of diabetic rats, the more abundant 117-kDa UT-A1 in lipid rafts was the mature glycosylation form, with high amounts of N-acetylglucosamine and sialic acid. In contrast, in the IM of normal rats, the predominant 97-kDa UT-A1 was the form enriched in mannose. Functionally, inhibition of glycosylation by tunicamycin or elimination of the glycosylation sites by mutation significantly reduced UT-A1 activity in oocytes. Taken together, our study reveals a new role of N-linked glycosylation in regulating UT-A1 activity by promoting UT-A1 trafficking into membrane lipid raft subdomains.

  15. Raft disorganization leads to reduced plasmin activity in Alzheimer's disease brains.

    Science.gov (United States)

    Ledesma, Maria Dolores; Abad-Rodriguez, José; Galvan, Cristian; Biondi, Elisa; Navarro, Pilar; Delacourte, Andre; Dingwall, Colin; Dotti, Carlos G

    2003-12-01

    The serine protease plasmin can efficiently degrade amyloid peptide in vitro, and is found at low levels in the hippocampus of patients with Alzheimer's disease (AD). The cause of such paucity remains unknown. We show here that the levels of total brain plasminogen and plasminogen-binding molecules are normal in these brain samples, yet plasminogen membrane binding is greatly reduced. Biochemical analysis reveals that the membranes of these brains have a mild, still significant, cholesterol reduction compared to age-matched controls, and anomalous raft microdomains. This was reflected by the loss of raft-enriched proteins, including plasminogen-binding and -activating molecules. Using hippocampal neurons in culture, we demonstrate that removal of a similar amount of membrane cholesterol is sufficient to induce raft disorganization, leading to reduced plasminogen membrane binding and low plasmin activity. These results suggest that brain raft alterations may contribute to AD by rendering the plasminogen system inefficient.

  16. Function of Membrane Rafts in Viral Lifecycles and Host Cellular Response

    Directory of Open Access Journals (Sweden)

    Tadanobu Takahashi

    2011-01-01

    Full Text Available Membrane rafts are small (10–200 nm sterol- and sphingolipid-enriched domains that compartmentalize cellular processes. Membrane rafts play an important role in viral infection cycles and viral virulence. Viruses are divided into four main classes, enveloped DNA virus, enveloped RNA virus, nonenveloped DNA virus, and nonenveloped RNA virus. General virus infection cycle is also classified into two sections, the early stage (entry process and the late stage (assembly, budding, and release processes of virus particles. In the viral cycle, membrane rafts act as a scaffold of many cellular signal transductions, which are associated with symptoms caused by viral infections. In this paper, we describe the functions of membrane rafts in viral lifecycles and host cellular response according to each virus classification, each stage of the virus lifecycle, and each virus-induced signal transduction.

  17. The Role of Lipid Rafts in Cancer Cell Adhesion and Migration

    Directory of Open Access Journals (Sweden)

    Toshiyuki Murai

    2012-01-01

    Full Text Available Lipid rafts are cholesterol-enriched microdomains of the cell membrane and possess a highly dynamic nature. They have been involved in various cellular functions including the regulation of cell adhesion and membrane signaling through proteins within lipid rafts. The dynamic features of the cancer cell surface may modulate the malignant phenotype of cancer, including adhesion disorders and aggressive phenotypes of migration and invasion. Recently, it was demonstrated that lipid rafts play critical roles in cancer cell adhesion and migration. This article summarizes the important roles of lipid rafts in cancer cell adhesion and migration, with a focus on the current state of knowledge. This article will improve the understanding of cancer progression and lead to the development of novel targets for cancer therapy.

  18. The association of thromboxane A2 receptor with lipid rafts is a determinant for platelet functional responses.

    Science.gov (United States)

    Moscardó, A; Vallés, J; Latorre, A; Santos, M T

    2014-08-25

    We have investigated the presence of thromboxane A2 (TXA2) receptor associated with lipid rafts in human platelets and the regulation of platelet function in response to TXA2 receptor agonists when lipid rafts are disrupted by cholesterol extraction. Platelet aggregation with TXA2 analogs U46619 and IBOP was almost blunted in cholesterol-depleted platelets, as well as αIIbβ3 integrin activation and P-selectin exposure. Raft disruption also inhibited TXA2-induced cytosolic calcium increase and nucleotide release, ruling out an implication of P2Y12 receptor. An important proportion of TXA2 receptor (40%) was colocalized at lipid rafts. The presence of the TXA2 receptor associated with lipid rafts in platelets is important for functional platelet responses to TXA2.

  19. You Sank My Lipid Rafts!

    Science.gov (United States)

    Campbell, Tessa N.

    2009-01-01

    The plasma membrane is the membrane that serves as a boundary between the interior of a cell and its extracellular environment. Lipid rafts are microdomains within a cellular membrane that possess decreased fluidity due to the presence of cholesterol, glycolipids, and phospholipids containing longer fatty acids. These domains are involved in many…

  20. The Functional Roles of Lipid Rafts in T-Cell Activation, Immune Diseases and HIV Infection and Prevention

    Institute of Scientific and Technical Information of China (English)

    Cheng Lou; Kou Wang; Dequan Liu; Yan Li; Qinshi Zhao

    2008-01-01

    The first appearance of lipid rafts, or lipid rafts-like structure, was occasionally observed by cryo-electronic microscopy in 1980s as cavity, such as caveolae. However, the fully understanding of lipid raft was attributed by the studies of T cell activation. virus entry/budding, and other membrane events. During the interaction of T cell and antigen presenting cell, a highly organized structure is formed at the interface of the two cells, where cholesterol and sphingolipids are enriched, and form a liquid ordered phase that facilitates the signaling proteins on and off. Lipid rafts are also involved in virus entry and assembly. In this review, we will discuss cholesterol sphingolipid floating micro domain, the lipid raft as a unique compartment of the plasma membrane, with biological functions that ensure correct intracellular traffic of proteins and lipids, such as protein-protein interactions by concentrating certain proteins in these micro domains, while excluding others. We also discuss the disruption of lipid rafts is re teed to different diseases and aging, and we especially exploit the lipid rafts as pharmaceutical targets for anti-virus and anti-inflammation. Particularly a new approach to control HIV infection for AIDS prevention and perfection by inhibition or disruption of lipid rafts. Cellular & Molecular Immunology 2008;5(1):1-7.

  1. The effects of Various Endodontic Irrigants on the Push-out Bond Strength of Calcium-Enriched Mixture Cement and Mineral Trioxide Aggregate.

    Science.gov (United States)

    Sahebi, Safoora; Sobhnamayan, Fereshte; Naghizade, Sina

    2016-01-01

    The aim of this in vitro study was to evaluate the effect of various irrigants on the push-out bond strength of calcium-enriched mixture (CEM) cement and mineral trioxide aggregate (MTA). A total of 140 dentin disks with a thickness of 1.5±0.2 mm and lumen size of 1.3 mm, were randomly divided into 12 groups (n=10) and 4 control groups (n=5). The lumen of disks in groups 1, 2, 3, 7, 8, 9 were filled with CEM and groups 4, 5, 6, 10, 11, 12 were filled with MTA. Control groups were filled with CEM and MTA. Specimens were incubated at 37(°)C for one day in groups 1 to 6 and seven days in groups 7 to 12. After incubation the samples were divided into three subgroups (n=10) that were either immersed for 30 min in 5.5% sodium hypochlorite (NaOCl), 2% chlorhexidine (CHX) or saline solution. The push-out bond strength values were measured by using a universal testing machine. The nature of the failures were determined by light microscope. Data was analyzed using the three-way ANOVA to evaluate the effect of material type, different irrigants and time intervals. Post hoc Tukey's test was used for two-by-two comparison of the groups. CEM cement significantly showed a higher push-out bond strength in comparison with MTA (P=0.001). The elapse of time significantly increased the bond strength (P=0.001). There was no significant difference between the irrigants used in this study (P=0.441). Bond failure was predominantly of mixed type in MTA and of cohesive type in CEM samples. Based on this study, endodontic irrigants did not influence the push-out bond strength of MTA and CEM cement.

  2. A comparison between gray and white mineral trioxide aggregate (MTA and calcium enriched mixture (CEM cytotoxicity in L929 and Saos-2 cell lines

    Directory of Open Access Journals (Sweden)

    Robab Farhang

    2016-12-01

    Full Text Available The purpose was to compare the cytotoxic effects of two commonly used mineral trioxide aggregate (MTA (gray & white with the recently introduced calcium enriched mixture (CEM in L929 and Saos-2 cell lines and to determine the oxidative stressinduced by each cement. Sterile discs of each cement were submerged and incubated in complete media for 24, 48 and 72-h. The cell lines were exposed to two fold serial dilutions (1, 0.5, 0.25 X of each extract. In addition to trypan blue (TB dye exclusion test, MTT assay was carried out after 24-h. To determine the oxidative stress mediated cell toxicity, malondialdehyde (MDA concentration and total ferric reduction activity potential (FRAP were measured in the media.The MTT and TB results with 48-h and 72-h CEM extracts showed that both extracts are cytotoxic in L929 cell line at 1 X and 0.5 X dilutions, while neither white MTA (WMTA nor gray MTA (GMTA showed any toxic effects in this cell line. On the other hand all three cements (undiluted 48-h and 72-h extracts were cytotoxic against Saos-2 cell line. The oxidative stress marker (MDA was proportionate to the cytotoxic effects of CEM while there was no significant changes in reductive capacity of the media measured by FRAP in both cell lines.The cytotoxic effects of CEM on L929 and Saos-2 cell lines seems to be higher than WMTA and GMTA and it is increased by the time of extraction up to 72-h.. However, CEM, WMTA and GMTA showed similar toxic effect in Saos-2 cell line proportionate to the oxidative stress measured by TBARS. It seems that while all three cements extracts don't change the antioxidant activity of the media, they could significantly increase lipid peroxidation, especially CEM with Saos-2 cell line which elucidate triggering oxidative stress mechanisms without having direct oxidative activity.

  3. The influence of an antitumor lipid - erucylphosphocholine - on artificial lipid raft system modeled as Langmuir monolayer.

    Science.gov (United States)

    Wnętrzak, Anita; Łątka, Kazimierz; Makyła-Juzak, Katarzyna; Zemla, Joanna; Dynarowicz-Łątka, Patrycja

    2015-01-01

    Outer layer of cellular membrane contains ordered domains enriched in cholesterol and sphingolipids, called 'lipid rafts', which play various biological roles, i.e., are involved in the induction of cell death by apoptosis. Recent studies have shown that these domains may constitute binding sites for selected drugs. For example alkylphosphocholines (APCs), which are new-generation antitumor agents characterized by high selectivity and broad spectrum of activity, are known to have their molecular targets located at cellular membrane and their selective accumulation in tumor cells has been hypothesized to be linked with the alternation of biophysical properties of lipid rafts. To get a deeper insight into this issue, interactions between representative APC: erucylphosphocholine, and artificial lipid raft system, modeled as Langmuir monolayer (composed of cholesterol and sphingomyelin mixed in 1:2 proportion) were investigated. The Langmuir monolayer experiments, based on recording surface pressure-area isotherms, were complemented with Brewster angle microscopy results, which enabled direct visualization of the monolayers structure. In addition, the investigated monolayers were transferred onto solid supports and studied with AFM. The interactions between model raft system and erucylphosphocholine were analyzed qualitatively (with mean molecular area values) as well as quantitatively (with ΔG(exc) function). The obtained results indicate that erucylphosphocholine introduced to raft-mimicking model membrane causes fluidizing effect and weakens the interactions between cholesterol and sphingomyelin, which results in phase separation at high surface pressures. This leads to the redistribution of cholesterol molecules in model raft, which confirms the results observed in biological studies.

  4. Sphingomyelin distribution in lipid rafts of artificial monolayer membranes visualized by Raman microscopy.

    Science.gov (United States)

    Ando, Jun; Kinoshita, Masanao; Cui, Jin; Yamakoshi, Hiroyuki; Dodo, Kosuke; Fujita, Katsumasa; Murata, Michio; Sodeoka, Mikiko

    2015-04-14

    Sphingomyelin (SM) and cholesterol (chol)-rich domains in cell membranes, called lipid rafts, are thought to have important biological functions related to membrane signaling and protein trafficking. To visualize the distribution of SM in lipid rafts by means of Raman microscopy, we designed and synthesized an SM analog tagged with a Raman-active diyne moiety (diyne-SM). Diyne-SM showed a strong peak in a Raman silent region that is free of interference from intrinsic vibrational modes of lipids and did not appear to alter the properties of SM-containing monolayers. Therefore, we used Raman microscopy to directly visualize the distribution of diyne-SM in raft-mimicking domains formed in SM/dioleoylphosphatidylcholine/chol ternary monolayers. Raman images visualized a heterogeneous distribution of diyne-SM, which showed marked variation, even within a single ordered domain. Specifically, diyne-SM was enriched in the central area of raft domains compared with the peripheral area. These results seem incompatible with the generally accepted raft model, in which the raft and nonraft phases show a clear biphasic separation. One of the possible reasons is that gradual changes of SM concentration occur between SM-rich and -poor regions to minimize hydrophobic mismatch. We believe that our technique of hyperspectral Raman imaging of a single lipid monolayer opens the door to quantitative analysis of lipid membranes by providing both chemical information and spatial distribution with high (diffraction-limited) spatial resolution.

  5. Probing Lipid Membrane Rafts (Microdomains) with Fluorescent Phospholipids

    Science.gov (United States)

    Gu, Yongwen; Mitchel, Drake

    2011-10-01

    Membrane rafts are enriched in sphingolipids and cholesterol, they exist in a more ordered state (the liquid-ordered phase; lo) than the bulk membrane (the liquid-disordered phase; ld). Ternary mixtures of palmitoyl-oleoyl-phosphocholine (POPC; 16:0,18:1 PC), sphingomyelin (SPM), and cholesterol (Chol) form membrane rafts over a wide range of molar ratios. We are examining the ability of two fluorescent probes, NBD linked to di-16:0 PE which partitions into the lo phase, and NBD linked to di-18:1 PE which partitions into the ld phase, to detect these two phases. We are also examining the effect of the highly polyunsaturated phospholipid stearoyl-docosahexanoyl-phosphocholine (SDPC; 18:0, 22:6 PC) on the size and stability of POPC/SPM/Chol membrane rafts. We report on the fluorescence lifetime and anisotropy decay dynamics of two fluorescent probes. Data were acquired via frequency-domain measurements from 5 to 250 MHz.

  6. The Effect of Different Mixing Methods on the pH and Solubility of Mineral Trioxide Aggregate and Calcium-Enriched Mixture

    Science.gov (United States)

    Shahi, Shahriar; Ghasemi, Negin; Rahimi, Saeed; Yavari, Hamid Reza; Samiei, Mohammad; Janani, Maryam; Bahari, Mahmood

    2015-01-01

    Introduction: The aim of this study was to evaluate the effect of different mixing techniques on the pH and solubility of mineral trioxide aggregate (MTA) and calcium-enriched mixture (CEM). Methods and Materials: Five samples were prepared from each biomaterial with different mixing techniques including hand-, amalgamator- or ultrasonic-mixing and were then placed in pre-weighted plastic tubes to determine their pH values. Each tube was then incubated in 10 mL deionized distilled water for 1 h at 37ºC. An electrode was placed in the fluid in each flask at 24ºC and the pH was recorded. In the next stage, six samples from each mixing technique/material were separately placed in glass bottles containing 50 mL of distilled water at 37ºC for 1 h and were let dry for 1 h at 37ºC. The samples’ weights were measured and recorded twice. The procedure was repeated at 1-, 7- and 21-day intervals. Data were analyzed with the repeated measures ANOVA (for solubility) and two-way ANOVA (for pH) and then the post-hoc Tukey’s test was done. Results: The pH of the materials was not significantly affected by mixing methods. (P=0.8 for CEM and P=0.1 for MTA). The solubility of all test groups was within the acceptable range (=3%). However, the solubility of CEM at 1- and 21-day intervals was significantly different (P=0.03 for 1 day and P=0.001 for 21 days). Different mixing techniques had significant effects on the solubility of MTA at the three time points (P=0.004, 0.003 and 0.002 for 1-, 7- and 21-day intervals, respectively). Conclusion: The pH of biomaterials was not influenced by the mixing technique and their solubility was within the acceptable range. PMID:25834601

  7. Simulation of Rate Retardation in RAFT Polymerization of Styrene with Low RAFT-Initiator Ratio

    Institute of Scientific and Technical Information of China (English)

    WANG Yanjun; YUE Liying; CHEN Wenhao; YUAN Caideng

    2005-01-01

    Bulk polymerizations of styrene (St) were carried out in the presence of three reversible addition fragmentation chain transfer (RAFT) agents benzyl dithiobenzoate (BDB), cumyl dithiobenzoate(CDB), and 1-phenylethyl dithiobenzoate (PEDB) under low ratio of RAFT agent to initiator. The kinetic model was developed to predict polymerization rate, which indicates that the RAFT polymerization of St is a first-order reaction. In the range of experimental conversions, the plots of -ln(1-x) against time t are approximately linear (x is monomer conversion). The kinetic study reveals the existence of strong rate retardation in RAFT polymerization of styrene. A coefficient K r is defined to estimate the rate retardation in the RAFT system considering the assumption that the retardation in polymerization rate is mainly attributed to slow fragmentation of the intermediate radicals. K r relates to the structure of RAFT agents as well as the concentrations of RAFT agent and azobis isobutyronitrile (AIBN). For a certain RAFT agent, the value of K r is enhanced by the increase in the initial concentration of RAFT agent and the higher ratio of RAFT to AIBN. With the same recipe for different RAFT agents, the increasing trend for the values of K r is BDB

  8. Lipid rafts participate in aberrant degradative autophagic-lysosomal pathway of amyloid-beta peptide in Alzheimer’s disease

    Institute of Scientific and Technical Information of China (English)

    Xin Zhou; Chun Yang; Yufeng Liu; Peng Li; Huiying Yang; Jingxing Dai; Rongmei Qu; Lin Yuan

    2014-01-01

    Amyloid-beta peptide is the main component of amyloid plaques, which are found in Alzhei-mer’s disease. The generation and deposition of amyloid-beta is one of the crucial factors for the onset and progression of Alzheimer’s disease. Lipid rafts are glycolipid-rich liquid domains of the plasma membrane, where certain types of protein tend to aggregate and intercalate. Lipid rafts are involved in the generation of amyloid-beta oligomers and the formation of amyloid-beta peptides. In this paper, we review the mechanism by which lipid rafts disturb the aberrant deg-radative autophagic-lysosomal pathway of amyloid-beta, which plays an important role in the pathological process of Alzheimer’s disease. Moreover, we describe this mechanism from the view of the Two-system Theory of fasciology and thus, suggest that lipid rafts may be a new target of Alzheimer’s disease treatment.

  9. Chemical driving force for rafting in superalloys

    CSIR Research Space (South Africa)

    Nabarro, FRN

    1997-08-15

    Full Text Available The author provides a brief overview of the chemical driving forces for rafting in superalloys. Until recently, all theories of the driving force for rafting have considered the compositions of the two phases to be fixed, although accepting...

  10. RAFT polymers for protein recognition

    Directory of Open Access Journals (Sweden)

    Alan F. Tominey

    2010-06-01

    Full Text Available A new family of linear polymers with pronounced affinity for arginine- and lysine-rich proteins has been created. To this end, N-isopropylacrylamide (NIPAM was copolymerized in water with a binding monomer and a hydrophobic comonomer using a living radical polymerization (RAFT. The resulting copolymers were water-soluble and displayed narrow polydispersities. They formed tight complexes with basic proteins depending on the nature and amount of the binding monomer as well as on the choice of the added hydrophobic comonomer.

  11. Role of lipid rafts/caveolae in the anticancer effect of endocannabinoids.

    Science.gov (United States)

    Grimaldi, Claudia; Capasso, Anna

    2012-10-01

    The endocannabinoid system comprises the cannabinoid receptors type 1 (CB1) and type 2 (CB2), their endogenous ligands (endocannabinoids) and the whole apparatus appointed of their synthesis and degradation. Recent studies investigated the possibility that drugs targeting the endocannabinoid system might be used to retard or block cancer growth. CB1, CB2 and metabolic enzymes of endocannabinoids, function in the context of lipid rafts, specialized membrane microdomains enriched in cholesterol, sphingolipids and glycosphingolipids which may be important in modulating signal transduction. Here, we analysed the role of lipid rafts/caveolae in the intracellular signaling and trafficking of cannabinoid receptor agonist in cancer cells. Perturbation of lipid rafts/caveolae may in fact represent a useful tool for the development of a novel therapy for endocannabinoids-related diseases, such as cancer. Also, we report the more recent developments of endocannabinoids in cancer drug discovery.

  12. The consolidation of rafted sea ice

    Science.gov (United States)

    Bailey, E.; Feltham, D.; Sammonds, P.

    2009-04-01

    Rafting is an important process in the deformation of sea ice that occurs when two ice sheets collide. This process is particularly common in the North Caspian Sea, where ice floes override one another multiple times to produce thick sea ice features. To date, rafting has received little attention in the literature perhaps because in most regions pressure ridges produce the greatest loads on offshore structures. In the North Caspian Sea the shallow waters constrain the size to which pressure ridges can grow and the low salinity seems to favor rafting over ridging. Therefore it is likely that multiply-rafted sea ice may be the governing design feature for ice loads in the Caspian Sea. Here we present a one-dimensional, thermal-consolidation model for rafted sea ice. This is of interest because the degree of consolidation will affect the strength of a rafted structure, and therefore may be of value for modeling rafted ice loads. Results show that the thickness of the liquid layers reduces asymptotically with time, such that there always remains a thin liquid layer. We propose that when the liquid layer is equal to the surface roughness the adjacent layers can be considered consolidated. Using parameters specific to the North Caspian Sea, calculations show that it took 1hr, 14mins for the ice sheets to consolidate. To test the accuracy of the model concurrent experiments were carried out in the HSVA ice basin. During an experiment, equally sized portions of level ice were manually piled on top of one another to produce a rafted section. The rate of consolidation or bonding of the layers was then monitored by coring and using thermistors that were frozen into the level ice prior to rafting. Once consolidated, strength tests were carried out on the rafted ice and compared with those of level ice.

  13. Association between tetrodotoxin resistant channels and lipid rafts regulates sensory neuron excitability.

    Directory of Open Access Journals (Sweden)

    Alessandro Pristerà

    Full Text Available Voltage-gated sodium channels (VGSCs play a key role in the initiation and propagation of action potentials in neurons. Na(V1.8 is a tetrodotoxin (TTX resistant VGSC expressed in nociceptors, peripheral small-diameter neurons able to detect noxious stimuli. Na(V1.8 underlies the vast majority of sodium currents during action potentials. Many studies have highlighted a key role for Na(V1.8 in inflammatory and chronic pain models. Lipid rafts are microdomains of the plasma membrane highly enriched in cholesterol and sphingolipids. Lipid rafts tune the spatial and temporal organisation of proteins and lipids on the plasma membrane. They are thought to act as platforms on the membrane where proteins and lipids can be trafficked, compartmentalised and functionally clustered. In the present study we investigated Na(V1.8 sub-cellular localisation and explored the idea that it is associated with lipid rafts in nociceptors. We found that Na(V1.8 is distributed in clusters along the axons of DRG neurons in vitro and ex vivo. We also demonstrated, by biochemical and imaging studies, that Na(V1.8 is associated with lipid rafts along the sciatic nerve ex vivo and in DRG neurons in vitro. Moreover, treatments with methyl-β-cyclodextrin (MβCD and 7-ketocholesterol (7KC led to the dissociation between rafts and Na(V1.8. By calcium imaging we demonstrated that the lack of association between rafts and Na(V1.8 correlated with impaired neuronal excitability, highlighted by a reduction in the number of neurons able to conduct mechanically- and chemically-evoked depolarisations. These findings reveal the sub-cellular localisation of Na(V1.8 in nociceptors and highlight the importance of the association between Na(V1.8 and lipid rafts in the control of nociceptor excitability.

  14. Phosphorylation and lipid raft association of fibroblast growth factor receptor-2 in oligodendrocytes.

    Science.gov (United States)

    Bryant, M R; Marta, C B; Kim, F S; Bansal, R

    2009-07-01

    Fibroblast growth factors (FGFs) and their receptors (FGFRs) initiate diverse cellular responses that contribute to the regulation of oligodendrocyte (OL) function. To understand the mechanisms by which FGFRs elicit these cellular responses, we investigated the phosphorylation of signal transduction proteins and the role of cholesterol-glycosphingolipid-enriched "lipid raft" microdomains in differentiated OLs. Surprisingly, we found that the most abundant tyrosine-phosphorylated protein in OLs was the 120-kd isoform of FGFR2 and that it was phosphorylated even in the absence of FGF2, suggesting a potential ligand-independent function for this receptor. Furthermore, FGFR2, but not FGFR1, was associated with lipid raft microdomains in OLs and myelin (but not in astrocytes). This provides the first evidence for the association of FGFR with TX-100-insoluble lipid raft fractions. FGFR2 phosphorylated the key downstream target, FRS2 in OLs. Raft disruption resulted in loss of phosphorylated FRS2 from lipid rafts, coupled with the loss of Akt but not of Mek or Erk phosphorylation. This suggests that FGFR2-FRS2 signaling in lipid rafts operates via the PI3-Kinase/Akt pathway rather than the Ras/Mek/Erk pathway, emphasizing the importance of microenvironments within the cell membrane. Also present in lipid rafts in OLs and myelin, but not in astrocytes, was a novel 52-kd isoform of FGFR2 that lacked the extracellular ligand-binding region. These results demonstrate that FGFR2 in OLs and myelin possess unique characteristics that are specific both to receptor type and to OLs and provide a novel mechanism to elicit distinct cellular responses that mediate both FGF-dependent and -independent functions.

  15. Raft River Geothermal Aquaculture Experiment. Phase II

    Energy Technology Data Exchange (ETDEWEB)

    Campbell, D.K.; Rose, F.L.; Kent, J.C.; Watson, L.R.; Sullivan, J.F.

    1979-08-01

    Channel catfish, tilapia and Malaysian prawns were cultured directly in geothermal water for approximately seven months at the Department of Energy, Raft River Geothermal Site, to evaluate the organisms throughout a grow-out cycle. Parameters evaluated included survival, growth, bioaccumulation of metals and fluoride, collagen synthesis, and bone calcium levels. Growth at Raft River was slightly lower than at a companion commercial facility at Buhl, Idaho, but was attributed to facility differences rather than an adverse impact of geothermal water. No significant differences were recorded between Raft River and Buhl fish for bone calcium or collagen concentrations. No significant accumulation of heavy metals by fish or prawns was recorded.

  16. Anesthetics interacting with lipid rafts.

    Science.gov (United States)

    Bandeiras, Cátia; Serro, Ana Paula; Luzyanin, Konstantin; Fernandes, Anabela; Saramago, Benilde

    2013-01-23

    The exact mechanism by which anesthetics induce cell membrane-mediated modifications is still an open question. Although the fluidization effect of the anesthetic molecules on the cellular membrane is widely recognized, it is not known if anesthetics show any preference for specific membrane domains, namely the lipid rafts. The importance of these membrane micro-domains derives from the fact that they have been associated with cell signaling pathways, as well as with specific drug interactions. The objective of this work is to contribute for the elucidation of this question through the comparison of the anesthetic interactions with membranes of various lipid compositions. Liposomes prepared with an equimolar mixture of POPC, sphingomyelin and cholesterol, were chosen as models for lipid rafts. The interactions of these liposomes with two local anesthetics, tetracaine and lidocaine, and one general anesthetic, propofol, were studied. The effect of cholesterol was investigated by comparing anesthetic interactions with POPC/SM liposomes and POPC/SM/CHOL liposomes. The following experimental techniques were used: quartz crystal microbalance with dissipation, differential scanning calorimetry and phosphorus nuclear magnetic resonance. Although the liposomes investigated by the different techniques are not in the same conditions, it is possible to assemble the information obtained from all experimental techniques employed to reach a general conclusion. Tetracaine interacts more with raftlike domains, lidocaine induces stronger modifications on POPC/SM liposomes and the results for propofol are not fully conclusive but it seems to be the least prone to lipid interactions. The results were compared with those obtained with DMPC-containing liposomes, reported in a previous work.

  17. Differential uPAR recruitment in caveolar-lipid rafts by GM1 and GM3 gangliosides regulates endothelial progenitor cells angiogenesis

    Science.gov (United States)

    Margheri, Francesca; Papucci, Laura; Schiavone, Nicola; D'Agostino, Riccardo; Trigari, Silvana; Serratì, Simona; Laurenzana, Anna; Biagioni, Alessio; Luciani, Cristina; Chillà, Anastasia; Andreucci, Elena; Del Rosso, Tommaso; Margheri, Giancarlo; Del Rosso, Mario; Fibbi, Gabriella

    2015-01-01

    Gangliosides and the urokinase plasminogen activator receptor (uPAR) tipically partition in specialized membrane microdomains called lipid-rafts. uPAR becomes functionally important in fostering angiogenesis in endothelial progenitor cells (EPCs) upon recruitment in caveolar-lipid rafts. Moreover, cell membrane enrichment with exogenous GM1 ganglioside is pro-angiogenic and opposite to the activity of GM3 ganglioside. On these basis, we first checked the interaction of uPAR with membrane models enriched with GM1 or GM3, relying on the adoption of solid-supported mobile bilayer lipid membranes with raft-like composition formed onto solid hydrophilic surfaces, and evaluated by surface plasmon resonance (SPR) the extent of uPAR recruitment. We estimated the apparent dissociation constants of uPAR-GM1/GM3 complexes. These preliminary observations, indicating that uPAR binds preferentially to GM1-enriched biomimetic membranes, were validated by identifying a pro-angiogenic activity of GM1-enriched EPCs, based on GM1-dependent uPAR recruitment in caveolar rafts. We have observed that addition of GM1 to EPCs culture medium promotes matrigel invasion and capillary morphogenesis, as opposed to the anti-angiogenesis activity of GM3. Moreover, GM1 also stimulates MAPKinases signalling pathways, typically associated with an angiogenesis program. Caveolar-raft isolation and Western blotting of uPAR showed that GM1 promotes caveolar-raft partitioning of uPAR, as opposed to control and GM3-challenged EPCs. By confocal microscopy, we have shown that in EPCs uPAR is present on the surface in at least three compartments, respectively, associated to GM1, GM3 and caveolar rafts. Following GM1 exogenous addition, the GM3 compartment is depleted of uPAR which is recruited within caveolar rafts thereby triggering angiogenesis. PMID:25313007

  18. Differential uPAR recruitment in caveolar-lipid rafts by GM1 and GM3 gangliosides regulates endothelial progenitor cells angiogenesis.

    Science.gov (United States)

    Margheri, Francesca; Papucci, Laura; Schiavone, Nicola; D'Agostino, Riccardo; Trigari, Silvana; Serratì, Simona; Laurenzana, Anna; Biagioni, Alessio; Luciani, Cristina; Chillà, Anastasia; Andreucci, Elena; Del Rosso, Tommaso; Margheri, Giancarlo; Del Rosso, Mario; Fibbi, Gabriella

    2015-01-01

    Gangliosides and the urokinase plasminogen activator receptor (uPAR) tipically partition in specialized membrane microdomains called lipid-rafts. uPAR becomes functionally important in fostering angiogenesis in endothelial progenitor cells (EPCs) upon recruitment in caveolar-lipid rafts. Moreover, cell membrane enrichment with exogenous GM1 ganglioside is pro-angiogenic and opposite to the activity of GM3 ganglioside. On these basis, we first checked the interaction of uPAR with membrane models enriched with GM1 or GM3, relying on the adoption of solid-supported mobile bilayer lipid membranes with raft-like composition formed onto solid hydrophilic surfaces, and evaluated by surface plasmon resonance (SPR) the extent of uPAR recruitment. We estimated the apparent dissociation constants of uPAR-GM1/GM3 complexes. These preliminary observations, indicating that uPAR binds preferentially to GM1-enriched biomimetic membranes, were validated by identifying a pro-angiogenic activity of GM1-enriched EPCs, based on GM1-dependent uPAR recruitment in caveolar rafts. We have observed that addition of GM1 to EPCs culture medium promotes matrigel invasion and capillary morphogenesis, as opposed to the anti-angiogenesis activity of GM3. Moreover, GM1 also stimulates MAPKinases signalling pathways, typically associated with an angiogenesis program. Caveolar-raft isolation and Western blotting of uPAR showed that GM1 promotes caveolar-raft partitioning of uPAR, as opposed to control and GM3-challenged EPCs. By confocal microscopy, we have shown that in EPCs uPAR is present on the surface in at least three compartments, respectively, associated to GM1, GM3 and caveolar rafts. Following GM1 exogenous addition, the GM3 compartment is depleted of uPAR which is recruited within caveolar rafts thereby triggering angiogenesis.

  19. Raft River geoscience case study: appendixes

    Energy Technology Data Exchange (ETDEWEB)

    Dolenc, M.R.; Hull, L.C.; Mizell, S.A.; Russell, B.F.; Skiba, P.A.; Strawn, J.A.; Tullis, J.A.

    1981-11-01

    The following are included in these appendices: lithology, x-ray analysis, and cores; well construction data; borehole geophysical logs; chemical analyses from wells at the Raft River geothermal site; and bibliography. (MHR)

  20. Drop floating on a granular raft

    Science.gov (United States)

    Jambon-Puillet, Etienne; Josserand, Christophe; Protiere, Suzie

    2015-11-01

    When a droplet comes in contact with a bath of the same liquid, it coalesces to minimize the surface energy. This phenomenon reduces emulsion stability and is usually fought with surfactant molecules. Another way to slow down coalescence is to use colloidal solid particles. In this case the particles spontaneously migrate to the interface to form ``Pickering'' emulsions and act as a barrier between droplets. Here we use dense, large particles (~ 500 μm) which form a monolayer at an oil/water interface that we call a granular raft. When a droplet is placed on top of such a raft, for a given set of particle properties (contact angle/size), the raft prevents coalescence indefinitely. However, in contrast to what happens when a droplet is placed on a hydrophobic surface and never wets the surface, here the droplet is strongly anchored to the raft and deforms it. We will use this specific configuration to probe the mechanical response of the granular raft: by controlling the droplet volume we can impose tensile or compressive stresses. Finally we will show that the drop, spherical at first, slowly takes a more complex shape as it's volume increases. This shape is not reversible as the drop volume is decreased. The drop can become oblate or prolate with wrinkling of the raft.

  1. Association of Vibrio parahaemolyticus thermostable direct hemolysin with lipid rafts is essential for cytotoxicity but not hemolytic activity.

    Science.gov (United States)

    Matsuda, Shigeaki; Kodama, Toshio; Okada, Natsumi; Okayama, Kanna; Honda, Takeshi; Iida, Tetsuya

    2010-02-01

    Thermostable direct hemolysin (TDH), a major virulence factor of Vibrio parahaemolyticus, induces cytotoxicity in cultured cells. However, the mechanism of TDH's cytotoxic effect including its target molecules on the plasma membrane of eukaryotic cells remains unclear. In this study, we identified the role of lipid rafts, cholesterol- and sphingolipid-enriched microdomains, in TDH cytotoxicity. Treatment of cells with methyl-beta-cyclodextrin (MbetaCD), a raft-disrupting agent, inhibited TDH cytotoxicity. TDH was associated with detergent-resistant membranes (DRMs), and MbetaCD eliminated this association. In contrast, there was no such association between a nontoxic TDH mutant and DRMs. The disruption of lipid rafts neither affected hemolysis nor inhibited Ca(2+) influx into HeLa cells induced by TDH. These findings indicate that the cytotoxicity but not the hemolytic activity of TDH is dependent on lipid rafts. The exogenous and endogenous depletion of cellular sphingomyelin also prevented TDH cytotoxicity, but a direct interaction between TDH and sphingomyelin was not detected with either a lipid overlay assay or a liposome absorption test. Treatment with sphingomyelinase (SMase) at 100 mU/ml disrupted the association of TDH with DRMs but did not affect the localization of lipid raft marker proteins (caveolin-1 and flotillin-1) with DRMs. These results suggest that sphingomyelin is important for the association of TDH with lipid rafts but is not a molecular target of TDH. We hypothesize that TDH may target a certain group of rafts that are sensitive to SMase at a certain concentration, which does not affect other types of rafts.

  2. Ceramide displaces cholesterol from lipid rafts and decreases the association of the cholesterol binding protein caveolin-1.

    Science.gov (United States)

    Yu, Cuijuan; Alterman, Michail; Dobrowsky, Rick T

    2005-08-01

    Addition of exogenous ceramide causes a significant displacement of cholesterol in lipid raft model membranes. However, whether ceramide-induced cholesterol displacement is sufficient to alter the protein composition of caveolin-enriched lipid raft membranes is unknown. Therefore, we examined whether increasing endogenous ceramide levels with bacterial sphingomyelinase (bSMase) depleted cholesterol and changed the protein composition of caveolin-enriched membranes (CEMs) isolated from immortalized Schwann cells. bSMase increased ceramide levels severalfold and decreased the cholesterol content of detergent-insoluble CEMs by 25-50% within 2 h. To examine the effect of ceramide on the protein composition of the CEMs, we performed a quantitative proteomic analysis using stable isotope labeling of cells in culture and matrix-assisted laser desorption ionization time-of-flight mass spectrometry. Although ceramide rapidly depleted lipid raft cholesterol, the levels of the cholesterol binding protein caveolin-1 (Cav-1) decreased by 25% only after 8 h. Importantly, replenishing the cells with cholesterol rapidly reversed the loss of Cav-1 from the CEMs. Ceramide-induced cholesterol depletion increased the association of 5'-nucleotidase and ATP synthase beta-subunit with the CEMs but had a minimal effect on changing the abundance of other lipid raft proteins, such as flotillin-1 and G-proteins. These results suggest that the ceramide-induced loss of cholesterol from CEMs may contribute to altering the lipid raft proteome.

  3. A comparative study on the raft chemical properties of various alginate antacid raft-forming products.

    Science.gov (United States)

    Dettmar, Peter W; Gil-Gonzalez, Diana; Fisher, Jeanine; Flint, Lucy; Rainforth, Daniel; Moreno-Herrera, Antonio; Potts, Mark

    2017-09-13

    Research to measure the chemical characterization of alginate rafts for good raft performance and ascertain how formulation can affect chemical parameters. A selection of alginate formulations was investigated all claiming to be proficient raft formers with significance between products established and ranked. Procedures were selected which demonstrated the chemical characterization allowing rafts to effectively impede the reflux into the esophagus or in severe cases to be refluxed preferentially into the esophagus and exert a demulcent effect, with focus of current research on methods which complement previous studies centered on physical properties. The alginate content was analyzed by a newly developed HPLC method. Methods were used to determine the neutralization profile and the acid neutralization within the raft determined along with how raft structure affects neutralization. Alginate content of Gaviscon Double Action (GDA) within the raft was significantly superior (p Alginate formulations require three chemical reactions to take place simultaneously: transformation to alginic acid, sodium carbonate reacting to form carbon dioxide, calcium releasing free calcium ions to bind with alginic acid providing strength to raft formation. GDA was significantly superior (p <.0001) to all other comparators.

  4. Accumulation of raft lipids in T-cell plasma membrane domains engaged in TCR signalling

    DEFF Research Database (Denmark)

    Zech, Tobias; Ejsing, Christer S.; Gaus, Katharina;

    2009-01-01

    domains were also enriched in plasmenyl phosphatidylethanolamine and phosphatidylserine. Modulating the T-cell lipidome with polyunsaturated fatty acids impaired the plasma membrane condensation at TCR signalling foci and resulted in a perturbed molecular lipid composition. These results correlate...... and saturated phosphatidylcholine species as compared with control plasma membrane fragments. This provides, for the first time, direct evidence that TCR activation domains comprise a distinct molecular lipid composition reminiscent of liquid-ordered raft phases in model membranes. Interestingly, TCR activation...

  5. Solid-state ¹³C NMR reveals annealing of raft-like membranes containing cholesterol by the intrinsically disordered protein α-Synuclein.

    Science.gov (United States)

    Leftin, Avigdor; Job, Constantin; Beyer, Klaus; Brown, Michael F

    2013-08-23

    Misfolding and aggregation of the intrinsically disordered protein α-Synuclein (αS) in Lewy body plaques are characteristic markers of late-stage Parkinson's disease. It is well established that membrane binding is initiated at the N-terminus of the protein and affects biasing of conformational ensembles of αS. However, little is understood about the effect of αS on the membrane lipid bilayer. One hypothesis is that intrinsically disordered αS alters the structural properties of the membrane, thereby stabilizing the bilayer against fusion. Here, we used two-dimensional (13)C separated local-field NMR to study interaction of the wild-type α-Synuclein (wt-αS) or its N-terminal (1-25) amino acid sequence (N-αS) with a cholesterol-enriched ternary membrane system. This lipid bilayer mimics cellular raft-like domains in the brain that are proposed to be involved in neuronal membrane fusion. The two-dimensional dipolar-recoupling pulse sequence DROSS (dipolar recoupling on-axis with scaling and shape preservation) was implemented to measure isotropic (13)C chemical shifts and (13)C-(1)H residual dipolar couplings under magic-angle spinning. Site-specific changes in NMR chemical shifts and segmental order parameters indicate that both wt-αS and N-αS bind to the membrane interface and change lipid packing within raft-like membranes. Mean-torque modeling of (13)C-(1)H NMR order parameters shows that αS induces a remarkable thinning of the bilayer (≈6Å), accompanied by an increase in phospholipid cross-sectional area (≈10Å(2)). This perturbation is characterized as membrane annealing and entails structural remodeling of the raft-like liquid-ordered phase. We propose this process is implicated in regulation of synaptic membrane fusion that may be altered by aggregation of αS in Parkinson's disease. Copyright © 2013 Elsevier Ltd. All rights reserved.

  6. Spatial and temporal control of signaling through lipid rafts.

    Science.gov (United States)

    Golub, Tamara; Wacha, Stefan; Caroni, Pico

    2004-10-01

    Sphingolipid- and cholesterol-dependent microdomains (rafts) order proteins at biological membranes and have been implicated in most signaling processes at the cell surface, but the principles and mechanisms through which lipid rafts influence signaling are not well understood. Recent studies have revealed how lipid rafts are rapidly redistributed and assembled locally in response to extracellular signals, and how components of raft-based signaling domains undergo rapid and regulated rearrangements influencing signal quality, duration, and strength. These findings highlight the exquisitely dynamic properties of signaling domains based on lipid rafts, and suggest that processes of raft trafficking and assembly take central roles in mediating spatial and temporal control of signaling.

  7. Distribution of C16:0, C18:0, C24:1, and C24:0 sulfatides in central nervous system lipid rafts by quantitative ultra-high-pressure liquid chromatography tandem mass spectrometry.

    Science.gov (United States)

    Moyano, Ana Lis; Li, Guannan; Lopez-Rosas, Aurora; Månsson, Jan-Eric; van Breemen, Richard B; Givogri, Maria Irene

    2014-12-15

    Sulfated galactosylceramides (sulfatides) are glycosphingolipids associated with cholesterol- and sphingolipid-enriched membrane microdomains (lipid rafts) and are highly expressed in brain tissue. Although it is known that sulfatide species show heterogeneity in their fatty acid acyl group composition throughout brain development, their lipid raft distribution and biological relevance is poorly understood. We validated a fast and sensitive ultra-high-pressure liquid chromatography tandem mass spectrometry (UHPLC-MS/MS) method to measure developmentally regulated sulfatide species (C16:0, C18:0, C24:1, and C24:0) in central nervous system (CNS) lipid rafts isolated without using detergent. Our UHPLC-MS/MS assay showed good accuracy and precision with a linear range of 5 to 1,000 nM for C18:0 and C24:1 sulfatides and 10 to 1,000 nM for C16:0 and C24:0 sulfatides. We applied this quantitative analysis to detergent-free lipid rafts isolated from wild-type mice and arylsulfatase A-deficient (ASA knockout) mice that accumulate sulfatides. All four sulfatide species were more abundant in raft membranes than in non-raft membranes, with a significant increase in lipid rafts isolated from ASA knockout mice. This is the first description of an analytical method to study these sulfatide species in raft and non-raft membranes and has the potential to be applied to preparations from other tissues.

  8. 风沙土不同粒径微团聚体对氨氮的富集特征%Enrichment Characteristic of Ammonia-Nitrogen on Different Grain Sizes Micro-Aggregate of Sandy Soil

    Institute of Scientific and Technical Information of China (English)

    王而力; 王嗣淇; 王雅迪

    2013-01-01

    Splash erosion and soil and water loss was liable to occur in sandy soil. Enrichment characteristic of ammonia-nitrogen on different grain sizes micro-aggregate of sandy soil was investigated by batch experiments of equilibrium adsorption in order to estimate the loss flux of its adsorption state. Results indicated that the enrichment effect on ammonia-nitrogen was attributed greatly to micro-aggregate of sandy soil. Firstly, humus content of fine grain size aggregate was higher than that of coarse grain size aggregate. Secondly, organic matter of fine grain size aggregate was enriched by clay mineral, which was combined with dissoluble organic matter. The content of stably combined humus in clay or silt was higher relatively, and there was a micro-hole filling function in ammonium-nitrogen sorption on complex. Stably combined humus is an important adhesive material in the formation of organo-mineral complex. Micro-hole filling mechanism was the cause of enrichment of ammonia-nitrogen on different grain sizes micro-aggregate. Furthermore, there was a highly obvious positive correlation between enrichment ratio and total humus content(R2=0.909), and so was it with stably combined humus content (R2=0.902). Consequently, mass percentages of adsorption state ammonia-nitrogen carried by clay and silt from West Liao River sandy soil under rainfall condition were estimated in accordance with 3 641.49 mg'kg-1 and 2 617.52 mg'kg-1 respectively, and enrichment ratios of clay and silt were estimated in accordance with 1.65 and 1.18 respectively.%风沙土是易发生溅蚀和水土流失严重的土类,为估算风沙土吸附态氨氮流失量,采用平衡吸附法研究了风沙土不同粒径微团聚体对氨氮的富集特征.结果表明,风沙土中微团聚体对氨氮具有富集作用.其原因有二:细粒级微团聚体中腐殖质含量高于粗粒级;细粒级微团聚体中有机质是通过可溶有机质与黏土矿物相互结合形成复合体而富集.

  9. Stable, inflatable life raft for high seas rescue operations

    Science.gov (United States)

    Barnett, J. H., Jr.; Harrison, F.; Marak, R.; Radnofsky, M. I.

    1971-01-01

    Raft is easily deployed and highly maneuverable in water. It has false bottom of water ballast containers attached to underside, making it exceptionally stable platform from which swimmers can operate. Raft is attachable to external moorings.

  10. Candida albicans Targets a Lipid Raft/Dectin-1 Platform to Enter Human Monocytes and Induce Antigen Specific T Cell Responses.

    Science.gov (United States)

    de Turris, Valeria; Teloni, Raffaela; Chiani, Paola; Bromuro, Carla; Mariotti, Sabrina; Pardini, Manuela; Nisini, Roberto; Torosantucci, Antonella; Gagliardi, Maria Cristina

    2015-01-01

    Several pathogens have been described to enter host cells via cholesterol-enriched membrane lipid raft microdomains. We found that disruption of lipid rafts by the cholesterol-extracting agent methyl-β-cyclodextrin or by the cholesterol-binding antifungal drug Amphotericin B strongly impairs the uptake of the fungal pathogen Candida albicans by human monocytes, suggesting a role of raft microdomains in the phagocytosis of the fungus. Time lapse confocal imaging indicated that Dectin-1, the C-type lectin receptor that recognizes Candida albicans cell wall-associated β-glucan, is recruited to lipid rafts upon Candida albicans uptake by monocytes, supporting the notion that lipid rafts act as an entry platform. Interestingly disruption of lipid raft integrity and interference with fungus uptake do not alter cytokine production by monocytes in response to Candida albicans but drastically dampen fungus specific T cell response. In conclusion, these data suggest that monocyte lipid rafts play a crucial role in the innate and adaptive immune responses to Candida albicans in humans and highlight a new and unexpected immunomodulatory function of the antifungal drug Amphotericin B.

  11. Candida albicans Targets a Lipid Raft/Dectin-1 Platform to Enter Human Monocytes and Induce Antigen Specific T Cell Responses.

    Directory of Open Access Journals (Sweden)

    Valeria de Turris

    Full Text Available Several pathogens have been described to enter host cells via cholesterol-enriched membrane lipid raft microdomains. We found that disruption of lipid rafts by the cholesterol-extracting agent methyl-β-cyclodextrin or by the cholesterol-binding antifungal drug Amphotericin B strongly impairs the uptake of the fungal pathogen Candida albicans by human monocytes, suggesting a role of raft microdomains in the phagocytosis of the fungus. Time lapse confocal imaging indicated that Dectin-1, the C-type lectin receptor that recognizes Candida albicans cell wall-associated β-glucan, is recruited to lipid rafts upon Candida albicans uptake by monocytes, supporting the notion that lipid rafts act as an entry platform. Interestingly disruption of lipid raft integrity and interference with fungus uptake do not alter cytokine production by monocytes in response to Candida albicans but drastically dampen fungus specific T cell response. In conclusion, these data suggest that monocyte lipid rafts play a crucial role in the innate and adaptive immune responses to Candida albicans in humans and highlight a new and unexpected immunomodulatory function of the antifungal drug Amphotericin B.

  12. Constitutive and functional association of the platelet collagen receptor glycoprotein VI-Fc receptor gamma-chain complex with membrane rafts.

    Science.gov (United States)

    Ezumi, Yasuharu; Kodama, Kumi; Uchiyama, Takashi; Takayama, Hiroshi

    2002-05-01

    The platelet collagen receptor glycoprotein (GP) VI-Fc receptor gamma-chain (FcRgamma) complex transduces signals in an immunoreceptorlike manner. We examined a role for the Triton X-100-insoluble membrane rafts in GPVI-FcRgamma complex signaling. Methyl-beta-cyclodextrin (MbetaCD)-induced disruption of the membrane rafts inhibited not only platelet aggregation and secretion but also tyrosine phosphorylation of signaling molecules on stimulation through the GPVI-FcRgamma complex. The GPVI-FcRgamma complex was constitutively associated with membrane rafts wherein the Src family kinases and LAT were also present. Their association was not affected by the complex engagement but was highly sensitive to MbetaCD treatment. Thus, we provide the first evidence that the GPVI-FcRgamma complex is constitutively and functionally associated with membrane rafts.

  13. The Settlement Behavior of Piled Raft Interaction in Undrained Soil

    DEFF Research Database (Denmark)

    Ghalesari, Abbasali Taghavi; Barari, Amin; Amini, Pedram Fardad

    2013-01-01

    Offshore piled raft foundations are one of the most commonly used foundations in offshore structures. When a raft foundation alone does not satisfy the design requirements, the addition of piles may improve both the ultimate load capacity and the settlement performance of the raft. In this paper,...

  14. Assessing the nature of lipid raft membranes.

    Directory of Open Access Journals (Sweden)

    Perttu S Niemelä

    2007-02-01

    Full Text Available The paradigm of biological membranes has recently gone through a major update. Instead of being fluid and homogeneous, recent studies suggest that membranes are characterized by transient domains with varying fluidity. In particular, a number of experimental studies have revealed the existence of highly ordered lateral domains rich in sphingomyelin and cholesterol (CHOL. These domains, called functional lipid rafts, have been suggested to take part in a variety of dynamic cellular processes such as membrane trafficking, signal transduction, and regulation of the activity of membrane proteins. However, despite the proposed importance of these domains, their properties, and even the precise nature of the lipid phases, have remained open issues mainly because the associated short time and length scales have posed a major challenge to experiments. In this work, we employ extensive atom-scale simulations to elucidate the properties of ternary raft mixtures with CHOL, palmitoylsphingomyelin (PSM, and palmitoyloleoylphosphatidylcholine. We simulate two bilayers of 1,024 lipids for 100 ns in the liquid-ordered phase and one system of the same size in the liquid-disordered phase. The studies provide evidence that the presence of PSM and CHOL in raft-like membranes leads to strongly packed and rigid bilayers. We also find that the simulated raft bilayers are characterized by nanoscale lateral heterogeneity, though the slow lateral diffusion renders the interpretation of the observed lateral heterogeneity more difficult. The findings reveal aspects of the role of favored (specific lipid-lipid interactions within rafts and clarify the prominent role of CHOL in altering the properties of the membrane locally in its neighborhood. Also, we show that the presence of PSM and CHOL in rafts leads to intriguing lateral pressure profiles that are distinctly different from corresponding profiles in nonraft-like membranes. The results propose that the functioning of

  15. Compartmentalisation of cAMP-dependent signalling in blood platelets: The role of lipid rafts and actin polymerisation.

    Science.gov (United States)

    Raslan, Zaher; Naseem, Khalid M

    2015-01-01

    Prostacyclin (PGI2) inhibits blood platelets through the activation of membrane adenylyl cyclases (ACs) and cyclic adenosine 3',5'-monophosphate (cAMP)-mediated signalling. However, the molecular mechanism controlling cAMP signalling in blood platelet remains unclear, and in particular how individual isoforms of AC and protein kinase A (PKA) are coordinated to target distinct substrates in order to modulate platelet activation. In this study, we demonstrate that lipid rafts and the actin cytoskeleton may play a key role in regulating platelet responses to cAMP downstream of PGI2. Disruption of lipid rafts with methyl-beta-cyclodextrin (MβCD) increased platelet sensitivity to PGI2 and forskolin, a direct AC cyclase activator, resulting in greater inhibition of collagen-stimulated platelet aggregation. In contrast, platelet inhibition by the direct activator of PKA, 8-CPT-6-Phe-cAMP was unaffected by MβCD treatment. Consistent with the functional data, lipid raft disruption increased PGI2-stimulated cAMP formation and proximal PKA-mediated signalling events. Platelet inhibition, cAMP formation and phosphorylation of PKA substrates in response to PGI2 were also increased in the presence of cytochalasin D, indicating a role for actin cytoskeleton in signalling in response to PGI2. A potential role for lipid rafts in cAMP signalling is strengthened by our finding that a pool of ACV/VI and PKA was partitioned into lipid rafts. Our data demonstrate partial compartmentalisation of cAMP signalling machinery in platelets, where lipid rafts and the actin cytoskeleton regulate the inhibitory effects induced by PGI2. The increased platelet sensitivity to cAMP-elevating agents signalling upon raft and cytoskeleton disruption suggests that these compartments act to restrain basal cAMP signalling.

  16. Lipid rafts, KCa/ClCa/Ca2+ channel complexes and EGFR signaling: Novel targets to reduce tumor development by lipids?

    Science.gov (United States)

    Guéguinou, Maxime; Gambade, Audrey; Félix, Romain; Chantôme, Aurélie; Fourbon, Yann; Bougnoux, Philippe; Weber, Günther; Potier-Cartereau, Marie; Vandier, Christophe

    2015-10-01

    Membrane lipid rafts are distinct plasma membrane nanodomains that are enriched with cholesterol, sphingolipids and gangliosides, with occasional presence of saturated fatty acids and phospholipids containing saturated acyl chains. It is well known that they organize receptors (such as Epithelial Growth Factor Receptor), ion channels and their downstream acting molecules to regulate intracellular signaling pathways. Among them are Ca2+ signaling pathways, which are modified in tumor cells and inhibited upon membrane raft disruption. In addition to protein components, lipids from rafts also contribute to the organization and function of Ca2+ signaling microdomains. This article aims to focus on the lipid raft KCa/ClCa/Ca2+ channel complexes that regulate Ca2+ and EGFR signaling in cancer cells, and discusses the potential modification of these complexes by lipids as a novel therapeutic approach in tumor development. This article is part of a Special Issue entitled: Membrane channels and transporters in cancers.

  17. Aβ promotes VDAC1 channel dephosphorylation in neuronal lipid rafts. Relevance to the mechanisms of neurotoxicity in Alzheimer's disease.

    Science.gov (United States)

    Fernandez-Echevarria, C; Díaz, M; Ferrer, I; Canerina-Amaro, A; Marin, R

    2014-10-10

    Voltage-dependent anion channel (VDAC) is a mitochondrial protein abundantly found in neuronal lipid rafts. In these membrane domains, VDAC is associated with a complex of signaling proteins that trigger neuroprotective responses. Loss of lipid raft integrity may result in disruption of multicomplex association and alteration of signaling responses that may ultimately promote VDAC activation. Some data have demonstrated that VDAC at the neuronal membrane may be involved in the mechanisms of amyloid beta (Aβ)-induced neurotoxicity, through yet unknown mechanisms. Aβ is generated from amyloid precursor protein (APP), and is released to the extracellular space where it may undergo self-aggregation. Aβ aggregate deposition in the form of senile plaques may lead to Alzheimer's disease (AD) neuropathology, although other pathological hallmarks (such as hyper-phosphorylated Tau deposition) also participate in this neurodegenerative process. The present study demonstrates that VDAC1 associates with APP and Aβ in lipid rafts of neurons. Interaction of VDAC1 with APP was observed in lipid rafts from the frontal and entorhinal cortex of human brains affected by AD at early stages (I-IV/0-B of Braak and Braak). Furthermore, Aβ exposure enhanced the dephosphorylation of VDAC1 that correlated with cell death. Both effects were reverted in the presence of tyrosine phosphatase inhibitors. VDAC1 dephosphorylation was corroborated in lipid rafts of AD brains. These results demonstrate that Aβ is involved in alterations of the phosphorylation state of VDAC in neuronal lipid rafts. Modulation of this channel may contribute to the development and progression of AD pathology.

  18. Preparation of transition metal nanoparticles and surfaces modified with (co)polymers synthesized by RAFT

    Science.gov (United States)

    McCormick, III, Charles L.; Lowe, Andrew B.; Sumerlin, Brent S.

    2011-12-27

    A new, facile, general one-phase method of generating thiol-functionalized transition metal nanoparticles and surfaces modified by (co)polymers synthesized by the RAFT method is described. The method includes the steps of forming a (co)polymer in aqueous solution using the RAFT methodology, forming a colloidal transition metal precursor solution from an appropriate transition metal; adding the metal precursor solution or surface to the (co)polymer solution, adding a reducing agent into the solution to reduce the metal colloid in situ to produce the stabilized nanoparticles or surface, and isolating the stabilized nanoparticles or surface in a manner such that aggregation is minimized. The functionalized surfaces generated using these methods can further undergo planar surface modifications, such as functionalization with a variety of different chemical groups, expanding their utility and application.

  19. The Inveterate Tinkerer: 6. Bubble Raft

    Indian Academy of Sciences (India)

    Bigyansu Behera; Chirag Kalelkar

    2017-08-01

    In this series of articles, the authors discuss various phenomena in fluid dhynamics, which may be investigated via tabletop experiments using low-cost or home-made instruments. The sixth article in this series explores crystalline defects and motion of dislocations using bubble rafts.

  20. The Continuing Mystery of Lipid Rafts.

    Science.gov (United States)

    Levental, Ilya; Veatch, Sarah L

    2016-12-04

    Since its initial formalization nearly 20 years ago, the concept of lipid rafts has generated a tremendous amount of attention and interest and nearly as much controversy. The controversy is perhaps surprising because the notion itself is intuitive: compartmentalization in time and space is a ubiquitous theme at all scales of biology, and therefore, the partitioning of cellular membranes into lateral subdivision should be expected. Nevertheless, the physicochemical principles responsible for compartmentalization and the molecular mechanisms by which they are functionalized remain nearly as mysterious today as they were two decades ago. Herein, we review recent literature on this topic with a specific focus on the major open questions in the field including: (1) what are the best tools to assay raft behavior in living membranes? (2) what is the function of the complex lipidome of mammalian cells with respect to membrane organization? (3) what are the mechanisms that drive raft formation and determine their properties? (4) how can rafts be modulated? (5) how is membrane compartmentalization integrated into cellular signaling? Despite decades of intensive research, this compelling field remains full of fundamental questions.

  1. Thermodynamic driving force for rafting in superalloys

    CSIR Research Space (South Africa)

    Nabarro, FRN

    1996-08-01

    Full Text Available Eshelby’s energy-momentum tensor is used to provide an analytical expression for the driving force for rafting in the elastic regime in a super alloy with a high volume fraction of gamma'. The structure is modeled as a simple cubic array of gamma...

  2. Involvement of lipid rafts in adhesion-induced activation of Met and EGFR

    Directory of Open Access Journals (Sweden)

    Lu Ying-Che

    2011-10-01

    Full Text Available Abstract Background Cell adhesion has been shown to induce activation of certain growth factor receptors in a ligand-independent manner. However, the mechanism for such activation remains obscure. Methods Human epidermal carcinoma A431 cells were used as a model to examine the mechanism for adhesion-induced activation of hepatocyte growth factor receptor Met and epidermal growth factor receptor (EGFR. The cells were suspended and replated on culture dishes under various conditions. The phosphorylation of Met at Y1234/1235 and EGFR at Y1173 were used as indicators for their activation. The distribution of the receptors and lipid rafts on the plasma membrane were visualized by confocal fluorescent microscopy and total internal reflection microscopy. Results We demonstrate that Met and EGFR are constitutively activated in A431 cells, which confers proliferative and invasive potentials to the cells. The ligand-independent activation of Met and EGFR in A431 cells relies on cell adhesion to a substratum, but is independent of cell spreading, extracellular matrix proteins, and substratum stiffness. This adhesion-induced activation of Met and EGFR cannot be attributed to Src activation, production of reactive oxygen species, and the integrity of the cytoskeleton. In addition, we demonstrate that Met and EGFR are independently activated upon cell adhesion. However, partial depletion of Met and EGFR prevents their activation upon cell adhesion, suggesting that overexpression of the receptors is a prerequisite for their self-activation upon cell adhesion. Although Met and EGFR are largely distributed in 0.04% Triton-insoluble fractions (i.e. raft fraction, their activated forms are detected mainly in 0.04% Triton-soluble fractions (i.e. non-raft fraction. Upon cell adhesion, lipid rafts are accumulated at the cell surface close to the cell-substratum interface, while Met and EGFR are mostly excluded from the membrane enriched by lipid rafts. Conclusions

  3. Using NK Cell Lipid Raft Fractionation to Understand the Role of Lipid Rafts in NK Cell Receptor Signaling.

    Science.gov (United States)

    Serrano-Pertierra, Esther; López-Larrea, Carlos

    2016-01-01

    Lipid rafts were first defined as detergent-resistant membranes (DRMs) due to their relative insolubility in non-ionic detergents. Although they should not be confused with lipid rafts, DRMs are a valuable starting point for the study of these membrane domains and the interactions of proteins with rafts.Here we describe the isolation of DRMs by ultracentrifugation on a sucrose gradient, a method we have used to study the role of lipid rafts in NKG2D-mediated signaling. We also describe raft fractionation of NK cells involving the selective solubility of β-octylglucoside (β-OG). OG is a non-ionic detergent that efficiently dissolves DRMs but does not disrupt protein associations with the cytoskeleton. Using these two techniques may yield useful information about the proteins involved in receptor recruitment into lipid rafts and the interactions of the actin cytoskeleton with lipid rafts.

  4. Localization of phosphatidylinositol 4,5-bisphosphate to lipid rafts and uroids in the human protozoan parasite Entamoeba histolytica.

    Science.gov (United States)

    Koushik, Amrita B; Powell, Rhonda R; Temesvari, Lesly A

    2013-06-01

    Entamoeba histolytica is an intestinal protozoan parasite and is the causative agent of amoebiasis. During invasive infection, highly motile amoebae destroy the colonic epithelium, enter the blood circulation, and disseminate to other organs such as liver, causing liver abscess. Motility is a key factor in E. histolytica pathogenesis, and this process relies on a dynamic actomyosin cytoskeleton. In other systems, phosphatidylinositol 4,5-bisphosphate [PI(4,5)P2] is known to regulate a wide variety of cellular functions, including signal transduction, actin remodeling, and cell motility. Little is known about the role of PI(4,5)P2 in E. histolytica pathogenicity. In this study, we demonstrate that PI(4,5)P2 is localized to cholesterol-rich microdomains, lipid rafts, and the actin-rich fractions of the E. histolytica membrane. Microscopy revealed that the trailing edge of polarized trophozoites, uroids, are highly enriched in lipid rafts and their constituent lipid, PI(4,5)P2. Polarization and enrichment of uroids and rafts with PI(4,5)P2 were enhanced upon treatment of E. histolytica cells with cholesterol. Exposure to cholesterol also increased intracellular calcium, which is a downstream effector of PI(4,5)P2, with a concomitant increase in motility. Together, our data suggest that in E. histolytica, PI(4,5)P2 may signal from lipid rafts and cholesterol may play a role in triggering PI(4,5)P2-mediated signaling to enhance the motility of this pathogen.

  5. Prion protein accumulation in lipid rafts of mouse aging brain.

    Directory of Open Access Journals (Sweden)

    Federica Agostini

    Full Text Available The cellular form of the prion protein (PrP(C is a normal constituent of neuronal cell membranes. The protein misfolding causes rare neurodegenerative disorders known as transmissible spongiform encephalopathies or prion diseases. These maladies can be sporadic, genetic or infectious. Sporadic prion diseases are the most common form mainly affecting aging people. In this work, we investigate the biochemical environment in which sporadic prion diseases may develop, focusing our attention on the cell membrane of neurons in the aging brain. It is well established that with aging the ratio between the most abundant lipid components of rafts undergoes a major change: while cholesterol decreases, sphingomyelin content rises. Our results indicate that the aging process modifies the compartmentalization of PrP(C. In old mice, this change favors PrP(C accumulation in detergent-resistant membranes, particularly in hippocampi. To confirm the relationship between lipid content changes and PrP(C translocation into detergent-resistant membranes (DRMs, we looked at PrP(C compartmentalization in hippocampi from acid sphingomyelinase (ASM knockout (KO mice and synaptosomes enriched in sphingomyelin. In the presence of high sphingomyelin content, we observed a significant increase of PrP(C in DRMS. This process is not due to higher levels of total protein and it could, in turn, favor the onset of sporadic prion diseases during aging as it increases the PrP intermolecular contacts into lipid rafts. We observed that lowering sphingomyelin in scrapie-infected cells by using fumonisin B1 led to a 50% decrease in protease-resistant PrP formation. This may suggest an involvement of PrP lipid environment in prion formation and consequently it may play a role in the onset or development of sporadic forms of prion diseases.

  6. Tailor-made polyfluoroacrylate and its block copolymer by RAFT polymerization in miniemulsion; improved hydrophobicity in the core-shell block copolymer.

    Science.gov (United States)

    Chakrabarty, Arindam; Singha, Nikhil K

    2013-10-15

    Controlled/living radical polymerization (CRP) of a fluoroacrylate was successfully carried out in miniemulsion by Reversible Addition Fragmentation chain Transfer (RAFT) process. In this case, 2,2,3,3,4,4,4-heptafluorobutyl acrylate (HFBA) was polymerized using 2-cyanopropyl dodecyl trithiocarbonate (CPDTC) as RAFT agent, Triton X-405 and sodium dodecyl sulfonate (SDS) as surfactant, and potassium persulphate (KPS) or 2,2'-azobis isobutyronitrile (AIBN) as initiator. Being compatible with hydrophobic fluoroacrylate, this RAFT agent offered very high conversion and good control over the molecular weight of the polymer. The miniemulsion was stable without any costabilizer. The long chain dodecyl group (-C12H25) (Z-group in the RAFT agent) had beneficial effect in stabilizing the miniemulsion. When 2-cyano 2-propyl benzodithioate (CPBD) (Z=-C6H5) was used as RAFT agent, the conversion was less and particle size distribution was very broad. Block copolymerization with butyl acrylate (BA) using PHFBA as macro-RAFT agent showed core-shell morphology with the aggregation of PHFBA segment in the shell. GPC as well as DSC analysis confirmed the formation of block copolymer. The core-shell morphology was confirmed by TEM analysis. The block copolymers (PHFBA-b-PBA) showed significantly higher water contact angle (WCA) showing much better hydrophobicity compared to PHFBA alone.

  7. Shear Bond Strength of a Self-adhering Flowable Composite and a Flowable Base Composite to Mineral Trioxide Aggregate, Calcium-enriched Mixture Cement, and Biodentine.

    Science.gov (United States)

    Altunsoy, Mustafa; Tanrıver, Mehmet; Ok, Evren; Kucukyilmaz, Ebru

    2015-10-01

    The purpose of this study was to investigate the shear bond strength (SBS) of a self-adhering flowable composite (Vertise Flow; Kerr, Orange, CA) and a flowable composite (X-tra base; Voco GmbH, Cuxhaven, Germany) to mineral trioxide aggregate (MTA), Biodentine (Septodent, Saint-Maur-des-Fosses Cedex, France), and calcium-enriched mixture (CEM; Yektazist Dandan, Tehran, Iran). Sixty cylindric acrylic blocks with a hole (3 mm in diameter and 1.5 mm in height) were prepared. The acrylic blocks were filled with MTA, Biodentine, and CEM (n = 20) and accordingly allocated into 3 groups. The specimens were stored for 72 hours at 37°C and 100% humidity. Then, each group was divided into 2 subgroups according to the composite resin type used (n = 10). Vertise Flow and X-tra base were applied over MTA, Biodentine, and CEM and then polymerized. SBS was tested in a universal testing machine with a crosshead speed of 1 mm/min. Data were analyzed using 2-way analysis of variance and the Tukey test. The Vertise Flow-CEM and X-tra base-MTA groups showed significantly higher SBS values than the group made of Vertise flow-Biodentine (P  .05). MTA and CEM exhibited higher SBS than Biodentine; therefore, they could be preferred under flowable composites. Copyright © 2015 American Association of Endodontists. Published by Elsevier Inc. All rights reserved.

  8. The Structure of Cholesterol in Lipid Rafts

    CERN Document Server

    Toppozini, Laura; Armstrong, Clare L; Yamani, Zahra; Kucerka, Norbert; Schmid, Friederike; Rheinstaedter, Maikel C

    2014-01-01

    Rafts, or functional domains, are transient nano- or mesoscopic structures in the plasma membrane and are thought to be essential for many cellular processes such as signal transduction, adhesion, trafficking and lipid/protein sorting. Observations of these membrane heterogeneities have proven challenging, as they are thought to be both small and short-lived. With a combination of coarse-grained molecular dynamics simulations and neutron diffraction using deuterium labeled cholesterol molecules we observe raft-like structures and determine the ordering of the cholesterol molecules in binary cholesterol-containing lipid membranes. From coarse-grained computer simulations, heterogenous membranes structures were observed and characterized as small, ordered domains. Neutron diffraction was used to study the lateral structure of the cholesterol molecules. We find pairs of strongly bound cholesterol molecules in the liquid-disordered phase, in accordance with the umbrella model. Bragg peaks corresponding to orderin...

  9. Lipid Rafts in Mast Cell Biology

    Directory of Open Access Journals (Sweden)

    Adriana Maria Mariano Silveira e Souza

    2011-01-01

    Full Text Available Mast cells have long been recognized to have a direct and critical role in allergic and inflammatory reactions. In allergic diseases, these cells exert both local and systemic responses, including allergic rhinitis and anaphylaxis. Mast cell mediators are also related to many chronic inflammatory conditions. Besides the roles in pathological conditions, the biological functions of mast cells include roles in innate immunity, involvement in host defense mechanisms against parasites, immunomodulation of the immune system, tissue repair, and angiogenesis. Despite their growing significance in physiological and pathological conditions, much still remains to be learned about mast cell biology. This paper presents evidence that lipid rafts or raft components modulate many of the biological processes in mast cells, such as degranulation and endocytosis, play a role in mast cell development and recruitment, and contribute to the overall preservation of mast cell structure and organization.

  10. Lipid Rafts Identified on Synaptic Vesicles from Rat Brain

    Institute of Scientific and Technical Information of China (English)

    HE Li; L(U) Jihua; ZHOU Qinghua; SUI Senfang

    2006-01-01

    For a long time, lipid rafts have been thought to participate in regulating neurotransmitter release. However,the existence of lipid rafts on synaptic vesicles (SVs) and the mechanism by which exocytosis-relative proteins distribute on this structure have not been fully investigated. There is also much controversial data concerning rafts on SVs and synaptic vesicle proteins which makes the results difficult to interpret. This study systematically analyzed the existence and properties of lipid rafts on purified SVs by sucrose density gradient centrifugation, cholesterol depletion, and temperature variation. The data reveals that typical lipid rafts on SVs are both cholesterol dependent and temperature sensitive. Previous confusing results may have been caused by improper treatment or side effects of particular reagent. We also screened the lateral distribution of major exocytosis-related SV proteins and found that only the synaptobrevin (syb) and synaptotagmin (syt) produce detectable association with lipid rafts in 1% Triton X-100.

  11. Collapse dynamics of bubble raft under compression

    Science.gov (United States)

    Kuo, Chin-Chang; Kachan, Devin; Levine, Alexander; Dennin, Michael; Department of Physics; Astronomy, University of California, Irvine Collaboration; Department of Physics; Astronomy, University of California, Los Angeles Collaboration

    2015-03-01

    We report on the collapse of bubble rafts under compression in a closed rectangular geometry. A bubble raft is a single layer of bubbles at the air-water interface. A collapse event occurs when bubbles submerge beneath the neighboring bubbles under applied compression causing the structure of the bubble raft to go from single-layer to multi-layer. We studied the collapse dynamics as a function of compression velocity. At higher compression velocity we observe a more uniform distribution of collapse events, whereas at lower compression velocities, the collapse events accumulate at the system boundaries. We will present results that compare the distribution of collapse probability in the experiments to simulations based on a one-dimensional Ising model with elastic coupling between spin elements. Both the experimental system and simulations are excellent models for collapse in a number of complex systems. By comparing the two systems, we can tune the simulation to better understand the role of the Ising and elastic couplings in determining the collapse dynamics. We acknowledge DMR-1309402.

  12. Planning and execution of Raft River stimulation treatments

    Energy Technology Data Exchange (ETDEWEB)

    Verity, R.V.; Crichlow, H.B. (ed.)

    1980-02-07

    The following topics are discussed for two Raft River Valley wells: well characteristics and treatment objectives, treatment selection and design, treatment history, mechanical arrangements and job costs. (MHR)

  13. Therapeutic MSC exosomes are derived from lipid raft microdomains in the plasma membrane

    Directory of Open Access Journals (Sweden)

    Soon Sim Tan

    2013-12-01

    Full Text Available Background: Mesenchymal stem cell (MSC was previously shown to secrete lipid vesicles that when purified by high performance liquid chromatography as a population of homogenously sized particles with a hydrodynamic radius of 55–65 nm reduce infarct size in a mouse model of myocardial ischemia/reperfusion injury. As these vesicles exhibit many biophysical and biochemical properties of exosomes, they were identified as exosomes. Here we investigated if these lipid vesicles were indeed exosomes that have an endosomal biogenesis. Method: In most cells, endocytosis is thought to occur at specialized microdomains known as lipid rafts. To demonstrate an endosomal origin for MSC exosomes, MSCs were pulsed with ligands e.g. transferrin (Tfs and Cholera Toxin B (CTB that bind receptors in lipid rafts. The endocytosed ligands were then chased to determine if they were incorporated into the exosomes. Results: A fraction of exogenous Tfs was found to recycle into MSC exosomes. When MSCs were pulsed with labelled Tfs in the presence of chlorpromazine, an inhibitor of clathrin-mediated endocytosis, Tf incorporation in CD81-immunoprecipitate was reduced during the chase. CTB which binds GM1 gangliosides that are enriched in lipid rafts extracted exosome-associated proteins, CD81, CD9, Alix and Tsg101 from MSC-conditioned medium. Exogenous CTBs were pulse-chased into secreted vesicles. Extraction of Tf- or CTB-binding vesicles in an exosome preparation mutually depleted each other. Inhibition of sphingomyelinases reduced CTB-binding vesicles. Conclusion: Together, our data demonstrated that MSC exosomes are derived from endocytosed lipid rafts and that their protein cargo includes exosome-associated proteins CD81, CD9, Alix and Tsg101.

  14. Targeting of pseudorabies virus structural proteins to axons requires association of the viral Us9 protein with lipid rafts.

    Directory of Open Access Journals (Sweden)

    Mathew G Lyman

    2008-05-01

    Full Text Available The pseudorabies virus (PRV Us9 protein plays a central role in targeting viral capsids and glycoproteins to axons of dissociated sympathetic neurons. As a result, Us9 null mutants are defective in anterograde transmission of infection in vivo. However, it is unclear how Us9 promotes axonal sorting of so many viral proteins. It is known that the glycoproteins gB, gC, gD and gE are associated with lipid raft microdomains on the surface of infected swine kidney cells and monocytes, and are directed into the axon in a Us9-dependent manner. In this report, we determined that Us9 is associated with lipid rafts, and that this association is critical to Us9-mediated sorting of viral structural proteins. We used infected non-polarized and polarized PC12 cells, a rat pheochromocytoma cell line that acquires many of the characteristics of sympathetic neurons in the presence of nerve growth factor (NGF. In these cells, Us9 is highly enriched in detergent-resistant membranes (DRMs. Moreover, reducing the affinity of Us9 for lipid rafts inhibited anterograde transmission of infection from sympathetic neurons to epithelial cells in vitro. We conclude that association of Us9 with lipid rafts is key for efficient targeting of structural proteins to axons and, as a consequence, for directional spread of PRV from pre-synaptic to post-synaptic neurons and cells of the mammalian nervous system.

  15. Sphingolipid signalling domains floating on rafts or buried in caves?

    Science.gov (United States)

    Dobrowsky, R T

    2000-02-01

    Ceramide is a novel lipid mediator involved in regulating cell growth, cell differentiation and cell death. Many studies have focused on characterizing the stimulus-induced production of ceramide and identifying putative downstream molecular targets. However, little remains known about the localization of the regulated production of ceramide through sphingomyelin metabolism in the plasma membrane. Additionally, it is unclear whether a localized increase in ceramide concentration is necessary to facilitate downstream signalling events initiated by this lipid. Recent studies have suggested that detergent-insoluble plasma membrane domains may be highly localized sites for initiating signal transduction cascades by both tyrosine kinase and sphingolipid signalling pathways. These domains are typically enriched in both sphingolipids and cholesterol and have been proposed to form highly ordered lipid rafts floating in a sea of glycerophospholipids. Alternatively, upon integration of the cholesterol binding protein caveolin, these domains may also form small cave-like structures called caveolae. Emerging evidence suggests that the enhanced sphingomyelin content of these lipid domains make them potential substrate pools for sphingomyelinases to produce a high local concentration of ceramide. The subsequent formation of ceramide microdomains in the plasma membrane may be a critical factor in regulating downstream signalling through this lipid messenger.

  16. Role of lipid rafts in liver health and disease

    Institute of Scientific and Technical Information of China (English)

    Angela Dolganiuc

    2011-01-01

    Liver diseases are an increasingly common cause of morbidity and mortality; new approaches for investigation of mechanisms of liver diseases and identification of therapeutic targets are emergent. Lipid rafts (LRs) are specialized domains of cellular membranes that are enriched in saturated lipids; they are small, mobile, and are key components of cellular architecture, protein partition to cellular membranes, and signaling events. LRs have been identified in the membranes of all liver cells, parenchymal and non-parenchymal; more importantly, LRs are active participants in multiple physiological and pathological conditions in individual types of liver cells. This article aims to review experimental-based evidence with regard to LRs in the liver, from the perspective of the liver as a whole organ composed of a multitude of cell types. We have gathered up-to-date information related to the role of LRs in individual types of liver cells, in liver health and diseases, and identified the possibilities of LR-dependent therapeutic targets in liver diseases.

  17. Sphingolipid symmetry governs membrane lipid raft structure.

    Science.gov (United States)

    Quinn, Peter J

    2014-07-01

    Lipid domain formation in membranes underlies the concept of rafts but their structure is controversial because the key role of cholesterol has been challenged. The configuration of glycosphingolipid receptors for agonists, bacterial toxins and enveloped viruses in plasma membrane rafts appears to be an important factor governing ligand binding and infectivity but the details are as yet unresolved. I have used X-ray diffraction methods to examine how cholesterol affects the distribution of glycosphingolipid in aqueous dispersions of an equimolar mixture of cholesterol and egg-sphingomyelin containing different proportions of glucosylceramide from human extracts. Three coexisting liquid-ordered bilayer structures are observed at 37°C in mixtures containing up to 20mol% glycosphingolipid. All the cholesterol was sequestered in one bilayer with the minimum amount of sphingomyelin (33mol%) to prevent formation of cholesterol crystals. The other two bilayers consisted of sphingomyelin and glucosylceramide. Asymmetric molecular species of glucosylceramide with N-acyl chains longer than 20 carbons form an equimolar complex with sphingomyelin in which the glycosidic residues are arranged in hexagonal array. Symmetric molecular species mix with sphingomyelin in proportions less than equimolar to form quasicrystalline bilayers. When the glycosphingolipid exceeds equimolar proportions with sphingomyelin cholesterol is incorporated into the structure and formation of a gel phase of glucosylceramide is prevented. The demonstration of particular structural features of ceramide molecular species combined with the diversity of sugar residues of glycosphingolipid classes paves the way for a rational approach to understanding the functional specificity of lipid rafts and how they are coupled across cell membranes.

  18. Insights on raft behavior from minimal phenomenological models

    Science.gov (United States)

    Garbès Putzel, G.; Schick, M.

    2011-07-01

    We construct a simple phenomenological theory of phase separation in ternary mixtures of cholesterol and saturated and unsaturated lipids. Such separation is relevant to the formation of 'rafts' in the plasma membrane. We also show how simple cross-linking of proteins which prefer one form of lipid to the other can trigger raft-formation, the first step in a signaling pathway.

  19. Lipid rafts in immune signalling: current progress and future perspective.

    Science.gov (United States)

    Varshney, Pallavi; Yadav, Vikas; Saini, Neeru

    2016-09-01

    Lipid rafts are dynamic assemblies of proteins and lipids that harbour many receptors and regulatory molecules and so act as a platform for signal transduction. They float freely within the liquid-disordered bilayer of cellular membranes and can cluster to form larger ordered domains. Alterations in lipid rafts are commonly found to be associated with the pathogenesis of several human diseases and recent reports have shown that the raft domains can also be perturbed by targeting raft proteins through microRNAs. Over the last few years, the importance of lipid rafts in modulating both innate and acquired immune responses has been elucidated. Various receptors present on immune cells like B cells, T cells, basophils and mast cells associate with lipid rafts on ligand binding and initiate signalling cascades leading to inflammation. Furthermore, disrupting lipid raft integrity alters lipopolysaccharide-induced cytokine secretion, IgE signalling, and B-cell and T-cell activation. The objective of this review is to summarize the recent progress in understanding the role of lipid rafts in the modulation of immune signalling and its related therapeutic potential for autoimmune diseases and inflammatory disorders.

  20. Ant workers exhibit specialization and memory during raft formation

    Science.gov (United States)

    Avril, Amaury; Purcell, Jessica; Chapuisat, Michel

    2016-06-01

    By working together, social insects achieve tasks that are beyond the reach of single individuals. A striking example of collective behaviour is self-assembly, a process in which individuals link their bodies together to form structures such as chains, ladders, walls or rafts. To get insight into how individual behavioural variation affects the formation of self-assemblages, we investigated the presence of task specialization and the role of past experience in the construction of ant rafts. We subjected groups of Formica selysi workers to two consecutive floods and monitored the position of individuals in rafts. Workers showed specialization in their positions when rafting, with the same individuals consistently occupying the top, middle, base or side position in the raft. The presence of brood modified workers' position and raft shape. Surprisingly, workers' experience in the first rafting trial with brood influenced their behaviour and raft shape in the subsequent trial without brood. Overall, this study sheds light on the importance of workers' specialization and memory in the formation of self-assemblages.

  1. 'Green' reversible addition-fragmentation chain-transfer (RAFT) polymerization

    Science.gov (United States)

    Semsarilar, Mona; Perrier, Sébastien

    2010-10-01

    Reversible addition-fragmentation chain-transfer (RAFT) polymerization has revolutionized the field of polymer synthesis as a versatile tool for the production of complex polymeric architectures. As for all chemical processes, research and development in RAFT have to focus on the design and application of chemical products and processes that have a minimum environmental impact, and follow the principles of 'green' chemistry. In this Review, we summarize some of the green features of the RAFT process, and review the recent advances in the production of degradable polymers obtained from RAFT polymerization. Its use to modify biodegradable and renewable inorganic and organic materials to yield more functional products with enhanced applications is also covered. RAFT is a promising candidate for answering both the increasing need of modern society to employ highly functional polymeric materials and the global requirements for developing sustainable chemicals and processes.

  2. Dynamic Reorganization and Correlation among Lipid Raft Components.

    Science.gov (United States)

    Lozano, Mónica M; Hovis, Jennifer S; Moss, Frank R; Boxer, Steven G

    2016-08-10

    Lipid rafts are widely believed to be an essential organizational motif in cell membranes. However, direct evidence for interactions among lipid and/or protein components believed to be associated with rafts is quite limited owing, in part, to the small size and intrinsically dynamic interactions that lead to raft formation. Here, we exploit the single negative charge on the monosialoganglioside GM1, commonly associated with rafts, to create a gradient of GM1 in response to an electric field applied parallel to a patterned supported lipid bilayer. The composition of this gradient is visualized by imaging mass spectrometry using a NanoSIMS. Using this analytical method, added cholesterol and sphingomyelin, both neutral and not themselves displaced by the electric field, are observed to reorganize with GM1. This dynamic reorganization provides direct evidence for an attractive interaction among these raft components into some sort of cluster. At steady state we obtain an estimate for the composition of this cluster.

  3. Monolayer curvature stabilizes nanoscale raft domains in mixed lipid bilayers

    CERN Document Server

    Meinhardt, Sebastian; Schmid, Friederike

    2013-01-01

    According to the lipid raft hypothesis, biological lipid membranes are laterally heterogeneous and filled with nanoscale ordered "raft" domains, which are believed to play an important role for the organization of proteins in membranes. However, the mechanisms stabilizing such small rafts are not clear, and even their existence is sometimes questioned. Here we report the observation of raft-like structures in a coarse-grained molecular model for multicomponent lipid bilayers. On small scales, our membranes demix into a liquid ordered (lo) and a liquid disordered (ld) phase. On large scales, phase separation is suppressed and gives way to a microemulsion-type state that contains nanometer size lo domains in a ld environment. Furthermore, we introduce a mechanism that generates rafts of finite size by a coupling between monolayer curvature and local composition. We show that mismatch between the spontaneous curvatures of monolayers in the lo and ld phase induces elastic interactions, which reduce the line tensi...

  4. Lipid Rafts Disruption Increases Ochratoxin A Cytotoxicity to Hepatocytes.

    Science.gov (United States)

    Zhang, Yu; Qi, Xiaozhe; Zheng, Juanjuan; Luo, Yunbo; Zhao, Changhui; Hao, Junran; Li, Xiaohong; Huang, Kunlun; Xu, Wentao

    2016-02-01

    Lipid rafts are microdomains in plasma membrane and can mediate cytotoxicity. In this study, the role of lipid rafts in ochratoxin A-induced toxicity was investigated using Hepatoblastoma Cell Line HepG-2 cells. Disruption of cholesterol-containing lipid rafts enhanced Ochratoxin A (OTA) toxicity, as shown by increased lactate dehydrogenase leakage, increased reactive oxygen species level and reduction of superoxide dismutase activity in a time-dependent manner. Isobaric tags for relative and absolute quantitation-based proteomics of the cell membranes showed that nearly 85.5% proteins were downregulated by OTA, indicating that OTA inhibited the membrane protein synthesis. Most of altered proteins were involved in Gene Ontology "transport", "cell adhesion" and "vesicle-mediated transport". In conclusion, lipid rafts play a key role in OTA-induced cytotoxicity. This study provides insight into how OTA toxicity is regulated by the plasma membrane, especially the lipid rafts.

  5. Raft tectonics in northern Campos Basin; Tectonica de jangada (raft tectonics) na area norte da Bacia de Campos

    Energy Technology Data Exchange (ETDEWEB)

    Castro, Marilia R. de [Universidade Estadual do Norte Fluminense (UENF), Campos dos Goytacases, RJ (Brazil)]|[PETROBRAS, Macae, RJ (Brazil). Unidade de Negocio da Bacia de Campos; Fugita, Adhemar M. [Universidade do Estado, Rio de Janeiro, RJ (Brazil). Programa de Recursos Humanos da ANP

    2004-07-01

    In the northern area of Campos Basin salt gliding/spreading processes promoted the break-up and transport of Cretaceous and Tertiary rocks overlying the evaporites. This process is known as raft tectonics, and it represents the most extreme form of thin-skinned extension above the salt decollement surface. Three distinct geotectonic domains were recognized that formed in response to the raft tectonics. The first one, confined to the shallower shelf portion of the basin, is characterized by minor extension (pre-raft domain), probably because of small salt thickness and low gradient. In the second domain (or disorganized rafts domain), located in distal platformal and slope areas, seismic sections show the occurrence of blocks or rafts with angular shapes, sometimes imbricated and frequently discontinuous. In the third domain, or domain of organized rafts, located in bacinal region, seismic sections show a more continuous raft pattern, often folded because of salt compression in the distal portions of the basin. The main purposes of this work is to characterize these three tectonic domains distinguished by raft tectonics, as well as their importance in hydrocarbon accumulations in calcarenites. (author)

  6. Lipid rafts control P2X3 receptor distribution and function in trigeminal sensory neurons of a transgenic migraine mouse model

    Directory of Open Access Journals (Sweden)

    Fabbretti Elsa

    2011-09-01

    Full Text Available Abstract Background A genetic knock-in mouse model expressing the R192Q mutation of the α1-subunit of the CaV2.1 channels frequently found in patients with familial hemiplegic migraine shows functional upregulation of ATP-sensitive P2X3 receptors of trigeminal sensory neurons that transduce nociceptive inputs to the brainstem. In an attempt to understand the basic mechanisms linked to the upregulation of P2X3 receptor activity, we investigated the influence of the lipid domain of these trigeminal sensory neurons on receptor compartmentalization and function. Results Knock-in neurons were strongly enriched with lipid rafts containing a larger fraction of P2X3 receptors at membrane level. Pretreatment with the CaV2.1 channel blocker ω-agatoxin significantly decreased the lipid raft content of KI membranes. After pharmacologically disrupting the cholesterol component of lipid rafts, P2X3 receptors became confined to non-raft compartments and lost their functional potentiation typically observed in KI neurons with whole-cell patch-clamp recording. Following cholesterol depletion, all P2X3 receptor currents decayed more rapidly and showed delayed recovery indicating that alteration of the lipid raft milieu reduced the effectiveness of P2X3 receptor signalling and changed their desensitization process. Kinetic modeling could reproduce the observed data when slower receptor activation was simulated and entry into desensitization was presumed to be faster. Conclusions The more abundant lipid raft compartment of knock-in neurons was enriched in P2X3 receptors that exhibited stronger functional responses. These results suggest that the membrane microenvironment of trigeminal sensory neurons is an important factor in determining sensitization of P2X3 receptors and could contribute to a migraine phenotype by enhancing ATP-mediated responses.

  7. Localization and signaling of GPCRs in lipid rafts.

    Science.gov (United States)

    Villar, Van Anthony M; Cuevas, Santiago; Zheng, Xiaoxu; Jose, Pedro A

    2016-01-01

    The understanding of how biological membranes are organized and how they function has evolved. Instead of just serving as a medium in which certain proteins are found, portions of the lipid bilayer have been demonstrated to form specialized platforms that foster the assembly of signaling complexes by providing a microenvironment that is conducive for effective protein-protein interactions. G protein-coupled receptors (GPCRs) and relevant signaling molecules, including the heterotrimeric G proteins, key enzymes such as kinases and phosphatases, trafficking proteins, and secondary messengers, preferentially partition to these highly organized cell membrane microdomains, called lipid rafts. As such, lipid rafts are crucial for the trafficking and signaling of GPCRs. The study of GPCR biology in the context of lipid rafts involves the localization of the GPCR of interest in lipid rafts, at the basal state and upon receptor agonism, and the evaluation of the biological functions of the GPCR in appropriate cell lines. The lack of standardized methodology to study lipid rafts, in general, and of the workings of GPCRs in lipid rafts, in particular, and the inherent drawbacks of current methods have hampered the complete understanding of the underlying molecular mechanisms. Newer methodologies that allow the study of GPCRs in their native form are needed. The use of complementary approaches that produce mutually supportive results appear to be the best way for drawing conclusions with regards to the distribution and activity of GPCRs in lipid rafts.

  8. Cholesterol-lowering drugs inhibit lectin-like oxidized low-density lipoprotein-1 receptor function by membrane raft disruption.

    Science.gov (United States)

    Matarazzo, Sara; Quitadamo, Maria Chiara; Mango, Ruggiero; Ciccone, Sarah; Novelli, Giuseppe; Biocca, Silvia

    2012-08-01

    Lectin-like oxidized low-density lipoprotein (LOX-1), the primary receptor for oxidized low-density lipoprotein (ox-LDL) in endothelial cells, is up-regulated in atherosclerotic lesions. Statins are the principal therapeutic agents for cardiovascular diseases and are known to down-regulate LOX-1 expression. Whether the effect on the LOX-1 receptor is related to statin-mediated cholesterol-lowering activity is unknown. We investigate the requirement of cholesterol for LOX-1-mediated lipid particle internalization, trafficking, and processing and the role of statins as inhibitors of LOX-1 function. Disruption of cholesterol-rich membrane microdomains by acute exposure of cells to methyl-β-cyclodextrin or chronic exposure to different statins (lovastatin and atorvastatin) led to a spatial disorganization of LOX-1 in plasma membranes and a marked loss of specific LOX-1 function in terms of ox-LDL binding and internalization. Subcellular fractionation and immunochemical studies indicate that LOX-1 is naturally present in caveolae-enriched lipid rafts and, by cholesterol reduction, the amount of LOX-1 in this fraction is highly decreased (≥60%). In contrast, isoprenylation inhibition had no effect on the distribution and function of LOX-1 receptors. Furthermore, in primary cultures from atherosclerotic human aorta lesions, we confirm the presence of LOX-1 in caveolae-enriched lipid rafts and demonstrate that lovastatin treatment led to down-regulation of LOX-1 in lipid rafts and rescue of the ox-LDL-induced apoptotic phenotype. Taken together, our data reveal a previously unrecognized essential role of membrane cholesterol for LOX-1 receptor activity and suggest that statins protect vascular endothelium against the adverse effect of ox-LDL by disruption of membrane rafts and impairment of LOX-1 receptor function.

  9. DJ-1 associates with lipid rafts by palmitoylation and regulates lipid rafts-dependent endocytosis in astrocytes.

    Science.gov (United States)

    Kim, Kwang Soo; Kim, Jin Soo; Park, Ji-Young; Suh, Young Ho; Jou, Ilo; Joe, Eun-Hye; Park, Sang Myun

    2013-12-01

    Parkinson's disease (PD) is the second most common progressive neurodegenerative disease. Several genes have been associated with familial type PD, providing tremendous insights into the pathogenesis of PD. Gathering evidence supports the view that these gene products may operate through common molecular pathways. Recent reports suggest that many PD-associated gene products, such as α-synuclein, LRRK2, parkin and PINK1, associate with lipid rafts and lipid rafts may be associated with neurodegeneration. Here, we observed that DJ-1 protein also associated with lipid rafts. Palmitoylation of three cysteine residues (C46/53/106) and C-terminal region of DJ-1 were required for this association. Lipopolysaccharide (LPS) induced the localization of DJ-1 into lipid rafts in astrocytes. The LPS-TLR4 signaling was more augmented in DJ-1 knock-out astrocytes by the impairment of TLR4 endocytosis. Furthermore, lipid rafts-dependent endocytosis including the endocytosis of CD14, which play a major role in regulating TLR4 endocytosis was also impaired, but clathrin-dependent endocytosis was not. This study provides a novel function of DJ-1 in lipid rafts, which may contribute the pathogenesis of PD. Moreover, it also provides the possibility that many PD-related proteins may operate through common molecular pathways in lipid rafts.

  10. Assessing the nature of lipid raft membranes

    DEFF Research Database (Denmark)

    Niemelä, Perttu S; Ollila, Samuli; Hyvönen, Marja T

    2007-01-01

    to intriguing lateral pressure profiles that are distinctly different from corresponding profiles in nonraft-like membranes. The results propose that the functioning of certain classes of membrane proteins is regulated by changes in the lateral pressure profile, which can be altered by a change in lipid content....... of highly ordered lateral domains rich in sphingomyelin and cholesterol (CHOL). These domains, called functional lipid rafts, have been suggested to take part in a variety of dynamic cellular processes such as membrane trafficking, signal transduction, and regulation of the activity of membrane proteins....... However, despite the proposed importance of these domains, their properties, and even the precise nature of the lipid phases, have remained open issues mainly because the associated short time and length scales have posed a major challenge to experiments. In this work, we employ extensive atom...

  11. Wave propelled ratchets and drifting rafts

    Science.gov (United States)

    Eddi, A.; Terwagne, D.; Fort, E.; Couder, Y.

    2008-05-01

    Several droplets, bouncing on a vertically vibrated liquid bath, can form various types of bound states, their interaction being due to the waves emitted by their bouncing. Though they associate droplets which are individually motionless, we show that these bound states are self-propelled when the droplets are of uneven size. The driving force is linked to the assymetry of the emitted surface waves. The direction of this ratchet-like displacement can be reversed, by varying the amplitude of forcing. This direction reversal occurs when the bouncing of one of the drops becomes sub-harmonic. As a generalization, a larger number of bouncing droplets form crystalline rafts which are also shown to drift or rotate when assymetrical.

  12. Atom-scale molecular interactions in lipid raft mixtures

    DEFF Research Database (Denmark)

    Niemelä, Perttu S; Hyvönen, Marja T; Vattulainen, Ilpo

    2009-01-01

    We review the relationship between molecular interactions and the properties of lipid environments. A specific focus is given on bilayers which contain sphingomyelin (SM) and sterols due to their essential role for the formation of lipid rafts. The discussion is based on recent atom-scale molecul....... As a particularly intriguing example of this, the lateral pressure profiles of raft-like and non-raft systems indicate that the lipid composition of membrane domains may have a major impact on membrane protein activation.......We review the relationship between molecular interactions and the properties of lipid environments. A specific focus is given on bilayers which contain sphingomyelin (SM) and sterols due to their essential role for the formation of lipid rafts. The discussion is based on recent atom-scale molecular...

  13. Environmental physiology of raft-grown mussels in Goa, India

    Digital Repository Service at National Institute of Oceanography (India)

    Parulekar, A.H.; Dalal, S.G.; Ansari, Z.A.; Harkantra, S.N.

    Mussels (@iPerna viridis@@ L.) transplanted from a marine intertidal region and grown under water in the estuarine environment (on a floating raft) display a wide array of physiological adaptations in growth, osmoregulation and annual reproduction...

  14. Insights on raft behavior from minimal phenomenological models

    Energy Technology Data Exchange (ETDEWEB)

    Garbes Putzel, G; Schick, M [Department of Physics, University of Washington, Box 351560, Seattle, WA 98195-1560 (United States)

    2011-07-20

    We construct a simple phenomenological theory of phase separation in ternary mixtures of cholesterol and saturated and unsaturated lipids. Such separation is relevant to the formation of 'rafts' in the plasma membrane. We also show how simple cross-linking of proteins which prefer one form of lipid to the other can trigger raft-formation, the first step in a signaling pathway.

  15. Proteomic Profiling of Detergent Resistant Membranes (Lipid Rafts) of Prostasomes.

    Science.gov (United States)

    Dubois, Louise; Ronquist, Karl K Göran; Ek, Bo; Ronquist, Gunnar; Larsson, Anders

    2015-11-01

    Prostasomes are exosomes derived from prostate epithelial cells through exocytosis by multivesicular bodies. Prostasomes have a bilayered membrane and readily interact with sperm. The membrane lipid composition is unusual with a high contribution of sphingomyelin at the expense of phosphatidylcholine and saturated and monounsaturated fatty acids are dominant. Lipid rafts are liquid-ordered domains that are more tightly packed than the surrounding nonraft phase of the bilayer. Lipid rafts are proposed to be highly dynamic, submicroscopic assemblies that float freely within the liquid disordered membrane bilayer and some proteins preferentially partition into the ordered raft domains. We asked the question whether lipid rafts do exist in prostasomes and, if so, which proteins might be associated with them. Prostasomes of density range 1.13-1.19g/ml were subjected to density gradient ultracentrifugation in sucrose fabricated by phosphate buffered saline (PBS) containing 1% Triton X-100 with capacity for banding at 1.10 g/ml, i.e. the classical density of lipid rafts. Prepared prostasomal lipid rafts (by gradient ultracentrifugation) were analyzed by mass spectrometry. The clearly visible band on top of 1.10g/ml sucrose in the Triton X-100 containing gradient was subjected to liquid chromatography-tandem MS and more than 370 lipid raft associated proteins were identified. Several of them were involved in intraluminal vesicle formation, e.g. tetraspanins, ESCRTs, and Ras-related proteins. This is the first comprehensive liquid chromatography-tandem MS profiling of proteins in lipid rafts derived from exosomes. Data are available via ProteomeXchange with identifier PXD002163.

  16. Role of the lipid rafts in the life cycle of canine coronavirus.

    Science.gov (United States)

    Pratelli, Annamaria; Colao, Valeriana

    2015-02-01

    Coronaviruses are enveloped RNA viruses that have evolved complex relationships with their host cells, and modulate their lipid composition, lipid synthesis and signalling. Lipid rafts, enriched in sphingolipids, cholesterol and associated proteins, are special plasma membrane microdomains involved in several processes in viral infections. The extraction of cholesterol leads to disorganization of lipid microdomains and to dissociation of proteins bound to lipid rafts. Because cholesterol-rich microdomains appear to be a general feature of the entry mechanism of non-eneveloped viruses and of several coronaviruses, the purpose of this study was to analyse the contribution of lipids to the infectivity of canine coronavirus (CCoV). The CCoV life cycle is closely connected to plasma membrane cholesterol, from cell entry to viral particle production. The methyl-β-cyclodextrin (MβCD) was employed to remove cholesterol and to disrupt the lipid rafts. Cholesterol depletion from the cell membrane resulted in a dose-dependent reduction, but not abolishment, of virus infectivity, and at a concentration of 15 mM, the reduction in the infection rate was about 68 %. MβCD treatment was used to verify if cholesterol in the envelope was required for CCoV infection. This resulted in a dose-dependent inhibitory effect, and at a concentration of 9 mM MβCD, infectivity was reduced by about 73 %. Since viral entry would constitute a target for antiviral strategies, inhibitory molecules interacting with viral and/or cell membranes, or interfering with lipid metabolism, may have strong antiviral potential. It will be interesting in the future to analyse the membrane microdomains in the CCoV envelope.

  17. A Novel RAFT Polymerization under UV Radiation at Ambient Temperature

    Institute of Scientific and Technical Information of China (English)

    Nianfa Yang; Lican Lu; Yuanli Cai

    2005-01-01

    @@ 1Introduction Reversible Addition Fragmentation chain Transfer (RAFT) polymerization has become a highly versatile technique for the controlled/"living" radical polymerization of a wide range of monomers under various conditions[1,2]. The RAFT polymerization was carried out using a dithiocarboxylate or trithiocarbonate as a Chain Transfer Agent (CTA), which mediates the growing chain radicals via an equilibrium[1,2]. From both academic and industrial standpoints, it is clearly desirable to develop a RAFT process under mild conditions. Rizzardo, et al [3] and McCormick's group[4] have respectively reported RAFT polymerization using conventional radical initiators at ambient temperature by adjusting the structure of CTA. The RAFT Polymerization initiated by γ-radiation has also reported recently[5]. Quinn, et al [6] have reported the RAFT polymerization under UV radiation using CTA as the source of primary radicals at 42 ℃, which was well controlled at low conversions (below 20% ) but less controlled at higher conversions (over 20% ) due to the photolysis of CTA residues under UV radiation.

  18. Lipid rafts both in cellular membrane and viral envelope are critical for PRRSV efficient infection.

    Science.gov (United States)

    Yang, Qian; Zhang, Qiong; Tang, Jun; Feng, Wen-Hai

    2015-10-01

    Porcine reproductive and respiratory syndrome virus (PRRSV) represents a significantly economical challenge to the swine industry worldwide. In this study, we investigated the importance of cellular and viral lipid rafts in PRRSV infection. First, we demonstrated that PRRSV glycoproteins, Gp3 and Gp4, were associated with lipid rafts during viral entry, and disruption of cellular lipid rafts inhibited PRRSV entry. We also showed the raft-location of CD163, which might contribute to the glycoproteins-raft association. Subsequently, raft disruption caused a significant reduction of viral RNA production. Moreover, Nsp9 was shown to be distributed in rafts, suggesting that rafts probably serve as a platform for PRRSV replication. Finally, we confirmed that disassembly of rafts on the virus envelope may affect the integrity of PRRSV particles and cause the leakage of viral proteins, which impaired PRRSV infectivity. These findings might provide insights on our understanding of the mechanism of PRRSV infection.

  19. Proving lipid rafts exist: membrane domains in the prokaryote Borrelia burgdorferi have the same properties as eukaryotic lipid rafts.

    Directory of Open Access Journals (Sweden)

    Timothy J LaRocca

    Full Text Available Lipid rafts in eukaryotic cells are sphingolipid and cholesterol-rich, ordered membrane regions that have been postulated to play roles in many membrane functions, including infection. We previously demonstrated the existence of cholesterol-lipid-rich domains in membranes of the prokaryote, B. burgdorferi, the causative agent of Lyme disease [LaRocca et al. (2010 Cell Host & Microbe 8, 331-342]. Here, we show that these prokaryote membrane domains have the hallmarks of eukaryotic lipid rafts, despite lacking sphingolipids. Substitution experiments replacing cholesterol lipids with a set of sterols, ranging from strongly raft-promoting to raft-inhibiting when mixed with eukaryotic sphingolipids, showed that sterols that can support ordered domain formation are both necessary and sufficient for formation of B. burgdorferi membrane domains that can be detected by transmission electron microscopy or in living organisms by Förster resonance energy transfer (FRET. Raft-supporting sterols were also necessary and sufficient for formation of high amounts of detergent resistant membranes from B. burgdorferi. Furthermore, having saturated acyl chains was required for a biotinylated lipid to associate with the cholesterol-lipid-rich domains in B. burgdorferi, another characteristic identical to that of eukaryotic lipid rafts. Sterols supporting ordered domain formation were also necessary and sufficient to maintain B. burgdorferi membrane integrity, and thus critical to the life of the organism. These findings provide compelling evidence for the existence of lipid rafts and show that the same principles of lipid raft formation apply to prokaryotes and eukaryotes despite marked differences in their lipid compositions.

  20. TNAP, an Essential Player in Membrane Lipid Rafts of Neuronal Cells.

    Science.gov (United States)

    Ermonval, Myriam; Baychelier, Florence; Fonta, Caroline

    2015-01-01

    The tissue non-specific alkaline phosphatase (TNAP) is a glycosyl-phosphatidylinositol (GPI) anchored glycoprotein which exists under different forms and is expressed in different tissues. As the other members of the ecto-phosphatase family, TNAP is targeted to membrane lipid rafts. Such micro domains enriched in particular lipids, are involved in cell sorting, are in close contact with the cellular cytoskeleton and play the role of signaling platform. In addition to its location in functional domains, the extracellular orientation of TNAP and the fact this glycoprotein can be shed from plasma membranes, contribute to its different phosphatase activities by acting as a phosphomonoesterase on various soluble substrates (inorganic pyrophosphate -PPi-, pyridoxal phosphate -PLP-, phosphoethanolamine -PEA-), as an ectonucleotidase on nucleotide-phosphate and presumably as a phosphatase able to dephosphorylate phosphoproteins and phospholipids associated to cells or to extra cellular matrix. More and more data accumulate on an involvement of the brain TNAP both in physiological and pathological situations. This review will summarize what is known and expected from the TNAP localization in lipid rafts with a particular emphasis on the role of a neuronal microenvironment on its potential function in the central nervous system.

  1. Caveolin-1 is enriched in the peroxisomal membrane of rat hepatocytes.

    NARCIS (Netherlands)

    Woudenberg, J.; Rembacz, K.P.; Heuvel, F.A. van den; Woudenberg-Vrenken, T.E.; Buist-Homan, M.; Geuken, M.; Hoekstra, M.; Deelman, L.E.; Enrich, C.; Henning, R.H.; Moshage, H.; Faber, K.N.

    2010-01-01

    Caveolae are a subtype of cholesterol-enriched lipid microdomains/rafts that are routinely detected as vesicles pinching off from the plasma membrane. Caveolin-1 is an essential component of caveolae. Hepatic caveolin-1 plays an important role in liver regeneration and lipid metabolism. Expression o

  2. Caveolin-1 Is Enriched in the Peroxisomal Membrane of Rat Hepatocytes

    NARCIS (Netherlands)

    Woudenberg, Jannes; Rembacz, Krzysztof P.; van den Heuvel, Fiona A. J.; Woudenberg-Vrenken, Titia E.; Buist-Homan, Manon; Geuken, Mariska; Hoekstra, Mark; Deelman, Leo E.; Enrich, Carlos; Henning, Rob H.; Moshage, Han; Faber, Klaas Nico

    2010-01-01

    Caveolae are a subtype of cholesterol-enriched lipid microdomains/rafts that are routinely detected as vesicles pinching off from the plasma membrane. Caveolin-1 is an essential component of caveolae. Hepatic caveolin-1 plays an important role in liver regeneration and lipid metabolism. Expression o

  3. Down-regulation of lipid raft-associated onco-proteins via cholesterol-dependent lipid raft internalization in docosahexaenoic acid-induced apoptosis.

    Science.gov (United States)

    Lee, Eun Jeong; Yun, Un-Jung; Koo, Kyung Hee; Sung, Jee Young; Shim, Jaegal; Ye, Sang-Kyu; Hong, Kyeong-Man; Kim, Yong-Nyun

    2014-01-01

    Lipid rafts, plasma membrane microdomains, are important for cell survival signaling and cholesterol is a critical lipid component for lipid raft integrity and function. DHA is known to have poor affinity for cholesterol and it influences lipid rafts. Here, we investigated a mechanism underlying the anti-cancer effects of DHA using a human breast cancer cell line, MDA-MB-231. We found that DHA decreased cell surface levels of lipid rafts via their internalization, which was partially reversed by cholesterol addition. With DHA treatment, caveolin-1, a marker for rafts, and EGFR were colocalized with LAMP-1, a lysosomal marker, in a cholesterol-dependent manner, indicating that DHA induces raft fusion with lysosomes. DHA not only displaced several raft-associated onco-proteins, including EGFR, Hsp90, Akt, and Src, from the rafts but also decreased total levels of those proteins via multiple pathways, including the proteasomal and lysosomal pathways, thereby decreasing their activities. Hsp90 overexpression maintained its client proteins, EGFR and Akt, and attenuated DHA-induced cell death. In addition, overexpression of Akt or constitutively active Akt attenuated DHA-induced apoptosis. All these data indicate that the anti-proliferative effect of DHA is mediated by targeting of lipid rafts via decreasing cell surface lipid rafts by their internalization, thereby decreasing raft-associated onco-proteins via proteasomal and lysosomal pathways and decreasing Hsp90 chaperone function.

  4. Structure of Cholesterol in Lipid Rafts

    Science.gov (United States)

    Toppozini, Laura; Meinhardt, Sebastian; Armstrong, Clare L.; Yamani, Zahra; Kučerka, Norbert; Schmid, Friederike; Rheinstädter, Maikel C.

    2014-11-01

    Rafts, or functional domains, are transient nano-or mesoscopic structures in the plasma membrane and are thought to be essential for many cellular processes such as signal transduction, adhesion, trafficking, and lipid or protein sorting. Observations of these membrane heterogeneities have proven challenging, as they are thought to be both small and short lived. With a combination of coarse-grained molecular dynamics simulations and neutron diffraction using deuterium labeled cholesterol molecules, we observe raftlike structures and determine the ordering of the cholesterol molecules in binary cholesterol-containing lipid membranes. From coarse-grained computer simulations, heterogenous membranes structures were observed and characterized as small, ordered domains. Neutron diffraction was used to study the lateral structure of the cholesterol molecules. We find pairs of strongly bound cholesterol molecules in the liquid-disordered phase, in accordance with the umbrella model. Bragg peaks corresponding to ordering of the cholesterol molecules in the raftlike structures were observed and indexed by two different structures: a monoclinic structure of ordered cholesterol pairs of alternating direction in equilibrium with cholesterol plaques, i.e., triclinic cholesterol bilayers.

  5. Impact of lipid rafts on the T -cell-receptor and peptide-major-histocompatibility-complex interactions under different measurement conditions

    Science.gov (United States)

    Li, Long; Xu, Guang-Kui; Song, Fan

    2017-01-01

    The interactions between T-cell receptor (TCR) and peptide-major-histocompatibility complex (pMHC), which enable T-cell development and initiate adaptive immune responses, have been intensively studied. However, a central issue of how lipid rafts affect the TCR-pMHC interactions remains unclear. Here, by using a statistical-mechanical membrane model, we show that the binding affinity of TCR and pMHC anchored on two apposing cell membranes is significantly enhanced because of the lipid raft-induced signaling protein aggregation. This finding may provide an alternative insight into the mechanism of T-cell activation triggered by very low densities of pMHC. In the case of cell-substrate adhesion, our results indicate that the loss of lateral mobility of the proteins on the solid substrate leads to the inhibitory effect of lipid rafts on TCR-pMHC interactions. Our findings help to understand why different experimental methods for measuring the impact of lipid rafts on the receptor-ligand interactions have led to contradictory conclusions.

  6. Reconstituting ring-rafts in bud-mimicking topography of model membranes

    Science.gov (United States)

    Ryu, Yong-Sang; Lee, In-Ho; Suh, Jeng-Hun; Park, Seung Chul; Oh, Soojung; Jordan, Luke R.; Wittenberg, Nathan J.; Oh, Sang-Hyun; Jeon, Noo Li; Lee, Byoungho; Parikh, Atul N.; Lee, Sin-Doo

    2014-07-01

    During vesicular trafficking and release of enveloped viruses, the budding and fission processes dynamically remodel the donor cell membrane in a protein- or a lipid-mediated manner. In all cases, in addition to the generation or relief of the curvature stress, the buds recruit specific lipids and proteins from the donor membrane through restricted diffusion for the development of a ring-type raft domain of closed topology. Here, by reconstituting the bud topography in a model membrane, we demonstrate the preferential localization of cholesterol- and sphingomyelin-enriched microdomains in the collar band of the bud-neck interfaced with the donor membrane. The geometrical approach to the recapitulation of the dynamic membrane reorganization, resulting from the local radii of curvatures from nanometre-to-micrometre scales, offers important clues for understanding the active roles of the bud topography in the sorting and migration machinery of key signalling proteins involved in membrane budding.

  7. Pigment encapsulation by emulsion polymerization using macro-RAFT copolymers.

    Science.gov (United States)

    Nguyen, Duc; Zondanos, Hollie S; Farrugia, Jason M; Serelis, Algirdas K; Such, Chris H; Hawkett, Brian S

    2008-03-04

    A new method is described, based on living amphipathic random macro-RAFT copolymers, which enables the efficient polymeric encapsulation of both inorganic and organic particulate materials via free-radical polymerization. The mechanism for this new approach is examined in the context of the polymer coating of zirconia- and alumina-coated titanium dioxide particles and its breadth of application demonstrated by the coating of organic phthalocyanine blue pigment particles. The particulate materials were first dispersed in water using a macro-RAFT copolymer as a stabilizer. Monomer and water-soluble initiator were then added to the system, and the monomer polymerized to form the coating. If nucleation of new polymer particles in the aqueous phase was to be avoided, it was found necessary to use a macro-RAFT copolymer that did not form micelles; within this constraint, a broad range of RAFT agents could be used. The macro-RAFT agents used in this work were found not to transfer competitively in the aqueous phase and therefore did not support growth of aqueous-phase polymer. Successful encapsulation of particles was demonstrated by TEM. The process described enables 100% of the particles to be encapsulated with greater than 95% of the polymer finishing up in the polymeric shells around the particles. Moreover, the coating reaction can be carried out at greater than 50% solids in many cases and avoids the agglomeration of particles during the coating step.

  8. Interaction of chiral rafts in self-assembled colloidal membranes

    Science.gov (United States)

    Xie, Sheng; Hagan, Michael F.; Pelcovits, Robert A.

    2016-03-01

    Colloidal membranes are monolayer assemblies of rodlike particles that capture the long-wavelength properties of lipid bilayer membranes on the colloidal scale. Recent experiments on colloidal membranes formed by chiral rodlike viruses showed that introducing a second species of virus with different length and opposite chirality leads to the formation of rafts—micron-sized domains of one virus species floating in a background of the other viruses [Sharma et al., Nature (London) 513, 77 (2014), 10.1038/nature13694]. In this article we study the interaction of such rafts using liquid crystal elasticity theory. By numerically minimizing the director elastic free energy, we predict the tilt angle profile for both a single raft and two rafts in a background membrane, and the interaction between two rafts as a function of their separation. We find that the chiral penetration depth in the background membrane sets the scale for the range of the interaction. We compare our results with the experimental data and find good agreement for the strength and range of the interaction. Unlike the experiments, however, we do not observe a complete collapse of the data when rescaled by the tilt angle at the raft edge.

  9. Lipid rafts and their possible involvements in neuroimmunological disorders.

    Science.gov (United States)

    Asakura, Kunihiko; Ueda, Akihiro; Mutoh, Tatsuro

    2015-01-01

    Multiple sclerosis (MS) and neuromyelitis optica (NMO) are presumed to be an autoimmune disease in the central nervous system (CNS). Although lipids are most abundant components in the nervous system, it has been believed that cellular and/or humoral immunity to various myelin proteins causes these neuroinflammatory diseases. Recent research advances enable us to study lipids in the membranes and some key molecules involved in various neurological disorders including Guillain-Barré syndrome, Alzheimer's disease, Parkinson's disease, and prion disease, are localized in lipid rafts. In MS and NMO, the key molecules for the pathogenesis or the target molecules for the treatments of MS and NMO are also localized in lipid rafts. Here in this article, we highlight on the possible involvement of lipid rafts in the pathogenesis and treatment of MS and NMO and introduce our recent observation of aquaporin 4 regarding NMO.

  10. Dynamics of surfactant-driven fracture of particle rafts.

    Science.gov (United States)

    Vella, Dominic; Kim, Ho-Young; Aussillous, Pascale; Mahadevan, L

    2006-05-05

    We investigate the dynamic fracture of a close-packed monolayer of particles, or particle raft, floating at a liquid-gas interface induced by the localized addition of surfactant. Unusually for a two-dimensional solid, our experiments show that the speed of crack propagation here is not affected by the elastic properties of the raft. Instead it is controlled by the rate at which surfactant is advected to the crack tip by means of the induced Marangoni flows. Further, the velocity of propagation is not constant in time and the length of the crack scales as t(3/4). More broadly, this surfactant-induced rupture of interfacial rafts suggests ways to manipulate them for applications.

  11. Construction aggregates

    Science.gov (United States)

    Nelson, T.I.; Bolen, W.P.

    2007-01-01

    Construction aggregates, primarily stone, sand and gravel, are recovered from widespread naturally occurring mineral deposits and processed for use primarily in the construction industry. They are mined, crushed, sorted by size and sold loose or combined with portland cement or asphaltic cement to make concrete products to build roads, houses, buildings, and other structures. Much smaller quantities are used in agriculture, cement manufacture, chemical and metallurgical processes, glass production and many other products.

  12. Lipid Rafts: Keys to Sperm Maturation, Fertilization, and Early Embryogenesis

    Directory of Open Access Journals (Sweden)

    Natsuko Kawano

    2011-01-01

    Full Text Available Cell membranes are composed of many different lipids and protein receptors, which are important for regulating intracellular functions and cell signaling. To orchestrate these activities, the cell membrane is compartmentalized into microdomains that are stably or transiently formed. These compartments are called “lipid rafts”. In gamete cells that lack gene transcription, distribution of lipids and proteins on these lipid rafts is focused during changes in their structure and functions such as starting flagella movement and membrane fusion. In this paper, we describe the role of lipid rafts in gamete maturation, fertilization, and early embryogenesis.

  13. Cellular strategies for regulating functional and nonfunctional protein aggregation.

    Science.gov (United States)

    Gsponer, Jörg; Babu, M Madan

    2012-11-29

    Growing evidence suggests that aggregation-prone proteins are both harmful and functional for a cell. How do cellular systems balance the detrimental and beneficial effect of protein aggregation? We reveal that aggregation-prone proteins are subject to differential transcriptional, translational, and degradation control compared to nonaggregation-prone proteins, which leads to their decreased synthesis, low abundance, and high turnover. Genetic modulators that enhance the aggregation phenotype are enriched in genes that influence expression homeostasis. Moreover, genes encoding aggregation-prone proteins are more likely to be harmful when overexpressed. The trends are evolutionarily conserved and suggest a strategy whereby cellular mechanisms specifically modulate the availability of aggregation-prone proteins to (1) keep concentrations below the critical ones required for aggregation and (2) shift the equilibrium between the monomeric and oligomeric/aggregate form, as explained by Le Chatelier's principle. This strategy may prevent formation of undesirable aggregates and keep functional assemblies/aggregates under control.

  14. Development of optimum design from static response of pile–raft interaction

    DEFF Research Database (Denmark)

    Taghavi Ghalesari, A; Barari, Amin; Fardad Amini, P;

    2015-01-01

    Piled raft foundations are among the most commonly used support structures for offshore projects. When a raft foundation alone does not satisfy the design requirements, piles may be added to improve the ultimate load capacity and the settlement performance of the raft. In this study, design...... for the piled raft were highly influenced by the number of piles and the raft thickness. Optimal design configurations of piles for cohesive soils are discussed. Increasing the pile spacing decreased the pile butt load ratio by allowing for a more uniform load distribution between the piles....

  15. Expression of HIV-1 Vpu leads to loss of the viral restriction factor CD317/Tetherin from lipid rafts and its enhanced lysosomal degradation.

    Directory of Open Access Journals (Sweden)

    Ruth Rollason

    Full Text Available CD317/tetherin (aka BST2 or HM1.24 antigen is an interferon inducible membrane protein present in regions of the lipid bilayer enriched in sphingolipids and cholesterol (often termed lipid rafts. It has been implicated in an eclectic mix of cellular processes including, most notably, the retention of fully formed viral particles at the surface of cells infected with HIV and other enveloped viruses. Expression of the HIV viral accessory protein Vpu has been shown to lead to intracellular sequestration and degradation of tetherin, thereby counteracting the inhibition of viral release. There is evidence that tetherin interacts directly with Vpu, but it remains unclear where in the cell this interaction occurs or if Vpu expression affects the lipid raft localisation of tetherin. We have addressed these points using biochemical and cell imaging approaches focused on endogenous rather than ectopically over-expressed tetherin. We find i no evidence for an interaction between Vpu and endogenous tetherin at the cell surface, ii the vast majority of endogenous tetherin that is at the cell surface in control cells is in lipid rafts, iii internalised tetherin is present in non-raft fractions, iv expression of Vpu in cells expressing endogenous tetherin leads to the loss of tetherin from lipid rafts, v internalised tetherin enters early endosomes, and late endosomes, in both control cells and cells expressing Vpu, but the proportion of tetherin molecules destined for degradation rather than recycling is increased in cells expressing Vpu vi lysosomes are the primary site for degradation of endogenous tetherin in cells expressing Vpu. Our studies underlie the importance of studying endogenous tetherin and let us propose a model in which Vpu intercepts newly internalised tetherin and diverts it for lysosomal destruction rather than recycling to the cell surface.

  16. Soil-Structure Interaction Analysis of Tall Reinforced Concrete Chimney with Piled Raft and Annular Raft under Along-Wind Load

    Directory of Open Access Journals (Sweden)

    B. R. Jayalekshmi

    2013-01-01

    Full Text Available A three-dimensional (3D soil-structure interaction (SSI analysis of 300 m high reinforced concrete chimneys having piled annular raft and annular raft foundations subjected to along-wind load is carried out in the present study. To understand the significance of SSI, four types of soils were considered based on their flexibility. The effect of stiffness of the raft was evaluated using three different ratios of external diameter to thickness of the annular raft. The along-wind load was computed according to IS:4998 (Part 1-1992. The integrated chimney-foundation-soil system was analysed by commercial finite element (FE software ANSYS, based on direct method of SSI assuming linear elastic behaviour. FE analyses were carried out for two cases of SSI (I chimney with annular raft foundation and (II chimney with piled raft foundation. The responses in chimney such as tip deflection, bending moments, and base moment and responses in raft such as bending moments and settlements were evaluated for both cases and compared to that obtained from the conventional method of analysis. It is found that the responses in chimney and raft depend on the flexibility of the underlying soil and thickness of the raft.

  17. Cholesterol lipids and cholesterol-containing lipid rafts in bacteria.

    Science.gov (United States)

    Huang, Zhen; London, Erwin

    2016-09-01

    Sterols are important components of eukaryotic membranes, but rare in bacteria. Some bacteria obtain sterols from their host or environment. In some cases, these sterols form membrane domains analogous the lipid rafts proposed to exist in eukaryotic membranes. This review describes the properties and roles of sterols in Borrelia and Helicobacter.

  18. Commercialization of raft oyster culture in Puerto Rico

    Energy Technology Data Exchange (ETDEWEB)

    Watters, K.W.

    1975-01-01

    The Oyster Culture Project of the Puerto Rico Nuclear Center has been investigating the feasibility of raft-culturing the local mangrove oyster (Crassostrea rhizophorae) for the past two years. Attempts to start culture efforts on a commercial scale are described. (CH)

  19. Raft River well stimulation experiments: geothermal reservoir well stimulation program

    Energy Technology Data Exchange (ETDEWEB)

    1980-08-01

    The Geothermal Reservoir Well Stimulation Program (GRWSP) performed two field experiments at the Raft River KGRA in 1979. Wells RRGP-4 and RRGP-5 were selected for the hydraulic fracture stimulation treatments. The well selection process, fracture treatment design, field execution, stimulation results, and pre- and post-job evaluations are presented.

  20. FEA for designing of floating raft shock-resistant system

    Institute of Scientific and Technical Information of China (English)

    ZHAO Ying-long; HE Lin; HUANG Ying-yun; WANG Yu

    2003-01-01

    Choosing the equipment with good shock-resistant performance and taking shock protection measures while designing the onboard settings, the safety of onboard settings can be assured when warships, especially submarine subjected to non-contact underwater explosion, that is, these means can be used to limit the rattlespace (i.e., the maximum displacement of the equipment relative to the base) and the peak acceleration experienced by the equipment. Using shock-resistant equipments is one of shock protection means. The shock-resistant performance of the shock-resistant equipments should be verified in the design phase of the equipments. The FEA (finite element analysis) software, for example, MSC.NASTRAN(R), can be used to verify the shock-resistant performance. MSC.PATRAN(R) and MSC.NASTRAN are used for modeling and analyzing the floating raft vibration isolating equipment. The model of the floating raft and the floating raft vibration isolating system are theoretically analyzed and calculated, and the analysis results are in agreement with the test results. The transient response analysis of the system model follows the modal analysis of the floating raft vibration isolating system. And it is used to verify the shock-resistant performance. The analysis and calculation method used in this paper can be used to analyze the shock-resistant performance of onboard shock-resistant equipments.

  1. Direct surface PEGylation of nanodiamond via RAFT polymerization

    Energy Technology Data Exchange (ETDEWEB)

    Shi, Yingge [Department of Chemistry and Jiangxi Provincial Key Laboratory of New Energy Chemistry, Nanchang University, 999 Xuefu Avenue, Nanchang 330031 (China); School of Chemistry and Chemical Engineering, Guangxi University, Nanning 530004 (China); Liu, Meiying [Department of Chemistry and Jiangxi Provincial Key Laboratory of New Energy Chemistry, Nanchang University, 999 Xuefu Avenue, Nanchang 330031 (China); Wang, Ke [Department of Chemistry and the Tsinghua Center for Frontier Polymer Research, Tsinghua University, Beijing 100084 (China); Huang, Hongye; Wan, Qing [Department of Chemistry and Jiangxi Provincial Key Laboratory of New Energy Chemistry, Nanchang University, 999 Xuefu Avenue, Nanchang 330031 (China); Tao, Lei [Department of Chemistry and the Tsinghua Center for Frontier Polymer Research, Tsinghua University, Beijing 100084 (China); Fu, Lihua [School of Chemistry and Chemical Engineering, Guangxi University, Nanning 530004 (China); Zhang, Xiaoyong, E-mail: xiaoyongzhang1980@gmail.com [Department of Chemistry and Jiangxi Provincial Key Laboratory of New Energy Chemistry, Nanchang University, 999 Xuefu Avenue, Nanchang 330031 (China); Wei, Yen, E-mail: weiyen@tsinghua.edu.cn [Department of Chemistry and the Tsinghua Center for Frontier Polymer Research, Tsinghua University, Beijing 100084 (China)

    2015-12-01

    Graphical abstract: In this paper, we describe an efficient, practical and novel method to modify ND via direct immobilization of chain transfer agent for RAFT polymerization. - Highlights: • Surface PEGylation of ND via RAFT polymerization. • ND with high water dispersibility and excellent biocompatibility. • Controlled living polymerization. - Abstract: Nanodiamond (ND) is a novel class of carbon nanomaterials, which has been extensively investigated for biomedical applications because of its small size, high surface area and excellent biocompatibility. However, the biomedical applications of unmodified ND are still largely restricted because of their poor dispersibility in both aqueous and organic medium. In this work, we reported a novel strategy for the surface modification of ND via reversible addition fragmentation chain transfer (RAFT) polymerization. For preparation of the PEGylated ND (pPEGMA-ND), chain transfer agent (CTA) was immobilized onto ND through reaction between the hydroxyl group of ND and the carboxyl group of CTA, which was used as the initiator for surface-initiated RAFT polymerization. The successful preparation of pPEGMA-ND was characterized by nuclear magnetic resonance spectroscopy, Fourier transform infrared spectroscopy, X-ray photoelectron spectra and thermal gravimetric analysis in detail. Results demonstrated that pPEGMA-ND exhibited enhanced water dispersibility and desirable biocompatibility, making it promising for biomedical applications.

  2. C2 domain of synaptotagminⅠassociates with lipid rafts of plasma membrane

    Institute of Scientific and Technical Information of China (English)

    L(U) JiHua; HE Li; SUI SenFang

    2008-01-01

    In this paper we report that the C2 domain of synaptotagmin I (syt I) could associate with lipid rafts of plasma membrane. We demonstrate that phosphatidylinositol 4,5-bisphosphate (PIP2) in the target membrane and Ca2+ are the key factors to enhance the raft association of the C2 domain. We also found that the raft association of the C2 domain could be fulfilled by either C2A or C2B alone, suggesting that their raft association might be complementary. Finally, we indicate that destroying lipid rafts or blocking syt I-raft association could significantly reduce the Ca2+-driven release of glutamates. Our data indicate that the raft association of the C2 domain might play an important role in the regulated exocytosis.

  3. Effects of RAFT Agent on the Selective Approach of Molecularly Imprinted Polymers

    Directory of Open Access Journals (Sweden)

    Saliza Asman

    2015-03-01

    Full Text Available Two types of reversible addition-fragmentation chain transfer molecularly imprinted polymers (RAFT-MIPs were synthesized using different monomers, which were methacrylic acid functionalized β-cyclodextrin (MAA-β-CD and 2-hydroxyethyl methacrylate functionalized β-cyclodextrin (HEMA-β-CD, via reversible addition-fragmentation chain transfer (RAFT polymerization, and were represented as RAFT-MIP(MAA-β-CD and RAFT-MIP(HEMA-β-CD, respectively. Both RAFT-MIPs were systematically characterized using Fourier Transform Infrared Spectroscopy (FTIR, Field Emission Scanning Electron Microscopy (FESEM, Brunauer-Emmett-Teller (BET, and rebinding experimental study. The results were compared with MIPs synthesized via the traditional radical polymerization (TRP process, and were represented as MIP(MAA-β-CD and MIP(HEMA-β-CD. Morphology results show that RAFT-MIP(MAA-β-CD has a slightly spherical feature with a sponge-like form, while RAFT-MIP(HEMA-β-CD has a compact surface. BET results show that the surface area of RAFT-MIP(MAA-β-CD is higher than MIP(MAA-β-CD, while the RAFT-MIP(HEMA-β-CD surface area is lower than that of MIP(HEMA-β-CD. Rebinding experiments indicate that the RAFT agent increased the binding capacity of RAFT-MIP(MAA-β-CD, but not of RAFT-MIP(HEMA-β-CD, which proves that a RAFT agent does not always improve the recognition affinity and selective adsorption of MIPs. The usability of a RAFT agent depends on the monomer used to generate potential MIPs.

  4. Measuring the strength of interaction between the Ebola fusion peptide and lipid rafts: implications for membrane fusion and virus infection.

    Directory of Open Access Journals (Sweden)

    Mônica S Freitas

    Full Text Available The Ebola fusion peptide (EBO₁₆ is a hydrophobic domain that belongs to the GP2 membrane fusion protein of the Ebola virus. It adopts a helical structure in the presence of mimetic membranes that is stabilized by the presence of an aromatic-aromatic interaction established by Trp8 and Phe12. In spite of its infectious cycle becoming better understood recently, several steps still remain unclear, a lacuna that makes it difficult to develop strategies to block infection. In order to gain insight into the mechanism of membrane fusion, we probed the structure, function and energetics of EBO₁₆ and its mutant W8A, in the absence or presence of different lipid membranes, including isolated domain-resistant membranes (DRM, a good experimental model for lipid rafts. The depletion of cholesterol from living mammalian cells reduced the ability of EBO₁₆ to induce lipid mixing. On the other hand, EBO₁₆ was structurally sensitive to interaction with lipid rafts (DRMs, but the same was not observed for W8A mutant. In agreement with these data, W8A showed a poor ability to promote membrane aggregation in comparison to EBO₁₆. Single molecule AFM experiments showed a high affinity force pattern for the interaction of EBO₁₆ and DRM, which seems to be a complex energetic event as observed by the calorimetric profile. Our study is the first to show a strong correlation between the initial step of Ebola virus infection and cholesterol, thus providing a rationale for Ebola virus proteins being co-localized with lipid-raft domains. In all, the results show how small fusion peptide sequences have evolved to adopt highly specific and strong interactions with membrane domains. Such features suggest these processes are excellent targets for therapeutic and vaccine approaches to viral diseases.

  5. A flow-cytometry method for analyzing the composition of membrane rafts.

    Science.gov (United States)

    Morales-García, M Guadalupe; Fournié, Jean-Jacques; Moreno-Altamirano, M Maximina Bertha; Rodríguez-Luna, Gabriela; Flores, Ricardo-Mondragón; Sánchez-García, F Javier

    2008-10-01

    Membrane rafts are involved in a broad variety of biological processes. Their protein composition under growth factor stimulation, anti-inflammatory or proinflammatory microenvironments, or in the course of pathogenic infections still remains to be determined. However, current techniques aimed at the identification of particular proteins on membrane rafts are not devoid of pitfalls. Membrane rafts were obtained by detergent-free based differential centrifugation from Jurkat T cells and J774 macrophages. Membrane rafts were labeled with fluorochrome-labeled antibodies directed against different cell membrane molecules, and with fluorochrome-labeled cholera toxin B that targets GM1 and analyzed by flow cytometry. CD3, CD11a, and GM1 were shown to be differentially expressed on Jurkat T cell-derived membrane rafts, indicating heterogeneity in membrane rafts composition. On the other hand, it was shown in J774 cell-derived membrane rafts that most but not all CD14 is present in the GM1-containing membrane fragments, thus confirming the heterogeneity of membrane rafts composition in other cell lines. The method described here allows the fluorometric assessment of the relative expression of more than one membrane raft component at a time, and at a single vesicle level in a fast and sensitive manner. This method seems to be a suitable approach to evaluate the molecular heterogeneity in membrane rafts composition.

  6. Extensive sphingolipid depletion does not affect lipid raft integrity or lipid raft localization and efflux function of the ABC transporter MRP1

    NARCIS (Netherlands)

    Klappe, Karin; Dijkhuis, Anne-Jan; Hummel, Ina; van Dam, Annie; Ivanova, Pavlina T.; Milne, Stephen B.; Myers, David S.; Brown, H. Alex; Permentier, Hjalmar; Kok, Jan W.

    2010-01-01

    We show that highly efficient depletion of sphingolipids in two different cell lines does not abrogate the ability to isolate Lubrol-based DRMs (detergent-resistant membranes) or detergent-free lipid rafts from these cells. Compared with control, DRM/detergent-free lipid raft fractions contain equal

  7. Tissue Engineering the Cornea: The Evolution of RAFT.

    Science.gov (United States)

    Levis, Hannah J; Kureshi, Alvena K; Massie, Isobel; Morgan, Louise; Vernon, Amanda J; Daniels, Julie T

    2015-01-22

    Corneal blindness affects over 10 million people worldwide and current treatment strategies often involve replacement of the defective layer with healthy tissue. Due to a worldwide donor cornea shortage and the absence of suitable biological scaffolds, recent research has focused on the development of tissue engineering techniques to create alternative therapies. This review will detail how we have refined the simple engineering technique of plastic compression of collagen to a process we now call Real Architecture for 3D Tissues (RAFT). The RAFT production process has been standardised, and steps have been taken to consider Good Manufacturing Practice compliance. The evolution of this process has allowed us to create biomimetic epithelial and endothelial tissue equivalents suitable for transplantation and ideal for studying cell-cell interactions in vitro.

  8. Settlement calculation for long-short composite piled raft foundation

    Institute of Scientific and Technical Information of China (English)

    ZHAO Ming-hua; ZHANG Ling; YANG Ming-hui

    2006-01-01

    The mechanism of long-short composite piled raft foundation was discussed. Assuming the relationship between shear stress and shear strain of the surrounding soil was elasto-plastic, shear displacement method was employed to establish the different explicit relational equations between the load and the displacement at the top of pile in either elastic or elasto-plastic period. Then Mylonakis & Gazetas model was introduced to simulate the interaction between two piles or between piles and soil. Considering the effect of cushion, the flexible coefficients of interaction were provided. With the addition of a relevant program, the settlement calculation for long-short composite piled raft foundation was developed which could be used to account for the interaction of piles,soil and cushion. Finally, the calculation method was used to analyze an engineering example. The calculated value of settlement is 10.2 mm, which is close to the observed value 8.8 mm.

  9. Tissue Engineering the Cornea: The Evolution of RAFT

    Directory of Open Access Journals (Sweden)

    Hannah J. Levis

    2015-01-01

    Full Text Available Corneal blindness affects over 10 million people worldwide and current treatment strategies often involve replacement of the defective layer with healthy tissue. Due to a worldwide donor cornea shortage and the absence of suitable biological scaffolds, recent research has focused on the development of tissue engineering techniques to create alternative therapies. This review will detail how we have refined the simple engineering technique of plastic compression of collagen to a process we now call Real Architecture for 3D Tissues (RAFT. The RAFT production process has been standardised, and steps have been taken to consider Good Manufacturing Practice compliance. The evolution of this process has allowed us to create biomimetic epithelial and endothelial tissue equivalents suitable for transplantation and ideal for studying cell-cell interactions in vitro.

  10. Involvement of Lipid Rafts and Cellular Actin in AcMNPV GP64 Distribution and Virus Budding

    Institute of Scientific and Technical Information of China (English)

    F. J. Haines; C. M. Griffiths; R. D. Possee; C. R. Hawes; L. A. King

    2009-01-01

    GP64 is the major envelope glycoprotein associated with the budded virus (BV) of Autographa californica nucleopolyhedrovirus (AcMNPV) and is essential for attachment and budding of BV particles.Confocal microscopy and flotation assays established the presence of lipid raft domains within the plasma membranes of AcMNPV-infected Sf9 cells and suggested the association of GP64 with lipid rafts during infection. GP64 and filamentous actin (F-actin) were found to co-localise at the cell cortex at 24 and 48 hpi and an additional restructuring of F-actin during infection was visualised, resulting in a strongly polarised distribution of both F-actin and GP64 at the cell cortex. Depletion of F-actin, achieved by treatment of St9 cells with latrunculin B (LB), resulted in the redistribution of GP64 with significant cytoplasmic aggregation and reduced presence at the plasma membrane. Treatment with LB also resulted in reduced production of BV in Sf9 cells. Analysis of virus gene transcription confirmed this reduction was not due to decreased trafficking of nucleocapsids to the nucleus or to decreased production of infectious progeny nucleoeapsids. Reduced BV production due to a lack of GP64 at the plasma membrane of AcMNPV-infected Sf9 cells treated with LB, suggests a key role for F-actin in the egress of BV.

  11. Rafting in single crystal nickel-base superalloys — An overview

    Indian Academy of Sciences (India)

    M Kamaraj

    2003-02-01

    Currently nickel-base single crystal (SX) superalloys are considered for the manufacture of critical components such as turbine blades, vanes etc., for aircraft engines as well as land-based power generation applications. Microstructure and high temperature mechanical properties are the major factors controlling the performance of SX superalloys. Rafting is an important phenomenon in these alloys which occurs during high temperature creep. It is essential to understand the rafting mechanism, and its characteristics on high temperature properties before considering the advanced applications. In this review article, the thermodynamic driving force for rafting with and without stress is explained. The nature and influence of rafting on creep properties including pre-rafted conditions are discussed. In addition, the effect of stress state on $\\gamma /\\gamma'$ rafting, kinetics and morphological evolution are discussed with the recent experimental results.

  12. Influence of lipid rafts on CD1d presentation by dendritic cells

    DEFF Research Database (Denmark)

    Peng, Wei; Martaresche, Cecile; Escande-Beillard, Nathalie

    2011-01-01

    corresponding to lipid rafts and we describe that alpha-GalCer enhanced CD1d amount in the low density detergent insoluble fraction. We conclude that the membrane environment of CD1d can influence antigen presentation mainly when the endocytic pathway is required. Flow cytometry analysis can provide additional...... information on lipid rafts in plasma membranes and allows a dynamics follow-up of lipid rafts partitioning. Using this method, we showed that CD1d plasma membrane expression was sensitive to low concentrations of detergent. This may suggest either that CD1d is associated with lipid rafts mainly......Our main objective was to analyze the role of lipid rafts in the activation of Valpha-14(-) and Valpha-14(+) T hybridomas by dendritic cells. We showed that activation of Valpha-14(+) hybridomas by dendritic cells or other CD1d-expressing cells was altered by disruption of lipid rafts...

  13. Thermoresponsive and Reducible Hyperbranched Polymers Synthesized by RAFT Polymerisation

    Directory of Open Access Journals (Sweden)

    Anna Tochwin

    2017-09-01

    Full Text Available Here, we report the synthesis of new thermoresponsive hyperbranched polymers (HBPs via one-pot reversible addition-fragmentation chain transfer (RAFT copolymerisation of poly(ethylene glycolmethyl ether methacrylate (PEGMEMA, Mn = 475 g/mol, poly(propylene glycolmethacrylate (PPGMA, Mn = 375 g/mol, and disulfide diacrylate (DSDA using 2-cyanoprop-2-yl dithiobenzoate as a RAFT agent. DSDA was used as the branching agent and to afford the HBPs with reducible disulfide groups. The resulting HBPs were characterised by Nuclear Magnetic Resonance Spectroscopy (NMR and Gel Permeation Chromatography (GPC. Differential Scanning Calorimetry (DSC was used to determine lower critical solution temperatures (LCSTs of these copolymers, which are in the range of 17–57 °C. Moreover, the studies on the reducibility of HBPs and swelling behaviours of hydrogels synthesized from these HBPs were conducted. The results demonstrated that we have successfully synthesized hyperbranched polymers with desired dual responsive (thermal and reducible and crosslinkable (via thiol-ene click chemistry properties. In addition, these new HBPs carry the multiplicity of reactive functionalities, such as RAFT agent moieties and multivinyl functional groups, which can afford them with the capacity for further bioconjugation and structure modifications.

  14. RAFT Polymerization of Vinyl Esters: Synthesis and Applications

    Directory of Open Access Journals (Sweden)

    Simon Harrisson

    2014-05-01

    Full Text Available This article is the first comprehensive review on the study and use of vinyl ester monomers in reversible addition fragmentation chain transfer (RAFT polymerization. It covers all the synthetic aspects associated with the definition of precision polymers comprising poly(vinyl ester building blocks, such as the choice of RAFT agent and reaction conditions in order to progress from simple to complex macromolecular architectures. Although vinyl acetate was by far the most studied monomer of the range, many vinyl esters have been considered in order to tune various polymer properties, in particular, solubility in supercritical carbon dioxide (scCO2. A special emphasis is given to novel poly(vinyl alkylates with enhanced solubilities in scCO2, with applications as reactive stabilizers for dispersion polymerization and macromolecular surfactants for CO2 media. Other miscellaneous uses of poly(vinyl esters synthesized by RAFT, for instance as a means to produce poly(vinyl alcohol with controlled characteristics for use in the biomedical area, are also covered.

  15. Perfluorocyclobutyl-containing Amphiphilic Block Copolymers Synthesized by RAFT Polymerization

    Institute of Scientific and Technical Information of China (English)

    LI, Yongjun; ZHANG, Sen; FENG, Chun; ZHANG, Yaqin; LI, Qingnuan; LI, Wenxin; HUANG, Xiaoyu

    2009-01-01

    Amphiphilic block copolymers containing hydrophobic perfluorocyclobutyl-based (PFCB) polyacrylate and hydrophilic poly(ethylene glycol) (PEG) segments were prepared via reversible addition-fragmentation chain transfer (RAP-T) polymerization. The PFCB-containing acrylate monomer, p-(2-(p-tolyloxy)perfluorocyclobutoxy)phenyl acrylate, was first synthesized from commercially available compounds in good yields, and this kind of acrylate monomer can be homopolymerized by free radical polymerization or RAFT polymerization. Kinetic study showed the 2,2'-azobis(isobutyronitrile) (AIBN) initiated and cumyl dithiobenzoate (CDB) mediated RAFT polymerization was in a living fashion, as suggested by the fact that the number-average molecular weights (M_n) increased linearly with the conversions of the monomer, while the polydispersity indices kept less than 1.10. The block polymers with narrow molecular weight distributions (M_w/M_n≤1.21) were prepared through RAFT polymerization using PEG monomethyl ether capped with 4-cyanopentanoic acid dithiobenzoate end group as the macro chain transfer agent (mPEG-CTA). The length of the hydrophobic segment can be tuned by the feed ratio of the PFCB-based acrylate monomer and the extending of the polymerization time. The micellization behavior of the block copolymers in aqueous media was investigated by the fluorescence probe technique.

  16. The foundation mass concrete construction technology of Hongyun Building B tower raft

    Science.gov (United States)

    Liu, Yu; Yin, Suhua; Wu, Yanli; Zhao, Ying

    2017-08-01

    The foundation of Hongyun building B tower is made of raft board foundation which is 3300mm in the thickness and 2800mm beside side of the core tube. It is researched that the raft foundation mass concrete construction technology is expatiated from temperature and cracks of the raft foundation and the temperature control and monitoring of the concrete base slab construction and concrete curing.

  17. EVALUASI KARAKTERISTIK PONDASI BAMBU RAFT & PILE SEBAGAI PERKUATAN TANAH PADA EMBANKMENT JALAN

    OpenAIRE

    Harianto, Tri; Maricar, Iskandar; Djamaluddin, Abd. Rahman; Sitepu, M.Farid; Abdi Putra, Pebryanto

    2012-01-01

    Desain pondasi dengan menggunakan bahan yang ramah lingkungan telah banyak digunakan sebagai inovasi dalam upaya mereduksi deformasi tanah dan penurunan sebagai uniform settlement. Tipe raft bambu digunakan untuk menghasilkan penurunan yang merata pada seluruh bidang lateral embankment jalan. Pile bambu dimanfaaatkan untuk dapat mendukung pondasi raft bambu yang pada aplikasinya sebagai tiang tekan yang mampu menahan tekanan vertical yang ditumpu oleh raft bambu. Untuk menginvestigasi efektif...

  18. Lipid raft facilitated ligation of K-{alpha}1-tubulin by specific antibodies on epithelial cells: Role in pathogenesis of chronic rejection following human lung transplantation

    Energy Technology Data Exchange (ETDEWEB)

    Tiriveedhi, Venkataswarup; Angaswamy, Nataraju [Department of Surgery, Pathology and Immunology, Washington University School of Medicine, St. Louis, MO (United States); Weber, Joseph [Department of Medicine, Washington University School of Medicine, St. Louis, MO (United States); Mohanakumar, T., E-mail: kumart@wustl.edu [Department of Surgery, Pathology and Immunology, Washington University School of Medicine, St. Louis, MO (United States)

    2010-08-20

    Research highlights: {yields} Addition of KAT Abs (+) sera to NHBE culture causes upregulation of growth factors. {yields} Cholesterol depletion causes down regulation of growth factor expression. {yields} Cholesterol depletion is accompanied by loss of membrane bound caveolin. {yields} Thus, we demonstrate lipid raft are critical for efficient ligation of the KAT Abs. -- Abstract: Long term function of human lung allografts is hindered by development of chronic rejection manifested as Bronchiolitis Obliterans Syndrome (BOS). We have previously identified the development of antibodies (Abs) following lung transplantation to K-{alpha}1-tubulin (KAT), an epithelial surface gap junction cytoskeletal protein, in patients who develop BOS. However, the biochemical and molecular basis of the interactions and signaling cascades mediated by KAT Abs are yet to be defined. In this report, we investigated the biophysical basis of the epithelial cell membrane surface interaction between KAT and its specific Abs. Towards this, we analyzed the role of the lipid raft-domains in the membrane interactions which lead to cell signaling and ultimately increased growth factor expression. Normal human bronchial epithelial (NHBE) cells, upon specific ligation with Abs to KAT obtained either from the serum of BOS(+) patients or monoclonal KAT Abs, resulted in upregulation of growth factors VEGF, PDGF, and bFGF (6.4 {+-} 1.1-, 3.2 {+-} 0.9-, and 3.4 {+-} 1.1-fold increase, respectively) all of which are important in the pathogenesis of BOS. To define the role for lipid raft in augmenting surface interactions, we analyzed the changes in the growth factor expression pattern upon depletion and enrichment with lipid raft following the ligation of the epithelial cell membranes with Abs specific for KAT. NHBE cells cultured in the presence of {beta}-methyl cyclodextran ({beta}MCD) had significantly reduced growth factor expression (1.3 {+-} 0.3, vs {beta}MCD untreated being 6.4 {+-} 1.1-fold

  19. Description and assessment of the Raft River Lotic system in the vicinity of the Raft River Geothermal Area. Annual report

    Energy Technology Data Exchange (ETDEWEB)

    1979-12-01

    The Raft River is the only perennial lotic system within this area and one concern has been the impact a spill of geothermal water would have on the biota of the stream. Identification of the structure of these communities is the baseline information which was the objective of this study. The results of the inventory in terms of potential recovery of downstream communities from the impact of geothermal water induced perturbations are discussed.

  20. A simplified analysis method for piled raft and pile group foundations with batter piles

    Science.gov (United States)

    Kitiyodom, Pastsakorn; Matsumoto, Tatsunori

    2002-11-01

    A simplified method of numerical analysis has been developed to estimate the deformation and load distribution of piled raft foundations subjected to vertical, lateral, and moment loads, using a hybrid model in which the flexible raft is modelled as thin plates and the piles as elastic beams and the soil is treated as springs. Both the vertical and lateral resistances of the piles as well as the raft base are incorporated into the model. Pile-soil-pile, pile-soil-raft and raft-soil-raft interactions are taken into account based on Mindlin's solutions for both vertical and lateral forces. The validity of the proposed method is verified through comparisons with several existing methods for single piles, pile groups and piled rafts. Workable design charts are given for the estimation of the lateral displacement and the load distribution of piled rafts from the stiffnesses of the raft alone and the pile group alone. Additionally, parametric studies were carried out concerning batter pile foundations. It was found that the use of batter piles can efficiently improve the deformation characteristics of pile foundations subjected to lateral loads.

  1. Structural determinants of protein partitioning into ordered membrane domains and lipid rafts.

    Science.gov (United States)

    Lorent, Joseph Helmuth; Levental, Ilya

    2015-11-01

    Increasing evidence supports the existence of lateral nanoscopic lipid domains in plasma membranes, known as lipid rafts. These domains preferentially recruit membrane proteins and lipids to facilitate their interactions and thereby regulate transmembrane signaling and cellular homeostasis. The functionality of raft domains is intrinsically dependent on their selectivity for specific membrane components; however, while the physicochemical determinants of raft association for lipids are known, very few systematic studies have focused on the structural aspects that guide raft partitioning of proteins. In this review, we describe biophysical and thermodynamic aspects of raft-mimetic liquid ordered phases, focusing on those most relevant for protein partitioning. Further, we detail the variety of experimental models used to study protein-raft interactions. Finally, we review the existing literature on mechanisms for raft targeting, including lipid post-translational modifications, lipid binding, and transmembrane domain features. We conclude that while protein palmitoylation is a clear raft-targeting signal, few other general structural determinants for raft partitioning have been revealed, suggesting that many discoveries lie ahead in this burgeoning field.

  2. Ageing and hypoxia cause protein aggregation in mitochondria.

    Science.gov (United States)

    Kaufman, Daniel M; Wu, Xia; Scott, Barbara A; Itani, Omar A; Van Gilst, Marc R; Bruce, James E; Michael Crowder, C

    2017-10-01

    Aggregation of cytosolic proteins is a pathological finding in disease states, including ageing and neurodegenerative diseases. We have previously reported that hypoxia induces protein misfolding in Caenorhabditis elegans mitochondria, and electron micrographs suggested protein aggregates. Here, we seek to determine whether mitochondrial proteins actually aggregate after hypoxia and other cellular stresses. To enrich for mitochondrial proteins that might aggregate, we performed a proteomics analysis on purified C. elegans mitochondria to identify relatively insoluble proteins under normal conditions (110 proteins identified) or after sublethal hypoxia (65 proteins). A GFP-tagged mitochondrial protein (UCR-11 - a complex III electron transport chain protein) in the normally insoluble set was found to form widespread aggregates in mitochondria after hypoxia. Five other GFP-tagged mitochondrial proteins in the normally insoluble set similarly form hypoxia-induced aggregates. Two GFP-tagged mitochondrial proteins from the soluble set as well as a mitochondrial-targeted GFP did not form aggregates. Ageing also resulted in aggregates. The number of hypoxia-induced aggregates was regulated by the mitochondrial unfolded protein response (UPRmt) master transcriptional regulator ATFS-1, which has been shown to be hypoxia protective. An atfs-1(loss-of-function) mutant and RNAi construct reduced the number of aggregates while an atfs-1(gain-of-function) mutant increased aggregates. Our work demonstrates that mitochondrial protein aggregation occurs with hypoxic injury and ageing in C. elegans. The UPRmt regulates aggregation and may protect from hypoxia by promoting aggregation of misfolded proteins.

  3. Analysis of detergent-free lipid rafts isolated from CD4+ T cell line: interaction with antigen presenting cells promotes coalescing of lipid rafts

    Directory of Open Access Journals (Sweden)

    Kennedy Colleen

    2011-12-01

    Full Text Available Abstract Background Lipid rafts present on the plasma membrane play an important role in spatiotemporal regulation of cell signaling. Physical and chemical characterization of lipid raft size and assessment of their composition before, and after cell stimulation will aid in developing a clear understanding of their regulatory role in cell signaling. We have used visual and biochemical methods and approaches for examining individual and lipid raft sub-populations isolated from a mouse CD4+ T cell line in the absence of detergents. Results Detergent-free rafts were analyzed before and after their interaction with antigen presenting cells. We provide evidence that the average diameter of lipid rafts isolated from un-stimulated T cells, in the absence of detergents, is less than 100 nm. Lipid rafts on CD4+ T cell membranes coalesce to form larger structures, after interacting with antigen presenting cells even in the absence of a foreign antigen. Conclusions Findings presented here indicate that lipid raft coalescence occurs during cellular interactions prior to sensing a foreign antigen.

  4. RAFT Synthesis and Self-Assembly of Free-Base Porphyrin Cored Star Polymers

    Directory of Open Access Journals (Sweden)

    Lin Wu

    2011-01-01

    Full Text Available Reversible addition fragmentation chain transfer (RAFT synthesis and self-assembly of free-base porphyrin cored star polymers are reported. The polymerization, in the presence of a free-base porphyrin cored chain transfer agent (CTA-FBP, produced porphyrin star polymers with controlled molecular weights and narrow polydispersities for a number of monomers including N, N-dimethylacrylamide (DMA and styrene (St. Well-defined amphiphilic star block copolymers, P-(PS-PDMA4 and P-(PDMA-PS4 (P: porphyrin, were also prepared and used for self-assembly studies. In methanol, a selective solvent for PDMA, spherical micelles were observed for both block copolymers as characterized by TEM. UV-vis studies suggested star-like micelles were formed from P-(PS-PDMA4, while P-(PDMA-PS4 aggregated into flower-like micelles. Spectrophotometric titrations indicated that the optical response of these two micelles to external ions was a function of micellar structures. These structure-related properties will be used for micelle studies and functional material development in the future.

  5. Geology and geophysics of the southern Raft River Valley geothermal area, Idaho, USA

    Science.gov (United States)

    Williams, Paul L.; Mabey, Don R.; Zohdy, Adel A.R.; Hans, Ackerman; Hoover, Donald B.; Pierce, Kenneth L.; Oriel, Steven S.

    1976-01-01

    The Raft River valley, near the boundary of the Snake River plain with the Basin and Range province, is a north-trending late Cenozoic downwarp bounded by faults on the west, south, and east. Pleistocene alluvium and Miocene-Pliocene tuffaceous sediments, conglomerate, and felsic volcanic rocks aggregate 2 km in thickness. Large gravity, magnetic, and total field resistivity highs probably indicate a buried igneous mass that is too old to serve as a heat source. Differing seismic velocities relate to known or inferred structures and to a suspected shallow zone of warm water. Resistivity anomalies reflect differences of both composition and degree of alteration of Cenozoic rocks. Resistivity soundings show a 2 to 5 ohm·m unit with a thickness of 1 km beneath a large part of the valley, and the unit may indicate partly hot water and partly clayey sediments. Observed self-potential anomalies are believed to indicate zones where warm water rises toward the surface. Boiling wells at Bridge, Idaho are near the intersection of north-northeast normal faults which have moved as recently as the late (?) Pleistocene, and an east-northeast structure, probably a right-lateral fault. Deep circulation of ground water in this region of relatively high heat flow and upwelling along faults is the probable cause of the thermal anomaly.

  6. Amphiphilic Fluorinated Block Copolymer Synthesized by RAFT Polymerization for Graphene Dispersions

    Directory of Open Access Journals (Sweden)

    Hyang Moo Lee

    2016-03-01

    Full Text Available Despite the superior properties of graphene, the strong π–π interactions among pristine graphenes yielding massive aggregation impede industrial applications. For non-covalent functionalization of highly-ordered pyrolytic graphite (HOPG, poly(2,2,2-trifluoroethyl methacrylate-block-poly(4-vinyl pyridine (PTFEMA-b-PVP block copolymers were prepared by reversible addition-fragmentation chain transfer (RAFT polymerization and used as polymeric dispersants in liquid phase exfoliation assisted by ultrasonication. The HOPG graphene concentrations were found to be 0.260–0.385 mg/mL in methanolic graphene dispersions stabilized with 10 wt % (relative to HOPG PTFEMA-b-PVP block copolymers after one week. Raman and atomic force microscopy (AFM analyses revealed that HOPG could not be completely exfoliated during the sonication. However, on-line turbidity results confirmed that the dispersion stability of HOPG in the presence of the block copolymer lasted for one week and that longer PTFEMA and PVP blocks led to better graphene dispersibility. Force–distance (F–d analyses of AFM showed that PVP block is a good graphene-philic block while PTFEMA is methanol-philic.

  7. Localization of Kv4.2 and KChIP2 in lipid rafts and modulation of outward K+ currents by membrane cholesterol content in rat left ventricular myocytes.

    Science.gov (United States)

    Rudakova, Elena; Wagner, Michael; Frank, Magdalena; Volk, Tilmann

    2015-02-01

    Lipid rafts are cholesterol-enriched microdomains of the cell membrane. Here we investigate the localization of the pore forming K(+)-channel α-subunit Kv4.2 and the β-subunit KChIP2, underlying the transient outward K(+) current (I to), in lipid rafts in left ventricular myocytes. Furthermore, we explored the impact of membrane cholesterol depletion (using 20 mM methyl-beta-cyclodextrin (MBCD)) on K(+) outward currents. Cholesterol-saturated MBCD (20 mM) served as control. Myocytes were isolated from the left ventricular free wall of Wistar rats. The Triton X-100 (4 °C) insoluble fraction of whole cell protein was analyzed by sucrose density gradient centrifugation followed by Western blot. Kv4.2 and KChIP2 were partially detected in low-density fractions (lipid rafts). MBCD treatment (5 min) resulted in a shift of Kv4.2 and KChIP2 towards high-density fractions. K(+) currents were assessed by whole-cell patch-clamp. MBCD treatment resulted in a 29 ± 3 % decrease in I to (20.0 ± 1.6pApF(-1) vs. 28.5 ± 2.0pApF(-1), n = 15, p lipid rafts. Membrane cholesterol depletion results in ~12 % net reduction of I to, a redistribution of the channel proteins Kv4.2 and KChIP2 and an increased delayed rectifier current.

  8. A raft-associated species of phosphatidylethanolamine interacts with cholesterol comparably to sphingomyelin. A Langmuir-Blodgett monolayer study.

    Directory of Open Access Journals (Sweden)

    Michal Grzybek

    Full Text Available BACKGROUND: Specific interactions between sphingomyelin (SM and cholesterol (Ch are commonly believed to play a key role in the formation of rafts in the biological membranes. A weakness of this model is the implication that these microdomains are confined to the outer bilayer leaflet. The cytoplasmic leaflet, which contains the bulk of phosphatidylethanolamine (PE, phosphatidylserine (PS and phosphatidylinositol (PI, is thought also to harbour half of the membrane cholesterol. Moreover, SLPE (1-stearoyl-2-linoleoyl-sn-glycero-3-phosphatidyl-ethanolamine has recently been shown to be enriched in isolated detergent-resistant membranes (DRM, and this enrichment was independent of the method of isolation of DRM. METHODOLOGY/PRINCIPAL FINDINGS: Here we present quantitative evidence coming from Langmuir-Blodgett monolayer experiments that SLPE forms complex with Ch similar to that between SM and Ch. The energies of these interactions as calculated form the monolayer studies are highly negative. FRAP analysis showed that NBD-Ch recovery was similar in liposomes composed of DOPC/Ch SM or SLPE but not DPPE, providing further evidence that SLPE may form an l(o phase in the presence of high Ch concentration. Experiments on the solubility of DOPC liposomes containing DPPE/Ch (1ratio1, SM/Ch (1ratio1 or SLPE/Ch (1ratio1 showed the presence of Triton X-100 insoluble floating fraction (TIFF in the case of SM/Ch or SLPE/Ch but not in DPPE/Ch containing liposomes. Quantitative determination of particular lipid species in the TIFF fraction confirms the conclusion that SLPE (or similar PE species could be an important constituent of the inner leaflet raft. CONCLUSION: Such interactions suggest a possible existence of inner-leaflet nanoscale assemblies composed of cholesterol complexes with SLPE or similar unsaturated PE species.

  9. Transcytosis of immunoglobulin A in the mouse enterocyte occurs through glycolipid raft- and rab17-containing compartments

    DEFF Research Database (Denmark)

    Hansen, Gert Helge; Niels-Christiansen, L L; Immerdal, Lissi;

    1999-01-01

    electron microscopy and radioactive labeling of mouse small intestinal explants were performed. RESULTS: IgA and the polymeric immunoglobulin receptor/secretory component were present in a raft compartment. Raft association occurred posttranslationally within 30 minutes, preceding secretion...

  10. Aspirin inhibits formation of cholesterol rafts in fluid lipid membranes.

    Science.gov (United States)

    Alsop, Richard J; Toppozini, Laura; Marquardt, Drew; Kučerka, Norbert; Harroun, Thad A; Rheinstädter, Maikel C

    2015-03-01

    Aspirin and other non-steroidal anti-inflammatory drugs have a high affinity for phospholipid membranes, altering their structure and biophysical properties. Aspirin has been shown to partition into the lipid head groups, thereby increasing membrane fluidity. Cholesterol is another well known mediator of membrane fluidity, in turn increasing membrane stiffness. As well, cholesterol is believed to distribute unevenly within lipid membranes leading to the formation of lipid rafts or plaques. In many studies, aspirin has increased positive outcomes for patients with high cholesterol. We are interested if these effects may be, at least partially, the result of a non-specific interaction between aspirin and cholesterol in lipid membranes. We have studied the effect of aspirin on the organization of 1,2-dipalmitoyl-sn-glycero-3-phosphatidylcholine (DPPC) membranes containing cholesterol. Through Langmuir-Blodgett experiments we show that aspirin increases the area per lipid and decreases compressibility at 32.5 mol% cholesterol, leading to a significant increase of fluidity of the membranes. Differential scanning calorimetry provides evidence for the formation of meta-stable structures in the presence of aspirin. The molecular organization of lipids, cholesterol and aspirin was studied using neutron diffraction. While the formation of rafts has been reported in binary DPPC/cholesterol membranes, aspirin was found to locally disrupt membrane organization and lead to the frustration of raft formation. Our results suggest that aspirin is able to directly oppose the formation of cholesterol structures through non-specific interactions with lipid membranes. Copyright © 2014 Elsevier B.V. All rights reserved.

  11. Separation of actin-dependent and actin-independent lipid rafts

    NARCIS (Netherlands)

    Klappe, Karin; Hummel, Ina; Kok, Jan Willem

    2013-01-01

    Lipid rafts have been isolated on the basis of their resistance to various detergents and more recently by using detergent-free procedures. The actin cytoskeleton is now recognized as a dynamic regulator of lipid raft stability. We carefully analyzed the effects of the cortical actin-disrupting agen

  12. Are lipid rafts involved in ABC transporter-mediated drug resistance of tumor cells?

    NARCIS (Netherlands)

    Kok, Jan Willem; Klappe, Karin; Hummel, Ina; Kroesen, Bart-Jan; Sietsma, Hannie; Meszaros, Peter

    2008-01-01

    Since their discovery, lipid rafts have been implicated in several cellular functions, including protein transport in polarized cells and signal transduction. Also in multidrug resistance lipid rafts may be important with regard to the localization of ATP-binding cassette (ABC) transporters in these

  13. Effect of docosahexaenoic acid on interleukin-2 receptor signaling pathway in lipid rafts

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    Recent studies have shown that polyunsaturated fatty acids (PUFA) regulated the functions of membrane receptors in T cells and suppressed T cell -mediated immune responses. But the molecular mechanisms of immune regulation are not yet elucidated. Lipid rafts are plasma membrane microdomains, in which many receptors localized. The purpose of this study was to investigate the effect of DHA on IL-2R signaling pathway in lipid rafts. We isolated lipid rafts by discontinuous sucrose density gradient ultracentrifugation, and found that DHA could change the composition of lipid rafts and alter the distribution of key molecules of IL-2R signaling pathway, which transferred from lipid rafts to detergent-soluble membrane fractions. These results revealed that DHA treatment increased the proportion of polyunsaturated fatty acids especially n(3 polyunsaturated fatty acids in lipid rafts and changed the lipid environment of membrane microdomains in T cells. Compared with controls, DHA changed the localization of IL-2R, STAT5a and STAT5b in lipid rafts and suppressed the expression of JAK1, JAK3 and tyrosine phosphotyrosine in soluble membrane fractions. Summarily, this study concluded the effects of DHA on IL-2R signaling pathway in lipid rafts and explained the regulation of PUFAs in T cell-mediated immune responses.

  14. Dynamic clustering and dispersion of lipid rafts contribute to fusion competence of myogenic cells

    Energy Technology Data Exchange (ETDEWEB)

    Mukai, Atsushi [Department of Regenerative Medicine, National Institute for Longevity Sciences, National Center for Geriatrics and Gerontology, 36-3 Gengo, Morioka, Oobu, Aichi 474-8522 (Japan); Kurisaki, Tomohiro [Department of Growth Regulation, Institute for Frontier Medical Sciences, Kyoto University, 53 Shogoin-Kawahara-cho, Sakyo-ku, Kyoto 606-8507 (Japan); Sato, Satoshi B. [Research Center for Low Temperature and Material Sciences, Kyoto University, Yoshida-honmachi, Kyoto 606-8501 (Japan); Kobayashi, Toshihide [Lipid Biology Laboratory, Discovery Research Institute, RIKEN, Wako, Saitama 351-0198 (Japan); Kondoh, Gen [Laboratory of Animal Experiments for Regeneration, Institute for Frontier Medical Sciences, Kyoto University, 53 Shogoin-Kawahara-cho, Sakyo-ku, Kyoto 606-8507 (Japan); Hashimoto, Naohiro, E-mail: nao@nils.go.jp [Department of Regenerative Medicine, National Institute for Longevity Sciences, National Center for Geriatrics and Gerontology, 36-3 Gengo, Morioka, Oobu, Aichi 474-8522 (Japan)

    2009-10-15

    Recent research indicates that the leading edge of lamellipodia of myogenic cells (myoblasts and myotubes) contains presumptive fusion sites, yet the mechanisms that render the plasma membrane fusion-competent remain largely unknown. Here we show that dynamic clustering and dispersion of lipid rafts contribute to both cell adhesion and plasma membrane union during myogenic cell fusion. Adhesion-complex proteins including M-cadherin, {beta}-catenin, and p120-catenin accumulated at the leading edge of lamellipodia, which contains the presumptive fusion sites of the plasma membrane, in a lipid raft-dependent fashion prior to cell contact. In addition, disruption of lipid rafts by cholesterol depletion directly prevented the membrane union of myogenic cell fusion. Time-lapse recording showed that lipid rafts were laterally dispersed from the center of the lamellipodia prior to membrane fusion. Adhesion proteins that had accumulated at lipid rafts were also removed from the presumptive fusion sites when lipid rafts were laterally dispersed. The resultant lipid raft- and adhesion complex-free area at the leading edge fused with the opposing plasma membrane. These results demonstrate a key role for dynamic clustering/dispersion of lipid rafts in establishing fusion-competent sites of the myogenic cell membrane, providing a novel mechanistic insight into the regulation of myogenic cell fusion.

  15. RAFTing with Raptors: Connecting Science, English Language Arts, and the Common Core State Standards

    Science.gov (United States)

    Senn, Gary J.; McMurtrie, Deborah H.; Coleman, Bridget K.

    2013-01-01

    This article explores using the RAFT strategy (Role, Audience, Format, Topic) for writing in science classes. The framework of the RAFT strategy will be explained, and connections with Common Core State Standards (CCSS) for ELA/Literacy will be discussed. Finally, there will be a discussion of a professional learning experience for teachers in…

  16. Inhibition of Akt signaling by exclusion from lipid rafts in normal and transformed epidermal keratinocytes

    DEFF Research Database (Denmark)

    Calay, Damien; Vind-Kezunovic, Dina; Frankart, Aurelie;

    2010-01-01

    of the phosphatidylinositol-3 kinase (PI3K)/Akt pathway. Raft disruption was achieved in normal human keratinocytes and precancerous (HaCaT) or transformed (A431) keratinocytes by cholesterol extraction or inactivation with methyl-beta-cyclodextrin, filipin III, or 5-cholestene-5-beta-ol. Lipid raft disruption did not affect...

  17. Aminopeptidase N/CD13 is associated with raft membrane microdomains in monocytes

    DEFF Research Database (Denmark)

    Navarrete Santos, A; Roentsch, J; Danielsen, E M;

    2000-01-01

    of monocytes were characterized by the presence of GM1 ganglioside as raft marker molecule and by the high level of tyrosine-phosphorylated proteins. Furthermore, similar to polarized cells, rafts in monocytic cells lack Na(+), K(+)-ATPase. Cholesterol depletion of monocytes by methyl-beta-cyclodextrin greatly...

  18. Dependency of Lipid Raft Diffusion on System Size

    Science.gov (United States)

    Davis, Ryan

    2009-11-01

    An inherit limitation in molecular dynamics is a finite system size. Although periodic boundary conditions can be used to mimic an infinite space, minimizing the artificial effects created by the physical dimensions of the system still remains an issue. Here I will discuss the undesirable relationship between system properties and system size observed via a dissipative particle dynamics approach. In particular, results illustrate a strong dependence between the diffusion of a lipid raft along a membrane and the length of the axis perpendicular to it, even at relatively large system sizes. Methods for obtaining system properties independently of simulation size are crucial for accurate results.

  19. A mechanism of raft formation on both plasma membrane layers

    Science.gov (United States)

    Sornbundit, Kan; Modchang, Charin; Triampo, Wannapong; Triampo, Darapond; Nuttavut, Narin

    2013-10-01

    A double-layered membrane model is proposed to explain raft formation and induction on extracellular (outer) and cytoplasmic (inner) leaflets of plasma membranes in a situation where only the outer layer has a tendency to phase-separate. In the model, lipid exchange with the surrounding medium is allowed on both layers, but lipid exchange between layers is not allowed. Simulations display domain stabilization on both layers. The effect of the lipid recycling frequencies on stationary domain sizes is also investigated. It is found that stationary domain sizes decrease when lipid recycling frequencies are stronger. Linear stability analysis is used to verify the results.

  20. Microvillar membrane microdomains exist at physiological temperature. Role of galectin-4 as lipid raft stabilizer revealed by "superrafts"

    DEFF Research Database (Denmark)

    Braccia, Anita; Villani, Maristella; Immerdal, Lissi

    2003-01-01

    and the transmembrane aminopeptidase N, whereas the peripheral lipid raft protein annexin 2 was essentially absent. In conclusion, in the microvillar membrane, galectin-4, functions as a core raft stabilizer/organizer for other, more loosely raft-associated proteins. The superraft analysis might be applicable to other...

  1. Lipid rafts exist as stable cholesterol-independent microdomains in the brush border membrane of enterocytes

    DEFF Research Database (Denmark)

    Hansen, Gert Helge; Immerdal, Lissi; Thorsen, Evy

    2001-01-01

    Glycosphingolipid/cholesterol-rich membranes ("rafts")can be isolated from many types of cells, but their existence as stable microdomains in the cell membrane has been elusive. Addressing this problem, we studied the distribution of galectin-4, a raft marker, and lactase, a protein excluded from...... rafts, on microvillar vesicles from the enterocyte brush border membrane. Magnetic beads coated with either anti-galectin-4 or anti-lactase antibodies were used for immunoisolation of vesicles followed by double immunogold labeling of the two proteins. A morphometric analysis revealed subpopulations...... of raft-rich and raft-poor vesicles by the following criteria: 1) the lactase/galectin-4 labeling ratio/vesicle captured by the anti-lactase beads was significantly higher (p

  2. Single-molecule microscopy reveals heterogeneous dynamics of lipid raft components upon TCR engagement.

    Science.gov (United States)

    Drbal, Karel; Moertelmaier, Manuel; Holzhauser, Christa; Muhammad, Arshad; Fuertbauer, Elke; Howorka, Stefan; Hinterberger, Maria; Stockinger, Hannes; Schütz, Gerhard J

    2007-05-01

    The existence of lipid rafts and their importance for immunoreceptor signaling is highly debated. By non-invasive single molecule imaging, we analyzed the dynamics of the T-cell antigen receptor (TCR), the lipid raft-associated glycosylphosphatidylinositol (GPI) proteins CD48 and CD59 and the major leukocyte phosphatase CD45 in living naive T lymphocytes. TCR triggering induced the immobilization of CD45 and CD48 at different positions within the T-cell interface. The second GPI protein, CD59, did not co-immobilize indicating lipid raft heterogeneity in living T lymphocytes. A novel biochemical approach confirmed that lipid raft components are not associated in the plasma membrane of resting cells, and variably associate with specific receptors to distinct lipid rafts upon activation.

  3. In Situ Visualization of Lipid Raft Domains by Fluorescent Glycol Chitosan Derivatives.

    Science.gov (United States)

    Jiang, Yao-Wen; Guo, Hao-Yue; Chen, Zhan; Yu, Zhi-Wu; Wang, Zhifei; Wu, Fu-Gen

    2016-07-01

    Lipid rafts are highly ordered small microdomains mainly composed of glycosphingolipids, cholesterol, and protein receptors. Optically distinguishing lipid raft domains in cell membranes would greatly facilitate the investigations on the structure and dynamics of raft-related cellular behaviors, such as signal transduction, membrane transport (endocytosis), adhesion, and motility. However, current strategies about the visualization of lipid raft domains usually suffer from the low biocompatibility of the probes, invasive detection, or ex situ observation. At the same time, naturally derived biomacromolecules have been extensively used in biomedical field and their interaction with cells remains a long-standing topic since it is closely related to various fundamental studies and potential applications. Herein, noninvasive visualization of lipid raft domains in model lipid bilayers (supported lipid bilayers and giant unilamellar vesicles) and live cells was successfully realized in situ using fluorescent biomacromolecules: the fluorescein isothiocyanate (FITC)-labeled glycol chitosan molecules. We found that the lipid raft domains in model or real membranes could be specifically stained by the FITC-labeled glycol chitosan molecules, which could be attributed to the electrostatic attractive interaction and/or hydrophobic interaction between the probes and the lipid raft domains. Since the FITC-labeled glycol chitosan molecules do not need to completely insert into the lipid bilayer and will not disturb the organization of lipids, they can more accurately visualize the raft domains as compared with other fluorescent dyes that need to be premixed with the various lipid molecules prior to the fabrication of model membranes. Furthermore, the FITC-labeled glycol chitosan molecules were found to be able to resist cellular internalization and could successfully visualize rafts in live cells. The present work provides a new way to achieve the imaging of lipid rafts and also

  4. Modelling white-water rafting suitability in a hydropower regulated Alpine River.

    Science.gov (United States)

    Carolli, Mauro; Zolezzi, Guido; Geneletti, Davide; Siviglia, Annunziato; Carolli, Fabiano; Cainelli, Oscar

    2017-02-01

    Cultural and recreational river ecosystem services and their relations with the flow regime are still poorly investigated. We develop a modelling-based approach to assess recreational flow requirements and the spatially distributed river suitability for white-water rafting, a typical service offered by mountain streams, with potential conflicts of interest with hydropower regulation. The approach is based on the principles of habitat suitability modelling using water depth as the main attribute, with preference curves defined through interviews with local rafting guides. The methodology allows to compute streamflow thresholds for conditions of suitability and optimality of a river reach in relation to rafting. Rafting suitability response to past, present and future flow management scenarios can be predicted on the basis of a hydrological model, which is incorporated in the methodology and is able to account for anthropic effects. Rafting suitability is expressed through a novel metric, the "Rafting hydro-suitability index" (RHSI) which quantifies the cumulative duration of suitable and optimal conditions for rafting. The approach is applied on the Noce River (NE Italy), an Alpine River regulated by hydropower production and affected by hydropeaking, which influences suitability at a sub-daily scale. A dedicated algorithm is developed within the hydrological model to resemble hydropeaking conditions with daily flow data. In the Noce River, peak flows associated with hydropeaking support rafting activities in late summer, highlighting the dual nature of hydropeaking in regulated rivers. Rafting suitability is slightly reduced under present, hydropower-regulated flow conditions compared to an idealized flow regime characterised by no water abstractions. Localized water abstractions for small, run-of-the-river hydropower plants are predicted to negatively affect rafting suitability. The proposed methodology can be extended to support decision making for flow

  5. Lipid raft disruption protects mature neurons against amyloid oligomer toxicity.

    Science.gov (United States)

    Malchiodi-Albedi, Fiorella; Contrusciere, Valentina; Raggi, Carla; Fecchi, Katia; Rainaldi, Gabriella; Paradisi, Silvia; Matteucci, Andrea; Santini, Maria Teresa; Sargiacomo, Massimo; Frank, Claudio; Gaudiano, Maria Cristina; Diociaiuti, Marco

    2010-04-01

    A specific neuronal vulnerability to amyloid protein toxicity may account for brain susceptibility to protein misfolding diseases. To investigate this issue, we compared the effects induced by oligomers from salmon calcitonin (sCTOs), a neurotoxic amyloid protein, on cells of different histogenesis: mature and immature primary hippocampal neurons, primary astrocytes, MG63 osteoblasts and NIH-3T3 fibroblasts. In mature neurons, sCTOs increased apoptosis and induced neuritic and synaptic damages similar to those caused by amyloid beta oligomers. Immature neurons and the other cell types showed no cytotoxicity. sCTOs caused cytosolic Ca(2+) rise in mature, but not in immature neurons and the other cell types. Comparison of plasma membrane lipid composition showed that mature neurons had the highest content in lipid rafts, suggesting a key role for them in neuronal vulnerability to sCTOs. Consistently, depletion in gangliosides protected against sCTO toxicity. We hypothesize that the high content in lipid rafts makes mature neurons especially vulnerable to amyloid proteins, as compared to other cell types; this may help explain why the brain is a target organ for amyloid-related diseases.

  6. Monte Carlo study of receptor-lipid raft formation on a cell membrane

    Science.gov (United States)

    Yu-Yang, Paul; Srinivas Reddy, A.; Raychaudhuri, Subhadip

    2012-02-01

    Receptors are cell surface molecules that bind with extracellular ligand molecules leading to propagation of downstream signals and cellular activation. Even though ligand binding-induced formation of receptor-lipid rafts has been implicated in such a process, the formation mechanism of such large stable rafts is not understood. We present findings from our Monte Carlo (MC) simulations involving (i) receptor interaction with the membrane lipids and (ii) lipid-lipid interactions between raft forming lipids. We have developed a hybrid MC simulation method that combines a probabilistic MC simulation with an explicit free energy-based MC scheme. Some of the lipid-mediated interactions, such as the cholesterol-lipid interactions, are simulated in an implicit way. We examine the effect of varying attractive interactions between raft forming lipids and ligand-bound receptors and show that strong coupling between receptor-receptor and receptor-sphingolipid molecules generate raft formation similar to that observed in recent biological experiments. We study the effect of variation of receptor affinity for ligands (as happens in adaptive immune cells) on raft formation. Such affinity dependence in receptor-lipid raft formation provides insight into important problems in B cell biology.

  7. Ginsenoside Rh2 induces ligand-independent Fas activation via lipid raft disruption

    Energy Technology Data Exchange (ETDEWEB)

    Yi, Jae-Sung; Choo, Hyo-Jung [College of Life Sciences and Biotechnology, Korea University, 1, 5-ka, Anam-dong, Sungbuk-gu, Seoul 136-701 (Korea, Republic of); Cho, Bong-Rae [Department of Chemistry, Korea University, Seoul 136-701 (Korea, Republic of); Kim, Hwan-Myung [Department of Chemistry, Ajou University, Suwon, Kyunggi-Do 443-749 (Korea, Republic of); Kim, Yong-Nyun [Division of Specific Organs Center, National Cancer Center, Kyunggi-Do 411-769 (Korea, Republic of); Ham, Young-Mi, E-mail: ymham2@hanmail.net [College of Life Sciences and Biotechnology, Korea University, 1, 5-ka, Anam-dong, Sungbuk-gu, Seoul 136-701 (Korea, Republic of); Ko, Young-Gyu, E-mail: ygko@korea.ac.kr [College of Life Sciences and Biotechnology, Korea University, 1, 5-ka, Anam-dong, Sungbuk-gu, Seoul 136-701 (Korea, Republic of)

    2009-07-24

    Lipid rafts are plasma membrane platforms mediating signal transduction pathways for cellular proliferation, differentiation and apoptosis. Here, we show that membrane fluidity was increased in HeLa cells following treatment with ginsenoside Rh2 (Rh2), as determined by cell staining with carboxy-laurdan (C-laurdan), a two-photon dye designed for measuring membrane hydrophobicity. In the presence of Rh2, caveolin-1 appeared in non-raft fractions after sucrose gradient ultracentrifugation. In addition, caveolin-1 and GM1, lipid raft landmarkers, were internalized within cells after exposure to Rh2, indicating that Rh2 might disrupt lipid rafts. Since cholesterol overloading, which fortifies lipid rafts, prevented an increase in Rh2-induced membrane fluidity, caveolin-1 internalization and apoptosis, lipid rafts appear to be essential for Rh2-induced apoptosis. Moreover, Rh2-induced Fas oligomerization was abolished following cholesterol overloading, and Rh2-induced apoptosis was inhibited following treatment with siRNA for Fas. This result suggests that Rh2 is a novel lipid raft disruptor leading to Fas oligomerization and apoptosis.

  8. Lipid rafts, caveolae, caveolin-1, and entry by Chlamydiae into host cells.

    Science.gov (United States)

    Stuart, Elizabeth S; Webley, Wilmore C; Norkin, Leonard C

    2003-07-01

    Obligate intracellular bacterial pathogens of the genus Chlamydia are reported to enter host cells by both clathrin-dependent and clathrin-independent processes. C. trachomatis serovar K recently was shown to enter cells via caveolae-like lipid raft domains. We asked here how widespread raft-mediated entry might be among the Chlamydia. We show that C. pneumoniae, an important cause of respiratory infections in humans that additionally is associated with cardiovascular disease, and C. psittaci, an important pathogen in domestic mammals and birds that also infects humans, each enter host cells via cholesterol-rich lipid raft microdomains. Further, we show that C. trachomatis serovars E and F also use these domains to enter host cells. The involvement of these membrane domains in the entry of these organisms was indicated by the sensitivity of their entry to the raft-disrupting agents Nystatin and filipin, and by their intracellular association with caveolin-1, a 22-kDa protein associated with the formation of caveolae in rafts. In contrast, caveolin-marked lipid raft domains do not mediate entry of C. trachomatis serovars A, 36B, and C, nor of LGV serovar L2 and MoPn. Finally, we show that entry of each of these chlamydial strains is independent of cellular expression of caveolin-1. Thus, entry via the Nystatin and filipin-sensitive pathway is dependent on lipid rafts containing cholesterol, rather than invaginated caveolae per se.

  9. RAFT: A simulator for ReActive Flow and Transport of groundwater contaminants

    Energy Technology Data Exchange (ETDEWEB)

    Chilakapati, A

    1995-07-01

    This report documents the use of the simulator RAFT for the ReActive flow and Transport of groundwater contaminants. RAFT can be used as a predictive tool in the design and analysis of laboratory and field experiments or it can be used for the estimation of model/process parameters from experiments. RAFT simulates the reactive transport of groundwater contaminants in one, two-, or three-dimensions and it can model user specified source/link configurations and arbitrary injection strategies. A suite of solvers for transport, reactions and regression are employed so that a combination of numerical methods best suited for a problem can be chosen. User specified coupled equilibrium and kinetic reaction systems can be incorporated into RAFT. RAFT is integrated with a symbolic computational language MAPLE, to automate code generation for arbitrary reaction systems. RAFT is expected to be used as a simulator for engineering design for field experiments in groundwater remediation including bioremediation, reactive barriers and redox manipulation. As an integrated tool with both the predictive ability and the ability to analyze experimental data, RAFT can help in the development of remediation technologies, from laboratory to field.

  10. Investigating physiological characteristics of mint in the Raft aquaponic system and perlite medium

    Directory of Open Access Journals (Sweden)

    H. R. Roosta

    2010-12-01

    Full Text Available Aquaponic is a combination of fish and plant cultivated in recirculating systems. Fish culture in closed recirculating systems causes organic waste accumulation in the system. If these metabolites are used for plant nutrition, they are not mere waste, but have economical value and however benefit the fish production systems. Most aquaponic systems are designed as perlite-filled media, thin layer of nutrient solution, or Raft system. Photosynthesis parameters and water relations are good indexes for recognition of healthy plants and are used as tools for studying physiological conditions of plants. In this experiment, mint plants were cultivated in Raft aquaponic system and perlite medium. In Raft system, plant roots were suspending in water and absorbed water from pot bottom. Whereas in perlite system, roots were in the perlite medium and irrigation water was applied from top of the pots. The plants grown in Raft system showed mineral elements’ deficiency as leaf chlorosis. Photosynthesis and water parameters analysis showed that photosynthesis rate, stomatal conductance, transpiration, mezophyll efficiency, water use efficiency and photosynthesis active radiation were higher in the plants grown in perlite than in raft aquaponic system. On the other hand, stomatal conductance, leaf temperature and sub-stomatal CO2 were higher in the raft aquaponic system than perlite medium. Thus, due to better physiological conditions of mint plants, perlite medium might yield better results compared to raft aquaponic system.

  11. Diet-induced docosahexaenoic acid non-raft domains and lymphocyte function.

    Science.gov (United States)

    Raza Shaikh, Saame

    2010-01-01

    Docosahexaenoic acid (DHA) is an n-3 polyunsaturated fatty acid (PUFA) that generally suppresses the function of T lymphocytes and antigen presenting cells (APCs). An emerging mechanism by which DHA modifies lymphocyte function is through changes in the organization of sphingolipid/cholesterol lipid raft membrane domains. Two contradictory models have been proposed to explain how DHA exerts its effects through changes in raft organization. The biophysical model, developed in model membranes, shows that DHA-containing phospholipids form unique non-raft membrane domains, that are organizationally distinct from lipid rafts, which serve to alter the conformation and/or lateral organization of lymphocyte proteins. In contrast, the cellular model on DHA and rafts shows that DHA suppresses lymphocyte function, in part, by directly incorporating into lipid rafts and altering protein activity. To reconcile opposing biophysical and cellular viewpoints, a major revision to existing models is presented herein. Based largely on quantitative microscopy data, it is proposed that DHA, consumed through the diet, modifies lymphocyte function, in part, through the formation of nanometer scale DHA-rich domains. These nano-scale domains disrupt the optimal raft-dependent clustering of proteins necessary for initial signaling. The data covered in this review highlights the importance of understanding how dietary n-3 PUFAs modify lymphocyte membranes, which is essential toward developing these fatty acids as therapeutic agents for treating inflammatory diseases.

  12. Lipid raft disarrangement as a result of neuropathological progresses: a novel strategy for early diagnosis?

    Science.gov (United States)

    Marin, R; Rojo, J A; Fabelo, N; Fernandez, C E; Diaz, M

    2013-08-15

    Lipid rafts are the preferential site of numerous membrane signaling proteins which are involved in neuronal functioning and survival. These proteins are organized in multiprotein complexes, or signalosomes, in close contact with lipid classes particularly represented in lipid rafts (i.e. cholesterol, sphingolipids and saturated fatty acids), which may contribute to physiological responses leading to neuroprotection. Increasing evidence indicates that alteration of lipid composition in raft structures as a consequence of neuropathologies, such as Alzheimer's disease (AD) and Parkinson's disease (PD), causes a dramatic increase in lipid raft order. These phenomena may correlate with perturbation of signalosome activities, likely contributing to neurodegenerative progression. Interestingly, significant disruption of stable raft microenvironments has been already observed in the first stages of either AD or PD, suggesting that these alterations may represent early events in the neuropathological development. In this regard, the search for biochemical markers, such as specific metabolic products altered in the brain at the first steps of the disease, presently represents an important challenge for early diagnostic strategies. Alterations of these biomarkers may be reflected in either plasma or cerebrospinal fluid, thus representing a potential strategy to predict an accurate diagnosis. We propose that pathologically-linked lipid raft markers may be interesting candidates to be explored at this level, although it has not been studied so far to what extent alteration of different signalosome components may be reflected in peripheral fluids. In this mini-review, we will discuss on relevant aspects of lipid rafts that contribute to the modulation of neuropathological events related to AD and PD. An interesting hypothesis is that anomalies on raft biomarkers measured at peripheral fluids might mirror the lipid raft pathology observed in early stages of AD and PD.

  13. Distinguishing aggregate formation and aggregate clearance using cell based assays

    NARCIS (Netherlands)

    E. Eenjes, E.; J.M. Dragich; H. Kampinga (Harm); A. Yamamoto, A.

    2016-01-01

    textabstractThe accumulation of ubiquitinated proteinaceous inclusions represents a complex process, reflecting the disequilibrium between aggregate formation and aggregate clearance. Although decreasing aggregate formation or augmenting aggregate clearance will ultimately lead to diminished aggrega

  14. The effect of consuming meat enriched in walnut paste on platelet aggregation and thrombogenesis varies in volunteers with different apolipoprotein A4 genotype El efecto del consumo de carne enriquecida en pasta de nuez sobre la agregacion plaquetaria y la trombogenesis varia en voluntarios con diferente genotipo para la apolipoproteina A4

    Directory of Open Access Journals (Sweden)

    A. Canales

    2010-10-01

    Full Text Available Background and aim: Low-fat meat (LM has been considered adequate under a cardiovascular disease point of view. Meat enriched in walnut paste (WM consumption produces beneficial antithrombogenic effects but with striking inter-individual variability that may be related to gene polymorphism. Variants in the APOA4 gene (APOA4 polymorphism are known to affect the cardiovascular risk. This study aimed to compare the effects of consumption of WM and LM on platelet aggregation, production of thromboxane A2 (TXA2 and prostacyclin I2 (PGI2, and the TXA2/PGI2 ratio in 22 volunteers with different APOA4 polymorphism. Subjects and Methods: Six volunteers carried the Gln allele (APOA4-2 while 16 were homozygous for the His allele (APOA4-1. Platelet aggregation, TXA2 (measured as TXB2, PGI2 (measured as 6-keto-PGF1α, and the thrombogenic ratio (TXB2/6-keto-PGF1α were determined at baseline and at weeks 3 and 5 for the WM and LM dietary periods. Results: Platelet aggregation decreased significantly (PAntecedentes y objetivos: La carne con bajo contenido graso (LM se considera adecuada bajo el punto de vista cardiovascular. La ingesta de carne enriquecida en pasta de nuez (WM, mejora los efectos antitrombogénicos con una variabilidad inter-individual que puede estar relacionada con el polimorfismo genético. Variaciones en los genes APOA4 (APOA4 del polimorfismo afectan el riesgo cardiovascular. Este estudio compara los efectos de la ingesta de WM y LM sobre la agregación plaquetaria, la producción de tromboxano A2 (TXA2 y prostaciclina I2 (PGI2, y el cociente TXA2/PGI2 ratio en 22 voluntarios con diferentes polimorfismos APOA4. Material y métodos: Seis voluntarios portaban el alelo Gln (APOA4-2 frente a los 16 homozigotos para el alelo His (APOA4-1. La agregación plaquetaria, el TXA2 (medido como TXB2, la PGI2 (medida como 6-keto-PGF1α, y el cociente trombogenético (TXB2/6-keto-PGF1α se determinaron al comienzo y en las semanas 3 y 5 de los periodos

  15. The reversible addition-fragmentation chain transfer (RAFT) miniemulsion polymerization of vinyl acetate mediated by xanthate

    Institute of Scientific and Technical Information of China (English)

    Bo Jiang; Qing Hua Zhang; Xiao Li Zhan; Feng Qiu Chen

    2009-01-01

    The reversible addition-fragmentation chain transfer (RAFT) miniemulsion polymerization of vinyl acetate (VAt) mediated by methyl (methoxycarbonothioyl) sulfanyl acetate (MMSA) was carried out. The results showed that polymerizations initiated by AIBN and KPS proceeded in a controlled way. The RAFT miniemulsion polymerization of VAc initiated by KPS showed the shorter inhibition period, higher propagation rate coefficient and final conversion than those in experiment initiated by AIBN. When the monomer conversion reached 25%, the polydispersity index (PDI) of polymer became broad, which was related to chain transfer reaction in RAFT miniemulsion of VAc.

  16. Selective association of outer surface lipoproteins with the lipid rafts of Borrelia burgdorferi.

    Science.gov (United States)

    Toledo, Alvaro; Crowley, Jameson T; Coleman, James L; LaRocca, Timothy J; Chiantia, Salvatore; London, Erwin; Benach, Jorge L

    2014-03-11

    Borrelia burgdorferi contains unique cholesterol-glycolipid-rich lipid rafts that are associated with lipoproteins. These complexes suggest the existence of macromolecular structures that have not been reported for prokaryotes. Outer surface lipoproteins OspA, OspB, and OspC were studied for their participation in the formation of lipid rafts. Single-gene deletion mutants with deletions of ospA, ospB, and ospC and a spontaneous gene mutant, strain B313, which does not express OspA and OspB, were used to establish their structural roles in the lipid rafts. All mutant strains used in this study produced detergent-resistant membranes, a common characteristic of lipid rafts, and had similar lipid and protein slot blot profiles. Lipoproteins OspA and OspB but not OspC were shown to be associated with lipid rafts by transmission electron microscopy. When the ability to form lipid rafts in live B. burgdorferi spirochetes was measured by fluorescence resonance energy transfer (FRET), strain B313 showed a statistically significant lower level of segregation into ordered and disordered membrane domains than did the wild-type and the other single-deletion mutants. The transformation of a B313 strain with a shuttle plasmid containing ospA restored the phenotype shared by the wild type and the single-deletion mutants, demonstrating that OspA and OspB have redundant functions. In contrast, a transformed B313 overexpressing OspC neither rescued the FRET nor colocalized with the lipid rafts. Because these lipoproteins are expressed at different stages of the life cycle of B. burgdorferi, their selective association is likely to have an important role in the structure of prokaryotic lipid rafts and in the organism's adaptation to changing environments. IMPORTANCE Lipid rafts are cholesterol-rich clusters within the membranes of cells. Lipid rafts contain proteins that have functions in sensing the cell environment and transmitting signals. Although selective proteins are present in

  17. Acute schistosomiasis among Americans rafting the Omo River, Ethiopia.

    Science.gov (United States)

    Istre, G R; Fontaine, R E; Tarr, J; Hopkins, R S

    1984-01-27

    An outbreak of acute schistosomiasis occurred among a group of adventurers who took part in a rafting expedition on the Omo River in Ethiopia in November 1981. Six (55%) of the 11 members of the expedition experienced Schistosoma mansoni infection confirmed by stool examination. Five of these six had symptoms compatible with acute schistosomiasis. Eosinophilia was the most frequent sign of infection (five of six), and fever, the most common symptom (four of six). Despite medical evaluations, illnesses had remained undiagnosed until January 1982. This outbreak should alert physicians to the risk of schistosomiasis among travelers to this part of Africa and the difficulty of correct diagnosis early in the course of the disease.

  18. [Leptospirosis in a family after whitewater rafting in Thailand].

    Science.gov (United States)

    Gallardo, C; Williams-Smith, J; Jaton, K; Asner, S; Cheseaux, J-J; Troillet, N; Manuel, O; Berthod, D

    2015-04-15

    Leptospirosis is a zoonosis found worldwide, with an incidence that is approximately 10 times higher in the tropics than in temperate regions. The main reservoir of leptospirosis is the rat and human infection usually results from exposure to infected animal urine or tissues. Only 10% of cases are symptomatic. We present here two confirmed and two probable cases of leptospirosis in a family returning from whitewater rafting in Thailand, illustrating the wide variety of the clinical manifestations of this infection. Two of the patients were hospitalized and presented a probable Jarisch-Herxheimer reaction after initiation of beta-lactam therapy. The two others patients were treated empirically with doxycycline. We discuss here some relevant aspects of the epidemiology, clinical manifestations, therapy and the challenge of an early diagnosis of leptospirosis.

  19. Integrated system tests of the LSST raft tower modules

    Science.gov (United States)

    O'Connor, P.; Antilogus, P.; Doherty, P.; Haupt, J.; Herrmann, S.; Huffer, M.; Juramy-Giles, C.; Kuczewski, J.; Russo, S.; Stubbs, C.; Van Berg, R.

    2016-07-01

    The science focal plane of the LSST camera is made up of 21 fully autonomous 144 Mpixel imager units designated raft tower modules (RTM). These imagers incorporate nine 4K x 4K fully-depleted CCDs and 144 channels of readout electronics, including a dedicated CMOS video processing ASIC and components that provide CCD biasing and clocking, video digitization, thermal stabilization, and a high degree of monitoring and telemetry. The RTM achieves its performance goals for readout speed, read noise, linearity, and crosstalk with a power budget of less than 400mW/channel. Series production is underway on the first units and the production will run until 2018. We present the RTM final design, tests of the integrated signal chain, and performance results for the fully-integrated module with pre-production CCDs.

  20. Accelerated Combinatorial High Throughput Star Polymer Synthesis via a Rapid One-Pot Sequential Aqueous RAFT (rosa-RAFT) Polymerization Scheme.

    Science.gov (United States)

    Cosson, Steffen; Danial, Maarten; Saint-Amans, Julien Rosselgong; Cooper-White, Justin J

    2017-02-21

    Advanced polymerization methodologies, such as reversible addition-fragmentation transfer (RAFT), allow unprecedented control over star polymer composition, topology, and functionality. However, using RAFT to produce high throughput (HTP) combinatorial star polymer libraries remains, to date, impracticable due to several technical limitations. Herein, the methodology "rapid one-pot sequential aqueous RAFT" or "rosa-RAFT," in which well-defined homo-, copolymer, and mikto-arm star polymers can be prepared in very low to medium reaction volumes (50 µL to 2 mL) via an "arm-first" approach in air within minutes, is reported. Due to the high conversion of a variety of acrylamide/acrylate monomers achieved during each successive short reaction step (each taking 3 min), the requirement for intermediary purification is avoided, drastically facilitating and accelerating the star synthesis process. The presented methodology enables RAFT to be applied to HTP polymeric bio/nanomaterials discovery pipelines, in which hundreds of complex polymeric formulations can be rapidly produced, screened, and scaled up for assessment in a wide range of applications.

  1. RAFT microemulsion polymerization with surface-active chain transfer agent

    Science.gov (United States)

    El-Hedok, Ibrahim Adnan

    The work described in this dissertation focuses on enhancing the polymer nanoparticle synthesis using RAFT (reversible-addition fragmentation chain transfer) in microemulsion polymerization in order to achieve predetermined molecular weight with narrow molecular weight polydispersity. The hypothesis is that the use of an amphiphilic chain transfer agent (surface-active CTA) will confine the CTA to the surface of the particle and thermodynamically favor partitioning of the CTA between micelles and particles throughout the polymerization. Thus, the CTA diffusion from micelles to polymer particles would be minimized and the breadth of the CTA per particle distribution would remain low. We report the successful improved synthesis of poly(butyl acrylate), poly(ethyl acrylate), and poly(styrene) nanoparticles using the RAFT microemulsion polymerization with surface-active CTA. The polymerization kinetics, polymer characteristics and latex size experimental data are presented. The data analysis indicates that the CTA remains partitioned between the micelles and particles by the end of the polymerization, as expected. We also report the synthesis of well-defined core/shell poly(styrene)/poly(butyl acrylate) nanoparticle, having polydispersity index value of 1.1, using semi-continuous microemulsion polymerization with the surface-active CTA. The surface-active CTA restricts the polymerization growth to the surface of the particle, which facilitates the formation of a shell block co-polymers with each subsequent second monomer addition instead of discrete homopolymers. This synthesis method can be used to create a wide range of core/shell polymer nanoparticles with well-defined morphology, given the right feeding conditions.

  2. Lipids in Amyloid-β Processing, Aggregation, and Toxicity.

    Science.gov (United States)

    Morgado, Isabel; Garvey, Megan

    2015-01-01

    Aggregation of amyloid-beta (Aβ) peptide is the major event underlying neuronal damage in Alzheimer's disease (AD). Specific lipids and their homeostasis play important roles in this and other neurodegenerative disorders. The complex interplay between the lipids and the generation, clearance or deposition of Aβ has been intensively investigated and is reviewed in this chapter. Membrane lipids can have an important influence on the biogenesis of Aβ from its precursor protein. In particular, increased cholesterol in the plasma membrane augments Aβ generation and shows a strong positive correlation with AD progression. Furthermore, apolipoprotein E, which transports cholesterol in the cerebrospinal fluid and is known to interact with Aβ or compete with it for the lipoprotein receptor binding, significantly influences Aβ clearance in an isoform-specific manner and is the major genetic risk factor for AD. Aβ is an amphiphilic peptide that interacts with various lipids, proteins and their assemblies, which can lead to variation in Aβ aggregation in vitro and in vivo. Upon interaction with the lipid raft components, such as cholesterol, gangliosides and phospholipids, Aβ can aggregate on the cell membrane and thereby disrupt it, perhaps by forming channel-like pores. This leads to perturbed cellular calcium homeostasis, suggesting that Aβ-lipid interactions at the cell membrane probably trigger the neurotoxic cascade in AD. Here, we overview the roles of specific lipids, lipid assemblies and apolipoprotein E in Aβ processing, clearance and aggregation, and discuss the contribution of these factors to the neurotoxicity in AD.

  3. Environmental and socio-cultural impacts of river rafting and camping on Ganga in Uttarakhand Himalaya

    National Research Council Canada - National Science Library

    Nehal A. Farooquee; Tarun K. Budal; R. K. Maikhuri

    2008-01-01

    .... All these attributes contribute towards wild land-based recreation. The objective of this article is to assess the environmental and socio-cultural impacts of camping and white-water rafting on this river...

  4. Rapid multiplex analysis of lipid raft components with single-cell resolution.

    Science.gov (United States)

    Schatzlmaier, Philipp; Supper, Verena; Göschl, Lisa; Zwirzitz, Alexander; Eckerstorfer, Paul; Ellmeier, Wilfried; Huppa, Johannes B; Stockinger, Hannes

    2015-09-22

    Lipid rafts, a distinct class of highly dynamic cell membrane microdomains, are integral to cell homeostasis, differentiation, and signaling. However, their quantitative examination is challenging when working with rare cells, developmentally heterogeneous cell populations, or molecules that only associate weakly with lipid rafts. We present a fast biochemical method, which is based on lipid raft components associating with the nucleus upon partial lysis during centrifugation through nonionic detergent. Requiring little starting material or effort, our protocol enabled the multidimensional flow cytometric quantitation of raft-resident proteins with single-cell resolution, thereby assessing the membrane components from a few cells in complex cell populations, as well as their dynamics resulting from cell signaling, differentiation, or genetic mutation.

  5. Lipid raft organization and function in the small intestinal brush border

    DEFF Research Database (Denmark)

    Danielsen, E M; Hansen, Gert Helge

    2008-01-01

    The enterocyte brush border of the small intestine is a highly specialized membrane designed to function both as a high capacity digestive/absorptive surface of dietary nutrients and a permeability barrier towards lumenal pathogens. It is characterized by an unusually high content of glycolipids...... (approximately 30% of the total microvillar membrane lipid), enabling the formation of liquid ordered microdomains, better known as lipid rafts. The glycolipid rafts are stabilized by galectin-4, a 36 kDa divalent lectin that cross-links galactosyl (and other carbohydrate) residues present on membrane lipids...... proteinases, are protected from untimely release into the gut lumen. Finally, anti-glycosyl antibodies, synthesized by plasma cells locally in the gut, are deposited on the brush border glycolipid rafts, protecting the epithelium from lumenal pathogens that exploit lipid rafts as portals for entry...

  6. Final Technical Resource Confirmation Testing at the Raft River Geothermal Project, Cassia County, Idaho

    Energy Technology Data Exchange (ETDEWEB)

    Glaspey, Douglas J.

    2008-01-30

    Incorporates the results of flow tests for geothermal production and injection wells in the Raft River geothermal field in southern Idaho. Interference testing was also accomplished across the wellfield.

  7. Phase diagrams of lipid mixtures relevant to the study of membrane rafts

    DEFF Research Database (Denmark)

    Goni, Felix; Alonso, Alicia; Bagatolli, Luis

    2008-01-01

    The present paper reviews the phase properties of phosphatidylcholine-sphingomyelin-cholesterol mixtures, that are often used as models for membrane "raft" microdomains. The available data based on X-ray, microscopic and spectroscopic observations, surface pressure and calorimetric measurements, ...

  8. Fire ants self-assemble into waterproof rafts to survive floods.

    Science.gov (United States)

    Mlot, Nathan J; Tovey, Craig A; Hu, David L

    2011-05-10

    Why does a single fire ant Solenopsis invicta struggle in water, whereas a group can float effortlessly for days? We use time-lapse photography to investigate how fire ants S. invicta link their bodies together to build waterproof rafts. Although water repellency in nature has been previously viewed as a static material property of plant leaves and insect cuticles, we here demonstrate a self-assembled hydrophobic surface. We find that ants can considerably enhance their water repellency by linking their bodies together, a process analogous to the weaving of a waterproof fabric. We present a model for the rate of raft construction based on observations of ant trajectories atop the raft. Central to the construction process is the trapping of ants at the raft edge by their neighbors, suggesting that some "cooperative" behaviors may rely upon coercion.

  9. Phase diagrams of lipid mixtures relevant to the study of membrane rafts

    DEFF Research Database (Denmark)

    Goni, Felix; Alonso, Alicia; Bagatolli, Luis

    2008-01-01

    The present paper reviews the phase properties of phosphatidylcholine-sphingomyelin-cholesterol mixtures, that are often used as models for membrane "raft" microdomains. The available data based on X-ray, microscopic and spectroscopic observations, surface pressure and calorimetric measurements, ...

  10. Fire ants self-assemble into waterproof rafts to survive floods

    Science.gov (United States)

    Mlot, Nathan J.; Tovey, Craig A.; Hu, David L.

    2011-01-01

    Why does a single fire ant Solenopsis invicta struggle in water, whereas a group can float effortlessly for days? We use time-lapse photography to investigate how fire ants S. invicta link their bodies together to build waterproof rafts. Although water repellency in nature has been previously viewed as a static material property of plant leaves and insect cuticles, we here demonstrate a self-assembled hydrophobic surface. We find that ants can considerably enhance their water repellency by linking their bodies together, a process analogous to the weaving of a waterproof fabric. We present a model for the rate of raft construction based on observations of ant trajectories atop the raft. Central to the construction process is the trapping of ants at the raft edge by their neighbors, suggesting that some “cooperative” behaviors may rely upon coercion. PMID:21518911

  11. Optimizing selection of bridge raft based on fuzzy matter-element model and combination weighting

    Institute of Scientific and Technical Information of China (English)

    Li Feng; Shao Fei; Wang Jianping; Li Zhigang

    2012-01-01

    It' s a necessary selection to support the maneuver across Yangtze River by floating bridge constructed by portable steel bridge and civilian ships. It is a comprehensive index for the scheme of bridge raft, containing a variety of technical factors and uncertainties. The optimization is the selection in the constructing time, quantity of equipments and man power. Based on the calculation result of bridge rafts, an evaluating system is established, consisting of index of spacing between interior bays, raft length, truss numbers, operation difficulty and maximal bending stress. A fuzzy matter element model of optimizing selection of bridge rafts was built up by combining quantitative analysis with qualitative analysis. The method of combination weighting was used to calculate the value of weights index to reduce the subjective randomness. The sequence of schemes and the optimization resuh were gained finally based on euclid approach degree. The application result shows that it is simple and practical.

  12. Study of Raft Domains in Model Membrane of DPPC/PE/Cholesterol

    Science.gov (United States)

    Lor, Chai; Hirst, Linda

    2010-10-01

    Raft domains in bilayer membrane are thought to play an important role in many cell functions such as cell signaling or trans-membrane protein activation. Here we use a model membrane consisting of DPPC/PE/cholesterol to examine the structure of membrane rafts and phase interactions. In particular we are interested in lipids containing the highly polyunsaturated fatty acid DHA. We use both atomic force microscopy (AFM) and fluorescence microscopy to obtain information on the structural properties of raft regions and track cholesterol. As expected, we find phase separation of raft regions between saturated and unsaturated lipids. Moreover, we find that the roughness of the domains change with varying cholesterol concentration possibly due to overpacking. This model study provides further understanding of the role of cholesterol in bilayer membrane leading towards a better knowledge of cell membranes.

  13. Analysis of raft foundation design based on considering influence of superstructure stiffness

    Institute of Scientific and Technical Information of China (English)

    WANG Bin; QIU Jianhui; ZHAO Dong; YANG Xi; DAI Shuai

    2009-01-01

    The finite element method was used for analysis of raft foundation design in high-rise building. Compared with other conventional methods, this method is more adapted to the practical condition since both superstructure stiffness and soil conditions were considered in calculation. The calculation results by example show that the base reaction is more uniform and the maximum reaction decreases obviously. Accordingly, the raft foundation design is more economic without any loss of security for high-rise building.

  14. Highly Efficient and Well-controlled Ambient Temperature Raft Polymerization Under Visible Light Radiation

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    1 Results A range of well-defined polymers and their corresponding block copolymers were synthesized via ambient temperature RAFT polymerization under environmentally friendly visible light radiation,using a (2,4,6-trimethylbenzoyl) diphenylphosphine oxide (TPO) photo-initiator[1].The results indicated that the photolysis of chain transfer agent (CTA) functionalities was significantly suppressed under visible light radiation,thus exerting well control over RAFT process,leading to a remarkably living beh...

  15. Pile Spacing Optimization of Short Piled Raft Foundation System for Obtaining Minimum Settlement on Peat

    Science.gov (United States)

    Suro, S. M.; Bakar, I.; Sulaeman, A.

    2016-07-01

    Short Piled Raft is a modified piled raft foundation system, which represents combination between raft foundation and pile foundation, but the length of pile is relatively shorter. The basic concept of the Short Piled Raft foundation system considers the passive soil pressure creating a stiff condition of slab-pile system. This means that the thin concrete slab floats on the supporting soil, while the piles serve as stiffeners concrete slab and also to reduce settlement of the foundation. Slab to pile ratio of such system has been mentioned by several researchers, however the optimum pile spacing of stability performance for obtaining minimum settlement on peat haven't been clearly discussed. In this study, finite element method to simulate the stability performance related to settlement of Short Piled Raft foundation system was used. Short Piled Raft foundation system with concrete slab of 7.0 m x 7.0 m square was assumed to be built on peat with the thickness of 3.5 m. The material properties of pile and raft were constant. The outer diameter of galvanized steel pipe as pile was 0.30 m; raft thickness was considered to be constant of 0.15 m and the length of pile was 3.0 m, while the pile spacing varied from 0.50 to 3.00 m. Point load varied from 0 to 100 kN with increment of 20 kN was also considered as a static load, acted on the centre of the concrete slab. Optimization was done by comparing each numerical result of simulations, thus conclusion can easily be drawn. The optimum pile spacing was 1.00 m which produced minimum settlement of 30.11 mm under the load of 100 kN.

  16. The Contribution of Personality to the Ability to Board a Lift Raft

    Science.gov (United States)

    2005-11-01

    The contribution of personality to the ability to board a life raft Emily -Ana Filardo Donna I. Pickering Megan M.Thompson Defence R&D Canada...DEFENCE DÉFENSE & The contribution of personality to the ability to board a life raft Emily -Ana Filardo Donna I. Pickering Megan M. Thompson...factors of personality. Journal of Personality and Social Psychology, 50, 116-123. 16. Ruiz, M. A., Pincus, A. L., & Dickinson , K. A. (2003). NEO PI

  17. The Contribution of Personality to the Ability to Board a Life Raft

    Science.gov (United States)

    2005-11-01

    The contribution of personality to the ability to board a life raft Emily -Ana Filardo Donna I. Pickering Megan M.Thompson Defence R&D Canada...DEFENCE DÉFENSE & The contribution of personality to the ability to board a life raft Emily -Ana Filardo Donna I. Pickering Megan M. Thompson...factors of personality. Journal of Personality and Social Psychology, 50, 116-123. 16. Ruiz, M. A., Pincus, A. L., & Dickinson , K. A. (2003). NEO PI

  18. Seaweed raft and farm design in the United States and China

    Energy Technology Data Exchange (ETDEWEB)

    McKay, L.B.

    1983-01-01

    The following topics are discussed in this report: pilot-scale mariculture of seaweeds in Washington; experimental-scale raft culture of marine macroalgae in inland marine waters; macroalgal culture in California and China; land-based cultivation of seaweeds: an assessment of their potential yields for 'energy farming'; a design for energy-independent seaweed raft culture in tidal creeks and rivers; and the New York State marine biomass program.

  19. Lipid raft-dependent plasma membrane repair interferes with the activation of B lymphocytes.

    Science.gov (United States)

    Miller, Heather; Castro-Gomes, Thiago; Corrotte, Matthias; Tam, Christina; Maugel, Timothy K; Andrews, Norma W; Song, Wenxia

    2015-12-21

    Cells rapidly repair plasma membrane (PM) damage by a process requiring Ca(2+)-dependent lysosome exocytosis. Acid sphingomyelinase (ASM) released from lysosomes induces endocytosis of injured membrane through caveolae, membrane invaginations from lipid rafts. How B lymphocytes, lacking any known form of caveolin, repair membrane injury is unknown. Here we show that B lymphocytes repair PM wounds in a Ca(2+)-dependent manner. Wounding induces lysosome exocytosis and endocytosis of dextran and the raft-binding cholera toxin subunit B (CTB). Resealing is reduced by ASM inhibitors and ASM deficiency and enhanced or restored by extracellular exposure to sphingomyelinase. B cell activation via B cell receptors (BCRs), a process requiring lipid rafts, interferes with PM repair. Conversely, wounding inhibits BCR signaling and internalization by disrupting BCR-lipid raft coclustering and by inducing the endocytosis of raft-bound CTB separately from BCR into tubular invaginations. Thus, PM repair and B cell activation interfere with one another because of competition for lipid rafts, revealing how frequent membrane injury and repair can impair B lymphocyte-mediated immune responses.

  20. Requirement of transmembrane domain for CD154 association to lipid rafts and subsequent biological events.

    Directory of Open Access Journals (Sweden)

    Nadir Benslimane

    Full Text Available Interaction of CD40 with CD154 leads to recruitment of both molecules into lipid rafts, resulting in bi-directional cell activation. The precise mechanism by which CD154 is translocated into lipid rafts and its impact on CD154 signaling remain largely unknown. Our aim is to identify the domain of CD154 facilitating its association to lipid rafts and the impact of such association on signaling events and cytokine production. Thus, we generated Jurkat cell lines expressing truncated CD154 lacking the cytoplasmic domain or chimeric CD154 in which the transmembrane domain was replaced by that of transferrin receptor I, known to be excluded from lipid rafts. Our results show that cell stimulation with soluble CD40 leads to the association of CD154 wild-type and CD154-truncated, but not CD154-chimera, with lipid rafts. This is correlated with failure of CD154-chimera to activate Akt and p38 MAP kinases, known effectors of CD154 signaling. We also found that CD154-chimera lost the ability to promote IL-2 production upon T cell stimulation with anti-CD3/CD28 and soluble CD40. These results demonstrate the implication of the transmembrane domain of CD154 in lipid raft association, and that this association is necessary for CD154-mediated Akt and p38 activation with consequent enhancement of IL-2 production.

  1. Structure and dynamics of nano-sized raft-like domains on the plasma membrane

    Science.gov (United States)

    Herrera, Fernando E.; Pantano, Sergio

    2012-01-01

    Cell membranes are constitutively composed of thousands of different lipidic species, whose specific organization leads to functional heterogeneities. In particular, sphingolipids, cholesterol and some proteins associate among them to form stable nanoscale domains involved in recognition, signaling, membrane trafficking, etc. Atomic-detail information in the nanometer/second scale is still elusive to experimental techniques. In this context, molecular simulations on membrane systems have provided useful insights contributing to bridge this gap. Here we present the results of a series of simulations of biomembranes representing non-raft and raft-like nano-sized domains in order to analyze the particular structural and dynamical properties of these domains. Our results indicate that the smallest (5 nm) raft domains are able to preserve their distinctive structural and dynamical features, such as an increased thickness, higher ordering, lower lateral diffusion, and specific lipid-ion interactions. The insertion of a transmembrane protein helix into non-raft, extended raft-like, and raft-like nanodomain environments result in markedly different protein orientations, highlighting the interplay between the lipid-lipid and lipid-protein interactions.

  2. Using a SVM to evaluate damage to vibration isolators in an elastic raft system

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    Predicting damage to vibration isolators in a raft experiencing heavy shock loadings from explosions is an important task when designing a raft system.It is also vital to be able to research the vulnerability of heavily shocked floating rafts.The conventional approach to prediction has been unreliable, especially when the allowable values or ultimate values of vibration isolators of supposedly uniform standard in a raft actually have differing and uncertain values due to defective workmanship.A new model for predicting damage to vibration isolators in a shocked floating raft system is presented in this paper.It is based on a support vector machine(SVM), which uses Artificial Intelligence to characterize complicated nonlinear mapping between the impacting environment and damage to the vibration isolators.The effectiveness of the new method for predicting damage was illustrated by numerical simulations, and shown to be effective when relevant parameters of the model were chosen reasonably.The effect determining parameters, including kernel function and penalty factors, has on prediction results is also discussed.It can be concluded that the SVM will probably become a valid tool to study damage or vulnerability in a shocked raft system.

  3. Constitutive modeling of creep behavior in single crystal superalloys: Effects of rafting at high temperatures

    Energy Technology Data Exchange (ETDEWEB)

    Fan, Ya-Nan, E-mail: fanyn12@mails.tsinghua.edu.cn; Shi, Hui-Ji, E-mail: shihj@mail.tsinghua.edu.cn; Qiu, Wen-Hui

    2015-09-17

    Rafting and creep modeling of single crystal superalloys at high temperatures are important for the safety assessment and life prediction in practice. In this research, a new model has been developed to describe the rafting evolution and incorporated into the Cailletaud single crystal plasticity model to simulate the creep behavior. The driving force of rafting is assumed to be the relaxation of the strain energy, and it is calculated with the local stress state, a superposition of the external and misfit stress tensors. In addition, the isotropic coarsening is introduced by the cube root dependence of the microstructure periodicity on creep time based on Ostwal ripening. Then the influence of rafting on creep deformation is taken into account as the Orowan stress in the single crystal plasticity model. The capability of the proposed model is validated with creep experiments of CMSX-4 at 950 °C and 1050 °C. It is able to predict the rafting direction at complex loading conditions and evaluate the channel width during rafting. For [001] tensile creep tests, good agreement has been shown between the model predictions and experimental results at different temperatures and stress levels. The creep acceleration can be captured with this model and is attributed to the microstructure degradation caused by the precipitate coarsening.

  4. Castaways can't be choosers - Homogenization of rafting assemblages on floating seaweeds

    Science.gov (United States)

    Gutow, Lars; Beermann, Jan; Buschbaum, Christian; Rivadeneira, Marcelo M.; Thiel, Martin

    2015-01-01

    After detachment from benthic habitats, the epibiont assemblages on floating seaweeds undergo substantial changes, but little is known regarding whether succession varies among different seaweed species. Given that floating algae may represent a limiting habitat in many regions, rafting organisms may be unselective and colonize any available seaweed patch at the sea surface. This process may homogenize rafting assemblages on different seaweed species, which our study examined by comparing the assemblages on benthic and floating individuals of the fucoid seaweeds Fucus vesiculosus and Sargassum muticum in the northern Wadden Sea (North Sea). Species richness was about twice as high on S. muticum as on F. vesiculosus, both on benthic and floating individuals. In both seaweed species benthic samples were more diverse than floating samples. However, the species composition differed significantly only between benthic thalli, but not between floating thalli of the two seaweed species. Separate analyses of sessile and mobile epibionts showed that the homogenization of rafting assemblages was mainly caused by mobile species. Among these, grazing isopods from the genus Idotea reached extraordinarily high densities on the floating samples from the northern Wadden Sea, suggesting that the availability of seaweed rafts was indeed limiting. Enhanced break-up of algal rafts associated with intense feeding by abundant herbivores might force rafters to recolonize benthic habitats. These colonization processes may enhance successful dispersal of rafting organisms and thereby contribute to population connectivity between sink populations in the Wadden Sea and source populations from up-current regions.

  5. Direct access to dithiobenzoate RAFT agent fragmentation rate coefficients by ESR spin-trapping.

    Science.gov (United States)

    Ranieri, Kayte; Delaittre, Guillaume; Barner-Kowollik, Christopher; Junkers, Thomas

    2014-12-01

    The β-scission rate coefficient of tert-butyl radicals fragmenting off the intermediate resulting from their addition to tert-butyl dithiobenzoate-a reversible addition-fragmentation chain transfer (RAFT) agent-is estimated via the recently introduced electron spin resonance (ESR)-trapping methodology as a function of temperature. The newly introduced ESR-trapping methodology is critically evaluated and found to be reliable. At 20 °C, a fragmentation rate coefficient of close to 0.042 s(-1) is observed, whereas the activation parameters for the fragmentation reaction-determined for the first time-read EA = 82 ± 13.3 kJ mol(-1) and A = (1.4 ± 0.25) × 10(13) s(-1) . The ESR spin-trapping methodology thus efficiently probes the stability of the RAFT adduct radical under conditions relevant for the pre-equilibrium of the RAFT process. It particularly indicates that stable RAFT adduct radicals are indeed formed in early stages of the RAFT poly-merization, at least when dithiobenzoates are employed as controlling agents as stipulated by the so-called slow fragmentation theory. By design of the methodology, the obtained fragmentation rate coefficients represent an upper limit. The ESR spin-trapping methodology is thus seen as a suitable tool for evaluating the fragmentation rate coefficients of a wide range of RAFT adduct radicals. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  6. Differential Association of the Na+/H+ Exchanger Regulatory Factor (NHERF Family of Adaptor Proteins with the Raft- and the Non-Raft Brush Border Membrane Fractions of NHE3

    Directory of Open Access Journals (Sweden)

    Ayesha Sultan

    2013-11-01

    Full Text Available Background/Aims: Trafficking, brush border membrane (BBM retention, and signal-specific regulation of the Na+/H+ exchanger NHE3 is regulated by the Na+/H+ Exchanger Regulatory Factor (NHERF family of PDZ-adaptor proteins, which enable the formation of multiprotein complexes. It is unclear, however, what determines signal specificity of these NHERFs. Thus, we studied the association of NHE3, NHERF1 (EBP50, NHERF2 (E3KARP, and NHERF3 (PDZK1 with lipid rafts in murine small intestinal BBM. Methods: Detergent resistant membranes (“lipid rafts” were isolated by floatation of Triton X-incubated small intestinal BBM from a variety of knockout mouse strains in an Optiprep step gradient. Acid-activated NHE3 activity was measured fluorometrically in BCECF-loaded microdissected villi, or by assessment of CO2/HCO3- mediated increase in fluid absorption in perfused jejunal loops of anethetized mice. Results: NHE3 was found to partially associate with lipid rafts in the native BBM, and NHE3 raft association had an impact on NHE3 transport activity and regulation in vivo. NHERF1, 2 and 3 were differentially distributed to rafts and non-rafts, with NHERF2 being most raft-associated and NHERF3 entirely non-raft associated. NHERF2 expression enhanced the localization of NHE3 to membrane rafts. The use of acid sphingomyelinase-deficient mice, which have altered membrane lipid as well as lipid raft composition, allowed us to test the validity of the lipid raft concept in vivo. Conclusions: The differential association of the NHERFs with the raft-associated and the non-raft fraction of NHE3 in the brush border membrane is one component of the differential and signal-specific NHE3 regulation by the different NHERFs.

  7. Aggregations in Flatworms.

    Science.gov (United States)

    Liffen, C. L.; Hunter, M.

    1980-01-01

    Described is a school project to investigate aggregations in flatworms which may be influenced by light intensity, temperature, and some form of chemical stimulus released by already aggregating flatworms. Such investigations could be adopted to suit many educational levels of science laboratory activities. (DS)

  8. Platelet activation and aggregation

    DEFF Research Database (Denmark)

    Jensen, Maria Sander; Larsen, O H; Christiansen, Kirsten

    2013-01-01

    This study introduces a new laboratory model of whole blood platelet aggregation stimulated by endogenously generated thrombin, and explores this aspect in haemophilia A in which impaired thrombin generation is a major hallmark. The method was established to measure platelet aggregation initiated...

  9. Genotype-induced changes in biophysical properties of frontal cortex lipid raft from APP/PS1 transgenic mice

    Directory of Open Access Journals (Sweden)

    Mario L Diaz

    2012-11-01

    Full Text Available Alterations in the lipid composition of lipid rafts have been demonstrated both in human brain and transgenic mouse models, and it has been postulated that aberrant lipid composition in lipid rafts is partly responsible for neuronal degeneration. In order to assess the impact of lipid changes on lipid raft functional properties, we have aimed at determining relevant physicochemical modifications in lipid rafts purified from frontal cortex of wild type (WT and APP/PS1 double transgenic mice. By means of steady-state fluorescence anisotropy analyses using two lipid soluble fluorescent probes, TMA-DPH (1-[(4-trimethyl-aminophenyl]-6-phenyl-1,3,5-hexatriene and DPH (1,6-diphenyl-1,3,5-hexatriene, we demonstrate that cortical lipid rafts from WT and APP/PS1 animals exhibit different biophysical behaviours, depending on genotype but also on age. Thus, aged APP/PS1 animals exhibited slightly more liquid-ordered lipid rafts than WT counterparts. Membrane microviscosity napp analyses demonstrate that WT lipid rafts are more fluid than APP/PS1 animals of similar age, both at the aqueous interface and hydrophobic core of the membrane. napp in APP/PS1 animals was higher for DPH than for TMA-DPH under similar experimental conditions, indicating that the internal core of the membrane is more viscous than the raft membrane at the aqueous interface. The most dramatic changes in biophysical properties of lipid rafts were observed when membrane cholesterol was depleted with methyl-beta-cyclodextrin. Overall, our results indicate that APP/PS1 genotype strongly affects physicochemical properties of lipid raft. Such alterations appear not to be homogeneous across the raft membrane axis, but rather are more prominent at the membrane plane. These changes correlate with aberrant proportions of sphingomyelin, cholesterol and saturated fatty acids, as well as polyunsaturated fatty acids, measured in lipid rafts from frontal cortex in this familial model of

  10. Triassic rift-raft tectonics in the German Southern North Sea; Flosstektonik in der Trias der Deutschen Suedlichen Nordsee

    Energy Technology Data Exchange (ETDEWEB)

    Thieme, B.; Rockenbauch, K. [BEB Erdgas und Erdoel GmbH, Hannover (Germany)

    2001-12-01

    This paper discusses extensional structures in the German Southern North Sea which were formed during Triassic rifting. Recent salt tectonic concepts and palinspastic methods provided the basis for structural interpretation. The results were compared with examples of the adjacent North Sea sectors and other raft provinces worldwide. Rifting in the German Southern North Sea began in Early Triassic times causing faulting and subsequent lateral movements and rotations of rigid Bunter blocks on the ductile Zechstein salinar substrate. This process, called >>raft-tectonics<<, exerted important controls on the further tectonic and sedimentary evolution during Triassic (and Early Jurassic) times. The structures created were formed by a complex interaction of basin extension, halokinesis and deposition of syn- and post-raft sediments. Variations in the controlling factors led to the different morphologies and styles observed. The German Southern North Sea did not undergo any inversion. As a consequence, the extensional rift-raft features remained without compressional overprint, allowing therefore a detailed interpretation of the deformation history. Main characteristics of the raft features in the German Southern North Sea are: raft structures represent an initial stage of development (extension and translation), rift-raft features within the Triassic interval are genetically related to basement extension (Triassic rifting), Triassic rifting was polyphase, rift-raft features are associated with reactive salt diapirs and/or syn- and post-rift depocenters, both of which developed syn-tectonically in the gaps created between the rafts, controlling factors on the morphologies observed are: moderate extension, low angle detachment (gentle regional dip and low strain rates), thick detachment layer (salt thickness of the Zechstein salinar), and lithology (sediment thickness and competence) of the raft- and post-raft Mesozoic sequences. Finally, the impact of raft tectonics on

  11. Disruption of Lipid Raft Function Increases Expression and Secretion of Monocyte Chemoattractant Protein-1 in 3T3-L1 Adipocytes.

    Science.gov (United States)

    Lu, Juu-Chin; Chiang, Yu-Ting; Lin, Yu-Chun; Chang, Yu-Tzu; Lu, Chia-Yun; Chen, Tzu-Yu; Yeh, Chia-Shan

    2016-01-01

    The adipocyte is unique in its capacity to store lipids. In addition to triglycerides, the adipocyte stores a significant amount of cholesterol. Moreover, obese adipocytes are characterized by a redistribution of cholesterol with depleted cholesterol in the plasma membrane, suggesting that cholesterol perturbation may play a role in adipocyte dysfunction. We used methyl-β-cyclodextrin (MβCD), a molecule with high affinity for cholesterol, to rapidly deplete cholesterol level in differentiated 3T3-L1 adipocytes. We tested whether this perturbation altered adipocyte secretion of monocyte chemoattractant protein-1 (MCP-1), a chemokine that is elevated in obesity and is linked to obesity-associated chronic diseases. Depletion of cholesterol by MβCD increased MCP-1 secretion as well as the mRNA and protein levels, suggesting perturbation at biosynthesis and secretion. Pharmacological inhibition revealed that NF-κB, but not MEK, p38 and JNK, was involved in MβCD-stimulated MCP-1 biosynthesis and secretion in adipocytes. Finally, another cholesterol-binding drug, filipin, also induced MCP-1 secretion without altering membrane cholesterol level. Interestingly, both MβCD and filipin disturbed the integrity of lipid rafts, the membrane microdomains enriched in cholesterol. Thus, the depletion of membrane cholesterol in obese adipocytes may result in dysfunction of lipid rafts, leading to the elevation of proinflammatory signaling and MCP-1 secretion in adipocytes.

  12. Aggregates from mineral wastes

    Directory of Open Access Journals (Sweden)

    Baic Ireneusz

    2016-01-01

    Full Text Available The problem concerning the growing demand for natural aggregates and the need to limit costs, including transportation from remote deposits, cause the increase in growth of interest in aggregates from mineral wastes as well as in technologies of their production and recovery. The paper presents the issue related to the group of aggregates other than natural. A common name is proposed for such material: “alternative aggregates”. The name seems to be fully justified due to adequacy of this term because of this raw materials origin and role, in comparison to the meaning of natural aggregates based on gravel and sand as well as crushed stones. The paper presents characteristics of the market and basic application of aggregates produced from mineral wastes, generated in the mining, power and metallurgical industries as well as material from demolished objects.

  13. Phase separation of myelin sheath in Triton X-114 solution: predominant localization of the 21.5-kDa isoform of myelin basic protein in the lipid raft-associated domain.

    Science.gov (United States)

    Uruse, Michihiro; Yamamoto, Masahiro; Sugawa, Makoto; Matsuura, Keiko; Sato, Yurie; Seiwa, Chika; Watanabe, Kenji; Aiso, Sadakazu; Asou, Hiroaki

    2014-04-01

    Myelin basic protein (MBP) isoforms in the myelin sheath are known to have distinct intracellular expression patterns, which are profoundly related to functional specificity. Determining the differential localization of MBP isoforms is therefore important for understanding their pathophysiological roles. In this study, we have developed a new method for phase separation of myelin. The non-ionic detergent Triton X-114 is used to solubilize myelin sheath which then undergoes phase separation to yield four fractions. The lipid raft-associated proteins and lipids in each fraction were analysed by immunoblotting and lipid analysis, respectively. The present method gives two lipid raft-enriched fractions, one of them was found to contain only lipid raft-associated galactocerebroside and cholesterol as the major lipids. The 21.5-kDa MBP isoforms (21.5 MBP), both unphosphorylated and phosphorylated, were exclusively contained in this fraction. Phosphorylated 21.5 MBP (21.5 pMBP) has been shown to specifically disappear from demyelinated loci. The present analytical method clearly indicated that disappearance of 21.5 pMBP corresponded to demyelination and its reappearance corresponded to prevention of demyelination. Demyelination was also associated with aging and was prevented by the myelin-protecting herbal medicine, Chinpi, a type of dried citrus peel.

  14. Marine Synechococcus Aggregation

    Science.gov (United States)

    Neuer, S.; Deng, W.; Cruz, B. N.; Monks, L.

    2016-02-01

    Cyanobacteria are considered to play an important role in the oceanic biological carbon pump, especially in oligotrophic regions. But as single cells are too small to sink, their carbon export has to be mediated by aggregate formation and possible consumption by zooplankton producing sinking fecal pellets. Here we report results on the aggregation of the ubiquitous marine pico-cyanobacterium Synechococcus as a model organism. We first investigated the mechanism behind such aggregation by studying the potential role of transparent exopolymeric particles (TEP) and the effects of nutrient (nitrogen or phosphorus) limitation on the TEP production and aggregate formation of these pico-cyanobacteria. We further studied the aggregation and subsequent settling in roller tanks and investigated the effects of the clays kaolinite and bentonite in a series of concentrations. Our results show that despite of the lowered growth rates, Synechococcus in nutrient limited cultures had larger cell-normalized TEP production, formed a greater volume of aggregates, and resulted in higher settling velocities compared to results from replete cultures. In addition, we found that despite their small size and lack of natural ballasting minerals, Synechococcus cells could still form aggregates and sink at measureable velocities in seawater. Clay minerals increased the number and reduced the size of aggregates, and their ballasting effects increased the sinking velocity and carbon export potential of aggregates. In comparison with the Synechococcus, we will also present results of the aggregation of the pico-cyanobacterium Prochlorococcus in roller tanks. These results contribute to our understanding in the physiology of marine Synechococcus as well as their role in the ecology and biogeochemistry in oligotrophic oceans.

  15. Lipid raft regulates the initial spreading of melanoma A375 cells by modulating β1 integrin clustering.

    Science.gov (United States)

    Wang, Ruifei; Bi, Jiajia; Ampah, Khamal Kwesi; Zhang, Chunmei; Li, Ziyi; Jiao, Yang; Wang, Xiaoru; Ba, Xueqing; Zeng, Xianlu

    2013-08-01

    Cell adhesion and spreading require integrins-mediated cell-extracellular matrix interaction. Integrins function through binding to extracellular matrix and subsequent clustering to initiate focal adhesion formation and actin cytoskeleton rearrangement. Lipid raft, a liquid ordered plasma membrane microdomain, has been reported to play major roles in membrane motility by regulating cell surface receptor function. Here, we identified that lipid raft integrity was required for β1 integrin-mediated initial spreading of melanoma A375 cells on fibronectin. We found that lipid raft disruption with methyl-β-cyclodextrin led to the inability of focal adhesion formation and actin cytoskeleton rearrangement by preventing β1 integrin clustering. Furthermore, we explored the possible mechanism by which lipid raft regulates β1 integrin clustering and demonstrated that intact lipid raft could recruit and modify some adaptor proteins, such as talin, α-actinin, vinculin, paxillin and FAK. Lipid raft could regulate the location of these proteins in lipid raft fractions and facilitate their binding to β1 integrin, which may be crucial for β1 integrin clustering. We also showed that lipid raft disruption impaired A375 cell migration in both transwell and wound healing models. Together, these findings provide a new insight for the relationship between lipid raft and the regulation of integrins.

  16. Antidepressants Accumulate in Lipid Rafts Independent of Monoamine Transporters to Modulate Redistribution of the G Protein, Gαs.

    Science.gov (United States)

    Erb, Samuel J; Schappi, Jeffrey M; Rasenick, Mark M

    2016-09-16

    Depression is a significant public health problem for which currently available medications, if effective, require weeks to months of treatment before patients respond. Previous studies have shown that the G protein responsible for increasing cAMP (Gαs) is increasingly localized to lipid rafts in depressed subjects and that chronic antidepressant treatment translocates Gαs from lipid rafts. Translocation of Gαs, which shows delayed onset after chronic antidepressant treatment of rats or of C6 glioma cells, tracks with the delayed onset of therapeutic action of antidepressants. Because antidepressants appear to specifically modify Gαs localized to lipid rafts, we sought to determine whether structurally diverse antidepressants accumulate in lipid rafts. Sustained treatment of C6 glioma cells, which lack 5-hydroxytryptamine transporters, showed marked concentration of several antidepressants in raft fractions, as revealed by increased absorbance and by mass fingerprint. Closely related molecules without antidepressant activity did not concentrate in raft fractions. Thus, at least two classes of antidepressants accumulate in lipid rafts and effect translocation of Gαs to the non-raft membrane fraction, where it activates the cAMP-signaling cascade. Analysis of the structural determinants of raft localization may both help to explain the hysteresis of antidepressant action and lead to design and development of novel substrates for depression therapeutics.

  17. A role for lipid rafts in the protection afforded by docosahexaenoic acid against ethanol toxicity in primary rat hepatocytes.

    Science.gov (United States)

    Aliche-Djoudi, Fatiha; Podechard, Normand; Collin, Aurore; Chevanne, Martine; Provost, Emilie; Poul, Martine; Le Hégarat, Ludovic; Catheline, Daniel; Legrand, Philippe; Dimanche-Boitrel, Marie-Thérèse; Lagadic-Gossmann, Dominique; Sergent, Odile

    2013-10-01

    Previously, we demonstrated that eicosapentaenoic acid enhanced ethanol-induced oxidative stress and cell death in primary rat hepatocytes via an increase in membrane fluidity and lipid raft clustering. In this context, another n-3 polyunsaturated fatty acid, docosahexaenoic acid (DHA), was tested with a special emphasis on physical and chemical alteration of lipid rafts. Pretreatment of hepatocytes with DHA reduced significantly ethanol-induced oxidative stress and cell death. DHA protection could be related to an alteration of lipid rafts. Indeed, rafts exhibited a marked increase in membrane fluidity and packing defects leading to the exclusion of a raft protein marker, flotillin. Furthermore, DHA strongly inhibited disulfide bridge formation, even in control cells, thus suggesting a disruption of protein-protein interactions inside lipid rafts. This particular spatial organization of lipid rafts due to DHA subsequently prevented the ethanol-induced lipid raft clustering. Such a prevention was then responsible for the inhibition of phospholipase C-γ translocation into rafts, and consequently of both lysosome accumulation and elevation in cellular low-molecular-weight iron content, a prooxidant factor. In total, the present study suggests that DHA supplementation could represent a new preventive approach for patients with alcoholic liver disease based upon modulation of the membrane structures.

  18. Omega-3 fatty acids, lipid rafts, and T cell signaling.

    Science.gov (United States)

    Hou, Tim Y; McMurray, David N; Chapkin, Robert S

    2016-08-15

    n-3 polyunsaturated fatty acids (PUFA) have been shown in many clinical studies to attenuate inflammatory responses. Although inflammatory responses are orchestrated by a wide spectrum of cells, CD4(+) T cells play an important role in the etiology of many chronic inflammatory diseases such as inflammatory bowel disease and obesity. In light of recent concerns over the safety profiles of non-steroidal anti-inflammatory drugs (NSAIDs), alternatives such as bioactive nutraceuticals are becoming more attractive. In order for these agents to be accepted into mainstream medicine, however, the mechanisms by which nutraceuticals such as n-3 PUFA exert their anti-inflammatory effects must be fully elucidated. Lipid rafts are nanoscale, dynamic domains in the plasma membrane that are formed through favorable lipid-lipid (cholesterol, sphingolipids, and saturated fatty acids) and lipid-protein (membrane-actin cytoskeleton) interactions. These domains optimize the clustering of signaling proteins at the membrane to facilitate efficient cell signaling which is required for CD4(+) T cell activation and differentiation. This review summarizes novel emerging data documenting the ability of n-3 PUFA to perturb membrane-cytoskeletal structure and function in CD4(+) T cells. An understanding of these underlying mechanisms will provide a rationale for the use of n-3 PUFA in the treatment of chronic inflammation.

  19. Partitioning, diffusion, and ligand binding of raft lipid analogs in model and cellular plasma membranes.

    Science.gov (United States)

    Sezgin, Erdinc; Levental, Ilya; Grzybek, Michal; Schwarzmann, Günter; Mueller, Veronika; Honigmann, Alf; Belov, Vladimir N; Eggeling, Christian; Coskun, Unal; Simons, Kai; Schwille, Petra

    2012-07-01

    Several simplified membrane models featuring coexisting liquid disordered (Ld) and ordered (Lo) lipid phases have been developed to mimic the heterogeneous organization of cellular membranes, and thus, aid our understanding of the nature and functional role of ordered lipid-protein nanodomains, termed "rafts". In spite of their greatly reduced complexity, quantitative characterization of local lipid environments using model membranes is not trivial, and the parallels that can be drawn to cellular membranes are not always evident. Similarly, various fluorescently labeled lipid analogs have been used to study membrane organization and function in vitro, although the biological activity of these probes in relation to their native counterparts often remains uncharacterized. This is particularly true for raft-preferring lipids ("raft lipids", e.g. sphingolipids and sterols), whose domain preference is a strict function of their molecular architecture, and is thus susceptible to disruption by fluorescence labeling. Here, we analyze the phase partitioning of a multitude of fluorescent raft lipid analogs in synthetic Giant Unilamellar Vesicles (GUVs) and cell-derived Giant Plasma Membrane Vesicles (GPMVs). We observe complex partitioning behavior dependent on label size, polarity, charge and position, lipid headgroup, and membrane composition. Several of the raft lipid analogs partitioned into the ordered phase in GPMVs, in contrast to fully synthetic GUVs, in which most raft lipid analogs mis-partitioned to the disordered phase. This behavior correlates with the greatly enhanced order difference between coexisting phases in the synthetic system. In addition, not only partitioning, but also ligand binding of the lipids is perturbed upon labeling: while cholera toxin B binds unlabeled GM1 in the Lo phase, it binds fluorescently labeled GMI exclusively in the Ld phase. Fluorescence correlation spectroscopy (FCS) by stimulated emission depletion (STED) nanoscopy on intact

  20. Altered dynamics of a lipid raft associated protein in a kidney model of Fabry disease.

    Science.gov (United States)

    Labilloy, Anatália; Youker, Robert T; Bruns, Jennifer R; Kukic, Ira; Kiselyov, Kirill; Halfter, Willi; Finegold, David; do Monte, Semiramis Jamil Hadad; Weisz, Ora A

    2014-02-01

    Accumulation of globotriaosylceramide (Gb3) and other neutral glycosphingolipids with galactosyl residues is the hallmark of Fabry disease, a lysosomal storage disorder caused by deficiency of the enzyme alpha-galactosidase A (α-gal A). These lipids are incorporated into the plasma membrane and intracellular membranes, with a preference for lipid rafts. Disruption of raft mediated cell processes is implicated in the pathogenesis of several human diseases, but little is known about the effects of the accumulation of glycosphingolipids on raft dynamics in the context of Fabry disease. Using siRNA technology, we have generated a polarized renal epithelial cell model of Fabry disease in Madin-Darby canine kidney cells. These cells present increased levels of Gb3 and enlarged lysosomes, and progressively accumulate zebra bodies. The polarized delivery of both raft-associated and raft-independent proteins was unaffected by α-gal A knockdown, suggesting that accumulation of Gb3 does not disrupt biosynthetic trafficking pathways. To assess the effect of α-gal A silencing on lipid raft dynamics, we employed number and brightness (N&B) analysis to measure the oligomeric status and mobility of the model glycosylphosphatidylinositol (GPI)-anchored protein GFP-GPI. We observed a significant increase in the oligomeric size of antibody-induced clusters of GFP-GPI at the plasma membrane of α-gal A silenced cells compared with control cells. Our results suggest that the interaction of GFP-GPI with lipid rafts may be altered in the presence of accumulated Gb3. The implications of our results with respect to the pathogenesis of Fabry disease are discussed.

  1. Drug Uptake, Lipid Rafts, and Vesicle Trafficking Modulate Resistance to an Anticancer Lysophosphatidylcholine Analogue in Yeast*

    Science.gov (United States)

    Cuesta-Marbán, Álvaro; Botet, Javier; Czyz, Ola; Cacharro, Luis M.; Gajate, Consuelo; Hornillos, Valentín; Delgado, Javier; Zhang, Hui; Amat-Guerri, Francisco; Acuña, A. Ulises; McMaster, Christopher R.; Revuelta, José Luis; Zaremberg, Vanina; Mollinedo, Faustino

    2013-01-01

    The ether-phospholipid edelfosine, a prototype antitumor lipid (ATL), kills yeast cells and selectively kills several cancer cell types. To gain insight into its mechanism of action, we performed chemogenomic screens in the Saccharomyces cerevisiae gene-deletion strain collection, identifying edelfosine-resistant mutants. LEM3, AGP2, and DOC1 genes were required for drug uptake. Edelfosine displaced the essential proton pump Pma1p from rafts, inducing its internalization into the vacuole. Additional ATLs, including miltefosine and perifosine, also displaced Pma1p from rafts to the vacuole, suggesting that this process is a major hallmark of ATL cytotoxicity in yeast. Radioactive and synthetic fluorescent edelfosine analogues accumulated in yeast plasma membrane rafts and subsequently the endoplasmic reticulum. Although both edelfosine and Pma1p were initially located at membrane rafts, internalization of the drug toward endoplasmic reticulum and Pma1p to the vacuole followed different routes. Drug internalization was not dependent on endocytosis and was not critical for yeast cytotoxicity. However, mutants affecting endocytosis, vesicle sorting, or trafficking to the vacuole, including the retromer and ESCRT complexes, prevented Pma1p internalization and were edelfosine-resistant. Our data suggest that edelfosine-induced cytotoxicity involves raft reorganization and retromer- and ESCRT-mediated vesicular transport and degradation of essential raft proteins leading to cell death. Cytotoxicity of ATLs is mainly dependent on the changes they induce in plasma membrane raft-located proteins that lead to their internalization and subsequent degradation. Edelfosine toxicity can be circumvented by inactivating genes that then result in the recycling of internalized cell-surface proteins back to the plasma membrane. PMID:23335509

  2. Drug uptake, lipid rafts, and vesicle trafficking modulate resistance to an anticancer lysophosphatidylcholine analogue in yeast.

    Science.gov (United States)

    Cuesta-Marbán, Álvaro; Botet, Javier; Czyz, Ola; Cacharro, Luis M; Gajate, Consuelo; Hornillos, Valentín; Delgado, Javier; Zhang, Hui; Amat-Guerri, Francisco; Acuña, A Ulises; McMaster, Christopher R; Revuelta, José Luis; Zaremberg, Vanina; Mollinedo, Faustino

    2013-03-22

    The ether-phospholipid edelfosine, a prototype antitumor lipid (ATL), kills yeast cells and selectively kills several cancer cell types. To gain insight into its mechanism of action, we performed chemogenomic screens in the Saccharomyces cerevisiae gene-deletion strain collection, identifying edelfosine-resistant mutants. LEM3, AGP2, and DOC1 genes were required for drug uptake. Edelfosine displaced the essential proton pump Pma1p from rafts, inducing its internalization into the vacuole. Additional ATLs, including miltefosine and perifosine, also displaced Pma1p from rafts to the vacuole, suggesting that this process is a major hallmark of ATL cytotoxicity in yeast. Radioactive and synthetic fluorescent edelfosine analogues accumulated in yeast plasma membrane rafts and subsequently the endoplasmic reticulum. Although both edelfosine and Pma1p were initially located at membrane rafts, internalization of the drug toward endoplasmic reticulum and Pma1p to the vacuole followed different routes. Drug internalization was not dependent on endocytosis and was not critical for yeast cytotoxicity. However, mutants affecting endocytosis, vesicle sorting, or trafficking to the vacuole, including the retromer and ESCRT complexes, prevented Pma1p internalization and were edelfosine-resistant. Our data suggest that edelfosine-induced cytotoxicity involves raft reorganization and retromer- and ESCRT-mediated vesicular transport and degradation of essential raft proteins leading to cell death. Cytotoxicity of ATLs is mainly dependent on the changes they induce in plasma membrane raft-located proteins that lead to their internalization and subsequent degradation. Edelfosine toxicity can be circumvented by inactivating genes that then result in the recycling of internalized cell-surface proteins back to the plasma membrane.

  3. Protein aggregate myopathies

    Directory of Open Access Journals (Sweden)

    Sharma M

    2005-01-01

    Full Text Available Protein aggregate myopathies (PAM are an emerging group of muscle diseases characterized by structural abnormalities. Protein aggregate myopathies are marked by the aggregation of intrinsic proteins within muscle fibers and fall into four major groups or conditions: (1 desmin-related myopathies (DRM that include desminopathies, a-B crystallinopathies, selenoproteinopathies caused by mutations in the, a-B crystallin and selenoprotein N1 genes, (2 hereditary inclusion body myopathies, several of which have been linked to different chromosomal gene loci, but with as yet unidentified protein product, (3 actinopathies marked by mutations in the sarcomeric ACTA1 gene, and (4 myosinopathy marked by a mutation in the MYH-7 gene. While PAM forms 1 and 2 are probably based on impaired extralysosomal protein degradation, resulting in the accumulation of numerous and diverse proteins (in familial types in addition to respective mutant proteins, PAM forms 3 and 4 may represent anabolic or developmental defects because of preservation of sarcomeres outside of the actin and myosin aggregates and dearth or absence of other proteins in these actin or myosin aggregates, respectively. The pathogenetic principles governing protein aggregation within muscle fibers and subsequent structural sarcomeres are still largely unknown in both the putative catabolic and anabolic forms of PAM. Presence of inclusions and their protein composition in other congenital myopathies such as reducing bodies, cylindrical spirals, tubular aggregates and others await clarification. The hitherto described PAMs were first identified by immunohistochemistry of proteins and subsequently by molecular analysis of their genes.

  4. Charged Dust Aggregate Interactions

    Science.gov (United States)

    Matthews, Lorin; Hyde, Truell

    2015-11-01

    A proper understanding of the behavior of dust particle aggregates immersed in a complex plasma first requires a knowledge of the basic properties of the system. Among the most important of these are the net electrostatic charge and higher multipole moments on the dust aggregate as well as the manner in which the aggregate interacts with the local electrostatic fields. The formation of elongated, fractal-like aggregates levitating in the sheath electric field of a weakly ionized RF generated plasma discharge has recently been observed experimentally. The resulting data has shown that as aggregates approach one another, they can both accelerate and rotate. At equilibrium, aggregates are observed to levitate with regular spacing, rotating about their long axis aligned parallel to the sheath electric field. Since gas drag tends to slow any such rotation, energy must be constantly fed into the system in order to sustain it. A numerical model designed to analyze this motion provides both the electrostatic charge and higher multipole moments of the aggregate while including the forces due to thermophoresis, neutral gas drag, and the ion wakefield. This model will be used to investigate the ambient conditions leading to the observed interactions. This research is funded by NSF Grant 1414523.

  5. Ethanol Enhances TGF-β Activity by Recruiting TGF-β Receptors From Intracellular Vesicles/Lipid Rafts/Caveolae to Non-Lipid Raft Microdomains.

    Science.gov (United States)

    Huang, Shuan Shian; Chen, Chun-Lin; Huang, Franklin W; Johnson, Frank E; Huang, Jung San

    2016-04-01

    Regular consumption of moderate amounts of ethanol has important health benefits on atherosclerotic cardiovascular disease (ASCVD). Overindulgence can cause many diseases, particularly alcoholic liver disease (ALD). The mechanisms by which ethanol causes both beneficial and harmful effects on human health are poorly understood. Here we demonstrate that ethanol enhances TGF-β-stimulated luciferase activity with a maximum of 0.5-1% (v/v) in Mv1Lu cells stably expressing a luciferase reporter gene containing Smad2-dependent elements. In Mv1Lu cells, 0.5% ethanol increases the level of P-Smad2, a canonical TGF-β signaling sensor, by ∼ 2-3-fold. Ethanol (0.5%) increases cell-surface expression of the type II TGF-β receptor (TβR-II) by ∼ 2-3-fold from its intracellular pool, as determined by I(125) -TGF-β-cross-linking/Western blot analysis. Sucrose density gradient ultracentrifugation and indirect immunofluorescence staining analyses reveal that ethanol (0.5% and 1%) also displaces cell-surface TβR-I and TβR-II from lipid rafts/caveolae and facilitates translocation of these receptors to non-lipid raft microdomains where canonical signaling occurs. These results suggest that ethanol enhances canonical TGF-β signaling by increasing non-lipid raft microdomain localization of the TGF-β receptors. Since TGF-β plays a protective role in ASCVD but can also cause ALD, the TGF-β enhancer activity of ethanol at low and high doses appears to be responsible for both beneficial and harmful effects. Ethanol also disrupts the location of lipid raft/caveolae of other membrane proteins (e.g., neurotransmitter, growth factor/cytokine, and G protein-coupled receptors) which utilize lipid rafts/caveolae as signaling platforms. Displacement of these membrane proteins induced by ethanol may result in a variety of pathologies in nerve, heart and other tissues.

  6. Regime of aggregate structures and magneto-rheological characteristics of a magnetic rod-like particle suspension: Monte Carlo and Brownian dynamics simulations

    Science.gov (United States)

    Okada, Kazuya; Satoh, Akira

    2017-09-01

    In the present study, we address a suspension composed ferromagnetic rod-like particles to elucidate a regime change in the aggregate structures and the magneto-rheological characteristics. Monte Carlo simulations have been employed for investigating the aggregate structures in thermodynamic equilibrium, and Brownian dynamics simulations for magneto-rheological features in a simple shear flow. The main results obtained here are summarized as follows. For the case of thermodynamic equilibrium, the rod-like particles aggregate to form thick chain-like clusters and the neighboring clusters incline in opposite directions. If the external magnetic field is increased, the thick chain-like clusters in the magnetic field direction grow thicker by adsorbing the neighboring clusters that incline in the opposite direction. Hence, a significant phase change in the particle aggregates is not induced by an increase in the magnetic field strength. For the case of a simple shear flow, even a weak shear flow induces a significant regime change from the thick chain-like clusters of thermodynamic equilibrium into wall-like aggregates composed of short raft-like clusters. A strong external magnetic field drastically changes these aggregates into wall-like aggregates composed of thick chain-like clusters rather than the short raft-like clusters. The internal structure of these aggregates is not strongly influenced by a shear flow, and the formation of the short raft-like clusters is maintained inside the aggregates. The main contribution to the net viscosity is the viscosity component due to magnetic particle-particle interaction forces in relation to the present volumetric fraction. Hence, a larger magnetic interaction strength and also a stronger external magnetic field give rise to a larger magneto-rheological effect. However, the dependence of the viscosity on these factors is governed in a complex manner by whether or not the wall-like aggregates are composed mainly of short raft

  7. Aggregated Computational Toxicology Online Resource

    Data.gov (United States)

    U.S. Environmental Protection Agency — Aggregated Computational Toxicology Online Resource (AcTOR) is EPA's online aggregator of all the public sources of chemical toxicity data. ACToR aggregates data...

  8. Identification of Novel Raft Marker Protein, FlotP in Bacillus anthracis.

    Science.gov (United States)

    Somani, Vikas K; Aggarwal, Somya; Singh, Damini; Prasad, Tulika; Bhatnagar, Rakesh

    2016-01-01

    Lipid rafts are dynamic, nanoscale assemblies of specific proteins and lipids, distributed heterogeneously on eukaryotic membrane. Flotillin-1, a conserved eukaryotic raft marker protein (RMP) harbor SPFH (Stomatin, Prohibitin, Flotillin, and HflK/C) and oligomerization domains to regulate various cellular processes through its interactions with other signaling or transport proteins. Rafts were thought to be absent in prokaryotes hitherto, but recent report of its presence and significance in physiology of Bacillus subtilis prompted us to investigate the same in pathogenic bacteria (PB) also. In prokaryotes, proteins of SPFH2a subfamily show highest identity to SPFH domain of Flotillin-1. Moreover, bacterial genome organization revealed that Flotillin homolog harboring SPFH2a domain exists in an operon with an upstream gene containing NFeD domain. Here, presence of RMP in PB was initially investigated in silico by analyzing the presence of SPFH2a, oligomerization domains in the concerned gene and NfeD domain in the adjacent upstream gene. After investigating 300 PB, four were found to harbor RMP. Among them, domains of Bas0525 (FlotP) of Bacillus anthracis (BA) showed highest identity with characteristic domains of RMP. Considering the global threat of BA as the bioterror agent, it was selected as a model for further in vitro characterization of rafts in PB. In silico and in vitro analysis showed significant similarity of FlotP with numerous attributes of Flotillin-1. Its punctate distribution on membrane with exclusive localization in detergent resistant membrane fraction; strongly favors presence of raft with RMP FlotP in BA. Furthermore, significant effect of Zaragozic acid (ZA), a raft associated lipid biosynthesis inhibitor, on several patho-physiological attributes of BA such as growth, morphology, membrane rigidity etc., were also observed. Specifically, a considerable decrease in membrane rigidity, strongly recommended presence of an unknown raft associated

  9. AFM of the ultrastructural and mechanical properties of lipid-raft-disrupted and/or cold-treated endothelial cells.

    Science.gov (United States)

    Wu, Li; Huang, Jie; Yu, Xiaoxue; Zhou, Xiaoqing; Gan, Chaoye; Li, Ming; Chen, Yong

    2014-02-01

    The nonionic detergent extraction at 4 °C and the cholesterol-depletion-induced lipid raft disruption are the two widely used experimental strategies for lipid raft research. However, the effects of raft disruption and/or cold treatment on the ultrastructural and mechanical properties of cells are still unclear. Here, we evaluated the effects of raft disruption and/or cold (4 °C) treatment on these properties of living human umbilical vein endothelial cells (HUVECs). At first, the cholesterol-depletion-induced raft disruption was visualized by confocal microscopy and atomic force microscopy (AFM) in combination with fluorescent quantum dots. Next, the cold-induced cell contraction and the formation of end-branched filopodia were observed by confocal microscopy and AFM. Then, the cell-surface ultrastructures were imaged by AFM, and the data showed that raft disruption and cold treatment induced opposite effects on cell-surface roughness (a significant decrease and a significant increase, respectively). Moreover, the cell-surface mechanical properties (stiffness and adhesion force) of raft-disrupted- and/or cold-treated HUVECs were measured by the force measurement function of AFM. We found that raft disruption and cold treatment induced parallel effects on cell stiffness (increase) or adhesion force (decrease) and that the combination of the two treatments caused dramatically strengthened effects. Finally, raft disruption was found to significantly impair cell migration as previously reported, whereas temporary cold treatment only caused a slight but nonsignificant decrease in cell migration performed at physiological temperature. Although the mechanisms for causing these results might be complicated and more in-depth studies will be needed, our data may provide important information for better understanding the effects of raft disruption or cold treatment on cells and the two strategies for lipid raft research.

  10. Lipid composition of membrane rafts, isolated with and without detergent, from the spleen of a mouse model of Gaucher disease.

    Science.gov (United States)

    Hattersley, Kathryn J; Hein, Leanne K; Fuller, Maria

    2013-12-01

    Biological membranes are composed of functionally relevant liquid-ordered and liquid-disordered domains that coexist. Within the liquid-ordered domains are low-density microdomains known as rafts with a unique lipid composition that is crucial for their structure and function. Lipid raft composition is altered in sphingolipid storage disorders, and here we determined the lipid composition using a detergent and detergent-free method in spleen tissue, the primary site of pathology, in a mouse model of the sphingolipid storage disorder, Gaucher disease. The accumulating lipid, glucosylceramide, was 30- and 50-fold elevated in the rafts with the detergent and detergent-free method, respectively. Secondary accumulation of di- and trihexosylceramide resided primarily in the rafts with both methods. The phospholipids distributed differently with more than half residing in the rafts with the detergent-free method and less than 10% with the detergent method, with the exception of the fully saturated species that were primarily in the rafts. Individual isoforms of sphingomyelin correlated with detergent-free extraction and more than half resided in the raft fractions. However, this correlation was not seen with the detergent extraction method as sphingomyelin species were spread across both the raft and non-raft domains. Therefore caution must be exercised when interpreting phospholipid distribution in raft domains as it differs considerably depending on the method of isolation. Importantly, both methods revealed the same lipid alterations in the raft domains in the spleen of the Gaucher disease mouse model highlighting that either method is appropriate to determine membrane lipid changes in the diseased state.

  11. Cold induces micro- and nano-scale reorganization of lipid raft markers at mounds of T-cell membrane fluctuations.

    Directory of Open Access Journals (Sweden)

    Yong Chen

    Full Text Available Whether and how cold causes changes in cell-membrane or lipid rafts remain poorly characterized. Using the NSOM/QD and confocal imaging systems, we found that cold caused microscale redistribution of lipid raft markers, GM1 for lipid and CD59 for protein, from the peripheral part of microdomains to the central part on Jurkat T cells, and that cold also induced the nanoscale size-enlargement (1/3- to 2/3-fold of the nanoclusters of lipid raft markers and even the colocalization of GM1 and CD59 nanoclusters. These findings indicate cold-induced lateral rearrangement/coalescence of raft-related membrane heterogeneity. The cold-induced re-distribution of lipid raft markers under a nearly-natural condition provide clues for their alternations, and help to propose a model in which raft lipids associate themselves or interact with protein components to generate functional membrane heterogeneity in response to stimulus. The data also underscore the possible cold-induced artifacts in early-described cold-related experiments and the detergent-resistance-based analyses of lipid rafts at 4 degrees C, and provide a biophysical explanation for recently-reported cold-induced activation of signaling pathways in T cells. Importantly, our fluorescence-topographic NSOM imaging demonstrated that GM1/CD59 raft markers distributed and re-distributed at mounds but not depressions of T-cell membrane fluctuations. Such mound-top distribution of lipid raft markers or lipid rafts provides spatial advantage for lipid rafts or contact molecules interacting readily with neighboring cells or free molecules.

  12. Improvement of Aconitum napellus micropropagation by liquid culture on floating membrane rafts.

    Science.gov (United States)

    Watad, A A; Kochba, M; Nissim, A; Gaba, V

    1995-03-01

    An efficient method was developed using floating membrane rafts (Liferaft(™)) for the micropropagation of Aconitum napellus (Ranunculaceae), a cut flower crop with a low natural propagation rate. This was achieved by introducing shoot tips into culture on Murashige and Skoog's (1962) solid medium, or liquid medium-supported rafts, supplemented by different levels of benzyl adenine (BA). Optimum shoot proliferation on solid medium required 4mg/l BA, whereas for expiants supported on rafts optimal proliferation was achieved at 0.25mg/l BA. Maximum shoot proliferation was found using the floating rafts (propagation ratio of 4.2 per month), 45% higher than the maximum value on solid medium. A similar value could be obtained on solid medium after a period of 2 months. The optimal response to BA was similar for fresh weight gain and shoot length. Growth in a shallow layer of liquid in shake flasks gives a similar shoot multiplication rate to that on floating rafts; however, submerged leaves brown and die.

  13. Effects of acrylonitrile on lymphocyte lipid rafts and RAS/RAF/MAPK/ERK signaling pathways.

    Science.gov (United States)

    Li, X J; Li, B; Huang, J S; Shi, J M; Wang, P; Fan, W; Zhou, Y L

    2014-09-26

    Acrylonitrile (ACN) is a widely used chemical in the production of plastics, resins, nitriles, acrylic fibers, and synthetic rubber. Previous epidemiological investigations and animal studies have confirmed that ACN affects the lymphocytes and spleen. However, the immune toxicity mechanism is unknown. Lipid rafts are cell membrane structures that are rich in cholesterol and involved in cell signal transduction. The B cell lymophoma-10 (Bcl10) protein is a joint protein that is important in lymphocyte development and signal pathways. This study was conducted to examine the in vitro effects of ACN. We separated lipid rafts, and analyzed Bcl10 protein and caveolin. Western blotting was used to detect mitogen-activated protein kinase (MAPK) and phosphorylated MAPK levels. The results indicated that with increasing ACN concentration, the total amount of Bcl10 remained stable, but was concentrated mainly in part 4 to part 11 in electrophoretic band district which is high density in gradient centrifugation. Caveolin-1 was evaluated as a lipid raft marker protein; caveolin-1 content and position were relatively unchanged. Western blotting showed that in a certain range, MAPK protein was secreted at a higher level. At some ACN exposure levels, MAPK protein secretion was significantly decreased compared to the control group (P lipid raft structures, causing Bcl10 protein and lipid raft separation and restraining Ras-Raf-MAPK-extracellular signal-regulated kinase signaling pathways.

  14. Uncoupling Neogenin association with lipid rafts promotes neuronal survival and functional recovery after stroke.

    Science.gov (United States)

    Shabanzadeh, A P; Tassew, N G; Szydlowska, K; Tymianski, M; Banerjee, P; Vigouroux, R J; Eubanks, J H; Huang, L; Geraerts, M; Koeberle, P D; Mueller, B K; Monnier, P P

    2015-05-07

    The dependence receptor Neogenin and its ligand, the repulsive guidance molecule a (RGMa), regulate apoptosis and axonal growth in the developing and the adult central nervous system (CNS). Here, we show that this pathway has also a critical role in neuronal death following stroke, and that providing RGMa to neurons blocks Neogenin-induced death. Interestingly, the Neogenin pro-death function following ischemic insult depends on Neogenin association with lipid rafts. Thus, a peptide that prevents Neogenin association with lipid rafts increased neuronal survival in several in vitro stroke models. In rats, a pro-survival effect was also observed in a model of ocular ischemia, as well as after middle cerebral artery occlusion (MCAO). Treatments that prevented Neogenin association with lipid rafts improved neuronal survival and the complexity of the neuronal network following occlusion of the middle artery. Toward the development of a treatment for stroke, we developed a human anti-RGMa antibody that also prevents Neogenin association with lipid rafts. We show that this antibody also protected CNS tissue from ischemic damage and that its application resulted in a significant functional improvement even when administrated 6 h after artery occlusion. Thus, our results draw attention to the role of Neogenin and lipid rafts as potential targets following stroke.

  15. Lipid Raft is required for PSGL-1 ligation induced HL-60 cell adhesion on ICAM-1.

    Directory of Open Access Journals (Sweden)

    Tingshuang Xu

    Full Text Available P-selectin glycoprotein ligand-1 (PSGL-1 and integrins are adhesion molecules that play critical roles in host defense and innate immunity. PSGL-1 mediates leukocyte rolling and primes leukocytes for integrin-mediated adhesion. However, the mechanism that PSGL-1 as a rolling receptor in regulating integrin activation has not been well characterized. Here, we investigate the function of lipid raft in regulating PSGL-1 induced β2 integrin-mediated HL-60 cells adhesion. PSGL-1 ligation with antibody enhances the β2 integrin activation and β2 integrin-dependent adhesion to ICAM-1. Importantly, with the treatment of methyl-β-cyclodextrin (MβCD, we confirm the role of lipid raft in regulating the activation of β2 integrin. Furthermore, we find that the protein level of PSGL-1 decreased in raft fractions in MβCD treated cells. PSGL-1 ligation induces the recruitment of spleen tyrosine kinase (Syk, a tyrosine kinase and Vav1 (the pivotal downstream effector of Syk signaling pathway involved in cytoskeleton regulation to lipid raft. Inhibition of Syk activity with pharmacologic inhibitor strongly reduces HL-60 cells adhesion, implicating Syk is crucial for PSGL-1 mediated β2 integrin activation. Taken together, we report that ligation of PSGL-1 on HL-60 cells activates β2 integrin, for which lipid raft integrity and Syk activation are responsible. These findings have shed new light on the mechanisms that connect leukocyte initial rolling with subsequent adhesion.

  16. Numerical modeling of fluid flow with rafts: An application to lava flows

    Science.gov (United States)

    Tsepelev, Igor; Ismail-Zadeh, Alik; Melnik, Oleg; Korotkii, Alexander

    2016-07-01

    Although volcanic lava flows do not significantly affect the life of people, its hazard is not negligible as hot lava kills vegetation, destroys infrastructure, and may trigger a flood due to melting of snow/ice. The lava flow hazard can be reduced if the flow patterns are known, and the complexity of the flow with debris is analyzed to assist in disaster risk mitigation. In this paper we develop three-dimensional numerical models of a gravitational flow of multi-phase fluid with rafts (mimicking rigid lava-crust fragments) on a horizontal and topographic surfaces to explore the dynamics and the interaction of lava flows. We have obtained various flow patterns and spatial distribution of rafts depending on conditions at the surface of fluid spreading, obstacles on the way of a fluid flow, raft landing scenarios, and the size of rafts. Furthermore, we analyze two numerical models related to specific lava flows: (i) a model of fluid flow with rafts inside an inclined channel, and (ii) a model of fluid flow from a single vent on an artificial topography, when the fluid density, its viscosity, and the effusion rate vary with time. Although the studied models do not account for lava solidification, crust formation, and its rupture, the results of the modeling may be used for understanding of flows with breccias before a significant lava cooling.

  17. Clathrin to Lipid Raft-Endocytosis via Controlled Surface Chemistry and Efficient Perinuclear Targeting of Nanoparticle.

    Science.gov (United States)

    Chakraborty, Atanu; Jana, Nikhil R

    2015-09-17

    Nanoparticle interacts with live cells depending on their surface chemistry, enters into cell via endocytosis, and is commonly trafficked to an endosome/lysozome that restricts subcellular targeting options. Here we show that nanoparticle surface chemistry can be tuned to alter their cell uptake mechanism and subcellular trafficking. Quantum dot based nanoprobes of 20-30 nm hydrodynamic diameters have been synthesized with tunable surface charge (between +15 mV to -25 mV) and lipophilicity to influence their cellular uptake processes and subcellular trafficking. It is observed that cationic nanoprobe electrostatically interacts with cell membrane and enters into cell via clathrin-mediated endocytosis. At lower surface charge (between +10 mV to -10 mV), the electrostatic interaction with cell membrane becomes weaker, and additional lipid raft endocytosis is initiated. If a lipophilic functional group is introduced on a weakly anionic nanoparticle surface, the uptake mechanism shifts to predominant lipid raft-mediated endocytosis. In particular, the zwitterionic-lipophilic nanoprobe has the unique advantage as it weakly interacts with anionic cell membrane, migrates toward lipid rafts for interaction through lipophilic functional group, and induces lipid raft-mediated endocytosis. While predominate or partial clathrin-mediated entry traffics most of the nanoprobes to lysozome, predominate lipid raft-mediated entry traffics them to perinuclear region, particularly to the Golgi apparatus. This finding would guide in designing appropriate nanoprobe for subcellular targeting and delivery.

  18. Intercalation and structural aspects of macroRAFT agents into MgAl layered double hydroxides

    Directory of Open Access Journals (Sweden)

    Dessislava Kostadinova

    2016-12-01

    Full Text Available Increasing attention has been devoted to the design of layered double hydroxide (LDH-based hybrid materials. In this work, we demonstrate the intercalation by anion exchange process of poly(acrylic acid (PAA and three different hydrophilic random copolymers of acrylic acid (AA and n-butyl acrylate (BA with molar masses ranging from 2000 to 4200 g mol−1 synthesized by reversible addition-fragmentation chain transfer (RAFT polymerization, into LDH containing magnesium(II and aluminium(III intralayer cations and nitrates as counterions (MgAl-NO3 LDH. At basic pH, the copolymer chains (macroRAFT agents carry negative charges which allowed the establishment of electrostatic interactions with the LDH interlayer and their intercalation. The resulting hybrid macroRAFT/LDH materials displayed an expanded interlamellar domain compared to pristine MgAl-NO3 LDH from 1.36 nm to 2.33 nm. Depending on the nature of the units involved into the macroRAFT copolymer (only AA or AA and BA, the intercalation led to monolayer or bilayer arrangements within the interlayer space. The macroRAFT intercalation and the molecular structure of the hybrid phases were further characterized by Fourier transform infrared (FTIR and solid-state 13C, 1H and 27Al nuclear magnetic resonance (NMR spectroscopies to get a better description of the local structure.

  19. Intercalation and structural aspects of macroRAFT agents into MgAl layered double hydroxides

    Science.gov (United States)

    Kostadinova, Dessislava; Cenacchi Pereira, Ana; Lansalot, Muriel; D’Agosto, Franck; Bourgeat-Lami, Elodie; Leroux, Fabrice; Taviot-Guého, Christine; Cadars, Sylvian

    2016-01-01

    Summary Increasing attention has been devoted to the design of layered double hydroxide (LDH)-based hybrid materials. In this work, we demonstrate the intercalation by anion exchange process of poly(acrylic acid) (PAA) and three different hydrophilic random copolymers of acrylic acid (AA) and n-butyl acrylate (BA) with molar masses ranging from 2000 to 4200 g mol−1 synthesized by reversible addition-fragmentation chain transfer (RAFT) polymerization, into LDH containing magnesium(II) and aluminium(III) intralayer cations and nitrates as counterions (MgAl-NO3 LDH). At basic pH, the copolymer chains (macroRAFT agents) carry negative charges which allowed the establishment of electrostatic interactions with the LDH interlayer and their intercalation. The resulting hybrid macroRAFT/LDH materials displayed an expanded interlamellar domain compared to pristine MgAl-NO3 LDH from 1.36 nm to 2.33 nm. Depending on the nature of the units involved into the macroRAFT copolymer (only AA or AA and BA), the intercalation led to monolayer or bilayer arrangements within the interlayer space. The macroRAFT intercalation and the molecular structure of the hybrid phases were further characterized by Fourier transform infrared (FTIR) and solid-state 13C, 1H and 27Al nuclear magnetic resonance (NMR) spectroscopies to get a better description of the local structure.

  20. Recycled aggregates concrete: aggregate and mix properties

    Directory of Open Access Journals (Sweden)

    González-Fonteboa, B.

    2005-09-01

    Full Text Available This study of structural concrete made with recycled concrete aggregate focuses on two issues: 1. The characterization of such aggregate on the Spanish market. This involved conducting standard tests to determine density, water absorption, grading, shape, flakiness and hardness. The results obtained show that, despite the considerable differences with respect to density and water absorption between these and natural aggregates, on the whole recycled aggregate is apt for use in concrete production. 2. Testing to determine the values of basic concrete properties: mix design parameters were established for structural concrete in non-aggressive environments. These parameters were used to produce conventional concrete, and then adjusted to manufacture recycled concrete aggregate (RCA concrete, in which 50% of the coarse aggregate was replaced by the recycled material. Tests were conducted to determine the physical (density of the fresh and hardened material, water absorption and mechanical (compressive strength, splitting tensile strength and modulus of elasticity properties. The results showed that, from the standpoint of its physical and mechanical properties, concrete in which RCA accounted for 50% of the coarse aggregate compared favourably to conventional concrete.

    Se aborda el estudio de hormigones estructurales fabricados con áridos reciclados procedentes de hormigón, incidiéndose en dos aspectos: 1. Caracterización de tales áridos, procedentes del mercado español. Para ello se llevan a cabo ensayos de densidad, absorción, granulometría, coeficiente de forma, índice de lajas y dureza. Los resultados obtenidos han puesto de manifiesto que, a pesar de que existen diferencias notables (sobre todo en cuanto a densidad y absorción con los áridos naturales, las características de los áridos hacen posible la fabricación de hormigones. 2. Ensayos sobre propiedades básicas de los hormigones: se establecen parámetros de dosificaci

  1. Protein Colloidal Aggregation Project

    Science.gov (United States)

    Oliva-Buisson, Yvette J. (Compiler)

    2014-01-01

    To investigate the pathways and kinetics of protein aggregation to allow accurate predictive modeling of the process and evaluation of potential inhibitors to prevalent diseases including cataract formation, chronic traumatic encephalopathy, Alzheimer's Disease, Parkinson's Disease and others.

  2. Propagation of Tau aggregates.

    Science.gov (United States)

    Goedert, Michel; Spillantini, Maria Grazia

    2017-05-30

    Since 2009, evidence has accumulated to suggest that Tau aggregates form first in a small number of brain cells, from where they propagate to other regions, resulting in neurodegeneration and disease. Propagation of Tau aggregates is often called prion-like, which refers to the capacity of an assembled protein to induce the same abnormal conformation in a protein of the same kind, initiating a self-amplifying cascade. In addition, prion-like encompasses the release of protein aggregates from brain cells and their uptake by neighbouring cells. In mice, the intracerebral injection of Tau inclusions induced the ordered assembly of monomeric Tau, followed by its spreading to distant brain regions. Short fibrils constituted the major species of seed-competent Tau. The existence of several human Tauopathies with distinct fibril morphologies has led to the suggestion that different molecular conformers (or strains) of aggregated Tau exist.

  3. Aggregation and Averaging.

    Science.gov (United States)

    Siegel, Irving H.

    The arithmetic processes of aggregation and averaging are basic to quantitative investigations of employment, unemployment, and related concepts. In explaining these concepts, this report stresses need for accuracy and consistency in measurements, and describes tools for analyzing alternative measures. (BH)

  4. Cell aggregation and sedimentation.

    Science.gov (United States)

    Davis, R H

    1995-01-01

    The aggregation of cells into clumps or flocs has been exploited for decades in such applications as biological wastewater treatment, beer brewing, antibiotic fermentation, and enhanced sedimentation to aid in cell recovery or retention. More recent research has included the use of cell aggregation and sedimentation to selectively separate subpopulations of cells. Potential biotechnological applications include overcoming contamination, maintaining plasmid-bearing cells in continuous fermentors, and selectively removing nonviable hybridoma cells from perfusion cultures.

  5. RAFT Polymerization of Styrene and Maleimide in the Presence of Fluoroalcohol: Hydrogen Bonding Effects with Classical Alternating Copolymerization as Reference

    Directory of Open Access Journals (Sweden)

    Fangjun Yao

    2017-03-01

    Full Text Available The impacts of hydrogen bonding on polymerization behavior has been of interest for a long time; however, universality and in-depth understanding are still lacking. For the first time, the effect of hydrogen bonding on the classical alternating-type copolymerization of styrene and maleimide was explored. N-phenylmaleimide (N-PMI/styrene was chosen as a model monomer pair in the presence of hydrogen bonding donor solvent 1,1,1,3,3,3-hexafluoro-2-propanol (HFIP, which interacted with N-PMI via hydrogen bonding. Reversible addition-fragmentation chain transfer polymerization (RAFT technique was used to guarantee the “living” polymerization and thus the homogeneity of chain compositions. In comparison with the polymerization in nonhydrogen bonding donor solvent (toluene, the copolymerization in HFIP exhibited a high rate and a slight deviation from alternating copolymerization tendency. The reactivity ratios of N-PMI and St were revealed to be 0.078 and 0.068, respectively, while the reactivity ratios in toluene were 0.026 and 0.050. These interesting results were reasonably explained by using computer simulations, wherein the steric repulsion and electron induction by the hydrogen bonding between HFIP and NPMI were revealed. This work first elucidated the hydrogen bonding interaction in the classical alternating-type copolymerization, which will enrich the research on hydrogen bonding-induced polymerizations.

  6. Membrane lipid rafts and neurobiology: age-related changes in membrane lipids and loss of neuronal function.

    Science.gov (United States)

    Egawa, Junji; Pearn, Matthew L; Lemkuil, Brian P; Patel, Piyush M; Head, Brian P

    2016-08-15

    A better understanding of the cellular physiological role that plasma membrane lipids, fatty acids and sterols play in various cellular systems may yield more insight into how cellular and whole organ function is altered during the ageing process. Membrane lipid rafts (MLRs) within the plasma membrane of most cells serve as key organizers of intracellular signalling and tethering points of cytoskeletal components. MLRs are plasmalemmal microdomains enriched in sphingolipids, cholesterol and scaffolding proteins; they serve as a platform for signal transduction, cytoskeletal organization and vesicular trafficking. Within MLRs are the scaffolding and cholesterol binding proteins named caveolin (Cav). Cavs not only organize a multitude of receptors including neurotransmitter receptors (NMDA and AMPA receptors), signalling proteins that regulate the production of cAMP (G protein-coupled receptors, adenylyl cyclases, phosphodiesterases (PDEs)), and receptor tyrosine kinases involved in growth (Trk), but also interact with components that modulate actin and tubulin cytoskeletal dynamics (e.g. RhoGTPases and actin binding proteins). MLRs are essential for the regulation of the physiology of organs such as the brain, and age-related loss of cholesterol from the plasma membrane leads to loss of MLRs, decreased presynaptic vesicle fusion, and changes in neurotransmitter release, all of which contribute to different forms of neurodegeneration. Thus, MLRs provide an active membrane domain that tethers and reorganizes the cytoskeletal machinery necessary for membrane and cellular repair, and genetic interventions that restore MLRs to normal cellular levels may be exploited as potential therapeutic means to reverse the ageing and neurodegenerative processes.

  7. Lipid Raft Size and Lipid Mobility in Non-raft Domains Increase during Aging and Are Exacerbated in APP/PS1 Mice Model of Alzheimer's Disease. Predictions from an Agent-Based Mathematical Model.

    Science.gov (United States)

    Santos, Guido; Díaz, Mario; Torres, Néstor V

    2016-01-01

    A connection between lipid rafts and Alzheimer's disease has been studied during the last decades. Mathematical modeling approaches have recently been used to correlate the effects of lipid composition changes in the physicochemical properties of raft-like membranes. Here we propose an agent based model to assess the effect of lipid changes in lipid rafts on the evolution and progression of Alzheimer's disease using lipid profile data obtained in an established model of familial Alzheimer's disease. We have observed that lipid raft size and lipid mobility in non-raft domains are two main factors that increase during age and are accelerated in the transgenic Alzheimer's disease mouse model. The consequences of these changes are discussed in the context of neurotoxic amyloid β production. Our agent based model predicts that increasing sterols (mainly cholesterol) and long-chain polyunsaturated fatty acids (LCPUFA) (mainly DHA, docosahexaenoic acid) proportions in the membrane composition might delay the onset and progression of the disease.

  8. Lipid raft-associated β-adducin is required for PSGL-1-mediated neutrophil rolling on P-selectin.

    Science.gov (United States)

    Xu, Tingshuang; Liu, Wenai; Yang, Chen; Ba, Xueqing; Wang, Xiaoguang; Jiang, Yong; Zeng, Xianlu

    2015-02-01

    Lipid rafts, a liquid-ordered plasma membrane microdomain, are related to cell-surface receptor function. PSGL-1, a major surface receptor protein for leukocyte, also acts as a signaling receptor in leukocyte rolling. To investigate the role of lipid raft in PSGL-1 signaling in human neutrophils, we quantitatively analyzed lipid raft proteome of human promyelocytic leukemia cell line HL-60 cells and identified a lipid raft-associated protein β-adducin. PSGL-1 ligation induced dissociation of the raft-associated protein β-adducin from lipid rafts and actin, as well as phosphorylation of β-adducin, indicating a transient uncoupling of lipid rafts from the actin cytoskeleton. Knockdown of β-adducin greatly attenuated HL-60 cells rolling on P-selectin. We also showed that Src kinase is crucial for PSGL-1 ligation-induced β-adducin phosphorylation and relocation. Taken together, these results show that β-adducin is a pivotal lipid raft-associated protein in PSGL-1-mediated neutrophil rolling on P-selectin.

  9. the role of the actin cytoskeleton and lipid rafts in the localization and function of the ABCC1 transporter

    NARCIS (Netherlands)

    Kok, Jan; Klappe, Katharina; Hummel, Ina

    2014-01-01

    ATP-binding cassette (ABC) transporters are known to be important factors in multidrug resistance of tumor cells. Lipid rafts have been implicated in their localization in the plasma membrane, where they function as drug efflux pumps. This specific localization in rafts may support the activity of A

  10. Nanoscopic substructures of raft-mimetic liquid-ordered membrane domains revealed by high-speed single-particle tracking

    Science.gov (United States)

    Wu, Hsiao-Mei; Lin, Ying-Hsiu; Yen, Tzu-Chi; Hsieh, Chia-Lung

    2016-02-01

    Lipid rafts are membrane nanodomains that facilitate important cell functions. Despite recent advances in identifying the biological significance of rafts, nature and regulation mechanism of rafts are largely unknown due to the difficulty of resolving dynamic molecular interaction of rafts at the nanoscale. Here, we investigate organization and single-molecule dynamics of rafts by monitoring lateral diffusion of single molecules in raft-containing reconstituted membranes supported on mica substrates. Using high-speed interferometric scattering (iSCAT) optical microscopy and small gold nanoparticles as labels, motion of single lipids is recorded via single-particle tracking (SPT) with nanometer spatial precision and microsecond temporal resolution. Processes of single molecules partitioning into and escaping from the raft-mimetic liquid-ordered (Lo) domains are directly visualized in a continuous manner with unprecedented clarity. Importantly, we observe subdiffusion of saturated lipids in the Lo domain in microsecond timescale, indicating the nanoscopic heterogeneous molecular arrangement of the Lo domain. Further analysis of the diffusion trajectory shows the presence of nano-subdomains of the Lo phase, as small as 10 nm, which transiently trap the lipids. Our results provide the first experimental evidence of non-uniform molecular organization of the Lo phase, giving a new view of how rafts recruit and confine molecules in cell membranes.

  11. Nanoscopic substructures of raft-mimetic liquid-ordered membrane domains revealed by high-speed single-particle tracking.

    Science.gov (United States)

    Wu, Hsiao-Mei; Lin, Ying-Hsiu; Yen, Tzu-Chi; Hsieh, Chia-Lung

    2016-01-01

    Lipid rafts are membrane nanodomains that facilitate important cell functions. Despite recent advances in identifying the biological significance of rafts, nature and regulation mechanism of rafts are largely unknown due to the difficulty of resolving dynamic molecular interaction of rafts at the nanoscale. Here, we investigate organization and single-molecule dynamics of rafts by monitoring lateral diffusion of single molecules in raft-containing reconstituted membranes supported on mica substrates. Using high-speed interferometric scattering (iSCAT) optical microscopy and small gold nanoparticles as labels, motion of single lipids is recorded via single-particle tracking (SPT) with nanometer spatial precision and microsecond temporal resolution. Processes of single molecules partitioning into and escaping from the raft-mimetic liquid-ordered (Lo) domains are directly visualized in a continuous manner with unprecedented clarity. Importantly, we observe subdiffusion of saturated lipids in the Lo domain in microsecond timescale, indicating the nanoscopic heterogeneous molecular arrangement of the Lo domain. Further analysis of the diffusion trajectory shows the presence of nano-subdomains of the Lo phase, as small as 10 nm, which transiently trap the lipids. Our results provide the first experimental evidence of non-uniform molecular organization of the Lo phase, giving a new view of how rafts recruit and confine molecules in cell membranes.

  12. Self-Assembly of Semiconducting Single-Walled Carbon Nanotubes into Dense, Aligned Rafts

    CERN Document Server

    Wu, Justin; Antaris, Alexander; Choi, Charina L; Xie, Liming; Wu, Yingpeng; Diao, Shuo; Chen, Changxin; Chen, Yongsheng; Dai, Hongjie

    2013-01-01

    Single-walled carbon nanotubes are promising nanoelectronic materials but face long-standing challenges including production of pure semiconducting SWNTs and integration into ordered structures. Here, highly pure semiconducting single-walled carbon nanotubes are separated from bulk materials and self-assembled into densely aligned rafts driven by depletion attraction forces. Microscopy and spectroscopy revealed a high degree of alignment and a high packing density of ~100 tubes/micron within SWNT rafts. Field-effect transistors made from aligned SWNT rafts afforded short channel (~150 nm long) devices comprised of tens of purely semiconducting SWNTs derived from chemical separation within a < 1 micron channel width, achieving unprecedented high on-currents (up to ~120 microamperes per device) with high on/off ratios. The average on-current was ~ 3-4 microamperes per tube. The results demonstrated densely aligned high quality semiconducting SWNTs for integration into high performance nanoelectronics.

  13. Membrane microdomains, rafts, and detergent-resistant membranes in plants and fungi.

    Science.gov (United States)

    Malinsky, Jan; Opekarová, Miroslava; Grossmann, Guido; Tanner, Widmar

    2013-01-01

    The existence of specialized microdomains in plasma membranes, postulated for almost 25 years, has been popularized by the concept of lipid or membrane rafts. The idea that detergent-resistant membranes are equivalent to lipid rafts, which was generally abandoned after a decade of vigorous data accumulation, contributed to intense discussions about the validity of the raft concept. The existence of membrane microdomains, meanwhile, has been verified by unequivocal independent evidence. This review summarizes the current state of research in plants and fungi with respect to common aspects of both kingdoms. In these organisms, principally immobile microdomains large enough for microscopic detection have been visualized. These microdomains are found in the context of cell-cell interactions (plant symbionts and pathogens), membrane transport, stress, and polarized growth, and the data corroborate at least three mechanisms of formation. As documented in this review, modern methods of visualization of lateral membrane compartments are also able to uncover the functional relevance of membrane microdomains.

  14. Activation of c-Src and Fyn kinases by protein tyrosine phosphatase RPTPalpha is substrate-specific and compatible with lipid raft localization

    DEFF Research Database (Denmark)

    Vacaresse, Nathalie; Møller, Bente; Danielsen, Erik Michael;

    2008-01-01

    and the lipid raft scaffolding protein Cbp/PAG. A significant fraction of RPTPa is present in lipid rafts, where its targets Fyn and Cbp/PAG reside, and growth factor-mediated SFK activation within this compartment is strictly dependent on RPTPa. Forced concentration of RPTPa into lipid rafts is compatible...

  15. Detergent-Based Isolation of Yeast Membrane Rafts: An Inquiry-Based Laboratory Series for the Undergraduate Cell Biology or Biochemistry Lab

    Science.gov (United States)

    Willhite, D. Grant; Wright, Stephen E.

    2009-01-01

    Lipid rafts have been implicated in numerous cellular processes including cell signaling, endocytosis, and even viral infection. Isolation of these lipid rafts often involves detergent treatment of the membrane to dissolve nonraft components followed by separation of raft regions in a density gradient. We present here an inquiry-based lab series…

  16. Detergent-Based Isolation of Yeast Membrane Rafts: An Inquiry-Based Laboratory Series for the Undergraduate Cell Biology or Biochemistry Lab

    Science.gov (United States)

    Willhite, D. Grant; Wright, Stephen E.

    2009-01-01

    Lipid rafts have been implicated in numerous cellular processes including cell signaling, endocytosis, and even viral infection. Isolation of these lipid rafts often involves detergent treatment of the membrane to dissolve nonraft components followed by separation of raft regions in a density gradient. We present here an inquiry-based lab series…

  17. Gel Domains in the Plasma Membrane of Saccharomyces cerevisiae: HIGHLY ORDERED, ERGOSTEROL-FREE, AND SPHINGOLIPID-ENRICHED LIPID RAFTS*

    OpenAIRE

    Aresta-Branco, Francisco; Cordeiro, André M.; Marinho, H. Susana; Cyrne, Luísa; Antunes, Fernando; de Almeida, Rodrigo F. M.

    2010-01-01

    The plasma membrane of Saccharomyces cerevisiae was studied using the probes trans-parinaric acid and diphenylhexatriene. Diphenylhexatriene anisotropy is a good reporter of global membrane order. The fluorescence lifetimes of trans-parinaric acid are particularly sensitive to the presence and nature of ordered domains, but thus far they have not been measured in yeast cells. A long lifetime typical of the gel phase (>30 ns) was found in wild-type (WT) cells from two different genetic backgro...

  18. On ripples and rafts: Curvature induced nanoscale structures in lipid membranes

    Science.gov (United States)

    Schmid, Friederike; Dolezel, Stefan; Lenz, Olaf; Meinhardt, Sebastian

    2014-03-01

    We develop an elastic theory that predicts the spontaneous formation of nanoscale structures in lipid bilayers which locally phase separate between two phases with different spontaneous monolayer curvature. The theory rationalizes in a unified manner the observation of a variety of nanoscale structures in lipid membranes: Rippled states in one-component membranes, lipid rafts in multicomponent membranes. Furthermore, we report on recent observations of rippled states and rafts in simulations of a simple coarse-grained model for lipid bilayers, which are compatible with experimental observations and with our elastic model.

  19. The concrete technology of post pouring zone of raft foundation of Hongyun Building B tower

    Science.gov (United States)

    Yin, Suhua; Yu, Liu; Wu, Yanli; Zhao, Ying

    2017-08-01

    The foundation of Hongyun building B tower is made of raft board foundation which is 3300mm in the thickness concreted pouring amount of large and the late poured band in the pouring settlement formed. The temperature of the pouring settlement was controlled in order to prevent the crack of the construction of the late poured band. The steel of post pouring band was designed and monitorred. The quality of post pouring band quality is guaranteed in the raft concrete foundation of Hongyun Building B tower.

  20. QM/MM Studies of Contemporary and Novel Membrane Raft Fluorescent Probes

    Directory of Open Access Journals (Sweden)

    Hannah L. Blake

    2014-07-01

    Full Text Available We have studied a number of contemporary and novel membrane probes, selected for their structural similarity to membrane raft components, in order to properly anchor themselves within a sphingolipid/cholesterol rich region. A QM/MM approach was adopted in order to understand the structural and electrostatic influences of fluorescence emission shifts of the probes in different lipid and solvation environments. The proposed modifications to the membrane probes have shown encouraging data relating not only to emission shifts within the membrane, but also their ability to anchor within a membrane raft domain and the stability to internalization within a membrane system.

  1. Graft Copolymerization of Styrene from Poly(vinyl alcohol via RAFT Process

    Directory of Open Access Journals (Sweden)

    Gholam Ali Koohmareh

    2011-01-01

    Full Text Available Polystyrene, PS, was grafted from poly(vinyl alcohol, PVA, backbone by reversible addition-fragmentation chain transfer (RAFT polymerization. The hydroxyl groups of the PVA were converted into aromatic dithioester RAFT agent and polymerization began in the presence of this agent. The structure of compounds was confirmed by FT-IR and 1HNMR spectroscopy. The graft copolymer was characterized by thermogravimetric analysis (TGA, X-ray diffraction (XRD, and scanning electron microscopy (SEM. Grafted polystyrene chains were cleaved from the PVA backbone by acidic hydrolysis of the PVA-g-PS, and its polydispersity index, PDI, was determined by gel permeation chromatography (GPC showing narrow molecular weight distribution.

  2. Results of short-term corrosion evaluation tests at Raft River

    Energy Technology Data Exchange (ETDEWEB)

    Miller, R.L.

    1977-10-01

    Four categories of short-term materials evaluation tests were conducted in geothermal fluid from Raft River Geothermal Experiment, Well No. 1, to obtain corrosion data relevant to the design of the Raft River Thermal Loop Facility. Test programs are described and the testing philosophies are discussed. All materials and configurations which were tested are identified and details of posttest visual examinations are presented. The materials are then assigned to appropriate performance categories on the basis of test behavior, and the possible service limitations are appraised.

  3. Optical dynamics of molecular aggregates

    NARCIS (Netherlands)

    de Boer, Steven

    2006-01-01

    The subject of this thesis is the spectroscopy and dynamics of molecular aggregates in amorphous matrices. Aggregates of three different molecules were studied. The molecules are depicted in Fig. (1.1). Supersaturated solutions of these molecules show aggregate formation. Aggregation is a process si

  4. Lipid raft-mediated Fas/CD95 apoptotic signaling in leukemic cells and normal leukocytes and therapeutic implications.

    Science.gov (United States)

    Gajate, Consuelo; Mollinedo, Faustino

    2015-11-01

    Plasma membrane is now recognized to contain tightly packed cholesterol/sphingolipid-rich domains, known as lipid or membrane rafts, which are more ordered than the surrounding lipid bilayer. Lipid rafts are crucial for the compartmentalization of signaling processes in the membrane, mostly involved in cell survival and immune response. However, in the last 15 years, a large body of evidence has also identified raft platforms as scaffolds for the recruitment and clustering of death receptor Fas/CD95 and downstream signaling molecules, leading to the concept of death-promoting lipid rafts. This raft-Fas/CD95 coclustering was first described at the early 2000s as the underlying mechanism for the proapoptotic action of the alkylphospholipid analog edelfosine in leukemic cells, hence facilitating protein-protein interactions and conveying apoptotic signals independently of Fas/CD95 ligand. Edelfosine induces apoptosis in hematologic cancer cells and activated T-lymphocytes. Fas/CD95 raft coclustering is also promoted by Fas/CD95 ligand, agonistic Fas/CD95 antibodies, and additional antitumor drugs. Thus, death receptor recruitment in rafts is a physiologic process leading to cell demise that can be pharmacologically modulated. This redistribution and local accumulation of apoptotic molecules in membrane rafts, which are usually accompanied by displacement of survival signaling molecules, highlight how alterations in the apoptosis/survival signaling balance in specialized membrane regions modulate cell fate. Membrane rafts might also modulate apoptotic and nonapoptotic death receptor signaling. Here, we discuss the role of lipid rafts in Fas/CD95-mediated apoptotic cell signaling in hematologic cancer cells and normal leukocytes, with a special emphasis on their involvement as putative therapeutic targets in cancer and autoimmune diseases.

  5. Observing Convective Aggregation

    Science.gov (United States)

    Holloway, Christopher E.; Wing, Allison A.; Bony, Sandrine; Muller, Caroline; Masunaga, Hirohiko; L'Ecuyer, Tristan S.; Turner, David D.; Zuidema, Paquita

    2017-06-01

    Convective self-aggregation, the spontaneous organization of initially scattered convection into isolated convective clusters despite spatially homogeneous boundary conditions and forcing, was first recognized and studied in idealized numerical simulations. While there is a rich history of observational work on convective clustering and organization, there have been only a few studies that have analyzed observations to look specifically for processes related to self-aggregation in models. Here we review observational work in both of these categories and motivate the need for more of this work. We acknowledge that self-aggregation may appear to be far-removed from observed convective organization in terms of time scales, initial conditions, initiation processes, and mean state extremes, but we argue that these differences vary greatly across the diverse range of model simulations in the literature and that these comparisons are already offering important insights into real tropical phenomena. Some preliminary new findings are presented, including results showing that a self-aggregation simulation with square geometry has too broad distribution of humidity and is too dry in the driest regions when compared with radiosonde records from Nauru, while an elongated channel simulation has realistic representations of atmospheric humidity and its variability. We discuss recent work increasing our understanding of how organized convection and climate change may interact, and how model discrepancies related to this question are prompting interest in observational comparisons. We also propose possible future directions for observational work related to convective aggregation, including novel satellite approaches and a ground-based observational network.

  6. Fractals of Silica Aggregates

    Institute of Scientific and Technical Information of China (English)

    ZhinhongLi; DongWu; Yuhansun; JunWang; YiLiu; BaozhongDong; Zhinhong

    2001-01-01

    Silica aggregates were prepared by base-catalyzed hydrolysis and condensation of alkoxides in alcohol.Polyethylene glycol(PEG) was used as organic modifier.The sols were characterized using Small Angle X-ray Scattering (SAXS) with synchrotron radiation as X-ray source.The structure evolution during the sol-gel process was determined and described in terms of the fractal geometry.As-produced silica aggregates were found to be mass fractals.The fractl dimensions spanned the regime 2.1-2.6 corresponding to more branched and compact structures.Both RLCA and Eden models dominated the kinetic growth under base-catalyzed condition.

  7. Uranium Conversion & Enrichment

    Energy Technology Data Exchange (ETDEWEB)

    Karpius, Peter Joseph [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2017-02-06

    The isotopes of uranium that are found in nature, and hence in ‘fresh’ Yellowcake’, are not in relative proportions that are suitable for power or weapons applications. The goal of conversion then is to transform the U3O8 yellowcake into UF6. Conversion and enrichment of uranium is usually required to obtain material with enough 235U to be usable as fuel in a reactor or weapon. The cost, size, and complexity of practical conversion and enrichment facilities aid in nonproliferation by design.

  8. STS-46 MS Chang-Diaz floats in life raft during water egress training at JSC

    Science.gov (United States)

    1992-01-01

    STS-46 Atlantis, Orbiter Vehicle (OV) 104, Mission Specialist (MS) Franklin R. Chang-Diaz, wearing launch and entry suit (LES) and launch and entry helmet (LEH), relies on a one-person life raft to get him to 'safety' during a launch emergency egress (bailout) simulation conducted in JSC's Weightless Environment Training Facility (WETF) Bldg 29 pool.

  9. Raft protein clustering alters N-Ras membrane interactions and activation pattern

    NARCIS (Netherlands)

    Eisenberg, Sharon; Beckett, Alison J; Prior, Ian A; Dekker, Frank J; Hedberg, Christian; Waldmann, Herbert; Ehrlich, Marcelo; Henis, Yoav I; Dekker, Frank

    2011-01-01

    The trafficking, membrane localization, and lipid raft association of Ras proteins, which are crucial oncogenic mediators, dictate their isoform-specific biological responses. Accordingly, their spatiotemporal dynamics are tightly regulated. While extensively studied for H- and K-Ras, such informati

  10. Further evidence that paroxysmal nocturnal haemoglobinuria is a disorder of defective cell membrane lipid rafts.

    Science.gov (United States)

    Ratajczak, Mariusz Z; Borkowska, Sylwia; Mierzejewska, Kasia; Kucia, Magda; Mendek-Czajkowska, Ewa; Suszynska, Malwina; Sharma, Vivek A; Deptala, Andrzej; Song, Wechao; Platzbecker, Uwe; Larratt, Loree; Janowska-Wieczorek, Anna; Maciejewski, Jarek; Ratajczak, Janina

    2015-09-01

    The glycolipid glycosylphosphatidylinositol anchor (GPI-A) plays an important role in lipid raft formation, which is required for proper expression on the cell surface of two inhibitors of the complement cascade, CD55 and CD59. The absence of these markers from the surface of blood cells, including erythrocytes, makes the cells susceptible to complement lysis, as seen in patients suffering from paroxysmal nocturnal haemoglobinuria (PNH). However, the explanation for why PNH-affected hematopoietic stem/progenitor cells (HSPCs) expand over time in BM is still unclear. Here, we propose an explanation for this phenomenon and provide evidence that a defect in lipid raft formation in HSPCs leads to defective CXCR4- and VLA-4-mediated retention of these cells in BM. In support of this possibility, BM-isolated CD34(+) cells from PNH patients show a defect in the incorporation of CXCR4 and VLA-4 into membrane lipid rafts, respond weakly to SDF-1 stimulation, and show defective adhesion to fibronectin. Similar data were obtained with the GPI-A(-) Jurkat cell line. Moreover, we also report that chimeric mice transplanted with CD55(-/-)  CD59(-/-) BM cells but with proper GPI-A expression do not expand over time in transplanted hosts. On the basis of these findings, we propose that a defect in lipid raft formation in PNH-mutated HSPCs makes these cells more mobile, so that they expand and out-compete normal HSPCs from their BM niches over time.

  11. Membrane lipid rafts, master regulators of hematopoietic stem cell retention in bone marrow and their trafficking.

    Science.gov (United States)

    Ratajczak, M Z; Adamiak, M

    2015-07-01

    Cell outer membranes contain glycosphingolipids and protein receptors, which are integrated into glycoprotein microdomains, known as lipid rafts, which float freely in the membrane bilayer. These structures have an important role in assembling signaling molecules (e.g., Rac-1, RhoH and Lyn) together with surface receptors, such as the CXCR4 receptor for α-chemokine stromal-derived factor-1, the α4β1-integrin receptor (VLA-4) for vascular cell adhesion molecule-1 and the c-kit receptor for stem cell factor, which together regulate several aspects of hematopoietic stem/progenitor cell (HSPC) biology. Here, we discuss the role of lipid raft integrity in the retention and quiescence of normal HSPCs in bone marrow niches as well as in regulating HSPC mobilization and homing. We will also discuss the pathological consequences of the defect in lipid raft integrity seen in paroxysmal nocturnal hemoglobinuria and the emerging evidence for the involvement of lipid rafts in hematological malignancies.

  12. Effects of Boreal Timber Rafting on the Composition of Arctic Driftwood

    Directory of Open Access Journals (Sweden)

    Lena Hellmann

    2016-10-01

    Full Text Available Wood from the boreal forest represents an important resource for paper production and sawmill processing. Due to poor infrastructure and high transportation costs on land, timbers are often transported over long distances along large river systems. Industrial river rafting activities started at the end of the 19th century and were intensified in western Russia and central Siberia from the 1920s to the 1980s. After initial single stem rafting, timber is today mostly floated in ship-guided rafts. Lost wood can be transported further to the Arctic Ocean, where it may drift within sea ice over several years and thousands of kilometers before being deposited along (sub-Arctic coastlines. Here, we introduce dendro-dated tree-ring width series of 383 driftwood samples from logged timber that were collected along different driftwood-recipient coastlines in Greenland, Iceland and Svalbard. The majority of driftwood is Pinus sylvestris from the southern Yenisei region in central Siberia, whereas Larix sp. and Picea sp. from western Russia and eastern Siberia are rare. Although our results are based on a small sample collection, they clearly show the importance of timber rafting on species, age and origin of Arctic driftwood and indicate the immense loss of material during wood industrial river floating.

  13. Inhibition of Akt signaling by exclusion from lipid rafts in normal and transformed epidermal keratinocytes

    DEFF Research Database (Denmark)

    Calay, Damien; Vind-Kezunovic, Dina; Frankart, Aurelie;

    2010-01-01

    in deactivation of mammalian target of rapamycin, activation of FoxO3a, and increased sensitivity to apoptosis stimuli. Lipid raft disruption abrogated the binding of Akt and the major Akt kinase, phosphatidylinositol-dependent kinase 1, to the membrane by pleckstrin-homology domains. Thus, the integrity of lipid...

  14. Motion induced passenger dislocations in life raft and life boat configurations

    NARCIS (Netherlands)

    Bos, J.E.; Andersen ,O.; Reinke, P.

    2010-01-01

    Within the European project SafeCrafts, dealing with the safe abandoning of ships, the dislocation of passengers aboard life boats and rafts has been considered to be a risk regarding passenger survival at sea. To get an idea about the risks and the affecting factors involved, we studied the effects

  15. Caveolae/lipid rafts in fibroblast-like synoviocytes: ectopeptidase-rich membrane microdomains

    DEFF Research Database (Denmark)

    Riemann, D; Hansen, Gert Helge; Niels-Christiansen, L;

    2001-01-01

    from about 60 to 160 nm. Cholesterol depletion of synoviocytes by methyl-beta-cyclodextrin disrupted >90% of the caveolae and reduced the raft localization of aminopeptidase N/CD13 without affecting Ala-p-nitroanilide-cleaving activity of confluent cell cultures. In co-culture experiments with T...

  16. Cholera toxin entry into pig enterocytes occurs via a lipid raft- and clathrin-dependent mechanism

    DEFF Research Database (Denmark)

    Hansen, Gert H; Dalskov, Stine-Mathilde; Rasmussen, Christina Rehné;

    2005-01-01

    accompanied the toxin internalization whereas no formation of caveolae was observed. CTB was strongly associated with the buoyant, detergent-insoluble fraction of microvillar membranes. Neither CTB's raft association nor uptake via clathrin-coated pits was affected by methyl-beta-cyclodextrin, indicating...

  17. RAFT Miniemulsion Polymerization of MMA with Cumyl Dithiobenzoate as Chain Transfer Agent

    Institute of Scientific and Technical Information of China (English)

    Tian Ying GUO; Dong Lin TANG; Jing Wei ZHU; Mou Dao SONG; Bang Hua ZHANG

    2006-01-01

    Reversible addition-fragmentation transfer (RAFT) miniemulsion polymerizations for PMMA with cumyl dithiobenzoate (CDB) as a chain transfer agent (CTA) has been carried out.Higher temperature made the polymerization much faster and the PDI remained below 1.20, when the temperature was upon 70 ℃.

  18. Bubble-raft collapse and the nonequilibrium dynamics of two-state elastica

    Science.gov (United States)

    Kuo, Chin-Chang; Kachan, Devin; Levine, Alex J.; Dennin, Michael

    2016-03-01

    We report on the collapse of bubble rafts under compression in a closed rectangular geometry. A bubble raft is a single layer of bubbles at the air-water interface. A collapse event occurs when bubbles submerge beneath the neighboring bubbles under compression, causing the structure of the bubble raft to go from single-layer to multilayer. We studied the collapse dynamics as a function of compression velocity. At higher compression velocity we observe a more uniform distribution of collapse events, whereas at lower compression velocities the collapse events accumulate at the system boundaries. We propose that this system can be understood in terms of a linear elastic sheet coupled to a local internal (Ising) degree of freedom. The two internal states, which represent one bubble layer versus two, couple to the elasticity of the sheet by locally changing the reference state of the material. By exploring the collapse dynamics of the bubble raft, one may address the basic nonlinear mechanics of a number of complex systems in which elastic stress is coupled to local internal variables.

  19. Molecular mediators for raft-dependent endocytosis of syndecan-1, a highly conserved, multifunctional receptor.

    Science.gov (United States)

    Chen, Keyang; Williams, Kevin Jon

    2013-05-17

    Endocytosis via rafts has attracted considerable recent interest, but the molecular mediators remain incompletely characterized. Here, we focused on the syndecan-1 heparan sulfate proteoglycan, a highly conserved, multifunctional receptor that we previously showed to undergo raft-dependent endocytosis upon clustering. Alanine scanning mutagenesis of three to five consecutive cytoplasmic residues at a time revealed that a conserved juxtamembrane motif, MKKK, was the only region required for efficient endocytosis after clustering. Endocytosis of clustered syndecan-1 occurs in two phases, each requiring a kinase and a corresponding cytoskeletal partner. In the initial phase, ligands trigger rapid MKKK-dependent activation of ERK and the localization of syndecan-1 into rafts. Activation of ERK drives the dissociation of syndecan-1 from α-tubulin, a molecule that may act as an anchor for syndecan-1 at the plasma membrane in the basal state. In the second phase, Src family kinases phosphorylate tyrosyl residues within the transmembrane and cytoplasmic regions of syndecan-1, a process that also requires MKKK. Tyrosine phosphorylation of syndecan-1 triggers the robust recruitment of cortactin, which we found to be an essential mediator of efficient actin-dependent endocytosis. These findings represent the first detailed characterization of the molecular events that drive endocytosis of a raft-dependent receptor and identify a novel endocytic motif, MKKK. Moreover, the results provide new tools to study syndecan function and regulation during uptake of its biologically and medically important ligands, such as HIV-1, atherogenic postprandial remnant lipoproteins, and molecules implicated in Alzheimer disease.

  20. Functions of cholera toxin B-subunit as a raft cross-linker.

    Science.gov (United States)

    Day, Charles A; Kenworthy, Anne K

    2015-01-01

    Lipid rafts are putative complexes of lipids and proteins in cellular membranes that are proposed to function in trafficking and signalling events. CTxB (cholera toxin B-subunit) has emerged as one of the most studied examples of a raft-associated protein. Consisting of the membrane-binding domain of cholera toxin, CTxB binds up to five copies of its lipid receptor on the plasma membrane of the host cell. This multivalency of binding gives the toxin the ability to reorganize underlying membrane structure by cross-linking otherwise small and transient lipid rafts. CTxB thus serves as a useful model for understanding the properties and functions of protein-stabilized domains. In the present chapter, we summarize current evidence that CTxB associates with and cross-links lipid rafts, discuss how CTxB binding modulates the architecture and dynamics of membrane domains, and describe the functional consequences of this cross-linking behaviour on toxin uptake into cells via endocytosis.

  1. Molecularly Imprinted Polymers on Chloromethyl Polystyrene Resin Prepared via RAFT Polymerization

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    Surface molecularly imprinted polymers (SMIP) was prepared via the reversible addition-fragmentation chain transfer (RAFT) polymerization on the chloromethyl polystyrene resin (CPR) in the presence of the template D-phenylalanine. The structure of SMIP was characterized by FTIR and SEM. The adsorption behavior of D-phenylalanine of SMIP was preliminarily investigated.

  2. The Role of Lipid Rafts in the Early Stage of Enterovirus 71 Infection

    Directory of Open Access Journals (Sweden)

    Yong-Zhe Zhu

    2015-02-01

    Full Text Available Background/Aims: Although it has been widely accepted that Enterovirus 71 (EV71 enters permissive cells via receptor-mediated endocytosis, the details of entry mechanism for EV71 still need more exploration. This study aimed to investigate the role of lipid rafts in the early stage of EV71 Infection. Methods: The effect of cholesterol depletion or addition of exogenous cholesterol was detected by immunofluorescence assays and quantitative real-time PCR. Effects of cholesterol depletion on the association of EV71 with lipid rafts were determined by flow cytometry and co-immunoprecipitation assays. Localization and internalization of EV71 and its receptor were assayed by confocal microscpoy and sucrose gradient analysis. The impact of cholesterol on the activation of phosphoinositide 3'-kinase/Akt signaling pathway during initial virus infection was analyzed by Western-blotting. Results: Disruption of membrane cholesterol by a pharmacological agent resulted in a significant reduction in the infectivity of EV71. The inhibitory effect could be reversed by the addition of exogenous cholesterol. Cholesterol depletion post-infection did not affect EV71 infection. While virus bound equally to cholesterol-depleted cells, EV71 particles failed to be internalized by cholesterol-depleted cells. EV71 capsid protein co-localized with cholera toxin B, a lipid-raft-dependent internalization marker. Conclusion: Lipid rafts play a critical role in virus endocytosis and in the activation of PI3K/Akt signaling pathway in the early stage of EV71 infection.

  3. Organization and Dynamics of Fas Transmembrane Domain in Raft Membranes and Modulation by Ceramide

    Science.gov (United States)

    Castro, Bruno M.; de Almeida, Rodrigo F.M.; Goormaghtigh, Erik; Fedorov, Aleksander; Prieto, Manuel

    2011-01-01

    To comprehend the molecular processes that lead to the Fas death receptor clustering in lipid rafts, a 21-mer peptide corresponding to its single transmembrane domain (TMD) was reconstituted into mammalian raft model membranes composed of an unsaturated glycerophospholipid, sphingomyelin, and cholesterol. The peptide membrane lateral organization and dynamics, and its influence on membrane properties, were studied by steady-state and time-resolved fluorescence techniques and by attenuated total reflection Fourier transformed infrared spectroscopy. Our results show that Fas TMD is preferentially localized in liquid-disordered membrane regions and undergoes a strong reorganization as the membrane composition is changed toward the liquid-ordered phase. This results from the strong hydrophobic mismatch between the length of the peptide hydrophobic stretch and the hydrophobic thickness of liquid-ordered membranes. The stability of nonclustered Fas TMD in liquid-disordered domains suggests that its sequence may have a protective function against nonligand-induced Fas clustering in lipid rafts. It has been reported that ceramide induces Fas oligomerization in lipid rafts. Here, it is shown that neither Fas TMD membrane organization nor its conformation is affected by ceramide. These results are discussed within the framework of Fas membrane signaling events. PMID:21961589

  4. RAFT-HDA Chemistry - Conception, Development and Application of a Facile Tool for Precision Macromolecular Engineering

    OpenAIRE

    Inglis, Andrew

    2010-01-01

    The conceptualization, development and application of the herein named RAFT-HDA Chemistry is reported. This chemistry is presented as a facile conjugation method (falling within the field of click chemistry) whereby synthetic polymeric materials may be covalently linked to other species, including other polymers with high efficiency.

  5. Effect of tamoxifen in RAFT miniemulsion polymerization during the synthesis of polymer nanoparticles

    Directory of Open Access Journals (Sweden)

    Tailane Sant'Anna Moreira

    2014-01-01

    Full Text Available Tamoxifen (TXF is currently the only hormonal agent used for treatment of breast cancer. Although very effective, TXF presents low solubility in water, which affects its absorption and bioavailability. A common strategy to overcome this barrier is the formulation of a drug delivery system (DDS in order to increase the drug stability and improve the treatment effectiveness. Reversible addition-fragmentation chain transfer (RAFT polymerization is the most versatile method of controlled/living radical polymerization (CLRP, allowing for synthesis of well-defined polymers and being adapted to a wide range of polymerization systems. Miniemulsion polymerization is a dispersed system that is commonly used to prepare nanoparticles (NP with 50 to 500 nm of diameter. The aim of this work was to evaluate the effect of the in situ incorporation of TXF during miniemulsion conventional and RAFT polymerizations, using methyl methacrylate (MMA as monomer. Although the in situ addition of TXF promoted a slight reduction of the reaction rate, it did not affect the final particle size distribution of the latex or the molecular weight control exerted by the RAFT agent. The obtained results suggest that in situ incorporation of TXF during the synthesis of polymer NP via RAFT polymerization allows for production of a polymer DDS for different uses, such as the breast cancer treatment.

  6. Polimerização RAFT em miniemulsão

    Directory of Open Access Journals (Sweden)

    Marco Antonio M. Oliveira

    2013-01-01

    Full Text Available Dentre as diversas técnicas para obter polímeros de maneira controlada, a técnica de Transferência Reversível de Cadeia por Adição-Fragmentação (RAFT é tida como uma das mais versáteis, uma vez que é compatível com uma grande quantidade de monômeros, solventes, condições reacionais e sistemas de polimerização. Utilizando essa metodologia, é possível sintetizar polímeros com diversas arquiteturas e com excelente controle do tamanho das cadeias. Neste trabalho, é apresentada uma revisão da técnica de polimerização RAFT em sistemas de miniemulsão. As principais características da técnica de polimerização RAFT e uma ampla revisão dos estudos em miniemulsão são apresentadas, abrangendo mais de 152 referências. Também é abordado nesta revisão o uso da polimerização RAFT em miniemulsão para obtenção de polímeros para aplicações biotecnológicas.

  7. STS-46 MS Chang-Diaz floats in life raft during water egress training at JSC

    Science.gov (United States)

    1992-01-01

    STS-46 Atlantis, Orbiter Vehicle (OV) 104, Mission Specialist (MS) Franklin R. Chang-Diaz, wearing launch and entry suit (LES) and launch and entry helmet (LEH), relies on a one-person life raft to get him to 'safety' during a launch emergency egress (bailout) simulation conducted in JSC's Weightless Environment Training Facility (WETF) Bldg 29 pool.

  8. Drawing The Red Line: Cost Benefit Analysis on Large Life Rafts

    Science.gov (United States)

    2013-06-13

    In the Aviation Consumer Action Project, Ralph Nader stated, “a wide-body jet would shatter like a raw egg dropped on pavement , killing most if...upon activation, a semi- rigid ladder will fall at four locations (1C-17A-1, 2012). The life rafts are ejected and tethered by a string (1C-17A-1

  9. Proximate biochemical composition and caloric potential in the raft-grown green mussel Perna viridis

    Digital Repository Service at National Institute of Oceanography (India)

    Rivonker, C.U.; Parulekar, A.H.

    The biochemical components of the mussel tissue, cultured on the raft were estimated. The range of variation in the content of moisture, protein, carbohydrates, lipid, organic carbon and ash were 66.8-90.1; 46.2-67.4; 11.7-18.6; 2.9-7.4; 19...

  10. Rheological investigation of the shear strength, durability, and recovery of alginate rafts formed by antacid medication in varying pH environments.

    Science.gov (United States)

    Elliott, Brooke M; Steckbeck, Kathleen E; Murray, Lisa R; Erk, Kendra A

    2013-11-30

    The mechanical response of alginate rafts formed by mixing liquid alginate antacid medication (Gaviscon Extra Strength Liquid Antacid) with acidic solutions was investigated by deforming isolated rafts in a shear rheometer. As rafts were deformed to varying magnitudes of applied strain, rheological parameters were identified and related to the overall strength, durability, and recoverability of rafts formed at different pH (1.1-1.7) and aging conditions (0.5-4 h). Rafts formed in the lowest acidity solutions (pH 1.4, 1.7) were elastically weak ( G'₀ = 60 , 42 Pa for un-aged raft) yet maintained their elasticity during applied shear deformation to large values of strain (γc∼90%, 50%, where G'≈G″), and displayed a low-to-moderate level of elastic recovery following large-strain deformation. Rafts formed in the highest acidity solution had the greatest strength ( G'₀ = 500 Pa for un-aged raft and 21.5 kPa for rafts after 0.5 h of aging), reduced durability (γc∼2.5%, independent of aging), and displayed the greatest recoverability. A trade-off existed between un-aged raft strength and durability while recovery was dependent on durability, solution pH, and age. Rheometry-based evaluations of alginate rafts could be used for the informed design of future gastric retention and antacid products.

  11. Geoinformation Generalization by Aggregation

    Directory of Open Access Journals (Sweden)

    Tomislav Jogun

    2016-12-01

    Full Text Available Geoinformation generalization can be divided into model generalization and cartographic generalization. Model generalization is the supervised reduction of data in a model, while cartographic generalization is the reduction of the complexity of map content adapted to the map scale, and/or use by various generalization operators (procedures. The topic of this paper is the aggregation of geoinformation. Generally, aggregation is the joining of nearby, congenial objects, when the distance between them is smaller than the minimum sizes. Most researchers in geoinformation generalization have focused on line features. However, the appearance of web-maps with point features and choropleth maps has led to the development of concepts and algorithms for the generalization of point and polygonal features. This paper considers some previous theoretical premises and actual examples of aggregation for point, line and polygonal features. The algorithms for aggregation implemented in commercial and free GIS software were tested. In the conclusion, unresolved challenges that occur in dynamic cartographic visualizations and cases of unusual geometrical features are highlighted.

  12. Erosion of dust aggregates

    CERN Document Server

    Seizinger, Alexander; Kley, Wilhelm

    2013-01-01

    Aims: The aim of this work is to gain a deeper insight into how much different aggregate types are affected by erosion. Especially, it is important to study the influence of the velocity of the impacting projectiles. We also want to provide models for dust growth in protoplanetary disks with simple recipes to account for erosion effects. Methods: To study the erosion of dust aggregates we employed a molecular dynamics approach that features a detailed micro-physical model of the interaction of spherical grains. For the first time, the model has been extended by introducing a new visco-elastic damping force which requires a proper calibration. Afterwards, different sample generation methods were used to cover a wide range of aggregate types. Results: The visco-elastic damping force introduced in this work turns out to be crucial to reproduce results obtained from laboratory experiments. After proper calibration, we find that erosion occurs for impact velocities of 5 m/s and above. Though fractal aggregates as ...

  13. Diffusion in aggregated soil.

    NARCIS (Netherlands)

    Rappoldt, C.

    1992-01-01

    The structure of an aggregated soil is characterized by the distribution of the distance from an arbitrary point in the soil to the nearest macropore or crack. From this distribution an equivalent model system is derived to which a diffusion model can be more easily applied. The model system consist

  14. Adsorption study of a macro-RAFT agent onto SiO2-coated Gd2O3:Eu3+ nanorods: Requirements and limitations

    Science.gov (United States)

    Zou, Hua; Melro, Liliana; de Camargo Chaparro, Thaissa; de Souza Filho, Isnaldi Rodrigues; Ananias, Duarte; Bourgeat-Lami, Elodie; dos Santos, Amilton Martins; Barros-Timmons, Ana

    2017-02-01

    The use of a macromolecular RAFT (macro-RAFT) agent to encapsulate anisotropic nano-objects via emulsion polymerization is an emerging route to prepare polymer/inorganic colloidal nanocomposites. However, a number of requirements have to be fulfilled. This work aims at highlighting the effects of the preparative procedure and dispersion method on the amount of macro-RAFT agent adsorbed onto SiO2-coated Gd2O3:Eu3+ nanorods. The adsorption of macro-RAFT agent was studied using the depletion method with UV-vis spectrophotometry. Measurements were performed at a fixed concentration of nanorods and varying concentrations of the macro-RAFT agent in aqueous dispersion at room temperature. The adsorption isotherms showed that for the same initial macro-RAFT agent concentration, the highest adsorption capacity of the macro-RAFT agent on nanorods was usually achieved for non-calcined thin SiO2-coated nanorods under mild bath sonication.

  15. The synaptic recruitment of lipid rafts is dependent on CD19-PI3K module and cytoskeleton remodeling molecules.

    Science.gov (United States)

    Xu, Liling; Auzins, Arturs; Sun, Xiaolin; Xu, Yinsheng; Harnischfeger, Fiona; Lu, Yun; Li, Zhanguo; Chen, Ying-Hua; Zheng, Wenjie; Liu, Wanli

    2015-08-01

    Sphingolipid- and cholesterol-rich lipid raft microdomains are important in the initiation of BCR signaling. Although it is known that lipid rafts promote the coclustering of BCR and Lyn kinase microclusters within the B cell IS, the molecular mechanism of the recruitment of lipid rafts into the B cell IS is not understood completely. Here, we report that the synaptic recruitment of lipid rafts is dependent on the cytoskeleton-remodeling proteins, RhoA and Vav. Such an event is also efficiently regulated by motor proteins, myosin IIA and dynein. Further evidence suggests the synaptic recruitment of lipid rafts is, by principle, an event triggered by BCR signaling molecules and second messenger molecules. BCR-activating coreceptor CD19 potently enhances such an event depending on its cytoplasmic Tyr421 and Tyr482 residues. The enhancing function of the CD19-PI3K module in synaptic recruitment of lipid rafts is also confirmed in human peripheral blood B cells. Thus, these results improve our understanding of the molecular mechanism of the recruitment of lipid raft microdomains in B cell IS.

  16. Activation of integrin α5 mediated by flow requires its translocation to membrane lipid rafts in vascular endothelial cells.

    Science.gov (United States)

    Sun, Xiaoli; Fu, Yi; Gu, Mingxia; Zhang, Lu; Li, Dan; Li, Hongliang; Chien, Shu; Shyy, John Y-J; Zhu, Yi

    2016-01-19

    Local flow patterns determine the uneven distribution of atherosclerotic lesions. Membrane lipid rafts and integrins are crucial for shear stress-regulated endothelial function. In this study, we investigate the role of lipid rafts and integrin α5 in regulating the inflammatory response in endothelial cells (ECs) under atheroprone versus atheroprotective flow. Lipid raft proteins were isolated from ECs exposed to oscillatory shear stress (OS) or pulsatile shear stress, and then analyzed by quantitative proteomics. Among 396 proteins redistributed in lipid rafts, integrin α5 was the most significantly elevated in lipid rafts under OS. In addition, OS increased the level of activated integrin α5 in lipid rafts through the regulation of membrane cholesterol and fluidity. Disruption of F-actin-based cytoskeleton and knockdown of caveolin-1 prevented the OS-induced integrin α5 translocation and activation. In vivo, integrin α5 activation and EC dysfunction were observed in the atheroprone areas of low-density lipoprotein receptor-deficient (Ldlr(-/-)) mice, and knockdown of integrin α5 markedly attenuated EC dysfunction in partially ligated carotid arteries. Consistent with these findings, mice with haploinsufficency of integrin α5 exhibited a reduction of atherosclerotic lesions in the regions under atheroprone flow. The present study has revealed an integrin- and membrane lipid raft-dependent mechanotransduction mechanism by which atheroprone flow causes endothelial dysfunction.

  17. Proteomics of MUC1-containing lipid rafts from plasma membranes and exosomes of human breast carcinoma cells MCF-7.

    Science.gov (United States)

    Staubach, Simon; Razawi, Hanieh; Hanisch, Franz-Georg

    2009-05-01

    Apically expressed human MUC1 is known to become endocytosed and either to re-enter the secretory pathway for recycling to the plasma membrane or to be exported by the cells via the formation of multi-vesicular bodies and the release of exosomes. By using recombinant fusion-tagged MUC1 as a bait protein we followed an anti-myc affinity-based approach for isolating subpopulations of lipid rafts from the plasma membranes and exosomes of MCF-7 breast cancer cells. MUC1(+) lipid rafts were not only found to contain genuine raft proteins (flotillin-1, prohibitin, G protein, annexin A2), but also raft-associated proteins linking these to the cytoskeleton (ezrin/villin-2, profilin II, HSP27, gamma-actin, beta-actin) or proteins in complexes with raft proteins, including the bait protein (HSP60, HSP70). Major overlaps were revealed for the subproteomes of plasma membranous and exosomal lipid raft preparations, indicating that MUC1 is sorted into subpopulations of rafts for its trafficking via flotillin-dependent pathways and export via exosomes.

  18. Development and evaluation of gastroretentive raft forming systems incorporating curcumin-Eudragit® EPO solid dispersions for gastric ulcer treatment.

    Science.gov (United States)

    Kerdsakundee, Nattha; Mahattanadul, Sirima; Wiwattanapatapee, Ruedeekorn

    2015-08-01

    Novel raft forming systems incorporating curcumin-Eudragit® EPO solid dispersions were developed to prolong the gastric residence time and provide for a controlled release therapy of curcumin to treat gastric ulcers. The solid dispersions of curcumin with Eudragit® EPO were prepared by the solvent evaporation method at various ratios to improve the solubility and the dissolution of curcumin. The optimum weight ratio of 1:5 for curcumin to Eudragit® EPO was used to incorporate into the raft forming systems. The raft forming formulations were composed of curcumin-Eudragit® EPO solid dispersions, sodium alginate as a gelling polymer and calcium carbonate for generating divalent Ca(2+) ions and carbon dioxide to form a floating raft. All formulations formed a gelled raft in 1min and sustained buoyancy on the 0.1N hydrochloric acid (pH 1.2) surface with a 60-85% release of curcumin within 8h. The curative effect on the acetic acid-induced chronic gastric ulcer in rats was determined. The curcumin raft forming formulations at 40mg/kg once daily showed a superior curative effect on the gastric ulcer in terms of the ulcer index and healing index than the standard antisecretory agent: lansoprazole (1mg/kg, twice daily) and a curcumin suspension (40mg/kg, twice daily). These studies demonstrated that the new raft forming systems containing curcumin solid dispersions are promising carriers for a stomach-specific delivery of poorly soluble lipophilic compounds.

  19. Lipid raft localization of EGFR alters the response of cancer cells to the EGFR tyrosine kinase inhibitor gefitinib.

    Science.gov (United States)

    Irwin, Mary E; Mueller, Kelly L; Bohin, Natacha; Ge, Yubin; Boerner, Julie L

    2011-09-01

    Epidermal growth factor receptor (EGFR) is overexpressed in many cancer types including ~30% of breast cancers. Several small molecule tyrosine kinase inhibitors (TKIs) targeting EGFR have shown clinical efficacy in lung and colon cancers, but no benefit has been noted in breast cancer. Thirteen EGFR expressing breast cancer cell lines were analyzed for response to EGFR TKIs. Seven were found to be EGFR TKI resistant; while shRNA knockdown of EGFR determined that four of these cell lines retained the requirement of EGFR protein expression for growth. Interestingly, EGFR localized to plasma membrane lipid rafts in all four of these EGFR TKI-resistant cell lines, as determined by biochemical raft isolation and immunofluorescence. When lipid rafts were depleted of cholesterol using lovastatin, all four cell lines were sensitized to EGFR TKIs. In fact, the effects of the cholesterol biosynthesis inhibitors and gefitinib were synergistic. While gefitinib effectively abrogated phosphorylation of Akt- and mitogen-activated protein kinase in an EGFR TKI-sensitive cell line, phosphorylation of Akt persisted in two EGFR TKI-resistant cell lines, however, this phosphorylation was abrogated by lovastatin treatment. Thus, we have shown that lipid raft localization of EGFR correlates with resistance to EGFR TKI-induced growth inhibition and pharmacological depletion of cholesterol from lipid rafts decreases this resistance in breast cancer cell lines. Furthermore, we have presented evidence to suggest that when EGFR localizes to lipid rafts, these rafts provide a platform to facilitate activation of Akt signaling in the absence of EGFR kinase activity.

  20. New EMBO members' review: actin cytoskeleton regulation through modulation of PI(4,5)P(2) rafts.

    Science.gov (United States)

    Caroni, P

    2001-08-15

    The phosphoinositide lipid PI(4,5)P(2) is now established as a key cofactor in signaling to the actin cytoskeleton and in vesicle trafficking. PI(4,5)P(2) accumulates at membrane rafts and promotes local co-recruitment and activation of specific signaling components at the cell membrane. PI(4,5)P(2) rafts may thus be platforms for local regulation of morphogenetic activity at the cell membrane. Raft PI(4,5)P(2) is regulated by lipid kinases (PI5-kinases) and lipid phosphatases (e.g. synaptojanin). In addition, GAP43-like proteins have recently emerged as a group of PI(4,5)P(2) raft-modulating proteins. These locally abundant proteins accumulate at inner leaflet plasmalemmal rafts where they bind to and co-distribute with PI(4,5)P(2), and promote actin cytoskeleton accumulation and dynamics. In keeping with their proposed role as positive modulators of PI(4,5)P(2) raft function, GAP43-like proteins confer competence for regulated morphogenetic activity on cells that express them. Their function has been investigated extensively in the nervous system, where their expression promotes neurite outgrowth, anatomical plasticity and nerve regeneration. Extrinsic signals and intrinsic factors may thus converge to modulate PI(4,5)P(2) rafts, upstream of regulated activity at the cell surface.

  1. Simulation study of directional coarsening (rafting) of gamma' in single crystal nickel-aluminum

    Science.gov (United States)

    Zhou, Ning

    Dislocation propagation in and work hardening of gamma channels and directional coarsening (rafting) of gamma' precipitates are the major microscopic processes taking place during high temperature deformation of single crystal Ni-base superalloys. Understanding of those processes is crucial for developing improved models of creep and fatigue of turbine blades in aircraft engines. Recent investigations of rafting in superalloys demonstrate clearly the importance of elastic modulus difference between the gamma and gamma' phases and dislocation-level activities in the gamma-channels in determining the kinetic pathway of the processes. The elastic modulus difference can lead to the non-uniform distribution of stresses through the interaction with the lattice misfit and external load. While work hardening in the gamma channels has a direct effect on differentiation of the stress state in the vertical and horizontal channels and on gamma/gamma' interface coherency and energy, and hence influences the diffusive flow and morphological changes of the gamma/gamma' microstructure. In turn, changes in particle shape and coherency of the interface alter the local stress state and thereby the Peach-Koehler force on dislocations. Although existing models treating these processes separately can offer a qualitative explanation about the direction of rafting for typical superalloys, a complete quantitative understanding of rafting phenomena requires these processes to be treated simultaneously in a common framework because of their intimate coupling. The objective of this thesis is to develop an integrated computational approach in simulating simultaneous evolution of both gamma/gamma' microstructure and dislocations in an elastically anisotropic and inhomogeneous system by using a single, consistent phase field methodology. In particular, the phase field dislocation model is used to simulate the initial dislocation gamma channel filling process and calculate stress distribution

  2. Enriching the Catalog

    Science.gov (United States)

    Tennant, Roy

    2004-01-01

    After decades of costly and time-consuming effort, nearly all libraries have completed the retrospective conversion of their card catalogs to electronic form. However, bibliographic systems still are really not much more than card catalogs on wheels. Enriched content that Amazon.com takes for granted--such as digitized tables of contents, cover…

  3. Preparation of hydrazine functionalized polymer brushes hybrid magnetic nanoparticles for highly specific enrichment of glycopeptides.

    Science.gov (United States)

    Huang, Guang; Sun, Zhen; Qin, Hongqiang; Zhao, Liang; Xiong, Zhichao; Peng, Xiaojun; Ou, Junjie; Zou, Hanfa

    2014-05-07

    Hydrazide chemistry is a powerful technique in glycopeptides enrichment. However, the low density of the monolayer hydrazine groups on the conventional hydrazine-functionalized magnetic nanoparticles limits the efficiency of glycopeptides enrichment. Herein, a novel magnetic nanoparticle grafted with poly(glycidyl methacrylate) (GMA) brushes was fabricated via reversible addition-fragmentation chain transfer (RAFT) polymerization, and a large amount of hydrazine groups were further introduced to the GMA brushes by ring-opening the epoxy groups with hydrazine hydrate. The resulting magnetic nanoparticles (denoted as Fe3O4@SiO2@GMA-NHNH2) demonstrated the high specificity of capturing glycopeptides from a tryptic digest of the sample comprising a standard non-glycosylated protein bovine serum albumin (BSA) and four standard glycoproteins with a weight ratio of 50 : 1, and the detection limit was as low as 130 fmol. In the analysis of a real complex biological sample, the tryptic digest of hepatocellular carcinoma, 179 glycosites were identified by the Fe3O4@SiO2@GMA-NHNH2 nanoparticles, surpassing that of 68 glycosites by Fe3O4@SiO2-single-NHNH2 (with monolayer hydrazine groups on the surface). It can be expected that the magnetic nanoparticles modified with hydrazine functionalized polymer brushes via RAFT technique will improve the specificity and the binding capacity of glycopeptides from complex samples, and show great potential in the analysis of protein glycosylation in biological samples.

  4. Syntaxin and VAMP association with lipid rafts depends on cholesterol depletion in capacitating sperm cells.

    Science.gov (United States)

    Tsai, Pei-Shiue; De Vries, Klaas J; De Boer-Brouwer, Mieke; Garcia-Gil, Nuria; Van Gestel, Renske A; Colenbrander, Ben; Gadella, Bart M; Van Haeften, Theo

    2007-01-01

    Sperm cells represent a special exocytotic system since mature sperm cells contain only one large secretory vesicle, the acrosome, which fuses with the overlying plasma membrane during the fertilization process. Acrosomal exocytosis is believed to be regulated by activation of SNARE proteins. In this paper, we identified specific members of the SNARE protein family, i.e., the t-SNAREs syntaxin1 and 2, and the v-SNARE VAMP, present in boar sperm cells. Both syntaxins were predominantly found in the plasma membrane whereas v-SNAREs are mainly located in the outer acrosomal membrane of these cells. Under non-capacitating conditions both syntaxins and VAMP are scattered in well-defined punctate structures over the entire sperm head. Bicarbonate-induced in vitro activation in the presence of BSA causes a relocalization of these SNAREs to a more homogeneous distribution restricted to the apical ridge area of the sperm head, exactly matching the site of sperm zona binding and subsequent induced acrosomal exocytosis. This redistribution of syntaxin and VAMP depends on cholesterol depletion and closely resembles the previously reported redistribution of lipid raft marker proteins. Detergent-resistant membrane isolation and subsequent analysis shows that a significant proportion of syntaxin emerges in the detergent-resistant membrane (raft) fraction under such conditions, which is not the case under those conditions where cholesterol depletion is blocked. The v-SNARE VAMP displays a similar cholesterol depletion-dependent lateral and raft redistribution. Taken together, our results indicate that redistribution of syntaxin and VAMP during capacitation depends on association of these SNAREs with lipid rafts and that such a SNARE-raft association may be essential for spatial control of exocytosis and/or regulation of SNARE functioning.

  5. Effect of glycyrrhetinic acid on lipid raft model at the air/water interface.

    Science.gov (United States)

    Sakamoto, Seiichi; Uto, Takuhiro; Shoyama, Yukihiro

    2015-02-01

    To investigate an interfacial behavior of the aglycon of glycyrrhizin (GC), glycyrrhetinic acid (GA), with a lipid raft model consisting of equimolar ternary mixtures of N-palmitoyl sphingomyelin (PSM), dioleoylphosphatidylcholine (DOPC), and cholesterol (CHOL), Langmuir monolayer techniques were systematically conducted. Surface pressure (π)-molecular area (A) and surface potential (ΔV)-A isotherms showed that the adsorbed GA at the air/water interface was desorbed into the bulk upon compression of the lipid monolayer. In situ morphological analysis by Brewster angle microscopy and fluorescence microscopy revealed that the raft domains became smaller as the concentrations of GA in the subphase (CGA) increased, suggesting that GA promotes the formation of fluid networks related to various cellular processes via lipid rafts. In addition, ex situ morphological analysis by atomic force microscopy revealed that GA interacts with lipid raft by lying down at the surface. Interestingly, the distinctive striped regions were formed at CGA=5.0 μM. This phenomenon was observed to be induced by the interaction of CHOL with adsorbed GA and is involved in the membrane-disrupting activity of saponin and its aglycon. A quantitative comparison of GA with GC (Sakamoto et al., 2013) revealed that GA interacts more strongly with the raft model than GC in the monolayer state. Various biological activities of GA are known to be stronger than those of GC. This fact allows us to hypothesize that differences in the interactions of GA/GC with the model monolayer correlate to their degree of exertion for numerous activities.

  6. Edelfosine and miltefosine effects on lipid raft properties: membrane biophysics in cell death by antitumor lipids.

    Science.gov (United States)

    Castro, Bruno M; Fedorov, Aleksander; Hornillos, Valentin; Delgado, Javier; Acuña, A Ulises; Mollinedo, Faustino; Prieto, Manuel

    2013-07-03

    Edelfosine (1-O-octadecyl-2-O-methyl-sn-glycero-phosphocholine) and miltefosine (hexadecylphosphocholine) are synthetic alkylphospholipids (ALPs) that are reported to selectively accumulate in tumor cell membranes, inducing Fas clustering and activation on lipid rafts, triggering apoptosis. However, the exact mechanism by which these lipids elicit these events is still not fully understood. Recent studies propose that their mode of action might be related with alterations of lipid rafts biophysical properties caused by these lipid drugs. To achieve a clear understanding of this mechanism, we studied the effects of pharmacologically relevant amounts of edelfosine and miltefosine in the properties of model and cellular membranes. The influence of these molecules on membrane order, lateral organization, and lipid rafts molar fraction and size were studied by steady-state and time-resolved fluorescence methods, Förster resonance energy transfer (FRET), confocal and fluorescence lifetime imaging microscopy (FLIM). We found that the global membrane and lipid rafts biophysical properties of both model and cellular membranes were not significantly affected by both the ALPs. Nonetheless, in model membranes, a mild increase in membrane fluidity induced by both alkyl lipids was detected, although this effect was more noticeable for edelfosine than miltefosine. This absence of drastic alterations shows for the first time that ALPs mode of action is unlikely to be directly linked to alterations of lipid rafts biophysical properties caused by these drugs. The biological implications of this result are discussed in the context of ALPs effects on lipid metabolism, mitochondria homeostasis modulation, and their relationship with tumor cell death.

  7. The spatiotemporal pattern of Src activation at lipid rafts revealed by diffusion-corrected FRET imaging.

    Directory of Open Access Journals (Sweden)

    Shaoying Lu

    Full Text Available Genetically encoded biosensors based on fluorescence resonance energy transfer (FRET have been widely applied to visualize the molecular activity in live cells with high spatiotemporal resolution. However, the rapid diffusion of biosensor proteins hinders a precise reconstruction of the actual molecular activation map. Based on fluorescence recovery after photobleaching (FRAP experiments, we have developed a finite element (FE method to analyze, simulate, and subtract the diffusion effect of mobile biosensors. This method has been applied to analyze the mobility of Src FRET biosensors engineered to reside at different subcompartments in live cells. The results indicate that the Src biosensor located in the cytoplasm moves 4-8 folds faster (0.93+/-0.06 microm(2/sec than those anchored on different compartments in plasma membrane (at lipid raft: 0.11+/-0.01 microm(2/sec and outside: 0.18+/-0.02 microm(2/sec. The mobility of biosensor at lipid rafts is slower than that outside of lipid rafts and is dominated by two-dimensional diffusion. When this diffusion effect was subtracted from the FRET ratio images, high Src activity at lipid rafts was observed at clustered regions proximal to the cell periphery, which remained relatively stationary upon epidermal growth factor (EGF stimulation. This result suggests that EGF induced a Src activation at lipid rafts with well-coordinated spatiotemporal patterns. Our FE-based method also provides an integrated platform of image analysis for studying molecular mobility and reconstructing the spatiotemporal activation maps of signaling molecules in live cells.

  8. Anti-glycosyl antibodies in lipid rafts of the enterocyte brush border: a possible host defense against pathogens

    DEFF Research Database (Denmark)

    Hansen, Gert Helge; Pedersen, Esben D K; Immerdal, Lissi;

    2005-01-01

    The pig small intestinal brush border is a glycoprotein- and glycolipid-rich membrane that functions as a digestive/absorptive surface for dietary nutrients as well as a permeability barrier for pathogens. The present work was performed to identify carbohydrate-binding (lectinlike) proteins...... a major part of the immunoglobulins at the lumenal surface of the gut. The antibodies were associated with lipid rafts at the brush border, and they frequently (52%) coclustered with the raft marker galectin 4. A lactose wash increased the susceptibility of the brush border toward lectin peanut agglutin...... the lipid raft microdomains of the brush border against pathogens....

  9. Membrane-lipid therapy in operation: the HSP co-inducer BGP-15 activates stress signal transduction pathways by remodeling plasma membrane rafts.

    Directory of Open Access Journals (Sweden)

    Imre Gombos

    Full Text Available Aging and pathophysiological conditions are linked to membrane changes which modulate membrane-controlled molecular switches, causing dysregulated heat shock protein (HSP expression. HSP co-inducer hydroxylamines such as BGP-15 provide advanced therapeutic candidates for many diseases since they preferentially affect stressed cells and are unlikely have major side effects. In the present study in vitro molecular dynamic simulation, experiments with lipid monolayers and in vivo ultrasensitive fluorescence microscopy showed that BGP-15 alters the organization of cholesterol-rich membrane domains. Imaging of nanoscopic long-lived platforms using the raft marker glycosylphosphatidylinositol-anchored monomeric green fluorescent protein diffusing in the live Chinese hamster ovary (CHO cell plasma membrane demonstrated that BGP-15 prevents the transient structural disintegration of rafts induced by fever-type heat stress. Moreover, BGP-15 was able to remodel cholesterol-enriched lipid platforms reminiscent of those observed earlier following non-lethal heat priming or membrane stress, and were shown to be obligate for the generation and transmission of stress signals. BGP-15 activation of HSP expression in B16-F10 mouse melanoma cells involves the Rac1 signaling cascade in accordance with the previous observation that cholesterol affects the targeting of Rac1 to membranes. Finally, in a human embryonic kidney cell line we demonstrate that BGP-15 is able to inhibit the rapid heat shock factor 1 (HSF1 acetylation monitored during the early phase of heat stress, thereby promoting a prolonged duration of HSF1 binding to heat shock elements. Taken together, our results indicate that BGP-15 has the potential to become a new class of pharmaceuticals for use in 'membrane-lipid therapy' to combat many various protein-misfolding diseases associated with aging.

  10. The binding of Aβ1-42 to lipid rafts of RBC is enhanced by dietary docosahexaenoic acid in rats: Implicates to Alzheimer's disease.

    Science.gov (United States)

    Hashimoto, Michio; Hossain, Shahdat; Katakura, Masanori; Al Mamun, Abdullah; Shido, Osamu

    2015-06-01

    Once amyloid β peptides (Aβs) of the Alzheimer's disease build up in blood circulation, they are capable of binding to red blood cell (RBC) and inducing hemolysis of RBC. The mechanisms of the interactions between RBC and Aβ are largely unknown; however, it is very important for the therapeutic target of Aβ-induced hemolysis. In the present study, we investigated whether Aβ1-42 interacts with caveolin-1-containing detergent-resistant membranes (DRMs) of RBC and whether the interaction could be modulated by dietary pre-administration of docosahexaenoic acid (DHA). DHA pre-administration to rats inhibited hemolysis by Aβ1-42. This activity was accompanied by increased DHA levels and membrane fluidity and decreased cholesterol level, lipid peroxidation, and reactive oxygen species in the RBCs of the DHA-pretreated rats, suggesting that the antioxidative property of DHA may rescue RBCs from oxidative damage by Aβ1-42. The level of caveolin-1 was augmented in the DRMs of DHA-pretreated rats. Binding between Aβ1-42 and DRMs of RBC significantly increased in DHA-rats. When fluorescently labeled Aβ1-42 (TAMRA-Aβ1-42) was directly infused into the bloodstream, it again occupied the caveolin-1-containing DRMs of the RBCs from the DHA-rats to a greater extent, indicating that circulating Aβs interact with the caveolin-1-rich lipid rafts of DRMs and the interaction is stronger in the DHA-enriched RBCs. The levels of TAMRA-Aβ1-42 also increased in liver DRMs, whereas it decreased in plasma of DHA-pretreated rats. DHA might help clearance of circulating Aβs by increased lipid raft-dependent degradation pathways and implicate to therapies in Alzheimer's disease.

  11. Proteins aggregation and human diseases

    Science.gov (United States)

    Hu, Chin-Kun

    2015-04-01

    Many human diseases and the death of most supercentenarians are related to protein aggregation. Neurodegenerative diseases include Alzheimer's disease (AD), Huntington's disease (HD), Parkinson's disease (PD), frontotemporallobar degeneration, etc. Such diseases are due to progressive loss of structure or function of neurons caused by protein aggregation. For example, AD is considered to be related to aggregation of Aβ40 (peptide with 40 amino acids) and Aβ42 (peptide with 42 amino acids) and HD is considered to be related to aggregation of polyQ (polyglutamine) peptides. In this paper, we briefly review our recent discovery of key factors for protein aggregation. We used a lattice model to study the aggregation rates of proteins and found that the probability for a protein sequence to appear in the conformation of the aggregated state can be used to determine the temperature at which proteins can aggregate most quickly. We used molecular dynamics and simple models of polymer chains to study relaxation and aggregation of proteins under various conditions and found that when the bending-angle dependent and torsion-angle dependent interactions are zero or very small, then protein chains tend to aggregate at lower temperatures. All atom models were used to identify a key peptide chain for the aggregation of insulin chains and to find that two polyQ chains prefer anti-parallel conformation. It is pointed out that in many cases, protein aggregation does not result from protein mis-folding. A potential drug from Chinese medicine was found for Alzheimer's disease.

  12. Deep-apical tubules: dynamic lipid-raft microdomains in the brush-border region of enterocytes

    DEFF Research Database (Denmark)

    Hansen, Gert H; Pedersen, Jens; Niels-Christiansen, Lise-Lotte

    2003-01-01

    microdomains. Deep-apical tubules were positioned close to the actin rootlets of adjacent microvilli in the terminal web region, which had a diameter of 50-100 nm, and penetrated up to 1 microm into the cytoplasm. Markers for transcytosis, IgA and the polymeric immunoglobulin receptor, as well as the resident...... lipid raft-containing compartments, but little is otherwise known about these raft microdomains. We therefore studied in closer detail apical lipid-raft compartments in enterocytes by immunogold electron microscopy and biochemical analyses. Novel membrane structures, deep-apical tubules, were visualized...... brush-border enzyme aminopeptidase N, were present in these deep-apical tubules. We propose that deep-apical tubules are a specialized lipid-raft microdomain in the brush-border region functioning as a hub in membrane trafficking at the brush border. In addition, the sensitivity to cholesterol depletion...

  13. Enhanced electrochemical performance of orientated VO2(B) raft-like nanobelt arrays through direct lithiation for lithium ion batteries

    Science.gov (United States)

    Liu, Liang; Liu, Qiang; Zhao, Wen; Li, Guochun; Wang, Limei; Shi, Weidong; Chen, Long

    2017-02-01

    Lithiation modification of VO2(B) has been carried out by a facile hydrothermal process, and the compact and locally ordered VO2(B) raft-like nanobelt arrays have been prepared. The synthesis route provides a new approach to elaborate a VO2(B) nanostructure under a mild environment condition. It is found that the growth mechanism of VO2(B) raft-like nanobelt arrays is different from the traditional nucleation-growth process. A novel chemical lithiating-exfoliating-splitting model is proposed. Compared with the bulk counterpart, the lithiated VO2(B) raft-like nanobelt arrays as cathodes exhibit a higher discharge capacity and an enhanced high-rate performance owing to their increased structural anisotropy and decreased polarization. This work indicates that VO2(B) raft-like nanobelt arrays have great potential applications as cathode materials for lithium ion batteries.

  14. Proteomic Analysis of ABCA1-Null Macrophages Reveals a Role for Stomatin-Like Protein-2 in Raft Composition and Toll-Like Receptor Signaling.

    Science.gov (United States)

    Chowdhury, Saiful M; Zhu, Xuewei; Aloor, Jim J; Azzam, Kathleen M; Gabor, Kristin A; Ge, William; Addo, Kezia A; Tomer, Kenneth B; Parks, John S; Fessler, Michael B

    2015-07-01

    Lipid raft membrane microdomains organize signaling by many prototypical receptors, including the Toll-like receptors (TLRs) of the innate immune system. Raft-localization of proteins is widely thought to be regulated by raft cholesterol levels, but this is largely on the basis of studies that have manipulated cell cholesterol using crude and poorly specific chemical tools, such as β-cyclodextrins. To date, there has been no proteome-scale investigation of whether endogenous regulators of intracellular cholesterol trafficking, such as the ATP binding cassette (ABC)A1 lipid efflux transporter, regulate targeting of proteins to rafts. Abca1(-/-) macrophages have cholesterol-laden rafts that have been reported to contain increased levels of select proteins, including TLR4, the lipopolysaccharide receptor. Here, using quantitative proteomic profiling, we identified 383 proteins in raft isolates from Abca1(+/+) and Abca1(-/-) macrophages. ABCA1 deletion induced wide-ranging changes to the raft proteome. Remarkably, many of these changes were similar to those seen in Abca1(+/+) macrophages after lipopolysaccharide exposure. Stomatin-like protein (SLP)-2, a member of the stomatin-prohibitin-flotillin-HflK/C family of membrane scaffolding proteins, was robustly and specifically increased in Abca1(-/-) rafts. Pursuing SLP-2 function, we found that rafts of SLP-2-silenced macrophages had markedly abnormal composition. SLP-2 silencing did not compromise ABCA1-dependent cholesterol efflux but reduced macrophage responsiveness to multiple TLR ligands. This was associated with reduced raft levels of the TLR co-receptor, CD14, and defective lipopolysaccharide-induced recruitment of the common TLR adaptor, MyD88, to rafts. Taken together, we show that the lipid transporter ABCA1 regulates the protein repertoire of rafts and identify SLP-2 as an ABCA1-dependent regulator of raft composition and of the innate immune response.

  15. Cytomegalovirus Restructures Lipid Rafts via a US28/CDC42-Mediated Pathway, Enhancing Cholesterol Efflux from Host Cells

    OpenAIRE

    2016-01-01

    Cytomegalovirus (HCMV) contains cholesterol, but how HCMV interacts with host cholesterol metabolism is unknown. We found that, in human fibroblasts, HCMV infection increased the efflux of cellular cholesterol, despite reducing the abundance of ABCA1. Mechanistically, viral protein US28 was acting through CDC42, rearranging actin microfilaments, causing association of actin with lipid rafts, and leading to a dramatic change in the abundance and/or structure of lipid rafts. These changes displ...

  16. Hydrophobic aggregation of ultrafine kaolinite

    Institute of Scientific and Technical Information of China (English)

    ZHANG Xiao-ping; HU Yue-hua; LIU Run-Qing

    2008-01-01

    The hydrophobic aggregation of ultrafine kaolinite in cationic surfactant suspension was investigated by sedimentation test, zeta potential measurement and SEM observation. SEM images reveal that kaolinite particles show the self-aggregation of edge-face in acidic media, the aggregation of edge-face and edge-edge in neutral media, and the dispersion in alkaline media due to electrostatic repulsion. In the presence of the dodecylammonium acetate cationic surfactant and in neutral and alkaline suspension, the hydrophobic aggregation of face-face is demonstrated. The zeta potential of kaolinite increases with increasing the concentration of cationic surfactant. The small and loose aggregation at a low concentration but big and tight aggregation at a high concentration is presented At pH=7 alkyl quarterly amine salt CTAB has the best hydrophobic aggregation among three cationic surfactants, namely, dodecylammonium acetate, alkyl quarterly amine salts 1227 and CTAB.

  17. Absorption Spectra of Astaxanthin Aggregates

    CERN Document Server

    Olsina, Jan; Minofar, Babak; Polivka, Tomas; Mancal, Tomas

    2012-01-01

    Carotenoids in hydrated polar solvents form aggregates characterized by dramatic changes in their absorption spectra with respect to monomers. Here we analyze absorption spectra of aggregates of the carotenoid astaxanthin in hydrated dimethylsulfoxide. Depending on water content, two types of aggregates were produced: H-aggregates with absorption maximum around 390 nm, and J-aggregates with red-shifted absorption band peaking at wavelengths >550 nm. The large shifts with respect to absorption maximum of monomeric astaxanthin (470-495 nm depending on solvent) are caused by excitonic interaction between aggregated molecules. We applied molecular dynamics simulations to elucidate structure of astaxanthin dimer in water, and the resulting structure was used as a basis for calculations of absorption spectra. Absorption spectra of astaxanthin aggregates in hydrated dimethylsulfoxide were calculated using molecular exciton model with the resonance interaction energy between astaxanthin monomers constrained by semi-e...

  18. Non-Arrhenius protein aggregation.

    Science.gov (United States)

    Wang, Wei; Roberts, Christopher J

    2013-07-01

    Protein aggregation presents one of the key challenges in the development of protein biotherapeutics. It affects not only product quality but also potentially impacts safety, as protein aggregates have been shown to be linked with cytotoxicity and patient immunogenicity. Therefore, investigations of protein aggregation remain a major focus in pharmaceutical companies and academic institutions. Due to the complexity of the aggregation process and temperature-dependent conformational stability, temperature-induced protein aggregation is often non-Arrhenius over even relatively small temperature windows relevant for product development, and this makes low-temperature extrapolation difficult based simply on accelerated stability studies at high temperatures. This review discusses the non-Arrhenius nature of the temperature dependence of protein aggregation, explores possible causes, and considers inherent hurdles for accurately extrapolating aggregation rates from conventional industrial approaches for selecting accelerated conditions and from conventional or more advanced methods of analyzing the resulting rate data.

  19. Alterations in cholesterol and ganglioside GM1 content of lipid rafts in platelets from patients with Alzheimer disease.

    Science.gov (United States)

    Liu, Li; Zhang, Ke; Tan, Liang; Chen, Yu-Hua; Cao, Yun-Peng

    2015-01-01

    The aim of this study was to investigate the changes in the protein, cholesterol, and ganglioside GM1 content of lipid rafts in platelets from patients with Alzheimer disease (AD), and identify potential blood biomarkers of the disease. A total of 31 Chinese patients with AD and 31 aged-matched control subjects were selected. Lipid rafts were isolated from platelets using Optiprep gradient centrifugation. The protein content of lipid rafts was evaluated using Micro BCA assay, the cholesterol content using molecular probes, ganglioside GM1 content using colorimetry and dot-blotting analysis. The results showed that the cholesterol and ganglioside GM1 content of lipid rafts from platelets was significantly higher in patients with AD than aged-matched control subjects, whereas the protein content of lipid rafts did not show any differences between the 2 groups. These results indicate that the increases in the cholesterol and ganglioside GM1 content of lipid rafts from the platelets of patients with AD might serve as a biochemical adjunct to the clinical diagnosis of AD.

  20. The stromal cell-surface protease fibroblast activation protein-α localizes to lipid rafts and is recruited to invadopodia.

    Science.gov (United States)

    Knopf, Julia D; Tholen, Stefan; Koczorowska, Maria M; De Wever, Olivier; Biniossek, Martin L; Schilling, Oliver

    2015-10-01

    Fibroblast activation protein alpha (FAPα) is a cell surface protease expressed by cancer-associated fibroblasts in the microenvironment of most solid tumors. As there is increasing evidence for proteases having non-catalytic functions, we determined the FAPα interactome in cancer-associated fibroblasts using the quantitative immunoprecipitation combined with knockdown (QUICK) method. Complex formation with adenosin deaminase, erlin-2, stomatin, prohibitin, Thy-1 membrane glycoprotein, and caveolin-1 was further validated by immunoblotting. Co-immunoprecipitation (co-IP) of the known stoichiometric FAPα binding partner dipeptidyl-peptidase IV (DPPIV) corroborated the proteomic strategy. Reverse co-IPs validated the FAPα interaction with caveolin-1, erlin-2, and stomatin while co-IP upon RNA-interference mediated knock-down of DPPIV excluded adenosin deaminase as a direct FAPα interaction partner. Many newly identified FAPα interaction partners localize to lipid rafts, including caveolin-1, a widely-used marker for lipid raft localization. We hypothesized that this indicates a recruitment of FAPα to lipid raft structures. In density gradient centrifugation, FAPα co-fractionates with caveolin-1. Immunofluorescence optical sectioning microscopy of FAPα and lipid raft markers further corroborates recruitment of FAPα to lipid rafts and invadopodia. FAPα is therefore an integral component of stromal lipid rafts in solid tumors. In essence, we provide one of the first interactome analyses of a cell surface protease and translate these results into novel biological aspects of a marker protein for cancer-associated fibroblasts.

  1. The Role of the Actin Cytoskeleton and Lipid Rafts in the Localization and Function of the ABCC1 Transporter

    Directory of Open Access Journals (Sweden)

    Jan Willem Kok

    2014-01-01

    Full Text Available ATP-binding cassette (ABC transporters are known to be important factors in multidrug resistance of tumor cells. Lipid rafts have been implicated in their localization in the plasma membrane, where they function as drug efflux pumps. This specific localization in rafts may support the activity of ABC/Abc transporters. This raises questions regarding the nature and composition of the lipid rafts that harbor ABC/Abc transporters and the dependence of ABC/Abc transporters—concerning their localization and activity—on lipid raft constituents. Here we review our work of the past 10 years aimed at evaluating whether ABC/Abc transporters are dependent on a particular membrane environment for their function. What is the nature of this membrane environment and which of the lipid raft constituents are important for this dependency? It turns out that cortical actin is of major importance for stabilizing the localization and function of the ABC/Abc transporter, provided it is localized in an actin-dependent subtype of lipid rafts, as is the case for human ABCC1/multidrug resistance-related protein 1 (MRP1 and rodent Abcc1/Mrp1 but not human ABCB1/P-glycoprotein (PGP. On the other hand, sphingolipids do not appear to be modulators of ABCC1/MRP1 (or Abcc1/Mrp1, even though they are coregulated during drug resistance development.

  2. Oviposition responses of gravid female Culex quinquefasciatus to egg rafts and low doses of oviposition pheromone under semifield conditions.

    Science.gov (United States)

    Braks, Marieta A; Leal, Walter S; Cardé, Ring T

    2007-03-01

    Semifield experiments were conducted to study the oviposition of gravid Culex quinquefasciatus females in response to one or 10 egg rafts, or 3.0 microg of synthetic oviposition pheromone, (-)-(5R, 6S)-6-acetoxy-5-hexadecanolide, a dose equivalent to 10 egg rafts. These treatments were added to the small bowls filled with either hay infusion or water in a small (0.3-m spacing) or a large-square design (3.4-m spacing). Oviposition choice was more pronounced in the "small square" assays. Mean number of egg rafts laid in response to a single egg raft in an oviposition jar filled with hay infusion was significantly greater than with all other treatments. When the oviposition pheromone dose was increased from one to 10 rafts or when 3.0 microg synthetic oviposition pheromone were dispensed on a floating receptacle, synergistic effects were observed between the oviposition pheromone and the hay infusion at both distances. This study is the first demonstration that the amount in a single raft induces oviposition of gravid Cx. quinquefasciatus females under semi-natural conditions.

  3. Effects of irrigation on crops and soils with Raft River geothermal water

    Energy Technology Data Exchange (ETDEWEB)

    Stanley, N.E.; Schmitt, R.C.

    1980-01-01

    The Raft River Irrigation Experiment investigated the suitability of using energy-expended geothermal water for irrigation of selected field-grown crops. Crop and soil behavior on plots sprinkled or surface irrigated with geothermal water was compared to crop and soil behavior on plots receiving water from shallow irrigation wells and the Raft River. In addition, selected crops were produced, using both geothermal irrigation water and special management techniques. Crops irrigated with geothermal water exhibited growth rates, yields, and nutritional values similar to comparison crops. Cereal grains and surface-irrigated forage crops did not exhibit elevated fluoride levels or accumulations of heavy metals. However, forage crops sprinkled with geothermal water did accumulate fluorides, and leaching experiments indicate that new soils receiving geothermal water may experience increased salinity, exchangeable sodium, and decreased permeability. Soil productivity may be maintained by leaching irrigations.

  4. Disruption of Lipid Rafts Interferes with the Interaction of Toxoplasma gondii with Macrophages and Epithelial Cells

    Science.gov (United States)

    Cruz, Karla Dias; Cruz, Thayana Araújo; Veras de Moraes, Gabriela; Paredes-Santos, Tatiana Christina; Attias, Marcia; de Souza, Wanderley

    2014-01-01

    The intracellular parasite Toxoplasma gondii can penetrate any warm-blooded animal cell. Conserved molecular assemblies of host cell plasma membranes should be involved in the parasite-host cell recognition. Lipid rafts are well-conserved membrane microdomains that contain high concentrations of cholesterol, sphingolipids, glycosylphosphatidylinositol, GPI-anchored proteins, and dually acylated proteins such as members of the Src family of tyrosine kinases. Disturbing lipid rafts of mouse peritoneal macrophages and epithelial cells of the lineage LLC-MK2 with methyl-beta cyclodextrin (MβCD) and filipin, which interfere with cholesterol or lidocaine, significantly inhibited internalization of T. gondii in both cell types, although adhesion remained unaffected in macrophages and decreased only in LLC-MK2 cells. Scanning and transmission electron microscopy confirmed these observations. Results are discussed in terms of the original role of macrophages as professional phagocytes versus the LLC-MK2 cell lineage originated from kidney epithelial cells. PMID:24734239

  5. Grafting amphiphilic brushes onto halloysite nanotubes via a living RAFT polymerization and their Pickering emulsification behavior.

    Science.gov (United States)

    Hou, Yifan; Jiang, Junqing; Li, Kai; Zhang, Yanwu; Liu, Jindun

    2014-02-20

    Amphiphilic brushes of poly(4-vinylpyridine)-block-polystyrene (P4VP-b-PS) and polystyrene-block-poly(4-vinylpyridine) (PS-b-P4VP) are grafted onto halloysite nanotubes (HNTs) via a surface reversible addition-fragmentation chain transfer (RAFT) living polymerization through anchoring R group in RAFT agent S-1-dodecyl-S'-(R,R'-dimethyl-R″-acetic acid) trithiocarbonates (DDMAT). The characterization of TGA, TEM, and GPC show that amphiphilic brushes are successfully grafted onto HNTs in a living manner. To verify the amphiphilicity of HNTs grafted with block copolymers, their Pickering emulsification behavior in water/soybean oil diphase mixture is studied. The results show that modified HNTs can emulsify water/soybean oil diphase mixture and the emulsification performance is dependent on microstructure of amphiphilic brushes such as hydrophilic/hydrophobic segment size and sequence.

  6. Complex and Multidimensional Lipid Raft Alterations in a Murine Model of Alzheimer's Disease

    Directory of Open Access Journals (Sweden)

    Wayne Chadwick

    2010-01-01

    Full Text Available Various animal models of Alzheimer's disease (AD have been created to assist our appreciation of AD pathophysiology, as well as aid development of novel therapeutic strategies. Despite the discovery of mutated proteins that predict the development of AD, there are likely to be many other proteins also involved in this disorder. Complex physiological processes are mediated by coherent interactions of clusters of functionally related proteins. Synaptic dysfunction is one of the hallmarks of AD. Synaptic proteins are organized into multiprotein complexes in high-density membrane structures, known as lipid rafts. These microdomains enable coherent clustering of synergistic signaling proteins. We have used mass analytical techniques and multiple bioinformatic approaches to better appreciate the intricate interactions of these multifunctional proteins in the 3xTgAD murine model of AD. Our results show that there are significant alterations in numerous receptor/cell signaling proteins in cortical lipid rafts isolated from 3xTgAD mice.

  7. RAFT Copolymerization of Glycidyl Methacrylate and N,N-Dimethylaminoethyl Methacrylate

    Institute of Scientific and Technical Information of China (English)

    曹俊; 张丽芬; 潘向强; 程振平; 朱秀林

    2012-01-01

    In this work, copolymerization of two functional monomers, glycidyl methacrylate (GMA) and N,N-dimethylaminoethyl methacrylate (DMAEMA), was firstly carried out via reversible addition-fragmentation chain transfer (RAFT) polymerization successfully. The copolymerization kinetics was investigated under the molar ratio of n[GMA+DMAEMA]o/n[AIBN]o/n[CPDN]o=300/1/3 at 60℃. The copolymerization showed typical "living" features such as first-order polymerization kinetics, linear increase of molecular weight with monomer conversion and narrow molecular weight distribution. The reactivity ratios of GMA and DMAEMA were calculated by the extended Kelen-Tudos linearization methods. The epoxy group of the copolymer PGMA-co-PDMAEMA remained intact under the conditions of RAFT copolymerization and could easily be post-modified by ethylenedia- mine. Moreover, the modified copolymer could be used as a gene carrier.

  8. Research on Judgment Aggregation Based on Logic

    Directory of Open Access Journals (Sweden)

    Li Dai

    2014-05-01

    Full Text Available Preference aggregation and judgment aggregation are two basic research models of group decision making. And preference aggregation has been deeply studied in social choice theory. However, researches of social choice theory gradually focus on judgment aggregation which appears recently. Judgment aggregation focuses on how to aggregate many consistent logical formulas into one, from the perspective of logic. We try to start with judgment aggregation model based on logic and then explore different solutions to problem of judgment aggregation.

  9. Dynamical clustering and a mechanism for raft-like structures in a model lipid membrane.

    Science.gov (United States)

    Starr, Francis W; Hartmann, Benedikt; Douglas, Jack F

    2014-05-01

    We use molecular dynamics simulations to examine the dynamical heterogeneity of a model single-component lipid membrane using a coarse-grained representation of lipid molecules. This model qualitatively reproduces the known phase transitions between disordered, ordered, and gel membrane phases, and the phase transitions are accompanied by significant changes in the nature of the lipid dynamics. In particular, lipid diffusion in the liquid-ordered phase is hindered by the transient trapping of molecules by their neighbors, similar to the dynamics of a liquid approaching its glass transition. This transient molecular caging gives rise to two distinct mobility groups within a single-component membrane: lipids that are transiently trapped, and lipids with displacements on the scale of the intermolecular spacing. Most significantly, lipids within these distinct mobility states spatially segregate, creating transient "islands" of enhanced mobility having a size and time scale compatible with lipid "rafts," dynamical structures thought to be important for cell membrane function. Although the dynamic lipid clusters that we observe do not themselves correspond to rafts (which are more complex, multicomponent structures), we hypothesize that such rafts may develop from the same universal mechanism, explaining why raft-like regions should arise, regardless of lipid structural or compositional details. These clusters are strikingly similar to the dynamical clusters found in glass-forming fluids, and distinct from phase-separation clusters. We also show that mobile lipid clusters can be dissected into smaller clusters of cooperatively rearranging molecules. The geometry of these clusters can be understood in the context of branched equilibrium polymers, related to percolation theory. We discuss how these dynamical structures relate to a range observations on the dynamics of lipid membranes.

  10. Settlement of Fouling Organisms at the JTTRE North Barnard Island Raft Site.

    Science.gov (United States)

    1981-04-01

    molluscs ) are each represented by several taxa at the raft site (Table 2). Numerous algal taxa were also present. Overall, the intensity, duration and...IDENTIFIED ON ONE-MONTH IMMERSION PANELS DURING THE STUDY PERIOD Group n Group n Green algae 4 Tubeworms 4 Brown algae 3 Bivalve molluscs 6 Red algae...Hill, ACT Director, Defence Research Centre, Ministry of Defence, Kuala Lumpur, Malaysia Exchange Section, British Library, Lending Division

  11. NGF causes TrkA to specifically attract microtubules to lipid rafts.

    Directory of Open Access Journals (Sweden)

    Shona Pryor

    Full Text Available Membrane protein sorting is mediated by interactions between proteins and lipids. One mechanism that contributes to sorting involves patches of lipids, termed lipid rafts, which are different from their surroundings in lipid and protein composition. Although the nerve growth factor (NGF receptors, TrkA and p75(NTR collaborate with each other at the plasma membrane to bind NGF, these two receptors are endocytosed separately and activate different cellular responses. We hypothesized that receptor localization in membrane rafts may play a role in endocytic sorting. TrkA and p75(NTR both reside in detergent-resistant membranes (DRMs, yet they responded differently to a variety of conditions. The ganglioside, GM1, caused increased association of NGF, TrkA, and microtubules with DRMs, but a decrease in p75(NTR. When microtubules were induced to polymerize and attach to DRMs by in vitro reactions, TrkA, but not p75(NTR, was bound to microtubules in DRMs and in a detergent-resistant endosomal fraction. NGF enhanced the interaction between TrkA and microtubules in DRMs, yet tyrosine phosphorylated TrkA was entirely absent in DRMs under conditions where activated TrkA was detected in detergent-sensitive membranes and endosomes. These data indicate that TrkA and p75(NTR partition into membrane rafts by different mechanisms, and that the fraction of TrkA that associates with DRMs is internalized but does not directly form signaling endosomes. Rather, by attracting microtubules to lipid rafts, TrkA may mediate other processes such as axon guidance.

  12. NCAM-140 Translocation into Lipid Rafts Mediates the Neuroprotective Effects of GDNF.

    Science.gov (United States)

    Li, Li; Chen, Huizhen; Wang, Meng; Chen, Fangfang; Gao, Jin; Sun, Shen; Li, Yunqing; Gao, Dianshuai

    2017-05-01

    Glial cell line-derived neurotrophic factor (GDNF) is a potent neurotrophic factor for substantia nigra dopaminergic (DA) neuronal cells. Recent studies have demonstrated that neural cell adhesion molecule functions as a signal transduction receptor for GDNF. The purpose of this study is to reveal whether neural cell adhesion molecule (NCAM) mediates the protective effects of GDNF on DA neuronal cells and further explore the mechanisms involved. We utilized SH-SY5Y cell line to establish a model of 6-hydroxydopamine (6-OHDA)-injured DA neuronal cells. Lentiviral vectors were constructed to knockdown or overexpress NCAM-140, and a density gradient centrifugation method was employed to separate membrane lipid rafts. 3-(4,5-Dimethythiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT), flow cytometric analysis, and western blotting were used to evaluate the protective effects of GDNF. The results showed that GDNF could protect 6-OHDA-injured SH-SY5Y cells via improving cell viability and decreasing the cell death rate and cleaved caspase-3 expression. NCAM-140 knockdown decreased cell viability and increased the cell death rate and cleaved caspase-3 expression, while its overexpression had the opposite effects. Notably, the amount of NCAM-140 located in lipid rafts increased after GDNF treatment. Pretreatment with 2-bromopalmitate, a specific inhibitor of protein palmitoylation, suppressed NCAM-140 translocation to lipid rafts and reduced the NCAM-mediated protective effects of GDNF on injured DA neuronal cells. Our results suggest that GDNF have the protective effects on injured DA cells by influencing NCAM-140 translocation into lipid rafts.

  13. LIPID RAFTS, FLUID/FLUID PHASE SEPARATION, AND THEIR RELEVANCE TO PLASMA MEMBRANE STRUCTURE AND FUNCTION

    OpenAIRE

    Sengupta, Prabuddha; Baird, Barbara; Holowka, David

    2007-01-01

    Novel biophysical approaches combined with modeling and new biochemical data have helped to recharge the lipid raft field and have contributed to the generation of a refined model of plasma membrane organization. In this review, we summarize new information in the context of previous literature to provide new insights into the spatial organization and dynamics of lipids and proteins in the plasma membrane of live cells. Recent findings of large-scale separation of liquid-ordered and liquid-di...

  14. Use of social information in seabirds: compass rafts indicate the heading of food patches.

    Directory of Open Access Journals (Sweden)

    Henri Weimerskirch

    Full Text Available Ward and Zahavi suggested in 1973 that colonies could serve as information centres, through a transfer of information on the location of food resources between unrelated individuals (Information Centre Hypothesis. Using GPS tracking and observations on group movements, we studied the search strategy and information transfer in two of the most colonial seabirds, Guanay cormorants (Phalacrocorax bougainvillii and Peruvian boobies (Sula variegata. Both species breed together and feed on the same prey. They do return to the same feeding zone from one trip to the next indicating high unpredictability in the location of food resources. We found that the Guanay cormorants use social information to select their bearing when departing the colony. They form a raft at the sea surface whose position is continuously adjusted to the bearing of the largest returning columns of cormorants. As such, the raft serves as a compass signal that gives an indication on the location of the food patches. Conversely, Peruvian boobies rely mainly on personal information based on memory to take heading at departure. They search for food patches solitarily or in small groups through network foraging by detecting the white plumage of congeners visible at long distance. Our results show that information transfer does occur and we propose a new mechanism of information transfer based on the use of rafts off colonies. The use of rafts for information transfer may be common in central place foraging colonial seabirds that exploit short lasting and/or unpredictably distributed food patches. Over the past decades Guanay cormorants have declined ten times whereas Peruvian boobies have remained relatively stable. We suggest that the decline of the cormorants could be related to reduced social information opportunities and that social behaviour and search strategies have the potential to play an important role in the population dynamics of colonial animals.

  15. Investigation of power flow in a continuous floating raft isolation system

    Institute of Scientific and Technical Information of China (English)

    SONG Kongjie; MAO Yinghong; LIN Li

    2001-01-01

    A general dynamic model of a floating raft isolation system with multiple machines and supports is established. Considering the coupling of the foundation in high frequency and basing on the mobility analysis of substructures, the expression of the power flow transmission spectrum of the finite continuous isolation system of asymmetry is derived. At the same time the mathematical calculation and analysis by figure are made to find the rules related to the isolation effect in the case of different parameters of the system.

  16. Corrosion engineering in the utilization of the Raft River geothermal resource

    Energy Technology Data Exchange (ETDEWEB)

    Miller, R.L.

    1976-08-01

    The economic impact of corrosion and the particular problems of corrosion in the utilization of geothermal energy resources are noted. Corrosion is defined and the parameters that control corrosion in geothermal systems are discussed. A general background of corrosion is presented in the context of the various forms of corrosion, in relation to the Raft River geothermal system. A basic reference for mechanical design engineers involved in the design of geothermal energy recovery systems is provided.

  17. Dynamical Clustering and the Origin of Raft-like Structures in a Model Lipid Membrane

    Science.gov (United States)

    Starr, Francis

    2014-03-01

    We investigate the dynamical heterogeneity of a model single-component lipid membrane using simulations of a coarse-grained representation of lipid molecules. In the liquid-ordered (LO) phase, lipid diffusion is hindered by the transient trapping of molecules by their neighbors, giving rise to two distinct mobility groups: low-mobility lipids which are temporarily ``caged'', and lipids with displacements on the scale of the intermolecular spacing. The lipid molecules within these distinct mobility states cluster, giving rise to transient ``islands'' of enhanced mobility having the size and time scale expected for lipid ``rafts''. These clusters are strikingly similar to the dynamical clusters found in glass-forming fluids, and distinct from phase-separation clusters. Such dynamic heterogeneity is ubiquitous in disordered condensed-phase systems. Thus, we hypothesize that rafts may originate from this universal mechanism, explaining why raft-like regions should arise, regardless of lipid structural or compositional details. This perspective provides a new approach to understand membrane transport.

  18. Hypoxia reduces the efficiency of elisidepsin by inhibiting hydroxylation and altering the structure of lipid rafts.

    Science.gov (United States)

    Király, Anna; Váradi, Tímea; Hajdu, Tímea; Rühl, Ralph; Galmarini, Carlos M; Szöllősi, János; Nagy, Peter

    2013-12-02

    The mechanism of action of elisidepsin (PM02734, Irvalec®) is assumed to involve membrane permeabilization via attacking lipid rafts and hydroxylated lipids. Here we investigate the role of hypoxia in the mechanism of action of elisidepsin. Culturing under hypoxic conditions increased the half-maximal inhibitory concentration and decreased the drug's binding to almost all cell lines which was reversed by incubation of cells with 2-hydroxy palmitic acid. The expression of fatty acid 2-hydroxylase was strongly correlated with the efficiency of the drug and inversely correlated with the effect of hypoxia. Number and brightness analysis and fluorescence anisotropy experiments showed that hypoxia decreased the clustering of lipid rafts and altered the structure of the plasma membrane. Although the binding of elisidepsin to the membrane is non-cooperative, its membrane permeabilizing effect is characterized by a Hill coefficient of ~3.3. The latter finding is in agreement with elisidepsin-induced clusters of lipid raft-anchored GFP visualized by confocal microscopy. We propose that the concentration of elisidepsin needs to reach a critical level in the membrane above which elisidepsin induces the disruption of the cell membrane. Testing for tumor hypoxia or the density of hydroxylated lipids could be an interesting strategy to increase the efficiency of elisidepsin.

  19. Enhancement of Lytic Activity by Leptin Is Independent From Lipid Rafts in Murine Primary Splenocytes.

    Science.gov (United States)

    Collin, Aurore; Noacco, Audrey; Talvas, Jérémie; Caldefie-Chézet, Florence; Vasson, Marie-Paule; Farges, Marie-Chantal

    2017-01-01

    Leptin, a pleiotropic adipokine, is known as a regulator of food intake, but it is also involved in inflammation, immunity, cell proliferation, and survival. Leptin receptor is integrated inside cholesterol-rich microdomains called lipid rafts, which, if disrupted or destroyed, could lead to a perturbation of lytic mechanism. Previous studies also reported that leptin could induce membrane remodeling. In this context, we studied the effect of membrane remodeling in lytic activity modulation induced by leptin. Thus, primary mouse splenocytes were incubated with methyl-β-cyclodextrin (β-MCD), a lipid rafts disrupting agent, cholesterol, a major component of cell membranes, or ursodeoxycholic acid (UDCA), a membrane stabilizer agent for 1 h. These treatments were followed by splenocyte incubation with leptin (absence, 10 and 100 ng/ml). Unlike β-MCD or cholesterol, UDCA was able to block leptin lytic induction. This result suggests that leptin increased the lytic activity of primary spleen cells against syngenic EO771 mammary cancer cells independently from lipid rafts but may involve membrane fluidity. Furthermore, natural killer cells were shown to be involved in the splenocyte lytic activity. To our knowledge it is the first publication in primary culture that provides the link between leptin lytic modulation and membrane remodeling. J. Cell. Physiol. 232: 101-109, 2017. © 2016 Wiley Periodicals, Inc.

  20. Cholesterol-rich lipid rafts play an important role in the Cyprinid herpesvirus 3 replication cycle.

    Science.gov (United States)

    Brogden, Graham; Adamek, Mikołaj; Proepsting, Marcus J; Ulrich, Reiner; Naim, Hassan Y; Steinhagen, Dieter

    2015-09-30

    The Cyprinus herpesvirus 3 (CyHV-3) is a member of the new Alloherpesviridae virus family in the Herpesvirales order. CyHV-3 has been implicated in a large number of disease outbreaks in carp populations causing up to 100% mortality. The aim of this study was to investigate the requirement of cholesterol-rich lipid rafts in CyHV-3 entry and replication in carp cells. Plasma membrane cholesterol was depleted from common carp brain (CCB) cells with methyl-β-cyclodextrin (MβCD). Treated and non-treated cells were infected with CyHV-3 and virus binding and infection parameters were assessed using RT-qPCR, immunocytochemistry and virus titration. The effect of cholesterol reduction severely stunted virus entry in vitro, however after cholesterol replenishment virus entry and subsequent replication rates were similar to the control infection. Furthermore, cholesterol depletion did not significantly influence virus binding and the subsequent post-entry replication stage, however had an impact on virus egress. Comparative analysis of the lipid compositions of CyHV-3 and CCB membrane fractions revealed strong similarities between the lipid composition of the CyHV-3 and CCB lipid rafts. The results presented here show that cholesterol-rich lipid rafts are important for the CyHV-3 replication cycle especially during entry and egress.

  1. Specific interaction of postsynaptic densities with membrane rafts isolated from synaptic plasma membranes.

    Science.gov (United States)

    Liu, Qian; Yao, Wei-Dong; Suzuki, Tatsuo

    2013-06-01

    Postsynaptic membrane rafts are believed to play important roles in synaptic signaling, plasticity, and maintenance. We recently demonstrated the presence, at the electron microscopic level, of complexes consisting of membrane rafts and postsynaptic densities (PSDs) in detergent-resistant membranes (DRMs) prepared from synaptic plasma membranes (SPMs) ( Suzuki et al., 2011 , J Neurochem, 119, 64-77). To further explore these complexes, here we investigated the nature of the binding between purified SPM-DRMs and PSDs in vitro. In binding experiments, we used SPM-DRMs prepared after treating SPMs with n-octyl-β-d-glucoside, because at concentrations of 1.0% or higher it completely separates SPM-DRMs and PSDs, providing substantially PSD-free unique SPM-DRMs as well as DRM-free PSDs. PSD binding to PSD-free DRMs was identified by mass spectrometry, Western blotting, and electron microscopy. PSD proteins were not incorporated into SPMs, and significantly less PSD proteins were incorporated into DRMs prepared from liver membranes, providing in vitro evidence that binding of PSDs to DRMs is specific and suggestion of the presence of specific interacting molecules. These specific interactions may have important roles in synaptic development, function, and plasticity in vivo. In addition, the binding system we developed may be a good tool to search for binding molecules and binding mechanisms between PSDs and rafts.

  2. HTLV-1 Tax deregulates autophagy by recruiting autophagic molecules into lipid raft microdomains.

    Science.gov (United States)

    Ren, T; Takahashi, Y; Liu, X; Loughran, T P; Sun, S-C; Wang, H-G; Cheng, H

    2015-01-15

    The retroviral oncoprotein Tax from human T-cell leukemia virus type 1 (HTLV-1), an etiological factor that causes adult T-cell leukemia and lymphoma, has a crucial role in initiating T-lymphocyte transformation by inducing oncogenic signaling activation. We here report that Tax is a determining factor for dysregulation of autophagy in HTLV-1-transformed T cells and Tax-immortalized CD4 memory T cells. Tax facilitated autophagic process by activating inhibitor of κB (IκB) kinase (IKK) complex, which subsequently recruited an autophagy molecular complex containing Beclin1 and Bif-1 to the lipid raft microdomains. Tax engaged a crosstalk between IKK complex and autophagic molecule complex by directly interacting with both complexes, promoting assembly of LC3+ autophagosomes. Moreover, expression of lipid raft-targeted Bif-1 or Beclin1 was sufficient to induce formation of LC3+ autophagosomes, suggesting that Tax recruitment of autophagic molecules to lipid rafts is a dominant strategy to deregulate autophagy in the context of HTLV-1 transformation of T cells. Furthermore, depletion of autophagy molecules such as Beclin1 and PI3 kinase class III resulted in impaired growth of HTLV-1-transformed T cells, indicating a critical role of Tax-deregulated autophagy in promoting survival and transformation of virally infected T cells.

  3. Adenylate cyclase toxin promotes internalisation of integrins and raft components and decreases macrophage adhesion capacity.

    Directory of Open Access Journals (Sweden)

    César Martín

    Full Text Available Bordetella pertussis, the bacterium that causes whooping cough, secretes an adenylate cyclase toxin (ACT that must be post-translationally palmitoylated in the bacterium cytosol to be active. The toxin targets phagocytes expressing the CD11b/CD18 integrin receptor. It delivers a catalytic adenylate cyclase domain into the target cell cytosol producing a rapid increase of intracellular cAMP concentration that suppresses bactericidal functions of the phagocyte. ACT also induces calcium fluxes into target cells. Biochemical, biophysical and cell biology approaches have been applied here to show evidence that ACT and integrin molecules, along with other raft components, are rapidly internalized by the macrophages in a toxin-induced calcium rise-dependent process. The toxin-triggered internalisation events occur through two different routes of entry, chlorpromazine-sensitive receptor-mediated endocytosis and clathrin-independent internalisation, maybe acting in parallel. ACT locates into raft-like domains, and is internalised, also in cells devoid of receptor. Altogether our results suggest that adenylate cyclase toxin, and maybe other homologous pathogenic toxins from the RTX (Repeats in Toxin family to which ACT belongs, may be endowed with an intrinsic capacity to, directly and efficiently, insert into raft-like domains, promoting there its multiple activities. One direct consequence of the integrin removal from the cell surface of the macrophages is the hampering of their adhesion ability, a fundamental property in the immune response of the leukocytes that could be instrumental in the pathogenesis of Bordetella pertussis.

  4. The C1 and C2 domains target human type 6 adenylyl cyclase to lipid rafts and caveolae.

    Science.gov (United States)

    Thangavel, Muthusamy; Liu, Xiaoqiu; Sun, Shu Qiang; Kaminsky, Joseph; Ostrom, Rennolds S

    2009-02-01

    Previous data has shown that adenylyl cyclase type 6 (AC6) is expressed principally in lipid rafts or caveolae of cardiac myocytes and other cell types while certain other isoforms of AC are excluded from these microdomains. The mechanism by which AC6 is localized to lipid rafts or caveolae is unknown. In this study, we show AC6 is localized in lipid rafts of COS-7 cells (expressing caveolin-1) and in HEK-293 cells or cardiac fibroblasts isolated from caveolin-1 knock-out mice (both of which lack prototypical caveolins). To determine the region of AC6 that confers raft localization, we independently expressed each of the major intracellular domains, the N-terminus, C1 and C2 domains, and examined their localization with various approaches. The N-terminus did not associate with lipid rafts or caveolae of either COS-7 or HEK-293 cells nor did it immunoprecipitate with caveolin-1 when expressed in COS-7 cells. By contrast, the C1 and C2 domains each associated with lipid rafts to varying degrees and were present in caveolin-1 immunoprecipitates. There were no differences in the pattern of localization of either the C1 or C2 domains between COS-7 and HEK-293 cells. Further dissection of the C1 domain into four individual proteins indicated that the N-terminal half of this domain is responsible for its raft localization. To probe for a role of a putative palmitoylation motif in the C-terminal portion of the C2 domain, we expressed various truncated forms of AC6 lacking most or all of the C-terminal 41 amino acids. These truncated AC6 proteins were not altered in terms of their localization in lipid rafts or their catalytic activity, implying that this C-terminal region is not required for lipid raft targeting of AC6. We conclude that while the C1 domain may be most important, both the C1 and C2 domains of AC6 play a role in targeting AC6 to lipid rafts.

  5. High Molecular Weight Complex Analysis of Epstein-Barr Virus Latent Membrane Protein 1 (LMP-1): Structural Insights into LMP-1’s Homo-Oligomerization and Lipid Raft Association

    Science.gov (United States)

    Wrobel, Christopher M.; Geiger, Timothy R.; Nix, Rebecca N.; Robitaille, Aaron M.; Balser, Sandra; Cervantes, Alfredo; Gonzalez, Miguel; Martin, Jennifer M.

    2013-01-01

    LMP-1 is a constitutively active Tumor Necrosis Factor Receptor analog encoded by Epstein-Barr virus. LMP-1 activation correlates with oligomerization and raft localization, but direct evidence of LMP-1 oligomers is limited. We report that LMP-1 forms multiple high molecular weight native LMP-1 complexes when analyzed by BN-PAGE, the largest of which are enriched in detergent resistant membranes. The largest of these high molecular weight complexes are not formed by purified LMP-1 or by loss of function LMP-1 mutants. Consistent with these results we find a dimeric form of LMP-1 that can be stabilized by disulfide crosslinking. We identify cysteine 238 in the C-terminus of LMP-1 as the crosslinked cysteine. Disulfide crosslinking occurs post-lysis but the dimer can be crosslinked in intact cells with membrane permeable crosslinkers. LMP-1/C238A retains wild type LMP-1 NF-κB activity. LMP-1’s TRAF binding, raft association and oligomerization are associated with the dimeric form of LMP-1. Our results suggest the possibility that the observed dimeric species results from inter-oligomeric crosslinking of LMP-1 molecules in adjacent core LMP-1 oligomers. PMID:24075898

  6. Novel aspects of platelet aggregation

    Directory of Open Access Journals (Sweden)

    Roka-Moya Y. M.

    2014-01-01

    Full Text Available The platelet aggregation is an important process, which is critical for the hemostatic plug formation and thrombosis. Recent studies have shown that the platelet aggregation is more complex and dynamic than it was previously thought. There are several mechanisms that can initiate the platelet aggregation and each of them operates under specific conditions in vivo. At the same time, the influence of certain plasma proteins on this process should be considered. This review intends to summarize the recent data concerning the adhesive molecules and their receptors, which provide the platelet aggregation under different conditions.

  7. Antiproliferative effects of γ-tocotrienol are associated with lipid raft disruption in HER2-positive human breast cancer cells.

    Science.gov (United States)

    Alawin, Osama A; Ahmed, Rayan A; Ibrahim, Baher A; Briski, Karen P; Sylvester, Paul W

    2016-01-01

    A large percentage of human breast cancers are characterized by excessive or aberrant HER2 activity. Lipid rafts are specialized microdomains within the plasma membrane that are required for HER2 activation and signal transduction. Since the anticancer activity of γ-tocotrienol is associated with suppression in HER2 signaling, studies were conducted to examine the effects of γ-tocotrienol on HER2 activation within the lipid raft microdomain in HER2-positive SKBR3 and BT474 human breast cancer cells. Treatment with 0-5μM γ-tocotrienol induced a significant dose-dependent inhibition in cancer cell growth after a 5-day culture period, and these growth inhibitory effects were associated with a reduction in HER2 dimerization and phosphorylation (activation). Phosphorylated HER2 was found to be primarily located in the lipid raft microdomain of the plasma membrane in vehicle-treated control groups, whereas γ-tocotrienol treatment significantly inhibited this effect. Assay of plasma membrane subcellular fractions showed that γ-tocotrienol also accumulates exclusively within the lipid raft microdomain. Hydroxypropyl-β-cyclodextrin (HPβCD) is an agent that disrupts lipid raft integrity. Acute exposure to 3mM HPβCD alone had no effect, whereas an acute 24-h exposure to 20μM γ-tocotrienol alone significantly decreased SKBR3 and BT474 cell viability. However, combined treatment with these agents greatly reduced γ-tocotrienol accumulation in the lipid raft microdomain and cytotoxicity. In summary, these findings demonstrate that the anticancer effects of γ-tocotrienol are associated with its accumulation in the lipid raft microdomain and subsequent interference with HER2 dimerization and activation in SKBR3 and BT474 human breast cancer cells.

  8. The RAFT Telemedicine Network in Low and Middle Income Countries: Educational and Clinical Services, Lessons Learnt and Perspectives

    Directory of Open Access Journals (Sweden)

    Georges eBediang

    2014-10-01

    Full Text Available Background: The objectives of this paper are to: i provide an overview of the educational and clinical experiences of the RAFT network, ii analyse key challenges and lessons learnt throughout a decade of activity and, iii draw a vision and perspectives of its sustainability.Methods: The study was carried out following three main stages: i a literature review, ii the analysis of key documents and iii discussions with key collaborators of the RAFT.Results: RAFT has been offering an important quantity of educational, clinical and public health activities during the last decade. The educational activities include: the weekly delivery of video-lectures for continuing and postgraduate medical education, the use of virtual patients for training in clinical decision making, research training activities using ICTs and other e-learning activities. The clinical and public health activities include: tele-expertise to support health professionals in the management of difficult clinical cases, the implementation of clinical information systems in African hospitals, the deployment of mHealth projects, etc. Since 2010, the RAFT has been extended to the Altiplano in Bolivia and Nepal (in progress. Lessons learnt and perspectives: Important lessons have been learnt from the accumulated experiences throughout these years. These lessons concern: social and organization, human resources, technologies and data security, policy and legislation, and economy and financing. Also, given the increase of the activities and the integration of eHealth and telemedicine in the health system of most of the countries, the RAFT network faces many other challenges and perspectives such as: learning throughout life, recognition and valorisation of teaching or learning activities, the impact evaluation of interventions, and the scaling up and transferability out of Africa of RAFT activities. Based on the RAFT experience, effective integration and optimum use of eHealth and

  9. Cholesterol accumulation in Niemann Pick type C (NPC) model cells causes a shift in APP localization to lipid rafts

    Energy Technology Data Exchange (ETDEWEB)

    Kosicek, Marko, E-mail: marko.kosicek@irb.hr [Division of Molecular Medicine, Ruder Boskovic Institute, Bijenicka 54, 10000 Zagreb (Croatia); Malnar, Martina, E-mail: martina.malnar@irb.hr [Division of Molecular Medicine, Ruder Boskovic Institute, Bijenicka 54, 10000 Zagreb (Croatia); Goate, Alison, E-mail: goate@icarus.wustl.edu [Department of Psychiatry, Washington University School of Medicine, 660 S. Euclid Ave., St. Louis, MO 63110 (United States); Hecimovic, Silva, E-mail: silva.hecimovic@irb.hr [Division of Molecular Medicine, Ruder Boskovic Institute, Bijenicka 54, 10000 Zagreb (Croatia)

    2010-03-12

    It has been suggested that cholesterol may modulate amyloid-{beta} (A{beta}) formation, a causative factor of Alzheimer's disease (AD), by regulating distribution of the three key proteins in the pathogenesis of AD ({beta}-amyloid precursor protein (APP), {beta}-secretase (BACE1) and/or presenilin 1 (PS1)) within lipid rafts. In this work we tested whether cholesterol accumulation upon NPC1 dysfunction, which causes Niemann Pick type C disease (NPC), causes increased partitioning of APP into lipid rafts leading to increased CTF/A{beta} formation in these cholesterol-rich membrane microdomains. To test this we used CHO NPC1{sup -/-} cells (NPC cells) and parental CHOwt cells. By sucrose density gradient centrifugation we observed a shift in fl-APP/CTF compartmentalization into lipid raft fractions upon cholesterol accumulation in NPC vs. wt cells. Furthermore, {gamma}-secretase inhibitor treatment significantly increased fl-APP/CTF distribution in raft fractions in NPC vs. wt cells, suggesting that upon cholesterol accumulation in NPC1-null cells increased formation of APP-CTF and its increased processing towards A{beta} occurs in lipid rafts. Our results support that cholesterol overload, such as in NPC disease, leads to increased partitioning of APP/CTF into lipid rafts resulting in increased amyloidogenic processing of APP in these cholesterol-rich membranes. This work adds to the mechanism of the cholesterol-effect on APP processing and the pathogenesis of Alzheimer's disease and supports the role of lipid rafts in these processes.

  10. Fractal Aggregation Under Rotation

    Institute of Scientific and Technical Information of China (English)

    WU Feng-Min; WU Li-Li; LU Hang-Jun; LI Qiao-Wen; YE Gao-Xiang

    2004-01-01

    By means of the Monte Carlo simulation, a fractal growth model is introduced to describe diffusion-limited aggregation (DLA) under rotation. Patterns which are different from the classical DLA model are observed and the fractal dimension of such clusters is calculated. It is found that the pattern of the clusters and their fractal dimension depend strongly on the rotation velocity of the diffusing particle. Our results indicate the transition from fractal to non-fractal behavior of growing cluster with increasing rotation velocity, i.e. for small enough angular velocity ω the fractal dimension decreases with increasing ω, but then, with increasing rotation velocity, the fractal dimension increases and the cluster becomes compact and tends to non-fractal.

  11. Fractal Aggregation Under Rotation

    Institute of Scientific and Technical Information of China (English)

    WUFeng-Min; WULi-Li; LUHang-Jun; LIQiao-Wen; YEGao-Xiang

    2004-01-01

    By means of the Monte Carlo simulation, a fractal growth model is introduced to describe diffusion-limited aggregation (DLA) under rotation. Patterns which are different from the classical DLA model are observed and the fractal dimension of such clusters is calculated. It is found that the pattern of the clusters and their fractal dimension depend strongly on the rotation velocity of the diffusing particle. Our results indicate the transition from fractal to non-fractal behavior of growing cluster with increasing rotation velocity, i.e. for small enough angular velocity ω; thefractal dimension decreases with increasing ω;, but then, with increasing rotation velocity, the fractal dimension increases and the cluster becomes compact and tends to non-fractal.

  12. Platelet aggregation following trauma

    DEFF Research Database (Denmark)

    Windeløv, Nis A; Sørensen, Anne M; Perner, Anders

    2014-01-01

    We aimed to elucidate platelet function in trauma patients, as it is pivotal for hemostasis yet remains scarcely investigated in this population. We conducted a prospective observational study of platelet aggregation capacity in 213 adult trauma patients on admission to an emergency department (ED......). Inclusion criteria were trauma team activation and arterial cannula insertion on arrival. Blood samples were analyzed by multiple electrode aggregometry initiated by thrombin receptor agonist peptide 6 (TRAP) or collagen using a Multiplate device. Blood was sampled median 65 min after injury; median injury...... severity score (ISS) was 17; 14 (7%) patients received 10 or more units of red blood cells in the ED (massive transfusion); 24 (11%) patients died within 28 days of trauma: 17 due to cerebral injuries, four due to exsanguination, and three from other causes. No significant association was found between...

  13. Widespread Protein Aggregation as an Inherent Part of Aging in C. elegans

    Science.gov (United States)

    David, Della C.; Ollikainen, Noah; Trinidad, Jonathan C.; Cary, Michael P.; Burlingame, Alma L.; Kenyon, Cynthia

    2010-01-01

    Aberrant protein aggregation is a hallmark of many age-related diseases, yet little is known about whether proteins aggregate with age in a non-disease setting. Using a systematic proteomics approach, we identified several hundred proteins that become more insoluble with age in the multicellular organism Caenorhabditis elegans. These proteins are predicted to be significantly enriched in β-sheets, which promote disease protein aggregation. Strikingly, these insoluble proteins are highly over-represented in aggregates found in human neurodegeneration. We examined several of these proteins in vivo and confirmed their propensity to aggregate with age. Different proteins aggregated in different tissues and cellular compartments. Protein insolubility and aggregation were significantly delayed or even halted by reduced insulin/IGF-1-signaling, which also slows aging. We found a significant overlap between proteins that become insoluble and proteins that influence lifespan and/or polyglutamine-repeat aggregation. Moreover, overexpressing one aggregating protein enhanced polyglutamine-repeat pathology. Together our findings indicate that widespread protein insolubility and aggregation is an inherent part of aging and that it may influence both lifespan and neurodegenerative disease. PMID:20711477

  14. Widespread protein aggregation as an inherent part of aging in C. elegans.

    Directory of Open Access Journals (Sweden)

    Della C David

    Full Text Available Aberrant protein aggregation is a hallmark of many age-related diseases, yet little is known about whether proteins aggregate with age in a non-disease setting. Using a systematic proteomics approach, we identified several hundred proteins that become more insoluble with age in the multicellular organism Caenorhabditis elegans. These proteins are predicted to be significantly enriched in beta-sheets, which promote disease protein aggregation. Strikingly, these insoluble proteins are highly over-represented in aggregates found in human neurodegeneration. We examined several of these proteins in vivo and confirmed their propensity to aggregate with age. Different proteins aggregated in different tissues and cellular compartments. Protein insolubility and aggregation were significantly delayed or even halted by reduced insulin/IGF-1-signaling, which also slows aging. We found a significant overlap between proteins that become insoluble and proteins that influence lifespan and/or polyglutamine-repeat aggregation. Moreover, overexpressing one aggregating protein enhanced polyglutamine-repeat pathology. Together our findings indicate that widespread protein insolubility and aggregation is an inherent part of aging and that it may influence both lifespan and neurodegenerative disease.

  15. Thermal breeder fuel enrichment zoning

    Science.gov (United States)

    Capossela, Harry J.; Dwyer, Joseph R.; Luce, Robert G.; McCoy, Daniel F.; Merriman, Floyd C.

    1992-01-01

    A method and apparatus for improving the performance of a thermal breeder reactor having regions of higher than average moderator concentration are disclosed. The fuel modules of the reactor core contain at least two different types of fuel elements, a high enrichment fuel element and a low enrichment fuel element. The two types of fuel elements are arranged in the fuel module with the low enrichment fuel elements located between the high moderator regions and the high enrichment fuel elements. Preferably, shim rods made of a fertile material are provided in selective regions for controlling the reactivity of the reactor by movement of the shim rods into and out of the reactor core. The moderation of neutrons adjacent the high enrichment fuel elements is preferably minimized as by reducing the spacing of the high enrichment fuel elements and/or using a moderator having a reduced moderating effect.

  16. Exciton dynamics in molecular aggregates

    NARCIS (Netherlands)

    Augulis, R.; Pugžlys, A.; Loosdrecht, P.H.M. van; Pugzlys, A

    2006-01-01

    The fundamental aspects of exciton dynamics in double-wall cylindrical aggregates of cyanine dyes are studied by means of frequency resolved femtosecond pump-probe spectroscopy. The collective excitations of the aggregates, resulting from intermolecular dipole-dipole interactions have the characteri

  17. Aggregate resources in the Netherlands

    NARCIS (Netherlands)

    Meulen, M.J. van der; Gessel, S.F. van; Veldkamp, J.G.

    2005-01-01

    We have built a 3D lithological model of the Netherlands, for the purpose of mapping on-land aggregate resources down to 50 m below the surface. The model consists of voxel cells (1000 · 1000 · 1 m), with lithological composition and aggregate content estimates as primary attributes. These attribute

  18. Exciton dynamics in molecular aggregates

    NARCIS (Netherlands)

    Augulis, R.; Pugžlys, A.; Loosdrecht, P.H.M. van; Pugzlys, A

    2006-01-01

    The fundamental aspects of exciton dynamics in double-wall cylindrical aggregates of cyanine dyes are studied by means of frequency resolved femtosecond pump-probe spectroscopy. The collective excitations of the aggregates, resulting from intermolecular dipole-dipole interactions have the

  19. Sterol carrier protein 2 regulates proximal tubule size in the Xenopus pronephric kidney by modulating lipid rafts.

    Science.gov (United States)

    Cerqueira, Débora M; Tran, Uyen; Romaker, Daniel; Abreu, José G; Wessely, Oliver

    2014-10-01

    The kidney is a homeostatic organ required for waste excretion and reabsorption of water, salts and other macromolecules. To this end, a complex series of developmental steps ensures the formation of a correctly patterned and properly proportioned organ. While previous studies have mainly focused on the individual signaling pathways, the formation of higher order receptor complexes in lipid rafts is an equally important aspect. These membrane platforms are characterized by differences in local lipid and protein compositions. Indeed, the cells in the Xenopus pronephric kidney were positive for the lipid raft markers ganglioside GM1 and Caveolin-1. To specifically interfere with lipid raft function in vivo, we focused on the Sterol Carrier Protein 2 (scp2), a multifunctional protein that is an important player in remodeling lipid raft composition. In Xenopus, scp2 mRNA was strongly expressed in differentiated epithelial structures of the pronephric kidney. Knockdown of scp2 did not interfere with the patterning of the kidney along its proximo-distal axis, but dramatically decreased the size of the kidney, in particular the proximal tubules. This phenotype was accompanied by a reduction of lipid rafts, but was independent of the peroxisomal or transcriptional activities of scp2. Finally, disrupting lipid micro-domains by inhibiting cholesterol synthesis using Mevinolin phenocopied the defects seen in scp2 morphants. Together these data underscore the importance for localized signaling platforms in the proper formation of the Xenopus kidney.

  20. Molecular aggregation of humic substances

    Science.gov (United States)

    Wershaw, R. L.

    1999-01-01

    Humic substances (HS) form molecular aggregates in solution and on mineral surfaces. Elucidation of the mechanism of formation of these aggregates is important for an understanding of the interactions of HS in soils arid natural waters. The HS are formed mainly by enzymatic depolymerization and oxidation of plant biopolymers. These reactions transform the aromatic and lipid plant components into amphiphilic molecules, that is, molecules that consist of separate hydrophobic (nonpolar) and hydrophilic (polar) parts. The nonpolar parts of the molecules are composed of relatively unaltered segments of plant polymers and the polar parts of carboxylic acid groups. These amphiphiles form membrane-like aggregates on mineral surfaces and micelle-like aggregates in solution. The exterior surfaces of these aggregates are hydrophilic, and the interiors constitute separate hydrophobic liquid-like phases.

  1. Optical monitoring of particle aggregates

    Institute of Scientific and Technical Information of China (English)

    John Gregory

    2009-01-01

    Methods for monitoring particle aggregation are briefly reviewed. Most of these techniques are based on some form of light scattering and may be greatly dependent on the optical properties of aggregates, which are not generally known. As fractal aggregates grow larger their density can become very low and this has important practical consequences for light scattering. For instance, the scattering coefficient may be much less than for solid objects, which means that the aggregates can appear much smaller than their actual size by a light transmission method. Also, for low-density objects, a high proportion of the scattered light energy is within a small angle of the incident beam, which may also be relevant for measurements with aggregates.Using the 'turbidity fluctuation' technique as an example, it is shown how the apparent size of hydroxide flocs depends mainly on the included impurity particles, rather than the hydroxide precipitate itself. Results using clay suspensions with hydrolyzing coagulants and under are discussed.

  2. Dye Aggregation in Ink Jet

    Institute of Scientific and Technical Information of China (English)

    Thomas Paul; Sarfraz Hussain

    2004-01-01

    Dye aggregation has long been recognised as a key factor in performance, and this is no less so in ink jet applications. The aggregation state was shown to be important in many different areas ranging from the use of dyes in photodynamic therapies all the way to colorants for dying of fabrics. Therefore different methods to investigate dye association qualitatively and quantitatively were developed. A simple procedure to study aggregation could be a useful tool to characterise dyes for ink jet printing. It is critically reviewed the methods used to study dye aggregation, and discussed some of the main conclusions. This will be illustrated by examples of ink jet dye aggregation and its study in aqueous and ink systems. The results are used to correlate the solution behaviour of dyes with their print performance.

  3. DRAG ON SUBMICRON NANOPARTICLE AGGREGATES

    Institute of Scientific and Technical Information of China (English)

    F.; Einar; Kruis

    2005-01-01

    A new procedure was developed for estimating the effective collision diameter of an aggregate composed of primary particles of any size. The coagulation coefficient of two oppositely charged particles was measured experimentally and compared with classic Fuchs theory, including a new method to account for particle non-sphericity. A second set of experiments were performed on well-defined nanoparticle aggregates at different stages of sintering, i.e. from the aggregate to the fully sintered stage. Here, electrical mobility was used to characterize the particle drag. The aggregates are being built from two different size-fractionated nanoparticle aerosols, the non-aggregated particles are discarded by an electrofilter and then they are passed through a furnace at concentrations low enough not to induce coagulation.

  4. The Slowly Aggregating Salmon Calcitonin: A Useful Tool for the Study of the Amyloid Oligomers Structure and Activity

    Directory of Open Access Journals (Sweden)

    Marco Diociaiuti

    2011-12-01

    Full Text Available Amyloid proteins of different aminoacidic composition share the tendency to misfold and aggregate in a similar way, following common aggregation steps. The process includes the formation of dimers, trimers, and low molecular weight prefibrillar oligomers, characterized by the typical morphology of globules less than 10 nm diameter. The globules spontaneously form linear or annular structures and, eventually, mature fibers. The rate of this process depends on characteristics intrinsic to the different proteins and to environmental conditions (i.e., pH, ionic strength, solvent composition, temperature. In the case of neurodegenerative diseases, it is now generally agreed that the pathogenic aggregates are not the mature fibrils, but the intermediate, soluble oligomers. However, the molecular mechanism by which these oligomers trigger neuronal damage is still unclear. Inparticular, it is not clear if there is a peculiar structure at the basis of the neurotoxic effect and how this structure interacts with neurons. This review will focus on the results we obtained using salmon Calcitonin, an amyloid protein characterized by a very slow aggregation rate, which allowed us to closely monitor the aggregation process. We used it as a tool to investigate the characteristics of amyloid oligomers formation and their interactions with neuronal cells. Our results indicate that small globules of about 6 nm could be the responsible for the neurotoxic effects. Moreover, our data suggest that the rich content in lipid rafts of neuronal cell plasma membrane may render neurons particularly vulnerable to the amyloid protein toxic effect.

  5. The slowly aggregating salmon Calcitonin: a useful tool for the study of the amyloid oligomers structure and activity.

    Science.gov (United States)

    Diociaiuti, Marco; Gaudiano, Maria Cristina; Malchiodi-Albedi, Fiorella

    2011-01-01

    Amyloid proteins of different aminoacidic composition share the tendency to misfold and aggregate in a similar way, following common aggregation steps. The process includes the formation of dimers, trimers, and low molecular weight prefibrillar oligomers, characterized by the typical morphology of globules less than 10 nm diameter. The globules spontaneously form linear or annular structures and, eventually, mature fibers. The rate of this process depends on characteristics intrinsic to the different proteins and to environmental conditions (i.e., pH, ionic strength, solvent composition, temperature). In the case of neurodegenerative diseases, it is now generally agreed that the pathogenic aggregates are not the mature fibrils, but the intermediate, soluble oligomers. However, the molecular mechanism by which these oligomers trigger neuronal damage is still unclear. In particular, it is not clear if there is a peculiar structure at the basis of the neurotoxic effect and how this structure interacts with neurons. This review will focus on the results we obtained using salmon Calcitonin, an amyloid protein characterized by a very slow aggregation rate, which allowed us to closely monitor the aggregation process. We used it as a tool to investigate the characteristics of amyloid oligomers formation and their interactions with neuronal cells. Our results indicate that small globules of about 6 nm could be the responsible for the neurotoxic effects. Moreover, our data suggest that the rich content in lipid rafts of neuronal cell plasma membrane may render neurons particularly vulnerable to the amyloid protein toxic effect.

  6. Perspectives on Preference Aggregation.

    Science.gov (United States)

    Regenwetter, Michel

    2009-07-01

    For centuries, the mathematical aggregation of preferences by groups, organizations, or society itself has received keen interdisciplinary attention. Extensive theoretical work in economics and political science throughout the second half of the 20th century has highlighted the idea that competing notions of rational social choice intrinsically contradict each other. This has led some researchers to consider coherent democratic decision making to be a mathematical impossibility. Recent empirical work in psychology qualifies that view. This nontechnical review sketches a quantitative research paradigm for the behavioral investigation of mathematical social choice rules on real ballots, experimental choices, or attitudinal survey data. The article poses a series of open questions. Some classical work sometimes makes assumptions about voter preferences that are descriptively invalid. Do such technical assumptions lead the theory astray? How can empirical work inform the formulation of meaningful theoretical primitives? Classical "impossibility results" leverage the fact that certain desirable mathematical properties logically cannot hold in all conceivable electorates. Do these properties nonetheless hold true in empirical distributions of preferences? Will future behavioral analyses continue to contradict the expectations of established theory? Under what conditions do competing consensus methods yield identical outcomes and why do they do so?

  7. Orthogonal flexible Rydberg aggregates

    Science.gov (United States)

    Leonhardt, K.; Wüster, S.; Rost, J. M.

    2016-02-01

    We study the link between atomic motion and exciton transport in flexible Rydberg aggregates, assemblies of highly excited light alkali-metal atoms, for which motion due to dipole-dipole interaction becomes relevant. In two one-dimensional atom chains crossing at a right angle adiabatic exciton transport is affected by a conical intersection of excitonic energy surfaces, which induces controllable nonadiabatic effects. A joint exciton-motion pulse that is initially governed by a single energy surface is coherently split into two modes after crossing the intersection. The modes induce strongly different atomic motion, leading to clear signatures of nonadiabatic effects in atomic density profiles. We have shown how this scenario can be exploited as an exciton switch, controlling direction and coherence properties of the joint pulse on the second of the chains [K. Leonhardt et al., Phys. Rev. Lett. 113, 223001 (2014), 10.1103/PhysRevLett.113.223001]. In this article we discuss the underlying complex dynamics in detail, characterize the switch, and derive our isotropic interaction model from a realistic anisotropic one with the addition of a magnetic bias field.

  8. Orthogonal flexible Rydberg aggregates

    CERN Document Server

    Leonhardt, K; Rost, J M

    2015-01-01

    We study the link between atomic motion and exciton transport in flexible Rydberg aggregates, assemblies of highly excited light alkali atoms, for which motion due to dipole-dipole interaction becomes relevant. In two one-dimensional atom chains crossing at a right angle adiabatic exciton transport is affected by a conical intersection of excitonic energy surfaces, which induces controllable non-adiabatic effects. A joint exciton/motion pulse that is initially governed by a single energy surface is coherently split into two modes after crossing the intersection. The modes induce strongly different atomic motion, leading to clear signatures of non-adiabatic effects in atomic density profiles. We have shown how this scenario can be exploited as an exciton switch, controlling direction and coherence properties of the joint pulse on the second of the chains [K.~Leonhardt {\\it et al.}, Phys.~Rev.~Lett. {\\bf 113} 223001 (2014)]. In this article we discuss the underlying complex dynamics in detail, characterise the ...

  9. ENRICHMENT OF OBO ONTOLOGIES

    Science.gov (United States)

    Bada, Michael; Hunter, Lawrence

    2006-01-01

    This paper describes a frame-based integration of the three GO subontologies, the Chemicals of Biological Interest ontology (ChEBI), and the Cell Type Ontology (CTO) in which relationships between elements of the ontologies are modeled in a way that better captures the relational semantics between biological concepts represented by the terms, rather than between the terms themselves, than previous frame-based efforts. We also describe a methodology for creating suggested enriching assertions of the form (subject, relationship, object) by identifying patterns in GO terms, mapping these patterns and subpatterns to relationships, matching concepts to these patterns and subpatterns, and integrating these assertions into the ontologies. Using this methodology, a large number of reliable assertions linking previously unlinked OBO terms using a wide variety of specific, hierarchically arranged relationships were created: A predicted assertion was made for 62% of GO terms that matched one of 31 patterns, and 97% of these predicted assertions were assessed to be valid; a further 429 assertions (corresponding to 6% of the matching terms) were manually created, resulting in an initial set of 4,497 assertions. Furthermore, this methodology programmatically integrates assertions into a base ontology such that each assertion is fully consistent with respect to higher (i.e., more general) relevant class and slot levels. Such an integration is absent from previous compositional efforts, and we argue its necessity for the creation of coherent biological ontologies when linking previously unlinked terms. PMID:17011833

  10. Earthquake forecast enrichment scores

    Directory of Open Access Journals (Sweden)

    Christine Smyth

    2012-03-01

    Full Text Available The Collaboratory for the Study of Earthquake Predictability (CSEP is a global project aimed at testing earthquake forecast models in a fair environment. Various metrics are currently used to evaluate the submitted forecasts. However, the CSEP still lacks easily understandable metrics with which to rank the universal performance of the forecast models. In this research, we modify a well-known and respected metric from another statistical field, bioinformatics, to make it suitable for evaluating earthquake forecasts, such as those submitted to the CSEP initiative. The metric, originally called a gene-set enrichment score, is based on a Kolmogorov-Smirnov statistic. Our modified metric assesses if, over a certain time period, the forecast values at locations where earthquakes have occurred are significantly increased compared to the values for all locations where earthquakes did not occur. Permutation testing allows for a significance value to be placed upon the score. Unlike the metrics currently employed by the CSEP, the score places no assumption on the distribution of earthquake occurrence nor requires an arbitrary reference forecast. In this research, we apply the modified metric to simulated data and real forecast data to show it is a powerful and robust technique, capable of ranking competing earthquake forecasts.

  11. City model enrichment

    Science.gov (United States)

    Smart, Philip D.; Quinn, Jonathan A.; Jones, Christopher B.

    The combination of mobile communication technology with location and orientation aware digital cameras has introduced increasing interest in the exploitation of 3D city models for applications such as augmented reality and automated image captioning. The effectiveness of such applications is, at present, severely limited by the often poor quality of semantic annotation of the 3D models. In this paper, we show how freely available sources of georeferenced Web 2.0 information can be used for automated enrichment of 3D city models. Point referenced names of prominent buildings and landmarks mined from Wikipedia articles and from the OpenStreetMaps digital map and Geonames gazetteer have been matched to the 2D ground plan geometry of a 3D city model. In order to address the ambiguities that arise in the associations between these sources and the city model, we present procedures to merge potentially related buildings and implement fuzzy matching between reference points and building polygons. An experimental evaluation demonstrates the effectiveness of the presented methods.

  12. Aggregation of Euphausia sibogae during Summer Monsoon along the Southwest Coast of India

    Directory of Open Access Journals (Sweden)

    K. J. Jayalakshmi

    2011-01-01

    Full Text Available The influence of environmental parameters on the spawning aggregation of Euphausia sibogae was investigated along the southwest coast of India during the peak phase of summer monsoon 2005. The prevailing ecological conditions between the aggregation period (peak phase and non-aggregation period (early phase were also compared. The aggregation was observed at station 1 (8∘N; 76.5∘E, 480 ind⋅m-3 and 6 (10∘N; 75.5∘E, 839 ind.m-3 during the peak phase of the summer monsoon. Eggs (14769 eggs m-3 and different developmental stages were observed in higher abundance at station 6. The physicochemical conditions indicated that the aggregation coincided with the upwelling. The nutrient enrichment due to the upwelling triggered phytoplankton blooms, and this appeared to provide a conducive environment for spawning and development of E. sibogae.

  13. Ligand binding alters dimerization and sequestering of urokinase receptors in raft-mimicking lipid mixtures.

    Science.gov (United States)

    Ge, Yifan; Siegel, Amanda P; Jordan, Rainer; Naumann, Christoph A

    2014-11-01

    Lipid heterogeneities, such as lipid rafts, are widely considered to be important for the sequestering of membrane proteins in plasma membranes, thereby influencing membrane protein functionality. However, the underlying mechanisms of such sequestration processes remain elusive, in part, due to the small size and often transient nature of these functional membrane heterogeneities in cellular membranes. To overcome these challenges, here we report the sequestration behavior of urokinase receptor (uPAR), a glycosylphosphatidylinositol-anchored protein, in a planar model membrane platform with raft-mimicking lipid mixtures of well-defined compositions using a powerful optical imaging platform consisting of confocal spectroscopy XY-scans, photon counting histogram, and fluorescence correlation spectroscopy analyses. This methodology provides parallel information about receptor sequestration, oligomerization state, and lateral mobility with single molecule sensitivity. Most notably, our experiments demonstrate that moderate changes in uPAR sequestration are not only associated with modifications in uPAR dimerization levels, but may also be linked to ligand-mediated allosteric changes of these membrane receptors. Our data show that these modifications in uPAR sequestration can be induced by exposure to specific ligands (urokinase plasminogen activator, vitronectin), but not via adjustment of the cholesterol level in the planar model membrane system. Good agreement of our key findings with published results on cell membranes confirms the validity of our model membrane approach. We hypothesize that the observed mechanism of receptor translocation in the presence of raft-mimicking lipid mixtures is also applicable to other glycosylphosphatidylinositol-anchored proteins.

  14. Campylobacter jejuni induces transcellular translocation of commensal bacteria via lipid rafts

    Directory of Open Access Journals (Sweden)

    Kalischuk Lisa D

    2009-02-01

    Full Text Available Abstract Background Campylobacter enteritis represents a risk factor for the development of inflammatory bowel disease (IBD via unknown mechanisms. As IBD patients exhibit inflammatory responses to their commensal intestinal microflora, factors that induce translocation of commensal bacteria across the intestinal epithelium may contribute to IBD pathogenesis. This study sought to determine whether Campylobacter induces translocation of non-invasive intestinal bacteria, and characterize underlying mechanisms. Methods Mice were infected with C. jejuni and translocation of intestinal bacteria was assessed by quantitative bacterial culture of mesenteric lymph nodes (MLNs, liver, and spleen. To examine mechanisms of Campylobacter-induced bacterial translocation, transwell-grown T84 monolayers were inoculated with non-invasive Escherichia coli HB101 ± wild-type Campylobacter or invasion-defective mutants, and bacterial internalization and translocation were measured. Epithelial permeability was assessed by measuring flux of a 3 kDa dextran probe. The role of lipid rafts was assessed by cholesterol depletion and caveolin co-localization. Results C. jejuni 81–176 induced translocation of commensal intestinal bacteria to the MLNs, liver, and spleen of infected mice. In T84 monolayers, Campylobacter-induced internalization and translocation of E. coli occurred via a transcellular pathway, without increasing epithelial permeability, and was blocked by depletion of epithelial plasma membrane cholesterol. Invasion-defective mutants and Campylobacter-conditioned cell culture medium also induced E. coli translocation, indicating that C. jejuni does not directly 'shuttle' bacteria into enterocytes. In C. jejuni-treated monolayers, translocating E. coli associated with lipid rafts, and this phenomenon was blocked by cholesterol depletion. Conclusion Campylobacter, regardless of its own invasiveness, promotes the translocation of non-invasive bacteria across

  15. The reduced GM-CSF priming of ROS production in granulocytes from patients with myelodysplasia is associated with an impaired lipid raft formation

    NARCIS (Netherlands)

    Fuhler, Gwenny M.; Blom, Nel R.; Coffer, Paul J.; Drayer, A. Lyndsay; Vellenga, Edo

    2007-01-01

    Patients with myelodysplasia (MDS) show an impaired reactive oxygen species (ROS) production in response to fMLP stimulation of GMCSF-primed nentrophils. In this study, we investigated the involvement of lipid rafts in this process and showed that treatment of neutrophils with the lipid raft-disrupt

  16. Effect of integral proteins in the phase stability of a lipid bilayer: Application to raft formation in cell membranes

    Science.gov (United States)

    Gómez, Jordi; Sagués, Francesc; Reigada, Ramon

    2010-04-01

    The existence of lipid rafts is a controversial issue. The affinity of cholesterol for saturated lipids is manifested in macroscopic phase separation in model membranes, and is believed to be the thermodynamic driving force for raft formation. However, there is no clear reason to explain the small (nanometric) size of raft domains in cell membranes. In a recent paper Yethiraj and Weisshaar [Biophys. J. 93, 3113 (2007)] proposed that the effect of neutral integral membrane proteins may prevent from the formation of large lipid domains. In this paper we extend this approach by studying the effect of the protein size, as well as the lipid-protein interaction. Depending on these factors, two different mechanisms for nanodomain stabilization are shown to be possible for static proteins. The application of these results to a biological context is discussed.

  17. Cytomegalovirus Restructures Lipid Rafts via a US28/CDC42-Mediated Pathway, Enhancing Cholesterol Efflux from Host Cells.

    Science.gov (United States)

    Low, Hann; Mukhamedova, Nigora; Cui, Huanhuan L; McSharry, Brian P; Avdic, Selmir; Hoang, Anh; Ditiatkovski, Michael; Liu, Yingying; Fu, Ying; Meikle, Peter J; Blomberg, Martin; Polyzos, Konstantinos A; Miller, William E; Religa, Piotr; Bukrinsky, Michael; Soderberg-Naucler, Cecilia; Slobedman, Barry; Sviridov, Dmitri

    2016-06-28

    Cytomegalovirus (HCMV) contains cholesterol, but how HCMV interacts with host cholesterol metabolism is unknown. We found that, in human fibroblasts, HCMV infection increased the efflux of cellular cholesterol, despite reducing the abundance of ABCA1. Mechanistically, viral protein US28 was acting through CDC42, rearranging actin microfilaments, causing association of actin with lipid rafts, and leading to a dramatic change in the abundance and/or structure of lipid rafts. These changes displaced ABCA1 from the cell surface but created new binding sites for apolipoprotein A-I, resulting in enhanced cholesterol efflux. The changes also reduced the inflammatory response in macrophages. HCMV infection modified the host lipidome profile and expression of several genes and microRNAs involved in cholesterol metabolism. In mice, murine CMV infection elevated plasma triglycerides but did not affect the level and functionality of high-density lipoprotein. Thus, HCMV, through its protein US28, reorganizes lipid rafts and disturbs cell cholesterol metabolism.

  18. Facile preparation of cobaltocenium-containing polyelectrolyte via click chemistry and RAFT polymerization.

    Science.gov (United States)

    Yan, Yi; Zhang, Jiuyang; Qiao, Yali; Tang, Chuanbing

    2014-01-01

    A facile method to prepare cationic cobaltocenium-containing polyelectrolyte is reported. Cobaltocenium monomer with methacrylate is synthesized by copper-catalyzed azide-alkyne cycloaddition (CuAAC) reaction between 2-azidoethyl methacrylate and ethynylcobaltocenium hexafluorophosphate. Further controlled polymerization is achieved by reversible addition-fragmentation chain transfer polymerization (RAFT) by using cumyl dithiobenzoate (CDB) as a chain transfer agent. Kinetic study demonstrates the controlled/living process of polymerization. The obtained side-chain cobaltocenium-containing polymer is a metal-containing polyelectrolyte that shows characteristic redox behavior of cobaltocenium. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  19. A plus-end raft to control microtubule dynamics and function.

    Science.gov (United States)

    Galjart, Niels; Perez, Franck

    2003-02-01

    Cells require a properly oriented and organised microtubule array to transmit positional information. Recent data have revealed a heterogeneous population of microtubule-binding proteins that accumulates mainly at distal ends of polymerising microtubules. Two mechanisms may account for this concentration: transient immobilisation, which involves association of proteins with growing ends, followed by release more proximally; and deposition at ends via a molecular motor. As with lipid rafts, protein concentration at distal ends may allow a cascade of interactions in the restricted area of a microtubule plus end. This may, in turn, control the dynamic behaviour of this cytoskeletal network and its anchoring to other structures.

  20. The mystery of membrane organization: composition, regulation and roles of lipid rafts.

    Science.gov (United States)

    Sezgin, Erdinc; Levental, Ilya; Mayor, Satyajit; Eggeling, Christian

    2017-06-01

    Cellular plasma membranes are laterally heterogeneous, featuring a variety of distinct subcompartments that differ in their biophysical properties and composition. A large number of studies have focused on understanding the basis for this heterogeneity and its physiological relevance. The membrane raft hypothesis formalized a physicochemical principle for a subtype of such lateral membrane heterogeneity, in which the preferential associations between cholesterol and saturated lipids drive the formation of relatively packed (or ordered) membrane domains that selectively recruit certain lipids and proteins. Recent studies have yielded new insights into this mechanism and its relevance in vivo, owing primarily to the development of improved biochemical and biophysical technologies.

  1. Synthesis of click-reactive HPMA copolymers using RAFT polymerization for drug delivery applications

    DEFF Research Database (Denmark)

    Ebbesen, Morten F; Schaffert, D.H.; Crowley, Michael L

    2013-01-01

    This study describes a versatile strategy combining reversible addition fragmentation transfer (RAFT) polymerization and click chemistry to synthesize well-defined, reactive copolymers of N-(2-hydroxypropyl)methacrylamide (HPMA) for drug delivery applications. A novel azide containing monomer N-(3......-alkyne cycloaddition (CuAAC) was demonstrated by efficient conjugation (up to 92%) of phosphocholine, a near infrared dye, and poly(ethylene glycol) (PEG) with different substitution degrees, either alone or in combination. This study introduces a novel and versatile method to synthesize well-defined click...

  2. Multidrug resistance protein 1 localization in lipid raft domains and prostasomes in prostate cancer cell lines

    Directory of Open Access Journals (Sweden)

    Gomà A

    2014-12-01

    Full Text Available Alba Gomà,1,* Roser Mir,1–3,* Fina Martínez-Soler,1,4 Avelina Tortosa,4 August Vidal,5,6 Enric Condom,5,6 Ricardo Pérez–Tomás,6 Pepita Giménez-Bonafé1 1Departament de Ciències Fisiològiques II, Faculty of Medicine, Campus of Health Sciences of Bellvitge, Universitat de Barcelona, IDIBELL, Barcelona, Spain; 2División de Investigación Básica, Instituto Nacional de Cancerología, México DF, Mexico; 3Instituto de Física, Universidad Nacional Autónoma de México (UNAM, México DF, Mexico; 4Department of Basic Nursing, School of Nursing of the Health Campus of Bellvitge, Universitat de Barcelona, 5Department of Pathology, Hospital Universitari de Bellvitge, 6Department of Pathology and Experimental Therapeutics, Universitat de Barcelona, IDIBELL, Barcelona, Spain*These authors contributed equally to this work Background: One of the problems in prostate cancer (CaP treatment is the appearance of the multidrug resistance phenotype, in which ATP-binding cassette transporters such as multidrug resistance protein 1 (MRP1 play a role. Different localizations of the transporter have been reported, some of them related to the chemoresistant phenotype.Aim: This study aimed to compare the localization of MRP1 in three prostate cell lines (normal, androgen-sensitive, and androgen-independent in order to understand its possible role in CaP chemoresistance.Methods: MRP1 and caveolae protein markers were detected using confocal microscopy, performing colocalization techniques. Lipid raft isolation made it possible to detect these proteins by Western blot analysis. Caveolae and prostasomes were identified by electron microscopy.Results: We show that MRP1 is found in lipid raft fractions of tumor cells and that the number of caveolae increases with malignancy acquisition. MRP1 is found not only in the plasma membrane associated with lipid rafts but also in cytoplasmic accumulations colocalizing with the prostasome markers Caveolin-1 and CD59

  3. Hydrogen-enriched fuels

    Energy Technology Data Exchange (ETDEWEB)

    Roser, R. [NRG Technologies, Inc., Reno, NV (United States)

    1998-08-01

    NRG Technologies, Inc. is attempting to develop hardware and infrastructure that will allow mixtures of hydrogen and conventional fuels to become viable alternatives to conventional fuels alone. This commercialization can be successful if the authors are able to achieve exhaust emission levels of less than 0.03 g/kw-hr NOx and CO; and 0.15 g/kw-hr NMHC at full engine power without the use of exhaust catalysts. The major barriers to achieving these goals are that the lean burn regimes required to meet exhaust emissions goals reduce engine output substantially and tend to exhibit higher-than-normal total hydrocarbon emissions. Also, hydrogen addition to conventional fuels increases fuel cost, and reduces both vehicle range and engine output power. Maintaining low emissions during transient driving cycles has not been demonstrated. A three year test plan has been developed to perform the investigations into the issues described above. During this initial year of funding research has progressed in the following areas: (a) a cost effective single-cylinder research platform was constructed; (b) exhaust gas speciation was performed to characterize the nature of hydrocarbon emissions from hydrogen-enriched natural gas fuels; (c) three H{sub 2}/CH{sub 4} fuel compositions were analyzed using spark timing and equivalence ratio sweeping procedures and finally; (d) a full size pick-up truck platform was converted to run on HCNG fuels. The testing performed in year one of the three year plan represents a baseline from which to assess options for overcoming the stated barriers to success.

  4. CLEAN: CLustering Enrichment ANalysis

    Directory of Open Access Journals (Sweden)

    Medvedovic Mario

    2009-07-01

    Full Text Available Abstract Background Integration of biological knowledge encoded in various lists of functionally related genes has become one of the most important aspects of analyzing genome-wide functional genomics data. In the context of cluster analysis, functional coherence of clusters established through such analyses have been used to identify biologically meaningful clusters, compare clustering algorithms and identify biological pathways associated with the biological process under investigation. Results We developed a computational framework for analytically and visually integrating knowledge-based functional categories with the cluster analysis of genomics data. The framework is based on the simple, conceptually appealing, and biologically interpretable gene-specific functional coherence score (CLEAN score. The score is derived by correlating the clustering structure as a whole with functional categories of interest. We directly demonstrate that integrating biological knowledge in this way improves the reproducibility of conclusions derived from cluster analysis. The CLEAN score differentiates between the levels of functional coherence for genes within the same cluster based on their membership in enriched functional categories. We show that this aspect results in higher reproducibility across independent datasets and produces more informative genes for distinguishing different sample types than the scores based on the traditional cluster-wide analysis. We also demonstrate the utility of the CLEAN framework in comparing clusterings produced by different algorithms. CLEAN was implemented as an add-on R package and can be downloaded at http://Clusteranalysis.org. The package integrates routines for calculating gene specific functional coherence scores and the open source interactive Java-based viewer Functional TreeView (FTreeView. Conclusion Our results indicate that using the gene-specific functional coherence score improves the reproducibility of the

  5. Regulation of the high-affinity choline transporter activity and trafficking by its association with cholesterol-rich lipid rafts.

    Science.gov (United States)

    Cuddy, Leah K; Winick-Ng, Warren; Rylett, Rebecca Jane

    2014-03-01

    The sodium-coupled, hemicholinium-3-sensitive, high-affinity choline transporter (CHT) is responsible for transport of choline into cholinergic nerve terminals from the synaptic cleft following acetylcholine release and hydrolysis. In this study, we address regulation of CHT function by plasma membrane cholesterol. We show for the first time that CHT is concentrated in cholesterol-rich lipid rafts in both SH-SY5Y cells and nerve terminals from mouse forebrain. Treatment of SH-SY5Y cells expressing rat CHT with filipin, methyl-β-cyclodextrin (MβC) or cholesterol oxidase significantly decreased choline uptake. In contrast, CHT activity was increased by addition of cholesterol to membranes using cholesterol-saturated MβC. Kinetic analysis of binding of [(3)H]hemicholinium-3 to CHT revealed that reducing membrane cholesterol with MβC decreased both the apparent binding affinity (KD) and maximum number of binding sites (Bmax ); this was confirmed by decreased plasma membrane CHT protein in lipid rafts in cell surface protein biotinylation assays. Finally, the loss of cell surface CHT associated with lipid raft disruption was not because of changes in CHT internalization. In summary, we provide evidence that CHT association with cholesterol-rich rafts is critical for transporter function and localization. Alterations in plasma membrane cholesterol cholinergic nerve terminals could diminish cholinergic transmission by reducing choline availability for acetylcholine synthesis. The sodium-coupled choline transporter CHT moves choline into cholinergic nerve terminals to serve as substrate for acetylcholine synthesis. We show for the first time that CHT is concentrated in cholesterol-rich lipid rafts, and decreasing membrane cholesterol significantly reduces both choline uptake activity and cell surface CHT protein levels. CHT association with cholesterol-rich rafts is critical for its function, and alterations in plasma membrane cholesterol could diminish cholinergic

  6. FIELD INVESTIGATIONS OF PILED-RAFT FOUNDATIONS WITH SHORT-LENGTH CONIC PILES IN BUILDING AREAS OF MINSK

    Directory of Open Access Journals (Sweden)

    V. A. Sernov

    2015-01-01

    Full Text Available In recent time piled foundations are extensively applied due to an increase of storeys in buildings constructed in Minsk and load increment on the soil. Preference is given to this approach even in the case when relatively firm soil occurs in the top part of the foundation bed. In this case maximum usage of the foundation bed bearing capacity and reduction of foundation cost are considered as top-priority tasks for designers. One of the ways to increase the bearing capacity of piled foundations is the necessity to take into account resistance of foundation bed soil located under raft bottom. The raft as well as a shallow foundation is capable to transfer a significant part of building load into the soil. Such approach makes it possible to reduce a number of piles in the foundation or shorten their length. Then it results in shortening of the construction period and significant reduction in zero cycle. However up to the present moment reliable calculation methods that permit to take into account soil resistance in the raft base. An analysis of previous investigations on the matter executed by various researchers and a number of field investigations have been carried out with the purpose to develop the proposed methods.The paper presents results of field investigations on foundations consisting of short stamped tapered piles which are joined together with the help of the raft fragment. Strength and deformation characteristics of the bases are increasing while making such foundations in the fill-up soil. In this case the filled-up ground layer becomes a bearing layer both for piles and rafts as well. Improvement of high-plastic clay-bearing soil properties is ensured by ramming dry concrete mix under pile foot. The paper describes an experience on application of the piled-raft foundation in complicated engineering and geological conditions while constructing the Orthodox Church in Minsk.

  7. Cutting Edge: Localization of linker for activation of T cells to lipid rafts is not essential in T cell activation and development.

    Science.gov (United States)

    Zhu, Minghua; Shen, Shudan; Liu, Yan; Granillo, Olivia; Zhang, Weiguo

    2005-01-01

    It has been proposed that upon T cell activation, linker for activation of T cells (LAT), a transmembrane adaptor protein localized to lipid rafts, orchestrates formation of multiprotein complexes and activates signaling cascades in lipid rafts. However, whether lipid rafts really exist or function remains controversial. To address the importance of lipid rafts in LAT function, we generated a fusion protein to target LAT to nonraft fractions using the transmembrane domain from a nonraft protein, linker for activation of X cells (LAX). Surprisingly, this fusion protein functioned well in TCR signaling. It restored MAPK activation, calcium flux, and NFAT activation in LAT-deficient cells. To further study the function of this fusion protein in vivo, we generated transgenic mice that express this protein. Analysis of these mice indicated that it was fully capable of replacing LAT in thymocyte development and T cell function. Our results demonstrate that LAT localization to lipid rafts is not essential during normal T cell activation and development.

  8. High-density lipoprotein affects antigen presentation by interfering with lipid raft: a promising anti-atherogenic strategy.

    Science.gov (United States)

    Wang, S-H; Yuan, S-G; Peng, D-Q; Zhao, S-P

    2010-05-01

    Atherosclerosis is a chronic inflammatory disease. Immunomodulation of atherosclerosis emerges as a promising approach to prevention and treatment of this widely prevalent disease. The function of high-density lipoprotein (HDL) to promote reverse cholesterol transport may explain the ability of its protection against atherosclerosis. Findings that HDL and apolipoprotein A-I (apoA-I) inhibited the ability of antigen presenting cells (APCs) to stimulate T cells might be attributed to lipid raft, a cholesterol-rich microdomain exhibiting functional properties depending largely upon its lipid composition. Thus, modulating cholesterol in lipid raft may provide a promising anti-atherogenic strategy.

  9. Enrichment study of hot intra-cluster gas through X-ray spectroscopy

    NARCIS (Netherlands)

    Plaa, J. de

    2007-01-01

    Enrichment study of hot intra-cluster gas through X-ray spectroscopy Clouds of hot X-ray emitting gas associated with clusters of galaxies are the biggest aggregates of baryons that we know, except for the cosmic web. A typical cloud contains the nuclear-fusion products of billions of supernovae. Th

  10. Liquid chromatography electrospray ionization and matrix-assisted laser desorption ionization tandem mass spectrometry for the analysis of lipid raft proteome of monocytes

    Energy Technology Data Exchange (ETDEWEB)

    Zhang Nan [Department of Chemistry, University of Alberta, Edmonton, Alberta (Canada); Shaw, Andrew R.E. [Department of Chemistry, University of Alberta, Edmonton, Alberta (Canada)], E-mail: andrewsh@cancerboard.ab.ca; Li Nan; Chen Rui [Department of Chemistry, University of Alberta, Edmonton, Alberta (Canada); Mak, Allan; Hu Xiuying [Department of Oncology, University of Alberta, Edmonton, Alberta (Canada); Young, Nelson; Wishart, David [Department of Computing Science, University of Alberta, Edmonton, Alberta (Canada); Li Liang, E-mail: Liang.Li@ualberta.ca

    2008-10-03

    Lipid rafts are dynamic assemblies of cholesterol and glycolipid that form detergent-insoluble microdomains within membrane lipid bilayers. Because rafts can be separated by flotation on sucrose gradients, interrogation by mass spectrometry (MS) provides a valuable new insight into lipid raft function. Here we combine liquid chromatography (LC) electrospray ionization (ESI) and matrix-assisted laser desorption ionization (MALDI) MS/MS to corroborate and extend our previous description of lipid raft proteomes derived from the monocytic cell line THP-1. Interestingly, LC-ESI and MALDI MS/MS identify largely non-overlapping, and therefore, potentially complementary protein populations. Using the combined approach, we detected 277 proteins compared to 52 proteins obtained with the original gel-based MALDI MS. We confirmed the presence of 47 of the original 52 proteins demonstrating the consistency of the lipid raft preparations. We demonstrated by immunoblotting that Rac 1 and Rac 2, two of the 52 proteins we failed to confirm, were indeed absent from the lipid raft fractions. The majority of new proteins were cytoskeletal proteins and their regulators, proteins implicated in membrane fusion and vesicular trafficking or signaling molecules. Our results therefore, confirm and extend previous evidence indicating lipid rafts of monocytic cells are specialized for cytoskeletal assembly and vesicle trafficking. Of particular interest, we detected SNAP-23, basigin, Glut-4 and pantophysin in lipid rafts. Since these proteins are implicated in both vesicular trafficking and gamete fusion, lipid rafts may play a common role in these processes. It is evident that the combination of LC-ESI and LC-MALDI MS/MS increases the proteome coverage which allows better understanding of the lipid raft function.

  11. Regulation of Renal Organic Anion Transporter 3 (SLC22A8 Expression and Function by the Integrity of Lipid Raft Domains and their Associated Cytoskeleton

    Directory of Open Access Journals (Sweden)

    Chutima Srimaroeng

    2013-04-01

    Full Text Available Background/Aims: In humans and rodents, organic anion transporter 3 (Oat3 is highly expressed on the basolateral membrane of renal proximal tubules and mediates the secretion of exogenous and endogenous anions. Regulation of Oat3 expression and function has been observed in both expression system and intact renal epithelia. However, information on the local membrane environment of Oat3 and its role is limited. Lipid raft domains (LRD; cholesterol-rich domains of the plasma membrane play important roles in membrane protein expression, function and targeting. In the present study, we have examined the role of LRD-rich membranes and their associated cytoskeletal proteins on Oat3 expression and function. Methods: LRD-rich membranes were isolated from rat renal cortical tissues and from HEK-293 cells stably expressing human OAT3 (hOAT3 by differential centrifugation with triton X-100 extraction. Western blots were subsequently analyzed to determine protein expression. In addition, the effect of disruption of LRD-rich membranes was examined on functional Oat3 mediated estrone sulfate (ES transport in rat renal cortical slices. Cytoskeleton disruptors were investigated in both hOAT3 expressing HEK-293 cells and rat renal cortical slices. Results: Lipid-enriched membranes from rat renal cortical tissues and hOAT3-expressing HEK-293 cells showed co-expression of rOat3/hOAT3 and several lipid raft-associated proteins, specifically caveolin 1 (Cav1, β-actin and myosin. Moreover, immunohistochemistry in hOAT3-expressing HEK-293 cells demonstrated that these LRD-rich proteins co-localized with hOAT3. Potassium iodide (KI, an inhibitor of protein-cytoskeletal interaction, effectively detached cytoskeleton proteins and hOAT3 from plasma membrane, leading to redistribution of hOAT3 into non-LRD-rich compartments. In addition, inhibition of cytoskeleton integrity and membrane trafficking processes significantly reduced ES uptake mediated by both human and rat

  12. Aggregating and Disaggregating Flexibility Objects

    DEFF Research Database (Denmark)

    Siksnys, Laurynas; Valsomatzis, Emmanouil; Hose, Katja

    2015-01-01

    In many scientific and commercial domains we encounter flexibility objects, i.e., objects with explicit flexibilities in a time and an amount dimension (e.g., energy or product amount). Applications of flexibility objects require novel and efficient techniques capable of handling large amounts...... energy data management and discuss strategies for aggregation and disaggregation of flex-objects while retaining flexibility. This paper further extends these approaches beyond flex-objects originating from energy consumption by additionally considering flex-objects originating from energy production...... and aiming at energy balancing during aggregation. In more detail, this paper considers the complete life cycle of flex-objects: aggregation, disaggregation, associated requirements, efficient incremental computation, and balance aggregation techniques. Extensive experiments based on real-world data from...

  13. Dependability in Aggregation by Averaging

    CERN Document Server

    Jesus, Paulo; Almeida, Paulo Sérgio

    2010-01-01

    Aggregation is an important building block of modern distributed applications, allowing the determination of meaningful properties (e.g. network size, total storage capacity, average load, majorities, etc.) that are used to direct the execution of the system. However, the majority of the existing aggregation algorithms exhibit relevant dependability issues, when prospecting their use in real application environments. In this paper, we reveal some dependability issues of aggregation algorithms based on iterative averaging techniques, giving some directions to solve them. This class of algorithms is considered robust (when compared to common tree-based approaches), being independent from the used routing topology and providing an aggregation result at all nodes. However, their robustness is strongly challenged and their correctness often compromised, when changing the assumptions of their working environment to more realistic ones. The correctness of this class of algorithms relies on the maintenance of a funda...

  14. International Standard Definition of Membrane Rafts%"膜筏"的国际规范定义

    Institute of Scientific and Technical Information of China (English)

    卢义钦; 沈士弼

    2007-01-01

    @@ 细胞膜上存有一种以鞘脂(sphingolipids)和胆固醇(Ch)为基本成分的微域(micro-domain),近年来引起广泛注意,本文作者曾予简介[1].鞘脂所含长的多饱和脂酰链呈高度有序排列,在其紧密填充之间又散布大量胆固醇,形成了质地较致密的富集胆固醇的小斑块结构,而其周围膜介质的流动性较强,因此该结构经常处于浮动状态,类似江流中拖运的木筏,故称为脂筏(lipid rafts).由于真核生物的细胞膜常含有筏式微域,因此命名为膜筏(membrane rafts).膜筏的结构模型由两部分组成:(1)富含鞘脂(鞘糖脂与鞘磷脂)的顶部域(apical domain);(2)富含磷脂酰胆碱(PC)的基侧部域(basolateral domain).

  15. Exogenous Alpha-Synuclein Alters Pre- and Post-Synaptic Activity by Fragmenting Lipid Rafts.

    Science.gov (United States)

    Emanuele, Marco; Esposito, Alessandro; Camerini, Serena; Antonucci, Flavia; Ferrara, Silvia; Seghezza, Silvia; Catelani, Tiziano; Crescenzi, Marco; Marotta, Roberto; Canale, Claudio; Matteoli, Michela; Menna, Elisabetta; Chieregatti, Evelina

    2016-05-01

    Alpha-synuclein (αSyn) interferes with multiple steps of synaptic activity at pre-and post-synaptic terminals, however the mechanism/s by which αSyn alters neurotransmitter release and synaptic potentiation is unclear. By atomic force microscopy we show that human αSyn, when incubated with reconstituted membrane bilayer, induces lipid rafts' fragmentation. As a consequence, ion channels and receptors are displaced from lipid rafts with consequent changes in their activity. The enhanced calcium entry leads to acute mobilization of synaptic vesicles, and exhaustion of neurotransmission at later stages. At the post-synaptic terminal, an acute increase in glutamatergic transmission, with increased density of PSD-95 puncta, is followed by disruption of the interaction between N-methyl-d-aspartate receptor (NMDAR) and PSD-95 with ensuing decrease of long term potentiation. While cholesterol loading prevents the acute effect of αSyn at the presynapse; inhibition of casein kinase 2, which appears activated by reduction of cholesterol, restores the correct localization and clustering of NMDARs.

  16. Lipid rafts-mediated endocytosis and physiology-based cell membrane traffic models of doxorubicin liposomes.

    Science.gov (United States)

    Li, Yinghuan; Gao, Lei; Tan, Xi; Li, Feiyang; Zhao, Ming; Peng, Shiqi

    2016-08-01

    The clathrin-mediated endocytosis is likely a major mechanism of liposomes' internalization. A kinetic approach was used to assess the internalization mechanism of doxorubicin (Dox) loaded cationic liposomes and to establish physiology-based cell membrane traffic mathematic models. Lipid rafts-mediated endocytosis, including dynamin-dependent or -independent endocytosis of noncaveolar structure, was a dominant process. The mathematic models divided Dox loaded liposomes binding lipid rafts (B) into saturable binding (SB) and nonsaturable binding (NSB) followed by energy-driven endocytosis. The intracellular trafficking demonstrated early endosome-late endosome-lysosome or early/late endosome-cytoplasm-nucleus pathways. The three properties of liposome structures, i.e., cationic lipid, fusogenic lipid, and pegylation, were investigated to compare their contributions to cell membrane and intracellular traffic. The results revealed great contribution of cationic lipid DOTAP and fusogenic lipid DOPE to cell membrane binding and internalization. The valid Dox in the nuclei of HepG2 and A375 cells treated with cationic liposomes containing 40mol% of DOPE were 1.2-fold and 1.5-fold higher than that in the nuclei of HepG2 and A375 cells treated with liposomes containing 20mol% of DOPE, respectively, suggesting the dependence of cell type. This tendency was proportional to the increase of cell-associated total liposomal Dox. The mathematic models would be useful to predict intracellular trafficking of liposomal Dox.

  17. The influence of coastal topography, circulation patterns, and rafting in structuring populations of an intertidal alga.

    Science.gov (United States)

    Muhlin, J F; Engel, C R; Stessel, R; Weatherbee, R A; Brawley, S H

    2008-03-01

    Understanding the dispersal processes that influence genetic structure in marine species requires estimating gene flow in a dynamic, fluid environment that is often poorly characterized at scales relevant to multiple dispersive stages (e.g. spores, gametes, zygotes, larvae, adults). We examine genetic structure in the marine alga Fucus vesiculosus L., which inhabits moderately exposed shores in the northern Atlantic but releases gametes only under sunny, calm conditions. We predicted genetic structure would correlate with coastal topography because weather frequently varies across coastal promontories on the Maine shore when F. vesiculosus is reproductive, which causes one side to experience high levels of water motion (= no gamete release) while one side is calm (= gamete release). Furthermore, we expected that the effect of low dispersal capacities of gametes and zygotes would result in spatial genetic structure over short distances. Using surface drifters, we characterized near-shore circulation patterns around the study sites to investigate whether directionality of gene flow was correlated with directionality of currents. We found significant genetic differentiation among sites sampled at two different peninsulas, but patterns of differentiation were unrelated to coastal topography and there was no within-site spatial structuring. Our genetic and near-shore circulation data, combined with an examination of gamete longevity, support the dependency of gene flow on storm-detached, rafting, reproductive adults. This study highlights the significance of rafting as a mechanism for structuring established populations of macroalgae and associated biota and demonstrates the importance of coupling population genetics' research with relevant hydrodynamic studies.

  18. Recent progress on lipid lateral heterogeneity in plasma membranes: From rafts to submicrometric domains.

    Science.gov (United States)

    Carquin, Mélanie; D'Auria, Ludovic; Pollet, Hélène; Bongarzone, Ernesto R; Tyteca, Donatienne

    2016-04-01

    The concept of transient nanometric domains known as lipid rafts has brought interest to reassess the validity of the Singer-Nicolson model of a fluid bilayer for cell membranes. However, this new view is still insufficient to explain the cellular control of surface lipid diversity or membrane deformability. During the past decades, the hypothesis that some lipids form large (submicrometric/mesoscale vs nanometric rafts) and stable (>min vs s) membrane domains has emerged, largely based on indirect methods. Morphological evidence for stable submicrometric lipid domains, well-accepted for artificial and highly specialized biological membranes, was further reported for a variety of living cells from prokaryot es to yeast and mammalian cells. However, results remained questioned based on limitations of available fluorescent tools, use of poor lipid fixatives, and imaging artifacts due to non-resolved membrane projections. In this review, we will discuss recent evidence generated using powerful and innovative approaches such as lipid-specific toxin fragments that support the existence of submicrometric domains. We will integrate documented mechanisms involved in the formation and maintenance of these domains, and provide a perspective on their relevance on membrane deformability and regulation of membrane protein distribution. Copyright © 2015 Elsevier Ltd. All rights reserved.

  19. The GM1 Ganglioside Forms GM1-Rich Gel Phase Microdomains within Lipid Rafts

    Directory of Open Access Journals (Sweden)

    Lucia Becucci

    2014-07-01

    Full Text Available Mercury-supported, self-assembled monolayers (SAMs of the sole dioleoylphosphatidylcholine (DOPC and of a raft-forming mixture of DOPC, cholesterol (Chol and palmitoylsphingomyelin (PSM of (59:26:15 mol% composition, were investigated by electrochemical impedance spectroscopy (EIS, both in the absence and in the presence of the monosialoganglioside GM1. The impedance spectra of these four SAMs were fitted by a series of parallel combinations of a resistance and a capacitance (RC meshes and displayed on plots of ωZ′ against −ωZ″, where Z′ and Z″ are the in-phase and quadrature components of the impedance and ω is the angular frequency. A comparison among these different impedance spectra points to the formation of GM1-rich gel phase microdomains within the lipid rafts of the DOPC/Chol/PSM mixture, thanks to the unique molecular-level smooth support provided by mercury, which allows EIS to detect the protruding gel phase microdomains by averaging them over a macroscopically large area.

  20. HSL-knockout mouse testis exhibits class B scavenger receptor upregulation and disrupted lipid raft microdomains.

    Science.gov (United States)

    Casado, María Emilia; Huerta, Lydia; Ortiz, Ana Isabel; Pérez-Crespo, Mirian; Gutiérrez-Adán, Alfonso; Kraemer, Fredric B; Lasunción, Miguel Ángel; Busto, Rebeca; Martín-Hidalgo, Antonia

    2012-12-01

    There is a tight relationship between fertility and changes in cholesterol metabolism during spermatogenesis. In the testis, class B scavenger receptors (SR-B) SR-BI, SR-BII, and LIMP II mediate the selective uptake of cholesterol esters from HDL, which are hydrolyzed to unesterified cholesterol by hormone-sensitive lipase (HSL). HSL is critical because HSL knockout (KO) male mice are sterile. The aim of the present work was to determine the effects of the lack of HSL in testis on the expression of SR-B, lipid raft composition, and related cell signaling pathways. HSL-KO mouse testis presented altered spermatogenesis associated with decreased sperm counts, sperm motility, and infertility. In wild-type (WT) testis, HSL is expressed in elongated spermatids; SR-BI, in Leydig cells and spermatids; SR-BII, in spermatocytes and spermatids but not in Leydig cells; and LIMP II, in Sertoli and Leydig cells. HSL knockout male mice have increased expression of class B scavenger receptors, disrupted caveolin-1 localization in lipid raft plasma membrane microdomains, and activated phospho-ERK, phospho-AKT, and phospho-SRC in the testis, suggesting that class B scavenger receptors are involved in cholesterol ester uptake for steroidogenesis and spermatogenesis in the testis.

  1. Hybrid and nonhybrid lipids exert common effects on membrane raft size and morphology.

    Science.gov (United States)

    Heberle, Frederick A; Doktorova, Milka; Goh, Shih Lin; Standaert, Robert F; Katsaras, John; Feigenson, Gerald W

    2013-10-01

    Nanometer-scale domains in cholesterol-rich model membranes emulate lipid rafts in cell plasma membranes (PMs). The physicochemical mechanisms that maintain a finite, small domain size are, however, not well understood. A special role has been postulated for chain-asymmetric or hybrid lipids having a saturated sn-1 chain and an unsaturated sn-2 chain. Hybrid lipids generate nanodomains in some model membranes and are also abundant in the PM. It was proposed that they align in a preferred orientation at the boundary of ordered and disordered phases, lowering the interfacial energy and thus reducing domain size. We used small-angle neutron scattering and fluorescence techniques to detect nanoscopic and modulated liquid phase domains in a mixture composed entirely of nonhybrid lipids and cholesterol. Our results are indistinguishable from those obtained previously for mixtures containing hybrid lipids, conclusively showing that hybrid lipids are not required for the formation of nanoscopic liquid domains and strongly implying a common mechanism for the overall control of raft size and morphology. We discuss implications of these findings for theoretical descriptions of nanodomains.

  2. Hybrid and Nonhybrid Lipids Exert Common Effects on Membrane Raft Size and Morphology

    Energy Technology Data Exchange (ETDEWEB)

    Heberle, Frederick A [ORNL; Doktorova, Milka [Cornell University; Goh, Shih Lin [Cornell University; Standaert, Robert F [ORNL; Katsaras, John [ORNL; Feigenson, Gerald [Cornell University

    2013-01-01

    Nanometer-scale domains in cholesterolrich model membranes emulate lipid rafts in cell plasma membranes (PMs). The physicochemical mechanisms that maintain a finite, small domain size are, however, not well understood. A special role has been postulated for chainasymmetric or hybrid lipids having a saturated sn-1 chain and an unsaturated sn-2 chain. Hybrid lipids generate nanodomains in some model membranes and are also abundant in the PM. It was proposed that they align in a preferred orientation at the boundary of ordered and disordered phases, lowering the interfacial energy and thus reducing domain size. We used small-angle neutron scattering and fluorescence techniques to detect nanoscopic and modulated liquid phase domains in a mixture composed entirely of nonhybrid lipids and cholesterol. Our results are indistinguishable from those obtained previously for mixtures containing hybrid lipids, conclusively showing that hybrid lipids are not required for the formation of nanoscopic liquid domains and strongly implying a common mechanism for the overall control of raft size and morphology. We discuss implications of these findings for theoretical descriptions of nanodomains.

  3. Exogenous Alpha-Synuclein Alters Pre- and Post-Synaptic Activity by Fragmenting Lipid Rafts

    Directory of Open Access Journals (Sweden)

    Marco Emanuele

    2016-05-01

    Full Text Available Alpha-synuclein (αSyn interferes with multiple steps of synaptic activity at pre-and post-synaptic terminals, however the mechanism/s by which αSyn alters neurotransmitter release and synaptic potentiation is unclear. By atomic force microscopy we show that human αSyn, when incubated with reconstituted membrane bilayer, induces lipid rafts' fragmentation. As a consequence, ion channels and receptors are displaced from lipid rafts with consequent changes in their activity. The enhanced calcium entry leads to acute mobilization of synaptic vesicles, and exhaustion of neurotransmission at later stages. At the post-synaptic terminal, an acute increase in glutamatergic transmission, with increased density of PSD-95 puncta, is followed by disruption of the interaction between N-methyl-d-aspartate receptor (NMDAR and PSD-95 with ensuing decrease of long term potentiation. While cholesterol loading prevents the acute effect of αSyn at the presynapse; inhibition of casein kinase 2, which appears activated by reduction of cholesterol, restores the correct localization and clustering of NMDARs.

  4. Alkyl ether lipids, ion channels and lipid raft reorganization in cancer therapy.

    Science.gov (United States)

    Jaffrès, Paul-Alain; Gajate, Consuelo; Bouchet, Ana Maria; Couthon-Gourvès, Hélène; Chantôme, Aurélie; Potier-Cartereau, Marie; Besson, Pierre; Bougnoux, Philippe; Mollinedo, Faustino; Vandier, Christophe

    2016-09-01

    Synthetic alkyl lipids, such as the ether lipids edelfosine (1-O-octadecyl-2-O-methyl-rac-glycero-3-phosphocholine) and ohmline (1-O-hexadecyl-2-O-methyl-rac-glycero-3-β-lactose), are forming a class of antitumor agents that target cell membranes to induce apoptosis and to decrease cell migration/invasion, leading to the inhibition of tumor and metastasis development. In this review, we present the structure-activity relationship of edelfosine and ohmline, and we point out differences and similarities between these two amphiphilic compounds. We also discuss the mechanisms of action of these synthetic alkyl ether lipids (involving, among other structures and molecules, membrane domains, Fas/CD95 death receptor signaling, and ion channels), and highlight a key role for lipid rafts in the underlying process. The reorganization of lipid raft membrane domains induced by these alkyl lipids affects the function of death receptors and ion channels, thus leading to apoptosis and/or inhibition of cancer cell migration. The possible therapeutic use of these alkyl lipids and the clinical perspectives for these lipids in prevention or/and treatment of tumor development and metastasis are also discussed.

  5. Simplified approach for design of raft foundations against fault rupture. Part Ⅱ: soil-structure interaction

    Institute of Scientific and Technical Information of China (English)

    I. Anastasopoulos; N. Gerolymos; G. Gazetas; M. F. Bransby

    2008-01-01

    This is the second paper of two, which describe the results of an integrated research effort to develop afour-step simplified approach for design of raft foundations against dip-slip (normal and thrust) fault rupture. The first twosteps dealing with fault rupture propagation in the free-field were presented in the companion paper. This paper develops anapproximate analytical method to analyze soil-foundation-structure interaction (SFSI), involving two additional phenomena:(i) fault rupture diversion (Step 3); and (ii) modification of the vertical displacement profile (Step 4). For the first phenomenon(Step 3), an approximate energy-based approach is developed to estimate the diversion of a fault rupture due to presence ofa raft foundation. The normalized critical load for complete diversion is shown to be a function of soil strength, coefficient ofearth pressure at rest, bedrock depth, and the horizontal position of the foundation relative to the outcropping fault rupture.For the second phenomenon (Step 4), a heuristic approach is proposed, which "scans" through possible equilibrium positionsto detect the one that best satisfies force and moment equilibrium. Thus, we account for the strong geometric nonlinearitiesthat govern this interaction, such as uplifting and second order (P-A) effects. Comparisons with centrifuge-validated finiteelement analyses demonstrate the efficacy of the method. Its simplicity makes possible its utilization for preliminary design.

  6. PENGARUH CITRA MEREK (BRAND IMAGE DAN KEPUASAN WISATAWAN TERHADAP LOYALITAS WISATAWAN PADA BALI ADVENTURE RAFTING

    Directory of Open Access Journals (Sweden)

    Ardilla Nathaurisia

    2017-01-01

    Full Text Available ith loyalty and high power of buying. Research impact of brand image and guest satisfaction on customer loyalty is important to do in order to obtain an explanation of the relationship between brand image and customer satisfaction on customer loyalty. The purpose of this study is 1 to identify the circumstance brand image on customer loyalty. 2 to identify the circumstance customer satisfaction on customer loyalty. 3 to determine the circumstance brand image and customer satisfaction on customer loyalty. This research was conducted at Bali Adventure Rafting. Result shows that branding and customer satisfaction has a significant effect on customer loyalty in Bali Adventure Rafting with result 41,7%. This result is obtained from the value of determination D x 100% = 0,417 x 100% = 41,7%. This means that the brand image and customer satisfaction contributing positively to customer loyalty of rating of 41,7% and the remaining 58,3% is influenced by others factors such as costumers satisfaction, marketing strategy.

  7. Glacitectonic rafting and associated deformation of mid-Pleistocene glacigenic sediments, near Central Graben, central North Sea; results of a 2D High-Resolution Geophysical Survey

    Science.gov (United States)

    Vaughan-Hirsch, David

    2013-04-01

    Glacitectonic rafts are defined as dislocated slabs of bedrock or unconsolidated sediments, transported from their original position by glacial action. These relatively thin, slab-like bodies feature transport distances ranging from tens of meters to hundreds of kilometers. They occur as either single rafts, or multiple stacked bodies associated with a variety of ice-pushed landforms. Internally, rafts frequently appear undeformed although at a larger scale, they may be folded or cut by shear zones and brittle faults. However, the processes leading to the detachment, transport and subsequent emplacement of the rafts remain uncertain. This work describes the results of a geophysical 2D seismic survey of thrust-bound glacitectonic rafts and associated deformation structures, occurring within mid-Pleistocene glacigenic sediments of the Central Graben, central North Sea. The total shortened length of the rafted section is 2.4km, comprising a series of nine discrete rafts which individually range from 235m to 1018m in length. The principle basal detachment occurs at the erosive contact between Aberdeen Ground Formation and overlying Ling Bank Formation. The ice-proximal (northern) limit of rafting is defined by the presence of a large-scale palaeo-channel oriented perpendicular to the direction of rafting, composed of sediments of the Ling Bank Formation and the Forth Formation. The observed deformation structures infer a mean tectonic direction of 178°, indicating that they are associated with an active glacial advance from the north. The resulting deformation creates a minimum lateral shortening throughout the observed sequence of 35%, typifying a strongly compressional regieme associated with rafting. Throughout the surveyed area, structurally younger rafts are found to be emplaced towards the south, compared to the structurally older rafts which are emplaced towards the south-east. This distinction is suggested to be caused by early rafts creating an obstacle to

  8. Model for amorphous aggregation processes

    Science.gov (United States)

    Stranks, Samuel D.; Ecroyd, Heath; van Sluyter, Steven; Waters, Elizabeth J.; Carver, John A.; von Smekal, Lorenz

    2009-11-01

    The amorphous aggregation of proteins is associated with many phenomena, ranging from the formation of protein wine haze to the development of cataract in the eye lens and the precipitation of recombinant proteins during their expression and purification. While much literature exists describing models for linear protein aggregation, such as amyloid fibril formation, there are few reports of models which address amorphous aggregation. Here, we propose a model to describe the amorphous aggregation of proteins which is also more widely applicable to other situations where a similar process occurs, such as in the formation of colloids and nanoclusters. As first applications of the model, we have tested it against experimental turbidimetry data of three proteins relevant to the wine industry and biochemistry, namely, thaumatin, a thaumatinlike protein, and α -lactalbumin. The model is very robust and describes amorphous experimental data to a high degree of accuracy. Details about the aggregation process, such as shape parameters of the aggregates and rate constants, can also be extracted.

  9. Aggregation and Linking of Observational Metadata in the ADS

    CERN Document Server

    Accomazzi, Alberto; Henneken, Edwin A; Grant, Carolyn S; Thompson, Donna M; Chyla, Roman; Holachek, Alexandra; Elliott, Jonathan

    2016-01-01

    We discuss current efforts behind the curation of observing proposals, archive bibliographies, and data links in the NASA Astrophysics Data System (ADS). The primary data in the ADS is the bibliographic content from scholarly articles in Astronomy and Physics, which ADS aggregates from publishers, arXiv and conference proceeding sites. This core bibliographic information is then further enriched by ADS via the generation of citations and usage data, and through the aggregation of external resources from astronomy data archives and libraries. Important sources of such additional information are the metadata describing observing proposals and high level data products, which, once ingested in ADS, become easily discoverable and citeable by the science community. Bibliographic studies have shown that the integration of links between data archives and the ADS provides greater visibility to data products and increased citations to the literature associated with them.

  10. An Amoeboid Olivine Aggregate in LEW 85300

    Science.gov (United States)

    Komatsu, M. D.; Yamaguchi, A.; Fagan, T. J.; Zolensky, M. E.; Shiran, N.; Mikouchi, T.

    2016-01-01

    Amoeboid Olivine aggregates (AOAs) are irregularly shaped objects commonly observed in carbonaceous chondrites. Because they are composed of fine-grained olivine and Ca-Al-rich minerals, they are sensitive indicators for nebular process and parent body alteration of their parent bodies. Recently an AOA was found in a carbonaceous clast in polymict eucrite LEW 85300. The bulk major element composition of the clast matrix in LEW 85300 suggests a relation to CM, CO and CV chondrites, whereas bulk clast trace and major element compositions do not match any carbonaceous chondrite, suggesting they have a unique origin. Here we characterize the mineralogy of AOA in LEW 85300 and discuss the origin of the carbonaceous clasts. Results and Discussion: The AOA is located in an impact melt vein. Half of the aggregate shows recrystallization textures (euhedral pyroxene and molten metal/FeS) due to impact melting, but the remaining part preserves the original texture. The AOA is composed of olivine, FeS and Mg,Al-phyllosilicate. Individual olivine grains measure 1-8 microns, with Fe-rich rims, probably due to impact heating. Olivines in the AOA are highly forsteritic (Fo95-99), indicating that the AOA escaped thermal metamorphism [4]. Although no LIME (Low-Fe, Mn-Enriched) olivine is observed, forsterite composition and the coexistence of Mg,Al-phyllosilicate suggest that the AOA is similar to those in the Bali-type oxidized CV (CVoxB) and CR chondrites. However, it should be noted that fayalitic olivine, which commonly occurs in CVoxB AOA, is not observed in this AOA. Also, the smaller grain size (olivine suggests they may be related to CM or CO chondrites. Therefore, we cannot exclude the possibility that the AOA originated from a unique carbonaceous chondrite.

  11. Ash Aggregates in Proximal Settings

    Science.gov (United States)

    Porritt, L. A.; Russell, K.

    2012-12-01

    Ash aggregates are thought to have formed within and been deposited by the eruption column and plume and dilute density currents and their associated ash clouds. Moist, turbulent ash clouds are considered critical to ash aggregate formation by facilitating both collision and adhesion of particles. Consequently, they are most commonly found in distal deposits. Proximal deposits containing ash aggregates are less commonly observed but do occur. Here we describe two occurrences of vent proximal ash aggregate-rich deposits; the first within a kimberlite pipe where coated ash pellets and accretionary lapilli are found within the intra-vent sequence; and the second in a glaciovolcanic setting where cored pellets (armoured lapilli) occur within Diamond Mine, Canada, are the residual deposits within the conduit and vent of the volcano and are characterised by an abundance of ash aggregates. Coated ash pellets are dominant but are followed in abundance by ash pellets, accretionary lapilli and rare cored pellets. The coated ash pellets typically range from 1 - 5 mm in diameter and have core to rim ratios of approximately 10:1. The formation and preservation of these aggregates elucidates the style and nature of the explosive phase of kimberlite eruption at A418 (and other pipes?). First, these pyroclasts dictate the intensity of the kimberlite eruption; it must be energetic enough to cause intense fragmentation of the kimberlite to produce a substantial volume of very fine ash (sustained plume attended by concomitant production of pyroclastic density currents. The size and internal structure of the armoured lapilli provide constraints on the nature of the initial explosive phase of eruption at Kima'Kho. Their proximity to the vent also indicates rapid aggregation within the eruption plume. Within both sequences rapid aggregation of ash particles occurred in proximity to the vent. However, the conditions were substantially different leading to the production of armoured

  12. Interaction of the human N-Ras protein with lipid raft model membranes of varying degrees of complexity.

    Science.gov (United States)

    Vogel, Alexander; Nikolaus, Jörg; Weise, Katrin; Triola, Gemma; Waldmann, Herbert; Winter, Roland; Herrmann, Andreas; Huster, Daniel

    2014-07-01

    Ternary lipid mixtures composed of cholesterol, saturated (frequently with sphingosine backbone), and unsaturated phospholipids show stable phase separation and are often used as model systems of lipid rafts. Yet, their ability to reproduce raft properties and function is still debated. We investigated the properties and functional aspects of three lipid raft model systems of varying degrees of biological relevance--PSM/POPC/Chol, DPPC/POPC/Chol, and DPPC/DOPC/Chol--using 2H solid-state nuclear magnetic resonance (NMR) spectroscopy, fluorescence microscopy, and atomic force microscopy. While some minor differences were observed, the general behavior and properties of all three model mixtures were similar to previously investigated influenza envelope lipid membranes, which closely mimic the lipid composition of biological membranes. For the investigation of the functional aspects, we employed the human N-Ras protein, which is posttranslationally modified by two lipid modifications that anchor the protein to the membrane. It was previously shown that N-Ras preferentially resides in liquid-disordered domains and exhibits a time-dependent accumulation in the domain boundaries of influenza envelope lipid membranes. For all three model mixtures, we observed the same membrane partitioning behavior for N-Ras. Therefore, we conclude that even relatively simple models of raft membranes are able to reproduce many of their specific properties and functions.

  13. Evidence for the involvement of lipid rafts localized at the ER-mitochondria associated membranes in autophagosome formation.

    Science.gov (United States)

    Garofalo, Tina; Matarrese, Paola; Manganelli, Valeria; Marconi, Matteo; Tinari, Antonella; Gambardella, Lucrezia; Faggioni, Alberto; Misasi, Roberta; Sorice, Maurizio; Malorni, Walter

    2016-06-01

    Mitochondria-associated membranes (MAMs) are subdomains of the endoplasmic reticulum (ER) that interact with mitochondria. This membrane scrambling between ER and mitochondria appears to play a critical role in the earliest steps of autophagy. Recently, lipid microdomains, i.e. lipid rafts, have been identified as further actors of the autophagic process. In the present work, a series of biochemical and molecular analyses has been carried out in human fibroblasts with the specific aim of characterizing lipid rafts in MAMs and to decipher their possible implication in the autophagosome formation. In fact, the presence of lipid microdomains in MAMs has been detected and, in these structures, a molecular interaction of the ganglioside GD3, a paradigmatic "brick" of lipid rafts, with core-initiator proteins of autophagy, such as AMBRA1 and WIPI1, was revealed. This association seems thus to take place in the early phases of autophagic process in which MAMs have been hypothesized to play a key role. The functional activity of GD3 was suggested by the experiments carried out by knocking down ST8SIA1 gene expression, i.e., the synthase that leads to the ganglioside formation. This experimental condition results in fact in the impairment of the ER-mitochondria crosstalk and the subsequent hindering of autophagosome nucleation. We thus hypothesize that MAM raft-like microdomains could be pivotal in the initial organelle scrambling activity that finally leads to the formation of autophagosome.

  14. Characterization of the profile of rafting practitioners in the Serra do Mar State Park, Nucleus Santa Virginia, SP

    Directory of Open Access Journals (Sweden)

    Ana Paula Pereira

    2013-12-01

    Full Text Available This study aimed to provide support for the implementation of rafting in the Parque Estadual Serra do Mar – Núcleo Santa Virgínia (PESM-NSV State Park based upon the profile and the level of satisfaction of the practitioners of rafting. Data was collected via questionnaires, with closed and open questions to assess the socioeconomic profile of the practitioners, information regarding commuter trips, motivations, preferences, level of satisfaction with respect to the activities engaged in , as well as the practitioners’ perceptions of the experience and minimum impact of the visits. After the data was tabulated, an Analysis of Correspondence technique was used to verify the relationship between the “satisfaction” and “age” variables using MINITAB™ statistical software. Out of 47 people interviewed, the majority were males (66%, of which 55.5% were between 19 and 30 years old and 49% of the participants had college degree. In general, participants were satisfied with the service, but made it clear that some aspects of the rafting business management could be improved upon, such as a reduction of the admission fee, use of availability announcements and improvement of the infrastructure of the landing area of the cruising. It is concluded that the rafting participants are from an elite class of society with a high level of education and a demand for a high quality of service.

  15. Cultivation of green mussel, Perna viridis L., on a floating raft in an estuary along the west coast of India

    Digital Repository Service at National Institute of Oceanography (India)

    Rivonker, C.U.; Ansari, Z.A.; Parulekar, A.H.

    Total production of green mussels, Perna viridis, grown on a raft (16 m sup(2)) for 1 year was 2144.64 kg and biomass (meat weight) was 1040.00 kg. Annual production (P) and biomass (B) estimated were 33.51 and 16.25 kg m sup(-1) respectively...

  16. Probing membrane protein interactions with their lipid raft environment using single-molecule tracking and Bayesian inference analysis.

    Directory of Open Access Journals (Sweden)

    Silvan Türkcan

    Full Text Available The statistical properties of membrane protein random walks reveal information on the interactions between the proteins and their environments. These interactions can be included in an overdamped Langevin equation framework where they are injected in either or both the friction field and the potential field. Using a Bayesian inference scheme, both the friction and potential fields acting on the ε-toxin receptor in its lipid raft have been measured. Two types of events were used to probe these interactions. First, active events, the removal of cholesterol and sphingolipid molecules, were used to measure the time evolution of confining potentials and diffusion fields. Second, passive rare events, de-confinement of the receptors from one raft and transition to an adjacent one, were used to measure hopping energies. Lipid interactions with the ε-toxin receptor are found to be an essential source of confinement. ε-toxin receptor confinement is due to both the friction and potential field induced by cholesterol and sphingolipids. Finally, the statistics of hopping energies reveal sub-structures of potentials in the rafts, characterized by small hopping energies, and the difference of solubilization energy between the inner and outer raft area, characterized by higher hopping energies.

  17. Sulfonated macro-RAFT agents for the surfactant-free synthesis of cerium oxide-based hybrid latexes.

    Science.gov (United States)

    Garnier, Jérôme; Warnant, Jérôme; Lacroix-Desmazes, Patrick; Dufils, Pierre-Emmanuel; Vinas, Jérôme; van Herk, Alex

    2013-10-01

    Three types of amphiphatic macro-RAFT agents were employed as compatibilizers to promote the polymerization reaction at the surface of nanoceria for the synthesis of CeO2-based hybrid latexes. Macro-RAFT copolymers and terpolymers were first synthesized employing various combinations of butyl acrylate as a hydrophobic monomer and acrylic acid (AA) and/or 2-acrylamido-2-methylpropane sulfonic acid (AMPS) as hydrophilic monomers. After characterizing the adsorption of these macro-RAFT agents at the cerium oxide surface by UV-visible spectrometry, emulsion copolymerization reactions of styrene and methyl acrylate were then carried out in the presence of the surface-modified nanoceria. Dynamic Light Scattering and cryo-Transmission Electron Microscopy were employed to confirm the hybrid structure of the final CeO2/polymer latexes, and proved that the presence of acrylic acid units in amphiphatic macro-RAFT agents enabled an efficient formation of hybrid structures, while the presence of AMPS units, when combined with AA units, resulted in a better distribution of cerium oxide nanoclusters between latex particles.

  18. Depletion of plankton in a raft culture of Mytilus galloprovincialis in Ría de Vigo, NW Spain. I. Phytoplankton

    NARCIS (Netherlands)

    Petersen, J.K.; Nielsen, T.G.; Van Duren, L.A.; Maar, M.

    2008-01-01

    Food depletion in mussel cultivation has been rarely studied and seldom demonstrated. In this study, concentrations of phytoplankton in and around a blue mussel Mytilus galloprovincialis raft culture unit in the Ría de Vigo were measured during a 2 wk study period in July 2004. Flow direction and cu

  19. Depletion of plankton in a raft culture of Mytilus galloprovincialis in Ría de Vigo, NW Spain. I. Phytoplankton

    NARCIS (Netherlands)

    Petersen, J.K.; Nielsen, T.G.; Van Duren, L.A.; Maar, M.

    2008-01-01

    Food depletion in mussel cultivation has been rarely studied and seldom demonstrated. In this study, concentrations of phytoplankton in and around a blue mussel Mytilus galloprovincialis raft culture unit in the Ría de Vigo were measured during a 2 wk study period in July 2004. Flow direction and

  20. Comparison of Polymer Networks Synthesized by Conventional Free Radical and RAFT Copolymerization Processes in Supercritical Carbon Dioxide

    Directory of Open Access Journals (Sweden)

    Patricia Pérez-Salinas

    2017-05-01

    Full Text Available There is a debate in the literature on whether or not polymer networks synthesized by reversible deactivation radical polymerization (RDRP processes, such as reversible addition-fragmentation radical transfer (RAFT copolymerization of vinyl/divinyl monomers, are less heterogeneous than those synthesized by conventional free radical copolymerization (FRP. In this contribution, the syntheses by FRP and RAFT of hydrogels based on 2-hydroxyethylene methacrylate (HEMA and ethylene glycol dimethacrylate (EGDMA in supercritical carbon dioxide (scCO2, using Krytox 157 FSL as the dispersing agent, and the properties of the materials produced, are compared. The materials were characterized by differential scanning calorimetry (DSC, swelling index (SI, infrared spectroscopy (FTIR and scanning electron microscopy (SEM. Studies on ciprofloxacin loading and release rate from hydrogels were also carried out. The combined results show that the hydrogels synthesized by FRP and RAFT are significantly different, with apparently less heterogeneity present in the materials synthesized by RAFT copolymerization. A ratio of experimental (Mcexp to theoretical (Mctheo molecular weight between crosslinks was established as a quantitative tool to assess the degree of heterogeneity of a polymer network.

  1. RAFT copolymerization of itaconic anhydride and 2-methoxyethyl acrylate: a multifunctional scaffold for preparation of “clickable” gold nanoparticles

    DEFF Research Database (Denmark)

    Javakhishvili, Irakli; Kasama, Takeshi; Jankova, Katja Atanasova

    2013-01-01

    RAFT copolymerization of 2-methoxyethyl acrylate and itaconic anhydride – a monomer derived from renewable resources – is carried out in a controlled fashion. The copolymer allows preparation of gold nanoparticles with abundant surficial carboxyl and alkyne functional groups that are dendronized ...... via Cu(i)-mediated “click” reaction....

  2. L-plastin is involved in NKG2D recruitment into lipid rafts and NKG2D-mediated NK cell migration.

    Science.gov (United States)

    Serrano-Pertierra, Esther; Cernuda-Morollón, Eva; Brdička, Tomáš; Hoøejši, Václav; López-Larrea, Carlos

    2014-09-01

    Membrane rafts are microdomains of the plasma membrane that have multiple biological functions. The involvement of these structures in the biology of T cells, namely in signal transduction by the TCR, has been widely studied. However, the role of membrane rafts in immunoreceptor signaling in NK cells is less well known. We studied the distribution of the activating NKG2D receptor in lipid rafts by isolating DRMs in a sucrose density gradient or by raft fractionation by β-OG-selective solubility in the NKL cell line. We found that the NKG2D-DAP10 complex and pVav are recruited into rafts upon receptor stimulation. Qualitative proteomic analysis of these fractions showed that the actin cytoskeleton is involved in this process. In particular, we found that the actin-bundling protein L-plastin plays an important role in the clustering of NKG2D into lipid rafts. Moreover, coengagement of the inhibitory receptor NKG2A partially disrupted NKG2D recruitment into rafts. Furthermore, we demonstrated that L-plastin participates in NKG2D-mediated inhibition of NK cell chemotaxis.

  3. The Important Role of Lipid Raft-Mediated Attachment in the Infection of Cultured Cells by Coronavirus Infectious Bronchitis Virus Beaudette Strain

    Science.gov (United States)

    Guo, Huichen; Huang, Mei; Yuan, Quan; Wei, Yanquan; Gao, Yuan; Mao, Lejiao; Gu, Lingjun; Tan, Yong Wah; Zhong, Yanxin; Liu, Dingxiang; Sun, Shiqi

    2017-01-01

    Lipid raft is an important element for the cellular entry of some viruses, including coronavirus infectious bronchitis virus (IBV). However, the exact role of lipid rafts in the cellular membrane during the entry of IBV into host cells is still unknown. In this study, we biochemically fractionated IBV-infected cells via sucrose density gradient centrifugation after depleting plasma membrane cholesterol with methyl-β-cyclodextrin or Mevastatin. Our results demonstrated that unlike IBV non-structural proteins, IBV structural proteins co-localized with lipid raft marker caveolin-1. Infectivity assay results of Vero cells illustrated that the drug-induced disruption of lipid rafts significantly suppressed IBV infection. Further studies revealed that lipid rafts were not required for IBV genome replication or virion release at later stages. However, the drug-mediated depletion of lipid rafts in Vero cells before IBV attachment significantly reduced the expression of viral structural proteins, suggesting that drug treatment impaired the attachment of IBV to the cell surface. Our results indicated that lipid rafts serve as attachment factors during the early stages of IBV infection, especially during the attachment stage. PMID:28081264

  4. Altered lipid composition in cortical lipid rafts occurs at early stages of sporadic Alzheimer's disease and facilitates APP/BACE1 interactions.

    Science.gov (United States)

    Fabelo, Noemí; Martín, Virginia; Marín, Raquel; Moreno, Dolores; Ferrer, Isidre; Díaz, Mario

    2014-08-01

    The presence of lipid alterations in lipid rafts from the frontal cortex in late stages of Alzheimer's disease (AD) has been recently demonstrated. Here, we have isolated and analyzed the lipid composition of lipid rafts from different brain areas from control and AD subjects at initial neuropathologic stages. We have observed that frontal cortex lipid rafts are profoundly altered in AD brains from the earliest stages of AD, namely AD I/II. These changes in the lipid matrix of lipid rafts affected both lipid classes and fatty acids and were also detected in the entorhinal cortex, but not in the cerebellum from the same subjects. Paralleling these changes, lipid rafts from AD frontal and entorhinal cortices displayed higher anisotropy for environment-sensitive probes, indicating that lipid changes in AD lipid rafts increased membrane order and viscosity in these domains. The pathophysiological consequences of these alterations in the development and progression of AD were strengthened by the significant, and specific, accumulation of β-secretase within the lipid rafts of AD subjects even at the earliest stages. Our results provide a mechanistic connection between lipid alterations in these microdomains and amyloidogenic processing of amyloid precursor protein.

  5. Hierarchical organization in aggregates of protein molecules

    DEFF Research Database (Denmark)

    Bohr, Henrik; Kyhle, Anders; Sørensen, Alexis Hammer

    1997-01-01

    The aggregation of proteins into small clusters is studied by atomic force and electron microscopy. Scaling laws and fractal behaviour in the growth of the aggregates and in the correlation between aggregates is seen. A phase diagram of the aggregation process where the protonic concentration...

  6. A Functional Reference Architecture for Aggregators

    DEFF Research Database (Denmark)

    Bondy, Daniel Esteban Morales; Heussen, Kai; Gehrke, Oliver;

    2015-01-01

    Aggregators are considered to be a key enabling technology for harvesting power system services from distributed energy resources (DER). As a precondition for more widespread use of aggregators in power systems, methods for comparing and validating aggregator designs must be established. This paper...... proposes a functional reference architecture for aggregators to address this requirement....

  7. Fractal Aggregates in Tennis Ball Systems

    Science.gov (United States)

    Sabin, J.; Bandin, M.; Prieto, G.; Sarmiento, F.

    2009-01-01

    We present a new practical exercise to explain the mechanisms of aggregation of some colloids which are otherwise not easy to understand. We have used tennis balls to simulate, in a visual way, the aggregation of colloids under reaction-limited colloid aggregation (RLCA) and diffusion-limited colloid aggregation (DLCA) regimes. We have used the…

  8. The raft

    CERN Document Server

    Lintott, Chris

    2020-01-01

    This is the story of what is happening in this, the era of 'big data', in which 'citizen scientists' can discover new planets. Drawing on his experience setting up the extraordinarily successful Zooniverse platform, where ordinary internet users contribute significantly to scientific research, Chris Lintott describes the origins and ongoing state of 'crowdsourcing'. In this inspiring, provocative argument, he shows how, collectively, we can beat the experts, digging deep into the science of human motivation to understand just what people think they're doing when they sign up to decode papyri or watch lions. Written just as crowdsourcing is poised to become a part of all of our lives, this is an impassioned reminder of what each of us can do when we put our minds to it, and a manifesto for what can happen if we learn the right lessons from the pioneering projects taking place right now.

  9. An exact approach for aggregated formulations

    DEFF Research Database (Denmark)

    Gamst, Mette; Spoorendonk, Simon; Røpke, Stefan

    optimality cannot be guaranteed by branching on aggregated variables. We present a generic exact solution method to remedy the drawbacks of aggregation. It combines the original and aggregated formulations and applies Benders' decomposition. We apply the method to the Split Delivery Vehicle Routing Problem.......Aggregating formulations is a powerful approach for problems to take on tractable forms. Aggregation may lead to loss of information, i.e. the aggregated formulation may be an approximation of the original problem. In branch-and-bound context, aggregation can also complicate branching, e.g. when...

  10. Numerical investigation of piled raft foundation in mitigating embankment vibrations induced by high-speed trains

    Institute of Scientific and Technical Information of China (English)

    付强; 刘汉龙; 丁选明; 郑长杰

    2015-01-01

    A three-dimensional dynamic finite element model of track-ballast-embankment and piled raft foundation system is established. Dynamic response of a railway embankment to a high-speed train is simulated for two cases: soft ground improved by piled raft foundation, and untreated soft ground. The obtained results are compared both in time domain and frequency domain to evaluate the effectiveness of the ground improvement in mitigating the embankment vibrations induced by high-speed trains. The results show that ground improving methods can significantly reduce the embankment vibrations at all considered train speeds(36-432 km/h). The ground response to a moving load is dictated largely by the relationship between load speed and characteristic value of wave velocities of the ground medium. At low speeds, the ground response from a moving load is essentially quasi-static. That is, the displacements fields are essential the static fields under the load simply moving with it. For the soft ground, the displacement on the ballast surface is large at all observed train speeds. For the model case where the ground is improved by piled raft foundation, the peak displacement is reduced at all considered train speeds compared with the case without ground improvement. Based on the effect of energy-dissipating of ballast-embankment-ground system with damping, the train-induced vibration waves moving in ballast and embankment are trapped and dissipated, and thus the vibration amplitudes of dynamic displacement outside the embankment are significantly reduced. But for the vibration amplitude of dynamic velocity, the vibration waves in embankment are absorbed or reflected back, and the velocity amplitudes at the ballast and embankment surface are enhanced. For the change of the vibration character of embankment and ballast, the bearing capacity and dynamic character are improved. Therefore, both of the static and dynamic displacements are reduced by ground improvement; the dynamic

  11. Numerical investigation of piled raft foundation in mitigating embankment vibrations induced by high-speed trains

    Institute of Scientific and Technical Information of China (English)

    付强; 刘汉龙; 丁选明; 郑长杰

    2015-01-01

    A three-dimensional dynamic finite element model of track-ballast-embankment and piled raft foundation system is established. Dynamic response of a railway embankment to a high-speed train is simulated for two cases: soft ground improved by piled raft foundation, and untreated soft ground. The obtained results are compared both in time domain and frequency domain to evaluate the effectiveness of the ground improvement in mitigating the embankment vibrations induced by high-speed trains. The results show that ground improving methods can significantly reduce the embankment vibrations at all considered train speeds (36− 432 km/h). The ground response to a moving load is dictated largely by the relationship between load speed and characteristic value of wave velocities of the ground medium. At low speeds, the ground response from a moving load is essentially quasi-static. That is, the displacements fields are essential the static fields under the load simply moving with it. For the soft ground, the displacement on the ballast surface is large at all observed train speeds. For the model case where the ground is improved by piled raft foundation, the peak displacement is reduced at all considered train speeds compared with the case without ground improvement. Based on the effect of energy-dissipating of ballast-embankment-ground system with damping, the train-induced vibration waves moving in ballast and embankment are trapped and dissipated, and thus the vibration amplitudes of dynamic displacement outside the embankment are significantly reduced. But for the vibration amplitude of dynamic velocity, the vibration waves in embankment are absorbed or reflected back, and the velocity amplitudes at the ballast and embankment surface are enhanced. For the change of the vibration character of embankment and ballast, the bearing capacity and dynamic character are improved. Therefore, both of the static and dynamic displacements are reduced by ground improvement; the dynamic

  12. Co-occurrence of Methanosarcina mazei and Geobacteraceae in an iron(III-reducing enrichment culture

    Directory of Open Access Journals (Sweden)

    Shiling eZheng

    2015-09-01

    Full Text Available Methanosaeta harundinacea and Methanosarcina barkeri, known as classic acetoclastic methanogens, are capable of directly accepting electrons from Geobacter metallireducens for the reduction of carbon dioxide to methane, having been revealed as direct interspecies electron transfer (DIET in the laboratory co-cultures. However, whether their co-occurrences are ubiquitous in the iron (III-reducing environments and the other species of acetoclastic methanogens such as Methanosarcina mazei are capable of DIET are still unknown. Instead of initiating the co-cultures with pure cultures, two-step cultivation was employed to selectively enrich iron (III-reducing microorganisms in a coastal gold mining river, Jiehe River, with rich iron content in the sediments. First, iron (III reducers including Geobacteraceae were successfully enriched by 3-months successive culture on amorphous Fe(III oxides as electron acceptor and acetate as electron donor. High-throughput Illumina sequencing, terminal restriction fragment length polymorphism (T-RFLP and clone library analysis based on 16S rRNA genes revealed that the enrichment cultures actively contained the bacteria belong to Geobacteraceae and Bacilli, exclusively dominated by the archaea belong to Methanosarcinaceae. Second, the enrichment cultures including methanogens and Geobacteraceae were transferred with ethanol as alternative electron donor. Remarkably, aggregates were successively formed in the enrichments after three transfers. The results revealed by RNA-based analysis demonstrate that the co-occurrence of Methanosarcina mazei and Geobacteraceae in an iron (III-reducing enrichment culture. Furthermore, the aggregates, as close physical contact, formed in the enrichment culture, indicate that DIET could be a possible option for interspecies electron transfer in the aggregates.

  13. Erythrocyte aggregation: Basic aspects and clinical importance

    OpenAIRE

    Oğuz K. Başkurt; Meiselman, Herbert J.

    2013-01-01

    Red blood cells (RBC) aggregate to form two- and three-dimensional structures when suspended in aqueous solutions containing large plasma proteins or polymers; this aggregation is reversible and shear dependent (i.e., dispersed at high shear and reformed at low or stasis). The extent of aggregation is the main determinant of low shear blood viscosity, thus predicting an inverse relationship between aggregation and in vivo blood flow. However, the effects of aggregation on hemodynamic mechanis...

  14. Molecular Aggregation in Disodium Cromoglycate

    Science.gov (United States)

    Singh, Gautam; Agra-Kooijman, D.; Collings, P. J.; Kumar, Satyendra

    2012-02-01

    Details of molecular aggregation in the mesophases of the anti-asthmatic drug disodium cromoglycate (DSCG) have been studied using x-ray synchrotron scattering. The results show two reflections, one at wide angles corresponding to π-π stacking (3.32 å) of molecules, and the other at small angles which is perpendicular to the direction of molecular stacking and corresponds to the distance between the molecular aggregates. The latter varies from 35 - 41 å in the nematic (N) phase and 27 -- 32 å in the columnar (M) phase. The temperature evolution of the stack height, positional order correlations in the lateral direction, and orientation order parameter were determined in the N, M, and biphasic regions. The structure of the N and M phases and the nature of the molecular aggregation, together with their dependence on temperature and concentration, will be presented.

  15. SHAPE CHARACTERIZATION OF CONCRETE AGGREGATE

    Directory of Open Access Journals (Sweden)

    Jing Hu

    2011-05-01

    Full Text Available As a composite material, the performance of concrete materials can be expected to depend on the properties of the interfaces between its two major components, aggregate and cement paste. The microstructure at the interfacial transition zone (ITZ is assumed to be different from the bulk material. In general, properties of conventional concrete have been found favoured by optimum packing density of the aggregate. Particle size is a common denominator in such studies. Size segregation in the ITZ among the binder particles in the fresh state, observed in simulation studies by concurrent algorithm-based SPACE system, additionally governs density as well as physical bonding capacity inside these shell-like zones around aggregate particles. These characteristics have been demonstrated qualitatively pertaining also after maturation of the concrete. Such properties of the ITZs have direct impact on composite properties. Despite experimental approaches revealed effects of aggregate grain shape on different features of material structure (among which density, and as a consequence on mechanical properties, it is still an underrated factor in laboratory studies, probably due to the general feeling that a suitable methodology for shape characterization is not available. A scientific argument hindering progress is the interconnected nature of size and shape. Presently, a practical problem preventing shape effects to be emphasized is the limitation of most computer simulation systems in concrete technology to spherical particles. New developments at Delft University of Technology will make it possible in the near future to generate jammed states, or other high-density fresh particle mixtures of non-spherical particles, which thereupon can be subjected to hydration algorithms. This paper will sketch the outlines of a methodological approach for shape assessment of loose (non-embedded aggregate grains, and demonstrate its use for two types of aggregate, allowing

  16. Environmentalism and natural aggregate mining

    Science.gov (United States)

    Drew, L.J.; Langer, W.H.; Sachs, J.S.

    2002-01-01

    Sustaining a developed economy and expanding a developing one require the use of large volumes of natural aggregate. Almost all human activity (commercial, recreational, or leisure) is transacted in or on facilities constructed from natural aggregate. In our urban and suburban worlds, we are almost totally dependent on supplies of water collected behind dams and transported through aqueducts made from concrete. Natural aggregate is essential to the facilities that produce energy-hydroelectric dams and coal-fired powerplants. Ironically, the utility created for mankind by the use of natural aggregate is rarely compared favorably with the environmental impacts of mining it. Instead, the empty quarries and pits are seen as large negative environmental consequences. At the root of this disassociation is the philosophy of environmentalism, which flavors our perceptions of the excavation, processing, and distribution of natural aggregate. The two end-member ideas in this philosophy are ecocentrism and anthropocentrism. Ecocentrism takes the position that the natural world is a organism whose arteries are the rivers-their flow must not be altered. The soil is another vital organ and must not be covered with concrete and asphalt. The motto of the ecocentrist is "man must live more lightly on the land." The anthropocentrist wants clean water and air and an uncluttered landscape for human use. Mining is allowed and even encouraged, but dust and noise from quarry and pit operations must be minimized. The large volume of truck traffic is viewed as a real menace to human life and should be regulated and isolated. The environmental problems that the producers of natural aggregate (crushed stone and sand and gravel) face today are mostly difficult social and political concerns associated with the large holes dug in the ground and the large volume of heavy truck traffic associated with quarry and pit operations. These concerns have increased in recent years as society's demand for

  17. Aggregating energy flexibilities under constraints

    DEFF Research Database (Denmark)

    Valsomatzis, Emmanouil; Pedersen, Torben Bach; Abello, Alberto

    2016-01-01

    The flexibility of individual energy prosumers (producers and/or consumers) has drawn a lot of attention in recent years. Aggregation of such flexibilities provides prosumers with the opportunity to directly participate in the energy market and at the same time reduces the complexity of scheduling...... the energy units. However, aggregated flexibility should support normal grid operation. In this paper, we build on the flex-offer (FO) concept to model the inherent flexibility of a prosumer (e.g., a single flexible consumption device such as a clothes washer). An FO captures flexibility in both time...

  18. Balancing energy flexibilities through aggregation

    DEFF Research Database (Denmark)

    Valsomatzis, Emmanouil; Hose, Katja; Pedersen, Torben Bach

    2014-01-01

    One of the main goals of recent developments in the Smart Grid area is to increase the use of renewable energy sources. These sources are characterized by energy fluctuations that might lead to energy imbalances and congestions in the electricity grid. Exploiting inherent flexibilities, which exist...... in both energy production and consumption, is the key to solving these problems. Flexibilities can be expressed as flex-offers, which due to their high number need to be aggregated to reduce the complexity of energy scheduling. In this paper, we discuss balance aggregation techniques that already during...

  19. Fusion of raft-like lipid bilayers operated by a membranotropic domain of the HSV-type I glycoprotein gH occurs through a cholesterol-dependent mechanism.

    Science.gov (United States)

    Vitiello, Giuseppe; Falanga, Annarita; Petruk, Ariel Alcides; Merlino, Antonello; Fragneto, Giovanna; Paduano, Luigi; Galdiero, Stefania; D'Errico, Gerardino

    2015-04-21

    A wealth of evidence indicates that lipid rafts are involved in the fusion of the viral lipid envelope with the target cell membrane. However, the interplay between these sterol- and sphingolipid-enriched ordered domains and viral fusion glycoproteins has not yet been clarified. In this work we investigate the molecular mechanism by which a membranotropic fragment of the glycoprotein gH of the Herpes Simplex Virus (HSV) type I (gH625) drives fusion of lipid bilayers formed by palmitoyl oleoyl phosphatidylcholine (POPC)-sphingomyelin (SM)-cholesterol (CHOL) (1 : 1 : 1 wt/wt/wt), focusing on the role played by each component. The comparative analysis of the liposome fusion assays, Dynamic Light Scattering (DLS), spectrofluorimetry, Neutron Reflectivity (NR) and Electron Spin Resonance (ESR) experiments, and Molecular Dynamics (MD) simulations shows that CHOL is fundamental for liposome fusion to occur. In detail, CHOL stabilizes the gH625-bilayer association by specific interactions with the peptide Trp residue. The interaction with gH625 causes an increased order of the lipid acyl chains, whose local rotational motion is significantly hampered. SM plays only a minor role in the process, favoring the propagation of lipid perturbation to the bilayer inner core. The stiffening of the peptide-interacting bilayer leaflet results in an asymmetric perturbation of the membrane, which is locally destabilized thus favoring fusion events. Our results show that viral fusion glycoproteins are optimally suited to exert a high fusogenic activity on lipid rafts and support the relevance of cholesterol as a key player of membrane-related processes.

  20. Supramolecular Nanofibers Enhance Growth Factor Signaling by Increasing Lipid Raft Mobility.

    Science.gov (United States)

    Newcomb, Christina J; Sur, Shantanu; Lee, Sungsoo S; Yu, Jeong Min; Zhou, Yan; Snead, Malcolm L; Stupp, Samuel I

    2016-05-11

    The nanostructures of self-assembling biomaterials have been previously designed to tune the release of growth factors in order to optimize biological repair and regeneration. We report here on the discovery that weakly cohesive peptide nanostructures in terms of intermolecular hydrogen bonding, when combined with low concentrations of osteogenic growth factor, enhance both BMP-2 and Wnt mediated signaling in myoblasts and bone marrow stromal cells, respectively. Conversely, analogous nanostructures with enhanced levels of internal hydrogen bonding and cohesion lead to an overall reduction in BMP-2 signaling. We propose that the mechanism for enhanced growth factor signaling by the nanostructures is related to their ability to increase diffusion within membrane lipid rafts. The phenomenon reported here could lead to new nanomedicine strategies to mediate growth factor signaling for translational targets.