WorldWideScience

Sample records for cell-surface tethered modulators

  1. Tethering of Ficolin-1 to cell surfaces through recognition of sialic acid by the fibrinogen-like domain

    DEFF Research Database (Denmark)

    Honoré, Christian; Rørvig, Sara; Hummelshøj, Tina; Skjoedt, Mikkel-Ole; Borregaard, Niels; Garred, Peter

    2010-01-01

    the cell surface is restricted to monocytes and granulocytes. Ficolin-1 is tethered to the cell surface of these cells through its fibrinogen-like domain, and the ligand involved in the binding of Ficolin-1 is shown to be sialic acid. Moreover, rFicolin-1 bound activated but not resting T lymphocytes...

  2. BST2/CD317 counteracts human coronavirus 229E productive infection by tethering virions at the cell surface

    International Nuclear Information System (INIS)

    Bone marrow stromal antigen 2 (BST2), an interferon-inducible antiviral factor, has been shown to block the release of various enveloped viruses from cells. It has also been identified as an innate immune system component. Most enveloped viruses subject to BST2 restriction bud at the plasma membrane. Here we report our findings that (a) the production of human coronavirus 229E (HCoV-229E) progeny viruses, whose budding occurs at the ER-Golgi intermediate compartment (ERGIC), markedly decreases in the presence of BST2; and (b) BST2 knockdown expression results in enhanced HCoV-229E virion production. Electron microscopy analyses indicate that HCoV-229E virions are tethered to cell surfaces or intracellular membranes by BST2. Our results suggest that BST2 exerts a broad blocking effect against enveloped virus release, regardless of whether budding occurs at the plasma membrane or intracellular compartments. - Highlights: • BST2 knockdown expression results in enhanced HCoV-229E egress. • HCoV-229E virions are tethered to cell surfaces or intracellular membranes by BST2. • HCoV-229E infection at high MOI can significantly downregulate HeLa BST2 and rescue HIV-1 egress

  3. BST2/CD317 counteracts human coronavirus 229E productive infection by tethering virions at the cell surface

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Shiu-Mei [Department of Medical Research and Education, Taipei Veterans General Hospital and Institute of Clinical Medicine, Taipei 11217, Taiwan (China); Institute of Clinical Medicine, National Yang-Ming University School of Medicine, Taipei, Taiwan (China); Huang, Kuo-Jung [Department of Medical Research and Education, Taipei Veterans General Hospital and Institute of Clinical Medicine, Taipei 11217, Taiwan (China); Wang, Chin-Tien, E-mail: chintien@ym.edu.tw [Department of Medical Research and Education, Taipei Veterans General Hospital and Institute of Clinical Medicine, Taipei 11217, Taiwan (China); Institute of Clinical Medicine, National Yang-Ming University School of Medicine, Taipei, Taiwan (China)

    2014-01-20

    Bone marrow stromal antigen 2 (BST2), an interferon-inducible antiviral factor, has been shown to block the release of various enveloped viruses from cells. It has also been identified as an innate immune system component. Most enveloped viruses subject to BST2 restriction bud at the plasma membrane. Here we report our findings that (a) the production of human coronavirus 229E (HCoV-229E) progeny viruses, whose budding occurs at the ER-Golgi intermediate compartment (ERGIC), markedly decreases in the presence of BST2; and (b) BST2 knockdown expression results in enhanced HCoV-229E virion production. Electron microscopy analyses indicate that HCoV-229E virions are tethered to cell surfaces or intracellular membranes by BST2. Our results suggest that BST2 exerts a broad blocking effect against enveloped virus release, regardless of whether budding occurs at the plasma membrane or intracellular compartments. - Highlights: • BST2 knockdown expression results in enhanced HCoV-229E egress. • HCoV-229E virions are tethered to cell surfaces or intracellular membranes by BST2. • HCoV-229E infection at high MOI can significantly downregulate HeLa BST2 and rescue HIV-1 egress.

  4. Rupture force of cell adhesion ligand tethers modulates biological activities of a cell-laden hydrogel.

    Science.gov (United States)

    Lee, Min Kyung; Park, Jooyeon; Wang, Xuefeng; Roein-Peikar, Mehdi; Ko, Eunkyung; Qin, Ellen; Lee, Jonghwi; Ha, Taekjip; Kong, Hyunjoon

    2016-04-01

    Recent efforts to design a synthetic extracellular matrix for cell culture, engineering, and therapies greatly contributed to addressing biological roles of types and spatial organization of cell adhesion ligands. It is often suggested that ligand-matrix bond strength is another path to regulate cell adhesion and activities; however tools are lacking. To this end, this study demonstrates that a hydrogel coupled with integrin-binding deoxyribonucleic acid (DNA) tethers with pre-defined rupture forces can modulate cell adhesion, differentiation, and secretion activities due to the changes in the number and, likely, force of cells adhered to a gel. The rupture force of DNA tethers was tuned by altering the spatial arrangement of matrix-binding biotin groups. The DNA tethers were immobilized on a hydrogel of alginate grafted with biotin using avidin. Mesenchymal stem cells showed enhanced adhesion, neural differentiation, and paracrine secretion when cultured on the gel coupled with DNA tethers with higher rupture forces. Such innovative cell-matrix interface engineering would be broadly useful for a series of materials used for fundamental and applied studies on biological cells. PMID:26912186

  5. Oxygen Modulates Human Decidual Natural Killer Cell Surface Receptor Expression and Interactions with Trophoblasts1

    Science.gov (United States)

    Wallace, Alison E.; Goulwara, Sonu S.; Whitley, Guy S.; Cartwright, Judith E.

    2014-01-01

    Decidual natural killer (dNK) cells have been shown to both promote and inhibit trophoblast behavior important for decidual remodeling in pregnancy and have a distinct phenotype compared to peripheral blood NK cells. We investigated whether different levels of oxygen tension, mimicking the physiological conditions of the decidua in early pregnancy, altered cell surface receptor expression and activity of dNK cells and their interactions with trophoblast. dNK cells were isolated from terminated first-trimester pregnancies and cultured in oxygen tensions of 3%, 10%, and 21% for 24 h. Cell surface receptor expression was examined by flow cytometry, and the effects of secreted factors in conditioned medium (CM) on the trophoblast cell line SGHPL-4 were assessed in vitro. SGHPL-4 cells treated with dNK cell CM incubated in oxygen tensions of 10% were significantly more invasive (P oxygen tensions of 3% or 21%. After 24 h, a lower percentage of dNK cells expressed CD56 at 21% oxygen (P oxygen (P oxygen tensions, with large patient variation. This study demonstrates dNK cell phenotype and secreted factors are modulated by oxygen tension, which induces changes in trophoblast invasion and endovascular-like differentiation. Alterations in dNK cell surface receptor expression and secreted factors at different oxygen tensions may represent regulation of function within the decidua during the first trimester of pregnancy. PMID:25232021

  6. The modulation of cell surface cAMP receptors from Dictyostelium disscoideum by ammonium sulfate

    NARCIS (Netherlands)

    Haastert, Peter J.M. van

    1985-01-01

    Dictyostelium discoideum cells contain a heterogeneous population of cell surface cAMP receptors with components possessing different affinities (Kd between 15 and 450 nM) and different off-rates of the cAMP-receptor complex (t½ between 0.7 and 150 s). The association of cAMP to the receptor and the

  7. Tumor suppressor protein SMAR1 modulates the roughness of cell surface: combined AFM and SEM study

    Directory of Open Access Journals (Sweden)

    Mamgain Hitesh

    2009-10-01

    Full Text Available Abstract Background Imaging tools such as scanning electron microscope (SEM and atomic force microscope (AFM can be used to produce high-resolution topographic images of biomedical specimens and hence are well suited for imaging alterations in cell morphology. We have studied the correlation of SMAR1 expression with cell surface smoothness in cell lines as well as in different grades of human breast cancer and mouse tumor sections. Methods We validated knockdown and overexpression of SMAR1 using RT-PCR as well as Western blotting in human embryonic kidney (HEK 293, human breast cancer (MCF-7 and mouse melanoma (B16F1 cell lines. The samples were then processed for cell surface roughness studies using atomic force microscopy (AFM and scanning electron microscopy (SEM. The same samples were used for microarray analysis as well. Tumors sections from control and SMAR1 treated mice as well as tissues sections from different grades of human breast cancer on poly L-lysine coated slides were used for AFM and SEM studies. Results Tumor sections from mice injected with melanoma cells showed pronounced surface roughness. In contrast, tumor sections obtained from nude mice that were first injected with melanoma cells followed by repeated injections of SMAR1-P44 peptide, exhibited relatively smoother surface profile. Interestingly, human breast cancer tissue sections that showed reduced SMAR1 expression exhibited increased surface roughness compared to the adjacent normal breast tissue. Our AFM data establishes that treatment of cells with SMAR1-P44 results into increase in cytoskeletal volume that is supported by comparative gene expression data showing an increase in the expression of specific cytoskeletal proteins compared to the control cells. Altogether, these findings indicate that tumor suppressor function of SMAR1 might be exhibited through smoothening of cell surface by regulating expression of cell surface proteins. Conclusion Tumor suppressor

  8. Tumor suppressor protein SMAR1 modulates the roughness of cell surface: combined AFM and SEM study

    International Nuclear Information System (INIS)

    Imaging tools such as scanning electron microscope (SEM) and atomic force microscope (AFM) can be used to produce high-resolution topographic images of biomedical specimens and hence are well suited for imaging alterations in cell morphology. We have studied the correlation of SMAR1 expression with cell surface smoothness in cell lines as well as in different grades of human breast cancer and mouse tumor sections. We validated knockdown and overexpression of SMAR1 using RT-PCR as well as Western blotting in human embryonic kidney (HEK) 293, human breast cancer (MCF-7) and mouse melanoma (B16F1) cell lines. The samples were then processed for cell surface roughness studies using atomic force microscopy (AFM) and scanning electron microscopy (SEM). The same samples were used for microarray analysis as well. Tumors sections from control and SMAR1 treated mice as well as tissues sections from different grades of human breast cancer on poly L-lysine coated slides were used for AFM and SEM studies. Tumor sections from mice injected with melanoma cells showed pronounced surface roughness. In contrast, tumor sections obtained from nude mice that were first injected with melanoma cells followed by repeated injections of SMAR1-P44 peptide, exhibited relatively smoother surface profile. Interestingly, human breast cancer tissue sections that showed reduced SMAR1 expression exhibited increased surface roughness compared to the adjacent normal breast tissue. Our AFM data establishes that treatment of cells with SMAR1-P44 results into increase in cytoskeletal volume that is supported by comparative gene expression data showing an increase in the expression of specific cytoskeletal proteins compared to the control cells. Altogether, these findings indicate that tumor suppressor function of SMAR1 might be exhibited through smoothening of cell surface by regulating expression of cell surface proteins. Tumor suppressor protein SMAR1 might be used as a phenotypic differentiation

  9. Modulation of cell surface GABA B receptors by desensitization,trafficking and regulated degradation

    Institute of Scientific and Technical Information of China (English)

    Dietmar; Benke; Khaled; Zemoura; Patrick; J; Maier

    2012-01-01

    Inhibitory neurotransmission ensures normal brain function by counteracting and integrating excitatory activity.-Aminobutyric acid (GABA) is the main inhibitory neurotransmitter in the mammalian central nervous system,and mediates its effects via two classes of receptors:the GABA A and GABA B receptors.GABA A receptors are heteropentameric GABA-gated chloride channels and responsible for fast inhibitory neurotransmission.GABA B receptors are heterodimeric G protein coupled receptors (GPCR) that mediate slow and prolonged inhibitory transmission.The extent of inhibitory neurotransmission is determined by a variety of factors,such as the degree of transmitter release and changes in receptor activity by posttranslational modifications (e.g.,phosphorylation),as well as by the number of receptors present in the plasma membrane available for signal transduction.The level of GABA B receptors at the cell surface critically depends on the residence time at the cell surface and finally the rates of endocytosis and degradation.In this review we focus primarily on recent advances in the understanding of trafficking mechanisms that determine the expression level of GABA B receptors in the plasma membrane,and thereby signaling strength.

  10. Down-Regulation of Cell Surface Receptors Is Modulated by Polar Residues within the Transmembrane Domain

    Science.gov (United States)

    Zaliauskiene, Lolita; Kang, Sunghyun; Brouillette, Christie G.; Lebowitz, Jacob; Arani, Ramin B.; Collawn, James F.

    2000-01-01

    How recycling receptors are segregated from down-regulated receptors in the endosome is unknown. In previous studies, we demonstrated that substitutions in the transferrin receptor (TR) transmembrane domain (TM) convert the protein from an efficiently recycling receptor to one that is rapidly down regulated. In this study, we demonstrate that the “signal” within the TM necessary and sufficient for down-regulation is Thr11Gln17Thr19 (numbering in TM). Transplantation of these polar residues into the wild-type TR promotes receptor down-regulation that can be demonstrated by changes in protein half-life and in receptor recycling. Surprisingly, this modification dramatically increases the TR internalization rate as well (∼79% increase). Sucrose gradient centrifugation and cross-linking studies reveal that propensity of the receptors to self-associate correlates with down-regulation. Interestingly, a number of cell surface proteins that contain TM polar residues are known to be efficiently down-regulated, whereas recycling receptors for low-density lipoprotein and transferrin conspicuously lack these residues. Our data, therefore, suggest a simple model in which specific residues within the TM sequences dramatically influence the fate of membrane proteins after endocytosis, providing an alternative signal for down-regulation of receptor complexes to the well-characterized cytoplasmic tail targeting signals. PMID:10930460

  11. Cell surface modulation of gene expression in brain cells by down regulation of glucocorticoid receptors

    Energy Technology Data Exchange (ETDEWEB)

    McGinnis, J.F.; de Vellis, J.

    1981-02-01

    The concentration of glycerol-3-phosphate dehydrogenase (GPDH; sn-glycerol-3-phosphate:NAD/sup +/ 2-oxidoreductase, EC 1.1.1.8) had previously been determined to be regulated by glucocorticoids in rat brain cells in vivo and in cell culture. We now demonstrate that concanavalin A (Con A) can inhibit the induction of GPDH in a dose-dependent manner in C6 rat glioma cells and in primary cultures of rat brain oligodendrocytes. The inhibition specifically prevents the appearance of new molecules of GPDH, although Con A does not significantly inhibit protein synthesis in these cells, nor does it affect the activity of another solube enzyme, lactate dehydrogenase. The ability to block enzyme induction is not limited to Con A, because other lectins also inhibit induction. The molecular mechanism by which Con A inhibits GPDH induction appears to be by the down regulation of the cytoplasmic glucocorticoid receptors, because exposure to Con A results in the loss of more than 90% of the receptor activity. Con A does not inhibit the receptor assay and no direct interaction between the receptor and Con A could be demonstrated. This down regulation is not tumor cell specific and appears to be a general phenomenon, because it occurs in normal oligodendrocytes and even in normal astrocytes (a cell type in which the gene for GPDH is not expressed). The down regulation of glucocorticoid receptors in normal brain cells suggests two important corollaries. First, it demonstrates the existence of a rate-limiting step controlling the glucocorticoid-dependent gene expression in brain cells and possibly represents a regulatory site common to all glucocorticoid target cells. Second, it suggests that the response to glucocorticoids of oligodendrocytes and astrocytes can be regulated in vivo by cell surface contact with endogenous lectins, neighboring cells, or both.

  12. Display of cell surface sites for fibronectin assembly is modulated by cell adherence to (1F3 and C-terminal modules of fibronectin.

    Directory of Open Access Journals (Sweden)

    Jielin Xu

    Full Text Available BACKGROUND: Fibronectin-null cells assemble soluble fibronectin shortly after adherence to a substrate coated with intact fibronectin but not when adherent to the cell-binding domain of fibronectin (modules (7F3-(10F3. Interactions of adherent cells with regions of adsorbed fibronectin other than modules (7F3-(10F3, therefore, are required for early display of the cell surface sites that initiate and direct fibronectin assembly. METHODOLOGY/PRINCIPAL FINDINGS: To identify these regions, coatings of proteolytically derived or recombinant pieces of fibronectin containing modules in addition to (7F3-(10F3 were tested for effects on fibronectin assembly by adherent fibronectin-null fibroblasts. Pieces as large as one comprising modules (2F3-(14F3, which include the heparin-binding and cell adhesion domains, were not effective in supporting fibronectin assembly. Addition of module (1F3 or the C-terminal modules to modules (2F3-(14F3 resulted in some activity, and addition of both (1F3 and the C-terminal modules resulted in a construct, (1F3-C, that best mimicked the activity of a coating of intact fibronectin. Constructs (1F3-C V0, (1F3-C V64, and (1F3-C Delta(V(15F3(10F1 were all able to support fibronectin assembly, suggesting that (1F3 through (11F1 and/or (12F1 were important for activity. Coatings in which the active parts of (1F3-C were present in different proteins were much less active than intact (1F3-C. CONCLUSIONS: These results suggest that (1F3 acts together with C-terminal modules to induce display of fibronectin assembly sites on adherent cells.

  13. HIV-1 Nef and Vpu Are Functionally Redundant Broad-Spectrum Modulators of Cell Surface Receptors, Including Tetraspanins

    Science.gov (United States)

    Haller, Claudia; Müller, Birthe; Fritz, Joëlle V.; Lamas-Murua, Miguel; Stolp, Bettina; Pujol, François M.; Keppler, Oliver T.

    2014-01-01

    ABSTRACT HIV-1 Nef and Vpu are thought to optimize virus replication in the infected host, at least in part via their ability to interfere with vesicular host cell trafficking. Despite the use of distinct molecular mechanisms, Nef and Vpu share specificity for some molecules such as CD4 and major histocompatibility complex class I (MHC-I), while disruption of intracellular transport of the host cell restriction factor CD317/tetherin represents a specialized activity of Vpu not exerted by HIV-1 Nef. To establish a profile of host cell receptors whose intracellular transport is affected by Nef, Vpu, or both, we comprehensively analyzed the effect of these accessory viral proteins on cell surface receptor levels on A3.01 T lymphocytes. Thirty-six out of 105 detectable receptors were significantly downregulated by HIV-1 Nef, revealing a previously unappreciated scope with which HIV-1 Nef remodels the cell surface of infected cells. Remarkably, the effects of HIV-1 Vpu on host cell receptor exposure largely matched those of HIV-1 Nef in breadth and specificity (32 of 105, all also targeted by Nef), even though the magnitude was generally less pronounced. Of particular note, cell surface exposure of all members of the tetraspanin (TSPAN) protein family analyzed was reduced by both Nef and Vpu, and the viral proteins triggered the enrichment of TSPANs in a perinuclear area of the cell. While Vpu displayed significant colocalization and physical association with TSPANs, interactions of Nef with TSPANs were less robust. TSPANs thus emerge as a major target of deregulation in host cell vesicular transport by HIV-1 Nef and Vpu. The conservation of this activity in two independent accessory proteins suggests its importance for the spread of HIV-1 in the infected host. IMPORTANCE In this paper, we define that HIV-1 Nef and Vpu display a surprising functional overlap and affect the cell surface exposure of a previously unexpected breadth of cellular receptors. Our analyses

  14. An In-tether Chiral Center Modulates the Helicity, Cell Permeability, and Target Binding Affinity of a Peptide.

    Science.gov (United States)

    Hu, Kuan; Geng, Hao; Zhang, Qingzhou; Liu, Qisong; Xie, Mingsheng; Sun, Chengjie; Li, Wenjun; Lin, Huacan; Jiang, Fan; Wang, Tao; Wu, Yun-Dong; Li, Zigang

    2016-07-01

    The addition of a precisely positioned chiral center in the tether of a constrained peptide is reported, yielding two separable peptide diastereomers with significantly different helicity, as supported by circular dichroism (CD) and NMR spectroscopy. Single crystal X-ray diffraction analysis suggests that the absolute configuration of the in-tether chiral center in helical form is R, which is in agreement with theoretical simulations. The relationship between the secondary structure of the short peptides and their biochemical/biophysical properties remains elusive, largely because of the lack of proper controls. The present strategy provides the only method for investigating the influence of solely conformational differences upon the biochemical/biophysical properties of peptides. The significant differences in permeability and target binding affinity between the peptide diastereomers demonstrate the importance of helical conformation. PMID:27167181

  15. Modulation of cell surface protein free thiols: a potential novel mechanism of action of the sesquiterpene lactone parthenolide.

    Directory of Open Access Journals (Sweden)

    Jolanta Skalska

    Full Text Available BACKGROUND: There has been much interest in targeting intracellular redox pathways as a therapeutic approach for cancer. Given recent data to suggest that the redox status of extracellular protein thiol groups (i.e. exofacial thiols effects cell behavior, we hypothesized that redox active anti-cancer agents would modulate exofacial protein thiols. METHODOLOGY/PRINCIPAL FINDINGS: To test this hypothesis, we used the sesquiterpene lactone parthenolide, a known anti-cancer agent. Using flow cytometry, and western blotting to label free thiols with Alexa Fluor 633 C(5 maleimide dye and N-(biotinoyl-N-(iodoacetyl ethylendiamine (BIAM, respectively, we show that parthenolide decreases the level of free exofacial thiols on Granta mantle lymphoma cells. In addition, we used immuno-precipitation techniques to identify the central redox regulator thioredoxin, as one of the surface protein thiol targets modified by parthenolide. To examine the functional role of parthenolide induced surface protein thiol modification, we pretreated Granta cells with cell impermeable glutathione (GSH, prior to exposure to parthenolide, and showed that GSH pretreatment; (a inhibited the interaction of parthenolide with exofacial thiols; (b inhibited parthenolide mediated activation of JNK and inhibition of NFkappaB, two well established mechanisms of parthenolide activity and; (c blocked the cytotoxic activity of parthenolide. That GSH had no effect on the parthenolide induced generation of intracellular reactive oxygen species supports the fact that GSH had no effect on intracellular redox. Together these data support the likelihood that GSH inhibits the effect of parthenolide on JNK, NFkappaB and cell death through its direct inhibition of parthenolide's modulation of exofacial thiols. CONCLUSIONS/SIGNIFICANCE: Based on these data, we postulate that one component of parthenolide's anti-lymphoma activity derives from its ability to modify the redox state of critical

  16. β1- and β3- voltage-gated sodium channel subunits modulate cell surface expression and glycosylation of Nav1.7 in HEK293 cells

    Directory of Open Access Journals (Sweden)

    Ninda Syam

    2013-08-01

    Full Text Available Voltage-gated sodium channels (Navs are glycoproteins composed of a pore-forming α-subunit and associated β-subunits that regulate Nav α-subunit plasma membrane density and biophysical properties. Glycosylation of the Nav α-subunit also directly affects Navs gating. β-subunits and glycosylation thus comodulate Nav α-subunit gating. We hypothesized that β-subunits could directly influence α-subunit glycosylation. Whole-cell patch clamp of HEK293 cells revealed that both β1- and β3-subunits coexpression shifted V1/2 of steady-state activation and inactivation and increased Nav1.7-mediated INa density. Biotinylation of cell surface proteins, combined with the use of deglycosydases, confirmed that Nav1.7 α-subunits exist in multiple glycosylated states. The α-subunit intracellular fraction was found in a core-glycosylated state, migrating at approximately 250 kDa. At the plasma membrane, in addition to the core-glycosylated form, a fully glycosylated form of Nav1.7 (~280 kDa was observed. This higher band shifted to an intermediate band (~260 kDa when β1-subunits were coexpressed, suggesting that the β1-subunit promotes an alternative glycosylated form of Nav1.7. Furthermore, the β1-subunit increased the expression of this alternative glycosylated form and the β3-subunit increased the expression of the core-glycosylated form of Nav1.7. This study describes a novel role for β1- and β3-subunits in the modulation of Nav1.7 α-subunit glycosylation and cell surface expression.

  17. Electrodynamics of the Getaway Tether Experiment

    Science.gov (United States)

    Greene, Michael; Baginski, Michael; Wheelock, Douglas

    1989-01-01

    An electrodynamic circuit model of the interaction of a pair of small tethered satellites and the ionosphere is developed and analyzed. The system under study, the Getaway Tether Experiment (GATE), is composed of two small satellites and 1 km of insulated conducting tether. The nonlinear model has elements representing the emission, collection, and resistive flow of charge through an electrically conductive tether, plasma contactors, and the ionosphere. The circuit model is incorporated into a dynamic orbital simulation to predict mission performance. Simulation results show the feasibility to bilaterally transfer energy between stored electrical energy and orbital momentum. A transient model is also developed using the circuit model and a string of N lumped-parameter modules, each consisting of resistance, capacitance, and induced potential for the tether. Transients are shown via simulation to occur over millisecond intervals.

  18. Site-directed mutagenesis of HIV-1 vpu gene demonstrates two clusters of replication-defective mutants with distinct ability to down-modulate cell surface CD4 and tetherin

    Directory of Open Access Journals (Sweden)

    Masako Nomaguchi

    2010-11-01

    Full Text Available HIV-1 Vpu acts positively on viral infectivity by mediating CD4 degradation in endoplasmic reticulum and enhances virion release by counteracting a virion release restriction factor, tetherin. In order to define the impact of Vpu activity on HIV-1 replication, we have generated a series of site-specific proviral vpu mutants. Of fifteen mutants examined, seven exhibited a replication-defect similar to that of a vpu-deletion mutant in a lymphocyte cell line H9. These mutations clustered in narrow regions within transmembrane domain (TMD and cytoplasmic domain (CTD. Replication-defective mutants displayed the reduced ability to enhance virion release from a monolayer cell line HEp2 without exception. Upon transfection with Vpu expression vectors, neither TMD mutants nor CTD mutants blocked CD4 expression at the cell surface in another monolayer cell line MAGI. While TMD mutants were unable to down-modulate cell surface tetherin in HEp2 cells, CTD mutants did quite efficiently. Confocal microscopy analysis revealed the difference of intracellular localization between TMD and CTD mutants. In total, replication capability of HIV-1 carrying vpu mutations correlates well with the ability of Vpu to enhance virion release and to impede the cell surface expression of CD4 but not with the ability to down-modulate cell surface tetherin. Our results here suggest that efficient viral replication requires not only down-regulation of cell surface tetherin but also its degradation.

  19. Conductive Tether Coating for Electrodynamic Tethers

    Science.gov (United States)

    Vaughn, Jason A.; Schuler, Pete

    2000-01-01

    The Propulsive Small Expendable Deployer System (ProSEDS), which is an on-orbit demonstration of the propulsion capabilities of electrodynamic tethers in space, is a secondary payload on a Delta 11 unmanned expendable booster. The ProSEDS tether consists of a 5 km bare electrodynamic tether and a 1 0-km non-conductive leader tether. Near the Delta 11, 160 m of the conductive tether is insulated to prevent plasma electron collection from the plasma contactor and for other science requirements. The remainder of the 5-km conductive tether is coated with a new conductive coating to collect plasma electrons. A bare metal tether easily collects electrons from the plasma, but thermal concerns preclude this design. A highly emissive conductive polymer developed by Triton Systems, Inc. has been optimized for both conductivity and thermo-optical properties. The current design for the ProSEDS conductive tether is seven individually coated strands of 28 AWG aluminum wire, coated with an atomic oxygen-resistant conductive polymer composed of a mixture of COR (Colorless Oxygen Resistant) and polyanaline (PANI) known as C-COR (Conductive-Colorless Oxygen Resistant). The conductive-coated wire strands are cold-welded to individually coated strands of the insulated tether. The insulated tether is coated with 1 mil of polyimide and an atomic oxygen resistant polymer TOR-BP. The insulated tether must stand off the entire voltage of the tether (1 200 V) at various times during the mission. All seven wires are twisted around a Kevlar-29 core using the Hi-wire design. Extensive testing has been performed at the Marshall Space Flight Center to qualify both the conductive coating and insulating coating for use on the ProSEDS tether. The conductive coating has been exposed to a plasma to verify the coatings ability to collect electrons from the space plasma from 0 to 1500 V, and to verify the coatings ability to collect electrons after atomic oxygen exposure. The insulated coating has been

  20. Tether Deployer And Brake

    Science.gov (United States)

    Carroll, Joseph A.; Alexander, Charles M.

    1993-01-01

    Design concept promises speed, control, and reliability. Scheme for deploying tether provides for fast, free, and snagless payout and fast, dependable braking. Developed for small, expendable tethers in outer space, scheme also useful in laying transoceanic cables, deploying guidance wires to torpedoes and missiles, paying out rescue lines from ship to ship via rockets, deploying antenna wires, releasing communication and power cables to sonobuoys and expendable bathythermographs, and in reeling out lines from fishing rods.

  1. Engineering an "infectious" T(reg) biomimetic through chemoselective tethering of TGF-β1 to PEG brush surfaces.

    Science.gov (United States)

    Yang, E Y; Kronenfeld, J P; Gattás-Asfura, K M; Bayer, A L; Stabler, C L

    2015-10-01

    Modulation of immunological responses to allografts following transplantation is of pivotal importance to improving graft outcome and duration. Of the many approaches, harnessing the dominant tolerance induced by regulatory T cells (Treg) holds tremendous promise. Recent studies have highlighted the unique potency of cell surface-bound TGF-β1 on Treg for promoting infectious tolerance, i.e. to confer suppressive capacity from one cell to another. To mimic this characteristic, TGF-β1 was chemoselectively tethered to inert and viable polymer grafting platforms using Staudinger ligation. We report the synthesis and functional characterization of these engineered TGF-β1 surfaces. Inert beads tethered with TGF-β1 were capable of efficiently converting naïve CD4(+) CD62L(hi) T cells to functional Treg. Concordantly, translation of conjugation scheme from inert surfaces to viable cells also led to efficient generation of functional Treg. Further, the capacity of these platforms to generate antigen-specific Treg was demonstrated. These findings illustrate the unique faculty of tethered TGF-β1 biomaterial platforms to function as an "infectious" Treg and provide a compelling approach for generating tolerogenic microenvironments for allograft transplantation. PMID:26197412

  2. GRASP: A Multitasking Tether.

    Science.gov (United States)

    Rabouille, Catherine; Linstedt, Adam D

    2016-01-01

    Originally identified as Golgi stacking factors in vitro, the Golgi reassembly stacking protein (GRASP) family has been shown to act as membrane tethers with multiple cellular roles. As an update to previous comprehensive reviews of the GRASP family (Giuliani et al., 2011; Vinke et al., 2011; Jarvela and Linstedt, 2012), we outline here the latest findings concerning their diverse roles. New insights into the mechanics of GRASP-mediated tethering come from recent crystal structures. The models of how GRASP65 and GRASP55 tether membranes relate directly to their role in Golgi ribbon formation in mammalian cells and the unlinking of the ribbon at the onset of mitosis. However, it is also clear that GRASPs act outside the Golgi with roles at the ER and ER exit sites (ERES). Furthermore, the proteins of this family display other roles upon cellular stress, especially in mediating unconventional secretion of both transmembrane proteins (Golgi bypass) and cytoplasmic proteins (through secretory autophagosomes). PMID:26858948

  3. The design conception of multipurpose underwater tethered systems with centralized data exchange

    OpenAIRE

    Блінцов, Олександр Володимирович

    2013-01-01

    The structure and design features of a typical tethered underwater system are given. The design complexity, limitations on the installation of additional equipment and the need for the creation of multi-purpose tethered underwater systems are shown.Logic modules, of which almost all tethered underwater systems consist: actuating mechanisms and sensors of the underwater robotic vehicle, control and display devices of the control station, documenting devices, are singled out.The concept of crea...

  4. Tethered float liquid level sensor

    Energy Technology Data Exchange (ETDEWEB)

    Daily, III, William Dean

    2016-09-06

    An apparatus for sensing the level of a liquid includes a float, a tether attached to the float, a pulley attached to the tether, a rotation sensor connected to the pulley that senses vertical movement of said float and senses the level of the liquid.

  5. Space Station tethered elevator system

    Science.gov (United States)

    Haddock, Michael H.; Anderson, Loren A.; Hosterman, K.; Decresie, E.; Miranda, P.; Hamilton, R.

    1989-01-01

    The optimized conceptual engineering design of a space station tethered elevator is presented. The tethered elevator is an unmanned, mobile structure which operates on a ten-kilometer tether spanning the distance between Space Station Freedom and a platform. Its capabilities include providing access to residual gravity levels, remote servicing, and transportation to any point along a tether. The report discusses the potential uses, parameters, and evolution of the spacecraft design. Emphasis is placed on the elevator's structural configuration and three major subsystem designs. First, the design of elevator robotics used to aid in elevator operations and tethered experimentation is presented. Second, the design of drive mechanisms used to propel the vehicle is discussed. Third, the design of an onboard self-sufficient power generation and transmission system is addressed.

  6. Enzymatic activity of soluble and membrane tethered peptide pro-hormone convertase 1.

    Science.gov (United States)

    Bruzzaniti, Angela; Mains, Richard E

    2002-05-01

    Pro-hormone convertases PC1 and PC2 perform endoproteolytic cleavages of precursors in peptide-containing secretory granules. PC1 and PC2 are soluble, secreted with bioactive peptides. Evolutionarily related PCs have membrane tethers, not secreted. We tethered PC1 to the transmembrane-cytoplasmic domains (CD) of a granule enzyme (peptidylglycine-alpha-amidating monooxygenase; PAM) and Golgi-localized PC8. The tethered PC1 is far more stable to elevated temperature and denaturants than soluble PC1, and more active. Both tethers allow PC1 to visit the cell surface transiently, cleaving soluble molecules outside the cell. Both membrane-bound PC1 chimeras cleave membrane PAM into soluble active fragments when PAM is expressed on adjacent cells. PMID:12084516

  7. Tethered cord syndrome: case report

    International Nuclear Information System (INIS)

    Tethered cord syndrome is one of the filum terminale congenital defects. It can coexist with anomalies of the spinal canal and column, as well as with anorectal defects. The authors present a case of tethered cord syndrome diagnosed in a 45-year-old woman. She showed typical lumbo-sacral radicular syndrome with no neurological deficits and no bowel/bladder dysfunction. The anomaly coexisted with fibrolipoma, spina bifida and Tarlov cyst. Magnetic resonance imaging is the method of choice in diagnostics of tethered cord syndrome. It provides crucial information, which is necessary for planning surgical treatment of the anomaly. (author)

  8. Tether Elevator Crawler Systems (TECS)

    Science.gov (United States)

    Swenson, Frank R.

    1987-01-01

    One of the needs of the experimenters on the space station is access to steady and controlled-variation microgravity environments. A method of providing these environments is to place the experiment on a tether attached to the space station. This provides a high degree of isolation from structural oscillations and vibrations. Crawlers can move these experiments along the tethers to preferred locations, much like an elevator. This report describes the motion control laws developed for these crawlers and the testing of laboratory models of these tether elevator crawlers.

  9. Enabling Tethered Exploration on Mars Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Strong science motivations exist for exploring hard to reach terrain on Mars and the leading systems proposed to do so require tethers. While tethers are used...

  10. The Tethered Moon

    Science.gov (United States)

    Zahnle, Kevin; Lupu, Roxana Elena; Dubrovolskis, A. R.

    2014-01-01

    that the Moon's orbit evolves is limited by the modest radiative cooling rate of Earth's atmosphere, which in effect tethers the Moon to the Earth. Consequently the Moon's orbit evolves orders of magnitude more slowly than in conventional models. Slow orbital evolution promotes capture by orbital resonances that may have been important in the Earth-Moon system

  11. Polymeric Coatings for Electrodynamic Tethers

    Science.gov (United States)

    Vaughn, Jason A.; Kamenetzky, Rachel R.; Finckenor, Miria M.; Schuler, Peter

    2000-01-01

    Two polymeric coatings have been developed for the Propulsive Small Expendable Deployer System (ProSEDS) mission. ProSEDS is designed to provide an on-orbit demonstration of the electrodynamic propulsion capabilities of tethers in space. The ProSEDS experiment will be a secondary payload on a Delta II unmanned expendable booster scheduled for launch in August 2000. A 5-km conductive tether is attached to the Delta 11 second stage and collects current from the low Earth orbit (LEO) plasma to facilitate de-orbit of the spent stage. The conductive tether is attached to a 10-km non-conductive tether, the other end of which is attached to an endmass containing several scientific instruments. A bare metal tether would have the best conductivity but thermal concerns preclude this design. A conductive polymer developed by Triton Systems has been optimized for conductivity and thermo-optical properties. The current design for the ProSEDS conductive tether is seven strands of 28 AWG aluminum wire individually coated with 8.7 micrometers (0.35 mil) of an atomic oxygen-resistant conductive polymer composed of a mixture of 87% Clear Oxygen-Resistant polymer (COR) and 13% polyanaline (PANi), wrapped around a braided Kevlar (TM) 49 core. Extensive testing has been performed at the Marshall Space Flight Center (MSFC) to qualify this material for flight on ProSEDS. Atomic oxygen exposure was performed, with solar absorptance and infrared emittance measured before and after exposure. Conductivity was measured before and after atomic oxygen exposure. High voltage tests, up to 1500 V, of the current collecting ability of the COR/PANi have been completed. Approximately 160 meters of the conductive tether closest to the Delta 11 second stage is insulated to prevent any electron reconnection to the tether from the plasma contactor. The insulation is composed of polyimide overcoated with TOR-BP, another polymeric coating developed by Triton for this mission. TOR-BP acts as both insulator

  12. Short, high current electrodynamic tether

    OpenAIRE

    Savich, N.A.; Sanmartín Losada, Juan Ramón

    1994-01-01

    An electrodynamic tether experiment, to be carried out in the Russian spacecraft Almaz, is proposed. A 10 km tether would be deployed downwards; the lower 8 km would be nonconductive, the upper 2 km would be conductive, bare, and 2.2 mm in diameter, and would act as a thruster, with power supply at the top. This hybrid arrangement allows for other, onelectrodynamic experiments,reducing costs; it also limits the induced electromotive force, reducing the power to be handled. The current-volt...

  13. Recent advances in yeast cell-surface display technologies for waste biorefineries.

    Science.gov (United States)

    Liu, Zhuo; Ho, Shih-Hsin; Hasunuma, Tomohisa; Chang, Jo-Shu; Ren, Nan-Qi; Kondo, Akihiko

    2016-09-01

    Waste biorefinery aims to maximize the output of value-added products from various artificial/agricultural wastes by using integrated bioprocesses. To make waste biorefinery economically feasible, it is thus necessary to develop a low-cost, environment-friendly technique to perform simultaneous biodegradation and bioconversion of waste materials. Cell-surface display engineering is a novel, cost-effective technique that can auto-immobilize proteins on the cell exterior of microorganisms, and has been applied for use with waste biofinery. Through tethering different enzymes (e.g., cellulase, lipase, and protease) or metal-binding peptides on cell surfaces, various yeast strains can effectively produce biofuels and biochemicals from sugar/protein-rich waste materials, catalyze waste oils into biodiesels, or retrieve heavy metals from wastewater. This review critically summarizes recent applications of yeast cell-surface display on various types of waste biorefineries, highlighting its potential and future challenges with regard to commercializing this technology. PMID:27039354

  14. Tethered Satellite System Contingency Investigation Board

    Science.gov (United States)

    1992-11-01

    The Tethered Satellite System (TSS-1) was launched aboard the Space Shuttle Atlantis (STS-46) on July 31, 1992. During the attempted on-orbit operations, the Tethered Satellite System failed to deploy successfully beyond 256 meters. The satellite was retrieved successfully and was returned on August 6, 1992. The National Aeronautics and Space Administration (NASA) Associate Administrator for Space Flight formed the Tethered Satellite System (TSS-1) Contingency Investigation Board on August 12, 1992. The TSS-1 Contingency Investigation Board was asked to review the anomalies which occurred, to determine the probable cause, and to recommend corrective measures to prevent recurrence. The board was supported by the TSS Systems Working group as identified in MSFC-TSS-11-90, 'Tethered Satellite System (TSS) Contingency Plan'. The board identified five anomalies for investigation: initial failure to retract the U2 umbilical; initial failure to flyaway; unplanned tether deployment stop at 179 meters; unplanned tether deployment stop at 256 meters; and failure to move tether in either direction at 224 meters. Initial observations of the returned flight hardware revealed evidence of mechanical interference by a bolt with the level wind mechanism travel as well as a helical shaped wrap of tether which indicated that the tether had been unwound from the reel beyond the travel by the level wind mechanism. Examination of the detailed mission events from flight data and mission logs related to the initial failure to flyaway and the failure to move in either direction at 224 meters, together with known preflight concerns regarding slack tether, focused the assessment of these anomalies on the upper tether control mechanism. After the second meeting, the board requested the working group to complete and validate a detailed integrated mission sequence to focus the fault tree analysis on a stuck U2 umbilical, level wind mechanical interference, and slack tether in upper tether

  15. Artificial Gravity: Tethers and Containers

    Science.gov (United States)

    Criswell, D. R.

    1985-01-01

    Tethers used in conjunction with containers offer a means of enhanced control of basic variables such as local acceleration, pointing and orientation, and protected or controlled environments against particle or electromagnetic radiation. Permanent occupancy of space will require the rapid exploration of the short and long term responses of many living organisms to the space environment or separated components of that environment. Tethers and ET facilities could provide the rapid establishment of laboratories in LEO within which to study living systems in a wide range of separate controlled environments for long periods of time, support large optical arrays; provide orbiting laboratories; and provide controlled environments within which the application of advanced manufacturing, assembly, control, and robotics could be developed to aid off-Earth industry and science and the conduct of more complex space operations.

  16. Two-Way Tether Gun

    Science.gov (United States)

    Sanger, George F.

    1994-01-01

    Safety-tether device enables crewmembers on spacecraft to retrieve crewmember drifting away from spacecraft. Alternatively, drifting crewmember who carries device uses it to grasp and return to spacecraft. Also used on Earth. For example, rescuer on vessel or pier uses it to retrieve and haul drowning or unconscious person to safety; drifting person or rescuer in water uses it to grasp and hold onto support.

  17. On the survivability of tethers in space

    OpenAIRE

    Anselmo, Luciano; Pardini, Carmen

    2000-01-01

    Tethers have been proposed for several space applications, like satellite de-orbiting or re-boost, electric energy generation, scientific research and so on. However, they may be vulnerable to orbital debris and meteoroid impacts. The problem was assessed, to assist tether systems design, by detailed numerical computations of the average impact rate of artificial debris, taking into account the specific geometric properties of tethers as debris targets, when compared to typical satellites. Th...

  18. Early Results of the Multi-Application Survivable Tether (MAST) Space Tether Experiment

    OpenAIRE

    Hoyt, Robert; Voronka, Nestor; Newton, Tyrel; Barnes, Ian; Shepherd, Jack; Frank, S. Scott; Slostad, Jeff; Jaroux, Belgacem; Twiggs, Robert

    2007-01-01

    The Multi-Application Survivable Tether (MAST) Experiment utilizes three tethered picosatellites to study the survivability of space tether structures and materials in the low Earth orbit environment. The MAST picosatellites initially deployed as a single body from a CubeSat PPOD deployer were designed to subsequently deploy a 1,000 meter long multi-line "Hoytether" between two of the picosatellites. The third picosatellite will then slowly crawl up and down the tether photographing it and tr...

  19. Get-Away tether experiment - Experimental plans

    Science.gov (United States)

    Greene, Michael; Walls, Justin; Carter, J. Theron; Rupp, Charles C.

    1988-01-01

    The experimental capabilities of the Get-Away Tether Experiment (GATE) are presented and a series of demonstration mission are proposed. The GATE is a free-flying tether system that will develop or demonstrate technology in the areas of tether dynamics (deployment and stabilization, retrieval, stationkeeping, and severance), tether electrodynamics, micrometeor hazards to tethers, and disturbance rejection. The system consists of two subsatellites connected by 1 km of tether. The free-flying system is ejected from the Orbiter via a Getaway Special (GAS) canister. Two dynamics missions are profiled along with a description of electrodynamic mission capabilities. The dynamic interactions of the end body and tether may be observed from the Orbiter or from an on-board video tracking system. Hence, GATE provides a unique, low cost capability to demonstrate various tether technologies, and address critical design and safety issues associated with future tether applications. An assessment of the significant measurable parameters and associated instrumentation is given. Future work and system development projection schedules are also outlined.

  20. The Disulfide Bonds within BST-2 Enhance Tensile Strength during Viral Tethering.

    Science.gov (United States)

    Du Pont, Kelly E; McKenzie, Aidan M; Kokhan, Oleksandr; Sumner, Isaiah; Berndsen, Christopher E

    2016-02-16

    Human BST-2/tetherin is a host factor that inhibits the release of enveloped viruses, including HIV-1, HIV-2, and SIV, from the cell surface by tethering viruses to the host cell membrane. BST-2 has an α-helical ectodomain that forms disulfide-linked dimers between two monomers forming a coiled coil. The ectodomain contains three cysteine residues that can participate in disulfide bond formation and are critical for viral tethering. The role of the disulfides in viral tethering is unknown but proposed to be for maintaining the dimer. We explored the role of the disulfides in the structure of BST-2 using experimental, biophysical methods. To understand the role of the disulfides in viral tethering, we used a new approach in viral tethering, steered molecular dynamics. We find that the disulfides coordinate the unfolding of the BST-2 monomers, which adds tensile strength to the coiled coil. Structural differences between oxidized and reduced BST-2 are apparent during unfolding, showing the monomers slide past each other in the absence of the disulfides. We found no evidence to support dissociation of the dimer upon reduction of the disulfide bonds. Moreover, the structure of BST-2 in the absence of the disulfides is similar to that of the oxidized form of BST-2, supporting previous X-ray crystallography and cellular work that showed the disulfides are not required for expression of BST-2. These data provide new insights into viral tethering by using novel techniques in the analysis of BST-2 to give amino acid level insight into functions of BST-2. PMID:26789136

  1. Mobile tethering: Overview, perspectives and challengess

    NARCIS (Netherlands)

    Constantinescu, M.; Onur, E.; Durmus, Y.; Nikou, S.; Reuver, M. de; Bouwman, H.; Djurica, M.; Glatz, P.M.

    2014-01-01

    Purpose: The purpose of this paper is to analyze mobile tethering from technological and social perspectives. Mobile tethering allows us to share cellular data connection with others over WiFi, Bluetooth or USB. Although the technology is ready and has promising outcomes, service providers and the u

  2. The cell surface of Trypanosoma cruzi

    Directory of Open Access Journals (Sweden)

    Wanderley de Souza

    1984-01-01

    Full Text Available The cell surface of trypanosomatids is formed by the plasma membrane and a layer of sub-pellicular microtubules which are connected to the plasma membrane. The plasma membrane is composed by proteins, lipids and carbohydrates which form the glycocalix. In this paper we will review briefly aspects related to the organization of the cell surface of Trypanosoma cruzi.

  3. The cell surface of Trypanosoma cruzi

    OpenAIRE

    Wanderley de Souza; Thais Souto-Padrón

    1984-01-01

    The cell surface of trypanosomatids is formed by the plasma membrane and a layer of sub-pellicular microtubules which are connected to the plasma membrane. The plasma membrane is composed by proteins, lipids and carbohydrates which form the glycocalix. In this paper we will review briefly aspects related to the organization of the cell surface of Trypanosoma cruzi.

  4. Seismic Response of Submerged Floating Tunnel Tether

    Institute of Scientific and Technical Information of China (English)

    SU Zhi-bin; SUN Sheng-nan

    2013-01-01

    A mathematical equation for vibration of submerged floating tunnel tether under the effects of earthquake and parametric excitation is presented.Multi-step Galerkin method is used to simplify this equation and the fourth-order Runge-Kuta integration method is used for numerical analysis.Finally,vibration response of submerged floating tunnel tether subjected to earthquake and parametric excitation is analyzed in a few numerical examples.The results show that the vibration response of tether varies with the seismic wave type; the steady maximum mid-span displacement of tether subjected to seismic wave keeps constant when parametric resonance takes place; the transient maximum mid-span displacement of tether is related to the peak value of input seismic wave acceleration.

  5. Activation and routing of membrane-tethered prohormone convertases 1 and 2.

    Science.gov (United States)

    Bruzzaniti, A; Marx, R; Mains, R E

    1999-08-27

    Many peptide hormones and neuropeptides are processed by members of the subtilisin-like family of prohormone convertases (PCs), which are either soluble or integral membrane proteins. PC1 and PC2 are soluble PCs that are primarily localized to large dense core vesicles in neurons and endocrine cells. We examined whether PC1 and PC2 were active when expressed as membrane-tethered proteins, and how tethering to membranes alters the biosynthesis, enzymatic activity, and intracellular routing of these PCs. PC1 and PC2 chimeras were constructed using the transmembrane domain and cytoplasmic domain of the amidating enzyme, peptidylglycine alpha-amidating monooxygenase (PAM). The membrane-tethered PCs were rerouted from large dense core vesicles to the Golgi region. In addition, the chimeras were transiently expressed at the cell surface and rapidly internalized to the Golgi region in a fashion similar to PAM. Membrane-tethered PC1 and PC2 exhibited changes in pro-domain maturation rates, N-glycosylation, and in the pH and calcium optima required for maximal enzymatic activity against a fluorogenic substrate. In addition, the PC chimeras efficiently cleaved endogenous pro-opiomelanocortin to the correct bioactive peptides. The PAM transmembrane domain/cytoplasmic domain also prevented stimulated secretion of pro-opiomelanocortin products in AtT-20 cells. PMID:10455138

  6. Tethered Lubricants for Small Systems

    Energy Technology Data Exchange (ETDEWEB)

    Lynden A. Archer

    2006-01-09

    The objective of this research project is two-fold. First, to fundamentally understand friction and relaxation dynamics of polymer chains near surfaces; and second, to develop novel self-lubricated substrates suitable for MEMS devices. During the three-year performance period of this study the PI and his students have shown using theory and experiments that systematic introduction of disorder into tethered lubricant coatings (e.g. by using self-assembled monolayer (SAM) mixtures or SAMs with nonlinear, branched architectures) can be used to significantly reduce the friction coefficient of a surface. They have also developed a simple procedure based on dielectric spectroscopy for quantifying the effect of surface disorder on molecular relaxation in lubricant coatings. Details of research accomplishments in each area of the project are described in the body of the report.

  7. The space station tethered elevator system

    Science.gov (United States)

    Anderson, Loren A.

    1989-01-01

    The optimized conceptual engineering design of a space station tethered elevator is presented. The elevator is an unmanned mobile structure which operates on a ten kilometer tether spanning the distance between the Space Station and a tethered platform. Elevator capabilities include providing access to residual gravity levels, remote servicing, and transportation to any point along a tether. The potential uses, parameters, and evolution of the spacecraft design are discussed. Engineering development of the tethered elevator is the result of work conducted in the following areas: structural configurations; robotics, drive mechanisms; and power generation and transmission systems. The structural configuration of the elevator is presented. The structure supports, houses, and protects all systems on board the elevator. The implementation of robotics on board the elevator is discussed. Elevator robotics allow for the deployment, retrieval, and manipulation of tethered objects. Robotic manipulators also aid in hooking the elevator on a tether. Critical to the operation of the tethered elevator is the design of its drive mechanisms, which are discussed. Two drivers, located internal to the elevator, propel the vehicle along a tether. These modular components consist of endless toothed belts, shunt-wound motors, regenerative power braking, and computer controlled linear actuators. The designs of self-sufficient power generation and transmission systems are reviewed. Thorough research indicates all components of the elevator will operate under power provided by fuel cells. The fuel cell systems will power the vehicle at seven kilowatts continuously and twelve kilowatts maximally. A set of secondary fuel cells provides redundancy in the unlikely event of a primary system failure. Power storage exists in the form of Nickel-Hydrogen batteries capable of powering the elevator under maximum loads.

  8. Golgi GRASPs: moonlighting membrane tethers

    Directory of Open Access Journals (Sweden)

    Jarvela T

    2012-05-01

    Full Text Available Timothy Jarvela, Adam D LinstedtDepartment of Biological Sciences, Carnegie Mellon University, Pittsburgh, PA, USAAbstract: The identification of mammalian Golgi reassembly stacking proteins (GRASPs 15 years ago was followed by experiments implicating them in diverse functions, including two differing structural roles in Golgi biogenesis and at least two distinct roles in the secretion of proteins. GRASP55 and GRASP65 are localized to cis and medial/trans Golgi cisternae, respectively. They are both required for stacking of Golgi membranes in a Golgi reassembly assay. Depletion of either GRASP from cultured cells prevents the linking of Golgi membranes into their normal ribbon-like network. While GRASPs are not required for transport of secretory cargo per se, they are required for ER-to-Golgi transport of certain specific cargo, such as those containing a C-terminal valine motif. Surprisingly, GRASPs also promote secretion of cargo by the so-called unconventional secretory pathway, which bypasses the Golgi apparatus where the GRASPs reside. Furthermore, regulation of GRASP activity is now recognized for its connections to cell cycle control, development, and disease. Underlying these diverse activities is the structurally conserved N-terminal GRASP domain whose crystal structure was recently determined. It consists of a tandem array of atypical PSD95–DlgA–Zo–1 (PDZ domains, which are well-known protein–protein interaction motifs. The GRASP PDZ domains are used to localize the proteins to the Golgi as well as GRASP-mediated membrane tethering and cargo interactions. These activities are regulated, in part, by phosphorylation of the large unstructured C-terminal domain.Keywords: GRASP, review, membrane, tether, PDZ domain, secretory chaperone, unconventional secretion

  9. Dynamic simulation of tethered satellite systems

    International Nuclear Information System (INIS)

    The idea of connecting several spacecrafts by tethers to create mechanical systems with interesting dynamic properties was first brought up by Tsiolkovskii at the end of the nineteenth century, long before the technical means for realization were available. Today, after about 30 years of worldwide research, Tethered Satellite Systems have evolved into a promising technology with a considerable number of possible applications. These systems can be used to build large structures in orbit and provide a fuel-saving way of returning payloads from a space station. Conducting tethers interacting with the Earth's magnetic field can serve as motors or generators, transforming kinetic and electric energy into each other very efficiently. To develop this new technology seventeen experiments have been carried out in orbit since 1966 with NASA's TSS missions being the most well known. The work introduced in this thesis is part of a project carried out by the Institute of Mechanics of the Vienna University of Technology as contractor of the European Space Agency. A software package for the dynamic simulation of Tethered Satellite Systems with variable tether length has been developed to serve as a tool for the development and testing of such systems. The focus is on the deployment and retrieval of the tether, which is an important but tricky process, and has to be controlled by proper control algorithms. This can elegantly be done by a force acting on the tether at the point where it leaves the satellite. In the simulation program a mechanical model consisting of two satellites and a massive, perfectly flexible, visco-elastic tether is considered. The actual length of the tether is not given as a prescribed function of time but is an additional unknown and has to be calculated from the dynamics of the entire system and the forces acting on the tether. Hence the deployment mechanism has an important influence on the deployment dynamics. In this work the tether is considered to

  10. Cell Surface Sensors: Lightning the Cellular Environment

    OpenAIRE

    Ali, Md Monsur; Kang, Dong-Ku; Tsang, Kyle; Fu, Moyu; Karp, Jeffrey M; Zhao, Weian

    2012-01-01

    Cell surface sensors are powerful tools to elucidate cell functions including cell signaling, metabolism and cell-to-cell communication. These sensors not only facilitate our understanding in basic biology but also advance the development of effective therapeutics and diagnostics. While genetically encoded fluorescent protein/peptide sensors have been most popular, emerging cell surface sensor systems including polymer-, nanoparticle-, and nucleic acid aptamer-based sensors have largely expan...

  11. FCAPD Protective Coating for Space Tethers Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Alameda Applied Sciences Corporation (AASC) proposes to demonstrate extended service lifetime of space tethers in the Low Earth Orbit (LEO) environment by using...

  12. Tethers in space handbook, second edition

    Science.gov (United States)

    Penzo, Paul A. (Editor); Ammann, Paul W. (Editor)

    1989-01-01

    The Tethers in Space Handbook, Second Edition represents an update to the initial volume issued in September 1986. As originally intended, this handbook is designed to serve as a reference manual for policy makers, program managers, educators, engineers, and scientists alike. It contains information for the uninitiated, providing insight into the fundamental behavior of tethers in space. For those familiar with space tethers, it includes a summary of past and ongoing studies and programs, a complete bibliography of tether publications, and names, addresses, and phone numbers of workers in the field. Perhaps its most valuable asset is the brief description of nearly 50 tether applications which have been proposed and analyzed over the past 10 years. The great variety of these applications, from energy generation to boosting satellites to gravity wave detection is an indication that tethers will play a significant part in the future of space development. This edition of the handbook preserves the major characteristics of the original; however, some significant rearrangements and additions have been made. The first section on Tether Programs has been brought up to date, and now includes a description of TSS-2, the aerodynamic NASA/Italian Space Agency (ASI) mission. Tether Applications follows, and this section has been substantially rearranged. First, the index and cross-reference for the applications have been simplified. Also, the categories have changed slightly, with Technology and Test changed to Aerodynamics, and the Constellations category removed. In reality, tether constellations may be applicable to many of the other categories, since it is simply a different way of using tethers. Finally, to separate out those applications which are obviously in the future, a Concepts category has been added. A new section included here on Conference Summaries recognizes the fact that the tether community is growing internationally, and that meetings provide a means of

  13. Tethered satellite system dynamics and control

    Science.gov (United States)

    Musetti, B.; Cibrario, B.; Bussolino, L.; Bodley, C. S.; Flanders, H. A.; Mowery, D. K.; Tomlin, D. D.

    1990-01-01

    The first tethered satellite system, scheduled for launch in May 1991, is reviewed. The system dynamics, dynamics control, and dynamics simulations are discussed. Particular attention is given to in-plane and out-of-plane librations; tether oscillation modes; orbiter and sub-satellite dynamics; deployer control system; the sub-satellite attitude measurement and control system; the Aeritalia Dynamics Model; the Martin-Marietta and NASA-MSFC Dynamics Model; and simulation results.

  14. Numerical modelling of elastic space tethers

    DEFF Research Database (Denmark)

    Kristiansen, Kristian Uldall; Palmer, P. L.; Roberts, R. M.

    2012-01-01

    , the numerical experiments of an orbiting tether system show that bending may introduce significant forces in some regions of phase space. Finally, numerical evidence for the existence of an almost invariant slow manifold of the singularly perturbed, regularised, non-dissipative massive tether model is provided....... It is also shown that on the slow manifold the dynamics of the satellites are well-approximated by the finite dimensional slack-spring model....

  15. Application of the NASCAP Spacecraft Simulation Tool to Investigate Electrodynamic Tether Current Collection in LEO

    Science.gov (United States)

    Adams, Mitzi; HabashKrause, Linda

    2012-01-01

    Recent interest in using electrodynamic tethers (EDTs) for orbital maneuvering in Low Earth Orbit (LEO) has prompted the development of the Marshall ElectroDynamic Tether Orbit Propagator (MEDTOP) model. The model is comprised of several modules which address various aspects of EDT propulsion, including calculation of state vectors using a standard orbit propagator (e.g., J2), an atmospheric drag model, realistic ionospheric and magnetic field models, space weather effects, and tether librations. The natural electromotive force (EMF) attained during a radially-aligned conductive tether results in electrons flowing down the tether and accumulating on the lower-altitude spacecraft. The energy that drives this EMF is sourced from the orbital energy of the system; thus, EDTs are often proposed as de-orbiting systems. However, when the current is reversed using satellite charged particle sources, then propulsion is possible. One of the most difficult challenges of the modeling effort is to ascertain the equivalent circuit between the spacecraft and the ionospheric plasma. The present study investigates the use of the NASA Charging Analyzer Program (NASCAP) to calculate currents to and from the tethered satellites and the ionospheric plasma. NASCAP is a sophisticated set of computational tools to model the surface charging of three-dimensional (3D) spacecraft surfaces in a time-varying space environment. The model's surface is tessellated into a collection of facets, and NASCAP calculates currents and potentials for each one. Additionally, NASCAP provides for the construction of one or more nested grids to calculate space potential and time-varying electric fields. This provides for the capability to track individual particles orbits, to model charged particle wakes, and to incorporate external charged particle sources. With this study, we have developed a model of calculating currents incident onto an electrodynamic tethered satellite system, and first results are shown

  16. Functional dynamics of cell surface membrane proteins

    Science.gov (United States)

    Nishida, Noritaka; Osawa, Masanori; Takeuchi, Koh; Imai, Shunsuke; Stampoulis, Pavlos; Kofuku, Yutaka; Ueda, Takumi; Shimada, Ichio

    2014-04-01

    Cell surface receptors are integral membrane proteins that receive external stimuli, and transmit signals across plasma membranes. In the conventional view of receptor activation, ligand binding to the extracellular side of the receptor induces conformational changes, which convert the structure of the receptor into an active conformation. However, recent NMR studies of cell surface membrane proteins have revealed that their structures are more dynamic than previously envisioned, and they fluctuate between multiple conformations in an equilibrium on various timescales. In addition, NMR analyses, along with biochemical and cell biological experiments indicated that such dynamical properties are critical for the proper functions of the receptors. In this review, we will describe several NMR studies that revealed direct linkage between the structural dynamics and the functions of the cell surface membrane proteins, such as G-protein coupled receptors (GPCRs), ion channels, membrane transporters, and cell adhesion molecules.

  17. The investigation of tethered satellite system dynamics

    Science.gov (United States)

    Lorenzini, E. C.

    1986-01-01

    The analysis of the rotational dynamics of the satellite was focused on the rotational amplitude increase of the satellite, with respect to the tether, during retrieval. The dependence of the rotational amplitude upon the tether tension variation to the power 1/4 was thoroughly investigated. The damping of rotational oscillations achievable by reel control was also quantified while an alternative solution that makes use of a lever arm attached with a universal joint to the satellite was proposed. Comparison simulations between the Smithsonian Astrophysical Observatory and the Martin Marietta (MMA) computer code of reteival maneuvers were also carried out. The agreement between the two, completely independent, codes was extremely close, demonstrating the reliability of the models. The slack tether dynamics during reel jams was analytically investigated in order to identify the limits of applicability of the SLACK3 computer code to this particular case. Test runs with SLACK3 were also carried out.

  18. Tethering Complexes in the Arabidopsis Endomembrane System.

    Science.gov (United States)

    Vukašinović, Nemanja; Žárský, Viktor

    2016-01-01

    Targeting of endomembrane transport containers is of the utmost importance for proper land plant growth and development. Given the immobility of plant cells, localized membrane vesicle secretion and recycling are amongst the main processes guiding proper cell, tissue and whole plant morphogenesis. Cell wall biogenesis and modification are dependent on vectorial membrane traffic, not only during normal development, but also in stress responses and in plant defense against pathogens and/or symbiosis. It is surprising how little we know about these processes in plants, from small GTPase regulation to the tethering complexes that act as their effectors. Tethering factors are single proteins or protein complexes mediating first contact between the target membrane and arriving membrane vesicles. In this review we focus on the tethering complexes of the best-studied plant model-Arabidopsis thaliana. Genome-based predictions indicate the presence of all major tethering complexes in plants that are known from a hypothetical last eukaryotic common ancestor (LECA). The evolutionary multiplication of paralogs of plant tethering complex subunits has produced the massively expanded EXO70 family, indicating a subfunctionalization of the terminal exocytosis machinery in land plants. Interpretation of loss of function (LOF) mutant phenotypes has to consider that related, yet clearly functionally-specific complexes often share some common core subunits. It is therefore impossible to conclude with clarity which version of the complex is responsible for the phenotypic deviations observed. Experimental interest in the analysis of plant tethering complexes is growing and we hope to contribute with this review by attracting even more attention to this fascinating field of plant cell biology. PMID:27243010

  19. Multi-mass dynamic model of a variable-length tether used in a high altitude wind energy system

    International Nuclear Information System (INIS)

    Highlights: • A multi-mass dynamics model of a variable length tether has been developed. • The modelling approach enables straightforward description of the aerodynamic drag. • The model is used in high altitude wind energy system control-oriented simulations. • The model accurately describes the shape, forces and vibrations of the tether. - Abstract: This paper presents a multibody approach to dynamics modelling of a variable-length tether moving through air, in a system where an airborne module generates aerodynamic lift and uses the tether to cyclically drive the winch-generator unit fixed on the ground. The rope is modelled as a series of straight, massless, elastic segments with the rope mass fragments lumped to the segment joints. Individual segment length is constant, with the exception of segment being wound out from the winch, while the number of segments is variable. For the segment being wound out, a special modelling approach is derived. The forces acting on the rope are also concentrated at the joints, thus simplifying computations and facilitating rope aerodynamic drag modelling. The proposed tether dynamics model is integrated into the overall model of controlled power production system and verified by computer simulation. The model is compared with two simpler tether dynamics models also proposed in the paper

  20. Passivity-Based Control of a Rigid Electrodynamic Tether

    OpenAIRE

    Larsen, Martin Birkelund; Blanke, Mogens

    2011-01-01

    Electrodynamic tethers provide actuation for performing orbit correction of spacecrafts. When an electrodynamic tether system is orbiting the Earth in an inclined orbit, periodic changes in the magnetic field result in a family of unstable periodic solutions in the attitude motion. This paper shows how these periodic solutions can be stabilized by controlling only the current through the tether. A port-controlled Hamiltonian formulation is employed to describe the tethered satellite system an...

  1. Dynamics of the Space Tug System with a Short Tether

    OpenAIRE

    Jiafu Liu; Naigang Cui; Fan Shen; Siyuan Rong

    2015-01-01

    The dynamics of the space tug system with a short tether similar to the ROGER system during deorbiting is presented. The kinematical characteristic of this system is significantly different from the traditional tethered system as the tether is tensional and tensionless alternately during the deorbiting process. The dynamics obtained based on the methods for the traditional tethered system is not suitable for the space tug system. Therefore, a novel method for deriving dynamics for the deorbit...

  2. MR imaging evaluation of tethered spinal cord

    International Nuclear Information System (INIS)

    Seven cases of tethered cord underwent magnetic resonance imaging. The associated findings included the following: case 1: caudal regression, inperforated anus, cutaneovesical fistula, and diverticulum of the bladder; case 2: Arnold-Chiari malformation, hydromyelia, and urinary reflux; case 3; lipoma; case 4: postoperative syringomyelia and residual lipoma; case 5: diastematomyelia and spinal bifida; case 6: dysraphism, diastematomyelia, and myelomeningocele; and case 7: postoperative split cord T1-weighted axial and sagittal images are sufficient for evaluation of tethered cord and associated anomalies and are also useful for postoperative follow-up and the detection of possible complications

  3. Tethers in Space: A propellantless propulsion in-orbit demonstration

    NARCIS (Netherlands)

    Kruijff, M.

    2011-01-01

    Space tethers are cables that connect satellites or other endmasses in orbit. The emptiness of space and the near-weightlessness there make it possible to deploy very long and thin tethers. By exploiting basic principles of physics, tethers can provide propellantless propulsion and enable unique app

  4. Ionic-Liquid-Tethered Nanoparticles: Hybrid Electrolytes

    KAUST Repository

    Moganty, Surya S.

    2010-10-22

    A new class of solventless electrolytes was created by tethering ionic liquids to hard inorganic ZrO2 nanostructures (see picture; NIM=nanoscale ionic material). These hybrid fluids exhibit exceptional redox stability windows, excellent thermal stability, good lithium transference numbers, long-term interfacial stability in the presence of a lithium anode and, when doped with lithium salt, reasonable ionic conductivities.

  5. Electrodynamic Tethers for Novel LEO Missions

    Science.gov (United States)

    Kantner, Michael; Hoyt, Robert; Scardera, Michael; Johnson, Charles

    2011-01-01

    The exponential increase of launch system size - and cost - with deltaV makes missions requiring large total impulse cost prohibitive. Northrop Grumman and partners have matured a fundamentally different method for generating propulsion using electrodynamic tethers (EDTs) that escapes the limitations of the rocket equation. With essentially unlimited delta V, we can perform new classes of missions that are currently unaffordable or unfeasible.

  6. The pancreatic beta cell surface proteome

    OpenAIRE

    Stützer, I.; Esterházy, D.; Stoffel, M.

    2012-01-01

    The pancreatic beta cell is responsible for maintaining normoglycaemia by secreting an appropriate amount of insulin according to blood glucose levels. The accurate sensing of the beta cell extracellular environment is therefore crucial to this endocrine function and is transmitted via its cell surface proteome. Various surface proteins that mediate or affect beta cell endocrine function have been identified, including growth factor and cytokine receptors, transporters, ion channels and prote...

  7. Conjunctions and Collision Avoidance with Electrodynamic Tethers

    Science.gov (United States)

    Levin, E.

    2013-09-01

    Electrodynamic propulsion technology is currently in development by NASA, ESA, and JAXA for the purpose of affordable removal of large debris objects from LEO. At the same time, the Naval Research Laboratory is preparing a 3U CubeSat with a 1-km electrodynamic tether for a flight demonstration of electrodynamic propulsion. This type of propulsion does not require fuel. The electrodynamic thrust is the Lorentz force acting on the electric current in a long conductor (tether) in the geomagnetic field. Electrons are collected from the ambient plasma on one end and emitted back into the plasma from the other end. The electric current loop is closed through the ionosphere, as demonstrated in two previous flights. The vehicle is solar powered. To support safe navigation of electrodynamic tethers, proper conjunction analysis and collision avoidance strategies are needed. The typical lengths of electrodynamic tethers for near-term applications are measured in kilometers, and the conjunction geometry is very different from the geometry of conjunctions between compact objects. It is commonly thought that the collision cross-section in a conjunction between a tether and a compact object is represented by the product of the tether length and the size of the object. However, rigorous analysis shows that this is not the case, and that the above assumption leads to grossly overestimated collision probabilities. The paper will present the results of a detailed mathematical analysis of the conjunction geometry and collision probabilities in close approaches between electrodynamic tethers and compact objects, such as satellites, rocket bodies, and debris fragments. Electrodynamic spacecraft will not require fuel, and therefore, can thrust constantly. Their orbit transfers can take many days, but can result in major orbit changes, including large rotations of the orbital plane, both in the inclination and the node. During these orbit transfers, the electrodynamic spacecraft will

  8. Coordinated coupling control of tethered space robot using releasing characteristics of space tether

    Science.gov (United States)

    Huang, Panfeng; Zhang, Fan; Xu, Xiudong; Meng, Zhongjie; Liu, Zhengxiong; Hu, Yongxin

    2016-04-01

    Tethered space robot (TSR) is a new concept of space robot, which is released from the platform satellite, and retrieved via connected tether after space debris capture. In this paper, we propose a new coordinate control scheme for optimal trajectory and attitude tracking, and use releasing motor torque to instead the tension force, since it is difficult to track in practical. Firstly, the 6-DOF dynamics model of TSR is derived, in which the dynamics of tether releasing system is taken into account. Then, we propose and design the coordinated coupled controller, which is composed of a 6-DOF sliding mode controller and a PD controller tether's releasing. Thrust is treated as control input of the 6-DOF sliding mode controller to control the in-plane and out-of-plane angle of the tether and attitude angles of the TSR. The torque of releasing motor is used as input of PD controller, which controls the length rate of space tether. After the verification of the control scheme, finally, the simulation experiment is presented in order to validate the effectiveness of this control method. The results show that TSR can track the optimal approaching trajectory accurately. Simultaneously, the attitude angles can be changed to the desired attitude angles in control period, and the terminal accuracy is ±0.3°.

  9. Surfactant Behavior of Amphiphilic Polymer-Tethered Nanoparticles.

    Science.gov (United States)

    Zhang, Yue; Zhao, Hanying

    2016-04-19

    In recent years, an emerging research area has been the surfactant behavior of polymer-tethered nanoparticles. In this feature article, we have provided a general introduction to the synthesis, self-assembly, and interfacial activity of polymer-tethered inorganic nanoparticles, polymer-tethered organic nanoparticles, and polymer-tethered natural nanoparticles. In addition, applications of the polymer-tethered nanoparticles in colloidal and materials science are briefly reviewed. All research demonstrates that amphiphilic polymer-tethered nanoparticles exhibit surfactant behavior and can be used as elemental building blocks for the fabrication of advanced structures by the self-assembly approach. The polymer-tethered nanoparticles provide new opportunities to engineer materials and biomaterials possessing specific functionality and physical properties. PMID:27018567

  10. Nanotomography of Cell Surfaces with Evanescent Fields

    Directory of Open Access Journals (Sweden)

    Michael Wagner

    2008-01-01

    Full Text Available The technique of variable-angle total internal reflection fluorescence microscopy (TIRFM and its application to nanotomography of cell surfaces are described. Present applications include (1 3D imaging of chromosomes in their metaphase to demonstrate axial resolution in the nanometre range, (2 measurements of cell-substrate topology, which upon cholesterol depletion shows some loosening of cell-substrate contacts, and (3 measurements of cell topology upon photodynamic therapy (PDT, which demonstrate cell swelling and maintenance of focal contacts. The potential of the method for in vitro diagnostics, but also some requirements and limitations are discussed.

  11. A Tethering Device for Mobile Robot Guidance

    Directory of Open Access Journals (Sweden)

    Sangik Na

    2009-11-01

    Full Text Available A new human and robot interface tool, so-called Navi-Guider, which makes it easy to handle mobile robots, is presented in this paper. The Navi-Guider is easily mounted on a mobile robot and is able to detect a length and a direction of the tether pulled out by a user. Those detected factors are utilized for the robot guidance and control. This paper addresses detailed hardware and software architecture of the Navi-Guider and demonstrates the practical usability of the system through actual experimental tests. The new device, NaviGuider, is an intuitive control tool for moving mobile robots from a place to another place just by pulling the tether.

  12. Magnetic Carbon Nanotubes Tethered with Maghemite Nanoparticles

    Science.gov (United States)

    Kim, Il Tae; Nunnery, Grady; Jacob, Karl; Schwartz, Justin; Liu, Xiaotao; Tannenbaum, Rina

    2011-03-01

    We describe a novel, facile method for the synthesis of magnetic carbon nanotubes (m-CNTs) decorated with monodisperse γ - Fe 2 O3 magnetic (maghemite) nanoparticles and their aligned feature in a magnetic field. The tethering of the nanoparticles was achieved by the initial activation of the surface of the CNTs with carboxylic acid groups, followed by the attachment of the γ - Fe 2 O3 nanoparticles via a modified sol-gel process. Sodium dodecylbenzene sulfonate (NaDDBS) was introduced into the suspension to prevent the formation of an iron oxide 3D network. Various characterization methods were used to confirm the formation of well-defined maghemite nanoparticles. The tethered nanoparticles imparted magnetic characteristics to the CNTs, which became superparamagnetic. The m-CNTs were oriented parallel to the direction of a magnetic field. This has the potential of enhancing various properties, e.g. mechanical and electrical properties, in composite materials.

  13. Tethered Forth system for FPGA applications

    Science.gov (United States)

    Goździkowski, Paweł; Zabołotny, Wojciech M.

    2013-10-01

    This paper presents the tethered Forth system dedicated for testing and debugging of FPGA based electronic systems. Use of the Forth language allows to interactively develop and run complex testing or debugging routines. The solution is based on a small, 16-bit soft core CPU, used to implement the Forth Virtual Machine. Thanks to the use of the tethered Forth model it is possible to minimize usage of the internal RAM memory in the FPGA. The function of the intelligent terminal, which is an essential part of the tethered Forth system, may be fulfilled by the standard PC computer or by the smartphone. System is implemented in Python (the software for intelligent terminal), and in VHDL (the IP core for FPGA), so it can be easily ported to different hardware platforms. The connection between the terminal and FPGA may be established and disconnected many times without disturbing the state of the FPGA based system. The presented system has been verified in the hardware, and may be used as a tool for debugging, testing and even implementing of control algorithms for FPGA based systems.

  14. Tethered nuclear power for the space station

    International Nuclear Information System (INIS)

    A nuclear space power system the SP-100 is being developed for future missions where large amounts of electrical power will be required. Although it is primarily intended for unmanned spacecraft, it can be adapted to a manned space platform by tethering it above the station through an electrical transmission line which isolates the reactor far away from the inhabited platform and conveys its power back to where it is needed. The transmission line, used in conjunction with an instrument rate shield, attenuates reactor radiation in the vicinity of the space station to less than one-one hundredth of the natural background which is already there. This combination of shielding and distance attenuation is less than one-tenth the mass of boom-mounted or onboard man-rated shields that are required when the reactor is mounted nearby. This paper describes how connection is made to the platform (configuration, operational requirements) and introduces a new element the coaxial transmission tube which enables efficient transmission of electrical power through long tethers in space. Design methodology for transmission tubes and tube arrays is discussed. An example conceptual design is presented that shows SP-100 at three power levels 100 kWe, 300 kWe, and 1000 kWe connected to space station via a 2 km HVDC transmission line/tether. Power system performance, mass, and radiation hazard are estimated with impacts on space station architecture and operation. 23 references

  15. Coat/Tether Interactions—Exception or Rule?

    Science.gov (United States)

    Schroeter, Saskia; Beckmann, Sabrina; Schmitt, Hans Dieter

    2016-01-01

    Coat complexes are important for cargo selection and vesicle formation. Recent evidence suggests that they may also be involved in vesicle targeting. Tethering factors, which form an initial bridge between vesicles and the target membrane, may bind to coat complexes. In this review, we ask whether these coat/tether interactions share some common mechanisms, or whether they are special adaptations to the needs of very specific transport steps. We compare recent findings in two multisubunit tethering complexes, the Dsl1 complex and the HOPS complex, and put them into context with the TRAPP I complex as a prominent example for coat/tether interactions. We explore where coat/tether interactions are found, compare their function and structure, and comment on a possible evolution from a common ancestor of coats and tethers. PMID:27243008

  16. Modeling of tethered satellite formations using graph theory

    DEFF Research Database (Denmark)

    Larsen, Martin Birkelund; Smith, Roy S; Blanke, Mogens

    2011-01-01

    could form stable formations in space are cumbersome when done at a case to case basis, and a common framework providing a basic model of the dynamics of tethered satellite formations can therefore be advantageous. This paper suggests the use of graph theoretical quantities to describe a tethered...... stationary configurations and an upper limit of their number is determined. The method is shown to be valid for general tethered satellite formations that form a tree structure....

  17. Electrodynamics of long metallic tethers in the ionospheric plasma

    Science.gov (United States)

    Dobrowolny, M.

    1978-01-01

    A study is presented of the electrodynamic interactions of long metallic tethers (lengths up to 100 km) with the ionospheric plasma. The study, which is of interest in view of possible future experiments using long tethers in space, includes the derivation of current and potential distribution along the tether, taking also the effects of internal resistance into account. Electrostatic and electrodynamic drag forces are computed and compared with aerodynamic drag.

  18. Lyapunov Orbits in the Jupiter System Using Electrodynamic Tethers

    Science.gov (United States)

    Bokelmann, Kevin; Russell, Ryan P.; Lantoine, Gregory

    2013-01-01

    Various researchers have proposed the use of electrodynamic tethers for power generation and capture from interplanetary transfers. The effect of tether forces on periodic orbits in Jupiter-satellite systems are investigated. A perturbation force is added to the restricted three-body problem model and a series of simplifications allows development of a conservative system that retains the Jacobi integral. Expressions are developed to find modified locations of equilibrium positions. Modified families of Lyapunov orbits are generated as functions of tether size and Jacobi integral. Zero velocity curves and stability analyses are used to evaluate the dynamical properties of tether-modified orbits.

  19. Dynamic analysis of tethered space system deployment process

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    Discusses in detail the deploying strategies and feature of themotion of the Tethered Space System and the effects of some parameters, such as the property and initial length of the tether, the perturbation of the atmosphere, the ellipse of the orbit and the mass distribution of the system and points out the deploying strategy is based on the controlling of tension and the length of tether. And concludes from the computer simulation results of a tethered atmosphere probing satellite deployment that the deploying strategy presented does work well.

  20. A proposed bare tether experiment on board a sounding rocket

    OpenAIRE

    Fujii, Hironori; OYAMA, Kohichiro; Sasaki, Susumu; Yamagiwa, Yoshiki; Cho, Mengu; Sanmartín Losada, Juan Ramón; Charro, Mario; Heide, Erik J. van der; Kruijff, Michiel; Lebreton, Jean-Pierre; Hilgers, Alain

    2005-01-01

    A sounding rocket experiment is proposed to carry out two experiments by the conductive bare-tether; 1) the test of the OML (Orbital-Motion-Limited) theory to collect electron, and II) the test of techniques to determine (neutral) density profile in critical E-layer. The main driver of the mission is provide a space tether technology experiment in low-Earth-Orbit (LEO) deploying a long tape tether in space and verify the performance of the bare electrodynamic tape tether. The sounding rocket ...

  1. The stochastic dynamics of tethered microcantilevers in a viscous fluid

    Energy Technology Data Exchange (ETDEWEB)

    Robbins, Brian A.; Paul, Mark R. [Department of Mechanical Engineering, Virginia Tech, Blacksburg, Virginia 24061 (United States); Radiom, Milad; Ducker, William A. [Department of Chemical Engineering, Virginia Tech, Blacksburg, Virginia 24061 (United States); Walz, John Y. [Department of Chemical Engineering, University of Kentucky, Lexington, Kentucky 40506 (United States)

    2014-10-28

    We explore and quantify the coupled dynamics of a pair of micron scale cantilevers immersed in a viscous fluid that are also directly tethered to one another at their tips by a spring force. The spring force, for example, could represent the molecular stiffness or elasticity of a biomolecule or material tethered between the cantilevers. We use deterministic numerical simulations with the fluctuation-dissipation theorem to compute the stochastic dynamics of the cantilever pair for the conditions of experiment when driven only by Brownian motion. We validate our approach by comparing directly with experimental measurements in the absence of the tether which shows excellent agreement. Using numerical simulations, we quantify the correlated dynamics of the cantilever pair over a range of tether stiffness. Our results quantify the sensitivity of the auto- and cross-correlations of equilibrium fluctuations in cantilever displacement to the stiffness of the tether. We show that the tether affects the magnitude of the correlations which can be used in a measurement to probe the properties of an attached tethering substance. For the configurations of current interest using micron scale cantilevers in water, we show that the magnitude of the fluid coupling between the cantilevers is sufficiently small such that the influence of the tether can be significant. Our results show that the cross-correlation is more sensitive to tether stiffness than the auto-correlation indicating that a two-cantilever measurement has improved sensitivity when compared with a measurement using a single cantilever.

  2. The stochastic dynamics of tethered microcantilevers in a viscous fluid

    International Nuclear Information System (INIS)

    We explore and quantify the coupled dynamics of a pair of micron scale cantilevers immersed in a viscous fluid that are also directly tethered to one another at their tips by a spring force. The spring force, for example, could represent the molecular stiffness or elasticity of a biomolecule or material tethered between the cantilevers. We use deterministic numerical simulations with the fluctuation-dissipation theorem to compute the stochastic dynamics of the cantilever pair for the conditions of experiment when driven only by Brownian motion. We validate our approach by comparing directly with experimental measurements in the absence of the tether which shows excellent agreement. Using numerical simulations, we quantify the correlated dynamics of the cantilever pair over a range of tether stiffness. Our results quantify the sensitivity of the auto- and cross-correlations of equilibrium fluctuations in cantilever displacement to the stiffness of the tether. We show that the tether affects the magnitude of the correlations which can be used in a measurement to probe the properties of an attached tethering substance. For the configurations of current interest using micron scale cantilevers in water, we show that the magnitude of the fluid coupling between the cantilevers is sufficiently small such that the influence of the tether can be significant. Our results show that the cross-correlation is more sensitive to tether stiffness than the auto-correlation indicating that a two-cantilever measurement has improved sensitivity when compared with a measurement using a single cantilever.

  3. Metabolic behavior of cell surface biotinylated proteins

    International Nuclear Information System (INIS)

    The turnover of proteins on the surface of cultured mammalian cells was measured by a new approach. Reactive free amino or sulfhydryl groups on surface-accessible proteins were derivatized with biotinyl reagents and the proteins solubilized from culture dishes with detergent. Solubilized, biotinylated proteins were then adsorbed onto streptavidin-agarose, released with sodium dodecyl sulfate and mercaptoethanol, and separated on polyacrylamide gels. Biotin-epsilon-aminocaproic acid N-hydroxysuccinimide ester (BNHS) or N-biotinoyl-N'-(maleimidohexanoyl)hydrazine (BM) were the derivatizing agents. Only 10-12 bands were adsorbed onto streptavidin-agarose from undervatized cells or from derivatized cells treated with free avidin at 4 degrees C. Two-dimensional isoelectric focusing-sodium dodecyl sulfate gel electrophoresis resolved greater than 100 BNHS-derivatized proteins and greater than 40 BM-derivatized proteins. There appeared to be little overlap between the two groups of derivatized proteins. Short-term pulse-chase studies showed an accumulation of label into both groups of biotinylated proteins up until 1-2 h of chase and a rapid decrease over the next 1-5 h. Delayed appearance of labeled protein at the cell surface was attributed to transit time from site of synthesis. The unexpected and unexplained rapid disappearance of pulse-labeled proteins from the cell surface was invariant for all two-dimensionally resolved proteins and was sensitive to temperature reduction to 18 degrees C. Long-term pulse-chase experiments beginning 4-8 h after the initiation of chase showed the disappearance of derivatized proteins to be a simple first-order process having a half-life of 115 h in the case of BNHS-derivatized proteins and 30 h in the case of BM-derivatized proteins

  4. Electrodynamic-tether time-domain reflectometer for analyzing tether faults and degradation

    Science.gov (United States)

    Bilén, Sven G.; Gilchrist, Brian E.

    2001-02-01

    We propose using time-domain-reflectometry (TDR) systems to locate and track faults along electrodynamic tether (EDT) systems. Inclusion of a TDR on long-duration EDT missions would facilitate tracking of the expected performance degradation due to faults caused by hazards such as micrometeors. The TDR technique has long been an effective tool for determining the location of loads and faults along common transmission lines (TLs) such as coaxial cables. Also sometimes known as pulse reflectometry, TDR works by sending an impulse down a TL and recording the reflected energy as a function of time. Measurement of the reflected TDR waveform provides insight into the physical structure of the TL and any loads, i.e., faults, along its length. In addition, the delay between launched and reflected signals determines the location of the load or fault. Hence, the TDR technique requires knowledge of the propagation characteristics of the TL under test. To examine the feasibility of extending the technique to EDTs we use a previously developed model for the tether transmission line. This model has temporal, and hence spatial, limitations, which may be overcome with enhancements to the tether TL model. We present some general parameters governing the development of such a tether TDR system as well as computer simulations of the TDR system's response. .

  5. Tethered Contactless Mobile Nuclear Environment Monitoring Robot

    International Nuclear Information System (INIS)

    In fact, the nuclear environment monitoring is significantly crucial for early detection of NPP accident, radiological emergency, the estimation of radiation exposure to nearby residents as well as the long term radioactivity. In the UAE, the nuclear environment monitoring is, however, quite challenging because sampling locations are far from NPPs and the outdoor temperature and humidity are very high for NPP workers to collect soil, air, and water samples. Therefore, nuclear environment monitoring robots (Nubos) are strongly needed for the NPPs in the UAE. The Nubos can be remotely controlled to collect samples in extreme environment instead of NPP workers. Moreover, the Nubos can be unmanned ground vehicles (UGVs), unmanned aerial vehicles (UAVs) and unmanned marine vehicles (UMVs) to collect soil, air, and water samples, respectively. In this paper, the prototype development of UGV type Nubos using power cable for a long distance power delivery, called Tethered contactless mobile Nubo is introduced and validated by experiments. In this paper, the prototype development of Tethered Contactless Mobile (TeCoM) Nubo, which can be powered continuously within several km distance and avoid tangled cable, and the indoor test are finished. As further works, outdoor demonstration and a grand scale R and D proposal of practical Nubo will be proceeded

  6. Lipid Gymnastics: Tethers and Fingers in membrane

    Science.gov (United States)

    Tayebi, Lobat; Miller, Gregory; Parikh, Atul

    2009-03-01

    A significant body of evidence now links local mesoscopic structure (e.g., shape and composition) of the cell membrane with its function; the mechanisms by which cellular membranes adopt the specific shapes remain poorly understood. Among all the different structures adopted by cellular membranes, the tubular shape is one of the most surprising one. While their formation is typically attributed to the reorganization of membrane cytoskeleton, many exceptions exist. We report the instantaneous formation of tubular membrane mesophases following the hydration under specific thermal conditions. The shapes emerge in a bimodal way where we have two distinct diameter ranges for tubes, ˜20μm and ˜1μm, namely fat fingers and narrow tethers. We study the roughening of hydrated drops of 3 lipids in 3 different spontaneous curvatures at various temp. and ionic strength to figure out the dominant effect in selection of tethers and fingers. Dynamics of the tubes are of particular interest where we observe four distinct steps of birth, coiling, uncoiling and retraction with different lifetime on different thermal condition. These dynamics appear to reflect interplay between membrane elasticity, surface adhesion, and thermal or hydrodynamic gradient.

  7. Incorporation of Nasutitermes takasagoensis endoglucanase into cell surface-displayed minicellulosomes in Pichia pastoris X33.

    Science.gov (United States)

    Ou, Jingshen; Cao, Yicheng

    2014-09-01

    In this study, the yeast Pichia pastoris was genetically modified to assemble minicellulosomes on its cell surface by the heterologous expression of a truncated scaffoldin CipA from Clostridium acetobutylicum. Fluorescence microscopy and western blot analysis confirmed that CipA was targeted to the yeast cell surface and that NtEGD, the Nasutitermes takasagoensis endoglucanase that was fused with dockerin, interacted with CipA on the yeast cell surface, suggesting that the cohesin and dockerin domains and cellulose-binding module of C. acetobutylicum were functional in the yeasts. The enzymatic activities of the cellulases in the minicellulosomes that were displayed on the yeast cell surfaces increased dramatically following interaction with the cohesin-dockerin domains. Additionally, the hydrolysis efficiencies of NtEGD for carboxymethyl cellulose, microcrystal cellulose, and filter paper increased up to 1.4-fold, 2.0-fold, and 3.2-fold, respectively. To the best of our knowledge, this is the first report describing the expression of C. acetobutylicum minicellulosomes in yeast and the incorporation of animal cellulases into cellulosomes. This strategy of heterologous cellulase incorporation lends novel insight into the process of cellulosome assembly. Potentially, the surface display of cellulosomes, such as that reported in this study, may be utilized in the engineering of S. cerevisiae for ethanol production from cellulose and additional future applications. PMID:24851815

  8. A Dual Receptor and Reporter for Multi-Modal Cell Surface Engineering.

    Science.gov (United States)

    Luo, Wei; Westcott, Nathan; Dutta, Debjit; Pulsipher, Abigail; Rogozhnikov, Dmitry; Chen, Jean; Yousaf, Muhammad N

    2015-10-16

    The rapid development of new small molecule drugs, nanomaterials, and genetic tools to modulate cellular function through cell surface manipulation has revolutionized the diagnosis, study, and treatment of disorders in human health. Since the cell membrane is a selective gateway barrier that serves as the first line of defense/offense and communication to its environment, new approaches that molecularly engineer or tailor cell membrane surfaces would allow for a new era in therapeutic design, therapeutic delivery, complex coculture tissue construction, and in situ imaging probe tracking technologies. In order to develop the next generation of multimodal therapies, cell behavior studies, and biotechnologies that focus on cell membrane biology, new tools that intersect the fields of chemistry, biology, and engineering are required. Herein, we develop a liposome fusion and delivery strategy to present a novel dual receptor and reporter system at cell surfaces without the use of molecular biology or metabolic biosynthesis. The cell surface receptor is based on bio-orthogonal functional groups that can conjugate a range of ligands while simultaneously reporting the conjugation through the emission of fluorescence. We demonstrate this dual receptor and reporter system by conjugating and tracking various cell surface ligands for temporal control of cell fluorescent signaling, cell-cell interaction, and tissue assembly construction. PMID:26204094

  9. Tethered actuator for vibration control of space structures

    Science.gov (United States)

    Fujii, H. A.; Sugimoto, Y.; Watanabe, T.; Kusagaya, T.

    2015-12-01

    Effectiveness of a micro-tension actuator for vibration control of such flexible space structures as the tethered space solar power satellites is experimentally studied on the ground. A flexible leverage is employed as the micro-tension actuator in order to control the microtension of tether. The flexible leverage is connected through a tether to the flexible beam as an experimental model of the flexible solar panel with the low first modal frequency of order 1 Hz. The nonlinearity of the flexible tether is taken into account for the vibration control since the tether becomes ineffective when it slacks, i.e., when it is tension-free. The feedback controller is designed by means of the Mission Function control algorithm. Flexural rigidity of the flexible leverage plays an important role in the vibration suppression and is studied experimentally to shed light on the effectiveness of the leverages with five different kinds of rigidity. The experimental results show not only the effect of the flexural rigidity of the flexible leverage on the control performance of the vibration suppression but also the importance of selection of the rigidity to control the vibration of tethered flexible space structures through the microtension of tethers in space.

  10. Development of a Tether Based Space Walking Robot to Be Tested on ISS/KIBO

    Science.gov (United States)

    Oda, Mitsushige; Yoshii, Masahiro; Kato, Hiroki; Suzuki, Satoshi; Hagiwara, Yusuke; Ueno, Taihei

    A unique space robot is proposed to support astronauts in space. The robot moves around the surface of a space facility, e.g. a space station using its handrails and tethers that the robot has. This unique mechanism of the proposed robot makes it possible to realize the robot in a small volume while the robot can move around the wide area. In order to demonstrate usefulness of this unique robot, an onboard experiment on the exposed facility of the International Space Station Japanese Experiment Module, “KIBO” will be conducted in the year 2012. Development of the experiment system is progressing now.

  11. Project 'VOLCANO': Electronics of tethered satellite system

    Science.gov (United States)

    Savich, N. A.

    The main goal of the 'VOLCANO' project developed jointly by the Institute of Radio Engineering and Electronics and space concern 'ENERGIA' is experimental investigation of the current-voltage characteristics of the 'Collector-Boom-Emitter' system simulating the long Tethered Satellite System (TSS) in the real space flight conditions on the transport ship 'PROGRESS'. These measurements will allow scientists to determine the attainable current values for different combinations of collectors and emitters (passive metallic sphere, thermocathode, hollow cathodes and show up some prospects of active TSS. The report is concerned with the concept, purpose and tasks of the project, the planned set up of the measurement equipment on the 'PROGRESS' ship and in the container extended on the deployable 100 m long boom end.

  12. Airborne Internet Providing Tethered Balloon System

    Directory of Open Access Journals (Sweden)

    Suvriti Dhawan1

    2015-12-01

    Full Text Available In this paper we shall introduce a new system for providing wireless network communication over a specified area using ’lighter than air’ balloons. This technology will replace the existing fiber optic network system. This will be done by using a tethered balloon along with the payload (containing a receiver, a transmitter and a radio communication device.This payload will be suspended from the ground at an altitude (depending on the area of coverage required. Users under this area will be able to access this system directly for internet connectivity. This system can be used over large areas like universities, companies and societies to provide internet facility to their users through Wi-Fi or over an area where the user is specified (commercial purposes. Currently Google is working on similar idea called the ’Google Loon’ in which they use high altitude balloons which float at an altitude twice as high as air planes and the weather. They recently tested this system over New-Zealand by providing internet to their pilot testers on ground. Their balloons not being stationary, move with directional winds and have to be replaced one after the other to maintain consistency. This can be a huge problem over the areas where upper atmospheric winds are not in favorable direction. We can resolve this problem by using our stationary tethered balloon system which can communicate with the loon balloons to provide internet facility over a desired area. Moreover when our balloon will communicate with the loon balloon it will increase the coverage area as the loon balloon has to communicate to a point which is above the ground. Our system will not only replace the existing fiber optic system but it will also be selfsustaining i.e. It will generate its own power using solar panels.

  13. Passivity-Based Control of a Rigid Electrodynamic Tether

    DEFF Research Database (Denmark)

    Larsen, Martin Birkelund; Blanke, Mogens

    2011-01-01

    Electrodynamic tethers provide actuation for performing orbit correction of spacecrafts. When an electrodynamic tether system is orbiting the Earth in an inclined orbit, periodic changes in the magnetic field result in a family of unstable periodic solutions in the attitude motion. This paper shows...... parts, a feedback connection, which stabilizes the open-loop equilibrium, and a bias term, which is able to drive the system trajectory away from this equilibrium, a feature necessary to obtain orbit adjustment capabilities of the electrodynamic tether. It is then shown how the periodic solutions of the...

  14. Calreticulin: Roles in Cell-Surface Protein Expression

    Directory of Open Access Journals (Sweden)

    Yue Jiang

    2014-09-01

    Full Text Available In order to perform their designated functions, proteins require precise subcellular localizations. For cell-surface proteins, such as receptors and channels, they are able to transduce signals only when properly targeted to the cell membrane. Calreticulin is a multi-functional chaperone protein involved in protein folding, maturation, and trafficking. However, evidence has been accumulating that calreticulin can also negatively regulate the surface expression of certain receptors and channels. In these instances, depletion of calreticulin enhances cell-surface expression and function. In this review, we discuss the role of calreticulin with a focus on its negative effects on the expression of cell-surface proteins.

  15. Laboratory experiments on the electrodynamic behavior of tethers in space

    Science.gov (United States)

    Stenzel, Reiner L.; Urrutia, Manuel J.

    1991-01-01

    The transient current systems between tethered plasmas in a large magnetoplasma are investigated experimentally for extrapolation to electrodynamic tethers in space. The studies measure the perturbed magnetic fields and the current density associated with pulsed currents to electrodes in three-dimensional space and time. The electrodes excite electron whistlers because they produce fields that dominantly couple to electrons, allowing pulsed currents to propagate and disperse as whistler wave packets. The wave packets evolve into force-free, flux-ropelike field configurations, and a whistler 'wedge' is formed in the plasma due to 'eddy' currents caused by insulated tethers with dc currents. Substantial radiation into the whistler mode happens with moving VLF antennas as well as tethers, and the wave spread within the ray cone is the most significant characteristic event. The wave spread widens the current channel, incites current closure, and is also associated with a 'phantom loop' phenomenon.

  16. Stationary Tether Device for Buoy Apparatus and System for Using

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — A rigid, neutrally buoyant hydrodynamicaly-faired tether and associated fastening hardware that loosely holds a bathymetric float at a predetermined distance from a...

  17. An updated review of nanotechnologies for the space elevator tether

    OpenAIRE

    Brambilla, G.

    2010-01-01

    The space elevator tether requires an extraordinary specific ultimate strength (ratio between ultimate strength and density) and carbon nanotubes (CNTs) have been identified as the ideal candidate because of their astonishing strength. This paper reviews CNT manufacture and measured strengths.

  18. Fiber Optic Shape Sensing for Tethered Marsupial Rovers Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Building upon the successful proof of concept work in Phase I, Luna Innovations Incorporated is proposing to design, build, and test a sensing tether for marsupial...

  19. Fiber Optic Shape Sensing for Tethered Marsupial Rovers Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Luna Innovations Incorporated is proposing to design, build, and test a shape, length, and tension sensing tether for robotic exploration and sample-gathering...

  20. Development of a Tethered Formation Flight Testbed for ISS Project

    Data.gov (United States)

    National Aeronautics and Space Administration — The development of a testbed for the development and demonstration of technologies needed by tethered formation flying satellites is proposed. Such a testbed would...

  1. Isothermal pumping analysis for high-altitude tethered balloons

    OpenAIRE

    Kuo, Kirsty A.; Hunt, Hugh E.M.

    2015-01-01

    High-altitude tethered balloons have potential applications in communications, surveillance, meteorological observations and climate engineering. To maintain balloon buoyancy, power fuel cells and perturb atmospheric conditions, fluids could be pumped from ground level to altitude using the tether as a hose. This paper examines the pumping requirements of such a delivery system. Cases considered include delivery of hydrogen, sulfur dioxide (SO2) and powders as fluid-based slurries. Isothermal...

  2. Role of the membrane for mechanosensing by tethered channels

    CERN Document Server

    Sabass, Benedikt

    2016-01-01

    Biologically important membrane channels are gated by force at attached tethers. Here, we generically characterize the non-trivial interplay of force, membrane tension, and channel deformations that can affect gating. A central finding is that minute conical channel deformation under force leads to significant energy release during opening. We also calculate channel-channel interactions and show that they can amplify force sensitivity of tethered channels.

  3. Single-particle tracking for DNA tether length monitoring

    OpenAIRE

    Pouget, Noëlle; Dennis, Cynthia; Turlan, Catherine; Grigoriev, Mikhail; Chandler, Michaël; Salomé, Laurence

    2004-01-01

    We describe a simple single-particle tracking approach for monitoring the length of DNA molecules in tethered particle motion experiments. In this method, the trajectory of a submicroscopic bead tethered by a DNA molecule to a glass surface is determined by videomicroscopy coupled to image analysis. The amplitude of motion of the bead is measured by the standard deviation of the distribution of successive positions of the bead in a given time interval. We were able to describe theoretically t...

  4. Survival Probability of Round and Tape Tethers Against Debris Impact

    OpenAIRE

    Khan, Shaker Bayajid; Sanmartin, Juan R.

    2013-01-01

    The current space environment, consisting of manmade debris and micrometeoroids, poses a risk to safe operations in space, and the situation is continuously deteriorating due to in-orbit debris collisions and to new satellite launches. Bare electrodynamic tethers can provide an efficient mechanism for rapid deorbiting of satellites from low Earth orbit at end of life. Because of its particular geometry (length very much larger than cross-sectional dimensions), a tether may have a relatively h...

  5. Analysis of tape tether survival in LEO against orbital debris

    OpenAIRE

    Khan, Shaker Bayajid; Sanmartin, Juan R.

    2014-01-01

    The low earth orbit (LEO) environment contains a large number of artificial debris, of which a significant portion is due to dead satellites and fragments of satellites resulted from explosions and in-orbit collisions. Deorbiting defunct satellites at the end of their life can be achieved by a successful operation of an Electrodynamic Tether (EDT) system. The effectiveness of an EDT greatly depends on the survivability of the tether, which can become debris itself if cut by debris particle...

  6. Space Test of Bare-Wire Anode Tethers

    Science.gov (United States)

    Johnson, L.; Fujii, H. A.; Sanmartin, J. R.

    2007-01-01

    An international team, lead by Tokyo Metropolitan University, is developing a mission concept for a suborbital test of orbital-motion-limited (OML) bare-wire anode current collection for application to electrodynamic tether propulsion. The tether is a tape with a 50-mm width, 0.05-mm thickness, and 1-km length. This will be the first space test of the OML theory. In addition, by being an engineering demonstration (of space tethers), the mission will demonstrate electric beam generation for "sounding" determination of the neutral density profile in the ionospheric "E-layer." If selected by the Institute of Space and Astronautical Science/Japanese Aerospace Exploration Agency (JAXA), the mission will launch in early 2009 using an $520 Sounding Rocket. During ascent, and above =100 km in attitude, the 1-km tape tether will be deployed at a rate of 8 m/s. Once deployed, the tape tether will serve as an anode, collecting ionospheric electrons. The electrons will be expelled into space by a hollow cathode device, thereby completing the circuit and allowing current to flow.This paper will describe the objectives of the proposed mission, the technologies to be employed, and the application of the results to future space missions using electrodynamic tethers for propulsion or power generation.

  7. Dynamics of single-stranded DNA tethered to a solid

    Science.gov (United States)

    Radiom, Milad; Paul, Mark R.; Ducker, William A.

    2016-06-01

    Tethering is used to deliver specific biological and industrial functions. For example, single-stranded DNA (ssDNA) is tethered to polymerases and long sequences of double-stranded DNA (dsDNA) during replication, and to solids in DNA microarrays. However, tethering ssDNA to a large object limits not only the available ssDNA conformations, but also the range of time-scales over which the mechanical responses of ssDNA are important. In this work we examine the effect of tethering by measurement of the mechanical response of ssDNA that is tethered at each end to two separate atomic force microscope cantilevers in aqueous solution. Thermal motion of the cantilevers drives the ends of the ssDNA chain at frequencies near 2 kHz. The presence of a tethered molecule makes a large difference to the asymmetric cross-correlation of two cantilevers, which enables resolution of the mechanical properties in our experiments. By analysis of the correlated motion of the cantilevers we extract the friction and stiffness of the ssDNA. We find that the measured friction is much larger than the friction that is usually associated with the unencumbered motion of ssDNA. We also find that the measured relaxation time, ∼30 μs, is much greater than prior measurements of the free-molecule relaxation time. We attribute the difference to the loss of conformational possibilities as a result of constraining the ends of the ssDNA.

  8. Dynamics of the Space Tug System with a Short Tether

    Directory of Open Access Journals (Sweden)

    Jiafu Liu

    2015-01-01

    Full Text Available The dynamics of the space tug system with a short tether similar to the ROGER system during deorbiting is presented. The kinematical characteristic of this system is significantly different from the traditional tethered system as the tether is tensional and tensionless alternately during the deorbiting process. The dynamics obtained based on the methods for the traditional tethered system is not suitable for the space tug system. Therefore, a novel method for deriving dynamics for the deorbiting system similar to the ROGER system is proposed by adopting the orbital coordinates of the two spacecraft and the Euler angles of ROGER spacecraft as the generalized coordinates instead of in- and out-plane librations and the length of the tether and so forth. Then, the librations of the system are equivalently obtained using the orbital positions of the two spacecraft. At last, the geostationary orbit (GEO and the orbit whose apogee is 300 km above GEO are chosen as the initial and target orbits, respectively, to perform the numerical simulations. The simulation results indicate that the dynamics can describe the characteristic of the tether-net system conveniently and accurately, and the deorbiting results are deeply affected by the initial conditions and parameters.

  9. Elastic issues and vibration reduction in a tethered deorbiting mission

    Science.gov (United States)

    Sabatini, Marco; Gasbarri, Paolo; Palmerini, Giovanni B.

    2016-05-01

    Recently proposed mission concepts involving harpoons or nets to capture and de-orbit debris represent an interesting application of the tethered systems, where the orbiting bodies are connected by a flexible link. These systems present a complex behavior, as flexible characteristics combine with orbital dynamics. The focus of the paper is on the dynamic behavior of the tethered system in the final phase of the de-orbiting mission, when a powerful apogee motor is used to change the debris orbit. The thrust action introduces significant issues, as elastic waves propagate along the tether, and the relevant oscillations couple with the orbital dynamics. Input shaping techniques are proposed to limit or cancel these oscillations. However, the performance of these techniques drops when non-ideal scenarios are considered. In particular, an initially slack tether is a serious issue that must be solved if acceptably low oscillations of the tether are to be obtained. Three strategies are proposed and discussed in this paper to remove the slack condition: a natural drift of the chaser by means of a single impulse, a controlled maneuver for precisely adjusting the relative distance between chaser spacecraft and debris, and a retrieval mechanism for changing the tether length.

  10. Chemistry and material science at the cell surface

    OpenAIRE

    Weian Zhao; Grace Sock Leng Teo; Namit Kumar; Karp, Jeffrey M.

    2010-01-01

    Cell surfaces are fertile ground for chemists and material scientists to manipulate or augment cell functions and phenotypes. This not only helps to answer basic biology questions but also has diagnostic and therapeutic applications. In this review, we summarize the most recent advances in the engineering of the cell surface. In particular, we focus on the potential applications of surface engineered cells for 1) targeting cells to desirable sites in cell therapy, 2) programming assembly of c...

  11. Cell surface hydrophobicity of dental plaque microorganisms in situ.

    OpenAIRE

    Rosenberg, M.; Judes, H; Weiss, E

    1983-01-01

    The cell surface hydrophobicity of bacteria obtained directly from human tooth surfaces was assayed by measuring their adherence to liquid hydrocarbons. Fresh samples of supragingival dental plaque were washed and dispersed in buffer. Adherence of the plaque microorganisms to hexadecane, octane, and xylene was tested turbidimetrically and by direct microscopic observation. The results clearly show that the vast majority of bacteria comprising dental plaque exhibit pronounced cell surface hydr...

  12. Analytical investigation of the dynamics of tethered constellations in Earth orbit, phase 2

    Science.gov (United States)

    Lorenzini, Enrico C.; Gullahorn, Gordon E.; Cosmo, Mario L.; Estes, Robert D.; Grossi, Mario D.

    1994-01-01

    This final report covers nine years of research on future tether applications and on the actual flights of the Small Expendable Deployment System (SEDS). Topics covered include: (1) a description of numerical codes used to simulate the orbital and attitude dynamics of tethered systems during station keeping and deployment maneuvers; (2) a comparison of various tethered system simulators; (3) dynamics analysis, conceptual design, potential applications and propagation of disturbances and isolation from noise of a variable gravity/microgravity laboratory tethered to the Space Station; (4) stability of a tethered space centrifuge; (5) various proposed two-dimensional tethered structures for low Earth orbit for use as planar array antennas; (6) tethered high gain antennas; (7) numerical calculation of the electromagnetic wave field on the Earth's surface on an electrodynamically tethered satellite; (8) reentry of tethered capsules; (9) deployment dynamics of SEDS-1; (10) analysis of SEDS-1 flight data; and (11) dynamics and control of SEDS-2.

  13. Adult idiopathic scoliosis: the tethered spine.

    Science.gov (United States)

    Whyte Ferguson, Lucy

    2014-01-01

    This article reports on an observational and treatment study using three case histories to describe common patterns of muscle and fascial asymmetry in adults with idiopathic scoliosis (IS) who have significant scoliotic curvatures that were not surgically corrected and who have chronic pain. Rather than being located in the paraspinal muscles, the myofascial trigger points (TrPs) apparently responsible for the pain were located at some distance from the spine, yet referred pain to locations throughout the thoracolumbar spine. Asymmetries in these muscles appear to tether the spine in such a way that they contribute to scoliotic curvatures. Evaluation also showed that each of these individuals had major ligamentous laxity and this may also have contributed to development of scoliotic curvatures. Treatment focused on release of TrPs found to refer pain into the spine, release of related fascia, and correction of related joint dysfunction. Treatment resulted in substantial relief of longstanding chronic pain. Treatment thus validated the diagnostic hypothesis that myofascial and fascial asymmetries were to some extent responsible for pain in adults with significant scoliotic curvatures. Treatment of these patterns of TrPs and muscle and fascial asymmetries and related joint dysfunction was also effective in relieving pain in each of these individuals after they were injured in auto accidents. Treatment of myofascial TrPs and asymmetrical fascial tension along with treatment of accompanying joint dysfunction is proposed as an effective approach to treating both chronic and acute pain in adults with scoliosis that has not been surgically corrected. PMID:24411157

  14. Tether-directed synthesis of highly substituted oxasilacycles via an intramolecular allylation employing allylsilanes

    Directory of Open Access Journals (Sweden)

    Cox Liam R

    2007-02-01

    Full Text Available Abstract Background Using a silyl tether to unite an aldehyde electrophile and allylsilane nucleophile into a single molecule allows a subsequent Lewis-acid-mediated allylation to proceed in an intramolecular sense and therefore receive all the benefits associated with such processes. However, with the ability to cleave the tether post allylation, a product that is the result of a net intermolecular reaction can be obtained. In the present study, four diastereoisomeric β-silyloxy-α-methyl aldehydes, which contain an allylsilane tethered through the β-carbinol centre, have been prepared, in order to probe how the relative configuration of the two stereogenic centres affects the efficiency and selectivity of the intramolecular allylation. Results Syn-aldehydes, syn-4a and syn-4b, both react poorly, affording all four possible diastereoisomeric oxasilacycle products. In contrast, the anti aldehydes anti-4a and anti-4b react analogously to substrates that lack substitution at the α-site, affording only two of the four possible allylation products. Conclusion The outcome of the reaction with anti-aldehydes is in accord with reaction proceeding through a chair-like transition state (T.S.. In these systems, the sense of 1,3-stereoinduction can be rationalised by the aldehyde electrophile adopting a pseudoaxial orientation, which will minimise dipole-dipole interactions in the T.S. The 1,4-stereoinduction in these substrates is modest and seems to be modulated by the R substituent in the starting material. In the case of the syn-substrates, cyclisation through a chair T.S. is unlikely as this would require the methyl substituent α to the reacting carbonyl group to adopt an unfavourable pseudoaxial position. It is therefore proposed that these substrates react through poorly-defined T.S.s and consequently exhibit essentially no stereoselectivity.

  15. Expanding the diversity of unnatural cell surface sialic acids

    Energy Technology Data Exchange (ETDEWEB)

    Luchansky, Sarah J.; Goon, Scarlett; Bertozzi, Carolyn R.

    2003-10-30

    Novel chemical reactivity can be introduced onto cell surfaces through metabolic oligosaccharide engineering. This technique exploits the substrate promiscuity of cellular biosynthetic enzymes to deliver unnatural monosaccharides bearing bioorthogonal functional groups into cellular glycans. For example, derivatives of N-acetylmannosamine (ManNAc) are converted by the cellular biosynthetic machinery into the corresponding sialic acids and subsequently delivered to the cell surface in the form of sialoglycoconjugates. Analogs of N-acetylglucosamine (GlcNAc) and N-acetylgalactosamine (GalNAc) are also metabolized and incorporated into cell surface glycans, likely through the sialic acid and GalNAc salvage pathways, respectively. Furthermore, GlcNAc analogs can be incorporated into nucleocytoplasmic proteins in place of {beta}-O-GlcNAc residues. These pathways have been exploited to integrate unique electrophiles such as ketones and azides into the target glycoconjugate class. These functional groups can be further elaborated in a chemoselective fashion by condensation with hydrazides and by Staudinger ligation, respectively, thereby introducing detectable probes onto the cell. In conclusion, sialic acid derivatives are efficient vehicles for delivery of bulky functional groups to cell surfaces and masking of their hydroxyl groups improves their cellular uptake and utilization. Furthermore, the successful introduction of photoactivatable aryl azides into cell surface glycans opens up new avenues for studying sialic acid-binding proteins and elucidating the role of sialic acid in essential processes such as signaling and cell adhesion.

  16. Numerical Simulation of Tethered Underwater Kites for Power Generation

    Science.gov (United States)

    Ghasemi, Amirmahdi; Olinger, David; Tryggvason, Gretar

    2015-11-01

    An emerging renewable energy technology, tethered undersea kites (TUSK), which is used to extract hydrokinetic energy from ocean and tidal currents, is studied. TUSK systems consist of a rigid-winged ``kite,'' or glider, moving in an ocean current which is connected by tethers to a floating buoy on the ocean surface. The TUSK kite is a current speed enhancement device since the kite can move in high-speed, cross-current motion at 4-6 times the current velocity, thus producing more power than conventional marine turbines. A computational simulation is developed to simulate the dynamic motion of an underwater kite and extendable tether. A two-step projection method within a finite volume formulation, along with an Open MP acceleration method, is employed to solve the Navier-Stokes equations. An immersed boundary method is incorporated to model the fluid-structure interaction of the rigid kite (with NACA 0012 airfoil shape in 2D and NACA 0021 airfoil shape in 3D simulations) and the fluid flow. PID control methods are used to adjust the kite angle of attack during power (tether reel-out) and retraction (reel-in) phases. Two baseline simulations (for kite motions in two and three dimensions) are studied, and system power output, flow field vorticity, tether tension, and hydrodynamic coefficients (lift and drag) for the kite are determined. The simulated power output shows good agreement with established theoretical results for a kite moving in two-dimensions.

  17. Tethered Pyrotechnic Apparatus for Acquiring a Ground Sample

    Science.gov (United States)

    Jones, Jack; Zimmerman, Wayne; Wu, Jiunn Jenq; Badescu, Mircea; Sherrit, Stewart

    2009-01-01

    A proposed alternative design for the balloon-borne ground-sampling system described in the immediately preceding article would not rely on free fall to drive a harpoonlike sample-collecting device into the ground. Instead, the harpoon-like sample-collecting device would be a pyrotechnically driven, tethered projectile. The apparatus would include a tripod that would be tethered to the gondola. A gun for shooting the projectile into the ground would be mounted at the apex of the tripod. The gun would include an electronic trigger circuit, a chamber at the breech end containing a pyrotechnic charge, and a barrel. A sabot would be placed in the barrel just below the pyrotechnic charge, and the tethered projectile would be placed in the barrel just below the sabot. The tripod feet would be equipped with contact sensors connected to the trigger circuit. In operation, the tripod would be lowered to the ground on its tether. Once contact with the ground was detected by the sensors on all three tripod feet, the trigger circuit would fire the pyrotechnic charge to drive the projectile into the ground. (Requiring contact among all three tripod feet and the ground would ensure that the projectile would be fired into the ground, rather than up toward the gondola or the balloon.) The tethered projectile would then be reeled back up to the gondola for analysis of the sample.

  18. Effect of chromosome tethering on nuclear organization in yeast.

    Directory of Open Access Journals (Sweden)

    Barış Avşaroğlu

    Full Text Available Interphase chromosomes in Saccharomyces cerevisiae are tethered to the nuclear envelope at their telomeres and to the spindle pole body (SPB at their centromeres. Using a polymer model of yeast chromosomes that includes these interactions, we show theoretically that telomere attachment to the nuclear envelope is a major determinant of gene positioning within the nucleus only for genes within 10 kb of the telomeres. We test this prediction by measuring the distance between the SPB and the silent mating locus (HML on chromosome III in wild-type and mutant yeast strains that contain altered chromosome-tethering interactions. In wild-type yeast cells we find that disruption of the telomere tether does not dramatically change the position of HML with respect to the SPB, in agreement with theoretical predictions. Alternatively, using a mutant strain with a synthetic tether that localizes an HML-proximal site to the nuclear envelope, we find a significant change in the SPB-HML distance, again as predicted by theory. Our study quantifies the importance of tethering at telomeres on the organization of interphase chromosomes in yeast, which has been shown to play a significant role in determining chromosome function such as gene expression and recombination.

  19. Tethered satellite system control using electromagnetic forces and reaction wheels

    Science.gov (United States)

    Alandi Hallaj, Mohammad Amin; Assadian, Nima

    2015-12-01

    In this paper a novel non-rotating space tethered configuration is introduced which its relative positions controlled using electromagnetic forces. The attitude dynamics is controlled by three reaction wheels in the body axes. The nonlinear coupled orbital dynamics of a dumbbell tethered satellite formation flight are derived through a constrained Lagrangian approach. These equations are presented in the leader satellite orbital frame. The tether is assumed to be mass-less and straight, and the J2 perturbation is included to the analysis. The forces and the moments of the electromagnetic coils are modeled based on the far-filed model of the magnetic dipoles. A guidance scheme for generating the desired positions as a function of time in Cartesian form is presented. The satellite tethered formation with variable length is controlled utilizing a linear controller. This approach is applied to a specified scenario and it is shown that the nonlinear guidance method and the linear controller can control the nonlinear system of the tethered formation and the results are compared with optimal control approach.

  20. Tethered Nanoparticle–Polymer Composites: Phase Stability and Curvature

    KAUST Repository

    Srivastava, Samanvaya

    2012-04-17

    Phase behavior of poly(ethylene glycol) (PEG) tethered silica nanoparticles dispersed in PEG hosts is investigated using small-angle X-ray scattering. Phase separation in dispersions of densely grafted nanoparticles is found to display strikingly different small-angle X-ray scattering signatures in comparison to phase-separated composites comprised of bare or sparsely grafted nanoparticles. A general diagram for the dispersion state and phase stability of polymer tethered nanoparticle-polymer composites incorporating results from this as well as various other contemporary studies is presented. We show that in the range of moderate to high grafting densities the dispersion state of nanoparticles in composites is largely insensitive to the grafting density of the tethered chains and chemistry of the polymer host. Instead, the ratio of the particle diameter to the size of the tethered chain and the ratio of the molecular weights of the host and tethered polymer chains (P/N) are shown to play a dominant role. Additionally, we find that well-functionalized nanoparticles form stable dispersions in their polymer host beyond the P/N limit that demarcates the wetting/dewetting transition in polymer brushes on flat substrates interacting with polymer melts. A general strategy for achieving uniform nanoparticle dispersion in polymers is proposed. © 2012 American Chemical Society.

  1. Numerical and Experimental Approaches on the Motion of a Tethered System

    Science.gov (United States)

    Takehara, Shoichiro; Terumichi, Yoshiaki; Nohmi, Masahiro; Sogabe, Kiyoshi

    In the present paper, the motion of a tethered system with large deformation and large displacement is discussed. In general, a tether is a cable or a wire rope, and a tethered system consists of a tether and the equipment attached to the tether. A tethered subsatellite in space is an example of a tethered system. In the present study, a tethered system consisting of a very flexible body (the tether) and a rigid body at one end is considered as the analytical model. A flexible body in planer motion is described using the Absolute Nodal Coordinate Formulation. Using this formulation, the motion of a flexible body with large deformation, rotation and translation can be expressed with the accuracy of rigid body motion. The combination of the flexible body motion and the rigid body motion is performed, and their interaction is discussed. Experiments are performed to investigate the fundamental motion of the tethered system and to evaluate the validity of the numerical formulation. Experiments were conducted using a steel tether and a rubber tether in gravity space. In addition, an experiment of the motion of the tethered system with a rigid body in microgravity space was conducted.

  2. Recent Insights into Cell Surface Heparan Sulphate Proteoglycans and Cancer.

    Science.gov (United States)

    Couchman, John R; Multhaupt, Hinke; Sanderson, Ralph D

    2016-01-01

    A small group of cell surface receptors are proteoglycans, possessing a core protein with one or more covalently attached glycosaminoglycan chains. They are virtually ubiquitous and their chains are major sites at which protein ligands of many types interact. These proteoglycans can signal and regulate important cell processes, such as adhesion, migration, proliferation, and differentiation. Since many protein ligands, such as growth factors, morphogens, and cytokines, are also implicated in tumour progression, it is increasingly apparent that cell surface proteoglycans impact tumour cell behaviour. Here, we review some recent advances, emphasising that many tumour-related functions of proteoglycans are revealed only after their modification in processes subsequent to synthesis and export to the cell surface. These include enzymes that modify heparan sulphate structure, recycling of whole or fragmented proteoglycans into exosomes that can be paracrine effectors or biomarkers, and lateral interactions between some proteoglycans and calcium channels that impact the actin cytoskeleton. PMID:27408707

  3. Recent Insights into Cell Surface Heparan Sulphate Proteoglycans and Cancer

    Science.gov (United States)

    Couchman, John R; Multhaupt, Hinke; Sanderson, Ralph D.

    2016-01-01

    A small group of cell surface receptors are proteoglycans, possessing a core protein with one or more covalently attached glycosaminoglycan chains. They are virtually ubiquitous and their chains are major sites at which protein ligands of many types interact. These proteoglycans can signal and regulate important cell processes, such as adhesion, migration, proliferation, and differentiation. Since many protein ligands, such as growth factors, morphogens, and cytokines, are also implicated in tumour progression, it is increasingly apparent that cell surface proteoglycans impact tumour cell behaviour. Here, we review some recent advances, emphasising that many tumour-related functions of proteoglycans are revealed only after their modification in processes subsequent to synthesis and export to the cell surface. These include enzymes that modify heparan sulphate structure, recycling of whole or fragmented proteoglycans into exosomes that can be paracrine effectors or biomarkers, and lateral interactions between some proteoglycans and calcium channels that impact the actin cytoskeleton. PMID:27408707

  4. Numerical simulation of tethered DNA in shear flow

    Energy Technology Data Exchange (ETDEWEB)

    Litvinov, S; Hu, X Y; Adams, N A [Institute of Aerodynamics, Technische Universitaet Muenchen, D-85747 Garching (Germany)

    2011-05-11

    The behavior of tethered DNA in shear flow is investigated numerically by the smoothed dissipative particle dynamics (SDPD) method. Unlike numerical methods used in previous studies, SDPD models the solvent explicitly, takes into account the fully coupled hydrodynamic interactions and is free of the numerical artifact of wall sticking. Based on numerical simulations the static and dynamic properties of a tethered DNA is studied both qualitatively and quantitatively. The observed properties are in general agreement with previous experimental, numerical and theoretical work. Furthermore, the cyclic-motion phenomenon is studied by power spectrum density and cross-correlation function analysis, which suggest that there is only a very weak coherent motion of tethered DNA for a characteristic timescale larger than the relaxation time. Cyclic motion is more likely relevant as an isolated event than a typical mode of DNA motion.

  5. Orbit Maneuver of Spinning Tether via Tidal Force

    CERN Document Server

    Baoyin, Hexi; Li, Junfeng

    2014-01-01

    Recently, the spinning tethered system is regarded as a typical and fundamental space structure attracting great interest of the aerospace engineers, and has been discussed primarily for specific space missions in past decades, including on-orbit capture and propellantless orbit transfer etc. The present work studies the dynamical behaviours of a fast spinning tethered binary system under central gravitational field, and derives principles of the basic laws of orbital maneuver. Considering the characteristics of coupled librational and orbital motions, an averaging method is introduced to deal with the slow-fast system equation, thus a definite equivalent model is derived. The general orbit motion is completely determined analytically, including the orbit geometry, periodicity, conversations and moving region etc. Since the possibility of orbit control using tether reaction has been proved by previous studies, special attention is paid to the transportation mode of angular momentum and mechanical energy betwe...

  6. The Secret Life of Tethers: The Role of Tethering Factors in SNARE Complex Regulation.

    Science.gov (United States)

    Dubuke, Michelle L; Munson, Mary

    2016-01-01

    Trafficking in eukaryotic cells is a tightly regulated process to ensure correct cargo delivery to the proper destination organelle or plasma membrane. In this review, we focus on how the vesicle fusion machinery, the SNARE complex, is regulated by the interplay of the multisubunit tethering complexes (MTC) with the SNAREs and Sec1/Munc18 (SM) proteins. Although these factors are used in different stages of membrane trafficking, e.g., Golgi to plasma membrane transport vs. vacuolar fusion, and in a variety of diverse eukaryotic cell types, many commonalities between their functions are being revealed. We explore the various protein-protein interactions and findings from functional reconstitution studies in order to highlight both their common features and the differences in their modes of regulation. These studies serve as a starting point for mechanistic explorations in other systems. PMID:27243006

  7. Soluble and cell surface receptors for tumor necrosis factor

    DEFF Research Database (Denmark)

    Wallach, D; Engelmann, H; Nophar, Y;

    1991-01-01

    Tumor necrosis factor (TNF) initiates its multiple effects on cell function by binding at a high affinity to specific cell surface receptors. Two different molecular species of these receptors, which are expressed differentially in different cells, have been identified. The cDNAs of both receptors...... certain pathological situations. Release of the soluble receptors from the cells seems to occur by proteolytic cleavage of the cell surface forms and appears to be a way of down-regulating the cell response to TNF. Because of their ability to bind TNF, the soluble receptors exert an inhibitory effect on...

  8. Chemistry and material science at the cell surface

    Directory of Open Access Journals (Sweden)

    Weian Zhao

    2010-04-01

    Full Text Available Cell surfaces are fertile ground for chemists and material scientists to manipulate or augment cell functions and phenotypes. This not only helps to answer basic biology questions but also has diagnostic and therapeutic applications. In this review, we summarize the most recent advances in the engineering of the cell surface. In particular, we focus on the potential applications of surface engineered cells for 1 targeting cells to desirable sites in cell therapy, 2 programming assembly of cells for tissue engineering, 3 bioimaging and sensing, and ultimately 4 manipulating cell biology.

  9. Anchoring a Leviathan: How the Nuclear Membrane Tethers the Genome

    Directory of Open Access Journals (Sweden)

    Rafal eCzapiewski

    2016-05-01

    Full Text Available It is well established that the nuclear envelope has many distinct direct connections to chromatin that contribute to genome organization. The functional consequences of genome organization on gene regulation are less clear. Even less understood is how interactions of lamins and nuclear envelope transmembrane proteins (NETs with chromatin can produce anchoring tethers that can withstand the physical forces of and on the genome. Chromosomes are the largest molecules in the cell, making megadalton protein structures like the nuclear pore complexes and ribosomes seem small by comparison. Thus to withstand strong forces from chromosome dynamics an anchoring tether is likely to be much more complex than a single protein-protein or protein-DNA interaction. Here we will briefly review known NE-genome interactions that likely contribute to spatial genome organization, postulate in the context of experimental data how these anchoring tethers contribute to gene regulation, and posit several hypotheses for the physical nature of these tethers that need to be investigated experimentally. Significantly, disruption of these anchoring tethers and the subsequent consequences for gene regulation could explain how mutations in nuclear envelope proteins cause diseases ranging from muscular dystrophy to lipodystrophy to premature ageing progeroid syndromes. The two favored hypotheses for nuclear envelope protein involvement in disease are 1 weakening nuclear and cellular mechanical stability, and 2 disrupting genome organization and gene regulation. Considerable experimental support has been obtained for both. The integration of both mechanical and gene expression defects in the disruption of anchoring tethers could provide a unifying hypothesis consistent with both.

  10. The Momentum-eXchange/Electrodynamic Reboost (MXER) Tether Concept

    Science.gov (United States)

    Sorenson, K. F.

    2004-12-01

    Within NASA's In-Space Propulsion Technology Projects Office exists Emerging Propulsion Technologies (EPT) Investment Area that is advancing emerging propulsion concepts that have potential to lower the cost of space transportation, enable new missions, and/or increase the payload capability. The current, primary investment of EPT is the Momentum-eXchange/Electrodynamic Reboost (MXER) tether concept. The MXER tether is a long, rotating cable in an elliptical Earth orbit whose rapid rotation allows it to catch a payload in a low Earth orbit and throw it to a high-energy orbit. The orbital energy transferred by the MXER tether to the payload is restored to the tether via electrodynamic tether propulsion. This technique uses solar power to drive electrical current collected from the ionosphere through the tether, resulting in a magnetic interaction with the terrestrial field. Since the Earth itself serves as the reaction mass, the thrust force is generated without propellant, and allows the MXER facility to be repeatedly reused without resupply. Essentially, the MXER facility is a `propellantless' upper stage that could assist nearly every mission going beyond low Earth orbit. Payloads to interplanetary destinations would especially benefit from the boost provided by the MXER facility, resulting in launch vehicle cost reductions, increased payload fractions, and more frequent mission opportunities. Some of the benefits to space exploration include: (1) Multi-use, in-space, `propellantless' infrastructure, (2) Useable by essentially all missions beyond LEO, (3) Lowers overall mission costs and/or enables larger payloads, (4) ``Panama Canal" of space transportation, (5) A spiral development for future generations, (6) Readily scales up or down, (7) Future transportation to and from Lunar surface.

  11. Evaluation of Power Conversion on Heavy Payload Tethered Hexarotors: A Strategic Approach

    Directory of Open Access Journals (Sweden)

    Wasantha Samarathunga

    2015-12-01

    Full Text Available This research article addresses the evaluation of power conversion on heavy payload tethered hexarotors where the payloads are high and hovering times are long. Modifications were added to the power conversion unit based on operation reliability perspective. Since the objective power conversion is large comparing to existing tethered UAVs today, a strategic engineering approach was proposed and tested based on partial observations on current spikes and power thresholds of DCDC switching regulators. Research problem is such that, when UAV motors are consuming low currents, the current spikes are not the plausible cause of direct power failure. But at higher currents even small current spikes could cause power failures. Risk increase with time and situations worsen when UAVs operate under high precision flight controls. When the number of parallel converters are small this becomes a mission critical problem. As a solution, fast switching high current diodes are used at the low voltage high current output to block reverse currents, and then apply low voltage bus bar to prevent dependency issues on particular DCDC module. At the cost of a small power dissipations over diodes, the total current thresholds of UAV become higher. Experiment results shows that with the use of proposed method large number of paralleling switching regulators become possible and heavy payload flights become reliable.

  12. Dynamics of an Electrodynamic Tether System in a Varying Space-Plasma Environment

    OpenAIRE

    Janeski, John

    2013-01-01

    Electrodynamic tethers have a wide range of proposed applications in the fields of satellite propulsion and space plasma research. The fundamental purpose of this dissertation is to improve the understanding of the behavior of an electrodynamic tether (EDT) system in Earth's ionosphere. An electrodynamic tether system consists of two satellites connected by a long tether that generates current to produce either power or thrust via the system's electromagnetic interaction with the space envir...

  13. Determination of single-bond association kinetics by tethered particle motion: concept and simulations

    OpenAIRE

    Merkus, Koen E.; Prins, Menno W. J.; Storm, Cornelis

    2016-01-01

    Tethered particle motion (TPM) --- the motion of a micro- or nanoparticle tethered to a substrate by a macromolecule --- is a system that has proven extremely useful for its ability to reveal physical features of the tether, because the thermal motion of the bound particle reports sensitively on parameters like the length, the rigidity, or the folding state of its tether. In this paper, we discuss a novel application of TPM, surveying its utility in probing the kinetics of single secondary bo...

  14. Dynamics of multi-tethered pyramidal satellite formation

    Science.gov (United States)

    Alary, D.; Andreev, K.; Boyko, P.; Ivanova, E.; Pritykin, D.; Sidorenko, V.; Tourneur, C.; Yarotsky, D.

    2015-12-01

    This paper is devoted to the dynamics of a multi-tethered pyramidal satellite formation rotating about its axis of symmetry in the nominal mode. Whereas the combination of rotation and gravity-gradient forces is insufficient to maintain the mutual positions of satellites, they are assumed to be equipped with low-thrust rocket engines. We propose a control strategy that allows the stabilization of the nominal spin state and demonstrate the system's proper operation by numerically simulating its controlled motion. The discussed multi-tethered formations could be employed, for example, to provide co-location of several satellites at a slot in geostationary orbit.

  15. Optimal Trajectories for Tethered Kite Mounted on a Vertical Axis Generator

    NARCIS (Netherlands)

    Williams, P.; Lansdorp, B.; Ockels, W.

    2007-01-01

    Tethered kite technology promises the enable the efficient extraction of energy from high altitude winds. One possible concept for converting the wind energy into electricity is to generate useful work at the ground by using a tether. The tether is able to drive a generator in one of two ways: eithe

  16. Nonlinear Control of Electrodynamic Tether in Equatorial or Somewhat Inclined Orbits

    DEFF Research Database (Denmark)

    Larsen, Martin Birkelund; Blanke, Mogens

    2007-01-01

    This paper applies different control design methods to a tethered satellite system (TSS) to investigate essential control properties of this under-actuated and nonlinear system. When the tether position in the orbit plane is controlled by the tether current, out of orbit plane motions occur as an...

  17. Immunogold labels: cell-surface markers in atomic force microscopy

    NARCIS (Netherlands)

    Putman, Constant A.J.; Grooth, de Bart G.; Hansma, Paul K.; Hulst, van Niek F.; Greve, Jan

    1993-01-01

    The feasibility of using immunogold labels as cell-surface markers in atomic force microscopy is shown in this paper. The atomic force microscope (AFM) was used to image the surface of immunogold-labeled human lymphocytes. The lymphocytes were isolated from whole blood and labeled by an indirect imm

  18. Dynamics and control of the tether elevator/crawler system

    Science.gov (United States)

    Lorenzini, E. C.; Cosmo, M.; Vetrella, S.; Moccia, A.

    1989-01-01

    This paper investigates the dynamics and acceleration levels of a new tethered system for micro- and variable-gravity applications. The system consists of two platforms tethered on opposite sides to the Space Station. A fourth platform, the elevator, is placed in between the Space Station and the upper platform. Variable-g levels on board the elevator are obtained by moving this facility along the upper tether, while microgravity experiments are carried out on board the Space Station. By controlling the length of the lower tether the position of the system center of mass can be maintained on board the Space Station despite variations of the system's distribution of mass. The paper illustrates the mathematical model, the environmental perturbations and the control techniques which have been adopted for the simulation and control of the system dynamics. Two sets of results from two different simulation runs are shown. The first set shows the system dynamics and the acceleration spectra on board the Space Station and the elevator during station-keeping. The second set of results demonstrates the capability of the elevator to attain a preselected g-level.

  19. Sounding rocket experiment of bare electrodynamic tether system

    OpenAIRE

    Fujii, Hironori; Watanabe, Takeo; Kojima, Hirohisa; Kusagaya, Tairo; Oyama, Koh-ichiro; Yamagiwa, Yoshiki; Ohtsu, Hirotaka; Cho, Mengu; Sasaki, Susumu; Tanaka, Koji; Williams, John; Rubin, Binyamin; Les Jhonson, Charles; Khazanov, George; Sanmartín Losada, Juan Ramón

    2009-01-01

    An overview of asounding rocket S-520-25th, project on space tether technology experiment is presented.The project is prepared by an international research group consisting of Japanese,European,American,andAustralianresearchers.The sounding rocket will be assembled by the ISAS/JAXA and will be launched in the summer of 2009.

  20. Sliding mode control of electromagnetic tethered satellite formation

    Science.gov (United States)

    Hallaj, Mohammad Amin Alandi; Assadian, Nima

    2016-08-01

    This paper investigates the control of tethered satellite formation actuated by electromagnetic dipoles and reaction wheels using the robust sliding mode control technique. Generating electromagnetic forces and moments by electric current coils provides an attractive control actuation alternative for tethered satellite system due to the advantages of no propellant consumption and no obligatory rotational motion. Based on a dumbbell model of tethered satellite in which the flexibility and mass of the tether is neglected, the equations of motion in Cartesian coordinate are derived. In this model, the J2 perturbation is taken into account. The far-field and mid-field models of electromagnetic forces and moments of two satellites on each other and the effect of the Earth's magnetic field are presented. A robust sliding mode controller is designed for precise trajectory tracking purposes and to deal with the electromagnetic force and moment uncertainties and external disturbances due to the Earth's gravitational and magnetic fields inaccuracy. Numerical simulation results are presented to validate the effectiveness of the developed controller and its superiority over the linear controller.

  1. Tether de-orbiting of satellites at end of mission

    Science.gov (United States)

    Sanmartin, Juan R.; Sánchez-Torres, Antonio

    2012-07-01

    The accumulation of space debris around the Earth has become critical for Space security. The BETs project, financed by the European Commission through its FP7-Space program, is focusing on preventing generation of new debris by de-orbiting satellites at end of mission. The de-orbiting system considered, involving an electrodynamic bare tape-tether, uses no propellant and no power supply, while generating power for on-board use during de-orbiting. As an example, preliminary results are here presented on a specific orbit/satellite case: 1300 km altitude and 65 degrees inclination, and 500 kg mass. Design tether dimensions are 8 km length, 1.5 cm width, and 0.05 mm thickness; subsystem masses are limited to twice tether mass. Simple calculations, using orbit-averaging, solar mid-cycle phase, and ionospheric and geomagnetic field models, yield 2.6 months time for de-orbiting down to 200 km, with a probability of about 1 percent of debris cutting the tape. References: Sanmartin, J.R., Lorenzini, E.C., and Martinez-Sanchez, M., Electrodynamic Tether Applications and Constraints, J. Space. Rockets 47, 442-456, 2010. Sanmartin, J.R. et al., A universal system to de-orbit satellites at end of life, Journal of Space Technology and Science, to appear.

  2. Position Control of an X4-Flyer Using a Tether

    Directory of Open Access Journals (Sweden)

    , Keigo Watanabe

    2014-10-01

    Full Text Available In Japan, aging of infrastructures, such as roads, bridges, and water and sewer services, etc. poses a problem, and it is required to extend the life-span of such infrastructures by maintenance. Among infrastructures, especially bridges are periodically inspected by short range visual observations, which check the damage and deterioration of the surface. However, since there are some cases where the short range visual observation is difficult, an alternative method is required so as to replace the short range visual observation with it. So, "X4-Flyer" is very attractive because of realizing a movement at high altitude easily. The objective of this study is to develop a tethered X4- Flyer, so that the conventional short range visual observation of bridges is replaced by it. In this paper, a method for the measurement and control of the position is described by using a tether for controlling the position of the X4-Flyer. In addition, it is checked whether the tethered X4-Flyer can control the position using the proposed method or not, letting it fly in a state in which a tether is being attached.

  3. Balloon Launched on Multiwall Carbon Nanotube Tether in Antarctica

    Czech Academy of Sciences Publication Activity Database

    Kletetschka, Günther; McKinney, E.; Kawasumiova, D.

    Cambridge: University of Cambridge, 2011. s. 1-1. [NT international Conference on the Science and Application of Nanotubes /11./. 10.07.2011-16.07.2011, Cambridge] Institutional research plan: CEZ:AV0Z30130516 Keywords : MWCNT * fibres * tether * strength * Antarctica Subject RIV: DB - Geology ; Mineralogy

  4. Hierarchical Structure in Semicrystalline Polymers Tethered to Nanospheres

    KAUST Repository

    Kim, Sung A

    2014-01-28

    We report on structural and dynamic transitions of polymers tethered to nanoparticles. In particular, we use X-ray diffraction, vibrational spectroscopy, and thermal measurements to investigate multiscale structure and dynamic transitions of poly(ethylene glycol) (PEG) chains densely grafted to SiO2 nanoparticles. The approach used for synthesizing these hybrid particles leads to homogeneous SiO2-PEG composites with polymer grafting densities as high as 1.5 chains/nm2, which allows the hybrid materials to exist as self-suspended suspensions with distinct hierarchical structure and thermal properties. On angstrom and nanometer length scales, the tethered PEG chains exhibit more dominant TTG conformations and helix unit cell structure, in comparison to the untethered polymer. The nanoparticle tethered PEG chains are also reported to form extended crystallites on tens of nanometers length scales and to exhibit more stable crystalline structure on small dimensions. On length scales comparable to the size of each hybrid SiO 2-PEG unit, the materials are amorphous presumably as a result of the difficulty fitting the nanoparticle anchors into the PEG crystal lattice. This structural change produces large effects on the thermal transitions of PEG molecules tethered to nanoparticles. © 2014 American Chemical Society.

  5. Fortissimo: A Japanese Space Test Of Bare Wire Anode Tethers

    Science.gov (United States)

    Johnson, Les; Fujii, H. A.; Sanmartin, J. R.

    2008-01-01

    A Japanese led international team is developing a suborbital test of orbital-motion-limited (OML) bare wire anode current collection for application to electrodynamic tether (EDT) propulsion. The tether is a tape with a width of 25 mm, thickness of 0.05 mm, and is 300 m in length. This will be the first space test of OML theory. The mission will launch in the summer of 2009 using an S520 Sounding Rocket. During ascent, and above approx. 100 km in attitude, the tape tether will be deployed at a rate of approx. 8 m/s. Once deployed, the tape tether will serve as an anode, collecting ionospheric electrons. The electrons will be expelled into space by a hollow cathode device, thereby completing the circuit and allowing current to flow. The total amount of current collected will be used to assess the validity of OML theory. This paper will describe the objectives of the proposed mission, the technologies to be employed, and the application of the results to future space missions using EDTs for propulsion or power generation.

  6. T-Rex: A Japanese Space Tether Experiment

    Science.gov (United States)

    Johnson, Les

    2009-01-01

    Electrodynamic tether (EDT) thrusters work by virtue of the force a magnetic field exerts on a wire carrying an electrical current. The force, which acts on any charged particle moving through a magnetic field (including the electrons moving in a current-carrying wire), were concisely expressed by Lorentz in 1895 in an equation that now bears his name. The force acts in a direction perpendicular to both the direction of current flow and the magnetic field vector. Electric motors make use of this force: a wire loop in a magnetic field is made to rotate by the torque the Lorentz Force exerts on it due to an alternating current in the loop times so as to keep the torque acting in the same sense. The motion of the loop is transmitted to a shaft, thus providing work. Although the working principle of EDT thrusters is not new, its application to space transportation may be significant. In essence, an EDT thruster is just a clever way of getting an electrical current to flow in a long orbiting wire (the tether) so that the Earth s magnetic field will accelerate the wire and, consequently the payload attached to the wire. The direction of current flow in the tether, either toward or away from the Earth along the local vertical, determines whether the magnetic force will raise or lower the orbit. The bias voltage of a vertically deployed metal tether, which results just from its orbital motion (assumed eastward) through Earth s magnetic field, is positive with respect to the ambient plasma at the top and negative at the bottom. This polarization is due to the action of the Lorentz force on the electrons in the tether. Thus, the natural current flow is the result of negative electrons being attracted to the upper end and then returned to the plasma at the lower end. The magnetic force in this case has a component opposite to the direction of motion, and thus leads to a lowering of the orbit and eventually to re-entry. In this generator mode of operation the Lorentz Force

  7. Modeling and Control of Electrodynamic Tethers - an Energy and Topology Approach

    OpenAIRE

    Larsen, Martin Birkelund; Blanke, Mogens

    2010-01-01

    A space tether is a cable used to connect spacecrafts in an orbiting structure. If an electrical current is lead through the tether, it can be utilized to provide propulsion for the spacecraft. In this case the cable is referred to as an electrodynamic tether. The system utilizes the magnetic field of the Earth for creating a Lorentz force along the tether which occur when a current carrying wire operates in a magnetic field. The use of electrodynamic tethers are interesting since they operat...

  8. Tethering of ferredoxin:NADP+ oxidoreductase to thylakoid membranes is mediated by novel chloroplast protein TROL.

    Science.gov (United States)

    Jurić, Snjezana; Hazler-Pilepić, Kroata; Tomasić, Ana; Lepedus, Hrvoje; Jelicić, Branka; Puthiyaveetil, Sujith; Bionda, Tihana; Vojta, Lea; Allen, John F; Schleiff, Enrico; Fulgosi, Hrvoje

    2009-12-01

    Working in tandem, two photosystems in the chloroplast thylakoid membranes produce a linear electron flow from H(2)O to NADP(+). Final electron transfer from ferredoxin to NADP(+) is accomplished by a flavoenzyme ferredoxin:NADP(+) oxidoreductase (FNR). Here we describe TROL (thylakoid rhodanese-like protein), a nuclear-encoded component of thylakoid membranes that is required for tethering of FNR and sustaining efficient linear electron flow (LEF) in vascular plants. TROL consists of two distinct modules; a centrally positioned rhodanese-like domain and a C-terminal hydrophobic FNR binding region. Analysis of Arabidopsis mutant lines indicates that, in the absence of TROL, relative electron transport rates at high-light intensities are severely lowered accompanied with significant increase in non-photochemical quenching (NPQ). Thus, TROL might represent a missing thylakoid membrane docking site for a complex between FNR, ferredoxin and NADP(+). Such association might be necessary for maintaining photosynthetic redox poise and enhancement of the NPQ. PMID:19682289

  9. Modelling a tethered mammalian sperm cell undergoing hyperactivation

    KAUST Repository

    Curtis, M.P.

    2012-09-01

    The beat patterns of mammalian sperm flagella can be categorised into two different types. The first involves symmetric waves propagating down the flagellum with a net linear propulsion of the sperm cell. The second, hyperactive, waveform is classified by vigorous asymmetric waves of higher amplitude, lower wavenumber and frequency propagating down the flagellum resulting in highly curved trajectories. The latter beat pattern is part of the capacitation process whereby sperm prepare for the prospective penetration of the zona pellucida and fusion with the egg. Hyperactivation is often observed to initiate as sperm escape from epithelial and ciliary bindings formed within the isthmic regions of the female oviducts, leading to a conjecture in the literature that this waveform is mechanically important for sperm escape. Hence, we explore the mechanical effects of hyperactivation on a tethered sperm, focussing on a Newtonian fluid. Using a resistive force theory model we demonstrate that hyperactivation can indeed generate forces that pull the sperm away from a tethering point and consequently a hyperactivated sperm cell bound to an epithelial surface need not always be pushed by its flagellum. More generally, directions of the forces generated by tethered flagella are insensitive to reductions in beat frequency and the detailed flagellar responses depend on the nature of the binding at the tethering point. Furthermore, waveform asymmetry and amplitude increases enhance the tendency for a tethered flagellum to start tugging on its binding. The same is generally predicted to be true for reductions in the wavenumber of the flagellum beat, but not universally so, emphasising the dynamical complexity of flagellar force generation. Finally, qualitative observations drawn from experimental data of human sperm bound to excised female reproductive tract are also presented and are found to be consistent with the theoretical predictions. © 2012 Elsevier Ltd.

  10. Relaxation Dynamics of Nanoparticle-Tethered Polymer Chains

    KAUST Repository

    Kim, Sung A

    2015-09-08

    © 2015 American Chemical Society. Relaxation dynamics of nanoparticle-tethered cis-1,4-polyisoprene (PI) are investigated using dielectric spectroscopy and rheometry. A model system composed of polymer chains densely grafted to spherical SiO2 nanoparticles to form self-suspended suspensions facilitates detailed studies of slow global chain and fast segmental mode dynamics under surface and geometrical confinement-from experiments performed in bulk materials. We report that unentangled polymer molecules tethered to nanoparticles relax far more slowly than their tethered entangled counterparts. Specifically, at fixed grafting density we find, counterintuitively, that increasing the tethered polymer molecular weight up to values close to the entanglement molecular weight speeds up chain relaxation dynamics. Decreasing the polymer grafting density for a fixed molecular weight has the opposite effect: it dramatically slows down chain relaxation, increases interchain coupling, and leads to a transition in rheological response from simple fluid behavior to viscoelastic fluid behavior for tethered PI chains that are unentangled by conventional measures. Increasing the measurement temperature produces an even stronger elastic response and speeds up molecular relaxation at a rate that decreases with grafting density and molecular weight. These observations are discussed in terms of chain confinement driven by crowding between particles and by the existence of an entropic attractive force produced by the space-filling constraint on individual chains in a self-suspended material. Our results indicate that the entropic force between densely grafted polymer molecules couples motions of individual chains in an analogous manner to reversible cross-links in associating polymers.

  11. Autonomous Vision-Based Tethered-Assisted Rover Docking

    Science.gov (United States)

    Tsai, Dorian; Nesnas, Issa A.D.; Zarzhitsky, Dimitri

    2013-01-01

    Many intriguing science discoveries on planetary surfaces, such as the seasonal flows on crater walls and skylight entrances to lava tubes, are at sites that are currently inaccessible to state-of-the-art rovers. The in situ exploration of such sites is likely to require a tethered platform both for mechanical support and for providing power and communication. Mother/daughter architectures have been investigated where a mother deploys a tethered daughter into extreme terrains. Deploying and retracting a tethered daughter requires undocking and re-docking of the daughter to the mother, with the latter being the challenging part. In this paper, we describe a vision-based tether-assisted algorithm for the autonomous re-docking of a daughter to its mother following an extreme terrain excursion. The algorithm uses fiducials mounted on the mother to improve the reliability and accuracy of estimating the pose of the mother relative to the daughter. The tether that is anchored by the mother helps the docking process and increases the system's tolerance to pose uncertainties by mechanically aligning the mating parts in the final docking phase. A preliminary version of the algorithm was developed and field-tested on the Axel rover in the JPL Mars Yard. The algorithm achieved an 80% success rate in 40 experiments in both firm and loose soils and starting from up to 6 m away at up to 40 deg radial angle and 20 deg relative heading. The algorithm does not rely on an initial estimate of the relative pose. The preliminary results are promising and help retire the risk associated with the autonomous docking process enabling consideration in future martian and lunar missions.

  12. Determination of single-bond association kinetics by tethered particle motion: concept and simulations

    CERN Document Server

    Merkus, Koen E; Storm, Cornelis

    2016-01-01

    Tethered particle motion (TPM) --- the motion of a micro- or nanoparticle tethered to a substrate by a macromolecule --- is a system that has proven extremely useful for its ability to reveal physical features of the tether, because the thermal motion of the bound particle reports sensitively on parameters like the length, the rigidity, or the folding state of its tether. In this paper, we discuss a novel application of TPM, surveying its utility in probing the kinetics of single secondary bonds: bonds that form and break between the tethered particle and a substrate due, for instance, to receptor/ligand pairs on particle and substrate. Much like the tether itself affects the motion pattern, so do the presence and absence of such secondary connections. Keeping the tether properties constant, we demonstrate how raw positional TPM data may be parsed to generate detailed insights into the association and dissociation kinetics of single secondary bonds. We do this using coarse-grained molecular dynamics simulatio...

  13. SPHERES tethered formation flight testbed: advancements in enabling NASA's SPECS mission

    Science.gov (United States)

    Chung, Soon-Jo; Adams, Danielle; Saenz-Otero, Alvar; Kong, Edmund; Miller, David W.; Leisawitz, David; Lorenzini, Enrico; Sell, Steve

    2006-06-01

    This paper reports on efforts to control a tethered formation flight spacecraft array for NASA's SPECS mission using the SPHERES test-bed developed by the MIT Space Systems Laboratory. Specifically, advances in methodology and experimental results realized since the 2005 SPIE paper are emphasized. These include a new test-bed setup with a reaction wheel assembly, a novel relative attitude measurement system using force torque sensors, and modeling of non-ideal tethers to account for tether vibration modes. The nonlinear equations of motion of multi-vehicle tethered spacecraft with elastic flexible tethers are derived from Lagrange's equations. The controllability analysis indicates that both array resizing and spin-up are fully controllable by the reaction wheels and the tether motor, thereby saving thruster fuel consumption. Based upon this analysis, linear and nonlinear controllers have been successfully implemented on the tethered SPHERES testbed, and tested at the NASA MSFC's flat floor facility using two and three SPHERES configurations.

  14. Cell surface recycling in yeast: mechanisms and machineries.

    Science.gov (United States)

    MacDonald, Chris; Piper, Robert C

    2016-04-15

    Sorting internalized proteins and lipids back to the cell surface controls the supply of molecules throughout the cell and regulates integral membrane protein activity at the surface. One central process in mammalian cells is the transit of cargo from endosomes back to the plasma membrane (PM) directly, along a route that bypasses retrograde movement to the Golgi. Despite recognition of this pathway for decades we are only beginning to understand the machinery controlling this overall process. The budding yeastSaccharomyces cerevisiae, a stalwart genetic system, has been routinely used to identify fundamental proteins and their modes of action in conserved trafficking pathways. However, the study of cell surface recycling from endosomes in yeast is hampered by difficulties that obscure visualization of the pathway. Here we briefly discuss how recycling is likely a more prevalent process in yeast than is widely appreciated and how tools might be built to better study the pathway. PMID:27068957

  15. Human Papillomavirus Infection Requires Cell Surface Heparan Sulfate

    OpenAIRE

    Giroglou, Tzenan; Florin, Luise; Schäfer, Frank; Streeck, Rolf E.; Sapp, Martin

    2001-01-01

    Using pseudoinfection of cell lines, we demonstrate that cell surface heparan sulfate is required for infection by human papillomavirus type 16 (HPV-16) and HPV-33 pseudovirions. Pseudoinfection was inhibited by heparin but not dermatan or chondroitin sulfate, reduced by reducing the level of surface sulfation, and abolished by heparinase treatment. Carboxy-terminally deleted HPV-33 virus-like particles still bound efficiently to heparin. The kinetics of postattachment neutralization by antis...

  16. Immunogold labels: cell-surface markers in atomic force microscopy

    OpenAIRE

    Putman, Constant A.J.; Grooth, de, B.G.; Hansma, Paul K.; Hulst, van der, R.W.M.; Greve, Jan

    1993-01-01

    The feasibility of using immunogold labels as cell-surface markers in atomic force microscopy is shown in this paper. The atomic force microscope (AFM) was used to image the surface of immunogold-labeled human lymphocytes. The lymphocytes were isolated from whole blood and labeled by an indirect immunolabeling method using the monoclonal antibody anti-CD3 and a secondary antibody (Goat-anti-Mouse) linked to 30 nm colloidal gold particles. Some of the samples were enhanced by silver deposition...

  17. Tether-mission design for multiple flybys of moon Europa

    Science.gov (United States)

    Sanmartin, J. R. S.; Charro, M. C.; Sanchez-Arriaga, G. S. A.; Sanchez-Torres, A. S. T.

    2015-10-01

    A tether mission to carry out multiple flybys of Jovian moon Europa is here presented. There is general agreement on elliptic-orbit flybys of Europa resulting in cost to attain given scientific goals lower than if actually orbiting the moon, tethers being naturally fit to fly-by rather than orbit moons1. The present mission is similar in this respect to the Clipper mission considered by NASA, the basic difference lying in location of periapsis, due to different emphasis on mission-challenge metrics. Clipper minimizes damaging radiation-dose by avoiding the Jupiter neighborhood and its very harsh environment; periapsis would be at Europa, apoapsis as far as moon Callisto. As in all past outer-planet missions, Clipper faces, however, critical power and propulsion needs. On the other hand, tethers can provide both propulsion and power, but must reach near the planet to find high plasma density and magnetic field values, leading to high induced tether current, and Lorentz drag and power. The bottom line is a strong radiation dose under the very intense Radiation Belts of Jupiter. Mission design focuses on limiting dose. Perijove would be near Jupiter, at about 1.2-1.3 Jovian radius, apojove about moon Ganymede, corresponding to 1:1 resonance with Europa, so as to keep dose down: setting apojove at Europa, for convenient parallel flybys, would require two perijove passes per flyby (the Ganymede apojove, resulting in high eccentricity, about 0.86, is also less requiring on tether operations). Mission is designed to attain reductions in eccentricity per perijove pass as high as Δe ≈ - 0.04. Due the low gravity-gradient, tether spinning is necessary to keep it straight, plasma contactors placed at both ends taking active turns at being cathodic. Efficiency of capture of the incoming S/C by the tether is gauged by the ratio of S/C mass to tether mass; efficiency is higher for higher tape-tether length and lower thickness and perijove. Low tether bowing due to the Lorentz

  18. Cargo binding promotes KDEL receptor clustering at the mammalian cell surface

    Science.gov (United States)

    Becker, Björn; Shaebani, M. Reza; Rammo, Domenik; Bubel, Tobias; Santen, Ludger; Schmitt, Manfred J.

    2016-01-01

    Transmembrane receptor clustering is a ubiquitous phenomenon in pro- and eukaryotic cells to physically sense receptor/ligand interactions and subsequently translate an exogenous signal into a cellular response. Despite that receptor cluster formation has been described for a wide variety of receptors, ranging from chemotactic receptors in bacteria to growth factor and neurotransmitter receptors in mammalian cells, a mechanistic understanding of the underlying molecular processes is still puzzling. In an attempt to fill this gap we followed a combined experimental and theoretical approach by dissecting and modulating cargo binding, internalization and cellular response mediated by KDEL receptors (KDELRs) at the mammalian cell surface after interaction with a model cargo/ligand. Using a fluorescent variant of ricin toxin A chain as KDELR-ligand (eGFP-RTAH/KDEL), we demonstrate that cargo binding induces dose-dependent receptor cluster formation at and subsequent internalization from the membrane which is associated and counteracted by anterograde and microtubule-assisted receptor transport to preferred docking sites at the plasma membrane. By means of analytical arguments and extensive numerical simulations we show that cargo-synchronized receptor transport from and to the membrane is causative for KDELR/cargo cluster formation at the mammalian cell surface. PMID:27353000

  19. Interaction of KSHV with Host Cell Surface Receptors and Cell Entry

    Directory of Open Access Journals (Sweden)

    Mohanan Valiya Veettil

    2014-10-01

    Full Text Available Virus entry is a complex process characterized by a sequence of events. Since the discovery of KSHV in 1994, tremendous progress has been made in our understanding of KSHV entry into its in vitro target cells. KSHV entry is a complex multistep process involving viral envelope glycoproteins and several cell surface molecules that is utilized by KSHV for its attachment and entry. KSHV has a broad cell tropism and the attachment and receptor engagement on target cells have an important role in determining the cell type-specific mode of entry. KSHV utilizes heparan sulfate, integrins and EphrinA2 molecules as receptors which results in the activation of host cell pre-existing signal pathways that facilitate the subsequent cascade of events resulting in the rapid entry of virus particles, trafficking towards the nucleus followed by viral and host gene expression. KSHV enters human fibroblast cells by dynamin dependant clathrin mediated endocytosis and by dynamin independent macropinocytosis in dermal endothelial cells. Once internalized into endosomes, fusion of the viral envelope with the endosomal membranes in an acidification dependent manner results in the release of capsids which subsequently reaches the nuclear pore vicinity leading to the delivery of viral DNA into the nucleus. In this review, we discuss the principal mechanisms that enable KSHV to interact with the host cell surface receptors as well as the mechanisms that are required to modulate cell signaling machinery for a successful entry.

  20. Establishment of cell surface engineering and its development.

    Science.gov (United States)

    Ueda, Mitsuyoshi

    2016-07-01

    Cell surface display of proteins/peptides has been established based on mechanisms of localizing proteins to the cell surface. In contrast to conventional intracellular and extracellular (secretion) expression systems, this method, generally called an arming technology, is particularly effective when using yeasts as a host, because the control of protein folding that is often required for the preparation of proteins can be natural. This technology can be employed for basic and applied research purposes. In this review, I describe various strategies for the construction of engineered yeasts and provide an outline of the diverse applications of this technology to industrial processes such as the production of biofuels and chemicals, as well as bioremediation and health-related processes. Furthermore, this technology is suitable for novel protein engineering and directed evolution through high-throughput screening, because proteins/peptides displayed on the cell surface can be directly analyzed using intact cells without concentration and purification. Functional proteins/peptides with improved or novel functions can be created using this beneficial, powerful, and promising technique. PMID:27305282

  1. Ancestral vascular lumen formation via basal cell surfaces.

    Directory of Open Access Journals (Sweden)

    Tomás Kucera

    Full Text Available The cardiovascular system of bilaterians developed from a common ancestor. However, no endothelial cells exist in invertebrates demonstrating that primitive cardiovascular tubes do not require this vertebrate-specific cell type in order to form. This raises the question of how cardiovascular tubes form in invertebrates? Here we discovered that in the invertebrate cephalochordate amphioxus, the basement membranes of endoderm and mesoderm line the lumen of the major vessels, namely aorta and heart. During amphioxus development a laminin-containing extracellular matrix (ECM was found to fill the space between the basal cell surfaces of endoderm and mesoderm along their anterior-posterior (A-P axes. Blood cells appear in this ECM-filled tubular space, coincident with the development of a vascular lumen. To get insight into the underlying cellular mechanism, we induced vessels in vitro with a cell polarity similar to the vessels of amphioxus. We show that basal cell surfaces can form a vascular lumen filled with ECM, and that phagocytotic blood cells can clear this luminal ECM to generate a patent vascular lumen. Therefore, our experiments suggest a mechanism of blood vessel formation via basal cell surfaces in amphioxus and possibly in other invertebrates that do not have any endothelial cells. In addition, a comparison between amphioxus and mouse shows that endothelial cells physically separate the basement membranes from the vascular lumen, suggesting that endothelial cells create cardiovascular tubes with a cell polarity of epithelial tubes in vertebrates and mammals.

  2. Structure of a Bacterial Cell Surface Decaheme Electron Conduit

    Energy Technology Data Exchange (ETDEWEB)

    Clarke, Thomas A.; Edwards, Marcus; Gates, Andrew J.; Hall, Andrea; White, Gaye; Bradley, Justin; Reardon, Catherine L.; Shi, Liang; Beliaev, Alex S.; Marshall, Matthew J.; Wang, Zheming; Watmough, Nicholas; Fredrickson, Jim K.; Zachara, John M.; Butt, Julea N.; Richardson, David J.

    2011-05-23

    Some bacterial species are able to utilize extracellular mineral forms of iron and manganese as respiratory electron acceptors. In Shewanella oneidensis this involves deca-heme cytochromes that are located on the bacterial cell surface at the termini of trans-outermembrane (OM) electron transfer conduits. The cell surface cytochromes can potentially play multiple roles in mediating electron transfer directly to insoluble electron sinks, catalyzing electron exchange with flavin electron shuttles or participating in extracellular inter-cytochrome electron exchange along ‘nanowire’ appendages. We present a 3.2 Å crystal structure of one of these deca-heme cytochromes, MtrF, that allows the spatial organization of the ten hemes to be visualized for the first time. The hemes are organized across four domains in a unique crossed conformation, in which a staggered 65 Å octa-heme chain transects the length of the protein and is bisected by a planar 45 Å tetra-heme chain that connects two extended Greek key split β-barrel domains. The structure provides molecular insight into how reduction of insoluble substrate (e.g. minerals), soluble substrates (e.g. flavins) and cytochrome redox partners might be possible in tandem at different termini of a trifurcated electron transport chain on the cell surface.

  3. Engineering novel cell surface chemistry for selective tumor cell targeting

    Energy Technology Data Exchange (ETDEWEB)

    Bertozzi, C.R. [Univ. of California, Berkeley, CA (United States)]|[Lawrence Berkeley National Lab., CA (United States)

    1997-12-31

    A common feature of many different cancers is the high expression level of the two monosaccharides sialic acid and fucose within the context of cell-surface associated glycoconjugates. A correlation has been made between hypersialylation and/or hyperfucosylation and the highly metastatic phenotype. Thus, a targeting strategy based on sialic acid or fucose expression would be a powerful tool for the development of new cancer cell-selective therapies and diagnostic agents. We have discovered that ketone groups can be incorporated metabolically into cell-surface associated sialic acids. The ketone is can be covalently ligated with hydrazide functionalized proteins or small molecules under physiological conditions. Thus, we have discovered a mechanism to selectively target hydrazide conjugates to highly sialylated cells such as cancer cells. Applications of this technology to the generation of novel cancer cell-selective toxins and MRI contrast reagents will be discussed, in addition to progress towards the use of cell surface fucose residues as vehicles for ketone expression.

  4. Preliminary Orbit Determination of a Tethered Satellite Using the p-Iteration Method

    Science.gov (United States)

    Cicci, D. A.; Qualls, C.

    2016-04-01

    The possibility of the future deployment of tethered satellites has created a need for a preliminary orbit determination method capable of determining whether or not a satellite is tethered to another satellite. Classical preliminary orbit determination methods, which are used for untethered satellites, typically require two or more position vectors along with their respective observation times in order to determine a preliminary orbital element set. However, these conventional methods can't distinguish between an untethered satellite and a tethered one, whose motion is modified due to the presence of a tether force. The use of conventional methods on a satellite which is part of a tethered satellite system will result in the calculation of inaccurate orbital elements. Modifications have been made to the p-iteration preliminary orbit determination method in order to allow for the identification of these tethered satellites. The modifications allow for the calculation of a modified gravitational parameter, which can be used to distinguish between a tethered satellite and an untethered one. This paper applies this modified p-iteration method to the problem of the quick identification of a tethered satellite. The performance of this method is evaluated through scenarios of differing tether lengths, levels of observation error, and orbital eccentricities. Due to the need for the preliminary orbit determination to be achieved quickly, only short time intervals between observations were considered. The manner in which this preliminary orbit information can be used to obtain tether parameters for the subsequent differential correction process is also described.

  5. Advances in dynamics and control of tethered satellite systems

    Institute of Scientific and Technical Information of China (English)

    Hao Wen; Dongping P. Jin; Haiyan Y. Hu

    2008-01-01

    The concept of tethered satellite system (TSS) promises to revolutionize many aspects of space exploration and exploitation. It provides not only numerous possible and valuable applications, but also challenging and interesting problems related to their dynamics, control, and physical implementation. Over the past decades, this exciting topic has attracted significant attention from many researchers and gained a vast number of analytical, numerical and experimental achievements with a focus on the two essential aspects of both dynamics and control. This review article presents the historic background and recent hot topics for the space tethers, and introduces the dynamics and control of TSSs in a progressive manner, from basic operating principles to the state-of-the-art achievements.

  6. Tethered elevator: A unique opportunity for space processing

    Science.gov (United States)

    Monti, R.

    1986-01-01

    The latest fluid dynamic and material science experiments in the microgravity environment have emphasized the importance of the residual gravity level and of the g-jitter on fluid physics phenomena. The tethered elevator presents the possibility of providing variable g-levels (both steady and g-jitter) around a very low steady g-level (that can be realized when the elevator is near the center of mass of the space station-tether complex). When positioning a variable periodic oscillation to the payload a clean g-jitter disturbance can be obtained that would not be otherwise obtainable by other systems. These two possibilities make the elevator a facility to help resolve a number of still open questions that are preventing wider utilization of the space environment in the microgravity area.

  7. Electrodynamic tethers for exploration of jupiter and its icy moons

    OpenAIRE

    Sanmartín Losada, Juan Ramón

    2006-01-01

    Use of electrodynamic bare tethers in exploring the Jovian system by tapping its rotational energy for power and propulsion is studied. The position of perijove and apojove in elliptical orbits, relative to the synchronous orbit at 2.24 times Jupiter’s radius, is exploited to conveniently make the induced Lorentz force to be drag or thrust, while generating power, and navigating the system. Capture and evolution to a low elliptical orbit near Jupiter, and capture into low circular orbits at m...

  8. Chemical tethering of motile bacteria to silicon surfaces

    OpenAIRE

    Bearinger, Jane P.; Dugan, Lawrence C.; Wu, Ligang; Hill, Haley; Christian, Allen T.; Hubbell, Jeffrey A.

    2009-01-01

    We chemically immobilized live, motile Escherichia coli on micrometer-scale, photocatalytically patterned silicon surfaces via amine- and carboxylic acid–based chemistries. Immobilization facilitated (i) controlled positioning; (ii) high resolution cell wall imaging via atomic force microscopy (AFM); and (iii) chemical analysis with time-of-flight-secondary ion mass spectrometry (ToF-SIMS). Spinning motion of tethered bacteria, captured with fast-acquisition video, proved microbe viability. W...

  9. Effect of Chromosome Tethering on Nuclear Organization in Yeast

    OpenAIRE

    Avşaroğlu, Barış; Bronk, Gabriel; Gordon-Messer, Susannah; Ham, Jungoh; Bressan, Debra A.; Haber, James E; Kondev, Jane

    2014-01-01

    Interphase chromosomes in Saccharomyces cerevisiae are tethered to the nuclear envelope at their telomeres and to the spindle pole body (SPB) at their centromeres. Using a polymer model of yeast chromosomes that includes these interactions, we show theoretically that telomere attachment to the nuclear envelope is a major determinant of gene positioning within the nucleus only for genes within 10 kb of the telomeres. We test this prediction by measuring the distance between the SPB and the sil...

  10. Crowded, Confined, and Frustrated: Dynamics of Molecules Tethered to Nanoparticles

    KAUST Repository

    Agarwal, Praveen

    2012-12-01

    Above a critical chemistry-dependent molecular weight, all polymer molecules entangle and, as a result, exhibit slow dynamics, enhanced viscosity, and elasticity. Herein we report on the dynamics of low molecular weight polymers tethered to nanoparticles and find that even conventionally unentangled chains manifest dynamical features similar to entangled, long-chain molecules. Our findings are shown to imply that crowding and confinement of polymers on particles produce topological constraints analogous to those in entangled systems. © 2012 American Physical Society.

  11. Investigation of force approximations in tethered cells simulations

    CERN Document Server

    Zakrisson, Johan; Axner, Ove; Andersson, Magnus

    2015-01-01

    Simulations of tethered cells in viscous sub-layers are frequently performed using the Stokes drag force, but without taking into account contributions from surface corrections, lift forces, buoyancy, the Basset force, the cells finite inertia, or added mass. In this work, we investigate to which extent such contributions influence, under a variety of hydrodynamic conditions, the force at the anchor point of a tethered cell and the survival probability of a bacterium that is attached to a host by either a slip or a catch bond via a tether with a few different biomechanical properties. We show that a consequence of not including some of these contributions is that the force to which a bond is exposed can be significantly underestimated; in general by ~32-46 %, where the influence of the surface corrections dominate (the parallel and normal correction coefficients contribute with ~5-8 or 23-26 %, respectively). The Basset force is a major contributor, up to 20 %, for larger cells and shear rates. The lift force...

  12. Surfactant mediated morphological tethering of Cu2O nanoparticles

    International Nuclear Information System (INIS)

    This communication describes a very simple and reproducible methodology to study the self-assembly of nanoparticles functionalized with a non-ionic tethering agent attached to the surface of the nanoparticle seeds. The synthesis starts with the [Cu(OH)4]2− species acting as a template, with varying concentration of the tethering agent Triton X-100 (TX100). The morphological alteration is systematically investigated. The effect of surfactant micelles, growth reaction time, and solution temperature has a tremendous impact on the morphology of the nanocrystals that govern the controlled synthesis of different shapes of nanostructures. The initial morphology of the nanocrystals is polyhedron in the absence of a tethering additive. The addition of TX100 suppresses the polymorph phase morphology and enhances the non-uniform spherical morphology of the nanocrystals. The surface modification effect enhances the morphological alteration, which potentially makes it applicable to various industrial uses such as water cleaning, hydrogen production, and third-generation solar cells. (paper)

  13. Evaluation of Relative Yeast Cell Surface Hydrophobicity Measured by Flow Cytometry

    Directory of Open Access Journals (Sweden)

    Lisa Colling

    2005-01-01

    Full Text Available Objective: To develop an efficient method for evaluating cell surface hydrophobicity and to apply the method to demonstrate the effects of fungal growth conditions on cell surface properties.

  14. Identification of astrocytoma associated genes including cell surface markers

    International Nuclear Information System (INIS)

    Despite intense effort the treatment options for the invasive astrocytic tumors are still limited to surgery and radiation therapy, with chemotherapy showing little or no increase in survival. The generation of Serial Analysis of Gene Expression (SAGE) profiles is expected to aid in the identification of astrocytoma-associated genes and highly expressed cell surface genes as molecular therapeutic targets. SAGE tag counts can be easily added to public expression databases and quickly disseminated to research efforts worldwide. We generated and analyzed the SAGE transcription profiles of 25 primary grade II, III and IV astrocytomas [1]. These profiles were produced as part of the Cancer Genome Anatomy Project's SAGE Genie [2], and were used in an in silico search for candidate therapeutic targets by comparing astrocytoma to normal brain transcription. Real-time PCR and immunohistochemistry were used for the validation of selected candidate target genes in 2 independent sets of primary tumors. A restricted set of tumor-associated genes was identified for each grade that included genes not previously associated with astrocytomas (e.g. VCAM1, SMOC1, and thymidylate synthetase), with a high percentage of cell surface genes. Two genes with available antibodies, Aquaporin 1 and Topoisomerase 2A, showed protein expression consistent with transcript level predictions. This survey of transcription in malignant and normal brain tissues reveals a small subset of human genes that are activated in malignant astrocytomas. In addition to providing insights into pathway biology, we have revealed and quantified expression for a significant portion of cell surface and extra-cellular astrocytoma genes

  15. Identification of astrocytoma associated genes including cell surface markers

    Directory of Open Access Journals (Sweden)

    Eberhart Charles G

    2004-07-01

    Full Text Available Abstract Background Despite intense effort the treatment options for the invasive astrocytic tumors are still limited to surgery and radiation therapy, with chemotherapy showing little or no increase in survival. The generation of Serial Analysis of Gene Expression (SAGE profiles is expected to aid in the identification of astrocytoma-associated genes and highly expressed cell surface genes as molecular therapeutic targets. SAGE tag counts can be easily added to public expression databases and quickly disseminated to research efforts worldwide. Methods We generated and analyzed the SAGE transcription profiles of 25 primary grade II, III and IV astrocytomas 1. These profiles were produced as part of the Cancer Genome Anatomy Project's SAGE Genie 2, and were used in an in silico search for candidate therapeutic targets by comparing astrocytoma to normal brain transcription. Real-time PCR and immunohistochemistry were used for the validation of selected candidate target genes in 2 independent sets of primary tumors. Results A restricted set of tumor-associated genes was identified for each grade that included genes not previously associated with astrocytomas (e.g. VCAM1, SMOC1, and thymidylate synthetase, with a high percentage of cell surface genes. Two genes with available antibodies, Aquaporin 1 and Topoisomerase 2A, showed protein expression consistent with transcript level predictions. Conclusions This survey of transcription in malignant and normal brain tissues reveals a small subset of human genes that are activated in malignant astrocytomas. In addition to providing insights into pathway biology, we have revealed and quantified expression for a significant portion of cell surface and extra-cellular astrocytoma genes.

  16. The cell-surface proteome of cultured adipose stromal cells.

    Science.gov (United States)

    Donnenberg, Albert D; Meyer, E Michael; Rubin, J Peter; Donnenberg, Vera S

    2015-07-01

    In this technical note we describe a method to evaluate the cell surface proteome of human primary cell cultures and cell lines. The method utilizes the BD Biosciences lyoplate, a system covering 242 surface proteins, glycoproteins, and glycosphingolipids plus relevant isotype controls, automated plate-based flow cytometry, conventional file-level analysis and unsupervised K-means clustering of markers on the basis of percent of positive events and mean fluorescence intensity of positive and total clean events. As an example, we determined the cell surface proteome of cultured adipose stromal cells (ASC) derived from 5 independent clinical isolates. Between-sample agreement of very strongly expressed (n = 32) and strongly expressed (n =16) markers was excellent, constituting a reliable profile for ASC identification and determination of functional properties. Known mesenchymal markers (CD29, CD44, CD73, CD90, CD105) were among the identified strongly expressed determinants. Among other strongly expressed markers are several that are potentially immunomodulatory including three proteins that protect from complement mediated effects (CD46, CD55, and CD59), two that regulate apoptosis (CD77 and CD95) and several with ectoenzymatic (CD10, CD26, CD13, CD73, and CD143) or receptor tyrosine kinase (CD140b (PDGFR), CD340 (Her-2), EGFR) activity, suggesting mechanisms for the anti-inflammatory and tissue remodeling properties of ASC. Because variables are standardized for K-means clustering, results generated using this methodology should be comparable between instrumentation platforms. It is widely generalizable to human primary explant cultures and cells lines and will prove useful to determine how cell passage, culture interventions, and gene expression and silencing affect the cell-surface proteome. PMID:25929697

  17. Remote Control of Tissue Interactions via Engineered Photo-switchable Cell Surfaces

    OpenAIRE

    Wei Luo; Abigail Pulsipher; Debjit Dutta; Lamb, Brian M.; Yousaf, Muhammad N.

    2014-01-01

    We report a general cell surface molecular engineering strategy via liposome fusion delivery to create a dual photo-active and bio-orthogonal cell surface for remote controlled spatial and temporal manipulation of microtissue assembly and disassembly. Cell surface tailoring of chemoselective functional groups was achieved by a liposome fusion delivery method and quantified by flow cytometry and characterized by a new cell surface lipid pull down mass spectrometry strategy. Dynamic co-culture ...

  18. The cell surface organisation of the Notch-1 receptor

    OpenAIRE

    Weisshuhn, Philip Christian; Handford, PA; Redfield, C.

    2014-01-01

    The Notch receptor family plays a key role in development and disease. In cancer, Notch can act either as an oncogene or as a tumour suppressor, and possibly as a cancer stem-cell factor. Whereas most research has focused on downstream signalling events, little is known about the cell surface organisation of Notch and its ligands. The extracellular part of Notch consists mainly of 36 epidermal growth factor-like domains (EGF-domains), many of which bind calcium. Studies have shown that tandem...

  19. Method of Deployment of a Space Tethered System Aligned to the Local Vertical

    Science.gov (United States)

    Zakrzhevskii, A. E.

    2016-04-01

    The object of this research is a space tether of two bodies connected by a flexible massless string. The research objective is the development and theoretical justification of a novel approach to the solution of the problem of deployment of the space tether in a circular orbit with its alignment to the local vertical. The approach is based on use of the theorem on the angular momentum change. It allows developing the open-loop control of the tether length that provides desired change of the angular momentum of the tether under the effect of the gravitational torque to the value, which corresponds to the angular momentum of the deployed tether aligned to the local vertical. The given example of application of the approach to a case of deployment of a tether demonstrates the simplicity of use of the method in practice, and also the method of validation of the mathematical model.

  20. Modeling of induced currents from electrodynamic tethers in a laboratory plasma

    Science.gov (United States)

    Urrutia, J. M.; Stenzel, R. L.

    1990-01-01

    The presently accepted picture of the current path for electrodynamic tethers envisions a quasi-dc current flow in a 'phantom loop' consisting of the tether, two field-aligned current channels into the ionosphere and a cross-field closing current in the E-layer. Predictions are made on the establishment and maintenance of a current loop in space based on observations of time-dependent currents between tethered electrodes in a large laboratory magnetoplasma. In addition to radiation from the contactors ('whistler wings'), the insulated tether is observed to emit waves (a 'whistler wedge'). The 'wedge' provides closure during loop formation by carrying cross-field polarization currents. Whistler spread within the ray cone leads to overlapping of the current wings not far from the tether hence minimizing the role of the ionospheric closure. Maintenance of the loop requires the continuous emission of whistler waves by the entire tether thereby providing severe radiation losses.

  1. Membrane tether formation from voltage-clamped outer hair cells using optical tweezers

    Science.gov (United States)

    Qian, Feng; Ermilov, Sergey A.; Murdock, David R.; Brownell, William E.; Anvari, Bahman

    2004-06-01

    Outer hair cells contribute an active mechanical feedback to the vibrations of the cochlear structures resulting in the high sensitivity and frequency selectivity of normal hearing. We have designed and implemented a novel experimental setup that combines optical tweezers with patch-clamp apparatus to investigate the electromechanical properties of cellular plasma membranes. A micron-size bead trapped by the optical tweezers is brought in contact with the membrane of a voltage-clamped cell, and subsequently moved away to form a plasma membrane tether. Bead displacement during tether elongation is monitored by a quadrant photodetector to obtain time-resolved measurements of the tethering force. Salient information associated with the mechanical properties of the membrane tether can thus be obtained. Tethers can be pulled from the cell membrane at different holding potentials, and the tether force response can be measured while changing transmembrane potential. Experimental results from outer hair cells and human embryonic kidney cells are presented.

  2. Dynamics of a Tether System Connected to an Irregularly Shaped Celestial Body

    Science.gov (United States)

    Jalali Mashayekhi, Mohammad; K. Misra, Arun; Keshmiri, Mehdi

    2016-04-01

    The problem of pendular oscillations of a tether attached to an irregularly shaped celestial body is studied in this paper. The dynamic analysis of the system is performed by examining the phase plane trajectories. The effect of the tether length as well as the higher order terms in the gravitational potential of the celestial body on the tether dynamics is investigated. It is demonstrated that consideration of the finite size of the celestial body can have significant effects on the tether dynamics, while the effect of the asphericity of the celestial body on the tether dynamics is negligible. This study is of practical relevance for asteroid deflection using tethers, as well as for the development of space elevators on small planets/moons.

  3. Biomimicry Enhances Sequential Reactions of Tethered Glycolytic Enzymes, TPI and GAPDHS

    OpenAIRE

    Mukai, Chinatsu; Gao, Lizeng; Bergkvist, Magnus; Nelson, Jacquelyn L.; Hinchman, Meleana M.; Travis, Alexander J.

    2013-01-01

    Maintaining activity of enzymes tethered to solid interfaces remains a major challenge in developing hybrid organic-inorganic devices. In nature, mammalian spermatozoa have overcome this design challenge by having glycolytic enzymes with specialized targeting domains that enable them to function while tethered to a cytoskeletal element. As a step toward designing a hybrid organic-inorganic ATP-generating system, we implemented a biomimetic site-specific immobilization strategy to tether two g...

  4. Interaction of the Betapapillomavirus E2 Tethering Protein with Mitotic Chromosomes▿

    OpenAIRE

    Sekhar, Vandana; Reed, Shawna C.; Alison A McBride

    2009-01-01

    During persistent papillomavirus infection, the viral E2 protein tethers the viral genome to the host cell chromosomes, ensuring maintenance and segregation of the viral genome during cell division. However, E2 proteins from different papillomaviruses interact with distinct chromosomal regions and targets. The tethering mechanism has been best characterized for bovine papillomavirus type 1 (BPV1), where the E2 protein tethers the viral genome to mitotic chromosomes in complex with the cellula...

  5. Nonlinear Control of Electrodynamic Tether in Equatorial or Somewhat Inclined Orbits

    OpenAIRE

    Larsen, Martin Birkelund; Blanke, Mogens

    2007-01-01

    This paper applies different control design methods to a tethered satellite system (TSS) to investigate essential control properties of this under-actuated and nonlinear system. When the tether position in the orbit plane is controlled by the tether current, out of orbit plane motions occur as an unwanted side effect, due to nonlinear interaction with the Earth’s magnetic field. This paper focus on the uncontrollable out-of-plane motions and the robustness against B-field uncertainty associat...

  6. Complex crystal structures formed by the self assembly of di-tethered nanospheres

    OpenAIRE

    Iacovella, Christopher R.; Glotzer, Sharon C.

    2009-01-01

    We report the results from a computational study of the self-assembly of amphiphilic di-tethered nanospheres using molecular simulation. As a function of the interaction strength and directionality of the tether-tether interactions, we predict the formation of four highly ordered phases not previously reported for nanoparticle systems. We find a double diamond structure comprised of a zincblende (binary diamond) arrangement of spherical micelles with a complementary diamond network of nanopar...

  7. Semiquantitative determination of circulating islet cell surface antibodies in diabetes

    International Nuclear Information System (INIS)

    Circulating pancreatic islet cell antibodies have been demonstrated in patients with insulin-dependent diabetes (IDD). The islet cell surface antibodies (ICSA) were determined by an indirect immunofluorescence test using a suspension of viable islet cells, and similar cytoplasmic antibodies which require the use of group O human pancreas were also found in the serum of some patients. A strong association exists between the presence of islet cell antibodies and the onset of insulin-dependent diabetes. The quantitative determination of circulating ICSA using 125I-protein A, which binds to IgG attached to the islet cell surface, was essentially as described by Lernmark et al. In the present study, we determined the circulating ICSA in diabetes, especially in IDD. The ICSA were estimated in various sera from both indirect immunofluorescence and 125I-protein A. Controls bound 125I-protein A. Sera from 4 IDD patients with circulating ICSA demonstrated by immunofluorescence showed >3,000 cpm 125I-protein A binding activity, and that from 5 patients without ICSA bound <2,000 cpm. Sera from newly-diagnosed diabetics who had severe hyperglycemia showed <2,000 cpm, with or without ICSA. (author)

  8. Methods To Identify Aptamers against Cell Surface Biomarkers

    Directory of Open Access Journals (Sweden)

    Frédéric Ducongé

    2011-09-01

    Full Text Available Aptamers are nucleic acid-based ligands identified through a process of molecular evolution named SELEX (Systematic Evolution of Ligands by Exponential enrichment. During the last 10-15 years, numerous aptamers have been developed specifically against targets present on or associated with the surface of human cells or infectious pathogens such as viruses, bacteria, fungi or parasites. Several of the aptamers have been described as potent probes, rivalling antibodies, for use in flow cytometry or microscopy. Some have also been used as drugs by inhibiting or activating functions of their targets in a manner similar to neutralizing or agonistic antibodies. Additionally, it is straightforward to conjugate aptamers to other agents without losing their affinity and they have successfully been used in vitro and in vivo to deliver drugs, siRNA, nanoparticles or contrast agents to target cells. Hence, aptamers identified against cell surface biomarkers represent a promising class of ligands. This review presents the different strategies of SELEX that have been developed to identify aptamers for cell surface-associated proteins as well as some of the methods that are used to study their binding on living cells.

  9. Characterization of cell-surface determinants important for baculovirus infection.

    Science.gov (United States)

    Tani, H; Nishijima, M; Ushijima, H; Miyamura, T; Matsuura, Y

    2001-01-01

    Baculovirus gp64 envelope glycoprotein is a major component of the envelope of the budded virus and is involved in virus entry into the host cells by endocytosis. To investigate the cell-surface molecules important for infection of baculovirus into mammalian cells, we constructed a recombinant baculovirus, Ac64-CAluc, which has gp64 and luciferase genes under the polyhedrin and the CAG promoter, respectively. For controls, we constructed recombinant viruses possessing vesicular stomatitis virus (VSV) G protein, mouse hepatitis virus (MHV) S protein, or green fluorescent protein (GFP) gene under the polyhedrin promoter and the luciferase gene under the CAG promoter (AcVSVG-CAluc, AcMHVS-CAluc, and AcGFP-CAluc). Treatment of HepG2 cells with phospholipase C markedly reduced the reporter gene expression by Ac64-CAluc or AcVSVG-CAluc in a dose-dependent manner, whereas AcMHVS-CAluc was shown to be resistant to the treatment. Inhibition with purified lipids and susceptibility to the mutant CHO hamster cell lines deficient in phospholipids synthesis suggest that the interaction of gp64 and phospholipids on the cell surface might play an important role in baculovirus infection into mammalian cells. PMID:11145915

  10. Cdon, a cell surface protein, mediates oligodendrocyte differentiation and myelination.

    Science.gov (United States)

    Wang, Li-Chun; Almazan, Guillermina

    2016-06-01

    During central nervous system development, oligodendrocyte progenitors (OLPs) establish multiple branched processes and axonal contacts to initiate myelination. A complete understanding of the molecular signals implicated in cell surface interaction to initiate myelination/remyelination is currently lacking. The objective of our study was to assess whether Cdon, a cell surface protein that was shown to participate in muscle and neuron cell development, is involved in oligodendrocyte (OLG) differentiation and myelination. Here, we demonstrate that endogenous Cdon protein is expressed in OLPs, increasing in the early differentiation stages and decreasing in mature OLGs. Immunocytochemistry of endogenous Cdon showed localization on both OLG cell membranes and cellular processes exhibiting puncta- or varicosity-like structures. Cdon knockdown with siRNA decreased protein levels by 62% as well as two myelin-specific proteins, MBP and MAG. Conversely, overexpression of full-length rat Cdon increased myelin proteins in OLGs. The complexity of OLGs branching and contact point numbers with axons were also increased in Cdon overexpressing cells growing alone or in coculture with dorsal root ganglion neurons (DRGNs). Furthermore, myelination of DRGNs was decreased when OLPs were transfected with Cdon siRNA. Altogether, our results suggest that Cdon participates in OLG differentiation and myelination, most likely in the initial stages of development. GLIA 2016;64:1021-1033. PMID:26988125

  11. Tethered elevator and platforms as space station facilities: Systems studies and demonstrative experiments

    Science.gov (United States)

    1986-01-01

    Several key concepts of the science and applications tethered platforms were studied. Some conclusions reached are herein listed. Tether elevator and platform could improve the space station scientific and applicative capabilities. The space elevator presents unique characteristics as microgravity facility and as a tethered platform servicing vehicle. Pointing platforms could represent a new kind of observation facility for large class of payloads. The dynamical, control and technological complexity of these concepts advised demonstrative experiments. The on-going tethered satellite system offers the opportunity to perform such experiments. And feasibility studies are in progress.

  12. A proposed bare-tether experiment on board a sounding rocket

    OpenAIRE

    Fujii, Hironori A.; OYAMA, Koichiro; Sasaki, Susumu; Yamagiwa, Yoshiki; 藤井 裕矩; 小山 孝一郎; 佐々木 進; 山極 芳樹; Cho, Mengu; Sanmartin, Juan R.; Charro, Mario; VanderHeide, Erick J.; Kruijff, Michiel; Lebreton, Jean-Pierre

    2005-01-01

    A sounding rocket experiment is proposed to carry out two experiments by the conductive bare-tether; (1) the test of the OML (Orbital-Motion-Limited) theory to collect electron, and (2) the test of techniques to determine (neutral) density profile in critical E-layer. The main driver of the mission is provide a space tether technology experiment in Low-Earth-Orbit (LEO) deploying a long tape tether in space and verify the performance of the bare electrodynamic tape tether. The sounding rocket...

  13. Microfluidics-based side view flow chamber reveals tether-to-sling transition in rolling neutrophils.

    Science.gov (United States)

    Marki, Alex; Gutierrez, Edgar; Mikulski, Zbigniew; Groisman, Alex; Ley, Klaus

    2016-01-01

    Neutrophils rolling at high shear stress (above 6 dyn/cm(2)) form tethers in the rear and slings in the front. Here, we developed a novel photo-lithographically fabricated, silicone(PDMS)-based side-view flow chamber to dynamically visualize tether and sling formation. Fluorescently membrane-labeled mouse neutrophils rolled on P-selectin substrate at 10 dyn/cm(2). Most rolling cells formed 5 tethers that were 2-30 μm long. Breaking of a single tether caused a reproducible forward microjump of the cell, showing that the tether was load-bearing. About 15% of all tether-breaking events resulted in slings. The tether-to-sling transition was fast (rolling cell, suggesting a very low bending modulus of the tether. The sling downstream of the rolling cell aligned according to the streamlines before landing on the flow chamber. These new observations explain how slings form from tethers and provide insight into their biomechanical properties. PMID:27357741

  14. Configuration maintaining control of three-body ring tethered system based on thrust compensation

    Science.gov (United States)

    Huang, Panfeng; Liu, Binbin; Zhang, Fan

    2016-06-01

    Space multi-tethered systems have shown broad prospects in remote observation missions. This paper mainly focuses on the dynamics and configuration maintaining control of space spinning three-body ring tethered system for such mission. Firstly, we establish the spinning dynamic model of the three-body ring tethered system considering the elasticity of the tether using Newton-Euler method, and then validate the suitability of this model by numerical simulation. Subsequently, LP (Likins-Pringle) initial equilibrium conditions for the tethered system are derived based on rigid body's equilibrium theory. Simulation results show that tether slack, snapping and interaction between the tethers exist in the three-body ring system, and its' configuration can not be maintained without control. Finally, a control strategy based on thrust compensation, namely thrust to simulate tether compression under LP initial equilibrium conditions is designed to solve the configuration maintaining control problem. Control effects are verified by numerical simulation compared with uncontrolled situation. Simulation results show that the configuration of the three-body ring tethered system could maintain under this active control strategy.

  15. Microfluidics-based side view flow chamber reveals tether-to-sling transition in rolling neutrophils

    Science.gov (United States)

    Marki, Alex; Gutierrez, Edgar; Mikulski, Zbigniew; Groisman, Alex; Ley, Klaus

    2016-01-01

    Neutrophils rolling at high shear stress (above 6 dyn/cm2) form tethers in the rear and slings in the front. Here, we developed a novel photo-lithographically fabricated, silicone(PDMS)-based side-view flow chamber to dynamically visualize tether and sling formation. Fluorescently membrane-labeled mouse neutrophils rolled on P-selectin substrate at 10 dyn/cm2. Most rolling cells formed 5 tethers that were 2–30 μm long. Breaking of a single tether caused a reproducible forward microjump of the cell, showing that the tether was load-bearing. About 15% of all tether-breaking events resulted in slings. The tether-to-sling transition was fast (<100 ms) with no visible material extending above the rolling cell, suggesting a very low bending modulus of the tether. The sling downstream of the rolling cell aligned according to the streamlines before landing on the flow chamber. These new observations explain how slings form from tethers and provide insight into their biomechanical properties. PMID:27357741

  16. Nonlinear dynamics and coupling effect of libration and vibration of tethered space robot in deorbiting process

    Institute of Scientific and Technical Information of China (English)

    王班; 郭吉丰; 冯吉根; 王剑

    2016-01-01

    In order to control the growth of space debris, a novel tethered space robot (TSR) was put forward. After capture,the platform, tether, and target constituted a tethered combination system. General nonlinear dynamics of the tethered combination system in the post-capture phase was established with the consideration of the attitudes of two spacecrafts and the quadratic nonlinear elasticity of the tether. The motion law of the tethered combination in the deorbiting process with different disturbances was simulated and discussed on the premise that the platform was only controlled by a constant thrust force. It is known that the four motion freedoms of the tethered combination are coupled with each other in the deorbiting process from the simulation results. A noticeable phenomenon is that the tether longitudinal vibration does not decay to vanish even under the large tether damping with initial attitude disturbances due to the coupling effect. The approximate analytical solutions of the dynamics for a simplified model are obtained through the perturbation method. The condition of the inter resonance phenomenon is the frequency ratioλ1=2. The case study shows good accordance between the analytical solutions and numerical results, indicating the effectiveness and correctness of approximate analytical solutions.

  17. Modulation of ganglioside expression in human melanoma cell lines

    International Nuclear Information System (INIS)

    Cell surface gangliosides in human melanoma cell lines were modulated by pretreatment and adaptation to 6-thioguanine and 5-bromo-deoxyuridine. Chemo- and radiation sensitivities were compared in original cell lines and modulated cells by the human tumor colony-forming assay. Modulated cells showed decreased expression of cell surface GM2 and GD2 gangliosides. This reduction was correlated with increased resistance to bleomycin, vincristine, cisplatin and radiation treatment. These results suggest that cell surface GM2 and GD2 ganglioside expression in human melanoma cells is intimately associated with several cellular biological properties, such as drug or radiation sensitivity and cellular differentiation. (author)

  18. Maneuver analysis for spinning thrusting spacecraft and spinning tethered spacecraft

    Science.gov (United States)

    Martin, Kaela M.

    During axial thrusting of a spin-stabilized spacecraft undergoing orbital injections or control maneuvers, misalignments and center-of-mass offset create undesired body-fixed torques. The effects of the body-fixed torques, which in turn cause velocity pointing errors, can be reduced by ramping up (and then ramping down) the thruster. The first topic discussed in this thesis derives closed-form solutions for the angular velocity, Euler angles, inertial velocity, and inertial displacement solutions with nonzero initial conditions. Using the closed-form solutions, the effect of variations in the spin-axis moment of inertia and spin-rate on the spacecraft velocity pointing error are shown. The analytical solutions closely match numerical simulations. The next topic considers various ramp-up profiles (including parabolic, cosine, logarithmic, exponential, and cubic) to heuristically find a suboptimal solution to reduce the velocity pointing error. Some of the considered cosine, logarithmic, exponential, parabolic, and cubic profiles drive the velocity pointing error to nearly zero and hence qualify as effective solutions. The third topic examines a large tethered spacecraft that produces artificial gravity with the propulsion system on one end of the tether. Instead of thrusting through the center of mass, the offset thrust occurs at an angle to the tether which is held in the desired direction by changing the spin rate to compensate for decreasing propellant mass. The dynamics and control laws of the system are derived for constant, time-varying, planar, and non-planar thrust as well as spin-up maneuvers. The final topic discusses how the Bodewadt solution of a self-excited rigid body is unable to accurately predict the motion compared to a numerical integration of the equations of motion.

  19. Cell surface carbohydrates as prognostic markers in human carcinomas

    DEFF Research Database (Denmark)

    Dabelsteen, Erik

    1996-01-01

    cell types; within a given tissue, variation in expression may be related to cell maturation. Tumour-associated carbohydrate structures often reflect a certain stage of cellular development; most of these moieties are structures normally found in other adult or embryonic tissues. There is no unique......Tumour development is usually associated with changes in cell surface carbohydrates. These are often divided into changes related to terminal carbohydrate structures, which include incomplete synthesis and modification of normally existing carbohydrates, and changes in the carbohydrate core...... tumour carbohydrate structure, since certain structures which are tumour-related in one organ may be normal constituents of other tissues. Tumour-associated carbohydrate changes have been used in the diagnosis of human cancers. Recently, however, it has been demonstrated that the expression of some...

  20. Vaccines based on the cell surface carbohydrates of pathogenic bacteria

    Directory of Open Access Journals (Sweden)

    Jones Christopher

    2005-01-01

    Full Text Available Glycoconjugate vaccines, in which a cell surface carbohydrate from a micro-organism is covalently attached to an appropriate carrier protein are proving to be the most effective means to generate protective immune responses to prevent a wide range of diseases. The technology appears to be generic and applicable to a wide range of pathogens, as long as antibodies against surface carbohydrates help protect against infection. Three such vaccines, against Haemophilus influenzae type b, Neisseria meningitidis Group C and seven serotypes of Streptococcus pneumoniae, have already been licensed and many others are in development. This article discusses the rationale for the development and use of glycoconjugate vaccines, the mechanisms by which they elicit T cell-dependent immune responses and the implications of this for vaccine development, the role of physicochemical methods in the characterisation and quality control of these vaccines, and the novel products which are under development.

  1. Cell surface topology creates high Ca2+ signalling microdomains

    DEFF Research Database (Denmark)

    Brasen, Jens Christian; Olsen, Lars Folke; Hallett, Maurice B

    2010-01-01

    It has long been speculated that cellular microdomains are important for many cellular processes, especially those involving Ca2+ signalling. Measurements of cytosolic Ca2+ report maximum concentrations of less than few micromolar, yet several cytosolic enzymes require concentrations of more than......-wrinkle location is also a strategic location at which Ca2+ acts as a regulator of the cortical cytoskeleton and plasma membrane expansion....... smooth cell surface predicts only moderate localized effects, the more realistic "wrinkled" surface topology predicts that Ca2+ concentrations up to 80 microM can persist within the folds of membranes for significant times. This intra-wrinkle location may account for 5% of the total cell volume. Using...

  2. Tethered Transition Metals Promoted Photocatalytic System for Efficient Hydrogen Evolutions

    KAUST Repository

    Takanabe, Kazuhiro

    2015-03-05

    The present invention is directed, at least in part, to a process for improving the efficiency of a photocatalyst (a semiconductor photocatalyst) by tethering (depositing) a metal (e.g., metal ions of a late transition metal, such as nickel) to the semiconductor (photocatalyst) surface through the use of an organic ligand. More specifically, 1,2-ethanedithiol (EDT) functions as an excellent molecular linker (organic ligand) to attach a transition metal complex (e.g., nickel (Ni.sup.2+ ions)) to the semiconductor surface, which can be in the form of a cadmium sulfide surface. The photocatalyst has particular utility in generating hydrogen from H.sub.2S.

  3. Formation and finite element analysis of tethered bilayer lipid structures.

    Science.gov (United States)

    Kwak, Kwang Joo; Valincius, Gintaras; Liao, Wei-Ching; Hu, Xin; Wen, Xuejin; Lee, Andrew; Yu, Bo; Vanderah, David J; Lu, Wu; Lee, L James

    2010-12-01

    Rapid solvent exchange of an ethanolic solution of diphytanoyl phosphatidylcholine (DPhyPC) in the presence of a mixed self-assembled monolayer (SAM) [thiolipid/β-mercaptoethanol (βME) (3/7 mol/mol) on Au] shows a transition from densely packed tethered bilayer lipid membranes [(dp)tBLMs], to loosely packed tethered bilayer lipid membranes [(lp)tBLMs], and tethered bilayer liposome nanoparticles (tBLNs) with decreasing DPhyPC concentration. The tethered lipidic constructs in the aqueous medium were analyzed by atomic force microscopy (AFM) and electrochemical impedance spectroscopy (EIS). Finite element analysis (FEA) was applied to interpret spectral EIS features without referring to equivalent circuit modeling. Using structural data obtained earlier from neutron reflectometry and dielectric constants of lipid bilayers, we reproduced experimentally observed features of the electrochemical impedance (EI) spectra of complex surface constructs involving small pinhole defects, large membrane-free patches, and bound liposomes. We demonstrated by FEA that highly insulating (dp)tBLMs with low-defect density exhibit EI spectra in the shape of a perfect semicircle with or without low-frequency upward "tails" in the Cole-Cole representation. Such EI spectra were observed at DPhyPC concentrations of >5 × 10(-3) mol L(-1). While AFM was not able to visualize very small lateral defects in such films, EI spectra unambiguously signaled their presence by increased low frequency "tails". Using FEA we demonstrate that films with large diameter visible defects (>25 nm by AFM) produce EI spectral features consisting of two semicircles of comparable size. Such films were typically obtained at DPhyPC concentrations of FEA revealed that, to account for these EI features for bound liposome systems (50-500 nm diameter), one needs to assume much lower tBLM conductivities of the submembrane space, which separates the electrode surface and the phospholipid bilayer. Alternatively, FEA

  4. Reconstitution of Cholesterol-Dependent Vaginolysin into Tethered Phospholipid Bilayers

    DEFF Research Database (Denmark)

    Budvytyte, Rima; Pleckaityte, M.; Zvirbliene, A.;

    2013-01-01

    Functional reconstitution of the cholesterol-dependent cytolysin vaginolysin (VLY) from Gardnerella vaginalis into artificial tethered bilayer membranes (tBLMs) has been accomplished. The reconstitution of VLY was followed in real-time by electrochemical impedance spectroscopy (EIS). Changes of the...... EIS parameters of the tBLMs upon exposure to VLY solutions were consistent with the formation of water-filled pores in the membranes. It was found that reconstitution of VLY is a strictly cholesterol-dependent, irreversible process. At a constant cholesterol concentration reconstitution of VLY...... platform for the detection of the activity of VLY and possibly other cholesterol-dependent cytolysins....

  5. Solvation force between tethered polyelectrolyte layers. A density functional approach

    Directory of Open Access Journals (Sweden)

    O. Pizio

    2012-10-01

    Full Text Available We use a version of the density functional theory to study the solvation force between two plates modified with a tethered layer of chains. The chains are built of tangentially jointed charged spherical segments. The plates are immersed in an electrolyte solution that involves cations, anions and solvent molecules. The latter molecules are modelled as hard spheres. We study the dependence of the solvation force and the structure of chains and of solute molecules on the grafting density, length of chains, architecture of the chains and on concentration of the solute.

  6. Fullerenic structures and such structures tethered to carbon materials

    Science.gov (United States)

    Goel, Anish; Howard, Jack B.; Vander Sande, John B.

    2010-01-05

    The fullerenic structures include fullerenes having molecular weights less than that of C.sub.60 with the exception of C.sub.36 and fullerenes having molecular weights greater than C.sub.60. Examples include fullerenes C.sub.50, C.sub.58, C.sub.130, and C.sub.176. Fullerenic structure chemically bonded to a carbon surface is also disclosed along with a method for tethering fullerenes to a carbon material. The method includes adding functionalized fullerene to a liquid suspension containing carbon material, drying the suspension to produce a powder, and heat treating the powder.

  7. Tethered spinal cord syndrome with symptomatic onset in adulthood

    Institute of Scientific and Technical Information of China (English)

    HE Shi-sheng; ZHAO Ying-chuan; SHI Zhi-cai; LI Ming; HOU Tie-sheng; ZHANG Ye; WU Yun-gang

    2009-01-01

    @@ Tethered spinal cord syndrome(TCS)is a condition of overstretching or compression of the caudal part of the spinal cord caused by various spinal lesions,such as a tight filum terminale or an intraspinal lipoma.~(1-9) Though it is a well-recognized cause of neurological deterioration in childhood,its symptomatic onset in adulthood is uncommon.~(10-23) Eleven cases of TCS are presented here.In addition,their related clinical features,surgical procedures and outcomes are investigated.

  8. Analytical investigation of the dynamics of tethered constellations in earth orbit

    Science.gov (United States)

    Lorenzini, Enrico C.; Gullahorn, Gordon E.; Estes, Robert D.

    1988-01-01

    This Quarterly Report on Tethering in Earth Orbit deals with three topics: (1) Investigation of the propagation of longitudinal and transverse waves along the upper tether. Specifically, the upper tether is modeled as three massive platforms connected by two perfectly elastic continua (tether segments). The tether attachment point to the station is assumed to vibrate both longitudinally and transversely at a given frequency. Longitudinal and transverse waves propagate along the tethers affecting the acceleration levels at the elevator and at the upper platform. The displacement and acceleration frequency-response functions at the elevator and at the upper platform are computed for both longitudinal and transverse waves. An analysis to optimize the damping time of the longitudinal dampers is also carried out in order to select optimal parameters. The analytical evaluation of the performance of tuned vs. detuned longitudinal dampers is also part of this analysis. (2) The use of the Shuttle primary Reaction Control System (RCS) thrusters for blowing away a recoiling broken tether is discussed. A microcomputer system was set up to support this operation. (3) Most of the effort in the tether plasma physics study was devoted to software development. A particle simulation code has been integrated into the Macintosh II computer system and will be utilized for studying the physics of hollow cathodes.

  9. Stabilization of periodic solutions in a tethered satellite system by damping injection

    DEFF Research Database (Denmark)

    Larsen, Martin Birkelund; Blanke, Mogens

    2009-01-01

    A spacecraft with electrodynamic tether orbiting the Earth will be subject to a periodic forcing term induced by the variation of the magnetic field along the orbit. The periodic forcing term leads to a family of unstable periodic solutions for a tether carrying a constant current. This paper...

  10. Control by damping Injection of Electrodynamic Tether System in an Inclined Orbit

    DEFF Research Database (Denmark)

    Larsen, Martin Birkelund; Blanke, Mogens

    2009-01-01

    Control of a satellite system with an electrodynamic tether as actuator is a time-periodic and underactuated control problem. This paper considers the tethered satellite in a Hamiltonian framework and determines a port-controlled Hamiltonian formulation that adequately describes the nonlinear...

  11. Flight mechanics applications for tethers in space: Cooperative Italian-US programs

    Science.gov (United States)

    Bevilacqua, Franco; Merlina, Pietro; Anderson, John L.

    1990-01-01

    Since the 1974 proposal by Giuseppe Colombo to fly a tethered subsatellite from the Shuttle Orbiter, the creative thinking of many scientists and engineers from Italy and U.S. has generated a broad range of potential tether applications in space. Many of these applications have promise for enabling innovative research and operational activities relating to flight mechanics in earth orbit and at suborbital altitudes. From a flight mechanics standpoint the most interesting of the currently proposed flight demonstrations are: the second Tethered Satellite System experiment which offers both the potential for aerothermodynamics and hypersonics research and for atmospheric science research; the Tethered Initiated Space Recovery System which would enable orbital deboost and recovery of a re-entry vehicle and waste removal from a space station; and the Tether Elevator/Crawler System which would provide a variable microgravity environment and space station center of mass management. The outer atmospheric and orbital flight mechanics characteristics of these proposed tether flight demonstrations are described. The second Tethered Satellite System mission will deploy the tethered satellite earthward and will bring it as low as 130 km from ground and thus into the transition region between the atmosphere (non-ionized) and the partially ionized ionosphere. The atmospheric flight mechanics of the tethered satellite is discussed and simulation results are presented. The Tether Initiated Space Recovery System experiment will demonstrate the ability of a simple tether system to deboost and recover a reentry vehicle. The main feature of this demonstration is the utilization of a Small Expendable Deployment System (SEDS) and the low-tension deployment assumed to separate the reentry vehicle from the Shuttle. This low-tension deployment maneuver is discussed and its criticalities are outlined. The Tether Elevator/Crawler System is a new space element able to move in a controlled way

  12. Modeling and Control of Electrodynamic Tethers - an Energy and Topology Approach

    DEFF Research Database (Denmark)

    Larsen, Martin Birkelund

    only be generated perpendicular to the instantaneous magnetic field. Furthermore, the control problem is complicated by the time variations in the magnetic field. This thesis solves these problems by utilizing an energy-based system description and a passivity-based control design. An advantage of the...... of the Earth for creating a Lorentz force along the tether which occur when a current carrying wire operates in a magnetic field. The use of electrodynamic tethers are interesting since they operate solely on electrical energy, which can be provided by solar panels of the spacecrafts. In this way the...... amount of propellant a spacecraft need to bring from Earth can be reduced. In this thesis the modeling and control of electrodynamic tethers are investigated, both when a single tether is used to connect two spacecrafts, and when the tethers are used i more general formations of spacecrafts. One of the...

  13. Shortest Path Planning for a Tethered Robot or an Anchored Cable

    Energy Technology Data Exchange (ETDEWEB)

    Xavier, P.G.

    1999-02-22

    We consider the problem of planning shortest paths for a tethered robot with a finite length tether in a 2D environment with polygonal obstacles. We present an algorithm that runs in time O((k{sub 1} + 1){sup 2}n{sup 4}) and finds the shortest path or correctly determines that none exists that obeys the constraints; here n is the number obstacle vertices, and k{sub 1} is the number loops in the initial configuration of the tether. The robot may cross its tether but nothing can cross obstacles, which cause the tether to bend. The algorithm applies as well for planning a shortest path for the free end of an anchored cable.

  14. Cholesterol tethered bioresponsive polycation as a candidate for gene delivery

    International Nuclear Information System (INIS)

    The efficient unpacking of viral protein shell gave the inspiration for the synthesized vectors. In this research, novel cholesterol tethered bioresponsive polyethylenimine (PEI) was specially designed via disulfide-containing cross-linker. The cholesterol lipid had proved to increase the permeability of gene vector through cell membrane. The acid-base titration indicated that the synthesized polycation possessed efficient proton sponge effect, which was suggested to increase endosomal release of pDNA complexes into the cytoplasm. The cholesterol tethered polycation could effectively induce DNA condensation and form spherical particles with diameter about 200 nm at N/P ratio of 10. At glutathione concentration of 3 mM, the polyplexes were unpacked due to the bioresponsive cleavage of the disulfide bonds. The in-vitro experiment indicated that the polyplexes showed efficient transfection efficiency to HEK293T cells. All the results indicated that the bioresponsive polycation could be served as an effective trigger to control the release of DNA at the intracellular environment. The novel bioresponsive polycation might have great potential in non-viral gene delivery research and application.

  15. Cellulose Microfibril Formation by Surface-Tethered Cellulose Synthase Enzymes.

    Science.gov (United States)

    Basu, Snehasish; Omadjela, Okako; Gaddes, David; Tadigadapa, Srinivas; Zimmer, Jochen; Catchmark, Jeffrey M

    2016-02-23

    Cellulose microfibrils are pseudocrystalline arrays of cellulose chains that are synthesized by cellulose synthases. The enzymes are organized into large membrane-embedded complexes in which each enzyme likely synthesizes and secretes a β-(1→4) glucan. The relationship between the organization of the enzymes in these complexes and cellulose crystallization has not been explored. To better understand this relationship, we used atomic force microscopy to visualize cellulose microfibril formation from nickel-film-immobilized bacterial cellulose synthase enzymes (BcsA-Bs), which in standard solution only form amorphous cellulose from monomeric BcsA-B complexes. Fourier transform infrared spectroscopy and X-ray diffraction techniques show that surface-tethered BcsA-Bs synthesize highly crystalline cellulose II in the presence of UDP-Glc, the allosteric activator cyclic-di-GMP, as well as magnesium. The cellulose II cross section/diameter and the crystal size and crystallinity depend on the surface density of tethered enzymes as well as the overall concentration of substrates. Our results provide the correlation between cellulose microfibril formation and the spatial organization of cellulose synthases. PMID:26799780

  16. Cholesterol tethered bioresponsive polycation as a candidate for gene delivery

    Energy Technology Data Exchange (ETDEWEB)

    Zhu Ying [Second Affiliated Hospital, Medical College, Zhejiang University, Hangzhou 310009 (China); Wang Youxiang, E-mail: yx_wang@zju.edu.cn [Department of Polymer Science and Engineering, Zhejiang University, Hangzhou 310027 (China); Key Laboratory of Macromolecular Synthesis and Functionalization, Ministry of Education, Zhejiang University, Hangzhou 310027 (China); Hu Qiaoling; Shen Jiacong [Department of Polymer Science and Engineering, Zhejiang University, Hangzhou 310027 (China); Key Laboratory of Macromolecular Synthesis and Functionalization, Ministry of Education, Zhejiang University, Hangzhou 310027 (China)

    2009-04-30

    The efficient unpacking of viral protein shell gave the inspiration for the synthesized vectors. In this research, novel cholesterol tethered bioresponsive polyethylenimine (PEI) was specially designed via disulfide-containing cross-linker. The cholesterol lipid had proved to increase the permeability of gene vector through cell membrane. The acid-base titration indicated that the synthesized polycation possessed efficient proton sponge effect, which was suggested to increase endosomal release of pDNA complexes into the cytoplasm. The cholesterol tethered polycation could effectively induce DNA condensation and form spherical particles with diameter about 200 nm at N/P ratio of 10. At glutathione concentration of 3 mM, the polyplexes were unpacked due to the bioresponsive cleavage of the disulfide bonds. The in-vitro experiment indicated that the polyplexes showed efficient transfection efficiency to HEK293T cells. All the results indicated that the bioresponsive polycation could be served as an effective trigger to control the release of DNA at the intracellular environment. The novel bioresponsive polycation might have great potential in non-viral gene delivery research and application.

  17. Forcing adsorption of a tethered polymer by pulling

    International Nuclear Information System (INIS)

    We present an analysis of a partially directed walk model of a polymer which at one end is tethered to a sticky surface and at the other end is subjected to a pulling force at fixed angle away from the point of tethering. Using the kernel method, we derive the full generating function for this model in two and three dimensions and obtain the respective phase diagrams. We observe adsorbed and desorbed phases with a thermodynamic phase transition in between. In the absence of a pulling force this model has a second-order thermal desorption transition which merely gets shifted by the presence of a lateral pulling force. On the other hand, if the pulling force contains a non-zero vertical component this transition becomes first order. Strikingly, we find that, if the angle between the pulling force and the surface is below a critical value, a sufficiently strong force will induce polymer adsorption, no matter how large the temperature of the system. Our findings are similar in two and three dimensions, an additional feature in three dimensions being the occurrence of a re-entrance transition at constant pulling force for low temperature, which has been observed previously for this model in the presence of pure vertical pulling. Interestingly, the re-entrance phenomenon vanishes under certain pulling angles, with details depending on how the three-dimensional polymer is modeled

  18. Piperidinium tethered nanoparticle-hybrid electrolyte for lithium metal batteries

    KAUST Repository

    Korf, Kevin S.

    2014-06-23

    We report on the synthesis of novel piperidinium-based ionic liquid tethered nanoparticle hybrid electrolytes and investigate their physical and electrochemical properties. Hybrid electrolytes based on the ionic liquid 1-methyl-1-propylpiperidinium bis(trifluoromethanesulfone) imide covalently tethered to silica nanoparticles (SiO2-PP-TFSI) were blended with propylene carbonate-1 M lithium bis(trifluoromethanesulfone) imide (LiTFSI). We employed NMR analysis to confirm the successful creation of the hybrid material. Dielectric and rheological measurements show that these electrolytes exhibit exceptional room-temperature DC ionic conductivity (10-2 to 10 -3 S cm-1) as well as high shear mechanical moduli (105 to 106 Pa). Lithium transference numbers were found to increase with particle loading and to reach values as high as 0.22 at high particle loadings where the particle jam to form a soft glassy elastic medium. Analysis of lithium electrodeposits obtained in the hybrid electrolytes using SEM and EDX spectra show that the SiO2-PP-TFSI nanoparticles are able to smooth lithium deposition and inhibit lithium dendrite proliferation in Li metal batteries. LTOSiO2-PP-TFSI/PC in 1 M LiTFSILi half-cells based on the SiO2-PP-TFSI hybrid electrolytes exhibit attractive voltage profiles and trouble-free extended cycling behavior over more than 1000 cycles of charge and discharge. This journal is © the Partner Organisations 2014.

  19. Engineering the cell surface display of cohesins for assembly of cellulosome-inspired enzyme complexes on Lactococcus lactis

    Directory of Open Access Journals (Sweden)

    Wieczorek Andrew S

    2010-09-01

    Full Text Available Abstract Background The assembly and spatial organization of enzymes in naturally occurring multi-protein complexes is of paramount importance for the efficient degradation of complex polymers and biosynthesis of valuable products. The degradation of cellulose into fermentable sugars by Clostridium thermocellum is achieved by means of a multi-protein "cellulosome" complex. Assembled via dockerin-cohesin interactions, the cellulosome is associated with the cell surface during cellulose hydrolysis, forming ternary cellulose-enzyme-microbe complexes for enhanced activity and synergy. The assembly of recombinant cell surface displayed cellulosome-inspired complexes in surrogate microbes is highly desirable. The model organism Lactococcus lactis is of particular interest as it has been metabolically engineered to produce a variety of commodity chemicals including lactic acid and bioactive compounds, and can efficiently secrete an array of recombinant proteins and enzymes of varying sizes. Results Fragments of the scaffoldin protein CipA were functionally displayed on the cell surface of Lactococcus lactis. Scaffolds were engineered to contain a single cohesin module, two cohesin modules, one cohesin and a cellulose-binding module, or only a cellulose-binding module. Cell toxicity from over-expression of the proteins was circumvented by use of the nisA inducible promoter, and incorporation of the C-terminal anchor motif of the streptococcal M6 protein resulted in the successful surface-display of the scaffolds. The facilitated detection of successfully secreted scaffolds was achieved by fusion with the export-specific reporter staphylococcal nuclease (NucA. Scaffolds retained their ability to associate in vivo with an engineered hybrid reporter enzyme, E. coli β-glucuronidase fused to the type 1 dockerin motif of the cellulosomal enzyme CelS. Surface-anchored complexes exhibited dual enzyme activities (nuclease and β-glucuronidase, and were

  20. Power Generation for a JUNO-type Mission using Electrodynamic Tethers

    Science.gov (United States)

    Bombardelli, C.; Lorenzini, E. C.; Sanmartin, J. R.

    2008-09-01

    Electrodynamic tethers are known to exhibit high performance in the Jupiter environment , both as propellantless propulsion devices and as power generating systems. In spite of the considerable amount of research work of electrodynamic tethers in the Jupiter environment the case involving high inclination orbit has never been addressed so far. We present a power generation scheme for rotating electrodynamic tethers which can be applied to a generic Jupiter science missions employing polar orbits. We show that when the orbit inclination reaches 90 degrees and the tether rotates in the orbital plane the effect of the tether electrodynamic force does not impact orbital energy but orbit inclination. Thanks to favorable environmental conditions at Jupiter (i.e. strong magnetic field and fast rotating plasmasphere) relatively high power levels can be obtained with tethers of modest length when the tether transits the low altitude regions around the planet. In addition the impact on orbit inclination is minimal thanks to the high specific angular momentum of jovian orbits. As a numerical example we consider an electrodynamic tether subsystem consisting of two 3- km-long 5-cm wide and 0.05-mm-thick tape tether arms deployed radially from a main central spacecraft whose orbit has the characteristic of the current baseline JUNO orbit. The tether subsystem, whose total mass is less than 50 kg, can provide kW level average power along a 120 degrees orbital arc around the equatorial plane crossing. The inclination variation induced by the Lorentz force in this case is below 1/1000 of a degree per orbit. Applications of the concept to future Jupiter exploration missions are discussed.

  1. Distribution, Arrangement and Interconnectedness of Cell Surface Receptor sites in the body of an Organism

    Directory of Open Access Journals (Sweden)

    Utoh-Nedosa

    2011-01-01

    Full Text Available Cell surface receptors have been identified as the sites of disease infectivity in living organisms in a previous study. Drugs used for the treatment or cure of infections have to eliminate infections through attacking infective organisms at the cell surface receptors to which the infective organisms are attached. Problem statement: The present study examines a wide sample of living things to get more information on the relationship of one cell surface receptor to other cell surface receptors in the body of an organism. Approach: The arrangement of cell surface receptors on the external covering of a few samples of fruits, leaves, stems, dry wood of a plant; wall gecko and some parts of the human body, were examined and photographed. Transverse and/or Longitudinal sections of soursop fruit and sycamore fruit were also examined and photographed. The five different coverings of the fleshy part of a coconut were also photographed. The photographs were studied to note the relationship of disease infection attached to cell surface receptors on the external surface of an organ to disease infection on the innermost covering of the same organ. Results: The results of the study showed that all living things had ubiquitous distribution of cell surface receptors which are usually observable with the unaided eye as dots or spots on the external covering of an organ, tissue or cell. The dots or receptor sites of cell surface receptors in the study are arranged in lines which were perpendicular, oblique, transverse or arranged in any other lineal geometrical form. The lineally arranged cell surface receptors were noted to be connected by grooves, channels or pipes which joined other receptor channels or intersected with them. Smaller cell surface receptor channels emptied into bigger channels or continued as small sized channels that ran side by side in a connective tissue bundle. These connective tissue bundles that carried many independent small-sized cell

  2. Down-Regulation of Cell Surface Receptors Is Modulated by Polar Residues within the Transmembrane Domain

    OpenAIRE

    Zaliauskiene, Lolita; Kang, Sunghyun; Brouillette, Christie G; Lebowitz, Jacob; Arani, Ramin B; Collawn, James F.

    2000-01-01

    How recycling receptors are segregated from down-regulated receptors in the endosome is unknown. In previous studies, we demonstrated that substitutions in the transferrin receptor (TR) transmembrane domain (TM) convert the protein from an efficiently recycling receptor to one that is rapidly down regulated. In this study, we demonstrate that the “signal” within the TM necessary and sufficient for down-regulation is Thr11Gln17Thr19 (numbering in TM). Transplant...

  3. Cell Surface Binding and Internalization of Aβ Modulated by Degree of Aggregation

    Directory of Open Access Journals (Sweden)

    David A. Bateman

    2011-01-01

    Full Text Available The amyloid peptides, Aβ40 and Aβ42, are generated through endoproteolytic cleavage of the amyloid precursor protein. Here we have developed a model to investigate the interaction of living cells with various forms of aggregated Aβ40/42. After incubation at endosomal pH 6, we observed a variety of Aβ conformations after 3 (Aβ3, 24 (Aβ24, and 90 hours (Aβ90. Both Aβ4224 and Aβ4024 were observed to rapidly bind and internalize into differentiated PC12 cells, leading to accumulation in the lysosome. In contrast, Aβ40/4290 were both found to only weakly associate with cells, but were observed as the most aggregated using dynamic light scattering and thioflavin-T. Internalization of Aβ40/4224 was inhibited with treatment of monodansylcadaverine, an endocytosis inhibitor. These studies indicate that the ability of Aβ40/42 to bind and internalize into living cells increases with degree of aggregation until it reaches a maximum beyond which its ability to interact with cells diminishes drastically.

  4. Cell Surface Proteome of Dental Pulp Stem Cells Identified by Label-Free Mass Spectrometry

    Science.gov (United States)

    Niehage, Christian; Karbanová, Jana; Steenblock, Charlotte

    2016-01-01

    Multipotent mesenchymal stromal cells (MSCs) are promising tools for regenerative medicine. They can be isolated from different sources based on their plastic-adherence property. The identification of reliable cell surface markers thus becomes the Holy Grail for their prospective isolation. Here, we determine the cell surface proteomes of human dental pulp-derived MSCs isolated from single donors after culture expansion in low (2%) or high (10%) serum-containing media. Cell surface proteins were tagged on intact cells using cell impermeable, cleavable sulfo-NHS-SS-biotin, which allows their enrichment by streptavidin pull-down. For the proteomic analyses, we first compared label-free methods to analyze cell surface proteomes i.e. composition, enrichment and proteomic differences, and we developed a new mathematical model to determine cell surface protein enrichment using a combinatorial gene ontology query. Using this workflow, we identified 101 cluster of differentiation (CD) markers and 286 non-CD cell surface proteins. Based on this proteome profiling, we identified 14 cell surface proteins, which varied consistently in abundance when cells were cultured under low or high serum conditions. Collectively, our analytical methods provide a basis for identifying the cell surface proteome of dental pulp stem cells isolated from single donors and its evolution during culture or differentiation. Our data provide a comprehensive cell surface proteome for the precise identification of dental pulp-derived MSC populations and their isolation for potential therapeutic intervention. PMID:27490675

  5. Cell Surface Proteome of Dental Pulp Stem Cells Identified by Label-Free Mass Spectrometry.

    Science.gov (United States)

    Niehage, Christian; Karbanová, Jana; Steenblock, Charlotte; Corbeil, Denis; Hoflack, Bernard

    2016-01-01

    Multipotent mesenchymal stromal cells (MSCs) are promising tools for regenerative medicine. They can be isolated from different sources based on their plastic-adherence property. The identification of reliable cell surface markers thus becomes the Holy Grail for their prospective isolation. Here, we determine the cell surface proteomes of human dental pulp-derived MSCs isolated from single donors after culture expansion in low (2%) or high (10%) serum-containing media. Cell surface proteins were tagged on intact cells using cell impermeable, cleavable sulfo-NHS-SS-biotin, which allows their enrichment by streptavidin pull-down. For the proteomic analyses, we first compared label-free methods to analyze cell surface proteomes i.e. composition, enrichment and proteomic differences, and we developed a new mathematical model to determine cell surface protein enrichment using a combinatorial gene ontology query. Using this workflow, we identified 101 cluster of differentiation (CD) markers and 286 non-CD cell surface proteins. Based on this proteome profiling, we identified 14 cell surface proteins, which varied consistently in abundance when cells were cultured under low or high serum conditions. Collectively, our analytical methods provide a basis for identifying the cell surface proteome of dental pulp stem cells isolated from single donors and its evolution during culture or differentiation. Our data provide a comprehensive cell surface proteome for the precise identification of dental pulp-derived MSC populations and their isolation for potential therapeutic intervention. PMID:27490675

  6. EXAFS Study of Uranyl Complexation at Pseudomonas fluorescens Cell Surfaces

    Science.gov (United States)

    Bencheikh, R.; Bargar, J. R.; Tebo, B. M.

    2002-12-01

    Little is known about the roles of microbial biomass as a sink and source for uranium in contaminated aquifers, nor of the impact of bacterial biochemistry on uranium speciation in the subsurface. A significant role is implied by the high affinities of both Gram positive and Gram negative cells for binding uranyl (UO2{ 2+}). In the present study, Extended X-ray Absorption Fine Structure (EXAFS) spectroscopy was used to identify membrane functional groups involved in uranyl binding to the Gram negative bacterium Pseudomonas fluorescens from pH 3 to pH 8. Throughout this pH-range, EXAFS spectra can be described primarily in terms of coordination of carboxylic groups to uranyl. U-C distances characteristic of 4-, 5- and 8- membered rings were observed, as well as the possibility of phosphato groups. Both shell-by-shell fits and principle component analyses indicate that the functional groups involved in binding of uranyl to the cell surface do not vary systematically across the pH range investigated. This result contrasts with EXAFS results of uranyl sorbed to Gram positive bacteria, and suggests an important role for long-chain carboxylate-terminated membrane functional groups in binding uranyl.

  7. Cell-surface acceleration of urokinase-catalyzed receptor cleavage

    DEFF Research Database (Denmark)

    Høyer-Hansen, G; Ploug, M; Behrendt, N;

    1997-01-01

    or indirectly mediated by uPA itself. In a soluble system, uPA can cleave purified uPAR, but the low efficiency of this reaction has raised doubts as to whether uPA is directly responsible for uPAR cleavage on the cells. We now report that uPA-catalyzed cleavage of uPAR on the cell surface is...... strongly favored relative to the reaction in solution. The time course of uPA-catalyzed cleavage of cell-bound uPAR was studied using U937 cells stimulated with phorbol 12-myristate 13-acetate. Only 30 min was required for 10 nM uPA to cleave 50% of the cell-bound uPAR. This uPA-catalyzed cleavage reaction...... was inhibited by a prior incubation of the cells with uPA inactivated by diisopropyl fluorophosphate, demonstrating a requirement for specific receptor binding of the active uPA to obtain the high-efficiency cleavage of cell-bound uPAR. Furthermore, amino-terminal sequence analysis revealed that u...

  8. RPE cell surface proteins in normal and dystrophic rats

    International Nuclear Information System (INIS)

    Membrane-bound proteins in plasma membrane enriched fractions from cultured rat RPE were analyzed by two-dimensional gel electrophoresis. Membrane proteins were characterized on three increasingly specific levels. Total protein was visualized by silver staining. A maximum of 102 separate proteins were counted in silver-stained gels. Glycoproteins were labeled with 3H-glucosamine or 3H-fucose and detected by autoradiography. Thirty-eight fucose-labeled and 61-71 glucosamine-labeled proteins were identified. All of the fucose-labeled proteins were labeled with glucosamine-derived radioactivity. Proteins exposed at the cell surface were labeled by lactoperoxidase-catalyzed radioiodination prior to preparation of membranes for two-dimensional analysis. Forty separate 125I-labeled surface proteins were resolved by two-dimensional electrophoresis/autoradiography. Comparison with the glycoprotein map showed that a number of these surface labeled proteins were glycoproteins. Two-dimensional maps of total protein, fucose-labeled, and glucosamine-labeled glycoproteins, and 125I-labeled surface proteins of membranes from dystrophic (RCS rdy-p+) and normal (Long Evans or RCS rdy+p+) RPE were compared. No differences in the total protein or surface-labeled proteins were observed. However, the results suggest that a 183K glycoprotein is more heavily glycosylated with glucosamine and fucose in normal RPE membranes as compared to membranes from dystrophic RPE

  9. Relationships between cell surface insulin binding and endocytosis in adipocytes

    International Nuclear Information System (INIS)

    Chymotrypsin substrate analogues, such as N-acetyl-Tyr ethyl ester, have recently been demonstrated to inhibit the endocytic uptake of insulin in isolated rat adipocytes. In this study, the effect of N-acetyl-Tyr ethyl ester on cell surface insulin binding and dissociation were examined. Surface-bound 125I-insulin was distinguished from intracellular 125I-insulin by the sensitivity of the former to rapid dissociation with an acidic buffer. Plateau levels of surface-bound insulin at 37 degree C were increased 70% by inhibiting the internalization pathway. This increase was temperature and insulin concentration dependent. Thus differences in surface binding were small at 12 degree C and also at high insulin concentrations. Inhibition of internalization with N-acetyl-Tyr ethyl ester markedly slowed the loss of surface-bound insulin observed during dissociation the loss of surface-bound insulin observed during dissociation studies. After 20-30 min of dissociation, the remaining levels of surface-bound insulin were three- to fourfold higher in treated adipocytes compared with control adipocytes. Added unlabeled insulin retained its ability to accelerate the dissociation of insulin in N-acetyl-Tyr ethyl ester-treated cells. These observations indicate that the internalization pathway is a quantitatively important factor in determining levels of surface binding at 37 degree C and in determining the rat of deactivation of insulin binding

  10. Studies of cell-surface glorin receptors, glorin degradation, and glorin-induced cellular responses during development of Polysphondylium violaceum.

    Science.gov (United States)

    De Wit, R J; van Bemmelen, M X; Penning, L C; Pinas, J E; Calandra, T D; Bonner, J T

    1988-12-01

    The chemoattractant mediating cell aggregation in the slime mold Polysphondylium violaceum is N-propionyl-gamma-L-glutamyl-L-ornithine-delta-lactam ethylester (glorin). Here we examine the binding properties of tritiated glorin to intact P. violaceum cells. Scatchard analysis of binding data yielded slightly curvilinear plots with Kd values in the range of 20 and 100 nM. The number of glorin receptors increased from 35,000 in the vegetative stage to 45,000 per cell during aggregation. Later, during culmination receptor numbers decreased to undetectable levels (less than 1000). The receptor binding kinetics show binding equilibrium within 30 s at 0 degrees C, and ligand dissociation occurs from two kinetically distinct receptors whose half-times were 2 s for 72% of the bound glorin and 28 s for the remainder. The enzymatic degradation of glorin did not affect binding data during incubations of up to 1 min at 0 degrees C. Two glorinase activities were observed. An ornithine delta-lactam cleaving activity with a Km of ca. 10(-4) M and a propionic acid removing activity (Km 10(-5) M), both of which were detected mainly on the cell surface. Cleavage of the lactam occurred at a higher rate than removal of propionic acid. Lactam-cleaved glorin showed no chemotactic activity nor did it bind to cell-surface glorin receptors. Cell-surface-bound glorinase activity and glorin-induced cGMP synthesis were developmentally regulated, peaking at aggregation. In the most sensitive stage half-maximal responses (cGMP synthesis, chemotaxis, light-scattering) were elicited in the 10-100 nM range. Neither cAMP synthesis nor glorin-induced glorin synthesis was observed. Guanine nucleotides specifically modulated glorin receptor binding on isolated membranes, and, conversely, glorin modulated GTP gamma S binding to membrane preparations. Our results support the notion that glorin mediates chemotactic cell aggregation in P. violaceum acting via cell-surface receptors, G-proteins, and c

  11. Design Concept for a Reusable/Propellantless MXER Tether Space Transportation System

    Science.gov (United States)

    McCandless, B., II; Kustas, F. m.; Marshall, L. S.; Lytle, W. B.; Hansen, N. P.

    2005-01-01

    The Momentum Exchange/Electrodynamic Reboost (MXER) tether facility is a transformational concept that significantly reduces the fuel requirements (and associated costs) in transferring payloads above low earth orbit (LEO). Facility reboost is accomplished without propellant by driving current against a voltage created by a conducting tether's interaction with the Earth's magnetic field (electrodynamic reboost). This system can be used for transferring a variety of payloads (scientific, cargo, and human space vehicles) to multiple destinations including geosynchronous transfer orbit, the Moon or Mars. MXER technology advancement requires development in two key areas: survivable, high tensile strength non-conducting tethers and reliable, lightweight payload catch/release mechanisms. Fundamental requirements associated with the MXER non-conducting strength tether and catch mechanism designs will be presented. Key requirements for the tether design include high specific-strength (tensile strength/material density), material survivability to the space environment (atomic oxygen and ultraviolet radiation), and structural survivability to micrometeoroid/orbital debris (MM/OD) impacts. The driving mechanism key,gequirements include low mass-to-capture-volume ratio, positional and velocity error tolerance, and operational reliability. Preliminary tether and catch mechanism design criteria are presented, which have been used as guidelines to "screen" and down-select initial concepts. Candidate tether materials and protective coatings are summarized along with their performance in simulated space environments (e.g., oxygen plasma, thermal cycling). A candidate catch mechanism design concept is presented along with examples of demonstration hardware.

  12. DOE Geothermal Data Repository - Tethering Data to Information: Preprint

    Energy Technology Data Exchange (ETDEWEB)

    Weers, J.; Anderson, A.

    2014-02-01

    Data are not inherently information. Without context, data are just numbers, figures, names, or points on a line. By assigning context to data, we can validate ideas, form opinions, and generate knowledge. This is an important distinction to information scientists, as we recognize that the context in which we keep our data plays a big part in generating its value. The mechanisms used to assign this context often include their own data, supplemental to the data being described and defining semantic relationships, commonly referred to as metadata. This paper provides the status of the DOE Geothermal Data Repository (DOE GDR), including recent efforts to tether data submissions to information, discusses the important distinction between data and information, outlines a path to generate useful knowledge from raw data, and details the steps taken in order to become a node on the National Geothermal Data System (NGDS).

  13. Tethered and Polymer Supported Bilayer Lipid Membranes: Structure and Function

    Directory of Open Access Journals (Sweden)

    Jakob Andersson

    2016-05-01

    Full Text Available Solid supported bilayer lipid membranes are model systems to mimic natural cell membranes in order to understand structural and functional properties of such systems. The use of a model system allows for the use of a wide variety of analytical tools including atomic force microscopy, impedance spectroscopy, neutron reflectometry, and surface plasmon resonance spectroscopy. Among the large number of different types of model membranes polymer-supported and tethered lipid bilayers have been shown to be versatile and useful systems. Both systems consist of a lipid bilayer, which is de-coupled from an underlying support by a spacer cushion. Both systems will be reviewed, with an emphasis on the effect that the spacer moiety has on the bilayer properties.

  14. Physisorbed Polymer-Tethered Lipid Bilayer with Lipopolymer Gradient

    Directory of Open Access Journals (Sweden)

    Christoph A. Naumann

    2012-11-01

    Full Text Available Physisorbed polymer-tethered lipid bilayers consisting of phospholipids and lipopolymers represent an attractive planar model membrane platform, in which bilayer fluidity and membrane elastic properties can be regulated through lipopolymer molar concentration. Herein we report a method for the fabrication of such a planar model membrane system with a lateral gradient of lipopolymer density. In addition, a procedure is described, which leads to a sharp boundary between regions of low and high lipopolymer molar concentrations. Resulting gradients and sharp boundaries are visualized on the basis of membrane buckling structures at elevated lipopolymer concentrations using epifluorescence microscopy and atomic force microscopy. Furthermore, results from spot photobleaching experiments are presented, which provide insight into the lipid lateral fluidity in these model membrane architectures. The presented experimental data highlight a planar, solid-supported membrane characterized by fascinating length scale-dependent dynamics and elastic properties with remarkable parallels to those observed in cellular membranes.

  15. Controlled Activation of Protein Rotational Dynamics Using Smart Hydrogel Tethering

    Energy Technology Data Exchange (ETDEWEB)

    Beech, Brenda M.; Xiong, Yijia; Boschek, Curt B.; Baird, Cheryl L.; Bigelow, Diana J.; Mcateer, Kathleen; Squier, Thomas C.

    2014-09-05

    Stimulus-responsive hydrogel materials that stabilize and control protein dynamics have the potential to enable a range of applications to take advantage of the inherent specificity and catalytic efficiencies of proteins. Here we describe the modular construction of a hydrogel using an engineered calmodulin (CaM) within a polyethylene glycol (PEG) matrix that involves the reversible tethering of proteins through an engineered CaM-binding sequence. For these measurements, maltose binding protein (MBP) was isotopically labeled with [13C] and [15N], permitting dynamic structural measurements using TROSY-HSQC NMR spectroscopy. Upon initial formation of hydrogels protein dynamics are suppressed, with concomitant increases in protein stability. Relaxation of the hydrogel matrix following transient heating results in the activation of protein dynamics and restoration of substrate-induced large-amplitude domain motions necessary for substrate binding.

  16. The HOPS/class C Vps complex tethers membranes by binding to one Rab GTPase in each apposed membrane.

    Science.gov (United States)

    Ho, Ruoya; Stroupe, Christopher

    2015-07-15

    Many Rab GTPase effectors are membrane-tethering factors, that is, they physically link two apposed membranes before intracellular membrane fusion. In this study, we investigate the distinct binding factors needed on apposed membranes for Rab effector-dependent tethering. We show that the homotypic fusion and protein-sorting/class C vacuole protein-sorting (HOPS/class C Vps) complex can tether low-curvature membranes, that is, liposomes with a diameter of ∼100 nm, only when the yeast vacuolar Rab GTPase Ypt7p is present in both tethered membranes. When HOPS is phosphorylated by the vacuolar casein kinase I, Yck3p, tethering only takes place when GTP-bound Ypt7p is present in both tethered membranes. When HOPS is not phosphorylated, however, its tethering activity shows little specificity for the nucleotide-binding state of Ypt7p. These results suggest a model for HOPS-mediated tethering in which HOPS tethers membranes by binding to Ypt7p in each of the two tethered membranes. Moreover, because vacuole-associated HOPS is presumably phosphorylated by Yck3p, our results suggest that nucleotide exchange of Ypt7p on multivesicular bodies (MVBs)/late endosomes must take place before HOPS can mediate tethering at vacuoles. PMID:25995379

  17. Minimally invasive tethered cord release in children: A technical note

    Directory of Open Access Journals (Sweden)

    S. Kağan Başarslan

    2014-03-01

    Full Text Available Tethered cord release is commonly performed in pediatric neurosurgery. Nowadays, minimally invasive procedures are created growing interest due to its highly tolerable nature for surgery. It has been main purpose a minimal damaging on access route and maximum protection of normal structures in surgery. We present a surgical treatment of tethered cord syndrome, by which is provided the cord releasing unlike the many methods being applied with tissue removal. The main advantage of performing this surgery through 2 cm hole is to avoid removing ligamentum flavum and bony structure like lamina in addition to reduce the length of the incision and the related scar tissue. J Clin Exp Invest 2014; 5 (1: 115-117 Technical note: the patient was taken on the operating table in the sitting-prone position, and L5-S1 distance was determined by fluoroscopy. The skin and subcutaneous tissues was passed via a 2 cm vertical incision settled in 0.5 cm laterally from midline. L5-S1 distance and its covering ligamentum flavum are displayed by the guidance of L5 lamina. Williams’s retractor was placed in the distance after fetching microscope. The foregoing procedures are the same with microdiscectomic surgery. By a vertical incision made on the flavum, its both layer was lifted up and hanged with simple suture on the back tissue for a comfortable exposure of the Dura. Thecal sac was opened by 0.5 cm long vertical incision on the Dura after obtaining secure CSF drainage with the help of yellow-tipped syringe needle. With finding by a nerve hook, the phylum was burned and released securely. Then the Dura was sutured primarily for the closure by means of microsurgery instruments, and flavum was laid on it again.

  18. Hydrophobic and electrostatic cell surface properties of thermophilic dairy streptococci.

    Science.gov (United States)

    van der Mei, H C; de Vries, J; Busscher, H J

    1993-12-01

    Microbial adhesion to hydrocarbons (MATH) and microelectrophoresis were done in 10 mM potassium phosphate solutions to characterize the surfaces of thermophilic dairy streptococci, isolated from pasteurizers. Regardless of whether they were grown (in M17 broth) with lactose, sucrose, or glucose added, strains were relatively hydrophilic (showing low initial removal rates by hexadecane) and slightly negatively charged. A tendency exists for cells grown with sucrose added to be more hydrophilic than cells grown with glucose or lactose added. Also, the lowest isoelectric points, i.e., the pH values for which the zeta potentials are zero, were measured for strains with glucose added to the growth medium. The isoelectric points for the strains were all rather high, between pH 3 and 5, indicative of protein-rich surfaces, although X-ray photoelectron spectroscopy did not measure excessively large amounts of nitrogen on the cell surfaces. Both MATH and microelectrophoresis were done as a function of pH. Maxima in hydrophobicity were observed at certain pH values. Usually these pH values were in the range of the isoelectric points of the cells. Thus it appears that MATH measures an interplay of hydrophobicity and electrostatic interactions. MATH measures solely hydrophobicity only when electrostatic interactions are absent, i.e., close to the isoelectric points of the cells. Considering that these thermophilic streptococci are all rather hydrophilic, a possible pathway to prevent fouling in the pasteurization process might be to render the heat exchanger plates of the pasteurizer more hydrophobic. PMID:16349127

  19. Cluster filtering/control of bending/torsional vibrations of a tape tether using smart-film sensors/actuators

    Science.gov (United States)

    Kojima, Hirohisa; Kunugi, Kouta; Trivailo, Pavel M.

    2016-06-01

    Tape tethers show great promise for application in space debris removal because they possess a large collecting area, which is crucial for the collection of electrons from a plasma environment in space. Tape tethers are therefore preferred over string tethers in electrodynamic tethered systems (EDTS), which operate based on the Lorentz force derived from the interaction between the electric current on the tether and the Earth's magnetic field. Vibrations of the tether may disturb the attitude of the mother satellite and the subsatellite, and are difficult to damp in space because the damping would be minimal owing to the almost zero drag force in space. Due to their relatively large width, tape tethers experience torsional deformation and therefore cannot be treated as a string tether. If torsional deformation of tape tethers is not avoided, the advantage of tape tethers as the materials for EDT systems will be deteriorated. Point-type sensors and actuators are usually used to sense and control vibrations. However, it is difficult to apply such sensors and actuators to tape tethers because of the substantial length of the tether as well as the need for a deployment mechanism, such as a reel. In order to overcome the difficulties related to vibrations, the use of smart-film sensors and actuators for sensing and controlling vibrations of tape tethers is considered in this study. In a previous study, we presented an application of smart film for sensing vibrations of tape tethers, but the actuation of tape tethers using smart-film actuators has not yet been reported. In the present paper, we mathematically derive suitable configurations of smart-film attachment to a tape tether for cluster filtering and actuation of bending and torsional vibrations of the tape tether, and carried out cluster actuation experiments. The experimental results reveal that the bending and torsional vibrations of a tape tether can be reduced by cluster actuation control based on direct

  20. X-ray photoelectron spectroscopy for the study of microbial cell surfaces

    NARCIS (Netherlands)

    van der Mei, Henderina C; de Vries, Jacob; Busscher, Hendrik J

    2000-01-01

    X-ray photoelectron spectroscopy (XPS) is well known for the characterisation of material surfaces, but at first glance, is an unexpected technique to study the composition of microbial cell surfaces. Despite the fact that intimate contact between materials and microbial cell surfaces occurs in many

  1. A reference guide to microbial cell surface hydrophobicity based on contact angles

    NARCIS (Netherlands)

    van der Mei, HC; Busscher, HJ; Bos, R.R.M.

    1998-01-01

    Acid-base interactions form the origin of the hydrophobicity of microbial cell-surfaces and can be quantitated from contact angle measurements on microbial lawns with water, formamide, methyleneiodide and/or alpha-bromonaphthalene. This review provides a reference guide to microbial cell surface hyd

  2. A simple approach to cancer therapy afforded by multivalent pseudopeptides that target cell-surface nucleoproteins

    NARCIS (Netherlands)

    Destouches, D.; Page, N.; Hamma-Kourbali, Y.; Machi, V.; Chaloin, O.; Frechault, S.; Birmpas, C.; Katsoris, P.; Beyrath, J.D.; Albanese, P.; Maurer, M.; Carpentier, G.; Strub, J.M.; Dorsselaer, A. van; Muller, S.; Bagnard, D.; Briand, J.P.; Courty, J.

    2011-01-01

    Recent studies have implicated the involvement of cell surface forms of nucleolin in tumor growth. In this study, we investigated whether a synthetic ligand of cell-surface nucleolin known as N6L could exert antitumor activity. We found that N6L inhibits the anchorage-dependent and independent growt

  3. Computational study of small molecule binding for both tethered and free conditions

    CERN Document Server

    Ytreberg, F Marty

    2009-01-01

    Using a calix[4]arene-benzene complex as a test system we compare the potential of mean force for when the calix[4]arene is tethered versus free. When the complex is in vacuum our results show that the difference between tethered and free is primarily due to the entropic contribution to the potential of mean force resulting in a binding free energy difference of 6.5 kJ/mol. By contrast, when the complex is in water our results suggest that the difference between tethered and free is due to the enthalpic contribution resulting in a binding free energy difference of 1.6 kJ/mol. This study elucidates the roles of entropy and enthalpy for this small molecule system and emphasizes the point that tethering the receptor has the potential to dramatically impact the binding properties. These findings should be taken into consideration when using calixarene molecules in nanosensor design.

  4. Advanced Particle-in-Cell (PIC) Tools for Simulation of Electrodynamic Tether Plasma Interactions Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Electrodynamic tethers are optimally suited for use in Low-Earth-Orbit (LEO) to generate thrust or drag maneuver satellites. LEO region is polluted with space...

  5. Significance of relative velocity in drag force or drag power estimation for a tethered float

    Digital Repository Service at National Institute of Oceanography (India)

    Vethamony, P.; Sastry, J.S.

    There is difference in opinion regarding the use of relative velocity instead of particle velocity alone in the estimation of drag force or power. In the present study, a tethered spherical float which undergoes oscillatory motion in regular waves...

  6. UV-Curable Hybrid Nanocomposite Coating to Protect Tether Polymer Materials Project

    Data.gov (United States)

    National Aeronautics and Space Administration — To address the NASA need for coatings to protect and strengthen tether materials for Momentum-exchange Electrodynamic Reboost (MXER) technology, Luminit, LLC,...

  7. Materials for advancement of MXER tether design (1000-371) Project

    Data.gov (United States)

    National Aeronautics and Space Administration — There exist a need to develop, identify, and classify various materials that can be used in the fabrication of electrodynamic tethers for various applications....

  8. Materials for Advancement of MXER Tether Design (1000-549) Project

    Data.gov (United States)

    National Aeronautics and Space Administration — There exist a need to develop, identify, and classify various materials that can be used in the fabrication of electrodynamic tethers for various applications....

  9. Construction and Structural Analysis of Tethered Lipid Bilayer Containing Photosynthetic Antenna Proteins for Functional Analysis

    Energy Technology Data Exchange (ETDEWEB)

    Sumino, Ayumi; Dewa, Takehisa; Takeuchi, Toshikazu; Sugiura, Ryuta; Sasaki, Nobuaki; Misawa, Nobuo; Tero, Ryugo; Urisu, Tsuneo; Gardiner, Alastair T; Cogdell, Richard J; Hashimoto, Hideki; Nango, Mamoru

    2011-07-11

    The construction and structural analysis of a tethered planar lipid bilayer containing bacterial photosynthetic membrane proteins, light-harvesting complex 2 (LH2), and light-harvesting core complex (LH1-RC) is described and establishes this system as an experimental platform for their functional analysis. The planar lipid bilayer containing LH2 and/or LH1-RC complexes was successfully formed on an avidin-immobilized coverglass via an avidin-biotin linkage. Atomic force microscopy (AFM) showed that a smooth continuous membrane was formed there. Lateral diffusion of these membrane proteins, observed by a fluorescence recovery after photobleaching (FRAY), is discussed in terms of the membrane architecture. Energy transfer from LH2 to LH1-RC within the tethered membrane architecture. Energy transfer from LH2 to LH1-RC within the tethered membrane was observed by steady-state fluorescence spectroscopy, indicating that the tethered membrane can mimic the natural situation.

  10. Attitude stabilization of electrodynamic tethers in elliptic orbits by time-delay feedback control

    Science.gov (United States)

    Iñarrea, Manuel; Lanchares, Víctor; Pascual, Ana Isabel; Salas, José Pablo

    2014-03-01

    It is well known that libration motion of electrodynamic tethers operating in inclined orbits is affected by dynamic instability due to the electromagnetic interaction between the tether and the geomagnetic field. We study the application of two feedback control methods in order to stabilize the periodic attitude motions of electrodynamic tethers in elliptic inclined orbits. Both control schemes are based on the time-delayed autosynchronization of the system. Numerical simulations of the controlled libration motion show that both control techniques are able to transform the uncontrolled unstable periodic motions into asymptotically stable ones. Such stabilized periodic attitude motions can be taken as starting points for the operation of the tether. The control domains of both methods have been computed for different values of the system parameters, as functions of the two control parameters shared by both control schemes. The relative effectiveness of the two techniques in the stabilization of the periodic attitude motion has also been studied.

  11. Polydopamine tethered enzyme/metal-organic framework composites with high stability and reusability

    Science.gov (United States)

    Wu, Xiaoling; Yang, Cheng; Ge, Jun; Liu, Zheng

    2015-11-01

    An enzyme/metal-organic framework (MOF) composite with both highly stable and easily reusable features was prepared via tethering enzyme/MOF nanocrystals with polydopamine (PDA). The micrometer-sized PDA tethered enzyme/MOF composite can be easily repeatedly used without obvious activity loss, promising for efficient enzymatic catalysis at low cost with long-term operational stability under harsh conditions.An enzyme/metal-organic framework (MOF) composite with both highly stable and easily reusable features was prepared via tethering enzyme/MOF nanocrystals with polydopamine (PDA). The micrometer-sized PDA tethered enzyme/MOF composite can be easily repeatedly used without obvious activity loss, promising for efficient enzymatic catalysis at low cost with long-term operational stability under harsh conditions. Electronic supplementary information (ESI) available: Synthesis of enzyme-MOF nanocrystals, SEM, TEM, CLSM characterization and measurements of enzymatic performances. See DOI: 10.1039/c5nr05190h

  12. Electron Emitter for small-size Electrodynamic Space Tether using MEMS Technology

    DEFF Research Database (Denmark)

    Fleron, René A. W.; Blanke, Mogens

    2004-01-01

    Adjustment of the orbit of a spacecraft using the forces created by an electro-dynamic space-tether has been shown as a theoretic possibility in recent literature. Practical implementation is being pursued for larger scale missions where a hot filament device controls electron emission and the...... current flowing in the electrodynamic space tether. Applications to small spacecraft, or space debris in the 1–10 kg range, possess difficulties with electron emission technology, as low power emitting devices are needed. This paper addresses the system concepts of a small spacecraft electrodynamic tether...... system with focus on electron emitter design and manufacture using micro-electro-mechanical- system (MEMS) technology. The paper addresses the system concepts of a small size electrodynamic tether mission and shows a novel electron emitter for the 1-2 mA range where altitude can be effectively affected...

  13. Validation, reliability, and complications of a tethering scoliosis model in the rabbit.

    Science.gov (United States)

    Kallemeier, Patricia M; Buttermann, Glenn R; Beaubien, Brian P; Chen, Xinqian; Polga, David J; Lew, William D; Wood, Kirkham B

    2006-04-01

    This study was conducted to refine a small animal model of scoliosis, and to quantify the deformities throughout its growth period. Subcutaneous scapula-to-contralateral pelvis tethering surgery was selected due to its minimally invasive nature and potential applicability for a large animal model. The procedure was performed in 7-week-old New Zealand white rabbits. Group A animals (n=9) underwent the tethering procedure with a suture that spontaneously released. Group B animals (n=17) had the identical procedure with a robust tether and pelvic fixation, which was maintained for 2 months during growth. All animals developed immediate post-operative scoliosis with a Cobb angle of 23 degrees (range, 6-39 degrees) in group A and 59 degrees (range, 24-90 degrees) in group B animals. During the 2 month post-tethering, group A animals lost their tether and scoliosis resolved, whereas all animals in group B maintained their tether until scheduled release at which time the mean scoliosis was 62 degrees. Immediately after tether release, group B scoliosis decreased to a mean 53 degrees. Over the following 4 months of adolescent growth, the scoliosis decreased to a mean of 43 degrees at skeletal maturity; the decrease usually occurred in animals with less than 45 degrees curves at tether release. Radiographs revealed apical vertebral wedging (mean 19 degrees ) in all group B animals. Sagittal spinal alignment was also assessed, and for group B animals, the scoliotic segment developed mild to moderate kyphosis (mean 28 degrees) and torsional deformity, but the kyphosis resolved by 4 months after tether-release. Complications specific to this technique included a high rate of transient scapulothoracic dissociation and cases of cor pulmonale. In conclusion, this tethering technique in immature rabbits consistently produced scoliosis with vertebral wedging when the tether was intact through the first 2 months of the protocol. The transient exaggeration of kyphosis suggests that

  14. Effect of Temperature on Tether Extraction, Surface Protrusion, and Cortical Tension of Human Neutrophils

    OpenAIRE

    Liu, Baoyu; Goergen, Craig J.; Shao, Jin-Yu

    2007-01-01

    Neutrophil rolling on endothelial cells, the initial stage of its migrational journey to a site of inflammation, is facilitated by tether extraction and surface protrusion. Both phenomena have been studied extensively at room temperature, which is considerably lower than human body temperature. It is known that temperature greatly affects cellular mechanical properties such as viscosity. Therefore, we carried out tether extraction, surface protrusion, and cortical tension experiments at 37°C ...

  15. Low work-function coating for an entirely propellantless bare electrodynamic tether

    OpenAIRE

    Williams, John D.; Sanmartin, Juan R.; Rand, Lauren P.

    2012-01-01

    We present the possibility of a low work-function material, calcium aluminate electride, being used for a coating on a bare electrodynamic tether system. Analyses suggest that the coating would eliminate the need for an active cathodic device like a hollow cathode and, consequently, eliminate the need for an expellant to the hollow cathode, thus resulting in an electrodynamic tether system that requires no consumables. Applications include on-orbit power generation and deorbiting debris fr...

  16. Tether Extrusion from Red Blood Cells: Integral Proteins Unbinding from Cytoskeleton

    OpenAIRE

    Borghi, N.; Brochard-Wyart, F.

    2007-01-01

    We investigate the mechanical strength of adhesion and the dynamics of detachment of the membrane from the cytoskeleton of red blood cells (RBCs). Using hydrodynamical flows, we extract membrane tethers from RBCs locally attached to the tip of a microneedle. We monitor their extrusion and retraction dynamics versus flow velocity (i.e., extrusion force) over successive extrusion-retraction cycles. Membrane tether extrusion is carried out on healthy RBCs and ATP-depleted or -inhibited RBCs. For...

  17. Validation, reliability, and complications of a tethering scoliosis model in the rabbit

    OpenAIRE

    Kallemeier, Patricia M.; Buttermann, Glenn R.; Beaubien, Brian P.; Chen, Xinqian; Polga, David J.; Lew, William D; Wood, Kirkham B.

    2005-01-01

    This study was conducted to refine a small animal model of scoliosis, and to quantify the deformities throughout its growth period. Subcutaneous scapula-to-contralateral pelvis tethering surgery was selected due to its minimally invasive nature and potential applicability for a large animal model. The procedure was performed in 7-week-old New Zealand white rabbits. Group A animals (n=9) underwent the tethering procedure with a suture that spontaneously released. Group B animals (n=17) had the...

  18. Biomimicry enhances sequential reactions of tethered glycolytic enzymes, TPI and GAPDHS.

    Directory of Open Access Journals (Sweden)

    Chinatsu Mukai

    Full Text Available Maintaining activity of enzymes tethered to solid interfaces remains a major challenge in developing hybrid organic-inorganic devices. In nature, mammalian spermatozoa have overcome this design challenge by having glycolytic enzymes with specialized targeting domains that enable them to function while tethered to a cytoskeletal element. As a step toward designing a hybrid organic-inorganic ATP-generating system, we implemented a biomimetic site-specific immobilization strategy to tether two glycolytic enzymes representing different functional enzyme families: triose phosphoisomerase (TPI; an isomerase and glyceraldehyde 3-phosphate dehydrogenase (GAPDHS; an oxidoreductase. We then evaluated the activities of these enzymes in comparison to when they were tethered via classical carboxyl-amine crosslinking. Both enzymes show similar surface binding regardless of immobilization method. Remarkably, specific activities for both enzymes were significantly higher when tethered using the biomimetic, site-specific immobilization approach. Using this biomimetic approach, we tethered both enzymes to a single surface and demonstrated their function in series in both forward and reverse directions. Again, the activities in series were significantly higher in both directions when the enzymes were coupled using this biomimetic approach versus carboxyl-amine binding. Our results suggest that biomimetic, site-specific immobilization can provide important functional advantages over chemically specific, but non-oriented attachment, an important strategic insight given the growing interest in recapitulating entire biological pathways on hybrid organic-inorganic devices.

  19. Off-set control of the tethered systems using a graph theoretic approach

    Science.gov (United States)

    Modi, V. J.; Pradhan, S.; Misra, A. K.

    1995-03-01

    A mathematical model is developed to study the dynamics and control of the tethered satellite systems undergoing planar motion in a Keplerian orbit. The system consists of a rigid platform from which a point mass subsatellite can be deployed or retrieved by a flexible tether. The model incorporates off-set of the tether attachment point from the platform centre of mass and its time-dependent variation. The governing equations of motion are obtained using the Lagrangian formulation. The effect of system parameters is analysed numerically. The off-set control strategy, which involves movement of the attachment point, is used to regulate the tether swing and the platform dynamics is controlled by a momentum gyro. The off-set control strategy can be implemented using a manipulator which moves the tether attachment point as required. It is shown that the control of only the rigid degrees of freedom is not sufficient as the flexible dynamics of the tether becomes unstable, particularly during retrieval. In the present study, passive dampers are proposed to control the flexible dynamics. The simulation results show that the control procedure regulates the system dynamics quite successfully. The state feedback controller for the system is designed using graph theoretic approach which has computational advantage particularly for higher order systems.

  20. Biomimicry enhances sequential reactions of tethered glycolytic enzymes, TPI and GAPDHS.

    Science.gov (United States)

    Mukai, Chinatsu; Gao, Lizeng; Bergkvist, Magnus; Nelson, Jacquelyn L; Hinchman, Meleana M; Travis, Alexander J

    2013-01-01

    Maintaining activity of enzymes tethered to solid interfaces remains a major challenge in developing hybrid organic-inorganic devices. In nature, mammalian spermatozoa have overcome this design challenge by having glycolytic enzymes with specialized targeting domains that enable them to function while tethered to a cytoskeletal element. As a step toward designing a hybrid organic-inorganic ATP-generating system, we implemented a biomimetic site-specific immobilization strategy to tether two glycolytic enzymes representing different functional enzyme families: triose phosphoisomerase (TPI; an isomerase) and glyceraldehyde 3-phosphate dehydrogenase (GAPDHS; an oxidoreductase). We then evaluated the activities of these enzymes in comparison to when they were tethered via classical carboxyl-amine crosslinking. Both enzymes show similar surface binding regardless of immobilization method. Remarkably, specific activities for both enzymes were significantly higher when tethered using the biomimetic, site-specific immobilization approach. Using this biomimetic approach, we tethered both enzymes to a single surface and demonstrated their function in series in both forward and reverse directions. Again, the activities in series were significantly higher in both directions when the enzymes were coupled using this biomimetic approach versus carboxyl-amine binding. Our results suggest that biomimetic, site-specific immobilization can provide important functional advantages over chemically specific, but non-oriented attachment, an important strategic insight given the growing interest in recapitulating entire biological pathways on hybrid organic-inorganic devices. PMID:23626684

  1. The mechanics of motorised momentum exchange tethers when applied to active debris removal from LEO

    International Nuclear Information System (INIS)

    The concept of momentum exchange when applied to space tethers for propulsion is well established, and a considerable body of literature now exists on the on-orbit modelling, the dynamics, and also the control of a large range of tether system applications. The authors consider here a new application for the Motorised Momentum Exchange Tether by highlighting three key stages of development leading to a conceptualisation that can subsequently be developed into a technology for Active Debris Removal. The paper starts with a study of the on-orbit mechanics of a full sized motorised tether in which it is shown that a laden and therefore highly massasymmetrical tether can still be forced to spin, and certainly to librate, thereby confirming its possible usefulness for active debris removal (ADR). The second part of the paper concentrates on the modelling of the centripetal deployment of a symmetrical MMET in order to get it initialized for debris removal operations, and the third and final part of the paper provides an entry into scale modelling for low cost mission design and testing. It is shown that the motorised momentum exchange tether offers a potential solution to the removal of large pieces of orbital debris, and that dynamic methodologies can be implemented to in order to optimise the emergent design

  2. Lipoproteins tethered dendrimeric nanoconstructs for effective targeting to cancer cells

    Energy Technology Data Exchange (ETDEWEB)

    Jain, Anupriya; Jain, Keerti, E-mail: keertijain02@gmail.com; Mehra, Neelesh Kumar, E-mail: neelesh81mph@gmail.com; Jain, N. K., E-mail: dr.jnarendr@gmail.com [Dr. H. S. Gour University, Pharmaceutics Research Laboratory, Department of Pharmaceutical Sciences (India)

    2013-10-15

    In the present investigation, poly (propylene imine) dendrimers up to fifth generation (PPI G5.0) were synthesized using ethylene diamine and acrylonitrile. Lipoproteins (high-density lipoprotein; HDL and low-density lipoprotein; LDL) were isolated from human plasma by discontinuous density gradient ultracentrifugation, characterized and tethered to G5.0 PPI dendrimers to construct LDL- and HDL-conjugated dendrimeric nanoconstructs for tumor-specific delivery of docetaxel. Developed formulations showed sustained release characteristics in in vitro drug release and in vivo pharmacokinetic studies. The cancer targeting potential of lipoprotein coupled dendrimers was investigated by ex vivo cytotoxicity and cell uptake studies using human hepatocellular carcinoma cell lines (HepG2 cells) and biodistribution studies in albino rats of Sprague-Dawley strain. Lipoprotein anchored dendrimeric nanoconstructs showed significant uptake by cancer cells as well as higher biodistribution of docetaxel to liver and spleen. It is concluded that these precisely synthesized engineered dendrimeric nanoconstructs could serve as promising drug carrier for fighting with the fatal disease, i.e., cancer, attributed to their defined targeting and therapeutic potential.

  3. Critical adsorption of copolymer tethered on selective surfaces

    Science.gov (United States)

    Li, Hong; Qian, Chang-Ji; Luo, Meng-Bo

    2016-04-01

    Critical adsorption behaviors of flexible copolymer chains tethered to a flat homogeneous surface are studied by using Monte Carlo simulations. We have compared the critical adsorption temperature Tc, estimated by a finite-size scaling method, for different AB copolymer sequences with A the attractive monomer and B the inert monomer. We find that Tc increases with an increase in the fraction of monomers A, fA, in copolymers, and it increases with an increase in the length of block A for the same fA. In particular, Tc of copolymer (AnBn)r can be expressed as a function of the block length, n, and Tc of copolymer (AnB)r and (ABm)r can be expressed as a linear function of fA. Tc of random copolymer chains also can be expressed as a linear function of fA and it can be estimated by using weight-average of Tc of different diblocks in the random copolymer. However, the crossover exponent is roughly independent of AB sequence distributions either for block copolymers or for random copolymers.

  4. Detergent interaction with tethered bilayer lipid membranes for protein reconstitution

    Science.gov (United States)

    Broccio, Matteo; Zan Goh, Haw; Loesche, Mathias

    2009-03-01

    Tethered bilayer lipid membranes (tBLMs) are self-assembled biomimetic structures in which the membrane is separated from a solid substrate by a nm-thick hydrated submembrane space. These model systems are being used in binding studies of peripheral proteins and exotoxins. Here we aim at their application for the reconstitution of water-insoluble integral membrane proteins. As an alternative to fusion of preformed proteoliposomes we study the direct reconstitution of such proteins for applications in biosensing and pharmaceutical screening. For reconstitution, highly insulating tBLMs (R˜10^5-10^6 φ) were temporarily incubated with a detergent to screen for conditions that keep the detergent-saturated membranestable and ready to incorporate detergent-solubilized proteins. We assess the electrical characteristics, i.e. specific resistance and capacitance, by means of electrochemical impedance spectroscopy (EIS) under timed incubation with decylmaltoside and dodecylmaltoside detergents in a regime around their critical micelle concentration, 1.8 mM and 0.17 mM respectively and demonstrate the restoration of the tBLM upon detergent removal. Thereby a range of concentration and incubation times was identified, that represents optimal conditions for the subsequent membrane protein reconstitution.

  5. Using tethered triblock copolymers to mediate the interaction between substrates

    International Nuclear Information System (INIS)

    Using scaling analysis and a self-consistent field (SCF) theory, we compress two copolymer-coated surfaces and isolate conditions that yield multiple, distinct minima in the interaction profile. We focus on planar surfaces that are coated with ABC triblock copolymers. Tethered to the surface by the last monomer in the C block, the copolymers are grafted at relatively low densities. The surrounding solution is a poor solvent for both the A and C blocks, and is a good solvent for the B blocks. Through scaling theory, we pinpoint the parameters that yield two minima in the interaction profile. The SCF calculations reveal the changes in the morphology of the polymers as the layers are compressed. Through both studies, we determine how the morphological changes give rise to the observed surface interactions. The results provide guidelines for creating polymer-coated colloidal systems that can form two stable crystal structures. Such systems could be used for bistable, optical switches. The findings also yield a prescription for creating systems that exhibit additional minima in the free energy of interaction. copyright 1998 American Institute of Physics

  6. SURFACE MODIFICATION OF POLYPROPYLENE MICROPOROUS MEMBRANE BY TETHERING POLYPEPTIDES

    Institute of Scientific and Technical Information of China (English)

    Zhen-mei Liu; Zhi-kang Xu; Mathias Ulbricht

    2006-01-01

    Two kinds of polypeptides were tethered onto the surface of polypropylene microporous membrane (PPMM)through a ring opening polymerization of L-glutamate N-carboxyanhydride initiated by amino groups which were introduced by ammonia plasma and γ-aminopropyl triethanoxysilane treatments. X-ray photoelectron spectroscopy (XPS), attenuated total reflectance Fourier transform infrared spectroscopy (FT-IR/ATR), scanning electron microscopy (SEM), together with water contact angle measurements were used to characterize the modified membranes. XPS analyses and FT-IR/ATR spectra demonstrated that polypeptides are actually grafted onto the membrane surface. The wettability of the membrane surface increases at first and then decreases with the increase in grafting degrees of polypeptide. Platelet adhesion and murine macrophage attachment experiments reveal an enhanced hemocompatibility for the polypeptide modified PPMMs. All these results give evidence that polypeptide grafting can simultaneously improve the hemocompatibility as well as reserve the hydrophobicity for the membrane, which will provide a potential approach to improve the performance of polypropylene hollow fiber microporous membrane used in artificial oxygenator.

  7. Wellcome Prize Lecture. Cell surface, ion-sensing receptors.

    Science.gov (United States)

    Riccardi, Daniela

    2002-07-01

    Changes in extracellular calcium (Ca(2+)o) concentration ([Ca2+]o) affect kidney function both under basal and hormone-stimulated conditions. The molecular identification of an extracellular Ca(2+)-sensing receptor (CaR) has confirmed a direct role of Ca(2+)o on parathyroid and kidney function (i.e. independent of calciotropic hormones) as a modulator of Ca2+ homeostasis. In addition, evidence accumulated over the last 10 years has shown that CaR is also expressed in regions outside the calcium homeostatic system where its role is largely undefined but seems to be linked to regulation of local ionic homeostasis. The parathyroid and kidney CaRs are 1081 and 1079 amino acids long, respectively, and belong to the type III family of G protein-coupled receptors (GPCRs), which includes other CaRs, metabotropic glutamate receptors and putative vomeronasal organ receptors. For the CaR, its low (millimolar) affinity for Ca2+, its positive cooperativity and its large ion-sensing extracellular domain, indicate that the receptor is more sensitive to changes in net cationic charge rather than to a specific ligand. Mg2+, trivalent cations of the lanthanide series and polyvalent cations such as spermine and aminoglycoside antibiotics can all activate the receptor in vitro with EC50 values in the micromolar range for trivalent and polyvalent cations or in the millimolar range for Ca2+ and Mg2+. In addition to true CaR agonists, CaR sensitivity to Ca(2+)o is also susceptible to allosteric modulation by ionic strength, L-amino acids and by pharmacological agents. This review will address endogenous and exogenous CaR agonists, the role of the receptor in the calcium homeostatic system and some speculation on possible role(s) of the CaR in regions not involved in mineral ion homeostasis. PMID:12392104

  8. Space demostration of bare electrodynamic tape-tether technology on the sounding rocket S520-25

    OpenAIRE

    Fujii, Hironori; Watanabe, Takeo; Sahara, Hironori; Kojima, Hirohisa; Takehara, Shoichiro; Yamagiwa, Yoshiki; Sasaki, Susumu; Abe, Takumi; Tanaka, Koji; Oyama, Khoichiro; Jhonson, Les; Khazanov, V.; Sanmartín Losada, Juan Ramón; Charro, Mario; Kruijff, Michiel

    2011-01-01

    A spaceflight validation of bare electro dynamic tape tether technology was conducted. A S520-25 sounding rocket was launched successfully at 05:00am on 31 August 2010 and successfully deployed 132.6m of tape tether over 120 seconds in a ballistic flight. The electrodynamic performance of the bare tape tether employed as an atmospheric probe was measured. Flight results are introduced through the present progressive report of the demonstration and the results of flight experiment are ex...

  9. T-REX: Bare electro-dynamic tape-tether technology experimetn on sounding rocket S520

    OpenAIRE

    Watanabe, Takeo; Fujii, Hironori; Kusagaya, Tairo; Sahara, Hironori; Kojima, Hirohisa; Takehara, Shoichiro; Yamagiwa, Yoshiki; Sasaki, Susumu; Abe, Takumi; Tanaka, Koji; Oyama, Khoichiro; Ebinuma, Takuji; Johson, Les; Khazanov, George; Sanmartín Losada, Juan Ramón

    2012-01-01

    The project to verify the performance of space tether technology was successfully demonstrated by the launch of the sounding rocket S520 the 25tu. The project is the space demonstration of science and engineering technologies of a bare tape electrodynamic tether (EDT) in the international campaign between Japan, USA, Europe and Australia. Method of "Inverse ORIGAMI (Tape tether folding)" was employed in order to deploy the bare tape EDT in a short period time of the suborbital flight. The ...

  10. Tethered swimming and dry land force parameters: useful tools to characterize front crawl performance in both genders

    OpenAIRE

    Morouço, Pedro Gil Frade

    2012-01-01

    The major purpose of this work was to examine possible relationships between tethered forces and dry-land exercises with swimming performance, for both males and female swimmers. Additionally, it was intended to verify if tethered swimming could be an easy, operative and accurate methodology for the biophysical evaluation of swimmers. For the accomplishment of these purposes the following sequence was used: (i) reviewing available literature; (ii) comparison of tethered swimming w...

  11. Regulation of ADAM12 cell-surface expression by protein kinase C epsilon

    DEFF Research Database (Denmark)

    Sundberg, Christina; Thodeti, Charles Kumar; Kveiborg, Marie;

    2004-01-01

    constitutively active protein. However, little is known about the regulation of ADAM12 cell-surface translocation. Here, we used human RD rhabdomyosarcoma cells, which express ADAM12 at the cell surface, in a temporal pattern. We report that protein kinase C (PKC) epsilon induces ADAM12 translocation to the cell......The ADAM (a disintegrin and metalloprotease) family consists of multidomain cell-surface proteins that have a major impact on cell behavior. These transmembrane-anchored proteins are synthesized as proforms that have (from the N terminus): a prodomain; a metalloprotease-, disintegrin......-immunoprecipitated from membrane-enriched fractions of PMA-treated cells, 3) RD cells transfected with EGFP-tagged, myristoylated PKCepsilon expressed more ADAM12 at the cell surface than did non-transfected cells, and 4) RD cells transfected with a kinase-inactive PKCepsilon mutant did not exhibit ADAM12 cell...

  12. Proteomic analysis and identification of cell surface-associated proteins of Clostridium chauvoei.

    Science.gov (United States)

    Jayaramaiah, Usharani; Singh, Neetu; Thankappan, Sabarinath; Mohanty, Ashok Kumar; Chaudhuri, Pallab; Singh, Vijendra Pal; Nagaleekar, Viswas Konasagara

    2016-06-01

    Blackleg is a highly fatal disease of cattle and sheep, caused by Clostridium chauvoei, a Gram positive, anaerobic, spore forming bacteria. Cell surface-associated proteins play a major role in inducing the protective immunity. However, the identity of a majority of cell surface-associated proteins of C. chauvoei is not known. In the present investigation, we have used SDS-PAGE, 2D-gel electrophoresis and Western blotting followed by mass spectrometry to identify cell surface-associated proteins of C. chauvoei. Among the identified proteins, which have shown to offer protective antigencity in other bacteria, Enolase, Chaperonin, Ribosomal protein L10, Glycosyl Hydrolase and Flavoprotein were characterized by sequencing and their overexpression in Escherichia coli. In conclusion, cell surface-associated proteins were identified using proteomic approach and the genes for the immunoreactive proteins were expressed, which may prove to be potential diagnostic or vaccine candidates. PMID:26971466

  13. Variability in expression of cell surface antigens of Candida albicans during morphogenesis.

    OpenAIRE

    Brawner, D L; Cutler, J. E.

    1986-01-01

    The location and expression of two different cell surface antigens on germinating and nongerminating Candida albicans cells was examined by using transmission electron microscopy after labeling with monoclonal antibodies (H9 or C6) and immunocolloidal gold. Immunodeterminant expression of the two carbohydrate antigens was followed from early germination events through 20 h of development. The determinant detected by H9 antibody, which was initially lost from the mother cell surface and prefer...

  14. The Na+/H+ Exchanger Regulatory Factor Stabilizes Epidermal Growth Factor Receptors at the Cell Surface

    OpenAIRE

    Lazar, Cheri S.; Cresson, Catherine M.; Lauffenburger, Douglas A.; Gill, Gordon N.

    2004-01-01

    Ligand binding to cell surface receptors initiates both signal transduction and endocytosis. Although signaling may continue within the endocytic compartment, down-regulation is the major mechanism that controls the concentration of cell surface receptors, their ability to receive environmental signals, and the ultimate strength of biological signaling. Internalization, recycling, and trafficking of receptor tyrosine kinases (RTKs) within the endosome compartment are each regulated to control...

  15. Exocellular esterase and emulsan release from the cell surface of Acinetobacter calcoaceticus.

    OpenAIRE

    Shabtai, Y; Gutnick, D. L.

    1985-01-01

    An esterase activity has been found, both in the cell-free growth medium and on the cell surface of the hydrocarbon-degrading Acinetobacter calcoaceticus RAG-1. The enzyme catalyzed the hydrolysis of acetyl and other acyl groups from triglycerides and aryl and alkyl esters. Emulsan, the extracellular heteropolysaccharide bioemulsifier produced by strain RAG-1, was also a substrate for the enzyme. Gel filtration showed that the cell-free enzyme was released from the cell surface either emulsan...

  16. SCAMP 37, a new marker within the general cell surface recycling system.

    OpenAIRE

    Brand, S H; Castle, J D

    1993-01-01

    Secretory carrier membrane proteins (SCAMPs) are widely distributed as components of post-Golgi membranes that function as recycling carriers to the cell surface. In fibroblasts, SCAMPs are concentrated in compartments involved in the endocytosis and recycling of cell surface receptors while in neurons and other cell types having regulated transport pathways, SCAMPs are also components of regulated carriers (synaptic vesicles, secretion granules and transporter vesicles). Their presence in mu...

  17. DMPD: Innate immune sensing of pathogens and danger signals by cell surface Toll-likereceptors. [Dynamic Macrophage Pathway CSML Database

    Lifescience Database Archive (English)

    Full Text Available 17275324 Innate immune sensing of pathogens and danger signals by cell surface Toll... Show Innate immune sensing of pathogens and danger signals by cell surface Toll-likereceptors. PubmedID 172...75324 Title Innate immune sensing of pathogens and danger signals by cell surface

  18. A new histochemical method using human placenta alkaline phosphatase for demonstrating concanavalin A binding sites on cell surfaces

    Directory of Open Access Journals (Sweden)

    Kanzaki,Yoshito

    1975-12-01

    Full Text Available Human placenta alkaline phosphatase (HP-ALP, a glycoprotein, was stained histochemically for the purpose of examining the concanavalin A (Con A binding sites on the cell surface. HP-ALP was bound to the cell surface by Con A. This simple method successfully detected Con A binding sites on the cell surface.

  19. A model of surfactant-induced surface tension effects on the parenchymal tethering of pulmonary airways.

    Science.gov (United States)

    Fujioka, Hideki; Halpern, David; Gaver, Donald P

    2013-01-18

    We developed a computational model of lung parenchyma, which is comprised of individual alveolar chamber models. Each alveolus is modeled by a truncated octahedron. Considering the force balance between the elastin and collagen fibers laying on the alveolar membrane and the pressures acting on the membrane, we computed the deformations of the parenchyma with a finite element method. We focused on the effect of surfactant on the force of parenchymal tethering an airway. As the lung inflates, the parenchyma becomes stiffer and the tethering force becomes stronger. As the alveolar surfactant concentration is reduced, the lung volume at a fixed alveolar pressure decreases, and thus, the tethering force becomes weaker. The distortion of parenchyma caused by the deformation of an airway extends widely around the airway. The displacement of parenchyma decays with distance from the airway wall, but deviates from the prediction based on a theory for a continuum material. Using results obtained from the present lung parenchyma model, we also developed a simple 1-dimensional model for parenchyma tethering force on an airway, which could be utilized for the analysis of liquid/gas transports in an axis-symmetric elastic airway. The effective shear modulus was calculated from the pressure-volume relation of parenchyma. By manipulating the pressure-volume curve, this simple model may be used to predict the parenchyma tethering force in diseased lungs. PMID:23235110

  20. Galectin-1-mediated cell adhesion, invasion and cell death in human anaplastic large cell lymphoma: regulatory roles of cell surface glycans.

    Science.gov (United States)

    Suzuki, Osamu; Abe, Masafumi

    2014-05-01

    Galectin-1 is known to be one of the extracellular matrix proteins. To elucidate the biological roles of galectin-1 in cell adhesion and invasion of human anaplastic large cell lymphoma, we performed cell adhesion and invasion assays using the anaplastic large cell lymphoma cell line H-ALCL, which was previously established in our laboratory. From the cell surface lectin array, treatment with neuraminidase from Arthrobacter ureafaciens which cleaves all linkage types of cell surface sialic acid enhanced Arachis hypogaea (PNA), Helix pomatia (HPA) and Phaseolus vulgaris-L (L-PHA) lectin binding reactivity to cell surface of lymphoma cells suggesting that neuraminidase removes cell surface sialic acid. In cell adhesion and invasion assays treatment with neuraminidase markedly enhanced cell adhesion to galectin-1 and decreased cell invasive capacity through galectin-1. α2,6-linked sialic acid may be involved in masking the effect of the interaction between galectin-1 and cell surface glycans. H-ALCL cells expressed the β-galactoside-α2,6-sialyltransferase ST6Gal1. On resialylation assay by recombinant ST6Gal1 with CMP-Neu5Ac, α2,6-resialylation of L-PHA reactive oligosaccharide by ST6Gal1 resulted in inhibition of H-ALCL cell adhesion to galectin-1 compared to the desialylated H-ALCL cells. On knockdown experiments, knockdown of ST6Gal1 dramatically enhanced cell adhesion to galectin-1. N-glycosylation inhibitor swainsonine treatment resulted in enhancement of cell adhesion to galectin-1. In glycomic analysis using the lectin blocking assay treatment with PNA, Artocarpus integrifolia (Jacalin), Glycine max (SBA), Helix pomatia (HPA), Vicia villosa (VVA), Ulex europaeus (UEA-1), Triticum vulgaris (WGA), Canavalia ensiformis (ConA), Phaseolus vulgaris-L (L-PHA), Phaseolus vulgaris-E4 (E-PHA), Datura stramonium (DSA) lectins resulted in modulation of lymphoma cell to galectin-1 suggesting that several types of glycans may regulate cell adhesion to galectin-1 by

  1. Role of Site-Specific N-Glycans Expressed on GluA2 in the Regulation of Cell Surface Expression of AMPA-Type Glutamate Receptors.

    Directory of Open Access Journals (Sweden)

    Yusuke Takeuchi

    Full Text Available The AMPA-type glutamate receptor (AMPAR, which is a tetrameric complex composed of four subunits (GluA1-4 with several combinations, mediates the majority of rapid excitatory synaptic transmissions in the nervous system. Cell surface expression levels of AMPAR modulate synaptic plasticity, which is considered one of the molecular bases for learning and memory formation. To date, a unique trisaccharide (HSO3-3GlcAβ1-3Galβ1-4GlcNAc, human natural killer-1 (HNK-1 carbohydrate, was found expressed specifically on N-linked glycans of GluA2 and regulated the cell surface expression of AMPAR and the spine maturation process. However, evidence that the HNK-1 epitope on N-glycans of GluA2 directly affects these phenomena is lacking. Moreover, it is thought that other N-glycans on GluA2 also have potential roles in the regulation of AMPAR functions. In the present study, using a series of mutants lacking potential N-glycosylation sites (N256, N370, N406, and N413 within GluA2, we demonstrated that the mutant lacking the N-glycan at N370 strongly suppressed the intracellular trafficking of GluA2 from the endoplasmic reticulum (ER in HEK293 cells. Cell surface expression of GluA1, which is a major subunit of AMPAR in neurons, was also suppressed by co-expression of the GluA2 N370S mutant. The N370S mutant and wild-type GluA2 were co-immunoprecipitated with GluA1, suggesting that N370S was properly associated with GluA1. Moreover, we found that N413 was the main potential site of the HNK-1 epitope that promoted the interaction of GluA2 with N-cadherin, resulting in enhanced cell surface expression of GluA2. The HNK-1 epitope on N-glycan at the N413 of GluA2 was also involved in the cell surface expression of GluA1. Thus, our data suggested that site-specific N-glycans on GluA2 regulate the intracellular trafficking and cell surface expression of AMPAR.

  2. Alteration in cell surface properties of Burkholderia spp. during surfactant-aided biodegradation of petroleum hydrocarbons

    Energy Technology Data Exchange (ETDEWEB)

    Mohanty, Sagarika; Mukherji, Suparna [Indian Institute of Technology Bombay, Mumbai (India). Centre for Environmental Science and Engineering (CESE)

    2012-04-15

    Chemical surfactants may impact microbial cell surface properties, i.e., cell surface hydrophobicity (CSH) and cell surface charge, and may thus affect the uptake of components from non-aqueous phase liquids (NAPLs). This work explored the impact of Triton X-100, Igepal CA 630, and Tween 80 (at twice the critical micelle concentration, CMC) on the cell surface characteristics of Burkholderia cultures, Burkholderia cepacia (ES1, aliphatic degrader) and Burkholderia multivorans (NG1, aromatic degrader), when grown on a six-component model NAPL. In the presence of Triton X-100, NAPL biodegradation was enhanced from 21% to 60% in B. cepacia and from 18% to 53% in B. multivorans. CSH based on water contact angle (50-52 ) was in the same range for both strains while zeta potential at neutral pH was -38 and -31 mV for B. cepacia and B. multivorans, respectively. In the presence of Triton X-100, their CSH increased to greater than 75 and the zeta potential decreased. This induced a change in the mode of uptake and initiated aliphatic hydrocarbon degradation by B. multivorans and increased the rate of aliphatic hydrocarbon degradation in B. cepacia. Igepal CA 630 and Tween 80 also altered the cell surface properties. For B. cepacia grown in the presence of Triton X-100 at two and five times its CMC, CSH increased significantly in the log growth phase. Growth in the presence of the chemical surfactants also affected the abundance of chemical functional groups on the cell surface. Cell surface changes had maximum impact on NAPL degradation in the presence of emulsifying surfactants, Triton X-100 and Igepal CA630.

  3. Diamond surface functionalization with biomimicry – Amine surface tether and thiol moiety for electrochemical sensors

    Energy Technology Data Exchange (ETDEWEB)

    Sund, James B., E-mail: jim@jamessund.com [Department of Electrical and Computer Engineering, Duke University, Durham, NC (United States); Causey, Corey P. [Departments of Chemistry and Biochemistry, Duke University, Durham, NC (United States); Wolter, Scott D. [Department of Physics, Elon University, Elon, NC 27244 (United States); Parker, Charles B., E-mail: charles.parker@duke.edu [Department of Electrical and Computer Engineering, Duke University, Durham, NC (United States); Stoner, Brian R. [Department of Electrical and Computer Engineering, Duke University, Durham, NC (United States); Research Triangle Institute (RTI) International, Research Triangle Park, NC (United States); Toone, Eric J. [Departments of Chemistry and Biochemistry, Duke University, Durham, NC (United States); Glass, Jeffrey T. [Department of Electrical and Computer Engineering, Duke University, Durham, NC (United States)

    2014-05-01

    Highlights: • Diamond surfaces were functionalized with organic molecules using a novel approach. • Used biomimicry to select a molecule to bind NO, similar to the human body. • Molecular orbital theory predicted the molecule-analyte oxidation behavior. • A thiol moiety was attached to an amine surface tether on the diamond surface. • XPS analysis verified each surface functionalization step. - Abstract: The surface of conducting diamond was functionalized with a terminal thiol group that is capable of binding and detecting nitrogen–oxygen species. The functionalization process employed multiple steps starting with doped diamond films grown by plasma enhanced chemical vapor deposition followed by hydrogen termination and photochemical attachment of a chemically protected amine alkene. The surface tether was deprotected to reveal the amine functionality, which enabled the tether to be extended with surface chemistry to add a terminal thiol moiety for electrochemical sensing applications. Each step of the process was validated using X-ray photoelectron spectroscopy analysis.

  4. Exploration of the Galilean Moons using Electrodynamic Tethers for Propellantless Maneuvers and Self-Powering

    Science.gov (United States)

    Lorenzini, E. C.; Curreli, D.; Zanutto, D.

    2010-01-01

    Recent studies have demonstrated the benefits of using electrodynamic tethers (EDT) for the exploration of the inner region of the Jovian system. Intense planetary magnetic field and reasonable environmental plasma density make the electrodynamic interaction of the conductive tether with the plasmasphere strong. The interaction is responsible for a Lorentz force that can be conveniently used for propellantless maneuvers and extraction of electrical power for on board use. Jupiter and the four Galilean Moons represent an exceptional gravitational environment for the study of the orbital dynamics of an EDT. The dynamics of such a system was analyzed using a 3-body model, consisting of the planet plus one of its moons (Io in this work) and the EDT itself. New and interesting features appear, like for example the possibility to place the tether in equilibrium with respect to a frame co-rotating with the moon at points that do not coincide with the classical Lagrangian points for non-null electrodynamic forces.

  5. Diamond surface functionalization with biomimicry – Amine surface tether and thiol moiety for electrochemical sensors

    International Nuclear Information System (INIS)

    Highlights: • Diamond surfaces were functionalized with organic molecules using a novel approach. • Used biomimicry to select a molecule to bind NO, similar to the human body. • Molecular orbital theory predicted the molecule-analyte oxidation behavior. • A thiol moiety was attached to an amine surface tether on the diamond surface. • XPS analysis verified each surface functionalization step. - Abstract: The surface of conducting diamond was functionalized with a terminal thiol group that is capable of binding and detecting nitrogen–oxygen species. The functionalization process employed multiple steps starting with doped diamond films grown by plasma enhanced chemical vapor deposition followed by hydrogen termination and photochemical attachment of a chemically protected amine alkene. The surface tether was deprotected to reveal the amine functionality, which enabled the tether to be extended with surface chemistry to add a terminal thiol moiety for electrochemical sensing applications. Each step of the process was validated using X-ray photoelectron spectroscopy analysis

  6. Sliding tethered ligands add topological interactions to the toolbox of ligand-receptor design

    Science.gov (United States)

    Bauer, Martin; Kékicheff, Patrick; Iss, Jean; Fajolles, Christophe; Charitat, Thierry; Daillant, Jean; Marques, Carlos M.

    2015-09-01

    Adhesion in the biological realm is mediated by specific lock-and-key interactions between ligand-receptor pairs. These complementary moieties are ubiquitously anchored to substrates by tethers that control the interaction range and the mobility of the ligands and receptors, thus tuning the kinetics and strength of the binding events. Here we add sliding anchoring to the toolbox of ligand-receptor design by developing a family of tethered ligands for which the spacer can slide at the anchoring point. Our results show that this additional sliding degree of freedom changes the nature of the adhesive contact by extending the spatial range over which binding may sustain a significant force. By introducing sliding tethered ligands with self-regulating length, this work paves the way for the development of versatile and reusable bio-adhesive substrates with potential applications for drug delivery and tissue engineering.

  7. Low density aerothermodynamics studies performed by means of the tethered satellite system

    Science.gov (United States)

    Carlomagno, Giovanni M.; De Luca, Luigi; Siemers, Paul M.; Wood, George M., Jr.

    1986-01-01

    Low density gas flow modeling and current ground wind-tunnel technologies are not presently able to produce fully reliable data concerning low density flow regimes. In order to answer some of these issues, the Shuttle Continuous Open Wind Tunnel (SCOWT) program has been proposed, which makes use of the tethered satellite system (TSS). SCOWT's objective is to investigate the energy and momentum transfer between the tethered satellite and its environmental medium within the range of the thermofluid-dynamic conditions experienced by TSS during its atmospheric flights. The feasibility and capability of SCOWT to perform low density aerothermodynamics studies are investigated. Some of the results, obtained by means of a tether simulation program, and the instrumentation and TSS design main requirements to meet SCOWT objectives are described.

  8. Numerical study of rocket upper stage deorbiting using passive electrodynamic tether drag

    Directory of Open Access Journals (Sweden)

    Alexandru IONEL

    2014-12-01

    Full Text Available The purpose of this article is a numerical study of the possibility of deorbiting a rocket upper stage from low Earth orbit at EOM (end of mission by means of passive electrodynamic tether drag. The article is structured as follows: the introduction presents the space debris problem in low Earth orbit and the possible methods of deorbiting spacecraft. The next part of the article describes summarily some space tether applications. The third part of the article presents the principle of operation behind passive electrodynamic tether drag. In the fourth part, this principle is detailed so as to represent the input for a numerical study for the deorbit time when using the passive electrodynamic drag concept as deorbiting application. Lastly, the results are presented and conclusions are drawn.

  9. Modeling and simulations of orbital capture with space tether-net system

    Institute of Scientific and Technical Information of China (English)

    ZHAI Guang; QIU Yue; LIANG Bin; LI Cheng

    2009-01-01

    A new flexible tether-net space robotic system used to capture, space debris is presented in this paper. With a mass point assumption, a dynamic model of the tether-net system was established in orbital frame by applying Lagrange Equations. In order to investigate the net in-plane trajectories after being cast, the noncontrolled R-bar and V-bar captures were simulated with ignoring the out-of-plane libration, and the effect of inplane libration on the trajectories of the capture net was demonstrated by simulation results. With an effort to damp the in-plane libration, the control scheme based on tether tension was investigated, then an integrated control scheme was proposed by introducing thrusters into the system, and the nonlinear close-loop dynamics was linearised by feedforward strategy. Simulation results show that the feedforward controller is effective for inplane libration damping and enables the capture net to track an expected trajectory.

  10. Differential regulation of synaptic vesicle tethering and docking by UNC-18 and TOM-1

    Directory of Open Access Journals (Sweden)

    Elena O Gracheva

    2010-10-01

    Full Text Available The assembly of SNARE complexes between syntaxin, SNAP-25 and synaptobrevin is required to prime synaptic vesicles for fusion. Since Munc18 and tomosyn compete for syntaxin interactions, the interplay between these proteins is predicted to be important in regulating synaptic transmission. We explored this possibility, by examining genetic interactions between C. elegans unc-18(Munc18, unc-64(syntaxin and tom-1(tomosyn. We have previously demonstrated that unc-18 mutants have reduced synaptic transmission, whereas tom-1 mutants exhibit enhanced release. Here we show that the unc-18 mutant release defect is associated with loss of two morphologically distinct vesicle pools; those tethered within 25nm of the plasma membrane and those docked with the plasma membrane. In contrast, priming defective unc-13 mutants accumulate tethered vesicles, while docked vesicles are greatly reduced, indicating tethering is UNC-18-dependent and occurs in the absence of priming. C. elegans unc-64 mutants phenocopy unc-18 mutants, losing both tethered and docked vesicles, whereas overexpression of open syntaxin preferentially increases vesicle docking, suggesting UNC-18/closed syntaxin interactions are responsible for vesicle tethering. Given the competition between vertebrate tomosyn and Munc18, for syntaxin binding, we hypothesized that C. elegans TOM-1 may inhibit both UNC-18-dependent vesicle targeting steps. Consistent with this hypothesis, tom-1 mutants exhibit enhanced UNC-18 plasma membrane localization and a concomitant increase in both tethered and docked synaptic vesicles. Furthermore, in tom-1;unc-18 double mutants the docked, primed vesicle pool is preferentially rescued relative to unc-18 single mutants. Together these data provide evidence for the differential regulation of two vesicle targeting steps by UNC-18 and TOM-1 through competitive interactions with syntaxin

  11. Remote Control of Tissue Interactions via Engineered Photo-switchable Cell Surfaces

    Science.gov (United States)

    Luo, Wei; Pulsipher, Abigail; Dutta, Debjit; Lamb, Brian M.; Yousaf, Muhammad N.

    2014-09-01

    We report a general cell surface molecular engineering strategy via liposome fusion delivery to create a dual photo-active and bio-orthogonal cell surface for remote controlled spatial and temporal manipulation of microtissue assembly and disassembly. Cell surface tailoring of chemoselective functional groups was achieved by a liposome fusion delivery method and quantified by flow cytometry and characterized by a new cell surface lipid pull down mass spectrometry strategy. Dynamic co-culture spheroid tissue assembly in solution and co-culture tissue multilayer assembly on materials was demonstrated by an intercellular photo-oxime ligation that could be remotely cleaved and disassembled on demand. Spatial and temporal control of microtissue structures containing multiple cell types was demonstrated by the generation of patterned multilayers for controlling stem cell differentiation. Remote control of cell interactions via cell surface engineering that allows for real-time manipulation of tissue dynamics may provide tools with the scope to answer fundamental questions of cell communication and initiate new biotechnologies ranging from imaging probes to drug delivery vehicles to regenerative medicine, inexpensive bioreactor technology and tissue engineering therapies.

  12. Investigation of the Cell Surface Proteome of Human Periodontal Ligament Stem Cells.

    Science.gov (United States)

    Xiong, Jimin; Menicanin, Danijela; Zilm, Peter S; Marino, Victor; Bartold, P Mark; Gronthos, Stan

    2016-01-01

    The present study examined the cell surface proteome of human periodontal ligament stem cells (PDLSC) compared to human fibroblasts. Cell surface proteins were prelabelled with CyDye before processing to extract the membrane lysates, which were separated using 2D electrophoresis. Selected differentially expressed protein "spots" were identified using Mass spectrometry. Four proteins were selected for validation: CD73, CD90, Annexin A2, and sphingosine kinase 1 previously associated with mesenchymal stem cells. Flow cytometric analysis found that CD73 and CD90 were highly expressed by human PDLSC and gingival fibroblasts but not by keratinocytes, indicating that these antigens could be used as potential markers for distinguishing between mesenchymal cells and epithelial cell populations. Annexin A2 was also found to be expressed at low copy number on the cell surface of human PDLSC and gingival fibroblasts, while human keratinocytes lacked any cell surface expression of Annexin A2. In contrast, sphingosine kinase 1 expression was detected in all the cell types examined using immunocytochemical analysis. These proteomic studies form the foundation to further define the cell surface protein expression profile of PDLSC in order to better characterise this cell population and help develop novel strategies for the purification of this stem cell population. PMID:27579043

  13. Model system for the analysis of cell surface expression of human ABCA1

    Directory of Open Access Journals (Sweden)

    Sarkadi Balázs

    2009-12-01

    Full Text Available Abstract Background The ABCA1 protein plays a pivotal role in reverse cholesterol transport, by mediating the generation of HDL particles and removing cellular cholesterol. Both the proper expression of ABCA1 in the plasma membrane and the internalization along with apoA-I are required for function. Therefore, we developed a model system to investigate the effect of clinically relevant drugs on the cell surface appearance of ABCA1. Results By retroviral transduction system, we established stable mammalian cell lines expressing functional and non-functional ABCA1 variants, tagged with an extracellular hemagglutinin epitope. After characterization of the expression, proper localization and function of different ABCA1 variants, we followed quantitatively their cell surface expression by immunofluorescent staining, using flow cytometry. As expected, we found increased cell surface expression of ABCA1 after treatment with a calpain inhibitor, and observed a strong decrease in plasma membrane ABCA1 expression upon treatment with a trans-Golgi transport inhibitor, Brefeldin A. We tested cholesterol level lowering drugs and other potential inhibitors of ABCA1. Here we demonstrate that ezetimibe affects ABCA1 cell surface expression only in the case of a functional ABCA1. Conclusions Our model system allows a quantitative detection of cell surface expression of ABCA1, screening of substrates or specific inhibitors, and investigating transport regulation.

  14. Characterization of fucosyltransferase activity during mouse spermatogenesis: Evidence for a cell surface fucosyltransferase

    International Nuclear Information System (INIS)

    Fucosyltransferase activity was quantified in mouse germ cells at different stages of spermatogenesis. Specifically, fucosyltransferase activities of pachytene spermatocytes, round spermatids, and cauda epididymal sperm were compared. Fucosyltranferase activity of mixed germ cells displayed an apparent Vmax of 17 pmol (mg of protein)-1 min-1 and an apparent Km of approximately 13 μM for GDP-L-[14C]fucose in the presence of saturating amounts of asialofetuin at 33 degree C. Under these conditions, cellular fucosyltransferase activity was found to increase during spermatogenesis. In agreement with assays of intact cells, examination of subcellular fractions indicated that a large fraction of fucosyltransferase activity was associated with the cell surface. The fraction of fucosyltransferase activity that was associated with the cell surface progressively increased throughout spermatogenesis and epididymal maturation so that nearly all of the fucosyltransferase in epididymal sperm was on the cell surface. Specifically, by comparison of activities in the presence and absence of the detergent NP-40, the fraction of fucosyltransferase activity that was associated with the cell surface in pachytene spermatocytes, round spermatids, and epididymal sperm was 0.36, 0.5, and 0.85, respectively. These results suggest that a cell surface fucosyltransferase may be important during differentiation of spermatogenic cells in the testis as well as during epididymal maturation and fertilization

  15. Determination of Force Coresponding to Maximal Lactate Steady State in Tethered Swimming

    OpenAIRE

    PAPOTI, MARCELO; VITÓRIO, RICARDO; de Araújo, Gustavo G.; Adelino S R da Silva; SANTHIAGO, VANESSA; MARTINS, LUIZ E. B.; CUNHA, SÉRGIO A.; Gobatto, Claudio A.

    2009-01-01

    The main aim of the present investigation was to verify if the aerobic capacity (AC) measured in tethered swimming corresponds to the maximal lactate steady state (MLSS) and its correlation with 30 min and 400m free style swimming. Twenty-five swimmers were submitted to an incremental tethered swimming test (ITS) with an initial load of 20N and increments of 10N each 3min. After each stage of 3min, the athletes had 30s of interval to blood sample collections that were used to measure blood la...

  16. Drop Tower tests in preparation of a Tethered Electromagnetic Docking space demonstration

    Science.gov (United States)

    Olivieri, Lorenzo; Francesconi, Alessandro; Antonello, Andrea; Bettiol, Laura; Branz, Francesco; Duzzi, Matteo; Mantellato, Riccardo; Sansone, Francesco; Savioli, Livia

    2016-07-01

    A group of students of the University of Padova is recently developing some technologies to implement a Tethered Electromagnetic Docking (TED) experiment, a novel system for close rendezvous and mating manoeuvres between two spacecraft, consisting in a small tethered probe ejected by the chaser and magnetically guided by a receiving electromagnet mounted on the target. Because of the generated magnetic field, automatic self-alignment and mating are possible; then, as the tether is rewinded, the chaser is able to dock with the target. This concept allows to simplify standard docking procedures, thanks to the reduction of proximity navigation and guidance requirements, as well as consequent fuel reduction. Other interesting applications are expected, from active debris removal to space tugging; in particular, the utilization of the tethered connection for detumbling operations is considered. The realization of a space demonstrator requires a preliminary verification of the critical technologies employed in TED, in particular the magnetic guidance and the probe deploy and retrieve; in the framework of ESA "Drop your Thesis!" 2014 and 2016 campaigns the experiments FELDs (Flexible Electromagnetic Leash Docking system) and STAR (System for Tether Automatic Retrieval) have been focused on the test of such critical elements in the relevant microgravity environment of ZARM Drop Tower in Bremen. In particular, FELDs consisted in a simplified model of TED with a magnetic target interface, a passive tethered probe and its launch system: the experiment allowed to assess the passive self-alignment of the probe with respect to the target and to study the effect of friction between the tether and the release system. Similarly, STAR is investigating the tether actively controlled deployment and retrieval, with the experiment campaign planned on November 2016. In addition, another microgravity experiment is in preparation for the investigation of active magnetic navigation: PACMAN

  17. Tethered satellite system dynamics and control review panel and related activities, phase 3

    Science.gov (United States)

    1991-01-01

    Two major tests of the Tethered Satellite System (TSS) engineering and flight units were conducted to demonstrate the functionality of the hardware and software. Deficiencies in the hardware/software integration tests (HSIT) led to a recommendation for more testing to be performed. Selected problem areas of tether dynamics were analyzed, including verification of the severity of skip rope oscillations, verification or comparison runs to explore dynamic phenomena observed in other simulations, and data generation runs to explore the performance of the time domain and frequency domain skip rope observers.

  18. Diamond surface functionalization with biomimicry - Amine surface tether and thiol moiety for electrochemical sensors

    Science.gov (United States)

    Sund, James B.; Causey, Corey P.; Wolter, Scott D.; Parker, Charles B.; Stoner, Brian R.; Toone, Eric J.; Glass, Jeffrey T.

    2014-05-01

    The surface of conducting diamond was functionalized with a terminal thiol group that is capable of binding and detecting nitrogen-oxygen species. The functionalization process employed multiple steps starting with doped diamond films grown by plasma enhanced chemical vapor deposition followed by hydrogen termination and photochemical attachment of a chemically protected amine alkene. The surface tether was deprotected to reveal the amine functionality, which enabled the tether to be extended with surface chemistry to add a terminal thiol moiety for electrochemical sensing applications. Each step of the process was validated using X-ray photoelectron spectroscopy analysis.

  19. Calculating the electromagnetic field on the earth due to an electrodynamic tethered system in the ionosphere

    Science.gov (United States)

    Estes, Robert D.

    1989-01-01

    A method is presented for calculating the electromagnetic wave field on the earth's surface associated with the operation of an electrodynamic tethered satellite system of constant or slowly varying current in the upper ionosphere. The wave field at the ionospheric boundary and on the earth's surface is obtained by numerical integration. The results suggest that the ionospheric waves do not propagate into the atmosphere and that the image of the Alfven wings from a steady-current tether should be greatly broadened on the earth's surface.

  20. Integrated test rig for tether hardware, real-time simulator and control algorithms: Robust momentum transfer validated

    Science.gov (United States)

    Kruijff, Michiel; van der Heide, Erik Jan

    2001-02-01

    In preparation of the ESA demonstration mission for a tethered sample return capability from ISS, a breadboard test has been performed to validate the robust StarTrack tether dynamics control algorithms in conjunction with the constructed hardware. The proposed mission will use hardware inherited from the YES mission (Kruijff, 1999). A tether spool is holding a 7 kg, 35 km Dyneema tether. A 45 kg re-entry capsule will be ejected by springs and then deployed by gravity gradient. The dynamics are solely controlled by a barberpole type friction brake, similar to the SEDS hardware. This hardware is integrated in a test rig, based on the TMM&M stand, that has been upgraded to accommodate both a Space Part (abruptly applied initial tether deployment speed, fine tensiometer, real-time space tether simulator using the tensiometer measurements as input, take-up roller deploying the tether at a simulator-controlled speed) and a Satellite Part (infra-red beams inside the tether canister, control computer estimating deployed length and required extra braking from the IRED interrupts, `barberpole' friction brake). So the set-up allows for a tether deployment with closed loop control, all governed by a real-time comprehensive tether dynamics simulation. The tether deployment is based on the two-stage StarTrack deployment. This scheme stabilizes the tether at an intermediate vertical stage (with 3 km deployed). When the orbit and landing site have synchronized, a high-speed deployment follows to a large angle. When the fully deployed 35-km tether swings to the vertical at approximately 40 m/s, it is cut at a prefixed time optimized for landing site accuracy. The paper discusses the tests performed to characterize the designed hardware, maturing of the developed algorithms with respect to the hardware noise levels and the difficulties and limitations of the test rig. It is found that the set-up can be applied to a variety of tether pre-mission tests. It is shown that the performed

  1. Cell surface estrogen receptor alpha is upregulated during subchronic metabolic stress and inhibits neuronal cell degeneration.

    Directory of Open Access Journals (Sweden)

    Cristiana Barbati

    Full Text Available In addition to the classical nuclear estrogen receptor, the expression of non-nuclear estrogen receptors localized to the cell surface membrane (mER has recently been demonstrated. Estrogen and its receptors have been implicated in the development or progression of numerous neurodegenerative disorders. Furthermore, the pathogenesis of these diseases has been associated with disturbances of two key cellular programs: apoptosis and autophagy. An excess of apoptosis or a defect in autophagy has been implicated in neurodegeneration. The aim of this study was to clarify the role of ER in determining neuronal cell fate and the possible implication of these receptors in regulating either apoptosis or autophagy. The human neuronal cell line SH-SY5Y and mouse neuronal cells in primary culture were thus exposed to chronic minimal peroxide treatment (CMP, a form of subcytotoxic minimal chronic stress previously that mimics multiple aspects of long-term cell stress and represents a limited molecular proxy for neurodegenerative processes. We actually found that either E2 or E2-bovine serum albumin construct (E2BSA, i.e. a non-permeant form of E2 was capable of modulating intracellular cell signals and regulating cell survival and death. In particular, under CMP, the up-regulation of mERα, but not mERβ, was associated with functional signals (ERK phosphorylation and p38 dephosphorylation compatible with autophagic cytoprotection triggering and leading to cell survival. The mERα trafficking appeared to be independent of the microfilament system cytoskeletal network but was seemingly associated with microtubular apparatus network, i.e., to MAP2 molecular chaperone. Importantly, antioxidant treatments, administration of siRNA to ERα, or the presence of antagonist of ERα hindered these events. These results support that the surface expression of mERα plays a pivotal role in determining cell fate, and that ligand-induced activation of mER signalling exerts a

  2. Recent Insights into Cell Surface Heparan Sulphate Proteoglycans and Cancer [version 1; referees: 3 approved

    Directory of Open Access Journals (Sweden)

    John R Couchman

    2016-06-01

    Full Text Available A small group of cell surface receptors are proteoglycans, possessing a core protein with one or more covalently attached glycosaminoglycan chains. They are virtually ubiquitous and their chains are major sites at which protein ligands of many types interact. These proteoglycans can signal and regulate important cell processes, such as adhesion, migration, proliferation, and differentiation. Since many protein ligands, such as growth factors, morphogens, and cytokines, are also implicated in tumour progression, it is increasingly apparent that cell surface proteoglycans impact tumour cell behaviour. Here, we review some recent advances, emphasising that many tumour-related functions of proteoglycans are revealed only after their modification in processes subsequent to synthesis and export to the cell surface. These include enzymes that modify heparan sulphate structure, recycling of whole or fragmented proteoglycans into exosomes that can be paracrine effectors or biomarkers, and lateral interactions between some proteoglycans and calcium channels that impact the actin cytoskeleton.

  3. Significance of Nano- and Microtopography for Cell-Surface Interactions in Orthopaedic Implants

    Directory of Open Access Journals (Sweden)

    M. Jäger

    2007-09-01

    Full Text Available Cell-surface interactions play a crucial role for biomaterial application in orthopaedics. It is evident that not only the chemical composition of solid substances influence cellular adherence, migration, proliferation and differentiation but also the surface topography of a biomaterial. The progressive application of nanostructured surfaces in medicine has gained increasing interest to improve the cytocompatibility and osteointegration of orthopaedic implants. Therefore, the understanding of cell-surface interactions is of major interest for these substances. In this review, we elucidate the principle mechanisms of nano- and microscale cell-surface interactions in vitro for different cell types onto typical orthopaedic biomaterials such as titanium (Ti, cobalt-chrome-molybdenum (CoCrMo alloys, stainless steel (SS, as well as synthetic polymers (UHMWPE, XLPE, PEEK, PLLA. In addition, effects of nano- and microscaled particles and their significance in orthopaedics were reviewed. The significance for the cytocompatibility of nanobiomaterials is discussed critically.

  4. Quantitative determination of islet cell surface antibodies using 125I-protein A

    International Nuclear Information System (INIS)

    A quantitative method to measure islet cell surface antibodies in human patients has been developed using 125I-protein A. Isolated, dispersed, viable rat islet cells prepared by collagenase digestion were fixed in 4% paraformaldehyde to allow storage for up to 7 wk at 4 degrees C. Human sera, heat inactivated and adsorbed with rat liver and kidney powder (100 mg/ml), were incubated with the fixed cells (50 x 10(3)) for 60 min at 37 degrees C. Thereafter the cells were washed and exposed to 5 x 10(5) cpm 125I-protein A, which binds to IgG attached to the cell surface. Assay precision (14%) and reproducibility (16%) were established by repeated analysis of pooled sera from healthy individuals and IDDM patients using pooled batches of islet cells. Using this method, islet cell surface antibodies were detected in 35% of insulin-dependent diabetic patients

  5. Adhesion defective BHK cell mutant has cell surface heparan sulfate proteoglycan of altered properties

    DEFF Research Database (Denmark)

    Couchman, J R; Austria, R; Woods, A; Hughes, R C

    1988-01-01

    In the light of accumulating data that implicate cell surface heparan sulfate proteoglycans (HSPGs) with a role in cell interactions with extracellular matrix molecules such as fibronectin, we have compared the properties of these molecules in wild-type BHK cells and an adhesion-defective ricin......-resistant mutant (RicR14). Our results showed that the mutant, unlike BHK cells, cannot form focal adhesions when adherent to planar substrates in the presence of serum. Furthermore, while both cell lines possess similar amounts of cell surface HSPG with hydrophobic properties, that of RicR14 cells had decreased...... sulfation, reduced affinity for fibronectin and decreased half-life on the cell surface when compared to the normal counterpart. Our conclusions based on this data are that these altered properties may, in part, account for the adhesion defect in the ricin-resistant mutant. Whether this results from the...

  6. A sensitive electrochemiluminescence cytosensor for quantitative evaluation of epidermal growth factor receptor expressed on cell surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Tang, Yanjuan; Zhang, Shaolian; Wen, Qingqing; Huang, Hongxing; Yang, Peihui, E-mail: typh@jnu.edu.cn

    2015-06-30

    Highlights: • EGF-cytosensor was used for evaluating EGFR expression level on cell surfaces. • CdSQDs and EGF were coated on magnetic beads (MBs) for ECL-probe. • Good sensitivity was achieved due to the signal amplification of ECL-probe. - Abstract: A sensitive electrochemiluminescence (ECL) strategy for evaluating the epidermal growth factor receptor (EGFR) expression level on cell surfaces was designed by integrating the specific recognition of EGFR expressed on MCF-7 cell surfaces with an epidermal growth factor (EGF)-funtionalized CdS quantum dots (CdSQDs)-capped magnetic bead (MB) probe. The high sensitivity of ECL probe of EGF-funtionalized CdSQD-capped-MB was used for competitive recognition with EGFR expressed on cell surfaces with recombinant EGFR protein. The changes of ECL intensity depended on both the cell number and the expression level of EGFR receptor on cell surfaces. A wide linear response to cells ranging from 80 to 4 × 10{sup 6} cells mL{sup −1} with a detection limit of 40 cells mL{sup −1} was obtained. The EGF-cytosensor was used to evaluate EGFR expression levels on MCF-7 cells, and the average number of EGFR receptor on single MCF-7 cells was 1.35 × 10{sup 5} with the relative standard deviation of 4.3%. This strategy was further used for in-situ and real-time evaluating EGFR receptor expressed on cell surfaces in response to drugs stimulation at different concentration and incubation time. The proposed method provided potential applications in the detection of receptors on cancer cells and anticancer drugs screening.

  7. A sensitive electrochemiluminescence cytosensor for quantitative evaluation of epidermal growth factor receptor expressed on cell surfaces

    International Nuclear Information System (INIS)

    Highlights: • EGF-cytosensor was used for evaluating EGFR expression level on cell surfaces. • CdSQDs and EGF were coated on magnetic beads (MBs) for ECL-probe. • Good sensitivity was achieved due to the signal amplification of ECL-probe. - Abstract: A sensitive electrochemiluminescence (ECL) strategy for evaluating the epidermal growth factor receptor (EGFR) expression level on cell surfaces was designed by integrating the specific recognition of EGFR expressed on MCF-7 cell surfaces with an epidermal growth factor (EGF)-funtionalized CdS quantum dots (CdSQDs)-capped magnetic bead (MB) probe. The high sensitivity of ECL probe of EGF-funtionalized CdSQD-capped-MB was used for competitive recognition with EGFR expressed on cell surfaces with recombinant EGFR protein. The changes of ECL intensity depended on both the cell number and the expression level of EGFR receptor on cell surfaces. A wide linear response to cells ranging from 80 to 4 × 106 cells mL−1 with a detection limit of 40 cells mL−1 was obtained. The EGF-cytosensor was used to evaluate EGFR expression levels on MCF-7 cells, and the average number of EGFR receptor on single MCF-7 cells was 1.35 × 105 with the relative standard deviation of 4.3%. This strategy was further used for in-situ and real-time evaluating EGFR receptor expressed on cell surfaces in response to drugs stimulation at different concentration and incubation time. The proposed method provided potential applications in the detection of receptors on cancer cells and anticancer drugs screening

  8. Interaction of herpes simplex virus glycoprotein gC with mammalian cell surface molecules.

    OpenAIRE

    Tal-Singer, R; Peng, C.; Ponce de Leon, M; Abrams, W R; Banfield, B W; Tufaro, F; Cohen, G H; Eisenberg, R J

    1995-01-01

    The entry of herpes simplex virus (HSV) into mammalian cells is a multistep process beginning with an attachment step involving glycoproteins gC and gB. A second step requires the interaction of glycoprotein gD with a cell surface molecule. We explored the interaction between gC and the cell surface by using purified proteins in the absence of detergent. Truncated forms of gC and gD, gC1(457t), gC2(426t), and gD1(306t), lacking the transmembrane and carboxyl regions were expressed in the bacu...

  9. Serotonin-induced down-regulation of cell surface serotonin transporter

    DEFF Research Database (Denmark)

    Jørgensen, Trine Nygaard; Christensen, Peter Møller; Gether, Ulrik

    2014-01-01

    The serotonin transporter (SERT) terminates serotonergic signaling and enables refilling of synaptic vesicles by mediating reuptake of serotonin (5-HT) released into the synaptic cleft. The molecular and cellular mechanisms controlling SERT activity and surface expression are not fully understood....... Here we demonstrate that the substrate 5-HT itself causes acute down-regulation of SERT cell surface expression. To assess surface SERT expression by ELISA, we used a SERT variant (TacSERT) where the N-terminus of SERT was fused to the intracellular tail of the extracellularly FLAG-tagged single...... neurons, indicting that endogenous cell-surface resident SERT likewise is down-regulated in the presence of substrate....

  10. Characterization of cell surface and extracellular matrix remodeling of Azospirillum brasilense chemotaxis-like 1 signal transduction pathway mutants by atomic force microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Doktycz, Mitchel John [ORNL; Morrell-Falvey, Jennifer L [ORNL

    2011-01-01

    To compete in complex microbial communities, bacteria must sense environmental changes and adjust cellular functions for optimal growth. Chemotaxis-like signal transduction pathways are implicated in the regulation of multiple behaviors in response to changes in the environment, including motility patterns, exopolysaccharide production, and cell-to-cell interactions. In Azospirillum brasilense, cell surface properties, including exopolysaccharide production, are thought to play a direct role in promoting flocculation. Recently, the Che1 chemotaxis-like pathway from A. brasilense was shown to modulate flocculation, suggesting an associated modulation of cell surface properties. Using atomic force microscopy, distinct changes in the surface morphology of flocculating A. brasilense Che1 mutant strains were detected. Whereas the wild-type strain produces a smooth mucosal extracellular matrix after 24 h, the flocculating Che1 mutant strains produce distinctive extracellular fibril structures. Further analyses using flocculation inhibition, lectin-binding assays, and comparison of lipopolysaccharides profiles suggest that the extracellular matrix differs between the cheA1 and the cheY1 mutants, despite an apparent similarity in the macroscopic floc structures. Collectively, these data indicate that disruption of the Che1 pathway is correlated with distinctive changes in the extracellular matrix, which likely result from changes in surface polysaccharides structure and/or composition.

  11. Tethered particle analysis of supercoiled circular DNA using peptide nucleic acid handles

    DEFF Research Database (Denmark)

    Norregaard, Kamilla; Andersson, Magnus; Nielsen, Peter Eigil;

    2014-01-01

    -digoxigenin-coated glass cover slide, and one conjugated with biotin for attachment to a submicron-sized streptavidin-coated polystyrene bead. Plasmids are constructed, purified and incubated with the PNA handles. The dynamics of the construct is analyzed by tracking the tethered bead using video microscopy: less...

  12. Titanium-tethered vancomycin prevents resistance to rifampicin in Staphylococcus aureus in vitro.

    Directory of Open Access Journals (Sweden)

    Martin Rottman

    Full Text Available Rifampicin is currently recognized as the most potent drug against Gram positive implant related infections. The use of rifampicin is limited by the emergence of bacterial resistance, which is often managed by coadministration of a second antibiotic. The purpose of this study was to determine the effectiveness of soluble rifampicin in combination with vancomycin tethered to titanium metal as a means to control bacterial growth and resistance in vitro. Bacterial growth was inhibited when the vancomycin-tethered titanium discs were treated with Staphylococcus aureus inocula of ≤2×10⁶ CFU, however inocula greater than 2×10⁶ CFU/disc adhered and survived. The combination of surface-tethered vancomycin with soluble rifampicin enhanced the inhibitory effect of rifampicin for an inoculum of 10⁶ CFU/cm² by one dilution (combination MIC of 0.008 mg/L versus 0.015 mg/L for rifampicin alone. Moreover, surface tethered vancomycin prevented the emergence of a rifampicin resistant population in an inoculum of 2×10⁸ CFU.

  13. Interplay between native topology and non-native interactions in the folding of tethered proteins

    International Nuclear Information System (INIS)

    We assessed the interplay of native topology and non-native interactions on surface-tethered protein folding via extensive Monte Carlo simulations of a simple lattice model. In particular, we investigated the thermodynamics and kinetics of protein-like sequences enclosing different amounts of non-native interactions to protein energetics, and which were designed to fold to distinct native topologies. Our results show that the high-contact order (CO) structure renders a folding transition that is robust to (external) steric constraints and non-native interactions. On the other hand, the folding process of the simple low-CO topology can be easily hampered by the presence of a nearby chemically inert plane. In this case, if non-native interactions are highly conspicuous during folding they can actually drive chain collapse into a very native-like trapped state, which impedes the formation of the native structure. The analysis of folding kinetics reveals that the empirical correlation between folding rate and CO may not apply to surface-tethered protein folding. Indeed, results reported here show that depending on the native environment of the tethered chain terminus the folding rate of a low-CO topology can become so drastically small that the high-CO topology actually folds faster under the same conditions. We predict that complex topologies are more likely to conserve their bulk folding mechanism upon surface tethering. (paper)

  14. Curvature sorting of proteins on a cylindrical lipid membrane tether connected to a reservoir

    Science.gov (United States)

    Singh, Pankaj; Mahata, Paritosh; Baumgart, Tobias; Das, Sovan Lal

    2012-05-01

    Membrane curvature of a biological cell is actively involved in various fundamental cell biological functions. It has been discovered that membrane curvature and binding of peripheral membrane proteins follow a symbiotic relationship. The exact mechanism behind this interplay of protein binding and membrane curvature has not yet been properly understood. To improve understanding of the mechanism, we study curvature sorting of proteins in a model system consisting of a tether pulled from a giant unilamellar vesicle using mechanical-thermodynamic models. The concentration of proteins bound to the membrane changes significantly due to curvature. This has also been observed in experiments by other researchers. We also find that there is a phase transition based on protein concentration and we discuss the coexistence of phases and stability of solutions. Furthermore, when sorting is favorable, the increase in protein concentration stabilizes the tether in the sense that less pulling force is required to maintain the tether. A similar mechanism may be in place, when motor proteins pull tethers from donor membranes.

  15. New amidines from intramolecular cyclization in triflic acid of nitroketene aminals with a tethered phenyl ring

    Indian Academy of Sciences (India)

    Soro Yaya; Bamba Fanté; Siaka Sorho; Coustard Jean-Marie; Adima A Augustin

    2007-05-01

    Nitroketene aminals with a tethered phenyl group underwent an intramolecular cyclization in trifluoromethanesulfonic acid to afford the corresponding N-(3-ethyl-hydrohydroxyiminobenzocycloalkenylidene) methylamine trifluoromethanesulfonate. The yields were fair to good excepted for the starting compound 1-[N-ethyl-N-(2-phenylethyl)amino]-1-methylamino-2-nitroethene.

  16. Mono- and bis(pyrrolo)tetrathiafulvalene derivatives tethered to C60

    DEFF Research Database (Denmark)

    Vico Solano, Marta; Della Pia, Eduardo Antonio; Jevric, Martyn; Schubert, Christina; Wang, Xintai; van der Pol, Cornelia; Kadziola, Anders; Nørgaard, Kasper; Guldi, Dirk M.; Nielsen, Mogens Brøndsted; Jeppesen, Jan Oskar

    2014-01-01

    A series of mono- (MPTTF) and bis(pyrrolo) tetrathiafulvalene (BPTTF) derivatives tethered to one or two C-60 moieties was synthesized and characterized. The synthetic strategy for these dumbbell-shaped compounds was based on a 1,3-dipolar cycloaddition reaction between aldehyde-functionalized MP...

  17. High-Voltage Tethers For Enhanced Particle Scattering In Van Allen Belts

    Science.gov (United States)

    Mirnov, Vladimir; Ü, Defne; Danilov, Valentin

    1996-11-01

    New applications of space tethers (HVTSS) are discussed in relation with the ideafootnote Yu.V.Vasilyev, V.V.Danilov, Physics-Doklady, (1995) 342, 5. of an active experiment at the Earth's radiation belts. Two conducting strings are supposed to be tethered between the main satellite and two small subsatellites flying through the ERB. A large potential difference ~1MV is applied between the tethers by means of a generator carried on the main satellite. The tethers effectively scatter the high energy particles into loss cone, providing a control of particle life time in ERB. The rigorous theory of the sheath layer formed by relatively cold plasma is developed for both DC and AC regimes yielding an electric field profile, which is then used for the treatment of the scattering problem. With the help of the Fokker-Planck equation, the average rate of particle losses, normalized per 1 km of the theter's length is found to be: (2.5 div 14)× 10^16 sec-1km-1 for electron belts and 1.8× 10^14div 2.5× 10^20 sec-1km-1 for proton belts. New active experiments in ERB become possible under the joint realization of HVTSS and HAARPfootnote D.Papadopoulos, P.Bernhardt et al. A Joint Program of Phillips Lab and the Office of Naval Research, June, 1995 projects.

  18. Synthetic Studies to Lyngbouilloside: A Phosphate Tether-Mediated Synthesis of the Macrolactone Core

    Science.gov (United States)

    Chegondi, Rambabu

    2015-01-01

    A concise synthetic pathway to the originally assigned structure of lyngbouilloside macrolactone (3) is reported. The core macrocycle 3 was synthesized via a phosphate tether-mediated, one-pot, sequential RCM/CM/chemoselective hydrogenation reaction, Roskamp homologation, and a high yielding Boeckman acylketene cyclization. PMID:26388654

  19. Power Module

    OpenAIRE

    Gang Fang

    2009-01-01

    Abstract: In this paper, we discuss the upgrade problem of module, and introduce the concepts of the power module, regular power module and uniform power module. We give some results of them. Key words: power group; power module; regular power module; uniform power module

  20. Dynamics and Power Generation Potential from a Tethered Kite Moving in a Horizontal Flightpath

    Science.gov (United States)

    Gavi, Glenn Romo

    Tethered-wing power systems are a viable possibility for collecting energy from stronger, more consistent winds found in the upper regions of the atmosphere where conventional wind turbines are incapable of reaching. To date, all of the tethered-wing systems fly with the tether oriented down-wind of the ground attachment point. Examined here are the dynamics and performance of a novel system where the tether is oriented both upwind and downwind of the ground attachment point during normal operation of the device. Certain prototypes built by Makani and Ampyx Power are considered to have motions analogous to the motions of the blade tips on conventional horizontal-axis wind turbines. If true, this system has motions that are analogous to conventional vertical-axis wind turbines. The system has a ground-based generator which is mechanical coupled to the aircraft and energy is generated on the reel-out phase of each cycle while a smaller amount of energy is consumed during the reel-in phase of each cycle. A simple model was developed which captures the dominant dynamics of this system and shows, via simulation, that the proposed system is viable and capable of stable and unstable periodic motions with a simulated closed-loop tether tension controller or a simple open loop reel-rate controller. In addition, it is capable of motions which produce net positive power. The small system examined, where parameter optimization was not performed, predicts an average cycle power of more than 500 watts in a 10 m/s wind.

  1. Dynamics of a flexible tethered satellite system utilising various materials for coplanar and non-coplanar models

    Science.gov (United States)

    Hong, Aaron Aw Teik; Varatharajoo, Renuganth

    2015-08-01

    This paper discusses the development of mathematical models for a flexible tethered satellite system (TSS) in both planar and co-planar states. The flexible tethered satellite system consists of three rigid bodies with two flexible tethers, each connecting two rigid bodies with one located in the centre and serving as the mothership. The TSS motion includes tether deformations, rotational dynamics, and orbital mechanics. The three materials that are possible to be used for a space tether are tungsten wire, Spectra-2000, and diamond; it should be noted that the diamond used here is in a form of a nanotube thread. The tether will undergo a spinning motion as well in the motorised option. In addition, the air drag perturbation is also considered since the entire TSS is flown around the Low Earth Orbit (LEO), where the air-drag perturbation is dominant. A survival analysis was then performed for planar and non-coplanar models in order to establish a dynamic performance envelope with respect to the tether's tension at different altitudes under the air-drag perturbation. The proposed models were treated numerically and analysed accordingly. Then a comparison study between the coplanar and non-coplanar models were conducted and the difference in their performances was observed and discussed. Although all materials have their own safe operation boundaries, the flexible TSS using tungsten shows a better dynamic performance than the other TSS options in a non-coplanar model.

  2. A cell-surface-anchored ratiometric i-motif sensor for extracellular pH detection.

    Science.gov (United States)

    Ying, Le; Xie, Nuli; Yang, Yanjing; Yang, Xiaohai; Zhou, Qifeng; Yin, Bincheng; Huang, Jin; Wang, Kemin

    2016-06-14

    A FRET-based sensor is anchored on the cell surface through streptavidin-biotin interactions. Due to the excellent properties of the pH-sensitive i-motif structure, the sensor can detect extracellular pH with high sensitivity and excellent reversibility. PMID:27241716

  3. Measuring cell surface elasticity on enteroaggregative Escherichia coli wild type and dispersin mutant by AFM

    International Nuclear Information System (INIS)

    Enteroaggregative Escherichia coli (EAEC) is pathogenic and produces severe diarrhea in humans. A mutant of EAEC that does not produce dispersin, a cell surface protein, is not pathogenic. It has been proposed that dispersin imparts a positive charge to the bacterial cell surface allowing the bacteria to colonize on the negatively charged intestinal mucosa. However, physical properties of the bacterial cell surface, such as rigidity, may be influenced by the presence of dispersin and may contribute to pathogenicity. Using the system developed in our laboratory for mounting and imaging bacterial cells by atomic force microscopy (AFM), in liquid, on gelatin coated mica surfaces, studies were initiated to measure cell surface elasticity. This was carried out in both wild type EAEC, that produces dispersin, and the mutant that does not produce dispersin. This was accomplished using AFM force-distance (FD) spectroscopy on the wild type and mutant grown in liquid or on solid medium. Images in liquid and in air of both the wild-type and mutant grown in liquid and on solid media are presented. This work represents an initial step in efforts to understand the pathogenic role of the dispersin protein in the wild-type bacteria

  4. Low temperature-induced cell surface membrane vesicle shedding is associated with DNA fragmentation

    International Nuclear Information System (INIS)

    Temperature shift conditions of 0 degree to 22 degrees C or 0 degree to 37 degrees C induce the formation and shedding of membrane vesicles (MV) from P815 tumor cell surfaces. When the MV shedding process takes place at 22 degrees C it occurs without changes in cell surface membrane permeability, whereas at 37 degrees C, changes in permeability to 51Cr and trypan blue do occur, thus mimicking the lymphocyte-mediated lytic process of tumor cells. The present studies demonstrate that nuclear DNA fragmentation also occurs in both 0 degree to 22 degrees C and 0 degree to 37 degrees C temperature shifts. However, cell surface membrane permeability to DNA fragments occurs only in the latter condition, i.e., 0 degree to 37 degrees C. The microtubule-stabilizing agent deuterium oxide (D2O) inhibited the MV shedding process, the changes in membrane permeability, and DNA fragmentation. When P815 cells which had been induced to shed MV by the 0 degree to 22 degrees C temperature shift were labeled with 51Cr and used as targets for alloimmune lymphocytes, they were found to be as susceptible to T-cell lysis as control P815 cells. This result indicates that the lytic effect of alloimmune T lymphocytes can be exerted at the target cell surface membrane level independently of nuclear DNA fragmentation

  5. Cell Surface Enzymatic Engineering-Based Approaches to Improve Cellular Therapies

    KAUST Repository

    Abuelela, Ayman F.

    2014-06-06

    The cell surface represents the interface between the cell and its environment. As such, the cell surface controls cell–cell interactions and functions such as adhesion and migration, and will transfer external cues to regulate processes such as survival, death, and differentiation. Redefining the cell surface by temporarily (or permanently) modifying the molecular landscape of the plasma membrane affects the way in which the cell interacts with its environment and influences the information that is relayed into the cell along downstream signaling pathways. This chapter outlines the role of key enzymes, the glycosyltransferases, in posttranslationally modifying proteins and lipids to fine-tune cells, ability to migrate. These enzymes are critical in controlling the formation of a platform structure, sialyl Lewis x (sLex), on circulating cells that plays a central role in the recognition and recruitment by selectin counter receptors on endothelial cells that line blood vessels of tissues throughout the body. By developing methods to manipulate the activity of these enzymes and hence the cell surface structures that result, treatments can be envisioned that direct the migration of therapeutic cells to specific locations throughout the body and also to inhibit metastasis of detrimental cells such as circulating tumor cells.

  6. Highly Sensitive Detection of Target Biomolecules on Cell Surface Using Gold Nanoparticle Conjugated with Aptamer Probe

    Science.gov (United States)

    Kim, Hyonchol; Terazono, Hideyuki; Hayashi, Masahito; Takei, Hiroyuki; Yasuda, Kenji

    2012-06-01

    A method of gold nanoparticle (Au NP) labeling with backscattered electron (BE) imaging of field emission scanning electron microscopy (FE-SEM) was applied for specific detection of target biomolecules on a cell surface. A single-stranded DNA aptamer, which specifically binds to the target molecule on a human acute lymphoblastic leukemia cell, was conjugated with a 20 nm Au NP and used as a probe to label its target molecule on the cell. The Au NP probe was incubated with the cell, and the interaction was confirmed using BE imaging of FE-SEM through direct counting of the number of Au NPs attached on the target cell surface. Specific Au NP-aptamer probes were observed on a single cell surface and their spatial distributions including submicron-order localizations were also clearly visualized, whereas the nonspecific aptamer probes were not observed on it. The aptamer probe can be potentially dislodged from the cell surface with treatment of nucleases, indicating that Au NP-conjugated aptamer probes can be used as sensitive and reversible probes to label target biomolecules on cells.

  7. Evidence of cell surface iron speciation of acidophilic iron-oxidizing microorganisms in indirect bioleaching process.

    Science.gov (United States)

    Nie, Zhen-yuan; Liu, Hong-chang; Xia, Jin-lan; Yang, Yi; Zhen, Xiang-jun; Zhang, Li-Juan; Qiu, Guan-zhou

    2016-02-01

    While indirect model has been widely accepted in bioleaching, but the evidence of cell surface iron speciation has not been reported. In the present work the iron speciation on the cell surfaces of four typically acidophilic iron-oxidizing microorganism (mesophilic Acidithiobacillus ferrooxidans ATCC 23270, moderately thermophilic Leptospirillum ferriphilum YSK and Sulfobacillus thermosulfidooxidans St, and extremely thermophilic Acidianus manzaensis YN25) grown on different energy substrates (chalcopyrite, pyrite, ferrous sulfate and elemental sulfur (S(0))) were studied in situ firstly by using synchrotron-based micro- X-ray fluorescence analysis and X-ray absorption near-edge structure spectroscopy. Results showed that the cells grown on iron-containing substrates had apparently higher surface iron content than the cells grown on S(0). Both ferrous iron and ferric iron were detected on the cell surface of all tested AIOMs, and the Fe(II)/Fe(III) ratios of the same microorganism were affected by different energy substrates. The iron distribution and bonding state of single cell of A. manzaensis were then studied in situ by scanning transmission soft X-ray microscopy based on dual-energy contrast analysis and stack analysis. Results showed that the iron species distributed evenly on the cell surface and bonded with amino, carboxyl and hydroxyl groups. PMID:26645388

  8. Genetic and proteomic evidences support the localization of yeast enolase in the cell surface

    DEFF Research Database (Denmark)

    López-Villar, Elena; Monteoliva, Lucía; Larsen, Martin Røssel;

    2006-01-01

    Although enolase, other glycolytic enzymes, and a variety of cytoplasmic proteins lacking an N-terminal secretion signal have been widely described as located at the cell surface in yeast and in mammalian cells, their presence in this external location is still controversial. Here, we report that...

  9. Erratum: Colorectal Cancer Cell Surface Protein Profiling Using an Antibody Microarray and Fluorescence Multiplexing.

    Science.gov (United States)

    2015-01-01

    The author's email has been corrected in the publication of Colorectal Cancer Cell Surface Protein Profiling Using an Antibody Microarray and Fluorescence Multiplexing. There was an error with the author, Jerry Zhou's, email. The author's email has been updated to: j.zhou@uws.edu.au from: jzho7551@mail.usyd.edu.au. PMID:26167960

  10. Effect of Growth Conditions on Flocculation and Cell Surface Hydrophobicity of Brewing Yeast

    Czech Academy of Sciences Publication Activity Database

    Kopecká, J.; Němec, M.; Matoulková, D.; Čejka, P.; Jelínková, Markéta; Felsberg, Jürgen; Sigler, Karel

    2015-01-01

    Roč. 73, č. 2 (2015), s. 143-150. ISSN 0361-0470 Institutional support: RVO:61388971 Keywords : Ale and lager yeast * Cell surface hydrophobicity * FLO genes Subject RIV: EI - Biotechnology ; Bionics Impact factor: 0.886, year: 2014

  11. Pigment epithelium-derived factor binds to cell-surface F(1)-ATP synthase.

    Science.gov (United States)

    Notari, Luigi; Arakaki, Naokatu; Mueller, David; Meier, Scott; Amaral, Juan; Becerra, S P

    2010-05-01

    Pigment epithelium-derived factor (PEDF), a potent blocker of angiogenesis in vivo, and of endothelial cell migration and tubule formation, binds with high affinity to an as yet unknown protein on the surfaces of endothelial cells. Given that protein fingerprinting suggested a match of a approximately 60 kDa PEDF-binding protein in bovine retina with Bos taurus F(1)-ATP synthase beta-subunit, and that F(1)F(o)-ATP synthase components have been identified recently as cell-surface receptors, we examined the direct binding of PEDF to F(1). Size-exclusion ultrafiltration assays showed that recombinant human PEDF formed a complex with recombinant yeast F(1). Real-time binding as determined by surface plasmon resonance demonstrated that yeast F(1) interacted specifically and reversibly with human PEDF. Kinetic evaluations revealed high binding affinity for PEDF, in agreement with PEDF affinities for endothelial cell surfaces. PEDF blocked interactions between F(1) and angiostatin, another antiangiogenic factor, suggesting overlapping PEDF-binding and angiostatin-binding sites on F(1). Surfaces of endothelial cells exhibited affinity for PEDF-binding proteins of approximately 60 kDa. Antibodies to F(1)beta-subunit specifically captured PEDF-binding components in endothelial plasma membranes. The extracellular ATP synthesis activity of endothelial cells was examined in the presence of PEDF. PEDF significantly reduced the amount of extracellular ATP produced by endothelial cells, in agreement with direct interactions between cell-surface ATP synthase and PEDF. In addition to demonstrating that PEDF binds to cell-surface F(1), these results show that PEDF is a ligand for endothelial cell-surface F(1)F(o)-ATP synthase. They suggest that PEDF-mediated inhibition of ATP synthase may form part of the biochemical mechanisms by which PEDF exerts its antiangiogenic activity. PMID:20412062

  12. Plet1 is an epigenetically regulated cell surface protein that provides essential cues to direct trophoblast stem cell differentiation

    Science.gov (United States)

    Murray, Alexander; Sienerth, Arnold R.; Hemberger, Myriam

    2016-01-01

    Gene loci that are hypermethylated and repressed in embryonic (ESCs) but hypomethylated and expressed in trophoblast (TSCs) stem cells are very rare and may have particularly important roles in early developmental cell fate decisions, as previously shown for Elf5. Here, we assessed another member of this small group of genes, Placenta Expressed Transcript 1 (Plet1), for its function in establishing trophoblast lineage identity and modulating trophoblast differentiation. We find that Plet1 is tightly repressed by DNA methylation in ESCs but expressed on the cell surface of TSCs and trophoblast giant cells. In hypomethylated ESCs that are prone to acquire some trophoblast characteristics, Plet1 is required to confer a trophoblast-specific gene expression pattern, including up-regulation of Elf5. Plet1 displays an unusual biphasic expression profile during TSC differentiation and thus may be pivotal in balancing trophoblast self-renewal and differentiation. Furthermore, overexpression and CRISPR/Cas9-mediated knockout in TSCs showed that high Plet1 levels favour differentiation towards the trophoblast giant cell lineage, whereas lack of Plet1 preferentially induces syncytiotrophoblast formation. Thus, the endogenous dynamics of Plet1 expression establish important patterning cues within the trophoblast compartment by promoting differentiation towards the syncytiotrophoblast or giant cell pathway in Plet1-low and Plet1-high cells, respectively. PMID:27121762

  13. Plet1 is an epigenetically regulated cell surface protein that provides essential cues to direct trophoblast stem cell differentiation.

    Science.gov (United States)

    Murray, Alexander; Sienerth, Arnold R; Hemberger, Myriam

    2016-01-01

    Gene loci that are hypermethylated and repressed in embryonic (ESCs) but hypomethylated and expressed in trophoblast (TSCs) stem cells are very rare and may have particularly important roles in early developmental cell fate decisions, as previously shown for Elf5. Here, we assessed another member of this small group of genes, Placenta Expressed Transcript 1 (Plet1), for its function in establishing trophoblast lineage identity and modulating trophoblast differentiation. We find that Plet1 is tightly repressed by DNA methylation in ESCs but expressed on the cell surface of TSCs and trophoblast giant cells. In hypomethylated ESCs that are prone to acquire some trophoblast characteristics, Plet1 is required to confer a trophoblast-specific gene expression pattern, including up-regulation of Elf5. Plet1 displays an unusual biphasic expression profile during TSC differentiation and thus may be pivotal in balancing trophoblast self-renewal and differentiation. Furthermore, overexpression and CRISPR/Cas9-mediated knockout in TSCs showed that high Plet1 levels favour differentiation towards the trophoblast giant cell lineage, whereas lack of Plet1 preferentially induces syncytiotrophoblast formation. Thus, the endogenous dynamics of Plet1 expression establish important patterning cues within the trophoblast compartment by promoting differentiation towards the syncytiotrophoblast or giant cell pathway in Plet1-low and Plet1-high cells, respectively. PMID:27121762

  14. Dynamics of an Electrodynamic Tether System in a Varying Space-Plasma Environment

    Science.gov (United States)

    Janeski, John A.

    Electrodynamic tethers have a wide range of proposed applications in the fields of satellite propulsion and space plasma research. The fundamental purpose of this dissertation is to improve the understanding of the behavior of an electrodynamic tether (EDT) system in Earth's ionosphere. An electrodynamic tether system consists of two satellites connected by a long tether that generates current to produce either power or thrust via the system's electromagnetic interaction with the space environment. Previous electrodynamic tether investigations decouple the interaction between the tether and the constantly changing plasma environment. The limiting factor inhibiting the development of a full system model that has an accurate characterization of the tether/plasma interaction is that the understanding of that interaction is not well developed over a wide range of system parameters. The EDT system model developed in this study uses a high fidelity dynamics model that includes a tether current described by an analytical current collection model whose plasma parameters are determine by the International Reference Ionosphere. It is first shown that new instabilities are induced in the system dynamics under a basic analytical current model versus a constant current model. A 2-D3v Particle-in-Cell (PIC) code has been developed to study the plasma dynamics near a positively charged EDT system end-body and their impact on the current collected. Simulations are run over a range of system parameters that occur throughout a LEO orbit. The azimuthal current structures observed during the TSS-1R mission are found to enhance the current collected by the satellite when the magnetic field is slightly off of perpendicular to the orbital velocity. When the in-plane component of the magnetic field becomes large, the electrons are not able to easily cross the field lines causing plasma lobes form above and below the satellite. The lobes limit the current arriving to the satellite and also

  15. Design, synthesis, and evaluation of mitomycin-tethered phosphorothioate oligodeoxynucleotides.

    Science.gov (United States)

    Huh, N; Rege, A A; Yoo, B; Kogan, T P; Kohn, H

    1996-01-01

    separate from 22. In the second procedure, phosphorothioate oligodexynucleotides that contained a hexylamino spacer at the 5'termini were coupled to 10-des(carbamoyloxy)-10-isothiocyanatoporfiromycin (9). Compound 9 was prepared in four steps from 11. Mesylation (methanesulfonyl chloride/pyridine) of 11 gave the C(10) mesylate 13, which was then treated with NaN3 (dimethylformamide, 90 degrees C) to give 10-des(carbamoyloxy)-10-azidoporfiromycin (14). Catalytic reduction (PtO2, H2) of 14 in pyridine afforded C(10) amine 15. Treatment of 15 with di-2-pyridyl thionocarbonate provided the desired 10-des(carbamoyloxy)-10-isothiocyanatoporfiromycin (9). Compound 9 readily coupled with 17 and base in both methylene chloride and aqueous buffered solutions to give 25. Use of the 5'hexylaminophosphorothioate oligodeoxynucleotides 32-35 in place of 17 gave the conjugated adducts 28-31, respectively, in a 12% to near-quantitative yield. The products were purified by semipreparative HPLC. Antisense agents 28-31 were designed to target a 30-base-long region from the coding region of the human FGFR1 gene. One adduct, 29, reduced the number of FGFR1 receptors in human aortic smooth cells for bFGF on the cell surface, which suggested down-regulation of FGFR1 gene expression. Further, 29 inhibited cultured human aortic smooth muscle cell proliferation and was less cytotoxic than porfiromycin (2). The biological assay data suggest that the phosphorothioate oligodexynucleotide porfiromycin conjugates may be more target selective and less toxic than either mitomycin or porfiromycin and thus be promising therapeutic agents. PMID:8950485

  16. Multibody dynamics driving GNC and system design in tethered nets for active debris removal

    Science.gov (United States)

    Benvenuto, Riccardo; Lavagna, Michèle; Salvi, Samuele

    2016-07-01

    Debris removal in Earth orbits is an urgent issue to be faced for space exploitation durability. Among different techniques, tethered-nets present appealing benefits and some open points to fix. Former and latter are discussed in the paper, supported by the exploitation of a multibody dynamics tool. With respect to other proposed capture mechanisms, tethered-net solutions are characterised by a safer capturing distance, a passive angular momentum damping effect and the highest flexibility to unknown shape, material and attitude of the target to interface with. They also allow not considering the centre of gravity alignment with thrust axis as a constraint, as it is for any rigid link solution. Furthermore, the introduction of a closing thread around the net perimeter ensures safer and more reliable grasping and holding. In the paper, a six degrees of freedom multibody dynamics simulator is presented: it was developed at Politecnico di Milano - Department of Aerospace Science and Technologies - and it is able to describe the orbital and attitude dynamics of tethered-nets systems and end-bodies during different phases, with great flexibility in dealing with different topologies and configurations. Critical phases as impact and wrapping are analysed by simulation to address the tethered-stack controllability. It is shown how the role of contact modelling is fundamental to describe the coupled dynamics: it is demonstrated, as a major novel contribution, how friction between the net and a tumbling target allows reducing its angular motion, stabilizing the system and allowing safer towing operations. Moreover, the so-called tethered space tug is analysed: after capture, the two objects, one passive and one active, are connected by the tethered-net flexible link, the motion of the system being excited by the active spacecraft thrusters. The critical modes prevention during this phase, by means of a closed-loop control synthesis is shown. Finally, the connection between

  17. Cell Surface Receptor Theory of Disease Infectivity; Body's Defence and Normal Body Functioning in Living Things

    Directory of Open Access Journals (Sweden)

    Utoh-Nedosa

    2011-01-01

    Full Text Available Problem statement: A study of the pattern of Candida spp. infection of the human body and the mode and pattern of reaction of the human body to this infection showed that disease infectivity and self healing by plants followed the same procedures and patterns. Approach: A comparism of these procedures and patterns of natural self- healing of disease infection by the human body and plants/plant parts with the cutaneous Candida spp. killing and elimination procedures and patterns of Vernonia amygdalina leaf extract, showed that cell surface receptors are the sites through which disease infects the body and also the sites at which the body is defended. They are also the sites where activities which result in normal body functioning are carried out. The mode and patterns of Cutaneous Candida infection in a human subject and its containment by the body was examined and photographed. The disease infection and self healing procedures and patterns of plants were also examined in comparism with those of their healthy counterparts and photographed. The findings from the observations on disease infectivity and natural body’s defence patterns and procedures of the plant parts studied and those of the human body in reaction to Candida spp. infection were compared with those of the Candida spp. killing procedures and patterns of aqueous and Arachis hypogeal oil extract of Vernonia amygdalina leaf. Results: The findings of this study also showed that disease-infective organisms gain access to the body of a host through attachment to the cell surface receptors of that host which are placed linearly and are interconnected by channels. The results of the study also indicated that living organisms have a main endogenous substance that mediates both their body’s defence and their normal physiological functioning which is therefore the owner of the cell surface receptor. Other endogenous substances which participate in normal body functioning/body’s defence or in

  18. Estimation of added-mass and damping coefficients of a tethered spherical float using potential flow theory

    Digital Repository Service at National Institute of Oceanography (India)

    Vethamony, P.; Chandramohan, P.; Sastry, J.S.; Narasimhan, S.

    Added-mass (alpha) and damping coefficients (beta) of a tethered spherical float, undergoing oscillatory motion in sinusoidal waves, have been derived from the motion generated velocity potential for one degree-of-freedom (surge) using potential...

  19. Cell-surface expression of Hsp70 on hematopoietic cancer cells after inhibition of HDAC activity

    DEFF Research Database (Denmark)

    Jensen, Helle

    frequently express Hsp70 on their cell surface, whereas the corresponding normal tissues do not. In addition, several clinically applied reagents, such as alkyl-lysophospholipides, chemotherapeutic agents, and anti-inflammatory reagents, have been found to enhance Hsp70 cell surface expression on cancer...... cells. We have found that inhibition of histone deacetylase (HDAC) activity leads to surface expression of Hsp70 on various hematopoietic cancer cells, an occurance that was not observed on naïve or activated peripheral blood cells. HDAC-inhibitor mediated Hsp70 cell surface expression was confined to...... transport and cell surface binding of Hsp70 after HDAC-inhibitor treatment remains elusive. Our data suggest that inhibition of HDAC activity selectively induces cell surface expression of Hsp70 on hematopoietic cancer cells, and this may increase the immunorecognition of these cells. It could be envisaged...

  20. Structure of the Membrane-tethering GRASP Domain Reveals a Unique PDZ Ligand Interaction That Mediates Golgi Biogenesis*

    OpenAIRE

    Truschel, Steven T.; Sengupta, Debrup; Foote, Adam; Heroux, Annie; Macbeth, Mark R.; Linstedt, Adam D.

    2011-01-01

    Biogenesis of the ribbon-like membrane network of the mammalian Golgi requires membrane tethering by the conserved GRASP domain in GRASP65 and GRASP55, yet the tethering mechanism is not fully understood. Here, we report the crystal structure of the GRASP55 GRASP domain, which revealed an unusual arrangement of two tandem PDZ folds that more closely resemble prokaryotic PDZ domains. Biochemical and functional data indicated that the interaction between the ligand-binding pocket of PDZ1 and an...

  1. Altered expression of epithelial cell surface glycoconjugates and intermediate filaments at the margins of mucosal wounds

    DEFF Research Database (Denmark)

    Dabelsteen, Erik; Grøn, B; Mandel, U;

    1998-01-01

    Alterations in cell to cell adhesion are necessary to enable the type of cell movements that are associated with epithelial wound healing and malignant invasion. Several studies of transformed cells have related epithelial cell movement to changes in the cell surface expression of the carbohydrate...... structures represented by the ABO blood group antigens and, in particular, by Lewis antigens and their biosynthetic precursors. To study further the relationship between cell surface carbohydrates and keratinocyte cell movement, experimental wounds were created in human oral mucosa and examined by...... immunohistochemical methods for their expression of selected cytokeratins (K5, K16, K19), basement membrane components (laminin alpha5 and gamma2-chains, BP180, collagen IV and collagen VII), and blood group antigen precursor structures Le(x), sialosyl-Le(x), Le(y), H antigen, N-acetyllactosamine, and sialosyl...

  2. Contribution of Cell Surface Hydrophobicity in the Resistance of Staphylococcus aureus against Antimicrobial Agents.

    Science.gov (United States)

    Lather, Puja; Mohanty, A K; Jha, Pankaj; Garsa, Anita Kumari

    2016-01-01

    Staphylococcus aureus is found in a wide variety of habitats, including human skin, where many strains are commensals that may be clinically significant or contaminants of food. To determine the physiological characteristics of resistant strain of Staphylococcus aureus against pediocin, a class IIa bacteriocin, a resistant strain was compared with wild type in order to investigate the contribution of hydrophobicity to this resistance. Additional clumping of resistant strain relative to wild type in light microscopy was considered as an elementary evidence of resistance attainment. A delay in log phase attainment was observed in resistant strain compared to the wild type strain. A significant increase in cell surface hydrophobicity was detected for resistant strain in both hexadecane and xylene indicating the contribution of cell surface hydrophobicity as adaptive reaction against antimicrobial agents. PMID:26966577

  3. Applications of yeast cell-surface display in bio-refinery.

    Science.gov (United States)

    Kondo, Akihiko; Tanaka, Tsutomu; Hasunuma, Tomohisa; Ogino, Chiaki

    2010-11-01

    The dependency on depleting natural resources is a challenge for energy security that can be potentially answered by bioenergy. Bioenergy is derived from starchy and lignocellulosic biomass in the form of bioethanol or from vegetable oils in the form of biodiesel fuel. The acid and enzymatic methods have been developed for the hydrolysis of biomass and for transesterifiaction of plant oils. However, acid hydrolysis results in the production of unnatural compounds which has adverse effects on yeast fermentation. Recent advancements in the yeast cell surface engineering developed strategies to genetically immobilize amylolytic, cellulolytic and xylanolytic enzymes on yeast cell surface for the production of fuel ethanol from biomass. This review gives an insight in to the recent technological developments in the production of bioenergy, i.e, bioethanol using surface engineered yeast. PMID:21171959

  4. SurfaceomeDB: a cancer-orientated database for genes encoding cell surface proteins.

    Science.gov (United States)

    de Souza, Jorge Estefano Santana; Galante, Pedro Alexandre Favoretto; de Almeida, Renan Valieris Bueno; da Cunha, Julia Pinheiro Chagas; Ohara, Daniel Takatori; Ohno-Machado, Lucila; Old, Lloyd J; de Souza, Sandro José

    2012-01-01

    Cell surface proteins (CSPs) are excellent targets for the development of diagnostic and therapeutic reagents, and it is estimated that 10-20% of all genes in the human genome encode CSPs. In an effort to integrate all data publicly available for genes encoding cell surface proteins, a database (SurfaceomeDB) was developed. SurfaceomeDB is a gene-centered portal containing different types of information, including annotation for gene expression, protein domains, somatic mutations in cancer, and protein-protein interactions for all human genes encoding CSPs. SurfaceomeDB was implemented as an integrative and relational database in a user-friendly web interface, where users can search for gene name, gene annotation, or keywords. There is also a streamlined graphical representation of all data provided and links to the most important data repositories and databases, such as NCBI, UCSC Genome Browser, and EBI. PMID:23390370

  5. Lectin-microarray technique for glycomic profiling of fungal cell surfaces.

    Science.gov (United States)

    Shibazaki, Azusa; Gonoi, Tohru

    2014-01-01

    Lectin microarrays are rows of lectins with different carbohydrate-binding specificities spotted on surfaces of glass slides. Lectin microarray technique enables glycomic analyses of carbohydrate composition of fungal cell walls. We will describe an application of the technique in analyzing cell surface glycome of yeast-form fungal cells in the living state. The analysis reveals genus- and species-dependent complex cell surface carbohydrate structures of fungi, and enabled us, therefore, to suggest that cell walls of yeast cells, which have been considered to have relatively simple structures, actually have a more complex structure containing galactose and fucose. This shows that the technique can be used to find new insights into the study of phylogenetic relations and into the classification of cells in the fungal kingdom based on cell wall glycome. PMID:25117243

  6. An electronic interface for a fiber optic tethered unmanned underwater vehicle

    Science.gov (United States)

    Sheakoski, J. R.

    1994-04-01

    As the sophistication of acoustic sensor and communication systems related to unmanned underwater vehicles (UUV) has increased, the requirement for greater volume and higher speed data transfers has emerged. Fiber optic technology provides an effective means for high bandwidth communications with a UUV while minimizing weight and space criteria aboard the UUV. Increase in data transmission speed has permitted real time processing of data on the launch platform when using large high powered computing systems. Maximum system reliability at advanced performance levels can also be realized. By designing and developing a full scale system comprised of the UUV, remote control and command platform, and data handling and routing electronics, fiber optic tethered UUV technology was demonstrated in lab field tests. This three year venture culminated in a series of successful in-water tests that proved the feasibility of fiber optic tethered UUV's and warranted the continuation of research on remotely operated UUV's.

  7. Experimental verification of chaotic control of an underactuated tethered satellite system

    Science.gov (United States)

    Pang, Zhaojun; Jin, Dongping

    2016-03-01

    This paper studies chaotic control of a tethered satellite system (TSS) driven only by a momentum-exchange device during its attitude adjustment. In dealing with such the underactuated system, an extended time-delay autosynchronization (ETDAS) is employed to stabilize the chaotic motion to a periodic motion. To obtain the control domains of the ETDAS method, a stability analysis of the controlled tethered satellite system in elliptical orbit is implemented. According to the principle of dynamic similarity, then, ground-based experiment setups are proposed and designed to emulate the in-plane motions of the TSS. Representative experiments are presented to demonstrate the effectiveness of the ETDAS scheme in controlling the chaotic motion of the underactuated TSS.

  8. In Vivo Quantification of Peroxisome Tethering to Chloroplasts in Tobacco Epidermal Cells Using Optical Tweezers.

    Science.gov (United States)

    Gao, Hongbo; Metz, Jeremy; Teanby, Nick A; Ward, Andy D; Botchway, Stanley W; Coles, Benjamin; Pollard, Mark R; Sparkes, Imogen

    2016-01-01

    Peroxisomes are highly motile organelles that display a range of motions within a short time frame. In static snapshots, they can be juxtaposed to chloroplasts, which has led to the hypothesis that they are physically interacting. Here, using optical tweezers, we tested the dynamic physical interaction in vivo. Using near-infrared optical tweezers combined with TIRF microscopy, we were able to trap peroxisomes and approximate the forces involved in chloroplast association in vivo in tobacco (Nicotiana tabacum) and observed weaker tethering to additional unknown structures within the cell. We show that chloroplasts and peroxisomes are physically tethered through peroxules, a poorly described structure in plant cells. We suggest that peroxules have a novel role in maintaining peroxisome-organelle interactions in the dynamic environment. This could be important for fatty acid mobilization and photorespiration through the interaction with oil bodies and chloroplasts, highlighting a fundamentally important role for organelle interactions for essential biochemistry and physiological processes. PMID:26518344

  9. The motion of tethered tug-debris system with fuel residuals

    Science.gov (United States)

    Aslanov, Vladimir S.; Yudintsev, Vadim V.

    2015-10-01

    Active debris removal using a space tug with a tether is one of the promising techniques to decrease the population of large non-functional satellites and orbital stages in near Earth orbits. Properties of debris should be taken into account in the development of the space tugs. In this paper we consider the motion of a debris objects with fuel residuals that can affect the safety of the debris transportation process. The equations of the attitude motion of the tug-debris system in a central gravitational field are derived. Stationary solutions of the equations are found. The system of linearized equations are introduced that can be used for short term analysis. The numerical simulation results are provided that show good accuracy of the linearized equations. Proposed equations can be used to analyze the attitude motion of the tug-debris system and to determine the conventional parameters for safe tethered transportation of space debris.

  10. Lectin binding profiles of SSEA-4 enriched, pluripotent human embryonic stem cell surfaces

    OpenAIRE

    Shin Soojung; Jones Karen; Lyons Ian; Mitalipova Maisam; Venable Alison; Pierce Michael; Stice Steven

    2005-01-01

    Abstract Background Pluripotent human embryonic stem cells (hESCs) have the potential to form every cell type in the body. These cells must be appropriately characterized prior to differentiation studies or when defining characteristics of the pluripotent state. Some developmentally regulated cell surface antigens identified by monoclonal antibodies in a variety of species and stem cell types have proven to be side chains of membrane glycolipids and glycoproteins. Therefore, to examine hESC s...

  11. Heparan sulfate proteoglycans mediate factor XIIa binding to the cell surface.

    Science.gov (United States)

    Wujak, Lukasz; Didiasova, Miroslava; Zakrzewicz, Dariusz; Frey, Helena; Schaefer, Liliana; Wygrecka, Malgorzata

    2015-03-13

    Hageman factor (FXIIa) initiates the intrinsic coagulation pathway and triggers the kallikrein-kinin and the complement systems. In addition, it functions as a growth factor by expressing promitogenic activities toward several cell types. FXIIa binds to the cell surface via a number of structurally unrelated surface receptors; however, the underlying mechanisms are not yet fully understood. Here, we demonstrate that FXIIa utilizes cell membrane-bound glycosaminoglycans to interact with the cell surface of human lung fibroblasts (HLF). The combination of enzymatic, inhibitory, and overexpression approaches identified a heparan sulfate (HS) component of proteoglycans as an important determinant of the FXIIa binding capacity of HLF. Moreover, cell-free assays and competition experiments revealed preferential binding of FXIIa to HS and heparin over dextran sulfate, dermatan sulfate, and chondroitin sulfate A and C. Finally, we demonstrate that fibroblasts isolated from the lungs of the patients suffering from idiopathic pulmonary fibrosis (IPF) exhibit enhanced FXIIa binding capacity. Increased sulfation of HS resulting from elevated HS 6-O-sulfotransferase-1 expression in IPF HLF accounted, in part, for this phenomenon. Application of RNA interference technology and inhibitors of intracellular sulfation revealed the cooperative action of cell surface-associated HS and urokinase-type plasminogen activator receptor in the accumulation of FXIIa on the cell surface of IPF HLF. Moreover, FXIIa stimulated IPF HLF migration, which was abrogated by pretreatment of cells with heparinase I. Collectively, our study uncovers a novel role of HS-type glycosaminoglycans in a local accumulation of FXIIa on the cell membrane. The enhanced association of FXIIa with IPF HLF suggests its contribution to fibrogenesis. PMID:25589788

  12. Isolation of pigmented and nonpigmented mutants of Serratia marcescens with reduced cell surface hydrophobicity.

    OpenAIRE

    Rosenberg, M

    1984-01-01

    Enrichment for nonhydrophobic mutants of Serratia marcescens yielded two types: (i) a nonpigmented mutant which exhibited partial hydrophobic characteristics compared with the wild type, as determined by adherence to hexadecane and polystyrene; and (ii) a pigmented, nonhydrophobic mutant whose colonies were translucent with respect to those of the wild type. The data suggest that the pronounced cell surface hydrophobicity of the wild type is mediated by a combination of several surface factors.

  13. Techniques to Study Specific Cell-Surface Receptor-Mediated Cellular Vitamin A Uptake

    OpenAIRE

    KAWAGUCHI, RIKI; Sun, Hui

    2010-01-01

    STRA6 is a multitransmembrane domain protein that was recently identified as the cell-surface receptor for plasma retinol binding protein (RBP), the vitamin A carrier protein in the blood. STRA6 binds to RBP with high affinity and mediates cellular uptake of vitamin A from RBP. It is not homologous to any known receptors, transporters, and channels, and it represents a new class of membrane transport protein. Consistent with the diverse physiological functions of vitamin A, STRA6 is widely ex...

  14. Comprehensive proteomic analysis of Trypanosoma cruzi epimastigote cell surface proteins by two complementary methods

    DEFF Research Database (Denmark)

    Queiroz, Rayner M L; Charneau, Sébastien; Motta, Flávia N; Santana, Jaime M; Roepstorff, Peter; Ricart, Carlos A O

    2013-01-01

    Trypanosoma cruzi is a protozoan that causes Chagas' disease, a neglected infectious illness that affects millions of people, mostly in Latin America. Here, the cell surface subproteome of the T. cruzi epimastigote life form was characterized. In order to prepare samples enriched in epimastigote...... of the labeled proteins. Both T. cruzi subproteomes were analyzed by LC-MS/MS. The results showed that the methodologies offered comprehensive and complementary information about the parasite's plasma membrane subproteome....

  15. Cell surface acetylcholinesterase molecules on multinucleated myotubes are clustered over the nucleus of origin

    OpenAIRE

    1992-01-01

    Multinucleated skeletal muscle fibers are compartmentalized with respect to the expression and organization of several intracellular and cell surface proteins including acetylcholinesterase (AChE). Mosaic muscle fibers formed from homozygous myoblasts expressing two allelic variants of AChE preferentially translate and assemble the polypeptides in the vicinity of the nucleus encoding the mRNA (Rotundo, R. L. 1990. J. Cell Biol. 110:715-719). To determine whether the locally synthesized AChE m...

  16. Cell surface polypeptides of murine T-cell clones expressing cytolytic or amplifier activity.

    OpenAIRE

    Sarmiento, M.; Glasebrook, A L; Fitch, F. W.

    1980-01-01

    Murine cytolytic T-cell and amplifier T-cell clones derived from secondary unidirectional mixed leukocyte cultures were labeled with 125I by the lactoperoxidase method and their polypeptide profiles were analyzed by NaDodSO4/polyacrylamide gel electrophoresis. All cytolytic T-cell clones derived from the same mouse strain yeilded similar cell surface polypeptide profiles. However, profiles obtained with three amplifier T-cell clones were strikingly different from each other as well as from th...

  17. Proteomic analysis of cell surface-associated proteins from probiotic Lactobacillus plantarum

    DEFF Research Database (Denmark)

    Beck, Hans Christian; Madsen, Søren M; Glenting, Jacob;

    2009-01-01

    In the present study, we used a proteomic approach to identify surface-associated proteins from the probiotic bacterium Lactobacillus plantarum 299v. Proteins were extracted from the cell surface using a mild wash in phosphate buffer and analysed by sodium dodecyl sulphate-polyacrylamide gel...... probiotics in the gastrointestinal tract. The results provide the basis for future studies on the molecular mechanisms of probiotics....

  18. Cell surface thiol isomerases may explain the platelet-selective action of S-nitrosoglutathione

    OpenAIRE

    Xiao, Fang; Gordge, Michael P

    2011-01-01

    S-nitrosoglutathione (GSNO) at low concentration inhibits platelet aggregation without causing vasodilation, suggesting platelet-selective nitric oxide delivery. The mechanism of this selectivity is unknown, but may involve cell surface thiol isomerases, in particular protein disulphide isomerase (csPDI) (EC 5.3.4.1). We have now compared csPDI expression and activity on platelets, endothelial cells and vascular smooth muscle cells, and the dependence on thiol reductase activity of these cell...

  19. Influence of growth conditions on cell surface hydrophobicity of Candida albicans and Candida glabrata.

    OpenAIRE

    Hazen, K C; Plotkin, B. J.; Klimas, D M

    1986-01-01

    The effect of cultural conditions on cell surface hydrophobicity of Candida albicans and Candida glabrata was tested. C. albicans cells grown at room temperature were more hydrophobic than cells grown at 37 degrees C. No consistent pattern was observed with C. glabrata. Relative hydrophobicity was found to vary with the growth phase and growth medium for both species. The implications for pathogenesis studies are discussed.

  20. A cell surface receptor complex for collagen type I recognizes the Arg- Gly-Asp sequence

    OpenAIRE

    1987-01-01

    To isolate collagen-binding cell surface proteins, detergent extracts of surface-iodinated MG-63 human osteosarcoma cells were chromatographed on affinity matrices of either type I collagen- Sepharose or Sepharose carrying a collagen-like triple-helical peptide. The peptide was designed to be triple helical and to contain the sequence Arg-Gly-Asp, which has been implicated as the cell attachment site of fibronectin, vitronectin, fibrinogen, and von Willebrand factor, and is also present in ty...

  1. Cell Surface Determinants Important for Biofilm-Based Solid Substrate Degradation

    OpenAIRE

    Jitka Dostálková; Vladimír Jirků; Gita Procházková; Lucie Křiklavová; Tomáš Lederer; Tomáš Brányik

    2013-01-01

    The study links targeted cell surface characterization to the quantified capacity of cellulose degrading Pseudomonas fluorescens cells to colonize a (similarly characterized) cellulosic carrier. The experiments were conducted to clarify the effect of cultivation conditions on the achieved state of this carrier colonization. The suggested approach seems to be sufficient to verify the right choice of cultivation medium as a major factor determining the binding complementarity between micro...

  2. Microassay for measurement of binding of radiolabelled ligands to cell surface molecules

    International Nuclear Information System (INIS)

    An improved technique for measuring the binding of radiolabelled ligands to cell surface molecules has been developed by modification of a procedure using centrifugation through a water-immiscible oil to separate free and cell-bound ligand. It maximises the percentage of ligand bound since cell-bound and free ligand can be separated easily and reproducibly even when very small reaction volumes are used. This permits low levels of ligand radiolabelling and relatively low numbers of cells to be used

  3. Extracellular Domain N-Glycosylation Controls Human Thrombopoietin Receptor Cell Surface Levels

    OpenAIRE

    Albu, Roxana I.; Stefan N. Constantinescu

    2011-01-01

    The thrombopoietin receptor (TpoR) is a type I transmembrane protein that mediates the signaling functions of thrombopoietin (Tpo) in regulating megakaryocyte differentiation, platelet formation, and hematopoietic stem cell renewal. We probed the role of each of the four extracellular domain putative N-glycosylation sites for cell surface localization and function of the receptor. Single N-glycosylation mutants at any of the four sites were able to acquire the mature N-glycosylated pattern, b...

  4. Extracellular Domain N-Glycosylation Controls Human Thrombopoietin Receptor Cell Surface Levels

    OpenAIRE

    Stefan N. Constantinescu

    2011-01-01

    The thrombopoietin receptor (TpoR) is a type I transmembrane protein that mediates the signaling functions of thrombopoietin (Tpo) in regulating megakaryocyte differentiation, platelet formation and hematopoietic stem cell renewal. We probed the role of each of the four extracellular domain putative N-glycosylation sites for cell surface localization and function of the receptor. Single N-glycosylation mutants at any of the four sites were able to acquire the mature N-glycosylated pattern, bu...

  5. Ultrastructural and biochemical studies of two dynamically expressed cell surface determinants on Candida albicans.

    OpenAIRE

    Brawner, D L; Cutler, J E

    1986-01-01

    Variability in the expression of two different cell surface carbohydrate determinants was examined with two agglutinating immunoglobulin M monoclonal antibodies (H9 and C6) and immunoelectron microscopy during growth of three strains of Candida albicans. A single strain of Candida parapsilosis did not express either antigen at any time during growth. Antigens were detected on the surface of C. albicans by agglutination tests with either H9 or C6 over a 48-h growth period. The difference in sp...

  6. Tethered Aminohydroxylation: Synthesis of the β-Amino Acid of Microsclerodermins A and B

    OpenAIRE

    Pullin, Robert D. C.; Rathi, Akshat H.; Melikhova, Ekaterina Y.; Winter, Christian; Thompson, Amber L.; Donohoe, Timothy J.

    2013-01-01

    The utility of the tethered aminohydroxylation (TA) has been demonstrated by synthesis of the complex β-amino acid residue of microsclerodermins A and B. The TA provided a regio- and stereoselective functionalization of a complex homoallylic alcohol. The route includes late-stage introduction of the aliphatic side chain via a cuprate addition and cross metathesis, a tactic designed to render the synthesis applicable to other microsclerodermins.

  7. Quantifying interspecific variation in dispersal ability of noctuid moths using an advanced tethered flight technique

    OpenAIRE

    Jones, Hayley B. C.; Lim, Ka S.; Bell, James R.; Hill, Jane K.; Chapman, Jason W.

    2015-01-01

    Abstract Dispersal plays a crucial role in many aspects of species' life histories, yet is often difficult to measure directly. This is particularly true for many insects, especially nocturnal species (e.g. moths) that cannot be easily observed under natural field conditions. Consequently, over the past five decades, laboratory tethered flight techniques have been developed as a means of measuring insect flight duration and speed. However, these previous designs have tended to focus on single...

  8. Tethered capsule endomicroscopy enables less-invasive imaging of gastrointestinal tract microstructure

    OpenAIRE

    Gora, Michalina J.; Sauk, Jenny S.; Carruth, Robert W.; Gallagher, Kevin A.; Suter, Melissa J.; Nishioka, Norman S.; Kava, Lauren E.; Rosenberg, Mireille; Bouma, Brett E.; Tearney, Guillermo J.

    2013-01-01

    Here, we introduce “tethered capsule endomicroscopy,” that involves swallowing an optomechanically-engineered pill that captures cross-sectional, 30 μm (lateral) × 7 μm (axial) resolution, microscopic images of the gut wall as it travels through the digestive tract. Results in human subjects show that this technique rapidly provides three-dimensional, microstructural images of the upper gastrointestinal tract in a simple and painless procedure, opening up new opportunities for screening for i...

  9. Simulation of tethered oligomers in nanochannels using multi-particle collision dynamics

    OpenAIRE

    Raghu, Riyad; Schofield, Jeremy

    2012-01-01

    The effect of a high Reynold's number, pressure-driven flow of a compressible gas on the conformation of an oligomer tethered to the wall of a square-channel is studied under both ideal solvent and poor solvent conditions using a hybrid multiparticle collision dynamics and molecular dynamics algorithm. Unlike previous studies, the flow field contains an elongational component in addition to a shear component as well as fluid slip near the walls and results in a Schmidt number for the polymer ...

  10. Template-Tethered Collagen Mimetic Peptides for Studying Heterotrimeric Triple-Helical Interactions

    OpenAIRE

    Li, Yang; Mo, Xiao; Kim, Daniel; Yu, S. Michael

    2010-01-01

    Collagen mimetic peptides (CMPs) have been used to elucidate the structure and stability of the triple helical conformation of collagen molecules. Although CMP homotrimers have been widely studied, very little work has been reported regarding CMP heterotrimers because of synthetic difficulties. Here we present the synthesis and characterization of homotrimers and ABB type heterotrimers comprising natural and synthetic CMP sequences that are covalently tethered to a template, a tris(2-aminoeth...

  11. TIN2-tethered TPP1 recruits human telomerase to telomeres in vivo.

    OpenAIRE

    Abreu, E.; Aritonovska, E.; Reichenbach, P.; Cristofari, G.; Culp, B.; Terns, R. M.; Lingner, J; Terns, M P

    2010-01-01

    Recruitment to telomeres is a pivotal step in the function and regulation of human telomerase; however, the molecular basis for recruitment is not known. Here, we have directly investigated the process of telomerase recruitment via fluorescence in situ hybridization (FISH) and chromatin immunoprecipitation (ChIP). We find that depletion of two components of the shelterin complex that is found at telomeres--TPP1 and the protein that tethers TPP1 to the complex, TIN2--results in a loss of telom...

  12. Analysis of a tethered stabilized Schmidt telescope asserved to the Space Station

    Science.gov (United States)

    Bertola, F.; Rafanelli, P.; Angrilli, F.; Bianchini, G.; da Forno, R.

    The concept of a Schmidt telescope connected to the Space Station by a 2-10 km long tether is discussed. A mission scenario and the optical characteristics of the telescope are described. A linearized mathematical model is used to study the dynamic behavior of the telescope platform in space. Simulations are conducted to account for environmental perturbations, thermal effects, atmospheric drag, micrometeor impact, and the dynamical response to slewing motion.

  13. Tether radiation in Juno-type and circular-equatorial Jovian orbits

    OpenAIRE

    Sánchez-Torres, Antonio; Sanmartín Losada, Juan Ramón

    2011-01-01

    Wave radiation by a conductor carrying a steady current in both a polar, highly eccentric, low perijove orbit, as in NASA's planned Juno mission, and an equatorial low Jovian orbit (LJO) mission below the intense radiation belts, is considered. Both missions will need electric power generation for scientific instruments and communication systems. Tethers generate power more efficiently than solar panels or radioisotope power systems (RPS). The radiation impedance is required to determin...

  14. Virtual migration in tethered flying monarch butterflies reveals their orientation mechanisms

    OpenAIRE

    Mouritsen, Henrik; Frost, Barrie J.

    2002-01-01

    A newly developed flight simulator allows monarch butterflies to fly actively for up to several hours in any horizontal direction while their fall migratory flight direction can be continuously recorded. From these data, long segments of virtual flight paths of tethered, flying, migratory monarch butterflies were reconstructed, and by advancing or retarding the butterflies' circadian clocks, we have shown that they possess a time-compensated sun compass. Control monarchs on local time fly app...

  15. Bacterial Tethering Analysis Reveals a “Run-Reverse-Turn” Mechanism for Pseudomonas Species Motility

    OpenAIRE

    Qian, Chen; Wong, Chui Ching; SWARUP, SANJAY; Chiam, Keng-Hwee

    2013-01-01

    We have developed a program that can accurately analyze the dynamic properties of tethered bacterial cells. The program works especially well with cells that tend to give rise to unstable rotations, such as polar-flagellated bacteria. The program has two novel components. The first dynamically adjusts the center of the cell's rotational trajectories. The second applies piecewise linear approximation to the accumulated rotation curve to reduce noise and separate the motion of bacteria into pha...

  16. Bordetella pertussis adenylate cyclase toxin translocation across a tethered lipid bilayer

    OpenAIRE

    Veneziano, Rémi; Rossi, Claire; Chenal, Alexandre; Devoisselle, Jean-Marie; Ladant, Daniel; Chopineau, Joel

    2013-01-01

    Many bacterial toxins can cross biological membranes to reach the cytosol of mammalian cells, although how they pass through a lipid bilayer remains largely unknown. Bordetella pertussis adenylate cyclase (CyaA) toxin delivers its catalytic domain directly across the cell membrane. To characterize this unique translocation process, we designed an in vitro assay based on a tethered lipid bilayer assembled over a biosensor surface derivatized with calmodulin, a natural activator of the toxin. C...

  17. Space-Based Tethered Array Radar (STAR) - A Distributed Small Satellite Network

    OpenAIRE

    Tomlinson, Philip; Brown, Thomas; Chakraborty, Dayamoy

    1988-01-01

    The Space-Based Tethered Array Radar (STAR) concept evolved from the DoD need for an affordable, launchable, survivable, and expandable Space-Based Radar for wide-area surveillance of airborne targets and for ballistic missile defense applications. Because low-observable threats can undermine conventional large monolithic Space-Based Radar satellite designs by forcing power-aperture products (inversely proportional to target radar cross-section) so high that the resulting heavy and expensive ...

  18. Optimum sizing of bare-tape tethers for de-orbiting satellites at end of mission

    Science.gov (United States)

    Sanmartín, J. R.; Sánchez-Torres, A.; Khan, S. B.; Sánchez-Arriaga, G.; Charro, M.

    2015-10-01

    De-orbiting satellites at end of mission would prevent generation of new space debris. A proposed de-orbit technology involves a bare conductive tape-tether, which uses neither propellant nor power supply while generating power for on-board use during de-orbiting. The present work shows how to select tape dimensions for a generic mission so as to satisfy requirements of very small tether-to-satellite mass ratio mt/MS and probability Nf of tether cut by small debris, while keeping de-orbit time tf short and product tf × tether length low to reduce maneuvers in avoiding collisions with large debris. Design is here discussed for particular missions (initial orbit of 720 km altitude and 63° and 92° inclinations, and 3 disparate MS values, 37.5, 375, and 3750 kg), proving it scalable. At mid-inclination and a mass-ratio of a few percent, de-orbit time takes about 2 weeks and Nf is a small fraction of 1%, with tape dimensions ranging from 1 to 6 cm, 10 to 54 μ m, and 2.8 to 8.6 km. Performance drop from middle to high inclination proved moderate: if allowing for twice as large mt/MS, increases are reduced to a factor of 4 in tf and a slight one in Nf, except for multi-ton satellites, somewhat more requiring because efficient orbital-motion-limited electron collection restricts tape-width values, resulting in tape length (slightly) increasing too.

  19. Dynamics, Control, and Estimation for Aerial Robots Tethered by Cables or Bars

    OpenAIRE

    Tognon, Marco; Franchi, Antonio

    2016-01-01

    The problem of controlling an aerial robot connected by a passive tether or a passive rigid link to the ground is considered here. We provide a thorough characterization of this nonlinear dynamical robotic system in terms of fundamental properties such as differential flatness, controllability, and observability. We prove that the robotic system is differentially flat with respect to two possible output pairs: elevation of the link and attitude of the vehicle; elevation of the link and longit...

  20. Sustained neurotensin exposure promotes cell surface recruitment of NTS2 receptors

    International Nuclear Information System (INIS)

    In this study, we investigated whether persistent agonist stimulation of NTS2 receptors gives rise to down-regulation, in light of reports that their activation induced long-lasting effects. To address this issue, we incubated COS-7 cells expressing the rat NTS2 with neurotensin (NT) for up to 24 h and measured resultant cell surface [125I]-NT binding. We found that NTS2-expressing cells retained the same surface receptor density despite efficient internalization mechanisms. This preservation was neither due to NTS2 neosynthesis nor recycling since it was not blocked by cycloheximide or monensin. However, it appeared to involve translocation of spare receptors from internal stores, as NT induced NTS2 migration from trans-Golgi network to endosome-like structures. This stimulation-induced regulation of cell surface NTS2 receptors was even more striking in rat spinal cord neurons. Taken together, these results suggest that sustained NTS2 activation promotes recruitment of intracellular receptors to the cell surface, thereby preventing functional desensitization

  1. Anti-obesity phenotypic screening looking to increase OBR cell surface expression.

    Science.gov (United States)

    Kim, Tae-Hee; Choi, Dong-Hwa; Vauthier, Virginie; Dam, Julie; Li, Xiaolan; Nam, Yeon-Ju; Ko, YoonAe; Kwon, Ho Jeong; Shin, Sang Hoon; Cechetto, Jonathan; Soloveva, Veronica; Jockers, Ralf

    2014-01-01

    The leptin receptor, OBR, is involved in the regulation of whole-body energy homeostasis. Most obese people are resistant to leptin and do not respond to the hormone. The prevention and reversal of leptin resistance is one of the major current goals of obesity research. We showed previously that increased OBR cell surface expression concomitantly increases cellular leptin signaling and prevents obesity development in mice. Improvement of OBR cell surface expression can thus be considered as an interesting anti-obesity therapeutic strategy. To identify compounds that increase the surface expression of OBR, we developed a cell-based, phenotypic assay to perform a high-content screen (HCS) against a library of 50,000 chemical compounds. We identified 67 compounds that increased OBR cell surface expression with AC50 values in the low micromolar range and no effect on total OBR expression and cellular toxicity. Compounds were classified into 16 chemical clusters, of which 4 potentiated leptin-promoted signaling through the JAK2/STAT3 pathway. In conclusion, development of a robust phenotypic screening approach resulted in the discovery of four new scaffolds that demonstrate the desired biological activity and could constitute an original therapeutic solution against obesity and associated disorders. PMID:23958651

  2. Yeast cell surface display for lipase whole cell catalyst and its applications

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Yun; Zhang, Rui; Lian, Zhongshuai; Wang, Shihui; Wright, Aaron T.

    2014-08-01

    The cell surface display technique allows for the expression of target proteins or peptides on the microbial cell surface by fusing an appropriate protein as an anchoring motif. Yeast display systems, such as Pichia pastoris, Yarowia lipolytica and Saccharomyces cerevisiae, are ideal, alternative and extensive display systems with the advantage of simple genetic manipulation and post-translational modification of expressed heterologous proteins. Engineered yeasts show high performance characteristics and variant utilizations. Herein, we comprehensively summarize the variant factors affecting lipase whole cell catalyst activity and display efficiency, including the structure and size of target proteins, screening anchor proteins, type and chain length of linkers, and the appropriate matching rules among the above-mentioned display units. Furthermore, we also address novel approaches to enhance stability and activity of recombinant lipases, such as VHb gene co-expression, multi-enzyme co-display technique, and the micro-environmental interference and self-assembly techniques. Finally, we represent the variety of applications of whole cell surface displayed lipases on yeast cells in non-aqueous phases, including synthesis of esters, PUFA enrichment, resolution of chiral drugs, organic synthesis and biofuels. We demonstrate that the lipase surface display technique is a powerful tool for functionalizing yeasts to serve as whole cell catalysts, and increasing interest is providing an impetus for broad application of this technique.

  3. Development of novel cell surface display in Corynebacterium glutamicum using porin.

    Science.gov (United States)

    Tateno, Toshihiro; Hatada, Kazuki; Tanaka, Tsutomu; Fukuda, Hideki; Kondo, Akihiko

    2009-09-01

    We have developed a novel cell surface display in Corynebacterium glutamicum using porin proteins as anchor proteins. Porins are localized at C. glutamicum mycolic acid layer and exist as a hexamer. We used alpha-amylase from Streptococcus bovis 148 (AmyA) as a model protein to be displayed on the C. glutamicum cell surface. AmyA was fused to the C terminus of the porins PorB, PorC, or PorH. Expression vectors using fused proteins under the control of the cspB promoter were constructed and introduced into the C. glutamicum Cm strain. Immunostaining microscopy and flow cytometric analysis revealed that PorB-AmyA, PorC-AmyA, and PorH-AmyA were displayed on the C. glutamicum cell surface. AmyA activity was only detected in the cell fraction of C. glutamicum cells that displayed AmyA fused to PorB, PorC or PorH and AmyA activity was not detected in the supernatants of C. glutamicum culture broths after 72 h cultivation. Thus, we have demonstrated that C. glutamicum porins are very efficient anchor proteins for protein display in C. glutamicum. PMID:19430772

  4. Controlled-surface-wettability-based fabrication of hydrogel substrates with matrix tethering density variations

    Science.gov (United States)

    Rahman, Md. Mahmudur; Lee, Donghee; Bhagirath, Divya; Zhao, Xiangshan; Band, Vimla; Ryu, Sangjin

    2014-03-01

    It is widely accepted that cells behave differently responding to the stiffness of extracellular matrix (ECM). Such observations were made by culturing cells on hydrogel substrates of tunable stiffness. However, it was recently proposed that cells actually sense how strongly they are tethered to ECM, not the local stiffness of ECM. To investigate the hypothesis, we develop constant-stiffness hydrogel substrates with varying matrix tethering density (the number of anchoring sites between the gel and the ECM protein molecules). We fabricate polyacrylamide gel of static stiffness and conjugate ECM proteins to the gel using a cross-linker. When treating the gel with the cross-linker, we control positioning of cross-linker solutions with different concentrations using superhydrophobic barriers on glass, functionalize the gel by pressing it to the aligned cross-linker solutions, and conjugate an ECM protein of constant concentration to the gel. We expect that the gel will be functionalized to different degrees depending on the concentration distribution of the cross-linker and thus the gel will have variations of matrix tethering density even with constant ECM protein concentration. We acknowledge support from Bioengineering for Human Health grant of UNL-UNMC.

  5. Biodegradable, Tethered Lipid Bilayer-Microsphere Systems with Membrane-Integrated α-Helical Peptide Anchors.

    Science.gov (United States)

    Fried, Eric S; Luchan, Joshua; Gilchrist, M Lane

    2016-04-12

    Supported lipid bilayers (SLBs) are ideally suited for the study of biomembrane-biomembrane interactions and for the biomimicry of cell-to-cell communication, allowing for surface ligand displays that contain laterally mobile elements. However, the SLB paradigm does not include three-dimensionality and biocompatibility. As a way to bypass these limitations, we have developed a biodegradable form of microsphere SLBs, also known as proteolipobeads (PLBs), using PLGA microspheres. Microspheres were synthesized using solvent evaporation and size selected with fluorescence activated cell sorting (FACS). Biomembranes were covalently tethered upon fusion to microsphere supports via short-chain PEG spacers connecting membrane-integrated α-helical peptides and the microsphere surface, affecting membrane diffusivity and mobility as indicated by confocal FRAP analysis. Membrane heterogeneities, which are attributed to PLGA hydrophobicity and rough surface topography, are curtailed by the addition of PEG tethers. This method allows for the presentation of tethered, laterally mobile biomembranes in three dimensions with functionally embedded attachment peptides for mobile ligand displays. PMID:26972467

  6. History of the current understanding and management of tethered spinal cord.

    Science.gov (United States)

    Safavi-Abbasi, Sam; Mapstone, Timothy B; Archer, Jacob B; Wilson, Christopher; Theodore, Nicholas; Spetzler, Robert F; Preul, Mark C

    2016-07-01

    An understanding of the underlying pathophysiology of tethered cord syndrome (TCS) and modern management strategies have only developed within the past few decades. Current understanding of this entity first began with the understanding and management of spina bifida; this later led to the gradual recognition of spina bifida occulta and the symptoms associated with tethering of the filum terminale. In the 17th century, Dutch anatomists provided the first descriptions and initiated surgical management efforts for spina bifida. In the 19th century, the term "spina bifida occulta" was coined and various presentations of spinal dysraphism were appreciated. The association of urinary, cutaneous, and skeletal abnormalities with spinal dysraphism was recognized in the 20th century. Early in the 20th century, some physicians began to suspect that traction on the conus medullaris caused myelodysplasia-related symptoms and that prophylactic surgical management could prevent the occurrence of clinical manifestations. It was not, however, until later in the 20th century that the term "tethered spinal cord" and the modern management of TCS were introduced. This gradual advancement in understanding at a time before the development of modern imaging modalities illustrates how, over the centuries, anatomists, pathologists, neurologists, and surgeons used clinical examination, a high level of suspicion, and interest in the subtle and overt clinical appearances of spinal dysraphism and TCS to advance understanding of pathophysiology, clinical appearance, and treatment of this entity. With the availability of modern imaging, spinal dysraphism can now be diagnosed and treated as early as the intrauterine stage. PMID:26967990

  7. The Atg1-kinase complex tethers Atg9-vesicles to initiate autophagy

    Science.gov (United States)

    Rao, Yijian; Perna, Marco G.; Hofmann, Benjamin; Beier, Viola; Wollert, Thomas

    2016-01-01

    Autophagosomes are double-membrane vesicles that sequester cytoplasmic material for lysosomal degradation. Their biogenesis is initiated by recruitment of Atg9-vesicles to the phagophore assembly site. This process depends on the regulated activation of the Atg1-kinase complex. However, the underlying molecular mechanism remains unclear. Here we reconstitute this early step in autophagy from purified components in vitro. We find that on assembly from its cytoplasmic subcomplexes, the Atg1-kinase complex becomes activated, enabling it to recruit and tether Atg9-vesicles. The scaffolding protein Atg17 targets the Atg1-kinase complex to autophagic membranes by specifically recognizing the membrane protein Atg9. This interaction is inhibited by the two regulatory subunits Atg31 and Atg29. Engagement of the Atg1-Atg13 subcomplex restores the Atg9-binding and membrane-tethering activity of Atg17. Our data help to unravel the mechanism that controls Atg17-mediated tethering of Atg9-vesicles, providing the molecular basis to understand initiation of autophagosome-biogenesis.

  8. Clustering of tethered satellite system simulation data by an adaptive neuro-fuzzy algorithm

    Science.gov (United States)

    Mitra, Sunanda; Pemmaraju, Surya

    1992-01-01

    Recent developments in neuro-fuzzy systems indicate that the concepts of adaptive pattern recognition, when used to identify appropriate control actions corresponding to clusters of patterns representing system states in dynamic nonlinear control systems, may result in innovative designs. A modular, unsupervised neural network architecture, in which fuzzy learning rules have been embedded is used for on-line identification of similar states. The architecture and control rules involved in Adaptive Fuzzy Leader Clustering (AFLC) allow this system to be incorporated in control systems for identification of system states corresponding to specific control actions. We have used this algorithm to cluster the simulation data of Tethered Satellite System (TSS) to estimate the range of delta voltages necessary to maintain the desired length rate of the tether. The AFLC algorithm is capable of on-line estimation of the appropriate control voltages from the corresponding length error and length rate error without a priori knowledge of their membership functions and familarity with the behavior of the Tethered Satellite System.

  9. From the Rocket Equation to Maxwell's Equations: Electrodynamic Tether Propulsion Nears Space Test

    Science.gov (United States)

    Johnson, Les; Estes, Robert

    1999-01-01

    The US space program is facing a growing challenge to its decades-long, global leadership position, as current launch costs consume valuable resources and limit achievements in science, exploration, and commercial development. More than 40% of projected launches over the next 10 years have payloads with intended destinations beyond low-Earth orbit. Therefore, more cost-effective upper stages and on-board propulsion systems are critical elements in reducing total space transportation costs. A new type of space propulsion, using electrodynamic tethers, may be capable of performing multiple sequential missions without resupply and have a potential usable lifetime of several years. They may provide an in-space infrastructure that has a very low life cycle cost and greatly enhanced mission flexibility, thus supporting the goal of reducing the cost of access to space. Electrodynamic tether thrusters work by virtue of the force the Earth's magnetic field exerts on a wire carrying an electrical current. The effect is the basis for electric motors and generators. The Propulsive Small Expendable Deployer System (ProSEDS) experiment, planned for launch in the summer of 2000, will demonstrate the use electrodynamic tether thrust by lowering the altitude of a Delta-H rocket's upper stage on which it will be flying. Applications of the technology include a passive deorbit system for spacecraft at their end-of-life, reusable Orbit Transfer Vehicles, propellantless reboost of the International Space Station, and propulsion and power generation for future missions to Jupiter.

  10. Postoperative epidural hematoma contributes to delayed upper cord tethering after decompression of Chiari malformation type I

    Directory of Open Access Journals (Sweden)

    Antonio Lopez-Gonzalez

    2014-01-01

    Full Text Available Background: Symptomatic arachnoiditis after posterior fossa surgical procedures such as decompression of Chiari malformation is a possible complication. Clinical presentation is generally insidious and delayed by months or years. It causes disturbances in the normal flow of cerebrospinal fluid and enlargement of a syrinx cavity in the upper spinal cord. Surgical de-tethering has favorable results with progressive collapse of the syrinx and relief of the associated symptoms. Case Description: A 30-year-old male with Chiari malformation type I was treated by performing posterior fossa bone decompression, dura opening and closure with a suturable bovine pericardium dural graft. Postoperative period was uneventful until the fifth day in which the patient suffered intense headache and progressive loose of consciousness caused by an acute posterior fossa epidural hematoma. It was quickly removed with complete clinical recovering. One year later, the patient experienced progressive worsened of his symptoms. Upper spinal cord tethering was diagnosed and a new surgery for debridement was required. Conclusions: The epidural hematoma compressing the dural graft against the neural structures contributes to the upper spinal cord tethering and represents a nondescribed cause of postoperative fibrosis, adhesion formation, and subsequent recurrent hindbrain compression.

  11. Shuttle-tethered satellite system definition study. Volume 1: Executive study

    Science.gov (United States)

    1979-01-01

    The Tethered Satellite System has great prospects for extending orbital operations capability of the Space Transportation System to science, applications, and technology projects not otherwise attainable. The system will installed in the Shuttle Orbiter and will have the capability to deploy a captive satellite up to 100 km away from the Orbiter. Control and retrieval of the satellite are accomplished by means of a tether line connecting the satellite and the cargo bay mounted equipment in the Orbiter. At low satellite altitudes, the system will permit investigations of a duration that could not be pursued with sounding rockets of free-flying spacecraft. The propose of the Shuttle/Tethered Satellite System Definition Study was to produce the preliminary design, preliminary specifications, gross program plans, and program cost estimate for a 1982 operational verification flight. This was accomplished during a fifteen month effort under by the NASA George C. Marshall Space Flight Center (MSFC). The MSFC Phase 1 and related studies demonstrated the feasibility of the system and served as a starting point for the Phase 2 definition study.

  12. A Structure-Based Mechanism for Vesicle Capture by the Multisubunit Tethering Complex Dsl1

    Energy Technology Data Exchange (ETDEWEB)

    Ren, Y.; Yip, C; Tripathi, A; Huie, D; Jeffrey, P; Walz, T; Hughson, F

    2009-01-01

    Vesicle trafficking requires membrane fusion, mediated by SNARE proteins, and upstream events that probably include tethering, an initial long-range attachment between a vesicle and its target organelle. Among the factors proposed to mediate tethering are a set of multisubunit tethering complexes (MTCs). The Dsl1 complex, with only three subunits, is the simplest known MTC and is essential for the retrograde traffic of COPI-coated vesicles from the Golgi to the ER. To elucidate structural principles underlying MTC function, we have determined the structure of the Dsl1 complex, revealing a tower containing at its base the binding sites for two ER SNAREs and at its tip a flexible lasso for capturing vesicles. The Dsl1 complex binds to individual SNAREs via their N-terminal regulatory domains and also to assembled SNARE complexes; moreover, it is capable of accelerating SNARE complex assembly. Our results suggest that even the simplest MTC may be capable of orchestrating vesicle capture, uncoating, and fusion.

  13. TI tether rig for solving secular spinrate change problem of electric sail

    CERN Document Server

    Janhunen, Pekka

    2016-01-01

    The electric solar wind sail (E-sail) is a way to propel a spacecraft by using the natural solar wind as a thrust source. The problem of secular spinrate change was identified earlier which is due to the orbital Coriolis effect and tends to slowly increase or decrease the sail's spinrate, depending on which way the sail is inclined with respect to the solar wind. Here we present an E-sail design and its associated control algorithm which enable spinrate control during propulsive flight by the E-sail effect itself. In the design, every other maintether ("T-tether") is galvanically connected through the remote unit with the two adjacent auxtethers, while the other maintethers ("I-tethers") are insulated from the tethers. This enables one to effectively control the maintether and auxtether voltages separately, which in turn enables spinrate control. We use a detailed numerical simulation to show that the algorithm can fully control the E-sail's spin state in real solar wind. The simulation includes a simple and ...

  14. System Dynamics and Feedforward Control for Tether-Net Space Robot System

    Directory of Open Access Journals (Sweden)

    Bin Liang

    2009-11-01

    Full Text Available A new concept using flexible tether-net system to capture space debris is presented in this paper. With a mass point assumption the tether-net system dynamic model is established in orbital frame by applying Lagrange Equations. In order to investigate the net in-plane trajectories during after cast, the non-control R-bar and V-bar captures are simulated with ignoring the out-of-plane libration, the effect of in-plane libration on the trajectories of the capture net is demonstrated by simulation results. With an effort to damp the in-plane libration, the control scheme based on tether tension is investigated firstly, after that an integrated control scheme is proposed by introduced the thrusters into the system, the nonlinear close-loop dynamics is linearised by feedforward strategy, the simulation results show that feedforward controllor is effective for in-plane libration damping and enable the capture net to track an expected trajectory.

  15. Out-of-Plane Translational PZT Bimorph Actuator with Archimedes’ Spiral Actuating Tethers

    Science.gov (United States)

    Yang, Chenye; Liu, Sanwei; Livermore, Carol

    2015-12-01

    The design, finite element analysis (FEA), and experimental characterization of a MEMS out-of-plane (vertical) translational lead-zirconate-titanate (PZT) bimorph actuator supported on Archimedes’ spiral tethers are presented. Two types of bimorph actuators with different electrode patterns (with spiral tethers half actuated or fully actuated) are designed and fabricated. Both designs are fabricated by commercial processes and are compatible with integration into more complex MEMS systems. Finite element analysis (FEA) was used to analyze and predict the displacements of both types of actuators. The deflections of both fully- actuated and half-actuated devices were measured experimentally to validate the design. At an applied voltage of 110V, the out-of-plane deflections of the actuators with half-actuated and fully-actuated tethers were measured at about 17 μm and 29 μm respectively, in good agreement with FEA predictions of 17.1 μm and 25.8 μm. The corresponding blocking forces are predicted as 10 mN and 17 mN by FEA.

  16. αB-Crystallin Interacts with Nav1.5 and Regulates Ubiquitination and Internalization of Cell Surface Nav1.5.

    Science.gov (United States)

    Huang, Yuan; Wang, Zhijie; Liu, Yinan; Xiong, Hongbo; Zhao, Yuanyuan; Wu, Ling; Yuan, Chao; Wang, Longfei; Hou, Yuxi; Yu, Gang; Huang, Zhengrong; Xu, Chengqi; Chen, Qiuyun; Wang, Qing K

    2016-05-20

    Nav1.5, the pore-forming α subunit of the cardiac voltage-gated Na(+) channel complex, is required for the initiation and propagation of the cardiac action potential. Mutations in Nav1.5 cause cardiac arrhythmias and sudden death. The cardiac Na(+) channel functions as a protein complex; however, its complete components remain to be fully elucidated. A yeast two-hybrid screen identified a new candidate Nav1.5-interacting protein, αB-crystallin. GST pull-down, co-immunoprecipitation, and immunostaining analyses validated the interaction between Nav1.5 and αB-crystallin. Whole-cell patch clamping showed that overexpression of αB-crystallin significantly increased peak sodium current (INa) density, and the underlying molecular mechanism is the increased cell surface expression level of Nav1.5 via reduced internalization of cell surface Nav1.5 and ubiquitination of Nav1.5. Knock-out of αB-crystallin expression significantly decreased the cell surface expression level of Nav1.5. Co-immunoprecipitation analysis showed that αB-crystallin interacted with Nedd4-2; however, a catalytically inactive Nedd4-2-C801S mutant impaired the interaction and abolished the up-regulation of INa by αB-crystallin. Nav1.5 mutation V1980A at the interaction site for Nedd4-2 eliminated the effect of αB-crystallin on reduction of Nav1.5 ubiquitination and increases of INa density. Two disease-causing mutations in αB-crystallin, R109H and R151X (nonsense mutation), eliminated the effect of αB-crystallin on INa This study identifies αB-crystallin as a new binding partner for Nav1.5. αB-Crystallin interacts with Nav1.5 and increases INa by modulating the expression level and internalization of cell surface Nav1.5 and ubiquitination of Nav1.5, which requires the protein-protein interactions between αB-crystallin and Nav1.5 and between αB-crystallin and functionally active Nedd4-2. PMID:26961874

  17. Cell surface glycan alterations in epithelial mesenchymal transition process of Huh7 hepatocellular carcinoma cell.

    Directory of Open Access Journals (Sweden)

    Shan Li

    Full Text Available BACKGROUND AND OBJECTIVE: Due to recurrence and metastasis, the mortality of Hepatocellular carcinoma (HCC is high. It is well known that the epithelial mesenchymal transition (EMT and glycan of cell surface glycoproteins play pivotal roles in tumor metastasis. The goal of this study was to identify HCC metastasis related differential glycan pattern and their enzymatic basis using a HGF induced EMT model. METHODOLOGY: HGF was used to induce HCC EMT model. Lectin microarray was used to detect the expression of cell surface glycan and the difference was validated by lectin blot and fluorescence cell lectin-immunochemistry. The mRNA expression levels of glycotransferases were determined by qRT-PCR. RESULTS: After HGF treatment, the Huh7 cell lost epithelial characteristics and obtained mesenchymal markers. These changes demonstrated that HGF could induce a typical cell model of EMT. Lectin microarray analysis identified a decreased affinity in seven lectins ACL, BPL, JAC, MPL, PHA-E, SNA, and SBA to the glycan of cell surface glycoproteins. This implied that glycan containing T/Tn-antigen, NA2 and bisecting GlcNAc, Siaα2-6Gal/GalNAc, terminal α or βGalNAc structures were reduced. The binding ability of thirteen lectins, AAL, LCA, LTL, ConA, NML, NPL, DBA, HAL, PTL II, WFL, ECL, GSL II and PHA-L to glycan were elevated, and a definite indication that glycan containing terminal αFuc and ± Sia-Le, core fucose, α-man, gal-β(α GalNAc, β1,6 GlcNAc branching and tetraantennary complex oligosaccharides structures were increased. These results were further validated by lectin blot and fluorescence cell lectin-immunochemistry. Furthermore, the mRNA expression level of Mgat3 decreased while that of Mgat5, FucT8 and β3GalT5 increased. Therefore, cell surface glycan alterations in the EMT process may coincide with the expression of glycosyltransferase. CONCLUSIONS: The findings of this study systematically clarify the alterations of cell surface

  18. Cellular Selenoprotein mRNA Tethering via Antisense Interactions with Ebola and HIV-1 mRNAs May Impact Host Selenium Biochemistry.

    Science.gov (United States)

    Taylor, Ethan Will; Ruzicka, Jan A; Premadasa, Lakmini; Zhao, Lijun

    2016-01-01

    Regulation of protein expression by non-coding RNAs typically involves effects on mRNA degradation and/or ribosomal translation. The possibility of virus-host mRNA-mRNA antisense tethering interactions (ATI) as a gain-of-function strategy, via the capture of functional RNA motifs, has not been hitherto considered. We present evidence that ATIs may be exploited by certain RNA viruses in order to tether the mRNAs of host selenoproteins, potentially exploiting the proximity of a captured host selenocysteine insertion sequence (SECIS) element to enable the expression of virally-encoded selenoprotein modules, via translation of in-frame UGA stop codons as selenocysteine. Computational analysis predicts thermodynamically stable ATIs between several widely expressed mammalian selenoprotein mRNAs (e.g., isoforms of thioredoxin reductase) and specific Ebola virus mRNAs, and HIV-1 mRNA, which we demonstrate via DNA gel shift assays. The probable functional significance of these ATIs is further supported by the observation that, in both viruses, they are located in close proximity to highly conserved in-frame UGA stop codons at the 3' end of open reading frames that encode essential viral proteins (the HIV-1 nef protein and the Ebola nucleoprotein). Significantly, in HIV/AIDS patients, an inverse correlation between serum selenium and mortality has been repeatedly documented, and clinical benefits of selenium in the context of multi-micronutrient supplementation have been demonstrated in several well-controlled clinical trials. Hence, in the light of our findings, the possibility of a similar role for selenium in Ebola pathogenesis and treatment merits serious investigation. PMID:26369818

  19. Cellular Selenoprotein mRNA Tethering via Antisense Interactions with Ebola and HIV-1 mRNAs May Impact Host Selenium Biochemistry

    Science.gov (United States)

    Taylor, Ethan Will; Ruzicka, Jan A.; Premadasa, Lakmini; Zhao, Lijun

    2016-01-01

    Regulation of protein expression by non-coding RNAs typically involves effects on mRNA degradation and/or ribosomal translation. The possibility of virus-host mRNA-mRNA antisense tethering interactions (ATI) as a gain-of-function strategy, via the capture of functional RNA motifs, has not been hitherto considered. We present evidence that ATIs may be exploited by certain RNA viruses in order to tether the mRNAs of host selenoproteins, potentially exploiting the proximity of a captured host selenocysteine insertion sequence (SECIS) element to enable the expression of virally-encoded selenoprotein modules, via translation of in-frame UGA stop codons as selenocysteine. Computational analysis predicts thermodynamically stable ATIs between several widely expressed mammalian selenoprotein mRNAs (e.g., isoforms of thioredoxin reductase) and specific Ebola virus mRNAs, and HIV-1 mRNA, which we demonstrate via DNA gel shift assays. The probable functional significance of these ATIs is further supported by the observation that, in both viruses, they are located in close proximity to highly conserved in-frame UGA stop codons at the 3′ end of open reading frames that encode essential viral proteins (the HIV-1 nef protein and the Ebola nucleoprotein). Significantly, in HIV/AIDS patients, an inverse correlation between serum selenium and mortality has been repeatedly documented, and clinical benefits of selenium in the context of multi-micronutrient supplementation have been demonstrated in several well-controlled clinical trials. Hence, in the light of our findings, the possibility of a similar role for selenium in Ebola pathogenesis and treatment merits serious investigation. PMID:26369818

  20. Experimental and numerical studies of tethered DNA dynamics in shear flow

    Science.gov (United States)

    Lueth, Christopher A.

    Polymer physics has a rich tradition spanning nearly two centuries. In the 1830s, Henri Braconnot and coworkers were perhaps the first to work on what is today known as polymer science when they derived semi-synthetic materials from naturally occurring cellulose. However, the true nature of polymers, as long chain molecules, had not been proposed until 1910 by Pickles. It was not until the 1950's when polymer models were developed using statistical mechanics. Recently, the field has been revitalized by the ability to study individual polymer molecules for the first time. The development of DNA single molecule fluorescence microscopy coupled with ever increasing computational power has opened the door to molecular level understanding of polymer physics, resolving old disputes and uncovering new interesting phenomena. In this work, we use a combination of theoretical predictions and lambda-phage DNA single molecule fluorescence microscopy to study the behavior of polymers tethered to surfaces. Brownian dynamics simulations of a number of coarse-grained polymer models---dynamic and equilibrium Kratky-Porod chains as well as bead-spring chains---were completed and compared with analytical and experimental results. First, an expression is developed for the entropic exclusion force experienced by a tethered polymer chain. We propose that, for a freely jointed chain, a modification to the free entropic force of kBT/y is needed in the direction normal to the surface. Analogously, we propose that for a wormlike chain, a modification of 2kBT/y is needed, due to the finite curvature of the model. Then, the reliability of discretized bead spring simulations containing this modified entropic force are analyzed using Kratky-Porod simulations and are found to reproduce most statistics, except for those very near the surface, such as end-wall contact. Next, experiments of tethered lambda-phage DNA in shear flow are presented for the first time in the flow-gradient plane. The

  1. An Automated System for Measuring Microphysical and Radiative Cloud Characteristics from a Tethered Balloon

    Energy Technology Data Exchange (ETDEWEB)

    Dr. Paul Lawson

    2004-03-15

    OAK-B135 The rate of climate change in polar regions is now felt to be a harbinger of possible global warming. Long-lived, relatively thin stratus clouds play a predominant role in transmitting solar radiation and trapping long wave radiation emitted from open water and melt ponds. In situ measurements of microphysical and radiative properties of Arctic and Antarctic stratus clouds are needed to validate retrievals from remote measurements and simulations using numerical models. While research aircraft can collect comprehensive microphysical and radiative data in clouds, the duration of these aircraft is relatively short (up to about 12 hours). During the course of the Phase II research, a tethered balloon system was developed that supports miniaturized meteorological, microphysical and radiation sensors that can collect data in stratus clouds for days at a time. The tethered balloon system uses a 43 cubic meter balloon to loft a 17 kg sensor package to altitudes u p to 2 km. Power is supplied to the instrument package via two copper conductors in the custom tether. Meteorological, microphysical and radiation data are recorded by the sensor package. Meteorological measurements include pressure, temperature, humidity, wind speed and wind direction. Radiation measurements are made using a 4-pi radiometer that measures actinic flux at 500 and 800 nm. Position is recorded using a GPS receiver. Microphysical data are obtained using a miniaturized version of an airborne cloud particle imager (CPI). The miniaturized CPI measures the size distribution of water drops and ice crystals from 9 microns to 1.4 mm. Data are recorded onboard the sensor package and also telemetered via a 802.11b wireless communications link. Command signals can also be sent to the computer in the sensor package via the wireless link. In the event of a broken tether, a GMRS radio link to the balloon package is used to heat a wire that burns 15 cm opening in the top of the balloon. The balloon and

  2. Discovery of dual-action membrane-anchored modulators of incretin receptors.

    Directory of Open Access Journals (Sweden)

    Jean-Philippe Fortin

    Full Text Available BACKGROUND: The glucose-dependent insulinotropic polypeptide (GIP and the glucagon-like peptide-1 (GLP-1 receptors are considered complementary therapeutic targets for type 2 diabetes. Using recombinant membrane-tethered ligand (MTL technology, the present study focused on defining optimized modulators of these receptors, as well as exploring how local anchoring influences soluble peptide function. METHODOLOGY/PRINCIPAL FINDINGS: Serial substitution of residue 7 in membrane-tethered GIP (tGIP led to a wide range of activities at the GIP receptor, with [G(7]tGIP showing enhanced efficacy compared to the wild type construct. In contrast, introduction of G(7 into the related ligands, tGLP-1 and tethered exendin-4 (tEXE4, did not affect signaling at the cognate GLP-1 receptor. Both soluble and tethered GIP and GLP-1 were selective activators of their respective receptors. Although soluble EXE4 is highly selective for the GLP-1 receptor, unexpectedly, tethered EXE4 was found to be a potent activator of both the GLP-1 and GIP receptors. Diverging from the pharmacological properties of soluble and tethered GIP, the newly identified GIP-R agonists, (i.e. [G(7]tGIP and tEXE4 failed to trigger cognate receptor endocytosis. In an attempt to recapitulate the dual agonism observed with tEXE4, we conjugated soluble EXE4 to a lipid moiety. Not only did this soluble peptide activate both the GLP-1 and GIP receptors but, when added to receptor expressing cells, the activity persists despite serial washes. CONCLUSIONS: These findings suggest that conversion of a recombinant MTL to a soluble membrane anchored equivalent offers a means to prolong ligand function, as well as to design agonists that can simultaneously act on more than one therapeutic target.

  3. Hole transfer dynamics from QDs to tethered ferrocene derivatives

    Science.gov (United States)

    Alivisatos, A. Paul

    Quantum dots (QDs) have shown particular promise in recent years as light absorbers in solar energy conversion schemes. However, in solution junction solar devices such as QD-sensitized solar cells and photocatalytic water splitting systems, efficiencies are often limited by hole transfer from the photoexcited QD. This process is sluggish and can lead to oxidative photocorrosion of the QD material. In order to design highly efficient nanocrystal systems with hole transfer rates that outcompete these undesirable processes, a fundamental understanding of the parameters that control these rates is imperative.We have developed a model system to study charge transfer from QDs to surface bound acceptors, to fundamentally understand the charge transfer processes for QD systems, namely electronic coupling between the donor and acceptor and the thermodynamic driving force for the hole transfer process. Specifically, we examine hole transfer from the nearly spherical CdSe-core CdS-shell QDs with photoluminescence (PL) quantum yields over 80% to ferrocene derivatives bound to the QD surface via an alkane thiol linker. In this system, we mitigate the ill-defined nonradiative charge dynamic pathways that are intrinsic to native CdSe cores, and then controllably engineer on the surface charge acceptors with well-defined oxidation potentials, spatial distribution, and quantity. By Measuring the PL lifetime decay and calibrating the number of hole acceptor ligands per QD via quantitative `H NMR, we extracted the hole transfer rate per acceptor. This rate per acceptor could be varied over four orders of magnitude by changing the coupling between donor and acceptor through modulations in the CdS shell thickness and alkane chain length of the molecule. Furthermore, owning to the large number of acceptors on the surface, we achieve systems in which ~99% of the photoexcited holes are transferred to these well-defined mediators.We further mapped the relationship between the

  4. Efficient display of active lipase LipB52 with a Pichia pastoris cell surface display system and comparison with the LipB52 displayed on Saccharomyces cerevisiae cell surface

    OpenAIRE

    Ma Yushu; Tao Xingyi; Ren Ren; Gao Bei; Jiang Zhengbing; Wei Dongzhi

    2008-01-01

    Abstract Background For industrial bioconversion processes, the utilization of surface-displayed lipase in the form of whole-cell biocatalysts is more advantageous, because the enzymes are displayed on the cell surface spontaneously, regarded as immobilized enzymes. Results Two Pichia pastoris cell surface display vectors based on the flocculation functional domain of FLO with its own secretion signal sequence or the α-factor secretion signal sequence were constructed respectively. The lipase...

  5. Association of cell surface heparan sulfate proteoglycans of Schwann cells with extracellular matrix proteins.

    Science.gov (United States)

    Carey, D J; Crumbling, D M; Stahl, R C; Evans, D M

    1990-11-25

    The terminal differentiation of Schwann cells is dependent on contact with basement membrane. The present study was undertaken to investigate the role of cell surface heparan sulfate proteoglycans (HSPGs) in mediating Schwann cell responses to extracellular matrix contact. Phosphatidylinositol-specific phospholipase C-releasable cell surface HSPGs purified from cultures of neonatal rat Schwann cells were subjected to affinity chromatography on immobilized laminin and fibronectin. Binding of the HSPG to both affinity matrices was observed. The strength of the association, however, was sensitive to the ionic strength of the buffer. In 0.1 M Tris-HCl, HSPG binding was essentially irreversible whereas in physiological ionic strength buffer (e.g. 0.142 M NaCl, 10 mM Tris), weaker binding was detected as a delay in elution of the HSPG from the affinity columns. Further studies of HSPG-laminin binding suggested that the binding was mediated by the glycosaminoglycan chains of the proteoglycans. Results of equilibrium gel filtration chromatography provided additional evidence for a reversible association of the HSPG and laminin with a Kd of approximately 1 x 10(-6) M. When Schwann cells were plated on plastic dishes coated with laminin, the cells attached and extended long slender processes. Inclusion of heparin, but not chondroitin sulfate, in the assay medium resulted in partial inhibition of process extension, but at concentrations of heparin which were higher than that needed to disrupt laminin-HSPG association in vitro. Addition of anti-integrin receptor antibodies resulted in more extensive inhibition of laminin-dependent process extension. Anti-integrin antibodies plus heparin essentially totally inhibited laminin-dependent process extension. These results demonstrate that cell surface HSPGs are capable of reversible association with extracellular matrix molecules and suggest that HSPG-laminin interactions play a role in laminin-dependent Schwann cell spreading. PMID

  6. Identification of cell surface targets for HIV-1 therapeutics using genetic screens

    International Nuclear Information System (INIS)

    Human immunodeficiency virus (HIV) drugs designed to interfere with obligatory utilization of certain host cell factors by virus are less likely to encounter development of resistant strains than drugs directed against viral components. Several cellular genes required for productive infection by HIV were identified by the use of genetic suppressor element (GSE) technology as potential targets for anti-HIV drug development. Fragmented cDNA libraries from various pools of human peripheral blood mononuclear cells (PBMC) were expressed in vitro in human immunodeficiency virus type 1 (HIV-1)-susceptible cell lines and subjected to genetic screens to identify GSEs that interfered with viral replication. After three rounds of selection, more than 15 000 GSEs were sequenced, and the cognate genes were identified. The GSEs that inhibited the virus were derived from a diverse set of genes including cell surface receptors, cytokines, signaling proteins, transcription factors, as well as genes with unknown function. Approximately 2.5% of the identified genes were previously shown to play a role in the HIV-1 life cycle; this finding supports the biological relevance of the assay. GSEs were derived from the following 12 cell surface proteins: CXCR4, CCR4, CCR7, CD11C, CD44, CD47, CD68, CD69, CD74, CSF3R, GABBR1, and TNFR2. Requirement of some of these genes for viral infection was also investigated by using RNA interference (RNAi) technology; accordingly, 10 genes were implicated in early events of the viral life cycle, before viral DNA synthesis. Thus, these cell surface proteins represent novel targets for the development of therapeutics against HIV-1 infection and AIDS

  7. High Cell Surface Death Receptor Expression Determines Type I Versus Type II Signaling*

    Science.gov (United States)

    Meng, Xue Wei; Peterson, Kevin L.; Dai, Haiming; Schneider, Paula; Lee, Sun-Hee; Zhang, Jin-San; Koenig, Alexander; Bronk, Steve; Billadeau, Daniel D.; Gores, Gregory J.; Kaufmann, Scott H.

    2011-01-01

    Previous studies have suggested that there are two signaling pathways leading from ligation of the Fas receptor to induction of apoptosis. Type I signaling involves Fas ligand-induced recruitment of large amounts of FADD (FAS-associated death domain protein) and procaspase 8, leading to direct activation of caspase 3, whereas type II signaling involves Bid-mediated mitochondrial perturbation to amplify a more modest death receptor-initiated signal. The biochemical basis for this dichotomy has previously been unclear. Here we show that type I cells have a longer half-life for Fas message and express higher amounts of cell surface Fas, explaining the increased recruitment of FADD and subsequent signaling. Moreover, we demonstrate that cells with type II Fas signaling (Jurkat or HCT-15) can signal through a type I pathway upon forced receptor overexpression and that shRNA-mediated Fas down-regulation converts cells with type I signaling (A498) to type II signaling. Importantly, the same cells can exhibit type I signaling for Fas and type II signaling for TRAIL (TNF-α-related apoptosis-inducing ligand), indicating that the choice of signaling pathway is related to the specific receptor, not some other cellular feature. Additional experiments revealed that up-regulation of cell surface death receptor 5 levels by treatment with 7-ethyl-10-hydroxy-camptothecin converted TRAIL signaling in HCT116 cells from type II to type I. Collectively, these results suggest that the type I/type II dichotomy reflects differences in cell surface death receptor expression. PMID:21865165

  8. Streptococcus salivarius strains carry either fibrils or fimbriae on the cell surface.

    Science.gov (United States)

    Handley, P S; Carter, P L; Fielding, J

    1984-01-01

    Strains of Streptococcus salivarius were screened by negative staining for the presence of surface structures. Two structural subgroups were found, carrying either fibrils or fimbriae, projecting from the cell surface. Eight strains carried a very dense peritrichous array of fibrils of two distinct lengths. Long fibrils had an average length of 175 nm, and short fibrils had an average length of 95 nm. Two strains carried only long fibrils, one strain carried only short fibrils, and another strain carried a lateral tuft of very prominent fibrils of two lengths, with a fibrillar fuzz covering the remainder of the cell surface. In all the strains in which they were present, the long fibrils were unaffected by protease or trypsin treatment. In contrast, the short fibrils were completely digested by protease and partially removed by trypsin. Neither long nor short fibrils were affected structurally by mild pepsin digestion or by lipase. The Lancefield extraction procedure removed both long and short fibrils. These twelve fibrillar strains were therefore divisible into four structural subgroups. Extracts of all the fibrillar strains reacted with group K antiserum. The second main structural subgroup consisted of nine strains of S. salivarius, all of which carried morphologically identical, flexible fimbriae arranged peritrichously over the cell surface. The fimbriae were structurally distinct from fibrils and measured 0.5 to 1.0 micron long and 3 to 4 nm wide, with an irregular outline and no obvious substructure. There was no obvious reduction in the number of fimbriae after protease or trypsin treatment. Extracts of the fimbriated strains did not react with the group K antiserum. The two serological and structural subgroups could also be distinguished by colony morphology. Images PMID:6197404

  9. Aged mice have increased inflammatory monocyte concentration and altered expression of cell-surface functional receptors

    Indian Academy of Sciences (India)

    Kelley Strohacker; Whitney L Breslin; Katie C Carpenter; Brian K McFarlin

    2012-03-01

    The expression of monocyte cell-surface receptors represents one index of immune dysfunction, which is common with aging. Although mouse models of aging are prevalent, monocyte subset assessment is rare. Our purpose was to compare cell receptor expression on classic (CD115+/Gr-1high) and non-classic (CD115+/Gr-1low) monocytes from 80- or 20-week-old CD-1 mice. Three-colour flow cytometry was used to determine the concentration of monocyte subsets and their respective cell-surface expression of TLR2, TLR4, CD80, CD86, MHC II and CD54. These receptors were selected because they have been previously associated with altered monocyte function. Data were analysed with independent -tests; significance was set at < 0.05. Old mice had a greater concentration of both classic (258%, =0.003) and non-classic (70%, =0.026) monocytes. The classic : non-classic monocyte ratio doubled in old as compared with that in young mice (=0.006), indicating a pro-inflammatory shift. TLR4 ($\\downarrow$27%, =0.001) and CD80 ($\\downarrow$37%, =0.004) were decreased on classic monocytes from old as compared with those from young mice. TLR2 ($\\uparrow$24%, =0.002) and MHCII ($\\downarrow$21%, =0.026) were altered on non-classic monocytes from old as compared with those from young mice. The increased classic : non-classic monocyte ratio combined with changes in the cell-surface receptor expression on both monocyte subsets is indicative of immune dysfunction, which may increase age-associated disease risk.

  10. Enterovirus 71 Uses Cell Surface Heparan Sulfate Glycosaminoglycan as an Attachment Receptor

    Science.gov (United States)

    Tan, Chee Wah; Poh, Chit Laa; Sam, I-Ching

    2013-01-01

    Enterovirus 71 (EV-71) infections are usually associated with mild hand, foot, and mouth disease in young children but have been reported to cause severe neurological complications with high mortality rates. To date, four EV-71 receptors have been identified, but inhibition of these receptors by antagonists did not completely abolish EV-71 infection, implying that there is an as yet undiscovered receptor(s). Since EV-71 has a wide range of tissue tropisms, we hypothesize that EV-71 infections may be facilitated by using receptors that are widely expressed in all cell types, such as heparan sulfate. In this study, heparin, polysulfated dextran sulfate, and suramin were found to significantly prevent EV-71 infection. Heparin inhibited infection by all the EV-71 strains tested, including those with a single-passage history. Neutralization of the cell surface anionic charge by polycationic poly-d-lysine and blockage of heparan sulfate by an anti-heparan sulfate peptide also inhibited EV-71 infection. Interference with heparan sulfate biosynthesis either by sodium chlorate treatment or through transient knockdown of N-deacetylase/N-sulfotransferase-1 and exostosin-1 expression reduced EV-71 infection in RD cells. Enzymatic removal of cell surface heparan sulfate by heparinase I/II/III inhibited EV-71 infection. Furthermore, the level of EV-71 attachment to CHO cell lines that are variably deficient in cell surface glycosaminoglycans was significantly lower than that to wild-type CHO cells. Direct binding of EV-71 particles to heparin-Sepharose columns under physiological salt conditions was demonstrated. We conclude that EV-71 infection requires initial binding to heparan sulfate as an attachment receptor. PMID:23097443

  11. Cell surface glycopeptides from human intestinal epithelial cell lines derived from normal colon and colon adenocarcinomas

    International Nuclear Information System (INIS)

    The cell surface glycopeptides from an epithelial cell line (CCL 239) derived from normal human colon were compared with those from three cell lines (HCT-8R, HCT-15, and CaCo-2) derived independently from human colonic adenocarcinomas. Cells were incubated with D-[2-3H]mannose or L-[5,6-3H]fucose for 24 h and treated with trypsin to release cell surface components which were then digested exhaustively with Pronase and fractionated on Bio-Gel P-6 before and after treatment with endo-beta-N-acetylglucosaminidase H. The most noticeable difference between the labeled glycopeptides from the tumor and CCL 239 cells was the presence in the former of an endo-beta-N-acetylglucosaminidase H-resistant high molecular weight glycopeptide fraction which was eluted in the void volume of Bio-Gel P-6. This fraction was obtained with both labeled mannose and fucose as precursors. However, acid hydrolysis of this fraction obtained after incubation with [2-3H]mannose revealed that as much as 60-90% of the radioactivity was recovered as fucose. Analysis of the total glycopeptides (cell surface and cell pellet) obtained after incubation with [2-3H]mannose showed that from 40-45% of the radioactivity in the tumor cells and less than 10% of the radioactivity in the CCL 239 cells was recovered as fucose. After incubation of the HCT-8R cells with D-[1,6-3H]glucosamine and L-[1-14C]fucose, strong acid hydrolysis of the labeled glycopeptide fraction excluded from Bio-Gel P-6 produced 3H-labeled N-acetylglucosamine and N-acetylgalactosamine

  12. Short-chain ceramides depress integrin cell surface expression and function in colorectal cancer cells.

    Science.gov (United States)

    Morad, Samy A F; Bridges, Lance C; Almeida Larrea, Alex D; Mayen, Anthony L; MacDougall, Matthew R; Davis, Traci S; Kester, Mark; Cabot, Myles C

    2016-07-01

    Colorectal cancer (CRC) is highly metastatic, significantly so to liver, a characteristic that embodies one of the most challenging aspects of treatment. The integrin family of cell-cell and cell-matrix adhesion receptors plays a central role in migration and invasion, functions that underlie metastatic potential. In the present work we sought to determine the impact of ceramide, which plays a key modulatory role in cancer suppression, on integrin cell surface expression and function in CRC cells in order to reveal possible ceramide-centric effects on tumor cell motility. Human CRC cells LoVo, HT-29, and HCT-116 were employed, which represent lines established from primary and metastatic sites. A cell-permeable, short-chain analog, C6-ceramide, was used as ceramide mimic. Exposure of cells to C6-ceramide (24 h) promoted a dose-dependent (2.5-10 µM) decrease in the expression of cell surface β1 and β4 integrin subunits in all cell lines; at 10 µM C6-ceramide, the decreases ranged from 30 to 50% of the control. Expression of cell surface αVβ6 integrin, which is associated with advanced invasion in CRC, was also suppressed by C6-ceramide. Decreases in integrin expression translated to diminished cellular adhesion, 50% of the control at 5 µM C6-ceramide, and markedly reduced cellular migration, approximately 30-40% of the control in all cell lines. Physicochemical examination revealed potent efficacy of nano-formulated C6-ceramide, but inferior activity of dihydro-C6-ceramide and L-C6-ceramide, compared to the unsaturated counterpart and the natural d-enantiomer, respectively. These studies demonstrate novel actions of ceramides that may have application in suppression of tumor metastasis, in addition to their known tumor suppressor effects. PMID:27045476

  13. Effects of DNP on the cell surface properties of marine bacteria and its implication for adhesion to surfaces

    Digital Repository Service at National Institute of Oceanography (India)

    Jain, A.; Nishad, K.K.; Bhosle, N.B.

    The effect of 2, 4-dinitrophenol (DNP) on extracelluar polysaccharides (EPS), cell surface charge, and hydrophobicity of six marine bacterial cultures was studied, and its influence on attachment of these bacteria to glass and polystyrene...

  14. Cell surface alteration in Epstein-Barr virus-transformed cells from patients with extreme insulin resistance

    International Nuclear Information System (INIS)

    An abnormality was detected in the morphology of the cell surface of Epstein-Barr virus-transformed lymphocytes of patients with genetic forms of insulin resistance. In cells from two patients with leprechaunism and two patients with type A extreme insulin resistance, scanning electron microscopy demonstrated a decrease in the percentage of the cell surface occupied by microvilli in cells from the patients with leprechaunism and type A insulin resistance compared with control cells. When cells from a healthy control subject and one of the patients with leprechaunism (Lep/Ark-1) were incubated with 125I-labeled insulin, there was a decrease in the percentage of 125I-insulin associated with microvilli on the cell surface. Thus, the decreased localization of insulin receptors with the microvillous region of the cell surface was in proportion to the decrease in microvilli

  15. Cell surface alteration in Epstein-Barr virus-transformed cells from patients with extreme insulin resistance

    Energy Technology Data Exchange (ETDEWEB)

    Gorden, D.L.; Robert, A.; Moncada, V.Y.; Taylor, S.I.; Muehlhauser, J.C.; Carpentier, J.L. (Univ. of Geneva School of Medicine (Switzerland))

    1990-08-01

    An abnormality was detected in the morphology of the cell surface of Epstein-Barr virus-transformed lymphocytes of patients with genetic forms of insulin resistance. In cells from two patients with leprechaunism and two patients with type A extreme insulin resistance, scanning electron microscopy demonstrated a decrease in the percentage of the cell surface occupied by microvilli in cells from the patients with leprechaunism and type A insulin resistance compared with control cells. When cells from a healthy control subject and one of the patients with leprechaunism (Lep/Ark-1) were incubated with {sup 125}I-labeled insulin, there was a decrease in the percentage of {sup 125}I-insulin associated with microvilli on the cell surface. Thus, the decreased localization of insulin receptors with the microvillous region of the cell surface was in proportion to the decrease in microvilli.

  16. Roles for glycosylation of cell surface receptors involved in cellular immune recognition.

    Science.gov (United States)

    Rudd, P M; Wormald, M R; Stanfield, R L; Huang, M; Mattsson, N; Speir, J A; DiGennaro, J A; Fetrow, J S; Dwek, R A; Wilson, I A

    1999-10-22

    The majority of cell surface receptors involved in antigen recognition by T cells and in the orchestration of the subsequent cell signalling events are glycoproteins. The length of a typical N-linked sugar is comparable with that of an immunoglobulin domain (30 A). Thus, by virtue of their size alone, oligosaccharides may be expected to play a significant role in the functions and properties of the cell surface proteins to which they are attached. A databank of oligosaccharide structures has been constructed from NMR and crystallographic data to aid in the interpretation of crystal structures of glycoproteins. As unambiguous electron density can usually only be assigned to the glycan cores, the remainder of the sugar is then modelled into the crystal lattice by superimposing the appropriate oligosaccharide from the database. This approach provides insights into the roles that glycosylation might play in cell surface receptors, by providing models that delineate potential close packing interactions on the cell surface. It has been proposed that the specific recognition of antigen by T cells results in the formation of an immunological synapse between the T cell and the antigen-presenting cell. The cell adhesion glycoproteins, such as CD2 and CD48, help to form a cell junction, providing a molecular spacer between opposing cells. The oligosaccharides located on the membrane proximal domains of CD2 and CD48 provide a scaffold to orient the binding faces, which leads to increased affinity. In the next step, recruitment of the peptide major histocompatibility complex (pMHC) by the T-cell receptors (TCRs) requires mobility on the membrane surface. The TCR sugars are located such that they could prevent non-specific aggregation. Importantly, the sugars limit the possible geometry and spacing of TCR/MHC clusters which precede cell signalling. We postulate that, in the final stage, the sugars could play a general role in controlling the assembly and stabilisation of the

  17. STUDY ON GLYCOCONJUGATE CHANGES ON CELL SURFACE IN PROGRESSIVE DEVELOPMENT OF PULMONARY TUMOR

    Institute of Scientific and Technical Information of China (English)

    WANG Xiao-mei; SHAN Jun; CHEN Zhuo-huai

    2002-01-01

    Aim: To investigate glycoconjugate changes on the cell surface of proliferative lesions and neoplasms of mice lungs at various stages of tumorigenesis, the relation between progressive development of mouse pulmonary tumors and expression of cell surface saccharide. Materials and methods: Thirty - one male A/J strain mice at 5 weeks of age were treated intraperitoneally with a single injection of 20 - methylcholanthrene (20 - MC), 292 pulmonary lesions including 31 hyperplasias, 145 alveolar adenomas, 61 papillary adenomas, 55 papillary adenocarcinomas and their combined type were obtained. The binding affinities of cells in normal respiratory epithelia and in proliferative lesions to four peroxidases - conjugated lectins, Maclura pomifera agglutinin (MPA), Arachis hypogea agglutinin (PNA), Ricinus communis agglutinin (RCA), and wheat germ agglutinin (WGA) were examined. Results: Cells of hyperplasia and alveolar adenoma showed fairly strong affinity to all the four lectins. However, part of papillary adenoma cells and greater part of papillary adenocarcinoma cells lost their binding affinity to MPA, PNA, and RCA, but not to WGA. The bindings of MPA, PNA and RNA were detected predominently on the luminal surfaces of benign tumors but not on the luminal surfaces of malignant tumors. WGA might bind to varied types of benign and malignant tumors. Pretreated with neuraminidase, the lesions enhanced the staining intensity for the four lectins, the binding sites of WGA to malignant tumor cells were numerous. A distinct difference in lectin binding affinity between hyperplasia / alveolar adenoma/papillary adenoma and papillary adenocarcinoma was clearly shown( x2 = 46.89, P < 0.01, x2 = 36.77, P < 0.01 and x2 = 52.87, P < 0.01 ) in this experiment. The complex glycoconjugates on the cell surface of malignant and benign lesions during the development of pulmonary tumor were changed,malignant tumor cells differed from the surface of benign tumor cells, the levels of

  18. Pigment Epithelium-derived Factor (PEDF) Binds to Cell-surface F1-ATP Synthase

    OpenAIRE

    NOTARI, LUIGI; Arakaki, Naokatu; Mueller, David; Meier, Scott; Amaral, Juan; Becerra, S. Patricia

    2010-01-01

    Pigment epithelium-derived factor (PEDF), a potent blocker of angiogenesis in vivo, and of endothelial cell migration and tubule formation, binds with high affinity to a yet unknown protein on the surface of endothelial cells. Given that protein fingerprinting suggested a match of a ~60-kDa PEDF-binding protein in bovine retina to Bos taurus F1-ATP synthase β-subunit, and that F1F0-ATP synthase components have been identified recently as cell-surface receptors, we examined the direct binding ...

  19. Keynote Paper: Cell-Surface Adhesive Interactions in Microchannels and Microvessels

    CERN Document Server

    King, M R

    2003-01-01

    Adhesive interactions between white blood cells and the interior surface of the blood vessels they contact is important in inflammation and in the progression of heart disease. Parallel-plate microchannels have been useful in characterizing the strength of these interactions, in conditions that are much simplified over the complex environment these cells experience in the body. Recent computational and experimental work by several laboratories have attempted to bridge this gap between behavior observed in flow chamber experiments, and cell-surface interactions observed in the microvessels of anesthetized animals.

  20. M135R Is a Novel Cell Surface Virulence Factor of Myxoma Virus▿

    OpenAIRE

    Barrett, John W.; Sypula, Joanna; Wang, Fuan; Alston, Lindsay R.; Shao, Zhuhong; Gao, Xiujuan; Irvine, Timothy S.; McFadden, Grant

    2006-01-01

    Myxoma virus (MV) encodes a cell surface protein (M135R) that is predicted to mimic the host alpha/beta interferon receptor (IFN-α/β-R) and thus prevent IFN-α/β from triggering a host antiviral response. This prediction is based on sequence similarity to B18R, the viral IFN-α/β-R from vaccinia virus (VV), which has been demonstrated to bind and inhibit type I interferons. However, M135R is only half the size of VV B18R. All other poxvirus-encoded IFN-α/β-R homologs align only to the amino-ter...

  1. Role of a cell surface-associated protein in adherence and dental caries.

    OpenAIRE

    Bowen, W. H.; Schilling, K.; Giertsen, E; Pearson, S.; Lee, S. F.; Bleiweis, A; Beeman, D

    1991-01-01

    Insertional inactivation of the Streptococcus mutans spaP gene was used to construct an isogenic mutant (834) of strain NG8 (serotype c) which lacked the major cell surface-associated protein referred to as P1 (15). Results of several studies suggest that P1 is involved in the adherence of S. mutans to saliva-coated apatite surfaces. With an in vitro model system of hydroxyapatite (HA) beads coated with parotid saliva (PS) and additional HA surfaces coated with PS and in situ-formed glucan, i...

  2. Microassay for measurement of binding of radiolabelled ligands to cell surface molecules.

    Science.gov (United States)

    Woof, J M; Burton, D R

    1988-07-22

    An improved technique for measuring the binding of radiolabelled ligands to cell surface molecules has been developed by modification of a procedure using centrifugation through a water-immiscible oil to separate free and cell-bound ligand. It maximises the percentage of ligand bound since cell-bound and free ligand can be separated easily and reproducibly even when very small reaction volumes are used. This permits low levels of ligand radiolabelling and relatively low numbers of cells to be used. PMID:2840465

  3. Tritium (3H) radiolabeling of protein A and antibody to high specific activity: Application to cell surface antigen radioimmunoassays

    International Nuclear Information System (INIS)

    Staphylococcal protein A and several different immunoglobulins have been radiolabeled to high specific activities (> 106 cpm/μg) by reductive methylation with tritiated (3H) sodium borohydride. The proteins retain excellent functional and antigenic properties. The utility of these reagents in a variety of assays for cell surface antigens is illustrated. The results indicate that this radiolabeling procedure may become the method of choice for many cell surface and solution immunoassays. (Auth.)

  4. Long-term dynamic modeling of tethered spacecraft using nodal position finite element method and symplectic integration

    Science.gov (United States)

    Li, G. Q.; Zhu, Z. H.

    2015-12-01

    Dynamic modeling of tethered spacecraft with the consideration of elasticity of tether is prone to the numerical instability and error accumulation over long-term numerical integration. This paper addresses the challenges by proposing a globally stable numerical approach with the nodal position finite element method (NPFEM) and the implicit, symplectic, 2-stage and 4th order Gaussian-Legendre Runge-Kutta time integration. The NPFEM eliminates the numerical error accumulation by using the position instead of displacement of tether as the state variable, while the symplectic integration enforces the energy and momentum conservation of the discretized finite element model to ensure the global stability of numerical solution. The effectiveness and robustness of the proposed approach is assessed by an elastic pendulum problem, whose dynamic response resembles that of tethered spacecraft, in comparison with the commonly used time integrators such as the classical 4th order Runge-Kutta schemes and other families of non-symplectic Runge-Kutta schemes. Numerical results show that the proposed approach is accurate and the energy of the corresponding numerical model is conservative over the long-term numerical integration. Finally, the proposed approach is applied to the dynamic modeling of deorbiting process of tethered spacecraft over a long period.

  5. Effect of the finite size of an asteroid on its deflection using a tether-ballast system

    Science.gov (United States)

    Mashayekhi, Mohammad J.; Misra, Arun K.

    2016-07-01

    Potentially hazardous near-Earth objects which can impose a significant threat on life on the planet have generated a lot of interest in the study of various asteroid deflection strategies. There are numerous asteroid deflection techniques suggested and discussed in the literature. This paper is focused on one of the non-destructive asteroid deflection strategies by attaching a long tether-ballast system to the asteroid. In the existing literature on this technique, very simplified models of the asteroid-tether-ballast system including a point mass model of the asteroid have been used. In this paper, the dynamical effect of using a finite size asteroid model on the asteroid deflection achieved is analyzed in detail. It has been shown that considering the finite size of the asteroid, instead of the point mass approximation, can have significant influence on the deflection predicted. Furthermore the effect of the tether-deployment stage, which is an essential part of any realistic asteroid deflection mission, on the predicted deflection is studied in this paper. Finally the effect of cutting the tether on the deflection achieved is analyzed and it has been shown that depending on the orbital properties of the asteroid as well as its size and rotational rate, cutting the tether at an appropriate time can increase the deflection achieved. Several numerical examples have been used in this paper to elaborate on the proposed technique and to quantitatively analyze the effect of different parameters on the asteroid deflection.

  6. Effect of the finite size of an asteroid on its deflection using a tether-ballast system

    Science.gov (United States)

    Mashayekhi, Mohammad J.; Misra, Arun K.

    2016-04-01

    Potentially hazardous near-Earth objects which can impose a significant threat on life on the planet have generated a lot of interest in the study of various asteroid deflection strategies. There are numerous asteroid deflection techniques suggested and discussed in the literature. This paper is focused on one of the non-destructive asteroid deflection strategies by attaching a long tether-ballast system to the asteroid. In the existing literature on this technique, very simplified models of the asteroid-tether-ballast system including a point mass model of the asteroid have been used. In this paper, the dynamical effect of using a finite size asteroid model on the asteroid deflection achieved is analyzed in detail. It has been shown that considering the finite size of the asteroid, instead of the point mass approximation, can have significant influence on the deflection predicted. Furthermore the effect of the tether-deployment stage, which is an essential part of any realistic asteroid deflection mission, on the predicted deflection is studied in this paper. Finally the effect of cutting the tether on the deflection achieved is analyzed and it has been shown that depending on the orbital properties of the asteroid as well as its size and rotational rate, cutting the tether at an appropriate time can increase the deflection achieved. Several numerical examples have been used in this paper to elaborate on the proposed technique and to quantitatively analyze the effect of different parameters on the asteroid deflection.

  7. Abelian modules

    OpenAIRE

    S. Halıcıoğlu; Harmanci, A.; GÜNGÖROĞLU, G.; N. Agayev

    2009-01-01

    In this note, we introduce abelian modules as a generalization of abelian rings. Let R be an arbitrary ring with identity. A module M is called abelian if, for any m Î M and any a Î R, any idempotent e Î R, mae=mea. We prove that every reduced module, every symmetric module, every semicommutative module and every Armendariz module is abelian. For an abelian ring R, we show that the module MR is abelian iff M[x]R[x] is abelian. We produce an example to show that M[x, α] need not be abe...

  8. Biodegradation and surfactant-mediated biodegradation of diesel fuel by 218 microbial consortia are not correlated to cell surface hydrophobicity

    Energy Technology Data Exchange (ETDEWEB)

    Owsianiak, Mikolaj; Szulc, Alicja; Chrzanowski, Lukasz; Bogacki, Mariusz [Poznan Univ. of Technology (Poland). Inst. of Chemical Technology and Engineering; Cyplik, Pawel; Olejnik-Schmidt, Agniezka K. [Poznan Univ. of Life Sciences (Poland). Dept. of Biotechnology and Food Microbiology; Heipieper, Hermann J. [Helmholtz Centre for Environmental Research - UFZ, Leipzig (Germany). Dept. of Environmental Biotechnology

    2009-09-15

    In this study, we elucidated the role of cell surface hydrophobicity (microbial adhesion to hydrocarbons method, MATH) and the effect of anionic rhamnolipids and nonionic Triton X-100 surfactants on biodegradation of diesel fuel employing 218 microbial consortia isolated from petroleum-contaminated soils. Applied enrichment procedure with floating diesel fuel as a sole carbon source in liquid cultures resulted in consortia of varying biodegradation potential and diametrically different cell surface properties, suggesting that cell surface hydrophobicity is a conserved parameter. Surprisingly, no correlations between cell surface hydrophobicity and biodegradation of diesel fuel were found. Nevertheless, both surfactants altered cell surface hydrophobicity of the consortia in similar manner: increased for the hydrophilic and decreased for the hydrophobic cultures. In addition to this, the surfactants exhibited similar influence on diesel fuel biodegradation: Increase was observed for initially slow-degrading cultures and the opposite for fast degraders. This indicates that in the surfactant-mediated biodegradation, effectiveness of surfactants depends on the specification of microorganisms and not on the type of surfactant. In contrary to what was previously reported for pure strains, cell surface hydrophobicity, as determined by MATH, is not a good descriptor of biodegrading potential for mixed cultures. (orig.)

  9. Elevated temperature treatment as a novel method for decreasing p57 on the cell surface of Renibacterium salmoninarum.

    Science.gov (United States)

    Piganelli, J D; Wiens, G D; Kaattari, S L

    1999-04-15

    Renibacterium salmoninarum is a Gram-positive diplo-bacillus and the causative agent of bacterial kidney disease, a prevalent disease of salmonid fish. Virulent isolates of R. salmoninarum have a hydrophobic cell surface and express the 57-58 kDa protein (p57). Here we have investigated parameters which effect cell hydrophobicity and p57 degradation. Incubation of R. salmoninarum cells at 37 degrees C for > 4 h decreased cell surface hydrophobicity as measured by the salt aggregation assay, and decreased the amount of cell associated p57. Incubation of cells at lower temperatures (22, 17, 4 or -20 degrees C) for up to 16 h did not reduce hydrophobicity or the amount of cell associated p57. Both the loss of cell surface hydrophobicity and the degradation of p57 were inhibited by pre-incubation with the serine protease inhibitor phenylmethylsulfonyl fluoride (PMSF). Cell surface hydrophobicity was specifically reconstituted by incubation with extracellular protein (ECP) concentrated from culture supernatant and was correlated with the reassociation of p57 onto the bacterial cell surface as determined by western blot and total protein stain analyses. The ability of p57 to reassociate suggests that the bacterial cell surface is not irreversibly modified by the 37 degrees C treatment and that p57 contributes to the hydrophobic nature of R. salmoninarum. In summary, we describe parameters effecting the removal of the p57 virulence factor and suggest the utility of this modification for generating a whole cell vaccine against bacterial kidney disease. PMID:10349550

  10. Outcome of hospital discharge on postoperative Day 1 following uncomplicated tethered spinal cord release.

    Science.gov (United States)

    Poonia, Seerat; Graber, Sarah; Corbett Wilkinson, C; O'neill, Brent R; Handler, Michael H; Hankinson, Todd C

    2016-06-01

    OBJECTIVE Postoperative management following the release of simple spinal cord-tethering lesions is highly variable. As a quality improvement initiative, the authors aimed to determine whether an institutional protocol of discharging patients on postoperative day (POD) 1 was associated with a higher rate of postoperative CSF leaks than the prior protocol of discharge on POD 2. METHODS This was a single-center retrospective review of all children who underwent release of a spinal cord-tethering lesion that was not associated with a substantial fascial or dural defect (i.e., simple spinal cord detethering) during 2 epochs: prior to and following the institution of a protocol for discharge on POD 1. Outcomes included the need for and timing of nonroutine care of the surgical site, including return to the operating room, wound suturing, and nonsurgical evaluation and management. RESULTS Of 169 patients identified, none presented with CSF-related complications prior to discharge. In the preintervention group (n = 113), the postoperative CSF leak rate was 4.4% (5/113). The mean length of stay was 2.3 days. In the postintervention group, the postoperative CSF leak rate was 1.9% (1/53) in the patients with postdischarge follow-up. The mean length of stay in that group was 1.3 days. CONCLUSIONS At a single academic children's hospital, a protocol of discharging patients on POD 1 following uncomplicated release of a simple spinal cord-tethering lesion was not associated with an increased rate of postoperative CSF leaks, relative to the previous protocol. The rates identified are consistent with the existing literature. The authors' practice has changed to discharge on POD 1 in most cases. PMID:26849810

  11. Tethered Balloon Operations at ARM AMF3 Site at Oliktok Point, AK

    Science.gov (United States)

    Dexheimer, D.; Lucero, D. A.; Helsel, F.; Hardesty, J.; Ivey, M.

    2015-12-01

    Oliktok Point has been the home of the Atmospheric Radiation Measurement Program's (ARM) third ARM Mobile Facility, or AMF3, since October 2013. The AMF3 is operated through Sandia National Laboratories and hosts instrumentation collecting continuous measurements of clouds, aerosols, precipitation, energy, and other meteorological variables. The Arctic region is warming more quickly than any other region due to climate change and Arctic sea ice is declining to record lows. Sparsity of atmospheric data from the Arctic leads to uncertainty in process comprehension, and atmospheric general circulation models (AGCM) are understood to underestimate low cloud presence in the Arctic. Increased vertical resolution of meteorological properties and cloud measurements will improve process understanding and help AGCMs better characterize Arctic clouds. SNL is developing a tethered balloon system capable of regular operation at AMF3 in order to provide increased vertical resolution atmospheric data. The tethered balloon can be operated within clouds at altitudes up to 7,000' AGL within DOE's R-2204 restricted area. Pressure, relative humidity, temperature, wind speed, and wind direction are recorded at multiple altitudes along the tether. These data were validated against stationary met tower data in Albuquerque, NM. The altitudes of the sensors were determined by GPS and calculated using a line counter and clinometer and compared. Wireless wetness sensors and supercooled liquid water content sensors have also been deployed and their data has been compared with other sensors. This presentation will provide an overview of the balloons, sensors, and test flights flown, and will provide a preliminary look at data from sensor validation campaigns and test flights.

  12. Numerical modeling of a spar platform tethered by a mooring cable

    Science.gov (United States)

    Zhu, Xiangqian; Yoo, Wan-Suk

    2015-07-01

    Virtual simulation is an economical and efficient method in mechanical system design. Numerical modeling of a spar platform, tethered by a mooring cable with a spherical joint is developed for the dynamic simulation of the floating structure in ocean. The geometry modeling of the spar is created using finite element methods. The submerged part of the spar bears the buoyancy, hydrodynamic drag force, and effect of the added mass and Froude-Krylov force. Strip theory is used to sum up the forces acting on the elements. The geometry modeling of the cable is established based on the lumped-mass-and-spring modeling through which the cable is divided into 10 elements. A new element-fixed local frame is used, which is created by the element orientation vector and relative velocity of the fluid, to express the loads acting on the cable. The bottom of the cable is fixed on the seabed by spring forces, while the top of the cable is connected to the bottom of the spar platform by a modified spherical joint. This system suffers the propagating wave and current in the X-direction and the linear wave theory is applied for setting of the propagating wave. Based on the numerical modeling, the displacement-load relationships are analyzed, and the simulation results of the numerical modeling are compared with those by the commercial simulation code, ProteusDS. The comparison indicates that the numerical modeling of the spar platform tethered by a mooring cable is well developed, which provides an instruction for the optimization of a floating structure tethered by a mooring cable system.

  13. Role of Double-Strand Break End-Tethering during Gene Conversion in Saccharomyces cerevisiae.

    Directory of Open Access Journals (Sweden)

    Suvi Jain

    2016-04-01

    Full Text Available Correct repair of DNA double-strand breaks (DSBs is critical for maintaining genome stability. Whereas gene conversion (GC-mediated repair is mostly error-free, repair by break-induced replication (BIR is associated with non-reciprocal translocations and loss of heterozygosity. We have previously shown that a Recombination Execution Checkpoint (REC mediates this competition by preventing the BIR pathway from acting on DSBs that can be repaired by GC. Here, we asked if the REC can also determine whether the ends that are engaged in a GC-compatible configuration belong to the same break, since repair involving ends from different breaks will produce potentially deleterious translocations. We report that the kinetics of repair are markedly delayed when the two DSB ends that participate in GC belong to different DSBs (termed Trans compared to the case when both DSB ends come from the same break (Cis. However, repair in Trans still occurs by GC rather than BIR, and the overall efficiency of repair is comparable. Hence, the REC is not sensitive to the "origin" of the DSB ends. When the homologous ends for GC are in Trans, the delay in repair appears to reflect their tethering to sequences on the other side of the DSB that themselves recombine with other genomic locations with which they share sequence homology. These data support previous observations that the two ends of a DSB are usually tethered to each other and that this tethering facilitates both ends encountering the same donor sequence. We also found that the presence of homeologous/repetitive sequences in the vicinity of a DSB can distract the DSB end from finding its bona fide homologous donor, and that inhibition of GC by such homeologous sequences is markedly increased upon deleting Sgs1 but not Msh6.

  14. Feasibility Study of Space Based Solar Power to Tethered Aerostat Systems

    Science.gov (United States)

    Blank, Stephen J.; Leete, Stephen J.; Jaffe, Paul

    2013-01-01

    The feasibility of two-stage Space-Based Solar Power to Tethered Aerostat to Earth (SSP-TA) system architectures that offer significant advantages over conventional single stage space-to-earth architectures is being studied. There have been many proposals for the transmission of solar power collected in space to the surface of the earth so that solar energy could provide a major part of the electric power requirements on earth. There are, however, serious difficulties in implementing the single stage space-based solar power systems that have been previously studied. These difficulties arise due to: i) the cost of transporting the components needed for the extremely large microwave transmit beaming aperture into space orbit, ii) the even larger collection apertures required on earth, iii) the potential radiation hazard to personnel and equipment on earth, and iv) a lack of flexibility in location of the collection station on the earth. Two candidate system architectures are described here to overcome these difficulties. In both cases a two-stage space to tethered aerostat to earth transmission system (SSP-TA) is proposed. The use of high altitude tethered aerostats (or powered airships) avoids the effects of attenuation of EM energy propagating through the earth s lower atmosphere. This allows the use of beaming frequencies to be chosen from the range of high millimeter (THz) to near-infra-red (NIR) to the visible. This has the potential for: i) greatly reduced transportation costs to space, ii) much smaller receiver collection apertures and ground stations, iii) elimination of the potential radiation hazard to personnel and equipment on earth, and iv) ease in transportation and flexibility in location of the collection station on the earth. A preliminary comparison of system performance and efficiencies is presented.

  15. Direct observations of tether-cutting reconnection during a major solar event in AR 11990

    Science.gov (United States)

    Chen, Huadong

    2015-08-01

    Using multi-wavelength data from the Atmospheric Imaging Assembly on board the Solar Dynamics Observatory, we investigated two successive solar flares, a C5.1 confined flare and an X4.9 ejective flare with a halo coronal mass ejection, in NOAA active region 11990 from 2014 February 24 to 25. Before the confined flare onset, EUV brightening beneath the filament was detected. As the flare began, a twisted helical flux rope (FR) wrapping around the filament moved upward and then stopped, and in the meantime an obvious X-ray source below it was observed. Prior to the ejective X4.9 flare, some pre-existing loop structures in the active region interacted with each other, which produced a brightening region beneath the filament. Meanwhile, a small flaring loop appeared below the interaction region and some new helical lines connecting the far ends of the loop structures were gradually formed and continually added into the former twisted FR. Then, due to the resulting imbalance between the magnetic pressure and tension, the new FR, together with the filament, erupted outward. Our observations coincide well with a tether-cutting model, suggesting that the two flares probably have the same triggering mechanism, i.e., tether- cutting reconnection. To our knowledge, this is the first direct observation of tether-cutting reconnection occurring between pre-existing loops in an active region. In the ejective flare case, the erupting filament exhibited an Ω-like kinked structure and underwent an exponential rise after a slow-rise phase, indicating that the kink instability might be also responsible for the eruption initiation.

  16. Tethered capsule OCT endomicroscopy: from bench to bedside at the primary care office (Conference Presentation)

    Science.gov (United States)

    Gora, Michalina J.; Simmons, Leigh H.; Tiernan, Aubrey R.; Grant, Catriona N.; Soomro, Amna R.; Walker Corkery, Elizabeth S.; Rosenberg, Mireille; Metlay, Joshua P.; Tearney, Guillermo J.

    2016-03-01

    We have developed a swallowable tethered capsule OCT endomicroscopy (TCE) device that acquires microscopic images of the entire esophagus in unsedated subjects in a quick and comfortable procedure. To test its capabilities of TCE to become a population-based screening device, we conducted a clinical feasibility study in the primary care office. The swept-source OCT imaging system (1310nm central wavelength, 40kHz A-line rate, 10um axial resolution) together with the tethered capsule catheter (11x25mm capsule attached to a flexible tether) were transferred to the PCP office where unsedated patients scheduled for non-urgent PCP visits swallowed the capsule and microscopic OCT images of the entire esophagus were collected. After the whole length of the esophagus was imaged, the catheter was disinfected for reuse. Twenty subjects were enrolled in the study, including nine female and eleven male. All TCE procedures were performed by a nurse and lasted in average 5:42 ± 1:54 min. High-resolution images of the esophagus were obtained in all seventeen subjects that swallowed the capsule. Our clinical experience in this cohort, subject feedback, image quality, and technological adaptations for efficient utilization in this setting will be presented. The ease and simplicity of the procedure combined with high quality of the images demonstrate the potential for this technology to become a population-based screening device. Technology limitations and future development guided by findings from this initial experience will be discussed with the goal of effectively translating TCE to the outpatient primary care setting.

  17. Cell surface expression and turnover of the alpha-subunit of the epithelial sodium channel.

    Science.gov (United States)

    Kleyman, T R; Zuckerman, J B; Middleton, P; McNulty, K A; Hu, B; Su, X; An, B; Eaton, D C; Smith, P R

    2001-08-01

    The renal epithelial cell line A6, derived from Xenopus laevis, expresses epithelial Na(+) channels (ENaCs) and serves as a model system to study hormonal regulation and turnover of ENaCs. Our previous studies suggest that the alpha-subunit of Xenopus ENaC (alpha-xENaC) is detectable as 150- and 180-kDa polypeptides, putative immature and mature alpha-subunit heterodimers. The 150- and 180-kDa alpha-xENaC were present in distinct fractions after sedimentation of A6 cell lysate through a sucrose density gradient. Two anti-alpha-xENaC antibodies directed against distinct domains demonstrated that only 180-kDa alpha-xENaC was expressed at the apical cell surface. The half-life of cell surface-expressed alpha-xENaC was 24-30 h, suggesting that once ENaC matures and is expressed at the plasma membrane, its turnover is similar to that reported for mature cystic fibrosis transmembrane conductance regulator. No significant changes in apical surface expression of alpha-xENaC were observed after treatment of A6 cells with aldosterone for 24 h, despite a 5.3-fold increase in short-circuit current. This lack of change in surface expression is consistent with previous observations in A6 cells and suggests that aldosterone regulates ENaC gating and increases channel open probability. PMID:11457713

  18. Developmental expression of a cell surface protein involved in sea urchin skeleton formation

    International Nuclear Information System (INIS)

    The authors have previously used a monoclonal antibody (1223) to identify a 130 Kd cell surface protein involved in skeleton formation is sea urchin embryos. In the current study the authors have examined the expression of the 1223 antigen over the course of development of embryos of two species, Strongylocentrotus purpuratus and Lytechinus pictus. The 130 Kd protein is detected in S. purp eggs on immunoblots. Labeling with [3H] leucine and immunoaffinity chromatography show that it also is synthesized shortly after fertilization. Immunofluroescence reveals that at this early stage the 1223 antigen is uniformly distributed on all of the cells. Synthesis decreases to a minimum by the time of hatching (18 h), as does the total amount of antigen present in the embryo. A second period of synthesis commences at the mesenchyme blastula stage, when the spicule-forming primary mesenchyme cells (PMCs) have appeared. During this later stage, synthesis and cell surface expression are restricted to the PMCs. In contrast to S. purp., in L. pictus the 130 Kd protein does not appear until the PMCs are formed. Hybrid embryos demonstrate a pattern of expression of the maternal species. These results suggest that early expression of 1223 antigen in S. purp. is due to utilization of maternal transcripts present in the egg. In both species later expression in PMCs appears to be the result of cell-type specific synthesis, perhaps encoded by embryonic transcripts

  19. Identification of Cell Surface Targets through Meta-analysis of Microarray Data

    Directory of Open Access Journals (Sweden)

    Henry Haeberle

    2012-07-01

    Full Text Available High-resolution image guidance for resection of residual tumor cells would enable more precise and complete excision for more effective treatment of cancers, such as medulloblastoma, the most common pediatric brain cancer. Numerous studies have shown that brain tumor patient outcomes correlate with the precision of resection. To enable guided resection with molecular specificity and cellular resolution, molecular probes that effectively delineate brain tumor boundaries are essential. Therefore, we developed a bioinformatics approach to analyze micro-array datasets for the identification of transcripts that encode candidate cell surface biomarkers that are highly enriched in medulloblastoma. The results identified 380 genes with greater than a two-fold increase in the expression in the medulloblastoma compared with that in the normal cerebellum. To enrich for targets with accessibility for extracellular molecular probes, we further refined this list by filtering it with gene ontology to identify genes with protein localization on, or within, the plasma membrane. To validate this meta-analysis, the top 10 candidates were evaluated with immunohistochemistry. We identified two targets, fibrillin 2 and EphA3, which specifically stain medulloblastoma. These results demonstrate a novel bioinformatics approach that successfully identified cell surface and extracellular candidate markers enriched in medulloblastoma versus adjacent cerebellum. These two proteins are high-value targets for the development of tumor-specific probes in medulloblastoma. This bioinformatics method has broad utility for the identification of accessible molecular targets in a variety of cancers and will enable probe development for guided resection.

  20. Cell surface heparan sulfate proteoglycans contribute to intracellular lipid accumulation in adipocytes

    Directory of Open Access Journals (Sweden)

    Orlando Robert A

    2005-01-01

    Full Text Available Abstract Background Transport of fatty acids within the cytosol of adipocytes and their subsequent assimilation into lipid droplets has been thoroughly investigated; however, the mechanism by which fatty acids are transported across the plasma membrane from the extracellular environment remains unclear. Since triacylglycerol-rich lipoproteins represent an abundant source of fatty acids for adipocyte utilization, we have investigated the expression levels of cell surface lipoprotein receptors and their functional contributions toward intracellular lipid accumulation; these include very low density lipoprotein receptor (VLDL-R, low density lipoprotein receptor-related protein (LRP, and heparan sulfate proteoglycans (HSPG. Results We found that expression of these three lipoprotein receptors increased 5-fold, 2-fold, and 2.5-fold, respectively, during adipocyte differentiation. The major proteoglycans expressed by mature adipocytes are of high molecular weight (>500 kD and contain both heparan and chondroitin sulfate moieties. Using ligand binding antagonists, we observed that HSPG, rather than VLDL-R or LRP, play a primary role in the uptake of DiI-lableled apoE-VLDL by mature adipocytes. In addition, inhibitors of HSPG maturation resulted in a significant reduction (>85% in intracellular lipid accumulation. Conclusions These results suggest that cell surface HSPG is required for fatty acid transport across the plasma membrane of adipocytes.

  1. Protein Kinase C Regulates the Cell Surface Activity of Endothelin-Converting Enzyme-1.

    Science.gov (United States)

    Smith, A Ian; Lew, Rebecca A; Thomas, Walter G; Tochon-Danguy, Nathalie

    2006-09-01

    The potent vasoconstrictor endothelin is a 21 amino acid peptide whose principal physiological function is to regulate vascular tone. The generation of endothelin is crucially dependent on the local presence and activity of endothelin converting enzyme-1 (ECE-1) expressed on the surface of vascular endothelial cells. In this study, we have shown in endothelial cells that the enzyme is phosphorylated, and that phosphorylation is increased by phorbol ester stimulation of protein kinase C (PKC). Furthermore, by monitoring specific ECE-1 activity on the surface of live cells, we also show that following PKC activation, enzyme activity is significantly increased at the cell surface, where it is positioned to catalyse the generation of active endothelin. We believe this novel finding is unprecedented for a peptide processing enzyme. Indeed, this new knowledge regarding the control of endothelin production by regulating ECE-1 activity at the cell surface opens up a new area of endothelin biology and will provide novel insights into the physiology and pathophysiology of endothelin and endothelin-associated diseases. In addition, the information generated in these studies may provide valuable new insights into potential extra- and intracellular targets for the pharmacological and perhaps even therapeutic regulation of endothelin production and thus vascular tone. PMID:19617920

  2. A secreted form of the human lymphocyte cell surface molecule CD8 arises from alternative splicing

    International Nuclear Information System (INIS)

    The human lymphocyte differentiation antigen CD8 is encoded by a single gene that gives rise to a 33- to 34-kDa glycoprotein expressed on the cell surface as a dimer and in higher molecular mass forms. The authors demonstrate that the mRNA is alternatively spliced so that an exon encoding a transmembrane domain is deleted. This gives rise to a 30-kDa molecule that is secreted and exists primarily as a monomer. mRNA corresponding to both forms is present in peripheral blood lymphocytes, Con A-activated peripheral blood lymphocytes, and three CD8+ T-cell lines, with the membrane form being the major species. However, differences in the ratio of mRNA for membrane CD8 and secreted CD8 exist. In addition, the splicing pattern observed differs from the pattern found for the mouse CD8 gene. This mRNA is also alternatively spliced, but an exon encoding a cytoplasmic region is deleted, giving rise to a cell surface molecule that differs in its cytoplasmic tail from the protein encoded by the longer mRNA. Neither protein is secreted. This is one of the first examples of a different splicing pattern between two homologous mouse and human genes giving rise to very different proteins. This represents one mechanism of generating diversity during speciation

  3. SNX15 Regulates Cell Surface Recycling of APP and Aβ Generation.

    Science.gov (United States)

    Feng, Tuancheng; Niu, Mengmeng; Ji, Chengxiang; Gao, Yuehong; Wen, Jing; Bu, Guojun; Xu, Huaxi; Zhang, Yun-Wu

    2016-08-01

    Amyloid-β (Aβ) peptide plays an essential role in the pathogenesis of Alzheimer's disease (AD) and is generated from amyloid-β precursor protein (APP) through sequential proteolytic cleavages by β-site APP cleaving enzyme 1 (BACE1) and γ-secretase. Trafficking dysregulation of APP, BACE1, and γ-secretase may affect Aβ generation and disease pathogenesis. Sorting nexin 15 (SNX15) is known to regulate protein trafficking. Here, we report that SNX15 is abundantly expressed in mouse neurons and astrocytes. In addition, we show that although not affecting the protein levels of APP, BACE1, and γ-secretase components and the activity of BACE1 and γ-secretase, overexpression and downregulation of SNX15 reduce and promote Aβ production, respectively. Furthermore, we find that overexpression of SNX15 increases APP protein levels in cell surface through accelerating APP recycling, whereas downregulation of SNX15 has an opposite effect. Finally, we show that exogenous expression of human SNX15 in the hippocampal dentate gyrus by adeno-associated virus (AAV) infection can significantly reduce Aβ pathology in the hippocampus and improve short-term working memory in the APPswe/PSEN1dE9 double transgenic AD model mice. Together, our results suggest that SNX15 regulates the recycling of APP to cell surface and, thus, its processing for Aβ generation. PMID:26115702

  4. Disulfide bond-mediated dimerization of HLA-G on the cell surface.

    Science.gov (United States)

    Boyson, Jonathan E; Erskine, Robert; Whitman, Mary C; Chiu, Michael; Lau, Julie M; Koopman, Louise A; Valter, Markus M; Angelisova, Pavla; Horejsi, Vaclav; Strominger, Jack L

    2002-12-10

    HLA-G is a nonclassical class I MHC molecule with an unknown function and with unusual characteristics that distinguish it from other class I MHC molecules. Here, we demonstrate that HLA-G forms disulfide-linked dimers that are present on the cell surface. Immunoprecipitation of HLA-G from surface biotinylated transfectants using the anti-beta2-microglobulin mAb BBM.1 revealed the presence of an approximately equal 78-kDa form of HLA-G heavy chain that was reduced by using DTT to a 39-kDa form. Mutation of Cys-42 to a serine completely abrogated dimerization of HLA-G, suggesting that the disulfide linkage formed exclusively through this residue. A possible interaction between the HLA-G monomer or dimer and the KIR2DL4 receptor was also investigated, but no interaction between these molecules could be detected through several approaches. The cell-surface expression of dimerized HLA-G molecules may have implications for HLA-Greceptor interactions and for the search for specific receptors that bind HLA-G. PMID:12454284

  5. Phospholipase D specific for the phosphatidylinositol anchor of cell-surface proteins is abundant in plasma

    International Nuclear Information System (INIS)

    An enzyme activity capable of degrading the glycosyl-phosphatidylinositol membrane anchor of cell-surface proteins has previously been reported in a number of mammalian tissues. The experiments reported here demonstrate that this anchor-degrading activity is also abundant in mammalian plasma. The activity was inhibited by EGTA or 1,10-phenanthroline. It was capable of removing the anchor from alkaline phosphatase, 5'-nucleotidase, and variant surface glycoprotein but had little or no activity toward phosphatidylinositol or phosphatidylcholine. Phosphatidic acid was the only 3H-labeled product when this enzyme hydrolyzed [3H]myristate-labeled variant surface glycoprotein. It could be distinguished from the Ca2=-dependent inositol phospholipid-specific phospholipase C activity in several rat tissues on the basis of its molecular size and its sensitivity to 1,10-phenanthroline. The data therefore suggest that this activity is due to a phospholipase D with specificity for glycosylphosphatidylinositol structures. Although the precise physiological function of this anchor-specific phospholipase D remains to be determined, these findings indicate that it could play an important role in regulating the expression and release of cell-surface proteins in vivo

  6. Cell surface appearance of unexpected host MHC determinants on thymocytes from radiation bone marrow chimeras

    International Nuclear Information System (INIS)

    The phenotypic appearance of cell surface antigens on murine thymocytes from long-term radiation bone marrow chimeras was analyzed using indirect immunofluorescence and flow microfluorometry. Cells maturing in the thymi of these mice were typed for MHC (Kk, I-Ak, H-2b, Kb, and Ib) and non-MHC (Lty 1, Ly 9, and TL) determinants. All cells were of donor origin as determined by non-MHC (Ly) phenotype in P1 leads to P2, P1 x P2 leads to P1, and P1 leads to P2 radiation chimeras. In contrast, the MHC phenotypes of these thymocytes were markedly affected by the host environment. Specifically, H-2 and I-A determinants of both parental phenotypes were detected on thymocytes from P1 leads to P1 x P2 chimeras; I-A determinants of host phenotype were present, whereas I-A determinants of donor phenotype were reduced on thymocytes from P1 x P2 leads to P1 chimeras; and thymocytes from P1 leads to P2 chimeras possessed H-2 and I-A determinants of host phenotype but showed reduction of donor I-A phenotype determinants. The appearance of host cell surface H-2 and I-A determinants on thymocytes from chimeras closely parallels the functional recognition of MHC determinants by T cells from chimeric mice and thus may be significantly related to the development of the self-recognition repertoire by maturing T cells

  7. Formation of nanofilms on cell surfaces to improve the insertion efficiency of a nanoneedle into cells

    Energy Technology Data Exchange (ETDEWEB)

    Amemiya, Yosuke [Biomedical Research Institute, National Institute of Advanced Industrial Science and Technology (AIST), Central 4, 1-1-1 Higashi, Tsukuba, Ibaraki 305-8562 (Japan); Kawano, Keiko [Department of Biotechnology and Life Science, Tokyo University of Agriculture and Technology, 2-24-26 Naka-cho, Koganei, Tokyo 184-8588 (Japan); Matsusaki, Michiya; Akashi, Mitsuru [Department of Applied Chemistry, Graduate School of Engineering Science, Osaka University, 2-1 Yamada-oka, Suita, Osaka 565-0871 (Japan); Nakamura, Noriyuki [Department of Biotechnology and Life Science, Tokyo University of Agriculture and Technology, 2-24-26 Naka-cho, Koganei, Tokyo 184-8588 (Japan); Nakamura, Chikashi, E-mail: chikashi-nakamura@aist.go.jp [Biomedical Research Institute, National Institute of Advanced Industrial Science and Technology (AIST), Central 4, 1-1-1 Higashi, Tsukuba, Ibaraki 305-8562 (Japan); Department of Biotechnology and Life Science, Tokyo University of Agriculture and Technology, 2-24-26 Naka-cho, Koganei, Tokyo 184-8588 (Japan)

    2012-04-13

    Highlights: Black-Right-Pointing-Pointer We examined the insertion efficiency of nanoneedles into fibroblast and neural cells. Black-Right-Pointing-Pointer Nanofilms formed on cell surfaces improved the insertion efficiency of nanoneedles. Black-Right-Pointing-Pointer Nanofilms improved the insertion efficiency even in Y27632-treated cells. -- Abstract: A nanoneedle, an atomic force microscope (AFM) tip etched to 200 nm in diameter and 10 {mu}m in length, can be inserted into cells with the aid of an AFM and has been used to introduce functional molecules into cells and to analyze intracellular information with minimal cell damage. However, some cell lines have shown low insertion efficiency of the nanoneedle. Improvement in the insertion efficiency of a nanoneedle into such cells is a significant issue for nanoneedle-based cell manipulation and analysis. Here, we have formed nanofilms composed of extracellular matrix molecules on cell surfaces and found that the formation of the nanofilms improved insertion efficiency of a nanoneedle into fibroblast and neural cells. The nanofilms were shown to improve insertion efficiency even in cells in which the formation of actin stress fibers was inhibited by the ROCK inhibitor Y27632, suggesting that the nanofilms with the mesh structure directly contributed to the improved insertion efficiency of a nanoneedle.

  8. Glycobiology of the cell surface: Its debt to cell electrophoresis 1940-65.

    Science.gov (United States)

    Cook, Geoffrey M W

    2016-06-01

    This Review describes how in the period 1940-1959 cell electrophoresis (in the earlier literature often referred to as 'microelectrophoresis') was used to explore the surface chemistry of cells. Using the erythrocyte as a suitable model for the study of biological membranes, the early investigators were agreed on the presence of negatively charged groups at the surface of this cell. The contemporary dogma was that these were phosphate groups associated with phospholipids. Work in the 1960s, particularly on changes in the electrokinetic properties of erythrocytes following treatment with proteolytic enzymes, lead to the realization that the negatively charged groups at the red cell surface are predominantly due to sialic acids carried on glycoproteins. It quickly became apparent from cell electrophoresis that sialic acids have a ubiquitous presence on the surface of animal cells. This finding required that any complete model of the plasma membrane must include glycosylated molecules at the cell periphery, thus laying the foundations for the field termed 'Glycobiology of the Cell Surface'. PMID:26717803

  9. Entangling the motion of two optically trapped objects via time-modulated driving fields

    International Nuclear Information System (INIS)

    We study entanglement of the motional degrees of freedom of two tethered and optically trapped microdisks inside a single cavity. By properly choosing the position of the trapped objects in the optical cavity and driving proper modes of the cavity, it is possible to equip the system with linear and quadratic optomechanical couplings. We show that a parametric coupling between the fundamental vibrational modes of two tethered microdisks can be generated via a time-modulated input laser. For a proper choice of the modulation frequency, this mechanism can drive the motion of the microdisks into an inseparable state in the long time limit via a two-mode squeezing process. We numerically confirm the performance of our scheme for current technology and briefly discuss an experimental setup that can be used for detecting this entanglement by employing the quadratic coupling. We also comment on the perspectives for generating such entanglement between the oscillations of optically levitated nanospheres. (paper)

  10. Use of Tethered Enzymes as a Platform Technology for Rapid Analyte Detection.

    Directory of Open Access Journals (Sweden)

    Roy Cohen

    Full Text Available Rapid diagnosis for time-sensitive illnesses such as stroke, cardiac arrest, and septic shock is essential for successful treatment. Much attention has therefore focused on new strategies for rapid and objective diagnosis, such as Point-of-Care Tests (PoCT for blood biomarkers. Here we use a biomimicry-based approach to demonstrate a new diagnostic platform, based on enzymes tethered to nanoparticles (NPs. As proof of principle, we use oriented immobilization of pyruvate kinase (PK and luciferase (Luc on silica NPs to achieve rapid and sensitive detection of neuron-specific enolase (NSE, a clinically relevant biomarker for multiple diseases ranging from acute brain injuries to lung cancer. We hypothesize that an approach capitalizing on the speed and catalytic nature of enzymatic reactions would enable fast and sensitive biomarker detection, suitable for PoCT devices.We performed in-vitro, animal model, and human subject studies. First, the efficiency of coupled enzyme activities when tethered to NPs versus when in solution was tested, demonstrating a highly sensitive and rapid detection of physiological and pathological concentrations of NSE. Next, in rat stroke models the enzyme-based assay was able in minutes to show a statistically significant increase in NSE levels in samples taken 1 hour before and 0, 1, 3 and 6 hours after occlusion of the distal middle cerebral artery. Finally, using the tethered enzyme assay for detection of NSE in samples from 20 geriatric human patients, we show that our data match well (r = 0.815 with the current gold standard for biomarker detection, ELISA-with a major difference being that we achieve detection in 10 minutes as opposed to the several hours required for traditional ELISA.Oriented enzyme immobilization conferred more efficient coupled activity, and thus higher assay sensitivity, than non-tethered enzymes. Together, our findings provide proof of concept for using oriented immobilization of active

  11. Electric-Field-Assisted Assembly of Polymer-Tethered Gold Nanorods in Cylindrical Nanopores.

    Science.gov (United States)

    Wang, Ke; Jin, Seon-Mi; Xu, Jiangping; Liang, Ruijing; Shezad, Khurram; Xue, Zhigang; Xie, Xiaolin; Lee, Eunji; Zhu, Jintao

    2016-05-24

    In this report, we demonstrate the confined assembly of polymer-tethered gold nanorods in anodic aluminum oxide (AAO) channels with the assistance of electric field (EF). Various interesting hybrid assemblies, such as single-, double-, triple-, or quadruple-helix, linear, and hexagonally packed structures are obtained by adjusting pore size in AAO channels, ligand length, and EF orientation. Correspondingly, surface plasmonic property of the assemblies can thus be tuned. This strategy, by coupling of external-field and cylindrically confined assembly, is believed to be a promising approach for generating ordered hybrid assemblies with hierarchical structures, which may find potential applications in photoelectric devices, biosensors, and data storage devices. PMID:27054687

  12. Iatrogenic intradural arachnoid cyst following tethered cord release in a child.

    Science.gov (United States)

    Glenn, Chad A; Bonney, Phillip; Cheema, Ahmed A; Conner, Andrew K; Gross, Naina L; Yaun, Amanda L

    2016-02-01

    Iatrogenic arachnoid cysts represent uncommon complications of intradural spinal procedures. Here we present the case of a 7-year-old girl who was found to have a symptomatic, pathologically proven, intradural arachnoid cyst 3 years following tethered cord release. The patient originally presented with abnormal urodynamics testing and was found to have fatty infiltration in her filum terminale. She underwent sectioning of the filum terminale without complications. The patient presented 3 years later with pain and neurogenic claudication. The patient was successfully treated with subarachnoid cyst fenestration with resolution of her bilateral lower extremity pain. Spinal intradural arachnoid cysts represent an important, though rare, postoperative complication of dural opening. PMID:26602801

  13. A Tethered Cord with Hemivertebra: A Case Report and Review of Literature

    Science.gov (United States)

    Asil, Kiyasettin; Yaldiz, Mahizer; Ozkal, Birol

    2015-01-01

    Spinal dysraphisms are defined as open and closed dysraphisms. A hemivertebra is a congenital condition seen in 61% of patients with congenital anomalies. The first report of the excision of a hemivertebra was by Royle in 1928. A sixteen-year-old girl was admitted to our clinic with a congenital stain on the waist and a normal neurological examination. No new cases have been reported in recent literature. Our case, which is also rare, is associated with a tethered cord only and no other congenital abnormalities. PMID:26512281

  14. Experimental and analytical determination of stability parameters for a balloon tethered in a wind

    Science.gov (United States)

    Redd, L. T.; Bennett, R. M.; Bland, S. R.

    1973-01-01

    Experimental and analytical techniques for determining stability parameters for a balloon tethered in a steady wind are described. These techniques are applied to a particular 7.64-meter-long balloon, and the results are presented. The stability parameters of interest appear as coefficients in linearized stability equations and are derived from the various forces and moments acting on the balloon. In several cases the results from the experimental and analytical techniques are compared and suggestions are given as to which techniques are the most practical means of determining values for the stability parameters.

  15. A complementary electrochromic device based on polyaniline-tethered polyhedral oligomeric silsesquioxane and tungsten oxide

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Liying; Xiong, Shanxin; Ma, Jan; Lu, Xuehong [School of Materials Science and Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798 (Singapore)

    2009-05-15

    In this paper we report a high-contrast complementary electrochromic device based on polyaniline-tethered polyhedral oligomeric silsesquioxane (POSS-PANI) and tungsten oxide (WO{sub 3}). The electrochromic properties, cyclic voltammetry behavior and coloration efficiency of the device are studied. Due to the loosely packed structure of POSS-PANI, it possesses more accessible doping sites and hence gives rise to a significantly higher electrochromic contrast than polyaniline (PANI). Furthermore, the replacement of PANI with POSS-PANI as the complementary layer for WO{sub 3} leads to an enhanced complementary effect, for which the underneath mechanism is also discussed. (author)

  16. Synaptic Vesicle Tethering and the CaV2.2 Distal C-terminal

    Directory of Open Access Journals (Sweden)

    Fiona K Wong

    2014-03-01

    Full Text Available . Evidence that synaptic vesicles (SVs can be gated by a single voltage sensitive calcium channel (CaV2.2 predict a molecular linking mechanism or ‘tether’[Stanley 1993]. Recent studies have proposed that the SV binds to the distal C-terminal on the CaV2.2 calcium channel [Kaeser et al. 2011;Wong, Li, and Stanley 2013] while genetic analysis proposed a double tether mechanism via RIM: directly to the C terminus PDZ ligand domain or indirectly via a more proximal proline rich site [Kaeser et al. 2011]. Using a novel in vitro SV-PD binding assay, we reported that SVs bind to a fusion protein comprising the C-terminal distal third (C3, aa 2137-2357 [Wong, Li, and Stanley 2013]. Here we limit the binding site further to the last 58 aa, beyond the proline rich site, by the absence of SV capture by a truncated C3 fusion protein (aa 2137-2299. To test PDZ-dependent binding we generated two C terminus-mutant C3 fusion proteins and a mimetic blocking peptide (H-WC, aa 2349-2357 and validated these by elimination of MINT-1 or RIM binding. Persistence of SV capture with all three fusion proteins or with the full length C3 protein but in the presence of the blocking peptide, demonstrated that SVs can bind to the distal C-terminal via a PDZ-independent mechanism. These results were supported in situ by normal SV turnover in H-WC-loaded synaptosomes, as assayed by a novel peptide cryoloading method. Thus, SVs tether to the CaV2.2 C-terminal within a 49 aa region immediately prior to the terminus PDZ ligand domain. Long tethers that could reflect extended C termini were imaged by electron microscopy of synaptosome ghosts. To fully account for SV tethering we propose a model where SVs are initially captured, or ‘grabbed’, from the cytoplasm by a binding site on the distal region of the channel C-terminal and are then retracted to be ‘locked’ close to the channel by a second attachment mechanism in preparation for single channel domain gating.

  17. A modular phosphate tether-mediated divergent strategy to complex polyols

    Directory of Open Access Journals (Sweden)

    Paul R. Hanson

    2014-10-01

    Full Text Available An efficient and divergent synthesis of polyol subunits utilizing a phosphate tether-mediated, one-pot, sequential RCM/CM/reduction process is reported. A modular, 3-component coupling strategy has been developed, in which, simple “order of addition” of a pair of olefinic-alcohol components to a pseudo-C2-symmetric phosphoryl chloride, coupled with the RCM/CM/reduction protocol, yields five polyol fragments. Each of the product polyols bears a central 1,3-anti-diol subunit with differential olefinic geometries at the periphery.

  18. Preparation of isospecific metallocene catalysts for olefin polymerization that are covalently tethered on solid surface

    OpenAIRE

    Suzuki, Noriyuki; Yu, Jian; Shioda, Nobuyuki; Asami, Hayato; Nakamura, Takashi; Huhn, Thomas; Fukuoka, Atsushi; Ichikawa, Masaru; Saburi, Masahiko; Wakatsuki, Yasuo

    2002-01-01

    A novel methodology was developed for the preparation of isospecific metallocene catalysts for olefin polymerization that are tethered on silica surfaces with covalent bonds. A racemic ansa-zirconocene complex that has a Si Cl moiety on its bridge was immobilized on SiO2 by the reaction of the Si Cl anchor with Si OH on the solid surface. The prepared solid catalyst was found to be effective for isospecific propene polymerization (catalyst A). Pretreatment of silica surfaces with Me3SiCl impr...

  19. Structure of the Membrane-tethering GRASP Domain Reveals a Unique PDZ Ligand Interaction That Mediates Golgi Biogenesis

    Energy Technology Data Exchange (ETDEWEB)

    S Truschel; D Sengupta; A Foote; A Heroux; M Macbeth; A Linstedt

    2011-12-31

    Biogenesis of the ribbon-like membrane network of the mammalian Golgi requires membrane tethering by the conserved GRASP domain in GRASP65 and GRASP55, yet the tethering mechanism is not fully understood. Here, we report the crystal structure of the GRASP55 GRASP domain, which revealed an unusual arrangement of two tandem PDZ folds that more closely resemble prokaryotic PDZ domains. Biochemical and functional data indicated that the interaction between the ligand-binding pocket of PDZ1 and an internal ligand on PDZ2 mediates the GRASP self-interaction, and structural analyses suggest that this occurs via a unique mode of internal PDZ ligand recognition. Our data uncover the structural basis for ligand specificity and provide insight into the mechanism of GRASP-dependent membrane tethering of analogous Golgi cisternae.

  20. Structure of the Membrane-tethering GRASP Domain Reveals a Unique PDZ Ligand Interaction That Mediates Golgi Biogenesis

    Energy Technology Data Exchange (ETDEWEB)

    Truschel, S.T.; Heroux, A.; Sengupta, D.; Foote, A.; Macbeth, M. R.; Linstedt, A. D.

    2011-06-10

    Biogenesis of the ribbon-like membrane network of the mammalian Golgi requires membrane tethering by the conserved GRASP domain in GRASP65 and GRASP55, yet the tethering mechanism is not fully understood. Here, we report the crystal structure of the GRASP55 GRASP domain, which revealed an unusual arrangement of two tandem PDZ folds that more closely resemble prokaryotic PDZ domains. Biochemical and functional data indicated that the interaction between the ligand-binding pocket of PDZ1 and an internal ligand on PDZ2 mediates the GRASP self-interaction, and structural analyses suggest that this occurs via a unique mode of internal PDZ ligand recognition. Our data uncover the structural basis for ligand specificity and provide insight into the mechanism of GRASP-dependent membrane tethering of analogous Golgi cisternae.

  1. Direct Measurement of Local Chromatin Fluidity Using Optical Trap Modulation Force Spectroscopy

    OpenAIRE

    Roopa, T.; Shivashankar, G. V.

    2006-01-01

    Chromatin assembly is condensed by histone tail-tail interactions and other nuclear proteins into a highly compact structure. Using an optical trap modulation force spectroscopy, we probe the effect of tail interactions on local chromatin fluidity. Chromatin fibers, purified from mammalian cells, are tethered between a microscope coverslip and a glass micropipette. Mechanical unzipping of tail interactions, using the micropipette, lead to the enhancement of local fluidity. This is measured us...

  2. Detection of specific DNA using a microfluidic device featuring tethered poly(N-isopropylacrylamide) on a silicon substrate

    Science.gov (United States)

    Chen, Jem-Kun; Li, Jun-Yan

    2010-08-01

    In this study, we grafted thermoresponsive poly(N-isopropylacrylamide) (PNIPAAm) onto a Si substrate as the medium in a microfluidic device to detect specific DNA molecules [human genomic DNA (hgDNA528), 528 bp] at extremely low concentrations (down to 2 ng/μl). After using the polymerase chain reaction to amplify the released human gDNA signal from the tethered PNIPAAm on the substrate, the amplified human gDNA molecules were characterized through agarose gel electrophoresis. The tethered PNIPAAm in the fluid device allowed the precise detection of the human gDNA.

  3. Calculating the mean time to capture for tethered ligands and its effect on the chemical equilibrium of bound ligand pairs.

    Science.gov (United States)

    Shen, Lu; Decker, Caitlin G; Maynard, Heather D; Levine, Alex J

    2016-09-01

    We present here the calculation of the mean time to capture of a tethered ligand to the receptor. This calculation is then used to determine the shift in the partitioning between (1) free, (2) singly bound, and (3) doubly bound ligands in chemical equilibrium as a function of the length of the tether. These calculations are used in the research article Fibroblast Growth Factor 2 Dimer with Superagonist in vitro Activity Improves Granulation Tissue Formation During Wound Healing (Decker et al., in press [1]) to explain quantitatively how changes in polymeric linker length in the ligand dimers modifies the efficacy of these molecules relative to that of free ligands. PMID:27408925

  4. Two cell surface proteins bind the sponge Microciona prolifera aggregation factor.

    Science.gov (United States)

    Varner, J A; Burger, M M; Kaufman, J F

    1988-06-15

    Two extracellular matrix cell surface proteins which bind the proteoglycan-like aggregation factor from the marine sponge Microciona prolifera (MAF) and which may function as physiological receptors for MAF were identified and characterized for the first time. By probing nitrocellulose blots of nonreducing sodium dodecyl sulfate gels containing whole sponge cell protein with iodinated MAF, a 210- and a 68-kDa protein, which have native molecular masses of approximately 200-400 and 70 kDa, were identified. MAF binding to blots is species-specific. It is also sensitive to reduction and is completely abolished by pretreatment of live cells with proteases, as was cellular aggregation, indicating that the 210- and 68-kDa proteins may be located on the cell surface. The additional observations that the 68 kDa is an endoglycosidase F-sensitive glycoprotein and that antisera against whole sponge cells or membranes can immunoprecipitate the 210 kDa when prebound to intact cells are consistent with a cell surface location. Both proteins can be isolated from sponge cell membranes and from the sponge skeleton (insoluble extracellular matrix), but the 210-kDa MAF-binding protein can also be found in the soluble extracellular matrix (buffer washes of cells and skeleton) as well. A third MAF-binding protein of molecular mass 95 kDa was also found in the sponge extracellular matrix but rarely on cells. Both of the cell-associated 210- and 68-kDa proteins are nonintegral membrane proteins, based on Triton X-114 phase separation, flotation of liposomes containing sponge membrane lysates, and their extraction from membranes by buffer washes. Both proteins bind MAF affinity resins, indicating that they each exhibit a moderate affinity for MAF under native conditions. They can also be separated from each other and from the bulk of the protein in an octylpolyoxyethylene extract of membranes by fast protein liquid chromatography Mono Q anion exchange chromatography, as assessed by native

  5. Vehicle tethered aerostat optoelectronic monitoring platform system for Shanghai World EXPO

    Science.gov (United States)

    Zhou, Weihu; Wang, Yawei; Han, Xiaoquan; Yuan, Jiang

    2010-08-01

    To monitor the whole Shanghai Expo Park, a vehicle tethered aerostat optoelectronic monitoring platform with the characteristic of time-sensitive and all-weather monitoring is described in detail in this paper, which is hung beneath the tethered balloon and equipped with a variety of payloads, including visible light monitoring system, infrared monitoring system, hyperspectral monitoring system, GPS/INS system, monitoring and control system and so on. These equipments can be used for real-time monitoring, environmental monitoring, and ground target location of Shanghai Expo Park. The output High Definition (HD) image of Shanghai Expo Park from visible light monitoring system is clear and stable, and the stabilization accuracy of visual axis is 0.07°(3δ). The optoelectronic monitoring platform system uses the target location technology based on Global Position System/Inertial Navigation System (GPS/INS) system to output real-time location data compatible with Geographic Information System (GIS). Test results show that the maximum errors between the location results (latitude and longitude) solved by the target location program and the reference target are 0.2 0/00(latitude) and 2 0/00(longitude). Now the whole system has been used for surveillance the Shanghai Expo Park since April 2010.

  6. Probing DNA conformational changes with high temporal resolution by tethered particle motion

    International Nuclear Information System (INIS)

    The tethered particle motion (TPM) technique informs about conformational changes of DNA molecules, e.g. upon looping or interaction with proteins, by tracking the Brownian motion of a particle probe tethered to a surface by a single DNA molecule and detecting changes of its amplitude of movement. We discuss in this context the time resolution of TPM, which strongly depends on the particle–DNA complex relaxation time, i.e. the characteristic time it takes to explore its configuration space by diffusion. By comparing theory, simulations and experiments, we propose a calibration of TPM at the dynamical level: we analyze how the relaxation time grows with both DNA contour length (from 401 to 2080 base pairs) and particle radius (from 20 to 150 nm). Notably we demonstrate that, for a particle of radius 20 nm or less, the hydrodynamic friction induced by the particle and the surface does not significantly slow down the DNA. This enables us to determine the optimal time resolution of TPM in distinct experimental contexts which can be as short as 20 ms

  7. Self-assembly of inorganic nanoparticle vesicles and tubules driven by tethered linear block copolymers.

    Science.gov (United States)

    He, Jie; Liu, Yijing; Babu, Taarika; Wei, Zengjiang; Nie, Zhihong

    2012-07-18

    Controllable self-assembly of nanoscale building blocks into larger specific structures provides an effective route for the fabrication of new materials with unique optical, electronic, and magnetic properties. The ability of nanoparticles (NPs) to self-assemble like molecules is opening new research frontiers in nanoscience and nanotechnology. We present a new class of amphiphilic "colloidal molecules" (ACMs) composed of inorganic NPs tethered with amphiphilic linear block copolymers (BCPs). Driven by the conformational changes of tethered BCP chains, such ACMs can self-assemble into well-defined vesicular and tubular nanostructures comprising a monolayer shell of hexagonally packed NPs in selective solvents. The morphologies and geometries of these assemblies can be controlled by the size of NPs and molecular weight of BCPs. Our approach also allows us to control the interparticle distance, thus fine-tuning the plasmonic properties of the assemblies of metal NPs. This strategy provides a general means to design new building blocks for assembling novel functional materials and devices. PMID:22746265

  8. Identification of Novel ROS Inducers: Quinone Derivatives Tethered to Long Hydrocarbon Chains.

    Science.gov (United States)

    Hong, Yeonsun; Sengupta, Sandip; Hur, Wooyoung; Sim, Taebo

    2015-05-14

    We performed the first synthesis of the 17-carbon chain-tethered quinone moiety 22 (SAN5201) of irisferin A, a natural product exhibiting anticancer activity, and its derivatives. We found that 22 is a potent ROS inducer and cytotoxic agent. Compound 25 (SAN7401), the hydroquinone form of 22, induced a significant release of intracellular ROS and apoptosis (EC50 = 1.3-2.6 μM) in cancer cell lines, including A549 and HCT-116. Compared with the activity of a well-known ROS inducer, piperlongumine, 22 and 25 showed stronger cytotoxicity and higher selectivity over noncancerous cells. Another hydroquinone tethering 12-carbon chain, 26 (SAN4601), generated reduced levels of ROS but showed more potent cytotoxicity (EC50 = 0.8-1.6 μM) in cancer cells, although it lacked selectivity over noncancerous cells, implying that the naturally occurring 17-carbon chain is also crucial for ROS production and a selective anticancer effect. Both 25 and 26 displayed strong, equipotent activities against vemurafenib-resistant SK-Mel2 melanoma cells and p53-deficient H1299 lung cancer cells as well, demonstrating their broad therapeutic potential as anticancer agents. PMID:25826398

  9. Fluorosilicone multi-block copolymers tethering quaternary ammonium salt groups for antimicrobial purpose

    Science.gov (United States)

    Zhou, Fang; Qin, Xiaoshuai; Li, Yancai; Ren, Lixia; Zhao, Yunhui; Yuan, Xiaoyan

    2015-08-01

    Symmetrically structured fluorosilicone multi-block copolymers containing poly(2-(dimethylamino)ethyl methacrylate) (PDMAEMA) and poly(hexafluorobutyl methacrylate) (PHFBMA) were sequentially synthesized via reversible addition-fragmentation chain transfer polymerization, using a polydimethylsiloxane (PDMS) chain transfer agent with dithiocarbonate groups at both ends. Then, the CBABC-type block copolymers were quaternized with n-octyliodide to tether quaternary ammonium salt (QAS) groups in the PDMAEMA blocks for the antimicrobial use. The obtained fluorosilicone copolymers showed clear variations in the C-N+ composition and surface morphology on their films depending on the content of the PHFBMA blocks, which were characterized by X-ray photoelectron spectroscopy and atomic force microscopy, respectively. The results indicated that the symmetrical CBABC structure favored PDMS and QAS tethered blocks migrating to the film surface. With the mass percentage of the PHFBMA increased from 0 to 32.5%, the surface roughness of the copolymer film decreased gradually with a tendency to form a smooth surface. Owing to the surface properties, fluorosilicone multi-block copolymers containing a certain amount of PHFBMA with higher C-N+ content and relatively smooth morphology demonstrated obvious antimicrobial activity against Gram-positive bacteria, Bacillus subtilis and Gram-negative bacteria, Escherichia coli. The functionalized multi-block copolymers based on fluorosilicone and QAS groups would have potential applications in antimicrobial coatings.

  10. Partner preference behavior of estrous female rats affected by castration of tethered male incentives.

    Science.gov (United States)

    Broekman, M; de Bruin, M; Smeenk, J; Slob, A K; van der Schoot, P

    1988-09-01

    Estrous female rats were allowed to interact with either of two tethered intact male rats or to stay in an empty middle part of a three-compartment observation cage during a 60-min test. Sexual interactions occurred with both males (resulting in one to five ejaculations) but most time was spent in the empty compartment. After castration of one of the males, females spent more time with this male than with the intact male, although sexual interactions continued with both incentive animals. This "preference" for the castrated male persisted through the second hour of observation in a second experiment (total test time 115 min) although sexual interactions had virtually ceased during this period. Females' preference for castrated males seemed largely the consequence of aversion to genital stimulation received during intromissions by intact animals: (a) when intromissions were prevented through vaginal occlusion, intact males became by far the preferred partners for the whole 2-hr period of testing while sexual behavior continued to occur throughout the test; (b) when choice was allowed between a testosterone-treated ovariectomized female and an intact male, sexual interaction occurred with both tethered incentive rats but the female became the preferred animal. The results suggest that two opposite tendencies play a role in sexual motivation of estrous female rats: attraction resulting from the action of ovarian hormones on the central nervous system and rejection resulting from genital sensory stimulation through the male's genitalia. PMID:3169698

  11. Turbulence observations over a desert basin using a kite/tethered-blimp platform

    Science.gov (United States)

    Eaton, Frank D.; Balsley, Ben B.; Frehlich, Rod G.; Hugo, Ronald J.; Jensen, Michael L.; McCrae, Kimberley A.

    2000-09-01

    Results of the (temperature) refractive index structure parameter (C2T), C2n, and the eddy dissipation rate (epsilon) derived from the velocity structure parameter C2v are presented from fast response sensor observations using a kite/tethered-blimp platform in the Tularosa Basin at White Sands Missile Range, New Mexico, during the spring of 1998. Comparisons of different sensors (fine-wire probes and pilot tubes) measuring the same parameter are displayed and discussed while salient features of all sensors (standard and fast response) and the kite and tethered-blimp platforms are outlined. The nature and statistics of turbulence, including intermittency, under different stability conditions is discussed, including those found in the residual layer above the nocturnal boundary layer and the entrainment zone at the top of the daytime planetary boundary layer. In addition to displaying time series of temperature C2n and (epsilon) results obtained at specific altitudes and times, histograms of all daytime and nighttime C2n and (epsilon) values are compared to log-normal distributions. Examples of profiles of C2n and (epsilon) for daytime, near sunset, and nighttime conditions are shown and discussed. The relationship of C2n with (epsilon) is displayed for all data as well as sorted by daytime and nighttime. These results are explained in terms of potential and kinetic energy considerations under different atmospheric stability conditions.

  12. Cholesterol-Induced Buckling in Physisorbed Polymer-Tethered Lipid Monolayers

    Directory of Open Access Journals (Sweden)

    Christoph A. Naumann

    2013-04-01

    Full Text Available The influence of cholesterol concentration on the formation of buckling structures is studied in a physisorbed polymer-tethered lipid monolayer system using epifluorescence microscopy (EPI and atomic force microscopy (AFM. The monolayer system, built using the Langmuir-Blodgett (LB technique, consists of 3 mol % poly(ethylene glycol (PEG lipopolymers and various concentrations of the phospholipid, 1-stearoyl-2-oleoyl-sn-glycero-3-phosphocholine (SOPC, and cholesterol (CHOL. In the absence of CHOL, AFM micrographs show only occasional buckling structures, which is caused by the presence of the lipopolymers in the monolayer. In contrast, a gradual increase of CHOL concentration in the range of 0–40 mol % leads to fascinating film stress relaxation phenomena in the form of enhanced membrane buckling. Buckling structures are moderately deficient in CHOL, but do not cause any notable phospholipid-lipopolymer phase separation. Our experiments demonstrate that membrane buckling in physisorbed polymer-tethered membranes can be controlled through CHOL-mediated adjustment of membrane elastic properties. They further show that CHOL may have a notable impact on molecular confinement in the presence of crowding agents, such as lipopolymers. Our results are significant, because they offer an intriguing prospective on the role of CHOL on the material properties in complex membrane architecture.

  13. Relative Contribution of Arms and Legs in 30 s Fully Tethered Front Crawl Swimming

    Directory of Open Access Journals (Sweden)

    Pedro G. Morouço

    2015-01-01

    Full Text Available The relative contribution of arm stroke and leg kicking to maximal fully tethered front crawl swimming performance remains to be solved. Twenty-three national level young swimmers (12 male and 11 female randomly performed 3 bouts of 30 s fully tethered swimming (using the whole body, only the arm stroke, and only the leg kicking. A load-cell system permitted the continuous measurement of the exerted forces, and swimming velocity was calculated from the time taken to complete a 50 m front crawl swim. As expected, with no restrictions swimmers were able to exert higher forces than that using only their arm stroke or leg kicking. Estimated relative contributions of arm stroke and leg kicking were 70.3% versus 29.7% for males and 66.6% versus 33.4% for females, with 15.6% and 13.1% force deficits, respectively. To obtain higher velocities, male swimmers are highly dependent on the maximum forces they can exert with the arm stroke (r=0.77, P<0.01, whereas female swimmers swimming velocity is more related to whole-body mean forces (r=0.81, P<0.01. The obtained results point that leg kicking plays an important role over short duration high intensity bouts and that the used methodology may be useful to identify strength and/or coordination flaws.

  14. Characterization of Cell Surface and EPS Remodeling of Azospirillum brasilense Chemotaxis-like 1 Signal Transduction Pathway mutants by Atomic Force Microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Billings, Amanda N [ORNL; Siuti, Piro [ORNL; Bible, Amber [University of Tennessee, Knoxville (UTK); Alexandre, Gladys [University of Tennessee, Knoxville (UTK); Retterer, Scott T [ORNL; Doktycz, Mitchel John [ORNL; Morrell-Falvey, Jennifer L [ORNL

    2011-01-01

    To compete in complex microbial communities, bacteria must quickly sense environmental changes and adjust cellular functions for optimal growth. Chemotaxis-like signal transduction pathways are implicated in the modulation of multiple cellular responses, including motility, EPS production, and cell-to-cell interactions. Recently, the Che1 chemotaxis-like pathway from Azospirillum brasilense was shown to modulate flocculation. In A. brasilense, cell surface properties, including EPS production, are thought to play a direct role in promoting flocculation. Using atomic force microscopy (AFM), we have detected distinct changes in the surface morphology of flocculating A. brasilense Che1 mutant strains that are absent in the wild type strain. Whereas the wild type strain produces a smooth mucosal extracellular matrix, the flocculating Che1 mutant strains produce distinctive extracellular fibril structures. Further analyses using flocculation inhibition and lectin-binding assays suggest that the composition of EPS components in the extracellular matrix differs between the cheA1 and cheY1 mutants, despite an apparent similarity in the macroscopic floc structures. Collectively, these data indicate that mutations in the Che1 pathway that result in increased flocculation are correlated with distinctive changes in the extracellular matrix structure produced by the mutants, including likely changes in the EPS structure and/or composition.

  15. Facile method to stain the bacterial cell surface for super-resolution fluorescence microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Gunsolus, Ian L.; Hu, Dehong; Mihai, Cosmin; Lohse, Samuel E.; Lee, Chang-Soo; Torelli, Marco; Hamers, Robert J.; Murphy, Catherine; Orr, Galya; Haynes, Christy L.

    2014-01-01

    A method to fluorescently stain the surfaces of both Gram-negative and Gram-positive bacterial cells compatible with super-resolution fluorescence microscopy is presented. This method utilizes a commercially-available fluorescent probe to label primary amines at the surface of the cell. We demonstrate efficient staining of two bacterial strains, the Gram-negative Shewanella oneidensis MR-1 and the Gram-positive Bacillus subtilis 168. Using structured illumination microscopy and stochastic optical reconstruction microscopy, which require high quantum yield or specialized dyes, we show that this staining method may be used to resolve the bacterial cell surface with sub-diffraction-limited resolution. We further use this method to identify localization patterns of nanomaterials, specifically cadmium selenide quantum dots, following interaction with bacterial cells.

  16. Effects of sodium on cell surface and intracellular TH-naloxone binding sites

    Energy Technology Data Exchange (ETDEWEB)

    Pollack, A.E.; Wooten, G.F.

    1987-07-27

    The binding of the opiate antagonist TH-naloxone was examined in rat whole brain homogenates and in crude subcellular fractions of these homogenates (nuclear, synaptosomal, and mitochondrial fractions) using buffers that approximated intra- (low sodium concentration) and extracellular (high sodium concentration) fluids. Saturation studies showed a two-fold decrease in the dissociation constant (Kd) in all subcellular fractions examined in extracellular buffer compared to intracellular buffer. In contrast, there was no significant effect of the buffers on the Bmax. Thus, TH-naloxone did not distinguish between binding sites present on cell surface and intracellular tissues in these two buffers. These results show that the sodium effect of opiate antagonist binding is probably not a function of altered selection of intra- and extracellular binding sites. 17 references, 2 tables.

  17. Effects of sodium on cell surface and intracellular 3H-naloxone binding sites

    International Nuclear Information System (INIS)

    The binding of the opiate antagonist 3H-naloxone was examined in rat whole brain homogenates and in crude subcellular fractions of these homogenates (nuclear, synaptosomal, and mitochondrial fractions) using buffers that approximated intra- (low sodium concentration) and extracellular (high sodium concentration) fluids. Saturation studies showed a two-fold decrease in the dissociation constant (Kd) in all subcellular fractions examined in extracellular buffer compared to intracellular buffer. In contrast, there was no significant effect of the buffers on the Bmax. Thus, 3H-naloxone did not distinguish between binding sites present on cell surface and intracellular tissues in these two buffers. These results show that the sodium effect of opiate antagonist binding is probably not a function of altered selection of intra- and extracellular binding sites. 17 references, 2 tables

  18. Indirect 125I-labeled protein A assay for monoclonal antibodies to cell surface antigens

    International Nuclear Information System (INIS)

    An assay for detection of monoclonal hybridoma antibodies against cell surface antigens is described. Samples of spent medium from the hybridoma cultures are incubated in microtest wells with cells, either as adherent monolayers or in suspension. Antibodies bound to surface antigens are detected by successive incubations with rabbit anti-immunoglobulin serum and 125I-labeled protein A from Staphylococcus aureus, followed by autoradiography of the microtest plate or scintillation counting of the individual wells. Particular advantages of this assay for screening hybridomas are: (1) commercially available reagents are used, (2) antibodies of any species and of any immunoglobulin class or subclass can be detected, and (3) large numbers of samples can be screened rapidly and inexpensively. The assay has been used to select hybridomas producing monoclonal antibodies to surface antigens of human melanomas and mouse sarcomas. (Auth.)

  19. Improved accuracy of cell surface shaving proteomics in Staphylococcus aureus using a false-positive control

    DEFF Research Database (Denmark)

    Solis, Nestor; Larsen, Martin Røssel; Cordwell, Stuart J

    2010-01-01

    lysis and were removed from the trypsin-shaved data set. We identified 42 predicted S. aureus COL surface proteins from 260 surface-exposed peptides. Trypsin and proteinase-K digests were highly complementary with ten proteins identified by both, 16 specific to proteinase-K treatment, 13 specific......0050 (pls) and penicillin-binding protein 2' (mecA), as well as bifunctional autolysin and the extracellular matrix-binding protein Ebh. The cell shaving strategy is a rapid method for identifying surface-exposed peptide epitopes that may be useful in the design of novel vaccines against S. aureus....... that complicate the final analysis. Staphylococcus aureus is a major human pathogen, causing community and hospital-acquired infections, and is a serious healthcare concern due to the increasing prevalence of multiple antibiotic resistances amongst clinical isolates. We employed a cell surface "shaving" technique...

  20. Fluid dynamics and noise in bacterial cell-cell and cell-surface scattering

    CERN Document Server

    Drescher, Knut; Cisneros, Luis H; Ganguly, Sujoy; Goldstein, Raymond E; 10.1073/pnas.1019079108

    2011-01-01

    Bacterial processes ranging from gene expression to motility and biofilm formation are constantly challenged by internal and external noise. While the importance of stochastic fluctuations has been appreciated for chemotaxis, it is currently believed that deterministic long-range fluid dynamical effects govern cell-cell and cell-surface scattering - the elementary events that lead to swarming and collective swimming in active suspensions and to the formation of biofilms. Here, we report the first direct measurements of the bacterial flow field generated by individual swimming Escherichia coli both far from and near to a solid surface. These experiments allowed us to examine the relative importance of fluid dynamics and rotational diffusion for bacteria. For cell-cell interactions it is shown that thermal and intrinsic stochasticity drown the effects of long-range fluid dynamics, implying that physical interactions between bacteria are determined by steric collisions and near-field lubrication forces. This dom...

  1. Signaling at the cell surface in the circulatory and ventilatory systems

    CERN Document Server

    Thiriet, Marc

    2012-01-01

    The volumes in this authoritative series present a multidisciplinary approach to modeling and simulation of flows in the cardiovascular and ventilatory systems, especially multiscale modeling and coupled simulations. The cardiovascular and respiratory systems are tightly coupled, as their primary function is to supply oxygen to and remove carbon dioxide from the body's cells. Because physiological conduits have deformable and reactive walls, macroscopic flow behavior and prediction must be coupled to nano- and microscopic events in a corrector scheme of regulated mechanisms when the vessel lumen caliber varies markedly. Therefore, investigation of flows of blood and air in physiological conduits requires an understanding of the biology, chemistry, and physics of these systems together with the mathematical tools to describe their functioning. Volume 3 is devoted to the set of mediators of the cell surface, especially ion and molecular carriers and catalytic receptors that, once liganded and activated, initiat...

  2. The microbial cell surface electric field: life in an ion cloud

    Science.gov (United States)

    Yee, N.

    2005-05-01

    Electrical charge on microbial cell surfaces arises from the ionization of proton-active functional groups attached to cell wall polymers. In Gram-positive cell walls, ionizable functional groups are associated with peptidoglycan and secondary polymers such as teichoic or teichuronic acids. Carboxyl functional groups attached to the unlinked peptide crosslinks of peptidoglycan and phosphoryl groups associated with the teichoic acids can deprotonate to form negatively charged surface sites. These anionic functional groups generate charge in the cell wall which results in the formation of an electric field that surrounds the entire cell. The cell surface electric field controls the concentration and spatial distribution of ions and counterions at the cell-water interface, and strongly affects microbe-fluid and microbe-mineral interactions. Recently, we have used potentiometric titration, infrared spectroscopy, electrophoretic mobility, metal sorption experiments to characterize the surface electrical potential properties of the various Gram-positive and Gram-negative bacterial species. Potentiometric titration experiments show that the deprotonation of acidic cell wall functional groups generate surface charge density values typically ranging from 1.1 to 2.2 mol sites/g of bacteria. Spectroscopic measurements have confirmed that the dominant proton-active sites in the cell wall are carboxyl functional groups. Electrophoretic mobility experiments show that the magnitude of the electrostatic surface potential increases with increasing pH, and decreases with increasing ionic strength. Metal sorption experiments conducted with Ca(II), Sr(II) and Ba(II) exhibit strong ionic strength dependence, suggesting that high concentrations of metal ions are electrostatically bound to bacterial cell walls via outer-sphere complexation. We demonstrate that the electrostatic potential effects on ion sorption at the cell-water interface can be quantified using the Donnan model.

  3. M135R is a novel cell surface virulence factor of myxoma virus.

    Science.gov (United States)

    Barrett, John W; Sypula, Joanna; Wang, Fuan; Alston, Lindsay R; Shao, Zhuhong; Gao, Xiujuan; Irvine, Timothy S; McFadden, Grant

    2007-01-01

    Myxoma virus (MV) encodes a cell surface protein (M135R) that is predicted to mimic the host alpha/beta interferon receptor (IFN-alpha/beta-R) and thus prevent IFN-alpha/beta from triggering a host antiviral response. This prediction is based on sequence similarity to B18R, the viral IFN-alpha/beta-R from vaccinia virus (VV), which has been demonstrated to bind and inhibit type I interferons. However, M135R is only half the size of VV B18R. All other poxvirus-encoded IFN-alpha/beta-R homologs align only to the amino-terminal half of M135R. Peptide antibodies raised against M135R were used for immunoblotting and immunofluorescence and indicate that M135R is expressed as an early gene and that the product is a cell surface N-linked glycoprotein that is not secreted. In contrast to the predicted properties of M135R as an inhibitor of type I interferon, all binding and inhibition assays designed to demonstrate whether M135R can interact with IFN-alpha/beta have been negative. However, pathogenesis studies with a targeted M135-knockout MV construct (vMyx135KO) indicate that the deletion of M135R severely attenuates MV pathogenesis in the European rabbit. We propose that M135R is an important immunomodulatory virulence factor for myxomatosis but that the target immune ligand is not from the predicted type I interferon family and remains to be identified. PMID:17065210

  4. Development of living cell force sensors for the interrogation of cell surface interactions

    Science.gov (United States)

    Brown, Scott Chang

    The measurement of cell surface interactions, or cell interaction forces, are critical for the early diagnosis and prevention of disease, the design of targeted drug and gene delivery vehicles, the development of next-generation implant materials, and much more. However, the technologies and devices that are currently available are highly limited with respect to the dynamic force range over which they can measure cell-cell or cell-substratum interactions, and with their ability to adequately mimic biologically relevant systems. Consequently, research efforts that involve cell surface interactions have been limited. In this dissertation, existing tools for research at the nanoscale (i.e., atomic force microscopy microcantilevers) are modified to develop living cell force sensors that allow for the highly sensitive measurement of cell-mediated interactions over the entire range of forces expected in biotechnology (and nano-biotechnology) research (from a single to millions of receptor-ligand bonds). Several force sensor motifs have been developed that can be used to measure interactions using single adherent cells, single suspension culture cell, and cell monolayers (tissues) over a wide range of interaction conditions (e.g., approach velocity, shear rate, contact time) using a conventional atomic force microscope. This new tool has been applied to study the pathogenesis of spontaneous pneumothorax and the interaction of cells with 14 man-made interfaces. Consequently, a new hypothesis of the interactions that manifest spontaneous pneumothorax has been developed. Additionally, these findings have the potential to lead to the development of tools for data mining materials and surfaces for unique cell interactions that could have an immense societal impact.

  5. Air pollution particles activate NF-κB on contact with airway epithelial cell surfaces

    International Nuclear Information System (INIS)

    Air pollution particles (PM) are known to elicit an acute inflammatory response in vivo that is mediated in part through PM-induced activation of the NF-κB signaling pathway. Many of the details of this process and particularly where in the cell it occurs are unclear. To determine whether contact of PM particles with an epithelial cell surface activates NF-κB, rat tracheal explants were exposed to Ottawa Urban Air Particles or iron-loaded fine TiO2, a model PM particle, for up to 2 h. During this period, there was no evidence of particle entry into the tracheal epithelial cells by light or electron microscopy, but both types of particle activated NF-κB as assayed by gel shifts. NF-κB activation could be inhibited by the active oxygen species scavenger, tetramethylthiourea; the redox-inactive metal chelator, deferoxamine; the Src inhibitor, PP2; and the epidermal growth factor (EGF) receptor inhibitor AG1478. An iron-containing citrate extract of both dusts also produced NF-κB activation. Both dusts and a citrate extract caused phosphorylation of the EGF receptor on tyrosine 845, an indicator of Src activity. We conclude that iron-containing PM particles can activate NF-κB via a pathway involving Src and the EGF receptor. This process does not require entry of particles into the airway epithelial cells but is dependent on the presence of iron and generation of active oxygen species by the dusts. These findings imply that even brief contact of PM with a pulmonary epithelial cell surface may produce deleterious effects in vivo

  6. Soluble CD44 interacts with intermediate filament protein vimentin on endothelial cell surface.

    Science.gov (United States)

    Päll, Taavi; Pink, Anne; Kasak, Lagle; Turkina, Marina; Anderson, Wally; Valkna, Andres; Kogerman, Priit

    2011-01-01

    CD44 is a cell surface glycoprotein that functions as hyaluronan receptor. Mouse and human serum contain substantial amounts of soluble CD44, generated either by shedding or alternative splicing. During inflammation and in cancer patients serum levels of soluble CD44 are significantly increased. Experimentally, soluble CD44 overexpression blocks cancer cell adhesion to HA. We have previously found that recombinant CD44 hyaluronan binding domain (CD44HABD) and its non-HA-binding mutant inhibited tumor xenograft growth, angiogenesis, and endothelial cell proliferation. These data suggested an additional target other than HA for CD44HABD. By using non-HA-binding CD44HABD Arg41Ala, Arg78Ser, and Tyr79Ser-triple mutant (CD443MUT) we have identified intermediate filament protein vimentin as a novel interaction partner of CD44. We found that vimentin is expressed on the cell surface of human umbilical vein endothelial cells (HUVEC). Endogenous CD44 and vimentin coprecipitate from HUVECs, and when overexpressed in vimentin-negative MCF-7 cells. By using deletion mutants, we found that CD44HABD and CD443MUT bind vimentin N-terminal head domain. CD443MUT binds vimentin in solution with a Kd in range of 12-37 nM, and immobilised vimentin with Kd of 74 nM. CD443MUT binds to HUVEC and recombinant vimentin displaces CD443MUT from its binding sites. CD44HABD and CD443MUT were internalized by wild-type endothelial cells, but not by lung endothelial cells isolated from vimentin knock-out mice. Together, these data suggest that vimentin provides a specific binding site for soluble CD44 on endothelial cells. PMID:22216242

  7. Role of calcium in growth inhibition induced by a novel cell surface sialoglycopeptide

    Science.gov (United States)

    Betz, N. A.; Westhoff, B. A.; Johnson, T. C.; Spooner, B. S. (Principal Investigator)

    1995-01-01

    Our laboratory has purified an 18 kDa cell surface sialoglycopeptide growth inhibitor (CeReS-18) from intact bovine cerebral cortex cells. Evidence presented here demonstrates that sensitivity to CeReS-18-induced growth inhibition in BALB-c 3T3 cells is influenced by calcium, such that a decrease in the calcium concentration in the growth medium results in an increase in sensitivity to CeReS-18. Calcium did not alter CeReS-18 binding to its cell surface receptor and CeReS-18 does not bind calcium directly. Addition of calcium, but not magnesium, to CeReS-18-inhibited 3T3 cells results in reentry into the cell cycle. A greater than 3-hour exposure to increased calcium is required for escape from CeReS-18-induced growth inhibition. The calcium ionophore ionomycin could partially mimic the effect of increasing extracellular calcium, but thapsigargin was ineffective in inducing escape from growth inhibition. Increasing extracellular calcium 10-fold resulted in an approximately 7-fold increase in total cell-associated 45Ca+2, while free intracellular calcium only increased approximately 30%. However, addition of CeReS-18 did not affect total cell-associated calcium or the increase in total cell-associated calcium observed with an increase in extracellular calcium. Serum addition induced mobilization of intracellular calcium and influx across the plasma membrane in 3T3 cells, and pretreatment of 3T3 cells with CeReS-18 appeared to inhibit these calcium mobilization events. These results suggest that a calcium-sensitive step exists in the recovery from CeReS-18-induced growth inhibition. CeReS-18 may inhibit cell proliferation through a novel mechanism involving altering the intracellular calcium mobilization/regulation necessary for cell cycle progression.

  8. Identification of cell surface proteins as potential immunotherapy targets in twelve pediatric cancers

    Directory of Open Access Journals (Sweden)

    RimasJOrentas

    2012-12-01

    Full Text Available Technological advances now allow us to rapidly produce CARs and other antibody-derived therapeutics targeting cell surface receptors. To maximize the potential of these new technologies, relevant extracellular targets must be identified. The Pediatric Oncology Branch of the NCI curates a freely accessible database of gene expression data for both pediatric cancers and normal tissues, through which we have defined discrete sets of over-expressed transcripts in twelve pediatric cancer subtypes as compared to normal tissues. We coupled gene expression profiles to current annotation databases (i.e., Affymetrix, Gene Ontology, Entrez Gene, in order to categorize transcripts by their subcellular location. In this manner we generated a list of potential immune targets expressed on the cell surface, ranked by their difference from normal tissue. Global differences from normal between each of the pediatric tumor types studied varied, indicating that some malignancies expressed transcript sets that were more highly diverged from normal tissues than others. The validity of our approach is seen by our findings for pre-B cell ALL, where targets currently in clinical trials were top-ranked hits (CD19, CD22. For some cancers, reagents already in development could potentially be applied to a new disease class, as exemplified by CD30 expression on sarcomas. Moreover, several potential new targets shared among several pediatric solid tumors are herein identified, such as MCAM (MUC18, MTDH (metadherin, and GPC2 (glypican-2. These targets have been identified at the mRNA level and are yet to be validated at the protein level. The safety of targeting these antigens has yet to be demonstrated and therefore the identified transcripts should be considered preliminary candidates for new CAR and therapeutic antibody targets. Prospective candidate targets will be evaluated by proteomic analysis including Westerns and immunohistochemistry of normal and tumor tissues.

  9. Degradation of insulin by isolated mouse pancreatic acini. Evidence for cell surface protease activity

    International Nuclear Information System (INIS)

    In the present study, we have used isolated mouse pancreatic acini were used to investigate the relationship between 125I-insulin binding and its degradation in order to probe the nature and cellular localization of the degradative process. In these cells, the proteolysis of 125I-insulin was dependent on time and cell concentration, and was saturated by unlabeled insulin with a Km of 290 nM. Since this value was much higher than the Kd for insulin binding to its receptor (1.1 nM), the data indicated that 125I-insulin degradation by acini occurred primarily via nonreceptor mechanisms. Several lines of evidence suggested that insulin was being degraded by the neutral thiol protease, insulin degrading enzyme (IDE). First, insulin degradation was inhibited by thiolreacting agents such as N-ethylmaleimide and p-chloromercuribenzoate. Second, the Km for degradation in acini was similar to the reported Km for IDE in other tissues. Third, the enzyme activity had a relative mol wt of approximately 130,000 by gel filtration, a value similar to that reported for purified IDE. Fourth, the degrading activity was removed with a specific antibody to IDE. Other lines of evidence suggested that enzymes located on the cell surface played a role in insulin degradation by acini. First, the nonpenetrating sulfhydryl reacting agent 5,5' dithiobis-2-nitrobenzoic acid blocked 125I-insulin degradation. Second, a specific antibody to IDE identified the presence of the enzyme on the cell surface. Third, chloroquine, leupeptin and antipain, agents that inhibit lysosomal function, did not influence 125I-insulin degradation. Fourth, highly purified pancreatic plasma membranes degraded 125I-insulin

  10. Changes in cell surface properties of shiga toxigenic Escherichia coli by Quercus infectoria G. Olivier.

    Science.gov (United States)

    Voravuthikunchai, Supayang Piyawan; Suwalak, Sakol

    2009-08-01

    The effects of Quercus infectoria (family Fagaceae) nutgalls on cell surface properties of Shiga toxigenic Escherichia coli (STEC) were investigated with an assay of microbial adhesion to hydrocarbon. The surface of bacterial cells treated with Q. infectoria exhibited a higher level of cell surface hydrophobicity (CSH) toward toluene than did the surface of untreated cells. With 50% ethanolic extract, the CSH of the three strains of STEC O157:H7 treated with 4X MIC of the extract resulted in moderate or strong hydrophobicity, whereas at 2x MIC and MIC, the CSH of only one strain of E. coli O157:H7 was significantly affected. The 95% ethanolic extract had a significant effect on CSH of all three strains at both 4X MIC and 2X MIC but not at the MIC. The effect on bacterial CSH was less pronounced with the other STEC strains. At 4X MIC, the 50% ethanolic extract increased the CSH of all non-O157 STEC strains significantly. At 2X MIC and 4X MIC, the 95% ethanolic extract affected the CSH of E. coli O26:H11 significantly but did not affect E. coli O111 :NM or E. coli O22. Electro microscopic examination revealed the loss of pili in the treated cells. The ability of Q. infectoria extract to modify hydrophobic domains enables this extract to partition the lipids of the bacterial cell membrane, rendering the membrane more permeable and allowing leakage of ions and other cell contents, which leads to cell death. Further studies are required to evaluate the effects of Q. infectoria extract in food systems or in vivo and provide support for the use of this extract as a food additive for control of these STEC pathogens. PMID:19722403

  11. Homodimers of the Antiviral Abacavir as Modulators of P-glycoprotein Transport in Cell Culture: Probing Tether Length

    OpenAIRE

    Namanja, Hilda A.; Emmert, Dana; Hrycyna, Christine A.; Chmielewski, Jean

    2013-01-01

    A major hurdle in permanently eliminating HIV from the body is the persistence of viral reservoirs, including those of the brain. One potential strategy towards eradicating HIV reservoirs of the brain is to block efflux transporters, such as P-glycoprotein (P-gp), that contribute to the limited penetration of antiviral agents across the blood-brain barrier (BBB). Herein, we described a series of dimeric inhibitors of P-gp based on the nucleoside reverse transcriptase inhibitor and P-gp substr...

  12. Curcumin induced nanoscale CD44 molecular redistribution and antigen-antibody interaction on HepG2 cell surface

    Energy Technology Data Exchange (ETDEWEB)

    Wang Mu [Department of Chemistry, Jinan University, 601 Huangpu Road West, Tianhe District, Guangzhou 510632 (China); Ruan Yuxia [Department of Ophthalmology, The First Affiliated Hospital, Jinan University, 601 Huangpu Road West, Tianhe District, Guangzhou 510632 (China); Xing Xiaobo; Chen Qian; Peng, Yuan [Department of Chemistry, Jinan University, 601 Huangpu Road West, Tianhe District, Guangzhou 510632 (China); Cai Jiye, E-mail: tjycai@jnu.edu.cn [Department of Chemistry, Jinan University, 601 Huangpu Road West, Tianhe District, Guangzhou 510632 (China)

    2011-07-04

    Graphical abstract: Highlights: > In this study, we investigate the changes of CD44 expression and distribution on HepG2 cells after curcumin treatment. > We find curcumin is able to change the morphology and ultrastructure of HepG2 cells. > Curcumin can reduce the expression of CD44 molecules and induce the nanoscale molecular redistribution on cell surface. > The binding force between CD44-modified AFM tip and the HepG2 cell surface decreases after curcumin-treatment. - Abstract: The cell surface glycoprotein CD44 was implicated in the progression, metastasis and apoptosis of certain human tumors. In this study, we used atomic force microscope (AFM) to monitor the effect of curcumin on human hepatocellular carcinoma (HepG2) cell surface nanoscale structure. High-resolution imaging revealed that cell morphology and ultrastructure changed a lot after being treated with curcumin. The membrane average roughness increased (10.88 {+-} 4.62 nm to 129.70 {+-} 43.72 nm) and the expression of CD44 decreased (99.79 {+-} 0.16% to 75.14 {+-} 8.37%). Laser scanning confocal microscope (LSCM) imaging showed that CD44 molecules were located on the cell membrane. The florescence intensity in control group was weaker than that in curcumin treated cells. Most of the binding forces between CD44 antibodies and untreated HepG2 cell membrane were around 120-220 pN. After being incubated with curcumin, the major forces focused on 70-150 pN (10 {mu}M curcumin-treated) and 50-120 pN (20 {mu}M curcumin-treated). These results suggested that, as result of nanoscale molecular redistribution, changes of the cell surface were in response to external treatment of curcumin. The combination of AFM and LSCM could be a powerful method to detect the distribution of cell surface molecules and interactions between molecules and their ligands.

  13. Tethered N-heterocyclic carbene-carboranes: unique ligands that exhibit unprecedented and versatile coordination modes at rhodium.

    Science.gov (United States)

    Holmes, Jordan; Pask, Christopher M; Fox, Mark A; Willans, Charlotte E

    2016-05-11

    Four brand new hybrid ligands combining an N-heterocyclic carbene tethered with two isomeric nido-dicarbaundecaborane dianions, a neutral closo-dicarbadodecaborane or a closo-dicarbadodecaborane anion are described. Versatile coordination of the ligands to Rh(I) is demonstrated, in which both NHC and carborane moieties covalently coordinate a metal centre. PMID:27098432

  14. The Human Acid-Sensing Ion Channel ASIC1a: Evidence for a Homotetrameric Assembly State at the Cell Surface

    OpenAIRE

    van Bemmelen, Miguel Xavier; Huser, Delphine; Gautschi, Ivan; Schild, Laurent

    2015-01-01

    The chicken acid-sensing ion channel ASIC1 has been crystallized as a homotrimer. We address here the oligomeric state of the functional ASIC1 in situ at the cell surface. The oligomeric states of functional ASIC1a and mutants with additional cysteines introduced in the extracellular pore vestibule were resolved on SDS-PAGE. The functional ASIC1 complexes were stabilized at the cell surface of Xenopus laevis oocytes or CHO cells either using the sulfhydryl crosslinker BMOE, or sodium tetrathi...

  15. Alterations of electrical charge and receptors to lectins mouse lymphoma cells surface in early terms after irradiation

    International Nuclear Information System (INIS)

    Modifications of structural and functional state of OH-1 mouse lymphoma cells surface in early terms after gamma-irradiation with doses from 0.1 Gy to 10 Gy were studied. For this purpose, the methods of cell separation in a two-phase polymer system (dextran-PEG) and cell surface receptors binding with some plant lectins were used. It was revealed the decreased surface electrical charge that reached its maximum deflection 3 hours after gamma-irradiation. At the same time-dose dependent expression of irradiated cells, membrane receptors to the lectins of various specificity was observed

  16. The structure and function of the urokinase receptor, a membrane protein governing plasminogen activation on the cell surface

    DEFF Research Database (Denmark)

    Behrendt, N; Rønne, E; Danø, K

    1995-01-01

    PA receptor, uPAR, is a cell-surface protein which plays an important role in the localization and regulation of these processes. In the present article a number of established conclusions concerning the structure and function of uPAR are presented, and in addition various models are discussed which might...... domain is directly involved in the molecular contact with uPA. The receptor binds uPA as well as its proenzyme, pro-uPA, in such a manner that the activation cascade can occur directly on the cell surface. Furthermore, the activation rates are enhanced relative to the situation in solution, probably due...

  17. Cell surface N-glycans influence the level of functional E-cadherin at the cell–cell border

    OpenAIRE

    M Kristen Hall; Douglas A Weidner; Sahil Dayal; Ruth A. Schwalbe

    2014-01-01

    E-cadherin is crucial for adhesion of cells to each other and thereby development and maintenance of tissue. While it is has been established that N-glycans inside the cell impact the level of E-cadherin at the cell surface of epithelial-derived cells, it is unclear whether N-glycans outside the cell control the clustering of E-cadherin at the cell–cell border. Here, we demonstrate reduction of N-glycans at the cell surface weakened the recruitment and retention of E-cadherin at the cell–cell...

  18. A new class of tunable hypersonic phononic crystals based on polymer-tethered colloids

    Science.gov (United States)

    Alonso-Redondo, E.; Schmitt, M.; Urbach, Z.; Hui, C. M.; Sainidou, R.; Rembert, P.; Matyjaszewski, K.; Bockstaller, M. R.; Fytas, G.

    2015-09-01

    The design and engineering of hybrid materials exhibiting tailored phononic band gaps are fundamentally relevant to innovative material technologies in areas ranging from acoustics to thermo-optic devices. Phononic hybridization gaps, originating from the anti-crossing between local resonant and propagating modes, have attracted particular interest because of their relative robustness to structural disorder and the associated benefit to `manufacturability'. Although hybridization gap materials are well known, their economic fabrication and efficient control of the gap frequency have remained elusive because of the limited property variability and expensive fabrication methodologies. Here we report a new strategy to realize hybridization gap materials by harnessing the `anisotropic elasticity' across the particle-polymer interface in densely polymer-tethered colloidal particles. Theoretical and Brillouin scattering analysis confirm both the robustness to disorder and the tunability of the resulting hybridization gap and provide guidelines for the economic synthesis of new materials with deliberately controlled gap position and width frequencies.

  19. Tether Transport System Study Summary Performed under Contract to Marshall Space Flight Center

    Science.gov (United States)

    Vonderwell, Dan; Bangham, Mike; Dionne, Heather; Fleming, Beth; Klus, Bill; Herring, Karmel; Suggs, Elton; Walker, Larry; Lorenzini, Enrico; Cosmo, Mario L.; Kaiser, Markus; Vestal, Linda; Johnson, Les; Carrington, Connie

    1998-01-01

    The main rationale for this study is to reduce the mission cost of transporting payloads to GEO. A two stage tether transport system was proposed for boosting payloads from LEO to GTO/GEO. The feasibility of the concept is addressed from the point of view of orbital mechanics and other principles of physics. The report presents the results of an engineering analysis that defines the system, major elements and subsystems, and assesses the feasibility (i.e., the technology readiness level) of designing and developing the system. Results indicate that significant cost savings can be realized over traditional upper stages within a few launches. Certain key technical issues, such as payload rendezvous and capture, need to be addressed in future studies. Advancements in certain technology areas, such as power generation and highly efficient propulsion systems, will have significant effects on the overall system design.

  20. Direct mechanical stimulation of tip links in hair cells through DNA tethers

    Science.gov (United States)

    Basu, Aakash; Lagier, Samuel; Vologodskaia, Maria; Fabella, Brian A; Hudspeth, AJ

    2016-01-01

    Mechanoelectrical transduction by hair cells commences with hair-bundle deflection, which is postulated to tense filamentous tip links connected to transduction channels. Because direct mechanical stimulation of tip links has not been experimentally possible, this hypothesis has not been tested. We have engineered DNA tethers that link superparamagnetic beads to tip links and exert mechanical forces on the links when exposed to a magnetic-field gradient. By pulling directly on tip links of the bullfrog's sacculus we have evoked transduction currents from hair cells, confirming the hypothesis that tension in the tip links opens transduction channels. This demonstration of direct mechanical access to tip links additionally lays a foundation for experiments probing the mechanics of individual channels. DOI: http://dx.doi.org/10.7554/eLife.16041.001 PMID:27331611