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Sample records for cell membrane fraction

  1. Lipids that determine detergent resistance of MDCK cell membrane fractions.

    PubMed

    Manni, Marco M; Cano, Ainara; Alonso, Cristina; Goñi, Félix M

    2015-10-01

    A comparative lipidomic study has been performed of whole Madin-Darby canine kidney epithelial cells and of the detergent-resistant membrane fraction (DRM) obtained after treating the cells with the non-ionic detergent Triton X-100. The DRM were isolated following a standard procedure that is extensively used in cell biology studies. Significant differences were found in the lipid composition of the whole cells and of DRM. The latter were enriched in all the analyzed sphingolipid classes: sphingomyelins, ceramides and hexosylceramides. Diacylglycerols were also preferentially found in DRM. The detergent-resistant fraction was also enriched in saturated over unsaturated fatty acyl chains, and in sn-1 acyl chains containing 16 carbon atoms, over the longer and shorter ones. The glycerophospholipid species phosphatidylethanolamines and phosphatidylinositols, that were mainly unsaturated, did not show a preference for DRM. Phosphatidylcholines were an intermediate case: the saturated, but not the unsaturated species were found preferentially in DRM. The question remains on whether these DRM, recovered from detergent-membrane mixtures by floatation over a sucrose gradient, really correspond to membrane domains existing in the cell membrane prior to detergent treatment. PMID:26320877

  2. Fraction Reduction in Membrane Systems

    PubMed Central

    Zhang, Hong

    2014-01-01

    Fraction reduction is a basic computation for rational numbers. P system is a new computing model, while the current methods for fraction reductions are not available in these systems. In this paper, we propose a method of fraction reduction and discuss how to carry it out in cell-like P systems with the membrane structure and the rules with priority designed. During the application of fraction reduction rules, synchronization is guaranteed by arranging some special objects in these rules. Our work contributes to performing the rational computation in P systems since the rational operands can be given in the form of fraction. PMID:24772037

  3. Fractional order models of viscoelasticity as an alternative in the analysis of red blood cell (RBC) membrane mechanics.

    PubMed

    Craiem, Damian; Magin, Richard L

    2010-01-01

    New lumped-element models of red blood cell mechanics can be constructed using fractional order generalizations of springs and dashpots. Such 'spring-pots' exhibit a fractional order viscoelastic behavior that captures a wide spectrum of experimental results through power-law expressions in both the time and frequency domains. The system dynamics is fully described by linear fractional order differential equations derived from first order stress-strain relationships using the tools of fractional calculus. Changes in the composition or structure of the membrane are conveniently expressed in the fractional order of the model system. This approach provides a concise way to describe and quantify the biomechanical behavior of membranes, cells and tissues. PMID:20090192

  4. Affinity labeling and binding of nitrobenzylthionosine (NBTI) to a membrane fraction (MF) of cultured cell lines

    SciTech Connect

    Woffendin, C.; Plagemann, P.G.W.

    1986-05-01

    Equilibrium binding identified high affinity NBTI binding sites (K/sub D/ = 1-3 nM) on the MF's of L929, L1210, P388, S49 and CHO cells. High affinity NBTI binding sites are associated with the nucleoside transporter since none were present in a MF of a transport-deficient mutant of S49 cells (AE1). MF's of Novikoff cells, like intact Novikoff cells, also lacked high affinity NBTI binding sites. MF's of the cell lines were equilibrium labeled with (/sup 3/H)NBTI using photoaffinity conditions and analyzed by SDS-polyacrylamide gel electrophoresis. Radioactivity was specifically incorporated covalently into a 50-70 Kd protein fraction, but the labeled proteins from CHO and L929 cells had a higher apparent molecular weight than those from S49 and P388 cells. In addition, in MF's from some cell lines lower molecular weight components became photoaffinity labeled. Maximum photoaffinity labeling of the MF proteins was observed with much higher (/sup 3/H)NBTI concentrations (100-200 nM) than those saturating the nucleoside transporter. This finding is explained by a reduced affinity of the photoactivated NBTI intermediate(s) for the transporter. When detergent solubilized MF's from cultured cells were chromotographed on a DEAE cellulose column, only 5-10% of the protein, but practically all high affinity NBTI sites, were recovered in the flow through fraction.

  5. Isolation of Endoplasmic Reticulum, Mitochondria, and Mitochondria-Associated Membrane and Detergent Resistant Membrane Fractions from Transfected Cells and from Human Cytomegalovirus-Infected Primary Fibroblasts.

    PubMed

    Williamson, Chad D; Wong, Daniel S; Bozidis, Petros; Zhang, Aiping; Colberg-Poley, Anamaris M

    2015-01-01

    Increasingly mechanistic virology studies require dependable and sensitive methods for isolating purified organelles containing functional cellular sub-domains. The mitochondrial network is, in part, closely apposed to the endoplasmic reticulum (ER). The mitochondria-associated membrane (MAM) fraction provides direct physical contact between the ER and mitochondria. Characterization of the dual localization and trafficking of human cytomegalovirus (HCMV) UL37 proteins required establishing protocols in which the ER and mitochondria could be reliably separated. Because of its documented role in lipid and ceramide transfer from the ER to mitochondria, a method to purify MAM from infected cells was also developed. Two robust procedures were developed to efficiently isolate mitochondria, ER, and MAM fractions while providing substantial protein yields from HCMV-infected primary fibroblasts and from transfected HeLa cells. Furthermore, this unit includes protocols for isolation of detergent resistant membranes from subcellular fractions as well as techniques that allow visualization of the mitochondrial network disruption that occurs in permissively infected cells by their optimal resolution in Percoll gradients. © 2015 by John Wiley & Sons, Inc. PMID:26331984

  6. Isolation and Analysis of Detergent-Resistant Membrane Fractions.

    PubMed

    Aureli, Massimo; Grassi, Sara; Sonnino, Sandro; Prinetti, Alessandro

    2016-01-01

    The hypothesis that the Golgi apparatus is capable of sorting proteins and sending them to the plasma membrane through "lipid rafts," membrane lipid domains highly enriched in glycosphingolipids, sphingomyelin, ceramide, and cholesterol, was formulated by van Meer and Simons in 1988 and came to a turning point when it was suggested that lipid rafts could be isolated thanks to their resistance to solubilization by some detergents, namely Triton X-100. An incredible number of papers have described the composition and properties of detergent-resistant membrane fractions. However, the use of this method has also raised the fiercest criticisms. In this chapter, we would like to discuss the most relevant methodological aspects related to the preparation of detergent-resistant membrane fractions, and to discuss the importance of discriminating between what is present on a cell membrane and what we can prepare from cell membranes in a laboratory tube. PMID:26552679

  7. Contamination of nuclear fractions with plasma membrane lipid rafts.

    PubMed

    Say, Yee-How; Hooper, Nigel M

    2007-04-01

    Subcellular fractionation is central to a range of cell biological, biochemical and proteomic studies. Purification of nuclear-enriched fractions is critical for studies on nuclear structure and function. Here we show that detergent-based nuclear isolation methods cause the redistribution of proteins associated with plasma membrane lipid rafts into nuclear fractions. The glycosyl-phosphatidylinositol (GPI)-anchored prion protein (PrP(C)) and a GPI-anchored construct of angiotensin converting enzyme (GPI-ACE), as well as the lipid raft markers flotillin-1 and -2, were present in the nuclear fractions derived using three different subcellular fractionation protocols. Incubation of intact cells with bacterial phosphatidylinositol-specific phospholipase C (PI-PLC), which cleaves GPI-anchored proteins from the cell surface, significantly reduced the amount of PrP(C) and GPI-ACE in the nuclear fraction. Buoyant sucrose density gradient centrifugation in the presence of Triton X-100 of the nuclear fraction resulted in a significant proportion of the GPI-anchored proteins being recovered in the low density lipid raft fractions. These data indicate that the nuclear fraction isolated using such subcellular fractionation protocols is contaminated with components of plasma membrane lipid rafts and raises questions as to the integrity of the nuclear fraction isolated by such protocols for use in detailed cell biological studies and proteomics analysis. PMID:17351887

  8. A novel regulatory mechanism for trimeric GTP-binding proteins in the membrane and secretory granule fractions of human and rodent beta cells.

    PubMed

    Kowluru, A; Seavey, S E; Rhodes, C J; Metz, S A

    1996-01-01

    Recently we described roles for heterotrimeric and low-molecular-mass GTP-binding proteins in insulin release from normal rat islets. During these studies, we observed that a protein with an apparent molecular mass (37 kDa) similar to that of the beta subunit of trimeric GTP-binding proteins underwent phosphorylation in each of five classes of insulin-secreting cells. Incubation of the beta cell total membrane fraction or the isolated secretory granule fraction (but not the cytosolic fraction) with [gamma-32P]ATP or [gamma-32P]GTP resulted in the phosphorylation of this protein, which was selectively immunoprecipitated by an anti-serum directed against the common beta subunit of trimeric G-proteins. Disruption of the alpha beta gamma trimer (by pretreatment with either fluoroaluminate or guanosine 5'(-)[gamma-thio]triphosphate) prevented beta subunit phosphorylation. Based on differential sensitivities to pH, heat and the histidine-selective reagent diethyl pyrocarbonate (and reversal of the latter by hydroxylamine), the phosphorylated amino acid was presumptively identified as histidine. Incubation of pure beta subunit alone or in combination with the exogenous purified alpha subunit of transducin did not result in the phosphorylation of the beta subunit, but addition of the islet cell membrane fraction did support this event, suggesting that membrane localization (or a membrane-associated factor) is required for beta subunit phosphorylation. Incubation of phosphorylated beta subunit with G alpha.GDP accelerated the dephosphorylation of the beta subunit, accompanied by the formation of G alpha-GTP. Immunoblotting detected multiple alpha subunits (of Gi, G(o) and Gq) and at least one beta subunit in the secretory granule fraction of normal rat islets and insulinoma cells. These data describe a potential alternative mechanism for the activation of GTP-binding proteins in beta cells which contrasts with the classical receptor-agonist mechanism: G beta undergoes transient phosphorylation at a histidine residue by a GTP-specific protein kinase; this phosphate, in turn, may be transferred via a classical Ping-Pong mechanism to G alpha.GDP (inactive), yielding the active configuration G alpha.GTP in secretory granules (a strategic location to modulate exocytosis). PMID:8546716

  9. Identification of novel autophagic Radix Polygalae fraction by cell membrane chromatography and UHPLC-(Q)TOF-MS for degradation of neurodegenerative disease proteins

    PubMed Central

    Wu, An-Guo; Kam-Wai Wong, Vincent; Zeng, Wu; Liu, Liang; Yuen-Kwan Law, Betty

    2015-01-01

    With its traditional use in relieving insomnia and anxiety, our previous study has identified onjisaponin B from Radix Polygalae (RP), as a novel autophagic enhancer with potential neuroprotective effects. In current study, we have further identified a novel active fraction from RP, contains 17 major triterpenoid saponins including the onjisaponin B, by the combinational use of cell membrane chromatography (CMC) and ultra-performance liquid chromatography coupled to (quadrupole) time-of-flight mass spectrometry {UHPLC-(Q)TOF-MS}. By exhibiting more potent autophagic effect in cells, the active fraction enhances the clearance of mutant huntingtin, and reduces protein level and aggregation of ?-synuclein in a higher extent when compared with onjisaponin B. Here, we have reported for the first time the new application of cell-based CMC and UHPLC-(Q)TOF-MS analysis in identifying new autophagy inducers with neuroprotective effects from Chinese medicinal herb. This result has provided novel insights into the possible pharmacological actions of the active components present in the newly identified active fraction of RP, which may help to improve the efficacy of the traditional way of prescribing RP, and also provide new standard for the quality control of decoction of RP or its medicinal products in the future. PMID:26598009

  10. Identification of novel autophagic Radix Polygalae fraction by cell membrane chromatography and UHPLC-(Q)TOF-MS for degradation of neurodegenerative disease proteins.

    PubMed

    Wu, An-Guo; Kam-Wai Wong, Vincent; Zeng, Wu; Liu, Liang; Yuen-Kwan Law, Betty

    2015-01-01

    With its traditional use in relieving insomnia and anxiety, our previous study has identified onjisaponin B from Radix Polygalae (RP), as a novel autophagic enhancer with potential neuroprotective effects. In current study, we have further identified a novel active fraction from RP, contains 17 major triterpenoid saponins including the onjisaponin B, by the combinational use of cell membrane chromatography (CMC) and ultra-performance liquid chromatography coupled to (quadrupole) time-of-flight mass spectrometry {UHPLC-(Q)TOF-MS}. By exhibiting more potent autophagic effect in cells, the active fraction enhances the clearance of mutant huntingtin, and reduces protein level and aggregation of ?-synuclein in a higher extent when compared with onjisaponin B. Here, we have reported for the first time the new application of cell-based CMC and UHPLC-(Q)TOF-MS analysis in identifying new autophagy inducers with neuroprotective effects from Chinese medicinal herb. This result has provided novel insights into the possible pharmacological actions of the active components present in the newly identified active fraction of RP, which may help to improve the efficacy of the traditional way of prescribing RP, and also provide new standard for the quality control of decoction of RP or its medicinal products in the future. PMID:26598009

  11. Composite fuel cell membranes

    DOEpatents

    Plowman, K.R.; Rehg, T.J.; Davis, L.W.; Carl, W.P.; Cisar, A.J.; Eastland, C.S.

    1997-08-05

    A bilayer or trilayer composite ion exchange membrane is described suitable for use in a fuel cell. The composite membrane has a high equivalent weight thick layer in order to provide sufficient strength and low equivalent weight surface layers for improved electrical performance in a fuel cell. In use, the composite membrane is provided with electrode surface layers. The composite membrane can be composed of a sulfonic fluoropolymer in both core and surface layers.

  12. Composite fuel cell membranes

    DOEpatents

    Plowman, Keith R. (Lake Jackson, TX); Rehg, Timothy J. (Lake Jackson, TX); Davis, Larry W. (West Columbia, TX); Carl, William P. (Marble Falls, TX); Cisar, Alan J. (Cypress, TX); Eastland, Charles S. (West Columbia, TX)

    1997-01-01

    A bilayer or trilayer composite ion exchange membrane suitable for use in a fuel cell. The composite membrane has a high equivalent weight thick layer in order to provide sufficient strength and low equivalent weight surface layers for improved electrical performance in a fuel cell. In use, the composite membrane is provided with electrode surface layers. The composite membrane can be composed of a sulfonic fluoropolymer in both core and surface layers.

  13. Plant cell membranes

    SciTech Connect

    Packer, L.; Douce, R.

    1987-01-01

    The contents of this book are: Cells, Protoplasts, Vacuoles and Liposomes; Tonoplasts; Nuclei, Endolplasmic Reticulum, and Plasma Membrane; Peroxisomes; Plastids; Teneral Physical and Biochemical Methods; and Mitochondira.

  14. Cellulose-Based Membranes for Solutes Fractionation

    NASA Astrophysics Data System (ADS)

    Anokhina, T. S.; Yushkin, A. A.; Volkov, V. V.; Antonov, S. V.; Volkov, A. V.

    This work was focused on investigation of industrial cellophane film as a membrane material for solvent nanofiltration. The effect of conditioning of cellophane membranes by stepwise changing of composition of ethanol-water binary mixtures (from ethanol to water and from water to ethanol) was studied. It was shown that such treatment leads to an increase of ethanol permeability more than two orders of magnitude over initial untreated film samples. Treated cellophane membranes possess the ethanol permeability coefficient comparable with the values for highly permeability glassy polymers. Investigation of cellophane swelling in water ethanol solutions allowed to conclude that during the treatment formation of porous in the film takes place due to increase of inter chain distances. Observed high ethanol permeability connected with the fact that formed porous structure remains after the replacement of water with ethanol. Also it was shown that rejection coefficients of a number of dyes (MW 350) were in good agreement with the degree of hydrophobicity/hydrophilicity and ability of the solvent to form hydrogen bonding with the solute molecules. It was demonstrated that cellulose-based membranes can be complimentary for other type of the membranes in fractionation of multi-components solutions.

  15. Membrane in cancer cells

    SciTech Connect

    Galeotti, T.; Cittadini, A.; Neri, G.; Scarpa, A.

    1988-01-01

    This book contains papers presented at a conference on membranes in cancer cells. Topics covered include Oncogenies, hormones, and free-radical processes in malignant transformation in vitro and Superoxide onion may trigger DNA strand breaks in human granulorytes by acting as a membrane target.

  16. Analysis of the Phosphoinositide Composition of Subcellular Membrane Fractions.

    PubMed

    Sarkes, Deborah A; Rameh, Lucia E

    2016-01-01

    Phosphoinositides play critical roles in the transduction of extracellular signals through the plasma membrane and also in endomembrane events important for vesicle trafficking and organelle function (Di Paolo and De Camilli, Nature 443(7112):651-657, 2006). The response triggered by these lipids is heavily dependent on the microenvironment in which they are found. HPLC analysis of labeled phosphoinositides allows quantification of the levels of each phosphoinositide species relative to their precursor, phosphatidylinositol. When combined with subcellular fractionation techniques, this strategy allows measurement of the relative phosphoinositide composition of each membrane fraction or organelle and determination of the microenvironment in which each species is enriched. Here, we describe the steps to separate and quantify total or localized phosphoinositides from cultured cells. PMID:26552687

  17. Membrane Cells for Brine Electrolysis.

    ERIC Educational Resources Information Center

    Tingle, M.

    1982-01-01

    Membrane cells were developed as alternatives to mercury and diaphragm cells for the electrolysis of brine. Compares the three types of cells, focusing on the advantages and disadvantages of membrane cells. (JN)

  18. Fuel cell membrane humidification

    DOEpatents

    Wilson, Mahlon S. (Los Alamos, NM)

    1999-01-01

    A polymer electrolyte membrane fuel cell assembly has an anode side and a cathode side separated by the membrane and generating electrical current by electrochemical reactions between a fuel gas and an oxidant. The anode side comprises a hydrophobic gas diffusion backing contacting one side of the membrane and having hydrophilic areas therein for providing liquid water directly to the one side of the membrane through the hydrophilic areas of the gas diffusion backing. In a preferred embodiment, the hydrophilic areas of the gas diffusion backing are formed by sewing a hydrophilic thread through the backing. Liquid water is distributed over the gas diffusion backing in distribution channels that are separate from the fuel distribution channels.

  19. Gas phase fractionation method using porous ceramic membrane

    DOEpatents

    Peterson, Reid A. (Madison, WI); Hill, Jr., Charles G. (Madison, WI); Anderson, Marc A. (Madison, WI)

    1996-01-01

    Flaw-free porous ceramic membranes fabricated from metal sols and coated onto a porous support are advantageously used in gas phase fractionation methods. Mean pore diameters of less than 40 .ANG., preferably 5-20 .ANG. and most preferably about 15 .ANG., are permeable at lower pressures than existing membranes. Condensation of gases in small pores and non-Knudsen membrane transport mechanisms are employed to facilitate and increase membrane permeability and permselectivity.

  20. Enzymatic activities in cell fractions of mycoplasmalike organisms purified from aster yellows-infected plants.

    PubMed Central

    Arora, Y K; Sinha, R C

    1985-01-01

    Mycoplasmalike organisms (MLOs), purified from aster yellows-infected plants were osmotically lysed, and the membranes were separated from the cytoplasmic fraction through differential centrifugation. Electron microscopic examinations of sections of the purified MLOs and the isolated membranes showed pleomorphic bodies and unit membranous empty vesicles, respectively. Cell fractions were tested for NADH oxidase, NADPH oxidase, ATPase, RNase, DNase, and p-nitrophenyl phosphatase activity. NADH oxidase and ATPase were confined to the membrane fraction and NADPH oxidase to the cytoplasmic fraction of the MLOs. para-Nitrophenyl phosphatase, RNase, and DNase activities were detected in both membrane and cytoplasmic fractions, but p-nitrophenyl phosphatase and RNase appeared to be associated with membranes and DNase with the cytoplasmic fraction. Glucose-6-phosphate dehydrogenase was found in the cytoplasmic fraction of the MLO cells. Our findings on the distribution of enzymes in MLO cells and cell fractions are the first basic documentation on nonhelical, nonculturable microbes parasitic to plants. Images PMID:2997132

  1. Membrane capacitive memory alters spiking in neurons described by the fractional-order Hodgkin-Huxley model.

    PubMed

    Weinberg, Seth H

    2015-01-01

    Excitable cells and cell membranes are often modeled by the simple yet elegant parallel resistor-capacitor circuit. However, studies have shown that the passive properties of membranes may be more appropriately modeled with a non-ideal capacitor, in which the current-voltage relationship is given by a fractional-order derivative. Fractional-order membrane potential dynamics introduce capacitive memory effects, i.e., dynamics are influenced by a weighted sum of the membrane potential prior history. However, it is not clear to what extent fractional-order dynamics may alter the properties of active excitable cells. In this study, we investigate the spiking properties of the neuronal membrane patch, nerve axon, and neural networks described by the fractional-order Hodgkin-Huxley neuron model. We find that in the membrane patch model, as fractional-order decreases, i.e., a greater influence of membrane potential memory, peak sodium and potassium currents are altered, and spike frequency and amplitude are generally reduced. In the nerve axon, the velocity of spike propagation increases as fractional-order decreases, while in a neural network, electrical activity is more likely to cease for smaller fractional-order. Importantly, we demonstrate that the modulation of the peak ionic currents that occurs for reduced fractional-order alone fails to reproduce many of the key alterations in spiking properties, suggesting that membrane capacitive memory and fractional-order membrane potential dynamics are important and necessary to reproduce neuronal electrical activity. PMID:25970534

  2. Membrane Capacitive Memory Alters Spiking in Neurons Described by the Fractional-Order Hodgkin-Huxley Model

    PubMed Central

    Weinberg, Seth H.

    2015-01-01

    Excitable cells and cell membranes are often modeled by the simple yet elegant parallel resistor-capacitor circuit. However, studies have shown that the passive properties of membranes may be more appropriately modeled with a non-ideal capacitor, in which the current-voltage relationship is given by a fractional-order derivative. Fractional-order membrane potential dynamics introduce capacitive memory effects, i.e., dynamics are influenced by a weighted sum of the membrane potential prior history. However, it is not clear to what extent fractional-order dynamics may alter the properties of active excitable cells. In this study, we investigate the spiking properties of the neuronal membrane patch, nerve axon, and neural networks described by the fractional-order Hodgkin-Huxley neuron model. We find that in the membrane patch model, as fractional-order decreases, i.e., a greater influence of membrane potential memory, peak sodium and potassium currents are altered, and spike frequency and amplitude are generally reduced. In the nerve axon, the velocity of spike propagation increases as fractional-order decreases, while in a neural network, electrical activity is more likely to cease for smaller fractional-order. Importantly, we demonstrate that the modulation of the peak ionic currents that occurs for reduced fractional-order alone fails to reproduce many of the key alterations in spiking properties, suggesting that membrane capacitive memory and fractional-order membrane potential dynamics are important and necessary to reproduce neuronal electrical activity. PMID:25970534

  3. The First Cell Membranes

    NASA Technical Reports Server (NTRS)

    Vondrak, Richard R. (Technical Monitor); Demner, David; Dworkin, Jason P.; Sandford, Scott A.; Bernstein, Max P.; Allamandola, Louis J.

    2002-01-01

    Organic compounds are synthesized in the interstellar medium and can be delivered to planetary surfaces such as the early Earth, where they mix with endogenous organic mixtures. Some of these compounds are amphiphilic, having polar and non-polar groups on the same molecule. Amphiphilic compounds spontaneously self-assembly into more complex structures such as bimolecular layers, which in turn form closed membranous vesicles. The first forms of cellular life required self-assembled membranes that were likely to be available on the prebiotic Earth. Laboratory simulations show that such vesicles readily encapsulate functional macromolecules, including nucleic acids and polymerases. A goal of future investigations is to fabricate artificial cells as models of the origin of life.

  4. The First Cell Membranes

    NASA Technical Reports Server (NTRS)

    Deamer, David; Dworkin, Jason P.; Sandford, Scott A.; Bernstein, Max P.; Allamandola, Louis J.

    2004-01-01

    Organic compounds are synthesized in the interstellar medium and can be delivered to planetary surfaces such as the early Earth, where they mix with endogenous organic mixtures. Some of these compounds are amphiphilic, having polar and non-polar groups on the same molecule. Amphiphilic compounds spontaneously self-assembly into more complex structures such as bimolecular layers, which in turn form closed membranous vesicles. The first forms of cellular life required self-assembled membranes that were likely to be available on the prebiotic Earth. Laboratory simulations show that such vesicles readily encapsulate functional macromolecules, including nucleic acids and polymerases. A goal of future investigations is to fabricate artificial cells as models of the origin of life.

  5. Fuel cell with ionization membrane

    NASA Technical Reports Server (NTRS)

    Hartley, Frank T. (Inventor)

    2007-01-01

    A fuel cell is disclosed comprising an ionization membrane having at least one area through which gas is passed, and which ionizes the gas passing therethrough, and a cathode for receiving the ions generated by the ionization membrane. The ionization membrane may include one or more openings in the membrane with electrodes that are located closer than a mean free path of molecules within the gas to be ionized. Methods of manufacture are also provided.

  6. The Molecules of the Cell Membrane.

    ERIC Educational Resources Information Center

    Bretscher, Mark S.

    1985-01-01

    Cell membrane molecules form a simple, two-dimensional liquid controlling what enters and leaves the cell. Discusses cell membrane molecular architecture, plasma membranes, epithelial cells, cycles of endocytosis and exocytosis, and other topics. Indicates that some cells internalize, then recycle, membrane area equivalent to their entire surface…

  7. Physical principles of membrane remodelling during cell mechanoadaptation.

    PubMed

    Kosmalska, Anita Joanna; Casares, Laura; Elosegui-Artola, Alberto; Thottacherry, Joseph Jose; Moreno-Vicente, Roberto; González-Tarragó, Víctor; del Pozo, Miguel Ángel; Mayor, Satyajit; Arroyo, Marino; Navajas, Daniel; Trepat, Xavier; Gauthier, Nils C; Roca-Cusachs, Pere

    2015-01-01

    Biological processes in any physiological environment involve changes in cell shape, which must be accommodated by their physical envelope--the bilayer membrane. However, the fundamental biophysical principles by which the cell membrane allows for and responds to shape changes remain unclear. Here we show that the 3D remodelling of the membrane in response to a broad diversity of physiological perturbations can be explained by a purely mechanical process. This process is passive, local, almost instantaneous, before any active remodelling and generates different types of membrane invaginations that can repeatedly store and release large fractions of the cell membrane. We further demonstrate that the shape of those invaginations is determined by the minimum elastic and adhesive energy required to store both membrane area and liquid volume at the cell-substrate interface. Once formed, cells reabsorb the invaginations through an active process with duration of the order of minutes. PMID:26073653

  8. Physical principles of membrane remodelling during cell mechanoadaptation

    PubMed Central

    Kosmalska, Anita Joanna; Casares, Laura; Elosegui-Artola, Alberto; Thottacherry, Joseph Jose; Moreno-Vicente, Roberto; González-Tarragó, Víctor; del Pozo, Miguel Ángel; Mayor, Satyajit; Arroyo, Marino; Navajas, Daniel; Trepat, Xavier; Gauthier, Nils C.; Roca-Cusachs, Pere

    2015-01-01

    Biological processes in any physiological environment involve changes in cell shape, which must be accommodated by their physical envelope—the bilayer membrane. However, the fundamental biophysical principles by which the cell membrane allows for and responds to shape changes remain unclear. Here we show that the 3D remodelling of the membrane in response to a broad diversity of physiological perturbations can be explained by a purely mechanical process. This process is passive, local, almost instantaneous, before any active remodelling and generates different types of membrane invaginations that can repeatedly store and release large fractions of the cell membrane. We further demonstrate that the shape of those invaginations is determined by the minimum elastic and adhesive energy required to store both membrane area and liquid volume at the cell–substrate interface. Once formed, cells reabsorb the invaginations through an active process with duration of the order of minutes. PMID:26073653

  9. Dielectric Breakdown of Cell Membranes

    PubMed Central

    Zimmermann, U.; Pilwat, G.; Riemann, F.

    1974-01-01

    With human and bovine red blood cells and Escherichia coli B, dielectric breakdown of cell membranes could be demonstrated using a Coulter Counter (AEG-Telefunken, Ulm, West Germany) with a hydrodynamic focusing orifice. In making measurements of the size distributions of red blood cells and bacteria versus increasing electric field strength and plotting the pulse heights versus the electric field strength, a sharp bend in the otherwise linear curve is observed due to the dielectric breakdown of the membranes. Solution of Laplace's equation for the electric field generated yields a value of about 1.6 V for the membrane potential at which dielectric breakdown occurs with modal volumes of red blood cells and bacteria. The same value is also calculated for red blood cells by applying the capacitor spring model of Crowley (1973. Biophys. J. 13:711). The corresponding electric field strength generated in the membrane at breakdown is of the order of 4 · 106 V/cm and, therefore, comparable with the breakdown voltages for bilayers of most oils. The critical detector voltage for breakdown depends on the volume of the cells. The volume-dependence predicted by Laplace theory with the assumption that the potential generated across the membrane is independent of volume, could be verified experimentally. Due to dielectric breakdown the red blood cells lose hemoglobin completely. This phenomenon was used to study dielectric breakdown of red blood cells in a homogeneous electric field between two flat platinum electrodes. The electric field was applied by discharging a high voltage storage capacitor via a spark gap. The calculated value of the membrane potential generated to produce dielectric breakdown in the homogeneous field is of the same order as found by means of the Coulter Counter. This indicates that mechanical rupture of the red blood cells by the hydrodynamic forces in the orifice of the Coulter Counter could also be excluded as a hemolysing mechanism. The detector voltage (or the electric field strength in the orifice) depends on the membrane composition (or the intrinsic membrane potential) as revealed by measuring the critical voltage in E. coli B harvested from the logarithmic and stationary growth phases. The critical detector voltage increased by about 30% for a given volume on reaching the stationary growth phase. PMID:4611517

  10. Rapid Fractionation of Wheat Leaf Protoplasts Using Membrane Filtration 1

    PubMed Central

    Lilley, Ross McC.; Stitt, Mark; Mader, Gerhard; Heldt, Hans W.

    1982-01-01

    A technique is presented for measuring the in vivo metabolite levels in the chloroplast stroma, the cytosol, and the mitochondrial matrix of wheat (Triticum aestivum, var `Timmo') leaf protoplasts, in which membrane filtration is used to prepare fractions enriched in the different subcellular fractions within 0.1 seconds after disruption of the protoplasts. By closing a syringe, protoplasts are forced through a net and disrupted, diluting the cytosol into the medium and also releasing intact chloroplasts and mitochondria which can then be immediately removed on membrane filters placed behind the nylon net. By varying the membrane filters, different filtrates are obtained corresponding to (a) mainly cytosol, or (b) cytosol and mitochondria with only low levels of chloroplasts; alternatively, (c) the entire protoplast contents are obtained by omitting the filters. The filtrates are immediately split, half flowing into HClO4 where they are immediately quenched for subsequent metabolite analyses; the other half flows into detergent and is used to monitor the exact distribution of marker enzymes in each individual fractionation. Using the measured distributions of metabolite and of marker enzymes in the three filtrates, the subcellular distribution of the metabolite can be algebraically calculated. The method is presented using ATP as an example. The quench time (0.1 second) made possible by membrane filtration is considerably faster than has been possible in the previously developed techniques using silicone oil centrifugation for chloroplasts (1 second) or mitochondria (1 minute). This rapid quench makes it possible to investigate subcellular pools which have a rapid turnover, like the adenine nucleotides. PMID:16662652

  11. Proteomics and Phosphoproteomics Analysis of Human Lens Fiber Cell Membranes

    PubMed Central

    Wang, Zhen; Han, Jun; David, Larry L.; Schey, Kevin L.

    2013-01-01

    Purpose. The human lens fiber cell insoluble membrane fraction contains important membrane proteins, cytoskeletal proteins, and cytosolic proteins that are strongly associated with the membrane. The purpose of this study was to characterize the lens fiber cell membrane proteome and phosphoproteome from human lenses. Methods. HPLC-mass spectrometry–based multidimensional protein identification technology (MudPIT), without or with phosphopeptide enrichment, was applied to study the proteome and phosphoproteome of lens fiber cell membranes, respectively. Results. In total, 951 proteins were identified, including 379 integral membrane and membrane-associated proteins. Enriched gene categories and pathways based on the proteomic analysis include carbohydrate metabolism (glycolysis/gluconeogenesis, pentose phosphate pathway, pyruvate metabolism), proteasome, cell-cell signaling and communication (GTP binding, gap junction, focal adhesion), glutathione metabolism, and actin regulation. The combination of TiO2 phosphopeptide enrichment and MudPIT analysis revealed 855 phosphorylation sites on 271 proteins, including 455 phosphorylation sites that have not been previously identified. PKA, PKC, CKII, p38MAPK, and RSK are predicted as the major kinases for phosphorylation on the sites identified in the human lens membrane fraction. Conclusions. The results presented herein significantly expand the characterized proteome and phosphoproteome of the human lens fiber cell and provide a valuable reference for future research in studies of lens development and disease. PMID:23349431

  12. Fractional Hereditariness of Lipid Membranes: Instabilities and Linearized Evolution

    E-print Network

    L. Deseri; P. Pollaci; M. Zingales; K. Dayal

    2015-09-21

    In this work lipid ordering phase changes arising in planar membrane bilayers is investigated both accounting for elas- ticity alone and for effective viscoelastic response of such assemblies. The mechanical response of such membranes is studied by minimizing the Gibbs free energy which penalizes perturbations of the changes of areal stretch and their gradients only [1]. As material instabilities arise whenever areal stretches characterizing homogeneous configurations lie inside the spinoidal zone of the free energy density, bifurcations from such configurations are shown to occur as oscillatory perturbations of the in-plane displacement. Experimental observations [2] show a power-law in-plane viscous behavior of lipid structures allowing for an effective viscoelastic behavior of lipid membranes [3], which falls in the framework of Fractional Hereditariness. A suitable generalization of the variational principle invoked for the elasticity is applied in this case, and the corresponding Euler-Lagrange equation is found together with a set of bound- ary and initial conditions. Separation of variables allows for showing how Fractional Hereditariness owes bifurcated modes with a larger number of spatial oscillations than the corresponding elastic analog. Indeed, the available range of areal stresses for material instabilities is found to increase with respect to the purely elastic case. Nevertheless, the time evolution of the perturbations solving the Euler-Lagrange equation above exhibits time-decay and the large number of spatial oscillation slowly relaxes, thereby keeping the features of a long-tail type time-response.

  13. Corrugated Membrane Fuel Cell Structures

    SciTech Connect

    Grot, Stephen President, Ion Power Inc.

    2013-09-30

    One of the most challenging aspects of traditional PEM fuel cell stacks is the difficulty achieving the platinum catalyst utilization target of 0.2 gPt/kWe set forth by the DOE. Good catalyst utilization can be achieved with state-of-the-art catalyst coated membranes (CCM) when low catalyst loadings (<0.3 mg/cm2) are used at a low current. However, when low platinum loadings are used, the peak power density is lower than conventional loadings, requiring a larger total active area and a larger bipolar plate. This results in a lower overall stack power density not meeting the DOE target. By corrugating the fuel cell membrane electrode structure, Ion Power?s goal is to realize both the Pt utilization targets as well as the power density targets of the DOE. This will be achieved by demonstrating a fuel cell single cell (50 cm2) with a twofold increase in the membrane active area over the geometric area of the cell by corrugating the MEA structure. The corrugating structure must be able to demonstrate the target properties of < 10 mOhm-cm2 electrical resistance at > 20 psi compressive strength over the active area, in combination with offering at least 80% of power density that can be achieved by using the same MEA in a flat plate structure. Corrugated membrane fuel cell structures also have the potential to meet DOE power density targets by essentially packaging more membrane area into the same fuel cell volume as compared to conventional stack constructions.

  14. Focus on membrane differentiation and membrane domains in the prokaryotic cell.

    PubMed

    Boekema, Egbert J; Scheffers, Dirk-Jan; van Bezouwen, Laura S; Bolhuis, Henk; Folea, I Mihaela

    2013-01-01

    A summary is presented of membrane differentiation in the prokaryotic cell, with an emphasis on the organization of proteins in the plasma/cell membrane. Many species belonging to the Eubacteria and Archaea have special membrane domains and/or membrane proliferation, which are vital for different cellular processes. Typical membrane domains are found in bacteria where a specific membrane protein is abundantly expressed. Lipid rafts form another example. Despite the rareness of conventional organelles as found in eukaryotes, some bacteria are known to have an intricate internal cell membrane organization. Membrane proliferation can be divided into curvature and invaginations which can lead to internal compartmentalization. This study discusses some of the clearest examples of bacteria with such domains and internal membranes. The need for membrane specialization is highest among the heterogeneous group of bacteria which harvest light energy, such as photosynthetic bacteria and halophilic archaea. Most of the highly specialized membranes and domains, such as the purple membrane, chromatophore and chlorosome, are found in these autotrophic organisms. Otherwise the need for membrane differentiation is lower and variable, except for those structures involved in cell division. Microscopy techniques have given essential insight into bacterial membrane morphology. As microscopy will further contribute to the unraveling of membrane organization in the years to come, past and present technology in electron microscopy and light microscopy is discussed. Electron microscopy was the first to unravel bacterial morphology because it can directly visualize membranes with inserted proteins, which no other technique can do. Electron microscopy techniques developed in the 1950s and perfected in the following decades involve the thin sectioning and freeze fractioning of cells. Several studies from the golden age of these techniques show amazing examples of cell membrane morphology. More recently, light microscopy in combination with the use of fluorescent dyes has become an attractive technique for protein localization with the natural membrane. However, the resolution problem in light microscopy remains and overinterpretation of observed phenomena is a pitfall. Thus, light microscopy as a stand-alone technique is not sufficient to prove, for instance, the long-range helical distribution of proteins in membrane such as MinD spirals in Bacillus subtilis. Electron tomography is an emerging electron microscopy technique that can provide three-dimensional reconstructions of small, nonchemically fixed bacteria. It will become a useful tool for studying prokaryotic membranes in more detail and is expected to collect information complementary to those of advanced light microscopy. Together, microscopy techniques can meet the challenge of the coming years: to specify membrane structures in more detail and to bring them to the level of specific protein-protein interactions. PMID:23920497

  15. Cell handling using microstructured membranes

    PubMed Central

    Irimia, Daniel

    2013-01-01

    Gentle and precise handling of cell suspensions is essential for scientific research and clinical diagnostic applications. Although different techniques for cell analysis at the micro-scale have been proposed, many still require that preliminary sample preparation steps be performed off the chip. Here we present a microstructured membrane as a new microfluidic design concept, enabling the implementation of common sample preparation procedures for suspensions of eukaryotic cells in lab-on-a-chip devices. We demonstrate the novel capabilities for sample preparation procedures by the implementation of metered sampling of nanoliter volumes of whole blood, concentration increase up to three orders of magnitude of sparse cell suspension, and circumferentially uniform, sequential exposure of cells to reagents. We implemented these functions by using microstructured membranes that are pneumatically actuated and allowed to reversibly decouple the flow of fluids and the displacement of eukaryotic cells in suspensions. Furthermore, by integrating multiple structures on the same membrane, complex sequential procedures are possible using a limited number of control steps. PMID:16511616

  16. Membrane proteins of dense lysosomes from Chinese hamster ovary cells

    SciTech Connect

    Chance, S.C.

    1987-01-01

    In this work membrane proteins from lysosomes were studied in order to gain more information on the biogenesis and intracellular sorting of this class of membrane proteins. Membrane proteins were isolated from a purified population of lysosomes. These proteins were then examined for various co- and post-translational modifications which could serve as potential intracellular sorting signals. Biochemical analysis using marker enzymatic activities detected no plasma membrane, Golgi, endoplasmic reticulum, peroxisomes, mitochondria, or cytosol. Analysis after incorporation of ({sup 3}H)thymidine or ({sup 3}H)uridine detected no nuclei or ribosomes. A fraction containing integral membrane proteins was obtained from the dense lysosomes by extraction with Triton X-114. Twenty-three polypeptides which incorporated both ({sup 35}S)methionine and ({sup 3}H)leucine were detected by SDS PAGE in this membrane fraction, and ranged in molecular weight from 30-130 kDa. After incorporation by cells of various radioactive metabolic precursors, the membrane fraction from dense lysosomes was examined and was found to be enriched in mannose, galactose, fucose, palmitate, myristate, and sulfate, but was depleted in phosphate. The membrane fraction from dense lysosomes was then analyzed by SDS PAGE to determine the apparent molecular weights of modified polypepties.

  17. In Vitro Enzymatic Reduction Kinetics of Mineral Oxides by Membrane Fractions from Shewanella oneidensis MR-1

    SciTech Connect

    Ruebush,S.; Icopini, G.; Brantley, S.; Tien, M.

    2006-01-01

    This study documents the first example of in vitro solid-phase mineral oxide reduction by enzyme-containing membrane fractions. Previous in vitro studies have only reported the reduction of aqueous ions. Total membrane (TM) fractions from iron-grown cultures of Shewanella oneidensis MR-1 were isolated and shown to catalyze the reduction of goethite, hematite, birnessite, and ramsdellite/pyrolusite using formate. In contrast, nicotinamide adenine dinucleotide (NADH) and succinate cannot function as electron donors. The significant implications of observations related to this cell-free system are: (i) both iron and manganese mineral oxides are reduced by the TM fraction, but aqueous U(VI) is not; (ii) TM fractions from anaerobically grown, but not aerobically grown, cells can reduce the mineral oxides; (iii) electron shuttles and iron chelators are not needed for this in vitro reduction, documenting conclusively that reduction can occur by direct contact with the mineral oxide; (iv) electron shuttles and EDTA stimulate the in vitro Fe(III) reduction, documenting that exogenous molecules can enhance rates of enzymatic mineral reduction; and (v) multiple membrane components are involved in solid-phase oxide reduction. The membrane fractions, consisting of liposomes of cytoplasmic and outer membrane segments, contain at least 100 proteins including the enzyme that oxidizes formate, formate dehydrogenase. Mineral oxide reduction was inhibited by the addition of detergent Triton X-100, which solubilizes membranes and their associated proteins, consistent with the involvement of multiple electron carriers that are disrupted by detergent addition. In contrast, formate dehydrogenase activity was not inhibited by Triton X-100. The addition of anthraquinone-2,6-disulfonate (AQDS) and menaquinone-4 was unable to restore activity; however, menadione (MD) restored 33% of the activity. The addition of AQDS and MD to reactions without added detergent increased the rate of goethite reduction. The Michaelis-Menten K{sub m} values of 71 {+-} 22 m{sup 2}/L for hematite and 50 {+-} 16 m{sup 2}/L for goethite were calculated as a function of surface area of the two insoluble minerals. V{sub max} was determined to be 123 {+-} 14 and 156 {+-} 13 nmol Fe(II)/min/mg of TM protein for hematite and goethite, respectively. These values are consistent with in vivo rates of reduction reported in the literature. These observations are consistent with our conclusion that the enzymatic reduction of mineral oxides is an effective probe that will allow elucidation of molecular chemistry of the membrane-mineral interface where electron transfer occurs.

  18. Role of membrane lipids and membrane fluidity in thermosensitivity and thermotolerance of mammalian cells.

    PubMed

    Konings, A W; Ruifrok, A C

    1985-04-01

    The role of membrane lipids and membrane fluidity in thermosensitivity of mammalian cells is not well understood. The limited experimental data in the literature have led to conflicting results. A detailed investigation of lipid composition and membrane fluidity of cellular membranes was undertaken to determine their relationship to cell survival after hyperthermia. Ehrlich ascites (EA) cells, mouse fibroblast LM cells, and HeLa S3 cells differed in thermosensitivity as expressed by a D0 of 3.1, 5.2, and 9.7 min, respectively, at 44 degrees C. No correlation with cellular thermosensitivity could be found with respect to the amount of cholesterol and to the cholesterol to phospholipid ratio in the particulate fraction of the cells. By growing the cells for some generations in different media, cholesterol and phospholipid content could be changed in the particulate fraction, but no difference in cell survival was observed. When mouse fibroblasts were grown for 24 hr in a serum-free medium supplemented with arachidonic acid (20:4), all subcellular membranes were about eight times richer in phospholipids containing polyunsaturated acyl (PUFA) chains and membrane fluidity was increased as measured by fluorescence polarization of diphenylhexatriene (DPH). The alterations resulted in a higher thermosensitivity. When mouse fibroblasts were made thermotolerant no change in cholesterol and phospholipid content could be found in the particulate fraction of the cells. The relative weights and the quality of the phospholipids as well as the fatty acid composition of the phospholipids appeared to be the same for normal and thermotolerant cells. Fluidity measurements in whole cells, isolated plasma membranes, and liposomes prepared from phospholipids extracted from the cells revealed no significant differences between normal and thermotolerant fibroblasts when assayed by fluorescence polarization (DPH) and electron spin resonance (5-nitroxystearate). It is concluded that the mechanism of thermal adaptation resulting in differences in lipid composition as reported in the literature differs from the mechanism of the acquisition of thermal tolerance. The lower heat sensitivity of thermotolerant cells, as initiated by a nonlethal triggering heat dose followed by an induction period at 37 degrees C, does not involve changes in lipid composition and membrane fluidity. However, a prompt and clear (also nonlethal) change in membrane fluidity by an increase in PUFA does result in an increased thermosensitivity, probably because of an indirect effect via the lipids in causing disfunctioning of proteins in the membrane and/or the cytoskeleton. PMID:3983372

  19. Cryptococcus neoformans cryoultramicrotomy and vesicle fractionation reveals an intimate association between membrane lipids and glucuronxylomannan

    PubMed Central

    Oliveira, Débora L.; Nimrichter, Leonardo; Miranda, Kildare; Frases, Susana; Faull, Kym F.; Casadevall, Arturo; Rodrigues, Marcio L.

    2009-01-01

    Cryptococcus neoformans is an encapsulated pathogenic fungus. The cryptococcal capsule is composed of polysaccharides and is necessary for virulence. It has been previously reported that glucuronoxylomannan (GXM), the major capsular component, is synthesized in cytoplasmic compartments and transported to the extracellular space in vesicles, but knowledge on the organelles involved in polysaccharide synthesis and traffic is extremely limited. In this paper we report the GXM distribution in C. neoformans cells sectioned by cryoultramicrotomy and visualized by transmission electron microscopy (TEM) and polysaccharide immunogold staining. Cryosections of fungal cells showed high preservation of intracellular organelles and cell wall structure. Incubation of cryosections with an antibody to GXM revealed that cytoplasmic structures associated to vesicular compartments and reticular membranes are in close proximity to the polysaccharide. GXM was generally found in association with the membrane of intracellular compartments and within different layers of the cell wall. Analysis of extracellular fractions from cryptococcal supernatants by transmission electron microscopy in combination with serologic, chromatographic and spectroscopic methods revealed fractions containing GXM and lipids. These results indicate an intimate association of GXM and lipids in both intracellular and extracellular spaces consistent with polysaccharide synthesis and transport in membrane-associated structures. PMID:19747978

  20. Tumor cell growth fraction in Hodgkin's disease.

    PubMed Central

    Gerdes, J.; Van Baarlen, J.; Pileri, S.; Schwarting, R.; Van Unnik, J. A.; Stein, H.

    1987-01-01

    The growth fraction of tumor cells was studied in 45 cases of Hodgkin's disease by means of a recently developed double immunostaining technique using monoclonal antibody Ki-1, which reacts selectively with Hodgkin and Reed-Sternberg cells in tissues affected by Hodgkin's disease, and antibody Ki-67, which recognizes a cell proliferation-associated nuclear antigen. The medians of the growth fractions of the tumor cells in all histologic subtypes of Hodgkin's disease varied between 78% and 83%. In none of the cases investigated did we find a growth fraction below 50%. Furthermore, mononucleated Hodgkin cells as well as multi-nucleated Reed-Sternberg cells showed a similar Ki-67 labeling index, indicating that both tumor cell types belong to the proliferating pool of this malignancy. Images Figure 1 PMID:3307442

  1. Lateral organization of membranes and cell shapes.

    PubMed Central

    Markin, V S

    1981-01-01

    The relations among membrane structure, mechanical properties, and cell shape have been investigated. The fluid mosaic membrane models used contains several components that move freely in the membrane plane. These components interact with each other and determine properties of the membrane such as curvature and elasticity. A free energy equation is postulated for such a multicomponent membrane and the condition of free energy minimum is used to obtain differential equations relating the distribution of membrane components and the local membrane curvature. The force that moves membrane components along the membrane in a variable curvature field is calculated. A change in the intramembrane interactions can bring about phase separation or particle clustering. This, in turn, may strongly affect the local curvature. The numerical solution of the set of equations for the two dimensional case allows determination of the cell shape and the component distribution along the membrane. The model has been applied to describe certain erythrocytes shape transformations. PMID:7284547

  2. The effect of passive mixing on pressure drop and oxygen mass fraction using opposing channel flow field design in a Proton Exchange Membrane Fuel Cell

    NASA Astrophysics Data System (ADS)

    Singh, Anant Bir

    This study investigates a flow field with opposing channel design. Previous studies on flow field designs have been focused on improving fuel utilization which often leads to increased pressure drop. This increased pressure drop is typical because standard designs employ either a single flow channel to clear blockages or dead end condition to force the flow through the gas diffusion layer. The disadvantage with these designs is the increased resistance to the flow which requires higher pressure, which becomes a parasitic loss that lowers the system efficiency. For this study the focus was to reduce the pressure drop by providing a less resistive path to the flow. To achieve a less resistive path, the inlet channel was split into two opposing channels. These channels are then recombined only to be split again for the next leg. Therefore, the split channel design should reduce the pressure drop which reduces the parasitic load and ultimately contributes to higher system efficiency. In addition the recombining of the streams at each leg should induce mixing. Having opposing channels should also increase cross flow under the lands to reduce mass transfer loses. The cathode side of the fuel cell is especially sensitive to the mass transport losses since air (oxygen mixed with nitrogen) is used for supplying oxygen unlike the anode side which uses pure hydrogen. To test the hypothesis of having benefits from an opposing channel design, both an experimental and analytical approach was taken. For the experiment, a serpentine flow field and opposing channel flow field plates were compared over several flow rates with compressed air. To test the hypothesis of increased mass transfer, the two flow fields were modeled using a CFD software package, COMSOL. It was found that the opposing channel configuration for high flow rate with multiple entry and exit conditions exhibited significant improvement over the single serpentine channel. Pressure drop was ? less than the serpentine channel with similar conditions. Simulations for mass transfer show that recombining of the flow streams generate more uniform current density unlike the serpentine configuration where the current density was concentrated at the entrance of the flow stream. The background section provides a brief overview of the governing equations, the theory of flow field operation and previous bodies of work on flow field design. Recommendations are made for further verification of the design using a real working cell based on the results.

  3. Actinide transport across cell membranes.

    PubMed

    Bulman, R A; Griffin, R J

    1980-01-01

    Protactinium uptake into the normal liver does not exceed 3%, but when the phospholipid levels in the liver are elevated by administration of thioacetamide this uptake increases to 31%. Phosphatidic acid, which is absent from the normal liver, has been shown to extract protactinium into organic solvents. However, phosphatidylserine, a component of normal liver cell membranes, does not extract protactinium. It might be conjectured that this is why so little protactinium is taken up by the normal liver. The hypothesis is advanced that phosphatidylserine, which is known to complex plutonium, americium and curium, may regulate the uptake of these elements by liver. PMID:7373293

  4. Electron microscopy: cytology of cell fractions.

    PubMed

    NOVIKOFF, A B

    1956-11-16

    It should be evident from this brief account that electron microscopy of thin sections is an invaluable asset in the study of fractions isolated by differential centrifugation. I have tried to indicate how the integrity of particles, purity of fractions, and the existence of new particles can be established through its use. I have also suggested the desirability of a common terminology for all cytology -classic, electron-microscopic, and biochemical. Some have expressed the opinion that neutral terms such as alpha, beta, and gamma membranes (59) are more useful than ergastoplasm, Golgi apparatus, and so forth. As helpful as such neutral terms may be in describing intracellular structures, they do not appear to me to substitute for historically rooted cytological names. Note added in proof: Since this article went to press there has appeared an important article by G. E. Palade and P. Siekevitz (60). These authors consider that the vesicles without granules found in the microsome fraction were "probably derived from the smooth surfaced parts of the endoplasmic reticulum." The latter were found to be continuous with the granule-studded membranes; "the two varieties of profiles represent local differentiation within a common system." The authors confirm the finding of Rouiller (18) and Novikoff et al. (7) of the dense bodies adjacent to the bile canaliculi and describe their presence in the microsome fraction as a "minor component." PMID:13380407

  5. A membrane reservoir at the cell surface

    PubMed Central

    Figard, Lauren; Sokac, Anna Marie

    2014-01-01

    Cell surface expansion is a necessary part of cell shape change. One long-standing hypothesis proposes that membrane for this expansion comes from the flattening out of cell surface projections such as microvilli and membrane folds. Correlative EM data of cells undergoing phagocytosis, cytokinesis, and morphogenesis has hinted at the existence of such an unfolding mechanism for decades; but unfolding has only recently been confirmed using live-cell imaging and biophysical approaches. Considering the wide range of cells in which plasma membrane unfolding has now been reported, it likely represents a fundamental mechanism of cell shape change. PMID:24844289

  6. Effect of aniracetam on phosphatidylinositol transfer protein alpha in cytosolic and plasma membrane fractions of astrocytes subjected to simulated ischemia in vitro.

    PubMed

    Gabryel, Bozena; Chalimoniuk, Ma?gorzata; Ma?ecki, Andrzej; Strosznajder, Joanna B

    2005-01-01

    Brain ischemia affects phosphoinositide metabolism and the level of lipid-derived second messengers. Phosphatidylinositol transfer proteins (PI-PTs) are responsible for the transport of phosphatidylinositol (PI) and other phospholipids through membranes. Isoform of PI-TPs (PI-TPalpha) is an essential component in ensuring substrate supply for phospholipase C (PLC). The current study was conducted to examine potential effect of aniracetam on PI-TPalpha expression and to characterize the PI-TPalpha isoform distribution between membrane and cytosol fractions of astrocytes exposed to simulated ischemia in vitro. After 8 h period of ischemia, the level of PI-TPalpha was significantly higher in cytosol (by about 28%) as well as in membrane fraction (by about 80%) in comparison with control. We have found that aniracetam treatment of astrocytes in normoxia significantly increased the level of PI-TPalpha in membrane fraction with a maximal effect at 0.1 microM concentration of aniracetam (by about 195% of control). In membrane fractions of ischemic cells, aniracetam increased PI-TPalpha expression in a concentration-dependent manner. In ischemic cells, aniracetam (10 microM) has elevated PI-TPalpha expression up to 155% and 428% in cytosolic and membrane fractions in comparison with ischemic untreated cells, respectively. The study has shown that aniracetam significantly activates PI-TPalpha in cell membrane fraction and this effect might be connected with previously described activation of MAP kinase cascade. PMID:16227651

  7. Polymer electrolyte membrane assembly for fuel cells

    NASA Technical Reports Server (NTRS)

    Yen, Shiao-Ping S. (Inventor); Kindler, Andrew (Inventor); Yavrouian, Andre (Inventor); Halpert, Gerald (Inventor)

    2000-01-01

    An electrolyte membrane for use in a fuel cell can contain sulfonated polyphenylether sulfones. The membrane can contain a first sulfonated polyphenylether sulfone and a second sulfonated polyphenylether sulfone, wherein the first sulfonated polyphenylether and the second sulfonated polyphenylether sulfone have equivalent weights greater than about 560, and the first sulfonated polyphenylether and the second sulfonated polyphenylether sulfone also have different equivalent weights. Also, a membrane for use in a fuel cell can contain a sulfonated polyphenylether sulfone and an unsulfonated polyphenylether sulfone. Methods for manufacturing a membrane electrode assemblies for use in fuel cells can include roughening a membrane surface. Electrodes and methods for fabricating such electrodes for use in a chemical fuel cell can include sintering an electrode. Such membranes and electrodes can be assembled into chemical fuel cells.

  8. Polymer electrolyte membrane assembly for fuel cells

    NASA Technical Reports Server (NTRS)

    Yen, Shiao-Ping S. (Inventor); Kindler, Andrew (Inventor); Yavrouian, Andre (Inventor); Halpert, Gerald (Inventor)

    2002-01-01

    An electrolyte membrane for use in a fuel cell can contain sulfonated polyphenylether sulfones. The membrane can contain a first sulfonated polyphenylether sulfone and a second sulfonated polyphenylether sulfone, wherein the first sulfonated polyphenylether and the second sulfonated polyphenylether sulfone have equivalent weights greater than about 560, and the first sulfonated polyphenylether and the second sulfonated polyphenylether sulfone also have different equivalent weights. Also, a membrane for use in a fuel cell can contain a sulfonated polyphenylether sulfone and an unsulfonated polyphenylether sulfone. Methods for manufacturing a membrane electrode assemblies for use in fuel cells can include roughening a membrane surface. Electrodes and methods for fabricating such electrodes for use in a chemical fuel cell can include sintering an electrode. Such membranes and electrodes can be assembled into chemical fuel cells.

  9. Cell membrane orientation visualized by polarized total internal reflection fluorescence.

    PubMed Central

    Sund, S E; Swanson, J A; Axelrod, D

    1999-01-01

    In living cells, variations in membrane orientation occur both in easily imaged large-scale morphological features, and also in less visualizable submicroscopic regions of activity such as endocytosis, exocytosis, and cell surface ruffling. A fluorescence microscopic method is introduced here to visualize such regions. The method is based on fluorescence of an oriented membrane probe excited by a polarized evanescent field created by total internal reflection (TIR) illumination. The fluorescent carbocyanine dye diI-C(18)-(3) (diI) has previously been shown to embed in the lipid bilayer of cell membranes with its transition dipoles oriented nearly in the plane of the membrane. The membrane-embedded diI near the cell-substrate interface can be fluorescently excited by evanescent field light polarized either perpendicular or parallel to the plane of the substrate coverslip. The excitation efficiency from each polarization depends on the membrane orientation, and thus the ratio of the observed fluorescence excited by these two polarizations vividly shows regions of microscopic and submicroscopic curvature of the membrane, and also gives information regarding the fraction of unoriented diI in the membrane. Both a theoretical background and experimental verification of the technique is presented for samples of 1) oriented diI in model lipid bilayer membranes, erythrocytes, and macrophages; and 2) randomly oriented fluorophores in rhodamine-labeled serum albumin adsorbed to glass, in rhodamine dextran solution, and in rhodamine dextran-loaded macrophages. Sequential digital images of the polarized TIR fluorescence ratios show spatially-resolved time-course maps of membrane orientations on diI-labeled macrophages from which low visibility membrane structures can be identified and quantified. To sharpen and contrast-enhance the TIR images, we deconvoluted them with an experimentally measured point spread function. Image deconvolution is especially effective and fast in our application because fluorescence in TIR emanates from a single focal plane. PMID:10512845

  10. Membrane fractions active in poliovirus RNA replication contain VPg precursor polypeptides

    SciTech Connect

    Takegami, T.; Semler, B.L.; Anderson, C.W.; Wimmer, E.

    1983-01-01

    The poliovirus specific polypeptide P3-9 is of special interest for studies of viral RNA replication because it contains a hydrophobic region and, separated by only seven amino acids from that region, the amino acid sequence of the genome-linked protein VPg. Membraneous complexes of poliovirus-infected HeLa cells that contain poliovirus RNA replicating proteins have been analyzed for the presence of P3-9 by immunoprecipitation. Incubation of a membrane fraction rich in P3-9 with proteinase leaves the C-terminal 69 amino acids of P3-9 intact, an observation suggesting that this portion is protected by its association with the cellular membrane. These studies have also revealed two hitherto undescribed viral polypeptides consisting of amino acid sequences of the P2 andf P3 regions of the polyprotein. Sequence analysis by stepwise Edman degradation show that these proteins are 3b/9 (M/sub r/77,000) and X/9 (M/sub r/50,000). 3b/9 and X/9 are membrane bound and are turned over rapidly and may be direct precursors to proteins P2-X and P3-9 of the RNA replication complex. P2-X, a polypeptide void of hydrophobic amino acid sequences but also found associated with membranes, is rapidly degraded when the membraneous complex is treated with trypsin. It is speculated that P2-X is associated with membranes by its affinity to the N-terminus of P3-9.

  11. Advanced composite polymer electrolyte fuel cell membranes

    SciTech Connect

    Wilson, M.S.; Zawodzinski, T.A.; Gottesfeld, S.; Kolde, J.A.; Bahar, B.

    1995-09-01

    A new type of reinforced composite perfluorinated polymer electrolyte membrane, GORE-SELECT{trademark} (W.L. Gore & Assoc.), is characterized and tested for fuel cell applications. Very thin membranes (5-20 {mu}m thick) are available. The combination of reinforcement and thinness provides high membrane, conductances (80 S/cm{sup 2} for a 12 {mu}m thick membrane at 25{degrees}C) and improved water distribution in the operating fuel cell without sacrificing longevity or durability. In contrast to nonreinforced perfluorinated membranes, the x-y dimensions of the GORE-SELECT membranes are relatively unaffected by the hydration state. This feature may be important from the viewpoints of membrane/electrode interface stability and fuel cell manufacturability.

  12. Fuel cell ion-exchange membrane investigation

    NASA Technical Reports Server (NTRS)

    Toy, M. S.

    1972-01-01

    The present deficiencies in the fluorocarbon sulfonic acid membrane used as the solid polymer electrolyte in the H2/O2 fuel cell are studied. Considered are: Adhesives selection, elastomeric formulations, scavenger exploration, and membrane characterization. The significant data are interpreted and recommendations are given for both short and long range further investigations in two of the four major areas: membrane adhesives and membrane stabilization.

  13. Filter-exchange PGSE NMR determination of cell membrane permeability

    NASA Astrophysics Data System (ADS)

    Åslund, Ingrid; Nowacka, Agnieszka; Nilsson, Markus; Topgaard, Daniel

    2009-10-01

    A new PGSE NMR sequence is introduced for measuring diffusive transport across the plasma membrane of living cells. A "diffusion filter" and a variable mixing time precedes a standard PGSE block for diffusion encoding of the NMR signal. The filter is a PGSE block optimized for selectively removing the magnetization of the extracellular water. With increasing mixing time the intra- and extracellular components approach their equilibrium fractional populations. The rate of exchange can be measured using only a few minutes of instrument time. Water exchange over the plasma membrane of starved yeast cells is studied in the temperature range +5 to +32 °C.

  14. Isolation of a hemidesmosome-rich fraction from a human squamous cell carcinoma cell line

    SciTech Connect

    Hirako, Yoshiaki; Yonemoto, Yuki; Yamauchi, Tomoe; Nishizawa, Yuji; Kawamoto, Yoshiyuki; Owaribe, Katsushi

    2014-06-10

    Hemidesmosomes are cell-to-matrix adhesion complexes anchoring keratinocytes to basement membranes. For the first time, we present a method to prepare a fraction from human cultured cells that are highly enriched in hemidesmosomal proteins. Using DJM-1 cells derived from human squamous cell carcinoma, accumulation of hemidesmosomes was observed when these cells were cultured for more than 10 days in a commercial serum-free medium without supplemental calcium. Electron microscopy demonstrated that numerous electron-dense adhesion structures were present along the basal cell membranes of DJM-1 cells cultured under the aforementioned conditions. After removing cellular materials using an ammonia solution, hemidesmosomal proteins and deposited extracellular matrix were collected and separated by electrophoresis. There were eight major polypeptides, which were determined to be plectin, BP230, BP180, integrin ?6 and ?4 subunits, and laminin-332 by immunoblotting and mass spectrometry. Therefore, we designated this preparation as a hemidesmosome-rich fraction. This fraction contained laminin-332 exclusively in its unprocessed form, which may account for the promotion of laminin deposition, and minimal amounts of Lutheran blood group protein, a nonhemidesmosomal transmembrane protein. This hemidesmosome-rich fraction would be useful not only for biological research on hemidesmosomes but also for developing a serum test for patients with blistering skin diseases. - Highlights: • A defined condition promoted accumulation of hemidesmosomes in human cultured cells. • A fraction isolated from the cells contained eight major polypeptides. • The polypeptides were the five major hemidesmosome proteins and laminin-332. • The cultured cells deposited laminin-332 in its unprocessed form under the condition. • We report a method to prepare a fraction highly enriched in hemidesmosome proteins.

  15. Proton Exchange Membranes for Fuel Cells

    SciTech Connect

    Devanathan, Ramaswami

    2010-11-01

    Proton exchange membrane, also known as polymer electrolyte membrane, fuel cells (PEMFCs) offer the promise of efficient conversion of chemical energy of fuel, such as hydrogen or methanol, into electricity with minimal pollution. Their widespread use to power zero-emission automobiles as part of a hydrogen economy can contribute to enhanced energy security and reduction in greenhouse gas emissions. However, the commercial viability of PEMFC technology is hindered by high cost associated with the membrane electrode assembly (MEA) and poor membrane durability under prolonged operation at elevated temperature. Membranes for automotive fuel cell applications need to perform well over a period comparable to the life of an automotive engine and under heavy load cycling including start-stop cycling under sub-freezing conditions. The combination of elevated temperature, changes in humidity levels, physical stresses and harsh chemical environment contribute to membrane degradation. Perfluorinated sulfonic acid (PFSA)-based membranes, such as Nafion®, have been the mainstay of PEMFC technology. Their limitations, in terms of cost and poor conductivity at low hydration, have led to continuing research into membranes that have good proton conductivity at elevated temperatures above 120 °C and under low humidity conditions. Such membranes have the potential to avoid catalyst poisoning, simplify fuel cell design and reduce the cost of fuel cells. Hydrocarbon-based membranes are being developed as alternatives to PFSA membranes, but concerns about chemical and mechanical stability and durability remain. Novel anhydrous membranes based on polymer gels infused with protic ionic liquids have also been recently proposed, but considerable fundamental research is needed to understand proton transport in novel membranes and evaluate durability under fuel cell operating conditions. In order to advance this promising technology, it is essential to rationally design the next generation of PEMs based on an understanding of chemistry, membrane morphology and proton transport obtained from experiment, theory and computer simulation.

  16. Isolation of a hemidesmosome-rich fraction from a human squamous cell carcinoma cell line.

    PubMed

    Hirako, Yoshiaki; Yonemoto, Yuki; Yamauchi, Tomoe; Nishizawa, Yuji; Kawamoto, Yoshiyuki; Owaribe, Katsushi

    2014-06-10

    Hemidesmosomes are cell-to-matrix adhesion complexes anchoring keratinocytes to basement membranes. For the first time, we present a method to prepare a fraction from human cultured cells that are highly enriched in hemidesmosomal proteins. Using DJM-1 cells derived from human squamous cell carcinoma, accumulation of hemidesmosomes was observed when these cells were cultured for more than 10 days in a commercial serum-free medium without supplemental calcium. Electron microscopy demonstrated that numerous electron-dense adhesion structures were present along the basal cell membranes of DJM-1 cells cultured under the aforementioned conditions. After removing cellular materials using an ammonia solution, hemidesmosomal proteins and deposited extracellular matrix were collected and separated by electrophoresis. There were eight major polypeptides, which were determined to be plectin, BP230, BP180, integrin ?6 and ?4 subunits, and laminin-332 by immunoblotting and mass spectrometry. Therefore, we designated this preparation as a hemidesmosome-rich fraction. This fraction contained laminin-332 exclusively in its unprocessed form, which may account for the promotion of laminin deposition, and minimal amounts of Lutheran blood group protein, a nonhemidesmosomal transmembrane protein. This hemidesmosome-rich fraction would be useful not only for biological research on hemidesmosomes but also for developing a serum test for patients with blistering skin diseases. PMID:24726610

  17. Optical rheology for live cell membranes

    E-print Network

    Park, YongKeun, S.M. Massachusetts Institute of Technology

    2007-01-01

    We present a novel optical methodology including both instrumentation and theory aimed at retrieving the full viscoelastic information of cell membrane material properties. Red blood cells (RBC) are chosen for this study ...

  18. Live cell imaging of membrane / cytoskeleton interactions and membrane topology

    NASA Astrophysics Data System (ADS)

    Chierico, Luca; Joseph, Adrian S.; Lewis, Andrew L.; Battaglia, Giuseppe

    2014-09-01

    We elucidate the interaction between actin and specific membrane components, using real time live cell imaging, by delivering probes that enable access to components, that cannot be accessed genetically. We initially investigated the close interplay between Phosphatidylinositol 4,5-bisphosphate (PIP2) and the F-actin network. We show that, during the early stage of cell adhesion, PIP2 forms domains within the filopodia membrane. We studied these domains alongside cell spreading and observed that these very closely follow the actin tread-milling. We show that this mechanism is associated with an active transport of PIP2 rich organelles from the cell perinuclear area to the edge, along actin fibers. Finally, mapping other phospholipids and membrane components we observed that the PIP2 domains formation is correlated with sphingosine and cholesterol rafts.

  19. Interaction of Sickle Cell Hemoglobin with Erythrocyte Membranes

    NASA Astrophysics Data System (ADS)

    Shaklai, N.; Sharma, V. S.; Ranney, H. M.

    1981-01-01

    The interactions of hemoglobin S with the erythrocyte membrane were compared with the corresponding interactions of hemoglobin A by measuring in both steady-state and kinetic experiments the quenching of the fluorescence of a probe embedded in erythrocyte membranes. Whereas hemoglobin A could be dissociated from membranes, a fraction of hemoglobin S was irreversibly bound even in the oxy state. Deoxyhemoglobin S interacted much more strongly with erythrocyte membranes than did deoxyhemoglobin A: a portion of the deoxyhemoglobin S was irreversibly bound, and the reversibly bound fraction of hemoglobin S dissociated more slowly than did deoxyhemoglobin A. It is suggested that the binding of deoxyhemoglobin S is a two-step reaction in which the first step involves electrostatic interaction with band III erythrocyte membrane protein and the second step involves a hydrophobic interaction with membrane lipids. The latter reaction reflects the greater hydrophobicity of hemoglobin S. The unique interaction of hemoglobin S with erythrocyte membranes may be important in the formation of irreversibly sickled cells.

  20. Functional dynamics of cell surface membrane proteins

    NASA Astrophysics Data System (ADS)

    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.

  1. Membrane glycoproteins of differentiating skeletal muscle cells

    SciTech Connect

    Miller, K.R.; Remy, C.N.; Smith, P.B.

    1987-05-01

    The composition of N-linked glycoprotein oligosaccharides was studied in myoblasts and myotubes of the C2 muscle cell line. Oligosaccharides were radioactively labelled for 15 hr with (TH) mannose and plasma membranes isolated. Ten glycopeptides were detected by SDS-PAGE and fluorography. The extent of labelling was 4-6 fold greater in myoblasts vs myotubes. A glycopeptide of Mr > 100,000 was found exclusively in myoblast membranes. Lectin chromatography revealed that the proportion of tri-, tetranntenary, biantennary and high mannose chains was similar throughout differentiation. The high mannose chain fraction was devoid of hybrid chains. The major high mannose chain contained nine mannose residues. The higher level of glycopeptide labelling in myoblasts vs myotubes corresponded to a 5-fold greater rate of protein synthesis. Pulse-chase experiments were used to follow the synthesis of the Dol-oligosaccharides. Myoblasts and myotubes labelled equivalently the glucosylated tetradecasaccharide but myoblasts labelled the smaller intermediates 3-4 greater than myotubes. Myoblasts also exhibited a 2-3 fold higher Dol-P dependent glycosyl transferase activity for chain elongation and Dol-sugar synthesis. Together these results show that the degree of protein synthesis and level of Dol-P are contributing factors in the higher capacity of myoblasts to produce N-glycoproteins compared to myotubes.

  2. Membrane proteomic analysis of pancreatic cancer cells

    PubMed Central

    2010-01-01

    Background Pancreatic cancer is one of the most aggressive human tumors due to its high potential of local invasion and metastasis. The aim of this study was to characterize the membrane proteomes of pancreatic ductal adenocarcinoma (PDAC) cells of primary and metastatic origins, and to identify potential target proteins related to metastasis of pancreatic cancer. Methods Membrane/membrane-associated proteins were isolated from AsPC-1 and BxPC-3 cells and identified with a proteomic approach based on SDS-PAGE, in-gel tryptic digestion and liquid chromatography with tandem mass spectrometry (LC-MS/MS). X! Tandem was used for database searching against the SwissProt human protein database. Results We identified 221 & 208 proteins from AsPC-1 and BxPC-3 cells, respectively, most of which are membrane or membrane-associated proteins. A hundred and nine proteins were found in both cell lines while the others were present in either AsPC-1 or BxPC-3 cells. Differentially expressed proteins between two cell lines include modulators of cell adhesion, cell motility or tumor invasion as well as metabolic enzymes involved in glycolysis, tricarboxylic acid cycle, or nucleotide/lipid metabolism. Conclusion Membrane proteomes of AsPC-1 (metastatic) and BxPC-3 (primary) cells are remarkably different. The differentially expressed membrane proteins may serve as potential targets for diagnostic and therapeutic interventions. PMID:20831833

  3. MEMBRANE FRACTIONS FROM Strongyloides venezuelensis IN THE IMMUNODIAGNOSIS OF HUMAN STRONGYLOIDIASIS

    PubMed Central

    Corral, Marcelo Andreetta; Paula, Fabiana Martins; Gottardi, Maiara; Meisel, Dirce Mary Correia Lima; Chieffi, Pedro Paulo; Gryschek, Ronaldo César Borges

    2015-01-01

    Strongyloides venezuelensis is a parasitic nematode of rodents frequently used to obtain heterologous antigens for the immunological diagnosis of human strongyloidiasis. The aim of this study was to evaluate membrane fractions from S. venezuelensis for human strongyloidiasis immunodiagnosis. Soluble and membrane fractions were obtained in phosphate saline (SS and SM) and Tris-HCl (TS and TM) from filariform larvae of S. venezuelensis. Ninety-two serum samples (n = 92) were obtained from 20 strongyloidiasis patients (Group I), 32 from patients with other parasitic diseases (Group II), and 40 from healthy individuals (Group III), and were analyzed by enzyme-linked immunosorbent assay (ELISA). Soluble fractions (SS and TS) showed 90.0% sensitivity and 88.9% specificity, whereas the membrane fractions (SM and TM) showed 95.0% sensitivity and 94.4% specificity. The present results suggest the possible use of membrane fractions of S. venezuelensis as an alternative antigen for human strongyloidiasis immunodiagnosis. PMID:25651330

  4. Membrane fractions from Strongyloides venezuelensis in the immunodiagnosis of human strongyloidiasis.

    PubMed

    Corral, Marcelo Andreetta; Paula, Fabiana Martins; Gottardi, Maiara; Meisel, Dirce Mary Correia Lima; Chieffi, Pedro Paulo; Gryschek, Ronaldo César Borges

    2015-01-01

    Strongyloides venezuelensis is a parasitic nematode of rodents frequently used to obtain heterologous antigens for the immunological diagnosis of human strongyloidiasis. The aim of this study was to evaluate membrane fractions from S. venezuelensis for human strongyloidiasis immunodiagnosis. Soluble and membrane fractions were obtained in phosphate saline (SS and SM) and Tris-HCl (TS and TM) from filariform larvae of S. venezuelensis. Ninety-two serum samples (n = 92) were obtained from 20 strongyloidiasis patients (Group I), 32 from patients with other parasitic diseases (Group II), and 40 from healthy individuals (Group III), and were analyzed by enzyme-linked immunosorbent assay (ELISA). Soluble fractions (SS and TS) showed 90.0% sensitivity and 88.9% specificity, whereas the membrane fractions (SM and TM) showed 95.0% sensitivity and 94.4% specificity. The present results suggest the possible use of membrane fractions of S. venezuelensis as an alternative antigen for human strongyloidiasis immunodiagnosis. PMID:25651330

  5. Rapid preparation of nuclei-depleted detergent-resistant membrane fractions suitable for proteomics analysis

    PubMed Central

    Adam, Rosalyn M; Yang, Wei; Di Vizio, Dolores; Mukhopadhyay, Nishit K; Steen, Hanno

    2008-01-01

    Background Cholesterol-rich membrane microdomains known as lipid rafts have been implicated in diverse physiologic processes including lipid transport and signal transduction. Lipid rafts were originally defined as detergent-resistant membranes (DRMs) due to their relative insolubility in cold non-ionic detergents. Recent findings suggest that, although DRMs are not equivalent to lipid rafts, the presence of a given protein within DRMs strongly suggests its potential for raft association in vivo. Therefore, isolation of DRMs represents a useful starting point for biochemical analysis of lipid rafts. The physicochemical properties of DRMs present unique challenges to analysis of their protein composition. Existing methods of isolating DRM-enriched fractions involve flotation of cell extracts in a sucrose density gradient, which, although successful, can be labor intensive, time consuming and results in dilute sucrose-containing fractions with limited utility for direct proteomic analysis. In addition, several studies describing the proteomic characterization of DRMs using this and other approaches have reported the presence of nuclear proteins in such fractions. It is unclear whether these results reflect trafficking of nuclear proteins to DRMs or whether they arise from nuclear contamination during isolation. To address these issues, we have modified a published differential detergent extraction method to enable rapid DRM isolation that minimizes nuclear contamination and yields fractions compatible with mass spectrometry. Results DRM-enriched fractions isolated using the conventional or modified extraction methods displayed comparable profiles of known DRM-associated proteins, including flotillins, GPI-anchored proteins and heterotrimeric G-protein subunits. Thus, the modified procedure yielded fractions consistent with those isolated by existing methods. However, we observed a marked reduction in the percentage of nuclear proteins identified in DRM fractions isolated with the modified method (15%) compared to DRMs isolated by conventional means (36%). Furthermore, of the 21 nuclear proteins identified exclusively in modified DRM fractions, 16 have been reported to exist in other subcellular sites, with evidence to suggest shuttling of these species between the nucleus and other organelles. Conclusion We describe a modified DRM isolation procedure that generates DRMs that are largely free of nuclear contamination and that is compatible with downstream proteomic analyses with minimal additional processing. Our findings also imply that identification of nuclear proteins in DRMs is likely to reflect legitimate movement of proteins between compartments, and is not a result of contamination during extraction. PMID:18534013

  6. Red cell membrane: past, present, and future

    PubMed Central

    Gallagher, Patrick G.

    2008-01-01

    As a result of natural selection driven by severe forms of malaria, 1 in 6 humans in the world, more than 1 billion people, are affected by red cell abnormalities, making them the most common of the inherited disorders. The non-nucleated red cell is unique among human cell type in that the plasma membrane, its only structural component, accounts for all of its diverse antigenic, transport, and mechanical characteristics. Our current concept of the red cell membrane envisions it as a composite structure in which a membrane envelope composed of cholesterol and phospholipids is secured to an elastic network of skeletal proteins via transmembrane proteins. Structural and functional characterization of the many constituents of the red cell membrane, in conjunction with biophysical and physiologic studies, has led to detailed description of the way in which the remarkable mechanical properties and other important characteristics of the red cells arise, and of the manner in which they fail in disease states. Current studies in this very active and exciting field are continuing to produce new and unexpected revelations on the function of the red cell membrane and thus of the cell in health and disease, and shed new light on membrane function in other diverse cell types. PMID:18988878

  7. Mastoparan selectively activates phospholipase D2 in cell membranes.

    PubMed

    Chahdi, Ahmed; Choi, Wahn Soo; Kim, Young Mi; Beaven, Michael A

    2003-04-01

    Both known isoforms of phospholipase (PL) D, PLD1 and PLD2, require phosphatidylinositol 4,5-bisphosphate for activity. However, PLD2 is fully active in the presence of this phospholipid, whereas PLD1 activation is dependent on additional factors such as ADP-ribosylation factor-1 (ARF-1) and protein kinase Calpha. We find that mastoparan, an activator of G(i) and mast cells, stimulates an intrinsic PLD activity, most likely PLD2, in fractions enriched in plasma membranes from rat basophilic leukemia 2H3 mast cells. Overexpression of PLD2, but not of PLD1, results in a large increase in the mastoparan-inducible PLD activity in membrane fractions, particularly those enriched in plasma membranes. As in previous studies, expressed PLD2 is localized primarily in the plasma membrane and PLD1 in granule membranes. Studies with pertussis toxin and other agents indicate that mastoparan stimulates PLD2 independently of G(i), ARF-1, protein kinase C, and calcium. Kinetic studies indicate that mastoparan interacts synergistically with phosphatidylinositol 4,5-bisphosphate and that oleate, itself a weak stimulant of PLD2 at low concentrations, is a competitive inhibitor of mastoparan stimulation of PLD2. Therefore, mastoparan may be useful for investigating the regulation of PLD2, particularly in view of the well studied molecular interactions of mastoparan with certain other strategic signaling proteins. PMID:12556526

  8. Proton conducting membrane for fuel cells

    DOEpatents

    Colombo, Daniel G.; Krumpelt, Michael; Myers, Deborah J.; Kopasz, John P.

    2005-12-20

    An ion conducting membrane comprising dendrimeric polymers covalently linked into a network structure. The dendrimeric polymers have acid functional terminal groups and may be covalently linked via linking compounds, cross-coupling reactions, or copolymerization reactions. The ion conducting membranes may be produced by various methods and used in fuel cells.

  9. Proton conducting membrane for fuel cells

    DOEpatents

    Colombo, Daniel G.; Krumpelt, Michael; Myers, Deborah J.; Kopasz, John P.

    2007-03-27

    An ion conducting membrane comprising dendrimeric polymers covalently linked into a network structure. The dendrimeric polymers have acid functional terminal groups and may be covalently linked via linking compounds, cross-coupling reactions, or copolymerization reactions. The ion conducting membranes may be produced by various methods and used in fuel cells.

  10. Identification of Glycan Structure Alterations on Cell Membrane Proteins in Desoxyepothilone B Resistant Leukemia Cells*

    PubMed Central

    Nakano, Miyako; Saldanha, Rohit; Göbel, Anja; Kavallaris, Maria; Packer, Nicolle H.

    2011-01-01

    Resistance to tubulin-binding agents used in cancer is often multifactorial and can include changes in drug accumulation and modified expression of tubulin isotypes. Glycans on cell membrane proteins play important roles in many cellular processes such as recognition and apoptosis, and this study investigated whether changes to the glycan structures on cell membrane proteins occur when cells become resistant to drugs. Specifically, we investigated the alteration of glycan structures on the cell membrane proteins of human T-cell acute lymphoblastic leukemia (CEM) cells that were selected for resistance to desoxyepothilone B (CEM/dEpoB). The glycan profile of the cell membrane glycoproteins was obtained by sequential release of N- and O-glycans from cell membrane fraction dotted onto polyvinylidene difluoride membrane with PNGase F and ?-elimination respectively. The released glycan alditols were analyzed by liquid chromatography (graphitized carbon)-electrospray ionization tandem MS. The major N-glycan on CEM cell was the core fucosylated ?2–6 monosialo-biantennary structure. Resistant CEM/dEpoB cells had a significant decrease of ?2–6 linked sialic acid on N-glycans. The lower ?2–6 sialylation was caused by a decrease in activity of ?-galactoside ?2–6 sialyltransferase (ST6Gal), and decreased expression of the mRNA. It is clear that the membrane glycosylation of leukemia cells changes during acquired resistance to dEpoB drugs and that this change occurs globally on all cell membrane glycoproteins. This is the first identification of a specific glycan modification on the surface of drug resistant cells and the mechanism of this downstream effect on microtubule targeting drugs may offer a route to new interventions to overcome drug resistance. PMID:21859949

  11. A novel bioactive membrane by cell electrospinning.

    PubMed

    Chen, Haiping; Liu, Yuanyuan; Hu, Qingxi

    2015-11-01

    Electrospinning permits fabrication of biodegradable matrices that can resemble the both scale and mechanical behavior of the native extracellular matrix. However, achieving high-cellular density and infiltration of cells within matrices with traditional technique remain challenging and time consuming. The cell electrospinning technique presented in this paper can mitigate the problems associated with these limitations. Cells encapsulated by the material in the cell electrospinning technique survived well and distributed homogenously within the nanofibrous membrane, and their vitality was improved to 133% after being cultured for 28 days. The electrospun nanofibrous membrane has a certain degradation property and favorable cell-membrane interaction that supports the active biocompatibility of the membrane. Its properties are helpful for supporting cell attachment and growth, maintaining phenotypic shape, and secreting an ample amount of extracellular matrix (ECM). This novel membrane may be a potential application within the field of tissue engineering. The ability of cell electrospinning to microintegrate cells into a biodegradable fibrous matrix embodies a novel tissue engineering approach that could be applied to fabricate a high cell density elastic tissue mimetic. PMID:26297530

  12. Alternate Fuel Cell Membranes for Energy Independence

    SciTech Connect

    Storey, Robson, F.; Mauritz, Kenneth, A.; Patton, Derek, L.; Savin, Daniel, A.

    2012-12-18

    The overall objective of this project was the development and evaluation of novel hydrocarbon fuel cell (FC) membranes that possess high temperature performance and long term chemical/mechanical durability in proton exchange membrane (PEM) fuel cells (FC). The major research theme was synthesis of aromatic hydrocarbon polymers of the poly(arylene ether sulfone) (PAES) type containing sulfonic acid groups tethered to the backbone via perfluorinated alkylene linkages and in some cases also directly attached to the phenylene groups along the backbone. Other research themes were the use of nitrogen-based heterocyclics instead of acid groups for proton conduction, which provides high temperature, low relative humidity membranes with high mechanical/thermal/chemical stability and pendant moieties that exhibit high proton conductivities in the absence of water, and synthesis of block copolymers consisting of a proton conducting block coupled to poly(perfluorinated propylene oxide) (PFPO) blocks. Accomplishments of the project were as follows: 1) establishment of a vertically integrated program of synthesis, characterization, and evaluation of FC membranes, 2) establishment of benchmark membrane performance data based on Nafion for comparison to experimental membrane performance, 3) development of a new perfluoroalkyl sulfonate monomer, N,N-diisopropylethylammonium 2,2-bis(p-hydroxyphenyl) pentafluoropropanesulfonate (HPPS), 4) synthesis of random and block copolymer membranes from HPPS, 5) synthesis of block copolymer membranes containing high-acid-concentration hydrophilic blocks consisting of HPPS and 3,3'-disulfonate-4,4'-dichlorodiphenylsulfone (sDCDPS), 6) development of synthetic routes to aromatic polymer backbones containing pendent 1H-1,2,3-triazole moieties, 7) development of coupling strategies to create phase-separated block copolymers between hydrophilic sulfonated prepolymers and commodity polymers such as PFPO, 8) establishment of basic performance properties of experimental membranes, 9) fabrication and FC performance testing of membrane electrode assemblies (MEA) from experimental membranes, and 10) measurement of ex situ and in situ membrane durability of experimental membranes. Although none of the experimental hydrocarbon membranes that issued from the project displayed proton conductivities that met DOE requirements, the project contributed to our basic understanding of membrane structure-property relationships in a number of key respects. An important finding of the benchmark studies is that physical degradation associated with humidity and temperature variations in the FC tend to open new fuel crossover pathways and act synergistically with chemical degradation to accelerate overall membrane degradation. Thus, for long term membrane survival and efficient fuel utilization, membranes must withstand internal stresses due to humidity and temperature changes. In this respect, rigid aromatic hydrocarbon fuel cell membranes, e.g. PAES, offer an advantage over un-modified Nafion membranes. The benchmark studies also showed that broadband dielectric spectroscopy is a potentially powerful tool in assessing shifts in the fundamental macromolecular dynamics caused by Nafion chemical degradation, and thus, this technique is of relevance in interrogating proton exchange membrane durability in fuel cells and macromolecular dynamics as coupled to proton migration, which is of fundamental relevance in proton exchange membranes in fuel cells. A key finding from the hydrocarbon membrane synthesis effort was that rigid aromatic polymers containing isolated ion exchange groups tethered tightly to the backbone (short tether), such as HPPS, provide excellent mechanical and durability properties but do not provide sufficient conductivity, in either random or block configuration, when used as the sole ion exchange monomer. However, we continue to hypothesize that longer tethers, and tethered groups spaced more closely within the hydrophilic chain elements of the polymer, will yield highly conductive materials with excellent mech

  13. Advanced membrane electrode assemblies for fuel cells

    DOEpatents

    Kim, Yu Seung; Pivovar, Bryan S

    2014-02-25

    A method of preparing advanced membrane electrode assemblies (MEA) for use in fuel cells. A base polymer is selected for a base membrane. An electrode composition is selected to optimize properties exhibited by the membrane electrode assembly based on the selection of the base polymer. A property-tuning coating layer composition is selected based on compatibility with the base polymer and the electrode composition. A solvent is selected based on the interaction of the solvent with the base polymer and the property-tuning coating layer composition. The MEA is assembled by preparing the base membrane and then applying the property-tuning coating layer to form a composite membrane. Finally, a catalyst is applied to the composite membrane.

  14. Advanced membrane electrode assemblies for fuel cells

    DOEpatents

    Kim, Yu Seung; Pivovar, Bryan S.

    2012-07-24

    A method of preparing advanced membrane electrode assemblies (MEA) for use in fuel cells. A base polymer is selected for a base membrane. An electrode composition is selected to optimize properties exhibited by the membrane electrode assembly based on the selection of the base polymer. A property-tuning coating layer composition is selected based on compatibility with the base polymer and the electrode composition. A solvent is selected based on the interaction of the solvent with the base polymer and the property-tuning coating layer composition. The MEA is assembled by preparing the base membrane and then applying the property-tuning coating layer to form a composite membrane. Finally, a catalyst is applied to the composite membrane.

  15. Durability of PEM Fuel Cell Membranes

    NASA Astrophysics Data System (ADS)

    Huang, Xinyu; Reifsnider, Ken

    Durability is still a critical limiting factor for the commercialization of polymer electrolyte membrane (PEM) fuel cells, a leading energy conversion technology for powering future hydrogen fueled automobiles, backup power systems (e.g., for base transceiver station of cellular networks), portable electronic devices, etc. Ionic conducting polymer (ionomer) electrolyte membranes are the critical enabling materials for the PEM fuel cells. They are also widely used as the central functional elements in hydrogen generation (e.g., electrolyzers), membrane cell for chlor-alkali production, etc. A perfluorosulfonic acid (PFSA) polymer with the trade name Nafion® developed by DuPont™ is the most widely used PEM in chlor-alkali cells and PEM fuel cells. Similar PFSA membranes have been developed by Dow Chemical, Asahi Glass, and lately Solvay Solexis. Frequently, such membranes serve the dual function of reactant separation and selective ionic conduction between two otherwise separate compartments. For some applications, the compromise of the "separation" function via the degradation and mechanical failure of the electrolyte membrane can be the life-limiting factor; this is particularly the case for PEM in hydrogen/oxygen fuel cells.

  16. Alginate block fractions and their effects on membrane fouling.

    PubMed

    Meng, Shujuan; Liu, Yu

    2013-11-01

    Alginate has been commonly used as a model foulant in studies of membrane organic fouling. As a complex polymer, alginate is composed of two different monomers, namely M ((1 ? 4) linked ?-D-mannopyranuronic acid) and G ((1 ? 4) linked ?-L-gulopyranuronic acid) which are randomly arranged into MG-, MM- and GG-blocks. So far, little information is available about fouling propensity of each block in microfiltration. In this study, microfiltration experiments were conducted respectively with MG-, MM- and GG-blocks separated from alginate under defined conditions. Results showed the severest fouling in the filtration of MG-block, and the least flux decline in the filtration of MM-block. The initial pore blocking was found to be responsible for the fouling observed in MG-block filtration, while the cake layer formed on membrane surface during the MM-block filtration could serve as a pre-filter that prevented membrane from further pore blocking. In order to look into fouling mechanisms, the effects of transparent exopolymeric particles (TEP) on membrane fouling were also studied. TEP were found to form through aggregation or cross-link of alginate blocks. As TEP were bigger than original alginate blocks, they could facilitate the formation of cake layer on membrane surface. It was observed that more TEP were produced from MM-blocks than from MG-blocks in solutions. This in turn explained why cake resistance was dominant in the filtration of MM-blocks as compared to MG-blocks. The analysis by the extended Derjaguin-Landau-Verwey-Overbeek (XDLVO) theory further revealed that MM-blocks had lowest cohesive interaction energy among all three alginate blocks, which favoured aggregation of MM-blocks, and ultimately leading to the formation of more TEP. This study provided insights into the roles of different alginate blocks in development of membrane fouling, and suggested that the membrane fouling would be related to molecular structure of alginate. PMID:24070866

  17. Proteomic Profiling of the Outer Membrane Fraction of the Obligate Intracellular Bacterial Pathogen Ehrlichia ruminantium

    PubMed Central

    Moumène, Amal; Marcelino, Isabel; Ventosa, Miguel; Gros, Olivier; Lefrançois, Thierry; Vachiéry, Nathalie

    2015-01-01

    The outer membrane proteins (OMPs) of Gram-negative bacteria play a crucial role in virulence and pathogenesis. Identification of these proteins represents an important goal for bacterial proteomics, because it aids in vaccine development. Here, we have developed such an approach for Ehrlichia ruminantium, the obligate intracellular bacterium that causes heartwater. A preliminary whole proteome analysis of elementary bodies, the extracellular infectious form of the bacterium, had been performed previously, but information is limited about OMPs in this organism and about their role in the protective immune response. Identification of OMPs is also essential for understanding Ehrlichia’s OM architecture, and how the bacterium interacts with the host cell environment. First, we developed an OMP extraction method using the ionic detergent sarkosyl, which enriched the OM fraction. Second, proteins were separated via one-dimensional electrophoresis, and digested peptides were analyzed via nano-liquid chromatographic separation coupled with mass spectrometry (LC-MALDI-TOF/TOF). Of 46 unique proteins identified in the OM fraction, 18 (39%) were OMPs, including 8 proteins involved in cell structure and biogenesis, 4 in transport/virulence, 1 porin, and 5 proteins of unknown function. These experimental data were compared to the predicted subcellular localization of the entire E. ruminantium proteome, using three different algorithms. This work represents the most complete proteome characterization of the OM fraction in Ehrlichia spp. The study indicates that suitable subcellular fractionation experiments combined with straightforward computational analysis approaches are powerful for determining the predominant subcellular localization of the experimentally observed proteins. We identified proteins potentially involved in E. ruminantium pathogenesis, which are good novel targets for candidate vaccines. Thus, combining bioinformatics and proteomics, we discovered new OMPs for E. ruminantium that are valuable data for those investigating new vaccines against this organism. In summary, we provide both pioneering data and novel insights into the pathogenesis of this obligate intracellular bacterium. PMID:25710494

  18. The Isolation and Partial Characterization of a Membrane Fraction Containing Phytochrome 12

    PubMed Central

    Marmé, Dieter; Mackenzie, John M.; Boisard, Jean; Briggs, Winslow R.

    1974-01-01

    If 4-day-old dark-grown zucchini squash seedlings (Cucurbita pepo L. cv. Black Beauty) are exposed briefly to red light, subsequent cell fractionation yields about 40% of the total extractable phytochrome in the far red-absorbing form bound to a particulate fraction. The amount of far red-absorbing phytochrome in the pellet is strongly dependent on the Mg concentration in the extraction medium. The apparent density of the Pfr-containing particles following sedimentation on sucrose gradients corresponds to 15% (w/w) sucrose with 0.1 mm Mg and 40% sucrose with 10 mm Mg. This particulate fraction could be readily separated from mitochondria and other particulate material by taking advantage of these apparent density changes with changes in Mg concentration. Electron microscopy of negatively stained preparations shows that with 1 mm Mg only minute particles are present. These were too small to reveal structural detail with this technique. With 3 mm Mg, separate membranous vesicles between 400 and 600 Ångstroms in diameter appear. At higher Mg concentrations, the vesicles aggregate, causing obvious turbity. The effect of Mg on vesicle formation and aggregation is completely reversible. Above 10 mm Mg, vesicle aggregation persists, but the percentage of bound Pfr decreases. Images PMID:16658871

  19. Isolation of H(+),K(+)-ATPase-enriched Membrane Fraction from Pig Stomachs.

    PubMed

    Abe, Kazuhiro; Olesen, Claus

    2016-01-01

    Gastric H(+),K(+)-ATPase is an ATP-driven proton pump responsible for the acid secretion. Here, we describe the procedure for the isolation of H(+),K(+)-ATPase-enriched membrane vesicle fractions by Ficoll/sucrose density gradient centrifugation. Further purification by SDS treatment of membrane fractions is also introduced. These procedures allow us to obtain purified protein preparations in a quantity of several tens of milligrams, with the specific activity of ~480 ?mol/mg/h. High purity and stability of H(+),K(+)-ATPase in the membrane preparation enable us to evaluate its detailed biochemical properties, and also to obtain 2D crystals for structural analysis. PMID:26695019

  20. Cell membrane softening in human breast and cervical cancer cells

    NASA Astrophysics Data System (ADS)

    Händel, Chris; Schmidt, B. U. Sebastian; Schiller, Jürgen; Dietrich, Undine; Möhn, Till; Kießling, Tobias R.; Pawlizak, Steve; Fritsch, Anatol W.; Horn, Lars-Christian; Briest, Susanne; Höckel, Michael; Zink, Mareike; Käs, Josef A.

    2015-08-01

    Biomechanical properties are key to many cellular functions such as cell division and cell motility and thus are crucial in the development and understanding of several diseases, for instance cancer. The mechanics of the cellular cytoskeleton have been extensively characterized in cells and artificial systems. The rigidity of the plasma membrane, with the exception of red blood cells, is unknown and membrane rigidity measurements only exist for vesicles composed of a few synthetic lipids. In this study, thermal fluctuations of giant plasma membrane vesicles (GPMVs) directly derived from the plasma membranes of primary breast and cervical cells, as well as breast cell lines, are analyzed. Cell blebs or GPMVs were studied via thermal membrane fluctuations and mass spectrometry. It will be shown that cancer cell membranes are significantly softer than their non-malignant counterparts. This can be attributed to a loss of fluid raft forming lipids in malignant cells. These results indicate that the reduction of membrane rigidity promotes aggressive blebbing motion in invasive cancer cells.

  1. Fuel cell subassemblies incorporating subgasketed thrifted membranes

    SciTech Connect

    Iverson, Eric J; Pierpont, Daniel M; Yandrasits, Michael A; Hamrock, Steven J; Obradovich, Stephan J; Peterson, Donald G

    2014-01-28

    A fuel cell roll good subassembly is described that includes a plurality of individual electrolyte membranes. One or more first subgaskets are attached to the individual electrolyte membranes. Each of the first subgaskets has at least one aperture and the first subgaskets are arranged so the center regions of the individual electrolyte membranes are exposed through the apertures of the first subgaskets. A second subgasket comprises a web having a plurality of apertures. The second subgasket web is attached to the one or more first subgaskets so the center regions of the individual electrolyte membranes are exposed through the apertures of the second subgasket web. The second subgasket web may have little or no adhesive on the subgasket surface facing the electrolyte membrane.

  2. Selectivity of Direct Methanol Fuel Cell Membranes.

    PubMed

    Aricò, Antonino S; Sebastian, David; Schuster, Michael; Bauer, Bernd; D'Urso, Claudia; Lufrano, Francesco; Baglio, Vincenzo

    2015-01-01

    Sulfonic acid-functionalized polymer electrolyte membranes alternative to Nafion(®) were developed. These were hydrocarbon systems, such as blend sulfonated polyetheretherketone (s-PEEK), new generation perfluorosulfonic acid (PFSA) systems, and composite zirconium phosphate-PFSA polymers. The membranes varied in terms of composition, equivalent weight, thickness, and filler and were investigated with regard to their methanol permeation characteristics and proton conductivity for application in direct methanol fuel cells. The behavior of the membrane electrode assemblies (MEA) was investigated in fuel cell with the aim to individuate a correlation between membrane characteristics and their performance in a direct methanol fuel cell (DMFC). The power density of the DMFC at 60 °C increased according to a square root-like function of the membrane selectivity. This was defined as the reciprocal of the product between area specific resistance and crossover. The power density achieved at 60 °C for the most promising s-PEEK-based membrane-electrode assembly (MEA) was higher than the benchmark Nafion(®) 115-based MEA (77 mW·cm(-2) vs. 64 mW·cm(-2)). This result was due to a lower methanol crossover (47 mA·cm(-2) equivalent current density for s-PEEK vs. 120 mA·cm(-2) for Nafion(®) 115 at 60 °C as recorded at OCV with 2 M methanol) and a suitable area specific resistance (0.15 Ohm cm² for s-PEEK vs. 0.22 Ohm cm² for Nafion(®) 115). PMID:26610582

  3. Cell or Cell Membrane-Based Drug Delivery Systems

    PubMed Central

    Tan, Songwei; Wu, Tingting; Zhang, Dan; Zhang, Zhiping

    2015-01-01

    Natural cells have been explored as drug carriers for a long period. They have received growing interest as a promising drug delivery system (DDS) until recently along with the development of biology and medical science. The synthetic materials, either organic or inorganic, are found to be with more or less immunogenicity and/or toxicity. The cells and extracellular vesicles (EVs), are endogenous and thought to be much safer and friendlier. Furthermore, in view of their host attributes, they may achieve different biological effects and/or targeting specificity, which can meet the needs of personalized medicine as the next generation of DDS. In this review, we summarized the recent progress in cell or cell membrane-based DDS and their fabrication processes, unique properties and applications, including the whole cells, EVs and cell membrane coated nanoparticles. We expect the continuing development of this cell or cell membrane-based DDS will promote their clinic applications. PMID:26000058

  4. Analysis of plasma membrane phosphoinositides from fusogenic carrot cells

    SciTech Connect

    Wheeler, J.J.; Boss, W.F.

    1987-04-01

    Phosphatidylinositol monophosphate (PIP) and phosphatidylinositol bisphosphate (PIP/sub 2/) were found to be associated with the plasma membrane-rich fractions isolated by aqueous polymer two-phase partitioning from fusogenic cells. They represented at least 5% and 0.7% of the total inositol-labeled lipids in the plasma membrane-rich fractions, respectively, and were present in a ratio of about 7:1 (PIP:PIP/sub 2/). In addition, two unidentified inositol-labeled compounds, which together were approximately 3% of the inositol-labeled lipids, were found predominantly in the plasma membrane-rich fractions and migrated between PIP/sub 2/ and PIP. The R/sub f/s of these compounds were approximately 0.31 and 0.34 in the solvent system CHCl/sub 3/:MeOH:15N NH/sub 4/OH:H/sub 2/O (90:90:7:22) using LK5 plates presoaked in 1% potassium oxalate. These compounds incorporated /sup 32/P/sub i/, (/sup 3/H)inositol and were hydrolyzed in mild base. These data suggested that they were glycero-phospholipids. Although the compounds did not comigrate with lysoPIP obtained from bovine brain (R/sub f/ approx. 0.35), when endogenous PIP was hydrolyzed to lysoPIP, the breakdown product migrated in the region of the unidentified inositol lipids.

  5. Cyclopropyl Sterol and Phospholipid Composition of Membrane Fractions from Maize Roots Treated with Fenpropimorph

    PubMed Central

    Grandmougin, Anne; Bouvier-Navé, Pierrette; Ullmann, Pascaline; Benveniste, Pierre; Hartmann, Marie-Andrée

    1989-01-01

    Maize (Zea mays L.) caryopses were grown in the presence of fenpropimorph, a systemic fungicide, for 7 days in the dark. Membrane fractions enriched, respectively, in endoplasmic reticulum, plasma membrane, and mitochondria were isolated from control and treated maize roots and analyzed for their free sterol, phospholipid, and fatty acid composition. In treated plants, the intracellular distribution of free sterols was dramatically modified both qualitatively and quantitatively. The normally occurring ?5-sterols disappeared almost completely and were replaced by 9?, 19-cyclopropyl sterols, mainly cycloeucalenol and 24-methyl pollinastanol. These new compounds were found to accumulate in all the membrane fractions in such a way that the endoplasmic reticulum-rich fraction became the richest one in free sterols instead of the plasma membrane. In contrast, the fenpropimorph treatment of maize roots was shown not to affect either the relative proportions or the amounts of the individual phospholipids, but an increase in the unsaturation index of phospholipid-fatty acyl chains of the endoplasmic reticulum-rich fraction was observed. The present data suggest that, in higher plant membranes, cyclopropyl sterols could play a structural role similar to that of the bulk of ?5-sterols. PMID:16666813

  6. Pattern formation in cell membrane adhesion

    NASA Astrophysics Data System (ADS)

    Discher, Dennis; Hategan, A.; Sengupta, K.; Sackmann, E.

    2004-03-01

    Strong adhesion of highly active cells often nucleates focal adhesions or related structures that are, over time, reinforced by cytoskeleton (actin, etc.). Red cells lack such complex adhesion systems, but they are shown here to also exhibit complex spatial patterns within an adhesive contact zone. While strong adhesion and spreading of the red cell to a dense poly-L-lysine surface appears complete in < 1 s by reflective interference microscopy, over longer times of 10-15 min or more distinct patterns in fluorescently labeled membrane components emerge. The fluorescent lipid Fl-PE (fluorescein phosphoethanolamine), in particular, is seen to diffuse and reorganize (eg. worm-like domains of <500 nm) within the contact zone, independent of whether the cell is intact or ruptured. Lipid patterns are accompanied by visible perturbations in band 3 distribution and weaker perturbations in membrane skeleton actin. Although fluorescent poly-L-lysine is shown to be uniform under cells, pressing down on the membrane quenches the lipid patterns and reveals the topographical basis for pattern formation. Regions of strong contact are thus separated by regions where the membrane is more distant from the surface.

  7. Synthesis of cell wall xylans and glucans by golgi membranes

    SciTech Connect

    Gibeaut, D.M.; Carpita, N.C. )

    1989-04-01

    We investigated the biosynthesis of mixed-linkage {beta}-D-glucan and glucuronoarabinoxylans which make up the hemicellulosic matrix of the primary cell walls of maize and other cereal grasses. The Golgi apparatus was enriched from plasma membrane and other organelles by flotation density gradient centrifugation. Glucan synthase I and II, which are established markers for Golgi and plasma membrane, respectively, displayed considerable overlap in conventional separations with sucrose density gradients. Flotation gradients improved separation of the membranes substantially, but the different synthases themselves also incorporated radioactivity from either 10 {mu}M or 1 mM UDP-({sup 14}C)-glucose into polymer. Relative incorporation of radioactivity into polymers from UDP-({sup 14}C)-xylose by the various membrane fractions was nearly identical to relative IDPase activities, indicating that combined xylosyl transferase-xylan synthase represents a new, unequivocal marker for the Golgi apparatus. We also have developed techniques of gas-liquid chromatography and radiogas proportional counting to achieve capillary quality separation of partially methylated alditol acetates with simultaneous determination of radioactivity in the derivatives. Digestion of polymeric products by specific endo-glycanohydrolases to diagnostic oligosaccharides also reveal specific kinds of polysaccharides synthesized by the Golgi membranes. A combination of these techniques provides unequivocal determination of the linkage structure of specific polymers synthesized by the purified Golgi apparatus.

  8. Hypercompliant Apical Membranes of Bladder Umbrella Cells

    PubMed Central

    Mathai, John C.; Zhou, Enhua H.; Yu, Weiqun; Kim, Jae Hun; Zhou, Ge; Liao, Yi; Sun, Tung-Tien; Fredberg, Jeffrey J.; Zeidel, Mark L.

    2014-01-01

    Urinary bladder undergoes dramatic volume changes during filling and voiding cycles. In the bladder the luminal surface of terminally differentiated urothelial umbrella cells is almost completely covered by plaques. These plaques (500 to 1000 nm) are made of a family of proteins called uroplakins that are known to form a tight barrier to prevent leakage of water and solutes. Electron micrographs from previous studies show these plaques to be interconnected by hinge regions to form structures that appear rigid, but these same structures must accommodate large changes in cell shape during voiding and filling cycles. To resolve this paradox, we measured the stiffness of the intact, living urothelial apical membrane and found it to be highly deformable, even more so than the red blood cell membrane. The intermediate cells underlying the umbrella cells do not have uroplakins but their membranes are an order of magnitude stiffer. Using uroplakin knockout mouse models we show that cell compliance is conferred by uroplakins. This hypercompliance may be essential for the maintenance of barrier function under dramatic cell deformation during filling and voiding of the bladder. PMID:25229135

  9. Membrane electrode assembly for a fuel cell

    NASA Technical Reports Server (NTRS)

    Prakash, Surya (Inventor); Narayanan, Sekharipuram R. (Inventor); Atti, Anthony (Inventor); Olah, George (Inventor); Smart, Marshall C. (Inventor)

    2006-01-01

    A catalyst ink for a fuel cell including a catalytic material and poly(vinylidene fluoride). The ink may be applied to a substrate to form an electrode, or bonded with other electrode layers to form a membrane electrode assembly (MEA).

  10. Polyphosphoinositides are present in plasma membranes isolated from fusogenic carrot cells

    SciTech Connect

    Wheeler, J.J.; Boss, W.F.

    1987-10-01

    Fusogenic carrot cells grown in suspension culture were labeled 12 hours with myo-(2-/sup 3/H)inositol. Plasma membranes were isolated from the prelabeled fusogenic carrot cells by both aqueous polymer two-phase partitioning and Renografin density gradients. With both methods, the plasma membrane-enriched fractions, as identified by marker enzymes, were enriched in (/sup 3/H)inositol-labeled phosphatidylinositol monophosphate (PIP) and phosphatidylinositol bisphosphate (PIP/sub 2/). An additional (/sup 3/H)inositol-labeled lipid, lysophosphatidylinositol monophosphate, which migrated between PIP and PIP/sub 2/ on thin layer plates, was found primarily in the plasma membrane-rich fraction of the fusogenic cells. This was in contrast to lysophosphatidylinositol which is found primarily in the lower phase, microsomal/mitchrondrial-rich fraction.

  11. Sputter-deposited fuel cell membranes and electrodes

    NASA Technical Reports Server (NTRS)

    Narayanan, Sekharipuram R. (Inventor); Jeffries-Nakamura, Barbara (Inventor); Chun, William (Inventor); Ruiz, Ron P. (Inventor); Valdez, Thomas I. (Inventor)

    2001-01-01

    A method for preparing a membrane for use in a fuel cell membrane electrode assembly includes the steps of providing an electrolyte membrane, and sputter-depositing a catalyst onto the electrolyte membrane. The sputter-deposited catalyst may be applied to multiple sides of the electrolyte membrane. A method for forming an electrode for use in a fuel cell membrane electrode assembly includes the steps of obtaining a catalyst, obtaining a backing, and sputter-depositing the catalyst onto the backing. The membranes and electrodes are useful for assembling fuel cells that include an anode electrode, a cathode electrode, a fuel supply, and an electrolyte membrane, wherein the electrolyte membrane includes a sputter-deposited catalyst, and the sputter-deposited catalyst is effective for sustaining a voltage across a membrane electrode assembly in the fuel cell.

  12. Membrane protein expression: no cells required.

    PubMed

    Katzen, Federico; Peterson, Todd C; Kudlicki, Wieslaw

    2009-08-01

    Structural and functional studies of membrane proteins have been severely hampered by difficulties in producing sufficient quantities of properly folded protein products. It is well established that cell-based expression of membrane proteins is generally problematic and frequently results in low yield, cell toxicity, protein aggregation and misfolding. Owing to its inherent open nature, cell-free protein expression has become a highly promising tool for the fast and efficient production of these difficult-to-express proteins. Here we review the most recent advances in this field, underscoring the potentials and weaknesses of the newly developed approaches and place specific emphasis on the use of nanolipoprotein particles (NLPs or nanodiscs). PMID:19616329

  13. Membrane processes relevant for the polymer electrolyte fuel cell

    E-print Network

    Kjelstrup, Signe

    Membrane processes relevant for the polymer electrolyte fuel cell Aleksander Kolstad Chemical. The important aspects concerning the Polymer Electrolyte Membrane Fuel Cell, more commonly known as Proton Exchange Membrane Fuel Cell (PEMFC), have been studied in two separate parts. Part 1 of the thesis

  14. Regulation of beta-catenin trafficking to the membrane in living cells.

    PubMed

    Johnson, Michael; Sharma, Manisha; Jamieson, Cara; Henderson, Jasmine M; Mok, Myth T S; Bendall, Linda; Henderson, Beric R

    2009-02-01

    Beta-catenin is a key mediator of the Wnt signaling process and accumulates in the nucleus and at the membrane in response to Wnt-mediated inhibition of GSK-3beta. In this study we used live cell photobleaching experiments to determine the dynamics and rate of recruitment of beta-catenin at membrane adherens junctions (cell adhesion) and membrane ruffles (cell migration). First, we confirmed the nuclear-cytoplasmic shuttling of GFP-tagged beta-catenin, and found that a small mobile pool of beta-catenin can move from the nucleus to membrane ruffles in NIH 3T3 fibroblasts with a t(0.5) of approximately 30 s. Thus, beta-catenin can shuttle between the nucleus and plasma membrane. The localized recruitment of beta-catenin-GFP to membrane ruffles was more rapid, and the strong recovery observed after bleaching (mobile fraction 53%, t(0.5) approximately 5 s) is indicative of high turnover and transient association. In contrast, beta-catenin-GFP displayed poor recovery at adherens junctions in MDCK epithelial cells (mobile fraction 10%, t(0.5) approximately 8 s), indicating stable retention at these membrane structures. We previously identified IQGAP1 as an upstream regulator of beta-catenin at the membrane, and this is supported by photobleaching assays which now reveal IQGAP1 to be more stably anchored at membrane ruffles than beta-catenin. Further analysis showed that LiCl-mediated inactivation of the kinase GSK-3beta increased beta-catenin membrane ruffle staining; this correlated with a faster rate of recruitment and not increased membrane retention of beta-catenin. In summary, beta-catenin displays a high turnover rate at membrane ruffles consistent with its dynamic internalization and recycling at these sites by macropinocytosis. PMID:19036347

  15. Interactions of Model Cell Membranes with Nanoparticles

    NASA Astrophysics Data System (ADS)

    D'Angelo, S. M.; Camesano, T. A.; Nagarajan, R.

    2011-12-01

    The same properties that give nanoparticles their enhanced function, such as high surface area, small size, and better conductivity, can also alter the cytotoxicity of nanomaterials. Ultimately, many of these nanomaterials will be released into the environment, and can cause cytotoxic effects to environmental bacteria, aquatic organisms, and humans. Previous results from our laboratory suggest that nanoparticles can have a detrimental effect on cells, depending on nanoparticle size. It is our goal to characterize the properties of nanomaterials that can result in membrane destabilization. We tested the effects of nanoparticle size and chemical functionalization on nanoparticle-membrane interactions. Gold nanoparticles at 2, 5,10, and 80 nm were investigated, with a concentration of 1.1x1010 particles/mL. Model cell membranes were constructed of of L-?-phosphatidylcholine (egg PC), which has negatively charged lipid headgroups. A quartz crystal microbalance with dissipation (QCM-D) was used to measure frequency changes at different overtones, which were related to mass changes corresponding to nanoparticle interaction with the model membrane. In QCM-D, a lipid bilayer is constructed on a silicon dioxide crystal. The crystals, oscillate at different harmonic frequencies depending upon changes in mass or energy dissipation. When mass is added to the crystal surface, such as through addition of a lipid vesicle solution, the frequency change decreases. By monitoring the frequency and dissipation, we could verify that a supported lipid bilayer (SLB) formed on the silica surface. After formation of the SLB, the nanoparticles can be added to the system, and the changes in frequency and dissipation are monitored in order to build a mechanistic understanding of nanoparticle-cell membrane interactions. For all of the smaller nanoparticles (2, 5, and 10 nm), nanoparticle addition caused a loss of mass from the lipid bilayer, which appears to be due to the formation of holes or pores in the cell membrane. The dissipation changes were small, which indicates that even with the membrane destabilization that occurs, the overall structure of the bilayer is not greatly perturbed. For the 80 nm nanoparticles, we initially saw the same pattern as the smaller nanoparticles with a mass loss from the membrane, but eventually we saw a large decrease in frequency, representing an increase in mass. This addition of mass may be attributed to adsorption of the gold nanoparticles onto the bilayer. The 80 nm particles also created a change in the energy dissipation, which suggests that the formation of the bilayer was altered with the adsorbed particles. This study suggests that nanoparticle size controls the mechanism by which nanoparticles interact with model cell membranes. We are extending this work to other types of gold nanoparticles. We are interested in examining the role of nanoparticle hydrophobicity and type of chemical functionalization on the interactions of the nanoparticle with a model membrane. We are also conducting studies on environmental bacteria, to correlate the mechanisms of nanoparticle cytoxicity with killing data on bacterial cells.

  16. Catalytic membranes for fuel cells

    DOEpatents

    Liu, Di-Jia (Naperville, IL); Yang, Junbing (Bolingbrook, IL); Wang, Xiaoping (Naperville, IL)

    2011-04-19

    A fuel cell of the present invention comprises a cathode and an anode, one or both of the anode and the cathode including a catalyst comprising a bundle of longitudinally aligned graphitic carbon nanotubes including a catalytically active transition metal incorporated longitudinally and atomically distributed throughout the graphitic carbon walls of said nanotubes. The nanotubes also include nitrogen atoms and/or ions chemically bonded to the graphitic carbon and to the transition metal. Preferably, the transition metal comprises at least one metal selected from the group consisting of Fe, Co, Ni, Mn, and Cr.

  17. Activation of intrinsic apoptotic signaling pathway in cancer cells by Cymbopogon citratus polysaccharide fractions.

    PubMed

    Thangam, Ramar; Sathuvan, Malairaj; Poongodi, Arasu; Suresh, Veeraperumal; Pazhanichamy, Kalailingam; Sivasubramanian, Srinivasan; Kanipandian, Nagarajan; Ganesan, Nalini; Rengasamy, Ramasamy; Thirumurugan, Ramasamy; Kannan, Soundarapandian

    2014-07-17

    Essential oils of Cymbopogon citratus were already reported to have wide ranging medical and industrial applications. However, information on polysaccharides from the plant and their anticancer activities are limited. In the present study, polysaccharides from C. citratus were extracted and fractionated by anion exchange and gel filtration chromatography. Two different polysaccharide fractions such as F1 and F2 were obtained, and these fractions were found to have distinct acidic polysaccharides as characterized by their molecular weight and sugar content. NMR spectral analysis revealed the presence of (1?4) linked b-d-Xylofuranose moiety in these polysaccharides. Using these polysaccharide fractions F1 and F2, anti-inflammatory and anticancer activities were evaluated against cancer cells in vitro and the mechanism of action of the polysaccharides in inducing apoptosis in cancer cells via intrinsic pathway was also proposed. Two different reproductive cancer cells such as Siha and LNCap were employed for in vitro studies on cytotoxicity, induction of apoptosis and apoptotic DNA fragmentation, changes in mitochondrial membrane potential, and profiles of gene and protein expression in response to treatment of cells by the polysaccharide fractions. These polysaccharide fractions exhibited potential cytotoxic and apoptotic effects on carcinoma cells, and they induced apoptosis in these cells through the events of up-regulation of caspase 3, down-regulation of bcl-2 family genes followed by cytochrome c release. PMID:24702929

  18. Analyzing the effects of surface distribution of pores in cell electroporation for a cell membrane containing cholesterol

    E-print Network

    Shil, Pratip; Vidyasagar, Pandit B

    2007-01-01

    This paper presents a model and numerical analysis of transmembrane potential induced in biological cell membrane under the influence of externally applied electric field (i.e., electroporation). This model differs from the established models in two distinct ways. Firstly, it incorporates the presence of cholesterol (~20% mole-fraction) in the membrane. Secondly, it considers the dependence of pore distribution on the variation of transmembrane potential from one region of the cell to the other. Formulation is based on the role of membrane tension and electrical forces in the formation of pores in a cell membrane, which is considered as an infinitesimally thin insulator. The model has been used to explore the creation and evolution of pores and to determine the number and size of pores as function of applied electric field (magnitude & duration). Results show that the presence of cholesterol enhances poration by changing the membrane tension. Analysis indicate that the number of pores, average pore radii ...

  19. Directing membrane chromatography to manufacture ?1-antitrypsin from human plasma fraction IV.

    PubMed

    Fan, Jinxin; Luo, Jianquan; Song, Weijie; Chen, Xiangrong; Wan, Yinhua

    2015-12-01

    The surging demand for plasma proteins, mainly driven by the growing market and the development of new therapeutic indications, is promoting manufacturers to improve the throughput of plasma proteins. Due to the inherent convective mass transfer, membrane chromatography has been proved to be an efficient approach for extracting a small amount of target proteins from large-volume feed. In this study, ?1-antitrypsin (AAT) was extracted from human plasma fraction IV by a two-step membrane chromatography. An anion-exchange membrane chromatography (AEMC) was used to capture the plasma proteins in bind/elute mode, and the obtained effluent was further polished by a hydrophobic interaction membrane chromatography (HIMC) in flow-through mode. Under optimal conditions, the recovery and purity of AAT achieved 87.0% and 0.58 AAT/protein (g/g) by AEMC, respectively. After the precise polishing by HIMC, the purity of AAT was 1.22 AAT/protein (g/g). The comparison results showed that membrane chromatography outperformed column chromatography in both steps because of its high throughput. This two-step membrane chromatography could obtain an AAT recovery of 83.3% and an activity recovery of 91.4%. The outcome of this work not only offers an alternative process for protein purification from plasma, but also provides guidelines for manufacturing product from a large-volume feed with multi-components by membrane chromatography. PMID:26518493

  20. Characteristics of polyethersulfone/sulfonated polyimide blend membrane for proton exchange membrane fuel cell.

    PubMed

    Wang, L; Yi, B L; Zhang, H M; Xing, D M

    2008-04-10

    Solution-cast membranes from sulfonated polyimide (SPI) and its blend were prepared from polyethersulfone (PES) and SPI. The water uptake and swelling were tested and compared between the SPI membrane and the four kinds of blend membranes. Through comparison of the stability of the membranes, we concluded that the PES could greatly increase the stability of the whole membrane and restrict the swelling. However, the PES did not decrease the water uptake very much. We also compared the fuel cell performance with different membranes. The performance was decreased when the content of the PES in the blend membrane increased. The loss of the fuel cell performance with the blend membranes did not decrease very much before the content of the PES was exceeded 20%. It was prospected that the blend membrane could increase the stability of the SPI and, more importantly, even replace the commercial Nafion membranes. PMID:18348564

  1. Role of membrane biophysics in Alzheimer's–related cell pathways

    PubMed Central

    Zhu, Donghui; Bungart, Brittani L.; Yang, Xiaoguang; Zhumadilov, Zhaxybay; Lee, James C-M.; Askarova, Sholpan

    2015-01-01

    Cellular membrane alterations are commonly observed in many diseases, including Alzheimer's disease (AD). Membrane biophysical properties, such as membrane molecular order, membrane fluidity, organization of lipid rafts, and adhesion between membrane and cytoskeleton, play an important role in various cellular activities and functions. While membrane biophysics impacts a broad range of cellular pathways, this review addresses the role of membrane biophysics in amyloid-? peptide aggregation, A?-induced oxidative pathways, amyloid precursor protein processing, and cerebral endothelial functions in AD. Understanding the mechanism(s) underlying the effects of cell membrane properties on cellular processes should shed light on the development of new preventive and therapeutic strategies for this devastating disease. PMID:26074758

  2. Fuel cell membranes and crossover prevention

    DOEpatents

    Masel, Richard I. (Champaign, IL); York, Cynthia A. (Newington, CT); Waszczuk, Piotr (White Bear Lake, MN); Wieckowski, Andrzej (Champaign, IL)

    2009-08-04

    A membrane electrode assembly for use with a direct organic fuel cell containing a formic acid fuel includes a solid polymer electrolyte having first and second surfaces, an anode on the first surface and a cathode on the second surface and electrically linked to the anode. The solid polymer electrolyte has a thickness t:.gtoreq..times..times..times..times. ##EQU00001## where C.sub.f is the formic acid fuel concentration over the anode, D.sub.f is the effective diffusivity of the fuel in the solid polymer electrolyte, K.sub.f is the equilibrium constant for partition coefficient for the fuel into the solid polymer electrolyte membrane, I is Faraday's constant n.sub.f is the number of electrons released when 1 molecule of the fuel is oxidized, and j.sub.f.sup.c is an empirically determined crossover rate of fuel above which the fuel cell does not operate.

  3. Vasoactive Intestinal Peptide Alters Membrane Potential and Cyclic Nucleotide Levels in Retinal Horizontal Cells

    NASA Astrophysics Data System (ADS)

    Lasater, Eric M.; Watling, Keith J.; Dowling, John E.

    1983-09-01

    Vasoactive intestinal peptide stimulated the synthesis of adenosine 3',5'-monophosphate in fractions of isolated carp horizontal cells. When applied extracellularly to isolated and cultured horizontal cells, the peptide also induced a slow depolarization (30 to 40 millivolts) accompanied by a decrease in membrane resistance. However, analogs of adenosine 3',5'-monophosphate applied extracellularly or intracellularly, and forscolin applied extracellularly, had no effect on the membrane potential of cultured horizontal cells, indicating that the induced depolarization was not related to the accumulation of adenosine 3',5'-monophosphate in these cells.

  4. Analytical characterization and purification of plasma membrane from cultured hepatoma cells (HTC cells).

    PubMed

    Sauvage, P; Lopez-Saura, P; Leroy-Houyet, M A; Tulkens, P; Trouet, A

    1981-06-01

    The plasma membrane of the hepatoma cell line, HTC cells, has been characterized and purified by cell fractionation techniques. In the absence of true 5'-nucleotidase in HTC cells, alkaline phosphodiesterase I has been used as a marker enzyme, following conclusions gained from differential and isopycnic centrifugation studies (Lopez-Saura, P., Trouet, A. and Tulkens, P. (1978) Biochim. Biophys. Acta 543, 430-449). To confirm this localization, HTC cells were exposed to anti-plasma membrane IgG at 4 degrees C and fractionated. Alkaline phosphodiesterase I and IgG showed superimposable distribution patterns in linear sucrose gradients. Alkaline phosphodiesterase I is, however, only poorly resolved from enzyme markers of other organelles, especially NADPH-cytochrome c reductase (endoplasmic reticulum) and galactosyltransferase (Golgi complex). Maximal purification from the homogenate is only 13-fold, on a protein basis, even when using a microsomal fraction (67 and 13% of alkaline phosphodiesterase I and protein, respectively) as the starting material. Improved resolution can be obtained after the addition of small quantities of digitonin (equimolar with respect to the cholesterol content). Digitonin increases the buoyant density of alkaline phosphodiesterase I by approx. 0.05 g/cm3, whereas the buoyant densities of galactosyltransferase and NADPH-cytochrome c reductase are increased only by 0.03 and 0.015 g/cm3, respectively. Accordingly, a procedure has been designed which yields a fraction containing 22.8% of alkaline phosphodiesterase I with a purification of 21-fold on a protein basis. The content of NADPH-cytochrome c reductase and galactosyltransferase is 1.2 and 2.1%, respectively. Electron microscopy shows smooth surface membrane elements and vesicles, with only occasional other recognizable elements. PMID:7260068

  5. Membrane catalyst layer for fuel cells

    DOEpatents

    Wilson, Mahlon S. (Los Alamos, NM)

    1993-01-01

    A gas reaction fuel cell incorporates a thin catalyst layer between a solid polymer electrolyte (SPE) membrane and a porous electrode backing. The catalyst layer is preferably less than about 10 .mu.m in thickness with a carbon supported platinum catalyst loading less than about 0.35 mgPt/cm.sup.2. The film is formed as an ink that is spread and cured on a film release blank. The cured film is then transferred to the SPE membrane and hot pressed into the surface to form a catalyst layer having a controlled thickness and catalyst distribution. Alternatively, the catalyst layer is formed by applying a Na.sup.+ form of a perfluorosulfonate ionomer directly to the membrane, drying the film at a high temperature, and then converting the film back to the protonated form of the ionomer. The layer has adequate gas permeability so that cell performance is not affected and has a density and particle distribution effective to optimize proton access to the catalyst and electronic continuity for electron flow from the half-cell reaction occurring at the catalyst.

  6. Fuel cell membrane hydration and fluid metering

    DOEpatents

    Jones, Daniel O. (Glenville, NY); Walsh, Michael M. (Fairfield, CT)

    1999-01-01

    A hydration system includes fuel cell fluid flow plate(s) and injection port(s). Each plate has flow channel(s) with respective inlet(s) for receiving respective portion(s) of a given stream of reactant fluid for a fuel cell. Each injection port injects a portion of liquid water directly into its respective flow channel in order to mix its respective portion of liquid water with the corresponding portion of the stream. This serves to hydrate at least corresponding part(s) of a given membrane of the corresponding fuel cell(s). The hydration system may be augmented by a metering system including flow regulator(s). Each flow regulator meters an injecting at inlet(s) of each plate of respective portions of liquid into respective portion(s) of a given stream of fluid by corresponding injection port(s).

  7. Fuel cell membrane hydration and fluid metering

    DOEpatents

    Jones, Daniel O. (Glenville, NY); Walsh, Michael M. (Fairfield, CT)

    2003-01-01

    A hydration system includes fuel cell fluid flow plate(s) and injection port(s). Each plate has flow channel(s) with respective inlet(s) for receiving respective portion(s) of a given stream of reactant fluid for a fuel cell. Each injection port injects a portion of liquid water directly into its respective flow channel. This serves to hydrate at least corresponding part(s) of a given membrane of the corresponding fuel cell(s). The hydration system may be augmented by a metering system including flow regulator(s). Each flow regulator meters an injecting at inlet(s) of each plate of respective portions of liquid into respective portion(s) of a given stream of fluid by corresponding injection port(s).

  8. In vitro and in vivo phosphorylation of polypeptides in plasma membrane and tonoplast-enriched fractions from barley roots

    SciTech Connect

    Garbarino, J.E.; Hurkman, W.J.; Tanaka, C.K.; DuPont, F.M. )

    1991-04-01

    Phosphorylation of polypeptides in membrane fractions from barley (Hordeum vulgare L. cv CM 72) roots was compared in in vitro and in vivo assays to assess the potential role of protein kinases in modification of membrane transport. Membrane fractions enriched in endoplasmic reticulum, tonoplast, and plasma membrane were isolated using sucrose gradients and the membrane polypeptides separated using sodium dodecyl sulfate polyacrylamide gel electrophoresis. When the membrane fractions were incubated with {gamma}(p{sup 32}P)ATP, phosphorylation occurred almost exclusively in the plasma membrane fraction. Phosphorylation of a band at 38 kilodaltons increased as the concentration of Mg{sup 2+} was decreased from millimolar to micromolar levels. Phosphorylation of bands at 125, 86, 58, 46 and 28 kilodaltons required millimolar Mg{sup 2+} concentrations and was greatly enhanced by Ca{sup 2+}. When roots of intact plants were labeled with ({sup 32}P)orthophosphate, polypeptides at approximately 135, 166, 90, 46 to 53, 32, 28, and 19 kilodaltons were labeled in the plasma membrane fraction and polypeptides at approximately 73, 66, and 48 kilodaltons were labeled in the tonoplast fraction. Treatment of the roots of intact plants with 150 millimolar NaCl resulted in increased phosphorylation of some polypeptides while treatment with 100 mM NaCl had no effect.

  9. Membrane tension feedback on shape and motility of eukaryotic cells

    E-print Network

    Benjamin Winkler; Igor S. Aranson; Falko Ziebert

    2015-09-02

    In the framework of a phase field model of a single cell crawling on a substrate, we investigate how the properties of the cell membrane affect the shape and motility of the cell. Since the membrane influences the cell dynamics on multiple levels and provides a nontrivial feedback, we consider the following fundamental interactions: (i) the reduction of the actin polymerization rate by membrane tension; (ii) area conservation of the cell's two-dimensional cross-section vs. conservation of its circumference (i.e. membrane inextensibility); and (iii) the contribution from the membrane's bending energy to the shape and integrity of the cell. As in experiments, we investigate two pertinent observables -- the cell's velocity and its aspect ratio. We find that the most important effect is the feedback of membrane tension on the actin polymerization. Bending rigidity has only minor effects, visible mostly in dynamic reshaping events, as exemplified by collisions of the cell with an obstacle.

  10. Microfabrication of High-Resolution Porous Membranes for Cell Culture

    PubMed Central

    Kim, Monica Y.; Li, David Jiang; Pham, Long K.; Wong, Brandon G.

    2014-01-01

    Microporous membranes are widely utilized in cell biology to study cell-cell signaling and cell migration. However, the thickness and low porosity of commercial track-etched membranes limit the quality of cell imaging and the degree of cell-cell contact that can be achieved on such devices. We employ photolithography-based microfabrication to achieve porous membranes with pore diameter as small as 0.9 ?m, up to 40% porosity, and less than 5% variation in pore size. Through the use of a soap release layer, membranes as thin as 1 ?m can be achieved. The thin membranes minimally disrupt contrast enhancement optics, thus allowing good quality imaging of unlabeled cells under white light, unlike commercial membranes. In addition, the polymer membrane materials display low autofluorescence even after patterning, facilitating high quality fluorescence microscopy. Finally, confocal imaging suggests that substantial cell-cell contact is possible through the pores of these thin membranes. This membrane technology can enhance existing uses of porous membranes in cell biology as well as enable new types of experiments. PMID:24567663

  11. Unraveling sterol-dependent membrane phenotypes by analysis of protein abundance-ratio distributions in different membrane fractions under biochemical and endogenous sterol depletion.

    PubMed

    Zauber, Henrik; Szymanski, Witold; Schulze, Waltraud X

    2013-12-01

    During the last decade, research on plasma membrane focused increasingly on the analysis of so-called microdomains. It has been shown that function of many membrane-associated proteins involved in signaling and transport depends on their conditional segregation within sterol-enriched membrane domains. High throughput proteomic analysis of sterol-protein interactions are often based on analyzing detergent resistant membrane fraction enriched in sterols and associated proteins, which also contain proteins from these microdomain structures. Most studies so far focused exclusively on the characterization of detergent resistant membrane protein composition and abundances. This approach has received some criticism because of its unspecificity and many co-purifying proteins. In this study, by a label-free quantitation approach, we extended the characterization of membrane microdomains by particularly studying distributions of each protein between detergent resistant membrane and detergent-soluble fractions (DSF). This approach allows a more stringent definition of dynamic processes between different membrane phases and provides a means of identification of co-purifying proteins. We developed a random sampling algorithm, called Unicorn, allowing for robust statistical testing of alterations in the protein distribution ratios of the two different fractions. Unicorn was validated on proteomic data from methyl-?-cyclodextrin treated plasma membranes and the sterol biosynthesis mutant smt1. Both, chemical treatment and sterol-biosynthesis mutation affected similar protein classes in their membrane phase distribution and particularly proteins with signaling and transport functions. PMID:24030099

  12. Glycerolipid transfer for the building of membranes in plant cells.

    PubMed

    Jouhet, Juliette; Maréchal, Eric; Block, Maryse A

    2007-01-01

    Membranes of plant organelles have specific glycerolipid compositions. Selective distribution of lipids at the levels of subcellular organelles, membrane leaflets and membrane domains reflects a complex and finely tuned lipid homeostasis. Glycerolipid neosynthesis occurs mainly in plastid envelope and endoplasmic reticulum membranes. Since most lipids are not only present in the membranes where they are synthesized, one cannot explain membrane specific lipid distribution by metabolic processes confined in each membrane compartment. In this review, we present our current understanding of glycerolipid trafficking in plant cells. We examine the potential mechanisms involved in lipid transport inside bilayers and from one membrane to another. We survey lipid transfers going through vesicular membrane flow and those dependent on lipid transfer proteins at membrane contact sites. By introducing recently described membrane lipid reorganization during phosphate deprivation and recent developments issued from mutant analyses, we detail the specific lipid transfers towards or outwards the chloroplast envelope. PMID:16970991

  13. Measurement of the nonlinear elasticity of red blood cell membranes

    E-print Network

    Park, YongKeun

    The membranes of human red blood cells (RBCs) are a composite of a fluid lipid bilayer and a triangular network of semiflexible filaments (spectrin). We perform cellular microrheology using the dynamic membrane fluctuations ...

  14. Specific binding of a fungal glucan phytoalexin elicitor to membrane fractions from soybean Glycine max

    SciTech Connect

    Schmidt, W.E.; Ebel, J.

    1987-06-01

    Treatment of soybean tissues with elicitors results in the production of phytoalexins, one of a number of inducible plant defense reactions against microbial infections. The present study uses a ..beta..-1,3-(/sup 3/H) glucan elicitor fraction from Phytophthora megasperma f.sp. glycinea, a fungal pathogen of soybean, to identify putative elicitor targets in soybean tissues. Use of the radiolabeled elicitor disclosed saturable high-affinity elicitor binding site(s) in membrane fractions of soybean roots. Highest binding activity is associated with a plasma membrane-enriched fraction. The apparent K/sub d/ value for ..beta..-glucan elicitor binding is approx. = 0.2 x 10/sup -6/ M and the maximum number of binding sites is 0.5 pmol per mg of protein. Competition studies the (/sup 3/H)glucan elicitor and a number of polysaccharides demonstrate that only polysaccharides of a branched ..beta..-glucan type effectively displace the radiolabeled ligand from membrane binding. Differential displacing activity of the glucans on P. megasperma elicitor binding corresponds closely to their respective ability to elicit phytoalexin production in a cotyledon bioassay.

  15. Preferential degradation of the terminal carbohydrate moiety of membrane glycoproteins in rat hepatoma cells and after transfer to the membranes of mouse fibroblasts

    PubMed Central

    1983-01-01

    Glycoproteins in the plasma membrane of rat hepatoma cells were labeled at their externally exposed tyrosine residues with 131I and at their galactose and sialic acid residues with 3H. The degradation of both isotopes in the total cell protein fraction, in glycoproteins purified by concanavalin A, and in glycoproteins separated on two-dimensional gels was determined. Similarly, the total cellular membrane glycoproteins were metabolically labeled with [35S]methionine and [3H]fucose. The fate of both incorporated labels was followed by lectin chromatography or by precipitation of the proteins with specific antibodies followed by electrophoretic gel separation. In both labeling experiments, the carbohydrate markers were lost from the ligand- recognized fraction with similar kinetics as from the total cell protein fraction. In some glycoprotein species which were separated by two-dimensional gel electrophoresis, the polypeptide portion exhibited up to a twofold slower rate of degradation relative to that of the carbohydrate moiety. This difference is most pronounced in carbohydrate- rich glycoproteins. To corroborate this finding, double-labeled membrane glycoproteins were incorporated into reconstituted phospholipid vesicles which were then transferred via fusion into the plasma membrane of mouse fibroblasts. Both the polypeptide and carbohydrate moieties of the transferred membrane glycoproteins were degraded with the same relative kinetics as in the original hepatoma cells. The rate of degradation is mostly a function of the structural properties of the membrane components as shown by the preservation of metabolically stable fucogangliosides of Reuber H-35 hepatoma cells transferred onto the fibroblasts. The technique of insertion of membrane components into the plasma membrane of another cell should assist in the elucidation of the exact route and mechanism of membrane protein destruction. PMID:6826644

  16. Interaction of Arginine-Rich Peptides with Model Cell Membranes

    NASA Astrophysics Data System (ADS)

    Mishra, Abhijit; Schmidt, Nathan; Gordon, Vernita; Cheng, Jianjun; Deming, Timothy; Wong, Gerard

    2008-03-01

    Cell-penetrating peptides have the ability to traverse the plasma membrane of eukaryotic cells. Furthermore, these peptides can transport cargo across a range of cell membranes, implying they have many potential biotechnological applications. In this study we compare the interaction of three commonly used arginine-rich cell-penetrating peptides, TAT, Penetratin, and pVEC, with model cell membranes of variable charge density and intrinsic curvature, using synchrotron small angle x-ray scattering (SAXS). To better understand the respective roles of arginine and hydrophobic residues in membrane reorganization we also examine the interaction of arginine-leucine (R60L20) block copolypeptides with model membranes, as well as the relationship between membrane composition and peptide induced changes in membrane topology.

  17. Calmodulin-binding proteins in chromaffin cell plasma membranes.

    PubMed

    Fournier, S; Trifaró, J M

    1988-11-01

    Calmodulin-binding proteins present in chromaffin cell plasma membranes were isolated and directly compared with calmodulin-binding proteins present in chromaffin granule membranes. Chromaffin cell plasma membranes were prepared using Cytodex 1 microcarriers. Marker enzyme studies on this preparation showed a nine- to 10-fold plasma membrane enrichment over cell homogenates and a low contamination of these plasma membranes by subcellular organelles. Plasma membranes prepared in this manner were solubilized with Triton X-100 and applied to a calmodulin-affinity column in the presence of calcium. Several major calmodulin-binding proteins (240, 105, and 65 kilodaltons) were eluted by an EGTA-containing buffer. 125I-Calmodulin overlay experiments on nitrocellulose sheets containing both chromaffin plasma and granule membranes showed that these two membranes have several calmodulin-binding proteins in common (65, 60, 53, and 50 kilodaltons), as well as unique calmodulin-binding proteins (34 kilodaltons in granule membranes and 240 and 160 kilodaltons in plasma membranes). The 65-kilodalton calmodulin-binding protein present in both membrane types was shown to consist of two isoforms (pI 6.0 and 6.2) by two-dimensional gel electrophoresis. Previous experiments from our laboratory, using two monoclonal antibodies (mAb 30 and mAb 48) specific for a rat brain synaptic vesicle membrane protein (p65), showed that the monoclonal antibodies reacted with a 65-kilodalton calmodulin-binding protein present in at least three neurosecretory vesicles (chromaffin granules, neurohypophyseal granules, and rat brain synaptic vesicles). When these monoclonal antibodies were tested on chromaffin cell plasma membranes and calmodulin-binding proteins isolated from these membranes, they recognized a 65-kilodalton protein. These results indicate that an immunologically identical calmodulin-binding protein is expressed in both chromaffin granule membranes (as well as other secretory vesicle membranes) and chromaffin cell plasma membranes, thus suggesting a possible role for this protein in granule/plasma membrane interaction. PMID:3171592

  18. Polybenzimidazole-multiwall carbon nanotubes composite membranes for polymer electrolyte membrane fuel cells

    NASA Astrophysics Data System (ADS)

    Guerrero Moreno, Nayibe; Gervasio, Dominic; Godínez García, Andrés; Pérez Robles, Juan Francisco

    2015-12-01

    Polymer membranes are prepared as a composite of polybenzimidazole and non-functionalized multiwall carbon nanotubes (PBI-CNT) and polybenzimidazole (PBI) only. Each is doped with H3PO4 (PA) and used as a proton exchange membrane (PEM) as the electrolyte in a fuel cell. The proton conductivities at 180 °C for the doped PBI membrane (PBIPA) and the doped PBI-CNT membrane (PBICNTPA) are 6.3 × 10-2 and 7.4 × 10-2 Scm-1 respectively. A single fuel cell having these membranes as electrolyte has a Pt catalyzed hydrogen gas fed anode and a similar oxygen cathode without humidification of feed gases; the cell with the PBICNTPA membrane has higher open circuit voltage (0.96 V) than that with a PBIPA membrane (0.8 V) at 180 °C. The mechanical stability of the membrane improves with CNTs addition. The tensile strength of the composite PBI-CNT membrane with 1 wt.% CNTs loading is 32% higher and the Young's Modulus is 147% higher than the values for a membrane of PBI alone. The improvement in conductivity and mechanical properties in the composite membrane due to the CNT addition indicates that a PBI-CNT membrane is a good alternative as a membrane electrolyte in a PEMFC.

  19. Ion transport through cell membrane channels

    E-print Network

    Jan Gomulkiewicz; Jacek Miekisz; Stanislaw Miekisz

    2007-06-05

    We discuss various models of ion transport through cell membrane channels. Recent experimental data shows that sizes of ion channels are compared to those of ions and that only few ions may be simultaneously in any single channel. Theoretical description of ion transport in such channels should therefore take into account interactions between ions and between ions and channel proteins. This is not satisfied by macroscopic continuum models based on Poisson-Nernst-Planck equations. More realistic descriptions of ion transport are offered by microscopic Brownian and molecular dynamics. One should also take into account a dynamical character of the channel structure. This is not yet addressed in the literature

  20. Membrane Cells in Chlor Alkali Application 

    E-print Network

    Lesker, K.

    1992-01-01

    decade ago. The decision makers therefore not only take the option for membrane lechnology in grass rool pla.JllS, but increasingly for conversions of diaphragm and mercury plants. Thc single clement dcsign of mcmbrane cells lias t:spl:cially pro... electrolysis technologies: The mercury process with a high ill~ldllt:J l-dpdl-il y ill Wc,leru Europe, the uidpllrdglll process whIch IS used extensIvely in the United Slalt:s am] lht: 1llt:lllorant: prOCt:ss which is ot:ing used exclusively for new...

  1. Membrane Purification Cell for Aluminum Recycling

    SciTech Connect

    David DeYoung; James Wiswall; Cong Wang

    2011-11-29

    Recycling mixed aluminum scrap usually requires adding primary aluminum to the scrap stream as a diluent to reduce the concentration of non-aluminum constituents used in aluminum alloys. Since primary aluminum production requires approximately 10 times more energy than melting scrap, the bulk of the energy and carbon dioxide emissions for recycling are associated with using primary aluminum as a diluent. Eliminating the need for using primary aluminum as a diluent would dramatically reduce energy requirements, decrease carbon dioxide emissions, and increase scrap utilization in recycling. Electrorefining can be used to extract pure aluminum from mixed scrap. Some example applications include producing primary grade aluminum from specific scrap streams such as consumer packaging and mixed alloy saw chips, and recycling multi-alloy products such as brazing sheet. Electrorefining can also be used to extract valuable alloying elements such as Li from Al-Li mixed scrap. This project was aimed at developing an electrorefining process for purifying aluminum to reduce energy consumption and emissions by 75% compared to conventional technology. An electrolytic molten aluminum purification process, utilizing a horizontal membrane cell anode, was designed, constructed, operated and validated. The electrorefining technology could also be used to produce ultra-high purity aluminum for advanced materials applications. The technical objectives for this project were to: - Validate the membrane cell concept with a lab-scale electrorefining cell; - Determine if previously identified voltage increase issue for chloride electrolytes holds for a fluoride-based electrolyte system; - Assess the probability that voltage change issues can be solved; and - Conduct a market and economic analysis to assess commercial feasibility. The process was tested using three different binary alloy compositions (Al-2.0 wt.% Cu, Al-4.7 wt.% Si, Al-0.6 wt.% Fe) and a brazing sheet scrap composition (Al-2.8 wt.% Si-0.7 wt.% Fe-0.8 wt.% Mn),. Purification factors (defined as the initial impurity concentration divided by the final impurity concentration) of greater than 20 were achieved for silicon, iron, copper, and manganese. Cell performance was measured using its current and voltage characteristics and composition analysis of the anode, cathode, and electrolytes. The various cells were autopsied as part of the study. Three electrolyte systems tested were: LiCl-10 wt. % AlCl3, LiCl-10 wt. % AlCl3-5 wt.% AlF3 and LiF-10 wt.% AlF3. An extended four-day run with the LiCl-10 wt.% AlCl3-5 wt.% AlF3 electrolyte system was stable for the entire duration of the experiment, running at energy requirements about one third of the Hoopes and the conventional Hall-Heroult process. Three different anode membranes were investigated with respect to their purification performance and survivability: a woven graphite cloth with 0.05 cm nominal thickness & > 90 % porosity, a drilled rigid membrane with nominal porosity of 33%, and another drilled rigid graphite membrane with increased thickness. The latter rigid drilled graphite was selected as the most promising membrane design. The economic viability of the membrane cell to purify scrap is sensitive to primary & scrap aluminum prices, and the cost of electricity. In particular, it is sensitive to the differential between scrap and primary aluminum price which is highly variable and dependent on the scrap source. In order to be economically viable, any scrap post-processing technology in the U.S. market must have a total operating cost well below the scrap price differential of $0.20-$0.40 per lb to the London Metal Exchange (LME), a margin of 65%-85% of the LME price. The cost to operate the membrane cell is estimated to be < $0.24/lb of purified aluminum. The energy cost is estimated to be $0.05/lb of purified aluminum with the remaining costs being repair and maintenance, electrolyte, labor, taxes and depreciation. The bench-scale work on membrane purification cell process has demonstrated technological advantages and subs

  2. Electrostatics of Cell Membranes Kevin Cahill January 21, 2011

    E-print Network

    Cahill, Kevin

    potential due to a charge in or near the plasma membrane of a eukaryotic cell is computed and applied to a charge q on the z-axis at the point (0, 0, h) in the phos- pholipid bilayer of a eukaryotic cell. We useElectrostatics of Cell Membranes Kevin Cahill January 21, 2011 cahill@unm.edu Biophysics Group

  3. Electrophoretic Characterization of a Detergent-Treated Plasma Membrane Fraction from Corn Roots 1

    PubMed Central

    Gallagher, Sean R.; Leonard, Robert T.

    1987-01-01

    Experiments were conducted to determine conditions essential for electrophoretic characterization of a detergent-extracted plasma membrane fraction from corn (Zea mays L.) roots. Sodium dodecyl sulfate (SDS) polyacrylamide gel electrophoresis (PAGE) initially gave poor resolution of polypeptides in the plasma membrane fraction and, upon detergent treatment for purification of the proton-pumping adenosine triphosphatase (ATPase), showed no enrichment for a 100 kilodalton catalytic subunit characteristic of the ATPase. In contrast to SDS-PAGE, phenol urea acetic acid (PAU)-PAGE clearly resolved two polypeptides in the 100 kilodalton region that were enriched during detergent treatment and indicated at least one polypeptide forms a phosphorylated intermediate characteristic of the ATPase. Problems with SDS-PAGE were found to be caused, in part, by a combination of endogenous proteases and heat-induced aggregation of high molecular weight proteins. The usually standard procedure of boiling the sample prior to SDS-PAGE caused the aggregation of the 100 kilodalton polypeptides. By controlling for proteases using chymostatin and/or phenylmethane sulfonyl floride, and not boiling the sample prior to electrophoresis, two polypeptides were clearly resolved by SDS-PAGE in the 100 kilodalton region of Triton X-114-extracted membranes from corn, oat, barley, and tomato. Images Fig. 1 Fig. 2 Fig. 3 Fig. 4 PMID:16665234

  4. Isolation and characterization of glycophorin from carp red blood cell membranes.

    PubMed

    Aoki, Takahiko; Chimura, Kenji; Nakao, Nobuhiro; Mizuno, Yasuko

    2014-01-01

    We isolated a high-purity carp glycophorin from carp erythrocyte membranes following extraction using the lithium diiodosalicylate (LIS)-phenol method and streptomycin treatment. The main carp glycophorin was observed to locate at the position of the carp and human band-3 proteins on an SDS-polyacrylamide gel. Only the N-glycolylneuraminic acid (NeuGc) form of sialic acid was detected in the carp glycophorin. The oligosaccharide fraction was separated into two components (P-1 and P-2) using a Glyco-Pak DEAE column. We observed bacteriostatic activity against five strains of bacteria, including two known fish pathogens. Fractions from the carp erythrocyte membrane, the glycophorin oligosaccharide and the P-1 also exhibited bacteriostatic activity; whereas the glycolipid fraction and the glycophorin fraction without sialic acid did not show the activity. The carp glycophorin molecules attach to the flagellum of V. anguillarum or the cell surface of M. luteus and inhibited bacterial growth. PMID:25110961

  5. Isolation and Characterization of Glycophorin from Carp Red Blood Cell Membranes

    PubMed Central

    Aoki, Takahiko; Chimura, Kenji; Nakao, Nobuhiro; Mizuno, Yasuko

    2014-01-01

    We isolated a high-purity carp glycophorin from carp erythrocyte membranes following extraction using the lithium diiodosalicylate (LIS)-phenol method and streptomycin treatment. The main carp glycophorin was observed to locate at the position of the carp and human band-3 proteins on an SDS-polyacrylamide gel. Only the N-glycolylneuraminic acid (NeuGc) form of sialic acid was detected in the carp glycophorin. The oligosaccharide fraction was separated into two components (P-1 and P-2) using a Glyco-Pak DEAE column. We observed bacteriostatic activity against five strains of bacteria, including two known fish pathogens. Fractions from the carp erythrocyte membrane, the glycophorin oligosaccharide and the P-1 also exhibited bacteriostatic activity; whereas the glycolipid fraction and the glycophorin fraction without sialic acid did not show the activity. The carp glycophorin molecules attach to the flagellum of V. anguillarum or the cell surface of M. luteus and inhibited bacterial growth. PMID:25110961

  6. Xyloglucan biosynthesis by Golgi membranes from suspension-cultured sycamore (Acer pseudoplatanus) cells

    SciTech Connect

    White, A.R.; Xin, Yi )

    1990-05-01

    Xyloglucan is a major hemicellulose polysaccharide in plant cell walls. Biosynthesis of such cell wall polysaccharides is closely linked to the process of plant cell growth and development. Xyloglucan polysaccharides consist of a {beta}-1,4 glucan backbone synthesized by xyloglucan synthase and sidechains of xylose, galactose, and fucose added by other transferase enzymes. Most plant Golgi and plasma membranes also contain glucan synthases I II, which make {beta}-1,4 and {beta}-1,3 glucans, respectively. All of these enzymes have very similar activities. Cell walls on suspension-cultured cells from Acer pseudoplatanus (sycamore maple) were enzymatically softened prior to cell disruption by passing through a 30 {mu}m nylon screen. Cell membranes from homogenates were separated by ultracentrifugation on top-loaded or flotation sucrose density gradients. Samples were collected by gradient fractionation and assayed for membrane markers and xyloglucan and glucan synthase activities. Standard marker assays (cyt. c reductase for eR, IDPase UDPase for Golgi, and eosin 5{prime}-malelmide binding for plasma membrane) showed partial separation of these three membrane types. Golgi and plasma membrane markers overlapped in most gradients. Incorporation of {sup 14}C-labeled sugars from UDP-glucose and UDP-xylose was used to detect xyloglucan synthase, glucan synthases I II, and xylosyl transferase in Golgi membrane fractions. These activities overlapped, although distinct peaks of xyloglucan synthase and xylosyl transferase were found. Ca{sup ++} had a stimulatory effect on glucan synthases I II, while Mn{sup ++} had an inhibitory effect on glucan synthase I in the presence of Ca{sup ++}. The similarity of these various synthase activities demonstrates the need for careful structural characterization of newly synthesized polysaccharides.

  7. Nonhumidified High-Temperature Membranes Developed for Proton Exchange Membrane Fuel Cells

    NASA Technical Reports Server (NTRS)

    Kinder, James D.

    2005-01-01

    Fuel cells are being considered for a wide variety of aerospace applications. One of the most versatile types of fuel cells is the proton-exchange-membrane (PEM) fuel cell. PEM fuel cells can be easily scaled to meet the power and space requirements of a specific application. For example, small 100-W PEM fuel cells are being considered for personal power for extravehicular activity suit applications, whereas larger PEM fuel cells are being designed for primary power in airplanes and in uninhabited air vehicles. Typically, PEM fuel cells operate at temperatures up to 80 C. To increase the efficiency and power density of the fuel cell system, researchers are pursuing methods to extend the operating temperature of the PEM fuel cell to 180 C. The most widely used membranes in PEM fuel cells are Nafion 112 and Nafion 117--sulfonated perfluorinated polyethers that were developed by DuPont. In addition to their relatively high cost, the properties of these membranes limit their use in a PEM fuel cell to around 80 C. The proton conductivity of Nafion membranes significantly decreases above 80 C because the membrane dehydrates. The useful operating range of Nafion-based PEM fuel cells can be extended to over 100 C if ancillary equipment, such as compressors and humidifiers, is added to maintain moisture levels within the membrane. However, the addition of these components reduces the power density and increases the complexity of the fuel cell system.

  8. Cell adhesion to protein-micropatterned-supported lipid bilayer membranes

    E-print Network

    Boxer, Steven G.

    Cell adhesion to protein-micropatterned-supported lipid bilayer membranes Lance Kam, Steven G. These fibronec- tin barriers also facilitate the adhesion of endothelial cells, which exhibit minimal adhesion bilayers; cell adhesion; endothelial cells INTRODUCTION Cell­cell communication is mediated in large part

  9. Stabilization/destabilization of cell membranes by multivalent ions: Implications for membrane fusion and division

    E-print Network

    Bae-Yeun Ha

    2000-06-02

    We propose a mechanism for the stabilization/destabilization of cell membranes by multivalent ions with an emphasis on its implications for the division and fusion of cells. We find that multivalent cations preferentially adsorbed onto a membrane dramatically changes the membrane stability. They not only reduce the surface charge density of the membrane but also induce a repulsive barrier to pore growth. While both of these effects lead to enhanced membrane stability against vesiculation and pore growth, the repulsive barrier arises from correlated fluctuations of the adsorbed cations and favors closure of a pore. Finally, the addition of a small amount of multivalent anions can reverse the membrane stabilization, providing an effective way to regulate membrane stability.

  10. Enzymatic Oxidation of Cholesterol: Properties and Functional Effects of Cholestenone in Cell Membranes

    PubMed Central

    Neuvonen, Maarit; Manna, Moutusi; Mokkila, Sini; Javanainen, Matti; Rog, Tomasz; Liu, Zheng; Bittman, Robert; Vattulainen, Ilpo; Ikonen, Elina

    2014-01-01

    Bacterial cholesterol oxidase is commonly used as an experimental tool to reduce cellular cholesterol content. That the treatment also generates the poorly degradable metabolite 4-cholesten-3-one (cholestenone) has received less attention. Here, we investigated the membrane partitioning of cholestenone using simulations and cell biological experiments and assessed the functional effects of cholestenone in human cells. Atomistic simulations predicted that cholestenone reduces membrane order, undergoes faster flip-flop and desorbs more readily from membranes than cholesterol. In primary human fibroblasts, cholestenone was released from membranes to physiological extracellular acceptors more avidly than cholesterol, but without acceptors it remained in cells over a day. To address the functional effects of cholestenone, we studied fibroblast migration during wound healing. When cells were either cholesterol oxidase treated or part of cellular cholesterol was exchanged for cholestenone with cyclodextrin, cell migration during 22 h was markedly inhibited. Instead, when a similar fraction of cholesterol was removed using cyclodextrin, cells replenished their cholesterol content in 3 h and migrated similarly to control cells. Thus, cholesterol oxidation produces long-term functional effects in cells and these are in part due to the generated membrane active cholestenone. PMID:25157633

  11. Roles of membrane trafficking in plant cell wall dynamics

    PubMed Central

    Ebine, Kazuo; Ueda, Takashi

    2015-01-01

    The cell wall is one of the characteristic components of plant cells. The cell wall composition differs among cell types and is modified in response to various environmental conditions. To properly generate and modify the cell wall, many proteins are transported to the plasma membrane or extracellular space through membrane trafficking, which is one of the key protein transport mechanisms in eukaryotic cells. Given the diverse composition and functions of the cell wall in plants, the transport of the cell wall components and proteins that are involved in cell wall-related events could be specialized for each cell type, i.e., the machinery for cell wall biogenesis, modification, and maintenance could be transported via different trafficking pathways. In this review, we summarize the recent progress in the current understanding of the roles and mechanisms of membrane trafficking in plant cells and focus on the biogenesis and regulation of the cell wall. PMID:26539200

  12. Polymer-electrolyte membrane, electrochemical fuel cell, and related method

    DOEpatents

    Krishnan, Lakshmi; Yeager, Gary William; Soloveichik, Grigorii Lev

    2014-12-09

    A polymer-electrolyte membrane is presented. The polymer-electrolyte membrane comprises an acid-functional polymer, and an additive incorporated in at least a portion of the membrane. The additive comprises a fluorinated cycloaliphatic additive, a hydrophobic cycloaliphatic additive, or combinations thereof, wherein the additive has a boiling point greater than about 120.degree. C. An electrochemical fuel cell including the polymer-electrolyte membrane, and a related method, are also presented.

  13. Moving towards sustainable resources: Recovery and fractionation of nutrients from dairy manure digestate using membranes.

    PubMed

    Gerardo, Michael L; Aljohani, Nasser H M; Oatley-Radcliffe, Darren L; Lovitt, Robert W

    2015-09-01

    The fractionation of nitrogen (as ammonia/ammonium) and phosphorus (as phosphate ions) present in the dairy manure digestate was investigated using a nanofiltration membrane NF270. The filtration and separation efficiencies were correlated to pH across the range 3 < pH < 11. Filtration at pH 11 enabled higher permeate flux of 125-150 LMH at 20 bar, however rejection of ammonia was high at 30-36% and phosphate was 96.4-97.2%. At pH 3 and pH 7, electrostatic charge effects led to higher permeation of ammonium and thus more efficient separation of nitrogen. The rejection of phosphorus was relatively constant at any given pH and determined as 83% at pH 3, 97% at pH 7 and 95% at pH 11. The fractionation of nitrogen and phosphorus from complex aqueous solutions was demonstrated to be highly dependent on the charge of the membrane and ionic speciation. Solutions rich in nitrogen (as ammonia/ammonium) were obtained with almost no phosphorus present (<1 ppm) whilst the purification of the PO4-P was achieved by series of diafiltration (DF) operations which further separated the nitrogen. The separation of nutrients benefited from an advantageous membrane process with potential added value for a wide range of industries. The analysis of the process economics for a membrane based plant illustrates that the recovery of nutrients, particularly NH3-N, may be commercially feasible when compared to manufactured anhydrous NH3. PMID:25996755

  14. The application of Dow Chemical's perfluorinated membranes in proton-exchange membrane fuel cells

    NASA Technical Reports Server (NTRS)

    Eisman, G. A.

    1989-01-01

    Dow Chemical's research activities in fuel cells revolve around the development of perfluorosulfonic acid membranes useful as the proton transport medium and separator. Some of the performance characteristics which are typical for such membranes are outlined. The results of tests utilizing a new experimental membrane useful in proton-exchange membrane fuel cells are presented. The high voltage at low current densities can lead to higher system efficiencies while, at the same time, not sacrificing other critical properties pertinent to membrane fuel cell operation. A series of tests to determine response times indicated that on-off cycles are on the order of 80 milliseconds to reach 90 percent of full power. The IR free voltage at 100 amps/sq ft was determined and the results indicating a membrane/electrode package resistance to be .15 ohm-sq cm at 100 amps/sq ft.

  15. Assay for CDP-Diacylglycerol Generation by CDS in Membrane Fractions.

    PubMed

    Waugh, Mark

    2016-01-01

    CDP-DAG is a liponucleotide formed by the condensation of CTP with the phospholipid phosphatidic acid in a reaction catalyzed by CDP-DAG synthase (CDS). CDP-DAG is required for the synthesis of phosphatidylinositol; the parent molecule whence all seven phosphoinositides including the signaling molecules PI4P, PI(4,5)P2, and PI(3,4,5)P3 are derived. This protocol describes a highly sensitive radiometric assay to detect the generation of CDP-DAG on isolated biological membrane fractions. PMID:26552690

  16. Membrane tension and cytoskeleton organization in cell motility

    NASA Astrophysics Data System (ADS)

    Sens, Pierre; Plastino, Julie

    2015-07-01

    Cell membrane shape changes are important for many aspects of normal biological function, such as tissue development, wound healing and cell division and motility. Various disease states are associated with deregulation of how cells move and change shape, including notably tumor initiation and cancer cell metastasis. Cell motility is powered, in large part, by the controlled assembly and disassembly of the actin cytoskeleton. Much of this dynamic happens in close proximity to the plasma membrane due to the fact that actin assembly factors are membrane-bound, and thus actin filaments are generally oriented such that their growth occurs against or near the membrane. For a long time, the membrane was viewed as a relatively passive scaffold for signaling. However, results from the last five years show that this is not the whole picture, and that the dynamics of the actin cytoskeleton are intimately linked to the mechanics of the cell membrane. In this review, we summarize recent findings concerning the role of plasma membrane mechanics in cell cytoskeleton dynamics and architecture, showing that the cell membrane is not just an envelope or a barrier for actin assembly, but is a master regulator controlling cytoskeleton dynamics and cell polarity.

  17. Exo70 Generates Membrane Curvature for Morphogenesis and Cell Migration

    PubMed Central

    Zhao, Yuting; Liu, Jianglan; Yang, Changsong; Capraro, Benjamin R.; Baumgart, Tobias; Bradley, Ryan P.; Ramakrishnan, N.; Xu, Xiaowei; Radhakrishnan, Ravi; Svitkina, Tatyana; Guo, Wei

    2013-01-01

    Dynamic shape changes of the plasma membrane are fundamental to many processes ranging from morphogenesis and cell migration to phagocytosis and viral propagation. Here we demonstrate that Exo70, a component of the exocyst complex, induces tubular membrane invaginations towards the lumen of synthetic vesicles in vitro and generates protrusions on the surface of cells. Biochemical analyses using Exo70 mutants and independent molecular dynamics simulations based on Exo70 structure demonstrate that Exo70 generates negative membrane curvature through an oligomerization-based mechanism. In cells, the membrane-deformation function of Exo70 is required for protrusion formation and directional cell migration. Exo70 thus represents a membrane-bending protein that may couple actin dynamics and plasma membrane remodeling for morphogenesis. PMID:23948253

  18. Electron-beam direct processing on living cell membrane

    SciTech Connect

    Hoshino, Takayuki; Morishima, Keisuke

    2011-10-24

    We demonstrated a direct processing on a living Hep G2 cell membrane in conventional cultivation conditions using an electron beam. Electron beam-induced deposition from liquid precursor 3,4-ethylenedioxythiophene and ablation was performed on the living cells. The 2.5-10 keV electron beam which was irradiated through a 100-nm-thick SiN nanomembrane could induce a deposition pattern and a ablation on a living cell membrane. This electron beam direct processing can provide simple in-situ cell surface modification for an analytical method of living cell membrane dynamic.

  19. Hemoglobin s polymerization and red cell membrane changes.

    PubMed

    Kuypers, Frans A

    2014-04-01

    Different pathways lead from the simple point mutation in hemoglobin to the membrane changes that characterize the altered interaction of the sickle red blood cell with its environment, including endothelial cells, white blood cells, and platelets. Polymerization and oxidation-induced damage to both lipid and protein components of the red cell membrane, as well as the generation of bioreactive membrane material (microparticles), has a profound effect on all tissues and organs, and defines the vasculopathy of the patient with sickle cell disease. PMID:24589260

  20. Conductivity Measurements of Synthesized Heteropoly Acid Membranes for Proton Exchange Membrane Fuel Cells

    SciTech Connect

    Record, K.A.; Haley, B.T.; Turner, J.

    2006-01-01

    Fuel cell technology is receiving attention due to its potential to be a pollution free method of electricity production when using renewably produced hydrogen as fuel. In a Proton Exchange Membrane (PEM) fuel cell H2 and O2 react at separate electrodes, producing electricity, thermal energy, and water. A key component of the PEM fuel cell is the membrane that separates the electrodes. DuPont’s Nafion® is the most commonly used membrane in PEM fuel cells; however, fuel cell dehydration at temperatures near 100°C, resulting in poor conductivity, is a major hindrance to fuel cell performance. Recent studies incorporating heteropoly acids (HPAs) into membranes have shown an increase in conductivity and thus improvement in performance. HPAs are inorganic materials with known high proton conductivities. The primary objective of this work is to measure the conductivity of Nafion, X-Ionomer membranes, and National Renewable Energy Laboratory (NREL) Developed Membranes that are doped with different HPAs at different concentrations. Four-point conductivity measurements using a third generation BekkTech? conductivity test cell are used to determine membrane conductivity. The effect of multiple temperature and humidification levels is also examined. While the classic commercial membrane, Nafion, has a conductivity of approximately 0.10 S/cm, measurements for membranes in this study range from 0.0030 – 0.58 S/cm, depending on membrane type, structure of the HPA, and the relative humidity. In general, the X-ionomer with H6P2W21O71 HPA gave the highest conductivity and the Nafion with the 12-phosphotungstic (PW12) HPA gave the lowest. The NREL composite membranes had conductivities on the order of 0.0013 – 0.025 S/cm.

  1. Effect of EMP fields on cell membrane potentials

    SciTech Connect

    Gailey, P.C.; Easterly, C.E.

    1993-06-01

    A simple model is presented for cell membrane potentials induced during exposure to electromagnetic pulse (EMP). Using calculated values of internal electric field strength induced during EMP exposure, the model predicts that cell membrane potentials of about 100 mV may be induced for time frames on the order of 10 ns. Possible biological effects of these potentials including electroporation area discussed.

  2. Water Visualization and Flooding in Polymer Electrolyte Membrane Fuel Cells

    E-print Network

    Petta, Jason

    Water Visualization and Flooding in Polymer Electrolyte Membrane Fuel Cells Brian Holsclaw West Conditions PFR Cell CSTR Cell Conclusions and Further Work Questions #12;Overview Background Objective Experimental Conditions PFR Cell CSTR Cell Conclusions and Further Work Questions #12;Catalyst (Pt) Hydrogen

  3. Finite element analysis of microelectrotension of cell membranes

    PubMed Central

    Bae, Chilman

    2011-01-01

    Electric fields can be focused by micropipette-based electrodes to induce stresses on cell membranes leading to tension and poration. To date, however, these membrane stress distributions have not been quantified. In this study, we determine membrane tension, stress, and strain distributions in the vicinity of a microelectrode using finite element analysis of a multiscale electro-mechanical model of pipette, media, membrane, actin cortex, and cytoplasm. Electric field forces are coupled to membranes using the Maxwell stress tensor and membrane electrocompression theory. Results suggest that micropipette electrodes provide a new non-contact method to deliver physiological stresses directly to membranes in a focused and controlled manner, thus providing the quantitative foundation for micreoelectrotension, a new technique for membrane mechanobiology. PMID:17657517

  4. Integrin-like proteins are localized to plasma membrane fractions, not plastids, in Arabidopsis

    NASA Technical Reports Server (NTRS)

    Swatzell, L. J.; Edelmann, R. E.; Makaroff, C. A.; Kiss, J. Z.

    1999-01-01

    Integrins are a large family of integral membrane proteins that function in signal transduction in animal systems. These proteins are conserved in vertebrates, invertebrates, and fungi. Evidence from previous research suggests that integrin-like proteins may be present in plants as well, and that these proteins may function in signal transduction during gravitropism. In past studies, researchers have used monoclonal and polyclonal antibodies to localize beta 1 integrin-like proteins in plants. However, there is a disparity between data collected from these studies, especially since molecular weights obtained from these investigations range from 55-120 kDa for integrin-like proteins. To date, a complete investigation which employs all three basic immunolabeling procedures, immunoblotting, immunofluorescence microscopy, and immunogold labeling, in addition to extensive fractionation and exhaustive controls, has been lacking. In this paper, we demonstrate that use of a polyclonal antibody against the cytoplasmic domain of avian beta 1-integrin can produce potential artifacts in immunolocalization studies. However, these problems can be eliminated through use of starchless mutants or proper specimen preparation prior to electrophoresis. We also show that this antibody, when applied within the described parameters and with careful controls, identifies a large (100 kDa) integrin-like protein that is localized to plasma membrane fractions in Arabidopsis.

  5. Studying the Nucleated Mammalian Cell Membrane by Single Molecule Approaches

    PubMed Central

    Wang, Feng; Wu, Jiazhen; Gao, Jing; Liu, Shuheng; Jiang, Junguang; Jiang, Shibo; Wang, Hongda

    2014-01-01

    The cell membrane plays a key role in compartmentalization, nutrient transportation and signal transduction, while the pattern of protein distribution at both cytoplasmic and ectoplasmic sides of the cell membrane remains elusive. Using a combination of single-molecule techniques, including atomic force microscopy (AFM), single molecule force spectroscopy (SMFS) and stochastic optical reconstruction microscopy (STORM), to study the structure of nucleated cell membranes, we found that (1) proteins at the ectoplasmic side of the cell membrane form a dense protein layer (4 nm) on top of a lipid bilayer; (2) proteins aggregate to form islands evenly dispersed at the cytoplasmic side of the cell membrane with a height of about 10–12 nm; (3) cholesterol-enriched domains exist within the cell membrane; (4) carbohydrates stay in microdomains at the ectoplasmic side; and (5) exposed amino groups are asymmetrically distributed on both sides. Based on these observations, we proposed a Protein Layer-Lipid-Protein Island (PLLPI) model, to provide a better understanding of cell membrane structure, membrane trafficking and viral fusion mechanisms. PMID:24806512

  6. Acetylcholine Receptor Organization in Membrane Domains in Muscle Cells

    PubMed Central

    Piguet, Joachim; Schreiter, Christoph; Segura, Jean-Manuel; Vogel, Horst; Hovius, Ruud

    2011-01-01

    Nicotinic acetylcholine receptors (nAChR) in muscle fibers are densely packed in the postsynaptic region at the neuromuscular junction. Rapsyn plays a central role in directing and clustering nAChR during cellular differentiation and neuromuscular junction formation; however, it has not been demonstrated whether rapsyn is the only cause of receptor immobilization. Here, we used single-molecule tracking methods to investigate nAChR mobility in plasma membranes of myoblast cells during their differentiation to myotubes in the presence and absence of rapsyn. We found that in myoblasts the majority of nAChR were immobile and that ?20% of the receptors showed restricted diffusion in small domains of ?50 nm. In myoblasts devoid of rapsyn, the fraction of mobile nAChR was considerably increased, accompanied by a 3-fold decrease in the immobile population of nAChR with respect to rapsyn-expressing cells. Half of the mobile receptors were confined to domains of ?120 nm. Measurements performed in heterologously transfected HEK cells confirmed the direct immobilization of nAChR by rapsyn. However, irrespective of the presence of rapsyn, about one-third of nAChR were confined in 300-nm domains. Our results show (i) that rapsyn efficiently immobilizes nAChR independently of other postsynaptic scaffold components; (ii) nAChR is constrained in confined membrane domains independently of rapsyn; and (iii) in the presence of rapsyn, the size of these domains is strongly reduced. PMID:20978122

  7. Favorable effect of in-situ generated platinum in the membrane on fuel cell membrane durability

    NASA Astrophysics Data System (ADS)

    Macauley, Natalia; Wong, Ka Hung; Watson, Mark; Kjeang, Erik

    2015-12-01

    The overall lifetime of polymer electrolyte fuel cells is often determined by the membrane durability. Platinum, which may dissolve from the catalyst layers during fuel cell operation and deposit in the membrane, has been shown to have both positive and negative effects on membrane stability. In the present work, we analyze what specific conditions are required in order to reach a favorable, membrane stabilizing effect with the controlled use of platinum in the membrane. Using accelerated membrane durability testing, field operated membrane samples, and electron microscopy, we demonstrate that a high platinum concentration with specific particle shapes and sizes is essential for enhanced membrane stability. Specifically, star shaped and dendritic particles with high particle density and high surface area are shown to be preferable. These particles contain high levels of Pt(111) and are expected to have high catalytic activity toward peroxide quenching and crossover gas consumption, thereby mitigating chemical membrane degradation. On the other hand, small, dispersed cubic particles are found to have no effect or the opposite, negative effect on membrane stability.

  8. Cell Membranes Under Hydrostatic Pressure Subjected to Micro-Injection

    NASA Astrophysics Data System (ADS)

    Vassilev, Vassil M.; Kostadinov, Kostadin G.; Mladenov, Ivaïlo M.; Shulev, Assen A.; Stoilov, Georgi I.; Djondjorov, Peter A.

    2011-04-01

    The work is concerned with the determination of the mechanical behaviour of cell membranes under uniform hydrostatic pressure subject to micro-injections. For that purpose, assuming that the shape of the deformed cell membrane is axisymmetric a variational statement of the problem is developed on the ground of the so-called spontaneous curvature model. In this setting, the cell membrane is regarded as an axisymmetric surface in the three-dimensional Euclidean space providing a stationary value of the shape energy functional under the constraint of fixed total area and fixed enclosed volume. The corresponding Euler-Lagrange equations and natural boundary conditions are derived, analyzed and used to express the forces and moments in the membrane. Several examples of such surfaces representing possible shapes of cell membranes under pressure subjected to micro injection are determined numerically.

  9. Radiation-Grafted Polymer Electrolyte Membranes for Water Electrolysis Cells: Evaluation of Key Membrane Properties.

    PubMed

    Albert, Albert; Barnett, Alejandro O; Thomassen, Magnus S; Schmidt, Thomas J; Gubler, Lorenz

    2015-10-14

    Radiation-grafted membranes can be considered an alternative to perfluorosulfonic acid (PFSA) membranes, such as Nafion, in a solid polymer electrolyte electrolyzer. Styrene, acrylonitrile, and 1,3-diisopropenylbenzene monomers are cografted into preirradiated 50 ?m ethylene tetrafluoroethylene (ETFE) base film, followed by sulfonation to introduce proton exchange sites to the obtained grafted films. The incorporation of grafts throughout the thickness is demonstrated by scanning electron microscopy/energy-dispersive X-ray spectroscopy (SEM/EDX) analysis of the membrane cross-sections. The membranes are analyzed in terms of grafting kinetics, ion-exchange capacity (IEC), and water uptake. The key properties of radiation-grafted membranes and Nafion, such as gas crossover, area resistance, and mechanical properties, are evaluated and compared. The plot of hydrogen crossover versus area resistance of the membranes results in a property map that indicates the target areas for membrane development for electrolyzer applications. Tensile tests are performed to assess the mechanical properties of the membranes. Finally, these three properties are combined to establish a figure of merit, which indicates that radiation-grafted membranes obtained in the present study are promising candidates with properties superior to those of Nafion membranes. A water electrolysis cell test is performed as proof of principle, including a comparison to a commercial membrane electrode assembly (MEA). PMID:26393461

  10. A Hybrid Microbial Fuel Cell Membrane Bioreactor with a Conductive Ultrafiltration Membrane Biocathode for Wastewater Treatment

    E-print Network

    Biocathode for Wastewater Treatment Lilian Malaeb,,§ Krishna P. Katuri,,§ Bruce E. Logan, Husnul Maab, S. P-biocathode microbial fuel cell- membrane bioreactor (MFC-MBR) system was developed to achieve simultaneous wastewater and the membrane for wastewater filtration. The MFC-MBR used an air-biocathode, and it was shown to have good

  11. Extracellular protease digestion to evaluate membrane protein cell surface localization.

    PubMed

    Besingi, Richard N; Clark, Patricia L

    2015-12-01

    Membrane proteins have crucial roles in signaling and as anchors for cell surface display. Proper secretion of a membrane protein can be evaluated by its susceptibility to digestion by an extracellular protease, but this requires a crucial control to confirm membrane integrity during digestion. This protocol describes how to use this approach to determine how efficiently a protein is secreted to the outer surface of Gram-negative bacteria. Its success relies upon careful selection of an appropriate intracellular reporter protein that will remain undigested if the membrane barrier remains intact, but that is rapidly digested when cells are lysed before evaluation. Reporter proteins that are resistant to proteases (e.g., maltose-binding protein) do not return accurate results; in contrast, proteins that are more readily digested (e.g., SurA) serve as more sensitive reporters of membrane integrity, yielding more accurate measurements of membrane protein localization. Similar considerations apply when evaluating membrane protein localization in other contexts, including eukaryotic cells and organelle membranes. Evaluating membrane protein localization using this approach requires only standard biochemistry laboratory equipment for cell lysis, gel electrophoresis and western blotting. After expression of the protein of interest, this procedure can be completed in 4 h. PMID:26584447

  12. High lipid order of Arabidopsis cell-plate membranes mediated by sterol and DYNAMIN-RELATED PROTEIN1A function

    PubMed Central

    Frescatada-Rosa, Márcia; Stanislas, Thomas; Backues, Steven K; Reichardt, Ilka; Men, Shuzhen; Boutté, Yohann; Jürgens, Gerd; Moritz, Thomas; Bednarek, Sebastian Y; Grebe, Markus

    2014-01-01

    Membranes of eukaryotic cells contain high lipid-order sterol-rich domains that are thought to mediate temporal and spatial organization of cellular processes. Sterols are crucial for execution of cytokinesis, the last stage of cell division, in diverse eukaryotes. The cell plate of higher-plant cells is the membrane structure that separates daughter cells during somatic cytokinesis. Cell-plate formation in Arabidopsis relies on sterol- and DYNAMIN-RELATED PROTEIN1A (DRP1A)-dependent endocytosis. However, functional relationships between lipid membrane order or lipid packing and endocytic machinery components during eukaryotic cytokinesis have not been elucidated. Using ratiometric live imaging of lipid order-sensitive fluorescent probes, we show that the cell plate of Arabidopsis thaliana represents a dynamic, high lipid-order membrane domain. The cell-plate lipid order was found to be sensitive to pharmacological and genetic alterations of sterol composition. Sterols co-localize with DRP1A at the cell plate, and DRP1A accumulates in detergent-resistant membrane fractions. Modifications of sterol concentration or composition reduce cell-plate membrane order and affect DRP1A localization. Strikingly, DRP1A function itself is essential for high lipid order at the cell plate. Our findings provide evidence that the cell plate represents a high lipid-order domain, and pave the way to explore potential feedback between lipid order and function of dynamin-related proteins during cytokinesis. PMID:25234576

  13. JournalofCellScience Membrane and actin reorganization in electropulse-

    E-print Network

    Schwarz, Ulrich

    JournalofCellScience Membrane and actin reorganization in electropulse- induced cell fusion Gu of Cell Science 126, 2069­2078 ß 2013. Published by The Company of Biologists Ltd doi: 10.1242/jcs.124073 Summary When cells of Dictyostelium discoideum are exposed to electric pulses they are induced to fuse

  14. Human hepatocytes and endothelial cells in organotypic membrane systems.

    PubMed

    Salerno, Simona; Campana, Carla; Morelli, Sabrina; Drioli, Enrico; De Bartolo, Loredana

    2011-12-01

    The realization of organotypic liver model that exhibits stable phenotype is a major challenge in the field of liver tissue engineering. In this study we developed liver organotypic co-culture systems by using synthetic and biodegradable membranes with primary human hepatocytes and human umbilical vein endothelial cells (HUVEC). Synthetic membranes prepared by a polymeric blend constituted of modified polyetheretherketone (PEEK-WC) and polyurethane (PU) and biodegradable chitosan membranes were developed by phase inversion technique and used in homotypic and organotypic culture systems. The morphological and functional characteristics of cells in the organotypic co-culture membrane systems were evaluated in comparison with homotypic cultures and traditional systems. Hepatocytes in the organotypic co-culture systems exhibit compact polyhedral cells with round nuclei and well demarcated cell-cell borders like in vivo, as a result of heterotypic interaction with HUVECs. In addition HUVECs formed tube-like structures directly through the interactions with the membranes and hepatocytes and indirectly through the secretion of ECM proteins which secretion improved in the organotypic co-culture membrane systems. The heterotypic cell-cell contacts have beneficial effect on the hepatocyte albumin production, urea synthesis and drug biotransformation. The developed organotypic co-culture membrane systems elicit liver specific functions in vitro and could be applied for the realization of engineered liver tissues to be used in tissue engineering, drug metabolism studies and bioartificial liver devices. PMID:21871658

  15. Measurement of the nonlinear elasticity of red blood cell membranes

    NASA Astrophysics Data System (ADS)

    Park, Yongkeun; Best, Catherine A.; Kuriabova, Tatiana; Henle, Mark L.; Feld, Michael S.; Levine, Alex J.; Popescu, Gabriel

    2011-05-01

    The membranes of human red blood cells (RBCs) are a composite of a fluid lipid bilayer and a triangular network of semiflexible filaments (spectrin). We perform cellular microrheology using the dynamic membrane fluctuations of the RBCs to extract the elastic moduli of this composite membrane. By applying known osmotic stresses, we measure the changes in the elastic constants under imposed strain and thereby determine the nonlinear elastic properties of the membrane. We find that the elastic nonlinearities of the shear modulus in tensed RBC membranes can be well understood in terms of a simple wormlike chain model. Our results show that the elasticity of the spectrin network can mostly account for the area compression modulus at physiological osmolality, suggesting that the lipid bilayer has significant excess area. As the cell swells, the elastic contribution from the now tensed lipid membrane becomes dominant.

  16. Partitioning of the matrix fraction of the Golgi apparatus during mitosis in animal cells.

    PubMed

    Seemann, Joachim; Pypaert, Marc; Taguchi, Tomohiko; Malsam, Jorg; Warren, Graham

    2002-02-01

    The Golgi apparatus is partitioned during mitosis in animal cells by a process of fragmentation, dispersal, and reassembly in each daughter cell. We fractionated the Golgi apparatus in vivo using the drug brefeldin A or a dominant-negative mutant of the Sar1p protein. After these treatments, Golgi enzymes moved back to the endoplasmic reticulum, leaving behind a matrix of Golgi structural proteins. Under these conditions, cells still entered and exited mitosis normally, and their Golgi matrix partitioned in a manner very similar to that of the complete organelle. Thus, the matrix may be the partitioning unit of the Golgi apparatus and may carry the Golgi enzyme-containing membranes into the daughter cells. PMID:11823640

  17. Radiation Interaction with Therapeutic Drugs and Cell Membranes

    SciTech Connect

    Martin, Diana I.; Manaila, Elena N.; Matei, Constantin I.; Iacob, Nicusor I.; Ighigeanu, Daniel I.; Craciun, Gabriela D.; Moisescu, Mihaela I.; Savopol, Tudor D.; Kovacs, Eugenia A.; Cinca, Sabin A.; Margaritescu, Irina D.

    2007-04-23

    This transient permeabilized state of the cell membrane, named the 'cell electroporation' (CE) can be used to increase cells uptake of drugs that do not readily pass cell membrane, thus enabling their cytotoxicity. The anticancer drugs, such as bleomycin (BL) and cisplatin, are the most candidates for the combined use with ionizing and non-ionizing radiation fields. The methods and installations for the cell electroporation by electron beam (EB) and microwave (MW) irradiation are presented. The viability tests of the human leukocytes under EB and MW exposure with/without the BL in the cell cultures are discussed.

  18. Improved Membrane Materials for PEM Fuel Cell Application

    SciTech Connect

    Kenneth A. Mauritz; Robert B. Moore

    2008-06-30

    The overall goal of this project is to collect and integrate critical structure/property information in order to develop methods that lead to significant improvements in the durability and performance of polymer electrolyte membrane fuel cell (PEMFC) materials. This project is focused on the fundamental improvement of PEMFC membrane materials with respect to chemical, mechanical and morphological durability as well as the development of new inorganically-modified membranes.

  19. How the antimicrobial peptides destroy bacteria cell membrane: Translocations vs. membrane buckling

    NASA Astrophysics Data System (ADS)

    Golubovic, Leonardo; Gao, Lianghui; Chen, Licui; Fang, Weihai

    2012-02-01

    In this study, coarse grained Dissipative Particle Dynamics simulation with implementation of electrostatic interactions is developed in constant pressure and surface tension ensemble to elucidate how the antimicrobial peptide molecules affect bilayer cell membrane structure and kill bacteria. We find that peptides with different chemical-physical properties exhibit different membrane obstructing mechanisms. Peptide molecules can destroy vital functions of the affected bacteria by translocating across their membranes via worm-holes, or by associating with membrane lipids to form hydrophilic cores trapped inside the hydrophobic domain of the membranes. In the latter scenario, the affected membranes are strongly corrugated (buckled) in accord with very recent experimental observations [G. E. Fantner et al., Nat. Nanotech., 5 (2010), pp. 280-285].

  20. The Flocculating Cationic Polypetide from Moringa oleifera Seeds Damages Bacterial Cell Membranes by Causing Membrane Fusion.

    PubMed

    Shebek, Kevin; Schantz, Allen B; Sines, Ian; Lauser, Kathleen; Velegol, Stephanie; Kumar, Manish

    2015-04-21

    A cationic protein isolated from the seeds of the Moringa oleifera tree has been extensively studied for use in water treatment in developing countries and has been proposed for use in antimicrobial and therapeutic applications. However, the molecular basis for the antimicrobial action of this peptide, Moringa oleifera cationic protein (MOCP), has not been previously elucidated. We demonstrate here that a dominant mechanism of MOCP antimicrobial activity is membrane fusion. We used a combination of cryogenic electron microscopy (cryo-EM) and fluorescence assays to observe and study the kinetics of fusion of membranes in liposomes representing model microbial cells. We also conducted cryo-EM experiments on E. coli cells where MOCP was seen to fuse the inner and outer membranes. Coarse-grained molecular dynamics simulations of membrane vesicles with MOCP molecules were used to elucidate steps in peptide adsorption, stalk formation, and fusion between membranes. PMID:25845029

  1. Investigating cell membrane structure and dynamics with TCSPC-FLIM

    NASA Astrophysics Data System (ADS)

    Le Marois, Alix; Owen, Dylan M.; Suhling, Klaus

    2015-03-01

    We report the use of Time-Correlated Single Photon Counting (TCSPC) in a polarization-resolved Fluorescence Lifetime Imaging (FLIM) setup for the investigation of cell membrane structural and dynamic properties. This technique allows us to study the orientation and mobility of fluorescent membrane dyes, namely di-4-ANEPPDHQ and DiO, in model bilayers of different lipid compositions. Dipole alignment and extent of rotational motion can be linked to membrane order and fluidity. Comparison of the time-resolved anisotropy decays of the two fluorescent dyes suggests that rotational motion of membrane constituents is restricted in liquid-ordered phases, and appears to be limited to the region of aliphatic tails in liquid-disordered phases. In living cells, understanding the membrane structure provides crucial information on its functional properties, such as exo- and endocytosis, cell mobility and signal transduction.

  2. The application of Dow Chemical's perfluorinated membranes in proton-exchange membrane fuel cells

    NASA Technical Reports Server (NTRS)

    Eisman, G. A.

    1989-01-01

    Dow Chemical's research activities in fuel cell devices revolves around the development and subsequent investigation of the perfluorinated inomeric membrane separator useful in proton-exchange membrane systems. Work is currently focusing on studying the effects of equivalent weight, thickness, water of hydration, pretreatment procedures, as well as the degree of water management required for a given membrane separator in the cell. The presentation will include details of certain aspects of the above as well as some of the requirements for high and low power generation.

  3. Membrane Transport Chloride Transport Across Vesicle and Cell

    E-print Network

    Smith, Bradley D.

    Membrane Transport Chloride Transport Across Vesicle and Cell Membranes by Steroid-Based Receptors of biological activity. Indeed, chloride transporters have direct medical potential as treatments for cystic of cationophores such as valino- mycin. We now report that cholapods 2 are indeed capable of transporting chloride

  4. Catalytic membranes for CO oxidation in fuel cells

    DOEpatents

    Sandi-Tapia, Giselle; Carrado Gregar, Kathleen; Kizilel, Riza

    2010-06-08

    A hydrogen permeable membrane, which includes a polymer stable at temperatures of about 200 C having clay impregnated with Pt or Au or Ru or Pd particles or mixtures thereof with average diameters of less than about 10 nanometers (nms) is disclosed. The membranes are useful in fuel cells or any device which requires hydrogen to be separated from carbon monoxide.

  5. Reusable, reversibly sealable parylene membranes for cell and protein patterning

    E-print Network

    Dokmeci, Mehmet

    Reusable, reversibly sealable parylene membranes for cell and protein patterning Dylan Wright,1- versible sealing of microfabricated parylene-C stencils on surfaces to enable surface patterning. Using demonstrated the reusability and mechanical integrity of the parylene membrane for at least 10 consecu- tive

  6. Biodegradation characteristics and size fractionation of landfill leachate for integrated membrane treatment.

    PubMed

    Insel, Güçlü; Dagdar, Mina; Dogruel, Serdar; Dizge, Nadir; Ubay Cokgor, Emine; Keskinler, Bülent

    2013-09-15

    The fate of organics and nitrogen during the biological treatment with MBR and subsequent membrane filtration processes (nano filtration, NF; reverse osmosis, RO) were investigated for a landfill leachate. The chemical oxygen demand (COD) and total Kjeldahl nitrogen (TKN) removal performances of membrane bioreactor (MBR) were obtained to be around 89% and 85%, respectively. The effluent COD of MBR was measured to be 1935 mg/L (30 kDa) which is much lower than experimentally determined soluble inert COD of 3200 mg/L using 0.45 ?m filter. The readily and slowly biodegradable COD fractions were estimated to be 17% and 52% of raw influent COD, respectively. The respirometry based modeling test performed on raw leachate exhibited much slower degradation kinetics compared to municipal wastewater. A unique subset of model parameters was extracted from batch respirometry by using acclimated MBR sludge. The sequential ultrafiltration (UF) experiments (particle size distribution, PSD) revealed that most of the organics was below 2 nm filter mesh size. In addition, NF/RO post treatment after MBR system was required to increase COD and total nitrogen (TN) removal performances up to 99%. Relatively lower salt rejection rates around 94% was obtained for RO system as a post treatment of MBR system. PMID:23856313

  7. Fractionation of proteins and carbohydrates of extracellular polymeric substances in a membrane bioreactor system.

    PubMed

    Malamis, Simos; Andreadakis, Andreas

    2009-07-01

    The major operational problem associated with membrane bioreactors (MBR) is membrane fouling, for which extracellular polymeric substances (EPS) are primarily responsible. In this work both the soluble and bound EPS (i.e. SMP and EPS) produced in an MBR system operating under sludge retention times (SRT) of 10, 15, 20 and 33 days were fractionized by means of membranes having variable molecular weight cutoffs (300 kDa, 100 kDa, 10 kDa & 1 kDa). The results show that increasing the SRT leads to a reduction of SMP and EPS and that these reductions are more pronounced for the SRTs in the range 10-20 days. This reduction is more significant for carbohydrates than for proteins. The decrease of SMP and EPS with increasing SRT from 10 to 20 days led to a significant decrease of the level of fouling. The further increase of SRT to 33 days did not significantly impact on the level of fouling as the SMP and EPS concentrations did not change much. Under the examined operating conditions, EPS were found to be composed mainly of large macromolecules having a size of 0.45 microm-300 kDa and to a lower extent of very small molecules (<1 kDa) that are not easily decomposed by the biomass activity. The majority of SMP is composed of very small molecules (<1 kDa), while some macromolecules in the range of 0.45 microm-300 kDa are present. Consequently, both EPS and SMP were found to have a bimodal character. PMID:19303770

  8. The Anti-angiogenic Peptide Anginex Disrupts the Cell Membrane

    PubMed Central

    Pilch, Jan; Franzin, Carla M.; Knowles, Lynn M.; Ferrer, Fernando J.; Marassi, Francesca M.; Ruoslahti, Erkki

    2010-01-01

    Anginex is a synthetic beta-sheet peptide with anti-angiogenic and anti-tumor activity. When added to cultured endothelial cells at concentrations ranging from 2.5 ?M to 25 ?M, anginex induced cell death, which was reflected by a strong increase of subdiploid cells and fragments, loss of cellular ATP, and LDH release. Cytotoxicity remained the same whether cells were treated with anginex at 4 °C or at 37 °C. At low temperatures, fluorescein-conjugated anginex accumulated on the endothelial surface, but did not reach into the cytoplasm, indicating that the cell membrane is the primary target for the peptide. Within minutes of treatment, anginex caused endothelial cells to take up propidium iodide and undergo depolarization, both parameters characteristic for permeabilization of the cell membrane. This process was amplified when cells were activated with hydrogen peroxide. Red blood cell membranes were essentially unaffected by anginex. Anginex bound lipid bilayers with high affinity and with a clear preference for anionic over zwitterionic phospholipids. Structural studies by circular dichroism and solid-state nuclear magnetic resonance showed that anginex forms a beta-sheet and adopts a unique and highly ordered conformation upon binding to lipid membranes. This is consistent with lipid micellization or the formation of pore-forming beta-barrels. The data suggest that the cytotoxicity of anginex stems from its ability to target and disrupt the endothelial cell membrane, providing a possible explanation for the angiostatic activity of the peptide. PMID:16403516

  9. Inhibition of SNARE-mediated membrane traffic impairs cell migration.

    PubMed

    Tayeb, Michael A; Skalski, Michael; Cha, Ming C; Kean, Michelle J; Scaife, Matthew; Coppolino, Marc G

    2005-04-15

    Cell migration occurs as a highly-regulated cycle of cell polarization, membrane extension at the leading edge, adhesion, contraction of the cell body, and release from the extracellular matrix at the trailing edge. In this study, we investigated the involvement of SNARE-mediated membrane trafficking in cell migration. Using a dominant-negative form of the enzyme N-ethylmaleimide-sensitive factor as a general inhibitor of SNARE-mediated membrane traffic and tetanus toxin as a specific inhibitor of VAMP3/cellubrevin, we conducted transwell migration assays and determined that serum-induced migration of CHO-K1 cells is dependant upon SNARE function. Both VAMP3-mediated and VAMP3-independent traffic were involved in regulating this cell migration. Inhibition of SNARE-mediated membrane traffic led to a decrease in the protrusion of lamellipodia at the leading edge of migrating cells. Additionally, the reduction in cell migration resulting from the inhibition of SNARE function was accompanied by perturbation of a Rab11-containing alpha(5)beta(1) integrin compartment and a decrease in cell surface alpha(5)beta(1) without alteration to total cellular integrin levels. Together, these observations suggest that inhibition of SNARE-mediated traffic interferes with the intracellular distribution of integrins and with the membrane remodeling that contributes to lamellipodial extension during cell migration. PMID:15777788

  10. Membrane Organization and Cell Fusion During Mating in Fission Yeast Requires Multipass Membrane Protein Prm1

    PubMed Central

    Curto, M.-Ángeles; Sharifmoghadam, Mohammad Reza; Calpena, Eduardo; De León, Nagore; Hoya, Marta; Doncel, Cristina; Leatherwood, Janet; Valdivieso, M.-Henar

    2014-01-01

    The involvement of Schizosaccharomyces pombe prm1+ in cell fusion during mating and its relationship with other genes required for this process have been addressed. S. pombe prm1? mutant exhibits an almost complete blockade in cell fusion and an abnormal distribution of the plasma membrane and cell wall in the area of cell–cell interaction. The distribution of cellular envelopes is similar to that described for mutants devoid of the Fig1-related claudin-like Dni proteins; however, prm1+ and the dni+ genes act in different subpathways. Time-lapse analyses show that in the wild-type S. pombe strain, the distribution of phosphatidylserine in the cytoplasmic leaflet of the plasma membrane undergoes some modification before an opening is observed in the cross wall at the cell–cell contact region. In the prm1? mutant, this membrane modification does not take place, and the cross wall between the mating partners is not extensively degraded; plasma membrane forms invaginations and fingers that sometimes collapse/retract and that are sometimes strengthened by the synthesis of cell-wall material. Neither prm1? nor prm1? dni? zygotes lyse after cell–cell contact in medium containing and lacking calcium. Response to drugs that inhibit lipid synthesis or interfere with lipids is different in wild-type, prm1?, and dni1? strains, suggesting that membrane structure/organization/dynamics is different in all these strains and that Prm1p and the Dni proteins exert some functions required to guarantee correct membrane organization that are critical for cell fusion. PMID:24514900

  11. Layer-by-layer cell membrane assembly

    NASA Astrophysics Data System (ADS)

    Matosevic, Sandro; Paegel, Brian M.

    2013-11-01

    Eukaryotic subcellular membrane systems, such as the nuclear envelope or endoplasmic reticulum, present a rich array of architecturally and compositionally complex supramolecular targets that are as yet inaccessible. Here we describe layer-by-layer phospholipid membrane assembly on microfluidic droplets, a route to structures with defined compositional asymmetry and lamellarity. Starting with phospholipid-stabilized water-in-oil droplets trapped in a static droplet array, lipid monolayer deposition proceeds as oil/water-phase boundaries pass over the droplets. Unilamellar vesicles assembled layer-by-layer support functional insertion both of purified and of in situ expressed membrane proteins. Synthesis and chemical probing of asymmetric unilamellar and double-bilayer vesicles demonstrate the programmability of both membrane lamellarity and lipid-leaflet composition during assembly. The immobilized vesicle arrays are a pragmatic experimental platform for biophysical studies of membranes and their associated proteins, particularly complexes that assemble and function in multilamellar contexts in vivo.

  12. Low Crossover Polymer Electrolyte Membranes for Direct Methanol Fuel Cells

    NASA Technical Reports Server (NTRS)

    Prakash, G. K. Surya; Smart, Marshall; Atti, Anthony R.; Olah, George A.; Narayanan, S. R.; Valdez, T.; Surampudi, S.

    1996-01-01

    Direct Methanol Fuel Cells (DMFC's) using polymer electrolyte membranes are promising power sources for portable and vehicular applications. State of the art technology using Nafion(R) 117 membranes (Dupont) are limited by high methanol permeability and cost, resulting in reduced fuel cell efficiencies and impractical commercialization. Therefore, much research in the fuel cell field is focused on the preparation and testing of low crossover and cost efficient polymer electrolyte membranes. The University of Southern California in cooperation with the Jet Propulsion Laboratory is focused on development of such materials. Interpenetrating polymer networks are an effective method used to blend polymer systems without forming chemical links. They provide the ability to modify physical and chemical properties of polymers by optimizing blend compositions. We have developed a novel interpenetrating polymer network based on poly (vinyl - difluoride)/cross-linked polystyrenesulfonic acid polymer composites (PVDF PSSA). Sulfonation of polystyrene accounts for protonic conductivity while the non-polar, PVDF backbone provides structural integrity in addition to methanol rejection. Precursor materials were prepared and analyzed to characterize membrane crystallinity, stability and degree of interpenetration. USC JPL PVDF-PSSA membranes were also characterized to determine methanol permeability, protonic conductivity and sulfur distribution. Membranes were fabricated into membrane electrode assemblies (MEA) and tested for single cell performance. Tests include cell performance over a wide range of temperatures (20 C - 90 C) and cathode conditions (ambient Air/O2). Methanol crossover values are measured in situ using an in-line CO2 analyzer.

  13. Heterogeneity of Arabinogalactan-Proteins on the Plasma Membrane of Rose Cells.

    PubMed Central

    Serpe, M. D.; Nothnagel, E. A.

    1996-01-01

    Arabinogalactan-proteins (AGPs) have been purified from the plasma membrane of suspension-cultured Paul's Scarlet rose (Rosa sp.) cells. The two most abundant and homogeneous plasma membrane AGP fractions were named plasma membrane AGP1 (PM-AGP1) and plasma membrane AGP2 (PM-AGP2) and had apparent molecular masses of 140 and 217 kD, respectively. Both PM-AGP1 and PM-AGP2 had [beta]-(1-3)-, [beta]-(1,6)-, and [beta]-(1,3,6)-galactopyranosyl residues, predominantly terminal [alpha]-arabinofuranosyl residues, and (1,4)- and terminal glucuronopyranosyl residues. The protein moieties of PM-AGP1 and PM-AGP2 were both rich in hydroxyproline, alanine, and serine, but differed in the abundance of hydroxyproline, which was 1.6 times higher in PM-AGP2 than in PM-AGP1. Another difference was the overall protein content, which was 3.7% (w/w) in PM-AGP1 and 15% in PM-AGP2. As judged by their behavior on reverse-phase chromatography, PM-AGP1 and PM-AGP2 were not more hydrophobic than AGPs from the cell wall or culture medium. In contrast, a minor plasma membrane AGP fraction eluted later on reverse-phase chromatography and was more negatively charged at pH 5 than either PM-AGP1 or PM-AGP2. The more negatively charged fraction contained molecules with a glycosyl composition characteristic of AGPs and included at least two different macromolecules. The results of this investigation indicate that Rosa plasma membrane contains at least four distinct AGPs or AGP-like molecules. These molecules differed from each other in size, charge, hydrophobicity, amino-acyl composition, and/or protein content. PMID:12226444

  14. Decreasing Outer Hair Cell Membrane Cholesterol Increases Cochlear Electromechanics

    NASA Astrophysics Data System (ADS)

    Brownell, William E.; Jacob, Stefan; Hakizimana, Pierre; Ulfendahl, Mats; Fridberger, Anders

    2011-11-01

    The effect of decreasing membrane cholesterol on the mechanical response of the cochlea to acoustic and/or electrical stimulation was monitored using laser interferometry. In contrast to pharmacological interventions that typically decrease cochlear electromechanics, reducing membrane cholesterol increased the response. The electromechanical response in untreated preparations was asymmetric with greater displacements in response to positive currents and cholesterol depletion increased the asymmetry. The results confirm that outer hair cell electromotility is enhanced by low membrane cholesterol. The asymmetry of the response indicates the outer hair cell resting membrane potential is hyperpolarized relative to the voltage of maximum gain for the outer hair cell voltage-displacement function. The magnitude of the response increase suggests a non-uniform distribution of cholesterol along the lateral wall of normal adult outer hair cells.

  15. Fibronectin coating of oxygenator membranes enhances endothelial cell attachment

    PubMed Central

    2013-01-01

    Background Extracorporeal membrane oxygenation (ECMO) can replace the lungs’ gas exchange capacity in refractory lung failure. However, its limited hemocompatibility, the activation of the coagulation and complement system as well as plasma leakage and protein deposition hamper mid- to long-term use and have constrained the development of an implantable lung assist device. In a tissue engineering approach, lining the blood contact surfaces of the ECMO device with endothelial cells might overcome these limitations. As a first step towards this aim, we hypothesized that coating the oxygenator’s gas exchange membrane with proteins might positively influence the attachment and proliferation of arterial endothelial cells. Methods Sheets of polypropylene (PP), polyoxymethylpentene (TPX) and polydimethylsiloxane (PDMS), typical material used for oxygenator gas exchange membranes, were coated with collagen, fibrinogen, gelatin or fibronectin. Tissue culture treated well plates served as controls. Endothelial cell attachment and proliferation were analyzed for a period of 4 days by microscopic examination and computer assisted cell counting. Results Endothelial cell seeding efficiency is within range of tissue culture treated controls for fibronectin treated surfaces only. Uncoated membranes as well as all other coatings lead to lower cell attachment. A confluent endothelial cell layer develops on fibronectin coated PDMS and the control surface only. Conclusions Fibronectin increases endothelial cells’ seeding efficiency on different oxygenator membrane material. PDMS coated with fibronectin shows sustained cell attachment for a period of four days in static culture conditions. PMID:23356939

  16. Tension of red blood cell membrane in simple shear flow

    NASA Astrophysics Data System (ADS)

    Omori, T.; Ishikawa, T.; Barthès-Biesel, D.; Salsac, A.-V.; Imai, Y.; Yamaguchi, T.

    2012-11-01

    When a red blood cell (RBC) is subjected to an external flow, it is deformed by the hydrodynamic forces acting on its membrane. The resulting elastic tensions in the membrane play a key role in mechanotransduction and govern its rupture in the case of hemolysis. In this study, we analyze the motion and deformation of an RBC in a simple shear flow and the resulting elastic tensions on the membrane. The large deformation of the red blood cell is modelled by coupling a finite element method to solve the membrane mechanics and a boundary element method to solve the flows of the internal and external liquids. Depending on the capillary number Ca, ratio of the viscous to elastic forces, we observe three kinds of RBC motion: tumbling at low Ca, swinging at larger Ca, and breathing at the transitions. In the swinging regime, the region of the high principal tensions periodically oscillates, whereas that of the high isotropic tensions is almost unchanged. Due to the strain-hardening property of the membrane, the deformation is limited but the membrane tension increases monotonically with the capillary number. We have quantitatively compared our numerical results with former experimental results. It indicates that a membrane isotropic tension O(10-6 N/m) is high enough for molecular release from RBCs and that the typical maximum membrane principal tension for haemolysis would be O(10-4 N/m). These findings are useful to clarify not only the membrane rupture but also the mechanotransduction of RBCs.

  17. Ion Exchange Membrane Cathodes for Scalable Microbial Fuel Cells

    E-print Network

    applications. Introduction A microbial fuel cell (MFC) is a new technology for bioenergy production becauseIon Exchange Membrane Cathodes for Scalable Microbial Fuel Cells Y I Z U O , S H A O A N C H E N G. One of the main challenges for using microbial fuel cells (MFCs) is developing materials

  18. Photobleaching Regions of Living Cells to Monitor Membrane Traffic

    E-print Network

    Snapp, Erik Lee

    on the CLSM, and bring it to the Adapted from Live Cell Imaging, 2nd edition (ed. Goldman et al.). CSHL Press and Patrick Lajoie Eukaryotic cells are composed of an intricate system of internal membranes specialized tasks within the cell. The localization and dynamics of intracellular compartments are now being

  19. Penetration of Cell Membranes and Synthetic Lipid Bilayers by Nanoprobes

    PubMed Central

    Angle, Matthew R.; Wang, Andrew; Thomas, Aman; Schaefer, Andreas T.; Melosh, Nicholas A.

    2014-01-01

    Nanoscale devices have been proposed as tools for measuring and controlling intracellular activity by providing electrical and/or chemical access to the cytosol. Unfortunately, nanostructures with diameters of 50–500 nm do not readily penetrate the cell membrane, and rationally optimizing nanoprobes for cell penetration requires real-time characterization methods that are capable of following the process of membrane penetration with nanometer resolution. Although extensive work has examined the rupture of supported synthetic lipid bilayers, little is known about the applicability of these model systems to living cell membranes with complex lipid compositions, cytoskeletal attachment, and membrane proteins. Here, we describe atomic force microscopy (AFM) membrane penetration experiments in two parallel systems: live HEK293 cells and stacks of synthetic lipid bilayers. By using the same probes in both systems, we were able to clearly identify membrane penetration in synthetic bilayers and compare these events with putative membrane penetration events in cells. We examined membrane penetration forces for three tip geometries and 18 chemical modifications of the probe surface, and in all cases the median forces required to penetrate cellular and synthetic lipid bilayers with nanoprobes were greater than 1 nN. The penetration force was sensitive to the probe's sharpness, but not its surface chemistry, and the force did not depend on cell surface or cytoskeletal properties, with cells and lipid stacks yielding similar forces. This systematic assessment of penetration under various mechanical and chemical conditions provides insights into nanoprobe-cell interactions and informs the design of future intracellular nanoprobes. PMID:25418094

  20. The surface charge of a cell lipid membrane

    E-print Network

    M. Pekker; M. N. Shneider

    2014-10-26

    In this paper the problem of surface charge of the lipid membrane immersed in the physiological solution is considered. It is shown that both side of the bilayer phospholipid membrane surface are negatively charged. A self-consistent model of the potential in solution is developed, and a stationary charge density on the membrane surface is found. It is shown that the ions of the surface charge are in a relatively deep (as compared to kBT) potential wells, which are localized near the dipole heads of phospholipid membrane. It makes impossible for ions to slip along the membrane surface. Simple experiments for verifying the correctness of the considered model are proposed. A developed approach can be used for estimations of the surface charges on the outer and inner membrane of the cell.

  1. Membrane-electrode assemblies for electrochemical cells

    DOEpatents

    Swathirajan, Sundararajan (Troy, MI); Mikhail, Youssef M. (Sterling Heights, MI)

    1993-01-01

    A combination, unitary, membrane and electrode assembly with a solid polymer electrolyte membrane, and first and second electrodes at least partially embedded in opposed surfaces of the membrane. The electrodes each comprise a respective group of finely divided carbon particles, very finely divided catalytic particles supported on internal and external surfaces of the carbon particles and a proton conductive material intermingled with the catalytic and carbon particles. A first group of finely divided carbon particles forming the first electrode has greater water attraction and retention properties, and is more hydrophilic than a second group of carbon particles forming the second electrode. In a preferred method, the membrane electrode assembly of the invention is prepared by forming a slurry of proton conductive material and at least one group of the carbon and catalyst particles. The slurry is applied to the opposed surfaces of the membrane and heated while being pressed to the membrane for a time and at a temperature and compressive load sufficient to embed at least a portion of the particles into the membrane.

  2. Redistribution of membrane proteins in isolated mouse intestinal epithelial cells

    PubMed Central

    1980-01-01

    Single mouse intestinal epithelial cells (IEC) may be isolated by the use of a combination of methods used for the isolation of IEC from other species. Isolated cells remain viable for several hours. The membrane integral enzymes alkaline phosphatase and leucine aminopeptidase of isolated IEC are localized to the brush borders of IEC in tissue and in most newly isolated IEC. With time, both enzymes are found distributed over the entire cell surface. Redistribution appears to occur by diffusion in the plane of the membrane. It is slowed, but not blocked, if cells are maintained at 0 degrees C instead of at 37 degrees C, and it is not blocked by fixation in 0.5-3% paraformaldehyde. Drugs that alter cell membrane potential or that affect cell levels of ATP enhance the rate of redistribution of the enzymes. PMID:7410482

  3. Adaptation of yeast cell membranes to ethanol

    SciTech Connect

    Jimenez, J.; Benitez, T.

    1987-05-01

    A highly ethanol-tolerant Saccharomyces wine strain is able, after growth in the presence of ethanol, to efficiently improve the ethanol tolerance of its membrane. A less-tolerant Saccharomyces laboratory strain, however, is unable to adapt its membrane to ethanol. Furthermore, after growth in the presence of ethanol, the membrane of the latter strain becomes increasingly sensitive, although this is a reversible process. Reversion to a higher tolerance occurs only after the addition of an energy source and does not take place in the presence of cycloheximide.

  4. The fractional viscoelastic response of human breast tissue cells

    NASA Astrophysics Data System (ADS)

    Carmichael, B.; Babahosseini, H.; Mahmoodi, S. N.; Agah, M.

    2015-07-01

    The mechanical response of a living cell is notoriously complicated. The complex, heterogeneous characteristics of cellular structure introduce difficulties that simple linear models of viscoelasticity cannot overcome, particularly at deep indentation depths. Herein, a nano-scale stress-relaxation analysis performed with an atomic force microscope reveals that isolated human breast cells do not exhibit simple exponential relaxation capable of being modeled by the standard linear solid (SLS) model. Therefore, this work proposes the application of the fractional Zener (FZ) model of viscoelasticity to extract mechanical parameters from the entire relaxation response, improving upon existing physical techniques to probe isolated cells. The FZ model introduces a new parameter that describes the fractional time-derivative dependence of the response. The results show an exceptional increase in conformance to the experimental data compared to that predicted by the SLS model, and the order of the fractional derivative (?) is remarkably homogeneous across the populations, with a median value of 0.48 ± 0.06 for the malignant population and 0.51 ± 0.07 for the benign. The cells’ responses exhibit power-law behavior and complexity not associated with simple relaxation (SLS, ? = 1) that supports the application of a fractional model. The distributions of some of the FZ parameters also preserve the distinction between the malignant and benign sample populations seen from the linear model and previous results while including the contribution of fast-relaxation behavior. The resulting viscosity, measured by a composite relaxation time, exhibits considerably less dispersion due to residual error than the distribution generated by the linear model and therefore serves as a more powerful marker for cell differentiation.

  5. Modeling of interactions between nanoparticles and cell membranes

    NASA Astrophysics Data System (ADS)

    Ban, Young-Min

    Rapid development of nanotechnology and ability to manufacture materials and devices with nanometer feature size leads to exciting innovations in many areas including the medical and electronic fields. However, the possible health and environmental impacts of manufactured nanomaterials are not fully known. Recent experimental reports suggest that some of the manufactured nanomaterials, such as fullerenes and carbon nanotubes, are highly toxic even in small concentrations. The goal of the current work is to understand the mechanisms responsible for the toxicity of nanomaterials. In the current study coarse-grained molecular dynamics simulations are employed to investigate the interactions between NPs and cellular membranes at a molecular level. One of the possible toxicity mechanisms of the nanomaterials is membrane disruption. Possibility of membrane disruption exposed to the manufactured nanomaterials are examined by considering chemical reactions and non-reactive physical interactions as chemical as well as physical mechanisms. Mechanisms of transport of carbon-based nanoparticles (fullerene and its derivative) across a phospholipid bilayer are investigated. The free energy profile is obtained using constrained simulations. It is shown that the considered nanoparticles are hydrophobic and therefore they tend to reside in the interior of the lipid bilayer. In addition, the dynamics of the membrane fluctuations is significantly affected by the nanoparticles at the bilayer-water interface. The hydrophobic interaction between the particles and membrane core induces the strong coupling between the nanoparticle motion and membrane deformation. It is observed that the considered nanoparticles affect several physical properties of the membrane. The nanoparticles embedded into the membrane interior lead to the membrane softening, which becomes more significant with increase in CNT length and concentration. The lateral pressure profile and membrane energy in the membrane containing the nanoparticles exhibit localized perturbation around the nanoparticle. The nanoparticles are not likely to affect membrane protein function by the weak perturbation of the internal stress in the membrane. Due to the short-ranged interactions between the nanoparticles, the nanoparticles would not form aggregates inside membranes. The effect of lipid peroxidation on cell membrane deformation is assessed. The peroxidized lipids introduce a perturbation to the internal structure of the membrane leading to higher amplitude of the membrane fluctuations. Higher concentration of the peroxidized lipids induces more significant perturbation. Cumulative effects of lipid peroxidation caused by nanoparticles are examined for the first time. The considered amphiphilic particle appears to reduce the perturbation of the membrane structure at its equilibrium position inside the peroxidized membrane. This suggests a possibility of antioxidant effect of the nanoparticle.

  6. Intravacuolar Membranes Regulate CD8 T Cell Recognition of Membrane-Bound Toxoplasma gondii Protective Antigen.

    PubMed

    Lopez, Jodie; Bittame, Amina; Massera, Céline; Vasseur, Virginie; Effantin, Grégory; Valat, Anne; Buaillon, Célia; Allart, Sophie; Fox, Barbara A; Rommereim, Leah M; Bzik, David J; Schoehn, Guy; Weissenhorn, Winfried; Dubremetz, Jean-François; Gagnon, Jean; Mercier, Corinne; Cesbron-Delauw, Marie-France; Blanchard, Nicolas

    2015-12-15

    Apicomplexa parasites such as Toxoplasma gondii target effectors to and across the boundary of their parasitophorous vacuole (PV), resulting in host cell subversion and potential presentation by MHC class I molecules for CD8 T cell recognition. The host-parasite interface comprises the PV limiting membrane and a highly curved, membranous intravacuolar network (IVN) of uncertain function. Here, using a cell-free minimal system, we dissect how membrane tubules are shaped by the parasite effectors GRA2 and GRA6. We show that membrane association regulates access of the GRA6 protective antigen to the MHC I pathway in infected cells. Although insertion of GRA6 in the PV membrane is key for immunogenicity, association of GRA6 with the IVN limits presentation and curtails GRA6-specific CD8 responses in mice. Thus, membrane deformations of the PV regulate access of antigens to the MHC class I pathway, and the IVN may play a role in immune modulation. PMID:26628378

  7. Cell-free system for synthesizing membrane proteins cell free method for synthesizing membrane proteins

    DOEpatents

    Laible, Philip D; Hanson, Deborah K

    2013-06-04

    The invention provides an in vitro method for producing proteins, membrane proteins, membrane-associated proteins, and soluble proteins that interact with membrane-associated proteins for assembly into an oligomeric complex or that require association with a membrane for proper folding. The method comprises, supplying intracytoplasmic membranes from organisms; modifying protein composition of intracytoplasmic membranes from organism by modifying DNA to delete genes encoding functions of the organism not associated with the formation of the intracytoplasmic membranes; generating appropriate DNA or RNA templates that encode the target protein; and mixing the intracytoplasmic membranes with the template and a transcription/translation-competent cellular extract to cause simultaneous production of the membrane proteins and encapsulation of the membrane proteins within the intracytoplasmic membranes.

  8. The temperature effect during pulse application on cell membrane fluidity and permeabilization

    E-print Network

    Ljubljana, University of

    The temperature effect during pulse application on cell membrane fluidity and permeabilization M Membrane order parameter Temperature In vitro Cell membrane permeabilization is caused by the application suspension was maintained at room temperature in order to allow cell membrane resealing. The cells were

  9. Shiga toxin induces tubular membrane invaginations for its uptake into cells

    E-print Network

    Sens, Pierre

    ARTICLES Shiga toxin induces tubular membrane invaginations for its uptake into cells Winfried RoB uptake via tubular membrane invaginations First, we analysed the localization in human HeLa cells membrane invaginations in human and mouse cells and model membranes. In cells, tubule occurrence increases

  10. Concentration-Dependent Vascularization of Adipose Stromal Vascular Fraction Cells.

    PubMed

    Maijub, John G; Boyd, Nolan L; Dale, Jacob R; Hoying, James B; Morris, Marvin E; Williams, Stuart K

    2015-01-01

    Adipose-derived stromal vascular fraction (SVF) cells have been shown to self-associate to form vascular structures under both in vitro and in vivo conditions. The angiogenic (new vessels from existing vessels) and vasculogenic (new vessels through self-assembly) potential of the SVF cell population may provide a cell source for directly treating (i.e., point of care without further cell isolation) ischemic tissues. However the correct dosage of adipose SVF cells required to achieve a functional vasculature has not been established. Accordingly, in vitro and in vivo dose response assays were performed evaluating the SVF cell vasculogenic potential. Serial dilutions of freshly isolated rat adipose SVF cells were plated on growth factor reduced Matrigel and vasculogenesis, assessed as cellular tube-like network assembly, was quantified after 3 days of culture. This in vitro vasculogenesis assay indicated that rat SVF cells reached maximum network length at a concentration of 2.5?×?10(5) cells/ml and network maintained at the higher concentrations tested. The same concentrations of rat and human SVF cells were used to evaluate vasculogenesis in vivo. SVF cells were incorporated into collagen gels and subcutaneously implanted into Rag1 immunodeficient mice. The 3D confocal images of harvested constructs were evaluated to quantify dose dependency of SVF cell vasculogenesis potential. Rat- and human-derived SVF cells yielded a maximum vasculogenic potential at 1?×?10(6) and 4?×?10(6) cells/ml, respectively. No adverse reactions (e.g., toxicity, necrosis, tumor formation) were observed at any concentration tested. In conclusion, the vasculogenic potential of adipose-derived SVF cell populations is dose dependent. PMID:25397993

  11. Thy-1-mediated activation of rat mast cells: the role of Thy-1 membrane microdomains.

    PubMed Central

    Dráberová, L; Amoui, M; Dráber, P

    1996-01-01

    The glycosyl-phosphatidylinositol (GPI)-anchored glycoprotein Thy-1 is one of the most abundant molecules expressed on the surface of rat mast cells and rat basophilic leukemia (RBL) cells. The finding that Thy-1 from detergent-solubilized RBL-2H3 cells forms complexes with src-related protein-tyrosine kinase p56/p53lyn suggested that this kinase may play a key role in Thy-1-mediated mast-cell activation. The molecular mechanism of this activation is, however, unknown. Here we show that in RBL-2H3-derived cells extracted by the standard procedure with several non-ionic detergents, the majority of Thy-1 and p56/p53lyn were not released into postnuclear supernatant but remained associated with the detergent-resistant cytoskeletal/nuclear fraction. Pretreatment of the cells with the cholesterol-complexing agents, saponin or digitonin, resulted in complete solubilization of Thy-1 and p56/p53lyn in non-ionic detergents and dissociation of the complexes; this implies that cholesterol plays a crucial role in stabilization of the complexes. This conclusion was supported by double immunofluorescence colocalization experiments which also allowed us to estimate the size of the insoluble complexes to be about 0.1 micron. Sequential treatment with saponin and Nonidet P-40 was used to fractionate tyrosine-phosphorylated proteins during Thy-1-mediated activation of RBL-2H3 cells. Among the soluble cytoplasmic proteins the most dramatic change in tyrosine phosphorylation was found in pp72, whereas pp40 and pp33 were found mainly in the membrane fraction. Our data suggest that surface aggregation of GPI-anchored Thy-1 molecules leads to aggregation of p56/p53lyn kinase located in the same membrane microdomain, followed by transphosphorylation of both soluble and membrane-bound substrates. Images Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 PMID:8666426

  12. Anhydrous Proton-Conducting Membranes for Fuel Cells

    NASA Technical Reports Server (NTRS)

    Narayanan, Sekharipuram; Yen, Shiao-Pin S.

    2005-01-01

    Polymeric electrolyte membranes that do not depend on water for conduction of protons are undergoing development for use in fuel cells. Prior polymeric electrolyte fuel-cell membranes (e.g., those that contain perfluorosulfonic acid) depend on water and must be limited to operation below a temperature of 125 C because they retain water poorly at higher temperatures. In contrast, the present developmental anhydrous membranes are expected to function well at temperatures up to 200 C. The developmental membranes exploit a hopping-and-reorganization proton- conduction process that can occur in the solid state in organic amine salts and is similar to a proton-conduction process in a liquid. This process was studied during the 1970s, but until now, there has been no report of exploiting organic amine salts for proton conduction in fuel cells.

  13. Controlled Bacterial Lysis for Electron Tomography of Native Cell Membranes

    PubMed Central

    Fu, Xiaofeng; Himes, Benjamin; Ke, Danxia; Rice, William J.; Ning, Jiying; Zhang, Peijun

    2014-01-01

    SUMMARY Cryo-electron tomography (cryoET) has become a powerful tool for direct visualization of 3D structures of native biological specimens at molecular resolution, but its application is limited to thin specimens (<300 nm). Recently, vitreous sectioning and cryo-FIB milling technologies were developed to physically reduce the specimen thickness; however, cryoET analysis of membrane protein complexes within native cell membranes remains a great challenge. Here, we use phage ?X174 lysis gene E to rapidly produce native, intact, bacterial cell membranes for high resolution cryoET. We characterized E gene-induced cell lysis using FIB/SEM and cryoEM and show that the bacteria cytoplasm was largely depleted through spot lesion, producing ghosts with the cell membranes intact. We further demonstrate the utility of E-gene-induced lysis for cryoET using the bacterial chemotaxis receptor signaling complex array. The described method should have a broad application for structural and functional studies of native, intact cell membranes and membrane protein complexes. PMID:25456413

  14. Proton conducting membranes for high temperature fuel cells with solid state water free membranes

    NASA Technical Reports Server (NTRS)

    Narayanan, Sekharipuram R. (Inventor); Yen, Shiao-Pin S. (Inventor)

    2006-01-01

    A water free, proton conducting membrane for use in a fuel cell is fabricated as a highly conducting sheet of converted solid state organic amine salt, such as converted acid salt of triethylenediamine with two quaternized tertiary nitrogen atoms, combined with a nanoparticulate oxide and a stable binder combined with the converted solid state organic amine salt to form a polymeric electrolyte membrane. In one embodiment the membrane is derived from triethylenediamine sulfate, hydrogen phosphate or trifiate, an oxoanion with at least one ionizable hydrogen, organic tertiary amine bisulfate, polymeric quaternized amine bisulfate or phosphate, or polymeric organic compounds with quaternizable nitrogen combined with Nafion to form an intimate network with ionic interactions.

  15. Apparatus for exposing cell membranes to rapid temperature transients.

    PubMed

    Steel, B; Bilek, M M; dos Remedios, C G; McKenzie, D R

    2004-04-01

    We seek to determine whether cell membranes contain sensors that trigger a downstream response to temperature excursions. To do this, we have developed a novel apparatus for exposing a cell membrane to an extremely rapid temperature excursion in the nanosecond range. Cells are plated on a gold surface that is back-heated by a pulsed laser and cooled by conduction of heat into the glass substrate and the liquid medium. Analysis using the heat diffusion equation shows that the greatest temperature rise is localized within a region tens of nanometres thick, suitable for specifically heating a cell membrane without heating the remainder of a cell. We refer to this device as a nanosecond hotplate. PMID:14508614

  16. Mechanoreception at the cell membrane: More than the integrins.

    PubMed

    Gasparski, Alexander N; Beningo, Karen A

    2015-11-15

    A cell receives mechanical cues from its surrounding microenvironment and transduces this mechanical information into a biochemical signal within the cell, ultimately resulting in physiological change. Several molecules within the plasma membrane have been identified that are capable of receiving and translating a mechanical signal. Although integrins are most often discussed as the cell's primary method of mechanoreception at the cell membrane, several non-integrin mechanoreceptors have emerged over the last decade. Specifically, multiple G-protein coupled receptors, the glycocalyx, ion channels, lipid rafts and receptor tyrosine kinases have been found to translate mechanical stimuli from the environment into cellular change. This review will discuss these non-integrin mechanoreceptors associated with the plasma membrane, and their impact on cell physiology. PMID:26241498

  17. Membrane Targeting of P-type ATPases in Plant Cells

    SciTech Connect

    Jeffrey F. Harper, Ph.D.

    2004-06-30

    How membrane proteins are targeted to specific subcellular locations is a very complex and poorly understood area of research. Our long-term goal is to use P-type ATPases (ion pumps), in a model plant system Arabidopsis, as a paradigm to understand how members of a family of closely related membrane proteins can be targeted to different subcellular locations. The research is divided into two specific aims. The first aim is focused on determining the targeting destination of all 10 ACA-type calcium pumps (Arabidopsis Calcium ATPase) in Arabidopsis. ACAs represent a plant specific-subfamily of plasma membrane-type calcium pumps. In contrast to animals, the plant homologs have been found in multiple membrane systems, including the ER (ACA2), tonoplast (ACA4) and plasma membrane (ACA8). Their high degree of similarity provides a unique opportunity to use a comparative approach to delineate the membrane specific targeting information for each pump. One hypothesis to be tested is that an endomembrane located ACA can be re-directed to the plasma membrane by including targeting information from a plasma membrane isoform, ACA8. Our approach is to engineer domain swaps between pumps and monitor the targeting of chimeric proteins in plant cells using a Green Fluorescence Protein (GFP) as a tag. The second aim is to test the hypothesis that heterologous transporters can be engineered into plants and targeted to the plasma membrane by fusing them to a plasma membrane proton pump. As a test case we are evaluating the targeting properties of fusions made between a yeast sodium/proton exchanger (Sod2) and a proton pump (AHA2). This fusion may potentially lead to a new strategy for engineering salt resistant plants. Together these aims are designed to provide fundamental insights into the biogenesis and function of plant cell membrane systems.

  18. Incorporation of Photosynthetic Reaction Centers in the Membrane of Human Cells: Toward a New Tool for Optical Control of Cell Activity

    SciTech Connect

    Pennisi, Cristian P.; Jensen, Poul Erik; Zachar, Vladimir; Greenbaum, Elias; Yoshida, Ken

    2009-01-01

    The Photosystem I (PSI) reaction center is a photosynthetic membrane complex in which light-induced charge separation is accompanied by the generation of an electric potential. It has been recently proposed as a means to confer light sensitivity to cells possessing voltage-activated ion channels, but the feasibility of heterologous incorporation has not been demonstrated. In this work, methods of delivery and detection of PSI in the membrane of human cells are presented. Purified fractions of PSI were reconstituted in proteoliposomes that were used as vehicles for the membrane incorporation. A fluorescent impermeable dye was entrapped in the vesicles to qualitatively analyze the nature of the vesicle cell interaction. After incorporation, the localization and orientation of the complexes in the membrane was studied using immuno-fluorescence microscopy. The results showed complexes oriented as in native membranes, which were randomly distributed in clusters over the entire surface of the cell. Additionally, analysis of cell viability showed that the incorporation process does not damage the cell membrane. Taken together, the results of this work suggest that the mammalian cellular membrane is a reasonable environment for the incorporation of PSI complexes, which opens the possibility of using these molecular photovoltaic structures for optical control of cell activity.

  19. Identification of effluent organic matter fractions responsible for low-pressure membrane fouling.

    PubMed

    Filloux, Emmanuelle; Gallard, Hervé; Croue, Jean-Philippe

    2012-11-01

    Anion exchange resin (AER), powder activated carbon (PAC) adsorption and ozonation treatments were applied on biologically treated wastewater effluent with the objective to modify the effluent organic matter (EfOM) matrix. Both AER and PAC led to significant total organic carbon (TOC) removal, while the TOC remained nearly constant after ozonation. Liquid Chromatography-Organic Carbon Detection (LC-OCD) analysis showed that the AER treatment preferentially removed high and intermediate molecular weight (MW) humic-like structures while PAC removed low MW compounds. Only a small reduction of the high MW colloids (i.e. biopolymers) was observed for AER and PAC treatments. Ozonation induced a large reduction of the biopolymers and an important increase of the low MW humic substances (i.e. building blocks). Single-cycle microfiltration (MF) and ultrafiltration (UF) tests were conducted using commercially available hollow fibres at a constant flux. After reconcentration to their original organic carbon content, the EfOM matrix modified by AER and PAC treatments exhibited higher UF membrane fouling compared to untreated effluent; result that correlated with the higher concentration of biopolymers. On the contrary, ozonation which induced a significant degradation of the biopolymers led to a minor flux reduction for both UF and MF filtration tests. Based on a single filtration, results indicate that biopolymers play a major role in low pressure membrane fouling and that intermediate and low MW compounds have minor impact. Thus, this approach has shown to be a valid methodology to identify the foulant fractions of EfOM. PMID:22884373

  20. Elastic Membrane Heterogeneity of Living Cells Revealed by Stiff Nanoscale Membrane Domains

    PubMed Central

    Roduit, Charles; van der Goot, F. Gisou; De Los Rios, Paolo; Yersin, Alexandre; Steiner, Pascal; Dietler, Giovanni; Catsicas, Stefan; Lafont, Frank; Kasas, Sandor

    2008-01-01

    Many approaches have been developed to characterize the heterogeneity of membranes in living cells. In this study, the elastic properties of specific membrane domains in living cells are characterized by atomic force microscopy. Our data reveal the existence of heterogeneous nanometric scale domains with specific biophysical properties. We focused on glycosylphosphatidylinositol (GPI)-anchored proteins, which play an important role in membrane trafficking and cell signaling under both physiological and pathological conditions and which are known to partition preferentially into cholesterol-rich microdomains. We demonstrate that these GPI-anchored proteins reside within domains that are stiffer than the surrounding membrane. In contrast, membrane domains containing the transferrin receptor, which does not associate with cholesterol-rich regions, manifest no such feature. The heightened stiffness of GPI domains is consistent with existing data relating to the specific condensation of lipids and the slow diffusion rates of lipids and proteins therein. Our quantitative data may forge the way to unveiling the links that exist between membrane stiffness, molecular diffusion, and signaling activation. PMID:17981897

  1. Gradiently crosslinked polymer electrolyte membranes in fuel cells

    NASA Astrophysics Data System (ADS)

    An, De; Wu, Bin; Zhang, Genlei; Zhang, Wen; Wang, Yuxin

    2016-01-01

    Polymer electrolyte membranes in fuel cells should be high in both ionic conductivity and mechanical strength. However, the two are often exclusive to each other. To solve this conundrum, a novel strategy is proposed in this paper, with extensively researched sulfonated poly (ether ether ketone) (SPEEK) membrane as a paradigm. A SPEEK membrane of high sulfonation degree is simply post-treated with NaBH4 and H2SO4 solution at ambient temperature for a certain time to afford the membrane with a gradient crosslinking structure. Measurements via 1H NMR, ATR-FTIR and SEM-EDS are conducted to verify such structural changes. The gradient crosslinks make practically no damage to proton conductance, but effectively restrain the membrane from over swelling and greatly enhance its tensile strength. A H2-O2 fuel cell with the gradiently crosslinked SPEEK membrane shows a maximal power density of 533 mW cm-2 at 80 °C, whereas the fuel cell with the pristine SPEEK membrane cannot be operated beyond 30 °C.

  2. Effect of gas diffusion layer and membrane properties in an annular proton exchange membrane fuel cell

    NASA Astrophysics Data System (ADS)

    Khazaee, I.; Ghazikhani, M.; Esfahani, M. Nasr

    2012-01-01

    A complete three-dimensional and single phase computational dynamics model for annular proton exchange membrane (PEM) fuel cell is used to investigate the effect of changing gas diffusion layer and membrane properties on the performances, current density and gas concentration. The proposed model is a full cell model, which includes all the parts of the PEM fuel cell, flow channels, gas diffusion electrodes, catalyst layers and the membrane. Coupled transport and electrochemical kinetics equations are solved in a single domain; therefore no interfacial boundary condition is required at the internal boundaries between cell components. This computational fluid dynamics code is used as the direct problem solver, which is used to simulate the two-dimensional mass, momentum and species transport phenomena as well as the electron- and proton-transfer process taking place in a PEMFC that cannot be investigated experimentally. The results show that by increasing the thickness and decreasing the porosity of GDL the performance of the cell enhances that it is different with planner PEM fuel cell. Also the results show that by decreasing the thickness of the membrane the performance of the cell increases.

  3. Fractionation of the Hypericum perforatum L. extract: PMF, and PDT effects of the fractions against HL-60 leukemic cells

    NASA Astrophysics Data System (ADS)

    Tsontou, M.; Dimitriou, H.; Filippidis, G.; Tsimaris, I.; Kalmanti, M.; Skalkos, D.

    2007-02-01

    In the last three years we have prepared and studied the polar methanolic extract PMF, of the herb Hypericum perforatum L, and studied as a new, alternative photosensitizing substance for PDT. Hypericum perforatum L., as well as PMF, contains a number of naphthodianthrone derivatives (hypericins), such as hypericin and pseudohypericin, as its main photosensitizing constituents. PMF has been tested as a PDT agent in vitro in bladder cancer cells, leukemia cells, and in vivo in rat tumor bearing urinary bladder. In order to evaluate the contribution of the hypericins in the overall PDT action, and prepare a better photosensitizing extract than PMF, we have separated the extract in four main fractions (1,2,3,4), and tested their PDT effects against the HL-60 leukemic cells. The concentration of hypericins in the extracts was found 0.08% for fraction 1, 0.09% for fraction 2, 0.8% for fraction 3, and 2,8% for fraction 4. The PDT activity observed among the fractions was proportional to their hypericins concentration, thus increasing in the order of increasing number: fraction 4 > fraction 3 > fraction 2 > fraction 1. Fraction 4 proved to be the most powerful fraction. However, despite its relatively high hypericins concentration (2.8%), compared with the total extract PMF (1.37%), fraction 4 proved to be less active in the cell line tested. This result indicates that there are other photosensitizing constituents within the PMF extract which contribute significantly in the overall PDT action, and therefore the extract should be used as it is for further PDT studies, without any further purification.

  4. Isolated primary squamous cell carcinoma of the tympanic membrane

    PubMed Central

    Wijaya, Clifton; Leonard, David S.; Kinsella, John B.; McShane, Donald P.

    2012-01-01

    INTRODUCTION Primary squamous cell carcinoma (SCC) of the tympanic membrane is exceptionally rare. We describe the history, investigation and management of this disease. PRESENTATION OF CASE A 68-year-old woman presented with a three month history of intermittent otorrhoea and external ear canal (EAC) pruritus. Otoscopy revealed a polypoidal granular nodule, confined to the posterior aspect of the tympanic membrane. Examination under anaesthesia (EUA) confirmed that the lesion was confined to the tympanic membrane, with a surrounding rim of normal drum. Biopsies were consistent with well differentiated SCC. DISCUSSION Following discussion at multi-disciplinary team meeting for treatment planning, the patient underwent lateral temporal bone resection with ipsilateral superficial parotidectomy and selective neck dissection. Post-operative histology confirmed an SCC confined to the tympanic membrane. CONCLUSION SCC of the tympanic membrane is an extremely rare condition. As with early temporal bone SCC, surgical resection with adjacent structure clearance remains the primary treatment modality. PMID:23123413

  5. Aluminum chloride and membrane potentials of barley root cells

    SciTech Connect

    Etherton, B.; Shane, M.

    1986-04-01

    Aluminum chloride at pH 4 hyperpolarizes the membrane potentials of barley root epidermal cells. The authors tested to see whether this hyperpolarization could be caused by an aluminum induced alteration of the permeability of the membrane to potassium or sodium ions by measuring the effect of .04 mM aluminum ions (the Ca/sup + +/ conc. was 0.1 mM) on the membrane potential changes induced by changing the potassium or sodium concentrations in the medium bathing the roots. Aluminum ions did not change the magnitude of potassium or sodium induced changes in membrane potentials but significantly altered the rates of potassium and sodium induced changes of the potential. The results indicate that aluminum ions did not change sodium or potassium ion permeabilities of barley root cells.

  6. Membrane Mechanics of Endocytosis in Cells with Turgor

    E-print Network

    Dmitrieff, Serge

    2015-01-01

    Endocytosis is an essential process by which cells internalize a piece of plasma membrane and material from the outside. In cells with turgor, pressure opposes membrane defor- mations, and increases the amount of force that has to be generated by the endocytic machinery. To determine this force, and calculate the shape of the membrane, we used physical theory to model an elastic surface under pressure. Accurate fits of experimental profiles are obtained assuming that the coated membrane is highly rigid and preferentially curved at the endocytic site. The forces required from the actin machinery peaks at the onset of deformation, indicating that once invagination has been initiated, endocytosis is unlikely to stall before completion. Coat proteins do not lower the initiation force but may affect the process by the curvature they induce. In the presence of isotropic curvature inducers, pulling the tip of the invagination can trigger the formation of a neck at the base of the invagination. Hence direct neck cons...

  7. Interaction of injectable neurotropic drugs with the red cell membrane.

    PubMed

    Reinhart, Walter H; Lubszky, Szabina; Thöny, Sandra; Schulzki, Thomas

    2014-10-01

    The normal red blood cell (RBC) shape is a biconcave discocyte. An intercalation of a drug in the outer half of the membrane lipid bilayer leads to echinocytosis, an intercalation in the inner half to stomatocytosis. We have used the shape transforming capacity of RBCs as a model to analyse the membrane interaction potential of various neurotropic drugs. Chlorpromazine, clomipramine, citalopram, clonazepam, and diazepam induced a reversible stomatocytosis, phenytoin induced echinocytosis, while the anticonvulsants levetiracetam, valproic acid and phenobarbital had no effect. This diversity of RBC shape transformations suggests that the pharmacological action is not linked to the membrane interaction. We conclude that this simple RBC shape transformation assay could be a useful tool to screen for potential drug interactions with cell membranes. PMID:24997296

  8. Fuel cell electrolyte membrane with basic polymer

    DOEpatents

    Larson, James M. (Saint Paul, MN); Pham, Phat T. (Little Canada, MN); Frey, Matthew H. (Cottage Grove, MN); Hamrock, Steven J. (Stillwater, MN); Haugen, Gregory M. (Edina, MN); Lamanna, William M. (Stillwater, MN)

    2010-11-23

    The present invention is an electrolyte membrane comprising an acid and a basic polymer, where the acid is a low-volatile acid that is fluorinated and is either oligomeric or non-polymeric, and where the basic polymer is protonated by the acid and is stable to hydrolysis.

  9. Fuel cell electrolyte membrane with basic polymer

    DOEpatents

    Larson, James M.; Pham, Phat T.; Frey, Matthew H.; Hamrock, Steven J.; Haugen, Gregory M.; Lamanna, William M.

    2012-12-04

    The present invention is an electrolyte membrane comprising an acid and a basic polymer, where the acid is a low-volatile acid that is fluorinated and is either oligomeric or non-polymeric, and where the basic polymer is protonated by the acid and is stable to hydrolysis.

  10. Fractionation of Tetrahymena ciliary membranes with triton X-114 and the identification of a ciliary membrane ATPase

    E-print Network

    Dentler, William L., Jr

    1988-12-01

    Cilia were isolated from Tetrahymena thermophila, extracted with Triton X-114, and the detergent-soluble membrane + matrix proteins separated into Triton X-114 aqueous and detergent phases. The aqueous phase polypeptides include a high molecular...

  11. Cryopreservation of cells: FT-IR monitoring of lipid membrane at freeze-thaw cycles.

    PubMed

    Giugliarelli, A; Sassi, P; Urbanelli, L; Paolantoni, M; Caponi, S; Ricci, M; Emiliani, C; Fioretto, D; Morresi, A

    2016-01-01

    In the present study, FTIR spectroscopy was used to monitor the freeze-thaw cycle of two cellular lines (HuDe and Jurkat) suspended in three different media: phosphate buffer solution (PBS); dimethylsulfoxide (DMSO)/PBS solution at 0.1 DMSO molar fraction; and CryoSure (0.1 DMSO molar fraction PBS solution+dextran 5% w/v) solution. The Trypan Blue test was also applied before freezing and after thawing each cell sample to estimate the recovery of membrane integrity after thermal treatment, and correlate this datum with spectroscopic results. By following the temperature evolution of two different spectral components (the libration and bending combination mode ?c(H2O) at 2000-2500cm(-1), and the methylene symmetric stretching vibration ?sym(CH2) at about 2850cm(-1)) in the -120÷28°C range, we evidenced the main transition of lipid membrane in connection with cell dehydration, as induced by ice formation in the extracellular medium. In particular, in DMSO/PBS and CryoSure samples we observed a transition to a more rigid state of the lipid membrane together with an increased amount of non-freezable water in the extracellular medium; these results are connected to the role of DMSO as a cryoprotective agent irrespective of the nature of cell type. PMID:26282883

  12. Theory on Plasmon Modes of the Cell Membranes

    E-print Network

    T. T. Nhan; N. T. Nhan; V. Thanh Ngo; N. A. Viet

    2007-06-12

    Considering the plasmon oscillation of each layer of the cell membranes as a quasi-particle, we introduce a simple model for the membrane collective charge excitations, take into account the surface effective potential of the plasmon-plasmon interaction between two layers. By using the useful Bogoliubov transformation method, we easily obtained the expressions of the frequencies of plasmon oscillations as a function of wave-number $k$ and membrane thickness $d$, magnitude of these frequencies is in the order of $\\sqrt{kd}$. Our results are in good agreement with ones obtained by E. Manousakis.

  13. A water and heat management model for proton-exchange-membrane fuel cells

    SciTech Connect

    Nguyen, T.V.; White, R.E. . Dept. of Chemical Engineering)

    1993-08-01

    Proper water and heat management are essential for obtaining high-power-density performance at high energy efficiency for proton-exchange-membrane fuel cells. A water and heat management model was developed and used to investigate the effectiveness of various humidification designs. The model accounts for water transport across the membrane by electro-osmosis and diffusion, heat transfer from the solid phase to the gas phase and latent heat associated with water evaporation and condensation in the flow channels. Results from the model showed that at high current (> 1A/cm[sup 2]) ohmic loss in the membrane accounts for a large fraction of the voltage loss in the cell and back diffusion of water from the cathode side of the membrane is insufficient to keep the membrane hydrated (i.e., conductive). Consequently, to minimize this ohmic loss the anode stream must be humidified, and when air is used instead of pure oxygen the cathode stream must also be humidified.

  14. Fractional killing arises from cell-to-cell variability in overcoming a caspase activity threshold

    PubMed Central

    Roux, Jérémie; Hafner, Marc; Bandara, Samuel; Sims, Joshua J; Hudson, Hannah; Chai, Diana; Sorger, Peter K

    2015-01-01

    When cells are exposed to death ligands such as TRAIL, a fraction undergoes apoptosis and a fraction survives; if surviving cells are re-exposed to TRAIL, fractional killing is once again observed. Therapeutic antibodies directed against TRAIL receptors also cause fractional killing, even at saturating concentrations, limiting their effectiveness. Fractional killing arises from cell-to-cell fluctuations in protein levels (extrinsic noise), but how this results in a clean bifurcation between life and death remains unclear. In this paper, we identify a threshold in the rate and timing of initiator caspase activation that distinguishes cells that live from those that die; by mapping this threshold, we can predict fractional killing of cells exposed to natural and synthetic agonists alone or in combination with sensitizing drugs such as bortezomib. A phenomenological model of the threshold also quantifies the contributions of two resistance genes (c-FLIP and Bcl-2), providing new insight into the control of cell fate by opposing pro-death and pro-survival proteins and suggesting new criteria for evaluating the efficacy of therapeutic TRAIL receptor agonists. PMID:25953765

  15. Extraction and fractionation of RNA and DNA from single cells using selective lysing and isotachophoresis

    NASA Astrophysics Data System (ADS)

    Shintaku, Hirofumi; Santiago, Juan G.

    2015-03-01

    Single cell analyses of RNA and DNA are crucial to understanding the heterogeneity of cell populations. The numbers of approaches to single cells analyses are expanding, but sequence specific measurements of nucleic acids have been mostly limited to studies of either DNA or RNA, and not both. This remains a challenge as RNA and DNA have very similar physical and biochemical properties, and cross-contamination with each other can introduce false positive results. We present an electrokinetic technique which creates the opportunity to fractionate and deliver cytoplasmic RNA and genomic DNA to independent downstream analyses. Our technique uses an on-chip system that enables selective lysing of cytoplasmic membrane, extraction of RNA (away from genomic DNA and nucleus), focusing, absolute quantification of cytoplasmic RNA mass. The absolute RNA mass quantification is performed using fluorescence observation without enzymatic amplification in < 5 min. The cell nucleus is left intact and the relative genomic DNA amount in the nucleus can be measured. We demonstrate the technique using single mouse B lymphocyte cells, for which we extracted an average of 14.1 pg total cytoplasmic RNA per cell. We also demonstrate correlation analysis between the absolute amount of cytoplasmic RNA and relative amount of genomic DNA, showing heterogeneity associated with cell cycle.

  16. Theory of proton exchange membranes fuel cells and the testing of performance characteristics of polymer electrolyte membranes

    E-print Network

    Cruz-Gonzalez, Tizoc, 1982-

    2004-01-01

    Proton exchange membrane (PEM) fuel cells hold great promise as source of power. A hydrogen and oxygen PEM fuel is a simple fuel cell that can be theoretically characterized. The performance of a PEM fuel cell can be ...

  17. Anion selective membrane. [ion exchange resins and ion exchange membrane electrolytes for electrolytic cells

    NASA Technical Reports Server (NTRS)

    Alexander, S. S.; Geoffroy, R. R.; Hodgdon, R. B.

    1975-01-01

    Experimental anion permselective membranes were prepared and tested for their suitability as cell separators in a chemical redox power storage system being developed at NASA-Lewis Research Center. The goals of long-term (1000 hr) oxidative and thermal stability at 80 C in FeCl3 and CrCl3 electrolytes were met by most of the weak base and strong base amino exchange groups considered in the program. Good stability is exhibited by several of the membrane substrate resins. These are 'styrene' divinylbenzene copolymer and PVC film. At least four membrane systems produce strong flexible films with electrochemical properties (resistivity, cation transfer) superior to those of the 103QZL, the most promising commercial membrane. The physical and chemical properties of the resins are listed.

  18. Composite polymer membranes for proton exchange membrane fuel cells operating at elevated temperatures and reduced humidities

    NASA Astrophysics Data System (ADS)

    Zhang, Tao

    Proton Exchange Membrane Fuel Cells (PEMFCs) are the leading candidate in the fuel cell technology due to the high power density, solid electrolyte, and low operational temperature. However, PEMFCs operating in the normal temperature range (60-80°C) face problems including poor carbon monoxide tolerance and heat rejection. The poisoning effect can be significantly relieved by operating the fuel cell at elevated temperature, which also improves the heat rejection and electrochemical kinetics. Low relative humidity (RH) operation is also desirable to simplify the reactant humidification system. However, at elevated temperatures, reduced RH PEMFC performance is seriously impaired due to irreversible water loss from presently employed state-of-the-art polymer membrane, Nafion. This thesis focuses on developing polymer electrolyte membranes with high water retention ability for operation in elevated temperature (110-150°C), reduced humidity (˜50%RH) PEMFCs. One approach is to alter Nafion by adding inorganic particles such as TiO2, SiO2, Zr(HPO 4)2, etc. While the presence of these materials in Nafion has proven beneficial, a reduction or no improvement in the PEMFC performance of Nafion/TiO2 and Nafion/Zr(HPO4)2 membranes is observed with reduced particle sizes or increased particle loadings in Nafion. It is concluded that the PEMFC performance enhancement associated with addition of these inorganic particles was not due to the particle hydrophilicity. Rather, the particle, partially located in the hydrophobic region of the membrane, benefits the cell performance by altering the membrane structure. Water transport properties of some Nafion composite membranes were investigated by NMR methods including pulsed field gradient spin echo diffusion, spin-lattice relaxation, and spectral measurements. Compared to unmodified Nafion, composite membranes materials exhibit longer longitudinal relaxation time constant T1. In addition to the Nafion material, sulfonated styrene-ethylene/butylene-styrene triblock copolymer (sSEBS) was investigated as an alternate membrane candidate. sSEBS was modified through introduction of polymer crosslinks using benzephenone as a photoinitiator and addition of a titania co-phase. A photocrosslinked membrane initially containing 15% benzophenone and 3% titania laminated with a 10 mum Nafion layer was found to produce the best PEMFC performance (120°C, 50%RH).

  19. The enriched fraction of Elephantopus scaber Triggers apoptosis and inhibits multi-drug resistance transporters in human epithelial cancer cells

    PubMed Central

    Beeran, Asmy Appadath; Maliyakkal, Naseer; Rao, Chamallamudi Mallikarjuna; Udupa, Nayanabhirama

    2015-01-01

    Background: Medicinal plants have played an important role in the development of clinically useful anticancer agents. Elephantopus scaber (Asteraceae) (ES) is widely used in Indian traditional system of medicine for the treatment of various ailments including cancer. Objective: To investigate anticancer effects of ES in human epithelial cancer cells. Materials and Methods: Cytotoxicity of ethanolic extract of ES (ES-ET) and its fractions, such as ES Petroleum ether fraction (ES-PET), ES Dichloromethane fraction (ES DCM), n Butyl alcohol fraction (ES-BT), and ES-Rest (ES-R) were assessed in human epithelial cancer cell lines using sulforhodamine B (SRB) assay. Acridine orange/ethidium bromide assay and Hoechst 33342 assays were used to gauge induction of apoptosis. Cell cycle analysis and micronuclei assay were used to assess cell cycle specific pharmacological effects and drug induced genotoxicty. Further, the ability of ES to inhibit multi drug resistant (MDR) transporters (ABC-B1 and ABC-G2) was determined by Rhodamine (Rho) and Mitoxantrone (MXR) efflux assays. Results: The enriched fraction of ES (ES DCM) possessed dose-dependent potent cytotoxicity in human epithelial cancer cells. Further, treatment of cancer cells (HeLa, A549, MCF-7, and Caco-2) with ES DCM showed hall mark properties of apoptosis (membrane blebbing, nuclear condensation etc.). Similarly, ES DCM caused enhanced sub G0 content and micronuclei formation indicating the induction of apoptosis and drug induced genotoxicity in cancer cells, respectively. Interestingly, ES DCM inhibited MDR transporters (ABC B1 and ABC G2) in cancer cells. Conclusion: The enriched fraction of ES imparted cytotoxic effects, triggered apoptosis, induced genotoxicity, and inhibited MDR transporters in human epithelial cancer cells. Thus, ES appears to be potential anticancer agent. PMID:25829763

  20. Understanding the transport processes in polymer electrolyte membrane fuel cells

    NASA Astrophysics Data System (ADS)

    Cheah, May Jean

    Polymer electrolyte membrane (PEM) fuel cells are energy conversion devices suitable for automotive, stationary and portable applications. An engineering challenge that is hindering the widespread use of PEM fuel cells is the water management issue, where either a lack of water (resulting in membrane dehydration) or an excess accumulation of liquid water (resulting in fuel cell flooding) critically reduces the PEM fuel cell performance. The water management issue is addressed by this dissertation through the study of three transport processes occurring in PEM fuel cells. Water transport within the membrane is a combination of water diffusion down the water activity gradient and the dragging of water molecules by protons when there is a proton current, in a phenomenon termed electro-osmotic drag, EOD. The impact of water diffusion and EOD on the water flux across the membrane is reduced due to water transport resistance at the vapor/membrane interface. The redistribution of water inside the membrane by EOD causes an overall increase in the membrane resistance that regulates the current and thus EOD, thereby preventing membrane dehydration. Liquid water transport in the PEM fuel cell flow channel was examined at different gas flow regimes. At low gas Reynolds numbers, drops transitioned into slugs that are subsequently pushed out of the flow channel by the gas flow. The slug volume is dependent on the geometric shape, the surface wettability and the orientation (with respect to gravity) of the flow channel. The differential pressure required for slug motion primarily depends on the interfacial forces acting along the contact lines at the front and the back of the slug. At high gas Reynolds number, water is removed as a film or as drops depending on the flow channel surface wettability. The shape of growing drops at low and high Reynolds number can be described by a simple interfacial energy minimization model. Under flooding conditions, the fuel cell local current can be significantly reduced due to diffusional limitation of the transport of gaseous reactants through inerts such as water vapor and nitrogen gas. A non-uniform current distribution across the membrane electrode assembly can cause pinhole formation and ultimately, fuel cell failure.

  1. A boron phosphate-phosphoric acid composite membrane for medium temperature proton exchange membrane fuel cells

    NASA Astrophysics Data System (ADS)

    Mamlouk, M.; Scott, K.

    2015-07-01

    A composite membrane based on a non-stoichiometric composition of BPO4 with excess of PO4 (BPOx) was synthesised and characterised for medium temperature fuel cell use (120-180 °C). The electrolyte was characterised by FTIR, SS-NMR, TGA and XRD and showed that the B-O is tetrahedral, in agreement with reports in the literature that boron phosphorus oxide compounds at B:P < 1 are exclusively built of borate and phosphate tetrahedra. Platinum micro electrodes were used to study the electrolyte compatibility and stability towards oxygen reduction at 150 °C and to obtain kinetic and mass transport parameters. The conductivities of the pure BPOx membrane electrolyte and a Polybenzimidazole (PBI)-4BPOx composite membrane were 7.9 × 10-2 S cm-1 and 4.5 × 10-2 S cm-1 respectively at 150 °C, 5%RH. Fuel cell tests showed a significant enhancement in performance of BPOx over that of typical 5.6H3PO4-PBI membrane electrolyte. The enhancement is due to the improved ionic conductivity (3×), a higher exchange current density of the oxygen reduction (30×) and a lower membrane gas permeability (10×). Fuel cell current densities at 0.6 V were 706 and 425 mA cm-2 for BPOx and 5.6H3PO4-PBI, respectively, at 150 °C with O2 (atm).

  2. Effects of chronic kidney disease on blood cells membrane properties.

    PubMed

    Kaderjakova, Z; Lajdova, I; Horvathova, M; Morvova, M; Sikurova, L

    2012-10-01

    Chronic kidney disease (CKD) is progressive loss of renal function associated among others with increased intracellular calcium concentration. The purpose of this study was to identify the effects of CKD on cell membrane properties such as human red blood cell Ca(2+) ATPase activity, lymphocyte plasma membrane P2X(7) receptor expression and function. This could help us in elucidating the origin of increased calcium concentration in blood cells. We found out Ca(2+) ATPase activity is decreased in early stage CKD patients resulting in altered calcium removal from cytoplasm. By means of flow cytometry we assessed that P2X(7) receptor expression on lymphocyte membrane is 1.5 fold increased for CKD patients. Moreover, we detected an increased uptake of ethidium bromide through this receptor in CKD at basal conditions. It means CKD lymphocyte membranes contain more receptors which are more permeable thus allowing increased calcium influx from extracellular milieu. Finally, we can state alterations in blood cell membranes are closely linked to CKD and may be responsible for intracellular calcium accumulation. PMID:22425286

  3. Plasma membrane reorganization induced by tumor promoters in an epithelial cell line

    SciTech Connect

    PACKARD, BEVERLY S.; SAXTON, MICHAEL J.; BISSELL, MINA J.; KLEIN, MELVIN P.

    1984-01-01

    The effects of phorbol ester tumor promoters on the lateral diffusion in plasma membrane lipid environments were examined by the technique of fluorescence recovery after photobleaching. To this end, the probe collarein, a fluorescent lipid analog that has the property of exclusive localization in the plasma membrane, was synthesized. Measured decreases in three parameters [percentage of fluorescence bleached (30%), percentage of recovery (52%), and half-time for recovery (52%)] connoted the appearance of an immobile fraction upon exposure to tumor promoters. These data are consistent with lipid reorganization in response to a reorganization of the intra- and perimembranous macromolecular scaffolding upon the interaction of cells with tumor promoters. The idea of induced reorganization is supported by experiments in which cell shape change, brought about by either exposure to cytochalasin B or growth on matrices of collagen, fibronectin, or laminin, resulted in values in the fluorescence recovery after photobleaching technique similar to those with active phorbol esters.

  4. The role of cell membranes in the regulation of lignification in pine cells

    NASA Technical Reports Server (NTRS)

    Hendrix, D. L.

    1978-01-01

    The identity of pine cell membranes bearing PAL enzyme activity, the isolation of a plasma membrane preparation from pine cells for testing as a regulatory barrier in lignification, and the measurement of the geopotential effect in pine stems are presented. A model to describe and predict the interaction of gravity and lignification of higher plants was developed.

  5. Biosynthesis of membrane dependent proteins in insect cell lysates: identification of limiting parameters for folding and processing.

    PubMed

    Merk, Helmut; Rues, Ralf-Bernhardt; Gless, Christine; Beyer, Kerstin; Dong, Fang; Dötsch, Volker; Gerrits, Michael; Bernhard, Frank

    2015-09-01

    G protein-coupled receptors, like many other membrane proteins, are notoriously difficult to synthesize in conventional cellular systems. Although expression in insect cells is considered the preferred technique for structural characterizations in particular, inefficient membrane translocation, instability, toxic effects and low yields still pose clear limitations for their production in living cells. Recent studies started to explore alternative strategies for the in vitro production of problematic membrane proteins in cell-free lysates in combination with supplied membranes. We provide a detailed study on the production efficiencies and quality of G protein-coupled receptors, Fab fragments and other proteins synthesized in insect cell lysates containing endogenous microsomes. Effects of different reaction kinetics, redox conditions and sample preparations on the specific activities of synthesized proteins have been analyzed. The extent of glycosylation, membrane translocation and percentages of ligand binding active fractions of synthesized protein samples have been determined. We provide strong evidence that membrane insertion of integral membrane proteins can represent a prime limiting factor for their preparative scale in vitro production. Improved expression protocols resulting into higher production rates yielded more active protein in case of Fab fragments, but not in case of the human endothelin B receptor. PMID:25999328

  6. Coarse-Grained Models for Protein-Cell Membrane Interactions

    PubMed Central

    Bradley, Ryan; Radhakrishnan, Ravi

    2015-01-01

    The physiological properties of biological soft matter are the product of collective interactions, which span many time and length scales. Recent computational modeling efforts have helped illuminate experiments that characterize the ways in which proteins modulate membrane physics. Linking these models across time and length scales in a multiscale model explains how atomistic information propagates to larger scales. This paper reviews continuum modeling and coarse-grained molecular dynamics methods, which connect atomistic simulations and single-molecule experiments with the observed microscopic or mesoscale properties of soft-matter systems essential to our understanding of cells, particularly those involved in sculpting and remodeling cell membranes. PMID:26613047

  7. Red Blood Cell Membrane-Cloaked Nanoparticles For Drug Delivery

    NASA Astrophysics Data System (ADS)

    Carpenter, Cody Westcott

    Herein we describe the development of the Red Blood Cell coated nanoparticle, RBC-NP. Purified natural erythrocyte membrane is used to coat drug-loaded poly(lacticco-glycolic acid) (PLGA). Synthetic PLGA co-polymer is biocompatible and biodegradable and has already received US FDA approval for drug-delivery and diagnostics. This work looks specifically at the retention of immunosuppressive proteins on RBC-NPs, right-sidedness of natural RBC membranes interfacing with synthetic polymer nanoparticles, sustained and retarded drug release of RBC-NPs as well as further surface modification of RBC-NPs for increased targeting of model cancer cell lines.

  8. Microstructured Electrolyte Membranes to Improve Fuel Cell Performance

    NASA Astrophysics Data System (ADS)

    Wei, Xue

    Fuel cells, with the advantages of high efficiency, low greenhouse gas emission, and long lifetime are a promising technology for both portable power and stationary power sources. The development of efficient electrolyte membranes with high ionic conductivity, good mechanical durability and dense structure at low cost remains a challenge to the commercialization of fuel cells. This thesis focuses on exploring novel composite polymer membranes and ceramic electrolytes with the microstructure engineered to improve performance in direct methanol fuel cells (DMFCs) and solid oxide fuel cells (SOFCs), respectively. Polymer/particle composite membranes hold promise to meet the demands of DMFCs at lower cost. The structure of composite membranes was controlled by aligning proton conducting particles across the membrane thickness under an applied electric field. The field-induced structural changes caused the membranes to display an enhanced water uptake, proton conductivity, and methanol permeability in comparison to membranes prepared without an applied field. Although both methanol permeability and proton conductivity are enhanced by the applied field, the permeability increase is relatively lower than the proton conductivity improvement, which results in enhanced proton/methanol selectivity and improved DMFC performance. Apatite ceramics are a new class of fast ion conductors being studied as alternative SOFC electrolytes in the intermediate temperature range. An electrochemical/hydrothermal deposition method was developed to grow fully dense apatite membranes containing well-developed crystals with c-axis alignment to promote ion conductivity. Hydroxyapatite seed crystals were first deposited onto a metal substrate electrochemically. Subsequent ion substitution during the hydrothermal growth process promoted the formation of dense, fully crystalline films with microstructure optimal for ion transport. The deposition parameters were systematically investigated, such as reactant type, reagent concentration, solution pH, and reaction time. Dense apatite films were formed on palladium substrates that can serve as intermediate temperature fuel cell anodes. The novel apatite membrane structure is promising for fuel cell applications, as well as in improving the biocompatibility of orthopedic implants when coated on stainless steel or titanium substrates.

  9. Platinum nanoparticle deposition on polymeric membranes for fuel cell applications

    NASA Astrophysics Data System (ADS)

    Moreira, A. J.; Lopera, S.; Ordonez, N.; Mansano, R. D.

    2012-06-01

    This work aimed to show an alternative to produce platinum nanoparticles directly on a polymeric membrane using plasma technique, in order to make these nanoparticles adhere to the membrane, in size, shape and homogeneity controlled by the process without damaging the polymeric material. In this manner the cell's production time is reduced since the catalyst is directly deposited on the polymeric membrane; the time of the process is approximately five minutes for each side of the membrane, and the total time for each membrane is 10 minutes. With this exposure time, and the advantage of controlling the other parameters such as pressure, RF power, gas flow rate and temperature of the electrode, it was possible to obtain platinum nanoparticles with dimensions of about 50 nm scattered homogenously on the membrane, without damaging the structure of the polymeric material and, consequently, affecting its performance. Together with platinum nanoparticles were also deposited carbon nanoparticles, so that these acted as catalyst support, avoiding self poisoning. Electrochemical activity tests were performed to test the efficiency of the cell where it was exposed to different pressures and flow rates of O2 and H2, reaching open-circuit voltage of 750 mVolts.

  10. Membrane Mechanics of Endocytosis in Cells with Turgor

    PubMed Central

    Dmitrieff, Serge; Nédélec, François

    2015-01-01

    Endocytosis is an essential process by which cells internalize a piece of plasma membrane and material from the outside. In cells with turgor, pressure opposes membrane deformations, and increases the amount of force that has to be generated by the endocytic machinery. To determine this force, and calculate the shape of the membrane, we used physical theory to model an elastic surface under pressure. Accurate fits of experimental profiles are obtained assuming that the coated membrane is highly rigid and preferentially curved at the endocytic site. The forces required from the actin machinery peaks at the onset of deformation, indicating that once invagination has been initiated, endocytosis is unlikely to stall before completion. Coat proteins do not lower the initiation force but may affect the process by the curvature they induce. In the presence of isotropic curvature inducers, pulling the tip of the invagination can trigger the formation of a neck at the base of the invagination. Hence direct neck constriction by actin may not be required, while its pulling role is essential. Finally, the theory shows that anisotropic curvature effectors stabilize membrane invaginations, and the loss of crescent-shaped BAR domain proteins such as Rvs167 could therefore trigger membrane scission. PMID:26517669

  11. Membrane Mechanics of Endocytosis in Cells with Turgor

    E-print Network

    Serge Dmitrieff; François Nédélec

    2015-09-02

    Endocytosis is an essential process by which cells internalize a piece of plasma membrane and material from the outside. In cells with turgor, pressure opposes membrane defor- mations, and increases the amount of force that has to be generated by the endocytic machinery. To determine this force, and calculate the shape of the membrane, we used physical theory to model an elastic surface under pressure. Accurate fits of experimental profiles are obtained assuming that the coated membrane is highly rigid and preferentially curved at the endocytic site. The forces required from the actin machinery peaks at the onset of deformation, indicating that once invagination has been initiated, endocytosis is unlikely to stall before completion. Coat proteins do not lower the initiation force but may affect the process by the curvature they induce. In the presence of isotropic curvature inducers, pulling the tip of the invagination can trigger the formation of a neck at the base of the invagination. Hence direct neck constriction by actin may not be required, while its pulling role is essential. Finally, the theory shows that anisotropic curvature effectors stabilize membrane invaginations, and the loss of crescent-shaped BAR domain proteins such as Rvs167 could therefore trigger membrane scission.

  12. Membrane with internal passages to permit fluid flow and an electrochemical cell containing the same

    NASA Technical Reports Server (NTRS)

    Cisar, Alan J. (Inventor); Gonzalez-Martin, Anuncia (Inventor); Hitchens, G. Duncan (Inventor); Murphy, Oliver J. (Inventor)

    1997-01-01

    The invention provides an improved proton exchange membrane for use in electrochemical cells having internal passages parallel to the membrane surface, an apparatus and process for making the membrane, membrane and electrode assemblies fabricated using the membrane, and the application of the membrane and electrode assemblies to a variety of devices, both electrochemical and otherwise. The passages in the membrane extend from one edge of the membrane to another and allow fluid flow through the membrane and give access directly to the membrane for purposes of hydration.

  13. Radiation effects on membranes - 1. Cellular permeability and cell survival

    SciTech Connect

    Khare, S.; Jayakumar, A.; Trivedi, A.; Kesavan, P.C.; Prasad, R.

    1982-05-01

    The effect of various doses of ..gamma.. radiation (5-60 krad) on the membrane permeability and cell survival of Candida albicans, a pathogenic yeast, was investigated. A reduction in the cell survival and in the accumulation of amino acids (proline, glycine, lysine, and glutamic acid) was observed following irradiation. The rate of oxygen uptake, which is often associated with transport, was also reduced. There was no damage to available sulfhydryl groups following the exposure of cells to various doses of ..gamma.. radiation. The membrane lipid composition of C. albicans cells can be altered by growing them in alkanes of varying chain lengths. The effects of such altered lipid composition on radiosensitivity was examined. It was observed that C. albicans cells with altered lipid content acquire resistance to ..gamma.. radiation.

  14. Optical Trapping Techniques Applied to the Study of Cell Membranes

    NASA Astrophysics Data System (ADS)

    Morss, Andrew J.

    Optical tweezers allow for manipulating micron-sized objects using pN level optical forces. In this work, we use an optical trapping setup to aid in three separate experiments, all related to the physics of the cellular membrane. In the first experiment, in conjunction with Brian Henslee, we use optical tweezers to allow for precise positioning and control of cells in suspension to evaluate the cell size dependence of electroporation. Theory predicts that all cells porate at a transmembrane potential VTMof roughly 1 V. The Schwann equation predicts that the transmembrane potential depends linearly on the cell radius r, thus predicting that cells should porate at threshold electric fields that go as 1/r. The threshold field required to induce poration is determined by applying a low voltage pulse to the cell and then applying additional pulses of greater and greater magnitude, checking for poration at each step using propidium iodide dye. We find that, contrary to expectations, cells do not porate at a constant value of the transmembrane potential but at a constant value of the electric field which we find to be 692 V/cm for K562 cells. Delivering precise dosages of nanoparticles into cells is of importance for assessing toxicity of nanoparticles or for genetic research. In the second experiment, we conduct nano-electroporation—a novel method of applying precise doses of transfection agents to cells—by using optical tweezers in conjunction with a confocal microscope to manipulate cells into contact with 100 nm wide nanochannels. This work was done in collaboration with Pouyan Boukany of Dr. Lee's group. The small cross sectional area of these nano channels means that the electric field within them is extremely large, 60 MV/m, which allows them to electrophoretically drive transfection agents into the cell. We find that nano electroporation results in excellent dose control (to within 10% in our experiments) compared to bulk electroporation. We also find that, unlike bulk electroporation, nano-electroporation directly injects nanoparticles, such as quantum dots, to the cell interior, bypassing the cell membrane without the need for endocytosis. The aging of RBC's can render them rigid, an issue for the survivability of transfusion patients. This rigidity can be assessed by examining the fluctuations in the cell membrane. In the third experiment, we use back focal plane detection—an interferometric detection scheme using an optical tweezers setup—to measure the membrane fluctuations of RBC's and K562 cells. Membrane fluctuations have long been observed in RBC's and a well developed theory exists linking them to the cells internal viscosity ?, the membrane bending modulus k and the surface tension of the membrane ?. We use back focal plane detection to measure the effect of ascorbic acid treatment on RBC aging and find no improvement in cell flexibility. K562 cells differ from RBC's in that they possess an actin cortex which the membrane attaches to. We demonstrate that K562 cells exhibit as much as an order of magnitude more variation in their fluctuations than RBC's do.

  15. The formin FMNL3 assembles plasma membrane protrusions that participate in cell–cell adhesion

    PubMed Central

    Gauvin, Timothy J.; Young, Lorna E.; Higgs, Henry N.

    2015-01-01

    FMNL3 is a vertebrate-specific formin protein previously shown to play a role in angiogenesis and cell migration. Here we define the cellular localization of endogenous FMNL3, the dynamics of GFP-tagged FMNL3 during cell migration, and the effects of FMNL3 suppression in mammalian culture cells. The majority of FMNL3 localizes in a punctate pattern, with >95% of these puncta being indistinguishable from the plasma membrane by fluorescence microscopy. A small number of dynamic cytoplasmic FMNL3 patches also exist, which enrich near cell–cell contact sites and fuse with the plasma membrane at these sites. These cytoplasmic puncta appear to be part of larger membranes of endocytic origin. On the plasma membrane, FMNL3 enriches particularly in filopodia and membrane ruffles and at nascent cell–cell adhesions. FMNL3-containing filopodia occur both at the cell–substratum interface and at cell–cell contacts, with the latter being 10-fold more stable. FMNL3 suppression by siRNA has two major effects: decrease in filopodia and compromised cell–cell adhesion in cells migrating as a sheet. Overall our results suggest that FMNL3 functions in assembly of actin-based protrusions that are specialized for cell–cell adhesion. PMID:25428984

  16. Highly Water Resistant Anion Exchange Membrane for Fuel Cells.

    PubMed

    Yang, Zhengjin; Hou, Jianqiu; Wang, Xinyu; Wu, Liang; Xu, Tongwen

    2015-07-01

    For anion exchange membranes (AEMs), achieving efficient hydroxide conductivity without excessive hydrophilicity presents a challenge. Hence, new strategies for constructing mechanically strengthened and hydroxide conductive (especially at controlled humidity) membranes are critical for developing better AEMs. Macromolecular modification involving ylide chemistry (Wittig reaction) for the fabrication of novel AEMs with an interpenetrating polymer network structure is reported. The macromolecular modification is cost effective, facile, and based on a one-pot synthesis. AEM water uptake is reduced to 3.6 wt% and a high hydroxide conductivity (69.7 mS cm(-1) , 90 °C) is achieved simultaneously. More importantly, the membrane exhibits similar tensile strength (>35 MPa) and comparable flexibility in both dry and wet states. These AEMs could find further applications within anion exchange membrane fuel cells with low humidity or photoelectric assemblies. PMID:25962480

  17. Fluctuations of red blood cell membranes: The role of cytoskeleton

    E-print Network

    Wonjune Choi; Juyeon Yi; Yong Woon Kim

    2015-08-28

    We theoretically investigate the membrane fluctuations of red blood cells with focus laid on the role of the cytoskeleton, viewing the system as a membrane coupled to sparse spring network. This model is exactly solvable and enables us to examine the coupling strength dependence of the membrane undulation. We find that the coupling modifies the fluctuation spectrum at wavelengths longer than the mesh size of the network, while leaving the fluid-like behavior of the membrane intact at shorter wavelengths. The fluctuation spectra can be markedly different, depending on not only the relative amplitude of the bilayer bending energy with respect to the cytoskeleton deformation energy but also the bilayer-cytoskelton coupling strength.

  18. Development of membrane electrode assembly for high temperature proton exchange membrane fuel cell by catalyst coating membrane method

    NASA Astrophysics Data System (ADS)

    Liang, Huagen; Su, Huaneng; Pollet, Bruno G.; Pasupathi, Sivakumar

    2015-08-01

    Membrane electrode assembly (MEA), which contains cathode and anode catalytic layer, gas diffusion layers (GDL) and electrolyte membrane, is the key unit of a PEMFC. An attempt to develop MEA for ABPBI membrane based high temperature (HT) PEMFC is conducted in this work by catalyst coating membrane (CCM) method. The structure and performance of the MEA are examined by scanning electron microscopy (SEM), electrochemical impedance spectroscopy (EIS) and I-V curve. Effects of the CCM preparation method, Pt loading and binder type are investigated for the optimization of the single cell performance. Under 160 °C and atmospheric pressure, the peak power density of the MEA, with Pt loading of 0.5 mg cm-2 and 0.3 mg cm-2 for the cathode and the anode, can reach 277 mW cm-2, while a current density of 620 A cm-2 is delivered at the working voltage of 0.4 V. The MEA prepared by CCM method shows good stability operating in a short term durability test: the cell voltage maintained at ?0.45 V without obvious drop when operated at a constant current density of 300 mA cm-2 and 160 °C under ambient pressure for 140 h.

  19. Purification of human adipose-derived stem cells from fat tissues using PLGA/silk screen hybrid membranes.

    PubMed

    Chen, Da-Chung; Chen, Li-Yu; Ling, Qing-Dong; Wu, Meng-Hsueh; Wang, Ching-Tang; Suresh Kumar, S; Chang, Yung; Munusamy, Murugan A; Alarfajj, Abdullah A; Wang, Han-Chow; Hsu, Shih-Tien; Higuchi, Akon

    2014-05-01

    The purification of human adipose-derived stem cells (hADSCs) from human adipose tissue cells (stromal vascular fraction) was investigated using membrane filtration through poly(lactide-co-glycolic acid)/silk screen hybrid membranes. Membrane filtration methods are attractive in regenerative medicine because they reduce the time required to purify hADSCs (i.e., less than 30 min) compared with conventional culture methods, which require 5-12 days. hADSCs expressing the mesenchymal stem cell markers CD44, CD73, and CD90 were concentrated in the permeation solution from the hybrid membranes. Expression of the surface markers CD44, CD73, and CD99 on the cells in the permeation solution from the hybrid membranes, which were obtained using 18 mL of feed solution containing 50 × 10? cells, was statistically significantly higher than that of the primary adipose tissue cells, indicating that the hADSCs can be purified in the permeation solution by the membrane filtration method. Cells expressing the stem cell-associated marker CD34 could be successfully isolated in the permeation solution, whereas CD34? cells could not be purified by the conventional culture method. The hADSCs in the permeation solution demonstrated a superior capacity for osteogenic differentiation based on their alkali phosphatase activity, their osterix gene expression, and the results of mineralization analysis by Alizarin Red S and von Kossa staining compared with the cells from the suspension of human adipose tissue. These results suggest that the hADSCs capable of osteogenic differentiation preferentially permeate through the hybrid membranes. PMID:24565521

  20. Autophagy modulates cell migration and ?1 integrin membrane recycling

    PubMed Central

    Tuloup-Minguez, Véronique; Hamaï, Ahmed; Greffard, Anne; Nicolas, Valérie; Codogno, Patrice; Botti, Joëlle

    2013-01-01

    Cell migration is dependent on a series of integrated cellular events including the membrane recycling of the extracellular matrix receptor integrins. In this paper, we investigate the role of autophagy in regulating cell migration. In a wound-healing assay, we observed that autophagy was reduced in cells at the leading edge than in cells located rearward. These differences in autophagy were correlated with the robustness of MTOR activity. The spatial difference in the accumulation of autophagic structures was not detected in rapamycin-treated cells, which had less migration capacity than untreated cells. In contrast, the knockdown of the autophagic protein ATG7 stimulated cell migration of HeLa cells. Accordingly, atg3?/? and atg5?/? MEFs have greater cell migration properties than their wild-type counterparts. Stimulation of autophagy increased the co-localization of ?1 integrin-containing vesicles with LC3-stained autophagic vacuoles. Moreover, inhibition of autophagy slowed down the lysosomal degradation of internalized ?1 integrins and promoted its membrane recycling. From these findings, we conclude that autophagy regulates cell migration, a central mechanism in cell development, angiogenesis, and tumor progression, by mitigating the cell surface expression of ?1 integrins. PMID:24036548

  1. New High-Temperature Membranes Developed for Proton Exchange Membrane Fuel Cells

    NASA Technical Reports Server (NTRS)

    Kinder, James D.

    2004-01-01

    Fuel cells are receiving a considerable amount of attention for potential use in a variety of areas, including the automotive industry, commercial power generation, and personal electronics. Research at the NASA Glenn Research Center has focused on the development of fuel cells for use in aerospace power systems for aircraft, unmanned air vehicles, and space transportation systems. These applications require fuel cells with higher power densities and better durability than what is required for nonaerospace uses. In addition, membrane cost is a concern for any fuel cell application. The most widely used membrane materials for proton exchange membrane (PEM) fuel cells are based on sulfonated perfluorinated polyethers, typically Nafion 117, Flemion, or Aciplex. However, these polymers are costly and do not function well at temperatures above 80 C. At higher temperatures, conventional membrane materials dry out and lose their ability to conduct protons, essential for the operation of the fuel cell. Increasing the operating temperature of PEM fuel cells from 80 to 120 C would significantly increase their power densities and enhance their durability by reducing the susceptibility of the electrode catalysts to carbon monoxide poisoning. Glenn's Polymers Branch has focused on developing new, low-cost membranes that can operate at these higher temperatures. A new series of organically modified siloxane (ORMOSIL) polymers were synthesized for use as membrane materials in a high-temperature PEM fuel cell. These polymers have an organic portion that can allow protons to transport through the polymer film and a cross-linked silica network that gives the polymers dimensional stability. These flexible xerogel polymer films are thermally stable, with decomposition onset as high as 380 C. Two types of proton-conducting ORMOSIL films have been produced: (1) NASA-A, which can coordinate many highly acid inorganic salts that facilitate proton conduction and (2) NASA-B, which has been produced and which incorporates strongly acidic (proton donating) functional groups into the polymer backbone. Both of these polymer films have demonstrated significantly higher proton conductivity than Nafion at elevated temperatures and low relative humidities. An added advantage is that these polymers are very inexpensive to produce because their starting materials are commodity chemicals that are commercially available in large volumes.

  2. Membrane and MEA Development in Polymer Electrolyte Fuel Cells

    NASA Astrophysics Data System (ADS)

    Trogadas, Panagiotis; Ramani, Vijay

    The polymer electrolyte fuel cell (PEFC) is based on Nafion polymer membranes operating at a temperature of 80°C. The main characteristics (structure and properties) and problems of Nafion-based PEFC technology are discussed. The primary drawbacks of Nafion membranes are poor conductivity at low relative humidities (and consequently at temperatures >100°C and ambient pressure) and large crossover of methanol in direct methanol fuel cell (DMFC) applications. These drawbacks have prompted an extensive effort to improve the properties of Nafion and identify alternate materials to replace Nafion. Polymer electrolyte membranes (PEMs) are classified in modified Nafion, membranes based on functionalized non-fluorinated backbones and acid-base polymer systems. Perhaps the most widely employed approach is the addition of inorganic additives to Nafion membranes to yield organic/inorganic composite membranes. Four major types of inorganic additives that have been studied (zirconium phosphates, heteropolyacids, metal hydrogen sulfates, and metal oxides) are reviewed in the following. DMFC and H2/O2 (air) cells based on modified Nafion membranes have been successfully operated at temperatures up to 120°C under ambient pressure and up to 150°C under 3-5 atm. Membranes based on functionalized non-fluorinated backbones are potentially promising for high-temperature operation. High conductivities have been obtained at temperatures up to 180°C. The final category of polymeric PEMs comprises non-functionalized polymers with basic character doped with proton-conducting acids such as phosphoric acid. The advanced features include high CO tolerance and thermal management. The advances made in the fabrication of electrodes for PEM fuel cells from the PTFE-bound catalyst layers of almost 20 years ago to the present technology are briefly discussed. There are two widely employed electrode designs: (1) PTFE-bound, and (2) thin-film electrodes. Emerging methods include those featuring catalyst layers formed with electrodeposition and vacuum deposition (sputtering). The thin-film electrodes have significantly increased performance and reduced the level of platinum loading required. Thin sputtered layers have shown promise for low catalyst loading with adequate performance. Electrodeposition methods are briefly discussed. Finally, the relationship between MEA processing and the durability of the membrane/electrode interface and hence the fuel cell as a whole is presented.

  3. Electrospun fiber membranes enable proliferation of genetically modified cells

    PubMed Central

    Borjigin, Mandula; Eskridge, Chris; Niamat, Rohina; Strouse, Bryan; Bialk, Pawel; Kmiec, Eric B

    2013-01-01

    Polycaprolactone (PCL) and its blended composites (chitosan, gelatin, and lecithin) are well-established biomaterials that can enrich cell growth and enable tissue engineering. However, their application in the recovery and proliferation of genetically modified cells has not been studied. In the study reported here, we fabricated PCL-biomaterial blended fiber membranes, characterized them using physicochemical techniques, and used them as templates for the growth of genetically modified HCT116-19 colon cancer cells. Our data show that the blended polymers are highly miscible and form homogenous electrospun fiber membranes of uniform texture. The aligned PCL nanofibers support robust cell growth, yielding a 2.5-fold higher proliferation rate than cells plated on standard plastic plate surfaces. PCL-lecithin fiber membranes yielded a 2.7-fold higher rate of proliferation, while PCL-chitosan supported a more modest growth rate (1.5-fold higher). Surprisingly, PCL-gelatin did not enhance cell proliferation when compared to the rate of cell growth on plastic surfaces. PMID:23467983

  4. Dispersion of atmospheric fine particulate matters in simulated lung fluid and their effects on model cell membranes.

    PubMed

    Zhou, Qiuhua; Wang, Lixin; Cao, Zhaoyu; Zhou, Xuehua; Yang, Fan; Fu, Pingqing; Wang, Zhenhua; Hu, Jingtian; Ding, Lei; Jiang, Wei

    2016-01-15

    Atmospheric fine particulate matter (PM2.5) was collected to investigate its dispersion in simulated lung fluid (SLF) and its interaction with model cell membranes. Organic acids, NH4(+), SO4(2-) and NO3(-) were detected in PM2.5 soluble fraction, and heavy metals were detected from the total mass. The insoluble fraction contained kaolinite, CaCO3, aliphatic carbons, aromatic rings, carboxyl and hydroxyl groups reflected by the infrared spectra. Proteins dispersed PM2.5 in SLF, resulted in smaller hydrodynamic diameter (dH) and slower sedimentation rate. Conversely, phospholipids increased dH value and accelerated sedimentation rate. Giant unilamellar vesicles (GUVs) and supported lipid bilayers (SLBs) were used as model cell membranes. PM2.5 adhered on and disrupted the membrane containing positively-charged lipids but not the membrane containing neutrally- and negatively-charged lipids, which was monitored by microscopy and a quartz crystal microbalance with dissipation (QCM-D). The cationic sites on membrane were necessary for PM2.5 adhesion, but membrane should be disrupted by the combined action of electrostatic forces and hydrogen bonds between PM2.5 oxygen containing groups and the lipid phosphate groups. Our results specified the roles of proteins and phospholipids in PM2.5 dispersion and transport, highly suggested that the health hazard of PM2.5 was related to the biomolecules in the lung fluid and the particle surface groups. PMID:26519565

  5. Durable, Low-cost, Improved Fuel Cell Membranes

    SciTech Connect

    Chris Roger; David Mountz; Wensheng He; Tao Zhang

    2011-03-17

    The development of low cost, durable membranes and membranes electrode assemblies (MEAs) that operate under reduced relative humidity (RH) conditions remain a critical challenge for the successful introduction of fuel cells into mass markets. It was the goal of the team lead by Arkema, Inc. to address these shortages. Thus, this project addresses the following technical barriers from the fuel cells section of the Hydrogen Fuel Cells and Infrastructure Technologies Program Multi-Year Research, Development and Demonstration Plan: (A) Durability (B) Cost Arkema’s approach consisted of using blends of polyvinylidenefluoride (PVDF) and proprietary sulfonated polyelectrolytes. In the traditional approach to polyelectrolytes for proton exchange membranes (PEM), all the required properties are “packaged” in one macromolecule. The properties of interest include proton conductivity, mechanical properties, durability, and water/gas transport. This is the case, for example, for perfluorosulfonic acid-containing (PFSA) membranes. However, the cost of these materials is high, largely due to the complexity and the number of steps involved in their synthesis. In addition, they suffer other shortcomings such as mediocre mechanical properties and insufficient durability for some applications. The strength and originality of Arkema’s approach lies in the decoupling of ion conductivity from the other requirements. Kynar® PVDF provides an exceptional combination of properties that make it ideally suited for a membrane matrix (Kynar® is a registered trademark of Arkema Inc.). It exhibits outstanding chemical resistance in highly oxidative and acidic environments. In work with a prior grant, a membrane known as M41 was developed by Arkema. M41 had many of the properties needed for a high performance PEM, but had a significant deficiency in conductivity at low RH. In the first phase of this work, the processing parameters of M41 were explored as a means to increase its proton conductivity. Optimizing the processing of M41 was found to increase its proton conductivity by almost an order of magnitude at 50% RH. Characterization of the membrane morphology with Karren More at Oak Ridge National Laboratory showed that the membrane morphology was complex. This technology platform was dubbed M43 and was used as a baseline in the majority of the work on the project. Although its performance was superior to M41, M43 still showed proton conductivity an order of magnitude lower than that of a PFSA membrane at 50% RH. The MEA performance of M43 could be increased by reducing the thickness from 1 to 0.6 mils. However, the performance of the thinner M43 still did not match that of a PFSA membrane.

  6. THE ENZYMATIC IODINATION OF THE RED CELL MEMBRANE

    PubMed Central

    Hubbard, Ann L.; Cohn, Zanvil A.

    1972-01-01

    An enzymatic iodination procedure utilizing lactoperoxidase (LPO), radioactive iodide, and hydrogen peroxide generated by a glucose oxidase-glucose system has been described and utilized for a study of the red cell membrane. 97% of the incorporated isotope is in the erythrocyte ghost and 3% is associated with hemoglobin. No significant labeling of the red cell membrane occurs in the absence of LPO or by the deletion of any of the other reagents. A 6 million-fold excess of chloride ions inhibits iodination by no more than 50%. Incorporation of up to 1 x 106 iodide atoms into a single erythrocyte membrane results in no significant cell lysis. The incorporated label is exclusively in tyrosine residues as monoiodotyrosine. 10–15% of the trichloroacetic acid-precipitable radioactivity can be extracted with lipid solvents but is present as either labeled protein or 125I. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis of solubilized membrane proteins reveals only two labeled protein bands out of the 15 present, and the presence of 50-1 x 106 iodide atoms per ghost does not alter this pattern. Component a has a molecular weight of 110,000, is carbohydrate poor, and represents 40% of the total label. Component b has an apparent molecular weight of 74,000, contains all of the demonstrable sialic acid, and accounts for 60% of the total label. Trypsinization of iodinated, intact red cells results in the disappearance of only component b, the appearance of labeled glycopeptides in the medium, and the absence of smaller, labeled peptides remaining in the membrane. Pronase treatment hydrolyzes component b in a similar fashion, but also cleaves component a to a 72,000 mol wt peptide which is retained in the membrane. A combination of protease treatment and double labeling with 125I and 131I does not reveal the appearance of previously unexposed proteins. PMID:5076780

  7. JosD1, a membrane-targeted deubiquitinating enzyme, is activated by ubiquitination and regulates membrane dynamics, cell motility, and endocytosis.

    PubMed

    Seki, Takahiro; Gong, Lijie; Williams, Aislinn J; Sakai, Norio; Todi, Sokol V; Paulson, Henry L

    2013-06-14

    The functional diversity of deubiquitinating enzymes (DUBs) is not well understood. The MJD family of DUBs consists of four cysteine proteases that share a catalytic "Josephin" domain. The family is named after the DUB ATXN3, which causes the neurodegenerative disease Machado-Joseph disease. The two closely related Josephin domain-containing (JosD) proteins 1 and 2 consist of little more than the Josephin domain. To gain insight into the properties of Josephin domains, we investigated JosD1 and JosD2. JosD1 and JosD2 were found to differ fundamentally in many respects. In vitro, only JosD2 can cleave ubiquitin chains. In contrast, JosD1 cleaves ubiquitin chains only after it is monoubiquitinated, a form of posttranslational-dependent regulation shared with ATXN3. A significant fraction of JosD1 is monoubiquitinated in diverse mouse tissues. In cell-based studies, JosD2 localizes to the cytoplasm whereas JosD1 preferentially localizes to the plasma membrane, particularly when ubiquitinated. The membrane occupancy by JosD1 suggests that it could participate in membrane-dependent events such as cell motility and endocytosis. Indeed, time-lapse imaging revealed that JosD1 enhances membrane dynamics and cell motility. JosD1 also influences endocytosis in cultured cells by increasing the uptake of endocytic markers of macropinocytosis while decreasing those for clathrin- and caveolae-mediated endocytosis. Our results establish that two closely related DUBs differ markedly in activity and function and that JosD1, a membrane-associated DUB whose activity is regulated by ubiquitination, helps regulate membrane dynamics, cell motility, and endocytosis. PMID:23625928

  8. CAPSTONE SENIOR DESIGN - SUPRAMOLECULAR PROTON EXCHANGE MEMBRANES FOR FUEL CELLS

    EPA Science Inventory

    In order to assume a leading role in the burgeoning hydrogen economy, new infrastructure will be required for fuel cell manufacturing and R&D capabilities. The objective of this proposal is the development of a new generation of advanced proton exchange membrane (PEM) technol...

  9. Role of pulse shape in cell membrane electropermeabilization , G. Pucihara

    E-print Network

    Ljubljana, University of

    Role of pulse shape in cell membrane electropermeabilization T. Kotnika , G. Pucihara , M for several modifications of the pulse shape: separate bipolar pulses, continuous bipolar waveforms, and sine-modulated pulses. In this paper, we present the results of a systematic study of the role of pulse shape

  10. Nonminimum-Phase Phenomenon of PEM Fuel Cell Membrane

    E-print Network

    Peng, Huei

    48109-2125 A membrane-based humidifier that uses cooling water of a fuel cell system to humidify to reject the effect of system disturbances, and a feed-forward algorithm is developed to ensure proper hydrated. Water management has been recognized as a critical issue for PEMFCs' performance. In addi- tion

  11. Alternative Sources of Adult Stem Cells: Human Amniotic Membrane

    NASA Astrophysics Data System (ADS)

    Wolbank, Susanne; van Griensven, Martijn; Grillari-Voglauer, Regina; Peterbauer-Scherb, Anja

    Human amniotic membrane is a highly promising cell source for tissue engineering. The cells thereof, human amniotic epithelial cells (hAEC) and human amniotic mesenchymal stromal cells (hAMSC), may be immunoprivileged, they represent an early developmental status, and their application is ethically uncontroversial. Cell banking strategies may use freshly isolated cells or involve in vitro expansion to increase cell numbers. Therefore, we have thoroughly characterized the effect of in vitro cultivation on both phenotype and differentiation potential of hAEC. Moreover, we present different strategies to improve expansion including replacement of animal-derived supplements by human platelet products or the introduction of the catalytic subunit of human telomerase to extend the in vitro lifespan of amniotic cells. Characterization of the resulting cultures includes phenotype, growth characteristics, and differentiation potential, as well as immunogenic and immunomodulatory properties.

  12. Mechanisms shaping cell membranes Michael M Kozlov1

    E-print Network

    McMahon, Harvey

    Chernomordik5 , Siewert J Marrink6 and Harvey T McMahon4 Membranes of intracellular organelles@post.tau.ac.il) and McMahon, Harvey T (hmm@mrc-lmb.cam.ac.uk) Current Opinion in Cell Biology 2014, 29:53­60 This review comes from a themed issue on Cell organelles Edited by William A Prinz and David K Banfield 0955

  13. Separation of cancer cells from white blood cells by pinched flow fractionation.

    PubMed

    Pødenphant, Marie; Ashley, Neil; Koprowska, Kamila; Mir, Kalim U; Zalkovskij, Maksim; Bilenberg, Brian; Bodmer, Walter; Kristensen, Anders; Marie, Rodolphe

    2015-12-21

    In this paper, the microfluidic size-separation technique pinched flow fractionation (PFF) is used to separate cancer cells from white blood cells (WBCs). The cells are separated at efficiencies above 90% for both cell types. Circulating tumor cells (CTCs) are found in the blood of cancer patients and can form new tumors. CTCs are rare cells in blood, but they are important for the understanding of metastasis. There is therefore a high interest in developing a method for the enrichment of CTCs from blood samples, which also enables further analysis of the separated cells. The separation is challenged by the size overlap between cancer cells and the 10(6) times more abundant WBCs. The size overlap prevents high efficiency separation, however we demonstrate that cell deformability can be exploited in PFF devices to gain higher efficiencies than expected from the size distribution of the cells. PMID:26510401

  14. How to Evaluate the Electric Noise in a Cell Membrane?

    NASA Astrophysics Data System (ADS)

    Bier, M.

    2006-05-01

    There has been considerable public anxiety about possible health effects of electromagnetic radiation emitted by high voltage power lines. Power frequencies (60 Hz in the US, 50 Hz in many other countries) are sufficiently slow for the associated electric fields to distribute themselves across the highly resistive cell membranes. To assess the ambient power frequency fields, researchers have compared the voltage that these fields induce across cell membranes to the strength of the electric noise that the membranes generate themselves through Brownian motion. However, there has been disagreement among researchers on how to evaluate this equilibrium membrane electric noise. I will review the different approaches and present an {ITALIC ab initio} modeling of membrane electric fields. I will show that different manifestations of Brownian noise lead to an electric noise intensity that is many times larger than what conventional estimates have yielded. Next, the legitimacy of gauging a nonequilibrium external signal against internal equilibrium noise is questioned and a more meaningful criterion is proposed. Finally, an estimate will be derived of the nonequilibrium noise intensity due to the driven ion traffic through randomly opening and closing ion channels.

  15. Free Energy Difference in Indolicidin Attraction to Eukaryotic and Prokaryotic Model Cell Membranes

    E-print Network

    Free Energy Difference in Indolicidin Attraction to Eukaryotic and Prokaryotic Model Cell Membranes and structural determinants of indolicidin interactions with eukaryotic and prokaryotic cell membranes using with two different compositions of zwitterionic and anionic phospholipids as model eukaryotic

  16. Membrane Tether Formation from Blebbing Cells Jianwu Dai and Michael P. Sheetz

    E-print Network

    Sniadecki, Nathan J.

    observations of melanoma cells that spontaneously bleb. In melanoma cells, tether forces on blebs forces, and T combines membrane tension (Tm) with membrane-cytoskeleton adhesion ( ), be- cause the two

  17. ``Lock and key mechanism'' for ligand binding with adrenergic receptors and the arising mechanical effects on the cell membrane

    NASA Astrophysics Data System (ADS)

    Lunghi, Laura; Deseri, Luca

    2013-03-01

    Chemicals hitting the surface of cell aggregates are known to give arise to cyclic Adenosine Mono Phosphate (cAMP), a second messenger that transduces inside the cell the effects of species that cannot get through the cell membrane. Ligands bind to a specific receptor following the so called ``lock and key mechanism'' (beta)-adrenergic receptors are proteins embedded in the lipid bilayer characterized by seven transmembrane helices. Thinning and thickening in cell membranes may be initiated by conformational changes of some of three of the seven domains above. The cell response is linked to the coupling of chemical, conformational and mechanical effects. Part of the cAMP remains intracellular, whereas the remaining fractions migrates outside the cell due to membrane transporters. A new Helmholtz free energy, accounting for receptor and transporter densities, receptor conformation field and membrane elasticity is investigated. It is shown how the density of active receptors is directly related to the conformation field and it enters the resulting balance equation for the membrane stress. Balance laws for fluxes of transporters and receptors, coupled with the former because of the outgoing cAMP flux caused by the transporters, as well as for the diffusive powers must be supplied. The Center for Nonlinear Analysis through the NSF Grant No. DMS-0635983 is gratefully acknowledged.

  18. Probing cell membrane dynamics using plasmon coupling microscopy

    NASA Astrophysics Data System (ADS)

    Rong, Guoxin

    The plasma membrane of mammalian cells is depicted as a two-dimensional hybrid material which is compartmentalized into submicron-sized domains. These membrane domains play a pivotal role in cellular signaling processes due to selective recruitment of specific cell surface receptors. The structural dynamics of the membrane domains and their exact biological functions are, however, still unclear, partially due to the wave nature of light, which limits the optical resolution in the visible light to approximately 400 nm in conventional optical microscopy. Here, we provide a non-fluorescence based approach for monitoring distance changes on subdiffraction limit length scales in a conventional far-field optical microscope. This approach, which is referred to as plasmon coupling microscopy (PCM), utilizes the distance dependent near-field coupling between noble metal nanoparticle (NP) labels to resolve close contacts on the length scale of approximately one NP diameter. We firstly utilize this PCM strategy to resolve interparticle separations during individual encounters of gold NP labeled fibronectin-integrin complexes in living HeLa cells. We then further refine this ratiometric detection methodology by augmenting it with a polarization-sensitive detection, which enables simultaneous monitoring of the distance and conformation changes in NP dimers and clusters. We apply this polarization resolved PCM approach to characterize the structural lateral heterogeneity of cell membranes on sub-micron length scales. Finally, we demonstrate that PCM can provide quantitative information about the structural dynamics of individual epidermal growth factor receptor (ErbB1)-enriched membrane domains in living cells.

  19. Buffalo (Bubalus bubalis) term amniotic-membrane-derived cells exhibited mesenchymal stem cells characteristics in vitro.

    PubMed

    Ghosh, Kaushalya; Kumar, Rajesh; Singh, Jarnail; Gahlawat, S K; Kumar, Dharmendra; Selokar, Naresh Lalaji; Yadav, S P; Gulati, B R; Yadav, P S

    2015-10-01

    Recent studies suggested that placentae amniotic membrane is a valuable source of stem cells in human as well as in livestock species. Advantages of amnion over other sources of stem cells included abundant availability, ethically non-objectionable and non-invasive source. The aim of the present study was the isolation, culture and characterization of amniotic-membrane-derived mesenchymal stem cells from term placentae collected postpartum in buffalo. We have observed that both presumptive epithelial-like and fibroblast-like cells were cultured and maintained from term amnion. These cells were shown the positive expression of pluripotency markers (OCT-4, SOX-2, NANOG, TERT), mesenchymal stem cell markers (CD29, CD44, CD105) and negative for haematopoietic marker (CD34) genes at different passages. In addition, these cells were also positive for alkaline phosphatase staining. Stem-ness potential of any stem cells is determined by their potential to differentiate into specific lineages of cell type. In the present study, we have successfully differentiated the amniotic-membrane-derived cells into adipogenic, chondrogenic and osteogenic lineages of cells in vitro. In conclusion, the results of this study demonstrate that amniotic-membrane-derived cells expressed pluripotent and mesenchymal stem cells markers and have propensity to differentiate into cells of mesenchymal lineage cell type upon directed differentiation in vitro. PMID:26019121

  20. Chemical Imaging of the Cell Membrane by NanoSIMS

    SciTech Connect

    Weber, P K; Kraft, M L; Frisz, J F; Carpenter, K J; Hutcheon, I D

    2010-02-23

    The existence of lipid microdomains and their role in cell membrane organization are currently topics of great interest and controversy. The cell membrane is composed of a lipid bilayer with embedded proteins that can flow along the two-dimensional surface defined by the membrane. Microdomains, known as lipid rafts, are believed to play a central role in organizing this fluid system, enabling the cell membrane to carry out essential cellular processes, including protein recruitment and signal transduction. Lipid rafts are also implicated in cell invasion by pathogens, as in the case of the HIV. Therefore, understanding the role of lipid rafts in cell membrane organization not only has broad scientific implications, but also has practical implications for medical therapies. One of the major limitations on lipid organization research has been the inability to directly analyze lipid composition without introducing artifacts and at the relevant length-scales of tens to hundreds of nanometers. Fluorescence microscopy is widely used due to its sensitivity and specificity to the labeled species, but only the labeled components can be observed, fluorophores can alter the behavior of the lipids they label, and the length scales relevant to imaging cell membrane domains are between that probed by fluorescence resonance energy transfer (FRET) imaging (<10 nm) and the diffraction limit of light. Topographical features can be imaged on this length scale by atomic force microscopy (AFM), but the chemical composition of the observed structures cannot be determined. Immuno-labeling can be used to study the distribution of membrane proteins at high resolution, but not lipid composition. We are using imaging mass spectrometry by secondary ion mass spectrometry (SIMS) in concert with other high resolution imaging methods to overcome these limitations. The experimental approach of this project is to combine molecule-specific stable isotope labeling with high-resolution SIMS using a Cameca NanoSIMS 50 to probe membrane organization and test microdomain hypotheses. The NanoSIMS is an imaging secondary ion mass spectrometer with an unprecedented combination of spatial resolution, sensitivity and mass specificity. It has 50 nm lateral resolution and is capable of detecting 1 in 20 nitrogen atoms while excluding near-neighbor isobaric interferences. The tightly focused cesium ion beam is rastered across the sample to produce simultaneous, quantitative digital images of up to five different masses. By labeling each specific components of a membrane with a unique rare stable isotope or element and mapping the location of the labels with the NanoSIMS, the location of the each labeled component can be determined and quantified. This new approach to membrane composition analysis allows molecular interactions of biological membranes to be probed at length-scales relevant to lipid rafts (10s to 100s of nm) that were not previously possible. Results from our most recent experiments analyzing whole cells will be presented.

  1. A Novel Unitized Regenerative Proton Exchange Membrane Fuel Cell

    NASA Technical Reports Server (NTRS)

    Murphy, O. J.; Cisar, A. J.; Gonzalez-Martin, A.; Salinas, C. E.; Simpson, S. F.

    1996-01-01

    A difficulty encountered in designing a unitized regenerative proton exchange membrane (PEM) fuel cell lies in the incompatibility of electrode structures and electrocatalyst materials optimized for either of the two functions (fuel cell or electrolyzer) with the needs of the other function. This difficulty is compounded in previous regenerative fuel cell designs by the fact that water, which is needed for proton conduction in the PEM during both modes of operation, is the reactant supplied to the anode in the electrolyzer mode of operation and the product formed at the cathode in the fuel cell mode. Drawbacks associated with existing regenerative fuel cells have been addressed. In a first innovation, electrodes function either as oxidation electrodes (hydrogen ionization or oxygen evolution) or as reduction electrodes (oxygen reduction or hydrogen evolution) in the fuel cell and electrolyzer modes, respectively. Control of liquid water within the regenerative fuel cell has been brought about by a second innovation. A novel PEM has been developed with internal channels that permit the direct access of water along the length of the membrane. Lateral diffusion of water along the polymer chains of the PEM provides the water needed at electrode/PEM interfaces. Fabrication of the novel single cell unitized regenerative fuel cell and results obtained on testing it are presented.

  2. Human T Cell Crosstalk Is Induced by Tumor Membrane Transfer

    PubMed Central

    Uzana, Ronny; Eisenberg, Galit; Merims, Sharon; Frankenburg, Shoshana; Pato, Aviad; Yefenof, Eitan; Engelstein, Roni; Peretz, Tamar

    2015-01-01

    Trogocytosis is a contact-dependent unidirectional transfer of membrane fragments between immune effector cells and their targets, initially detected in T cells following interaction with professional antigen presenting cells (APC). Previously, we have demonstrated that trogocytosis also takes place between melanoma-specific cytotoxic T lymphocytes (CTLs) and their cognate tumors. In the present study, we took this finding a step further, focusing on the ability of melanoma membrane-imprinted CD8+ T cells to act as APCs (CD8+T-APCs). We demonstrate that, following trogocytosis, CD8+T-APCs directly present a variety of melanoma derived peptides to fraternal T cells with the same TCR specificity or to T cells with different TCRs. The resulting T cell-T cell immune synapse leads to (1) Activation of effector CTLs, as determined by proliferation, cytokine secretion and degranulation; (2) Fratricide (killing) of CD8+T-APCs by the activated CTLs. Thus, trogocytosis enables cross-reactivity among CD8+ T cells with interchanging roles of effectors and APCs. This dual function of tumor-reactive CTLs may hint at their ability to amplify or restrict reactivity against the tumor and participate in modulation of the anti-cancer immune response. PMID:25671577

  3. Synthesis and characterization of Nafion/TiO2 nanocomposite membrane for proton exchange membrane fuel cell.

    PubMed

    Kim, Tae Young; Cho, Sung Yong

    2011-08-01

    In this study, the syntheses and characterizations of Nafion/TiO2 membranes for a proton exchange membrane fuel cell (PEMFC) were investigated. Porous TiO2 powders were synthesized using the sol-gel method; with Nafion/TiO2 nanocomposite membranes prepared using the casting method. An X-ray diffraction analysis demonstrated that the synthesized TiO2 had an anatase structure. The specific surface areas of the TiO2 and Nafion/TiO2 nanocomposite membrane were found to be 115.97 and 33.91 m2/g using a nitrogen adsorption analyzer. The energy dispersive spectra analysis indicated that the TiO2 particles were uniformly distributed in the nanocomposite membrane. The membrane electrode assembly prepared from the Nafion/TiO2 nanocomposite membrane gave the best PEMFC performance compared to the Nafion/P-25 and Nafion membranes. PMID:22103220

  4. Analysis of Membrane Topology of Prestin Expressing in CHO Cells

    NASA Astrophysics Data System (ADS)

    Murakoshi, Michio; Kawase, Tomohiro; Kumano, Shun; Wada, Hiroshi

    2011-11-01

    Outer hair cell (OHC) motility is thought to be based on the voltage-dependent conformational changes of the motor protein prestin. However, little is known about its structure and function. In this study, the membrane topology of prestin was investigated by single molecule force spectroscopy using an atomic force microscope (AFM). The C-terminus of prestin was tagged with an Avi-tag and biotinylated. Prestin was then connected with a streptavidin-coated AFM cantilever via biotin-streptavidin binding. The prestin was pulled out from the plasma membrane by retracting the cantilever and force curves were obtained. Obtained force curves suggested the existence of 12 transmembrane domains of prestin.

  5. Block copolymers for alkaline fuel cell membrane materials

    NASA Astrophysics Data System (ADS)

    Li, Yifan

    Alkaline fuel cells (AFCs) using anion exchange membranes (AEMs) as electrolyte have recently received considerable attention. AFCs offer some advantages over proton exchange membrane fuel cells, including the potential of non-noble metal (e.g. nickel, silver) catalyst on the cathode, which can dramatically lower the fuel cell cost. The main drawback of traditional AFCs is the use of liquid electrolyte (e.g. aqueous potassium hydroxide), which can result in the formation of carbonate precipitates by reaction with carbon dioxide. AEMs with tethered cations can overcome the precipitates formed in traditional AFCs. Our current research focuses on developing different polymer systems (blend, block, grafted, and crosslinked polymers) in order to understand alkaline fuel cell membrane in many aspects and design optimized anion exchange membranes with better alkaline stability, mechanical integrity and ionic conductivity. A number of distinct materials have been produced and characterized. A polymer blend system comprised of poly(vinylbenzyl chloride)-b-polystyrene (PVBC-b-PS) diblock copolymer, prepared by nitroxide mediated polymerization (NMP), with poly(2,6-dimethyl-1,4-phenylene oxide) (PPO) or brominated PPO was studied for conversion into a blend membrane for AEM. The formation of a miscible blend matrix improved mechanical properties while maintaining high ionic conductivity through formation of phase separated ionic domains. Using anionic polymerization, a polyethylene based block copolymer was designed where the polyethylene-based block copolymer formed bicontinuous morphological structures to enhance the hydroxide conductivity (up to 94 mS/cm at 80 °C) while excellent mechanical properties (strain up to 205%) of the polyethylene block copolymer membrane was observed. A polymer system was designed and characterized with monomethoxy polyethylene glycol (mPEG) as a hydrophilic polymer grafted through substitution of pendent benzyl chloride groups of a PVBC-b-PS. The incorporation of the hydrophilic polymer allows for an investigation of the effect of hydration on ionic conductivity, resulting in the increase in membrane water affinity, enhancement of conductivity and reduced dependence of conductivity on relative humidity. A study of crosslinking of block copolymers was done wherein the crosslinking occurs in the non-matrix phase in order to maintain mechanical properties. The formation of a cationic crosslinked structure improves the mechanical integrity of the membrane in water while showing little deleterious effect on ionic conductivity and mechanical properties.

  6. Macroporous thin membranes for cell transplant in regenerative medicine.

    PubMed

    Antolinos-Turpín, C M; Morales Román, R M; Rodenas-Rochina, J; Gómez Ribelles, J L; Gómez-Tejedor, J A

    2015-10-01

    The aim of this paper is to present a method to produce macroporous thin membranes made of poly (ethyl acrylate-co-hydroxyethyl acrylate) copolymer network with varying cross-linking density for cell transplantation and prosthesis fabrication. The manufacture process is based on template techniques and anisotropic pore collapse. Pore collapse was produced by swelling the membrane in acetone and subsequently drying and changing the solvent by water to produce 100 microns thick porous membranes. These very thin membranes are porous enough to hold cells to be transplanted to the organism or to be colonized by ingrowth from neighboring tissues in the organism, and they present sufficient tearing stress to be sutured with surgical thread. The obtained pore morphology was observed by Scanning Electron Microscope, and confocal laser microscopy. Mechanical properties were characterized by stress-strain experiments in tension and tearing strength measurements. Morphology and mechanical properties were related to the different initial thickness of the scaffold and the cross-linking density of the polymer network. Seeding efficiency and proliferation of mesenchymal stem cells inside the pore structure were determined at 2 h, 1, 7, 14 and 21 days from seeding. PMID:26231916

  7. Integration of Cell Membranes and Nanotube Transistors

    E-print Network

    Gruner, George

    as transistors, and that the two systems interact. Further, we use the interaction to study the charge, while biological systems ranging from lipids7 to living cells2 have been assembled on nanotube Manuscript Received March 23, 2005 ABSTRACT We report the integration of a complex biological system

  8. New materials for polymer electrolyte membrane fuel cell current collectors

    NASA Astrophysics Data System (ADS)

    Hentall, Philip L.; Lakeman, J. Barry; Mepsted, Gary O.; Adcock, Paul L.; Moore, Jon M.

    Polymer Electrolyte Membrane Fuel cells for automotive applications need to have high power density, and be inexpensive and robust to compete effectively with the internal combustion engine. Development of membranes and new electrodes and catalysts have increased power significantly, but further improvements may be achieved by the use of new materials and construction techniques in the manufacture of the bipolar plates. To show this, a variety of materials have been fabricated into flow field plates, both metallic and graphitic, and single fuel cell tests were conducted to determine the performance of each material. Maximum power was obtained with materials which had lowest contact resistance and good electrical conductivity. The performance of the best material was characterised as a function of cell compression and flow field geometry.

  9. An inorganicorganic proton exchange membrane for fuel cells with a controlled nanoscale

    E-print Network

    Brinker, C. Jeffrey

    forward in low-temperature fuel cell technology. In addition, developing a membrane compatibleAn inorganic­organic proton exchange membrane for fuel cells with a controlled nanoscale pore used as a proton exchange membrane in hydrogen fuel cells--including higher proton conductivity, a lack

  10. MOLECULAR SIEVING ACTION OF THE CELL MEMBRANE DURING GRADUAL OSMOTIC HEMOLYSIS

    E-print Network

    MacGregor II, R.D.

    2010-01-01

    in cell membranes at the growth temperature (McConnell,temperatures at which two phases are present in the phospholipid system. Cell membranes,temperature at which many proteins undergo an a-helix to random-coil conformational transition and because the native red cell membrane

  11. Diffuse Charge Effects in Fuel Cell Membranes P. Maarten Biesheuvel,a,b,z

    E-print Network

    Bazant, Martin Z.

    Diffuse Charge Effects in Fuel Cell Membranes P. Maarten Biesheuvel,a,b,z Alejandro A. Franco membranes in fuel cells are electrically neutral, except in unsteady situations, when the double pressure, which is a thermodynamic constant of the fuel cell membrane. Diffuse layer polarization

  12. A homologous cell-free system for studying protein translocation across the endoplasmic reticulum membrane in fission yeast.

    PubMed

    Brennwald, P; Wise, J A

    1994-02-01

    We report the development of a homologous in vitro assay system for analysing translocation of proteins across the endoplasmic reticulum (ER) membrane of the fission yeast Schizosaccharomyces pombe. Our protocol for preparing an S. pombe extract capable of translating natural messenger RNAs was modified from a procedure previously used for Saccharomyces cerevisiae, in which cells are lysed in a bead-beater. However, we were unable to prepare fission yeast microsomes active in protein translocation using existing budding yeast protocols. Instead, our most efficient preparations were isolated by fractionating spheroplasts, followed by extensive washing and size exclusion chromatography of the crude membranes. Translocation of two ER-targeted proteins, pre-acid phosphatase from S. pombe and prepro-alpha-factor from S. cerevisiae, was monitored using two distinct assays. First, evidence that a fraction of both proteins was sequestered within membrane-enclosed vesicles was provided by resistance to exogenously added protease. Second, the protected fraction of each protein was converted to a higher molecular weight, glycosylated form; attachment of carbohydrate to the translocated proteins was confirmed by their ability to bind Concanavalin A-Sepharose. Finally, we examined whether proteins could be translocated across fission yeast microsomal membranes after their synthesis was complete. Our results indicate that S. cerevisiae prepro-alpha-factor can be post-translationally imported into the fission yeast ER, while S. pombe pre-acid phosphatase crosses the membrane only by a co-translational mechanism. PMID:8203158

  13. Sodium channels in membrane vesicles from cultured toad bladder cells

    SciTech Connect

    Asher, C.; Moran, A.; Rossier, B.C.; Garty, H. Ben Gurion Univ., Beer-Sheva Institut de Pharmacologie de l'Universite de Lausanne )

    1988-04-01

    Electrical potential-driven {sup 22}Na{sup +} fluxes were measured in membrane vesicles prepared from TBM-18(cl23) cells (a clone of the established cell line TB-M). Fifty to seventy percent of the tracer uptake in vesicles derived from cells that were cultivated on a porous support were blocked by the diuretic amiloride. The amiloride inhibition constant was <0.1 {mu}M, indicating that this flux is mediated by the apical Na{sup +}-specific channels. Vesicles prepared from cells that were not grown on a porous support exhibited much smaller amiloride-sensitive fluxes. Two Ca{sup 2+}-dependent processes that down-regulated the channel conductance and were previously identified in native epithelia were found in the cultured cells as well. Vesicles isolated from cells that were preincubated with 5 {times} 10{sup {minus}7} M aldosterone for 16-20 h exhibited higher amiloride-sensitive conductance than vesicles derived from control, steroid-depleted cells. Thus membrane derived from TBM-18(cl23) cells can be used to characterize the epithelial Na{sup +} channel and its hormonal regulation.

  14. Proton exchange membrane fuel cell technology for transportation applications

    SciTech Connect

    Swathirajan, S.

    1996-04-01

    Proton Exchange Membrane (PEM) fuel cells are extremely promising as future power plants in the transportation sector to achieve an increase in energy efficiency and eliminate environmental pollution due to vehicles. GM is currently involved in a multiphase program with the US Department of Energy for developing a proof-of-concept hybrid vehicle based on a PEM fuel cell power plant and a methanol fuel processor. Other participants in the program are Los Alamos National Labs, Dow Chemical Co., Ballard Power Systems and DuPont Co., In the just completed phase 1 of the program, a 10 kW PEM fuel cell power plant was built and tested to demonstrate the feasibility of integrating a methanol fuel processor with a PEM fuel cell stack. However, the fuel cell power plant must overcome stiff technical and economic challenges before it can be commercialized for light duty vehicle applications. Progress achieved in phase I on the use of monolithic catalyst reactors in the fuel processor, managing CO impurity in the fuel cell stack, low-cost electrode-membrane assembles, and on the integration of the fuel processor with a Ballard PEM fuel cell stack will be presented.

  15. CLN3 loss disturbs membrane microdomain properties and protein transport in brain endothelial cells.

    PubMed

    Tecedor, Luis; Stein, Colleen S; Schultz, Mark L; Farwanah, Hany; Sandhoff, Konrad; Davidson, Beverly L

    2013-11-13

    Juvenile neuronal ceroid lipofuscinosis (JNCL) is a fatal childhood-onset neurodegenerative disorder caused by mutations in ceroid lipofuscinosis neuronal-3 (CLN3), a hydrophobic transmembrane protein of unresolved function. Previous studies indicate blood-brain barrier (BBB) defects in JNCL, and our earlier report showed prominent Cln3 expression in mouse brain endothelium. Here we find that CLN3 is necessary for normal trafficking of the microdomain-associated proteins caveolin-1, syntaxin-6, and multidrug resistance protein 1 (MDR1) in brain endothelial cells. Correspondingly, CLN3-null cells have reduced caveolae, and impaired caveolae- and MDR1-related functions including endocytosis, drug efflux, and cell volume regulation. We also detected an abnormal blood-brain barrier response to osmotic stress in vivo. Evaluation of the plasma membrane with fluorescent sphingolipid probes suggests microdomain destabilization and enhanced fluidity in CLN3-null cells. In further work we found that application of the glycosphingolipid lactosylceramide to CLN3-deficient cells rescues protein transport and caveolar endocytosis. Last, we show that CLN3 localizes to the trans-Golgi network (TGN) and partitions with buoyant microdomain fractions. We propose that CLN3 facilitates TGN-to-plasma membrane transport of microdomain-associated proteins. Insult to this pathway may underlie BBB dysfunction and contribute to JNCL pathogenesis. PMID:24227717

  16. CLN3 Loss Disturbs Membrane Microdomain Properties and Protein Transport in Brain Endothelial Cells

    PubMed Central

    Tecedor, Luis; Stein, Colleen S.; Schultz, Mark L.; Farwanah, Hany; Sandhoff, Konrad

    2013-01-01

    Juvenile neuronal ceroid lipofuscinosis (JNCL) is a fatal childhood-onset neurodegenerative disorder caused by mutations in ceroid lipofuscinosis neuronal-3 (CLN3), a hydrophobic transmembrane protein of unresolved function. Previous studies indicate blood–brain barrier (BBB) defects in JNCL, and our earlier report showed prominent Cln3 expression in mouse brain endothelium. Here we find that CLN3 is necessary for normal trafficking of the microdomain-associated proteins caveolin-1, syntaxin-6, and multidrug resistance protein 1 (MDR1) in brain endothelial cells. Correspondingly, CLN3-null cells have reduced caveolae, and impaired caveolae- and MDR1-related functions including endocytosis, drug efflux, and cell volume regulation. We also detected an abnormal blood–brain barrier response to osmotic stress in vivo. Evaluation of the plasma membrane with fluorescent sphingolipid probes suggests microdomain destabilization and enhanced fluidity in CLN3-null cells. In further work we found that application of the glycosphingolipid lactosylceramide to CLN3-deficient cells rescues protein transport and caveolar endocytosis. Last, we show that CLN3 localizes to the trans-Golgi network (TGN) and partitions with buoyant microdomain fractions. We propose that CLN3 facilitates TGN-to-plasma membrane transport of microdomain-associated proteins. Insult to this pathway may underlie BBB dysfunction and contribute to JNCL pathogenesis. PMID:24227717

  17. LAPTM5: A novel lysosomal-associated multispanning membrane protein preferentially expressed in hematopoietic cells

    SciTech Connect

    Adra, C.N.; Zhu, Shaochun; Ko, Jone-Long

    1996-07-15

    While a large body of knowledge about cell membrane proteins exists, much less is known about the repertoire and function of integral membrane proteins of intracellular organelles. In looking for novel classes of genes that are functionally important to hematopoietic cells, we have cloned the cDNA for a gene preferentially expressed in adult hematopoietic tissues. During embryonic development the gene is expressed in both hematopoietic and nonhematopoietic tissues. In cell lines the gene is expressed specifically in hematopoietic lineages, whereas in normal adult tissues the mRNA is preferentially detected at high levels in lymphoid and myeloid tissues. The predicted protein is a pentaspanner with no homology to known genes and conserved across evolution. Immunocytological and cell fractionation studies with a specific antibody revealed a protein localizing in lysosomes. The gene, provisionally named LAPTM5, maps to chromosome 1p34. The expression pattern of the gene together with preliminary evidence that the protein interacts with ubiquitin indicates that the protein may have a special functional role during embryogenesis and in adult hematopoietic cells. 53 refs., 9 figs.

  18. Cell immobilization with polyurethane foam for retaining Trichoderma reesei cells during foam fractionation for cellulase collection.

    PubMed

    Zhang, Qin; Lo, Chi-Ming; Ju, Lu-Kwang

    2009-05-01

    In situ affinity foam fractionation is a potential powerful tool for continuous, selective removal of products from bioprocesses. When evaluating its applicability to cellulase production by Trichoderma reesei fermentation, we encountered the difficulty of significant removal of fungal mycelia along with the cellulase. To solve this problem, cell immobilization using cut pieces of hydrophilic polyurethane (PU) foam was evaluated. Five commercial PU foams with different pore sizes and porosities were tested. Two were found to support good cell growth, cellulase production, and cell loading (about 0.6 g dry cells per g PU). The PU-immobilized mycelia were successfully retained in the foaming process. PMID:19127442

  19. Cell Surface and Membrane Engineering: Emerging Technologies and Applications.

    PubMed

    Saeui, Christopher T; Mathew, Mohit P; Liu, Lingshui; Urias, Esteban; Yarema, Kevin J

    2015-01-01

    Membranes constitute the interface between the basic unit of life-a single cell-and the outside environment and thus in many ways comprise the ultimate "functional biomaterial". To perform the many and often conflicting functions required in this role, for example to partition intracellular contents from the outside environment while maintaining rapid intake of nutrients and efflux of waste products, biological membranes have evolved tremendous complexity and versatility. This article describes how membranes, mainly in the context of living cells, are increasingly being manipulated for practical purposes with drug discovery, biofuels, and biosensors providing specific, illustrative examples. Attention is also given to biology-inspired, but completely synthetic, membrane-based technologies that are being enabled by emerging methods such as bio-3D printers. The diverse set of applications covered in this article are intended to illustrate how these versatile technologies-as they rapidly mature-hold tremendous promise to benefit human health in numerous ways ranging from the development of new medicines to sensitive and cost-effective environmental monitoring for pathogens and pollutants to replacing hydrocarbon-based fossil fuels. PMID:26096148

  20. Cell Surface and Membrane Engineering: Emerging Technologies and Applications

    PubMed Central

    Saeui, Christopher T.; Mathew, Mohit P.; Liu, Lingshui; Urias, Esteban; Yarema, Kevin J.

    2015-01-01

    Membranes constitute the interface between the basic unit of life—a single cell—and the outside environment and thus in many ways comprise the ultimate “functional biomaterial”. To perform the many and often conflicting functions required in this role, for example to partition intracellular contents from the outside environment while maintaining rapid intake of nutrients and efflux of waste products, biological membranes have evolved tremendous complexity and versatility. This article describes how membranes, mainly in the context of living cells, are increasingly being manipulated for practical purposes with drug discovery, biofuels, and biosensors providing specific, illustrative examples. Attention is also given to biology-inspired, but completely synthetic, membrane-based technologies that are being enabled by emerging methods such as bio-3D printers. The diverse set of applications covered in this article are intended to illustrate how these versatile technologies—as they rapidly mature—hold tremendous promise to benefit human health in numerous ways ranging from the development of new medicines to sensitive and cost-effective environmental monitoring for pathogens and pollutants to replacing hydrocarbon-based fossil fuels. PMID:26096148

  1. Determining TGF-? Receptor Levels in the Cell Membrane.

    PubMed

    Zhang, Long; Zhou, Fangfang; van Dinther, Maarten; Ten Dijke, Peter

    2016-01-01

    Transforming growth factor-? (TGF-?) is a pleiotropic cytokine that signals via transmembrane TGF-? type I and type II serine/threonine kinases receptors, i.e., T?RI and T?RII. Upon TGF-?-induced receptor complex formation, the T?RII kinase phosphorylates T?RI. Subsequently, the activated T?RI induces the phosphorylation of receptor regulated SMAD2 and SMAD3, which can form heteromeric complexes with Smad4. These heteromeric SMAD complexes accumulate in the nucleus, where they regulate target gene expression. The stability and membrane localization of T?RI is an important determinant to control the intensity and duration of TGF-? signaling. T?RI is targeted for poly-ubiquitylation-mediated proteasomal degradation by the SMAD7-SMURF E3 ligase complex. We recently identified another important regulatory factor that controls T?RI levels in the cell membrane. As a strong inducer of TGF-? signaling, ubiquitin-specific protease (USP) 4 was found to directly interact with T?RI and act as a deubiquitylating enzyme, thereby stabilizing T?RI levels at the plasma membrane. This chapter introduces methods for examining cell membrane receptor (T?RI) levels. PMID:26520116

  2. Efficiency of Membrane Protein Expression Following Infection with Recombinant Adenovirus of Polarized Non-Transformed Human Retinal Pigment Epithelial Cells.

    PubMed

    Müller, Claudia; Blenkinsop, Timothy A; Stern, Jeffrey H; Finnemann, Silvia C

    2016-01-01

    Transient expression of exogenous proteins facilitates studies of molecular mechanisms and utility for transplantation of retinal pigment epithelial (RPE) cells in culture. Here, we compared expression of the membrane protein ?5 integrin-GFP (?5-GFP) in two recently established models of differentiated human RPE, adult RPE stem cell-derived RPE and primary fetal RPE, upon infection with recombinant adenovirus or transfection with DNA in liposomes. We varied viral titer and duration of virus incubation and examined ?5-GFP and the tight junction marker ZO-1 in manipulated cells by confocal microscopy. Fewer than 5 % of cells expressed ?5-GFP after liposome-mediated transfection. The percentage of cells with detectable ?5-GFP exceeded 90 % after adenovirus infection for as little as 1 h. Decreasing virus titer two-fold did not alter the fraction of cells expressing ?5-GFP but increased variability of ?5-GFP level among cells. In cells with low expression levels, ?5-GFP localized mostly to the apical plasma membrane like endogenous ?v?5 integrin. In cells with high expression levels, ?5-GFP localized to the cytoplasm in addition to the apical surface suggesting accumulation in trafficking compartments. Altogether, adenovirus delivery yields efficient exogenous membrane protein expression of correct polarity in differentiated human RPE cells in culture. PMID:26427482

  3. In vitro synthesis of cellulose II from a cytoplasmic membrane fraction of Acetobacter xylinum

    SciTech Connect

    Bureau, T.E.; Brown, R.M. Jr.

    1987-10-01

    The cytoplasmic and outer membranes of Acetobacter xylinum were isolated by discontinuous sucrose density ultracentrifugation. Both lysozyme and trypsin were required for efficient crude membrane separation. Primary dehydrogenases and NADH oxidase were used as cytoplasmic membrane markers, and 2-keto-3-deoxyoctulosonic acid was used to identify the outer membranes. Cellulose synthetase activity was assayed as the conversion of radioactivity from UDP-(/sup 14/C)glucose into an alkali-insoluble ..beta..-1,4-D-(/sup 14/C)glucan. This activity was predominantly found in the cytoplasmic membrane. The cellulose nature of the product was demonstrated by (i) enzymatic hydrolysis followed by TLC, (ii) methylation analysis followed by TLC, and (iii) GC/MS. Further, the weight-average and number-average degree of polymerization of the in vitro product, determined by high-performance gel permeation chromatography, were 4820 and 5270, respectively. In addition, x-ray diffraction analysis indicated that the in vitro product is cellulose II, which is in contrast to the in vivo product--namely, cellulose I.

  4. Ambidextrous Binding of Cell and Membrane Bilayers by Soluble Matrix Metalloproteinase-12

    PubMed Central

    Koppisetti, Rama K.; Fulcher, Yan G.; Jurkevich, Alexander; Prior, Stephen H.; Xu, Jia; Lenoir, Marc; Overduin, Michael; Van Doren, Steven R.

    2014-01-01

    Matrix metalloproteinases (MMPs) regulate tissue remodeling, inflammation, and disease progression. Some soluble MMPs are inexplicably active near cell surfaces. Here, we demonstrate binding of MMP-12 directly to bilayers and cellular membranes using paramagnetic NMR and fluorescence. Opposing sides of the catalytic domain engage spin-labeled membrane mimics. Loops project from the ?-sheet interface to contact the phospholipid bilayer with basic and hydrophobic residues. The distal membrane interface comprises loops on the other side of the catalytic cleft. Both interfaces mediate MMP-12 association with vesicles and cell membranes. MMP-12 binds plasma membranes and is internalized to hydrophobic perinuclear features, the nuclear membrane, and inside the nucleus within minutes. While binding of TIMP-2 to MMP-12 hinders membrane interactions beside the active site, TIMP-2-inhibited MMP-12 binds vesicles and cells, suggesting compensatory rotation of its membrane approaches. MMP-12 association with diverse cell membranes may target its activities to modulate innate immune responses and inflammation. PMID:25412686

  5. Airborne elements, cell membranes, and chlorophyll in transplanted lichens

    SciTech Connect

    Garty, J.; Cohen, Y.; Kloog, N.

    1998-07-01

    The objective of the present study was to test the concentration of airborne mineral elements in the lichen Ramalina lacera (with.) J.R. Laund. in comparison with its physiological status. Thalli of Ramalina lacera were collected in a remote unpolluted site and transplanted in a polluted region for 10 mo. An analysis of 20 elements in addition to an analysis of the status of cell membranes and the integrity of chlorophyll was performed after this period of transplantation. The lichen manifested a great potential for the accumulation of Pb, V, Ni, Zn, and Cu. Potassium and P were found to leach out. High concentrations of Ni, Mg, and B coincided with damage caused to cell membranes. The integrity of chlorophyll correlated with the concentration of K and correlated inversely with the concentration of Cr, Fe, Mn, Ni, Pb, and B.

  6. Manipulation of cell volume and membrane pore comparison following single cell permeabilization with 60- and 600-ns electric pulses

    PubMed Central

    Nesin, Olena M.; Pakhomova, Olga N.; Xiao, Shu; Pakhomov, Andrei G.

    2010-01-01

    Intense nanosecond-duration electric pulses (nsEP) open stable nanopores in cell plasma membrane, followed by cell volume changesdue to water uptake or expulsion, as regulated by the osmolality balance of pore-impermeable solutes inside and outside the cell. The size of pores opened by 50, 60-ns EP (10 Hz, ~13 kV/cm) and 5, 600-ns EP (1 Hz, ~6 kV/cm) in GH3 cells was estimated by isoosmotic replacement of bath NaCl with (polyethylene glycols and sugars. Such replacement reduced cell swelling and/or turned it into a transient or sustained shrinking, depending on the availability of pores permeable to the test solute. Unexpectedly, solute substitutions showed that for the same integral area of pores opened by 60- and 600-ns treatments (as indicated by cell volume changes), the pore sizes were similar. However, the 600-ns exposure triggered significantly higher cell uptake of propidium. We concluded that 600-ns EP opened a greater number of larger (propidium-permeable pores), but the fraction of the larger pores in the entire pore population was insufficient to contribute to cell volume changes. For both the 60- and 600-ns exposures, cell volume changes were determined by pores smaller than 0.9 nm in diameter; however, the diameter increased with increasing the nsEP intensity. PMID:21182825

  7. Fractional Proliferation: A method to deconvolve cell population dynamics from single-cell data

    PubMed Central

    Tyson, Darren R.; Garbett, Shawn P.; Frick, Peter L.; Quaranta, Vito

    2012-01-01

    We present an integrated method that exploits extended time-lapse automated imaging to quantify dynamics of cell proliferation. Cell counts are fit with a Quiescence-Growth model that estimates rates of cell division, entry into quiescence and death. The model is constrained with rates extracted experimentally from the behavior of tracked single cells over time. We visualize the output of the analysis in Fractional Proliferation graphs, which deconvolve dynamic proliferative responses to perturbations into the relative contributions of dividing, quiescent (non-dividing) and dead cells. The method reveals that the response of “oncogene-addicted” human cancer cells to tyrosine kinase inhibitors is a composite of altered rates of division, death and entry into quiescence, challenging the notion that such cells simply ‘die’ in response to oncogene-targeted therapy. PMID:22886092

  8. Characterization of Plasma Membrane Proteins from Ovarian Cancer Cells Using Mass Spectrometry

    DOE PAGESBeta

    Springer, David L.; Auberry, Deanna L.; Ahram, Mamoun; Adkins, Joshua N.; Feldhaus, Jane M.; Wahl, Jon H.; Wunschel, David S.; Rodland, Karin D.

    2004-01-01

    To determine how the repertoire of plasma membrane proteins change with disease state, specifically related to cancer, several methods for preparation of plasma membrane proteins were evaluated. Cultured cells derived from stage IV ovarian tumors were grown to 90% confluence and harvested in buffer containing CHAPS detergent. This preparation was centrifuged at low speed to remove insoluble cellular debris resulting in a crude homogenate. Glycosylated proteins in the crude homogenate were selectively enriched using lectin affinity chromatography. The crude homogenate and the lectin purified sample were prepared for mass spectrometric evaluation. The general procedure for protein identification began with trypsinmore »digestion of protein fractions followed by separation by reversed phase liquid chromatography that was coupled directly to a conventional tandem mass spectrometer (i.e. LCQ ion trap). Mass and fragmentation data for the peptides were searched against a human proteome data base using the informatics program SEQUEST. Using this procedure 398 proteins were identified with high confidence, including receptors, membrane-associated ligands, proteases, phosphatases, as well as structural and adhesion proteins. Results indicate that lectin chromatography provides a select subset of proteins and that the number and quality of the identifications improve as does the confidence of the protein identifications for this subset. These results represent the first step in development of methods to separate and successfully identify plasma membrane proteins from advanced ovarian cancer cells. Further characterization of plasma membrane proteins will contribute to our understanding of the mechanisms underlying progression of this deadly disease and may lead to new targeted interventions as well as new biomarkers for diagnosis.« less

  9. Development of structured polymer electrolyte membranes for fuel cell applications

    NASA Astrophysics Data System (ADS)

    Gasa, Jeffrey

    The objective of this research was to explore structure-property relationships to develop the understanding needed for introduction of superior PEM materials. Polymer electrolyte membranes based on sulfonated poly(ether ketone ketone) (SPEKK) were fabricated using N-methyl pyrrolidone as casting solvent. The membranes were characterized in terms of properties that were relevant to fuel cell applications, such as proton conductivity, methanol permeability, and swelling properties, among others. It was found in this study that the proton conductivity of neat SPEKK membranes could reach the conductivity of commercial membranes such as NafionRTM. However, when the conductivity of SPEKK was comparable to NafionRTM, the swelling of SPEKK in water was quite excessive. The swelling problem was remedied by modifying the microstructure of SPEKK using different techniques. One of them involved blending of lightly sulfonated PEKK with highly acidic particles (sulfonated crosslinked polystyrene-SXLPS). Low sulfonation level of SPEKK was used to reduce the swelling of the membrane in water and the role of the highly acidic particles was to enhance the proton conductivity of the membrane. Because of the residual crystallinity in SPEKK with low sulfonation levels (IEC < 1 meq/g), the composite membranes exhibited excellent dimensional stability in water at elevated temperatures (30-90 °C). Also, the resistance to swelling of these composite membranes in methanol-water mixtures was far better than NafionRTM, and so was the methanol permeability. Another technique explored was blending with non-conductive polymers (poly(ether imide) and poly(ether sulfone)) to act as mechanical reinforcement. It was found that miscibility behavior of the blends had a significant impact on the transport and swelling properties of these blends, which could be explained by the blend microstructure. The miscibility behavior was found to be strongly dependent on the sulfonation level of SPEKK. The conductivities of the blends were enhanced by as much as two orders of magnitude when the morphology was modified by electric field. The last approach was ionic crosslinking of the sulfonate groups in SPEKK using divalent cations, specifically barium ions. The crosslinking treatment has greatly improved the thermal stability of the membranes in both dry and wet conditions.

  10. Cell surface energy and membrane associated actin in lymphocytes.

    PubMed

    Mely-Goubert, B; Bellgrau, D; Gerson, D F

    1988-08-01

    We have shown previously that membrane associated actin correlates with the migratory abilities of lymphocytes during recirculation, and that cell surface energy correlates with the adhesiveness of lymphocytes to other cells. In this study, measurements of actin content and cell surface energy have been made for various lymphocyte subpopulations to examine the possibility that recirculation ability may be related to nonspecific adhesiveness. We have found that: both cell surface energy and actin content combine to provide a consistent explanation for the relative rates of recirculation of various lymphocyte subpopulations, and cell surface energies and actin contents vary independently in these lymphocyte subpopulations. Comparison of the actin contents and cell surface energies of metastatic and nonmetastatic lymphoma cell lines indicated that the differences in metastatic potential were more likely attributable to specific receptor-ligand interactions than to nonspecific adhesiveness. Cell surface energy and actin content are consistent with the greater adhesiveness of B cells than T cells to nylon wool, providing a physical basis for this common cell separation technique. PMID:2456153

  11. Latent progenitor cells as potential regulators for tympanic membrane regeneration

    PubMed Central

    Kim, Seung Won; Kim, Jangho; Seonwoo, Hoon; Jang, Kyung-Jin; Kim, Yeon Ju; Lim, Hye Jin; Lim, Ki-Taek; Tian, Chunjie; Chung, Jong Hoon; Choung, Yun-Hoon

    2015-01-01

    Tympanic membrane (TM) perforation, in particular chronic otitis media, is one of the most common clinical problems in the world and can present with sensorineural healing loss. Here, we explored an approach for TM regeneration where the latent progenitor or stem cells within TM epithelial layers may play an important regulatory role. We showed that potential TM stem cells present highly positive staining for epithelial stem cell markers in all areas of normal TM tissue. Additionally, they are present at high levels in perforated TMs, especially in proximity to the holes, regardless of acute or chronic status, suggesting that TM stem cells may be a potential factor for TM regeneration. Our study suggests that latent TM stem cells could be potential regulators of regeneration, which provides a new insight into this clinically important process and a potential target for new therapies for chronic otitis media and other eardrum injuries. PMID:26100219

  12. Latent progenitor cells as potential regulators for tympanic membrane regeneration

    NASA Astrophysics Data System (ADS)

    Kim, Seung Won; Kim, Jangho; Seonwoo, Hoon; Jang, Kyung-Jin; Kim, Yeon Ju; Lim, Hye Jin; Lim, Ki-Taek; Tian, Chunjie; Chung, Jong Hoon; Choung, Yun-Hoon

    2015-06-01

    Tympanic membrane (TM) perforation, in particular chronic otitis media, is one of the most common clinical problems in the world and can present with sensorineural healing loss. Here, we explored an approach for TM regeneration where the latent progenitor or stem cells within TM epithelial layers may play an important regulatory role. We showed that potential TM stem cells present highly positive staining for epithelial stem cell markers in all areas of normal TM tissue. Additionally, they are present at high levels in perforated TMs, especially in proximity to the holes, regardless of acute or chronic status, suggesting that TM stem cells may be a potential factor for TM regeneration. Our study suggests that latent TM stem cells could be potential regulators of regeneration, which provides a new insight into this clinically important process and a potential target for new therapies for chronic otitis media and other eardrum injuries.

  13. 2?-Hydroxy ceramide in membrane homeostasis and cell signaling

    PubMed Central

    Kota, Venkatesh; Hama, Hiroko

    2013-01-01

    Ceramide is a precursor of complex sphingolipids and also plays important roles in cell signaling. With the advances in lipid analytical technologies, the structural diversity of ceramide species have become evident, and the complexity of cellular metabolism and function associated with distinct ceramide species is beginning to be revealed. One of the common structural variations of ceramide is 2?-hydroxylation of the N-acyl chain. Fatty acid 2-hydroxylase (FA2H) is one of the enzymes that introduce the hydroxyl group during de novo synthesis of ceramide. FA2H is essential for the normal functioning of the nervous system, as evidenced by demyelinating disorder associated with FA2H mutations in humans and mice. Studies of Fa2h mutant mice indicate that lack of 2?-hydroxy galactosylceramide in the myelin membrane results in loss of long-term stability of myelin and eventual demyelination. FA2H also regulates differentiation of various cell types (epidermal keratinocytes, schwannoma cells, adipocytes). When provided exogenously, ceramide induces apoptosis in many cell types. Interestingly, the effective concentration of 2?-hydroxy ceramide that induces apoptosis is significantly lower compared to non-hydroxy ceramide, and cells die much more rapidly, suggesting that 2?-hydroxy ceramide can mediate proapoptotic signaling distinct from non-hydroxy ceramide. Collectively, current evidence clearly shows that 2?-hydroxy ceramide and 2?-hydroxy complex sphingolipids have unique functions in membrane homeostasis and cell signaling that could not be substituted by non-hydroxy counterparts. PMID:24139861

  14. Do heavy ions cause microlesions in cell membranes?

    NASA Technical Reports Server (NTRS)

    Koniarek, Jan P.; Worgul, Basil V.

    1992-01-01

    The microlesion question is investigated by monitoring the electrical potential difference across the endothelium of rat corneas in vitro before, during, and after irradiation. When the corneas were exposed to 1 Gy of Fe-56 ions (450 and 600 MeV/a.m.u.), no effect was detected on this parameter. These results suggest that direct physical damage to cell membranes, as predicted by the microlesion theory, does not take place.

  15. Cell-free transfer of sterols by plant fractions

    SciTech Connect

    Morre, D.J.; Wilkinson, F.E.; Morre, D.M. ); Moreau, P. ); Sandelius, A.S. ); Penel, C.; Greppin, H. )

    1990-05-01

    Microsomes from etiolated hypocotyls of soybean or leaves of light-grown spinach radiolabeled in vivo with ({sup 3}H)acetate or in vitro with ({sup 3}H)squalene or ({sup 3}H)cholesterol as donor transferred radioactivity to unlabeled acceptor membranes immobilized on nitrocellulose. Most efficient transfer was with plasma membrane or tonoplast as the acceptor. The latter were highly purified by aqueous two-phase partition (plasma membrane) and preparative free-flow electrophoresis (tonoplast and plasma membrane). Plasma membrane- and tonoplast-free microsomes and purified mitochondria were less efficient acceptors. Sterol transfer was verified by thin-layer chromatography of extracted lipids. Transfer was time- and temperature-dependent, required ATP but was not promoted by cytosol. The nature of the donor (endoplasmic reticulum, Golgi apparatus or both) and of the transfer mechanism is under investigation.

  16. Ultrafiltration by a compacted clay membrane-I. Oxygen and hydrogen isotopic fractionation

    USGS Publications Warehouse

    Coplen, T.B.; Hanshaw, B.B.

    1973-01-01

    Laboratory experiments were carried out to determine the magnitude of the isotopic fractionation of distilled water and of 0.01 N NaCl forced to flow at ambient temperature under a hydraulic pressure drop of 100 bars across a montmorillonite disc compacted to a porosity of 35 per cent by a pressure of 330 bars. The ultrafiltrates in both experiments were depleted in D by 2.5%. and in O18 by 0.8%. relative to the residual solution. No additional isotopic fractionation due to a salt filtering mechanism was observed at NaCl concentrations up to 0.01 N. Adsorption is most likely the principal mechanism which produces isotopic fractionation, but molecular diffusion may play a minor role. The results suggest that oxygen and hydrogen isotopic fractionation of ground water during passage through compacted clayey sediments should be a common occurrence, in accord with published interpretations of isotopic data from the Illinois and Alberta basins. ?? 1973.

  17. Amniotic membrane transplantation for partial limbal stem cell deficiency

    PubMed Central

    Anderson, D.; Ellies, P.; Pires, R.; Tseng, S.

    2001-01-01

    AIM—To examine the efficacy, safety, and long term outcomes of amniotic membrane transplantation for corneal surface reconstruction in cases of partial limbal stem cell deficiency.?METHODS—17 eyes of 15 patients with partial limbal stem cell deficiency underwent superficial keratectomy of the conjunctivalised corneal surface followed by amniotic membrane transplantation. Cases were followed up for at least a year.?RESULTS—All eyes exhibited a stable, intact corneal epithelial surface after a mean follow up period of 25.8 months with no eyes developing recurrent erosion or persistent epithelial defect. The mean time to re-epithelialisation was 22.8 days. Overall improvement in visual acuity was observed in 92.9% of 14 eyes with visual potential. Of those, five eyes gained six or more lines, two eyes gained between four and five lines, six eyes gained between one and three lines, and one eye lost three lines of Snellen acuity. Pain and photophobia were abolished in 86% of cases and substantially reduced in 14%, with all eyes exhibiting decreased vascularisation and inflammation at final follow up.?CONCLUSIONS—Amniotic membrane transplantation appears to be a safe and effective method of restoring a stable corneal epithelium for cases of partial limbal stem cell deficiency and can be considered as an alternative to limbal autograft or allograft.?? PMID:11316719

  18. Estrogen-induced membrane alterations and growth associated with proteinase activity in endometrial cells

    PubMed Central

    1979-01-01

    Endometrial cells isolated from uteri of ovariectomized rats were treated in vitro with 1 X 10(-9) M estradiol-17 beta (E2beta) to analyze early changes in membrane properties during hormone-induced growth. After 30-min exposure to E2beta at 22 degrees C, cells exhibited an enhanced capacity to bind erythrocytes (hemadsorption) in the presence of concanavalin A (Con A) to 237% of the level in paired controls. Fluorescence microscopy revealted that approximately 25% of cells exposed to E2beta, but not estradiol-17 alpha (E2alpha), showed a redistribution into polar clusters of Con A-binding sites that were dispersed in random patches at the external surfaces of control cells. These hormore-induced membrane alterations were abolished by prior treatment of cells with inhibitors of thiol proteinase activity of the cathepsin B1 (CB1) type, such as leupeptin and iodoacetate. Leupeptin at 4.5 X 10(-7) M also reduced the affinity of [3H]E2beta binding to intact cells but did not influence specific binding of the hormone to macromolecular components of cytosol. A pronounced increase in the availability of endogenous CB1, But not of alkaline phosphatase, succinate, or lactate dehydrogenase, in the extracellular media was elicited within 30 min after E2beta treatment. In cells cultured in chemically defined medium for up to 48 h, E2beta, but not E2alpha, enhanced cell proliferation and stimulated [3H]thymidine incorporation into macromolecular form. These E2beta-induced effects were abolished by prior treatment of cells with liposome-entrapped leupeptin at a final concentration of 7 X 10(-8) M. The net rate of intercellular adhesion among endometrial cells was also enhanced by E2beta. This hormonal response was diminished by prior exposure to leupeptin. Fractionation of cells by selection for adhesiveness due to E2beta exposure for 30 min yielded a subpopulation of rapidly dividing cells which surpassed their less adhesive counterparts in cathepsin secretion and in Con A-mediated hemadsorption. These results indicate that leupeptin-sensitive proteinase activity may contribute to membrane and growth modifications elicited by E2beta treatment in endometrial cells. PMID:457777

  19. Correlation of cell membrane dynamics and cell motility

    E-print Network

    Veronika, Merlin

    Abstract Background Essential events of cell development and homeostasis are revealed by the associated changes of cell morphology and therefore have been widely used as a key indicator of physiological states and molecular ...

  20. Quantitative Proteomics of the Neisseria Gonorrhoeae Cell Envelope and Membrane Vesicles for the Discovery of Potential Therapeutic Targets*

    PubMed Central

    Zielke, Ryszard A.; Wierzbicki, Igor H.; Weber, Jacob V.; Gafken, Philip R.; Sikora, Aleksandra E.

    2014-01-01

    Neisseria gonorrhoeae (GC) is a human-specific pathogen, and the agent of a sexually transmitted disease, gonorrhea. There is a critical need for new approaches to study and treat GC infections because of the growing threat of multidrug-resistant isolates and the lack of a vaccine. Despite the implied role of the GC cell envelope and membrane vesicles in colonization and infection of human tissues and cell lines, comprehensive studies have not been undertaken to elucidate their constituents. Accordingly, in pursuit of novel molecular therapeutic targets, we have applied isobaric tagging for absolute quantification coupled with liquid chromatography and mass spectrometry for proteome quantitative analyses. Mining the proteome of cell envelopes and native membrane vesicles revealed 533 and 168 common proteins, respectively, in analyzed GC strains FA1090, F62, MS11, and 1291. A total of 22 differentially abundant proteins were discovered including previously unknown proteins. Among those proteins that displayed similar abundance in four GC strains, 34 were found in both cell envelopes and membrane vesicles fractions. Focusing on one of them, a homolog of an outer membrane protein LptD, we demonstrated that its depletion caused loss of GC viability. In addition, we selected for initial characterization six predicted outer membrane proteins with unknown function, which were identified as ubiquitous in the cell envelopes derived from examined GC isolates. These studies entitled a construction of deletion mutants and analyses of their resistance to different chemical probes. Loss of NGO1985, in particular, resulted in dramatically decreased GC viability upon treatment with detergents, polymyxin B, and chloramphenicol, suggesting that this protein functions in the maintenance of the cell envelope permeability barrier. Together, these findings underscore the concept that the cell envelope and membrane vesicles contain crucial, yet under-explored determinants of GC physiology, which may represent promising targets for designing new therapeutic interventions. PMID:24607996

  1. Intra-membrane ligand diffusion and cell shape modulate juxtacrine patterning

    E-print Network

    Intra-membrane ligand diffusion and cell shape modulate juxtacrine patterning Steven D Webb in the cell membrane, and the role of polarity has been largely ignored. In this paper we determine the role membrane segments, diffusive transport of proteins and receptors between these segments, and production

  2. Water free proton conducting membranes based on poly-4-vinylpyridinebisulfate for fuel cells

    NASA Technical Reports Server (NTRS)

    Narayanan, Sekharipuram R. (Inventor); Yen, Shiao-Pin S. (Inventor)

    2007-01-01

    Disclosed are methods for forming a water-free electrolyte membrane useful in fuel cells. Also provided is a water-free electrolyte membrane comprising a quaternized amine salt including poly-4-vinylpyridinebisulfate, a poly-4-vinylpyridinebisulfate silica composite, and a combination thereof and a fuel cell comprising the membrane.

  3. Membrane Cholesterol Modulates LOX-1 Shedding in Endothelial Cells

    PubMed Central

    Testa, Barbara; Raniolo, Sofia; Fasciglione, Giovanni Francesco; Coletta, Massimiliano; Biocca, Silvia

    2015-01-01

    The lectin-like oxidized low-density lipoprotein receptor-1 (LOX-1) is a scavenger receptor responsible for ox-LDL recognition, binding and internalization, which is up-regulated during atherogenesis. Its activation triggers endothelium dysfunction and induces inflammation. A soluble form of LOX-1 has been identified in the human blood and its presence considered a biomarker of cardiovascular diseases. We recently showed that cholesterol-lowering drugs inhibit ox-LDL binding and internalization, rescuing the ox-LDL induced apoptotic phenotype in primary endothelial cells. Here we have investigated the molecular bases of human LOX-1 shedding by metalloproteinases and the role of cell membrane cholesterol on the regulation of this event by modulating its level with M?CD and statins. We report that membrane cholesterol affects the release of different forms of LOX-1 in cells transiently and stably expressing human LOX-1 and in a human endothelial cell line (EA.hy926). In particular, our data show that i) cholesterol depletion triggers the release of LOX-1 in exosomes as a full-length transmembrane isoform and as a truncated ectodomain soluble fragment (sLOX-1); ii) endothelial cells secrete a soluble metalloproteinase which induces LOX-1 ectodomain shedding and iii) long term statins treatment enhances sLOX-1 proteolytic shedding. PMID:26495844

  4. Mathematical and Computational Modeling of Polymer Exchange Membrane Fuel Cells

    NASA Astrophysics Data System (ADS)

    Ulusoy, Sehribani

    In this thesis a comprehensive review of fuel cell modeling has been given and based on the review, a general mathematical fuel cell model has been developed in order to understand the physical phenomena governing the fuel cell behavior and in order to contribute to the efforts investigating the optimum performance at different operating conditions as well as with different physical parameters. The steady state, isothermal model presented here accounts for the combined effects of mass and species transfer, momentum conservation, electrical current distribution through the gas channels, the electrodes and the membrane, and the electrochemical kinetics of the reactions in the anode and cathode catalyst layers. One of the important features of the model is that it proposes a simpler modified pseudo-homogeneous/agglomerate catalyst layer model which takes the advantage of the simplicity of pseudo-homogenous modeling while taking into account the effects of the agglomerates in the catalyst layer by using experimental geometric parameters published. The computation of the general mathematical model can be accomplished in 3D, 2D and 1D with the proper assumptions. Mainly, there are two computational domains considered in this thesis. The first modeling domain is a 2D Membrane Electrode Assembly (MEA) model including the modified agglomerate/pseudo-homogeneous catalyst layer modeling with consistent treatment of water transport in the MEA while the second domain presents a 3D model with different flow filed designs: straight, stepped and tapered. COMSOL Multiphysics along with Batteries and Fuel Cell Module have been used for 2D & 3D model computations while ANSYS FLUENT PEMFC Module has been used for only 3D two-phase computation. Both models have been validated with experimental data. With 2D MEA model, the effects of temperature and water content of the membrane as well as the equivalent weight of the membrane on the performance have been addressed. 3D COMSOL simulation results showed that the fuel performance can be improved by using flow field designs alleviating the reactant depletion along the channels and supplying more uniform reactant distribution. Stepped flow field was found to show better performance when compared to straight and tapered ones. ANSYS FLUENT model is evaluated in terms of predicting the two phase flow in the fuel cell components. It is proposed that it is not capable of predicting the entire fuel cell polarization due to the lack of agglomerate catalyst layer modeling and well-established two-phase flow modeling. Along with the comprehensive modeling efforts, also an analytical model has been computed by using MathCAD and it is found that this simpler model is able to predict the performance in a general trend according to the experimental data obtained for a new novel membrane. Therefore, it can be used for robust prediction of the cell performance at different operating conditions such as temperature and pressure, and the electrochemical properties such as the catalyst loading, the exchange current density and the diffusion coefficients of the reactants. In addition to the modeling efforts, this thesis also presents a very comprehensive literature review on the models developed in the literature so far, the modeling efforts in fuel cell sandwich including membrane, catalyst layer and gas diffusion layer and fuel cell model properties. Moreover, a summary of possible directions of research in fuel cell analysis and computational modeling has been presented.

  5. Physical, functional and structural characterization of the cell wall fractions from baker's yeast Saccharomyces cerevisiae.

    PubMed

    Borchani, Chema; Fonteyn, Fabienne; Jamin, Guilhem; Paquot, Michel; Thonart, Philippe; Blecker, Christophe

    2016-03-01

    The yeast cell wall of Saccharomyces cerevisiae is an important source of ?-d-glucan, a glucose homopolymer with many functional, nutritional and human health benefits. In the present study, the yeast cell wall fractionation process involving enzymatic treatments (savinase and lipolase enzymes) affected most of the physical and functional characteristics of extracted fractions. Thus, the fractionation process showed that ?-d-glucan fraction F4 had significantly higher swelling power and fat binding capacity compared to other fractions (F1, F2 and F3). It also exhibited a viscosity of 652.12mPas and a high degree of brightness of extracted ?-d-glucan fraction. Moreover, the fractionation process seemed to have an effect on structural and thermal properties of extracted fractions. Overall, results showed that yeast ?-d-glucan had good potential for use as a prebiotic ingredient in food, as well as medicinal and pharmaceutical products. PMID:26471666

  6. Better Proton-Conducting Polymers for Fuel-Cell Membranes

    NASA Technical Reports Server (NTRS)

    Narayan, Sri; Reddy, Prakash

    2012-01-01

    Polyoxyphenylene triazole sulfonic acid has been proposed as a basis for development of improved proton-conducting polymeric materials for solid-electrolyte membranes in hydrogen/air fuel cells. Heretofore, the proton-conducting membrane materials of choice have been exemplified by a family of perfluorosulfonic acid-based polymers (Nafion7 or equivalent). These materials are suitable for operation in the temperature of 75 to 85 C, but in order to reduce the sizes and/or increase the energy-conversion efficiencies of fuel-cell systems, it would be desirable to increase temperatures to as high as 120 C for transportation applications, and to as high as 180 C for stationary applications. However, at 120 C and at relative humidity values below 50 percent, the loss of water from perfluorosulfonic acid-based polymer membranes results in fuel-cell power densities too low to be of practical value. Therefore, membrane electrolyte materials that have usefully high proton conductivity in the temperature range of 180 C at low relative humidity and that do not rely on water for proton conduction at 180 C would be desirable. The proposed polyoxyphenylene triazole sulfonic acid-based materials have been conjectured to have these desirable properties. These materials would be free of volatile or mobile acid constituents. The generic molecular structure of these materials is intended to exploit the fact, demonstrated in previous research, that materials that contain ionizable acid and base groups covalently attached to thermally stable polymer backbones exhibit proton conduction even in the anhydrous state.

  7. Anaerobic digestion of the organic fraction of municipal solid waste in a two-stage membrane process.

    PubMed

    Trzcinski, A P; Stuckey, D C

    2009-01-01

    A batch of the Organic Fraction of Municipal Solid Waste (OFMSW) was treated in a two-step process with effluent recirculation comprising a novel hydrolytic reactor (HR) followed by a Submerged Anaerobic Membrane Bioreactor (SAMBR) operating at a stable permeate flux of 5.6 L/m(2) hr (LMH). A soluble COD removal higher than 95% was obtained from the SAMBR. The soluble COD as well as the Total Suspended Solids (TSS) did not build up due to efficient hydrolysis inside the SAMBR, and no VFA accumulation occurred due to the complete retention of methanogens by the membrane as well as the formation of syntrophic associations. Because of the microfiltration membrane in the second reactor a stabilized leachate was obtained from the very first days of the treatment and the highly stable process enabled shorter treatment periods compared to traditional leach bed processes. This experiment showed that the recycle of the stabilised leachate does not lead to a build up of SCOD. Size exclusion chromatography analysis confirmed that high molecular weight compounds were completely degraded and did not appear in the SAMBR permeate, and that low molecular weight fulvic-like and medium MW material were present in the permeate of the SAMBR but their concentration remained stable with time. PMID:19844043

  8. Noncontact microsurgery of cell membranes using femtosecond laser pulses for optoinjection of specified substances into cells

    SciTech Connect

    Il'ina, I V; Ovchinnikov, A V; Chefonov, O V; Sitnikov, D S; Agranat, Mikhail B; Mikaelyan, A S

    2013-04-30

    IR femtosecond laser pulses were used for microsurgery of a cell membrane aimed at local and short-duration change in its permeability and injection of specified extracellular substances into the cells. The possibility of noncontact laser delivery of the propidium iodide fluorescent dye and the pEGFP plasmid, encoding the green fluorescent protein, into the cells with preservation of the cell viability was demonstrated. (extreme light fields and their applications)

  9. Age-Dependent Changes in the Sphingolipid Composition of Mouse CD4+ T Cell Membranes and Immune Synapses Implicate Glucosylceramides in Age-Related T Cell Dysfunction

    PubMed Central

    Molano, Alberto; Huang, Zhaofeng; Marko, Melissa G.; Azzi, Angelo; Wu, Dayong; Wang, Elaine; Kelly, Samuel L.; Merrill, Alfred H.; Bunnell, Stephen C.; Meydani, Simin Nikbin

    2012-01-01

    To determine whether changes in sphingolipid composition are associated with age-related immune dysfunction, we analyzed the core sphingolipidome (i.e., all of the metabolites through the first headgroup additions) of young and aged CD4+ T cells. Since sphingolipids influence the biophysical properties of membranes, we evaluated the compositions of immune synapse (IS) and non-IS fractions prepared by magnetic immuno-isolation. Broadly, increased amounts of sphingomyelins, dihydrosphingomyelins and ceramides were found in aged CD4+ T cells. After normalizing for total sphingolipid content, a statistically significant decrease in the molar fraction of glucosylceramides was evident in both the non-IS and IS fractions of aged T cells. This change was balanced by less dramatic increases in the molar fractions of sphingomyelins and dihydrosphingomyelins in aged CD4+ T cells. In vitro, the direct or enzymatic enhancement of ceramide levels decreased CD4+ T cell proliferation without regard for the age of the responding T cells. In contrast, the in vitro inhibition of glucosylceramidase preferentially increased the proliferation of aged CD4+ T cells. These results suggest that reductions in glucosylceramide abundance contribute to age-related impairments in CD4+ T cell function. PMID:23110086

  10. Properties of electrophoretic fractions of human embryonic kidney cells separated on space shuttle flight STS-8

    NASA Technical Reports Server (NTRS)

    Morrison, D. R.; Lewis, M. L.; Barlow, G. H.; Todd, P. W.; Kunze, M. E.; Sarnoff, B. E.; Li, Z. K.

    1985-01-01

    Suspensions of cultured primary human embryonic kidney cells were subjected to continuous flow electrophoresis on Space Shuttle flight STS-8. The objectives of the experiments were to obtain electrophoretically separated fractions of the original cell populations and to test these fractions for the amount and kind of urokinase (a kidney plasminogen activator that is used medically for digesting blood clots), the morphologies of cells in the individual fractions, and their cellular electrophoretic mobilities after separation and subsequent proliferation. Individual fractions were successfully cultured after return from orbit, and they were found to differ substantially from one another and from the starting sample with respect to all of these properties.

  11. Time-Lapse Imaging of Membrane Traffic in Living Cells Erik Lee Snapp and Patrick Lajoie

    E-print Network

    Snapp, Erik Lee

    Protocol Time-Lapse Imaging of Membrane Traffic in Living Cells Erik Lee Snapp and Patrick Lajoie Eukaryotic cells are composed of an intricate system of internal membranes that are organized into different Cells (Snapp and Lajoie 2011a). Temperature control hardware Adapted from Live Cell Imaging, 2nd edition

  12. Performance of a Polymer Electrolyte Membrane Fuel Cell Exposed to Transient CO Concentrations

    E-print Network

    Van Zee, John W.

    Performance of a Polymer Electrolyte Membrane Fuel Cell Exposed to Transient CO Concentrations fuel cell PEMFC . The data include relatively high 500 and 3000 ppm CO levels at 70°C cell temperature of polymer electrolyte membrane PEM fuel cells in electric vehicles probably will require the use of reformed

  13. Process for recycling components of a PEM fuel cell membrane electrode assembly

    DOEpatents

    Shore, Lawrence (Edison, NJ)

    2012-02-28

    The membrane electrode assembly (MEA) of a PEM fuel cell can be recycled by contacting the MEA with a lower alkyl alcohol solvent which separates the membrane from the anode and cathode layers of the assembly. The resulting solution containing both the polymer membrane and supported noble metal catalysts can be heated under mild conditions to disperse the polymer membrane as particles and the supported noble metal catalysts and polymer membrane particles separated by known filtration means.

  14. The Appropriateness of Unbiased Optical Fractionators to Assess Cell Proliferation in the Adult Hippocampus

    PubMed Central

    Noori, Hamid R.; Fornal, Casimir A.

    2011-01-01

    Optical fractionators have dominated the field of neural cell counting for two decades. These unbiased stereological techniques are often used for the quantification of hippocampal cell proliferation in neurogenesis experiments. However, the heterogeneous distribution of labeled cells, especially in the form of clusters, confounds the application of these techniques. A critical evaluation of the applicability of the optical fractionator suggests that absolute counting achieves higher efficiency in the quantification of cell proliferation than unbiased estimations. PMID:22207833

  15. Elisidepsin Interacts Directly with Glycosylceramides in the Plasma Membrane of Tumor Cells to Induce Necrotic Cell Death

    PubMed Central

    Molina-Guijarro, José Manuel; García, Carolina; Macías, Álvaro; García-Fernández, Luis Francisco; Moreno, Cristina; Reyes, Fernando; Martínez-Leal, Juan Fernando; Fernández, Rogelio; Martínez, Valentín; Valenzuela, Carmen; Lillo, M. Pilar; Galmarini, Carlos M.

    2015-01-01

    Plasma membrane integrity is essential for cell life. Any major break on it immediately induces the death of the affected cell. Different molecules were described as disrupting this cell structure and thus showing antitumor activity. We have previously defined that elisidepsin (Irvalec®, PM02734) inserts and self-organizes in the plasma membrane of tumor cells, inducing a rapid loss of membrane integrity, cell permeabilization and necrotic death. Here we show that, in sensitive HCT-116 colorectal cells, all these effects are consequence of the interaction of elisidepsin with glycosylceramides in the cell membrane. Of note, an elisidepsin-resistant subline (HCT-116-Irv) presented reduced levels of glycosylceramides and no accumulation of elisidepsin in the plasma membrane. Consequently, drug treatment did not induce the characteristic necrotic cell death. Furthermore, GM95, a mutant derivative from B16 mouse melanoma cells lacking ceramide glucosyltransferase (UGCG) activity and thus the synthesis of glycosylceramides, was also resistant to elisidepsin. Over-expression of UGCG gene in these deficient cells restored glycosylceramides synthesis, rendering them sensitive to elisidepsin, at a similar level than parental B16 cells. These results indicate that glycosylceramides act as membrane targets of elisidepsin, facilitating its insertion in the plasma membrane and the subsequent membrane permeabilization that leads to drug-induced cell death. They also indicate that cell membrane lipids are a plausible target for antineoplastic therapy. PMID:26474061

  16. InVited Feature Article Water Dynamics and Proton Transfer in Nafion Fuel Cell Membranes

    E-print Network

    Fayer, Michael D.

    is the most widely used polyelectrolyte membrane in fuel cells. Ultrafast infrared spectroscopy of the O the membrane. Proton transport, both by the vehicle mechanism and the Grotthu¨s mechanism, depends on the natu

  17. Demonstrating Cell Traction--Using Hens' Egg Vitelline Membrane as Substratum.

    ERIC Educational Resources Information Center

    Downie, Roger

    1987-01-01

    Suggests ways in which hens' egg vitelline membranes can be used to demonstrate cell traction effects. Reviews procedures for using and culturing the membranes and identifies topic areas for student projects. (ML)

  18. Direct liquid-feed fuel cell with membrane electrolyte and manufacturing thereof

    NASA Technical Reports Server (NTRS)

    Narayanan, Sekharipuram (Inventor); Surampudi, Subbarao (Inventor); Halpert, Gerald (Inventor)

    1999-01-01

    An improved direct liquid-feed fuel cell having a solid membrane electrolyte for electrochemical reactions of an organic fuel. Improvements in interfacing of the catalyst layer and the membrane and activating catalyst materials are disclosed.

  19. Molecular modeling of membrane responses to the adsorption of rotating nanoparticles: promoted cell uptake and mechanical membrane rupture.

    PubMed

    Yue, Tongtao; Zhang, Xianren; Huang, Fang

    2015-01-21

    Recently, a unique dynamic magnetic field was developed to induce the rotational movement of superparamagnetic iron oxide nanoparticles. This technique has been applied to remotely control both cellular internalization and apoptosis. Therefore, a thorough understanding of how a lipid membrane responds to the introduction of rotating NPs is quite important to promote the applications of this technique in a variety of biomedical area. Here, we performed Dissipative Particle Dynamics (DPD) simulations to systematically investigate the interaction mechanism between lipid membranes and rotating NPs. Two kinds of membrane responses are observed. One is the promoted cell uptake and the other is the mechanical membrane rupture. The promoting effect of NP rotation on the cell uptake is ascribed to the enhanced membrane monolayer protrusion, which can wrap the NP from the top side. Meanwhile, the rotating NP exerts a shearing force on the membrane. Accordingly, the membrane undergoes a local distortion around the NP. If the shearing force exceeds a critical value, the local membrane distortion develops into a mechanical rupture. A number of factors, like NP size, NP shape, ligand density and rotation speed, are critical in both of the above membrane responses. PMID:25388826

  20. Nanocomposite membranes based on polybenzimidazole and ZrO2 for high-temperature proton exchange membrane fuel cells.

    PubMed

    Nawn, Graeme; Pace, Giuseppe; Lavina, Sandra; Vezzù, Keti; Negro, Enrico; Bertasi, Federico; Polizzi, Stefano; Di Noto, Vito

    2015-04-24

    Owing to the numerous benefits obtained when operating proton exchange membrane fuel cells at elevated temperature (>100?°C), the development of thermally stable proton exchange membranes that demonstrate conductivity under anhydrous conditions remains a significant goal for fuel cell technology. This paper presents composite membranes consisting of poly[2,2'-(m-phenylene)-5,5'-bibenzimidazole] (PBI4N) impregnated with a ZrO2 nanofiller of varying content (ranging from 0 to 22?wt?%). The structure-property relationships of the acid-doped and undoped composite membranes have been studied using thermogravimetric analysis, differential scanning calorimetry, dynamic mechanical analysis, wide-angle X-ray scattering, infrared spectroscopy, and broadband electrical spectroscopy. Results indicate that the level of nanofiller has a significant effect on the membrane properties. From 0 to 8?wt?%, the acid uptake as well as the thermal and mechanical properties of the membrane increase. As the nanofiller level is increased from 8 to 22?wt?% the opposite effect is observed. At 185?°C, the ionic conductivity of [PBI4N(ZrO2 )0.231 ](H3 PO4 )13 is found to be 1.04×10(-1) ?S?cm(-1) . This renders membranes of this type promising candidates for use in high-temperature proton exchange membrane fuel cells. PMID:25801848

  1. Antigenic Properties of the Cell Wall and Other Fractions of the Yeast Form of Histoplasma capsulatum

    PubMed Central

    Pine, Leo; Boone, Clarence J.; McLaughlin, Dave

    1966-01-01

    Pine, Leo (Communicable Disease Center, Atlanta, Ga.), Clarence J. Boone, and Dave McLaughlin. Antigenic properties of the cell wall and other fractions of the yeast form of Histoplasma capsulatum. J. Bacteriol. 91:2158–2168. 1966.—Yeast-form cells of Histoplasma capsulatum were fractionated in an attempt to obtain complement-fixing antigens with greater specificity than those of the currently used whole yeast form. No specific fraction was isolated. Rupture of the whole cell produced soluble and insoluble highly antigenic fractions. The soluble fractions rapidly lost antigenicity. Marked reduction of activity of some particulate fractions was also observed. The purified cell wall, stripped of its protein components, was antigenic, relatively stable, and demonstrated low cross-reactivity with heterologous sera. All fractions cross-reacted with sera from cases of North American blastomycosis to a greater degree than did the whole yeast-form antigen of H. capsulatum. The production of certain cellular fractions varied with the strains used. In complement-fixation tests, insignificant differences in specificity and antigenicity were found with whole-cell antigens from 13 H. capsulatum strains as well as with purified cell wall fractions prepared from 2 of these strains. PMID:5943933

  2. Elastic thickness compressibilty of the red cell membrane.

    PubMed

    Heinrich, V; Ritchie, K; Mohandas, N; Evans, E

    2001-09-01

    We have used an ultrasensitive force probe and optical interferometry to examine the thickness compressibility of the red cell membrane in situ. Pushed into the centers of washed-white red cell ghosts lying on a coverglass, the height of the microsphere-probe tip relative to its closest approach on the adjacent glass surface revealed the apparent material thickness, which began at approximately 90 nm per membrane upon detection of contact (force approximately 1-2 pN). With further impingement, the apparent thickness per membrane diminished over a soft compliant regime that spanned approximately 40 nm and stiffened on approach to approximately 50 nm under forces of approximately 100 pN. The same force-thickness response was obtained on recompression after retraction of the probe, which demonstrated elastic recoverability. Scaled by circumferences of the microspheres, the forces yielded energies of compression per area which exhibited an inverse distance dependence resembling that expected for flexible polymers. Attributed to the spectrin component of the membrane cytoskeleton, the energy density only reached one thermal energy unit (k(B)T) per spectrin tetramer near maximum compression. Hence, we hypothesized that the soft compliant regime probed in the experiments represented the compressibility of the outer region of spectrin loops and that the stiff regime < 50 nm was the response of a compact mesh of spectrin backed by a hardcore structure. To evaluate this hypothesis, we used a random flight theory for the entropic elasticity of polymer loops to model the spectrin network. We also examined the possibility that additional steric repulsion and apparent thickening could arise from membrane thermal-bending excitations. Fixing the energy scale to k(B)T/spectrin tetramer, the combined elastic response of a network of ideal polymer loops plus the membrane steric interaction correlated well with the measured dependence of energy density on distance for a statistical segment length of approximately 5 nm for spectrin (i.e., free chain end-to-end length of approximately 29 nm) and a hardcore limit of approximately 30 nm for underlying structure. PMID:11509359

  3. High temperature polymers for proton exchange membrane fuel cells

    NASA Astrophysics Data System (ADS)

    Einsla, Brian Russel

    Novel proton exchange membranes (PEMs) were investigated that show potential for operating at higher temperatures in both direct methanol (DMFC) and H 2/air PEM fuel cells. The need for thermally stable polymers immediately suggests the possibility of heterocyclic polymers bearing appropriate ion conducting sites. Accordingly, monomers and random disulfonated poly(arylene ether) copolymers containing either naphthalimide, benzoxazole or benzimidazole moieties were synthesized via direct copolymerization. The ion exchange capacity (IEC) was varied by simply changing the ratio of disulfonated monomer to nonsulfonated monomer in the copolymerization step. Water uptake and proton conductivity of cast membranes increased with IEC. The water uptake of these heterocyclic copolymers was lower than that of comparable disulfonated poly(arylene ether) systems, which is a desirable improvement for PEMs. Membrane electrode assemblies were prepared and the initial fuel cell performance of the disulfonated polyimide and polybenzoxazole (PBO) copolymers was very promising at 80°C compared to the state-of-the-art PEM (NafionRTM); nevertheless these membranes became brittle under operating conditions. Several series of poly(arylene ether)s based on disodium-3,3'-disulfonate-4,4 '-dichlorodiphenylsulfone (S-DCDPS) and a benzimidazole-containing bisphenol were synthesized and afforded copolymers with enhanced stability. Selected properties of these membranes were compared to separately prepared miscible blends of disulfonated poly(arylene ether sulfone) copolymers and polybenzimidazole (PBI). Complexation of the sulfonic acid groups with the PBI structure reduced water swelling and proton conductivity. The enhanced proton conductivity of NafionRTM membranes has been proposed to be due to the aggregation of the highly acidic side-chain sulfonic acid sites to form ion channels. A series of side-chain sulfonated poly(arylene ether sulfone) copolymers based on methoxyhydroquinone was synthesized in order to investigate this possible advantage and to couple this with the excellent hydrolytic stability of poly(arylene ether)s. The methoxy groups were deprotected to afford reactive phenolic sites and nucleophilic substitution reactions with functional aryl sulfonates were used to prepare simple aryl or highly acidic fluorinated sulfonated copolymers. The proton conductivity and water sorption of the resulting copolymers increased with the ion exchange capacity, but changing the acidity of the sulfonic acid had no apparent effect.

  4. Characteristics of Subfreezing Operation of Polymer Electrolyte Membrane Fuel Cells

    NASA Astrophysics Data System (ADS)

    Mishler, Jeffrey Harris

    Polymer Electrolyte Membrane (PEM) Fuel Cells are capable of high efficiency operation, and are free of NOx, SOx, and CO2 emissions when using hydrogen fuel, and ideally suited for use in transportation applications due to their high power density and low operating temperatures. However, under subfreezing conditions which may be encountered during winter seasons in some areas, product water will freeze within the membrane, cathode side catalyst layer and gas diffusion media, leading to voltage loss and operation failure. Experiments were undertaken in order to characterize the amount and location of water during fuel cell operation. First, in-situ neutron radiography was undertaken on the fuel cells at a normal operating temperature for various operating current densities, inlet relative humidities, and diffusion media hydrophobicities. It was found that more hydrophobic cathode microporous layer (MPL) or hydrophilic anode MPL may result in a larger amount of water transporting back to the anode. The water profiles along the channels were measured and the point of liquid water emergence, where two phase flow begins, was compared to previous models. Secondly, under subfreezing temperatures, neutron imaging showed that water ice product accumulates because of lack of a water removal mechanism. Water was observed under both the lands and channels, and increased almost linearly with time. It is found that most ice exists in the cathode side. With evidence from experimental observation, a cold start model was developed and explained, following existing approaches in the literature. Three stages of cold start are explained: membrane saturation, ice storage in catalyst layer pores, and then ice melting. The voltage losses due to temperature change, increased transport resistance, and reduced electrochemical surface area. The ionic conductivity of the membrane at subfreezing temperatures was modeled. Voltage evolution over time for isothermal cold starts was predicted and validated against experimental data. The ice coverage coefficient was shown to be a key variable in matching with experimental data. From model analysis, it appears that the coulombs of charge passed before operation failure is an important parameter characterizing PEM fuel cell cold start. To investigate the coulombs of charge and its determining factors, PEM fuel cells were constructed to measure the effects of membrane configuration (thickness and initial state), catalyst layer configuration (thickness and ionomer-carbon ratio), current density, and temperature on the quantity. It was found that subfreezing temperature, ionomer-catalyst ratio, and catalyst-layer thickness significantly affect the amount of charge transferred before operational failure, whereas the membrane thickness and initial hydration level have limited effect for the considered cases. In addition, degradation of the catalyst layer was observed and quantified. These results improve the fundamental understanding of characteristics of subfreezing operation and thus are valuable for automobile applications of PEM fuel cells. The model directly relates the material properties to voltage loss, and predicts voltage evolution, thus providing a way for material optimization and diagnostics. Additionally, insights into component design and operating conditions can be used to better optimize the fuel cell for cold start-up of the vehicle.

  5. Ionic Liquids and New Proton Exchange Membranes for Fuel Cells

    NASA Technical Reports Server (NTRS)

    Belieres, Jean-Philippe

    2004-01-01

    There is currently a great surge of activity in fuel cell research as laboratories across the world seek to take advantage of the high energy capacity provided by &el cells relative to those of other portable electrochemical power systems. Much of this activity is aimed at high temperature fie1 cells, and a vital component of such &el cells must be the availability of a high temperature stable proton-permeable membrane. NASA Glenn Research Center is greatly involved in developing this technology. Other approaches to the high temperature fuel cell involve the use of single- component or almost-single-component electrolytes that provide a path for protons through the cell. A heavily researched case is the phosphoric acid fuel cell, in which the electrolyte is almost pure phosphoric acid and the cathode reaction produces water directly. The phosphoric acid fie1 cell delivers an open circuit voltage of 0.9 V falling to about 0.7 V under operating conditions at 170 C. The proton transport mechanism is mainly vehicular in character according to the viscosity/conductance relation. Here we describe some Proton Transfer Ionic Liquids (PTILs) with low vapor pressure and high temperature stability that have conductivities of unprecedented magnitude for non-aqueous systems. The first requirement of an ionic liquid is that, contrary to experience with most liquids consisting of ions, it must have a melting point that is not much above room temperature. The limit commonly suggested is 100 C. PTILs constitute an interesting class of non-corrosive proton-exchange electrolyte, which can serve well in high temperature (T = 100 - 250 C) fuel cell applications. We will present cell performance data showing that the open circuit voltage output, and the performance of a simple H2(g)Pt/PTIL/Pt/O2(g) fuel cell may be superior to those of the equivalent phosphoric acid electrolyte fuel cell both at ambient temperature and temperatures up to and above 200 C. My work at NASA Glenn Research Center during this summer is to develop and characterize proton exchange membranes doped with ionic liquids. The main techniques used to characterize these materials are: Impedance Spectroscopy, NMR, DSC, TGA, DMA, IR, and SEM ...

  6. Membrane-Dependent Bystander Effect Contributes to Amplification of the Response to Alpha-Particle Irradiation in Targeted and Nontargeted Cells

    SciTech Connect

    Hanot, Maite; Hoarau, Jim; Carriere, Marie; Angulo, Jaime F.; Khodja, Hicham

    2009-11-15

    Purpose: Free radicals are believed to play an active role in the bystander response. This study investigated their origin as well as their temporal and spatial impacts in the bystander effect. Methods and Materials: We employed a precise alpha-particle microbeam to target a small fraction of subconfluent osteoblastic cells (MC3T3-E1). gammaH2AX-53BP1 foci, oxidative metabolism changes, and micronuclei induction in targeted and bystander cells were assessed. Results: Cellular membranes and mitochondria were identified as two distinct reactive oxygen species producers. The global oxidative stress observed after irradiation was significantly attenuated after cells were treated with filipin, evidence for the primal role of membrane in the bystander effect. To determine the membrane's impact at a cellular level, micronuclei yield was measured when various fractions of the cell population were individually targeted while the dose per cell remained constant. Induction of micronuclei increased in bystander cells as well as in targeted cells and was attenuated by filipin treatment, demonstrating a role for bystander signals between irradiated cells in an autocrine/paracrine manner. Conclusions: A complex interaction of direct irradiation and bystander signals leads to a membrane-dependent amplification of cell responses that could influence therapeutic outcomes in tissues exposed to low doses or to environmental exposure.

  7. Percolation in a Proton Exchange Membrane Fuel Cell Catalyst Layer

    SciTech Connect

    Stacy, Stephen; Allen, Jeffrey

    2012-07-01

    Water management in the catalyst layers of proton exchange membrane fuel cells (PEMFC) is confronted by two issues, flooding and dry out, both of which result in improper functioning of the fuel cell and lead to poor performance and degradation. At the present time, the data that has been reported about water percolation and wettability within a fuel cell catalyst layer is limited. A method and apparatus for measuring the percolation pressure in the catalyst layer has been developed based upon an experimental apparatus used to test water percolation in porous transport layers (PTL). The experimental setup uses a pseudo Hele-Shaw type testing where samples are compressed and a fluid is injected into the sample. Testing the samples gives percolation pressure plots which show trends in increasing percolation pressure with an increase in flow rate. A decrease in pressure was seen as percolation occurred in one sample, however the pressure only had a rising effect in the other sample.

  8. Cell Labeling via Membrane-Anchored Lipophilic MR Contrast Agents

    PubMed Central

    2015-01-01

    Cell tracking in vivo with MR imaging requires the development of contrast agents with increased sensitivity that effectively label and are retained by cells. Most clinically approved Gd(III)-based contrast agents require high incubation concentrations and prolonged incubation times for cellular internalization. Strategies to increase contrast agent permeability have included conjugating Gd(III) complexes to cell penetrating peptides, nanoparticles, and small molecules which have greatly improved cell labeling but have not resulted in improved cellular retention. To overcome these challenges, we have synthesized a series of lipophilic Gd(III)-based MR contrast agents that label cell membranes in vitro. Two of the agents were synthesized with a multiplexing strategy to contain three Gd(III) chelates (1 and 2) while the third contains a single Gd(III) chelate (3). These new agents exhibit significantly enhanced labeling and retention in HeLa and MDA-MB-231-mcherry cells compared to agents that are internalized by cells (4 and Prohance). PMID:24787689

  9. Chimerism of buccal membrane cells in a monochorionic dizygotic twin.

    PubMed

    Fumoto, Seiko; Hosoi, Kenichiro; Ohnishi, Hiroaki; Hoshina, Hiroaki; Yan, Kunimasa; Saji, Hiroh; Oka, Akira

    2014-04-01

    No monochorionic dizygotic twins (MCDZTs) with cellular chimerism involving cells other than blood cells have been reported in the literature to date. Here we report a probable first case of MCDZTs with buccal cell chimerism. A 32-year-old woman conceived twins by in vitro fertilization by using 2 cryopreserved blastocysts that were transferred into her uterus. An ultrasound scan at 8 weeks' gestation showed signs indicative of monochorionic twins. A healthy boy and a healthy girl were born, showing no sexual ambiguity. Cytogenetic analyses and microsatellite studies demonstrated chimerism in blood cells of both twins. Notably, repeated fluorescence in situ hybridization and microsatellite studies revealed chimerism in buccal cells obtained from 1 of the twins. Although the mechanism through which buccal cell chimerism was generated remains to be elucidated, ectopic differentiation of chimeric hematopoietic cells that migrated to the buccal membrane or the cellular transfer between the 2 embryos at the early stage of development might be responsible for the phenomenon. This hypothesis raises an interesting issue regarding embryonic development and cellular differentiation into organs during fetal development. Given the possibility of cryptic chimerism in various organs including gonadal tissues in MCDZTs, close observation will be required to determine whether complications develop in the course of the patients' growth. PMID:24685957

  10. Inhibition by Methylphenidate of Transport Across the Yeast Cell Membrane

    PubMed Central

    Spoerl, Edward; Doyle, R. J.

    1968-01-01

    The influence of methylphenidate on glycolysis in yeast cells was studied to describe more fully the nature of the reactions in which this drug participates. CO2 production and O2 uptake of yeast cells was inhibited 75% by a 10 mm concentration of the compound. This effect, with glucose as a substrate, occurred at pH 7.0, but not at pH 4.5. Kinetic data indicated that the reaction was noncompetitive and complex; the methylphenidate effect on CO2 production could not readily be reversed. Glycolysis by cell-free extracts was not inhibited at the 10-mm concentration, but was affected at 100 mm. Utilization of O2 with maltose and ethyl alcohol as substrates also was reduced. Entry into the cells of a number of different carbohydrates and of glycine was inhibited to different degrees. The loss from suspended cells of materials absorbing at 280 nm was reduced, and the efflux of sorbose, arabinose, and lactose was decreased. Thus, transport into and out of the cells was inhibited and leakage, or permeability, was reduced. It is hypothesized that methylphenidate reacts with a cell membrane constituent, or constituents, and inhibits glycolysis by blocking sugar passage. PMID:5732507

  11. Inhibition by methylphenidate of transport across the yeast cell membrane.

    PubMed

    Spoerl, E; Doyle, R J

    1968-09-01

    The influence of methylphenidate on glycolysis in yeast cells was studied to describe more fully the nature of the reactions in which this drug participates. CO(2) production and O(2) uptake of yeast cells was inhibited 75% by a 10 mm concentration of the compound. This effect, with glucose as a substrate, occurred at pH 7.0, but not at pH 4.5. Kinetic data indicated that the reaction was noncompetitive and complex; the methylphenidate effect on CO(2) production could not readily be reversed. Glycolysis by cell-free extracts was not inhibited at the 10-mm concentration, but was affected at 100 mm. Utilization of O(2) with maltose and ethyl alcohol as substrates also was reduced. Entry into the cells of a number of different carbohydrates and of glycine was inhibited to different degrees. The loss from suspended cells of materials absorbing at 280 nm was reduced, and the efflux of sorbose, arabinose, and lactose was decreased. Thus, transport into and out of the cells was inhibited and leakage, or permeability, was reduced. It is hypothesized that methylphenidate reacts with a cell membrane constituent, or constituents, and inhibits glycolysis by blocking sugar passage. PMID:5732507

  12. Cooperative binding of Annexin A5 to phosphatidylserine on apoptotic cell membranes

    NASA Astrophysics Data System (ADS)

    Janko, Christina; Jeremic, Ivica; Biermann, Mona; Chaurio, Ricardo; Schorn, Christine; Muñoz, Luis E.; Herrmann, Martin

    2013-12-01

    Healthy cells exhibit an asymmetric plasma membrane with phosphatidylserine (PS) located on the cytoplasmic leaflet of the plasma membrane bilayer. Annexin A5-FITC, a PS binding protein, is commonly used to evaluate apoptosis in flow cytometry. PS exposed by apoptotic cells serves as a major ‘eat-me’ signal for phagocytes. Although exposition of PS has been observed after alternative stimuli, no clearance of viable, PS exposing cells has been detected. Thus, besides PS exposure, membranes of viable and apoptotic cells might exhibit specific characteristics. Here, we show that Annexin A5 binds in a cooperative manner to different types of dead cells. Shrunken apoptotic cells thereby showed the highest Hill coefficient values. Contrarily, parafomaldehyde fixation of apoptotic cells completely abrogates the cooperativity effect seen with dead and dying cells. We tend to speculate that the cooperative binding of Annexin A5 to the membranes of apoptotic cells reflects higher fluidity of the exposed membranes facilitating PS clustering.

  13. Quantitative analysis of the lipidomes of the influenza virus envelope and MDCK cell apical membrane

    PubMed Central

    Gerl, Mathias J.; Sampaio, Julio L.; Urban, Severino; Kalvodova, Lucie; Verbavatz, Jean-Marc; Binnington, Beth; Lindemann, Dirk; Lingwood, Clifford A.; Shevchenko, Andrej; Schroeder, Cornelia

    2012-01-01

    The influenza virus (IFV) acquires its envelope by budding from host cell plasma membranes. Using quantitative shotgun mass spectrometry, we determined the lipidomes of the host Madin–Darby canine kidney cell, its apical membrane, and the IFV budding from it. We found the apical membrane to be enriched in sphingolipids (SPs) and cholesterol, whereas glycerophospholipids were reduced, and storage lipids were depleted compared with the whole-cell membranes. The virus membrane exhibited a further enrichment of SPs and cholesterol compared with the donor membrane at the expense of phosphatidylcholines. Our data are consistent with and extend existing models of membrane raft-based biogenesis of the apical membrane and IFV envelope. PMID:22249292

  14. The Effect of Platinum Electrocatalyst on Membrane Degradation in Polymer Electrolyte Fuel Cells.

    PubMed

    Bodner, Merit; Cermenek, Bernd; Rami, Mija; Hacker, Viktor

    2015-01-01

    Membrane degradation is a severe factor limiting the lifetime of polymer electrolyte fuel cells. Therefore, obtaining a deeper knowledge is fundamental in order to establish fuel cells as competitive product. A segmented single cell was operated under open circuit voltage with alternating relative humidity. The influence of the catalyst layer on membrane degradation was evaluated by measuring a membrane without electrodes and a membrane-electrode-assembly under identical conditions. After 100 h of accelerated stress testing the proton conductivity of membrane samples near the anode and cathode was investigated by means of ex situ electrochemical impedance spectroscopy. The membrane sample near the cathode inlet exhibited twofold lower membrane resistance and a resulting twofold higher proton conductivity than the membrane sample near the anode inlet. The results from the fluoride ion analysis have shown that the presence of platinum reduces the fluoride emission rate; which supports conclusions drawn from the literature. PMID:26670258

  15. Isolation and characterization of membranes from a hydrocarbon-oxidizing Acinetobacter sp.

    PubMed Central

    Scott, C C; Makula, S R; Finnerty, W R

    1976-01-01

    Membranes were isolated and purified from nutrient broth-yeast extract- and hexadecane-grown cells of Acinetobacter sp. strain HO1-N. Two membrane fractions were isolated from nutrient broth-yeast extract-grown cells, the cytoplasmic membrane and the outer membrane. In addition to these two membrane fractions, a unique membrane fraction was isolated from hexadecane-grown cells (band 1) and characterized as a lipid-rich, low-density membrane containing high concentrations of hexadecane. The outer membrane preparations of Acinetobacter, obtained from nutrient broth-yeast extract- and hexadecane-grown cells, exhibited a low ratio of lipid phosphorus to protein and contained phospholipase activity and 2-keto-3-deoxyoctulosonic acid. Phosphatidic acid cytidyltransferase, adenosine triphosphatase, and reduced nicotinamide adenine dinucleotide oxidase were recovered almost exclusively in the cytoplasmic membrane fractions. The cytoplasmic membrane fractions contained 20 to 25 polypeptide species on sodium dodecyl sulfate-polyacrylamide gels, and the outer membrane fractions contained 15 to 20 polypeptide species. A major polypeptide species with an apparent molecular weight of approximately 42,000 to 44,000 was found for all outer membrane fractions. The buoyant densities of the cytoplasmic membrane fractions and the outer membrane fractions were closely similar, necessitating their separation by differential centrifugation. Band 1 of hexadecane-grown cells had a ratio of lipid phosphorus to protein that was almost twice that of cytoplasmic membrane and a correspondingly low buoyant density (1.086 g/cm3). Enzyme activities associated with band 1 were identical to those associated with the cytoplasmic membrane. The electrophoretic banding pattern of band 1 was essentially identical to the banding pattern of the cytoplasmic membrane. The phospholipid and neutral lipid compositions of the isolated membrane fractions were determined as qualitatively similar, with significant quantitative differences. The ultrastructure characteristics of the respective membrane fractions were examined by the negative-stain technique. Images PMID:132429

  16. Structural and functional changes in the membrane and membrane skeleton of red blood cells induced by peroxynitrite.

    PubMed

    Starodubtseva, Maria N; Tattersall, Amanda L; Kuznetsova, Tatyana G; Yegorenkov, Nicolai I; Ellory, J Clive

    2008-08-01

    The changes in passive ion permeability of the red blood cell membrane after peroxynitrite action (3 microM-3 mM) have been studied by biophysical (using radioisotopes of rubidium, sodium and sulphur (sulphate)) and electrophysiological methods. The enhancement of passive membrane permeability to cations (potassium and sodium ions) and the inhibition of anion flux through the anion exchanger in peroxynitrite-treated red blood cells were revealed. In patch-clamp experiments the whole-cell conductance after peroxynitrite (80 microM) treatment of red blood cells increased 3-3.5-fold with a shift in the reversal potential from -7.0+/-1.5 mV to -4.3+/-0.9 mV (n=7, p=0.005). The addition of cobalt and nickel ions to red blood cell suspensions before peroxynitrite treatment had no effect on the peroxynitrite-induced cation flux but zinc ions in the same condition decreased cation flux about 2-fold. Using atomic force microscopy methods we revealed an increase in red blood cell membrane stiffness and the membrane skeleton complexity after peroxynitrite action. We conclude that the peroxynitrite-induced water and ion imbalance and reorganization in membrane structure lead to crenation of red blood cells. PMID:18339585

  17. Effective Temperature of Red Blood Cell Membrane Fluctuations

    E-print Network

    Eyal Ben-Isaac; YongKeun Park; Gabriel Popescu; Frank L. H. Brown; Nir S. Gov; Yair Shokef

    2011-05-04

    Biologically driven non-equilibrium fluctuations are often characterized by their non-Gaussianity or by an "effective temperature", which is frequency dependent and higher than the ambient temperature. We address these two measures theoretically by examining a randomly kicked "particle", with a variable number of kicking "motors", and show how these two indicators of non-equilibrium behavior can contradict. Our results are compared with new experiments on shape fluctuations of red-blood cell membranes, and demonstrate how the physical nature of the motors in this system can be revealed using these global measures of non-equilibrium.

  18. Effective Temperature of Red Blood Cell Membrane Fluctuations

    E-print Network

    Ben-Isaac, Eyal; Popescu, Gabriel; Brown, Frank L H; Gov, Nir S; Shokef, Yair

    2011-01-01

    Biologically driven non-equilibrium fluctuations are often characterized by their non-Gaussianity or by an "effective temperature", which is frequency dependent and higher than the ambient temperature. We address these two measures theoretically by examining a randomly kicked "particle", with a variable number of kicking "motors". We show how these two indicators of non-equilibrium behavior can contradict. We compare our results with new experiments on shape fluctuations of red-blood cell membranes, for which these two indicators were independently measured.

  19. 2011 Alkaline Membrane Fuel Cell Workshop Final Report

    SciTech Connect

    Pivovar, B.

    2012-02-01

    A workshop addressing the current state-of-the-art in alkaline membrane fuel cells (AMFCs) was held May 8-9, 2011, at the Crystal Gateway Marriott in Arlington, Virginia. This workshop was the second of its kind, with the first being held December 11-13, 2006, in Phoenix, Arizona. The 2011 workshop and associated workshop report were created to assess the current state of AMFC technology (taking into account recent advances), investigate the performance potential of AMFC systems across all possible power ranges and applications, and identify the key research needs for commercial competitiveness in a variety of areas.

  20. Grafted polyelectrolyte membranes for lithium batteries and fuel cells

    SciTech Connect

    Kerr, John B.

    2003-06-24

    Polyelectrolyte materials have been developed for lithium battery systems in response to the severe problems due to salt concentration gradients that occur in composite electrodes (aka membrane-electrode assemblies). Comb branch polymer architectures are described which allow for grafting of appropriate anions on to the polymer and also for cross-linking to provide for appropriate mechanical properties. The interactions of the polymers with the electrode surfaces are critical for the performance of the system and some of the structural features that influence this will be described. Parallels with the fuel cell MEA structures exist and will also be discussed.

  1. Engineered cell instructive matrices for fetal membrane healing.

    PubMed

    Kivelio, A; Ochsenbein-Koelble, N; Zimmermann, R; Ehrbar, M

    2015-03-01

    Iatrogenic preterm prelabour rupture of fetal membranes (iPPROM) occurs in 6-45% of the cases after fetoscopic procedures, posing a significant threat to fetal survival and well-being. The number of diagnostic and therapeutic prenatal interventions available is increasing, thus developing treatment options for iPPROM is becoming more important than ever before. Fetal membranes exhibit very restricted regeneration and little is known about factors which might modulate their healing potential, rendering various materials and strategies to seal or heal fetal membranes pursued over the past decades relatively fruitless. Additionally, biocompatible materials with tunable in vivo stability and mechanical and biological properties have not been available. Using poly(ethylene glycol)-based biomimetic matrices, we provide evidence that, upon presentation of appropriate biological cues in three dimensions, mesenchymal progenitor cells from the amnion can be mobilized, induced to proliferate and supported in maintaining their native extracellular matrix production, thus creating a suitable environment for healing to take place. These data suggest that engineering materials with defined mechanical and biochemical properties and the ability to present migration- and proliferation-inducing factors, such as platelet-derived growth factor, basic fibroblast growth factor or epidermal growth factor, could be key in resolving the clinical problem of iPPROM and allowing the field of fetal surgery to move forward. PMID:25536031

  2. Structural transition of actin filament in a cell-sized water droplet with a phospholipid membrane

    NASA Astrophysics Data System (ADS)

    Hase, M.; Yoshikawa, K.

    2006-03-01

    Actin filament, F-actin, is a semiflexible polymer with a negative charge, and is one of the main constituents of cell membranes. To clarify the effect of cross talk between a phospholipid membrane and actin filaments in cells, we conducted microscopic observations on the structural changes in actin filaments in a cell-sized (several tens of micrometers in diameter) water droplet coated with a phospholipid membrane such as phosphatidylserine (PS; negatively charged head group) or phosphatidylethanolamine (PE; neutral head group) as a simple model of a living cell membrane. With PS, actin filaments are distributed uniformly in the water phase without adsorption onto the membrane surface between 2 and 6mM Mg2+, while between 6 and 12mM Mg2+, actin filaments are adsorbed onto the inner membrane surface. With PE, the actin filaments are uniformly adsorbed onto the inner membrane surface between 2 and 12mM Mg2+. With both PS and PE membranes, at Mg2+ concentrations higher than 12mM, thick bundles are formed in the bulk water droplet accompanied by the dissolution of actin filaments from the membrane surface. The attraction between actin filaments and membrane is attributable to an increase in the translational entropy of counterions accompanied by the adsorption of actin filaments onto the membrane surface. These results suggest that a microscopic water droplet coated with phospholipid can serve as an easy-to-handle model of cell membranes.

  3. Fusion of Legionella pneumophila outer membrane vesicles with eukaryotic membrane systems is a mechanism to deliver pathogen factors to host cell membranes.

    PubMed

    Jäger, Jens; Keese, Susanne; Roessle, Manfred; Steinert, Michael; Schromm, Andra B

    2015-05-01

    The formation and release of outer membrane vesicles (OMVs) is a phenomenon observed in many bacteria, including Legionella pneumophila. During infection, this human pathogen primarily invades alveolar macrophages and replicates within a unique membrane-bound compartment termed Legionella-containing vacuole. In the current study, we analysed the membrane architecture of L.?pneumophila?OMVs by small-angle X-ray scattering and biophysically characterized OMV membranes. We investigated the interaction of L.?pneumophila?OMVs with model membranes by Förster resonance energy transfer and Fourier transform infrared spectroscopy. These experiments demonstrated the incorporation of OMV membrane material into liposomes composed of different eukaryotic phospholipids, revealing an endogenous property of OMVs to fuse with eukaryotic membranes. Cellular co-incubation experiments showed a dose- and time-dependent binding of fluorophore-labelled OMVs to macrophages. Trypan blue quenching experiments disclosed a rapid internalization of OMVs into macrophages at 37 and 4 °C. Purified OMVs induced tumour necrosis factor-? production in human macrophages at concentrations starting at 300?ng?ml(-1). Experiments on HEK293-TLR2 and TLR4/MD-2 cell lines demonstrated a dominance of TLR2-dependent signalling pathways. In summary, we demonstrate binding, internalization and biological activity of L.?pneumophila?OMVs on human macrophages. Our data support OMV membrane fusion as a mechanism for the remote delivery of virulence factors to host cells. PMID:25363599

  4. Ethambutol-induced toxicity is mediated by zinc and lysosomal membrane permeabilization in cultured retinal cells

    SciTech Connect

    Chung, Hyewon; Yoon, Young Hee; Hwang, Jung Jin; Cho, Kyung Sook; Koh, Jae Young; Kim, June-Gone

    2009-03-01

    Ethambutol, an efficacious antituberculosis agent, can cause irreversible visual loss in a small but significant fraction of patients. However, the mechanism of ocular toxicity remains to be established. We previously reported that ethambutol caused severe vacuole formation in cultured retinal cells, and that the addition of zinc along with ethambutol aggravated vacuole formation whereas addition of the cell-permeable zinc chelator, N,N,N',N'-tetrakis (2-pyridylmethyl) ethylenediamine (TPEN), reduced vacuole formation. To investigate the origin of vacuoles and to obtain an understanding of drug toxicity, we used cultured primary retinal cells from newborn Sprague-Dawley rats and imaged ethambutol-treated cells stained with FluoZin-3, zinc-specific fluorescent dye, under a confocal microscope. Almost all ethambutol-induced vacuoles contained high levels of labile zinc. Double staining with LysoTracker or MitoTracker revealed that almost all zinc-containing vacuoles were lysosomes and not mitochondria. Intracellular zinc chelation with TPEN markedly blocked both vacuole formation and zinc accumulation in the vacuole. Immunocytochemistry with antibodies to lysosomal-associated membrane protein-2 (LAMP-2) and cathepsin D, an acid lysosomal hydrolase, disclosed lysosomal activation after exposure to ethambutol. Immunoblotting after 12 h exposure to ethambutol showed that cathepsin D was released into the cytosol. In addition, cathepsin inhibitors attenuated retinal cell toxicity induced by ethambutol. This is consistent with characteristics of lysosomal membrane permeabilization (LMP). TPEN also inhibited both lysosomal activation and LMP. Thus, accumulation of zinc in lysosomes, and eventual LMP, may be a key mechanism of ethambutol-induced retinal cell death.

  5. Bioenergetic coupling between membrane transport systems and biosynthetic pathways essential for cell cycle progression

    SciTech Connect

    Leister, K.J.; Cutry, A.F.; Wenner, C.E.

    1986-05-01

    Recently, it has been shown that there exists a point in the cell cycle (approximately 2 h prior to S phase entry) when (Na/sup +//K/sup +/)ATPase pump activity is no longer needed for progression through the cycle. These data suggests that pump activity is critical in the biosynthetic processes which enables the cell to proceed through the G/sub 1/ phase. A scheme is proposed which is currently being tested that (Na/sup +//K/sup +/)ATPase pump activity serves as the driving force in the regulation of other membrane transport processes critical for cell proliferation. For example, in post-confluent quiescent C3H-10T1/2 fibroblasts, when (K/sup +/)/sub o/ is lowered just below the K/sub m/ of the pump for K/sup +/ there is a 10-fold increase in /sup 3/H-uridine uptake into both acid soluble and insoluble cell fractions. By modulation of the pump in this manner, glucose utilization is enhanced whereas inhibition of the pump by ouabain suppresses glucose utilization. In both methods of affecting the pump, /sup 3/H-leucine incorporation is inhibited. Electron acceptors that influence the redox state of the cell have been shown to both stimulate or inhibit cell cycle progression. Under conditions where (K/sup +/)/sub o/ is lowered, the nucleoside uptake responses observed were modified by electron acceptors depending on the ability to oxidize NAD(P)H directly or to interact with a cytochrome-like component, (e.g. phenazine methosulfate) reversed the enhanced uridine uptake and p-phenylene diamine further enhanced the uridine uptake response. These findings suggest that a plasma membrane redox system (presumably cyt-c like) is linked to nucleoside transport which is subject to (Na/sup +//K/sup +/)ATPase activity.

  6. Investigation of transient phenomena of proton exchange membrane fuel cells

    NASA Astrophysics Data System (ADS)

    Songprakorp, Roongrojana

    The research presented in this thesis is a contribution to the modeling and understanding of the dynamic behavior of proton exchange membrane fuel cells (PEMFCs). A time-dependent, two-phase non-isothermal model of the membrane electrode assembly was developed and implemented using the finite element method. In addition to solving a phenomenological transport equation for water in the membrane, the model takes into consideration the non-equilibrium water sorption to better capture some of the dynamic characteristics of water transport in the MEA. Mass transfer using Fickian diffusion is implemented in the model. Two different models describing the electrochemical reactions in the catalyst layer including a macro-homogeneous model and an agglomerate model, are also implemented. Conservation of energy is included in the solution procedure in order to assess the impact of thermal effects on the dynamics of the transport in the MEA. For the purpose of model and concept validation, the model was first solved in a steady two-dimensional mode for a through-plane computational domain using a commercial software package, COMSOL Multiphysics version 3.2b. The impact of using a single- and two-phase modeling approaches was evaluated, and the predicted current-voltage performance characteristic are found in good agreement with the experimental data available in the literature. In addition, the developed model was benchmarked against a finite element-based in-house code for further validation and to evaluate numerical accuracy and computational performance. Transient simulations of operation under dynamic voltage sweeps are presented, and parametric studies are conducted to investigate the impact of various model, operation and transport properties on the predicted dynamic cell performance. In particular, the rate of load change, the difference in water content between the anode and cathode, and the water sorptions rate are shown to have significant impact on cell performance in unsteady operation, especially at higher current densities. Parametric studies also address the sensitivity of the model results to physical properties, highlighting the importance of accurately determining certain physical properties of the fuel cell components. Finally, the application of the model to air-breathing fuel cells provides further insight into the dynamic performance characteristic of such type of fuel cells.

  7. Computational modeling and optimization of proton exchange membrane fuel cells

    NASA Astrophysics Data System (ADS)

    Secanell Gallart, Marc

    Improvements in performance, reliability and durability as well as reductions in production costs, remain critical prerequisites for the commercialization of proton exchange membrane fuel cells. In this thesis, a computational framework for fuel cell analysis and optimization is presented as an innovative alternative to the time consuming trial-and-error process currently used for fuel cell design. The framework is based on a two-dimensional through-the-channel isothermal, isobaric and single phase membrane electrode assembly (MEA) model. The model input parameters are the manufacturing parameters used to build the MEA: platinum loading, platinum to carbon ratio, electrolyte content and gas diffusion layer porosity. The governing equations of the fuel cell model are solved using Netwon's algorithm and an adaptive finite element method in order to achieve quadratic convergence and a mesh independent solution respectively. The analysis module is used to solve two optimization problems: (i) maximize performance; and, (ii) maximize performance while minimizing the production cost of the MEA. To solve these problems a gradient-based optimization algorithm is used in conjunction with analytical sensitivities. The presented computational framework is the first attempt in the literature to combine highly efficient analysis and optimization methods to perform optimization in order to tackle large-scale problems. The framework presented is capable of solving a complete MEA optimization problem with state-of-the-art electrode models in approximately 30 minutes. The optimization results show that it is possible to achieve Pt-specific power density for the optimized MEAs of 0.422 gPt/kW. This value is extremely close to the target of 0.4 gPt/kW for large-scale implementation and demonstrate the potential of using numerical optimization for fuel cell design.

  8. Enrichment of putative stem cells from adipose tissue using dielectrophoretic field-flow fractionation.

    PubMed

    Vykoukal, Jody; Vykoukal, Daynene M; Freyberg, Susanne; Alt, Eckhard U; Gascoyne, Peter R C

    2008-08-01

    We have applied the microfluidic cell separation method of dielectrophoretic field-flow fractionation (DEP-FFF) to the enrichment of a putative stem cell population from an enzyme-digested adipose tissue derived cell suspension. A DEP-FFF separator device was constructed using a novel microfluidic-microelectronic hybrid flex-circuit fabrication approach that is scaleable and anticipates future low-cost volume manufacturing. We report the separation of a nucleated cell fraction from cell debris and the bulk of the erythrocyte population, with the relatively rare (<2% starting concentration) NG2-positive cell population (pericytes and/or putative progenitor cells) being enriched up to 14-fold. This work demonstrates a potential clinical application for DEP-FFF and further establishes the utility of the method for achieving label-free fractionation of cell subpopulations. PMID:18651083

  9. A critical review of cooling techniques in proton exchange membrane fuel cell stacks

    E-print Network

    Kandlikar, Satish

    Review A critical review of cooling techniques in proton exchange membrane fuel cell stacks November 2011 Keywords: Proton exchange membrane fuel cell PEMFC Stacks Heat generation Cooling Review a b fuel cell (PEMFC) stacks with high power. The narrow range of operating temperature and the small

  10. Growth of Pt nanoparticle for proton-exchange-membrane fuel cells by

    E-print Network

    PEMFC Growth of Pt nanoparticle for proton-exchange-membrane fuel cells at anode side of a polymer electrolyte membrane (PEM) fuel cell. With a Pt loading of 25 g-Pt/cm2 , current of the electrochemical test result and fuel cell performance agree with each other. Key word : Pulsed laser deposition

  11. Research Paper New uorescent probes for the measurement of cell membrane

    E-print Network

    Theodorakis, Emmanuel

    viscosity in cultured cells. Commercially available rotors, however, stain not only the cell membrane- nyl)-julolidine (DCVJ), which featured hydrocarbon chains of different length to increase membrane of diseases, such as atherosclerosis [6], cell malig- nancy [7], hypercholesterolemia [8] and diabetes [9

  12. Establishment of endogenous human tympanic membrane-derived somatic stem cells for stem cell therapy.

    PubMed

    Choi, Mi Young; Park, Kyoung Ho

    2014-09-01

    We examined whether somatic stem cells (SSCs) exist in human tympanis membrane (hTM) and whether they could be differentiated into neural lineage cells. The hTM-SSCs could generate neurospheres, which could differentiate into specific neural linage cells under specific differentiation conditions. Also, we conducted another experiment that led to differentiation into neurospheres and neuronal lineage cells, which occurred independent of each other. Independent of each other condition, hTM-SSCs could differentiate into neurospheres, and subsequently, into neuronal lineage cells. However, NS-NR neural differentiation rates are higher than independent of each other culture system. PMID:24771506

  13. Thermoase-Derived Flaxseed Protein Hydrolysates and Membrane Ultrafiltration Peptide Fractions Have Systolic Blood Pressure-Lowering Effects in Spontaneously Hypertensive Rats

    PubMed Central

    Nwachukwu, Ifeanyi D.; Girgih, Abraham T.; Malomo, Sunday A.; Onuh, John O.; Aluko, Rotimi E.

    2014-01-01

    Thermoase-digested flaxseed protein hydrolysate (FPH) samples and ultrafiltration membrane-separated peptide fractions were initially evaluated for in vitro inhibition of angiotensin I-converting enzyme (ACE) and renin activities. The two most active FPH samples and their corresponding peptide fractions were subsequently tested for in vivo antihypertensive activity in spontaneously hypertensive rats (SHR). The FPH produced with 3% thermoase digestion showed the highest ACE- and renin-inhibitory activities. Whereas membrane ultrafiltration resulted in significant (p < 0.05) increases in ACE inhibition by the <1 and 1–3 kDa peptides, only a marginal improvement in renin-inhibitory activity was observed for virtually all the samples after membrane ultrafiltration. The FPH samples and membrane fractions were also effective in lowering systolic blood pressure (SBP) in SHR with the largest effect occurring after oral administration (200 mg/kg body weight) of the 1–3 kDa peptide fraction of the 2.5% FPH and the 3–5 kDa fraction of the 3% FPH. Such potent SBP-lowering capacity indicates the potential of flaxseed protein-derived bioactive peptides as ingredients for the formulation of antihypertensive functional foods and nutraceuticals. PMID:25302619

  14. DRAM Triggers Lysosomal Membrane Permeabilization and Cell Death in CD4+ T Cells Infected with HIV

    PubMed Central

    Laforge, Mireille; Limou, Sophie; Harper, Francis; Casartelli, Nicoletta; Rodrigues, Vasco; Silvestre, Ricardo; Haloui, Houda; Zagury, Jean-Francois; Senik, Anna; Estaquier, Jerome

    2013-01-01

    Productive HIV infection of CD4+ T cells leads to a caspase-independent cell death pathway associated with lysosomal membrane permeabilization (LMP) and cathepsin release, resulting in mitochondrial outer membrane permeabilization (MOMP). Herein, we demonstrate that HIV infection induces damage-regulated autophagy modulator (DRAM) expression in a p53-dependent manner. Knocking down the expression of DRAM and p53 genes with specific siRNAs inhibited autophagy and LMP. However, inhibition of Atg5 and Beclin genes that prevents autophagy had a minor effect on LMP and cell death. The knock down of DRAM gene inhibited cytochrome C release, MOMP and cell death. However, knocking down DRAM, we increased viral infection and production. Our study shows for the first time the involvement of DRAM in host-pathogen interactions, which may represent a mechanism of defense via the elimination of infected cells. PMID:23658518

  15. Circulating cell membrane microparticles transfer heme to endothelial cells and trigger vasoocclusions in sickle cell disease

    PubMed Central

    Camus, Stéphane M.; De Moraes, João A.; Bonnin, Philippe; Abbyad, Paul; Le Jeune, Sylvain; Lionnet, François; Loufrani, Laurent; Grimaud, Linda; Lambry, Jean-Christophe; Charue, Dominique; Kiger, Laurent; Renard, Jean-Marie; Larroque, Claire; Le Clésiau, Hervé; Tedgui, Alain; Bruneval, Patrick; Barja-Fidalgo, Christina; Alexandrou, Antigoni; Tharaux, Pierre-Louis; Boulanger, Chantal M.

    2015-01-01

    Intravascular hemolysis describes the relocalization of heme and hemoglobin (Hb) from erythrocytes to plasma. We investigated the concept that erythrocyte membrane microparticles (MPs) concentrate cell-free heme in human hemolytic diseases, and that heme-laden MPs have a physiopathological impact. Up to one-third of cell-free heme in plasma from 47 patients with sickle cell disease (SCD) was sequestered in circulating MPs. Erythrocyte vesiculation in vitro produced MPs loaded with heme. In silico analysis predicted that externalized phosphatidylserine (PS) in MPs may associate with and help retain heme at the cell surface. Immunohistology identified Hb-laden MPs adherent to capillary endothelium in kidney biopsies from hyperalbuminuric SCD patients. In addition, heme-laden erythrocyte MPs adhered and transferred heme to cultured endothelial cells, inducing oxidative stress and apoptosis. In transgenic SAD mice, infusion of heme-laden MPs triggered rapid vasoocclusions in kidneys and compromised microvascular dilation ex vivo. These vascular effects were largely blocked by heme-scavenging hemopexin and by the PS antagonist annexin-a5, in vitro and in vivo. Adversely remodeled MPs carrying heme may thus be a source of oxidant stress for the endothelium, linking hemolysis to vascular injury. This pathway might provide new targets for the therapeutic preservation of vascular function in SCD. PMID:25827830

  16. Cell-Culture Reactor Having a Porous Organic Polymer Membrane

    NASA Technical Reports Server (NTRS)

    Koontz, Steven L. (Inventor)

    2000-01-01

    A method for making a biocompatible polymer article using a uniform atomic oxygen treatment is disclosed. The substrate may be subsequently optionally grated with a compatibilizing compound. Compatibilizing compounds may include proteins, phosphory1choline groups, platelet adhesion preventing polymers, albumin adhesion promoters, and the like. The compatibilized substrate may also have a living cell layer adhered thereto. The atomic oxygen is preferably produced by a flowing afterglow microwave discharge, wherein the substrate resides in a sidearm out of the plasma. Also, methods for culturing cells for various purposes using the various membranes are disclosed as well. Also disclosed are porous organic polymers having a distributed pore chemistry (DPC) comprising hydrophilic and hydrophobic regions, and a method for making the DPC by exposing the polymer to atomic oxygen wherein the rate of hydrophilization is greater than the rate of mass loss.

  17. Infectious rotavirus enters cells by direct cell membrane penetration, not by endocytosis

    SciTech Connect

    Kaljot, K.T.; Shaw, R.D.; Greenberg, H.B. Palo Alto Veterans Administration Medical Center, CA ); Rubin, D.H. )

    1988-04-01

    Rotaviruses are icosahedral viruses with a segmented, double-stranded RNA genome. They are the major cause of severe infantile infectious diarrhea. Rotavirus growth in tissue culture is markedly enhanced by pretreatment of virus with trypsin. Trypsin activation is associated with cleavage of the viral hemagglutinin (viral protein 3 (VP3); 88 kilodaltons) into two fragments (60 and 28 kilodaltons). The mechanism by which proteolytic cleavage leads to enhanced growth is unknown. To determine whether trypsin treatment affected rotavirus internalization, the authors studied the kinetics of entry of infectious rhesus rotavirus (RRV) into MA104 cells. Trypsin-activated RRV was internalized with a half-time of 3 to 5 min, while nonactivated virus disappeared from the cell surface with a half-time of 30 to 50 min. In contrast to trypsin-activated RRV, loss of nonactivated RRV from the cell surface did not result in the appearance of infection, as measured by plaque formation. Purified trypsin-activated RRV added to cell monolayers at pH 7.4 mediated {sup 51}Cr, ({sup 14}C)choline, and ({sup 3}H)inositol released from prelabeled MA104 cells. This release could be specifically blocked by neutralizing antibodies to VP3. These results suggest that MA104 cell infection follows the rapid entry of trypsin-activated RRV by direct cell membrane penetration. Cell membrane penetration of infectious RRV is initiated by trypsin cleavage of VP3. Neutralizing antibodies can inhibit this direct membrane penetration.

  18. Association rates of membrane-coupled cell adhesion molecules.

    PubMed

    Bihr, Timo; Fenz, Susanne; Sackmann, Erich; Merkel, Rudolf; Seifert, Udo; Sengupta, Kheya; Smith, Ana-Sun?ana

    2014-12-01

    Thus far, understanding how the confined cellular environment affects the lifetime of bonds, as well as the extraction of complexation rates, has been a major challenge in studies of cell adhesion. Based on a theoretical description of the growth curves of adhesion domains, we present a new (to our knowledge) method to measure the association rate k(on) of ligand-receptor pairs incorporated into lipid membranes. As a proof of principle, we apply this method to several systems. We find that the k(on) for the interaction of biotin with neutravidin is larger than that for integrin binding to RGD or sialyl Lewis(x) to E-selectin. Furthermore, we find k(on) to be enhanced by membrane fluctuations that increase the probability for encounters between the binders. The opposite effect on k(on) could be attributed to the presence of repulsive polymers that mimic the glycocalyx, which points to two potential mechanisms for controlling the speed of protein complexation during the cell recognition process. PMID:25468354

  19. Direct deposit of catalyst on the membrane of direct feed fuel cells

    NASA Technical Reports Server (NTRS)

    Chun, William (Inventor); Narayanan, Sekharipuram R. (Inventor); Jeffries-Nakamura, Barbara (Inventor); Valdez, Thomas I. (Inventor); Linke, Juergen (Inventor)

    2001-01-01

    An improved direct liquid-feed fuel cell having a solid membrane electrolyte for electrochemical reactions of an organic fuel. Catalyst utilization and catalyst/membrane interface improvements are disclosed. Specifically, the catalyst layer is applied directly onto the membrane electrolyte.

  20. Microfluidic characterization of specific membrane capacitance and cytoplasm conductivity of single cells

    E-print Network

    Sun, Yu

    Microfluidic characterization of specific membrane capacitance and cytoplasm conductivity of single membrane capacitance and cytoplasm conductivity) characterization at a speed of 5­10 cells/s (vs. minutes the impedance data and to determine the specific membrane capacitance and cytoplasm conductivity of individual

  1. DEVELOPMENT OF NOVEL ELECTROCATALYSTS FOR PROTON EXCHANGE MEMBRANE FUEL CELLS

    SciTech Connect

    Shamsuddin Ilias

    2002-06-11

    The Proton Exchange Membrane Fuel Cell (PEMFC) is one of the most promising power sources for stand-alone utility and electric vehicle applications. Platinum (Pt) Catalyst is used for both fuel and air electrodes in PEMFCs. However, carbon monoxide (CO) contamination of H{sub 2} greatly affects electro catalysts used at the anode of PEMFCs and decreases cell performance. The irreversible poisoning of the anode can occur even in CO concentrations as low as few parts per million (ppm). In this work, we have synthesized several novel elctrocatalysts (Pt/C, Pt/Ru/C, Pt/Mo/C, Pt/Ir and Pt/Ru/Mo) for PEMFCs. These catalysts have been tested for CO tolerance in the H{sub 2}/air fuel cell, using CO concentrations in the H{sub 2} fuel that varies from 10 to 100 ppm. The performance of the electrodes was evaluated by determining the cell potential against current density. The effects of catalyst composition and electrode film preparation method on the performance of PEM fuel cell were also studied. It was found that at 70 C and 3.5 atm pressure at the cathode, Pt-alloy catalyst (10 wt% Pt/Ru/C, 20 wt% Pt/Mo/C) were more CO tolerant than the 20 wt% Pt/C catalyst alone. It was also observed that spraying method was better than the brushing technique for the preparation of electrode film.

  2. The oncolytic peptide LTX-315 kills cancer cells through Bax/Bak-regulated mitochondrial membrane permeabilization.

    PubMed

    Zhou, Heng; Forveille, Sabrina; Sauvat, Allan; Sica, Valentina; Izzo, Valentina; Durand, Sylvère; Müller, Kevin; Liu, Peng; Zitvogel, Laurence; Rekdal, Øystein; Kepp, Oliver; Kroemer, Guido

    2015-09-29

    LTX-315 has been developed as an amphipathic cationic peptide that kills cancer cells. Here, we investigated the putative involvement of mitochondria in the cytotoxic action of LTX-315. Subcellular fractionation of LTX-315-treated cells, followed by mass spectrometric quantification, revealed that the agent was enriched in mitochondria. LTX-315 caused an immediate arrest of mitochondrial respiration without any major uncoupling effect. Accordingly, LTX-315 disrupted the mitochondrial network, dissipated the mitochondrial inner transmembrane potential, and caused the release of mitochondrial intermembrane proteins into the cytosol. LTX-315 was relatively inefficient in stimulating mitophagy. Cells lacking the two pro-apoptotic multidomain proteins from the BCL-2 family, BAX and BAK, were less susceptible to LTX-315-mediated killing. Moreover, cells engineered to lose their mitochondria (by transfection with Parkin combined with treatment with a protonophore causing mitophagy) were relatively resistant against LTX-315, underscoring the importance of this organelle for LTX-315-mediated cytotoxicity. Altogether, these results support the notion that LTX-315 kills cancer cells by virtue of its capacity to permeabilize mitochondrial membranes. PMID:26378049

  3. Porous polybenzimidazole membranes with excellent chemical stability and ion conductivity for direct borohydride fuel cells

    NASA Astrophysics Data System (ADS)

    Chen, Dongju; Yu, Shanshan; Liu, Xue; Li, Xianfeng

    2015-05-01

    Porous membranes based on polybenzimidazole (PBI) are firstly introduced in direct borohydride fuel cell application (DBFC). Membranes with different thicknesses and porosity are successfully fabricated via water vapor phase inversion process. The prepared membranes show excellent ion conductivity and chemical stability under DBFC operating condition. Compare with Nafion 115, the prepared membranes show higher ion conductivity, as a result, much higher peak power density. No weight loss is observed after immersing the prepared membranes in a 3 M NaOH solution for 30 days, indicating the excellent chemical stability of porous PBI membranes. And the DBFC cells assembled with prepared membranes could discharge at 200 mA cm-2 for more than 250 h without voltage decay, which is the longest time reported by far. This work provides a totally new idea for fabricating versatile DBFC membranes.

  4. Sensory transduction at the frog semicircular canal: how hair cell membrane potential controls junctional transmission

    PubMed Central

    Martini, Marta; Canella, Rita; Rubbini, Gemma; Fesce, Riccardo; Rossi, Maria Lisa

    2015-01-01

    At the frog semicircular canals, the afferent fibers display high spontaneous activity (mEPSPs), due to transmitter release from hair cells. mEPSP and spike frequencies are modulated by stimulation that activates the hair cell receptor conductance. The relation between receptor current and transmitter release cannot be studied at the intact semicircular canal. To circumvent the problem, we combined patch-clamp recordings at the isolated hair cell and electrophysiological recordings at the cytoneural junction in the intact preparation. At isolated hair cells, the K channel blocker tetraethylammonium (TEA) is shown to block a fraction of total voltage-dependent K-conductance (IKD) that depends on TEA concentration but not on membrane potential (Vm). Considering the bioelectric properties of the hair cell, as previously characterized by this lab, a fixed fractional block of IKD is shown to induce a relatively fixed shift in Vm, provided it lies in the range ?30 to ?10 mV. The same concentrations of TEA were applied to the intact labyrinth while recording from single afferent fibers of the posterior canal, at rest and during mechanical stimulation. At the peak of stimulation, TEA produced increases in mEPSP rate that were linearly related to the shifts produced by the same TEA concentrations (0.1–3 mM) in hair cell Vm (0.7–5 mV), with a slope of 29.8 Hz/mV. The membrane potential of the hair cell is not linearly related to receptor conductance, so that the slope of quantal release vs. receptor conductance depends on the prevailing Vm (19.8 Hz/nS at ?20 mV; 11 Hz/nS at ?10 mV). Changes in mEPSP peak size were negligible at rest as well as during stimulation. Since ample spatial summation of mEPSPs occurs at the afferent terminal and threshold-governed spike firing is intrinsically nonlinear, the observed increases in mEPSP frequency, though not very large, may suffice to trigger afferent spike discharge. PMID:26157360

  5. Sensory transduction at the frog semicircular canal: how hair cell membrane potential controls junctional transmission.

    PubMed

    Martini, Marta; Canella, Rita; Rubbini, Gemma; Fesce, Riccardo; Rossi, Maria Lisa

    2015-01-01

    At the frog semicircular canals, the afferent fibers display high spontaneous activity (mEPSPs), due to transmitter release from hair cells. mEPSP and spike frequencies are modulated by stimulation that activates the hair cell receptor conductance. The relation between receptor current and transmitter release cannot be studied at the intact semicircular canal. To circumvent the problem, we combined patch-clamp recordings at the isolated hair cell and electrophysiological recordings at the cytoneural junction in the intact preparation. At isolated hair cells, the K channel blocker tetraethylammonium (TEA) is shown to block a fraction of total voltage-dependent K-conductance (IKD) that depends on TEA concentration but not on membrane potential (V m). Considering the bioelectric properties of the hair cell, as previously characterized by this lab, a fixed fractional block of IKD is shown to induce a relatively fixed shift in V m, provided it lies in the range -30 to -10 mV. The same concentrations of TEA were applied to the intact labyrinth while recording from single afferent fibers of the posterior canal, at rest and during mechanical stimulation. At the peak of stimulation, TEA produced increases in mEPSP rate that were linearly related to the shifts produced by the same TEA concentrations (0.1-3 mM) in hair cell V m (0.7-5 mV), with a slope of 29.8 Hz/mV. The membrane potential of the hair cell is not linearly related to receptor conductance, so that the slope of quantal release vs. receptor conductance depends on the prevailing V m (19.8 Hz/nS at -20 mV; 11 Hz/nS at -10 mV). Changes in mEPSP peak size were negligible at rest as well as during stimulation. Since ample spatial summation of mEPSPs occurs at the afferent terminal and threshold-governed spike firing is intrinsically nonlinear, the observed increases in mEPSP frequency, though not very large, may suffice to trigger afferent spike discharge. PMID:26157360

  6. Fhit Delocalizes Annexin A4 from Plasma Membrane to Cytosol and Sensitizes Lung Cancer Cells to Paclitaxel

    PubMed Central

    Gaudio, Eugenio; Paduano, Francesco; Spizzo, Riccardo; Ngankeu, Apollinaire; Zanesi, Nicola; Gaspari, Marco; Ortuso, Francesco; Lovat, Francesca; Rock, Jonathan; Hill, Grace A.; Kaou, Mohamed; Cuda, Giovanni; Aqeilan, Rami I.; Alcaro, Stefano; Croce, Carlo M.; Trapasso, Francesco

    2013-01-01

    Fhit protein is lost or reduced in a large fraction of human tumors, and its restoration triggers apoptosis and suppresses tumor formation or progression in preclinical models. Here, we describe the identification of candidate Fhit-interacting proteins with cytosolic and plasma membrane localization. Among these, Annexin 4 (ANXA4) was validated by co-immunoprecipitation and confocal microscopy as a partner of this novel Fhit protein complex. Here we report that overexpression of Fhit prevents Annexin A4 translocation from cytosol to plasma membrane in A549 lung cancer cells treated with paclitaxel. Moreover, paclitaxel administration in combination with AdFHIT acts synergistically to increase the apoptotic rate of tumor cells both in vitro and in vivo experiments. PMID:24223161

  7. Disentangling Membrane Dynamics and Cell Migration; Differential Influences of F-actin and Cell-Matrix Adhesions

    PubMed Central

    Kowalewski, Jacob M.; Shafqat-Abbasi, Hamdah; Jafari-Mamaghani, Mehrdad; Endrias Ganebo, Bereket; Gong, Xiaowei

    2015-01-01

    Cell migration is heavily interconnected with plasma membrane protrusion and retraction (collectively termed “membrane dynamics”). This makes it difficult to distinguish regulatory mechanisms that differentially influence migration and membrane dynamics. Yet such distinctions may be valuable given evidence that cancer cell invasion in 3D may be better predicted by 2D membrane dynamics than by 2D cell migration, implying a degree of functional independence between these processes. Here, we applied multi-scale single cell imaging and a systematic statistical approach to disentangle regulatory associations underlying either migration or membrane dynamics. This revealed preferential correlations between membrane dynamics and F-actin features, contrasting with an enrichment of links between cell migration and adhesion complex properties. These correlative linkages were often non-linear and therefore context-dependent, strengthening or weakening with spontaneous heterogeneity in cell behavior. More broadly, we observed that slow moving cells tend to increase in area, while fast moving cells tend to shrink, and that the size of dynamic membrane domains is independent of cell area. Overall, we define macromolecular features preferentially associated with either cell migration or membrane dynamics, enabling more specific interrogation and targeting of these processes in future. PMID:26248038

  8. In situ single molecule imaging of cell membranes: linking basic nanotechniques to cell biology, immunology and medicine

    NASA Astrophysics Data System (ADS)

    Pi, Jiang; Jin, Hua; Yang, Fen; Chen, Zheng W.; Cai, Jiye

    2014-10-01

    The cell membrane, which consists of a viscous phospholipid bilayer, different kinds of proteins and various nano/micrometer-sized domains, plays a very important role in ensuring the stability of the intracellular environment and the order of cellular signal transductions. Exploring the precise cell membrane structure and detailed functions of the biomolecules in a cell membrane would be helpful to understand the underlying mechanisms involved in cell membrane signal transductions, which could further benefit research into cell biology, immunology and medicine. The detection of membrane biomolecules at the single molecule level can provide some subtle information about the molecular structure and the functions of the cell membrane. In particular, information obtained about the molecular mechanisms and other information at the single molecule level are significantly different from that detected from a large amount of biomolecules at the large-scale through traditional techniques, and can thus provide a novel perspective for the study of cell membrane structures and functions. However, the precise investigations of membrane biomolecules prompts researchers to explore cell membranes at the single molecule level by the use of in situ imaging methods, as the exact conformation and functions of biomolecules are highly controlled by the native cellular environment. Recently, the in situ single molecule imaging of cell membranes has attracted increasing attention from cell biologists and immunologists. The size of biomolecules and their clusters on the cell surface are set at the nanoscale, which makes it mandatory to use high- and super-resolution imaging techniques to realize the in situ single molecule imaging of cell membranes. In the past few decades, some amazing imaging techniques and instruments with super resolution have been widely developed for molecule imaging, which can also be further employed for the in situ single molecule imaging of cell membranes. In this review, we attempt to summarize the characteristics of these advanced techniques for use in the in situ single molecule imaging of cell membranes. We believe that this work will help to promote the technological and methodological developments of super-resolution techniques for the single molecule imaging of cell membranes and help researchers better understand which technique is most suitable for their future exploring of membrane biomolecules; ultimately promoting further developments in cell biology, immunology and medicine.

  9. Hyperthermic potentiation of cisplatin by magnetic nanoparticle heaters is correlated with an increase in cell membrane fluidity.

    PubMed

    Alvarez-Berríos, Merlis P; Castillo, Amalchi; Mendéz, Janet; Soto, Orlando; Rinaldi, Carlos; Torres-Lugo, Madeline

    2013-01-01

    Magnetic fluid hyperthermia as a cancer treatment method is an attractive alternative to other forms of hyperthermia. It is based on the heat released by magnetic nanoparticles subjected to an alternating magnetic field. Recent studies have shown that magnetic fluid hyperthermia-treated cells respond significantly better to chemotherapeutic treatment compared with cells treated with hot water hyperthermia under the same temperature conditions. We hypothesized that this synergistic effect is due to an additional stress on the cellular membrane, independent of the thermal heat dose effect that is induced by nanoparticles exposed to an alternating magnetic field. This would result in an increase in Cis-diammine-dichloroplatinum (II) (cDDP, cisplatin) uptake via passive transport. To test this hypothesis, we exposed cDDP-treated cells to extracellular copper in order to hinder the human cell copper transporter (hCTR1)-mediated active transport of cDDP. This, in turn, can increase the passive transport of the drug through the cell membrane. Our results did not show statistically significant differences in surviving fractions for cells treated concomitantly with magnetic fluid hyperthermia and cDDP, in the presence or absence of copper. Nonetheless, significant copper-dependent variations in cell survival were observed for samples treated with combined cDDP and hot water hyperthermia. These results correlated with platinum uptake studies, which showed that cells treated with magnetic fluid hyperthermia had higher platinum uptake than cells treated with hot water hyperthermia. Changes in membrane fluidity were tested through fluorescence anisotropy measurements using trimethylamine-diphenylhexatriene. Additional uptake studies were conducted with acridine orange and measured by flow cytometry. These studies indicated that magnetic fluid hyperthermia significantly increases cell membrane fluidity relative to hot water hyperthermia and untreated cells, and hence this could be a factor contributing to the increase of cDDP uptake in magnetic fluid hyperthermia-treated cells. Overall, our data provide convincing evidence that cell membrane permeability induced by magnetic fluid hyperthermia is significantly greater than that induced by hot water hyperthermia under similar temperature conditions, and is at least one of the mechanisms responsible for potentiation of cDDP by magnetic fluid hyperthermia in Caco-2 cells. PMID:23493492

  10. Water-Free Proton-Conducting Membranes for Fuel Cells

    NASA Technical Reports Server (NTRS)

    Narayanan, Sekharipuram; Yen, Shiao-Pin

    2007-01-01

    Poly-4-vinylpyridinebisulfate (P4VPBS) is a polymeric salt that has shown promise as a water-free proton-conducting material (solid electrolyte) suitable for use in membrane/electrode assemblies in fuel cells. Heretofore, proton-conducting membranes in fuel cells have been made from perfluorinated ionomers that cannot conduct protons in the absence of water and, consequently, cannot function at temperatures >100 C. In addition, the stability of perfluorinated ionomers at temperatures >100 C is questionable. However, the performances of fuel cells of the power systems of which they are parts could be improved if operating temperatures could be raised above 140 C. What is needed to make this possible is a solid-electrolyte material, such as P4VPBS, that can be cast into membranes and that both retains proton conductivity and remains stable in the desired higher operating temperature range. A family of solid-electrolyte materials different from P4VPBS was described in Anhydrous Proton-Conducting Membranes for Fuel Cells (NPO-30493), NASA Tech Briefs, Vol. 29, No. 8 (August 2005), page 48. Those materials notably include polymeric quaternized amine salts. If molecules of such a polymeric salt could be endowed with flexible chain structures, it would be possible to overcome the deficiencies of simple organic amine salts that must melt before being able to conduct protons. However, no polymeric quaternized amine salts have yet shown to be useful in this respect. The present solid electrolyte is made by quaternizing the linear polymer poly- 4-vinylpyridine (P4VP) to obtain P4VPBS. It is important to start with P4VP having a molecular weight of 160,000 daltons because P4VPBS made from lower-molecular-weight P4VP yields brittle membranes. In an experimental synthesis, P4VP was dissolved in methanol and then reacted with an excess of sulfuric acid to precipitate P4VPBS. The precipitate was recovered, washed several times with methanol to remove traces of acid, and dried to a white granular solid. In another synthesis, nanoparticles of silica rich with surface hydroxyl groups were added to P4VP in methanol solution, which was then reacted with excess sulfuric acid to precipitate granules of a composite that most probably had the composition (P4VPBS)-SiO2-SiO(HSO4)2. The granular P4VPBS produced in the first-mentioned synthesis was dissolved in water to make a glue-like, turbid solution; the granular P4VPBS/silica composite produced in the second-mentioned synthesis was mixed with water to make a turbid, glue-like suspension. The proportions of polymer salt to water in such preparations can be varied; it was found that approximately equal parts of water and polymer salt yield a solution or suspension amenable to further processing.

  11. Volume Fractions and Surface Areas for 3-D Grid Cells Cut by an Dongyung Kim,1

    E-print Network

    New York at Stoney Brook, State University of

    . Consider a cell with n edge crossing points, each one belonging to a distinct edge. 2 #12;Definition I.1, and that crosses the cell edges exactly at the n given edge crossing points. Definition I.2 An interface surfaceVolume Fractions and Surface Areas for 3-D Grid Cells Cut by an Interface Dongyung Kim,1 Jean N

  12. DEVELOPMENT OF NOVEL ELECTROCATALYSTS FOR PROTON EXCHANGE MEMBRANE FUEL CELLS

    SciTech Connect

    Shamsuddin Ilias

    2003-04-24

    Fuel cells are electrochemical devices that convert the available chemical free energy directly into electrical energy, without going through heat exchange process. Of all different types of fuel cells, the Proton Exchange Membrane Fuel Cell (PEMFC) is one of the most promising power sources for stand-alone utility and electric vehicle applications. Platinum (Pt) Catalyst is used for both fuel and air electrodes in PEMFCs. However, carbon monoxide (CO) contamination of H{sub 2} greatly affects electro catalysts used at the anode of PEMFCs and decreases cell performance. The irreversible poisoning of the anode can occur even in CO concentrations as low as few parts per million (ppm). In this work, we have synthesized several novel elctrocatalysts (Pt/C, Pt/Ru/C, Pt/Mo/C, Pt/Ir and Pt/Ru/Mo) for PEMFCs. These catalysts have been tested for CO tolerance in the H{sub 2}/air fuel cell, using CO concentrations in the H{sub 2} fuel that varies from 10 to 100 ppm. The performance of the electrodes was evaluated by determining the cell potential against current density. The effects of catalyst composition and electrode film preparation method on the performance of PEM fuel cell were also studied. It was found that at 70 C and 3.5 atm pressure at the cathode, Pt-alloy catalyst (10 wt% Pt/Ru/C, 20 wt% Pt/Mo/C) were more CO tolerant than the 20 wt% Pt/C catalyst alone. It was also observed that spraying method was better than the brushing technique for the preparation of electrode film.

  13. Pfaffosidic Fraction from Hebanthe paniculata Induces Cell Cycle Arrest and Caspase-3-Induced Apoptosis in HepG2 Cells

    PubMed Central

    da Silva, Tereza Cristina; Cogliati, Bruno; Latorre, Andréia Oliveira; Akisue, Gokithi; Nagamine, Márcia Kazumi; Haraguchi, Mitsue; Hansen, Daiane; Sanches, Daniel Soares; Dagli, Maria Lúcia Zaidan

    2015-01-01

    Hebanthe paniculata roots (formerly Pfaffia paniculata and popularly known as Brazilian ginseng) show antineoplastic, chemopreventive, and antiproliferative properties. Functional properties of these roots and their extracts are usually attributed to the pfaffosidic fraction, which is composed mainly by pfaffosides A–F. However, the therapeutic potential of this fraction in cancer cells is not yet entirely understood. This study aimed to analyze the antitumoral effects of the purified pfaffosidic fraction or saponinic fraction on the human hepatocellular carcinoma HepG2 cell line. Cellular viability, proliferation, and apoptosis were evaluated, respectively, by MTT assay, BrdU incorporation, activated caspase-3 immunocytochemistry, and DNA fragmentation assay. Cell cycle was analyzed by flow cytometry and the cell cycle-related proteins were analyzed by quantitative PCR and Western blot. The cells exposed to pfaffosidic fraction had reduced viability and cellular growth, induced G2/M at 48?h or S at 72?h arrest, and increased sub-G1 cell population via cyclin E downregulation, p27KIP1 overexpression, and caspase-3-induced apoptosis, without affecting the DNA integrity. Antitumoral effects of pfaffosidic fraction from H. paniculata in HepG2 cells originated by multimechanisms of action might be associated with cell cycle arrest in the S phase, by CDK2 and cyclin E downregulation and p27KIP1 overexpression, besides induction of apoptosis through caspase-3 activation. PMID:26075002

  14. Pfaffosidic Fraction from Hebanthe paniculata Induces Cell Cycle Arrest and Caspase-3-Induced Apoptosis in HepG2 Cells.

    PubMed

    da Silva, Tereza Cristina; Cogliati, Bruno; Latorre, Andréia Oliveira; Akisue, Gokithi; Nagamine, Márcia Kazumi; Haraguchi, Mitsue; Hansen, Daiane; Sanches, Daniel Soares; Dagli, Maria Lúcia Zaidan

    2015-01-01

    Hebanthe paniculata roots (formerly Pfaffia paniculata and popularly known as Brazilian ginseng) show antineoplastic, chemopreventive, and antiproliferative properties. Functional properties of these roots and their extracts are usually attributed to the pfaffosidic fraction, which is composed mainly by pfaffosides A-F. However, the therapeutic potential of this fraction in cancer cells is not yet entirely understood. This study aimed to analyze the antitumoral effects of the purified pfaffosidic fraction or saponinic fraction on the human hepatocellular carcinoma HepG2 cell line. Cellular viability, proliferation, and apoptosis were evaluated, respectively, by MTT assay, BrdU incorporation, activated caspase-3 immunocytochemistry, and DNA fragmentation assay. Cell cycle was analyzed by flow cytometry and the cell cycle-related proteins were analyzed by quantitative PCR and Western blot. The cells exposed to pfaffosidic fraction had reduced viability and cellular growth, induced G2/M at 48?h or S at 72?h arrest, and increased sub-G1 cell population via cyclin E downregulation, p27(KIP1) overexpression, and caspase-3-induced apoptosis, without affecting the DNA integrity. Antitumoral effects of pfaffosidic fraction from H. paniculata in HepG2 cells originated by multimechanisms of action might be associated with cell cycle arrest in the S phase, by CDK2 and cyclin E downregulation and p27(KIP1) overexpression, besides induction of apoptosis through caspase-3 activation. PMID:26075002

  15. A novel Bruch's membrane-mimetic electrospun substrate scaffold for human retinal pigment epithelium cells.

    PubMed

    Xiang, Ping; Wu, Kun-Chao; Zhu, Ying; Xiang, Lue; Li, Chong; Chen, Deng-Long; Chen, Feng; Xu, Guotong; Wang, Aijun; Li, Min; Jin, Zi-Bing

    2014-12-01

    Various artificial membranes have been used as scaffolds for retinal pigment epithelium cells (RPE) for monolayer reconstruction, however, long-term cell viability and functionality are still largely unknown. This study aimed to construct an ultrathin porous nanofibrous film to mimic Bruch's membrane, and in particular to investigate human RPE cell responses to the resultant substrates. An ultrathin porous nanofibrous membrane was fabricated by using regenerated wild Antheraea pernyi silk fibroin (RWSF), polycaprolactone (PCL) and gelatin (Gt) and displayed a thickness of 3-5 ?m, with a high porosity and an average fiber diameter of 166 ± 85 nm. Human RPE cells seeded on the RWSF/PCL/Gt membranes showed a higher cell growth rate (p < 0.05), and a typical expression pattern of RPE signature genes, with reduced expression of inflammatory mediators. With long-term cultivation on the substrates, RPE cells exhibited characteristic polygonal morphology and development of apical microvilli. Immunocytochemisty demonstrated RPE-specific expression profiles in cells after 12-weeks of co-culture on RWSF/PCL/Gt membranes. Interestingly, the cells on the RWSF/PCL/Gt membranes functionally secreted polarized PEDF and phagocytosed labeled porcine POS. Furthermore, RWSF/PCL/Gt membranes transplanted subsclerally exhibited excellent biocompatibility without any evidence of inflammation or rejection. In conclusion, we established a novel RWSF-based substrate for growth of RPE cells with excellent cytocompatibility in vitro and biocompatibility in vivo for potential use as a prosthetic Bruch's membrane for RPE transplantation. PMID:25220295

  16. Thylakoid Membrane Maturation and PSII Activation Are Linked in Greening Synechocystis sp. PCC 6803 Cells1

    PubMed Central

    Barthel, Sandra; Bernát, Gábor; Seidel, Tobias; Rupprecht, Eva; Kahmann, Uwe; Schneider, Dirk

    2013-01-01

    Thylakoid membranes are typical and essential features of both chloroplasts and cyanobacteria. While they are crucial for phototrophic growth of cyanobacterial cells, biogenesis of thylakoid membranes is not well understood yet. Dark-grown Synechocystis sp. PCC 6803 cells contain only rudimentary thylakoid membranes but still a relatively high amount of phycobilisomes, inactive photosystem II and active photosystem I centers. After shifting dark-grown Synechocystis sp. PCC 6803 cells into the light, “greening” of Synechocystis sp. PCC 6803 cells, i.e. thylakoid membrane formation and recovery of photosynthetic electron transport reactions, was monitored. Complete restoration of a typical thylakoid membrane system was observed within 24 hours after an initial lag phase of 6 to 8 hours. Furthermore, activation of photosystem II complexes and restoration of a functional photosynthetic electron transport chain appears to be linked to the biogenesis of organized thylakoid membrane pairs. PMID:23922268

  17. Ultrastructure and lipid composition of detergent-resistant membranes derived from mammalian sperm and two types of epithelial cells.

    PubMed

    van Gestel, Renske A; Brouwers, Jos F; Ultee, Anton; Helms, J Bernd; Gadella, Bart M

    2016-01-01

    Lipid rafts are micro-domains of ordered lipids (Lo phase) in biological membranes. The Lo phase of cellular membranes can be isolated from disordered lipids (Ld phase) after treatment with 1 % Triton? X-100 at 4 °C in which the Lo phase forms the detergent-resistant membrane (DRM) fraction. The lipid composition of DRM derived from Madin-Darby canine kidney (MDCK) cells, McArdle cells and porcine sperm is compared with that of the whole cell. Remarkably, the unsaturation and chain length degree of aliphatic chains attached to phospholipids is virtually the same between DRM and whole cells. Cholesterol and sphingomyelin were enriched in DRMs but to a cell-specific molar ratio. Sulfatides (sphingolipids from MDCK cells) were enriched in the DRM while a seminolipid (an alkylacylglycerolipid from sperm) was depleted from the DRM. Treatment with?<5 mM methyl-ß-cyclodextrin (MBCD) caused cholesterol removal from the DRM without affecting the composition and amount of the phospholipid while higher levels disrupted the DRM. The substantial amount of (poly)unsaturated phospholipids in DRMs as well as a low stoichiometric amount of cholesterol suggest that lipid rafts in biological membranes are more fluid and dynamic than previously anticipated. Using negative staining, ultrastructural features of DRM were monitored and in all three cell types the DRMs appeared as multi-lamellar vesicular structures with a similar morphology. The detergent resistance is a result of protein-cholesterol and sphingolipid interactions allowing a relatively passive attraction of phospholipids to maintain the Lo phase. For this special issue, the relevance of our findings is discussed in a sperm physiological context. PMID:26378009

  18. Quantitative Analysis of Surface Plasma Membrane Proteins of Primary and Metastatic Melanoma Cells

    PubMed Central

    Qiu, Haibo; Wang, Yinsheng

    2016-01-01

    Plasma membrane proteins play critical roles in cell-to-cell recognition, signal transduction and material transport. Because of their accessibility, membrane proteins constitute the major targets for protein-based drugs. Here, we described an approach, which included stable isotope labeling by amino acids in cell culture (SILAC), cell surface biotinylation, affinity peptide purification and LC-MS/MS for the identification and quantification of cell surface membrane proteins. We applied the strategy for the quantitative analysis of membrane proteins expressed by a pair of human melanoma cell lines, WM-115 and WM-266-4, which were derived initially from the primary and metastatic tumor sites of the same individual. We were able to identify more than 100 membrane and membrane-associated proteins from these two cell lines, including cell surface histones. We further confirmed the surface localization of histone H2B and three other proteins by immunocytochemical analysis with confocal microscopy. The contamination from cytoplasmic and other nonmembrane-related sources is greatly reduced by using cell surface biotinylation and affinity purification of biotinylated peptides. We also quantified the relative expression of 62 identified proteins in the two types of melanoma cells. The application to quantitative analysis of membrane proteins of primary and metastatic melanoma cells revealed great potential of the method in the comprehensive identification of tumor progression markers as well as in the discovery of new protein-based therapeutic targets. PMID:18410138

  19. Novel Polyoxometalate Containing Membranes for PEM Fuel Cells

    SciTech Connect

    Mason K. Harrup; Frederick F. Stewart; Thomas A Luther; Tammy Trowbridge

    2009-03-01

    Current proton exchange membrane (PEM) technologies are inadequate to address the projected needs for fuel cell performance above 80 ºC. Continuing research into traditional ion carriers in novel membrane materials offers the promise of marginal improvement, representing only an evolutionary increase in performance. This conclusion is supported by the role of water in conduction. Thus, the key to better PEMs is not to eliminate water, but to change the role of water by developing ion carriers that will bind water more tightly than traditional sulfur or phosphorus based carriers resulting in materials that will conduct at higher temperatures. This change entails having a carrier structure that interacts more intimately with water and by increasing the ion carrier anionic charge to result in more tightly held inner shell protonated waters of hydration. Both of these factors synergistically act to maintain a critical water concentration at the carrier necessary for conduction. In this work, polyoxometalate (POM) clusters were selected to serve as these different proton carriers.

  20. Thermodynamics, Structure and Transport in Model Fuel Cell Membranes

    NASA Astrophysics Data System (ADS)

    Balsara, Nitash

    2008-03-01

    Polymer electrolyte membranes (PEM), used to conduct protons from the anode to the cathode of hydrogen fuel cells, are open systems that exchange water with the surrounding air. Proton conductivity is closely coupled to the presence of contiguous hydrated channels within the membrane. In an attempt to understand the underpinnings of the morphology of these systems, the phase behavior of model PEMs comprising block copolymers in equilibrium with humidified air was studied as a function of the relative humidity of the surrounding air, ion content of the copolymer, and temperature. At low humidity, the copolymers exhibit an order-to-disorder transition as a function of increasing temperature. At high humidity, however, increasing temperature results in a disorder-to-order transition. In-situ small angle neutron scattering experiments on the open block copolymer system, when combined with water uptake measurement indicate that the disorder-to-order transition is driven by an increase in the partial molar entropy of the water molecules in the ordered phase relative to that in the disordered phase. This is in contrast to most systems wherein increasing entropy results in stabilization of the disordered phase. The coupling between entropy and proton conductivity will be discussed.

  1. Dichloromethane fractions of Scrophularia oxysepala extract induce apoptosis in MCF-7 human breast cancer cells

    PubMed Central

    Hosseini, Behnaz- Alsadat; Pasdaran, Ardalan; Kazemi, Tohid; Shanehbandi, Dariush; Karami, Hadi; Orangi, Mona; Baradaran, Behzad

    2015-01-01

    Breast cancer is a prevalent malignancy among women, especially in developing countries. A large number of anticancer agents with herbal origins have been reported. Hence, herbals may play an essential role in prevention and treatment of cancers. We investigated cytotoxic effects of dichloromethane fractions of Scrophularia oxysepala extract on the MCF-7 breast cancer cell line. The cytotoxic activity of Scrophularia oxysepala fractions on the MCF-7 cells was assessed using Trypan Blue dye exclusion and MTT (3-(4, 5-dimetylthiazol-2-yl) -2, 5-diphenyltetrazolium bromide) assays. In addition, apoptosis induction was determined using TUNEL (terminal deoxy transferase (TdT)-mediated dUTP nick- end labeling) assay and DNA fragmentation analysis. Quantitative Real-Time PCR was also used for analyzing the changes in Caspase-3, Caspase-9, and Bcl-2 genes’ expression. Results revealed an effective inhibition of growth and viability in MCF-7 cells treated with dichloromethane fractions. Cell death assay and DNA fragmentation analysis using the TUNEL test confirmed the induction of apoptosis in the MCF-7 cell line. Further, the fractions have resulted in an increased expression of Caspase-3and Caspase-9 mRNA, which highlights the possibility of apoptosis in the treatments. The expression study of Caspase-9 mRNA confirmed that, the fractions have triggered apoptosis via intrinsic mitochondrial pathway. In summary, fractions of Scrophularia oxysepala extract were found to be promising in growth inhibition and induction of apoptosis in MCF-7 breast cancer cells. PMID:25725141

  2. Dichloromethane fractions of Scrophularia oxysepala extract induce apoptosis in MCF-7 human breast cancer cells.

    PubMed

    Hosseini, Behnaz-Alsadat; Pasdaran, Ardalan; Kazemi, Tohid; Shanehbandi, Dariush; Karami, Hadi; Orangi, Mona; Baradaran, Behzad

    2015-01-01

    Breast cancer is a prevalent malignancy among women, especially in developing countries. A large number of anticancer agents with herbal origins have been reported. Hence, herbals may play an essential role in prevention and treatment of cancers. We investigated cytotoxic effects of dichloromethane fractions of Scrophularia oxysepala extract on the MCF-7 breast cancer cell line. The cytotoxic activity of Scrophularia oxysepala fractions on the MCF-7 cells was assessed using Trypan Blue dye exclusion and MTT (3-(4, 5-dimetylthiazol-2-yl) -2, 5-diphenyltetrazolium bromide) assays. In addition, apoptosis induction was determined using TUNEL (terminal deoxy transferase (TdT)-mediated dUTP nick- end labeling) assay and DNA fragmentation analysis. Quantitative Real-Time PCR was also used for analyzing the changes in Caspase-3, Caspase-9, and Bcl-2 genes' expression. Results revealed an effective inhibition of growth and viability in MCF-7 cells treated with dichloromethane fractions. Cell death assay and DNA fragmentation analysis using the TUNEL test confirmed the induction of apoptosis in the MCF-7 cell line. Further, the fractions have resulted in an increased expression of Caspase-3 and Caspase-9 mRNA, which highlights the possibility of apoptosis in the treatments. The expression study of Caspase-9 mRNA confirmed that, the fractions have triggered apoptosis via intrinsic mitochondrial pathway. In summary, fractions of Scrophularia oxysepala extract were found to be promising in growth inhibition and induction of apoptosis in MCF-7 breast cancer cells. PMID:25725141

  3. Tuning nano electric field to affect restrictive membrane area on localized single cell nano-electroporation

    NASA Astrophysics Data System (ADS)

    Santra, Tuhin Subhra; Wang, Pen-Cheng; Chang, Hwan-You; Tseng, Fan-Gang

    2013-12-01

    Interaction of electric field with biological cells is an important phenomenon for field induced drug delivery system. We demonstrate a selective and localized single cell nano-electroporation (LSCNEP) by applying an intense electric field on a submicron region of the single cell membrane, which can effectively allow high efficient molecular delivery but low cell damage. The delivery rate is controlled by adjusting transmembrane potential and manipulating membrane status. Thermal and ionic influences are deteriorated from the cell membrane by dielectric passivation. Either reversible or irreversible by LSCNEP can fully controlled with potential applications in medical diagnostics and biological studies.

  4. Red fluorescent luminogen from pyrrole derivatives with aggregation-enhanced emission for cell membrane imaging.

    PubMed

    Liu, Guogang; Chen, Didi; Kong, Lingwei; Shi, Jianbing; Tong, Bin; Zhi, Junge; Feng, Xiao; Dong, Yuping

    2015-05-18

    A dye emitted red fluorescence with aggregation-enhanced emission properties was reported here. It can be utilized to specifically recognize the cell membrane of MCF-7 and 293T cell lines during bio-imaging. PMID:25896404

  5. Investigation of the performance and water transport of a polymer electrolyte membrane (pem) fuel cell 

    E-print Network

    Park, Yong Hun

    2009-05-15

    Fuel cell performance was obtained as functions of the humidity at the anode and cathode sites, back pressure, flow rate, temperature, and channel depth. The fuel cell used in this work included a membrane and electrode assembly (MEA) which...

  6. Macrophage Cell Membrane Camouflaged Mesoporous Silica Nanocapsules for In Vivo Cancer Therapy.

    PubMed

    Xuan, Minjun; Shao, Jingxin; Dai, Luru; He, Qiang; Li, Junbai

    2015-08-01

    Engineering natural macrophage cell membrane-camouflaged mesoporous silica nanocapsules can reduce the arrested percentage of immune cells and tissues, effectively prolong the survival time of nanoparticles in blood circulation system, and improve the accumulation in tumor. PMID:25960053

  7. Changes of Saccharomyces cerevisiae cell membrane components and promotion to ethanol tolerance during the bioethanol fermentation.

    PubMed

    Dong, Shi-Jun; Yi, Chen-Feng; Li, Hao

    2015-12-01

    During bioethanol fermentation process, Saccharomyces cerevisiae cell membrane might provide main protection to tolerate accumulated ethanol, and S. cerevisiae cells might also remodel their membrane compositions or structure to try to adapt to or tolerate the ethanol stress. However, the exact changes and roles of S. cerevisiae cell membrane components during bioethanol fermentation still remains poorly understood. This study was performed to clarify changes and roles of S. cerevisiae cell membrane components during bioethanol fermentation. Both cell diameter and membrane integrity decreased as fermentation time lasting. Moreover, compared with cells at lag phase, cells at exponential and stationary phases had higher contents of ergosterol and oleic acid (C18:1) but lower levels of hexadecanoic (C16:0) and palmitelaidic (C16:1) acids. Contents of most detected phospholipids presented an increase tendency during fermentation process. Increased contents of oleic acid and phospholipids containing unsaturated fatty acids might indicate enhanced cell membrane fluidity. Compared with cells at lag phase, cells at exponential and stationary phases had higher expressions of ACC1 and HFA1. However, OLE1 expression underwent an evident increase at exponential phase but a decrease at following stationary phase. These results indicated that during bioethanol fermentation process, yeast cells remodeled membrane and more changeable cell membrane contributed to acquiring higher ethanol tolerance of S. cerevisiae cells. These results highlighted our knowledge about relationship between the variation of cell membrane structure and compositions and ethanol tolerance, and would contribute to a better understanding of bioethanol fermentation process and construction of industrial ethanologenic strains with higher ethanol tolerance. PMID:26515124

  8. Journal of Neuroscience Methods 155 (2006) 180186 Measuring cell viability with membrane impermeable

    E-print Network

    Li, Yang V.

    2006-01-01

    Journal of Neuroscience Methods 155 (2006) 180­186 Measuring cell viability with membrane+ dye to penetrate their plasma membranes, subsequently exhibiting cytosolic and nuclear fluorescence. Two other cell impermeable fluorescent Zn2+ dyes, Fluozin-3 and Zinpyr-4, also stained cytosolic Zn2

  9. Pharmacological targeting of membrane rigidity: implications on cancer cell migration and invasion

    NASA Astrophysics Data System (ADS)

    Braig, Simone; Schmidt, B. U. Sebastian; Stoiber, Katharina; Händel, Chris; Möhn, Till; Werz, Oliver; Müller, Rolf; Zahler, Stefan; Koeberle, Andreas; Käs, Josef A.; Vollmar, Angelika M.

    2015-08-01

    The invasive potential of cancer cells strongly depends on cellular stiffness, a physical quantity that is not only regulated by the mechanical impact of the cytoskeleton but also influenced by the membrane rigidity. To analyze the specific role of membrane rigidity in cancer progression, we treated cancer cells with the Acetyl-CoA carboxylase inhibitor Soraphen A and revealed an alteration of the phospholipidome via mass spectrometry. Migration, invasion, and cell death assays were employed to relate this alteration to functional consequences, and a decrease of migration and invasion without significant impact on cell death has been recorded. Fourier fluctuation analysis of giant plasma membrane vesicles showed that Soraphen A increases membrane rigidity of carcinoma cell membranes. Mechanical measurements of the creep deformation response of whole intact cells were performed using the optical stretcher. The increase in membrane rigidity was observed in one cell line without changing the creep deformation response indicating no restructuring of the cytoskeleton. These data indicate that the increase of membrane rigidity alone is sufficient to inhibit invasiveness of cancer cells, thus disclosing the eminent role of membrane rigidity in migratory processes.

  10. Nitrogen Front Evolution in Purged Polymer Electrolyte Membrane Fuel Cell with Dead-Ended Anode

    E-print Network

    Stefanopoulou, Anna

    Nitrogen Front Evolution in Purged Polymer Electrolyte Membrane Fuel Cell with Dead-Ended Anode in a proton exchange membrane fuel cell operating with a dead-ended anode that is fed by dry hydrogen under dead- ended anode DEA conditions are modeled and measured in this paper. Although a flow

  11. Mathematical modeling of fluorescence diffuse optical imaging of cell membrane potential

    E-print Network

    Ammari, Habib

    Mathematical modeling of fluorescence diffuse optical imaging of cell membrane potential changes optical to- mography. We derive the resolving power of the imaging method in the presence of measurement noise. The proposed mathematical model can be used for cell membrane tracking with the resolution

  12. Three steps in the anode reaction of the polymer electrolyte membrane fuel cell. Effect of CO

    E-print Network

    Kjelstrup, Signe

    Three steps in the anode reaction of the polymer electrolyte membrane fuel cell. Effect of CO Anne in the polymer electrolyte membrane fuel cell (PEMFC) using electrochemical impedance spectroscopy (EIS in the reaction mechanism, the slow adsorption/diffusion step, the charge transfer step and the proton hydration

  13. Increasing Proton Exchange Membrane Fuel Cell Catalyst Effectiveness Through Sputter Deposition

    E-print Network

    Increasing Proton Exchange Membrane Fuel Cell Catalyst Effectiveness Through Sputter Deposition, New York 12203, USA Sputter deposition has been investigated as a tool for manufacturing proton January 29, 2002. Proton exchange membrane fuel cells PEMFCs are gaining popularity due to their high

  14. Increased phorbol 12,13-dibutyrate (PDBu) receptor function associated with sickle red cell membrane ghosts

    SciTech Connect

    Ramachandran, M.; Nair, C.N.; Abraham, E.C.

    1987-05-01

    The biological receptor for tumor-promoting phorbol esters has been identified as the CaS /phospholipid dependent enzyme, protein kinase C. In the red cell, this enzyme is mainly cytosolic but becomes translocated to the membrane if the cellular CaS is allowed to rise. Since cellular CaS in sickle red cells is high, it was reasoned that this enzyme may become more membrane-bound. In fact, the authors noticed a four-fold increase in the binding of TH-PDBu by membrane ghosts isolated from sickle red cells compared to normal red cells (pmoles PDBu bound/mg protein; normal = 0.3 vs sickle cell = 1.4). Attempts to assay the enzyme directly as phospholipid-activated TSP incorporation into the acid-precipitable membrane proteins also indicated a two-fold increase in the radiolabelling of sickle cell membrane ghosts. Autophosphorylation of membrane proteins and analysis of the phosphorylation profile by SDS-PAGE and autoradiography revealed phosphorylation predominantly of bands 3, 4.1 and 4.9 which are known protein kinase C substrates for the red cell enzyme. The increased membrane-associated protein kinase C in sickle red cells may have a bearing on the altered membrane properties reported in this condition.

  15. Dynamic maintenance of stochastic molecular clusters on cell membranes

    NASA Astrophysics Data System (ADS)

    Mugler, Andrew; Wehrens, Martijn; Ten Wolde, Pieter Rein

    2015-03-01

    Clustering of molecules on cell membranes is a widely observed phenomenon. A key example is the oncoprotein Ras. Maintenance of Ras clusters has been linked to proper Ras signaling. Yet, the mechanism by which Ras clusters are maintained remains unclear. Recently it was discovered that activated Ras promotes further Ras activation. We show using particle-based simulation that this positive feedback link is sufficient to produce persistent clusters of active Ras molecules via a dynamic nucleation mechanism. The cluster statistics are consistent with experimental observations. Interestingly, our model does not support a Turing regime of macroscopic reaction-diffusion patterning. This means that the clustering we observe is a purely stochastic effect, arising from the coupling of the positive feedback network with the discrete nature of individual molecules. These findings underscore the importance of stochastic and dynamic properties of reaction diffusion systems for biological behavior.

  16. Ezrin is a Major Regulator of Membrane Tension in Epithelial Cells.

    PubMed

    Rouven Brückner, Bastian; Pietuch, Anna; Nehls, Stefan; Rother, Jan; Janshoff, Andreas

    2015-01-01

    Plasma membrane tension is responsible for a variety of cellular functions such as motility, cell division, and endocytosis. Since membrane tension is dominated by the attachment of the actin cortex to the inner leaflet of the plasma membrane, we investigated the importance of ezrin, a major cross-linker of the membrane-cytoskeleton interface, for cellular mechanics of confluent MDCK II cells. For this purpose, we carried out ezrin depletion experiments and also enhanced the number of active ezrin molecules at the interface. Mechanical properties were assessed by force indentation experiments followed by membrane tether extraction. PIP2 micelles were injected into individual living cells to reinforce the linkage between plasma membrane and actin-cortex, while weakening of this connection was reached by ezrin siRNA and administration of the inhibitors neomycin and NSC 668394, respectively. We observed substantial stiffening of cells and an increase in membrane tension after addition of PIP2 micelles. In contrast, reduction of active ezrin led to a decrease of membrane tension accompanied by loss of excess surface area, increase in cortical tension, remodelling of actin cytoskeleton, and reduction of cell height. The data confirm the importance of the ezrin-mediated connection between plasma membrane and cortex for cellular mechanics and cell morphology. PMID:26435322

  17. Ezrin is a Major Regulator of Membrane Tension in Epithelial Cells

    PubMed Central

    Rouven Brückner, Bastian; Pietuch, Anna; Nehls, Stefan; Rother, Jan; Janshoff, Andreas

    2015-01-01

    Plasma membrane tension is responsible for a variety of cellular functions such as motility, cell division, and endocytosis. Since membrane tension is dominated by the attachment of the actin cortex to the inner leaflet of the plasma membrane, we investigated the importance of ezrin, a major cross-linker of the membrane-cytoskeleton interface, for cellular mechanics of confluent MDCK II cells. For this purpose, we carried out ezrin depletion experiments and also enhanced the number of active ezrin molecules at the interface. Mechanical properties were assessed by force indentation experiments followed by membrane tether extraction. PIP2 micelles were injected into individual living cells to reinforce the linkage between plasma membrane and actin-cortex, while weakening of this connection was reached by ezrin siRNA and administration of the inhibitors neomycin and NSC 668394, respectively. We observed substantial stiffening of cells and an increase in membrane tension after addition of PIP2 micelles. In contrast, reduction of active ezrin led to a decrease of membrane tension accompanied by loss of excess surface area, increase in cortical tension, remodelling of actin cytoskeleton, and reduction of cell height. The data confirm the importance of the ezrin-mediated connection between plasma membrane and cortex for cellular mechanics and cell morphology. PMID:26435322

  18. Multiphase transport in polymer electrolyte membrane fuel cells

    NASA Astrophysics Data System (ADS)

    Gauthier, Eric D.

    Polymer electrolyte membrane fuel cells (PEMFCs) enable efficient conversion of fuels to electricity. They have enormous potential due to the high energy density of the fuels they utilize (hydrogen or alcohols). Power density is a major limitation to wide-scale introduction of PEMFCs. Power density in hydrogen fuel cells is limited by accumulation of water in what is termed fuel cell `flooding.' Flooding may occur in either the gas diffusion layer (GDL) or within the flow channels of the bipolar plate. These components comprise the electrodes of the fuel cell and balance transport of reactants/products with electrical conductivity. This thesis explores the role of electrode materials in the fuel cell and examines the fundamental connection between material properties and multiphase transport processes. Water is generated at the cathode catalyst layer. As liquid water accumulates it will utilize the largest pores in the GDL to go from the catalyst layer to the flow channels. Water collects to large pores via lateral transport at the interface between the GDL and catalyst layer. We have shown that water may be collected in these large pores from several centimeters away, suggesting that we could engineer the GDL to control flooding with careful placement and distribution of large flow-directing pores. Once liquid water is in the flow channels it forms slugs that block gas flow. The slugs are pushed along the channel by a pressure gradient that is dependent on the material wettability. The permeable nature of the GDL also plays a major role in slug growth and allowing bypass of gas between adjacent channels. Direct methanol fuel cells (DMFCs) have analogous multiphase flow issues where carbon dioxide bubbles accumulate, `blinding' regions of the fuel cell. This problem is fundamentally similar to water management in hydrogen fuel cells but with a gas/liquid phase inversion. Gas bubbles move laterally through the porous GDL and emerge to form large bubbles within the flow channel. We have compared the role of GDL materials in liquid drop and gas bubble formation and movement within fuel cells.

  19. C8-glycosphingolipids preferentially insert into tumor cell membranes and promote chemotherapeutic drug uptake.

    PubMed

    Cordeiro Pedrosa, Lília R; van Cappellen, Wiggert A; Steurer, Barbara; Ciceri, Dalila; ten Hagen, Timo L M; Eggermont, Alexander M M; Verheij, Marcel; Goñi, Felix María; Koning, Gerben A; Contreras, F-Xabier

    2015-08-01

    Insufficient drug delivery into tumor cells limits the therapeutic efficacy of chemotherapy. Co-delivery of liposome-encapsulated drug and synthetic short-chain glycosphingolipids (SC-GSLs) significantly improved drug bioavailability by enhancing intracellular drug uptake. Investigating the mechanisms underlying this SC-GSL-mediated drug uptake enhancement is the aim of this study. Fluorescence microscopy was used to visualize the cell membrane lipid transfer intracellular fate of fluorescently labeled C6-NBD-GalCer incorporated in liposomes in tumor and non-tumor cells. Additionally click chemistry was applied to image and quantify native SC-GSLs in tumor and non-tumor cell membranes. SC-GSL-mediated flip-flop was investigated in model membranes to confirm membrane-incorporation of SC-GSL and its effect on membrane remodeling. SC-GSL enriched liposomes containing doxorubicin (Dox) were incubated at 4°C and 37°C and intracellular drug uptake was studied in comparison to standard liposomes and free Dox. SC-GSL transfer to the cell membrane was independent of liposomal uptake and the majority of the transferred lipid remained in the plasma membrane. The transfer of SC-GSL was tumor cell-specific and induced membrane rearrangement as evidenced by a transbilayer flip-flop of pyrene-SM. However, pore formation was measured, as leakage of hydrophilic fluorescent probes was not observed. Moreover, drug uptake appeared to be mediated by SC-GSLs. SC-GSLs enhanced the interaction of doxorubicin (Dox) with the outer leaflet of the plasma membrane of tumor cells at 4°C. Our results demonstrate that SC-GSLs preferentially insert into tumor cell plasma membranes enhancing cell intrinsic capacity to translocate amphiphilic drugs such as Dox across the membrane via a biophysical process. PMID:25917957

  20. Effects of motor patterns on water-soluble and membrane proteins and cholinesterase activity in subcellular fractions of rat brain tissue

    NASA Technical Reports Server (NTRS)

    Pevzner, L. Z.; Venkov, L.; Cheresharov, L.

    1980-01-01

    Albino rats were kept for a year under conditions of daily motor load or constant hypokinesia. An increase in motor activity results in a rise in the acetylcholinesterase activity determined in the synaptosomal and purified mitochondrial fractions while hypokinesia induces a pronounced decrease in this enzyme activity. The butyrylcholinesterase activity somewhat decreases in the synaptosomal fraction after hypokinesia but does not change under the motor load pattern. Motor load causes an increase in the amount of synaptosomal water-soluble proteins possessing an intermediate electrophoretic mobility and seem to correspond to the brain-specific protein 14-3-2. In the synaptosomal fraction the amount of membrane proteins with a low electrophoretic mobility and with the cholinesterase activity rises. Hypokinesia, on the contrary, decreases the amount of these membrane proteins.

  1. Osteogenic cell fractions isolated from mouse tongue muscle

    PubMed Central

    HARADA, KOJI; HARADA, TOYOKO; FERDOUS, TARANNUM; TAKENAWA, TAKANORI; UEYAMA, YOSHIYA

    2015-01-01

    The use of stem cells represents a promising approach for the treatment of bone defects. However, successful treatments rely upon the availability of cells that are easily obtained and that appropriately differentiate into osteoblasts. The tongue potentially represents a source of autologous cells for such purposes. In the present study, the ability of stem cell antigen-1 (Sca-1) positive cells derived from tongue muscle to differentiate into osteoblasts was investigated. The tongue muscles were excised from Jcl-ICR mice and tongue muscle-derived Sca-1-positive cells (TDSCs) were isolated from the tongue muscle using a magnetic cell separation system with microbeads. TDSCs were cultured in plastic dishes or gelatin sponges of ?-tricalcium phosphate (?-TCP) with bone differentiation-inducing medium. The expression of osteogenic markers (Runx2, osterix, alkaline phosphatase, fibronectin, osteocalcin, osteonectin and osteopontin) was investigated in cultured TDSCs by western blot analysis. The formation of mineralized matrices was examined using alizarin red S and Von Kossa staining. Bone formation was investigated in cultured TDSCs by hematoxylin-eosin staining and immunohistochemstry. In the present study, the expression of Sca-1 in mouse tongue muscle was demonstrated and TDSCs were isolated at high purity. TDSCs differentiated into cells of osteoblast lineage, as demonstrated by the upregulation of osteoblastic marker expression. The formation of mineralized matrices was confirmed by alizarin red S or Von Kossa staining in vitro. Bone formation was observed in the gelatin sponges of ?-TCP, which were subsequently implanted under the skin of the backs of nude mice. These results suggested that TDSCs retain their osteogenic differentiation potential and therefore the tongue muscle may be used as a source of stem cells for bone regeneration. PMID:25684092

  2. Osteogenic cell fractions isolated from mouse tongue muscle.

    PubMed

    Harada, Koji; Harada, Toyoko; Ferdous, Tarannum; Takenawa, Takanori; Ueyama, Yoshiya

    2015-07-01

    The use of stem cells represents a promising approach for the treatment of bone defects. However, successful treatments rely upon the availability of cells that are easily obtained and that appropriately differentiate into osteoblasts. The tongue potentially represents a source of autologous cells for such purposes. In the present study, the ability of stem cell antigen-1 (Sca-1) positive cells derived from tongue muscle to differentiate into osteoblasts was investigated. The tongue muscles were excised from Jcl-ICR mice and tongue muscle-derived Sca-1-positive cells (TDSCs) were isolated from the tongue muscle using a magnetic cell separation system with microbeads. TDSCs were cultured in plastic dishes or gelatin sponges of ?-tricalcium phosphate (?-TCP) with bone differentiation-inducing medium. The expression of osteogenic markers (Runx2, osterix, alkaline phosphatase, fibronectin, osteocalcin, osteonectin and osteopontin) was investigated in cultured TDSCs by western blot analysis. The formation of mineralized matrices was examined using alizarin red S and Von Kossa staining. Bone formation was investigated in cultured TDSCs by hematoxylin-eosin staining and immunohistochemistry. In the present study, the expression of Sca-1 in mouse tongue muscle was demonstrated and TDSCs were isolated at high purity. TDSCs differentiated into cells of osteoblast lineage, as demonstrated by the upregulation of osteoblastic marker expression. The formation of mineralized matrices was confirmed by alizarin red S or Von Kossa staining in vitro. Bone formation was observed in the gelatin sponges of ?-TCP, which were subsequently implanted under the skin of the backs of nude mice. These results suggested that TDSCs retain their osteogenic differentiation potential and therefore the tongue muscle may be used as a source of stem cells for bone regeneration. PMID:25684092

  3. Thylakoid membrane biogenesis in Chlamydomonas reinhardtii 137+. II. Cell-cycle variations in the synthesis and assembly of pigment

    PubMed Central

    1982-01-01

    Synthesis of the chlorophyll and the major carotenoid pigments and their assembly into thylakoid membrane have been studied throughout the 12-h light/12-h dark vegetative cell cycle of synchronous Chlamydomonas reinhardtii 137+ (wild-type). Pulse exposure of cells to radioactive acetate under conditions in which labeling accurately reflects lipogenesis, followed by cellular fractionation to purify thylakoid membrane, allowed direct analysis of the pigment synthesis and assembly attendant to thylakoid biogenesis. All pigments are synthesized and assembled into thylakoids continuously, but differentially, with respect to cell-cycle time. Highest synthesis and assembly rates are confined to the photoperiod (mid-to-late G1) and support chlorophyll and carotenoid accretion before M-phase. The lower levels at which these processes take place during the dark period (S, M, and early-to- mid G1) have been ascribed to pigment turnover. Within this general periodic pattern, pigment synthesis and assembly occur in a "multi- step" manner, i.e., by a temporally-ordered, stepwise integration of the various pigments into the thylakoid membrane matrix. The cell-cycle kinetics of pigment assembly at the subcellular level mirror the kinetics of pigment synthesis at the cellular level, indicating that pigment synthesis not only provides chlorophyll and carotenoid for thylakoid biogenesis but may also serve as a critical rate-determinant to pigment assembly. PMID:7096445

  4. Analysis of Nuclear RNA Interference (RNAi) in Human Cells by Subcellular Fractionation and Argonaute Loading

    PubMed Central

    Gagnon, Keith T.; Li, Liande; Janowski, Bethany A.; Corey, David R.

    2014-01-01

    RNA interference (RNAi) is well known for its ability to regulate gene expression in the cytoplasm of mammalian cells. In mammalian cell nuclei, however, the impact of RNAi has remained more controversial. A key technical hurdle has been a lack of optimized protocols for the isolation and analysis of cell nuclei. Here we describe a simplified protocol for nuclei isolation from cultured cells that incorporates a method for obtaining nucleoplasmic and chromatin fractions and removing cytoplasmic contamination. Cell fractions can then be used to detect the presence and activity of RNAi factors in the nucleus. We present a protocol for investigating an early step in RNAi, Argonaute protein loading with small RNAs, which is enabled by our improved extract preparations. These protocols facilitate characterization of nuclear RNAi and can be applied to the analysis of other nuclear proteins and pathways. From cellular fractionation to analysis of Argonaute loading results, this protocol takes 4–6 d to complete. PMID:25079428

  5. Fabrication of a membrane filter with controlled pore shape and its application to cell separation and strong single cell trapping

    NASA Astrophysics Data System (ADS)

    Choi, Dong-Hoon; Yoon, Gun-Wook; Park, Jeong Won; Ihm, Chunhwa; Lee, Dae-Sik; Yoon, Jun-Bo

    2015-10-01

    A porous membrane filter is one of the key components for sample preparation in lab-on-a-chip applications. However, most of the membranes reported to date have only been used for size-based separation since it is difficult to provide functionality to the membrane or improve the performance of the membrane. In this work, as a method to functionalize the membrane filter, controlling the shape of the membrane pores is suggested, and a convenient and mass-producible fabrication method is provided. With the proposed method, membrane filters with round, conical and funnel shape pores were successfully fabricated, and we demonstrated that the sidewall slope of the conical shape pores could be precisely controlled. To verify that the membrane filter can be functionalized by controlled pore shape, we investigated filtration and trapping performance of the membrane filter with conical shape pores. In a filtration test of 1000 cancer cells (MCF-7, a breast cancer cell line) spiked in phosphate buffered saline (PBS) solution, 77% of the total cancer cells were retained on the membrane, and each cell from among 99.3% of the retained cells was automatically isolated in a single conical pore during the filtration process. Thanks to its engineered pore shape, trapping ability of the membrane with conical pores is dramatically improved. Microparticles trapped in the conical pores maintain their locations without any losses even at a more than 30 times faster external flow rate com-pared with those mounted on conventional cylindrical pores. Also, 78% of the cells trapped in the conical pores withstand an external flow of over 300 ?l min-1 whereas only 18% of the cells trapped in the cylindrical pores remain on the membrane after 120 ?l min-1 of an external flow is applied.

  6. The Structure of Catalyst Layers and Cell Performance in Proton Exchange Membrane Fuel Cells

    NASA Astrophysics Data System (ADS)

    Inoue, Hiroyuki; Daiguji, Hirofumi; Hihara, Eiji

    A catalyst layer is one of the key elements in polymer electrolyte membrane fuel cells (PEMFC). Improvements in the performance of a membrane electrode assembly (MEA) for PEMFC are much influenced by an electrochemically active surface area in a catalyst layer. But the relation between the structure of a catalyst layer and the cell performance has not been clarified yet. In the present study, catalyst layers with different structure and composition were fabricated, and the structural properties of catalyst layers, such as thickness and roughness, and the polarization curves were measured. The experimental results suggested that there is an optimum mass ratio of electrolyte in a catalyst layer for the cell performance, and the thickness and roughness of a catalyst layer change significantly at the optimum mass ratio.

  7. A semipolar fraction of petroleum ether extract of Artemisia aucheri induces apoptosis and enhances the apoptotic response to doxorubicin in human neuroblastoma SKNMC cell line

    PubMed Central

    Ahmadi, Farahnaz; Mojarrab, Mahdi; Ghazi-Khansari, Mahmoud; Hosseinzadeh, Leila

    2015-01-01

    Artemisia is an important genus of Iranian flora whose potent anti-proliferative effect has been demonstrated previously on human cancerous cell lines. In the current study, further fractionation was carried out on the petroleum ether extract of A. aucheri and their cytotoxic effects were evaluated on three human cancer cell lines. Cell viability was determined by 3-(4,5-dimethylthiazol-2yl)-2,5-diphenyltetrazolium bromide assay. Real time polymerase chain reaction (RT-PCR) was used to evaluate the expression of apoptotic related genes. Activation of caspases and detection of intracellular doxorubicin (DOX) accumulation were evaluated using a spectrophotometer. Mitochondrial membrane potential (MMP) was measured using flow cytometry. The fraction NO-7 (F7) of petroleum ether extract showed the highest anti-proliferative effect, especially against SKNMC cells. Therefore, we focused on a description of the cytotoxic mechanism of the most potent fraction on SKNMC cells. The results indicated that F7 was able to induce apoptosis through MMP disruption, activation of caspases and increament of proapoptotic genes Bax and Smac/DIABLO. Moreover, our observation indicated that F7 is able to increase the cytotoxicity of DOX in SKNMC cells. The combination of F7+DOX significantly increased the intracellular accumulation of DOX. These results indicated that F7 induces apoptosis in SKNMC cells. Moreover, it might enhance the antitumor activity of DOX, through modulating the activity of multidrug resistant cancer cells and inducing apoptosis. PMID:26600860

  8. Kinetics of small molecule interactions with membrane proteins in single cells measured with mechanical amplification

    PubMed Central

    Guan, Yan; Shan, Xiaonan; Zhang, Fenni; Wang, Shaopeng; Chen, Hong-Yuan; Tao, Nongjian

    2015-01-01

    Measuring small molecule interactions with membrane proteins in single cells is critical for understanding many cellular processes and for screening drugs. However, developing such a capability has been a difficult challenge. We show that molecular interactions with membrane proteins induce a mechanical deformation in the cellular membrane, and real-time monitoring of the deformation with subnanometer resolution allows quantitative analysis of small molecule–membrane protein interaction kinetics in single cells. This new strategy provides mechanical amplification of small binding signals, making it possible to detect small molecule interactions with membrane proteins. This capability, together with spatial resolution, also allows the study of the heterogeneous nature of cells by analyzing the interaction kinetics variability between different cells and between different regions of a single cell. PMID:26601298

  9. Nanoporous gold membranes: From morphological control to fuel cell catalysis

    NASA Astrophysics Data System (ADS)

    Ding, Yi

    Porous noble metals are particularly attractive for scientific research and industrial applications such as catalysis, sensing, and filtration. In this thesis, I will discuss the fabrication, characterization, and application of a new class of porous metals, called nanoporous metals (NPM). NPM is made during selective dissolution (also called dealloying) of reactive components (e.g., silver) from multi-component alloys (e.g., Ag/Au alloy). Commercially available white gold leaf (Ag65Au35) can, for example, be etched into nanoporous gold (NPG) membrane by simply floating the leaf on concentrated nitric acid for periods of a few minutes. NPG leaf adopts a single crystal porous structure within individual grains. The microstructure of NPG, such as the pore size, is tunable between a few nanometers to sub-micron length scale by either thermal annealing or post-treatment in nitric acid for extended period of time. A new gas-liquid-solid interface electroless plating technique is developed to uniformly cover the NPG surface with other metals, such as silver and platinum. This technique allows new opportunities of making functionalized nanostructures. We show that a combination of silver plating and dealloying can be used to make multimodal porous metals, which are expected to have application in sensing field. Electroless platinum plating onto NPG shows very usual growth mode. TEM observation indicates that the platinum layer on NPG surface takes a novel form of layer-islanding growth (Stranski-Krastanov growth). Annealing the Pt/NPG composite smoothens the Pt islands and forms a 1 nm coherent Pt layer on the NPG backbone, possibly with dislocation formation at the Pt/Au interface. Furthermore, it was found that we could dissolve the gold away in aqueous gold etchant, leaving behind the 1 nm-thick Pt shell, a structure we call nanotubular mesoporous platinum (NMP). Pt plated NPG has a series of unique structural properties, such as high active surface area, thermally stable, low Pt usage, and better tolerance to CO poisoning. We incorporated it as a membrane electrode into a working proton exchange membrane fuel cells (PEMFC). Preliminary results show that Pt/NPG has very good fuel cell performance at a very low platinum loading.

  10. Calcium fluxes across the plasma membrane of Commelina communis L. assayed in a cell-free system

    SciTech Connect

    Siebers, B.; Graef, P.; Weiler, E.W. )

    1990-07-01

    The inside-out fraction of plasma membrane-rich vesicles prepared from leaves of Commelina communis L. by aqueous two-phase partitioning was loaded with {sup 45}Ca{sup 2+} through the action of the plasma membrane Ca{sup 2+}-ATPase. Results suggest the presence of a Ca{sup 2+} channel in the plasma membrane of C. communis. The channel is obtained in a Ca{sup 2+}-inactivated state after preparation and Ca{sup 2+}-loading of the vesicles. The inactivation is removed by TFP (trifluoperazine) or W-7 (N-(6-aminohexyl)-5-chloro-1-naphthalenesulfonamide), presumably due to the Ca{sup 2+}-mobilizing effect of these compounds. The activated Ca{sup 2+} channel is La{sup 3+} sensitive and, in the cell, would allow for passage of Ca{sup 2+} into the cell. The possibility that TFP or W-7 act independent of CM, or through CM tightly associated with the plasma membrane, is discussed.

  11. Affinity Flow Fractionation for label-free cell sorting

    E-print Network

    Bose, Suman

    2014-01-01

    Capture and isolation of flowing cells from body fluids such as peripheral blood, bone marrow or pleural effusion has enormous implications in diagnosis, disease monitoring, and drug testing. However, in many situations ...

  12. Novel pore-filled polyelectrolyte composite membranes for cathodic microbial fuel cell application

    NASA Astrophysics Data System (ADS)

    Gohil, J. M.; Karamanev, D. G.

    2013-12-01

    Novel pore-filled polyelectrolyte membrane (PEM) was produced using track etched polycarbonate (PC) as porous substrate and poly(vinyl alcohol) (PVA) as pore filling material. PVA in PC pores was stabilized through cross-linking of PVA matrix with glutaraldehyde (GA). Cross-link time was varied from 24 h to 96 h while keeping the membranes in GA solution. Pore sizes of substrate PC membrane tested were 0.01, 0.1 and 0.2 ?m. The membranes were characterized by Fourier-transform infrared spectroscopy and scanning electron microscopy. Ionic conductivity, water uptake, contact angle and gel content have been measured to determine membranes performance. The ionic crossover (iron ions and protons) through membranes was studied in a complete fuel cell. The single-cell performance of membrane was tested in a cathodic microbial fuel cell (MFC, Biogenerator). The physiochemical properties and membranes fuel cell performance were highly depended on the cross-link density of PVA matrices. Membranes cross-liked with GA for 72 h showed maximum gel content and their peak power density has reached 110 mW cm-2 at current density of 378 mA cm-2. Among all, membrane cross-linked for 72 h was studied for continuous long-term stability, which showed consistency for application in MFC.

  13. Mechanisms regulating cell membrane localization of the chemokine receptor CXCR4 in human hepatocarcinoma cells.

    PubMed

    Cepeda, Edgar B; Dediulia, Tatjana; Fernando, Joan; Bertran, Esther; Egea, Gustavo; Navarro, Estanislao; Fabregat, Isabel

    2015-05-01

    Hepatocellular carcinoma (HCC) cells with a mesenchymal phenotype show an asymmetric subcellular distribution of the chemokine receptor CXCR4, which is required for cell migration and invasion. In this work we examine the mechanisms that regulate the intracellular trafficking of CXCR4 in HCC cells. Results indicate that HCC cells present CXCR4 at the cell surface, but most of this protein is in endomembranes colocalizing with markers of the Golgi apparatus and recycling endosomes. The presence of high protein levels of CXCR4 present at the cell surface correlates with a mesenchymal-like phenotype and a high autocrine activation of the Transforming Growth Factor-beta (TGF-?) pathway. CXCR4 traffics along the Golgi/exocyst/plasma membrane pathway and requires EXOC4 (Sec8) component of the exocyst complex. HCC cells use distinct mechanisms for the CXCR4 internalization such as dynamin-dependent endocytosis and macropinocytosis. Regardless of the endocytic mechanisms, colocalization of CXCR4 and Rab11 is observed, which could be involved not only in receptor recycling but also in its post-Golgi transport. In summary, this work highlights membrane trafficking pathways whose pharmacological targeting could subsequently result in the inactivation of one of the main guiding mechanisms used by metastatic cells to colonize secondary organs and tissues. PMID:25704914

  14. High heterogeneity of plasma membrane microfluidity in multidrug-resistant cancer cells

    NASA Astrophysics Data System (ADS)

    Boutin, Céline; Roche, Yann; Millot, Christine; Deturche, Régis; Royer, Pascal; Manfait, Michel; Plain, Jérôme; Jeannesson, Pierre; Millot, Jean-Marc; Jaffiol, Rodolphe

    2009-05-01

    Diffusion-time distribution analysis (DDA) has been used to explore the plasma membrane fluidity of multidrug-resistant cancer cells (LR73 carcinoma cells) and also to characterize the influence of various membrane agents present in the extracellular medium. DDA is a recent single-molecule technique, based on fluorescence correlation spectroscopy (FCS), well suited to retrieve local organization of cell membrane. The method was conducted on a large number of living cells, which enabled us to get a detailed overview of plasma membrane microviscosity, and plasma membrane micro-organization, between the cells of the same line. Thus, we clearly reveal the higher heterogeneity of plasma membrane in multidrug-resistant cancer cells in comparison with the nonresistant ones (denoted sensitive cells). We also display distinct modifications related to a membrane fluidity modulator, benzyl alcohol, and two revertants of multidrug resistance, verapamil and cyclosporin-A. A relation between the distribution of the diffusion-time values and the modification of membrane lateral heterogeneities is proposed.

  15. Imaging of the membrane surface of MDCK cells by atomic force microscopy.

    PubMed Central

    Le Grimellec, C; Lesniewska, E; Cachia, C; Schreiber, J P; de Fornel, F; Goudonnet, J P

    1994-01-01

    The membrane surface of polarized renal epithelial cells (MDCK cells) grown as a monolayer was imaged with the atomic force microscope. The surface topography of dried cells determined by this approach was consistent with electron microscopy images previously reported. Fixed and living cells in aqueous medium gave more fuzzy images, likely because of the presence of the cell glycocalix. Treatment of living cells with neuraminidase, an enzyme that partly degrades the glycocalix, allowed sub-micrometer imaging. Protruding particles, 10 to 60 nm xy size, occupy most of the membrane surface. Protease treatment markedly reduced the size of these particles, indicating that they corresponded to proteins. Tip structure effects were probably involved in the exaggerated size of imaged membrane proteins. Although further improvements in the imaging conditions, including tip sharpness, are required, atomic force microscope already offers the unique possibility to image proteins at the membrane surface of living cells. Images FIGURE 1 FIGURE 2 PMID:7919007

  16. Liposome-based engineering of cells to package hydrophobic compounds in membrane vesicles for tumor penetration.

    PubMed

    Lee, Junsung; Kim, Jiyoung; Jeong, Moonkyoung; Lee, Hyoungjin; Goh, Unbyeol; Kim, Hyaeyeong; Kim, Byungji; Park, Ji-Ho

    2015-05-13

    Natural membrane vesicles (MVs) derived from various types of cells play an essential role in transporting biological materials between cells. Here, we show that exogenous compounds are packaged in the MVs by engineering the parental cells via liposomes, and the MVs mediate autonomous intercellular migration of the compounds through multiple cancer cell layers. Hydrophobic compounds delivered selectively to the plasma membrane of cancer cells using synthetic membrane fusogenic liposomes were efficiently incorporated into the membrane of MVs secreted from the cells and then transferred to neighboring cells via the MVs. This liposome-mediated MV engineering strategy allowed hydrophobic photosensitizers to significantly penetrate both spheroids and in vivo tumors, thereby enhancing the therapeutic efficacy. These results suggest that innate biological transport systems can be in situ engineered via synthetic liposomes to guide the penetration of chemotherapeutics across challenging tissue barriers in solid tumors. PMID:25806671

  17. Detergent Induction of HEK 293A Cell Membrane Permeability Measured under Quiescent and Superfusion Conditions Using Whole Cell Patch Clamp

    PubMed Central

    2015-01-01

    Detergents have several biological applications but present cytotoxicity concerns, since they can solubilize cell membranes. Using the IonFlux 16, an ensemble whole cell planar patch clamp, we observed that anionic sodium dodecyl sulfate (SDS), cationic cetyltrimethylammonium bromide (CTAB), and cationic, fluorescent octadecyl rhodamine B (ORB) increased the membrane permeability of cells substantially within a second of exposure, under superfusion conditions. Increased permeability was irreversible for 15 min. At subsolubilizing detergent concentrations, patched cells showed increased membrane currents that reached a steady state and were intact when imaged using fluorescence microscopy. SDS solubilized cells at concentrations of 2 mM (2× CMC), while CTAB did not solubilize cells even at concentrations of 10 mM (1000× CMC). The relative activity for plasma membrane current induction was 1:20:14 for SDS, CTAB, and ORB, respectively. Under quiescent conditions, the relative ratio of lipid to detergent in cell membranes at the onset of membrane permeability was 1:7:5 for SDS, CTAB, and ORB, respectively. The partition constants (K) for SDS, CTAB, and ORB were 23000, 55000, and 39000 M–1, respectively. Combining the whole cell patch clamp data and XTT viability data, SDS ? 0.2 mM and CTAB and ORB ? 1 mM induced cell membrane permeability without causing acute toxicity. PMID:24548291

  18. A self-humidifying acidic-alkaline bipolar membrane fuel cell

    NASA Astrophysics Data System (ADS)

    Peng, Sikan; Xu, Xin; Lu, Shanfu; Sui, Pang-Chieh; Djilali, Ned; Xiang, Yan

    2015-12-01

    To maintain membrane hydration and operate effectively, polymer electrolyte membrane fuel cells (PEMFCs) require elaborate water management, which significantly increases the complexity and cost of the fuel cell system. Here we propose a novel and entirely different approach to membrane hydration by exploiting the concept of bipolar membranes. Bipolar membrane (BPM) fuel cells utilize a composite membrane consisting of an acidic polymer electrolyte membrane on the anode side and an alkaline electrolyte membrane on the cathode side. We present a novel membrane electrode assembly (MEA) fabrication method and demonstrate experimentally and theoretically that BPM fuel cells can (a) self-humidify to ensure high ionic conductivity; and (b) allow use of non-platinum catalysts due to inherently faster oxygen reduction kinetics on an alkaline cathode. Our Pt-based BPM fuel cell achieves a two orders of magnitude gain in power density of 327 mW cm-2 at 323 K under dry gas feed, the highest power output achieved under anhydrous operation conditions. A theoretical analysis and in situ measurements are presented to characterize the unique interfacial water generation and transport behavior that make self-humidification possible during operation. Further optimization of these features and advances in fabricating bipolar MEAs would open the way for a new generation of self-humidifying and water-management-free PEMFCs.

  19. Chitosan and alginate types of bio-membrane in fuel cell application: An overview

    NASA Astrophysics Data System (ADS)

    Shaari, N.; Kamarudin, S. K.

    2015-09-01

    The major problems of polymer electrolyte membrane fuel cell technology that need to be highlighted are fuel crossovers (e.g., methanol or hydrogen leaking across fuel cell membranes), CO poisoning, low durability, and high cost. Chitosan and alginate-based biopolymer membranes have recently been used to solve these problems with promising results. Current research in biopolymer membrane materials and systems has focused on the following: 1) the development of novel and efficient biopolymer materials; and 2) increasing the processing capacity of membrane operations. Consequently, chitosan and alginate-based biopolymers seek to enhance fuel cell performance by improving proton conductivity, membrane durability, and reducing fuel crossover and electro-osmotic drag. There are four groups of chitosan-based membranes (categorized according to their reaction and preparation): self-cross-linked and salt-complexed chitosans, chitosan-based polymer blends, chitosan/inorganic filler composites, and chitosan/polymer composites. There are only three alginate-based membranes that have been synthesized for fuel cell application. This work aims to review the state-of-the-art in the growth of chitosan and alginate-based biopolymer membranes for fuel cell applications.

  20. The Anti-inflammatory Drug Indomethacin Alters Nanoclustering in Synthetic and Cell Plasma Membranes*

    PubMed Central

    Zhou, Yong; Plowman, Sarah J.; Lichtenberger, Lenard M.; Hancock, John F.

    2010-01-01

    The nonsteroidal anti-inflammatory drug indomethacin exhibits diverse biological effects, many of which have no clear molecular mechanism. Membrane-bound receptors and enzymes are sensitive to their phospholipid microenvironment. Amphipathic indomethacin could therefore potentially modulate cell signaling by changing membrane properties. Here we examined the effect of indomethacin on membrane lateral heterogeneity. Fluorescence lifetime imaging of cells expressing lipid-anchored probes revealed that treatment of BHK cells with therapeutic levels of indomethacin enhances cholesterol-dependent nanoclustering, but not cholesterol-independent nanoclustering. Immuno-electron microscopy and quantitative spatial mapping of intact plasma membrane sheets similarly showed a selective effect of indomethacin on promoting cholesterol-dependent, but not cholesterol-independent, nanoclustering. To further evaluate the biophysical effects of indomethacin, we measured fluorescence polarization of the phase-sensitive probe Laurdan and FRET between phase-partitioning probes in model bilayers. Therapeutic levels of indomethacin enhanced phase seperation in DPPC/DOPC/Chol (1:1:1) and DPPC/Chol membranes in a temperature-dependent manner, but had minimal effect on the phase behavior of pure DOPC at any temperature. Taken together, the imaging results on intact epithelial cells and the biophysical assays of model membranes suggest that indomethacin can enhance phase separation and stabilize cholesterol-dependent nanoclusters in biological membranes. These effects on membrane lateral heterogeneity may have significant consequences for cell signaling cascades that are assembled on the plasma membrane. PMID:20826816

  1. Flavonoid Fraction of Orange and Bergamot Juices Protect Human Lung Epithelial Cells from Hydrogen Peroxide-Induced Oxidative Stress.

    PubMed

    Ferlazzo, Nadia; Visalli, Giuseppa; Smeriglio, Antonella; Cirmi, Santa; Lombardo, Giovanni Enrico; Campiglia, Pietro; Di Pietro, Angela; Navarra, Michele

    2015-01-01

    It has been reported that oxidant/antioxidant imbalance triggers cell damage that in turn causes a number of lung diseases. Flavonoids are known for their health benefits, and Citrus fruits juices are one of the main food sources of these secondary plant metabolites. The present study was designed to evaluate the effect of the flavonoid fraction of bergamot and orange juices, on H2O2-induced oxidative stress in human lung epithelial A549 cells. First we tested the antioxidant properties of both extracts in cell-free experimental models and then we assayed their capability to prevent the cytotoxic effects induced by H2O2. Our results demonstrated that both Citrus juice extracts reduce the generation of reactive oxygen species and membrane lipid peroxidation, improve mitochondrial functionality, and prevent DNA-oxidative damage in A549 cells incubated with H2O2. Our data indicate that the mix of flavonoids present in both bergamot and orange juices may be of use in preventing oxidative cell injury and pave the way for further research into a novel healthy approach to avoid lung disorders. PMID:26221182

  2. Flavonoid Fraction of Orange and Bergamot Juices Protect Human Lung Epithelial Cells from Hydrogen Peroxide-Induced Oxidative Stress

    PubMed Central

    Ferlazzo, Nadia; Visalli, Giuseppa; Smeriglio, Antonella; Cirmi, Santa; Lombardo, Giovanni Enrico; Campiglia, Pietro; Di Pietro, Angela; Navarra, Michele

    2015-01-01

    It has been reported that oxidant/antioxidant imbalance triggers cell damage that in turn causes a number of lung diseases. Flavonoids are known for their health benefits, and Citrus fruits juices are one of the main food sources of these secondary plant metabolites. The present study was designed to evaluate the effect of the flavonoid fraction of bergamot and orange juices, on H2O2-induced oxidative stress in human lung epithelial A549 cells. First we tested the antioxidant properties of both extracts in cell-free experimental models and then we assayed their capability to prevent the cytotoxic effects induced by H2O2. Our results demonstrated that both Citrus juice extracts reduce the generation of reactive oxygen species and membrane lipid peroxidation, improve mitochondrial functionality, and prevent DNA-oxidative damage in A549 cells incubated with H2O2. Our data indicate that the mix of flavonoids present in both bergamot and orange juices may be of use in preventing oxidative cell injury and pave the way for further research into a novel healthy approach to avoid lung disorders. PMID:26221182

  3. Resonance energy transfer microscopy: observations of membrane-bound fluorescent probes in model membranes and in living cells

    PubMed Central

    1986-01-01

    A conventional fluorescence microscope was modified to observe the sites of resonance energy transfer (RET) between fluorescent probes in model membranes and in living cells. These modifications, and the parameters necessary to observe RET between membrane-bound fluorochromes, are detailed for a system that uses N-4-nitrobenzo-2-oxa- 1,3-diazole (NBD) or fluorescein as the energy donor and sulforhodamine as the energy acceptor. The necessary parameters for RET in this system were first optimized using liposomes. Both quenching of the energy donor and sensitized fluorescence of the energy acceptor could be directly observed in the microscope. RET microscopy was then used in cultured fibroblasts to identify those intracellular organelles labeled by the lipid probe, N-SRh-decylamine (N-SRh-C10). This was done by observing the sites of RET in cells doubly labeled with N-SRh-C10 and an NBD-labeled lipid previously shown to label the endoplasmic reticulum, mitochondria, and nuclear envelope. RET microscopy was also used in cells treated with fluorescein-labeled Lens culinaris agglutinin and a sulforhodamine derivative of phosphatidylcholine to examine the internalization of plasma membrane lipid and protein probes. After internalization, the fluorescent lectin resided in most, but not all of the intracellular compartments labeled by the fluorescent lipid, suggesting sorting of the membrane-bound lectin into a subset of internal compartments. We conclude that RET microscopy can co-localize different membrane-bound components at high resolution, and may be particularly useful in examining temporal and spatial changes in the distribution of fluorescent molecules in membranes of the living cell. PMID:3771633

  4. Static Magnetic Field Attenuates Lipopolysaccharide-Induced Inflammation in Pulp Cells by Affecting Cell Membrane Stability

    PubMed Central

    Tsao, Jeng-Ting; Lee, Lin-Wen; Lin, Che-Tong

    2015-01-01

    One of the causes of dental pulpitis is lipopolysaccharide- (LPS-) induced inflammatory response. Following pulp tissue inflammation, odontoblasts, dental pulp cells (DPCs), and dental pulp stem cells (DPSCs) will activate and repair damaged tissue to maintain homeostasis. However, when LPS infection is too serious, dental repair is impossible and disease may progress to irreversible pulpitis. Therefore, the aim of this study was to examine whether static magnetic field (SMF) can attenuate inflammatory response of dental pulp cells challenged with LPS. In methodology, dental pulp cells were isolated from extracted teeth. The population of DPSCs in the cultured DPCs was identified by phenotypes and multilineage differentiation. The effects of 0.4?T SMF on DPCs were observed through MTT assay and fluorescent anisotropy assay. Our results showed that the SMF exposure had no effect on surface markers or multilineage differentiation capability. However, SMF exposure increases cell viability by 15%. In addition, SMF increased cell membrane rigidity which is directly related to higher fluorescent anisotropy. In the LPS-challenged condition, DPCs treated with SMF demonstrated a higher tolerance to LPS-induced inflammatory response when compared to untreated controls. According to these results, we suggest that 0.4?T SMF attenuates LPS-induced inflammatory response to DPCs by changing cell membrane stability. PMID:25884030

  5. Cell-based capacitance sensor for analysis of EGFR expression on cell membrane

    NASA Astrophysics Data System (ADS)

    Shin, Dong-Myeong; Shin, Yong-Cheol; Ha, Ji Hye; Lee, Jong-Ho; Han, Dong-Wook; Kim, Jong-Man; Kim, Hyung Kook; Hwang, Yoon-Hwae

    2013-02-01

    Cancer cells have many kinds of cancer biomarkers. Among them, the epidermal growth factor (EGF) receptors can show a possibility for a cancer marker because the over-expression of EGF receptor is related with fibrous, colorectal, cervical and gastric tumorigenesis. We fabricated the capacitance sensor with a gap area of 50 ?m × 200 ?m by using photolithography and lift-off method. Using the capacitance sensor, we investigated the time dependent capacitance changes of different kinds of fibrous cells, such as HT1080 fibrosarcoma, L-929 fibroblast cell line and nHDF dermal fibroblast primary cell. We found that when we put the EGF, the capacitance decreased due to the immobilization of EGF to EGF receptor on the cell membrane. The quantitative determination of EGF receptor level for various fibrous cells was carried out and the results showed good correlation with conventional method. Based on our results, we suggest that the capacitance sensor can measure the expression level of the EGF receptor on cell membrane and be a good candidate as a cancer diagnosis.

  6. Induction of apoptosis in acute lymphoblastic leukemia cells by isolated fractions from strawberries

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Strawberries contain phytochemicals that have anti-inflammatory and anti-cancer activity. We investigated the ability of isolated fractions from strawberry extracts to induce apoptotic cell death in three pre-B acute lymphoblastic leukemia (ALL) lines, including SEM and RS4;11 cell lines derived fr...

  7. Performance enhancement of polymer electrolyte membrane fuel cells by dual-layered membrane electrode assembly structures with carbon nanotubes.

    PubMed

    Jung, Dong-Won; Kim, Jun-Ho; Kim, Se-Hoon; Kim, Jun-Bom; Oh, Eun-Suok

    2013-05-01

    The effect of dual-layered membrane electrode assemblies (d-MEAs) on the performance of a polymer electrolyte membrane fuel cell (PEMFC) was investigated using the following characterization techniques: single cell performance test, electrochemical impedance spectroscopy (EIS), and cyclic voltammetry (CV). It has been shown that the PEMFC with d-MEAs has better cell performance than that with typical mono-layered MEAs (m-MEAs). In particular, the d-MEA whose inner layer is composed of multi-walled carbon nanotubes (MWCNTs) showed the best fuel cell performance. This is due to the fact that the d-MEAs with MWCNTs have the highest electrochemical surface area and the lowest activation polarization, as observed from the CV and EIS test. PMID:23858921

  8. Modeling of durability of polyelectrolyte membrane of O2/H2 fuel cell

    E-print Network

    Atrazhev, Vadim V

    2014-01-01

    In this paper, we discuss critical aspects of the mechanisms and features of polymer proton exchange membrane (PEM) degradation in low-temperature H2/O2 fuel cell. In this paper, we focused on chemical mechanism of OH radical generation and their distribution in operational fuel cell. According to the current concept, free radicals are generated from hydrogen and oxygen crossover gases at the surface of Pt particles that precipitated in the membrane. We explicitly calculate Pt precipitation rate and electrochemical potential distribution in the membrane that controls it. Based on radical generation rate and Pt distribution we calculate degradation rate of the membrane taking advantage of simple kinetics equations.

  9. Effects of microwaves on cell membrane permeability. Report No. 3 (final) July 1981-June 1984

    SciTech Connect

    Liburdy, R.P.

    1984-07-02

    The objective of this research project was to identify and characterize cell membrane responses to microwave radiation and, importantly, to determine specific conditions or modulators required for these responses. This study has revealed that membrane permeability changes in the erythrocyte and in liposome vesicles, as well as protein shedding in the erythrocyte, are induced by microwaves at the membrane phase transition, and that these responses are strongly dependent on plasma, oxygen tension, and antioxidant free radical scavengers. These findings provide new insight into both the physical and chemical nature of microwave radiation interaction with the cell membrane.

  10. High power density proton exchange membrane fuel cells

    NASA Technical Reports Server (NTRS)

    Murphy, Oliver J.; Hitchens, G. Duncan; Manko, David J.

    1993-01-01

    Proton exchange membrane (PEM) fuel cells use a perfluorosulfonic acid solid polymer film as an electrolyte which simplifies water and electrolyte management. Their thin electrolyte layers give efficient systems of low weight, and their materials of construction show extremely long laboratory lifetimes. Their high reliability and their suitability for use in a microgravity environment makes them particularly attractive as a substitute for batteries in satellites utilizing high-power, high energy-density electrochemical energy storage systems. In this investigation, the Dow experimental PEM (XUS-13204.10) and unsupported high platinum loading electrodes yielded very high power densities, of the order of 2.5 W cm(exp -2). A platinum black loading of 5 mg per cm(exp 2) was found to be optimum. On extending the three-dimensional reaction zone of fuel cell electrodes by impregnating solid polymer electrolyte into the electrode structures, Nafion was found to give better performance than the Dow experimental PEM. The depth of penetration of the solid polymer electrolyte into electrode structures was 50-70 percent of the thickness of the platinum-catalyzed active layer. However, the degree of platinum utilization was only 16.6 percent and the roughness factor of a typical electrode was 274.

  11. Facilitated Anion Transport Induces Hyperpolarization of the Cell Membrane That Triggers Differentiation and Cell Death in Cancer Stem Cells.

    PubMed

    Soto-Cerrato, Vanessa; Manuel-Manresa, Pilar; Hernando, Elsa; Calabuig-Fariñas, Silvia; Martínez-Romero, Alicia; Fernández-Dueñas, Víctor; Sahlholm, Kristoffer; Knöpfel, Thomas; García-Valverde, María; Rodilla, Ananda M; Jantus-Lewintre, Eloisa; Farràs, Rosa; Ciruela, Francisco; Pérez-Tomás, Ricardo; Quesada, Roberto

    2015-12-23

    Facilitated anion transport potentially represents a powerful tool to modulate various cellular functions. However, research into the biological effects of small molecule anionophores is still at an early stage. Here we have used two potent anionophore molecules inspired in the structure of marine metabolites tambjamines to gain insight into the effect induced by these compounds at the cellular level. We show how active anionophores, capable of facilitating the transmembrane transport of chloride and bicarbonate in model phospholipid liposomes, induce acidification of the cytosol and hyperpolarization of plasma cell membranes. We demonstrate how this combined effect can be used against cancer stem cells (CSCs). Hyperpolarization of cell membrane induces cell differentiation and loss of stemness of CSCs leading to effective elimination of this cancer cell subpopulation. PMID:26632983

  12. Induction of gel-phase lipid in plasma membrane of chick intestinal cells after coccidial infection.

    PubMed

    Thompson, J E; Fernando, M A; Pasternak, J

    1979-08-23

    When chickens are infected with the coccidial parasite Eimeria necatrix, the plasma membrane of intestinal cells harbouring second-generation schizonts becomes refractory to mechanical shearing, hypotonic shock and ultrasonication. Plasma membrane from these infected cells was isolated to high purity as judged by enriched levels of ouabain-sensitive (Na+ + K+)-stimulated Mg2-dependent ATPase activity and sialic acid content, the lack of detectable cytochrome oxidase and glucose-6-phosphatase activities and electron microscopic analysis of the final preparation. Wide-angle X-ray diffraction patterns recorded from the isolated membranes revealed that during the later stages of parasite maturation the host cell plasma membrane acquires increasing proportions of gel-phase lipid. By contrast, purified membrane from isolated parasites is in a liquid-crystalline state. The transition temperature of host cell plasmalemma at 100 h postinfection is 61 degrees C, about 20 degrees C above physiological temperature. By contrast, liposomes of plasma membranes from infected cells undergo a thermal transition at about 28 degrees C. The accumulation of gel-phase lipid in the host cell plasma membrane is not attributable either to an increase in the constituent ratio of saturated to unsaturated fatty acids or to a significant change in the cholesterol to phospholipid ratio. During the late stages of infection, the cells become stainable with trypan blue which suggests that the acquisition of crystalline phase lipid disrupts the permeability of the host cell plasmalemma. PMID:486463

  13. Proteomic analysis of post-nuclear supernatant fraction and percoll-purified membranes prepared from brain cortex of rats exposed to increasing doses of morphine

    PubMed Central

    2014-01-01

    Background Proteomic analysis was performed in post-nuclear supernatant (PNS) and Percoll-purified membranes (PM) prepared from fore brain cortex of rats exposed to increasing doses of morphine (10–50 mg/kg) for 10 days. Results In PNS, the 10 up (?)- or down (?)-regulated proteins exhibiting the largest morphine-induced change were selected, excised manually from the gel and identified by MALDI-TOF MS/MS: 1-(gi|148747414, Guanine deaminase), ?2.5×; 2-(gi|17105370, Vacuolar-type proton ATP subunit B, brain isoform), ?2.6×; 3-(gi|1352384, Protein disulfide-isomerase A3), ?3.4×; 4-(gi|40254595, Dihydropyrimidinase-related protein 2), ?3.6×; 5-(gi|149054470, N-ethylmaleimide sensitive fusion protein, isoform CRAa), ?2.0×; 6-(gi|42476181, Malate dehydrogenase, mitochondrial precursor), ?1.4×; 7-(gi|62653546, Glyceraldehyde-3-phosphate dehydrogenase), ?1.6×; 8-(gi|202837, Aldolase A), ?1.3×; 9-(gi|31542401, Creatine kinase B-type), ?0.86×; 10-(gi|40538860, Aconitate hydratase, mitochondrial precursor), ?1.3×. The identified proteins were of cytoplasmic (1, 4, 5, 7, 9), cell membrane (2), endoplasmic reticulum (3) and mitochondrial (6, 8, 10) origin and 9 of them were significantly increased, 1.3-3.6×. The 4 out of 9 up-regulated proteins (4, 6, 7, 10) were described as functionally related to oxidative stress; the 2 proteins participate in genesis of apoptotic cell death. In PM, the 18 up (?)- or down (?)-regulated proteins were identified by LC-MS/MS and were of plasma membrane [Brain acid soluble protein, ?2.1×; trimeric G? subunit, ?2.0x], myelin membrane [MBP, ?2.5×], cytoplasmic [Internexin, ?5.2×; DPYL2, ?4.9×; Ubiquitin hydrolase, ?2.0×; 60S ribosomal protein, ?2.7×; KCRB, ?2.6×; Sirtuin-2, ?2.5×; Peroxiredoxin-2, ?2.2×; Septin-11, ?2.2×; TERA, ?2.1×; SYUA, ?2.0×; Coronin-1A, ?5.4×] and mitochondrial [Glutamate dehydrogenase 1, ?2.7×; SCOT1, ?2.2×; Prohibitin, ?2.2×; Aspartate aminotransferase, ?2.2×] origin. Surprisingly, the immunoblot analysis of the same PM resolved by 2D-ELFO indicated that the “active”, morphine-induced pool of G? subunits represented just a minor fraction of the total signal of G? which was decreased 1.2x only. The dominant signal of G? was unchanged. Conclusion Brain cortex of rats exposed to increasing doses of morphine is far from being adapted. Significant up-regulation of proteins functionally related to oxidative stress and apoptosis suggests a major change of energy metabolism resulting in the state of severe brain cell “discomfort” or even death. PMID:24528483

  14. Assessing the utility of bipolar membranes for use in photoelectrochemical water-splitting cells.

    PubMed

    Vargas-Barbosa, Nella M; Geise, Geoffrey M; Hickner, Michael A; Mallouk, Thomas E

    2014-11-01

    Membranes are important in water-splitting solar cells because they prevent crossover of hydrogen and oxygen. Here, bipolar membranes (BPMs) were tested as separators in water electrolysis cells. Steady-state membrane and solution resistances, electrode overpotentials, and pH gradients were measured at current densities relevant to solar photoelectrolysis. Under forward bias conditions, electrodialysis of phosphate buffer ions creates a pH gradient across a BPM. Under reverse bias, the BPM can maintain a constant buffer pH on both sides of the cell, but a large membrane potential develops. Thus, the BPM does not present a viable solution for electrolysis in buffered electrolytes. However, the membrane potential is minimized when the anode and cathode compartments of the cell contain strongly basic and acidic electrolytes, respectively. PMID:25256955

  15. Efficient Targeting of Fatty-Acid Modified Oligonucleotides to Live Cell Membranes through Stepwise Assembly

    PubMed Central

    2014-01-01

    Lipid modifications provide efficient targeting of oligonucleotides to live cell membranes in a range of applications. Targeting efficiency is a function of the rate of lipid DNA insertion into the cell surface and its persistence over time. Here we show that increasing lipid hydrophobicity increases membrane persistence, but decreases the rate of membrane insertion due to the formation of nonproductive aggregates in solution. To ameliorate this effect, we split the net hydrophobicity of the membrane anchor between two complementary oligonucleotides. When prehybridized in solution, doubly anchored molecules also aggregate due to their elevated hydrophobicity. However, when added sequentially to cells, aggregation does not occur so membrane insertion is efficient. Hybridization between the two strands locks the complexes at the cell surface by increasing net hydrophobicity, increasing their total concentration and lifetime, and dramatically improving their utility in a variety of biomedical applications. PMID:25325667

  16. Contribution of effluent organic matter (EfOM) to ultrafiltration (UF) membrane fouling: isolation, characterization, and fouling effect of EfOM fractions.

    PubMed

    Zheng, Xing; Khan, Muhammad Tariq; Croué, Jean-Philippe

    2014-11-15

    EfOM has been regarded as a major organic foulant resulting in UF membrane fouling in wastewater reclamation. To investigate fouling potential of different EfOM fractions, the present study isolated EfOM into hydrophobic neutrals (HPO-N), colloids, hydrophobic acids (HPO-A), transphilic neutrals and acids (TPI), and hydrophilics (HPI), and tested their fouling effect in both salt solution and pure water during ultrafiltration (UF). Major functional groups and chemical structure of the isolates were identified using Fourier transform infrared spectroscopy (FT-IR) and solid-state carbon nuclear magnetic resonance ((13)C NMR) analysis. The influence of the isolation process on the properties of EfOM fractions was minor because the raw and reconstituted secondary effluents were found similar with respect to UV absorbance, molecular size distribution, and fluorescence character. In membrane filtration tests, unified membrane fouling index (UMFI) and hydraulic resistance were used to quantify irreversible fouling potential of different water samples. Results show that under similar DOC level in feed water, colloids present much more irreversible fouling than other fractions. The fouling effect of the isolates is related to their size, chemical properties, and solution chemistry. Further investigations have identified that the interaction between colloids and other fractions also influences the performance of colloids in fouling phenomena. PMID:25173435

  17. Temperature-Dependent Simulations of Dry Gas Transport in the Electrodes of Proton Exchange Membrane Fuel Cells

    E-print Network

    Stockie, John

    Membrane Fuel Cells M. J. Kermani1 J. M. Stockie2 mkermani@unb.ca stockie@unb.ca 1 Post Doctoral Fellow the cathode of a proton exchange membrane (PEM) fuel cell is studied numerically. The di usion membrane (PEM) fuel cell. ature onmodelingoftransport processes inPEM fuelcells. The vast majority of work

  18. An alkaline direct ethanol fuel cell with a cation exchange membrane Liang An and T. S. Zhao*

    E-print Network

    Zhao, Tianshou

    An alkaline direct ethanol fuel cell with a cation exchange membrane Liang An and T. S. Zhao the performance of anion exchange membrane (AEM) direct ethanol fuel cells (DEFCs) is that state-of-the-art AEMs exchange membrane direct ethanol fuel cells (AEM- DEFCs) have received ever-increasing attention, mainly

  19. Relationships between Membrane Binding, Affinity and Cell Internalization Efficacy of a Cell-Penetrating Peptide: Penetratin as a Case Study

    PubMed Central

    Alves, Isabel D.; Bechara, Cherine; Walrant, Astrid; Zaltsman, Yefim; Jiao, Chen-Yu; Sagan, Sandrine

    2011-01-01

    Background Penetratin is a positively charged cell-penetrating peptide (CPP) that has the ability to bind negatively charged membrane components, such as glycosaminoglycans and anionic lipids. Whether this primary interaction of penetratin with these cell surface components implies that the peptide will be further internalized is not clear. Methodology Using mass spectrometry, the amount of internalized and membrane bound penetratin remaining after washings, were quantified in three different cell lines: wild type (WT), glycosaminoglycans- (GAGneg) and sialic acid-deficient (SAneg) cells. Additionally, the affinity and kinetics of the interaction of penetratin to membrane models composed of pure lipids and membrane fragments from the referred cell lines was investigated, as well as the thermodynamics of such interactions using plasmon resonance and calorimetry. Principal Findings Penetratin internalized with the same efficacy in the three cell lines at 1 µM, but was better internalized at 10 µM in SAneg>WT>GAGneg. The heat released by the interaction of penetratin with these cells followed the ranking order of internalization efficiency. Penetratin had an affinity of 10 nM for WT cells and µM for SAneg and GAGneg cells and model membrane of phospholipids. The remaining membrane-bound penetratin after cells washings was similar in WT and GAGneg cells, which suggested that these binding sites relied on membrane phospholipids. The interaction of penetratin with carbohydrates was more superficial and reversible while it was stronger with phospholipids, likely because the peptide can intercalate between the fatty acid chains. Conclusion/Significance These results show that accumulation and high-affinity binding of penetratin at the cell-surface do not reflect the internalization efficacy of the peptide. Altogether, these data further support translocation (membrane phospholipids interaction) as being the internalization pathway used by penetratin at low micromolecular concentration, while endocytosis is activated at higher concentration and requires accumulation of the peptide on GAG and GAG clustering. PMID:21915283

  20. Multiphoton Process and Anomalous Potential of Cell Membrane by Laser Radiation

    NASA Technical Reports Server (NTRS)

    Zhang, Kaixi; Zhao, Qingxun; Cui, Zhiyun; Zhar, Ping; Dong, Lifang

    1996-01-01

    In this paper, by the use of quantum biology and quantum optics, the laser induced potential variation of cell membrane has been studied. Theoretically, we have found a method of calculating the monophoton and multiphoton processes in the formation of the anomalous potential of cell membrane. In contrast with the experimental results, our numerical result is in the same order. Therefore, we have found the possibility of cancer caused by the laser induced anomalous cell potential.

  1. Photoaffinity labeling of regulatory subunits of protein kinase A in cardiac cell fractions of rats

    NASA Technical Reports Server (NTRS)

    Mednieks, M. I.; Popova, I.; Grindeland, R. E.

    1992-01-01

    Photoaffinity labeling in heart tissue of rats flown on Cosmos 2044 was used to measure the regulatory (R) subunits of adenosine monophosphate-dependent protein kinase. A significant decrease of RII subunits in the particulate cell fraction extract (S2; P less than 0.05 in all cases) was observed when extracts of tissue samples from vivarium controls were compared with those from flight animals. Photoaffinity labeling of the soluble fraction (S1) was observed to be unaffected by spaceflight or any of the simulation conditions. Proteins of the S2 fraction constitute a minor (less than 10 percent) component of the total, whereas the S1 fraction contained most of the cell proteins. Changes in a relatively minor aspect of adenosine monophosphate-mediated reactions are considered to be representative of a metabolic effect.

  2. Electrochemistry of Fuel Cells and Batteries (ME/MS 545) Course Description: Electrochemistry of fuel cells, batteries, sensors, membrane

    E-print Network

    Lin, Xi

    Electrochemistry of Fuel Cells and Batteries (ME/MS 545) Course Description: Electrochemistry of fuel cells, batteries, sensors, membrane separation and electrolytic methods are discussed such as those represented by fuel cells, batteries, and various sensors and electrolytic cells. Exam schedule

  3. Identifying the Membrane Proteome of HIV-1 Latently Infected Cells*S

    E-print Network

    Vertes, Akos

    Identifying the Membrane Proteome of HIV-1 Latently Infected Cells*S Received for publication, **Department of Biochemistry/ Center for Sickle Cell Disease, Howard University, Washington, D. C. 20059 of established human immunodeficiency virus-1 (HIV-1) latent cell models and parental cell lines. To this end we

  4. Distinct Regulation of Cytoplasmic Calcium Signals and Cell Death Pathways by Different Plasma Membrane Calcium

    E-print Network

    Kenny, Paraic

    Membrane Calcium ATPase Isoforms in MDA-MB-231 Breast Cancer Cells* Received for publication,March 20, 2012-dependent and -independent cell death in MDA-MB-231 cells. Conclusion: PMCA isoforms have distinct roles in the control viability in MDA-MB-231 breast cancer cells. The PMCA1 isoform was the predominant regulator of global Ca2

  5. Growth of Carbon Support for Proton-Exchange-Membrane Fuel Cell by

    E-print Network

    Growth of Carbon Support for Proton-Exchange-Membrane Fuel Cell by Pulsed-Laser Deposition (PLDGDL)(catalyst) (pulsed laser deposition PLD) (plasma plume) () #12;III Abstract key word: Fuel CellPulsed Laser. People begin to develop fuel cells for seeking alternative energy sources. Fuel cell use the chemical

  6. Detection of anti-liver cell membrane antibody using a human hepatocellular carcinoma cell line

    SciTech Connect

    Lobo-Yeo, A.; McSorley, C.; McFarlane, B.M.; Mieli-Vergani, G.; Mowat, A.P.; Vergani, D.

    1989-02-01

    A radioimmunometric technique for the detection of autoantibodies to liver membrane antigens has been developed using Alexander cells, a human hepatocellular carcinoma cell line. After incubation of Alexander cells with serum, antimembrane antibodies were detected by addition of /sup 125/I-labeled Protein A. Binding ratios in 15 children with uncontrolled autoimmune chronic active hepatitis and in seven children with primary sclerosing cholangitis were significantly higher than in 18 age-matched normal controls. Nine patients with inactive autoimmune chronic active hepatitis, 13 with alpha 1-antitrypsin deficiency and five with fulminant hepatic failure had ratios similar to controls. In nine patients with Wilson's disease, there was a modest but significant increase in binding ratio. In four children with autoimmune chronic active hepatitis, binding ratios fell during effective immunosuppressive therapy. Sera from patients with systemic lupus erythematosus or rheumatoid arthritis gave normal results, excluding that binding derives from Fc-mediated immune complex capture. A positive correlation was found between Alexander cell binding values and anti-liver-specific protein antibody titers, suggesting that the two assays detect antibodies against shared antigenic determinants. The Alexander cell assay is a simple, rapid and sensitive technique to detect antibody to liver cell membrane antigens.

  7. Prolongation of lifetime of high temperature proton exchange membrane fuel cells

    NASA Astrophysics Data System (ADS)

    Oono, Yuka; Sounai, Atsuo; Hori, Michio

    2013-11-01

    In a previous study on the long-term operation of high-temperature proton exchange membrane fuel cells (HT-PEMFCs) with polybenzimidazole (PBI) membranes, it was found that the main cause of the observed decrease in cell voltage with time was phosphoric acid depletion due to evaporation. Based on this result, in the present study, the effects of using a different kind of cell membrane were investigated. Instead of PBI membranes, phosphoric-acid-doped, chemically cross-linked poly(2,5-benzimidazole) (ABPBI) membranes were employed in HT-PEMFCs and long-term power generation tests were carried out. Two separate cells were operated for 1000 and 17,500 h at a temperature of 150 °C and a current density of 0.2 A cm-2. Their membrane electrode assemblies were then subjected to electron probe microanalysis. The results for the cell operated for 17,500 h were directly compared with those for a cell with a PBI membrane operated for 17,800 h in a previous study, allowing the mechanism of cell performance reduction in HT-PEMFCs to be further elucidated.

  8. Reversible Membrane Pearling in Live Cells upon Destruction of the Actin Cortex

    PubMed Central

    Heinrich, Doris; Ecke, Mary; Jasnin, Marion; Engel, Ulrike; Gerisch, Günther

    2014-01-01

    Membrane pearling in live cells is observed when the plasma membrane is depleted of its support, the cortical actin network. Upon efficient depolymerization of actin, pearls of variable size are formed, which are connected by nanotubes of ?40 nm diameter. We show that formation of the membrane tubes and their transition into chains of pearls do not require external tension, and that they neither depend on microtubule-based molecular motors nor pressure generated by myosin-II. Pearling thus differs from blebbing. The pearling state is stable as long as actin is prevented from polymerizing. When polymerization is restored, the pearls are retracted into the cell, indicating continuity of the membrane. Our data suggest that the alternation of pearls and strings is an energetically favored state of the unsupported plasma membrane, and that one of the functions of the actin cortex is to prevent the membrane from spontaneously assuming this configuration. PMID:24606932

  9. Multiplex lithography for multilevel multiscale architectures and its application to polymer electrolyte membrane fuel cell

    NASA Astrophysics Data System (ADS)

    Cho, Hyesung; Moon Kim, Sang; Sik Kang, Yun; Kim, Junsoo; Jang, Segeun; Kim, Minhyoung; Park, Hyunchul; Won Bang, Jung; Seo, Soonmin; Suh, Kahp-Yang; Sung, Yung-Eun; Choi, Mansoo

    2015-09-01

    The production of multiscale architectures is of significant interest in materials science, and the integration of those structures could provide a breakthrough for various applications. Here we report a simple yet versatile strategy that allows for the LEGO-like integrations of microscale membranes by quantitatively controlling the oxygen inhibition effects of ultraviolet-curable materials, leading to multilevel multiscale architectures. The spatial control of oxygen concentration induces different curing contrasts in a resin allowing the selective imprinting and bonding at different sides of a membrane, which enables LEGO-like integration together with the multiscale pattern formation. Utilizing the method, the multilevel multiscale Nafion membranes are prepared and applied to polymer electrolyte membrane fuel cell. Our multiscale membrane fuel cell demonstrates significant enhancement of performance while ensuring mechanical robustness. The performance enhancement is caused by the combined effect of the decrease of membrane resistance and the increase of the electrochemical active surface area.

  10. Multiplex lithography for multilevel multiscale architectures and its application to polymer electrolyte membrane fuel cell

    PubMed Central

    Cho, Hyesung; Moon Kim, Sang; Sik Kang, Yun; Kim, Junsoo; Jang, Segeun; Kim, Minhyoung; Park, Hyunchul; Won Bang, Jung; Seo, Soonmin; Suh, Kahp-Yang; Sung, Yung-Eun; Choi, Mansoo

    2015-01-01

    The production of multiscale architectures is of significant interest in materials science, and the integration of those structures could provide a breakthrough for various applications. Here we report a simple yet versatile strategy that allows for the LEGO-like integrations of microscale membranes by quantitatively controlling the oxygen inhibition effects of ultraviolet-curable materials, leading to multilevel multiscale architectures. The spatial control of oxygen concentration induces different curing contrasts in a resin allowing the selective imprinting and bonding at different sides of a membrane, which enables LEGO-like integration together with the multiscale pattern formation. Utilizing the method, the multilevel multiscale Nafion membranes are prepared and applied to polymer electrolyte membrane fuel cell. Our multiscale membrane fuel cell demonstrates significant enhancement of performance while ensuring mechanical robustness. The performance enhancement is caused by the combined effect of the decrease of membrane resistance and the increase of the electrochemical active surface area. PMID:26412619

  11. Multiplex lithography for multilevel multiscale architectures and its application to polymer electrolyte membrane fuel cell.

    PubMed

    Cho, Hyesung; Moon Kim, Sang; Sik Kang, Yun; Kim, Junsoo; Jang, Segeun; Kim, Minhyoung; Park, Hyunchul; Won Bang, Jung; Seo, Soonmin; Suh, Kahp-Yang; Sung, Yung-Eun; Choi, Mansoo

    2015-01-01

    The production of multiscale architectures is of significant interest in materials science, and the integration of those structures could provide a breakthrough for various applications. Here we report a simple yet versatile strategy that allows for the LEGO-like integrations of microscale membranes by quantitatively controlling the oxygen inhibition effects of ultraviolet-curable materials, leading to multilevel multiscale architectures. The spatial control of oxygen concentration induces different curing contrasts in a resin allowing the selective imprinting and bonding at different sides of a membrane, which enables LEGO-like integration together with the multiscale pattern formation. Utilizing the method, the multilevel multiscale Nafion membranes are prepared and applied to polymer electrolyte membrane fuel cell. Our multiscale membrane fuel cell demonstrates significant enhancement of performance while ensuring mechanical robustness. The performance enhancement is caused by the combined effect of the decrease of membrane resistance and the increase of the electrochemical active surface area. PMID:26412619

  12. Normal and tumor-derived myoepithelial cells differ in their ability to interact with luminal breast epithelial cells for polarity and basement membrane deposition

    SciTech Connect

    Gudjonsson, Thorarinn; Ronnov-Jessen, Lone; Villadsen, Rene; Rank, Fritz; Bissell, Mina J.; Petersen, Ole William

    2001-10-04

    The signals that determine the correct polarity of breast epithelial structures in vivo are not understood. We have shown previously that luminal epithelial cells can be polarized when cultured within a reconstituted basement membrane gel. We reasoned that such cues in vivo may be given by myoepithelial cells. Accordingly, we used an assay where luminal epithelial cells are incorrectly polarized to test this hypothesis. We show that culturing human primary luminal epithelial cells within collagen-I gels leads to formation of structures with no lumina and with reverse polarity as judged by dual stainings for sialomucin, epithelial specific antigen or occludin. No basement membrane is deposited, and {beta}4-integrin staining is negative. Addition of purified human myoepithelial cells isolated from normal glands corrects the inverse polarity, and leads to formation of double-layered acini with central lumina. Among the laminins present in the human breast basement membrane (laminin-1, -5 and -10/11), laminin-1 was unique in its ability to substitute for myoepithelial cells in polarity reversal. Myoepithelial cells were purified also from four different breast cancer sources including a biphasic cell line. Three out of four samples either totally lacked the ability to interact with luminal epithelial cells, or conveyed only correction of polarity in a fraction of acini. This behavior was directly related to the ability of the tumor myoepithelial cells to produce {alpha}-1 chain of laminin. In vivo, breast carcinomas were either negative for laminin-1 (7/12 biopsies) or showed a focal, fragmented deposition of a less intensely stained basement membrane (5/12 biopsies). Dual staining with myoepithelial markers revealed that tumorassociated myoepithelial cells were either negative or weakly positive for expression of laminin-1, establishing a strong correlation between loss of laminin-1 and breast cancer. We conclude that the double-layered breast acinus may be recapitulated in culture and that one reason for the ability of myoepithelial cells to induce polarity is because they are the only source of laminin-1 in the breast in vivo. A further conclusion is that a majority of tumor-derived/-associated myoepithelial cells are deficient in their ability to impart polarity because they have lost their ability to synthesize sufficient or functional laminin-1. These results have important implications for the role of myoepithelial cells in maintenance of polarity in normal breast and how they may function as structural tumor suppressors.

  13. Membrane interactions of two arginine-rich peptides with different cell internalization capacities.

    PubMed

    Walrant, Astrid; Vogel, Alexander; Correia, Isabelle; Lequin, Olivier; Olausson, Bjoern E S; Desbat, Bernard; Sagan, Sandrine; Alves, Isabel D

    2012-07-01

    Cell penetrating peptides (CPPs) can cross cell membranes in a receptor independent manner and transport cargo molecules inside cells. These peptides can internalize through two independent routes: energy dependent endocytosis and energy independent translocation across the membrane, but the exact mechanisms are still unknown. The interaction of the CPP with different membrane components is certainly a preliminary key point that triggers internalization, such as the interaction with lipids to lead to the translocation process. In this study, we used two arginine-rich peptides, RW9 (RRWWRRWRR-NH2), which is a potent CPP, and RL9 (RRLLRRLRR-NH2) that, although binding tightly and accumulating on membranes, does not enter into cells. Using a set of experimental and theoretical techniques, we studied the binding, insertion and orientation of the peptides into different model membranes as well as the subsequent membrane reorganization. Herein we show that although the two peptides had rather similar behavior regarding lipid membrane interaction, subtle differences were found concerning the depth of peptide insertion, effect on the lipid chain ordering and kinetics of peptide insertion in the membrane, which altogether might explain their different cell internalization capacities. Molecular dynamics simulation studies show that some peptide molecules flipped their orientation over the course of the simulation such that the hydrophobic residues penetrated deeper in the lipid core region while Arg-residues maintained H-bonds with the lipid headgroups, serving as a molecular hinge in a conformation that appeared to correspond to the equilibrium one. PMID:22402267

  14. Physiological and transcriptional responses of Saccharomyces cerevisiae to d-limonene show changes to the cell wall but not to the plasma membrane.

    PubMed

    Brennan, Timothy C R; Krömer, Jens O; Nielsen, Lars K

    2013-06-01

    Monoterpenes can, upon hydrogenation, be used as light-fraction components of sustainable aviation fuels. Fermentative production of monoterpenes in engineered microorganisms, such as Saccharomyces cerevisiae, has gained attention as a potential route to deliver these next-generation fuels from renewable biomass. However, end product toxicity presents a formidable problem for microbial synthesis. Due to their hydrophobicity, monoterpene inhibition has long been attributed to membrane interference, but the molecular mechanism remains largely unsolved. In order to gain a better understanding of the mode of action, we analyzed the composition and structural integrity of the cell envelope as well as the transcriptional response of yeast cells treated with an inhibitory amount of d-limonene (107 mg/liter). We found no alterations in membrane fluidity, structural membrane integrity, or fatty acid composition after the solvent challenge. A 4-fold increase in the mean fluorescence intensity per cell (using calcofluor white stain) and increased sensitivity to cell wall-degrading enzymes demonstrated that limonene disrupts cell wall properties. Global transcript measurements confirmed the membrane integrity observations by showing no upregulation of ergosterol or fatty acid biosynthesis pathways, which are commonly overexpressed in yeast to reinforce membrane rigidity during ethanol exposure. Limonene shock did cause a compensatory response to cell wall damage through overexpression of several genes (ROM1, RLM1, PIR3, CTT1, YGP1, MLP1, PST1, and CWP1) involved with the cell wall integrity signaling pathway. This is the first report demonstrating that cell wall, rather than plasma membrane, deterioration is the main source of monoterpene inhibition. We show that limonene can alter the structure and function of the cell wall, which has a clear effect on cytokinesis. PMID:23542628

  15. Physiological and Transcriptional Responses of Saccharomyces cerevisiae to d-Limonene Show Changes to the Cell Wall but Not to the Plasma Membrane

    PubMed Central

    Brennan, Timothy C. R.; Nielsen, Lars K.

    2013-01-01

    Monoterpenes can, upon hydrogenation, be used as light-fraction components of sustainable aviation fuels. Fermentative production of monoterpenes in engineered microorganisms, such as Saccharomyces cerevisiae, has gained attention as a potential route to deliver these next-generation fuels from renewable biomass. However, end product toxicity presents a formidable problem for microbial synthesis. Due to their hydrophobicity, monoterpene inhibition has long been attributed to membrane interference, but the molecular mechanism remains largely unsolved. In order to gain a better understanding of the mode of action, we analyzed the composition and structural integrity of the cell envelope as well as the transcriptional response of yeast cells treated with an inhibitory amount of d-limonene (107 mg/liter). We found no alterations in membrane fluidity, structural membrane integrity, or fatty acid composition after the solvent challenge. A 4-fold increase in the mean fluorescence intensity per cell (using calcofluor white stain) and increased sensitivity to cell wall-degrading enzymes demonstrated that limonene disrupts cell wall properties. Global transcript measurements confirmed the membrane integrity observations by showing no upregulation of ergosterol or fatty acid biosynthesis pathways, which are commonly overexpressed in yeast to reinforce membrane rigidity during ethanol exposure. Limonene shock did cause a compensatory response to cell wall damage through overexpression of several genes (ROM1, RLM1, PIR3, CTT1, YGP1, MLP1, PST1, and CWP1) involved with the cell wall integrity signaling pathway. This is the first report demonstrating that cell wall, rather than plasma membrane, deterioration is the main source of monoterpene inhibition. We show that limonene can alter the structure and function of the cell wall, which has a clear effect on cytokinesis. PMID:23542628

  16. How does carbon dioxide permeate cell membranes? A discussion of concepts, results and methods

    PubMed Central

    Endeward, Volker; Al-Samir, Samer; Itel, Fabian; Gros, Gerolf

    2013-01-01

    We review briefly how the thinking about the permeation of gases, especially CO2, across cell and artificial lipid membranes has evolved during the last 100 years. We then describe how the recent finding of a drastic effect of cholesterol on CO2 permeability of both biological and artificial membranes fundamentally alters the long-standing idea that CO2—as well as other gases—permeates all membranes with great ease. This requires revision of the widely accepted paradigm that membranes never offer a serious diffusion resistance to CO2 or other gases. Earlier observations of “CO2-impermeable membranes” can now be explained by the high cholesterol content of some membranes. Thus, cholesterol is a membrane component that nature can use to adapt membrane CO2 permeability to the functional needs of the cell. Since cholesterol serves many other cellular functions, it cannot be reduced indefinitely. We show, however, that cells that possess a high metabolic rate and/or a high rate of O2 and CO2 exchange, do require very high CO2 permeabilities that may not be achievable merely by reduction of membrane cholesterol. The article then discusses the alternative possibility of raising the CO2 permeability of a membrane by incorporating protein CO2 channels. The highly controversial issue of gas and CO2 channels is systematically and critically reviewed. It is concluded that a majority of the results considered to be reliable, is in favor of the concept of existence and functional relevance of protein gas channels. The effect of intracellular carbonic anhydrase, which has recently been proposed as an alternative mechanism to a membrane CO2 channel, is analysed quantitatively and the idea considered untenable. After a brief review of the knowledge on permeation of O2 and NO through membranes, we present a summary of the 18O method used to measure the CO2 permeability of membranes and discuss quantitatively critical questions that may be addressed to this method. PMID:24409149

  17. Apical Membrane Localization of the Adenomatous Polyposis Coli Tumor Suppressor Protein and Subcellular Distribution of the ?-Catenin Destruction Complex in Polarized Epithelial Cells

    PubMed Central

    Reinacher-Schick, Anke; Gumbiner, Barry M.

    2001-01-01

    The adenomatous polyposis coli (APC) protein is implicated in the majority of hereditary and sporadic colon cancers. APC is known to function as a tumor suppressor through downregulation of ?-catenin as part of a high molecular weight complex known as the ?-catenin destruction complex. The molecular composition of the intact complex and its site of action in the cell are still not well understood. Reports on the subcellular localization of APC in various cell systems have differed significantly and have been consistent with an association with a cytosolic complex, with microtubules, with the nucleus, or with the cortical actin cytoskeleton. To better understand the role of APC and the destruction complex in colorectal cancer, we have begun to characterize and isolate these complexes from confluent polarized human colon epithelial cell monolayers and other epithelial cell types. Subcellular fractionation and immunofluorescence microscopy reveal that a predominant fraction of APC associates tightly with the apical plasma membrane in a variety of epithelial cell types. This apical membrane association is not dependent on the mutational status of either APC or ?-catenin. An additional pool of APC is cytosolic and fractionates into two distinct high molecular weight complexes, 20S and 60S in size. Only the 20S fraction contains an appreciable portion of the cellular axin and small but detectable amounts of glycogen synthase kinase 3? and ?-catenin. Therefore, it is likely to correspond to the previously characterized ?-catenin destruction complex. Dishevelled is almost entirely cytosolic, but does not significantly cofractionate with the 20S complex. The disproportionate amount of APC in the apical membrane and the lack of other destruction complex components in the 60S fraction of APC raise questions about whether these pools of APC take part in the degradation of ?-catenin, or alternatively, whether they could be involved in other functions of the protein that still must be determined. PMID:11157977

  18. Affordable Hydrogen Fuel Cell Vehicles: Quaternary Phosphonium Based Hydroxide Exchange Membranes

    SciTech Connect

    2010-01-01

    Broad Funding Opportunity Announcement Project: The University of Delaware is developing a new fuel cell membrane for vehicles that relies on cheaper and more abundant materials than those used in current fuel cells. Conventional fuel cells are very acidic, so they require acid-resistant metals like platinum to generate electricity. The University of Delaware is developing an alkaline fuel cell membrane that can operate in a non-acidic environment where cheaper materials like nickel and silver, instead of platinum, can be used. In addition to enabling the use of cheaper metals, the University of Delaware’s membrane is 500 times less expensive than other polymer membranes used in conventional fuel cells.

  19. Basement Membrane and Cell Integrity of Self-Tissues in Maintaining Drosophila Immunological Tolerance

    PubMed Central

    Kim, Moon Jong; Choe, Kwang-Min

    2014-01-01

    The mechanism underlying immune system recognition of different types of pathogens has been extensively studied over the past few decades; however, the mechanism by which healthy self-tissue evades an attack by its own immune system is less well-understood. Here, we established an autoimmune model of melanotic mass formation in Drosophila by genetically disrupting the basement membrane. We found that the basement membrane endows otherwise susceptible target tissues with self-tolerance that prevents autoimmunity, and further demonstrated that laminin is a key component for both structural maintenance and the self-tolerance checkpoint function of the basement membrane. Moreover, we found that cell integrity, as determined by cell-cell interaction and apicobasal polarity, functions as a second discrete checkpoint. Target tissues became vulnerable to blood cell encapsulation and subsequent melanization only after loss of both the basement membrane and cell integrity. PMID:25329560

  20. High-level cell-free production of membrane proteins with nanodiscs.

    PubMed

    Roos, Christian; Kai, Lei; Haberstock, Stefan; Proverbio, Davide; Ghoshdastider, Umesh; Ma, Yi; Filipek, Slawomir; Wang, Xiaoning; Dötsch, Volker; Bernhard, Frank

    2014-01-01

    This chapter addresses two major bottlenecks in cell-free membrane protein production. Firstly, we describe the optimization of expression templates for obtaining membrane proteins in preparative scales. We present details for a newly established tag variation screen providing high success rates in improving expression efficiencies while having only minimal impacts on the target protein structure. Secondly, we present protocols for the efficient co-translational insertion of membrane proteins into defined lipid bilayers. We describe the production of nanodiscs and their implementation into cell-free expression reactions for the co-translational reconstitution of membrane proteins. In addition we give guidelines for the loading of nanodiscs with different lipids in order to systematically analyze effects of lipids on the translocation, functional folding, and stability of cell-free expressed membrane proteins. PMID:24395412

  1. Role of membrane components in thermal injury of cells and development of thermotolerance.

    PubMed

    Jó?wiak, Z; Leyko, W

    1992-12-01

    Exposure of cells to hyperthermia induces a transient resistance to subsequent heat treatment. The specific mechanisms responsible for hyperthermic cell killing and thermotolerance development are not well understood. It seems that heat may induce at least two different states of thermotolerance, of which one is dependent on protein synthesis. The expression of thermotolerance may include multiple cytoplasmic and membrane components. A number of studies have indicated that membranes play an important role in governing the thermal injury of cells. It seems, therefore, that heat denatured plasma membrane proteins may be a potential target for thermal stress and a trigger for the induction of thermotolerance. The localization of heat shock proteins in the plasma membrane and the suggestion of thermal resistance in enucleate erythrocytes support this suggestion. However, a direct relationship between the plasma membrane and hyperthermic killing or development of thermotolerance has not been found. PMID:1362768

  2. Fractional calculus in bioengineering.

    PubMed

    Magin, Richard L

    2004-01-01

    Fractional calculus (integral and differential operations of noninteger order) is not often used to model biological systems. Although the basic mathematical ideas were developed long ago by the mathematicians Leibniz (1695), Liouville (1834), Riemann (1892), and others and brought to the attention of the engineering world by Oliver Heaviside in the 1890s, it was not until 1974 that the first book on the topic was published by Oldham and Spanier. Recent monographs and symposia proceedings have highlighted the application of fractional calculus in physics, continuum mechanics, signal processing, and electromagnetics, but with few examples of applications in bioengineering. This is surprising because the methods of fractional calculus, when defined as a Laplace or Fourier convolution product, are suitable for solving many problems in biomedical research. For example, early studies by Cole (1933) and Hodgkin (1946) of the electrical properties of nerve cell membranes and the propagation of electrical signals are well characterized by differential equations of fractional order. The solution involves a generalization of the exponential function to the Mittag-Leffler function, which provides a better fit to the observed cell membrane data. A parallel application of fractional derivatives to viscoelastic materials establishes, in a natural way, hereditary integrals and the power law (Nutting/Scott Blair) stress-strain relationship for modeling biomaterials. In this review, I will introduce the idea of fractional operations by following the original approach of Heaviside, demonstrate the basic operations of fractional calculus on well-behaved functions (step, ramp, pulse, sinusoid) of engineering interest, and give specific examples from electrochemistry, physics, bioengineering, and biophysics. The fractional derivative accurately describes natural phenomena that occur in such common engineering problems as heat transfer, electrode/electrolyte behavior, and sub-threshold nerve propagation. By expanding the range of mathematical operations to include fractional calculus, we can develop new and potentially useful functional relationships for modeling complex biological systems in a direct and rigorous manner. PMID:15248549

  3. Cell-free Expression and In Meso Crystallisation of an Integral Membrane Kinase for Structure Determination

    PubMed Central

    Shah, Syed Tasadaque Ali; Haberstock, Stefan; Dötsch, Volker; Bernhard, Frank; Caffrey, Martin

    2014-01-01

    Membrane proteins are key elements in cell physiology and drug targeting, but getting a high-resolution structure by crystallographic means is still enormously challenging. Novel strategies are in big demand to facilitate the structure determination process that will ultimately hasten the day when sequence information alone can provide a 3-dimensional model. Cell-free or in vitro expression enables rapid access to large quantities of high quality membrane proteins suitable for an array of applications. Despite its impressive efficiency, to date only two membrane proteins produced by the in vitro approach have yielded crystal structures. Here, we have analysed synergies of cell-free expression and crystallisation in lipidic mesophases for generating an X-ray structure of the integral membrane enzyme diacylglycerol kinase to 2.28 Å resolution. The quality of cellular and cell-free expressed kinase samples have been evaluated systematically by comparing i) spectroscopic properties, ii) purity and oligomer formation, iii) lipid content and iv) functionality. DgkA is the first membrane enzyme crystallised based on cell-free expression. The study provides a basic standard for the crystallisation of cell-free expressed membrane proteins and the methods detailed here should prove generally useful and contribute to accelerating the pace at which membrane protein structures are solved. PMID:25012698

  4. Cell-free expression and in meso crystallisation of an integral membrane kinase for structure determination.

    PubMed

    Boland, Coilín; Li, Dianfan; Shah, Syed Tasadaque Ali; Haberstock, Stefan; Dötsch, Volker; Bernhard, Frank; Caffrey, Martin

    2014-12-01

    Membrane proteins are key elements in cell physiology and drug targeting, but getting a high-resolution structure by crystallographic means is still enormously challenging. Novel strategies are in big demand to facilitate the structure determination process that will ultimately hasten the day when sequence information alone can provide a three-dimensional model. Cell-free or in vitro expression enables rapid access to large quantities of high-quality membrane proteins suitable for an array of applications. Despite its impressive efficiency, to date only two membrane proteins produced by the in vitro approach have yielded crystal structures. Here, we have analysed synergies of cell-free expression and crystallisation in lipid mesophases for generating an X-ray structure of the integral membrane enzyme diacylglycerol kinase to 2.28-Å resolution. The quality of cellular and cell-free-expressed kinase samples has been evaluated systematically by comparing (1) spectroscopic properties, (2) purity and oligomer formation, (3) lipid content and (4) functionality. DgkA is the first membrane enzyme crystallised based on cell-free expression. The study provides a basic standard for the crystallisation of cell-free-expressed membrane proteins and the methods detailed here should prove generally useful and contribute to accelerating the pace at which membrane protein structures are solved. PMID:25012698

  5. Comparison of the phosphorylation events in membranes prepared from proliferating versus quiescent endothelial cells

    SciTech Connect

    Kazlauskas, A.; DiColeto, P.E.

    1986-05-01

    Little is known of the intracellular events which regulate the proliferation of endothelial cells (EC). Triton-solubilized membranes from proliferating (sparse) and quiescent (confluent) EC were incubated at pH 6.5 in the presence of divalent cations and (/sup 32/P)ATP. Membrane proteins were analyzed by sodium dodecyl sulfate polyacrylamide gel electrophoresis and autoradiography. The overall kinase activity per mg protein was slightly greater in membranes prepared from proliferating versus quiescent cells. They found four proteins labeled in sparse cells to a dramatically greater extent having the following approximate molecular masses: 180, 100, 97 and 55 kilodalton (kd). The first two phosphoproteins were phosphorylated on serine residues exclusively; the 97 kd phosphoprotein contained 39% phosphoserine (p-ser) and 61% phosphothreonine (p-thr); and the 55 kd phosphoprotein contained 62% p-ser, 16% p-thr, and 22% phosphotyrosine (p-tyr). The kinases acting on all four phosphoproteins were independent of Ca/sup 2 +/, cAMP, cGMP, or phorbol 12-myristate 13-acetate. The observed differences in phosphorylation events between sparse and confluent membranes occurred in membranes from two EC lines - pig aortic and bovine aortic - but were not apparent in membranes prepared from human foreskin fibroblasts or 3T3 cells. Sparse endothelial cells made quiescent by serum deprivation were found to resemble confluent cells in the kinase activity; therefore, the enhanced kinase activity in sparse membranes may be growth dependent.

  6. The role of CD4 on mechanical properties of live cell membrane.

    PubMed

    Bui, Van-Chien; Nguyen, Thi-Huong

    2016-01-01

    Although much progress has been made in the characterization and identification of CD4 functions, its role in mechanical properties of cell membrane remains largely unknown. Here an atomic force microscopy (AFM) was used to investigate the roles of CD4 in the elasticity of the leukemic human Jurkat (clone E6-1) cell membranes. Analysis of the approach force curves with Hertz model for a completely elastic soft sample measured on the selected CD4+ and CD4- cells showed that CD4+ cell membrane was softer than CD4- one. To confirm that CD4 plays a role in altering cell elasticity, human embryonic kidney 293T cells were transiently transfected with wild type (wt) CD4 plasmid before being used in AFM nanoindentation experiments. The results also demonstrated CD4- membrane was stiffer than CD4+ one suggesting that CD4 integrated into plasma membrane and altered its mechanical properties. The study gives insights into the role of CD4 on cell membrane mechanical characteristics and might be helpful for development of cell biology and medicine. © 2015 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 104A: 239-244, 2016. PMID:26362701

  7. Composite Nafion/zirconium phosphate fuel cell membranes: Operation at elevated temperature and reduced relative humidity

    NASA Astrophysics Data System (ADS)

    Yang, Christopher

    High temperature polymer electrolyte fuel cells are being developed because of expected improvements in the operating tolerance for carbon morioxide (CO) in the hydrogen fuel stream. However, increases in fuel cell operating temperature typically lead to reductions in membrane water content due to evaporation, and the associated increase in membrane resistance decreases power output and thermal efficiency. Modifications to traditional perfluorinated sulfonic acid membranes (such as Dupont NafionRTM) can improve the performance of these membranes at higher temperature and reduced relative humidity. The addition of inorganic additives like zirconium hydrogen phosphate (Zr(HPO4)2) modifies specific membrane properties relevant for operation under these conditions. Fuel cell testing of the composite Nafion/zirconium phosphate membranes in both hydrogen and methanol fuel cells demonstrates significantly improved performance over unmodified membranes at high temperature (130--150°C) and dehydrating conditions. To understand the reasons for these membrane improvements in more detail, specific physical and chemical membrane characteristics were studied. The ionic cluster structure of modified membranes and changes upon swelling in water was investigated using small angle x-ray scattering (SAXS). A barometric sorption technique and AC impedance spectroscopy were used to measure equilibrium water uptake and conductivity over a range of relative humidities and temperatures. Finally, water transport measurements and a water flux model were used to investigate the effects of changes to diffusion and evaporative resistances on membrane water content. When compared to unmodified membranes, Nafion/zirconium phosphate membranes exhibit an increase in water uptake but a decrease in extent of membrane reorganization with water uptake. This change relates to the reduction in membrane chemical potential due to the hydrophilic zirconium phosphate and greater stability of the composite membrane to thermal treatments. Despite these improvements, the proton conductivity and diffusive transport are reduced, due to lower water and proton mobility in the ionic clusters. To explain the discrepancy between the reduced proton conductivity and the improvement in fuel cell performance, a simple water flux model is proposed, which indicates that reducing evaporative flux with respect to the diffusive flux can increase steady state water content and proton conductivity.

  8. Patterned ion exchange membranes for improved power production in microbial reverse-electrodialysis cells

    NASA Astrophysics Data System (ADS)

    Liu, Jia; Geise, Geoffrey M.; Luo, Xi; Hou, Huijie; Zhang, Fang; Feng, Yujie; Hickner, Michael A.; Logan, Bruce E.

    2014-12-01

    Power production in microbial reverse-electrodialysis cells (MRCs) can be limited by the internal resistance of the reverse electrodialysis stack. Typical MRC stacks use non-conductive spacers that block ion transport by the so-called spacer shadow effect. These spacers can be relatively thick compared to the membrane, and thus they increase internal stack resistance due to high solution (ohmic) resistance associated with a thick spacer. New types of patterned anion and cation exchange membranes were developed by casting membranes to create hemispherical protrusions on the membranes, enabling fluid flow between the membranes without the need for a non-conductive spacer. The use of the patterned membrane decreased the MRC stack resistance by ˜22 ?, resulting in a 38% increase in power density from 2.50 ± 0.04 W m-2 (non-patterned membrane with a non-conductive spacer) to 3.44 ± 0.02 W m-2 (patterned membrane). The COD removal rate, coulombic efficiency, and energy efficiency of the MRC also increased using the patterned membranes compared to the non-patterned membranes. These results demonstrate that these patterned ion exchange membranes can be used to improve performance of an MRC.

  9. Diagnostic tool for red blood cell membrane disorders: Assessment of a new generation ektacytometer.

    PubMed

    Da Costa, Lydie; Suner, Ludovic; Galimand, Julie; Bonnel, Amandine; Pascreau, Tiffany; Couque, Nathalie; Fenneteau, Odile; Mohandas, Narla

    2016-01-01

    Inherited red blood cell (RBC) membrane disorders, such as hereditary spherocytosis, elliptocytosis and hereditary ovalocytosis, result from mutations in genes encoding various RBC membrane and skeletal proteins. The RBC membrane, a composite structure composed of a lipid bilayer linked to a spectrin/actin-based membrane skeleton, confers upon the RBC unique features of deformability and mechanical stability. The disease severity is primarily dependent on the extent of membrane surface area loss. RBC membrane disorders can be readily diagnosed by various laboratory approaches that include RBC cytology, flow cytometry, ektacytometry, electrophoresis of RBC membrane proteins and genetics. The reference technique for diagnosis of RBC membrane disorders is the osmotic gradient ektacytometry. However, in spite of its recognition as the reference technique, this technique is rarely used as a routine diagnosis tool for RBC membrane disorders due to its limited availability. This may soon change as a new generation of ektacytometer has been recently engineered. In this review, we describe the workflow of the samples shipped to our Hematology laboratory for RBC membrane disorder analysis and the data obtained for a large cohort of French patients presenting with RBC membrane disorders using a newly available version of the ektacytomer. PMID:26603718

  10. A high selectivity quaternized polysulfone membrane for alkaline direct methanol fuel cells

    NASA Astrophysics Data System (ADS)

    Abuin, Graciela C.; Franceschini, Esteban A.; Nonjola, Patrick; Mathe, Mkhulu K.; Modibedi, Mmalewane; Corti, Horacio R.

    2015-04-01

    Alkaline membranes based on quaternized poly(arylene ether sulfone) (QPAES) were characterized in relation to their water and methanol uptake, methanol permeability, electrical conductivity, and mechanical properties. The performance of QPAES as electrolyte in alkaline direct methanol fuel cells was studied using a free-breathing single fuel cell at room temperature. Methanol uptake by QPAES membranes is lower than water, while their methanol permeability, determined in the temperature range from 30 °C to 75 °C, was much lower than for Nafion membranes. Young modulus of QPAES membranes decrease with the degree of alkalization of the membrane, although mechanical properties are still satisfactory for fuel cell applications for membrane alkalized with 2 M KOH, which additionally exhibit optimal hydroxide conductivity. Although the specific conductivity of QPAES membranes was lower than that reported for Nafion, its methanol selectivity (conductivity/methanol permeability ratio), is much higher than that reported for Nafion 117, and a commercial amminated polysulfone. In view of these results, QPAES membranes are expected to exhibit promising performance as an electrolyte in alkaline direct methanol fuel cells.

  11. Simplified process for leaching precious metals from fuel cell membrane electrode assemblies

    DOEpatents

    Shore, Lawrence (Edison, NJ); Matlin, Ramail (Berkeley Heights, NJ)

    2009-12-22

    The membrane electrode assemblies of fuel cells are recycled to recover the catalyst precious metals from the assemblies. The assemblies are cryogenically embrittled and pulverized to form a powder. The pulverized assemblies are then mixed with a surfactant to form a paste which is contacted with an acid solution to leach precious metals from the pulverized membranes.

  12. INTERACTION OF INORGANIC MERCURY SALTS WITH MODEL AND RED CELL MEMBRANES: IMPORTANCE OF LIPID BINDING SALTS

    EPA Science Inventory

    The effect induced by two mercury salts, HgCl2 and Hg(NO3)2, on the thermotropic properties of PS model membranes (multilamellar vesicles) and rat red cell membranes was investigated employing 1,6-diphenyl-1,3,5-hexatriene (DPH) fluorescence polarization. ercury(II) interacts wit...

  13. Unsynchronized Translational and Rotational Diffusion of Nanocargo on a Living Cell Membrane

    SciTech Connect

    Xiao, Lehui; Wei, Lin; Liu, Chang; He, Yan; Yeung, Edward

    2012-03-16

    A robust high-speed and high-precision single nanoparticle translational and rotational tracking method has been developed to directly monitor the interactions between transferrin-modified nanocargos (gold nanorods) and the membrane proteins prior to endocytosis. This approach shows that the translational and rotational diffusions of nanocargos on living cell membranes are unsynchronized in space and in time.

  14. Extensional flow of erythrocyte membrane from cell body to elastic tether. I. Analysis.

    PubMed Central

    Hochmuth, R M; Evans, E A

    1982-01-01

    This is the first of two papers on an analytical and experimental study of the flow of the erythrocyte membrane. In the experiment to be discussed in detail in the second paper, preswollen human erythrocytes are sphered by aspirating a portion of the cell membrane into a small micropipette; and long, thin, membrane filaments or "tethers" are steadily withdrawn from the cell at a point diametrically opposite to the point of aspiration. The aspirated portion of the membrane furnished a "reservoir" of material that replaces the membrane as it flows as a liquid from the nearly spherical cell body to the cylindrical tether. In this paper we show that an application of the principle of conservation of mass permits the tether radius (approximately 200 A or less) to be measured with the light microscope as the tether is formed and extended at a constant rate. A static analysis of the axisymmetric cell deformation and tether formation process reveals that the tether radius is uniquely determined by the isotropic tension in the membrane and the elastic constitutive (material) behavior of the tether itself. A dynamic analysis of the extensional flow process reveals that the tether radius must decrease as the velocity of the tether is increased and that the decrease depends on both the viscosity of the membrane and the elasticity of the tether. The analysis also shows that these two factors (membrane viscosity and tether elasticity) are readily decomposed and determined separately when flow experiments are performed at different isotropic tensions. Images FIGURE 5 PMID:7104453

  15. Initiation of poliovirus plus-strand RNA synthesis in a membrane complex of infected HeLa cells

    SciTech Connect

    Takeda, N.; Kuhn, R.J.; Yang, C.F.; Takegami, T.; Wimmer, E.

    1986-10-01

    An in vitro poliovirus RNA-synthesizing system derived from a crude membrance fraction of infected HeLa cells was used to analyze the mechanism of initiation of poliovirus plus-strand RNA synthesis. This system contains an activity that synthesizes the nucleotidyl proteins VPg-pU and VPg-pUpU. These molecules represent the 5'-terminal structure of nascent RNA molecules and of virion RNA. The membranous replication complex is also capable of synthesizing mucleotidyl proteins containing nine or more of the poliovirus 5'-proximal nucleotides as assayed by the formation of the RNase T/sub 1/-resistant oligonucleotide VPg-pUUAAAACAGp or by fingerprint analysis of the in vitro-synthesized /sup 32/P-RNA. Incubation of preformed VPg-pUpU with unlabeled nucleoside triphosphates resulted in the formation of VPg-pUUAAAACAGp. This reaction, which appeared to be an elongation of VPg-pUpU, was stimulated by the addition of a soluble fraction (S-10) obtained from uninfected HeLa cells. Preformed VPg-pU could be chased into VPg-pUpU in the presence of UTP. The data are consistent with a model that VPg-pU can function as a primer for poliovirus plus-strand RNA synthesis in the membranous replication complex and that the elongation reaction may be stimulated by a host cellular factor.

  16. Cytotoxicity of fucosterol containing fraction of marine algae against breast and colon carcinoma cell line

    PubMed Central

    Khanavi, Mahnaz; Gheidarloo, Razieh; Sadati, Nargess; Ardekani, Mohammad Reza Shams; Nabavi, Seyed Mohammad Bagher; Tavajohi, Shohreh; Ostad, Seyed Nasser

    2012-01-01

    Context: Marine algae produce different secondary metabolites with a wide range of biological activities. Many studies have been achieved on the screening of biological effects of marine organisms and a lot of active compounds were isolated and characterized. Aims: In an attempt to find cytotoxic compound of hexane fraction, isolation, identification, and cytotoxicity of active compound of this fraction were performed. Materials and Methods: In this study, total methanolic (70%) extract and partition fractions of hexane, chloroform (CHCl3), ethyl acetate (EtOAc), and MeOH–H2O of Sargassum angustifolium, Chondria dasyphylla, and Ulva flexuosa, collected from coastlines of the Persian Gulf in south of Iran, were studied against colon carcinoma (HT-29), colorectal adenocarcinoma (Caco-2), breast ductal carcinoma (T47D), and Swiss mouse embryo fibroblast (NIH 3T3) cell lines by MTT assay. Statistical Analysis Used: IC50 (median growth inhibitory concentration) values were calculated by Sigmaplot (10) software. Results: Hexane fraction of Chondria dasyphylla (IC50 82.26 ± 4.09 ?g/ml) and MeOH-H2O fraction of Ulva flexuosa (IC50 116.92 ± 8.58 ?g/ml) showed cytotoxic activity against proliferation of T47D cells. Hexane fraction of Sargassum angustifolium was also observed for cytotoxicity against T47D and HT-29 cell lines (IC50 166.42 ± 26.7 and 190.24 ± 52.8 ?g/ml), respectively. An investigation of a component from the hexane fraction of Sargassum angustifolium yielded a steroidal metabolite, fucosterol, with cytotoxicity in T47D and HT29 (IC50 27.94 ± 9.3 and 70.41 ± 7.5 ?g/ml). Conclusions: These results indicated that fucosterol, the most abundant phytosterol in brown algae, is responsible for cytotoxic effect of this extract against breast and colon carcinoma cell lines. PMID:22438665

  17. Interface-designed Membranes with Shape-controlled Patterns for High-performance Polymer Electrolyte Membrane Fuel Cells

    PubMed Central

    Jeon, Yukwon; Kim, Dong Jun; Koh, Jong Kwan; Ji, Yunseong; Kim, Jong Hak; Shul, Yong-Gun

    2015-01-01

    Polymer electrolyte membrane fuel cell is a promising zero-emission power generator for stationary/automotive applications. However, key issues, such as performance and costs, are still remained for an economical commercialization. Here, we fabricated a high-performance membrane electrode assembly (MEA) using an interfacial design based on well-arrayed micro-patterned membranes including circles, squares and hexagons with different sizes, which are produced by a facile elastomeric mold method. The best MEA performance is achieved using patterned Nafion membrane with a circle 2??m in size, which exhibited a very high power density of 1906?mW/cm2 at 75?°C and Pt loading of 0.4?mg/cm2 with 73% improvement compared to the commercial membrane. The improved performance are attributed to the decreased MEA resistances and increased surface area for higher Pt utilization of over 80%. From these enhanced properties, it is possible to operate at lower Pt loading of 0.2?mg/cm2 with an outstanding performance of 1555?mW/cm2 and even at air/low humidity operations. PMID:26552839

  18. Interface-designed Membranes with Shape-controlled Patterns for High-performance Polymer Electrolyte Membrane Fuel Cells.

    PubMed

    Jeon, Yukwon; Kim, Dong Jun; Koh, Jong Kwan; Ji, Yunseong; Kim, Jong Hak; Shul, Yong-Gun

    2015-01-01

    Polymer electrolyte membrane fuel cell is a promising zero-emission power generator for stationary/automotive applications. However, key issues, such as performance and costs, are still remained for an economical commercialization. Here, we fabricated a high-performance membrane electrode assembly (MEA) using an interfacial design based on well-arrayed micro-patterned membranes including circles, squares and hexagons with different sizes, which are produced by a facile elastomeric mold method. The best MEA performance is achieved using patterned Nafion membrane with a circle 2??m in size, which exhibited a very high power density of 1906?mW/cm(2) at 75?°C and Pt loading of 0.4?mg/cm(2) with 73% improvement compared to the commercial membrane. The improved performance are attributed to the decreased MEA resistances and increased surface area for higher Pt utilization of over 80%. From these enhanced properties, it is possible to operate at lower Pt loading of 0.2?mg/cm(2) with an outstanding performance of 1555?mW/cm(2) and even at air/low humidity operations. PMID:26552839

  19. Interface-designed Membranes with Shape-controlled Patterns for High-performance Polymer Electrolyte Membrane Fuel Cells

    NASA Astrophysics Data System (ADS)

    Jeon, Yukwon; Kim, Dong Jun; Koh, Jong Kwan; Ji, Yunseong; Kim, Jong Hak; Shul, Yong-Gun

    2015-11-01

    Polymer electrolyte membrane fuel cell is a promising zero-emission power generator for stationary/automotive applications. However, key issues, such as performance and costs, are still remained for an economical commercialization. Here, we fabricated a high-performance membrane electrode assembly (MEA) using an interfacial design based on well-arrayed micro-patterned membranes including circles, squares and hexagons with different sizes, which are produced by a facile elastomeric mold method. The best MEA performance is achieved using patterned Nafion membrane with a circle 2??m in size, which exhibited a very high power density of 1906?mW/cm2 at 75?°C and Pt loading of 0.4?mg/cm2 with 73% improvement compared to the commercial membrane. The improved performance are attributed to the decreased MEA resistances and increased surface area for higher Pt utilization of over 80%. From these enhanced properties, it is possible to operate at lower Pt loading of 0.2?mg/cm2 with an outstanding performance of 1555?mW/cm2 and even at air/low humidity operations.

  20. Isolation of Chinese hamster ovary cell lines temperature conditional for the cell-surface expression of integral membrane glycoproteins

    PubMed Central

    1989-01-01

    A procedure is described to select mutants of Chinese hamster ovary cells that are conditionally defective for the cell-surface expression of integral membrane glycoproteins, including the hemagglutinin (HA) of influenza virus. Using a combination of cell sorting and biochemical screening, seven cell lines were obtained that express more cell- surface HA at 32 degrees C than at 39 degrees C. The production of infectious vesicular stomatitis virus, whose growth requires insertion of an integral membrane protein into the plasma membrane, was also temperature conditional in the majority of these mutant cell lines. Five of the lines synthesized apparently normally core-glycosylated HA at the elevated temperature but the protein was neither displayed on the cell surface nor accumulated intracellularly. In these cell lines, little or no terminally glycosylated HA molecules were observed after synthesis at 39 degrees C. By contrast, the core glycosylation of HA and several other integral membrane proteins was abnormal in the remaining two cell lines at both permissive and restrictive temperatures, due to a lesion in a cellular gene(s) that affects the formation of and/or the addition of mannose-rich oligosaccharide chains to newly synthesized polypeptides. Although HA was transported to the plasma membrane at both 32 and 39 degrees C, it did not accumulate on the cell surface at the higher temperature, apparently because of an increased rate of degradation. PMID:2537314

  1. The connection of cytoskeletal network with plasma membrane and the cell wall

    PubMed Central

    Liu, Zengyu; Persson, Staffan; Zhang, Yi

    2015-01-01

    The cell wall provides external support of the plant cells, while the cytoskeletons including the microtubules and the actin filaments constitute an internal framework. The cytoskeletons contribute to the cell wall biosynthesis by spatially and temporarily regulating the transportation and deposition of cell wall components. This tight control is achieved by the dynamic behavior of the cytoskeletons, but also through the tethering of these structures to the plasma membrane. This tethering may also extend beyond the plasma membrane and impact on the cell wall, possibly in the form of a feedback loop. In this review, we discuss the linking components between the cytoskeletons and the plasma membrane, and/or the cell wall. We also discuss the prospective roles of these components in cell wall biosynthesis and modifications, and aim to provide a platform for further studies in this field. PMID:25693826

  2. Proton exchange membrane fuel cell conductivity and system analysis

    NASA Astrophysics Data System (ADS)

    Han, Qian

    A fuel cell converts chemical energy to electrical energy. It is a device that uses the electrochemical reaction of hydrogen and an oxidant, to produce electrical energy silently, without combustion. The role of the electrolyte in a PEM fuel cell is played by a proton exchange membrane. NafionRTM and its derivatives are the most widely used and studied polymers. Percolation theory holds a key to understanding the behavior of these polymers. In this dissertation, the percolation phenomenon was first simulated for the thermal conductivity of a representative polymer material. The simulation program was based on the finite element method, using Ansys software, which not only simplifies the method of calculation, but also increases the accuracy of the result. Ansys programs were developed to study the effects of matrix thickness, filler particle volume percentage, and various conductivities of the base material and filler particles. Comparison with existing experimental results and other models showed that the results from the finite element method were more accurate than the other models, especially the three-dimensional model. A similar Ansys program was utilized to predict the percolation threshold for the polymer electric conductivity, and its relationship with extra water content over the studied temperature range. The result showed that the percolation threshold varied with temperature and is in the range of 22% to 26% at room temperature, and matches the experimental data within 10% error margin. A natural gas fuel cell (NGFC) is a direct-energy conversion system which uses natural gas as the hydrogen carrier. A parametric model was developed to predict the overall system performance of a natural-gas-fueled PEM fuel cell system sized for a residential or small commercial building. The model accounts for interactions between various operating parameters: fuel consumption, air and water requirements, power produced, and heat and waste water discharge. For example, for 10 kW electrical output and usage factors of 90% and 80% for the hydrogen and methane respectively, the methane consumption rate is 1.77 kg/h, the heat rejection rate is 16.26 kW, the water discharge rate is 5.13 kg/hr, the overall system efficiency eta is 41.2%. The theoretical maximum system efficiency of a natural-gas-fueled PEM fuel cell was also predicted, providing a standard to value the performance of any commercial system. Finally, a transient model of a PEM fuel cell stack for a short circuit event was developed. The effects of different cooling methods---natural convection, forced air convection, and forced water convection---were discussed. The fuel cell stack reaches 100°C during a short circuit event within 28 seconds under the forced air condition, which should be enough time for a protective device to operate.

  3. An organelle-free assay for pea chloroplast Mg-chelatase: Resolution of the activity into soluble and membrane bound fractions

    SciTech Connect

    Walker, C.J.; Weinstein, J.D. )

    1991-05-01

    Mg-chelatase, which catalyzes the insertion of magnesium into protoporphyrin, lies at the branchpoint of heme and chlorophyll biosynthesis in chloroplasts. Since magnesium chelation is the first step unique to chlorophyll synthesis, one would expect this step to be highly regulated. However, to date little is known about the enzymology or regulation of Mg-chelatase due mostly to an inability to assay it's activity outside of the intact plastid. Here the authors report the first truly in vitro i.e. organelle-free, assay for Mg-chelatase. Mg-chelatase activity in intact pea chloroplasts which is 3 to 4 fold higher than in cucumber chloroplasts, survived chloroplast lysis and could be fractionated, by centrifugation, into supernatant and pellet components. Both of these fractions were required to reconstitute Mg-chelatase activity and both were inactivated by boiling; indicating that the enzyme is composed of soluble and membrane bound protein(s). The specific activity of the reconstituted system was typically 1 nmol Mg-Deuteroporphyrin/h/mg protein and activity was linear for at least 60 min under our assay conditions. ATP and magnesium were required for Mg-chelatase activity. The soluble component could be fractionated with ammonium sulfate. The product of the reaction was confirmed fluorometrically as the magnesium chelate of the porphyrin substrate. Crude separation of chloroplast membranes into thylakoids and envelopes, suggested that the membrane-bound component of Mg-chelatase is probably located in the envelope.

  4. Process engineering and economic evaluations of diaphragm and membrane chlorine cell technologies. Final report

    SciTech Connect

    Not Available

    1980-12-01

    The chlor-alkali manufacturing technologies of (1), diaphragm cells (2), current technology membrane cells (3), catalytic cathode membrane cells (4), oxygen-cathode membrane cells and to a lesser extent several other related emerging processes are studied. Comparisons have been made on the two bases of (1) conventional industrial economics, and (2) energy consumption. The current diaphragm cell may have a small economic advantage over the other technologies at the plant size of 544 metric T/D (600 T/D). The three