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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

    Guo, Ping; Zhang, Hong; Chen, Haizhu; Liu, Ran

    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 Central

    Craiem, Damian; Magin, Richard L

    2011-01-01

    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. Membrane characteristics and osmotic fragility of red cells, fractionated with anglehead centrifugation and counterflow centrifugation.

    PubMed

    van der Vegt, S G; Ruben, A M; Werre, J M; de Gier, J; Staal, G E

    1985-11-01

    Red cell populations were separated on the basis of differences in density using anglehead centrifugation and on the basis of differences in mean cell volume using counterflow centrifugation. In the different fractions, mean surface area was calculated, phospholipid and cholesterol content determined as well as the osmotic behaviour in hypotonic salt solutions. Older red cells appeared to be more resistant to hypotonic salt solutions, due to favourable surface area to volume ratio. PMID:4063204

  5. 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.

  6. Toxic Membrane Fractions from Mycoplasma fermentans1

    PubMed Central

    Gabridge, Michael G.; Murphy, William H.

    1971-01-01

    A recent isolate of Mycoplasma fermentans (strain K10, from human leukemic bone marrow) induced a lethal toxicity syndrome in mice. High doses of both viable and inactivated cells were toxic when injected intraperitoneally. Whole lysates and membranes from osmotically shocked cells killed mice, but cytoplasm did not. When membranes were dissolved in detergents and reaggregated by dialysis in the presence of Mg2+, the lipid-protein complex thus formed was toxic. Lipids extracted from membranes with chloroform-methanol did not kill mice. Protein-rich fractions (obtained by reaggregation plus acetone washes or ammonium sulfate precipitation of dissolved membranes) were also not toxic. No qualitative differences in proteins from three toxic isolates and three nontoxic laboratory strains of M. fermentans were detectable by polyacrylamide gel electrophoresis. The toxic factor contained in reaggregated membranes was heat-stable but sensitive to Pronase, trypsin, and lipase. Images PMID:5154902

  7. Isolation of differentiated membrane domains from Escherichia coli and Salmonella typhimurium, including a fraction containing sites between the inner and outer membranes and Murein skeleton of the cell envelope

    SciTech Connect

    Not Available

    1986-01-05

    Cell envelopes of Salmonella typhimurium and Escherichia coli were disrupted in a French pressure cell and fractionated by successive cycles of sedimentation and floatation density gradient centrifugation. This permitted the identification and isolation of several membrane fractions in addition to the major inner membrane and murein-outer membrane fractions. One of these fractions (fraction OM/sub L/) accounted for about 10% of the total cell envelope protein, and is likely to include the murein-membrane adhesion zones that are seen in electron micrographs of plasmolyzed cells. Fraction OM/sub L/ contained inner membrane, murein, and outer membrane in an apparently normal configuration, was capable of synthesizing murein from UDP-(/sup 3/H)N-acetylglucosamine and UDP-N-acetylmuramyl-pentapeptide and covalently linking it to the endogenous murein of the preparation. It showed a labeling pattern in (/sup 3/H)galactose pulse-chase experiments that was consistent with its acting as an intermediate in the movement of newly synthesized lipopolysaccharide from inner membrane to outer membrane.

  8. Two Bioactive Molecular Weight Fractions of a Conditioned Medium Enhance RPE Cell Survival on Age-Related Macular Degeneration and Aged Bruch's Membrane

    PubMed Central

    Sugino, Ilene K.; Sun, Qian; Springer, Carola; Cheewatrakoolpong, Noounanong; Liu, Tong; Li, Hong; Zarbin, Marco A.

    2016-01-01

    Purpose To characterize molecular weight fractions of bovine corneal endothelial cell conditioned medium (CM) supporting retinal pigment epithelium (RPE) cell survival on aged and age-related macular degeneration (AMD) Bruch's membrane. Methods CM was subject to size separation using centrifugal filters. Retentate and filtrate fractions were tested for bioactivity by analyzing RPE survival on submacular Bruch's membrane of aged and AMD donor eyes and behavior on collagen I-coated tissue culture wells. Protein and peptide composition of active fractions was determined by mass spectrometry. Results Two bioactive fractions, 3-kDa filtrate and a 10-50–kDa fraction, were necessary for RPE survival on aged and AMD Bruch's membrane. The 3-kDa filtrate, but not the 10-50–kDa fraction, supported RPE growth on collagen 1‐coated tissue culture plates. Mass spectrometry of the 10-50–kDa fraction identified 175 extracellular proteins, including growth factors and extracellular matrix molecules. Transforming growth factor (TGF)β-2 was identified as unique to active CM. Peptides representing 29 unique proteins were identified in the 3-KDa filtrate. Conclusions These results indicate there is a minimum of two bioactive molecules in CM, one found in the 3-kDa filtrate and one in the 10-50–kDa fraction, and that bioactive molecules in both fractions must be present to ensure RPE survival on Bruch's membrane. Mass spectrometry analysis suggested proteins to test in future studies to identify proteins that may contribute to CM bioactivity. Translational Relevance Results of this study are the first steps in development of an adjunct to cell-based therapy to ensure cell transplant survival and functionality in AMD patients. PMID:26933521

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

    PubMed Central

    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

  10. 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 α-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. 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; Wong, Vincent Kam-Wai; Zeng, Wu; Liu, Liang; Law, Betty Yuen-Kwan

    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 α-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

  12. Peptidyl - tRNA hydrolase and RNase activities in cell fractions of rat liver used in in vitro reconstitution of rough membrane.

    PubMed Central

    Hochberg, A A; Czosnek, H H; Ziv, E

    1975-01-01

    Peptidyl-tRNA hydrolase and RNase activities have been studied in those fractions of rat liver, which are used in in vitro reconstitution of rough membrane, because these enzymes may interfere with the in vitro reconstitution. It was found that smooth membrane has an active peptidyl-tRNA hydrolase, while the other fractions tested, polyribosomes, rough membrane, stripped rough membrane and the post-microsomal supernatant had no, or very low, peptidyl-tRNA hydrolase activity. Polyribosomes, rough and stripped rough membrane have RNase activity; this activity could be completely inhibited by rat liver RNase inhibitor. It is shown that RNase inhibitor is an obligatory component in in vitro experiments, in which rough membrane is reconstituted from stripped rough membrane, ribosomes and mRNA. PMID:1144067

  13. 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.

  14. Composite fuel cell membranes

    DOEpatents

    Plowman, Keith R.; Rehg, Timothy J.; Davis, Larry W.; Carl, William P.; Cisar, Alan J.; Eastland, Charles S.

    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.

  15. 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.

  16. 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.

  17. Electroporation of cell membranes.

    PubMed

    Tsong, T Y

    1991-08-01

    Electric pulses of intensity in kilovolts per centimeter and of duration in microseconds to milliseconds cause a temporary loss of the semipermeability of cell membranes, thus leading to ion leakage, escape of metabolites, and increased uptake by cells of drugs, molecular probes, and DNA. A generally accepted term describing this phenomenon is "electroporation." Other effects of a high-intensity electric field on cell membranes include membrane fusions, bleb formation, cell lysis... etc. Electroporation and its related phenomena reflect the basic bioelectrochemistry of cell membranes and are thus important for the study of membrane structure and function. These phenomena also occur in such events as electric injury, electrocution, and cardiac procedures involving electric shocks. Electroporation has found applications in: (a) introduction of plasmids or foreign DNA into living cells for gene transfections, (b) fusion of cells to prepare heterokaryons, hybridoma, hybrid embryos... etc., (c) insertion of proteins into cell membranes, (d) improving drug delivery and hence effectiveness in chemotherapy of cancerous cells, (e) constructing animal model by fusing human cells with animal tissues, (f) activation of membrane transporters and enzymes, and (g) alteration of genetic expression in living cells. A brief review of mechanistic studies of electroporation is given. PMID:1912274

  18. Electroporation of cell membranes.

    PubMed Central

    Tsong, T Y

    1991-01-01

    Electric pulses of intensity in kilovolts per centimeter and of duration in microseconds to milliseconds cause a temporary loss of the semipermeability of cell membranes, thus leading to ion leakage, escape of metabolites, and increased uptake by cells of drugs, molecular probes, and DNA. A generally accepted term describing this phenomenon is "electroporation." Other effects of a high-intensity electric field on cell membranes include membrane fusions, bleb formation, cell lysis... etc. Electroporation and its related phenomena reflect the basic bioelectrochemistry of cell membranes and are thus important for the study of membrane structure and function. These phenomena also occur in such events as electric injury, electrocution, and cardiac procedures involving electric shocks. Electroporation has found applications in: (a) introduction of plasmids or foreign DNA into living cells for gene transfections, (b) fusion of cells to prepare heterokaryons, hybridoma, hybrid embryos... etc., (c) insertion of proteins into cell membranes, (d) improving drug delivery and hence effectiveness in chemotherapy of cancerous cells, (e) constructing animal model by fusing human cells with animal tissues, (f) activation of membrane transporters and enzymes, and (g) alteration of genetic expression in living cells. A brief review of mechanistic studies of electroporation is given. PMID:1912274

  19. 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.

  20. Gas phase fractionation method using porous ceramic membrane

    DOEpatents

    Peterson, Reid A.; Hill, Jr., Charles G.; Anderson, Marc A.

    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.

  1. 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)

  2. Fuel cell membrane humidification

    DOEpatents

    Wilson, Mahlon S.

    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.

  3. 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

  4. 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

  5. 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.

  6. Cell Membrane Softening in Cancer Cells

    NASA Astrophysics Data System (ADS)

    Schmidt, Sebastian; Händel, Chris; Käs, Josef

    Biomechanical properties are useful characteristics and regulators of the cell's state. Current research connects mechanical properties of the cytoskeleton to many cellular processes but does not investigate the biomechanics of the plasma membrane. We evaluated thermal fluctuations of giant plasma membrane vesicles, directly derived from the plasma membranes of primary breast and cervical cells and observed a lowered rigidity in the plasma membrane of malignant cells compared to non-malignant cells. To investigate the specific role of membrane rigidity changes, we treated two cell lines with the Acetyl-CoA carboxylase inhibitor Soraphen A. It changed the lipidome of cells and drastically increased membrane stiffness by up regulating short chained membrane lipids. These altered cells had a decreased motility in Boyden chamber assays. Our results indicate that the thermal fluctuations of the membrane, which are much smaller than the fluctuations driven by the cytoskeleton, can be modulated by the cell and have an impact on adhesion and motility.

  7. 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.

  8. Fractionation of liver plasma membranes prepared by zonal centrifugation

    PubMed Central

    Evans, W. H.

    1970-01-01

    1. Plasma membranes were isolated from crude nuclear sediments from mouse and rat liver by a rate-dependent centrifugation through a sucrose density gradient contained in the `A' type zonal rotor. 2. The membranes were further purified by isopycnic centrifugation, and characterized enzymically, chemically and morphologically. 3. When the plasma-membrane fraction of sucrose density 1.17g/cm3 was dispersed in a tight-fitting homogenizer, two subfractions of densities 1.12 and 1.18 were obtained by isopycnic centrifugation. 4. The light subfraction contained 5′-nucleotidase, nucleoside diphosphatase, leucine naphthylamidase and Mg2+-stimulated adenosine triphosphatase activities at higher specific activities than unfractionated membranes. The heavy subfraction was deficient in the above enzymes but contained higher Na++K+-stimulated adenosine triphosphatase activity. 5. The light subfraction contained twice as much phospholipid and cholesterol, and three times as much N-acetylneuraminic acid relative to unit protein weight as the heavy subfraction. Polyacrylamide-gel electrophoresis indicated differences in protein composition. 6. Electron microscopy showed the light subfraction to be vesicular. The heavy subfraction contained membrane strips with junctional complexes in addition to vesicles. ImagesPLATE 2PLATE 3PLATE 1 PMID:4315049

  9. Peptide separations by on-line MudPIT compared to isoelectric focusing in an off-gel format: Application to a membrane-enriched fraction from C2C12 mouse skeletal muscle cells

    PubMed Central

    Elschenbroich, Sarah; Ignatchenko, Vladimir; Sharma, Parveen; Schmitt-Ulms, Gerold; Gramolini, Anthony O.; Kislinger, Thomas

    2013-01-01

    High resolution peptide separation is pivotal for successful shot-gun proteomics. The need for capable techniques propels invention and improvement of ever more sophisticated approaches. Recently, Agilent Technologies has introduced the OFFGEL fractionator, which conducts peptide separation by isoelectric focusing in an off-gel setup. This platform has been shown to accomplish high resolution of peptides for diverse sample types, yielding valuable advantages over comparable separation techniques. In this study, we deliver the first comparison of the newly emerging OFFGEL approach to the well-established on-line MudPIT platform. Samples from a membrane-enriched fraction isolated from murine C2C12 cells were subjected to replicate analysis by OFFGEL (12 fractions, pH 3 – 10) followed by RP-LC-MS/MS or 12-step on-line MudPIT. OFFGEL analyses yielded 1398 proteins (identified by 10,269 peptides) while 1428 proteins (11,078 peptides) were detected with the MudPIT approach. Thus, our data shows that both platforms produce highly comparable results in terms of protein/peptide identifications and reproducibility for the sample type analyzed. We achieve more accurate peptide focusing after OFFGEL fractionation with 88 % of all peptides binned to a single fraction, as compared to 61 % of peptides detected in only one step in MudPIT analyses. Our study suggests that both platforms are equally capable of high quality peptide separation of a sample with medium complexity, rendering them comparably valuable for comprehensive proteomic analyses. PMID:19670906

  10. Fractional hereditariness of lipid membranes: Instabilities and linearized evolution.

    PubMed

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

    2016-05-01

    In this work lipid ordering phase changes arising in planar membrane bilayers is investigated both accounting for elasticity 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 (Deseri and Zurlo, 2013). 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 (Espinosa et al., 2011) show a power-law in-plane viscous behavior of lipid structures allowing for an effective viscoelastic behavior of lipid membranes, 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 boundary 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. PMID:26897568

  11. 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…

  12. Theoretical Analysis of Membrane Tension in Moving Cells

    PubMed Central

    Schweitzer, Yonatan; Lieber, Arnon D.; Keren, Kinneret; Kozlov, Michael M.

    2014-01-01

    Lateral tension in cell plasma membranes plays an essential role in regulation of a number of membrane-related intracellular processes and cell motion. Understanding the physical factors generating the lateral tension and quantitative determination of the tension distribution along the cell membrane is an emerging topic of cell biophysics. Although experimental data are accumulating on membrane tension values in several cell types, the tension distribution along the membranes of moving cells remains largely unexplored. Here we suggest and analyze a theoretical model predicting the tension distribution along the membrane of a cell crawling on a flat substrate. We consider the tension to be generated by the force of actin network polymerization against the membrane at the cell leading edge. The three major factors determining the tension distribution are the membrane interaction with anchors connecting the actin network to the lipid bilayer, the membrane interaction with cell adhesions, and the force developing at the rear boundary due to the detachment of the remaining cell adhesion from the substrate in the course of cell crawling. Our model recovers the experimentally measured values of the tension in fish keratocytes and their dependence on the number of adhesions. The model predicts, quantitatively, the tension distribution between the leading and rear membrane edges as a function of the area fractions of the anchors and the adhesions. PMID:24411240

  13. 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

  14. In vitro enzymatic reduction kinetics of mineral oxides by membrane fractions from Shewanella oneidensis MR-1

    NASA Astrophysics Data System (ADS)

    Ruebush, Shane S.; Icopini, Gary A.; Brantley, Susan L.; Tien, Ming

    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

  15. Physical principles of membrane remodelling during cell mechanoadaptation

    NASA Astrophysics Data System (ADS)

    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

    2015-06-01

    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.

  16. 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

  17. Tannin-rich fraction from pomegranate rind damages membrane of Listeria monocytogenes.

    PubMed

    Li, Guanghui; Xu, Yunfeng; Wang, Xin; Zhang, Baigang; Shi, Chao; Zhang, Weisong; Xia, Xiaodong

    2014-04-01

    Pomegranate rind has been reported to inhibit several foodborne pathogens, and its antimicrobial activity has been attributed mainly to its tannin fraction. This study aimed to investigate the antimicrobial activity of the tannin-rich fraction from pomegranate rind (TFPR) against Listeria monocytogenes and its mechanism of action. The tannin-related components of TFPR were analyzed by high-performance liquid chromatography and liquid chromatography-mass spectrometry, and the minimum inhibitory concentration (MIC) of TFPR was determined using the agar dilution method. Extracellular potassium concentration, the release of cell constituents, intra- and extracellular ATP concentrations, membrane potential, and intracellular pH (pHin) were measured to elucidate a possible antibacterial mechanism. Punicalagin (64.2%, g/g) and ellagic acid (3.1%, g/g) were detected in TFPR, and the MICs of TFPR were determined to be 1.25-5.0 mg/mL for different L. monocytogenes strains. Treatment with TFPR induced a decrease of the intracellular ATP concentration, an increase of the extracellular concentrations of potassium and ATP, and the release of cell constituents. A reduction of pHin and cell membrane hyperpolarization were observed after treatment. Electron microscopic observations showed that the cell membrane structures of L. monocytogenes were apparently impaired by TFPR. It is concluded that TFPR could destroy the integrity of the cell membrane of L. monocytogenes, leading to a loss of cell homeostasis. These findings indicate that TFPR has the potential to be used as a food preservative in order to control L. monocytogenes contamination in food and reduce the risk of listeriosis. PMID:24447173

  18. 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 ⅓ less than the

  19. Corrugated Membrane Fuel Cell Structures

    SciTech Connect

    Grot, Stephen

    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.

  20. Hydrophobic allergens from the bottom fraction membrane of Hevea brasiliensis.

    PubMed

    Mengumpun, Kesajee; Tayapiwatana, Chatchai; Hamilton, Robert G; Sangsupawanich, Pasuree; Wititsuwannakul, Rapepun

    2008-01-01

    Several proteins of rubber latex have been recognized as allergens causing immediate hypersensitivity in humans. In this study, a bottom fraction membrane (BFM) protein preparation from Hevea brasiliensis trees grown in southern Thailand was used to detect specific IgE in four groups of serum samples. The first group included 170 samples of latex glove factory workers (LGWs); group 2 consisted of the sera of 35 health care workers (HCWs) who were repeatedly exposed to powdered latex gloves; groups 3 and 4 were 31 positive and 22 negative sera, respectively, obtained from Johns Hopkins University School of Medicine, Baltimore, USA, tested for IgE to latex allergen. It was found that 56/170 (33%), 5/35 (14%), 11/31 (35.5%) and 1/22 (4.5%) samples of the LGWs, HCWs, CAP+ and CAP- groups had significant IgE to the BFM proteins, respectively. However, of all subjects only one subject of group 1 had experienced allergic morbidity consisting of eczema, conjunctivitis and asthma. The IgE of this subject bound to a 55 kDa component in the rubber latex BFM preparation. Thus, this protein may be regarded as a novel, although minor, latex allergen. Further investigation is needed to characterize the component and to pinpoint its allergenic role. PMID:19054931

  1. Cell membranes: A subjective perspective.

    PubMed

    Simons, Kai

    2016-10-01

    Cell membranes have developed a tremendous complexity of lipids and proteins geared to perform the functions cells require. The lipids have for long remained in the background and are now regaining their role as important building blocks of cells. Their main function is to form the matrix of our cell membranes where they support a variety of functions essential for life. This 2-dimensional fluid matrix has evolved unexpected material properties that involve both lipid-lipid and lipid-protein interactions. This perspective is a short summary of the challenges that this field faces and discusses potential ways and means for coming to grips with the properties of this incredible fluid. This article is part of a Special Issue entitled: Biosimulations edited by Ilpo Vattulainen and Tomasz Róg. PMID:26827711

  2. 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.

  3. HPLC fractions of human uremic plasma inhibit the RBC membrane calcium pump.

    PubMed

    Lindner, A; Vanholder, R; De Smet, R; Hinds, T R; Vogeleere, P; Sandra, P; Foxall, P; Ringoir, S

    1997-04-01

    We have reported that uremic plasma filtrates (UF) inhibit the red blood cell (RBC) membrane calcium pump. The inhibitor was dialyzable, smaller than 3,000 molecular weight, heat-stable, and protease-resistant. In the present study, we used reverse-phase preparative HPLC, analytical HPLC, and Sephadex G-25 elution to identify inhibitory fractions. Inhibition was confirmed in three different bioassays: (1) Sr2+ efflux in intact RBC, the primary bio-assay; (2) 45Ca efflux in intact RBC; and (3) calcium ATPase activity in isolated RBC membranes. Active fractions were analyzed by mass spectrometry, capillary electrophoresis, enzymatic analysis, gas chromatography-mass spectrometry, and nuclear magnetic resonance spectroscopy. These demonstrated a number of compounds, including: sugars, polyols, osmolytes like betaine and myoinositol, amino acids, and other metabolites, such as 3-D-hydroxybutyrate, dimethylglycine, trimethylamine-N-oxide, guanidinoacetic acid and glycine. Many individual compounds were then tested for an effect on the calcium pump. Thus, HPLC was able to separate a substantial number of compounds in inhibitory fractions. Efforts are under way for precise identification of the inhibitor, to advance our understanding of uremic toxicity and/or hypertension in CRF. PMID:9083269

  4. 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

  5. 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

  6. Fuel-Cell Structure Prevents Membrane Drying

    NASA Technical Reports Server (NTRS)

    Mcelroy, J.

    1986-01-01

    Embossed plates direct flows of reactants and coolant. Membrane-type fuel-cell battery has improved reactant flow and heat removal. Compact, lightweight battery produces high current and power without drying of membranes.

  7. 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 α6 and β4 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.

  8. 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

  9. Characteristics of different fractions of microbial flocs and their role in membrane fouling.

    PubMed

    Lin, H J; Gao, W J; Leung, K T; Liao, B Q

    2011-01-01

    Characteristics of different fractions (small flocs vs. large flocs) of sludge flocs from a submerged anaerobic membrane bioreactor treating thermomechanical pulping (TMP) whitewater were determined using various analytic techniques, including extraction and chemical analysis of extracellular polymeric substances (EPS), particle size analyzer, and polymer chain reaction (PCR)-denaturing gradient gel electrophoresis (DGGE). The results showed that the fraction of smaller flocs contained a higher level of bound EPS and had a higher fractal dimension as compared to the fraction of larger flocs. PCR-DGGE analysis indicated that there were significant differences in microbial community between the fraction of smaller flocs and large flocs. The microbial community of the smaller flocs was similar to that of the sludge cake layers, indicating the pioneering role of the microbial community in smaller flocs in membrane fouling. These findings provide a new insight in the difference of membrane fouling potential between smaller flocs and larger flocs fraction. PMID:21252429

  10. Chemical degradation mechanisms of membranes for alkaline membrane fuel cells

    NASA Astrophysics Data System (ADS)

    Choe, Yoong-Kee; Henson, Neil J.; Kim, Yu Seung

    2015-12-01

    Chemical degradation mechanisms of membranes for alkaline membrane fuel cells have been investigated using density functional theory (DFT). We have elucidated that the aryl-ether moiety of membranes is one of the weakest site against attack of hydroxide ions. The results of DFT calculations for hydroxide initiated aryl-ether cleavage indicated that the aryl-ether cleavage occurred prior to degradation of cationic functional group. Such a weak nature of the aryl-ether group arises from the electron deficiency of the aryl group as well as the low bond dissociation energy. The DFT results suggests that removal of the aryl-ether group in the membrane should enhance the stability of membranes under alkaline conditions. In fact, an ether fee poly(phenylene) membrane exhibits excellent stability against the attack from hydroxide ions.

  11. Chemical degradation mechanisms of membranes for alkaline membrane fuel cells

    SciTech Connect

    Choe, Yoong-Kee; Henson, Neil J.; Kim, Yu Seung

    2015-12-31

    Chemical degradation mechanisms of membranes for alkaline membrane fuel cells have been investigated using density functional theory (DFT). We have elucidated that the aryl-ether moiety of membranes is one of the weakest site against attack of hydroxide ions. The results of DFT calculations for hydroxide initiated aryl-ether cleavage indicated that the aryl-ether cleavage occurred prior to degradation of cationic functional group. Such a weak nature of the aryl-ether group arises from the electron deficiency of the aryl group as well as the low bond dissociation energy. The DFT results suggests that removal of the aryl-ether group in the membrane should enhance the stability of membranes under alkaline conditions. In fact, an ether fee poly(phenylene) membrane exhibits excellent stability against the attack from hydroxide ions.

  12. In-membrane micro fuel cell

    DOEpatents

    Omosebi, Ayokunle; Besser, Ronald

    2016-09-06

    An in-membrane micro fuel cell comprises an electrically-insulating membrane that is permissive to the flow of cations, such as protons, and a pair of electrodes deposited on channels formed in the membrane. The channels are arranged as conduits for fluids, and define a membrane ridge between the channels. The electrodes are porous and include catalysts for promoting the liberation of a proton and an electron from a chemical species and/or or the recombination of a proton and an electron with a chemical specie. The fuel cell may be provided a biosensor, an electrochemical sensor, a microfluidic device, or other microscale devices fabricated in the fuel cell membrane.

  13. Iodixanol Gradient Centrifugation to Separate Components of the Low-Density Membrane Fraction from 3T3-L1 Adipocytes.

    PubMed

    Sadler, Jessica B A; Lamb, Christopher A; Gould, Gwyn W; Bryant, Nia J

    2016-02-01

    We optimized a set of fractionation techniques to facilitate the isolation of subcellular compartments containing insulin-sensitive glucose transporter isoform 4 (GLUT4), which is mobilized from GLUT4 storage vesicles (GSVs) in fat and muscle cells in response to insulin. In the absence of insulin, GLUT4 undergoes a continuous cycle of GSV formation and fusion with other compartments. Full membrane fractionation of 3T3-L1 adipocytes produces a low-density membrane fraction that contains both the constitutive recycling pool (the endosomal recycling compartments) and the insulin-sensitive pool (the GSVs). These two pools can be separated based on density using iodixanol gradient centrifugation, described here. PMID:26832683

  14. Red blood cell membrane defects.

    PubMed

    Iolascon, Achille; Perrotta, Silverio; Stewart, Gordon W

    2003-03-01

    We present an overview of the currently known molecular basis of red cell membrane disorders. A detailed discussion of the structure of the red cell membrane and the pathophysiology and clinical aspects of its disorders is reported. Generally speaking, hereditary spherocytosis (HS) results from a loss of erythrocyte surface area. The mutations of most cases of HS are located in the following genes: ANK1, SPTB, SLC4A1, EPB42 and SPTA1, which encode for ankyrin, spectrin beta-chain, the anion exchanger 1 (band 3), protein 4.2 and spectrin alpha-chain, respectively. Hereditary elliptocytosis (HE) reflects a diminished elasticity of the skeleton. Its aggravated form, hereditary pyropoikilocytosis (HPP), implies that the skeleton undergoes further destabilization. The mutations responsible for HE and HPP, lie in the SPTA1 and SPTB gene, and in the EPB41 gene encoding protein 4.1. Allele alpha LELY is a common polymorphic allele, which plays the role of an aggravating factor when it occurs in trans of an elliptocytogenic allele of the SPTA1 gene. Southeast Asian ovalocytosis derives from a change in band 3. The genetic disorders of membrane permeability to monovalent cations required a positional cloning approach. In this respect, channelopathies represent a new frontier in the field. Dehydrated hereditary stomatocytosis (DHS) was shown to belong to a pleiotropic syndrome: DHS + fetal edema + pseudohyperkalemia, which maps 16q23-24. Splenectomy is strictly contraindicated in DHS and another disease of the same class, overhydrated hereditary stomatocytosis, because it increases the risk of thromboembolic accidents. PMID:14692233

  15. Antioxidant activities of bambara groundnut (Vigna subterranea) protein hydrolysates and their membrane ultrafiltration fractions.

    PubMed

    Arise, Abimbola K; Alashi, Adeola M; Nwachukwu, Ifeanyi D; Ijabadeniyi, Oluwatosin A; Aluko, Rotimi E; Amonsou, Eric O

    2016-05-18

    In this study, the bambara protein isolate (BPI) was digested with three proteases (alcalase, trypsin and pepsin), to produce bambara protein hydrolysates (BPHs). These hydrolysates were passed through ultrafiltration membranes to obtain peptide fractions of different sizes (<1, 1-3, 3-5 and 5-10 kDa). The hydrolysates and their peptide fractions were investigated for antioxidant activities. The membrane fractions showed that peptides with sizes <3 kDa had significantly (p < 0.05) reduced surface hydrophobicity when compared with peptides >3 kDa. This is in agreement with the result obtained for the ferric reducing power, metal chelating and hydroxyl radical scavenging activities where higher molecular weight peptides exhibited better activity (p < 0.05) when compared to low molecular weight peptide fractions. However, for all the hydrolysates, the low molecular weight peptides were more effective diphenyl-1-picrylhydrazyl (DPPH) radical scavengers but not superoxide radicals when compared to the bigger peptides. In comparison with glutathione (GSH), BPHs and their membrane fractions had better (p < 0.05) reducing power and ability to chelate metal ions except for the pepsin hydrolysate and its membrane fractions that did not show any metal chelating activity. However, the 5-10 kDa pepsin hydrolysate peptide fractions had greater (88%) hydroxyl scavenging activity than GSH, alcalase and trypsin hydrolysates (82%). These findings show the potential use of BPHs and their peptide fraction as antioxidants in reducing food spoilage or management of oxidative stress-related metabolic disorders. PMID:27156453

  16. 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

  17. 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 μmol/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

  18. A Major Fraction of Glycosphingolipids in Model and Cellular Cholesterol-containing Membranes Is Undetectable by Their Binding Proteins*

    PubMed Central

    Mahfoud, Radhia; Manis, Adam; Binnington, Beth; Ackerley, Cameron; Lingwood, Clifford A.

    2010-01-01

    Glycosphingolipids (GSLs) accumulate in cholesterol-enriched cell membrane domains and provide receptors for protein ligands. Lipid-based “aglycone” interactions can influence GSL carbohydrate epitope presentation. To evaluate this relationship, Verotoxin binding its receptor GSL, globotriaosyl ceramide (Gb3), was analyzed in simple GSL/cholesterol, detergent-resistant membrane vesicles by equilibrium density gradient centrifugation. Vesicles separated into two Gb3/cholesterol-containing populations. The lighter, minor fraction (<5% total GSL), bound VT1, VT2, IgG/IgM mAb anti-Gb3, HIVgp120 or Bandeiraea simplicifolia lectin. Only IgM anti-Gb3, more tolerant of carbohydrate modification, bound both vesicle fractions. Post-embedding cryo-immuno-EM confirmed these results. This appears to be a general GSL-cholesterol property, because similar receptor-inactive vesicles were separated for other GSL-protein ligand systems; cholera toxin (CTx)-GM1, HIVgp120-galactosyl ceramide/sulfatide. Inclusion of galactosyl or glucosyl ceramide (GalCer and GlcCer) rendered VT1-unreactive Gb3/cholesterol vesicles, VT1-reactive. We found GalCer and GlcCer bind Gb3, suggesting GSL-GSL interaction can counter cholesterol masking of Gb3. The similar separation of Vero cell membrane-derived vesicles into minor “binding,” and major “non-binding” fractions when probed with VT1, CTx, or anti-SSEA4 (a human GSL stem cell marker), demonstrates potential physiological relevance. Cell membrane GSL masking was cholesterol- and actin-dependent. Cholesterol depletion of Vero and HeLa cells enabled differential VT1B subunit labeling of “available” and “cholesterol-masked” plasma membrane Gb3 pools by fluorescence microscopy. Thus, the model GSL/cholesterol vesicle studies predicted two distinct membrane GSL formats, which were demonstrated within the plasma membrane of cultured cells. Cholesterol masking of most cell membrane GSLs may impinge many GSL receptor functions. PMID

  19. Membrane distribution of sodium-hydrogen and chloride-bicarbonate exchangers in crypt and villus cell membranes from rabbit ileum.

    PubMed Central

    Knickelbein, R G; Aronson, P S; Dobbins, J W

    1988-01-01

    Present evidence suggests that in the small intestine, villus cells are primarily absorptive and crypt cells are primarily secretory. In order to further confirm that there are differences in transport properties between villus and crypt cells, we have separated villus from crypt cells, using calcium chelations techniques, and determined the distribution of Na:H and Cl:HCO3 exchange activity on brush border membrane and basolateral membrane preparations from these two cell populations. Separation of cells was determined utilizing alkaline phosphatase and maltase activity as a marker of villus cells and thymidine kinase activity as a marker of crypt cells. Utilizing these techniques, we were able to sequentially collect cells along the villus-crypt axis. Na-stimulated glucose and alanine uptake in brush border membrane vesicles diminished from the villus to the crypt region in the sequentially collected cells fractions, further suggesting separation of these cells. Brush border and basolateral membranes were then prepared from cells from the villus and crypt areas, utilizing a continuous sucrose gradient. In the villus cells, Na:H exchange activity was found associated with both the brush border and basolateral membrane, whereas, in crypt cells, Na:H exchange activity was only found on the basolateral membrane. Cl:HCO3 exchange activity was found only on the brush border membrane, in both villus and crypt cells. These studies suggest functional heterogeneity in ion transport between villus and crypt cells. PMID:2848868

  20. Optically absorbing nanoparticle mediated cell membrane permeabilization.

    PubMed

    Bhattacharyya, Kiran; Mehta, Smit; Viator, John

    2012-11-01

    Membrane permeabilization is imperative for gene and drug delivery systems, along with other cell manipulation methods, since the average eukaryotic cell membrane is not permeable to polar and large nonpolar molecules. Antibody conjugated optically absorbing gold nanospheres are targeted to the cell membrane of T47D breast cancer cell line and irradiated with 5 ns pulse, 20 Hz, 532 nm light to increase membrane permeability. Up to 90% permeabilization with less than 6% death is reported at radiant exposures up to 10 times lower than those of other comparable studies. PMID:23114334

  1. 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.

  2. 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.

  3. 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.

  4. 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.

  5. [Isolation and characteristics of the plasma membrane fraction from the swine myometrium].

    PubMed

    Kondratiuk, T P; Bychenok, S F; Prishchepa, L A; Babich, L G; Kurskiĭ, M D

    1986-01-01

    An accelerated method is developed for isolating a fraction of plasma membranes of pig myometrium using ultracentrifugation within the sucrose density gradient (15% and 30%). The membranes possessed the high activity of 5'-nucleotidase and Na+, K+-ATPase and the low activity of rhotenon-insensitive NADH-cytochrome c reductase. The vesicularized preparations of plasma membranes are able of ATP-dependent accumulation of Ca2+ (7.5 +/- 0.3 nmol. 45Ca2+ per 1 mg of protein for 15 min). Phosphate increases the calcium accumulation in the presence of ATP and Mg2+. Ionophore A 23187 promotes a complete and rapid release of the previously active-accumulated calcium. The release of 45Ca2+ accumulated by the membrane fraction may be reached by introduction of 1 mM EGTA or DS-Na into the incubation medium, that evidences for the cation accumulation inside closed structures. Using concanavalin-A-sepharose 4B it is shown that 60% of membrane vesicles are turned inside out. The low saponine concentrations (0.0005%) which inhibit Ca2+-accumulation by plasma membranes but not by the endoplasmic reticulum inhibit this process by 60-70% in preparations of the isolated membrane fraction. The method has certain advantages over the previously applied methods used for isolating of plasma membrane fragments from smooth muscles. PMID:3016962

  6. Fuel cell and membrane therefore

    DOEpatents

    Aindow, Tai-Tsui

    2016-08-09

    A fuel cell includes first and second flow field plates, and an anode electrode and a cathode electrode between the flow field plates. A polymer electrolyte membrane (PEM) is arranged between the electrodes. At least one of the flow field plates influences, at least in part, an in-plane anisotropic physical condition of the PEM that varies in magnitude between a high value direction and a low value direction. The PEM has an in-plane physical property that varies in magnitude between a high value direction and a low value direction. The PEM is oriented with its high value direction substantially aligned with the high value direction of the flow field plate.

  7. 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.

  8. The isolation and fractionation of malaria-infected cells*

    PubMed Central

    Kreier, Julius P.

    1977-01-01

    This paper is a critical review of procedures for the isolation of malarial parasites from host cells and their fractionation. The procedures are grouped according to the stage of parasite being isolated, and the procedures for isolation of the erythrocytic stages are further grouped by techniques used. Some types of procedure are described for isolation of all stages of the parasite, both those in the invertebrate and vertebrate hosts. The uses and limitations of the various procedures are described. It is concluded that all the procedures are useful for some purposes, but that from a morphological standpoint only natural release in culture and continuous flow oscillation provide large yields of intact erythrocytic parasites free of host cell membranes. PMID:338186

  9. 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

  10. 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.

  11. Subcellular Fractionation Analysis of the Extraction of Ubiquitinated Polytopic Membrane Substrate during ER-Associated Degradation.

    PubMed

    Nakatsukasa, Kunio; Kamura, Takumi

    2016-01-01

    During ER-associated degradation (ERAD), misfolded polytopic membrane proteins are ubiquitinated and retrotranslocated to the cytosol for proteasomal degradation. However, our understanding as to how polytopic membrane proteins are extracted from the ER to the cytosol remains largely unclear. To better define the localization and physical properties of ubiquitinated polytopic membrane substrates in vivo, we performed subcellular fractionation analysis of Ste6*, a twelve transmembrane protein that is ubiquitinated primarily by Doa10 E3 ligase in yeast. Consistent with previous in vitro studies, ubiquitinated Ste6* was extracted from P20 (20,000 g pellet) fraction to S20 (20,000 g supernatant) fraction in a Cdc48/p97-dependent manner. Similarly, Ubx2p, which recruits Cdc48/p97 to the ER, facilitated the extraction of Ste6*. By contrast, lipid droplet formation, which was suggested to be dispensable for the degradation of Hrd1-substrates in yeast, was not required for the degradation of Ste6*. Intriguingly, we found that ubiquitinated Ste6* in the S20 fraction could be enriched by further centrifugation at 100,000 g. Although it is currently uncertain whether ubiquitinated Ste6* in P100 fraction is completely free from any lipids, membrane flotation analysis suggested the existence of two distinct populations of ubiquitinated Ste6* with different states of membrane association. Together, these results imply that ubiquitinated Ste6* may be sequestered into a putative quality control sub-structure by Cdc48/p97. Fractionation assays developed in the present study provide a means to further dissect the ill-defined post-ubiquitination step during ERAD of polytopic membrane substrates. PMID:26849222

  12. Isolation of plasma membranes from cultured glioma cells and application to evaluation of membrane sphingomyelin turnover

    SciTech Connect

    Cook, H.W.; Palmer, F.B.; Byers, D.M.; Spence, M.W.

    1988-11-01

    A rapid and reliable method for the isolation of plasma membranes and microsomes of high purity and yield from cultured glioma cells is described. The procedure involves disruption by N2 cavitation, preliminary separation by centrifugation in Tricine buffer, and final separation on a gradient formed from 40% Percoll at pH 9.3. Enzyme and chemical markers indicated greater than 60% yield with six- to eightfold enrichment for plasma membranes and greater than 25% yield with three- to fourfold enrichment for a microsomal fraction consisting mainly of endoplasmic reticulum. The final fractions were obtained with high reproducibility in less than 1 h from the time of cell harvesting. Application of this procedure to human fibroblasts in culture is assessed. The isolation procedure was applied to investigations of synthesis and turnover of sphingomyelin and phosphatidylcholine in plasma membranes of glioma cells following incubation for 4-24 h with (methyl-/sup 3/H)choline. These studies indicated that radioactivity from phosphatidylcholine synthesized in microsomes from exogenous choline may serve as a precursor of the head-group of sphingomyelin accumulating in the plasma membrane.

  13. 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 Δ5-sterols disappeared almost completely and were replaced by 9β, 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 Δ5-sterols. PMID:16666813

  14. Mechanical degradation of fuel cell membranes under fatigue fracture tests

    NASA Astrophysics Data System (ADS)

    Khorasany, Ramin M. H.; Sadeghi Alavijeh, Alireza; Kjeang, Erik; Wang, G. G.; Rajapakse, R. K. N. D.

    2015-01-01

    The effects of cyclic stresses on the fatigue and mechanical stability of perfluorosulfonic acid (PFSA) membranes are experimentally investigated under standard fuel cell conditions. The experiments are conducted ex-situ by subjecting membrane specimens to cyclic uniaxial tension at controlled temperature and relative humidity. The fatigue lifetime is measured in terms of the number of cycles until ultimate fracture. The results indicate that the membrane fatigue lifetime is a strong function of the applied stress, temperature, and relative humidity. The fatigue life increases exponentially with reduced stresses in all cases. The effect of temperature is found to be more significant than that of humidity, with reduced fatigue life at high temperatures. The maximum membrane strain at fracture is determined to decrease exponentially with increasing membrane lifetime. At a given fatigue life, a membrane exposed to fuel cell conditions is shown to accommodate more plastic strain before fracture than one exposed to room conditions. Overall, the proposed ex-situ membrane fatigue experiment can be utilized to benchmark the fatigue lifetime of new materials in a fraction of the time and cost associated with conventional in-situ accelerated stress testing methods.

  15. Cell membrane array fabrication and assay technology

    PubMed Central

    Yamazaki, Victoria; Sirenko, Oksana; Schafer, Robert J; Nguyen, Luat; Gutsmann, Thomas; Brade, Lore; Groves, Jay T

    2005-01-01

    Background Microarray technology has been used extensively over the past 10 years for assessing gene expression, and has facilitated precise genetic profiling of everything from tumors to small molecule drugs. By contrast, arraying cell membranes in a manner which preserves their ability to mediate biochemical processes has been considerably more difficult. Results In this article, we describe a novel technology for generating cell membrane microarrays for performing high throughput biology. Our robotically-arrayed supported membranes are physiologically fluid, a critical property which differentiates this technology from other previous membrane systems and makes it useful for studying cellular processes on an industrialized scale. Membrane array elements consist of a solid substrate, above which resides a fluid supported lipid bilayer containing biologically-active molecules of interest. Incorporation of transmembrane proteins into the arrayed membranes enables the study of ligand/receptor binding, as well as interactions with live intact cells. The fluidity of these molecules in the planar lipid bilayer facilitates dimerization and other higher order interactions necessary for biological signaling events. In order to demonstrate the utility of our fluid membrane array technology to ligand/receptor studies, we investigated the multivalent binding of the cholera toxin B-subunit (CTB) to the membrane ganglioside GM1. We have also displayed a number of bona fide drug targets, including bacterial endotoxin (also referred to as lipopolysaccharide (LPS)) and membrane proteins important in T cell activation. Conclusion We have demonstrated the applicability of our fluid cell membrane array technology to both academic research applications and industrial drug discovery. Our technology facilitates the study of ligand/receptor interactions and cell-cell signaling, providing rich qualitative and quantitative information. PMID:15960850

  16. 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

  17. Nuclear myosin I regulates cell membrane tension.

    PubMed

    Venit, Tomáš; Kalendová, Alžběta; Petr, Martin; Dzijak, Rastislav; Pastorek, Lukáš; Rohožková, Jana; Malohlava, Jakub; Hozák, Pavel

    2016-01-01

    Plasma membrane tension is an important feature that determines the cell shape and influences processes such as cell motility, spreading, endocytosis and exocytosis. Unconventional class 1 myosins are potent regulators of plasma membrane tension because they physically link the plasma membrane with adjacent cytoskeleton. We identified nuclear myosin 1 (NM1) - a putative nuclear isoform of myosin 1c (Myo1c) - as a new player in the field. Although having specific nuclear functions, NM1 localizes predominantly to the plasma membrane. Deletion of NM1 causes more than a 50% increase in the elasticity of the plasma membrane around the actin cytoskeleton as measured by atomic force microscopy. This higher elasticity of NM1 knock-out cells leads to 25% higher resistance to short-term hypotonic environment and rapid cell swelling. In contrast, overexpression of NM1 in wild type cells leads to an additional 30% reduction of their survival. We have shown that NM1 has a direct functional role in the cytoplasm as a dynamic linker between the cell membrane and the underlying cytoskeleton, regulating the degree of effective plasma membrane tension. PMID:27480647

  18. Nuclear myosin I regulates cell membrane tension

    PubMed Central

    Venit, Tomáš; Kalendová, Alžběta; Petr, Martin; Dzijak, Rastislav; Pastorek, Lukáš; Rohožková, Jana; Malohlava, Jakub; Hozák, Pavel

    2016-01-01

    Plasma membrane tension is an important feature that determines the cell shape and influences processes such as cell motility, spreading, endocytosis and exocytosis. Unconventional class 1 myosins are potent regulators of plasma membrane tension because they physically link the plasma membrane with adjacent cytoskeleton. We identified nuclear myosin 1 (NM1) - a putative nuclear isoform of myosin 1c (Myo1c) - as a new player in the field. Although having specific nuclear functions, NM1 localizes predominantly to the plasma membrane. Deletion of NM1 causes more than a 50% increase in the elasticity of the plasma membrane around the actin cytoskeleton as measured by atomic force microscopy. This higher elasticity of NM1 knock-out cells leads to 25% higher resistance to short-term hypotonic environment and rapid cell swelling. In contrast, overexpression of NM1 in wild type cells leads to an additional 30% reduction of their survival. We have shown that NM1 has a direct functional role in the cytoplasm as a dynamic linker between the cell membrane and the underlying cytoskeleton, regulating the degree of effective plasma membrane tension. PMID:27480647

  19. Membrane aging during cell growth ascertained by Laurdan generalized polarization.

    PubMed

    Parasassi, T; Di Stefano, M; Ravagnan, G; Sapora, O; Gratton, E

    1992-10-01

    The sensitivity of the fluorescent probe Laurdan to the phase state of lipids has been utilized to detect modifications in the composition and physical state of cell membranes during cell growth. In phospholipid vesicles, the Laurdan emission spectrum shows a 50-nm red shift by passing from the gel to the liquid-crystalline phase. The Generalized Polarization (GP) value has been used for the data treatment instead of the ratiometric method common in investigations utilizing other fluorescent probes that display spectral sensitivity to medium properties. The GP value can be measured easily and quickly and possesses all the properties of "classical" polarization, including the additivity rule. Once Laurdan limiting GP values have been established for the gel and the liquid-crystalline phase of lipids, the quantitative determination of coexisting phases in natural samples is possible. In the present work the observation of a relevant decrease in the fractional intensity of the liquid-crystalline phase in K562 cell membranes during 5 days of asynchronous growth is reported. A decrease in the "fluidity" of cell membranes in K562 cells kept in culture for several months is also reported. The procedure developed for labeling cell membranes with Laurdan is reported and the influence of cell metabolism on fluorescence parameters is discussed. Also discussed is the influence of cholesterol on Laurdan GP. PMID:1397095

  20. 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.

  1. 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.

  2. Sequential fractionation and isolation of subcellular proteins from tissue or cultured cells

    PubMed Central

    Baghirova, Sabina; Hughes, Bryan G.; Hendzel, Michael J.; Schulz, Richard

    2015-01-01

    Many types of studies require the localization of a protein to, or isolation of enriched protein from a specific cellular compartment. Many protocols in the literature and from commercially available kits claim to yield pure cellular fractions. However, in our hands, the former often do not work effectively and the latter may be prohibitively expensive if a large number of fractionations are required. Furthermore, the largely proprietary composition of reagents in commercial kits means that the user is not able to make adjustments if, for example, a particular component affects the activity of a protein of interest. The method described here allows the isolation of purified proteins from three cellular fractions: the cytosol, membrane-bound organelles, and the nucleus. It uses gentle buffers with increasing detergent strength that sequentially lyse the cell membrane, organelle membranes and finally the nuclear membrane.•Quick, simple to replicate or adjust; this method does not require expensive reagents or use of commercial kits•The protocol can be applied to tissue samples or cultured cells without changing buffer components•Yields purified fractions of cytosolic, membrane bound and nuclear proteins, with the proper distribution of the appropriate subcellular markers: GAPDH, VDAC, SERCA2 and lamin A/C PMID:26740924

  3. Membrane Elastic Properties and Cell Function

    PubMed Central

    Pontes, Bruno; Ayala, Yareni; Fonseca, Anna Carolina C.; Romão, Luciana F.; Amaral, Racκele F.; Salgado, Leonardo T.; Lima, Flavia R.; Farina, Marcos; Viana, Nathan B.; Moura-Neto, Vivaldo; Nussenzveig, H. Moysés

    2013-01-01

    Recent studies indicate that the cell membrane, interacting with its attached cytoskeleton, is an important regulator of cell function, exerting and responding to forces. We investigate this relationship by looking for connections between cell membrane elastic properties, especially surface tension and bending modulus, and cell function. Those properties are measured by pulling tethers from the cell membrane with optical tweezers. Their values are determined for all major cell types of the central nervous system, as well as for macrophage. Astrocytes and glioblastoma cells, which are considerably more dynamic than neurons, have substantially larger surface tensions. Resting microglia, which continually scan their environment through motility and protrusions, have the highest elastic constants, with values similar to those for resting macrophage. For both microglia and macrophage, we find a sharp softening of bending modulus between their resting and activated forms, which is very advantageous for their acquisition of phagocytic functions upon activation. We also determine the elastic constants of pure cell membrane, with no attached cytoskeleton. For all cell types, the presence of F-actin within tethers, contrary to conventional wisdom, is confirmed. Our findings suggest the existence of a close connection between membrane elastic constants and cell function. PMID:23844071

  4. Membrane-filtered olive mill wastewater: Quality assessment of the dried phenolic-rich fraction

    Technology Transfer Automated Retrieval System (TEKTRAN)

    A current trend in olive mill wastewater (OMWW) management is to not only decrease environmental pollution but also extract and utilize valuable by-products. Therefore, the objectives of this study were to explore different techniques for drying a phenolic-rich membrane filtration fraction of OMWW a...

  5. Detection of Molecular Charges at Cell Membrane

    NASA Astrophysics Data System (ADS)

    Sakata, Toshiya; Miyahara, Yuji

    2008-01-01

    Molecular charges at the cell membrane have been successfully detected using cell-based field-effect devices. Mouse fibroblast cells were adhered to the Si3N4 gate surface of the field-effect devices. The negative charges of sialic acid at the surface of the cell membrane could be detected as a shift of the flatband voltage of the field-effect devices. Quantitative analysis of molecular charges at the cell membrane could be demonstrated in relation to the number of adhered cells on the Si3N4 gate surface. The platform based on the field-effect devices is suitable for a simple, accurate and non-invasive system for cell functional analysis.

  6. Preparation of stroma, thylakoid membrane, and lumen fractions from Arabidopsis thaliana chloroplasts for proteomic analysis.

    PubMed

    Hall, Michael; Mishra, Yogesh; Schröder, Wolfgang P

    2011-01-01

    For many studies regarding important chloroplast processes such as oxygenic photosynthesis, fractionation of the total chloroplast proteome is a necessary first step. Here, we describe a method for isolating the stromal, the thylakoid membrane, and the thylakoid lumen subchloroplast fractions from Arabidopsis thaliana leaf material. All three fractions can be isolated sequentially from the same plant material in a single day preparation. The isolated fractions are suitable for various proteomic analyses such as simple mapping studies or for more complex experiments such as differential expression analysis using two-dimensional difference gel electrophoresis (2D-DIGE) or mass spectrometry (MS)-based techniques. Besides this, the obtained fractions can also be used for many other purposes such as immunological assays, enzymatic activity assays, and studies of protein complexes by native-polyacrylamide gel electrophoresis (native-PAGE). PMID:21863445

  7. 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

  8. 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.

  9. Advanced membrane electrode assemblies for fuel cells

    SciTech Connect

    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.

  10. 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

  11. Impact of cell density on microbially induced stable isotope fractionation.

    PubMed

    Kampara, Makeba; Thullner, Martin; Harms, Hauke; Wick, Lukas Y

    2009-01-01

    Quantification of microbial contaminant biodegradation based on stable isotope fractionation analysis (SIFA) relies on known, invariable isotope fractionation factors. The microbially induced isotope fractionation is caused by the preferential cleavage of bonds containing light rather than heavy isotopes. However, a number of non-isotopically sensitive steps preceding the isotopically sensitive bond cleavage may affect the reaction kinetics of a degradation process and reduce the observed (i.e., the macroscopically detectable) isotope fractionation. This introduces uncertainty to the use of isotope fractionation for the quantification of microbial degradation processes. Here, we report on the influence of bacterial cell density on observed stable isotope fractionation. Batch biodegradation experiments were performed under non-growth conditions to quantify the toluene hydrogen isotope fractionation by exposing Pseudomonas putida mt-2(pWWO) at varying cell densities to different concentrations of toluene. Observed isotope fractionation depended significantly on the cell density. When the cell density rose from 5 x 10(5) to 5 x 10(8)cells/mL, the observed isotope fractionation declined by 70% and went along with a 55% decrease of the degradation rates of individual cells. Theoretical estimates showed that uptake-driven diffusion to individual cells depended on cell density via the overlap of the cells' diffusion-controlled boundary layers. Our data suggest that biomass effects on SIFA have to be considered even in well-mixed systems such as the cell suspensions used in this study. PMID:19015849

  12. 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.

  13. Photothermal nanoblade for patterned cell membrane cutting.

    PubMed

    Wu, Ting-Hsiang; Teslaa, Tara; Teitell, Michael A; Chiou, Pei-Yu

    2010-10-25

    We report a photothermal nanoblade that utilizes a metallic nanostructure to harvest short laser pulse energy and convert it into a highly localized and specifically shaped explosive vapor bubble. Rapid bubble expansion and collapse punctures a lightly-contacting cell membrane via high-speed fluidic flows and induced transient shear stress. The membrane cutting pattern is controlled by the metallic nanostructure configuration, laser pulse polarization, and energy. Highly controllable, sub-micron sized circular hole pairs to half moon-like, or cat-door shaped, membrane cuts were realized in glutaraldehyde treated HeLa cells. PMID:21164656

  14. Vesicle trafficking and cell surface membrane patchiness.

    PubMed

    Tang, Q; Edidin, M

    2001-07-01

    Membrane proteins and lipids often appear to be distributed in patches on the cell surface. These patches are often assumed to be membrane domains, arising from specific molecular associations. However, a computer simulation (Gheber and Edidin, 1999) shows that membrane patchiness may result from a combination of vesicle trafficking and dynamic barriers to lateral mobility. The simulation predicts that the steady-state patches of proteins and lipids seen on the cell surface will decay if vesicle trafficking is inhibited. To test this prediction, we compared the apparent sizes and intensities of patches of class I HLA molecules, integral membrane proteins, before and after inhibiting endocytic vesicle traffic from the cell surface, either by incubation in hypertonic medium or by expression of a dominant-negative mutant dynamin. As predicted by the simulation, the apparent sizes of HLA patches increased, whereas their intensities decreased after endocytosis and vesicle trafficking were inhibited. PMID:11423406

  15. MYADM regulates Rac1 targeting to ordered membranes required for cell spreading and migration.

    PubMed

    Aranda, Juan F; Reglero-Real, Natalia; Kremer, Leonor; Marcos-Ramiro, Beatriz; Ruiz-Sáenz, Ana; Calvo, María; Enrich, Carlos; Correas, Isabel; Millán, Jaime; Alonso, Miguel A

    2011-04-15

    Membrane organization into condensed domains or rafts provides molecular platforms for selective recruitment of proteins. Cell migration is a general process that requires spatiotemporal targeting of Rac1 to membrane rafts. The protein machinery responsible for making rafts competent to recruit Rac1 remains elusive. Some members of the MAL family of proteins are involved in specialized processes dependent on this type of membrane. Because condensed membrane domains are a general feature of the plasma membrane of all mammalian cells, we hypothesized that MAL family members with ubiquitous expression and plasma membrane distribution could be involved in the organization of membranes for cell migration. We show that myeloid-associated differentiation marker (MYADM), a protein with unique features within the MAL family, colocalizes with Rac1 in membrane protrusions at the cell surface and distributes in condensed membranes. MYADM knockdown (KD) cells had altered membrane condensation and showed deficient incorporation of Rac1 to membrane raft fractions and, similar to Rac1 KD cells, exhibited reduced cell spreading and migration. Results of rescue-of-function experiments by expression of MYADM or active Rac1L61 in cells knocked down for Rac1 or MYADM, respectively, are consistent with the idea that MYADM and Rac1 act on parallel pathways that lead to similar functional outcomes. PMID:21325632

  16. Directing membrane chromatography to manufacture α1-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, α1-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

  17. NOM fractionation and fouling of low-pressure membranes in microgranular adsorptive filtration.

    PubMed

    Cai, Zhenxiao; Benjamin, Mark M

    2011-10-15

    Membrane fouling by natural organic matter (NOM) was investigated in microgranular adsorptive filtration (μGAF) systems, in which a thin layer of adsorbent is predeposited on low-pressure membranes. The adsorbents tested included heated aluminum oxide particles (HAOPs), ion exchange (IX) resin, and powdered activated carbon (PAC). Size exclusion chromatography (SEC) separated the NOM into four apparent MW fractions with significant UV₂₅₄. HAOPs and the IX resin performed almost identically with respect to removal of these fractions, and differently from PAC. However, while HAOPs and PAC reduced fouling substantially, IX resin did not, indicating that fouling could not be attributed to the NOM fractions detected by SEC. Rather, the key foulants appear to comprise a very small fraction of the NOM with almost no UV₂₅₄ absorbance. Alginate, a strongly fouling surrogate for natural polysaccharides, is adsorbed effectively by HAOPs, but not by IX resin or PAC, suggesting that polysaccharides sometimes play a key role in membrane fouling by NOM. PMID:21905711

  18. Fixed charge in the cell membrane

    PubMed Central

    Elul, R.

    1967-01-01

    1. Focal electric field was generated by passing a current of 5 × 10-7 to 1 × 10-5 A from a micropipette into the culture medium. Movement of cells at a distance of 5-50 μ from the electrode tip was observed. In case of cells embedded in the culture only local deformation of the membrane was observed. 2. The cell species explored included neurones, glia, muscle fibres, connective cells, malignant cells and erythrocytes. All cells responded in a similar manner to the electric field, and the current required was in the same range. 3. Cells were attracted to a positive micropipette and repelled from a negative one: the only exception was observed in certain malignant cells which moved in the opposite direction. 4. Movement and membrane deformation could be obtained with electrodes filled with various concentrated and isotonic solutions. The composition of the culture medium also had no qualitative influence on these effects. 5. Metabolic poisons or rupture of the cell membrane had no effect on the movement. Isolated membrane fragments showed movement similar to that of intact cells. 6. The possibility of artifacts due to proximity of the focal electrode is considered. It is shown that electro-osmosis cannot account for the present observations. Some other artifacts are also excluded. 7. It is proposed that the most satisfactory way to account for the present observations is by a membrane carrying negative fixed charge of the order of 2·5 × 103 e.s.u./cm2. Some physiological consequences of presence of negative charge in the membrane are briefly discussed. ImagesFig. 1Fig. 2Fig. 3 PMID:6040152

  19. Acute hydrodynamic damage induced by SPLITT fractionation and centrifugation in red blood cells.

    PubMed

    Urbina, Adriana; Godoy-Silva, Ruben; Hoyos, Mauricio; Camacho, Marcela

    2016-05-01

    Though blood bank processing traditionally employs centrifugation, new separation techniques may be appealing for large scale processes. Split-flow fractionation (SPLITT) is a family of techniques that separates in absence of labelling and uses very low flow rates and force fields, and is therefore expected to minimize cell damage. However, the hydrodynamic stress and possible consequent damaging effects of SPLITT fractionation have not been yet examined. The aim of this study was to investigate the hydrodynamic damage of SPLITT fractionation to human red blood cells, and to compare these effects with those induced by centrifugation. Peripheral whole blood samples were collected from healthy volunteers. Samples were diluted in a buffered saline solution, and were exposed to SPLITT fractionation (flow rates 1-10ml/min) or centrifugation (100-1500g) for 10min. Cell viability, shape, diameter, mean corpuscular hemoglobin, and membrane potential were measured. Under the operating conditions employed, both SPLITT and centrifugation maintained cell viability above 98%, but resulted in significant sublethal damage, including echinocyte formation, decreased cell diameter, decreased mean corpuscular hemoglobin, and membrane hyperpolarization which was inhibited by EGTA. Wall shear stress and maximum energy dissipation rate showed significant correlation with lethal and sublethal damage. Our data do not support the assumption that SPLITT fractionation induces very low shear stress and is innocuous to cell function. Some changes in SPLITT channel design are suggested to minimize cell damage. Measurement of membrane potential and cell diameter could provide a new, reliable and convenient basis for evaluation of hydrodynamic effects on different cell models, allowing identification of optimal operating conditions on different scales. PMID:27023157

  20. Fuel cell subassemblies incorporating subgasketed thrifted membranes

    DOEpatents

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

    2013-03-01

    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.

  1. Fuel cell subassemblies incorporating subgasketed thrifted membranes

    DOEpatents

    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. Engineering supported membranes for cell biology

    PubMed Central

    Yu, Cheng-han

    2010-01-01

    Cell membranes exhibit multiple layers of complexity, ranging from their specific molecular content to their emergent mechanical properties and dynamic spatial organization. Both compositional and geometrical organizations of membrane components are known to play important roles in life processes, including signal transduction. Supported membranes, comprised of a bilayer assembly of phospholipids on the solid substrate, have been productively served as model systems to study wide range problems in cell biology. Because lateral mobility of membrane components is readily preserved, supported lipid membranes with signaling molecules can be utilized to effectively trigger various intercellular reactions. The spatial organization and mechanical deformation of supported membranes can also be manipulated by patterning underlying substrates with modern micro- and nano-fabrication techniques. This article focuses on various applications and methods to spatially patterned biomembranes by means of curvature modulations and spatial reorganizations, and utilizing them to interface with live cells. The integration of biological components into synthetic devices provides a unique approach to investigate molecular mechanisms in cell biology. PMID:20559751

  3. 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.

  4. Acetylation in vitro of constituent polypeptides by smooth endoplasmic reticulum (SER) and Golgi membrane fractions

    SciTech Connect

    Sambasivam, H.; Murray, R.K.

    1986-05-01

    Many polypeptides of the membranes of the ER are phosphorylated. To determine if any such polypeptides are acetylated, microsomal and other classical subcellular fractions were incubated with (/sup 3/H) acetyl-CoA; the specific activity of the microsomal fraction (MF) was the greatest. SDS-PAGE revealed that some 20 polypeptides of the MF were acetylated; 2-D electrophoretograms extended this number to approximately 60. Separation of the MF into smooth (S) and rough (R) fractions showed that the great majority of the labelled polypeptides belonged to the former. Isolation of a Golgi fraction revealed that its acetylation activity was approximately 3-fold greater than the SER fraction. Extensive proteolytic digestion of the MF followed by radiochromatography disclosed some 9 components whose precise nature (acetylated amino acids and/or sialic acids, etc.) is under study. Assuming that the majority of the radioactivity is in the former components and that a similar process occurs in vivo, the authors suggest that the Golgi apparatus may be a major site of acetylation of membrane and possibly other proteins.

  5. Basement Membranes: Cell Scaffoldings and Signaling Platforms

    PubMed Central

    Yurchenco, Peter D.

    2011-01-01

    Basement membranes are widely distributed extracellular matrices that coat the basal aspect of epithelial and endothelial cells and surround muscle, fat, and Schwann cells. These extracellular matrices, first expressed in early embryogenesis, are self-assembled on competent cell surfaces through binding interactions among laminins, type IV collagens, nidogens, and proteoglycans. They form stabilizing extensions of the plasma membrane that provide cell adhesion and that act as solid-phase agonists. Basement membranes play a role in tissue and organ morphogenesis and help maintain function in the adult. Mutations adversely affecting expression of the different structural components are associated with developmental arrest at different stages as well as postnatal diseases of muscle, nerve, brain, eye, skin, vasculature, and kidney. PMID:21421915

  6. Chemical compositions and antiproliferation activities of the chloroform fraction from Pyropolyporus fomentarius in K562 cells.

    PubMed

    Zhang, Y; Wang, P; Xiao, Y; Wang, X; Yang, S; Liu, Q

    2015-07-01

    Pyropolyporus fomentarius, a fungus of the polyporaceae family, has been used in the treatment of various diseases, such as gastroenteric disorder, hepatocirrhosis, oral ulcer, inflammation, and several cancers. This study was conducted to investigate the compositions and cell growth inhibition effects of P. fomentarius chloroform (CHCl3) fraction and to clarify the possible mechanisms. Gas chromatography-mass spectrometry analysis was performed to investigate the composition of the P. fomentarius CHCl3 fraction. Cell viability was measured using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay. Cell membrane damage was evaluated with a scanning electron microscope and flow cytometry following propidium iodide and bis-(1,3-dibarbituric acid)-trimethine oxanol staining. Apoptosis was analyzed using annexin V-PE/7-amino-actinomycin D (7-AAD) staining. Generation of intracellular calcium ion (Ca(2+)), reactive oxygen species (ROS), and changes of mitochondrial membrane potential (Δψ m) were detected by flow cytometry using fluo 3-acetoxymethyl ester, 2',7'-dichlorofluorescin-diacetate, and rhodamine 123. Our obtained data indicate that P. fomentarius CHCl3 fraction could inhibit proliferation of K562 cells depending on both the dosage and the incubation time, cause cell membrane damage, influence intracellular [Ca(2+)]i variation, promote the yield of ROS, decrease the level of Δψ m, and initiate the apoptotic response in K562 cells. PMID:25403175

  7. Top Down Proteomics of Human Membrane Proteins from Enriched Mitochondrial Fractions

    PubMed Central

    Catherman, Adam D.; Li, Mingxi; Tran, John C.; Durbin, Kenneth R.; Compton, Philip D.; Early, Bryan P.; Thomas, Paul M.; Kelleher, Neil L.

    2013-01-01

    The interrogation of intact integral membrane proteins has long been a challenge for biological mass spectrometry. Here, we demonstrate the application of Top Down mass spectrometry to whole membrane proteins below 60 kDa with up to 8 transmembrane helices. Analysis of enriched mitochondrial membrane preparations from human cells yielded identification of 83 integral membrane proteins, along with 163 membrane-associated or soluble proteins, with a median q value of 3 × 10−10. An analysis of matching fragment ions demonstrated that significantly more fragment ions were found within transmembrane domains than would be expected based upon the observed protein sequence. Forty-six proteins from the complexes of oxidative phosphorylation were identified which exemplifies the increasing ability of Top Down Proteomics to provide extensive coverage in a biological network. PMID:23305238

  8. 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.

  9. Microalgal biomass production by using ultra- and nanofiltration membrane fractions of olive mill wastewater.

    PubMed

    Cicci, A; Stoller, M; Bravi, M

    2013-09-01

    Olive milling produces huge amounts of wastewater (OMWW) characterized by an extremely high organic load. Its polyphenols content is a hindrance to conventional biological treatment and to using it as growing medium for common microbial biomasses. The practice to dump it on soil is in conflict with the latest EU directives about waste management. OMWW can be effectively and efficiently treated by means of membrane technology to a fraction of the initial volume, but membrane processing concentrates still require treatment. Reversing the overall cost balance of membrane processing and subsequent treatment requires valorizing the concentrates through their reuse, as well as ensuring long-term service of the membrane system through effective wastewater pretreatment and sustainable, fouling-controlling, membrane operation conduite. Aim of this work is to reuse and valorize the ultra- and nanofiltration membrane concentrates as media for biomass production of microalgae and cyanobacteria. Scenedesmus dimorphus and Arthrospira platensis, usable as a food, feed, nutraceutical component or feedstock for biofuels, were selected for this investigation. Microalgal growth was experimentally determined and related to the composition of the concentrate-based media and to the irradiance distribution within the photobioreactor volume to decouple light limitation and medium chemical composition effects. PMID:23770485

  10. Involvement of the Host Cell Nuclear Envelope Membranes in the Replication of Japanese Encephalitis Virus

    PubMed Central

    Zebovitz, E.; Leong, J. K. L.; Doughty, S. C.

    1974-01-01

    The distribution of viral ribonucleic acid (RNA) on various cell membrane fractions derived from a porcine kidney cell line infected with Japanese encephalitis virus was investigated. At 40 h postinfection, after virus growth had reached its peak, three viral RNAs, 45S, 27S, and 20S, were associated with the cytoplasmic membranes and intact nuclei. The amount of each RNA associated with the nucleus was two- to fivefold greater than that present with the cytoplasmic membranes. Treatment of washed infected nuclei with 1.0% Triton X-100, which removed the outer nuclear envelope membrane, also removed the viral RNA. When the nucleus was fractionated into nuclear envelope membranes and a large particle fraction which sedimented at 600 × g, nearly all of the viral RNA remained associated with the envelope membranes. The nuclear envelope membranes contained higher viral RNA polymerase activity than the cytoplasmic membranes derived from the same cells. These data suggest that major sites for Japanese encephalitis virus RNA synthesis may be localized on or in very close association with the nuclear envelope membranes. PMID:4842128

  11. 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

  12. Blend Concepts for Fuel Cell Membranes

    NASA Astrophysics Data System (ADS)

    Kerres, Jochen

    Differently cross-linked blend membranes were prepared from commercial arylene main-chain polymers from the classes of poly(ether-ketones) and poly(ethersulfones) modified with sulfonate groups, sulfinate cross-linking groups and basic N-groups. The following membrane types have been prepared: (a) van-der Waals/dipole-dipole blends by mixing a polysulfonate with unmodified PSU. This membrane type showed a heterogeneous morphology, leading to extreme swelling and even dissolution of the sulfonated component at elevated temperatures. (b) Hydrogen bridge blends by mixing a polysulfonate with a polyamide or polyetherimide. This membrane type showed a partially heterogeneous morphology, also leading to extreme swelling/dissolution of the sulfonated blend component at elevated temperatures. (c) Acid-base blends by mixing a polysulfonate with a polymeric N-base (self-developed/commercial). With this membrane type, we could reach a wide variability of properties by variation of different parameters. Membranes showing excellent stability and good fuel cell performance up to 100°C (PEFC) and 130°C (DMFC) were obtained. (d) Covalently cross-linked (blend) membranes by either mixing of a polysulfonate with a polysulfinate or by preparation of a polysulfinatesulfonate, followed by reaction of the sulfinate groups in solution with a dihalogeno compound under S-alkylation. Membranes were prepared that showed effective suppression of swelling without H+-conductivity loss. The membranes showed good PEFC (up to 100°C) and DMFC (up to 130°C) performance. (e) Covalent-ionically cross-linked blend membranes by mixing polysulfonates with polysulfinates and polybases or by mixing a polysulfonate with a polymer carrying both sulfinate and basic N-groups. The covalent-ionically cross-linked membranes were tested in DMFC up to 110°C and showed a good performance. (f) Differently cross-linked organic-inorganic blend composite membranes via different procedures. The best results were

  13. 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

  14. Influence of increased membrane cholesterol on membrane fluidity and cell function in human red blood cells.

    PubMed

    Cooper, R A

    1978-01-01

    Cholesterol and phospholipid are the two major lipids of the red cell membrane. Cholesterol is insoluble in water but is solubilized by phospholipids both in membranes and in plasma lipoproteins. Morever, cholesterol exchanges between membranes and lipoproteins. An equilibrium partition is established based on the amount of cholesterol relative to phospholipid (C/PL) in these two compartments. Increases in the C/PL of red cell membranes have been studied under three conditions: First, spontaneous increases in vivo have been observed in the spur red cells of patients with severe liver disease; second, similar red cell changes in vivo have been induced by the administration of cholesterol-enriched diets to rodents and dogs; third, increases in membrane cholesterol have been induced in vitro by enriching the C/PL of the lipoprotein environment with cholesterol-phospholipid dispersions (liposomes) having a C/PL of greater than 1.0. In each case, there is a close relationship between the C/PL of the plasma environment and the C/PL of the red cell membrane. In vivo, the C/PL mole ratio of red cell membranes ranges from a normal value of 0.09--1.0 to values which approach but do not reach 2.0. In vitro, this ratio approaches 3.0. Cholesterol enrichment of red cell membranes directly influences membrane lipid fluidity, as assessed by the rotational diffusion of hydrophobic fluorescent probes such as diphenyl hexatriene (DPH). A close correlation exists between increases in red cell membrane C/PL and decreases in membrane fluidity over the range of membrane C/PL from 1.0 to 2.0; however, little further change in fluidity occurs when membrane C/PL is increased to 2.0--3.0. Cholesterol enrichment of red cell membranes is associated with the transformation of cell contour to one which is redundant and folded, and this is associated with a decrease in red cell filterability in vitro. Circulation in vivo in the presence of the spleen further modifies cell shape to a spiny

  15. Separation and identification of the light harvesting proteins contained in grana and stroma thylakoid membrane fractions.

    PubMed

    Timperio, Anna Maria; Huber, Christian G; Zolla, Lello

    2004-06-18

    This paper presents the results of a study performed to develop a rapid and straightforward method to resolve and simultaneously identify the light-harvesting proteins of photosystem I (LHCI) and photosystem II (LHCII) present in the grana and stroma of the thylakoid membranes of higher plants. These hydrophobic proteins are embedded in the phospholipid membrane, and their extraction usually requires detergent and time consuming manipulations that may introduce artifacts. The method presented here makes use of digitonin, a detergent which causes rapid (within less than 3 min) cleavage of the thylakoid membrane into two subfractions: appressed (grana) and non-appressed (stroma) membranes, the former enriched in photosystem II and the latter containing mainly photosystem I. From these two fractions identification of the protein components was performed by separating them by reversed-phase high-performance liquid chromatography (RP-HPLC) and determining the intact molecular mass by electrospray ionization mass spectrometry (ESI-MS). By this strategy the ion suppression during ESI-MS that normally occurs in the presence of membrane phospholipids was avoided, since RP-HPLC removed most phospholipids from the analytes. Consequently, high quality mass spectra were extracted from the reconstructed ion chromatograms. The specific cleavage of thylakoid membranes by digitonin, as well as the rapid identification and quantification of the antenna composition of the two complexes facilitate future studies of the lateral migration of the chlorophyll-protein complexes along thylakoid membranes, which is well known to be induced by high intensity light or other environmental stresses. Such investigations could not be performed by sodium dodecylsulfate-polyacrylamide gel electrophoresis because of insufficient resolution of the proteins having molecular masses between 22,000 and 25,000. PMID:15248427

  16. 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

  17. 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).

  18. Cell cycle regulation of Golgi membrane dynamics.

    PubMed

    Tang, Danming; Wang, Yanzhuang

    2013-06-01

    The Golgi apparatus is a membranous organelle in the cell that plays essential roles in protein and lipid trafficking, sorting, processing, and modification. Its basic structure is a stack of closely aligned flattened cisternae. In mammalian cells, dozens of Golgi stacks are often laterally linked into a ribbon-like structure. Biogenesis of the Golgi during cell division occurs through a sophisticated disassembly and reassembly process that can be divided into three distinct but cooperative steps, including the deformation and reformation of the Golgi cisternae, stacks, and ribbon. Here, we review our current understanding of the protein machineries that control these three steps in the cycle of mammalian cell division: GRASP65 and GRASP55 in Golgi stack and ribbon formation; ubiquitin and AAA ATPases in postmitotic Golgi membrane fusion; and golgins and cytoskeleton in Golgi ribbon formation. PMID:23453991

  19. Fractionation of different PEGylated forms of a protein by chromatography using environment-responsive membranes.

    PubMed

    Yu, Deqiang; Shang, Xiaojiao; Ghosh, Raja

    2010-08-27

    PEGylation of therapeutic proteins can enhance their efficacy as biopharmaceuticals through increased stability and hydrophilicity, and decreased immunogenicity. A site-specific PEGylated protein (e.g. mono-PEGylated at N-terminus) is frequently desirable as a product. However, multiple-PEGylated forms are frequently produced as byproducts. In this paper we discuss the fractionation of the different PEGylated forms of a protein by hydrophobic interaction chromatography using a stack of hydrophilized PVDF membrane, which has been shown to be environment responsive, as stationary phase. With the model protein examined in this study (i.e. lysozyme), the apparent hydrophobicity in the presence of a lyotropic salt increased with the degree of PEGylation. Based on this, unmodified lysozyme and its mono-, di- and tri-PEGylated forms could each be resolved into separate chromatographic peaks. Such fractionation was not feasible using conventional hydrophobic interaction chromatography using a butyl column. The use of membrane chromatography also ensured that the fractionation was fast and hence suitable for analytical applications such as product purity determination and monitoring of the extent of PEGylation reactions. PMID:20638664

  20. Compositional characteristics of a chloroform/methanol soluble protein fraction from spinach chloroplast membranes.

    PubMed

    Henriques, F; Park, R B

    1976-05-14

    Extraction of an aqueous suspension of spinach chloroplast lamellae with a chloroform/methanol mixture leads to solubilization of about 1/3 of the total membrane protein. Amino acid analysis of the chloroform/methanol-soluble protein shows that this fraction is largely enriched in the hydrophobic residues proline, leucine, alanine and phenylalanine and considerably depleted in polar amino acids, namely lysine and arginine. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis of the solubilized material reveals the presence of a variety of low molecular weight polypeptides (molecular weight less than or equal to 25 000), with more than 50% of the total fraction being contributed by a 25 000 dalton band. This band, which accounts for about 25% of the total chloroplast lamellar protein, has recently been identified as the main component of the light-harvesting chlorophyll-protein complex. The physiological role of most of the chloroform/methanol-soluble protein fraction is not known at present. From its chemical properties and apparent biological inertness, we propose that it plays mainly a structural role in situ, interacting with the lipid moiety of the chloroplast membrane. The material insoluble in the aqueous chloroform/methanol mixture is largely enriched in manganese, iron, cytochrome and water-soluble proteins, such as chloroplast coupling factor and ribulose diphosphate carboxylase. PMID:179588

  1. 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.

  2. Selectivity of Direct Methanol Fuel Cell Membranes

    PubMed Central

    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. Collective charge excitations along cell membranes

    NASA Astrophysics Data System (ADS)

    Manousakis, E.

    2005-07-01

    A significant part of the thin layers of counter-ions adjacent to the exterior and interior surfaces of a cell membrane form quasi-two-dimensional (2D) layers of mobile charge. Collective charge density oscillations, known as plasmon modes, in these 2D charged systems of counter-ions are predicted in the present paper. This is based on a calculation of the self-consistent response of this system to a fast electric field fluctuation. The possibility that the membrane channels might be using these excitations to carry out fast communication is suggested and experiments are proposed to reveal the existence of such excitations.

  4. Aging of cell membranes: facts and theories.

    PubMed

    Zs-Nagy, Imre

    2014-01-01

    This chapter is intended to outline the main results of a research trend realized by the author during the last 45 years, focused on the main role played by the cell membrane in the aging process. It is a very wide field; therefore, the reader cannot expect in this limited space a detailed description, but will be given a wide, interdisciplinary insight into the main facts and theories regarding cellular aging. The central idea described here is the concept called the membrane hypothesis of aging (MHA). The history, the chemical roots, physicochemical facts, biophysical processes, as well as the obligatory biochemical consequences are all touched in by indicating the most important sources of detailed knowledge for those who are more interested in the basic biology of the aging process. This chapter covers also the available anti-aging interventions on the cell membrane by means of the centrophenoxine treatment based on the MHA. It also briefly interprets the possibilities of a just developing anti-aging method by using the recombinant human growth hormone, essential basis of which is the species specificity, and the general presence of receptors of this hormone in the plasma membrane of all types of cells. PMID:24862015

  5. Proteomic Analysis of Lipid Raft-Like Detergent-Resistant Membranes of Lens Fiber Cells

    PubMed Central

    Wang, Zhen; Schey, Kevin L.

    2015-01-01

    Purpose Plasma membranes of lens fiber cells have high levels of long-chain saturated fatty acids, cholesterol, and sphingolipids—key components of lipid rafts. Thus, lipid rafts are expected to constitute a significant portion of fiber cell membranes and play important roles in lens biology. The purpose of this study was to characterize the lens lipid raft proteome. Methods Quantitative proteomics, both label-free and iTRAQ methods, were used to characterize lens fiber cell lipid raft proteins. Detergent-resistant, lipid raft membrane (DRM) fractions were isolated by sucrose gradient centrifugation. To confirm protein localization to lipid rafts, protein sensitivity to cholesterol removal by methyl-β-cyclodextrin was quantified by iTRAQ analysis. Results A total of 506 proteins were identified in raft-like detergent-resistant membranes. Proteins identified support important functions of raft domains in fiber cells, including trafficking, signal transduction, and cytoskeletal organization. In cholesterol-sensitivity studies, 200 proteins were quantified and 71 proteins were strongly affected by cholesterol removal. Lipid raft markers flotillin-1 and flotillin-2 and a significant fraction of AQP0, MP20, and AQP5 were found in the DRM fraction and were highly sensitive to cholesterol removal. Connexins 46 and 50 were more abundant in nonraft fractions, but a small fraction of each was found in the DRM fraction and was strongly affected by cholesterol removal. Quantification of modified AQP0 confirmed that fatty acylation targeted this protein to membrane raft domains. Conclusions These data represent the first comprehensive profile of the lipid raft proteome of lens fiber cells and provide information on membrane protein organization in these cells. PMID:26747763

  6. Gravitational field-flow fractionation of human hemopoietic stem cells.

    PubMed

    Roda, Barbara; Reschiglian, Pierluigi; Alviano, Francesco; Lanzoni, Giacomo; Bagnara, Gian Paolo; Ricci, Francesca; Buzzi, Marina; Tazzari, Pier Luigi; Pagliaro, Pasqualepaolo; Michelini, Elisa; Roda, Aldo

    2009-12-25

    New cell sorting methodologies, which are simple, fast, non-invasive, and able to isolate homogeneous cell populations, are needed for applications ranging from gene expression analysis to cell-based therapy. In particular, in the forefront of stem cell isolation, progenitor cells have to be separated under mild experimental conditions from complex heterogeneous mixtures prepared from human tissues. Most of the methodologies now employed make use of immunological markers. However, it is widely acknowledged that specific markers for pluripotent stem cells are not as yet available, and cell labelling may interfere with the differentiation process. This work presents for the first time gravitational field-flow fractionation (GrFFF), as a tool for tag-less, direct selection of human hematopoietic stem and progenitor cells from cell samples obtained by peripheral blood aphaeresis. These cells are responsible to repopulate the hemopoietic system and they are used in transplantation therapies. Blood aphaeresis sample were injected into a GrFFF system and collected fractions were characterized by flow cytometry for CD34 and CD45 expression, and then tested for viability and multi-differentiation potential. The developed GrFFF method allowed obtaining high enrichment levels of viable, multi-potent hematopoietic stem cells in specific fraction and it showed to fulfil major requirements of analytical performance, such as selectivity and reproducibility of the fractionation process and high sample recovery. PMID:19647835

  7. Microfluidic microbial fuel cells: from membrane to membrane free

    NASA Astrophysics Data System (ADS)

    Yang, Yang; Ye, Dingding; Li, Jun; Zhu, Xun; Liao, Qiang; Zhang, Biao

    2016-08-01

    Microfluidic microbial fuel cells (MMFCs) are small carbon-neutral devices that use self-organized bacteria to degrade organic substrates and harness energy from the waste water. Conventional MMFCs have made great strides in the past decade and have overcome some limitations, such as high capital costs and low energy output. A co-laminar flow MFC has been first proposed in 2011 with the potential to be an attractively power source to niche applications. Co-laminar MFCs typically operate without any physical membranes separating the reactants, and bacterial ecosystems can be easily manipulated by regulating the inlet conditions. This paper highlights recent accomplishments in the development of co-laminar MFCs, emphasizing basic principles, mass transport and fluid dynamics including boundary layer theory, entrance conditions and mixing zone issues. Furthermore, the development of current techniques, major challenges and the potential research directions are discussed.

  8. 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

  9. Effect of reactive oxygen species on lysosomal membrane integrity. A study on a lysosomal fraction.

    PubMed

    Zdolsek, J M; Svensson, I

    1993-01-01

    Using a lysosome-enriched "light mitochondrial" fraction of a rat liver homogenate, the effects of the reactive oxygen species hydrogen peroxide, superoxide- and hydroxyl radicals were determined. Alterations in the intralysosomal pH and the release of a lysosomal marker enzyme, N-acetyl-glucosaminidase, were used as indicators of changes in the lysosomal membrane integrity. Lipid peroxidation of the fraction was assayed by TBARS measurement. Neither superoxide radicals, generated by hypoxanthine/xanthine oxidase, nor a bolus dose of hydrogen peroxide (0.5-1.5 mM) induced any lysosomal damage. If, however, Fe(III)ADP was included in the superoxide radical-generating system, lysosomal membrane damage was detected, both as an increase in lysosomal pH and as a release of N-acetyl-glucosaminidase, but only after a lag phase of about 7 min. Lipid peroxidation, on the other hand, proceeded gradually. Lysosomes treated with hydrogen peroxide displayed similar dose-dependent alterations, albeit only if both Fe(III)ADP and the reducing amino acid cysteine were added. In the latter system, however, alterations of the lysosomal membrane stability occurred more rapidly, showing a lag phase of only 2 min. Lipid peroxidation, which proceeded faster and displayed no lag phase, levelled out within 10 min. The results indicate that neither superoxide radicals nor hydrogen peroxide are by themselves damaging to lysosomes. Available catalytically active iron in Fe(II) form, however, allows reactions yielding powerful oxidative species--probably hydroxyl radicals formed via Fenton reactions--to take place inducing peroxidation of the lysosomal membranes resulting in dissipation of the proton-gradient and leakage of their enzyme contents. PMID:8148962

  10. Noncontact microsurgery of living cell membrane using femtosecond laser pulses

    NASA Astrophysics Data System (ADS)

    Ilina, I. V.; Ovchinnikov, A. V.; Sitnikov, D. S.; Chefonov, O. V.; Agranat, M. B.; Mikaelyan, A. S.

    2013-06-01

    Near-infrared femtosecond laser pulses were applied to initiate reversible permeabilization of cell membrane and inject extrinsic substances into the target cells. Successful laser-based injection of a membrane impermeable dye, as well as plasmid DNA was demonstrated.

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

    PubMed

    Waugh, Mark G

    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

  12. Interaction of peptides with cell membranes: insights from molecular modeling

    NASA Astrophysics Data System (ADS)

    Li, Zhen-lu; Ding, Hong-ming; Ma, Yu-qiang

    2016-03-01

    The investigation of the interaction of peptides with cell membranes is the focus of active research. It can enhance the understanding of basic membrane functions such as membrane transport, fusion, and signaling processes, and it may shed light on potential applications of peptides in biomedicine. In this review, we will present current advances in computational studies on the interaction of different types of peptides with the cell membrane. Depending on the properties of the peptide, membrane, and external environment, the peptide-membrane interaction shows a variety of different forms. Here, on the basis of recent computational progress, we will discuss how different peptides could initiate membrane pores, translocate across the membrane, induce membrane endocytosis, produce membrane curvature, form fibrils on the membrane surface, as well as interact with functional membrane proteins. Finally, we will present a conclusion summarizing recent progress and providing some specific insights into future developments in this field.

  13. 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.

  14. 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-α-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

  15. Dynamics of photoinduced cell plasma membrane injury.

    PubMed Central

    Thorpe, W P; Toner, M; Ezzell, R M; Tompkins, R G; Yarmush, M L

    1995-01-01

    We have developed a video microscopy system designed for real-time measurement of single cell damage during photolysis under well defined physicochemical and photophysical conditions. Melanoma cells cultured in vitro were treated with the photosensitizer (PS), tin chlorin e6 (SnCe6) or immunoconjugate (SnCe6 conjugated to a anti-ICAM monoclonal antibody), and illuminated with a 10 mW He/Ne laser at a 630 nm wavelength. Cell membrane integrity was assessed using the vital dye calcein-AM. In experiments in which the laser power density and PS concentration were varied, it was determined that the time lag before cell rupture was inversely proportional to the estimated singlet oxygen flux to the cell surface. Microscopic examination of the lytic event indicated that photo-induced lysis was caused by a point rupture of the plasma membrane. The on-line nature of this microscopy system offers an opportunity to monitor the dynamics of the cell damage process and to gain insights into the mechanism governing photolytic cell injury processes. Images FIGURE 2 FIGURE 3 FIGURE 6 FIGURE 7 PMID:7612864

  16. Functional phosphoproteomic profiling of phosphorylation sites in membrane fractions of salt-stressed Arabidopsis thaliana

    PubMed Central

    2009-01-01

    Background Under conditions of salt stress, plants respond by initiating phosphorylation cascades. Many key phosphorylation events occur at the membrane. However, to date only limited sites have been identified that are phosphorylated in response to salt stress in plants. Results Membrane fractions from three-day and 200 mM salt-treated Arabidopsis suspension plants were isolated, followed by protease shaving and enrichment using Zirconium ion-charged magnetic beads, and tandem mass spectrometry analyses. From this isolation, 18 phosphorylation sites from 15 Arabidopsis proteins were identified. A unique phosphorylation site in 14-3-3-interacting protein AHA1 was predominately identified in 200 mM salt-treated plants. We also identified some phosphorylation sites in aquaporins. A doubly phosphorylated peptide of PIP2;1 as well as a phosphopeptide containing a single phosphorylation site (Ser-283) and a phosphopeptide containing another site (Ser-286) of aquaporin PIP2;4 were identified respectively. These two sites appeared to be novel of which were not reported before. In addition, quantitative analyses of protein phosphorylation with either label-free or stable-isotope labeling were also employed in this study. The results indicated that level of phosphopeptides on five membrane proteins such as AHA1, STP1, Patellin-2, probable inactive receptor kinase (At3g02880), and probable purine permease 18 showed at least two-fold increase in comparison to control in response to 200 mM salt-stress. Conclusion In this study, we successfully identified novel salt stress-responsive protein phosphorylation sites from membrane isolates of abiotic-stressed plants by membrane shaving followed by Zr4+-IMAC enrichment. The identified phosphorylation sites can be important in the salt stress response in plants. PMID:19900291

  17. Lipolytic activity in adipocyte cell fractions.

    PubMed

    Oschry, Y; Shapiro, B

    1980-05-28

    Adipocytes release only negligible amounts of free fatty acids unless stimulated, but reveal considerable lipolytic activity when homogenized. Epinephrine treatment of the cells caused only a 20-40% increase in the activity of infranatants of homogenates while raising the activity associated with the fat layer up to 10-fold. Full activity (i.e. that of intact-activated cells) could be revealed by epinephrine treatment of the homogenate as well as by sonication of the fat layer in buffer. The combination of both treatments did not yield higher activities. The fat cake contains the bulk of the potential activities which are only realized when dispersed in the aqueous phase by sonication, or upon hormone activation of the whole homogenate. Increase in activity could also be obtained by removal of most of the lipid from the fat layer by extraction with petroleum ether. Re-introduction of extracted lipid inhibited lipolysis. The active enzyme could be separated by flotation at 1.12 specific gravity. The data suggest that the lack of activity in the intact non-stimulated cell may be due to the lack of availability of the aqueous phase to the enzyme. PMID:7378439

  18. Isolation and characterization of membranes from normal and transformed tissue-culture cells

    PubMed Central

    Graham, John M.

    1972-01-01

    Homogenates of baby-hamster kidney cells and rat embryo fibroblasts prepared by nitrogen cavitation contain a small population of slowly sedimenting mitochondria or mitochondrial fragments, which contaminate the microsomal fraction. This appears to limit the resolution of surface membrane and endoplasmic reticulum on magnesium-containing dextran gradients. The microsomal material and mitochondria can, however, be completely separated on a 10–60% (w/w) sucrose zonal gradient containing a 30% sucrose plateau. On magnesium-containing dextran gradients this mitochondria-free microsomal material can be resolved into at least two surface membrane fractions and at least two endoplasmic reticulum fractions. Comparison of polyoma virus-transformed and normal baby-hamster kidney cells reveals some interesting differences in their microsomal fractionation patterns and the characteristics of the Na+/K+-Mg2+ adenosine triphosphatase of their surface membranes, in particular a tenfold lower Km in the virus-transformed cells. The fractionation patterns of normal and spontaneously transformed rat embryo fibroblasts are also briefly discussed, particularly in relation to the significance of the observation that both the surface membrane and endoplasmic reticulum from these cells can be subfractionated. PMID:4348259

  19. Fuel cell membranes and crossover prevention

    DOEpatents

    Masel, Richard I.; York, Cynthia A.; Waszczuk, Piotr; Wieckowski, Andrzej

    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.

  20. Complement-mediated production of plasma-membrane vesicles from rat fat-cells.

    PubMed

    Richardson, P J; Luzio, J P

    1980-03-15

    1. Rat isolated fat-cells were coated with rabbit anti-(rat erythrocyte) antibody and incubated with fresh guinea-pig serum for 25 min at 37 degrees C, which resulted in a more than 95% release of the cytosolic enzyme lactate dehydrogenase. 2. Under these conditions fragmentation of the plasma membrane was examined by following the plasma-membrane markers 5'-nucleotidase, adrenaline-sensitive adenylate cyclase and membrane-bound rabbit immunoglobulin G through a differential-centrifugation fractionation procedure. 3. Approx. 50% of the plasma-membrane markers remained associated with triacylglycerol. Of the remainder more than half was pelleted by centrifugation at 10 000 g for 30 min. 4. The 10 000 g supernatant was fractionated by centrifugation on a sucrose density gradient (15-50%, w/w). This procedure resulted in the production of two visible white bands on the density gradient. The bands consisted of vesicles derived from the plasma membrane, since they coincided with peaks of 5'-nucleotidase activity, contained membrane-bound immunoglobulin G and the denser one had adenylate cyclase activity. The phospholipid and protein contents of the vesicles were determined and compared with those in purified plasma membrane. 5. It is suggested that complement-mediated lysis of rat fat-cells caused the production of plasma-membrane vesicles that differ in composition from the whole plasma membrane. PMID:6249263

  1. 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.

  2. Correlation of cell membrane dynamics and cell motility

    PubMed Central

    2011-01-01

    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 pathways affecting various cellular functions via cytoskeleton. Cell motility is a complex phenomenon primarily driven by the actin network, which plays an important role in shaping the morphology of the cells. Most of the morphology based features are approximated from cell periphery but its dynamics have received none to scant attention. We aim to bridge the gap between membrane dynamics and cell states from the perspective of whole cell movement by identifying cell edge patterns and its correlation with cell dynamics. Results We present a systematic study to extract, classify, and compare cell dynamics in terms of cell motility and edge activity. Cell motility features extracted by fitting a persistent random walk were used to identify the initial set of cell subpopulations. We propose algorithms to extract edge features along the entire cell periphery such as protrusion and retraction velocity. These constitute a unique set of multivariate time-lapse edge features that are then used to profile subclasses of cell dynamics by unsupervised clustering. Conclusions By comparing membrane dynamic patterns exhibited by each subclass of cells, correlated trends of edge and cell movements were identified. Our findings are consistent with published literature and we also identified that motility patterns are influenced by edge features from initial time points compared to later sampling intervals. PMID:22372978

  3. Proliferation of Schwann cells induced by axolemmal and myelin membranes

    SciTech Connect

    Dinneen, M..

    1985-01-01

    Purified Schwann Cells were cultured from neonatal rat sciatic nerve using a modification of the method of Brockes. Schwann cells and contaminating fibroblasts were unambiguously identified using fluorescent antibodies of 2'3' cyclic nucleotide 3'-phosphodiesterase and the thy 1.1 antigen respectively. The Schwann cells were quiescent unless challenged with mitogens. They proliferated rapidly in response to the soluble mitogen, cholera toxin, or to membrane fractions from rat CNS or PNS, prepared by the method of DeVries. Mitogenic activity was present in both axolemmal and myelin enriched fractions and promoted a 10-15 fold increase in the rate of /sup 3/H-thymidine uptake. The axolemmal mitogen was sensitive to heat (80/sup 0/C for 10 minutes), trypsin digestion (0.05% x 30 mins) or to treatment with endoglycosidase D, suggesting that it could be a glycoprotein. Fifty percent of the axolemmal mitogenic activity was solubilized in 1% octyl-glucoside. The solubilized material, however, was very unstable and further purification was not possible. The myelin associated mitogenic activity was markedly different. It was resistant to freeze thaw cycles, trypsin digestion of endoglycosidase treatment and the activity was actually enhanced by heating at 100/sup 0/C for two hours. It is proposed that the axolemmal activity is responsible for Schwann cell proliferation during development and that the myelin associated activity promotes Schwann cell proliferation during Wallerian degeneration.

  4. Quality improvements of cell membrane chromatographic column.

    PubMed

    Ding, Xuan; Chen, Xiaofei; Cao, Yan; Jia, Dan; Wang, Dongyao; Zhu, Zhenyu; Zhang, Juping; Hong, Zhanying; Chai, Yifeng

    2014-09-12

    Cell Membrane Chromatography (CMC) is a biological affinity chromatographic method using a silica stationary phase covered with specific cell membrane. However, its short life span and poor quality control was highlighted in a lot of research articles. In this study, special attention has been paid to the disruption, cell load and packing procedure in order to improve the quality of the CMC columns. Hereto, two newly established CMC models, HSC-T6/CMC and SMMC-7721/CMC have been developed and used in this research project. The optimization of the abovementioned parameters resulted in a better reproducibility of the retention time of the compound GFT (RSD<10%) and improved significantly the quality of the CMC columns. 3.5×10(7)cells were the optimal cell load for the preparation of the CMC columns, the disruption condition was optimized to 5 cycles (400W and 20s interval per cycle) by an ultrasonic processor reducing the total time of cell disruption to 1.5min and the packing flow rate was optimized by applying a linear gradient program. Additionally, 4% paraformaldehyde (PFA) was employed to improve the column quality and prolong the column life span. The results showed that the retention time was longer with PFA treated columns than the ones obtained with the control groups. PMID:25115453

  5. Proton-exchange membrane regenerative fuel cells

    NASA Astrophysics Data System (ADS)

    Swette, Larry L.; LaConti, Anthony B.; McCatty, Stephen A.

    This paper will update the progress in developing electrocatalyst systems and electrode structures primarily for the positive electrode of single-unit solid polymer proton-exchange membrane (PEM) regenerative fuel cells. The work was done with DuPont Nafion 117 in complete fuel cells (40 cm 2 electrodes). The cells were operated alternately in fuel cell mode and electrolysis mode at 80°C. In fuel cell mode, humidified hydrogen and oxygen were supplied at 207 kPa (30 psi); in electrolysis mode, water was pumped over the positive electrode and the gases were evolved at ambient pressure. Cycling data will be presented for Pt-Ir catalysts and limited bifunctional data will be presented for Pt. Ir, Ru. Rh and Na xPt 3O 4 catalysts as well as for electrode structure variations.

  6. Membrane catalyst layer for fuel cells

    DOEpatents

    Wilson, Mahlon S.

    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.

  7. A review of radiation-grafted polymer electrolyte membranes for alkaline polymer electrolyte membrane fuel cells

    NASA Astrophysics Data System (ADS)

    Zhou, Tianchi; Shao, Rong; Chen, Song; He, Xuemei; Qiao, Jinli; Zhang, Jiujun

    2015-10-01

    The past two decades have witnessed many efforts to develop radiation-grafted alkaline membranes for alkaline PEM fuel cell applications, as such membranes have certain advantages over other kinds of alkaline membranes, including well-controlled composition, functionality, and other promising properties. To facilitate research and development in this area, the present paper reviews radiation-grafted alkaline membranes. We examine their synthesis/fabrication/characterization, membrane material selection, and theoretical approaches for fundamental understanding. We also present detailed examinations of their application in fuel cell in terms of the working principles of the radiation grafting process, the fabrication of MEAs using radiation-grafted membranes, the membranes' corresponding performance in alkaline PEM fuel cells, as well as performance optimization. The paper also summarizes the challenges and mitigation strategies for radiation-grafted alkaline membranes and their application in PEM fuel cells, presenting an overall picture of the technology as it presently stands.

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

    NASA Astrophysics Data System (ADS)

    Eisman, G. A.

    1990-02-01

    Dow Chemical's research activities in fuel cells revolve around the development of perfluorosulfonic acid membranes, useful as the proton transport medium and separator. The following work will outline some of the performance characteristics which are typical for such membranes.

  9. Size Control and Fractionation of Ionic Liquid Filled Polymersomes with Glassy and Rubbery Bilayer Membranes.

    PubMed

    So, Soonyong; Lodge, Timothy P

    2016-05-17

    We demonstrate control over the size of ionic liquid (IL) filled polymeric vesicles (polymersomes) by three distinct methods: mechanical extrusion, cosolvent-based processing in an IL, and fractionation of polymersomes in a biphasic system of IL and water. For the representative ionic liquid (1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl) imide ([EMIM][TFSI])), the size and dispersity of polymersomes formed from 1,2-polybutadiene-b-poly(ethylene oxide) (PB-PEO) and polystyrene-b-poly(ethylene oxide) (PS-PEO) diblock copolymers were shown to be sensitive to assembly conditions. During mechanical extrusion through a polycarbonate membrane, the relatively larger polymersomes were broken up and reorganized into vesicles with mean size comparable to the membrane pore (100 nm radius); the distribution width also decreased significantly after only a few passes. Other routes were studied using the solvent-switch or cosolvent (CS) method, whereby the initial content of the cosolvent and the PEO block length of PS-PEO were systemically changed. The nonvolatility of the ionic liquid directly led to the desired concentration of polymersomes in the ionic liquid using a single step, without the dialysis conventionally used in aqueous systems, and the mean vesicle size depended on the amount of cosolvent employed. Finally, selective phase transfer of PS-PEO polymersomes based on size was used to extract larger polymersomes from the IL to the aqueous phase via interfacial tension controlled phase transfer. The interfacial tension between the PS membrane and the aqueous phase was varied with the concentration of sodium chloride (NaCl) in the aqueous phase; then the larger polymersomes were selectively separated to the aqueous phase due to differences in shielding of the hydrophobic core (PS) coverage by the hydrophilic corona brush (PEO). This novel fractionation is a simple separation process without any special apparatus and can help to prepare monodisperse polymersomes

  10. Fractionation of human liver mitochondria: enzymic and morphological characterization of the inner and outer membranes as compared to rat liver mitochondria.

    PubMed

    Benga, G; Hodarnau, A; Tilinca, R; Porutiu, D; Dancea, S; Pop, V; Wrigglesworth, J

    1979-02-01

    The fractionation of human liver mitochondria into inner membrane, outer membrane and matrix material is reported. Compared with rat, human liver mitochondria are more fragile. Fractionation can be achieved in only 2 steps, a digitonin treatment for removal of the outer membrane and centrifugation of the inner membrane plus matrix particles through a linear sucrose gradient resulting in purified inner membranes and matrix. PMID:422680

  11. Sodium selectivity of Reissner's membrane epithelial cells

    PubMed Central

    2011-01-01

    Background Sodium absorption by Reissner's membrane is thought to contribute to the homeostasis of the volume of cochlear endolymph. It was previously shown that the absorptive transepithelial current was blocked by amiloride and benzamil. The most commonly-observed target of these drugs is the epithelial sodium channel (ENaC), which is composed of the three subunits α-,β- and γ-ENaC. However, other less-selective cation channels have also been observed to be sensitive to benzamil and amiloride. The aim of this study was to determine whether Reissner's membrane epithelial cells could support parasensory K+ absorption via amiloride- and benzamil-sensitive electrogenic pathways. Results We determined the molecular and functional expression of candidate cation channels with gene array (GEO GSE6196), RT-PCR, and whole-cell patch clamp. Transcript expression analysis of Reissner's membrane detected no amiloride-sensitive acid-sensing ion channels (ASIC1a, ASIC2a, ASIC2b) nor amiloride-sensitive cyclic-nucleotide gated channels (CNGA1, CNGA2, CNGA4, CNGB3). By contrast, α-,β- and γ-ENaC were all previously reported as present in Reissner's membrane. The selectivity of the benzamil-sensitive cation currents was observed in whole-cell patch clamp recordings under Cl--free conditions where cations were the only permeant species. The currents were carried by Na+ but not K+, and the permeability of Li+ was greater than that of Na+ in Reissner's membrane. Complete replacement of bath Na+ with the inpermeable cation NMDG+ led to the same inward current as with benzamil in a Na+ bath. Conclusions These results are consistent with the amiloride/benzamil-sensitive absorptive flux of Reissner's membrane mediated by a highly Na+-selective channel that has several key characteristics in common with αβγ-ENaC. The amiloride-sensitive pathway therefore absorbs only Na+ in this epithelium and does not provide a parasensory K+ efflux route from scala media. PMID:21284860

  12. Fuel cell membrane hydration and fluid metering

    DOEpatents

    Jones, Daniel O.; Walsh, Michael M.

    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).

  13. Fuel cell membrane hydration and fluid metering

    DOEpatents

    Jones, Daniel O.; Walsh, Michael M.

    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).

  14. 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

  15. Heat-shock protein expression on the membrane of T cells undergoing apoptosis.

    PubMed Central

    Poccia, F; Piselli, P; Vendetti, S; Bach, S; Amendola, A; Placido, R; Colizzi, V

    1996-01-01

    Heat-shock proteins (hsp) represent a highly conserved family of proteins, normally localized in the cytoplasm and nucleus, whose expression is induced in situations involving cell stress. This paper reports the unusual translocation of hsp to the cell membrane of T cells undergoing apoptosis. We observed that glucocorticosteroid-induced thymocyte death is associated to the surface expression of hsp 60 and hsp 70 in a discrete fraction of apoptotic cells. hsp surface expression is closely related to a thymic subset of immature CD3low/- T cells. The expression of surface hsp 60 appears early after treatment with dexamethasone (3 hr) whereas the membrane expression of hsp 70 follows different kinetics and peaks later. Morphological analysis of the hsp+ apoptotic cells suggest that this subset represents late-stage apoptotic cells at their minimal volume before fragmentation into apoptotic bodies. Membrane expression of hsp is also associated with apoptosis in peripheral blood mononuclear cells from AIDS patients cultured in vitro. Altogether, we show that a discrete fraction of cells undergoing apoptosis expresses membrane hsp 60 and hsp 70, supporting the hypothesis that apoptosis causes a radical alteration in the expression of cell surface molecules. Surface hsp expressed during apoptosis may constitute a novel immune-context able to generate packages of self- and exogenous antigens, originating from degradation of altered cells. Images Figure 1 Figure 3 PMID:8707351

  16. Polymer synthesis toward fuel cell membrane materials

    NASA Astrophysics Data System (ADS)

    Rebeck, Nathaniel T.

    Fuel cells are a promising technology that will be part of the future energy landscape. New membranes for alkaline and proton exchange membrane fuel cells are needed to improve the performance, simplify the system, and reduce cost. Polymer chemistry can be applied to develop new polymers and to assemble polymers into improved membranes that need less water, have increased performance and are less expensive, thereby removing the deficiencies of current membranes. Nucleophilic aromatic substitution polymerization typically produces thermally stable engineering polymers that can be easily functionalized. New functional monomers were developed to explore new routes to novel functional polymers. Sulfonamides were discovered as new activating groups for polymerization of high molecular weight thermooxidatively stable materials with sulfonic acid latent functionality. While the sulfonamide functional polymers could be produced, the sulfonamide group proved to be too stable to convert into a sulfonic acid after reaction. The reactivity of 2-aminophenol was investigated to search for a new class of ion conducting polymer materials. Both the amine and the phenol groups are found to be reactive in a nucleophilic aromatic substitution, however not to the extent to allow the formation of high molecular weight polymer materials. Layer-by-layer films were assembled from aqueous solutions of poly(styrene sulfonate) and trimethylammonium functionalized poly(phenylene oxide). The deposition conditions were adjusted to increase the free charge carrier content, and chloride conductivites reached almost 30 mS/cm for the best films. Block and random poly(phenylene oxide) copolymers were produced from 2,6-dimethylphenol and 2,6-diphenylphenol and the methyl substituted repeat units were functionalized with trimethylammonium bromide. The block copolymers displayed bromide conductivities up to 26 mS/cm and outperformed the random copolymers, indicating that morphology has an effect on ion

  17. 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 μm, 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 μm 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

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

    NASA Astrophysics Data System (ADS)

    Winkler, Benjamin; Aranson, Igor S.; Ziebert, Falko

    2016-04-01

    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 the 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.

  19. Plasma membrane microdomains regulate TACE-dependent TNFR1 shedding in human endothelial cells

    PubMed Central

    D’Alessio, Alessio; Esposito, Bianca; Giampietri, Claudia; Ziparo, Elio; Pober, Jordan S; Filippini, Antonio

    2012-01-01

    Abstract Upon stimulation by histamine, human vascular endothelial cells (EC) shed a soluble form of tumour necrosis factor receptor 1 (sTNFR1) that binds up free TNF, dampening the inflammatory response. Shedding occurs through proteolytic cleavage of plasma membrane-expressed TNFR1 catalysed by TNF-α converting enzyme (TACE). Surface expressed TNFR1 on EC is largely sequestered into specific plasma membrane microdomains, the lipid rafts/caveolae. The purpose of this study was to determine the role of these domains in TACE-mediated TNFR1 shedding in response to histamine. Human umbilical vein endothelial cells derived EA.hy926 cells respond to histamine via H1 receptors to shed TNFR1. Both depletion of cholesterol by methyl-β-cyclodextrin and small interfering RNA knockdown of the scaffolding protein caveolin-1 (cav-1), treatments that disrupt caveolae, reduce histamine-induced shedding of membrane-bound TNFR1. Moreover, immunoblotting of discontinuous sucrose gradient fractions show that TACE, such as TNFR1, is present within low-density membrane fractions, concentrated within caveolae, in unstimulated EA.hy926 endothelial cells and co-immunoprecipitates with cav-1. Silencing of cav-1 reduces the levels of both TACE and TNFR1 protein and displaces TACE, from low-density membrane fractions where TNFR1 remains. In summary, we show that endothelial lipid rafts/caveolae co-localize TACE to surface expressed TNFR1, promoting efficient shedding of sTNFR1 in response to histamine. PMID:21645239

  20. Effects of detergents on Na+ + K+-dependent ATPase activity in plasma-membrane fractions prepared from frog muscles. Studies of insulin action on Na+ and K+ transport.

    PubMed Central

    Omatsu-Kanbe, M; Kitasato, H

    1987-01-01

    The increase in Na+/K+ transport activity in skeletal muscles exposed to insulin was analysed. Plasma-membrane fractions were prepared from frog (Rana catesbeiana) skeletal muscles, and examination of the Na,K-ATPase (Na+ + K+-dependent ATPase) activity showed that it was insensitive to ouabain. In contrast, plasma-membrane fractions prepared from ouabain-pretreated muscles, by the same procedures, showed extremely low Na,K-ATPase activity. On adding saponin to the membrane suspension, the Na,K-ATPase activity increased, according to the detergent concentration. The maximum activity was about twice the control value, at 0.33 mg of saponin/mg of protein. Thus saponin makes vesicle membranes leaky, allowing ouabain in assay solutions to reach receptors on the inner surface of vesicles. Addition of insulin to saponin-treated membrane suspensions had no effect on the Na,K-ATPase activity, whereas the maximum activity of Na,K-ATPase in whole muscles was stimulated by exposure to insulin. The results show that the stimulation of Na+/K+ transport by insulin is not directly due to insulin binding to receptors on the cell surface, but rather support the view that the increase in the Na,K-ATPase induced by insulin requires an alteration of intracellular events. PMID:2825643

  1. 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.

  2. Tunable Microfluidic Devices for Hydrodynamic Fractionation of Cells and Beads: A Review

    PubMed Central

    Alvankarian, Jafar; Majlis, Burhanuddin Yeop

    2015-01-01

    The adjustable microfluidic devices that have been developed for hydrodynamic-based fractionation of beads and cells are important for fast performance tunability through interaction of mechanical properties of particles in fluid flow and mechanically flexible microstructures. In this review, the research works reported on fabrication and testing of the tunable elastomeric microfluidic devices for applications such as separation, filtration, isolation, and trapping of single or bulk of microbeads or cells are discussed. Such microfluidic systems for rapid performance alteration are classified in two groups of bulk deformation of microdevices using external mechanical forces, and local deformation of microstructures using flexible membrane by pneumatic pressure. The main advantage of membrane-based tunable systems has been addressed to be the high capability of integration with other microdevice components. The stretchable devices based on bulk deformation of microstructures have in common advantage of simplicity in design and fabrication process. PMID:26610519

  3. 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 μm 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

  4. Fractionation of protein hydrolysates of fish and chicken using membrane ultrafiltration: investigation of antioxidant activity.

    PubMed

    Centenaro, Graciela Salete; Salas-Mellado, Myriam; Pires, Carla; Batista, Irineu; Nunes, Maria L; Prentice, Carlos

    2014-03-01

    In this work, chicken and fish peptides were obtained using the proteolytic enzymes α-Chymotrypsin and Flavourzyme. The muscle was hydrolyzed for 4 h, and the resulting peptides were evaluated. Hydrolysates were produced from Argentine croaker (Umbrina canosai) with a degree of hydrolysis (DH) of 25.9 and 27.6% and from chicken (Gallus domesticus) with DH of 17.8 and 20.6% for Flavourzyme and α-Chymotrypsin, respectively. Membrane ultrafiltration was used to separate fish and chicken hydrolysates from Flavourzyme and α-Chymotrypsin based on molecular weight cutoff of >1,000, <1,000 and >500, and <500 Da, to produce fractions (F1,000, F1,000-500, and F500) with antioxidant activity. Fish hydrolysates produced with Flavourzyme (FHF) and α-Chymotrypsin showed 60.8 and 50.9% of peptides with a molecular weight of <3 kDa in its composition, respectively. To chicken hydrolysates produced with Flavourzyme and α-Chymotrypsin (CHC) was observed 83 and 92.4% of peptides with a molecular weight of <3 kDa. The fraction that showed, in general, higher antioxidant potential was F1,000 from FHF. When added 40 mg/mL of FHF and CHC, 93 and 80% of lipid oxidation in ground beef homogenates was inhibited, respectively. The composition of amino acids indicated higher amino acids hydrophobic content and amino acids containing sulfuric residues for FHF, which showed antioxidant potential. PMID:24449375

  5. Review: Annexin-A5 and cell membrane repair.

    PubMed

    Bouter, A; Carmeille, R; Gounou, C; Bouvet, F; Degrelle, S A; Evain-Brion, D; Brisson, A R

    2015-04-01

    Annexins are soluble proteins that bind to biological membranes containing negatively charged phospholipids, principally phosphatidylserine, in a Ca(2+)-dependent manner. Annexin-A5 (AnxA5), the smallest member of the annexin family, presents unique properties of membrane binding and self-assembly into ordered two-dimensional (2D) arrays on membrane surfaces. We have previously reported that AnxA5 plays a central role in the machinery of membrane repair by enabling rapid resealing of plasma membrane disruption in murine perivascular cells. AnxA5 promotes membrane repair via the formation of a protective 2D bandage at membrane damaged site. Here, we review current knowledge on cell membrane repair and present recent findings on the role of AnxA5 in membrane resealing of human trophoblasts. PMID:25701430

  6. Membrane thickness is an important variable in membrane scaffolds: Influence of chitosan membrane structure on the behavior of cells

    PubMed Central

    Uygun, Basak E.; Bou-Akl, Therese; Albanna, Mohammad

    2009-01-01

    Cell and tissue responses to polymeric materials are orchestrated in part by the conformations of adsorbed plasma proteins. Thus, the chemical properties of a polymer membrane that govern protein adsorption behaviour can play an important role in determining the biological properties of tissue engineered scaffolds derived from that polymer. In this study, we explored the role of membrane thickness as a factor influencing cell adhesion and proliferation on chitosan membranes with and without covalently-attached glycosaminoglycans. Rat mesenchymal stem cells cultured on chitosan membranes of various thicknesses demonstrated significantly improved cell adhesion, spreading and proliferation as membrane thickness was increased. Hepatocytes displayed increased spreading on the substrate with increasing membrane thickness similar to MSCs. Increased thickness reduced the overall crystallinity of the membrane, and the data indicate that the improved cellular responses were likely due to enhanced adsorption of serum vitronectin, presumably due to reduced membrane crystallinity. These results demonstrate that membrane thickness is an important design variable that can be manipulated in chitosan-based scaffolds to achieve enhanced cell spreading, proliferation and function. PMID:19925888

  7. Vaccination of feedlot cattle with extracts and membrane fractions from two Mycoplasma bovis isolates results in strong humoral immune responses but does not protect against an experimental challenge.

    PubMed

    Mulongo, Musa; Prysliak, Tracy; Perez-Casal, Jose

    2013-02-27

    Mycoplasma bovis is one of the most significant contributors to the bovine respiratory syndrome (BRD) that causes major losses in feedlot and dairy farms. Current experimental vaccines against M. bovis are ineffective and in some cases seem to enhance disease. Experimental infection with M. bovis induces a predominantly Th2 response and high levels of IgG1, which is an inferior opsonin and hence lacks protective capacity. In an attempt to induce a balanced (Th1/Th2) immune response, we have used CpG ODN 2007 as an adjuvant in a trial involving vaccination of cattle with M. bovis total extracts and/or membrane fractions and subsequent intranasal inoculation with an infective dose of M. bovis prepared from two different clinical isolates. Significant IgG1 serum responses were observed against both, extracts and fractions while IgG2 responses were significant against the extracts only. Proliferation of peripheral blood mononuclear cells (PBMC) after incubation with M. bovis cells was only observed in post-challenge samples of cattle vaccinated with both extracts and fractions but not in samples of cattle immunized with the membrane fractions alone. All groups showed transient weight losses and increased temperatures however, there were no significant differences in clinical parameters and survival rates between the groups. PMID:23340004

  8. Ethacrynic acid inhibitable Ca2+ and Mg2+-activated membrane adenosine triphosphatase in rat mast cells.

    PubMed Central

    Magro, A M

    1977-01-01

    A crude plasma membrane fraction from the homogenate of purified rat mast cells demonstrates a high degree of Ca2+-dependent and Mg2+-dependent adenosine triphosphatase (ATPase) activity. The microsomal and mitochondrial fractions show negligible amounts of the Ca2+ and Mg2+-activated ATPases. The broad ATPase inhibitor, ethacrynic acid, effectively blocks the mast cell ATPase activity while ouabain demonstrates little inhibitory effect. Correspondingly, ethacrynic acid inhibits histamine release from antigen-challenged mast cells while ouabain does not. Both ATPase inhibition and histamine release inhibition by ethacrynic acid require the presence of the olefinic bond in the ethacrynic acid molecule. PMID:75076

  9. 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

  10. Kinetics and mechanism of cell membrane electrofusion.

    PubMed Central

    Abidor, I G; Sowers, A E

    1992-01-01

    A new quantitative approach to study cell membrane electrofusion has been developed. Erythrocyte ghosts were brought into close contact using dielectrophoresis and then treated with one square or even exponentially decaying fusogenic pulse. Individual fusion events were followed by lateral diffusion of the fluorescent lipid analogue 1,1'-dihexadecyl-3,3,3',3'-tetramethylindocarbocyanine perchlorate (Dil) from originally labeled to unlabeled adjacent ghosts. It was found that ghost fusion can be described as a first-order rate process with corresponding rate constants; a true fusion rate constant, k(f), for the square waveform pulse and an effective fusion rate constant, k(ef), for the exponential pulse. Compared with the fusion yield, the fusion rate constants are more fundamental characteristics of the fusion process and have implications for its mechanisms. Values of k(f) for rabbit and human erythrocyte ghosts were obtained at different electric field strength and temperatures. Arrhenius k(f) plots revealed that the activation energy of ghost electrofusion is in the range of 6-10 kT. Measurements were also made with the rabbit erythrocyte ghosts exposed to 42 degrees C for 10 min (to disrupt the spectrin network) or 0.1-1.0 mM uranyl acetate (to stabilize the bilayer lipid matrix of membranes). A correlation between the dependence of the fusion and previously published pore-formation rate constants for all experimental conditions suggests that the cell membrane electrofusion process involve pores formed during reversible electrical breakdown. A statistical analysis of fusion products (a) further supports the idea that electrofusion is a stochastic process and (b) shows that the probability of ghost electrofusion is independent of the presence of Dil as a label as well as the number of fused ghosts. PMID:1617138

  11. Lysosome fusion to the cell membrane is mediated by the dysferlin C2A domain in coronary arterial endothelial cells

    PubMed Central

    Han, Wei-Qing; Xia, Min; Xu, Ming; Boini, Krishna M.; Ritter, Joseph K.; Li, Ning-Jun; Li, Pin-Lan

    2012-01-01

    Dysferlin has recently been reported to participate in cell membrane repair in muscle and other cells through lysosome fusion. Given that lysosome fusion is a crucial mechanism that leads to membrane raft clustering, the present study attempted to determine whether dysferlin is involved in this process and its related signalling, and explores the mechanism underlying dysferlin-mediated lysosome fusion in bovine coronary arterial endothelial cells (CAECs). We found that dysferlin is clustered in membrane raft macrodomains after Fas Ligand (FasL) stimulation as detected by confocal microscopy and membrane fraction flotation. Small-interfering RNA targeted to dysferlin prevented membrane raft clustering. Furthermore, the translocation of acid sphingomyelinase (ASMase) to membrane raft clusters, whereby local ASMase activation and ceramide production – an important step that mediates membrane raft clustering – was attenuated. Functionally, silencing of the dysferlin gene reversed FasL-induced impairment of endothelium-dependent vasodilation in isolated small coronary arteries. By monitoring fluorescence quenching or dequenching, silencing of the dysferlin gene was found to almost completely block lysosome fusion to plasma membrane upon FasL stimulation. Further studies to block C2A binding and silencing of AHNAK (a dysferlin C2A domain binding partner), showed that the dysferlin C2A domain is required for FasL-induced lysosome fusion to the cell membrane, ASMase translocation and membrane raft clustering. We conclude that dysferlin determines lysosome fusion to the plasma membrane through its C2A domain and it is therefore implicated in membrane-raft-mediated signaling and regulation of endothelial function in coronary circulation. PMID:22349696

  12. The relevance of membrane models to understand nanoparticles-cell membrane interactions

    NASA Astrophysics Data System (ADS)

    Rascol, Estelle; Devoisselle, Jean-Marie; Chopineau, Joël

    2016-02-01

    Over the past two decades, numerous types of nanoparticles (NPs) have been developed for medical applications; however only a few nanomedicines are actually available on the market. One reason is the lack of understanding and data concerning the NP fate and their behavior upon contact with biological media and cell membranes. Biomimetic membrane models are interesting tools to approach and understand NPs-cell membrane interactions. The use of these models permits one to control physical and chemical parameters and to rapidly compare membrane types and the influence of different media conditions. The interactions between NPs and cell membranes can be qualified and quantified using analytical and modeling methods. In this review, the major studies concerning NPs-cell membrane models and associated methods are described. The advantages and drawbacks for each method are compared for the different models. The key mechanisms of interactions between NPs and cell membranes are revealed using cell membrane models and are interrogated in comparison with the NP behavior in cellulo or in vivo. Investigating the interactions between NPs and cell membrane models is now proposed as an intermediate step between physicochemical characterization of NPs and biological assays.

  13. 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

  14. Protective effects of fractions from Artemisia biennis hydro-ethanolic extract against doxorubicin-induced oxidative stress and apoptosis in PC12 cells

    PubMed Central

    Mojarrab, Mahdi; Mehrabi, Mehran; Ahmadi, Farahnaz; Hosseinzadeh, Leila

    2016-01-01

    Objective(s): This study was designed to indicate whether different fractions from Artemisia biennis hydroethanolic extract could provide cytoprotection against oxidative stress and apoptosis induced by doxorubicin (DOX) in rat pheochromocytoma cell line (PC12). Material and Methods: Cell viability was determined by MTT assay. Also, activation of caspase-3 and superoxide dismutase were evaluated by spectrophotometry. Detection of reactive oxygen species (ROS) and measurement of mitochondrial membrane potential (MMP) were performed by flowcytometry. Results: Treatment of PC12 cells with DOX reduced viability dose dependently. For evaluation of the effect of fractions (A-G) on DOX-induced cytotoxicity, PC12 cells were pretreated for 24 hr with the A. biennis fractions and then cells were treated with DOX. The fractions C and D increased PC12 cells viability significantly compared to DOX treated cells. Moreover, pretreatment with fractions C and D for 24 hr attenuated DOX-mediated apoptosis and the anti-apoptotic action of A. biennis fractions was partially dependent on inhibition of caspase 3 activity and also increasing the mitochondrial membrane potential (MMP). Selected A. biennis fractions also suppressed the generation of ROS and increased superoxide dismutase (SOD) activity. Conclusion: Taken together our observation indicated that subtoxic concentration of aforementioned fractions of A. biennis hydroetanolic extract has protective effect against apoptosis induced by DOX in PC12 cell. The results highlighted that fractions C and D may exert cytoprotective effects through their antioxidant actions. PMID:27403257

  15. Cell Adhesion and Growth on the Anodized Aluminum Oxide Membrane.

    PubMed

    Park, Jeong Su; Moon, Dalnim; Kim, Jin-Seok; Lee, Jin Seok

    2016-03-01

    Nanotopological cues are popular tools for in vivo investigation of the extracellular matrix (ECM) and cellular microenvironments. The ECM is composed of multiple components and generates a complex microenvironment. The development of accurate in vivo methods for the investigation of ECM are important for disease diagnosis and therapy, as well as for studies on cell behavior. Here, we fabricated anodized aluminum oxide (AAO) membranes using sulfuric and oxalic acid under controlled voltage and temperature. The membranes were designed to possess three different pore and interpore sizes, AAO-1, AAO-2, and AAO-3 membranes, respectively. These membranes were used as tools to investigate nanotopology-signal induced cell behavior. Cancerous cells, specifically, the OVCAR-8 cell-line, were cultured on porous AAO membranes and the effects of these membranes on cell shape, proliferation, and viability were studied. AAO-1 membranes bearing small sized pores were found to maintain the spreading shape of the cultured cells. Cells cultured on AAO-2 and AAO-3 membranes, bearing large pore-sized AAO membranes, changed shape from spreading to rounding. Furthermore, cellular area decreased when cells were cultured on all three AAO membranes that confirmed decreased levels of focal adhesion kinase (FAK). Additionally, OVCAR-8 cells exhibited increased proliferation on AAO membranes possessing various pore sizes, indicating the importance of the nanosurface structure in regulating cell behaviors, such as cell proliferation. Our results suggest that porous-AAO membranes induced nanosurface regulated cell behavior as focal adhesion altered the intracellular organization of the cytoskeleton. Our results may find potential applications as tools in in vivo cancer research studies. PMID:27280255

  16. Characterization of membrane fraction lipid composition and function of cirrhotic rat liver. Role of S-adenosyl-L-methionine.

    PubMed

    Muriel, P; Mourelle, M

    1992-01-01

    The effect of S-adenosyl-L-methionine (SAM) administration on the lipid composition of the membrane fraction obtained from livers of cirrhotic rats was studied. Four groups of animals were used: group 1 received CCl4 for 8 weeks to induce cirrhosis. Animals in group 2 received 3 daily i.m. injections of SAM 20 mg/kg in addition to CCl4. Groups 3 and 4 were control groups of SAM and vehicles. Seventy-two h after the end of treatment all animals were killed and livers were studied to measure glycogen, cAMP contents and to isolate membrane fractions. The membrane activity of Na+,K(+)- and Ca(2+)-ATPases was measured and the lipid content was analyzed in extracts. Phospholipids were determined by thin-layer chromatography and fatty acids by gas chromatography. Chronic CCl4 treatment led to increases in cholesterol and in the cholesterol/phospholipid ratio. Analysis of phospholipids revealed an increase in phosphatidylserines. Saturated fatty acids increased, while unsaturated decreased significantly. The CCl4-treated group showed a decrease in glycogen and an increase in cAMP contents. Na+,K(+)- and Ca(2+)-ATPases activity were highly reduced in cirrhotic membranes. In the group receiving CCl4 + SAM the lipid composition and the function of liver membrane fraction showed no difference compared to normal controls, except for fatty acid composition which was similar to concentrations in the CCl4-treated group. Glycogen depletion was only partially prevented whereas cAMP levels were normalized in the CCl4 + SAM group. Our results showed that membrane lipid alterations were accompanied by changes in the activity of enzymes embedded in the membrane fraction derived from CCl4-cirrhotic rats.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:1310704

  17. Reassessing ecdysteroidogenic cells from the cell membrane receptors’ perspective

    PubMed Central

    Alexandratos, Alexandros; Moulos, Panagiotis; Nellas, Ioannis; Mavridis, Konstantinos; Dedos, Skarlatos G.

    2016-01-01

    Ecdysteroids secreted by the prothoracic gland (PG) cells of insects control the developmental timing of their immature life stages. These cells have been historically considered as carrying out a single function in insects, namely the biochemical conversion of cholesterol to ecdysteroids and their secretion. A growing body of evidence shows that PG cells receive multiple cues during insect development so we tested the hypothesis that they carry out more than just one function in insects. We characterised the molecular nature and developmental profiles of cell membrane receptors in PG cells of Bombyx mori during the final larval stage and determined what receptors decode nutritional, developmental and physiological signals. Through iterative approaches we identified a complex repertoire of cell membrane receptors that are expressed in intricate patterns and activate previously unidentified signal transduction cascades in PG cells. The expression patterns of some of these receptors explain precisely the mechanisms that are known to control ecdysteroidogenesis. However, the presence of receptors for the notch, hedgehog and wingless signalling pathways and the expression of innate immunity-related receptors such as phagocytosis receptors, receptors for microbial ligands and Toll-like receptors call for a re-evaluation of the role these cells play in insects. PMID:26847502

  18. Reassessing ecdysteroidogenic cells from the cell membrane receptors' perspective.

    PubMed

    Alexandratos, Alexandros; Moulos, Panagiotis; Nellas, Ioannis; Mavridis, Konstantinos; Dedos, Skarlatos G

    2016-01-01

    Ecdysteroids secreted by the prothoracic gland (PG) cells of insects control the developmental timing of their immature life stages. These cells have been historically considered as carrying out a single function in insects, namely the biochemical conversion of cholesterol to ecdysteroids and their secretion. A growing body of evidence shows that PG cells receive multiple cues during insect development so we tested the hypothesis that they carry out more than just one function in insects. We characterised the molecular nature and developmental profiles of cell membrane receptors in PG cells of Bombyx mori during the final larval stage and determined what receptors decode nutritional, developmental and physiological signals. Through iterative approaches we identified a complex repertoire of cell membrane receptors that are expressed in intricate patterns and activate previously unidentified signal transduction cascades in PG cells. The expression patterns of some of these receptors explain precisely the mechanisms that are known to control ecdysteroidogenesis. However, the presence of receptors for the notch, hedgehog and wingless signalling pathways and the expression of innate immunity-related receptors such as phagocytosis receptors, receptors for microbial ligands and Toll-like receptors call for a re-evaluation of the role these cells play in insects. PMID:26847502

  19. Hydrocarbon-based polymer electrolyte cerium composite membranes for improved proton exchange membrane fuel cell durability

    NASA Astrophysics Data System (ADS)

    Lee, Hyejin; Han, Myungseong; Choi, Young-Woo; Bae, Byungchan

    2015-11-01

    Hydrocarbon-based cerium composite membranes were prepared for proton exchange membrane fuel cell applications to increase oxidative stability. Different amounts of cerium ions were impregnated in sulfonated poly(arylene ether sulfone) (SPES) membranes and their physicochemical properties were investigated according to the cerium content. Field-emission scanning electron microscopy and inductively coupled plasma analyses confirmed the presence of cerium ions in the composite membranes and 1H NMR indicated the successful coordination of sulfonic acid groups with the metal ions. Increasing amounts of cerium ions resulted in decreases in the proton conductivity and water uptake, but enhanced oxidative stability. The oxidative stability of the composite membranes was proven via a hydrogen peroxide exposure experiment which mimicked fuel cell operating conditions. In addition, more than 2200 h was achieved with the composite membrane under in situ accelerated open circuit voltage (OCV) durability testing (DOE protocol), whereas the corresponding pristine SPES membrane attained only 670 h.

  20. Development of composite membranes of PVA-TEOS doped KOH for alkaline membrane fuel cell

    NASA Astrophysics Data System (ADS)

    Haryadi, Sugianto, D.; Ristopan, E.

    2015-12-01

    Anion exchange membranes (AEMs) play an important role in separating fuel and oxygen (or air) in the Alkaline Membrane Fuel Cells. Preparation of hybrid organic inorganic materials of Polyvinylalcohol (PVA) - Tetraethylorthosilicate (TEOS) composite membrane doped KOH for direct alcohol alkaline fuel cell application has been investigated. The sol-gel method has been used to prepare the composite membrane of PVA-TEOS through crosslinking step and catalyzed by concentrated of hydrochloric acid. The gel solution was cast on the membrane plastic plate to obtain membrane sheets. The dry membranes were then doped by immersing in various concentrations of KOH solutions for about 4 hours. Investigations of the cross-linking process and the presence of hydroxyl group were conducted by FTIR as shown for frequency at about 1600 cm-1 and 3300 cm-1 respectively. The degree of swelling in ethanol decreased as the KOH concentration for membrane soaking process increased. The ion exchange capacity (IEC) of the membrane was 0.25meq/g. This composite membranes display significant ionic conductivity of 3.23 x 10-2 S/cm in deionized water at room temperature. In addition, the morphology observation by scanning electron microscope (SEM) of the membrane indicates that soaking process of membrane in KOH increased thermal resistant.

  1. Development of composite membranes of PVA-TEOS doped KOH for alkaline membrane fuel cell

    SciTech Connect

    Haryadi, Sugianto, D.; Ristopan, E.

    2015-12-29

    Anion exchange membranes (AEMs) play an important role in separating fuel and oxygen (or air) in the Alkaline Membrane Fuel Cells. Preparation of hybrid organic inorganic materials of Polyvinylalcohol (PVA) - Tetraethylorthosilicate (TEOS) composite membrane doped KOH for direct alcohol alkaline fuel cell application has been investigated. The sol-gel method has been used to prepare the composite membrane of PVA-TEOS through crosslinking step and catalyzed by concentrated of hydrochloric acid. The gel solution was cast on the membrane plastic plate to obtain membrane sheets. The dry membranes were then doped by immersing in various concentrations of KOH solutions for about 4 hours. Investigations of the cross-linking process and the presence of hydroxyl group were conducted by FTIR as shown for frequency at about 1600 cm{sup −1} and 3300 cm{sup −1} respectively. The degree of swelling in ethanol decreased as the KOH concentration for membrane soaking process increased. The ion exchange capacity (IEC) of the membrane was 0.25meq/g. This composite membranes display significant ionic conductivity of 3.23 x 10{sup −2} S/cm in deionized water at room temperature. In addition, the morphology observation by scanning electron microscope (SEM) of the membrane indicates that soaking process of membrane in KOH increased thermal resistant.

  2. Viola tricolor Induces Apoptosis in Cancer Cells and Exhibits Antiangiogenic Activity on Chicken Chorioallantoic Membrane

    PubMed Central

    Sadeghnia, Hamid Reza; Ghorbani Hesari, Taghi; Mortazavian, Seyed Mohsen; Mousavi, Seyed Hadi; Tayarani-Najaran, Zahra

    2014-01-01

    In the present study, the cytotoxic and apoptogenic properties of hydroalcoholic extract and ethyl acetate (EtOAc), n-butanol, and water fractions (0–800 μg/mL) of Viola tricolor were investigated in Neuro2a mouse neuroblastoma and MCF-7 human breast cancer cells. In addition, antiangiogenic effect of EtOAc fraction was evaluated on chicken chorioallantoic membrane (CAM). The quality of EtOAc fraction was also characterized using high performance liquid chromatography (HPLC) fingerprint. Cytotoxicity assay revealed that EtOAc fraction was the most potent among all fractions with maximal effect on MCF-7 and minimal toxicity against normal murine fibroblast L929 cells. Apoptosis induction by EtOAc fraction was confirmed by increased sub-G1 peak of propidium iodide (PI) stained cells. This fraction triggered the apoptotic pathway by increased Bax/Bcl-2 ratio and cleaved caspase-3 level. Moreover, treatment with EtOAc fraction significantly decreased the diameter of vessels on CAM, while the number of newly formed blood vessels was not suppressed significantly. Analysis of quality of EtOAc fraction using HPLC fingerprint showed six major peaks with different retention times. The results of the present study suggest that V. tricolor has potential anticancer property by inducing apoptosis and inhibiting angiogenesis. PMID:25243166

  3. 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.

  4. 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.

  5. Selective effect of cell membrane on synaptic neurotransmission.

    PubMed

    Postila, Pekka A; Vattulainen, Ilpo; Róg, Tomasz

    2016-01-01

    Atomistic molecular dynamics simulations were performed with 13 non-peptidic neurotransmitters (NTs) in three different membrane environments. The results provide compelling evidence that NTs are divided into membrane-binding and membrane-nonbinding molecules. NTs adhere to the postsynaptic membrane surface whenever the ligand-binding sites of their synaptic receptors are buried in the lipid bilayer. In contrast, NTs that have extracellular ligand-binding sites do not have a similar tendency to adhere to the membrane surface. This finding is a seemingly simple yet important addition to the paradigm of neurotransmission, essentially dividing it into membrane-independent and membrane-dependent mechanisms. Moreover, the simulations also indicate that the lipid composition especially in terms of charged lipids can affect the membrane partitioning of NTs. The revised paradigm, highlighting the importance of cell membrane and specific lipids for neurotransmission, should to be of interest to neuroscientists, drug industry and the general public alike. PMID:26782980

  6. Selective effect of cell membrane on synaptic neurotransmission

    NASA Astrophysics Data System (ADS)

    Postila, Pekka A.; Vattulainen, Ilpo; Róg, Tomasz

    2016-01-01

    Atomistic molecular dynamics simulations were performed with 13 non-peptidic neurotransmitters (NTs) in three different membrane environments. The results provide compelling evidence that NTs are divided into membrane-binding and membrane-nonbinding molecules. NTs adhere to the postsynaptic membrane surface whenever the ligand-binding sites of their synaptic receptors are buried in the lipid bilayer. In contrast, NTs that have extracellular ligand-binding sites do not have a similar tendency to adhere to the membrane surface. This finding is a seemingly simple yet important addition to the paradigm of neurotransmission, essentially dividing it into membrane-independent and membrane-dependent mechanisms. Moreover, the simulations also indicate that the lipid composition especially in terms of charged lipids can affect the membrane partitioning of NTs. The revised paradigm, highlighting the importance of cell membrane and specific lipids for neurotransmission, should to be of interest to neuroscientists, drug industry and the general public alike.

  7. Membrane-Filtered Olive Mill Wastewater: Quality Assessment of the Dried Phenolic-Rich Fraction.

    PubMed

    Sedej, Ivana; Milczarek, Rebecca; Wang, Selina C; Sheng, Runqi; de Jesús Avena-Bustillos, Roberto; Dao, Lan; Takeoka, Gary

    2016-04-01

    A current trend in olive mill wastewater (OMWW) management is to not only decrease environmental pollution but also to extract and utilize valuable by-products. Therefore, the objectives of this study were to explore different techniques for drying a phenolic-rich membrane filtration fraction of OMWW and compare the techniques in terms of the dried product quality and feasibility of the process. The OMWW from 2 (3-phase and 2-phase) California mills was subjected to a 2-step membrane filtration process using a novel vibratory system. The reverse osmosis retentate (RO-R) is a phenolic-rich coproduct stream, and the reverse osmosis permeate is a near-pure water stream that could be recycled into the milling process. Spray-, freeze-, and infrared-drying were applied to obtain solid material from the RO-R. Drying of the RO-R was made possible only with addition of 10% maltodextrin as a carrier. The total soluble phenolics in dried RO-R were in the range 0.15 to 0.58 mg gallic acid equivalents/g of dry weight for 2-phase RO-R, and 1.38 to 2.17 mg gallic acid equivalents/g of dry weight for the 3-phase RO-R. Spray-dried RO-R from 3-phase OMWW showed remarkable antioxidant activity. Protocatechuic acid, tyrosol, vanillic acid, and p-coumaric acid were quantified in all dried RO-R, whereas 3-hydroxytyrosol was found in 3-phase dried RO-R. This combination of separation and drying technologies helps to add value and shelf-stability to an olive oil by-product and increase environmental sustainability of its production. PMID:26989993

  8. 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

  9. 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.

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

    NASA Astrophysics Data System (ADS)

    Eisman, G. A.

    1989-12-01

    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.

  11. Production of mouse lymphotoxin by phytohemagglutinin-stimulated spleen cells requires two cell fractions.

    PubMed Central

    Aksamit, R R; Leonard, E J

    1982-01-01

    The appearance of lymphotoxin in the culture fluid of phytohemagglutinin (PHA)-stimulated mouse spleen cells required two cell fractions that were separated by adherence to plastic. Upon stimulation with PHA, neither cell fraction alone produced significant amounts of lymphotoxin; however, when the cell fractions were combined and then stimulated with PHA, full activity was produced. Cytotoxic activity was not fully restored by combining PHA-stimulated cultured fluids from adherent and nonadherent cell fractions. This indicated that the cytotoxic activity was not the result of two factors, one produced by each cell fraction, that acted on the target cells, but rather, two cells interacted to produce lymphotoxin. Treatment of the unfractionated spleen cells with monoclonal anti-Thy1.2 and complement before PHA stimulation greatly reduced the production of lymphotoxin and indicated that at least one of the cells was a T cell. Lymphotoxin production was partially restored by the addition of nonadherent cells to the anti-Thy1.2-treated cells, suggesting that the T cell was nonadherent. Treatment of unfractionated cells with either silica or carrageenan had no effect on the subsequent production of lymphotoxin by PHA, suggesting that the adherent cell was not actively phagocytic. PMID:6980190

  12. Optomechanical characterization of proton-exchange membrane fuel cells

    NASA Astrophysics Data System (ADS)

    Jalani, Nikhil H.; Mizar, Shivananda P.; Choi, Pyoungho; Furlong, Cosme; Datta, Ravindra

    2004-08-01

    Nafion is widely used as the polymer electrolyte in proton exchange membrane (PEM) fuel cells. The properties that make the Nafion membrane indispensable are the combination of good water uptake, ion-exchange capacity, proton conductivity, gas permeability, and excellent electrochemical stability. The amount of water sorbed in the Nafion membrane is critical as the proton conductivity depends directly on the water content of the membrane which determines the fuel cell performance. The factors which affect the extent of the solvent uptake by Nafion are temperature, ion-exchange capacity, pretreatment of membrane, and the physical state of absorbing water, whether it is in liquid or vapor phase. The water sorption in the membrane is explained in terms of thermodynamic equilibrium of water in the vapor and absorption phases. As the membrane imbibes more water, the membrane matrix expands and exerts a pressure on the pore liquid which affects its chemical potential and limits extent of swelling. The extent of matrix expansion of the membranes depends on the elastic modulus, E, of the membrane, which directly affects the sorption. Hence, it is important to understand the variation of E for Nafion membrane with relative humidity (RH) and temperature. Optoelectronic holography (OEH) techniques are applied to perform quantitative, noninvasive, full field of view investigations to determine temperature and water activity dependence of E. The results obtained confirm that with the increase in temperature, E decreases and the membranes imbibes more water. Such results will allow optimization and realization of fuel cells with improved efficiency and performance.

  13. Antioxidant supplementation of boar spermatozoa from different fractions of the ejaculate improves cryopreservation: changes in sperm membrane lipid architecture.

    PubMed

    Peña, F J; Johannisson, A; Wallgren, M; Rodriguez Martinez, H

    2004-05-01

    Previous studies have shown sperm quality after cryopreservation differs depending on the fraction of seminal plasma the boar spermatozoa are contained in. Thus, spermatozoa contained in the first 10 ml of the sperm-rich fraction (portion I) withstand handling procedures (extension, handling and freezing/thawing) better than those contained in the latter part of a fractionated ejaculate (second portion of the sperm-rich fraction and the post-spermatic fraction; portion II). The present study evaluated whether an exogenous antioxidant, the water-soluble vitamin E analogue Trolox (6-hydroxy-2,5,7,8-tetramethylchroman-2-carboxylic acid), could, when added to the freezing extender in a split-sample design trial, improve the post-thaw viability and membrane quality of this particular portion of the ejaculate, with particular attention to the status of the plasma membrane. Using a split-sample design, the initial changes in the fluidity status of the sperm plasmalemma after thawing were measured by flow cytometry (FC) after loading with Merocyanine-540 and YO-PRO-1. The FC-derived data revealed a clear ejaculate portion-dependent effect of the antioxidant supplementation. While no beneficial effect of the antioxidant supplementation was visible in spermatozoa from portion I, more spermatozoa with intact membranes were observed in the supplemented samples of portion II, suggesting the protective effect of vitamin E is dependent of the portion of the boar ejaculate considered. PMID:15460106

  14. 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

  15. 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 (α) 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, α = 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.

  16. 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

  17. Seminal plasma arising from the whole boar sperm-rich fraction increases the stability of sperm membrane after thawing.

    PubMed

    Torres, M A; Ravagnani, G M; Leal, D F; Martins, S M M K; Muro, B B D; Meirelles, F V; Papa, F O; Dell'aqua, J A; Alvarenga, M A; Moretti, A S; De Andrade, A F C

    2016-05-01

    Boar spermatozoa arising from the sperm-rich ejaculate fraction are reported to have a more stable plasma membrane and are more resistant to cold shock and premature acrosome reaction than spermatozoa from the whole ejaculate. Furthermore, seminal plasma (SP) can increase the cryotolerance of boar spermatozoa, and in other domestic species, it has the ability to reverse cryopreservation damage. This study aimed to evaluate the effects of boar SP arising from the whole sperm-rich ejaculate fraction (SP-SRF) on the integrity, stability, and peroxidation of sperm membranes after thawing. Each ejaculate ( = 24) was divided among 4 treatments: control (CT), centrifuged and suspended in autologous SP-SRF (CS), centrifuged with withdrawn SP-SRF (CW), and post-thawed SP arising from the whole sperm-rich fraction addition to CW (CWSP). After thawing, all treatments were incubated for 5, 60, and 120 min and were analyzed for membrane integrity, fluidity, and peroxidation by flow cytometer. The absence of SP-SRF increased the lipid disorder ( < 0.05) but had no effect on lipid peroxidation ( > 0.05) or membrane integrity ( > 0.05). However, the increase in lipid disorder by withdrawal of SP-SRF was reversed by SP-SRF addition ( < 0.05) to the post-thawing medium, whereas plasma and acrosomal membrane integrity ( > 0.05) and lipid peroxidation ( > 0.05) were unchanged. In conclusion, despite the centrifugation effects, the addition of SP arising from the whole sperm-rich fraction to post-thawed boar semen decreased sperm lipid disorder without an influence of the sperm membrane integrity and peroxidation. PMID:27285688

  18. 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.

  19. 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

  20. Engineered nanoparticles mimicking cell membranes for toxin neutralization.

    PubMed

    Fang, Ronnie H; Luk, Brian T; Hu, Che-Ming J; Zhang, Liangfang

    2015-08-01

    Protein toxins secreted from pathogenic bacteria and venomous animals rely on multiple mechanisms to overcome the cell membrane barrier to inflict their virulence effect. A promising therapeutic concept toward developing a broadly applicable anti-toxin platform is to administer cell membrane mimics as decoys to sequester these virulence factors. As such, lipid membrane-based nanoparticulates are an ideal candidate given their structural similarity to cellular membranes. This article reviews the virulence mechanisms employed by toxins at the cell membrane interface and highlights the application of cell-membrane mimicking nanoparticles as toxin decoys for systemic detoxification. In addition, the implication of particle/toxin nanocomplexes in the development of toxoid vaccines is discussed. PMID:25868452

  1. Cholesterol modulates CFTR confinement in the plasma membrane of primary epithelial cells.

    PubMed

    Abu-Arish, Asmahan; Pandzic, Elvis; Goepp, Julie; Matthes, Elizabeth; Hanrahan, John W; Wiseman, Paul W

    2015-07-01

    The cystic fibrosis transmembrane conductance regulator (CFTR) is a plasma-membrane anion channel that, when mutated, causes the disease cystic fibrosis. Although CFTR has been detected in a detergent-resistant membrane fraction prepared from airway epithelial cells, suggesting that it may partition into cholesterol-rich membrane microdomains (lipid rafts), its compartmentalization has not been demonstrated in intact cells and the influence of microdomains on CFTR lateral mobility is unknown. We used live-cell imaging, spatial image correlation spectroscopy, and k-space image correlation spectroscopy to examine the aggregation state of CFTR and its dynamics both within and outside microdomains in the plasma membrane of primary human bronchial epithelial cells. These studies were also performed during treatments that augment or deplete membrane cholesterol. We found two populations of CFTR molecules that were distinguishable based on their dynamics at the cell surface. One population showed confinement and had slow dynamics that were highly cholesterol dependent. The other, more abundant population was less confined and diffused more rapidly. Treatments that deplete the membrane of cholesterol caused the confined fraction and average number of CFTR molecules per cluster to decrease. Elevating cholesterol had the opposite effect, increasing channel aggregation and the fraction of channels displaying confinement, consistent with CFTR recruitment into cholesterol-rich microdomains with dimensions below the optical resolution limit. Viral infection caused the nanoscale microdomains to fuse into large platforms and reduced CFTR mobility. To our knowledge, these results provide the first biophysical evidence for multiple CFTR populations and have implications for regulation of their surface expression and channel function. PMID:26153705

  2. 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.

  3. Distribution of Intact and Core Membrane Lipids of Archaeal Glycerol Dialkyl Glycerol Tetraethers among Size-Fractionated Particulate Organic Matter in Hood Canal, Puget Sound

    PubMed Central

    Huguet, Carme; Truxal, Laura T.

    2012-01-01

    There is great interest in the membrane lipids of archaea (glycerol dialkyl glycerol tetraethers [GDGTs]) as tracers of archaeal biomass because of their utility as paleoproxies and because of the biogeochemical importance of archaea. While core GDGTs (formed by hydrolysis of polar head groups of intact GDGTs after cell death) are appropriate for paleostudies, they have also been used to trace archaeal populations. Also, despite the small size (0.2 by 0.7 μm) of cultivated marine archaea, 0.7-μm glass-fiber filters (GFFs) are typically used to collect GDGTs from natural waters. We quantified both core and intact GDGTs in free-living (0.2- to 0.7-μm), suspended (0.7- to 60-μm), and aggregate (>60-μm) particle size fractions in Puget Sound (Washington State). On average, the free-living fraction contained 36% of total GDGTs, 90% of which were intact. The intermediate-size fraction contained 62% of GDGTs, and 29% of these were intact. The aggregate fraction contained 2% of the total GDGT pool, and 29% of these were intact. Our results demonstrate that intact GDGTs are largely in the free-living fraction. Because only intact GDGTs are present in living cells, protocols that target this size fraction and analyze the intact GDGT pool are necessary to track living populations in marine waters. Core GDGT enrichment in larger-size fractions indicates that archaeal biomass may quickly become attached or entrained in particles once the archaea are dead or dying. While the concentrations of the two pools were generally not correlated, the similar sizes of the core and intact GDGT pools suggest that core GDGTs are removed from the water column on timescales similar to those of cell replication, on timescales of days to weeks. PMID:22226949

  4. Houttuynia cordata Thunb fraction induces human leukemic Molt-4 cell apoptosis through the endoplasmic reticulum stress pathway.

    PubMed

    Prommaban, Adchara; Kodchakorn, Kanchanok; Kongtawelert, Prachya; Banjerdpongchai, Ratana

    2012-01-01

    Houttuynia cordata Thunb (HCT) is a native herb found in Southeast Asia which features various pharmacological activities against allergy, inflammation, viral and bacterial infection, and cancer. The aims of this study were to determine the cytotoxic effect of 6 fractions obtained from silica gel column chromatography of alcoholic HCT extract on human leukemic Molt-4 cells and demonstrate mechanisms of cell death. Six HCT fractions were cytotoxic to human lymphoblastic leukemic Molt-4 cells in a dose-dependent manner by MTT assay, fraction 4 exerting the greatest effects. Treatment with IC50 of HCT fraction 4 significantly induced Molt-4 apoptosis detected by annexinV-FITC/propidium iodide for externalization of phosphatidylserine to the outer layer of cell membrane. The mitochondrial transmembrane potential was reduced in HCT fraction 4-treated Molt-4 cells. Moreover, decreased expression of Bcl-xl and increased levels of Smac/Diablo, Bax and GRP78 proteins were noted on immunoblotting. In conclusion, HCT fraction 4 induces Molt-4 apoptosis cell through an endoplasmic reticulum stress pathway. PMID:22901157

  5. Anatomy of the red cell membrane skeleton: unanswered questions.

    PubMed

    Lux, Samuel E

    2016-01-14

    The red cell membrane skeleton is a pseudohexagonal meshwork of spectrin, actin, protein 4.1R, ankyrin, and actin-associated proteins that laminates the inner membrane surface and attaches to the overlying lipid bilayer via band 3-containing multiprotein complexes at the ankyrin- and actin-binding ends of spectrin. The membrane skeleton strengthens the lipid bilayer and endows the membrane with the durability and flexibility to survive in the circulation. In the 36 years since the first primitive model of the red cell skeleton was proposed, many additional proteins have been discovered, and their structures and interactions have been defined. However, almost nothing is known of the skeleton's physiology, and myriad questions about its structure remain, including questions concerning the structure of spectrin in situ, the way spectrin and other proteins bind to actin, how the membrane is assembled, the dynamics of the skeleton when the membrane is deformed or perturbed by parasites, the role lipids play, and variations in membrane structure in unique regions like lipid rafts. This knowledge is important because the red cell membrane skeleton is the model for spectrin-based membrane skeletons in all cells, and because defects in the red cell membrane skeleton underlie multiple hemolytic anemias. PMID:26537302

  6. Lysozyme fractionation from egg white at pilot scale by means of tangential flow membrane adsorbers: Investigation of the flow conditions.

    PubMed

    Brand, Janina; Voigt, Katharina; Zochowski, Bianca; Kulozik, Ulrich

    2016-03-18

    The application of membrane adsorbers instead of classical packed bed columns for protein fractionation is still a growing field. In the case of egg white protein fractionation, the application of classical chromatography is additionally limited due to its high viscosity that impairs filtration. By using tangential flow membrane adsorbers as stationary phase this limiting factor can be left out, as they can be loaded with particle containing substrates. The flow conditions existing in tangential flow membrane adsorbers are not fully understood yet. Thus, the aim of the present study was to gain a deeper understanding of the transport mechanisms in tangential flow membrane adsorbers. It was found that loading in recirculation mode instead of single pass mode increased the binding capacity (0.39 vs. 0.52mgcm(-2)). Further, it was shown that either higher flow rates (0.39mgcm(-2) vs. 0.57mgcm(-2) at 1CVmin(-1) or 20CVmin(-1), respectively) or higher amounts of the target protein in the feed (0.24mgcm(-2) vs. 0.85mgcm(-2) for 2.5 or 39.0g lysozyme, respectively) led to more protein binding. These results show that, in contrast to radial flow or flat sheet membrane adsorbers, the transport in tangential flow membrane adsorbers is not purely based on convection, but on a mix of convection and diffusion. Additionally, investigations concerning the influence of fouling formation were performed that can lead to transport limitations. It was found that this impact is neglectable. It can be concluded that the usage of tangential flow membrane adsorbers is very recommendable for egg white protein fractionations, although the transport is partly diffusion-limited. PMID:26898148

  7. Water and methanol uptakes in Nafion membranes and membrane effects on direct methanol cell performance

    SciTech Connect

    Ren, X.; Springer, T.E.; Gottesfeld, S.

    2000-01-01

    This paper compares direct methanol fuel cells (DMFCs) employing two types of Nafion{reg{underscore}sign} (E.I.DuPont de Nemours and Company) membranes of different equivalent weight (EW). Methanol and water uptakes in 1,100 and 1,200 EW Nafion membranes were determined by weighing P{sub 2}O{sub 5}-dried and methanol solution-equilibrated membranes. Both methanol and water uptakes in the 1,200 EW membrane were about 70--74% of those in the 1,100 EW membrane. The methanol crossover rate corresponding to that in a DMFC at open circuit was measured using a voltammetric method in the DMFC configuration and under the same cell operating conditions. After accounting for the thickness difference between the membrane samples, the methanol crossover rate through a 1,200 EW membrane was 52% of that through an 1,100 EW membrane. To resolve the cathode and anode performances in an operating DMFC, a dynamic hydrogen electrode was used as a reference electrode. Results show that in an operating DMFC the cathode can be easily flooded, as shown in a DMFC using 1,100 EW membrane. An increase in methanol crossover rate decreases the DMFC cathode potential at open circuit. At a high cell current density, the DMFC cathode potential can approach that of a H{sub 2}/air cell.

  8. Dendrimers as synthetic gene vectors: Cell membrane attachment

    NASA Astrophysics Data System (ADS)

    Voulgarakis, N. K.; Rasmussen, K. Ø.; Welch, P. M.

    2009-04-01

    We present molecular-level simulations of dendrimer/DNA complexes in the presence of a model cell membrane. We determine the required conditions for the complex to arrive intact at the membrane, and the lifetime of the complex as it resides attached to the membrane. Our simulations directly pertain to critical issues arising in emerging gene delivery therapeutic applications, where a molecular carrier is required to deliver DNA segments to the interior of living cells.

  9. Plasmonic nanoparticle interaction with cell membrane for diagnostic applications

    NASA Astrophysics Data System (ADS)

    Das, Sumana; Arikady, Akshata; Vasireddi, Ramakrishna; Harika Villa, Krishna; Konnur, Manish C.; Hegde, Gopalkrishna M.; Roy Mahapatra, D.

    2014-03-01

    Optofluidic schemes of inhibition, transport and activation by carrier molecules through cell membrane have interesting applications. Through plasmonic excitation of nanoparticles integrated in microfluidic channel, we observe cell membrane structural changes. Related phenomena are studied in situ in a microfluidic channel via fluorescence imaging. Detailed analysis is carried out to understand the possible application of this scheme in optically induced transport and expression of cell membrane protein. Optical properties of the cells undergoing plasmonic transport are monitored and correlated to cell expression assay. Plasmonic charge transport and optical transmission are measured in the microfluidic lab-on-chip along with in-situ imaging.

  10. Cultivation of MDCK epithelial cells on chitosan membranes.

    PubMed

    Popowicz, P; Kurzyca, J; Dolińska, B; Popowicz, J

    1985-01-01

    Deacetylated chitin upon evaporation from aqueous acetic acid solutions forms a thin, permeable and transparent porous membrane which can be successfully used as support of cell culture. An established MDCK cell line grown as monolayer on both chitosan membrane and millipore filter generates comparable bioelectrical properties when studied in a typical transporting chamber. PMID:4084278

  11. 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.

  12. Accurate control of oxygen level in cells during culture on silicone rubber membranes with application to stem cell differentiation.

    PubMed

    Powers, Daryl E; Millman, Jeffrey R; Bonner-Weir, Susan; Rappel, Michael J; Colton, Clark K

    2010-01-01

    Oxygen level in mammalian cell culture is often controlled by placing culture vessels in humidified incubators with a defined gas phase partial pressure of oxygen (pO(2gas)). Because the cells are consuming oxygen supplied by diffusion, a difference between pO(2gas) and that experienced by the cells (pO(2cell)) arises, which is maximal when cells are cultured in vessels with little or no oxygen permeability. Here, we demonstrate theoretically that highly oxygen-permeable silicone rubber membranes can be used to control pO(2cell) during culture of cells in monolayers and aggregates much more accurately and can achieve more rapid transient response following a disturbance than on polystyrene and fluorinated ethylene-propylene copolymer membranes. Cell attachment on silicone rubber was achieved by physical adsorption of fibronectin or Matrigel. We use these membranes for the differentiation of mouse embryonic stem cells to cardiomyocytes and compare the results with culture on polystyrene or on silicone rubber on top of polystyrene. The fraction of cells that are cardiomyocyte-like increases with decreasing pO(2) only when using oxygen-permeable silicone membrane-based dishs, which contract on silicone rubber but not polystyrene. The high permeability of silicone rubber results in pO(2cell) being equal to pO(2gas) at the tissue-membrane interface. This, together with geometric information from histological sections, facilitates development of a model from which the pO(2) distribution within the resulting aggregates is computed. Silicone rubber membranes have significant advantages over polystyrene in controlling pO(2cell), and these results suggest they are a valuable tool for investigating pO(2) effects in many applications, such as stem cell differentiation. PMID:20039374

  13. Synthesis and assembly of membrane skeletal proteins in mammalian red cell precursors

    SciTech Connect

    Hanspal, M.; Palek, J.

    1987-09-01

    The synthesis of membrane skeletal proteins in avian nucleated red cells has been the subject of extensive investigation, whereas little is known about skeletal protein synthesis in bone marrow erythroblasts and peripheral blood reticulocytes in mammals. To address this question, we have isolated nucleated red cell precursors and reticulocytes from spleens and from the peripheral blood, respectively, of rats with phenylhydrazine-induced hemolytic anemia and pulse-labeled them with (/sup 35/S)methionine. Pulse-labeling of nucleated red cell precursors shows that the newly synthesized alpha- and beta-spectrins are present in the cytosol, with a severalfold excess of alpha-spectrin over beta-spectrin. However, in the membrane-skeletal fraction, newly synthesized alpha- and beta-spectrins are assembled in stoichiometric amounts, suggesting that the association of alpha-spectrin with the membrane skeleton may- be rate-limited by the amount of beta-spectrin synthesized, as has been shown recently in avian erythroid cells. Pulse-chase experiments in the rat nucleated red cell precursors show that the newly synthesized alpha- and beta-spectrin of the cytosol turn over coordinately and extremely rapidly. In contrast, in the membrane-skeletal fraction, the newly synthesized polypeptides of spectrin are stable. In contrast to nucleated erythroid cells, in reticulocytes the synthesis of alpha- and beta-spectrins is markedly diminished compared with the synthesis and assembly of proteins comigrating with bands 2.1 and 4.1 on SDS gels. Thus, in nucleated red cell precursors, the newly synthesized spectrin may be attached to the plasma membrane before proteins 2.1 and 4.1 are completely synthesized and incorporated in the membrane.

  14. 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.

  15. Molecular basis of red cell membrane disorders.

    PubMed

    Delaunay, Jean

    2002-01-01

    We will consider an array of genetic disorders of the red cell membrane. Some affect well-known genes. The mutations of most cases of hereditary spherocytosis (HS) are located in the following genes: ANK1, SPTB, SLC4A1, EPB42 and SPTA1, which encode ankyrin, spectrin beta-chain, the anion exchanger 1 (band 3), protein 4.2 and spectrin alpha-chain, respectively. A dominant form of distal renal tubular acidosis also stems from distinct mutations in the SLC4A1 gene. The mutations responsible for hereditary elliptocytosis (HE) and its aggravated form, poikilocytosis (HP), lie in the SPTA1 and SPTB gene, already mentioned, and in the EPB41 gene encoding protein 4.1. Whereas in HS, the SPTA1 and SPTB gene mutations tend to abolish the synthesis of the corresponding chains, in HE/HP, they hinder spectrin tetramerization. Allele alpha(LELY) is a common polymorphic allele which plays the role of an aggravating factor when it occurs in trans of an elliptocytogenic allele of the SPTA1 gene. Southeast Asian ovalocytosis results from a 27- nucleotide deletion in the SLC4A1 gene. Besides these conditions in which the mutations were reached from known alterations in the proteins, other conditions required a positional cloning approach. Such are the genetic disorders of membrane permeability to monovalent cations. Knowledge is the most advanced as regards dehydrated hereditary stomatocytois (DHS). DHS was shown to belong to a pleiotropic syndrome: DHS + fetal edema + pseudohyperkalemia, which maps to 16q23-24. Concerning DHS and another disease of the same class, overhydrated hereditary stomatocytosis, splenectomy almost certainly appears to elicit thromboembolic accidents. PMID:12432217

  16. Lactobacillus casei combats acid stress by maintaining cell membrane functionality.

    PubMed

    Wu, Chongde; Zhang, Juan; Wang, Miao; Du, Guocheng; Chen, Jian

    2012-07-01

    Lactobacillus casei strains have traditionally been recognized as probiotics and frequently used as adjunct culture in fermented dairy products where lactic acid stress is a frequently encountered environmental condition. We have investigated the effect of lactic acid stress on the cell membrane of L. casei Zhang [wild type (WT)] and its acid-resistant mutant Lbz-2. Both strains were grown under glucose-limiting conditions in chemostats; following challenge by low pH, the cell membrane stress responses were investigated. In response to acid stress, cell membrane fluidity decreased and its fatty acid composition changed to reduce the damage caused by lactic acid. Compared with the WT, the acid-resistant mutant exhibited numerous survival advantages, such as higher membrane fluidity, higher proportions of unsaturated fatty acids, and higher mean chain length. In addition, cell integrity analysis showed that the mutant maintained a more intact cellular structure and lower membrane permeability after environmental acidification. These results indicate that alteration in membrane fluidity, fatty acid distribution, and cell integrity are common mechanisms utilized by L. casei to withstand severe acidification and to reduce the deleterious effect of lactic acid on the cell membrane. This detailed comparison of cell membrane responses between the WT and mutant add to our knowledge of the acid stress adaptation and thus enable new strategies to be developed aimed at improving the industrial performance of this species under acid stress. PMID:22366811

  17. 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

  18. Durability of symmetrically and asymmetrically porous polybenzimidazole membranes for high temperature proton exchange membrane fuel cells

    NASA Astrophysics Data System (ADS)

    Jheng, Li-Cheng; Chang, Wesley Jen-Yang; Hsu, Steve Lien-Chung; Cheng, Po-Yang

    2016-08-01

    Two types of porous polybenzimidazole (PBI) membranes with symmetric and asymmetric morphologies were fabricated by the template-leaching method and characterized by scanning electron microscope (SEM). Their physicochemical properties were compared in terms of acid-doping level, proton conductivity, mechanical strength, and oxidative stability. The durability of fuel cell operation is one of the most challenging for the PBI based membrane electrode assembly (MEA) used in high-temperature proton exchange membrane fuel cells (HT-PEMFCs). In the present work, we carried out a long-term steady-state fuel cell test to compare the effect of membrane structure on the cell voltage degradation. It has also been demonstrated that the asymmetrically porous PBI could bring some notable improvements on the durability of fuel cell operation, the fuel crossover problem, and the phosphoric acid leakage.

  19. 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 μm 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

  20. Evaluating the interfacial reaction kinetics of the bipolar membrane interface in the bipolar membrane fuel cell.

    PubMed

    Peng, Sikan; Lu, Shanfu; Zhang, Jin; Sui, Pang-Chieh; Xiang, Yan

    2013-07-21

    A reaction kinetic model of the bipolar membrane interface in the bipolar membrane fuel cell (BPMFC) was proposed based on the p-n junction theory and chemical reaction kinetics. It verified the self-humidification feasibility of the BPMFC successfully. PMID:23744271

  1. G-protein-coupled glucocorticoid receptors on the pituitary cell membrane.

    PubMed

    Maier, Christina; Rünzler, Dominik; Schindelar, Julia; Grabner, Gottfried; Waldhäusl, Werner; Köhler, Gottfried; Luger, Anton

    2005-08-01

    Rapid, nongenomic actions of glucocorticoids (GCs) have been well documented, but information about putative membrane receptors that mediate them is scarce. We used fluorescence correlation spectroscopy to search for membrane GC-binding on the mouse pituitary cell line AtT-20. A slowly diffusing fraction (tau3; diffusion constant 3x10(-10) cm2 s-1) of fluorescein-labeled dexamethasone on the cell membrane corresponds to fluorescein-dexamethasone binding. Preincubation experiments were performed to test binding specificity: a 500-fold excess of unlabeled dexamethasone abolished subsequent fluorescein-dexamethasone membrane binding from 58+/-2 (control) to 8+/-1 (% of tau3, mean+/-s.e.m.), the natural ligand corticosterone prevented it partially (29+/-2), while the sex steroids estradiol (56+/-4) and progesterone (50+/-4) and the GC-receptor antagonist RU486 (56+/-2) had no effect. Preincubation with pertussis toxin resulted in disappearance of the slowest diffusion component (11+/-4) suggesting association of the receptor with a G-protein. Varying the concentration of fluorescein-dexamethasone showed that membrane binding is highly cooperative with an apparent Kd of 180 nM and Bmax of 230 nM. Taken together, these results demonstrate high-affinity GC-binding on the cell membrane of AtT-20 cells with characteristics distinct from intracellular binding. PMID:16079279

  2. Identification of DNA-binding proteins on human umbilical vein endothelial cell plasma membrane.

    PubMed Central

    Chan, T M; Frampton, G; Cameron, J S

    1993-01-01

    The binding of anti-DNA antibodies to the endothelial cell is mediated through DNA, which forms a bridge between the immunoglobulin and the plasma membrane. We have shown that 32P-labelled DNA bound to the plasma membrane of human umbilical vein endothelial cells (HUVEC) by a saturable process, which could be competitively inhibited by non-radiolabelled DNA. In addition, DNA-binding was enhanced in HUVEC that had been treated with IL-1 alpha or tumour necrosis factor-alpha (TNF-alpha). DNA-binding proteins of mol. wt 46,000, 92,000, and 84,000 were identified by the binding of 32P-labelled DNA to plasma membrane proteins separated on SDS-PAGE. DNA-binding proteins of mol. wt 46,000 and 84,000 were also present in the cytosol and nucleus. Murine anti-DNA MoAb410 bound to a single band, at mol. wt 46,000, of plasma membrane protein, in the presence of DNA. Our results showed that DNA-binding proteins are present in different cellular fractions of endothelial cells. DNA-binding proteins on the cell membrane could participate in the in situ formation of immune deposits; and their presence in the cell nucleus suggests a potential role in the modulation of cell function. Images Fig. 3 Fig. 4 PMID:8419070

  3. Cell membrane potentials induced during exposure to EMP fields

    SciTech Connect

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

    1994-09-01

    Internal current densities and electric fields induced in the human body during exposure to EMP fields are reviewed and used to predict resulting cell membrane potentials. Using several different approaches, membrane potentials of about 100 mV are predicted. These values are comparable to the static membrane potentials maintained by cells as a part of normal physiological function, but the EMP-induced potentials persist for only about 10 ns. Possible biological implications of EMP-induced membrane potentials including conformational changes and electroporation are discussed.

  4. Cardiotoxicity of Jamesoni's mamba (Dendroaspis jamesoni) venom and its fractionated components in primary cultures of rat myocardial cells.

    PubMed

    Mbugua, P M; Welder, A A; Acosta, D

    1988-08-01

    Primary cultures of spontaneously beating myocardial cells isolated from neonatal rat hearts were used to screen the cardiotoxic effects of Jamesoni's mamba (Dendroaspis jamesoni) venom and components isolated from the venom by gel filtration and ion exchange chromatography. Cardiotoxicity was evaluated on the basis of leakage of lactate dehydrogenase (LDH), changes in morphology, cell membrane lysis, cellular viability, and alterations in spontaneous beating activity. The whole venom caused dose- and time-dependent leakage of LDH, disruption of the cell monolayer, decreases in viability, and inhibition of beating activity. Gel filtration of the venom yielded eight fractions (DjI to DjVIII). DjI (30 micrograms/ml), DjII (20 micrograms/ml), and DjV (20 micrograms/ml) caused significant (P less than 0.001) leakage of LDH, extensive morphologic damage, and decreases in viability. At lower concentrations DjI to DjVIII caused progressive inhibition of spontaneous beating activity. The main fraction (DjV), which was the most toxic, was further separated into 14 polypeptides (Dj1 to Dj14) by ion-exchange chromatography using Bio-Rex 70. Based on the ability to induce LDH leakage, produce morphologic damage, lyse cell membranes, and arrest beating activity, four categories of polypeptides were identified: cardiotoxins, Dj1 and Dj2; cardiotoxinlike polypeptides, Dj3 to Dj8; less active membrane lytic polypeptides, Dj9 to Dj13; and membrane lytic polypeptide, Dj14. PMID:3410805

  5. Revealing the Dynamics of Thylakoid Membranes in Living Cyanobacterial Cells

    NASA Astrophysics Data System (ADS)

    Stingaciu, Laura-Roxana; O'Neill, Hugh; Liberton, Michelle; Urban, Volker S.; Pakrasi, Himadri B.; Ohl, Michael

    2016-01-01

    Cyanobacteria are photosynthetic prokaryotes that make major contributions to the production of the oxygen in the Earth atmosphere. The photosynthetic machinery in cyanobacterial cells is housed in flattened membrane structures called thylakoids. The structural organization of cyanobacterial cells and the arrangement of the thylakoid membranes in response to environmental conditions have been widely investigated. However, there is limited knowledge about the internal dynamics of these membranes in terms of their flexibility and motion during the photosynthetic process. We present a direct observation of thylakoid membrane undulatory motion in vivo and show a connection between membrane mobility and photosynthetic activity. High-resolution inelastic neutron scattering experiments on the cyanobacterium Synechocystis sp. PCC 6803 assessed the flexibility of cyanobacterial thylakoid membrane sheets and the dependence of the membranes on illumination conditions. We observed softer thylakoid membranes in the dark that have three-to four fold excess mobility compared to membranes under high light conditions. Our analysis indicates that electron transfer between photosynthetic reaction centers and the associated electrochemical proton gradient across the thylakoid membrane result in a significant driving force for excess membrane dynamics. These observations provide a deeper understanding of the relationship between photosynthesis and cellular architecture.

  6. Revealing the Dynamics of Thylakoid Membranes in Living Cyanobacterial Cells

    DOE PAGESBeta

    Stingaciu, Laura-Roxana; O’Neill, Hugh; Liberton, Michelle; Urban, Volker S.; Pakrasi, Himadri B.; Ohl, Michael

    2016-01-21

    Cyanobacteria are photosynthetic prokaryotes that make major contributions to the production of the oxygen in the Earth atmosphere. The photosynthetic machinery in cyanobacterial cells is housed in flattened membrane structures called thylakoids. The structural organization of cyanobacterial cells and the arrangement of the thylakoid membranes in response to environmental conditions have been widely investigated. However, there is limited knowledge about the internal dynamics of these membranes in terms of their flexibility and motion during the photosynthetic process. We present a direct observation of thylakoid membrane undulatory motion in vivo and show a connection between membrane mobility and photosynthetic activity. High-resolutionmore » inelastic neutron scattering experiments on the cyanobacterium Synechocystis sp. PCC 6803 assessed the flexibility of cyanobacterial thylakoid membrane sheets and the dependence of the membranes on illumination conditions. We observed softer thylakoid membranes in the dark that have three-to four fold excess mobility compared to membranes under high light conditions. We find our analysis indicates that electron transfer between photosynthetic reaction centers and the associated electrochemical proton gradient across the thylakoid membrane result in a significant driving force for excess membrane dynamics. Lastly, these observations provide a deeper understanding of the relationship between photosynthesis and cellular architecture.« less

  7. Revealing the Dynamics of Thylakoid Membranes in Living Cyanobacterial Cells

    PubMed Central

    Stingaciu, Laura-Roxana; O’Neill, Hugh; Liberton, Michelle; Urban, Volker S.; Pakrasi, Himadri B.; Ohl, Michael

    2016-01-01

    Cyanobacteria are photosynthetic prokaryotes that make major contributions to the production of the oxygen in the Earth atmosphere. The photosynthetic machinery in cyanobacterial cells is housed in flattened membrane structures called thylakoids. The structural organization of cyanobacterial cells and the arrangement of the thylakoid membranes in response to environmental conditions have been widely investigated. However, there is limited knowledge about the internal dynamics of these membranes in terms of their flexibility and motion during the photosynthetic process. We present a direct observation of thylakoid membrane undulatory motion in vivo and show a connection between membrane mobility and photosynthetic activity. High-resolution inelastic neutron scattering experiments on the cyanobacterium Synechocystis sp. PCC 6803 assessed the flexibility of cyanobacterial thylakoid membrane sheets and the dependence of the membranes on illumination conditions. We observed softer thylakoid membranes in the dark that have three-to four fold excess mobility compared to membranes under high light conditions. Our analysis indicates that electron transfer between photosynthetic reaction centers and the associated electrochemical proton gradient across the thylakoid membrane result in a significant driving force for excess membrane dynamics. These observations provide a deeper understanding of the relationship between photosynthesis and cellular architecture. PMID:26790980

  8. Humidification studies on polymer electrolyte membrane fuel cell

    NASA Astrophysics Data System (ADS)

    Sridhar, P.; Perumal, Ramkumar; Rajalakshmi, N.; Raja, M.; Dhathathreyan, K. S.

    Two methods of humidifying the anode gas, namely, external and membrane humidification, for a polymer electrolyte membrane fuel (PEMFC) cell are explained. It is found that the water of solvation of protons decreases with increase in the current density and the electrode area. This is due to insufficient external humidification. In a membrane-based humidification, an optimum set of parameters, such as gas flow rate, area and type of the membrane, must be chosen to achieve effective humidification. The present study examines the dependence of water pick-up by hydrogen on the temperature, area and thickness of the membrane in membrane humidification. Since the performance of the fuel cell is dependent more on hydrogen humidification than on oxygen humidification, the scope of the work is restricted to the humidification of hydrogen using Nafion ® membrane. An examination is made on the dependence of water pick-up by hydrogen in membrane humidification on the temperature, area and thickness of the membrane. The dependence of fuel cell performance on membrane humidification and external humidification in the anode gas is also considered.

  9. Functional Implications of Plasma Membrane Condensation for T Cell Activation

    PubMed Central

    Quinn, Carmel M.; Engelhardt, Karin; Williamson, David; Grewal, Thomas; Jessup, Wendy; Harder, Thomas; Gaus, Katharina

    2008-01-01

    The T lymphocyte plasma membrane condenses at the site of activation but the functional significance of this receptor-mediated membrane reorganization is not yet known. Here we demonstrate that membrane condensation at the T cell activation sites can be inhibited by incorporation of the oxysterol 7-ketocholesterol (7KC), which is known to prevent the formation of raft-like liquid-ordered domains in model membranes. We enriched T cells with 7KC, or cholesterol as control, to assess the importance of membrane condensation for T cell activation. Upon 7KC treatment, T cell antigen receptor (TCR) triggered calcium fluxes and early tyrosine phosphorylation events appear unaltered. However, signaling complexes form less efficiently on the cell surface, fewer phosphorylated signaling proteins are retained in the plasma membrane and actin restructuring at activation sites is impaired in 7KC-enriched cells resulting in compromised downstream activation responses. Our data emphasizes lipids as an important medium for the organization at T cell activation sites and strongly indicates that membrane condensation is an important element of the T cell activation process. PMID:18509459

  10. Photocatalytic Degradation of Cell Membrane Coatings for Controlled Drug Release.

    PubMed

    Rao, Lang; Meng, Qian-Fang; Huang, Qinqin; Liu, Pei; Bu, Lin-Lin; Kondamareddy, Kiran Kumar; Guo, Shi-Shang; Liu, Wei; Zhao, Xing-Zhong

    2016-06-01

    Biomimetic cell-membrane-camouflaged particles with desirable features have been widely used for various biomedical applications. However, there are few reports on employing these particles for cancer drug delivery due to the failure of the membrane coatings to be efficiently degraded in the tumor microenvironment which hampers the drug release. In this work, core-shell SiO2 @TiO2 nanoparticles with enhanced photocatalytic activity are used for controlled degradation of surface erythrocyte membrane coatings. The antitumor drug docetaxel is encapsulated into nanocarriers to demonstrate the controlled drug release under ultraviolet irradiation, and the drug-loaded nanoparticles are further used for enhanced cancer cell therapy. Here, a simple but practical method for degradation of cell membrane coatings is presented, and a good feasibility of using cell membrane-coated nanocarriers for controlled drug delivery is demonstrated. PMID:27191802

  11. 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.

  12. Fractionated stem cell infusions for patients with plasma cell myeloma undergoing autologous hematopoietic cell transplantation.

    PubMed

    Landau, Heather; Wood, Kevin; Chung, David J; Koehne, Guenther; Lendvai, Nikoletta; Hassoun, Hani; Lesokhin, Alexander; Hoover, Elizabeth; Zheng, Junting; Devlin, Sean M; Giralt, Sergio

    2016-08-01

    We conducted a phase II trial investigating the impact of fractionated hematopoietic cell infusions on engraftment kinetics and symptom burden in patients with plasma cell myeloma (PCM) undergoing autologous hematopoietic cell transplant (AHCT). We hypothesized that multiple hematopoietic cell infusions would reduce duration of neutropenia and enhance immune recovery resulting in a better tolerated procedure. Twenty-six patients received high-dose melphalan followed by multiple cell infusions (Days 0, +2, +4, +6) and were compared to PCM patients (N = 77) who received high-dose melphalan and a single infusion (Day 0) (concurrent control group). The primary endpoint was number of days with ANC <500K/mcL. Symptom burden was assessed using the MSK-modified MD Anderson Symptom Inventory. Median duration of neutropenia was similar in study (4 days, range 3-5) and control patients (4 days, range 3-9) (p = 0.654). There was no significant difference in the number of red cell or platelet transfusions, days of fever, diarrhea, antibiotics, number of documented infections, or length of admission. Symptom burden surveys showed that AHCT was well-tolerated in both study and control patients. We conclude that fractionated stem cell infusions following high-dose melphalan do not enhance engraftment kinetics or significantly alter patients' clinical course following AHCT in PCM. PMID:26758672

  13. Extracellular Protease Digestion to Evaluate Membrane Protein Cell Surface Localization

    PubMed Central

    Besingi, Richard N.; Clark, Patricia L.

    2016-01-01

    Membrane proteins play 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 is rapidly digested when cells are lysed prior to 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

  14. 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].

  15. Lipid membrane domains in cell surface and vacuolar systems.

    PubMed

    Kobayashi, T; Hirabayashi, Y

    2000-01-01

    Detergent insoluble sphingolipid-cholesterol enriched 'raft'-like membrane microdomains have been implicated in a variety of biological processes including sorting, trafficking, and signaling. Mutant cells and knockout animals of sphingolipid biosynthesis are clearly useful to understand the biological roles of lipid components in raft-like domains. It is suggested that raft-like domains distribute in internal vacuolar membranes as well as plasma membranes. In addition to sphingolipid-cholesterol-rich membrane domains, recent studies suggest the existence of another lipid-membrane domain in the endocytic pathway. This domain is enriched with a unique phospholipid, lysobisphosphatidic acid (LBPA) and localized in the internal membrane of multivesicular endosome. LBPA-rich membrane domains are involved in lipid and protein sorting within the endosomal system. Possible interaction between sphingolipids and LBPA in sphingolipid-storage disease is discussed. PMID:11201787

  16. Peptides in common bean fractions inhibit human colorectal cancer cells.

    PubMed

    Luna Vital, Diego A; González de Mejía, Elvira; Dia, Vermont P; Loarca-Piña, Guadalupe

    2014-08-15

    The aim of this study was to characterize peptides present in common bean non-digestible fractions (NDF) produced after enzymatic digestion and determine their antiproliferative action on human colorectal cancer cells. Five NDF peptides represented 70% of total protein (GLTSK, LSGNK, GEGSGA, MPACGSS and MTEEY) with antiproliferative activity on human colon cancer cells. Based on the antiproliferative effect, HCT116 cell line was most sensitive to bean Azufrado Higuera (IC50=0.53 mg/ml) and RKO to Bayo Madero (IC50=0.51 mg/ml) peptide extracts. Both cultivars increased significantly (p<0.05) the expression of p53 in HCT116 by 76% and 68%, respectively. Azufrado Higuera modified the expression of cell cycle regulation proteins p21 and cyclin B1. Bayo Madero modified the expression of mitochondrial activated apoptotic proteins BAD, cytC, c-casp3, Survivin, BIRC7. Results suggest that peptides present in common bean NDF contributed to the antiproliferative effect on human colorectal cancer cells by modifying molecules involved in either cell cycle arrest or apoptosis. PMID:24679790

  17. 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.

  18. Membrane curvature in cell biology: An integration of molecular mechanisms.

    PubMed

    Jarsch, Iris K; Daste, Frederic; Gallop, Jennifer L

    2016-08-15

    Curving biological membranes establishes the complex architecture of the cell and mediates membrane traffic to control flux through subcellular compartments. Common molecular mechanisms for bending membranes are evident in different cell biological contexts across eukaryotic phyla. These mechanisms can be intrinsic to the membrane bilayer (either the lipid or protein components) or can be brought about by extrinsic factors, including the cytoskeleton. Here, we review examples of membrane curvature generation in animals, fungi, and plants. We showcase the molecular mechanisms involved and how they collaborate and go on to highlight contexts of curvature that are exciting areas of future research. Lessons from how membranes are bent in yeast and mammals give hints as to the molecular mechanisms we expect to see used by plants and protists. PMID:27528656

  19. Chemical Analysis of the Outer Membrane and Other Layers of the Cell Envelope of Acinetobacter sp

    PubMed Central

    Thorne, Kareen J. I.; Thornley, Margaret J.; Glauert, Audrey M.

    1973-01-01

    Chemical analysis of fractions of the cell envelope of Acinetobacter sp. strain MJT/F5/199A, prepared by breakage in the French press and removal of plasma membranes, followed by sequential treatment with lysozyme and with papain, confirmed the existence of layers previously identified by electron microscopy. Outside the plasma membrane and periplasmic space, the envelope is composed of (i) a peptidoglycan-containing dense layer, (ii) an intermediate layer, (iii) a lipopolysaccharide-containing outer membrane, and (iv) an ordered array of protein subunits. A small amount of carbohydrate (3%) is found associated with protein in the fraction containing both the surface subunits and the intermediate layer. The papain-treated outer membranes contain 67% protein, 24% lipid, together with 11% lipopolysaccharide, and about 6% of non-lipopolysaccharide hexosamine. Lipid is located only in the papain-treated outer-membrane and is mainly phospholipid: 29% phosphatidyl glycerol, 30% phosphatidyl ethanolamine, and 40% cardiolipin. The principal fatty acid is C18:1. Significant amounts of alcohols16:1 and alcohols18:1, which are found in Acinetobacter waxes, were recovered from the outer membrane. Images PMID:4745422

  20. Mechanisms of gold nanoparticle mediated ultrashort laser cell membrane perforation

    NASA Astrophysics Data System (ADS)

    Schomaker, M.; Baumgart, J.; Motekaitis, D.; Heinemann, D.; Krawinkel, J.; Pangalos, M.; Bintig, W.; Boulais, E.; Lachaine, R.; St.-Louis Lalonde, B.; Ngezahayo, A.; Meunier, M.; Heisterkamp, A.

    2011-03-01

    The gold nanoparticle (AuNP) mediated ultrashort laser cell membrane perforation has been proven as an efficient delivery method to bring membrane impermeable molecules into the cytoplasm. Nevertheless, the underlying mechanisms have not been fully determined yet. Different effects may occur when irradiating a AuNP with ultrashort laser pulses and finally enable the molecule to transfer. Depending on the parameters (pulse length, laser fluence and wavelength, particle size and shape, etc.) light absorption or an enhanced near field scattering can lead to perforation of the cell membrane when the particle is in close vicinity. Here we present our experimental results to clarify the perforation initiating mechanisms. The generation of cavitation and gas bubbles due to the laser induced effects were observed via time resolved imaging. Additionally, pump-probe experiments for bubble detection was performed. Furthermore, in our patch clamp studies a depolarization of the membrane potential and the current through the membrane of AuNP loaded cell during laser treatment was detected. This indicates an exchange of extra- and intra cellular ions trough the perforated cell membrane for some milliseconds. Additionally investigations by ESEM imaging were applied to study the interaction of cells and AuNP after co incubation. The images show an attachment of AuNP at the cell membrane after several hours of incubation. Moreover, images of irradiated and AuNP loaded cells were taken to visualize the laser induced effects.

  1. 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

  2. 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

  3. 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

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

    PubMed

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

    2015-05-01

    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

  5. 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.

  6. 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.

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

    NASA Astrophysics Data System (ADS)

    Eisman, G. A.

    1989-12-01

    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.

  8. 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.

  9. Effect of Hydroperoxides on Red Blood Cell Membrane Mechanical Properties

    PubMed Central

    Hale, John P.; Winlove, C. Peter; Petrov, Peter G.

    2011-01-01

    We investigate the effect of oxidative stress on red blood cell membrane mechanical properties in vitro using detailed analysis of the membrane thermal fluctuation spectrum. Two different oxidants, the cytosol-soluble hydrogen peroxide and the membrane-soluble cumene hydroperoxide, are used, and their effects on the membrane bending elastic modulus, surface tension, strength of confinement due to the membrane skeleton, and 2D shear elastic modulus are measured. We find that both oxidants alter significantly the membrane elastic properties, but their effects differ qualitatively and quantitatively. While hydrogen peroxide mainly affects the elasticity of the membrane protein skeleton (increasing the membrane shear modulus), cumene hydroperoxide has an impact on both membrane skeleton and lipid bilayer mechanical properties, as can be seen from the increased values of the shear and bending elastic moduli. The biologically important implication of these results is that the effects of oxidative stress on the biophysical properties, and hence the physiological functions, of the cell membrane depend on the nature of the oxidative agent. Thermal fluctuation spectroscopy provides a means of characterizing these different effects, potentially in a clinical milieu. PMID:22004746

  10. Existence of a Flat Phase in Red Cell Membrane Skeletons

    NASA Astrophysics Data System (ADS)

    Schmidt, Christoph F.; Svoboda, Karel; Lei, Ning; Petsche, Irena B.; Berman, Lonny E.; Safinya, Cyrus R.; Grest, Gary S.

    1993-02-01

    Biomolecular membranes display rich statistical mechanical behavior. They are classified as liquid in the absence of shear elasticity in the plane of the membrane and tethered (solid) when the neighboring molecules or subunits are connected and the membranes exhibit solid-like elastic behavior in the plane of the membrane. The spectrin skeleton of red blood cells was studied as a model tethered membrane. The static structure factor of the skeletons, measured by small-angle x-ray and light scattering, was fitted with a structure factor predicted with a model calculation. The model describes tethered membrane sheets with free edges in a flat phase, which is a locally rough but globally flat membrane configuration. The fit was good for large scattering vectors. The membrane roughness exponent, zeta, defined through h propto L^zeta, where h is the average amplitude of out-of-plane fluctuations and L is the linear membrane dimension, was determined to be 0.65 ± 0.10. Computer simulations of model red blood cell skeletons also showed this flat phase. The value for the roughness exponent, which was determined from the scaling properties of membranes of different sizes, was consistent with that from the experiments.

  11. 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.

  12. Cytoskeletal control of the red-blood cell membrane

    NASA Astrophysics Data System (ADS)

    Gov, Nir; Safran, Sam

    2004-03-01

    We have shown (Physical Review Letters, 90, 228101 (2003)) that the thermal fluctuations of red blood cells can be accounted for by a model of a nearly-free, but confined bilayer membrane with a finite tension; both the confinement and tension arise from the coupling of the membrane with the cytoskeleton. Recently, we have shown that these relatively gentle effects of the cytoskeleton-membrane couplings on the membrane fluctuations are due to the dilute nature of the coupling molecules. To quantify this, we predict the fluctuation amplitude for a microscopic model of the inhomogeneous coupling of a fluid membrane and a fixed cytoskeleton. The coupling is modeled as periodic and harmonic, and we consider the linear response of the membrane. We find that there is indeed, an effective surface tension and confinement of such a membrane, in accord with our phenomenological model, and relate these quantities to the strength and periodicity of the microscopic coupling. We also find, surprisingly, that the membrane can develop a spontaneous breaking of the cytoskeleton symmetry, at low confinements. Finally we address the role of ATP activity on the cytoskeleton-driven fluctuations and the equilibrium shape of the cell. We examine in detail the role of spectrin disconnections as the main ATP-activated network defects on the global cell shape and membrane fluctuations.

  13. 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.

  14. Direct measurements of membrane potential and membrane resistance of human red cells

    PubMed Central

    Lassen, U. V.; Sten-Knudsen, O.

    1968-01-01

    1. In order to evaluate the membrane potentials calculated from the distribution of chloride ions in human red cells and plasma, it is desirable to have a direct measurement of the transmembrane potential of these cells. 2. A method has been devised for introducing a capillary micro-electrode into human red cells. The method allows simultaneous measurements of potential and membrane resistance with only one micro-electrode located in the cell. 3. Upon impalement of single cells in plasma, a scatter of membrane potentials and of resistance values was obtained. The potential drop never exceeded -14 mV and the maximum resistances were about 7 Ω. cm2. Positive potentials were obtained on impalement of red cell aggregates. 4. Arguments are given to support the view that it is in these cells which suffer least damage from the impalement that maximum values of membrane potentials and resistances are observed. The errors caused by the change in the liquid junction during the impalement have been estimated. 5. As judged from this study, it seems permissible under normal conditions to calculate the membrane potential of the red cell from the chloride concentrations in plasma and in intracellular water. PMID:5649641

  15. Cell-cell communication via extracellular membrane vesicles and its role in the immune response.

    PubMed

    Hwang, Inkyu

    2013-08-01

    The host immune response involves a variety of cell types, including specialized immune and non-immune cells. The delicate coordination among these cells via close communication is central for the proper operation of immune system. Cell-cell communication is mediated by a complex network that includes soluble factors such as cytokines, chemokines, and metabolites exported from cells, as well as membrane-bound receptors and their ligands. Cell-cell communication is also mediated by membrane vesicles (e.g., exosomes, ectosomes), which are either shed by distant cells or exchanged by cells that are making direct contact. Intercellular communication via extracellular membrane vesicles has drawn much attention recently, as they have been shown to carry various biomolecules that modulate the activities of recipient cells. In this review, I will discuss current views on cell-cell communication via extra-cellular membrane vesicles, especially shedded membrane vesicles, and their effects on the control of the immune system. PMID:23807045

  16. Biosynthesis of proteokeratan sulfate in the bovine cornea. 2) Isolation of subcellular membrane fragments from bovine cornea cells with keratan sulfate synthesizing activity.

    PubMed

    Keller, R; Stein, T; Weber, W; Kehrer, T; Stuhlsatz, H W; Greiling, H; Keyserlingk, D G

    1983-03-01

    Cornea cells were isolated from bovine corneae after collagenase treatment. Subcellular fragments were fractionated by density gradient centrifugation. The density gradient run was monitored by determination of the marker enzyme activities for mitochondria, plasma membranes, lysosomes and endoplasmatic reticulum, of the enzyme activities involved in keratan sulfate synthesis and of the protein content. The fractions were further investigated by electron microscopy. Two membrane fractions with keratan sulfate-synthesizing activity (UDP-N-acetylglucosamine:keratan-N-acetylglucosaminyl-transferase, UDPgalactose:keratan galactosyltransferase and keratan sulfotransferase) were detected: a heavy fraction separated from the other organells investigated and a light fraction exhibiting the same density as plasma membranes. The activities of the three enzymes were found in the same density gradient fractions with a similar distribution pattern between the fractions, which suggests a joint localization of these 3 enzymes at the same intracellular sites. PMID:6222957

  17. Cell and membrane lipid analysis by proton magnetic resonance spectroscopy in five breast cancer cell lines.

    PubMed

    Le Moyec, L; Tatoud, R; Eugène, M; Gauvillé, C; Primot, I; Charlemagne, D; Calvo, F

    1992-10-01

    The lipid composition of five human breast cancer cell lines (MCF-7, T47D, ZR-75-1, SKBR3 and MDA-MB231) was assessed by proton magnetic resonance spectroscopy (MRS) in whole cells and membrane-enriched fractions. The proportions of the three main lipid resonances in 1D spectra were different for each cell line. These resonances included mobile methyl and methylene functions from fatty acids of triglycerides and phospholipids and N-trimethyl from choline of phospholipids. T47D and ZR-75-1 cells presented a high methylene/methyl ratio (6.02 +/- 0.35 and 6.28 +/- 0.90). This ratio was significantly lower for SKBR3, MCF-7 and MDA-MB231 cells (2.76 +/- 0.22, 2.27 +/- 0.57 and 1.39 +/- 0.39). The N-trimethyl/methyl ratio was high for MDA-MB231 and SKBR3 cells (1.38 +/- 0.54 and 0.86 +/- 0.32), but lower for MCF-7, T47D and ZR-75-1 cells (0.49 +/- 0.11, 0.16 +/- 0.07 and 0.07 +/- 0.03). 2D COSY spectra confirmed these different proportions in mobile lipids. From 1D spectra obtained on membrane preparations, T47D and ZR-75-1 were the only cell lines to retain a signal from mobile methylene functions. These differences might be related to the heterogeneity found for several parameters of these cells (tumorigenicity, growth rate, hormone receptors); an extended number of cases from fresh samples might enable clinical correlations. PMID:1329906

  18. A Facile Approach to Functionalize Cell Membrane-Coated Nanoparticles

    PubMed Central

    Zhou, Hao; Fan, Zhiyuan; Lemons, Pelin K.; Cheng, Hao

    2016-01-01

    Convenient strategies to provide cell membrane-coated nanoparticles (CM-NPs) with multi-functionalities beyond the natural function of cell membranes would dramatically expand the application of this emerging class of nanomaterials. We have developed a facile approach to functionalize CM-NPs by chemically modifying live cell membranes prior to CM-NP fabrication using a bifunctional linker, succinimidyl-[(N-maleimidopropionamido)-polyethyleneglycol] ester (NHS-PEG-Maleimide). This method is particularly suitable to conjugate large bioactive molecules such as proteins on cell membranes as it establishes a strong anchorage and enable the control of linker length, a critical parameter for maximizing the function of anchored proteins. As a proof of concept, we show the conjugation of human recombinant hyaluronidase, PH20 (rHuPH20) on red blood cell (RBC) membranes and demonstrate that long linker (MW: 3400) is superior to short linker (MW: 425) for maintaining enzyme activity, while minimizing the changes to cell membranes. When the modified membranes were fabricated into RBC membrane-coated nanoparticles (RBCM-NPs), the conjugated rHuPH20 can assist NP diffusion more efficiently than free rHuPH20 in matrix-mimicking gels and the pericellular hyaluronic acid matrix of PC3 prostate cancer cells. After quenching the unreacted chemical groups with polyethylene glycol, we demonstrated that the rHuPH20 modification does not reduce the ultra-long blood circulation time of RBCM-NPs. Therefore, this surface engineering approach provides a platform to functionlize CM-NPs without sacrificing the natural function of cell membranes. PMID:27217834

  19. 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.

  20. 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.

  1. Membrane-electrode assemblies for electrochemical cells

    DOEpatents

    Swathirajan, Sundararajan; Mikhail, Youssef M.

    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. Prism-patterned Nafion membrane for enhanced water transport in polymer electrolyte membrane fuel cell

    NASA Astrophysics Data System (ADS)

    Kim, Sang Moon; Kang, Yun Sik; Ahn, Chiyeong; Jang, Segeun; Kim, Minhyoung; Sung, Yung-Eun; Yoo, Sung Jong; Choi, Mansoo

    2016-06-01

    Here, we report a simple and effective strategy to enhance the performance of the polymer electrolyte membrane fuel cell by imprinting prism-patterned arrays onto the Nafion membrane, which provides three combined effects directly related to the device performance. First, a locally thinned membrane via imprinted micro prism-structures lead to reduced membrane resistance, which is confirmed by electrochemical impedance spectroscopy. Second, increments of the geometrical surface area of the prism-patterned Nafion membrane compared to a flat membrane result in the increase in the electrochemical active surface area. Third, the vertically asymmetric geometry of prism structures in the cathode catalyst layer lead to enhanced water transport, which is confirmed by oxygen gain calculation. To explain the enhanced water transport, we propose a simple theoretical model on removal of water droplets existing in the asymmetric catalyst layer. These three combined effects achieved via incorporating prism patterned arrays into the Nafion membrane effectively enhance the performance of the polymer electrolyte membrane fuel cell.

  3. Correlations between the Dielectric Properties and Exterior Morphology of Cells Revealed by Dielectrophoretic Field-Flow Fractionation

    PubMed Central

    Gascoyne, Peter R. C.; Shim, Sangjo; Noshari, Jamileh; Becker, Frederick F.; Stemke-Hale, Katherine

    2013-01-01

    Although dielectrophoresis (DEP) has great potential for addressing clinical cell isolation problems based on cell dielectric differences, a biological basis for predicting the DEP behavior of cells has been lacking. Here, the dielectric properties of the NCI-60 panel of tumor cell types have been measured by dielectrophoretic (DEP) field-flow fractionation, correlated with the exterior morphologies of the cells during growth, and compared with the dielectric and morphological characteristics of the subpopulations of peripheral blood. In agreement with earlier findings, cell total capacitance varied with both cell size and plasma membrane folding and the dielectric properties of the NCI-60 cell types in suspension reflected the plasma membrane area and volume of the cells at their growth sites. Therefore, the behavior of cells in DEP-based manipulations is largely determined by their exterior morphological characteristics prior to release into suspension. As a consequence, DEP is able to discriminate between cells of similar size having different morphological origins, offering a significant advantage over size-based filtering for isolating circulating tumor cells, for example. The findings provide a framework for anticipating cell dielectric behavior on the basis of structure-function relationships and suggest that DEP should be widely applicable as a surface marker-independent method for sorting cells. PMID:23172680

  4. Membrane organization and cell fusion during mating in fission yeast requires multipass membrane protein Prm1.

    PubMed

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

    2014-04-01

    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 prm1Δ 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 prm1Δ 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 prm1Δ nor prm1Δ dniΔ 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, prm1Δ, and dni1Δ 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

  5. Ultrafiltration by a compacted clay membrane. I - Oxygen and hydrogen isotopic fractionation. II - Sodium ion exclusion at various ionic strengths.

    NASA Technical Reports Server (NTRS)

    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 0.01N NaCl forced to flow at ambient temperature under a hydraulic pressure drop of 100 bars across a montmorillonite disk compacted to a porosity of 35% by a pressure of 330 bars. The ultrafiltrates in both experiments were depleted in D by 2.5% and in O-18 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 0.01N. 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. It is shown how it is possible to proceed from the ion exchange capacity of clay minerals and, by means of the Donnan membrane equilibrium concept and the Teorell-Meyer-Siever theory, develop a theory to explain why and to what extent ultrafiltration occurs when solutions of known concentration are forced to flow through a clay membrane.

  6. Graphene can wreak havoc with cell membranes.

    PubMed

    Dallavalle, Marco; Calvaresi, Matteo; Bottoni, Andrea; Melle-Franco, Manuel; Zerbetto, Francesco

    2015-02-25

    Molecular dynamics--coarse grained to the level of hydrophobic and hydrophilic interactions--shows that small hydrophobic graphene sheets pierce through the phospholipid membrane and navigate the double layer, intermediate size sheets pierce the membrane only if a suitable geometric orientation is met, and larger sheets lie mainly flat on the top of the bilayer where they wreak havoc with the membrane and create a patch of upturned phospholipids. The effect arises in order to maximize the interaction between hydrophobic moieties and is quantitatively explained in terms of flip-flops by the analysis of the simulations. Possible severe biological consequences are discussed. PMID:25648559

  7. Enzyme Activities in Polarized Cell Membranes

    PubMed Central

    Bass, L.; McIlroy, D. K.

    1968-01-01

    The theoretical pH dependence of enzyme activities in membranes of low dielectric constant is estimated. It is shown that in biological membranes some types of enzymes may attain a limiting pH sensitivity such that an increment of only 0.2 pH unit (sufficient to induce action potentials in squid axons) causes a relative activity change of over 25%. The transients of enzyme activity generated by membrane depolarization and by pH increments in the bathing solution are discussed in relation to the transients of nervous excitation. PMID:5641405

  8. 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

  9. Sulfated Titania-Silica Reinforced Nafion Nanocomposite Membranes for Proton Exchange Membrane Fuel Cells.

    PubMed

    Abu Sayeed, M D; Kim, Hee Jin; Gopalan, A I; Kim, Young Ho; Lee, Kwang-Pill; Choi, Sang-June

    2015-09-01

    Sulfated titania-silica (SO4(2-)-/TiO2-SiO2) composites were prepared by a sol-gel method with sulfate reaction and characterized by X-ray diffraction (XRD) and energy-dispersive X-ray spectroscopy (EDS). The nanometric diameter and geometry of the sulfated titania-silica (STS) was investigated by transmission electron microscopy (TEM). A small amount of the STS composite in the range of 0.5-3 wt% was then added as reinforcing into the Nafion membrane by water-assisted solution casting method to prepare STS reinforced Nafion nanocomposite membranes (STS-Nafion nanocomposite membranes). The additional functional groups, sulfate groups, of the nanocomposite membrane having more surface oxygenated groups enhanced the fuel cell membrane properties. The STS-Nafion nanocomposite membranes exhibited improved water uptake compared to that of neat Nafion membranes, whereas methanol uptake values were decreased dramatically improved thermal property of the prepared nanocomposite membranes were measured by thermogravimetric analysis (TGA). Furthermore, increased ion exchange capacity values were obtained by thermoacidic pretreatment of the nanocomposite membranes. PMID:26716283

  10. 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

  11. Band 3 and glycophorin are progressively aggregated in density-fractionated sickle and normal red blood cells. Evidence from rotational and lateral mobility studies.

    PubMed Central

    Corbett, J D; Golan, D E

    1993-01-01

    Band 3 aggregation in the plane of the red blood cell (RBC) membrane is postulated to be important in the pathophysiology of hemolysis of dense sickle and normal RBCs. We used the fluorescence photobleaching recovery and polarized fluorescence depletion techniques to measure the lateral and rotational mobility of band 3, glycophorins, and phospholipid analogues in membranes of density-separated intact RBCs from seven patients with sickle cell disease and eight normal controls. The fractions of laterally mobile band 3 and glycophorin decreased progressively as sickle RBC density increased. Normal RBCs also showed a progressive decrease in band 3 fractional mobility with increasing buoyant density. Rapidly rotating, slowly rotating, and rotationally immobile forms of band 3 were observed in both sickle and normal RBC membranes. The fraction of rapidly rotating band 3 progressively decreased and the fraction of rotationally immobile band 3 progressively increased with increasing sickle RBC density. Changes in the fraction of rotationally immobile band 3 were not reversible upon hypotonic swelling of dense sickle RBCs, and normal RBCs osmotically shrunken in sucrose buffers failed to manifest band 3 immobilization at median cell hemoglobin concentration values characteristic of dense sickle RBCs. We conclude that dense sickle and normal RBCs acquire irreversible membrane abnormalities that cause transmembrane protein immobilization and band 3 aggregation. Band 3 aggregates could serve as cell surface sites of autologous antibody binding and thereby lead to removal of dense sickle and normal (senescent) RBCs from the circulation. PMID:8423219

  12. Cd and Hg ions stimulate cell membrane potassium conductance

    SciTech Connect

    Jungwirth, A.; Paulmichl, M.; Lang, F. )

    1989-02-09

    Intracellular microelectrodes have been applied to study the effect of cadmium (Cd) and mercury (Hg) ions on cultured renal epitheloid Madin Darby Canine Kidney (MDCK) cells. Within 10 seconds Cd and within 50 seconds Hg hyperpolarize the cell membrane from - 53 {plus minus} 1 mV to - 68 {plus minus} 1 mV and - 67 {plus minus} 1 mV, resp., increase the potassium selectivity of the cell membrane (tk) from 0.33 {plus minus} 0.02 to 0.64 {plus minus} 0.03 and 0.77 {plus minus} 0.02, resp., and reduce the apparent cell membrane resistance from 40 {plus minus} 2 MOhm to 27 {plus minus} 2 MOhm and 22 {plus minus} 2 MOhm, resp.. Thus, both, Cd and Hg hyperpolarize the cell membrane by enhancement of the potassium conductance. The concentration required to elicit half maximal hyperpolarization is some 400 nmol/1 for either, Cd or Hg. Barium (1 mmol/1) depolarizes the cell membrane to - 34 {plus minus} 1 mV and virtually abolishes tk in the absence of Cd and Hg. In the presence of barium Cd leads to a transient, Hg to a sustained reappearance of tk and hyperpolarization. Thus, the Cd induced potassium conductance is blocked by barium with delay, the Hg induced potassium conductance is insensitive to barium. Quinidine (1 mmol/1) depolarizes the cell membrane to - 3 {plus minus}1 mV and abolishes the effect of both, Cd and Hg. In the nominal absence of extracellular calcium Cd leads to transient, Hg to sustained increase of tk and hyperpolarization of the cell membrane. In conclusion, both, CD and Hg at the low concentrations encountered during Cd and Hg intoxication enhance potassium conductance of MDCK cell membranes. However, the channels activated apparently differ.

  13. Antiproliferative activity of buttermilk lipid fractions isolated using food grade and non-food grade solvents on human cancer cell lines.

    PubMed

    Castro-Gómez, Pilar; Rodríguez-Alcalá, Luis M; Monteiro, Karin M; Ruiz, Ana L T G; Carvalho, João E; Fontecha, Javier

    2016-12-01

    Buttermilk is a dairy by-product with a high content of milk fat globule membranes (MFGMs), whose protein constituents are reported to be antiproliferative. Lipids represent about half of the composition of MFGM. The aim of this study was to isolate buttermilk lipid fractions and evaluate their potential antiproliferative effect. Selective extraction with food grade or non-food grade solvents was performed. Antiproliferative effectiveness of lipid extracts and their neutral and polar fractions was evaluated on nine human cancer cell lines. Fractions obtained using food grade ethanol gave a higher yield than those obtained using non-food grade solvents, and they effectively inhibited cell viability of the cancer cell lines investigated. These fractions, rich in phospho- and sphingolipids, were strongly antiproliferative against human ovary and colon cancer cells. This observation allowed us to hypothesize further analyses aimed at promoting the use of buttermilk polar lipid fractions as functional food additives. PMID:27374586

  14. Mechanical and water sorption properties of nafion and composite nafion/titanium dioxide membranes for polymer electrolyte membrane fuel cells

    NASA Astrophysics Data System (ADS)

    Satterfield, May Barclay

    The mechanical properties of the membranes used in polymer electrolyte membrane fuel cells are important to the performance and longevity of the cell. The speed and extent of membrane water uptake depend on the membrane's viscoelastic mechanical properties, which are themselves dependent on membrane hydration, and increased hydration improves membrane proton conductivity and fuel cell performance. Membrane mechanical properties also affect durability and cell longevity, preventing membrane failure from stresses induced by changing temperature and water content during operational cycling. Further, membrane creep and stress-relaxation can change the extent of membrane/electrode contact, also changing cell behavior. New composite membrane materials have exhibited superior performance in fuel cells, and it is suspected that improved mechanical properties are responsible. Studies of polymer electrolyte membrane (PEM) fuel cell dynamics using Nafion membranes have demonstrated the importance of membrane mechanical properties, swelling and water-absorption behavior to cell performance. Nonlinear and delayed dynamic responses to changing operating parameters were unexpected, but reminiscent of polymer viscoelastic behavior and water sorption dynamics, illustrating the need to better understand membrane properties to design and operate fuel cells. Further, Nafion/TiO2 composite membranes developed by the Princeton Chemistry Department improve fuel cell performance, which may be due to changes in membrane microstructure and enhanced mechanical properties. Mechanical properties, stress-relaxation behavior, water sorption and desorption rates and pressures exerted during hydration by a confined membrane have been measured for Nafion and for Nafion/TiO2 composite membranes. Mechanical properties, including the Young's modulus and limits of elastic deformation are dependent on temperature and membrane water content. The Young's modulus decreases with increasing water content and

  15. Adipocyte cell size enlargement involves plasma membrane area increase.

    PubMed

    Chowdhury, H H; Zorec, R

    2012-07-01

    The adipocyte enlargement is associated with an increase in the cytoplasmic lipid content, but how the plasma membrane area follows this increase is poorly understood. We monitored single-cell membrane surface area fluctuations, which mirror the dynamics of exocytosis and endocytosis. We employed the patch-clamp technique to measure membrane capacitance (C(m)), a parameter linearly related to the plasma membrane area. Specifically, we studied whether insulin affects membrane area dynamics in adipocytes. A five-minute cell exposure to insulin increased resting C(m) by 12 ± 4%; in controls the change in C(m) was not different from zero. We measured cell diameter of isolated rat adipocytes microscopically. Twenty-four hour exposure of cells to insulin resulted in a significant increase in cell diameter by 5.1 ± 0.6%. We conclude that insulin induces membrane area increase, which may in chronic hyperinsulinemia promote the enlargement of plasma membrane area, acting in concert with other insulin-mediated metabolic effects on adipocytes. PMID:22540353

  16. Selectivity of biopolymer membranes using HepG2 cells

    PubMed Central

    Lü, Dongyuan; Gao, Yuxin; Luo, Chunhua; Lü, Shouqian; Wang, Qian; Xu, Xianghong; Sun, Shujin; Wang, Chengzhi; Long, Mian

    2015-01-01

    Bioartificial liver (BAL) system has emerged as an alternative treatment to bridge acute liver failure to either liver transplantation or liver regeneration. One of the main reasons that the efficacy of the current BAL systems was not convincing in clinical trials is attributed to the lack of friendly interface between the membrane and the hepatocytes in liver bioreactor, the core unit of BAL system. Here, we systematically compared the biological responses of hepatosarcoma HepG2 cells seeded on eight, commercially available biocompatible membranes made of acetyl cellulose-nitrocellulose mixed cellulose (CA-NC), acetyl cellulose (CA), nylon (JN), polypropylene (PP), nitrocellulose (NC), polyvinylidene fluoride (PVDF), polycarbonate (PC) and polytetrafluoroethylene (PTFE). Physicochemical analysis and mechanical tests indicated that CA, JN and PP membranes yield high adhesivity and reasonable compressive and/or tensile features with friendly surface topography for cell seeding. Cells prefer to adhere on CA, JN, PP or PTFE membranes with high proliferation rate in spheriod-like shape. Actin, albumin and cytokeratin 18 expressions are favorable for cells on CA or PP membrane, whereas protein filtration is consistent among all the eight membranes. These results further the understandings of cell growth, morphology and spreading, as well as protein filtration on distinct membranes in designing a liver bioreactor. PMID:26816630

  17. 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.

  18. 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.

  19. Membrane stress increases cation permeability in red cells.

    PubMed

    Johnson, R M

    1994-11-01

    The human red cell is known to increase its cation permeability when deformed by mechanical forces. Light-scattering measurements were used to quantitate the cell deformation, as ellipticity under shear. Permeability to sodium and potassium was not proportional to the cell deformation. An ellipticity of 0.75 was required to increase the permeability of the membrane to cations, and flux thereafter increased rapidly as the limits of cell extension were reached. Induction of membrane curvature by chemical agents also did not increase cation permeability. These results indicate that membrane deformation per se does not increase permeability, and that membrane tension is the effector for increased cation permeability. This may be relevant to some cation permeabilities observed by patch clamping. PMID:7858123

  20. Dynamics of cell membrane permeability changes at supraphysiological temperatures.

    PubMed Central

    Bischof, J C; Padanilam, J; Holmes, W H; Ezzell, R M; Lee, R C; Tompkins, R G; Yarmush, M L; Toner, M

    1995-01-01

    A quantitative fluorescent microscopy system was developed to characterize, in real time, the effects of supraphysiological temperatures between 37 degrees and 70 degrees C on the plasma membrane of mouse 3T3 fibroblasts and isolated rat skeletal muscle cells. Membrane permeability was assessed by monitoring the leakage as a function of time of the fluorescent membrane integrity probe calcein. The kinetics of dye leakage increased with increasing temperature in both the 3T3 fibroblasts and the skeletal muscle cells. Analytical solutions derived from a two-compartment transport model showed that, for both cell types, a time-dependent permeability assumption provided a statistically better fit of the model predictions to the data than a constant permeability assumption. This finding suggests that the plasma membrane integrity is continuously being compromised while cells are subjected to supraphysiological temperatures. Images FIGURE 1 FIGURE 2 FIGURE 3 PMID:7647264

  1. 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.

  2. Substrate hydrophobicity and cell composition influence the extent of rate limitation and masking of isotope fractionation during microbial reductive dehalogenation of chlorinated ethenes.

    PubMed

    Renpenning, Julian; Rapp, Insa; Nijenhuis, Ivonne

    2015-04-01

    This study investigated the effect of intracellular microscale mass transfer on microbial carbon isotope fractionation of tetrachloroethene (PCE) and trichloroethene (TCE). Significantly stronger isotope fractionation was observed for crude extracts vs intact cells of Sulfurospirillum multivorans, Geobacter lovleyi, Desulfuromonas michiganensis, Desulfitobacterium hafniense strain PCE-S, and Dehalobacter restrictus. Furthermore, carbon stable isotope fractionation was stronger for microorganisms with a Gram-positive cell envelope compared to those with a Gram-negative cell envelope. Significant differences were observed between model organisms in cellular sorption capacity for PCE (S. multivorans-K(d-PCE) = 0.42-0.51 L g(-1); D. hafniense-K(d-PCE) = 0.13 L g(-1)), as well as in envelope hydrophobicity (S. multivorans 33.0° to 72.2°; D. hafniense 59.1° to 60.8°) when previously cultivated with fumarate or PCE as electron acceptor, but not for TCE. Cell envelope properties and the tetrachloroethene reductive dehalogenase (PceA-RDase) localization did not result in significant effects on observed isotope fractionation of TCE. For PCE, however, systematic masking of isotope effects as a result of microscale mass transfer limitation at microbial membranes was observed, with carbon isotope enrichment factors of -2.2‰, -1.5 to -1.6‰, and -1.0‰ (CI95% < ± 0.2‰) for no membrane, hydrophilic outer membrane, and outer + cytoplasmic membrane, respectively. Conclusively, rate-limiting mass transfer barriers were (a) the outer membrane or cell wall and (b) the cytoplasmic membrane in case of a cytoplasmic location of the RDase enzyme. Overall, our results indicate that masking of isotope fractionation is determined by (1) hydrophobicity of the degraded compound, (2) properties of the cell envelope, and (3) the localization of the reacting enzyme. PMID:25734359

  3. Membrane Protein Mobility and Orientation Preserved in Supported Bilayers Created Directly from Cell Plasma Membrane Blebs.

    PubMed

    Richards, Mark J; Hsia, Chih-Yun; Singh, Rohit R; Haider, Huma; Kumpf, Julia; Kawate, Toshimitsu; Daniel, Susan

    2016-03-29

    Membrane protein interactions with lipids are crucial for their native biological behavior, yet traditional characterization methods are often carried out on purified protein in the absence of lipids. We present a simple method to transfer membrane proteins expressed in mammalian cells to an assay-friendly, cushioned, supported lipid bilayer platform using cell blebs as an intermediate. Cell blebs, expressing either GPI-linked yellow fluorescent proteins or neon-green fused transmembrane P2X2 receptors, were induced to rupture on glass surfaces using PEGylated lipid vesicles, which resulted in planar supported membranes with over 50% mobility for multipass transmembrane proteins and over 90% for GPI-linked proteins. Fluorescent proteins were tracked, and their diffusion in supported bilayers characterized, using single molecule tracking and moment scaling spectrum (MSS) analysis. Diffusion was characterized for individual proteins as either free or confined, revealing details of the local lipid membrane heterogeneity surrounding the protein. A particularly useful result of our bilayer formation process is the protein orientation in the supported planar bilayer. For both the GPI-linked and transmembrane proteins used here, an enzymatic assay revealed that protein orientation in the planar bilayer results in the extracellular domains facing toward the bulk, and that the dominant mode of bleb rupture is via the "parachute" mechanism. Mobility, orientation, and preservation of the native lipid environment of the proteins using cell blebs offers advantages over proteoliposome reconstitution or disrupted cell membrane preparations, which necessarily result in significant scrambling of protein orientation and typically immobilized membrane proteins in SLBs. The bleb-based bilayer platform presented here is an important step toward integrating membrane proteomic studies on chip, especially for future studies aimed at understanding fundamental effects of lipid interactions

  4. Evaluation of composite membranes for direct methanol fuel cells

    NASA Astrophysics Data System (ADS)

    Li, X.; Roberts, E. P. L.; Holmes, S. M.

    The performance of direct methanol fuel cells (DMFCs) can be significantly affected by the transport of methanol through the membrane, depolarising the cathode. In this paper, the literature on composite membranes that have been developed for reduction of methanol crossover in DMFCs is reviewed. While such membranes can be effective in reducing methanol permeability, this is usually combined with a reduction in proton conductivity. Measurements of methanol permeability and proton conductivity are relatively straightforward, and these parameters (or a membrane 'selectivity' based on the ratio between them) are often used to characterize DMFC membranes. However, we have carried out one-dimensional simulations of DMFC performance for a wide range of membrane properties, and the results indicate that DMFC performance is normally either limited by methanol permeability or proton conductivity. Thus use of a 'selectivity' is not appropriate for comparison of membrane materials, and results from the model can be used to compare different membranes. The results also show that Nafion ® 117 has an optimum thickness, where DMFC performance is equally limited by both methanol permeability and proton conductivity. The model also indicates that new composite membranes based on Nafion ® can only offer significant improvement in DMFC performance by enabling operation with increased methanol concentration in the fuel. A number of composite membrane materials that have been reported in the literature are shown to deliver significant reduction in DMFC performance due to reduced proton conductivity, although improved performance at high methanol concentration may be possible.

  5. Membrane Composition Tunes the Outer Hair Cell Motor

    NASA Astrophysics Data System (ADS)

    Rajagopalan, L.; Sfondouris, J.; Oghalai, J. S.; Pereira, F. A.; Brownell, W. E.

    2009-02-01

    Cholesterol and docosahexaenoic acid (DHA), an ω-3 fatty acid, affect membrane mechanical properties in different ways and modulate the function of membrane proteins. We have probed the functional consequence of altering cholesterol and DHA levels in the membranes of OHCs and prestin expressing HEK cells. Large, dynamic and reversible changes in prestin-associated charge movement and OHC motor activity result from altering the concentration of membrane cholesterol. Increasing membrane cholesterol shifts the q/V function ~ 50 mV in the hyperpolarizing direction, possibly a response related to increases in membrane stiffness. The voltage shift is linearly related to total membrane cholesterol. Increasing cholesterol also decreases the total charge moved in a linear fashion. Decreasing membrane cholesterol shifts the q/V function ~ 50 mV in the depolarizing direction with little or no effect on the amount of charge moved. In vivo increases in membrane cholesterol transiently increase but ultimately lead to decreases in DPOAE. Docosahexaenoic acid shifts the q/V function in the hyperpolarizing direction < 15 mV and increases total charge moved. Tuning of cochlear function by membrane cholesterol contributes to the exquisite temporal and frequency processing of mammalian hearing by optimizing the cochlear amplifier.

  6. Methanotroph outer membrane preparation.

    PubMed

    Karlsen, Odd A; Berven, Frode S; Jensen, Harald B; Fjellbirkeland, Anne

    2011-01-01

    All presently known methanotrophs are gram-negative bacteria suggesting that they are surrounded by a two-layered membrane: an inner or cytoplasmic membrane and an outer membrane. In the methanotroph Methylococcus capsulatus (Bath), separation of the two membranes has allowed studies on protein and lipid composition of the outer membrane. Its outer membrane can be isolated from purified cell envelopes by selective solubilization of the inner membranes with the detergent Triton X-100. The proteins associated with the outer membrane can further be fractionated into integral and tightly associated proteins and peripheral loosely associated proteins. We present here protocols for this fractionation and show how the proteins associated with the outer leaflet of the outer membrane can be isolated and identified by whole-cell biotin surface labeling. PMID:21419921

  7. Purification and characterization of thiol-reagent-sensitive glycerol-3-phosphate acyltransferase from the membrane fraction of an oleaginous fungus.

    PubMed Central

    Mishra, S; Kamisaka, Y

    2001-01-01

    Glycerol-3-phosphate acyltransferase (GPAT), responsible for the first committed, rate-limiting, step of glycerolipid synthesis, was purified to homogeneity from the membrane fraction of an oleaginous fungus, Mortierella ramanniana var. angulispora. The enzyme was solubilized from the membrane fraction by pretreatment with 0.05% Triton X-100 and treatment of the resulting pellet with 0.3% Triton X-100. The enzyme was subsequently purified by column chromatography on heparin-Sepharose, Yellow 86 agarose, a second heparin-Sepharose column, Superdex-200 and hydroxylapatite Bio-Gel. Enzyme activity was finally enriched 1308-fold over that of the starting membrane fraction. SDS/PAGE of the purified fraction revealed a single band with a molecular mass of 45 kDa. Native PAGE showed a major band that corresponded to GPAT activity. Enzyme activity was inhibited by thiol reagents, suggesting that it originated from microsomes rather than mitochondria. Purified GPAT depended on exogenous oleoyl-CoA and sn-glycerol-3-phosphate, with the highest activity at approx. 50 and 250 microM, respectively, and preferred oleoyl-CoA 5.4-fold over palmitoyl-CoA as an acyl donor. Anionic phospholipids, such as phosphatidic acid and phosphatidylserine, were absolutely required for activity of the purified enzyme, and their ability to activate GPAT was influenced by the purity of the GPAT preparation. Bivalent cations, such as Mg(2+) and Ca(2+), inhibited purified GPAT activity, whereas 5 mM Mn(2+) elevated activity approx. 2-fold. These results provide new insights into the molecular characterization of microsomal GPAT, which has not been well characterized compared with mitochondrial and plastidic GPAT. PMID:11284717

  8. Optimization of protein fractionation by skim milk microfiltration: Choice of ceramic membrane pore size and filtration temperature.

    PubMed

    Jørgensen, Camilla Elise; Abrahamsen, Roger K; Rukke, Elling-Olav; Johansen, Anne-Grethe; Schüller, Reidar B; Skeie, Siv B

    2016-08-01

    The objective of this study was to investigate how ceramic membrane pore size and filtration temperature influence the protein fractionation of skim milk by cross flow microfiltration (MF). Microfiltration was performed at a uniform transmembrane pressure with constant permeate flux to a volume concentration factor of 2.5. Three different membrane pore sizes, 0.05, 0.10, and 0.20µm, were used at a filtration temperature of 50°C. Furthermore, at pore size 0.10µm, 2 different filtration temperatures were investigated: 50 and 60°C. The transmission of proteins increased with increasing pore size, giving the permeate from MF with the 0.20-µm membrane a significantly higher concentration of native whey proteins compared with the permeates from the 0.05- and 0.10-µm membranes (0.50, 0.24, and 0.39%, respectively). Significant amounts of caseins permeated the 0.20-µm membrane (1.4%), giving a permeate with a whitish appearance and a casein distribution (αS2-CN: αS1-CN: κ-CN: β-CN) similar to that of skim milk. The 0.05- and 0.10-µm membranes were able to retain all caseins (only negligible amounts were detected). A permeate free from casein is beneficial in the production of native whey protein concentrates and in applications where transparency is an important functional characteristic. Microfiltration of skim milk at 50°C with the 0.10-µm membrane resulted in a permeate containing significantly more native whey proteins than the permeate from MF at 60°C. The more rapid increase in transmembrane pressure and the significantly lower concentration of caseins in the retentate at 60°C indicated that a higher concentration of caseins deposited on the membrane, and consequently reduced the native whey protein transmission. Optimal protein fractionation of skim milk into a casein-rich retentate and a permeate with native whey proteins were obtained by 0.10-µm MF at 50°C. PMID:27265169

  9. Controlled permeation of cell membrane by single bubble acoustic cavitation.

    PubMed

    Zhou, Y; Yang, K; Cui, J; Ye, J Y; Deng, C X

    2012-01-10

    Sonoporation is the membrane disruption generated by ultrasound and has been exploited as a non-viral strategy for drug and gene delivery. Acoustic cavitation of microbubbles has been recognized to play an important role in sonoporation. However, due to the lack of adequate techniques for precise control of cavitation activities and real-time assessment of the resulting sub-micron process of sonoporation, limited knowledge has been available regarding the detail processes and correlation of cavitation with membrane disruption at the single cell level. In the current study, we developed a combined approach including optical, acoustical, and electrophysiological techniques to enable synchronized manipulation, imaging, and measurement of cavitation of single bubbles and the resulting cell membrane disruption in real-time. Using a self-focused femtosecond laser and high frequency ultrasound (7.44MHz) pulses, a single microbubble was generated and positioned at a desired distance from the membrane of a Xenopus oocyte. Cavitation of the bubble was achieved by applying a low frequency (1.5MHz) ultrasound pulse (duration 13.3 or 40μs) to induce bubble collapse. Disruption of the cell membrane was assessed by the increase in the transmembrane current (TMC) of the cell under voltage clamp. Simultaneous high-speed bright field imaging of cavitation and measurements of the TMC were obtained to correlate the ultrasound-generated bubble activities with the cell membrane poration. The change in membrane permeability was directly associated with the formation of a sub-micrometer pore from a local membrane rupture generated by bubble collapse or bubble compression depending on ultrasound amplitude and duration. The impact of the bubble collapse on membrane permeation decreased rapidly with increasing distance (D) between the bubble (diameter d) and the cell membrane. The effective range of cavitation impact on membrane poration was determined to be D/d=0.75. The maximum mean

  10. Spray deposition of Nafion membranes: Electrode-supported fuel cells

    NASA Astrophysics Data System (ADS)

    Bayer, Thomas; Pham, Hung Cuong; Sasaki, Kazunari; Lyth, Stephen Matthew

    2016-09-01

    Fuel cells are a key technology for the successful transition towards a hydrogen society. In order to accelerate fuel cell commercialization, improvements in performance are required. Generally, polymer electrolyte membrane fuel cells (PEFCs) are membrane-supported; the electrocatalyst layer is sprayed onto both sides of the membrane, and sandwiched between carbon-based gas diffusion layers (GDLs). In this work we redesign the membrane electrode assembly (MEA) and fabricate an electrode-supported PEFC. First the electrocatalyst layer is sprayed onto the GDL, and then Nafion dispersion is sprayed over the top of this to form a thin membrane. This method has the advantage of simplifying the fabrication process, allowing the fabrication of extremely thin electrolyte layers (down to ∼10 μm in this case), and reducing the amount of ionomer required in the cell. Electrode-supported PEFCs operate at significantly increased power density compared to conventional membrane-supported PEFCs, with a maximum of 581 mW/cm2 at 80 °C (atmospheric pressure, air at the cathode). Impedance spectroscopy confirmed that the origin of the improved performance was an 80% reduction in the membrane resistance due the thinner Nafion layer. This novel fabrication method is a step towards cheaper, thinner, fully printable PEFCs with high power density and efficiency.

  11. 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.

  12. 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 prm1Δ 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 prm1Δ 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 prm1Δ nor prm1Δ dniΔ 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, prm1Δ, and dni1Δ 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

  13. Protein diffusion in plant cell plasma membranes: the cell-wall corral

    PubMed Central

    Martinière, Alexandre; Runions, John

    2013-01-01

    Studying protein diffusion informs us about how proteins interact with their environment. Work on protein diffusion over the last several decades has illustrated the complex nature of biological lipid bilayers. The plasma membrane contains an array of membrane-spanning proteins or proteins with peripheral membrane associations. Maintenance of plasma membrane microstructure can be via physical features that provide intrinsic ordering such as lipid microdomains, or from membrane-associated structures such as the cytoskeleton. Recent evidence indicates, that in the case of plant cells, the cell wall seems to be a major player in maintaining plasma membrane microstructure. This interconnection / interaction between cell-wall and plasma membrane proteins most likely plays an important role in signal transduction, cell growth, and cell physiological responses to the environment. PMID:24381579

  14. 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.

  15. Why can hydrogen sulfide permeate cell membranes?

    PubMed

    Riahi, Saleh; Rowley, Christopher N

    2014-10-29

    The high membrane permeability of H2S was studied using polarizable molecular dynamics simulations of a DPPC lipid bilayer. The solubility-diffusion model predicts permeability coefficients of H2S and H2O that are in good agreement with experiment. The computed diffusion coefficient profile shows H2S to diffuse at a lower rate than H2O, but the barrier for H2S permeation on the Gibbs energy profile is negligible. The hydrophobicity of H2S allows it to partition into the paraffinic interior of the membrane readily. PMID:25323018

  16. Cytotoxicity of bovine and porcine collagen membranes in mononuclear cells.

    PubMed

    Moura, Camilla Christian Gomes; Soares, Priscilla Barbosa Ferreira; Carneiro, Karine Fernandes; Souza, Maria Aparecida de; Magalhães, Denildo

    2012-01-01

    This study compared the cytotoxicity and the release of nitric oxide induced by collagen membranes in human mononuclear cells. Peripheral blood was collected from each patient and the separation of mononuclear cells was performed by Ficoll. Then, 2x10(5) cells were plated in 48-well culture plates under the membranes in triplicate. The polystyrene surface was used as negative control. Cell viability was assessed by measuring mitochondrial activity (MTT) at 4, 12 and 24 h, with dosage levels of nitrite by the Griess method for the same periods. Data had non-normal distribution and were analyzed by the Kruskal-Wallis test (p<0.05). Statistically significant differences (p<0.05) were observed between the membranes and the control in the experimental period, although there was a significant reduction in viability over time (p<0.01). At 4 and 12 h, the porcine membrane induced a higher release of nitrite compared with the control and bovine membrane, respectively (p<0.01), and this difference was maintained at 24 h (p<0.05). This in vitro study showed that the porcine collagen membrane induces an increased production of proinflammatory mediators by mononuclear cells in the first hours of contact, decreasing with time. PMID:22460313

  17. Membrane trafficking and osmotically induced volume changes in guard cells.

    PubMed

    Shope, Joseph C; Mott, Keith A

    2006-01-01

    Guard cells rapidly adjust their plasma membrane surface area while responding to osmotically induced volume changes. Previous studies have shown that this process is associated with membrane internalization and remobilization. To investigate how guard cells maintain membrane integrity during rapid volume changes, the effects of two membrane trafficking inhibitors on the response of intact guard cells of Vicia faba to osmotic treatments were studied. Using confocal microscopy and epidermal peels, the relationship between the area of a medial paradermal guard-cell section and guard-cell volume was determined. This allowed estimates of guard-cell volume to be made from single paradermal confocal images, and therefore allowed rapid determination of volume as cells responded to osmotic treatments. Volume changes in control cells showed exponential kinetics, and it was possible to calculate an apparent value for guard-cell hydraulic conductivity from these kinetics. Wortmannin and cytochalasin D inhibited the rate of volume loss following a 0-1.5 MPa osmotic treatment. Cytochalasin D also inhibited volume increases following a change from 1.5 MPa to 0 MPa, but wortmannin had no effect. Previous studies showing that treatment with arabinanase inhibits changes in guard-cell volume in response to osmotic treatments were confirmed. However, pressure volume curves show that the effects of arabinanase and the cytochalasin D were not due to changes in cell wall elasticity. It is suggested that arabinanase, cytochalasin D, and wortmannin cause reductions in the hydraulic conductivity of the plasma membrane, possibly via gating of aquaporins. A possible role for aquaporins in co-ordinating volume changes with membrane trafficking is discussed. PMID:17088361

  18. 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.

  19. How Leucocyte Cell Membrane Modified Janus Microcapsules are Phagocytosed by Cancer Cells.

    PubMed

    He, Wenping; Frueh, Johannes; Wu, Zhenwei; He, Qiang

    2016-02-01

    Modern drug delivery systems rely on either antibody-based single-surface recognition or on surface-hydrophobicity-based approaches. For a tumor showing various surface mutations, both approaches fail. This publication hereby presents Janus capsules based on polyelectrolyte multilayer microcapsules exhibiting human leucocyte (THP-1 cell line) cell membranes for discriminating HUVEC cells from three different cancer cell lines. Despite destroying the cellular integrity of leucocyte cells, the modified Janus capsules are able to adhere to cancer cells. Leucocyte cell-membrane-coated Janus capsules are phagocytosed with the cellular membrane part pointing to the cells. PMID:26824329

  20. A Journey of Cytolethal Distending Toxins through Cell Membranes

    PubMed Central

    Boesze-Battaglia, Kathleen; Alexander, Desiree; Dlakić, Mensur; Shenker, Bruce J.

    2016-01-01

    The multifunctional role of lipids as structural components of membranes, signaling molecules, and metabolic substrates makes them an ideal partner for pathogens to hijack host cell processes for their own survival. The properties and composition of unique membrane micro-domains such as membrane rafts make these regions a natural target for pathogens as it affords them an opportunity to hijack cell signaling and intracellular trafficking pathways. Cytolethal distending toxins (Cdts), members of the AB2 family of toxins are comprised of three subunits, the active, CdtB unit, and the binding, CdtA-CdtC unit. Cdts are cyclomodulins leading to cell cycle arrest and apoptosis in a wide variety of cell types. Cdts from several species share a requirement for membrane rafts, and often cholesterol specifically for cell binding and CdtB mediated cytotoxicity. In this review we focus on how host–cell membrane bilayer organization contributes to the cell surface association, internalization, and action of bacteria derived cytolethal distending toxins (Cdts), with an emphasis on Aggregatibacter actinomycetemcomitans Cdt. PMID:27559534

  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. A new class of partially fluorinated fuel cell membranes

    SciTech Connect

    Buechi, F.N.; Gupta, B.; Halim, J.; Haas, O.; Scherer, G.G.

    1994-12-31

    A series of differently crosslinked FEP-g-polystyrene proton exchange membranes has been synthesized by the pre-irradiation grafting method. Divinylbenzene (DVB) and/or triallyl cyanurate (TAC) were used as crosslinkers in the membranes. It was found, that the physical properties of the membranes, such as water-uptake and specific resistance are strongly influenced by the nature of the crosslinker. Generally it can be stated, that DVB decreases water-uptake and increases specific resistance, on the other hand TAC increases swelling and decreases specific resistance to values as low as 5.0 {Omega}cm at 60 C. The membranes were tested in H{sub 2}/O{sub 2} fuel cells for stability and performance. It was found, that thick (170 {mu}m) DBV crosslinked membranes showed stable operation for 1,400 hours at temperatures up to 80 C. The highest power density in the fuel cell was found for the DVB and TAC double crosslinked membrane, it exceeded the value of a cell with a Nafion{reg_sign} 117 membrane by more than 60%.

  3. 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.

  4. 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.

    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.

  5. 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.

  6. 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.

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

    PubMed Central

    Bureau, Thomas E.; Brown, R. Malcolm

    1987-01-01

    The cytoplasmic and outer membranes of Acetobacter xylinum (ATCC 53582) were isolated by discontinuous sucrose density ultracentrifugation. Both lysozyme (EC 3.2.1.17) and trypsin (EC 3.4.21.4) 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 (UDP-glucose:1,4-β-D-glucan 4-β-D-glucosyltransferase; EC 2.4.1.12) activity was assayed as the conversion of radioactivity from UDP-[14C]glucose into an alkali-insoluble β-1,4-D-[14C]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. Images PMID:16593877

  8. Detection of cytoplasmic and surface membrane markers in cells of some human hematopoietic cell lines.

    PubMed

    Koníková, E; Babusíková, O; Kusenda, J; Glasová, M

    1992-01-01

    The cells of some human leukemia-lymphoma T cell lines (JURKAT, MOLT4), B cell lines (DAUDI, U-266) and of myeloid U-937 cell line were characterized for their surface membrane and cytoplasmic marker profiles. The usefulness of some fixation and permeabilization methods of cell membrane for detection of cytoplasmic markers by flow cytometry was studied. The methods of cell fixation in suspension were found to be more sensitive than the methods of cell fixation in smears. With the very short buffered formaldehyde-acetone (BFA) fixation used in this study an optimal penetration of the monoclonal antibodies (MoAbs) through the plasma membrane and specific binding to the appropriate structures were achieved. CD22 antigen was detected in cytoplasm but not on membrane of DAUDI cells. In another B cell line, U-266, CD22 antigen was present both in cell membrane and cytoplasm. The marker corresponding to anti-CD19 MoAb was detected in cytoplasm but was absent on membrane of U-266 cells. Furthermore, the antigen estimated by anti-CD3 MoAb could be detected intracellularly in cells of both T cell lines tested, while it was absent on cell membrane of these cells. The phenotypic study of U-937 cells showed that the majority of cells expressed myeloid associated antigens. In our study the CD14 marker detected on cell surface membrane of U-937 cells was missing in their cytoplasm. The surface antigens remained intact after BFA fixation enabling a simultaneous detection of membrane and cytoplasmic markers in double immunofluorescence studies. Through this combination of markers minor cell populations could be detected. Human hematopoietic cell lines could serve as a reliable model system for a rapid and quantitative immunodiagnosis. PMID:1491722

  9. Bioassay-Guided Fractionation and In Vitro Antiproliferative Effects of Fractions of Artemisia nilagirica on THP-1 cell line.

    PubMed

    Gul, Mir Zahoor; Chandrasekaran, Sambamurthy; K, Manjulatha; Bhat, Mohd Yasin; Maurya, Radheshyam; Qureshi, Insaf Ahmed; Ghazi, Irfan Ahmad

    2016-10-01

    ABSTACT Artemisia nilagirica (Clarke) is a widely used medicinal herb in Indian traditional system of medicine. Therefore, the present study was designed to evaluate the effects of A. nilagirica extracts/fractions on inhibition of proliferation and apoptosis in a human monocytic leukemia (THP-1) cell line. The crude extracts (A. nilagirica ethyl acetate extract [ANE] and A. nilagirica methanolic extract [ANA]) showed cytotoxic activity toward THP-1 cells with the IC50 values of 38.21 ± 7.37 and 132.41 ± 7.19 µg/ml, respectively. However, the cytotoxic activity of active fractions (ANE-B and ANM-9) obtained after column chromatography was found to be much more pronounced than their parent extracts. The IC50 values of ANE-B and ANM-9 were found to be 27.04 ± 2.54 µg/ml and 12.70 ± 4.79 µg/ml, respectively, suggesting greater susceptibility of the malignant cells. Cell cycle analysis and terminal deoxynucleotidyl transferase (TdT)-mediated dUTP nick-end-labeling (TUNEL) assay revealed that inhibition of cell growth by A. nilagirica fractions on THP-1 cells was mediated by apoptosis. Active fractions of A. nilagirica increased the expression levels of caspase-3, -7, and poly-ADP-ribose polymerase (PARP), a critical member of the apoptotic pathway. These results suggested that active fractions of A. nilagirica may play a promising role in growth suppression by inducing apoptosis in human monocytic leukemic cells via mitochondria-dependent and death receptor-dependent apoptotic pathways. PMID:27618154

  10. Calcium movements across the membrane of human red cells

    PubMed Central

    Schatzmann, H. J.; Vincenzi, F. F.

    1969-01-01

    1. A study has been made of the cellular content and movement of Ca across the membrane of human red blood cells. 2. The [Ca] in the cellular contents of fresh red cells is 4·09 × 10-2 mM. The intracellular concentration of free ionic Ca ([Ca2+]) is considered to be less than this value and therefore less than extracellular [Ca2+] under normal conditions. 3. Observation of unidirectional Ca fluxes with 45Ca confirms previous reports of low permeability of the red cell membrane for Ca. After nearly 1 week of loading in the cold, intracellular 45Ca content is 1·8% of extracellular 45Ca content. Appearance in extracellular fluid of 45Ca from coldloaded cells can be considered to arise from two compartments. Efflux of 45Ca from the `slower compartment' is accelerated by the addition of glucose. 4. Starved red cells, incubated at 37° C, after reversible haemolysis for loading with Ca and Mg-ATP, exhibit an outward net transport of Ca against an electrochemical gradient. The transport is associated with the appearance of inorganic phosphate (Pi). Cells treated similarly, but without ATP show no transport and no appearance of Pi. 5. During the initial phase of transport, 1·3 mole Pi appear per mole Ca transported. 6. The transport of Ca from ATP-loaded cells is highly temperature-dependent, with a Q10 of 3·5. 7. Cell membrane adenosine triphosphatase (ATPase) activity of reversibly haemolysed cells is stimulated only by intracellular, and not by extracellular Ca. 8. Neither Ca transport in reversibly haemolysed cells, nor the Ca-Mg activated ATPase of isolated cell membranes is sensitive to Na, K, ouabain or oligomycin. 9. Mg is not transported under the conditions which reveal Ca transport, but Mg appears to be necessary for Ca transport. 10. Sr is transported from reversibly haemolysed Mg-ATP-loaded cells. Sr also can substitute for Ca, but not for Mg, in the activation of membrane ATPase. 11. It is concluded that, in addition to a low passive permeability, an

  11. Molecular interactions between gold nanoparticles and model cell membranes.

    PubMed

    Hu, Peipei; Zhang, Xiaoxian; Zhang, Chi; Chen, Zhan

    2015-04-21

    The interactions between nanoparticles (NPs) and cells are of huge interest because NPs have been extensively researched for biomedical applications. For the cellular entry of NPs, it remains unclear how the cell membrane molecules respond to the exposure of NPs due to a lack of appropriate surface/interface-sensitive techniques to study NP-cell membrane interactions in situ in real time. In this study, sum frequency generation (SFG) vibrational spectroscopy was employed to examine the interactions between lipid bilayers (serving as model mammalian cell membranes) and Au NPs of four different sizes with the same mass, or the same NP number, or the same NP surface area. It was found that lipid flip-flop was induced by Au NPs of all four sizes. Interestingly, the lipid flip-flop rate was found to increase as the Au NP size increased with respect to the same particle number or the same NP surface area. However, the induced lipid flip-flop rate was the same for Au NPs with different sizes with the same mass, which was interpreted by the same "effective surface contact area" between Au NPs and the model cell membrane. We believe that this study provided the first direct observation of the lipid flip-flop induced by the interactions between Au NPs and the model mammalian cell membrane. PMID:25776800

  12. Coating nanofiber scaffolds with beta cell membrane to promote cell proliferation and function

    NASA Astrophysics Data System (ADS)

    Chen, Wansong; Zhang, Qiangzhe; Luk, Brian T.; Fang, Ronnie H.; Liu, Younian; Gao, Weiwei; Zhang, Liangfang

    2016-05-01

    The cell membrane cloaking technique has emerged as an intriguing strategy in nanomaterial functionalization. Coating synthetic nanostructures with natural cell membranes bestows the nanostructures with unique cell surface antigens and functions. Previous studies have focused primarily on development of cell membrane-coated spherical nanoparticles and the uses thereof. Herein, we attempt to extend the cell membrane cloaking technique to nanofibers, a class of functional nanomaterials that are drastically different from nanoparticles in terms of dimensional and mechanophysical characteristics. Using pancreatic beta cells as a model cell line, we demonstrate successful preparation of cell membrane-coated nanofibers and validate that the modified nanofibers possess an antigenic exterior closely resembling that of the source beta cells. When such nanofiber scaffolds are used to culture beta cells, both cell proliferation rate and function are significantly enhanced. Specifically, glucose-dependent insulin secretion from the cells is increased by near five-fold compared with the same beta cells cultured in regular, unmodified nanofiber scaffolds. Overall, coating cell membranes onto nanofibers could add another dimension of flexibility and controllability in harnessing cell membrane functions and offer new opportunities for innovative applications.

  13. Coating nanofiber scaffolds with beta cell membrane to promote cell proliferation and function.

    PubMed

    Chen, Wansong; Zhang, Qiangzhe; Luk, Brian T; Fang, Ronnie H; Liu, Younian; Gao, Weiwei; Zhang, Liangfang

    2016-05-21

    The cell membrane cloaking technique has emerged as an intriguing strategy in nanomaterial functionalization. Coating synthetic nanostructures with natural cell membranes bestows the nanostructures with unique cell surface antigens and functions. Previous studies have focused primarily on development of cell membrane-coated spherical nanoparticles and the uses thereof. Herein, we attempt to extend the cell membrane cloaking technique to nanofibers, a class of functional nanomaterials that are drastically different from nanoparticles in terms of dimensional and mechanophysical characteristics. Using pancreatic beta cells as a model cell line, we demonstrate successful preparation of cell membrane-coated nanofibers and validate that the modified nanofibers possess an antigenic exterior closely resembling that of the source beta cells. When such nanofiber scaffolds are used to culture beta cells, both cell proliferation rate and function are significantly enhanced. Specifically, glucose-dependent insulin secretion from the cells is increased by near five-fold compared with the same beta cells cultured in regular, unmodified nanofiber scaffolds. Overall, coating cell membranes onto nanofibers could add another dimension of flexibility and controllability in harnessing cell membrane functions and offer new opportunities for innovative applications. PMID:27139582

  14. Inorganic fouling of an anaerobic membrane bioreactor treating leachate from the organic fraction of municipal solid waste (OFMSW) and a polishing aerobic membrane bioreactor.

    PubMed

    Trzcinski, Antoine P; Stuckey, David C

    2016-03-01

    The treatment of leachate (Average TCOD=11.97 g/L, 14.4% soluble) from the organic fraction of municipal solid waste was investigated using a Submerged Anaerobic Membrane BioReactor (SAMBR), followed by an aerobic membrane bioreactor (AMBR) to polish this effluent. This paper investigated the exact nature and composition of the inorganic precipitate in each of the reactors in the process. The flux decreased due to precipitation of calcium as monohydrocalcite (CaCO3·H2O) containing traces of metals onto the SAMBR membrane because of high CO2 partial pressures. Precipitation of calcium in the AMBR was also observed due to a higher pH. In this case, phosphorus also precipitated with calcium in two different phases: the background layer contained calcium, oxygen, carbon and small amounts of phosphorus (2-6.7%), while flakes containing calcium, oxygen and higher amounts of phosphorus (10-17%) were probably hydroxyapatite (Ca5(PO4)3OH). PMID:26771921

  15. Cell Membrane-Cloaked Nanoparticles for Targeted Therapeutics

    NASA Astrophysics Data System (ADS)

    Luk, Brian Tsengchi

    The advent of nanoparticle-based delivery systems has made a significant impact on clinical patient outcomes. In recent decades, myriad nanoparticle-based therapeutic agents have been developed for the treatment and management of ailments such as cancer, diabetes, pain, bacterial infections, and asthma, among many others. Nanotherapeutics offer many distinct advantages over conventional free drug formulations. For example, nanoparticles are able to accumulate at tumor sites by extravasation through leaky vasculature at tumor sites via the enhanced permeability and retention (EPR) effect; nanoparticles can also be tailored to have desirable characteristics, such as prolonged circulation in the blood stream, improved drug encapsulation, and sustained or triggered drug release. Currently, a growing number of nanoformulations with favorable pharmacological profiles and promising efficacy are being used in clinical trials for the treatment of various cancers. Building on the success of these encouraging clinical results, new engineering strategies have emerged that combine synthetic nanoparticles with natural biomaterials to create nature-inspired biomimetic delivery systems. The work presented in this dissertation focuses on the biointerfacing between synthetic and natural materials, namely in the manifestation of cell membrane-coated nanoparticles. By exploiting the natural functionalities of source cell membranes, cell membrane-cloaked nanoparticles have huge potential in the delivery of therapeutic agents for a variety of applications. The first portion of this thesis will focus on understanding the fundamentals underlying cell membrane coating on synthetic nanoparticles. First introduced in 2011, cell membrane-cloaked nanoparticles showed immediate promise in drug delivery applications, but further understanding was necessary to be able to harness the full potential of the membrane coating platform. The first section provides further insight into the interfacial

  16. 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.

  17. Activation of Membrane NADPH Oxidase Associated with Lysosome-Targeted Acid Sphingomyelinase in Coronary Endothelial Cells

    PubMed Central

    Bao, Jun-Xiang; Jin, Si; Zhang, Fan; Wang, Zheng-Chao; Li, Ningjun

    2010-01-01

    Abstract This study explored the mechanism mediating the aggregation of membrane NADPH oxidase (NOX) subunits and subsequent activation of this enzyme in bovine coronary arterial endothelial cells (CAECs). With confocal microscopy, we found that FasL stimulated lipid rafts (LRs) clustering with NOX subunit aggregation and acid sphingomyelinase (ASM) gathering, which was blocked by the siRNA of sortilin, an intracellular protein responsible for the binding and targeting of ASM to lysosomes. Correspondingly, FasL-induced O2·− production through NOX in LRs fractions was abolished by sortilin siRNA. Further, with flow-cytometry and fluorescence resonance energy transfer (FRET) analysis, we surprisingly demonstrated that after FasL stimulation, sortilin was exposed to cell membranes from lysosomes together with Lamp-1 and ASM, and these lysosomal components were aggregated and form a signaling complex in cell membranes. With co-immunoprecipitation, lysosomal sortilin and ASM were found to interact more strongly when CAECs were stimulated by FasL. Functionally, inhibition of either sortilin expression, lysosome function, LRs clustering, or NOX activity significantly attenuated FasL-induced decrease in nitric oxide (NO) levels. It is concluded that lysosome-targeted ASM, through sortilin, is able to traffic to and expose to cell-membrane surface, which may lead to LRs clustering and NOX activation in CAECs. Antioxid. Redox Signal. 12, 703–712. PMID:19761405

  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. Attachment of killed Mycoplasma gallisepticum cells and membranes to erythrocytes

    SciTech Connect

    Banai, M.; Kahane, I.; Feldner, J.; Razin, S.

    1981-11-01

    To correlate viability with attachment capacity, Mycoplasma gallisepticum cells harvested at different growth phases and treated by various agents were tested for their capacity to attach to human erythrocytes. The results show that viability per se is not essential for M. gallisepticum attachment to erythrocytes, as cells killed by ultraviolet irradiation and membranes isolated by lysing M. gallisepticum cells by various means retained attachment capacity. However, treatment of the mycoplasmas by protein-denaturing agents, such as heart, glutaraldehyde, or prolonged exposure to low pH, drastically affected or even abolished attachment, supporting the protein nature of the mycoplasma membrane components responsible for specific binding to the sialoglycoprotein receptors on the erythrocytes.

  20. 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

  1. Direct Cytoskeleton Forces Cause Membrane Softening in Red Blood Cells

    PubMed Central

    Rodríguez-García, Ruddi; López-Montero, Iván; Mell, Michael; Egea, Gustavo; Gov, Nir S.; Monroy, Francisco

    2015-01-01

    Erythrocytes are flexible cells specialized in the systemic transport of oxygen in vertebrates. This physiological function is connected to their outstanding ability to deform in passing through narrow capillaries. In recent years, there has been an influx of experimental evidence of enhanced cell-shape fluctuations related to metabolically driven activity of the erythroid membrane skeleton. However, no direct observation of the active cytoskeleton forces has yet been reported to our knowledge. Here, we show experimental evidence of the presence of temporally correlated forces superposed over the thermal fluctuations of the erythrocyte membrane. These forces are ATP-dependent and drive enhanced flickering motions in human erythrocytes. Theoretical analyses provide support for a direct force exerted on the membrane by the cytoskeleton nodes as pulses of well-defined average duration. In addition, such metabolically regulated active forces cause global membrane softening, a mechanical attribute related to the functional erythroid deformability. PMID:26083919

  2. 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.

  3. Endothelial monolayers on collagen-coated nanofibrous membranes: cell-cell and cell-ECM interactions.

    PubMed

    Kang, Donggu; Kim, Jeong Hwa; Jeong, Young Hun; Kwak, Jong-Young; Yoon, Sik; Jin, Songwan

    2016-06-01

    Endothelial cells (ECs) form a monolayer lining over the entire vascular wall and play an important role in maintaining vascular homeostasis and cancer metastasis. Loss of proper endothelial function can lead to vascular diseases. Therefore, the endothelial monolayer is particularly important in tissue regeneration and mimicking vascular tissue in vitro. Numerous studies have described the effects of ECs on nanofibers made from a variety of synthetic polymer materials designed to mimic the extracellular matrix (ECM). However, little is known about maintaining the integrity of ECs in in vitro systems. Here we describe polycaprolactone nanofibrous membranes coated with collagen gel that overcome many limitations of conventional nanofibers used for engineering endothelia. We investigated cell-cell and cell-ECM junctional complexes using collagen-coated and conventional nanofibrous membranes. Conventional nanofibrous membranes alone did not form a monolayer with ECs, whereas collagen-coated nanofibrous membranes did. Several concentrations of collagen in the gel coating promoted the formation of cell-cell junctional complexes, facilitated the deposition of laminin, and increased the focal contact organization of ECs. These results suggest the possible use of collagen-coated nanofibrous membranes for vascular tissue engineering applications and a vascular platform for organ-on-a-chip systems. PMID:27186924

  4. Cytotoxic effects of Kingella kingae outer membrane vesicles on human cells

    PubMed Central

    Maldonado, R; Wei, R; Kachlany, SC; Kazi, M; Balashova, NV

    2011-01-01

    Kingella kingae is an emerging pathogen causing osteoarticular infections in pediatric patients. Electron microscopy of K. kingae clinical isolates revealed the heterogeneously-sized membranous structures blebbing from the outer membrane that were classified as outer membrane vesicles (OMVs). OMVs purified from the secreted fraction of a septic arthritis K. kingae isolate were characterized. Among several major proteins, K. kingae OMVs contained virulence factors RtxA toxin and PilC2 pilus adhesin. RtxA was also found secreted as a soluble protein in the extracellular environment indicating that the bacterium may utilize different mechanisms for the toxin delivery. OMVs were shown to be hemolytic and possess some leukotoxic activity while high leukotoxicity was detected in the non-hemolytic OMV-free component of the secreted fraction. OMVs were internalized by human osteoblasts and synovial cells. Upon interaction with OMVs, the cells produced increased levels of human granulocyte-macrophage colony-stimulating factor (GM-CSF) and interleuskin 6 (IL-6) suggesting that these cytokines might be involved in the signaling response of infected joint and bone tissues during natural K. kingae infection. This study is the first report of OMV production by K. kingae and demonstrates that OMVs are a complex virulence factor of the organism causing cytolytic and inflammatory effects on host cells. PMID:21443941

  5. 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 νc(H2O) at 2000-2500 cm(-1), and the methylene symmetric stretching vibration νsym(CH2) at about 2850 cm(-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

  6. Virus and Host Mechanics Support Membrane Penetration and Cell Entry.

    PubMed

    Greber, Urs F

    2016-04-01

    Viruses are quasi-inert macromolecular assemblies. Their metastable conformation changes during entry into cells, when chemical and mechanical host cues expose viral membrane-interacting proteins. This leads to membrane rupture or fusion and genome uncoating. Importantly, virions tune their physical properties and enhance penetration and uncoating. For example, influenza virus softens at low pH to uncoat. The stiffness and pressure of adenovirus control uncoating and membrane penetration. Virus and host mechanics thus present new opportunities for antiviral therapy. PMID:26842477

  7. [Membrane permeability of brain cell processes after death].

    PubMed

    Agafonov, V A

    1975-07-01

    Experiments were conducted on rats. A study was made of persistence of semipermeability of the membranes of the cell processes of the brain (contraction) with the action of a hypertonic buffer at various periods after death. The membranes of the processes proved to retain the property of semi-permeability even 48 hours after death. Prefixation of the postmortem material in the glutaraldehyde did not influence the sensitivity of the membranes of the processes to the osmotic strength of the surrounding solution. PMID:1227661

  8. 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).

  9. 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.

  10. Cationic nanoparticles induce nanoscale disruption in living cell plasma membranes.

    PubMed

    Chen, Jiumei; Hessler, Jessica A; Putchakayala, Krishna; Panama, Brian K; Khan, Damian P; Hong, Seungpyo; Mullen, Douglas G; Dimaggio, Stassi C; Som, Abhigyan; Tew, Gregory N; Lopatin, Anatoli N; Baker, James R; Holl, Mark M Banaszak; Orr, Bradford G

    2009-08-13

    It has long been recognized that cationic nanoparticles induce cell membrane permeability. Recently, it has been found that cationic nanoparticles induce the formation and/or growth of nanoscale holes in supported lipid bilayers. In this paper, we show that noncytotoxic concentrations of cationic nanoparticles induce 30-2000 pA currents in 293A (human embryonic kidney) and KB (human epidermoid carcinoma) cells, consistent with a nanoscale defect such as a single hole or group of holes in the cell membrane ranging from 1 to 350 nm(2) in total area. Other forms of nanoscale defects, including the nanoparticle porating agents adsorbing onto or intercalating into the lipid bilayer, are also consistent; although the size of the defect must increase to account for any reduction in ion conduction, as compared to a water channel. An individual defect forming event takes 1-100 ms, while membrane resealing may occur over tens of seconds. Patch-clamp data provide direct evidence for the formation of nanoscale defects in living cell membranes. The cationic polymer data are compared and contrasted with patch-clamp data obtained for an amphiphilic phenylene ethynylene antimicrobial oligomer (AMO-3), a small molecule that is proposed to make well-defined 3.4 nm holes in lipid bilayers. Here, we observe data that are consistent with AMO-3 making approximately 3 nm holes in living cell membranes. PMID:19606833

  11. 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.

  12. Scalable nanostructured membranes for solid-oxide fuel cells

    NASA Astrophysics Data System (ADS)

    Tsuchiya, Masaru; Lai, Bo-Kuai; Ramanathan, Shriram

    2011-05-01

    The use of oxide fuel cells and other solid-state ionic devices in energy applications is limited by their requirement for elevated operating temperatures, typically above 800 °C (ref. 1). Thin-film membranes allow low-temperature operation by reducing the ohmic resistance of the electrolytes. However, although proof-of-concept thin-film devices have been demonstrated, scaling up remains a significant challenge because large-area membranes less than ~100 nm thick are susceptible to mechanical failure. Here, we report that nanoscale yttria-stabilized zirconia membranes with lateral dimensions on the scale of millimetres or centimetres can be made thermomechanically stable by depositing metallic grids on them to function as mechanical supports. We combine such a membrane with a nanostructured dense oxide cathode to make a thin-film solid-oxide fuel cell that can achieve a power density of 155 mW cm-2 at 510 °C. We also report a total power output of more than 20 mW from a single fuel-cell chip. Our large-area membranes could also be relevant to electrochemical energy applications such as gas separation, hydrogen production and permeation membranes.

  13. Dependence of synergistic fungicidal activity of Cu2+ and allicin, an allyl sulfur compound from garlic, on selective accumulation of the ion in the plasma membrane fraction via allicin-mediated phospholipid peroxidation.

    PubMed

    Ogita, Akira; Fujita, Ken-Ichi; Taniguchi, Makoto; Tanaka, Toshio

    2006-08-01

    Allicin was effective in decreasing the lethal concentration of Cu (2+) against various fungal strains including a plant pathogen, Fusarium oxysporum, so that the minimum fungicidal concentration (MFC) of the ion for the fungus could be reduced to 2 % of that detected without allicin. In Saccharomyces cerevisiae, Cu (2+) was not apparently taken up by cells when added alone at a non-lethal concentration, whereas the ion was efficiently incorporated into cells in the presence of allicin, as in the case of cells treated with the ion at a lethal concentration. Although allicin likely increased cellular permeability to Cu (2+) due to its promotive effect on plasma membrane phospholipid peroxidation, these cell-surface events did not result in endogenous reactive oxygen species (ROS) production, a typical toxic effect of the ion. Cu (2+) was detected in the cytoplasmic fraction of cells that had been treated with the ion at a lethal concentration, whereas the ion was entrapped in the plasma membrane fraction upon their treatment with the ion at a low concentration in combination with allicin. Cu (2+) could be solubilized from the plasma membrane fraction by a procedure for the extraction of hydrophobic proteins rather than the extraction of phospholipids, suggesting its complexation with a plasma membrane protein as a result of allicin treatment. Such a subcellular localization of Cu (2+) resulted in the selective leakage of intracellular K (+), but not in the disruptive damage on the plasma membrane, and was considered to underlie the synergistic fungicidal activity of Cu (2+) and allicin. PMID:16972197

  14. 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

  15. Regulation of nitrite transport in red blood cells by hemoglobin oxygen fractional saturation.

    PubMed

    Vitturi, Dario A; Teng, Xinjun; Toledo, José C; Matalon, Sadis; Lancaster, Jack R; Patel, Rakesh P

    2009-05-01

    Allosteric regulation of nitrite reduction by deoxyhemoglobin has been proposed to mediate nitric oxide (NO) formation during hypoxia. Nitrite is predominantly an anion at physiological pH, raising questions about the mechanism by which it enters the red blood cell (RBC) and whether this is regulated and coupled to deoxyhemoglobin-mediated reduction. We tested the hypothesis that nitrite transport by RBCs is regulated by fractional saturation. Using human RBCs, nitrite consumption was faster at lower fractional saturations, consistent with faster reactions with deoxyheme. A membrane-based regulation was suggested by slower nitrite consumption with intact versus lysed RBCs. Interestingly, upon nitrite addition, intracellular nitrite concentrations attained a steady state that, despite increased rates of consumption, did not change with decreasing oxygen tensions, suggesting a deoxygenation-sensitive step that either increases nitrite import or decreases the rate of nitrite export. A role for anion exchanger (AE)-1 in the control of nitrite export was suggested by increased intracellular nitrite concentrations in RBCs treated with DIDS. Moreover, deoxygenation decreased steady-state levels of intracellular nitrite in AE-1-inhibited RBCs. Based on these data, we propose a model in which deoxyhemoglobin binding to AE-1 inhibits nitrite export under low oxygen tensions allowing for the coupling between deoxygenation and nitrite reduction to NO along the arterial-to-venous gradient. PMID:19286940

  16. Detecting protein association at the T cell plasma membrane.

    PubMed

    Baumgart, Florian; Schütz, Gerhard J

    2015-04-01

    At the moment, many models on T cell signaling rely on results obtained via rather indirect methodologies, which makes direct comparison and conclusions to the in vivo situation difficult. Recently, a variety of new imaging methods were developed, which have the potential to directly shed light onto the mysteries of protein association at the T cell membrane. While the new modalities are extremely promising, for a broad readership it may be difficult to judge the results, since technological shortcomings are not always obvious. In this review article, we put key questions on the mechanism of protein interactions in the T cell plasma membrane into relation with techniques that allow to address such questions. We discuss applicability of the techniques, their strengths and weaknesses. This article is part of a Special Issue entitled: Nanoscale membrane organisation and signalling. PMID:25300585

  17. 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.

  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. Cell Fractionation and Quantitative Analysis of HIV-1 Reverse Transcription in Target Cells

    PubMed Central

    Shah, Vaibhav B; Aiken, Christopher

    2016-01-01

    This is a protocol to detect HIV-1 reverse transcription products in cytoplasmic and nuclear fractions of cells infected with VSV-G-pseudotyped envelope-defective HIV-1. This protocol can also be extended to HIV-1 with regular envelope.

  20. 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

  1. Determination of apical membrane polarity in mammary epithelial cell cultures: The role of cell-cell, cell-substratum, and membrane-cytoskeleton interactions

    SciTech Connect

    Parry, G.; Beck, J.C.; Moss, L.; Bartley, J. ); Ojakian, G.K. )

    1990-06-01

    The membrane glycoprotein, PAS-O, is a major differentiation antigen on mammary epithelial cells and is located exclusively in the apical domain of the plasma membrane. The authors have used 734B cultured human mammary carcinoma cells as a model system to study the role of tight junctions, cell-substratum contacts, and submembranous cytoskeletal elements in restricting PAS-O to the apical membrane. Immunofluorescence and immunoelectronmicroscopy experiments demonstrated that while tight junctions demarcate PAS-O distribution in confluent cultures, apical polarity could be established at low culture densities when cells could not form tight junctions with neighboring cells. They suggest, then, that interactions between vitronectin and its receptor, are responsible for establishment of membrane domains in the absence of tight junctions. The role of cytoskeletal elements in restricting PAS-O distribution was examined by treating cultures with cytochalasin D, colchicine, or acrylamide. Cytochalasin D led to a redistribution of PAS0O while colchicine and acrylamide did not. They hypothesize that PAS-O is restricted to the apical membrane by interactions with a microfilament network and that the cytoskeletal organization is dependent upon cell-cell and cell-substratum interactions.

  2. 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

  3. 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.

  4. 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

  5. Dual network model for red blood cell membranes

    NASA Astrophysics Data System (ADS)

    Boal, David H.; Seifert, Udo; Zilker, Andreas

    1992-12-01

    A two-component network is studied by Monte Carlo simulation to model the lipid/spectrin membrane of red blood cells. The model predicts that the shear modulus decreases rapidly with the maximum length of the model spectrin and should be in the 10-7 J/m2 range for human red blood cells. A simplified model for the isolated spectrin network shows a negative Lamé coefficient λ. Transverse fluctuations of the dual membrane are found to be fluidlike over the range of wavelengths investigated.

  6. [Studies on potassium transport through glial cell membranes (author's transl)].

    PubMed

    Coles, J A; Gardner-Medwin, A R; Tsacopoulos, M

    1980-04-01

    The retina of the honeybee drone is used as a model for the study of ion movements across the membranes of the glial cells caused by changes in the extracellular potassium concentration. The values found for changes in extracellular potential suggest that at least some of the potassium that enters glial cells in an active region of tissue is associated with an efflux of potassium from parts of the glial syncytium not affected by an increase in extracellular potassium concentration. In addition, it appears that ions other than K+ cross the glial membrane. PMID:7421023

  7. 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

  8. 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 β-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 β-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 β-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 β-d-glucan had good potential for use as a prebiotic ingredient in food, as well as medicinal and pharmaceutical products. PMID:26471666

  9. New protein kinase from plasma membrane of Ehrlich ascites tumor cells activated by natural polypeptides.

    PubMed Central

    Racker, E; Abdel-Ghany, M; Sherrill, K; Riegler, C; Blair, E A

    1984-01-01

    A polypeptide-dependent protein kinase was purified about 80-fold from an extract of plasma membranes of Ehrlich ascites tumor cells. The membranes were extracted with Nonidet P-40, and the extract was purified by ammonium sulfate fractionation and hydroxylapatite and affinity chromatography. The activity was stimulated 10-fold or more by polypeptide preparations from a variety of tissues, including placenta and hypothalamus. Polypeptide-dependent protein kinase had a pH optimum of about 7.5 and required Mg2+ for activity. Mn2+ at low concentrations (200 microM) stimulated enzyme activity somewhat but inhibited activity strongly at higher concentrations. The best available substrate for polypeptide-dependent protein kinase was beta-casein, and little or no phosphorylation was observed with alpha-casein, kappa-casein, phosvitin, alpha-lactalbumin, alpha-lactoglobulin, and histone. However, several endogenous substrates from plasma membranes of Ehrlich ascites tumor cells were phosphorylated. Polypeptide-dependent protein kinase activity was not inhibited by 10 mM N-ethylmaleimide, and this resistance was useful in differentiating this protein kinase from other protein kinases that were present in crude fractions and sensitive to the inhibitor. Images PMID:6589591

  10. 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

  11. 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

  12. Membrane patterned by pulsed laser micromachining for proton exchange membrane fuel cell with sputtered ultra-low catalyst loadings

    NASA Astrophysics Data System (ADS)

    Cuynet, S.; Caillard, A.; Kaya-Boussougou, S.; Lecas, T.; Semmar, N.; Bigarré, J.; Buvat, P.; Brault, P.

    2015-12-01

    Proton exchange membranes were nano- and micro-patterned on their cathode side by pressing them against stainless steel molds previously irradiated by a Ti:Sapphire femtosecond laser. The membranes were associated to ultra-low loaded thin catalytic layers (25 μgPt cm-2) prepared by plasma magnetron sputtering. The Pt catalyst was sputtered either on the membrane or on the porous electrode. The fuel cell performance in dry conditions were found to be highly dependent on the morphology of the membrane surface. When nanometric ripples covered by a Pt catalyst were introduced on the surface of the membrane, the fuel cell outperformed the conventional one with a flat membrane. By combining nano- and micro-patterns (nanometric ripples and 11-24 μm deep craters), the performance of the cells was clearly enhanced. The maximum power density achieved by the fuel cell was multiplied by a factor of 3.6 (at 50 °C and 3 bar): 438 mW cm-2 vs 122 mW cm-2. This improvement is due to high catalyst utilization with a high membrane conductivity. When Pt is sputtered on the porous electrode (and not on the membrane), the contribution of the patterned membrane to the fuel cell efficiency was less significant, except in the presence of nanometric ripples. This result suggests that the patterning of the membrane must be consistent with the way the catalyst is synthesized, on the membrane or on the porous electrode.

  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. 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

  15. 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.

  16. Inorganic Nanoporous Membranes for Immunoisolated Cell-Based Drug Delivery

    PubMed Central

    Mendelsohn, Adam; Desai, Tejal

    2014-01-01

    Materials advances enabled by nanotechnology have brought about promising approaches to improve the encapsulation mechanism for immunoisolated cell-based drug delivery. Cell-based drug delivery is a promising treatment for many diseases but has thus far achieved only limited clinical success. Treatment of insulin dependent diabetes mellitus (IDDM) by transplantation of pancreatic β-cells represents the most anticipated application of cell-based drug delivery technology. This review outlines the challenges involved with maintaining transplanted cell viability and discusses how inorganic nanoporous membranes may be useful in achieving clinical success. PMID:20384222

  17. PIG7 promotes leukemia cell chemosensitivity via lysosomal membrane permeabilization

    PubMed Central

    Niu, Ting; Wu, Yu; Li, Jianjun; Wang, Fangfang; Zheng, Yuhuan; Liu, Ting

    2016-01-01

    PIG7 localizes to lysosomal membrane in leukemia cells. Our previous work has shown that transduction of pig7 into a series of leukemia cell lines did not result in either apoptosis or differentiation of most tested cell lines. Interestingly, it did significantly sensitize these cell lines to chemotherapeutic drugs. Here, we further investigated the mechanism underlying pig7-induced improved sensitivity of acute leukemia cells to chemotherapy. Our results demonstrated that the sensitization effect driven by exogenous pig7 was more effective in drug-resistant leukemia cell lines which had lower endogenous pig7 expression. Overexpression of pig7 did not directly activate the caspase apoptotic pathway, but decreased the lysosomal stability. The expression of pig7 resulted in lysosomal membrane permeabilization (LMP) and lysosomal protease (e.g. cathepsin B, D, L) release. Moreover, we also observed increased reactive oxygen species (ROS) and decreased mitochondrial membrane potential (ΔΨm) induced by pig7. Some autophagy markers such as LC3I/II, ATG5 and Beclin-1, and necroptosis maker MLKL were also stimulated. However, intrinsic antagonism such as serine/cysteine protease inhibitors Spi2A and Cystatin C prevented downstream effectors from triggering leukemia cells, which were only on the “verge of apoptosis”. When combined with chemotherapy, LMP increased and more proteases were released. Once this process was beyond the limit of intrinsic antagonism, it induced programmed cell death cooperatively via caspase-independent and caspase-dependent pathways. PMID:26716897

  18. 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

  19. 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.

  20. Nitrogen Isotope Fractionation Increases with the Cell-Specific Dissimilatory Nitrate Reduction Rate

    NASA Astrophysics Data System (ADS)

    Kritee, K.; Sigman, D. M.; Granger, J.

    2009-12-01

    The use of the nitrogen (N) isotopes to estimate the impacts and rates of different N transformations depends on knowledge of their extent of isotope fractionation under environmentally relevant physico-chemical conditions. Though the extent of N isotope fractionation during denitrification by pure cultures of bacteria has been determined in the past, relatively large variation in the isotope effect during apparently replicate experiments has been perplexing and the values that should be most relevant for environmental applications have not been clear. We measured the extent of N and O isotope fractionation during nitrate reduction by two bacterial denitrifiers, Pseudomonas chlororaphis ATCC 43928 and Paracoccus denitrificans ATCC 19367 that were grown in 1L batch reactors in the presence of differing carbon sources that included complex organic (e.g, bactopeptone and casein) or defined (e.g., glucose and acetate) carbon compounds and varying concentrations of dissolved oxygen (0 - 4 mM) and nitrate (25 - 800 mM) in the assay medium. For P. denitrificans and P. Chlororaphis , the total range of the N isotope effect (15ɛ) varied from 22.3 to 9.3 ‰ and 34.3 to 15.6 ‰, respectively. Despite this large variation, the O-to-N isotope effect ratio centered around 1, consistent with our previous work. A systematic pattern that has emerged from these studies is that the N and O isotope effect during denitrification increases with increasing cell specific nitrate reduction (CSNR) rate. This sense of variation runs counter to expectations from studies of carbon and sulfur isotope effects during methanogenesis and sulfate reduction, respectively, in which higher substrate consumption rates are associated with lower isotope effects. As with many multi-step microbial processes, variability in the dissimilatory nitrate reduction isotope effect may arise from variation in the “relative” rate and reversibility of (1) nitrate uptake into the denitrifying cell, and/or (2

  1. Plasma Membrane Nucleolin Is a Receptor for the Anticancer Aptamer AS1411 in MV4-11 Leukemia Cells

    PubMed Central

    Soundararajan, Sridharan; Wang, Li; Sridharan, Vijayalakshmi; Chen, Weiwei; Courtenay-Luck, Nigel; Jones, David; Spicer, Eleanor K.

    2009-01-01

    AS1411 is a DNA aptamer that is in phase II clinical trials for relapsed or refractory acute myeloid leukemia and for renal cell carcinoma. AS1411 binds to nucleolin, a protein that is overexpressed in the cytoplasm and on the plasma membrane of some tumor cells compared with normal cells. Studies were performed to determine whether cell surface nucleolin is a receptor for AS1411 in the acute myeloid leukemia cell line MV4-11. Biotinylation of MV4-11 cell surface proteins followed by immunoblotting of the biotinylated proteins showed that full-length (106 kDa) and truncated forms of nucleolin were present on the cell surface. In contrast, K-562 cells, which are 4-fold less sensitive than MV4-11 cells to AS1411, showed no full-length nucleolin and lesser amounts of the truncated forms of nucleolin on the cell surface. Incubation of MV4-11 cells with [32P]AS1411 and immunoprecipitation of the plasma membrane fraction with anti-nucleolin antibody demonstrated the presence of [32P]AS1411-nucleolin complexes. Anti-nucleolin antibody inhibited binding of fluorescein isothiocyanate (FITC)-AS1411 to plasma membrane nucleolin 56 ± 10% SE (P < 0.01) compared with cells incubated with FITC-AS1411 only. Cellular uptake of [32P]AS1411 into MV4-11 cells was blocked by a 20-fold excess of unlabeled AS1411 but not by a 20-fold excess of the biologically inactive oligonucleotide CRO-26. Uptake was approximately 3-fold faster into MV4-11 cells than into K-562 cells. Partial knockdown of plasma membrane and cytosolic nucleolin in MCF-7 cells resulted in a 3-fold decrease in AS1411 uptake. These results provide evidence that plasma membrane nucleolin is a functional receptor for AS1411 in MV4-11 cells. PMID:19657047

  2. 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.

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

    NASA Astrophysics Data System (ADS)

    Morrison, Dennis R.; Lewis, Marian L.; Barlow, Grant H.; Todd, Paul; Kunze, M. Elaine; Sarnoff, Burton E.; Li, Zhankui

    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.

  4. Extracellular Heme Uptake and the Challenges of Bacterial Cell Membranes

    PubMed Central

    Smith, Aaron D.; Wilks, Angela

    2013-01-01

    In bacteria, the fine balance of maintaining adequate iron levels while preventing the deleterious effects of excess iron has led to the evolution of sophisticated cellular mechanisms to obtain, store, and regulate iron. Iron uptake provides a significant challenge given its limited bioavailability and need to be transported across the bacterial cell wall and membranes. Pathogenic bacteria have circumvented the iron-availability issue by utilizing the hosts' heme-containing proteins as a source of iron. Once internalized, iron is liberated from the porphyrin enzymatically for cellular processes within the bacterial cell. Heme, a lipophilic and toxic molecule, poses a significant challenge in terms of transport given its chemical reactivity. As such, pathogenic bacteria have evolved sophisticated membrane transporters to coordinate, sequester, and transport heme. Recent advances in the biochemical and structural characterization of the membrane-bound heme transport proteins are discussed in the context of ligand coordination, protein–protein interaction, and heme transfer. PMID:23046657

  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

  6. Nano mineral fiber enhanced catalyst coated membranes for improving polymer electrolyte membrane fuel cell durability

    NASA Astrophysics Data System (ADS)

    Xu, Feng; Xu, Ran; Mu, Shichun

    In order to protect the perfluorosulfonic acid (PFSA) ionomer from an attack of contaminant metal ions as well as to enhance the mechanical stability of catalyst layers, palygorskite (PGS) is introduced into the catalyst layer of polymer electrolyte membrane fuel cells. PGS is a widely used natural nano-sized silicate mineral fiber with unique nano-sized channel structure, has a strong absorption capacity for heavy metal ions. We identify a negative influence of Fe 2+ on PFSA membranes to make a comparative study. Subsequently catalyst coated membranes (CCMs) prepared with a PGS-Pt/C composite catalyst show a great effect in reducing Fe 2+ ion crossover. Results display that PGS absorbs Fe 2+ in nano-structure channels, and effectively protect PFSA ionomer in both the catalyst layer and membrane from hydroxyl radicals (OH rad) attack. Thus, the chemical stability of PFSA ionomer in both the catalyst layer and membrane is greatly improved. Furthermore, the enhancement of the mechanical performance of catalyst layers is discussed.

  7. 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

  8. Single cell electric impedance topography: mapping membrane capacitance.

    PubMed

    Dharia, Sameera; Ayliffe, Harold E; Rabbitt, Richard D

    2009-12-01

    Single-cell electric impedance topography (sceTopo), a technique introduced here, maps the spatial distribution of capacitance (i.e. displacement current) associated with the membranes of isolated, living cells. Cells were positioned in the center of a circular recording chamber surrounded by eight electrodes. Electrodes were evenly distributed on the periphery of the recording chamber. Electric impedance measured between adjacent electrode pairs (10 kHz-5 MHz) was used to construct topographical maps of the spatial distribution of membrane capacitance. Xenopus Oocytes were used as a model cell to develop sceTopo because these cells consist of two visually distinguishable hemispheres, each with distinct membrane composition and structure. Results showed significant differences in the imaginary component of the impedance between the two oocyte hemispheres. In addition, the same circumferential array was used to map the size of the extracellular electrical shunt path around the cell, providing a means to estimate the location and shape of the cell in the recording chamber. PMID:19904403

  9. Sol-gel based silica electrodes for inorganic membrane direct methanol fuel cells

    NASA Astrophysics Data System (ADS)

    Kim, Hyea; Kohl, Paul A.

    Inorganic glass electrodes are of interest for use with inorganic proton exchange membranes for direct methanol fuel cells. Platinum-ruthenium glass electrodes (PtRu/C-SiO 2) have been prepared by incorporating the PtRu/C nanoparticles into a silica-based matrix. The SiO 2 matrix was synthesized through the sol-gel reaction of 3-(trihydroxysilyl)-1-propanesulfonic acid (3TPS) and 3-glycidoxypropyltrimethoxysilane (GPTMS). The distribution of the PtRu/C particles can be controlled by changing the properties of the gel matrix. The effect of gelation time, mole fraction of reactants within the sol, curing temperature, and glass ionomer content were investigated. The adhesion of the catalyst layer on the membrane, catalytic activity for methanol oxidation, and inhibition of methanol permeation through the membrane have been characterized and optimized. The electroless deposition of PtRu onto the PtRu/C nanoparticles was performed to increase the sheet conductivity of the electrode. It was found that the electrolessly deposited metal improved the catalytic activity for methanol oxidation and decreased the methanol cross-over. The methanol fuel cell performance using the inorganic membrane electrode assembly was 236 μA cm -2 at 0.4 V and was stable for more than 10 days.

  10. Sulfonated Nanoplates in Proton Conducting Membranes for Fuel Cells

    SciTech Connect

    Chen, W.F.; Ni’mah, H.; Yu-Cheng Shen, Y.-C.; Kuo, P.-L.

    2011-09-29

    Surface-functionalized nanoplates are synthesized by anchoring sulfonic acid containing siloxanes on zirconium phosphate, and in turn blended with Nafion to fabricate proton conducting membranes. The effects of these sulfonated nanoplates on proton conduction, hydro-characteristics and fuel cell performance are reported.

  11. 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...

  12. Cell outer membrane mimetic chitosan nanoparticles: preparation, characterization and cytotoxicity.

    PubMed

    Zhao, Jing; Liang, Fei; Kong, Lingheng; Zheng, Lina; Fan, Tao

    2015-01-01

    A negatively charged copolymer poly (MPC-co-AMPS) of 2-methacryloyloxyethyl phosphorylcholine (MPC) and 2-acrylamide-2-methyl propane sulfonic acid (AMPS) was designed and synthesized. Chitosan nanoparticles with cell outer membrane mimetic structure were prepared by electrostatic interaction between the sulfonic acid groups of poly (MPC-co-AMPS) and the protonated amino groups of chitosan. Effects of factors on influencing the particle size, distribution, and stability were investigated. The experimental results showed that cell membrane mimetic chitosan nanoparticles with controllable and homogeneous size ranged from 100 to 300 nm were prepared at the concentration of 0.1-2.0 mg/mL and the charge ratio of 0.5-1.1. Chitosan nanoparticles prepared can exist stably for more than 45 days when placed at 4 °C and pH < 7.5. The cytotoxicity of the chitosan nanoparticles reduced significantly after surface modification with cell membrane mimetic structure, meeting the basic requirements of biomedical materials. The results suggest cell membrane mimetic chitosan nanoparticles prepared with polyanion and polycation obtain good biological compatibility and immune stealth ability, which has important academic significance and great application prospects. PMID:26230052

  13. Monocyte cell membrane-derived nanoghosts for targeted cancer therapy

    NASA Astrophysics Data System (ADS)

    Krishnamurthy, S.; Gnanasammandhan, M. K.; Xie, C.; Huang, K.; Cui, M. Y.; Chan, J. M.

    2016-03-01

    Core-shell type `nanoghosts' were synthesized with a drug-loaded biodegradable PLGA core and a monocyte cell membrane-derived shell. The nanoghosts were monodisperse with an average size <200 nm, and showed good serum stability for 120 h. Doxorubicin-loaded nanoghosts showed greater cellular uptake and cytotoxicity compared to non-coated nanoparticle controls in metastatic MCF-7 breast cancer cell lines.Core-shell type `nanoghosts' were synthesized with a drug-loaded biodegradable PLGA core and a monocyte cell membrane-derived shell. The nanoghosts were monodisperse with an average size <200 nm, and showed good serum stability for 120 h. Doxorubicin-loaded nanoghosts showed greater cellular uptake and cytotoxicity compared to non-coated nanoparticle controls in metastatic MCF-7 breast cancer cell lines. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr07588b

  14. Dynamic membrane patterning, signal localization and polarity in living cells.

    PubMed

    Zamparo, M; Chianale, F; Tebaldi, C; Cosentino-Lagomarsino, M; Nicodemi, M; Gamba, A

    2015-02-01

    We review the molecular and physical aspects of the dynamic localization of signaling molecules on the plasma membranes of living cells. At the nanoscale, clusters of receptors and signaling proteins play an essential role in the processing of extracellular signals. At the microscale, "soft" and highly dynamic signaling domains control the interaction of individual cells with their environment. At the multicellular scale, individual polarity patterns control the forces that shape multicellular aggregates and tissues. PMID:25563791

  15. The nuclear membranes in hypertrophied human cardiac muscle cells.

    PubMed Central

    Ferrans, V. J.; Jones, M.; Maron, B. J.; Roberts, W. C.

    1975-01-01

    Nuclear membranes of cardiac muscle cells were studied in 134 patients with cardiac hypertrophy of various causes. Abnormalities observed consisted of: a) increased foldings and convolutions; b) nuclear pseudoinclusions formed by cytoplasmic organelles protruding into saccular invaginations of the nuclear membranes, and c) intranuclear tubules. The increased foldings and convolutions of the nuclear membranes and the nuclear pseudoinclusions appear to result from synthesis of nuclear membranes in excess of that needed to accommodate the increase in nuclear volume which occurs in hypertrophy. Intranuclear tubules were found in 6 patients and consisted of tubular invaginations, 400 to 650 A in diameter, of the inner nuclear membranes into the nucleoplasm. Some of these tubules were straight and cylindrical, and were associated with a peripheral layer of marginated chromatin; others were not associated with chromatin, appeared coiled and followed irregular courses. Intranuclear tubules in cardiac muscle cells probably represent an extreme cellular response to the stimulus of hypertrophy. Images Fig 21 Fig 11 Fig 12 Fig 13 Fig 14 Fig 1 Fig 15 Fig 2 Figs 3 and 4 Fig 5 Fig 16 Fig 17 Fig 6 Fig 18 Fig 7 Fig 8 Fig 9 Fig 10 Fig 19 Fig 20 PMID:164122

  16. Evaluating the efficacy of subcellular fractionation of blast cells using live cell labeling and 2D DIGE.

    PubMed

    Ho, Yin Ying; Penno, Megan; Perugini, Michelle; Lewis, Ian; Hoffmann, Peter

    2012-01-01

    Labeling of exposed cell surface proteins of live cells using CyDye DIGE fluor minimal dyes is an efficient strategy for cell surface proteome profiling and quantifying differentially expressed proteins in diseases. Here we describe a strategy to evaluate a two-step detergent-based protein fractionation method using live cell labeling followed by visualization of the fluorescently labeled cell surface proteins and fractionated proteins within a single 2D gel. PMID:22311770

  17. Ankyrin-B directs membrane tethering of periaxin and is required for maintenance of lens fiber cell hexagonal shape and mechanics.

    PubMed

    Maddala, Rupalatha; Walters, Mark; Brophy, Peter J; Bennett, Vann; Rao, Ponugoti V

    2016-01-15

    Periaxin (Prx), a PDZ domain protein expressed preferentially in myelinating Schwann cells and lens fibers, plays a key role in membrane scaffolding and cytoarchitecture. Little is known, however, about how Prx is anchored to the plasma membrane. Here we report that ankyrin-B (AnkB), a well-characterized adaptor protein involved in linking the spectrin-actin cytoskeleton to integral membrane proteins, is required for membrane association of Prx in lens fibers and colocalizes with Prx in hexagonal fiber cells. Under AnkB haploinsufficiency, Prx accumulates in the soluble fraction with a concomitant loss from the membrane-enriched fraction of mouse lenses. Moreover, AnkB haploinsufficiency induced age-dependent disruptions in fiber cell hexagonal geometry and radial alignment and decreased compressive stiffness in mouse lenses parallel to the changes observed in Prx null mouse lens. Both AnkB- and Prx-deficient mice exhibit disruptions in membrane organization of the spectrin-actin network and the dystrophin-glycoprotein complex in lens fiber cells. Taken together, these observations reveal that AnkB is required for Prx membrane anchoring and for maintenance of lens fiber cell hexagonal geometry, membrane skeleton organization, and biomechanics. PMID:26538089

  18. 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.

  19. The amniotic membrane as a source of stem cells.

    PubMed

    Insausti, Carmen L; Blanquer, Miguel; Bleda, Patricia; Iniesta, Paqui; Majado, María J; Castellanos, Gregorio; Moraleda, José M

    2010-01-01

    Cellular therapy has emerged as a new potential tool for curing a wide range of degenerative diseases and tissue necrosis. Embryonic stem cells possess potential for differentiation into a wide range of cell lineages, but the ethical issues associated with establishment of this human cell line have to be resolved prior to any use. The bone marrow (BM) is the usual source of adult stem cells for hematopoietic stem cell transplants and cellular therapy, but the BM harvest is a surgical procedure that requires general anesthesia or sedation, and there seems to be a reduction of the proliferative potential and differentiation capacity of the marrow mesenchymal stem cells in older donors. For these reasons there is an increasing interest in other sources of stem cells from adult and fetal tissues. The amniotic membrane (AM) or amnion is a tissue of particular interest because its cells possess characteristics of stem cells with multipotent differentiation ability, and because of low immunogenicity and easy procurement from the placenta, which is a discarded tissue after parturition, thus avoiding the current controversies associated with the use of human embryonic stem cells. Therefore, amniotic membrane has been proposed as a good candidate to be used in cellular therapy and regenerative medicine. PMID:19924645

  20. Lipid profiles of detergent resistant fractions of the plasma membrane in oat and rye in association with cold acclimation and freezing tolerance.

    PubMed

    Takahashi, Daisuke; Imai, Hiroyuki; Kawamura, Yukio; Uemura, Matsuo

    2016-04-01

    Cold acclimation (CA) results in alteration of the plasma membrane (PM) lipid composition in plants, which plays a crucial role in the acquisition of freezing tolerance via membrane stabilization. Recent studies have indicated that PM structure is consistent with the fluid mosaic model but is laterally non-homogenous and contains microdomains enriched in sterols, sphingolipids and specific proteins. In plant cells, the function of these microdomains in relation to CA and freezing tolerance is not yet fully understood. The present study aimed to investigate the lipid compositions of detergent resistant fractions of the PM (DRM) which are considered to represent microdomains. They were prepared from leaves of low-freezing tolerant oat and high-freezing tolerant rye. The DRMs contained higher proportions of sterols, sphingolipids and saturated phospholipids than the PM. In particular, one of the sterol lipid classes, acylated sterylglycoside, was the predominant sterol in oat DRM while rye DRM contained free sterol as the major sterol. Oat and rye showed different patterns (or changes) of sterols and 2-hydroxy fatty acids of sphingolipids of DRM lipids during CA. Taken together, these results suggest that CA-induced changes of lipid classes and molecular species in DRMs are associated with changes in the thermodynamic properties and physiological functions of microdomains during CA and hence, influence plant freezing tolerance. PMID:26904981

  1. 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.

  2. Influence of water and membrane microstructure on the transport properties of proton exchange membrane fuel cells

    NASA Astrophysics Data System (ADS)

    Siu, Ana Rosa

    Proton transport in proton exchange membranes (PEMs) depends on interaction between water and acid groups covalently bound to the polymer. Although the presence of water is important in maintaining the PEM's functions, a thorough understanding of this topic is still lacking. The objective of this work is to provide a better understanding of how the nature water, confined to ionic domains of the polymer, influences the membrane's ability to transport protons, methanol and water. Understanding this topic will facilitate development of new materials with favorable transport properties for fuel cells use. Five classes of polymer membranes were used in this work: polyacrylonitrile-graft-poly(styrenesulfonic) acid (PAN-g-macPSSA); poly(vinylidene difluoride) irradiation-graft-poly(styrenesulfonic) acid (PVDF-g-PSSA); poly(ethylenetetrafluoroethylene) irradiation-graft-poly(styrenesulfonic) acid (ETFE-gPSSA); PVDF-g-PSSA with hydroxyethylmethacrylate (HEMA); and perfluorosulfonic acid membrane (Nafion). The nature of water within the polymers (freezable versus non-freezable states) was measured by systematically freezing samples, and observing the temperature at which water freezes and the amount of heat released in the process. Freezing water-swollen membranes resulted in a 4-fold decrease in the proton conductivity of the PEM. Activation energies of proton transport before and after freezing were ˜ 0.15 eV and 0.5 eV, consistent with proton transport through liquid water and bound water, respectively. Reducing the content of water in membrane samples decreased the amount of freezable and non-freezable water. Calorimetric measurements of membranes in various degrees of hydration showed that water molecules became non-freezable when lambda, (water molecules per sulfonic acid group) was less than ˜14. Proton conduction through membranes containing only non-freezable water was demonstrated to be feasible. Diffusion experiments showed that the permeability of methanol

  3. Role of Rad52 in fractionated irradiation induced signaling in A549 lung adenocarcinoma cells.

    PubMed

    Ghosh, Somnath; Krishna, Malini

    2012-01-01

    The effect of fractionated doses of γ-irradiation (2Gy per fraction over 5 days), as delivered in cancer radiotherapy, was compared with acute doses of 10 and 2Gy, in A549 cells. A549 cells were found to be relatively more radioresistant if the 10Gy dose was delivered as a fractionated regimen. Microarray analysis showed upregulation of DNA repair and cell cycle arrest genes in the cells exposed to fractionated irradiation. There was intense activation of DNA repair pathway-associated genes (DNA-PK, ATM, Rad52, MLH1 and BRCA1), efficient DNA repair and phospho-p53 was found to be translocated to the nucleus of A549 cells exposed to fractionated irradiation. MCF-7 cells responded differently in fractionated regimen. Silencing of the Rad52 gene in fractionated group of A549 cells made the cells radiosensitive. The above result indicated increased radioresistance in A549 cells due to the activation of Rad52 gene. PMID:22001234

  4. Proteomic Approach for Characterization of Immunodominant Membrane-Associated 30- to 36-Kilodalton Fraction Antigens of Leishmania infantum Promastigotes, Reacting with Sera from Mediterranean Visceral Leishmaniasis Patients

    PubMed Central

    Kamoun-Essghaier, Sayda; Guizani, Ikram; Strub, Jean Marc; Van Dorsselaer, Alain; Mabrouk, Kamel; Ouelhazi, Lazhar; Dellagi, Koussay

    2005-01-01

    The aim of the present study was to identify and characterize proteins of a 30- to 36-kDa fraction of Leishmania infantum promastigote membranes previously shown to be an immunodominant antigen(s) in Mediterranean visceral leishmaniasis (MVL) and a consistent and reliable serological marker of this disease. By the first approach, Coomassie-stained protein bands (32- and 33-kDa fractions) that specifically reacted by immunoblotting with sera from MVL patients were excised from the gel and submitted to enzymatic digestion to generate peptides. Four peptides were sequenced, three of which were shown to be definitely associated with MVL-reactive antigens and ascribed to a mitochondrial integral ADP-ATP carrier protein from L. major, a putative NADH cytochrome b5 reductase, and a putative mitochondrial carrier protein, respectively. The second approach combined two-dimensional gel electrophoresis of membrane antigens and mass spectrometry (liquid chromatography-mass spectrometry/mass spectrometry) by using a quadrupole time-of-flight analysis. Six immunoreactive spots that resolved within a molecular mass range of 30 to 36 kDa and a pH range of 6.7 to 7.4 corresponded to four Leishmania products. The sequences derived from two spots were ascribed to a beta subunit-like guanine nucleotide binding protein, known as the activated protein kinase C receptor homolog antigen LACK, and to a probable member of the aldehyde reductase family. One spot was identified as a probable ubiquinol-cytochrome c reductase (EC 1.10.2.2) Rieske iron-sulfur protein precursor. The remaining three spots were identified as truncated forms of elongation factor 1α. These antigens correspond to conserved proteins ubiquitously expressed in eukaryotic cells and represent potential candidates for the design of a reliable tool for the diagnosis of this disease. PMID:15699427

  5. T cell proliferative responses to molecular fractions of periodontopathic bacteria.

    PubMed Central

    Ivanyi, L; Newman, H N; Marsh, P D

    1991-01-01

    Soluble antigenic preparations of Veillonella parvula and Bacteroides gingivalis were separated by SDS-PAGE and used after electroblotting and solubilization for in vitro lymphocyte stimulation in 13 patients with severe periodontitis and 12 controls. The cellular responses of controls and patients to V. parvula antigens were represented by four main proliferation-inducing fractions with 74-66, 52-46, 22-19 and 12 kD mol. wt. These fractions induced slightly enhanced DNA synthesis in lymphocytes from eight patients who failed to respond to whole antigenic extract. Lymphocyte samples from Veillonella whole extract unresponsive patients were also examined for in vitro proliferation by B. gingivalis fractions. Almost all stimulatory activities could be classified into five regions of 84-74, 35-31, 28-25, 17-15 and 12 kD. PMID:1988218

  6. 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

  7. Novel phosphoric acid doped polybenzimidazole membranes for fuel cells

    NASA Astrophysics Data System (ADS)

    Zhang, Haifeng

    Acid doped polybenzimidazole (PBIRTM, called mPBI in this thesis) membranes are applied as electrolytes in high temperature polymer electrolyte membrane fuel cells (PEMFCs). Several series of homopolymers and copolymers with high I.V. were synthesized in PPA solution. A novel membrane fabrication and acid doping process, called the PPA process, was developed by casting the polymer-polyphosphoric acid (PPA) solution directly after polymerization without isolation or redissolution of the polymers. The PPA absorbed moisture from the atmosphere and hydrolyzed to phosphoric acid, which induced a sol-gel transition and produced a high acid doped PBI membrane. A water spray method was developed to make an acid doped ABPBI membrane by spraying water or dilute phosphoric acid onto the cast solution directly. This process induced film formation for ABPBI, but washed out most of the phosphoric acid dopant. A more rigid pPBI homopolymer was synthesized in PPA solution with high inherent viscosity (2˜3 dL/g). Acid doped pPBI membranes showed high acid doping level (pPBI·69H3PO4) and high conductivity (0.24 S/cm at 160°C). Fuel cells based on pPBI/PA showed good performance at various conditions. For example, a fuel cell based on pPBI/PA showed a maximum power density of 0.92 W/cm2 at 160°C and ambient pressure (H2/O2). The degradation rate of the cell potential was -21 mV/1,000 hours and -35 mV/1,000 hours at 160°C and 180°C, respectively in continuous testing. Fuel cells also showed good performance and tolerance to carbon monoxide poisoning when operated at temperatures higher than 120°C. The voltage drop was only 31 mV (from 0.657 V to 0.626 V at 0.3 A/cm2) when reformate gas (40.0% H2, 0.2% CO, 19.0% CO2, 40.8% N2) was used instead of pure hydrogen at one atmosphere pressure and 160°C. The structure-property relationships were investigated on the homopolymers and copolymers with different rigidities in the main chain. It is found that para-oriented structures

  8. 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

  9. Nonisothermal water transport through hydrophobic membranes in a stirred cell

    SciTech Connect

    Vazquez-Gonzalez, M.I.; Martinez, L.

    1994-10-01

    This paper studies the transport of pure water through microporous hydrophobic membranes in a stirred cell when bathed by two phases at different temperatures. The dependence of the phenomena on the stirring rate and on the average temperature has been investigated. The influence of these operating conditions on the mass transfer rate is discussed while keeping in mind the theories of mass and heat transfer within the membrane and adjoining liquids. The concept of temperature polarization is introduced in the transport equations, and it is shown to be important in the interpretation of our experimental results.

  10. Brucella fractions behave as nonspecific mitogens and polyclonal B-cell activators for human lymphocytes.

    PubMed Central

    Vendrell, J P; Rabesandratana, H; Huguet, M F; Cannat, A; Serre, A

    1985-01-01

    Two lipid-A-free fractions which were extracted from Brucella melitensis and were designated PI and SF stimulated human unsensitized mononuclear cells to proliferate and to secrete immunoglobulins. Both of these effects were observed in cultures of peripheral blood, tonsils, and cord blood lymphocytes. Neither B cells nor T cells alone proliferated in the presence of these fractions, whereas the proliferative response of T cells plus B cells was largely independent of accessory cells. Polyclonal activation was estimated by counting the cells which secreted immunoglobulins of different isotypes into culture supernatants. This phenomenon was strongly T dependent. PMID:3876286

  11. Fractionation of Plant Bioactives from Black Carrots (Daucus carota subspecies sativus varietas atrorubens Alef.) by Adsorptive Membrane Chromatography and Analysis of Their Potential Anti-Diabetic Activity.

    PubMed

    Esatbeyoglu, Tuba; Rodríguez-Werner, Miriam; Schlösser, Anke; Liehr, Martin; Ipharraguerre, Ignacio; Winterhalter, Peter; Rimbach, Gerald

    2016-07-27

    Black and purple carrots have attracted interest as colored extracts for coloring food due to their high content of anthocyanins. This study aimed to investigate the polyphenol composition of black carrots. Particularly, the identification and quantification of phenolic compounds of the variety Deep Purple carrot (DPC), which presents a very dark color, was performed by HPLC-PDA and HPLC-ESI-MS(n) analyses. The separation of polyphenols from a DPC XAD-7 extract into an anthocyanin fraction (AF) and co-pigment fraction (CF; primarily phenolic acids) was carried out by membrane chromatography. Furthermore, possible anti-diabetic effects of the DPC XAD-7 extract and its AF and CF were determined. DPC samples (XAD-7, CF, and AF) inhibited α-amylase and α-glucosidase in a dose-dependent manner. Moreover, DPC XAD-7 and chlorogenic acid, but not DPC CF and DPC AF, caused a moderate inhibition of intestinal glucose uptake in Caco-2 cells. However, DPC samples did not affect glucagon-like peptide-1 (GLP-1) secretion and dipeptidyl peptidase IV (DPP-4) activity. Overall, DPC exhibits an inhibitory effect on α-amylase and α-glucosidase activity and on cellular glucose uptake indicating potential anti-diabetic properties. PMID:27362825

  12. Plasma membrane growth during the cell cycle: unsolved mysteries and recent progress

    PubMed Central

    McCusker, Derek; Kellogg, Douglas R.

    2012-01-01

    Growth of the plasma membrane is as fundamental to cell reproduction as DNA replication, chromosome segregation and ribosome biogenesis, yet little is known about the underlying mechanisms. Membrane growth during the cell cycle requires mechanisms that control the initiation, location, and extent of membrane growth, as well as mechanisms that coordinate membrane growth with cell cycle progression. Recent experiments have established links between membrane growth and core cell cycle regulators. Further analysis of these links will yield insights into conserved and fundamental mechanisms of cell growth. A better understanding of the post-Golgi pathways by which membrane growth occurs will be essential for future progress. PMID:23141634

  13. The importance of extracellular speciation and corrosion of copper nanoparticles on lung cell membrane integrity.

    PubMed

    Hedberg, Jonas; Karlsson, Hanna L; Hedberg, Yolanda; Blomberg, Eva; Odnevall Wallinder, Inger

    2016-05-01

    Copper nanoparticles (Cu NPs) are increasingly used in various biologically relevant applications and products, e.g., due to their antimicrobial and catalytic properties. This inevitably demands for an improved understanding on their interactions and potential toxic effects on humans. The aim of this study was to investigate the corrosion of copper nanoparticles in various biological media and to elucidate the speciation of released copper in solution. Furthermore, reactive oxygen species (ROS) generation and lung cell (A549 type II) membrane damage induced by Cu NPs in the various media were studied. The used biological media of different complexity are of relevance for nanotoxicological studies: Dulbecco's modified eagle medium (DMEM), DMEM(+) (includes fetal bovine serum), phosphate buffered saline (PBS), and PBS+histidine. The results show that both copper release and corrosion are enhanced in DMEM(+), DMEM, and PBS+histidine compared with PBS alone. Speciation results show that essentially no free copper ions are present in the released fraction of Cu NPs in neither DMEM(+), DMEM nor histidine, while labile Cu complexes form in PBS. The Cu NPs were substantially more membrane reactive in PBS compared to the other media and the NPs caused larger effects compared to the same mass of Cu ions. Similarly, the Cu NPs caused much more ROS generation compared to the released fraction only. Taken together, the results suggest that membrane damage and ROS formation are stronger induced by Cu NPs and by free or labile Cu ions/complexes compared with Cu bound to biomolecules. PMID:26859121

  14. 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.

  15. ``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.

  16. 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

  17. Morphological features (defects) in fuel cell membrane electrode assemblies

    NASA Astrophysics Data System (ADS)

    Kundu, S.; Fowler, M. W.; Simon, L. C.; Grot, S.

    Reliability and durability issues in fuel cells are becoming more important as the technology and the industry matures. Although research in this area has increased, systematic failure analysis, such as a failure modes and effects analysis (FMEA), are very limited in the literature. This paper presents a categorization scheme of causes, modes, and effects related to fuel cell degradation and failure, with particular focus on the role of component quality, that can be used in FMEAs for polymer electrolyte membrane (PEM) fuel cells. The work also identifies component defects imparted on catalyst-coated membranes (CCM) by manufacturing and proposes mechanisms by which they can influence overall degradation and reliability. Six major defects have been identified on fresh CCM materials, i.e., cracks, orientation, delamination, electrolyte clusters, platinum clusters, and thickness variations.

  18. Oxytocin binding by myoepithelial cell membranes from involuted mammary tissue.

    PubMed

    Ruberti, A; Olins, G M; Eakle, K A; Bremel, R D

    1983-04-29

    Oxytocin binding activity of myoepithelial cell membranes from mammary tissue was measured under a variety of different experimental conditions. Mammary tissue from non-lactating rats bound oxytocin with a Kd of 9.2 +/- 1.6 nM (+/- S.E.) and indicates that receptors are retained by the myoepithelial cells in a non-lactating state. Ovariectomy of non-lactating rats did not depress the binding activity of the membranes. Administration of the estrogenic compounds estradiol-17 beta and diethylstibestrol at doses which affect uterine weight and are known to increase uterine oxytocin binding did not influence the binding activity of the myoepithelial cells. This indicates that the oxytocin receptors of the mammary gland are not under the same endocrine control as the uterine receptors. PMID:6303330

  19. Gold Nanoparticles-Enhanced Proton Exchange Membrane (PEM) Fuel Cell

    NASA Astrophysics Data System (ADS)

    Li, Hongfei; Pan, Cheng; Liu, Ping; Zhu, Yimei; Adzic, Radoslav; Rafailovich, Miriam

    Proton exchange membrane fuel cells have drawn great attention and been taken as a promising alternated energy source. One of the reasons hamper the wider application of PEM fuel cell is the catalytic poison effect from the impurity of the gas flow. Haruta has predicted that gold nanoparticles that are platelet shaped and have direct contact with the metal oxide substrate to be the perfect catalysts of the CO oxidization, yet the synthesis method is difficult to apply in the Fuel Cell. In our approach, thiol-functionalized gold nanoparticles were synthesized through two-phase method developed by Brust et al. We deposit these Au particles with stepped surface directly onto the Nafion membrane in the PEM fuel cell by Langmuir-Blodgett method, resulting in over 50% enhancement of the efficiency of the fuel cell. DFT calculations were conducted to understand the theory of this kind of enhancement. The results indicated that only when the particles were in direct surface contact with the membrane, where AuNPs attached at the end of the Nafion side chains, it could reduce the energy barrier for the CO oxidation that could happen at T<300K.

  20. Membrane electrode assemblies for unitised regenerative polymer electrolyte fuel cells

    NASA Astrophysics Data System (ADS)

    Wittstadt, U.; Wagner, E.; Jungmann, T.

    Membrane electrode assemblies for regenerative polymer electrolyte fuel cells were made by hot pressing and sputtering. The different MEAs are examined in fuel cell and water electrolysis mode at different pressure and temperature conditions. Polarisation curves and ac impedance spectra are used to investigate the influence of the changes in coating technique. The hydrogen gas permeation through the membrane is determined by analysing the produced oxygen in electrolysis mode. The analysis shows, that better performances in both process directions can be achieved with an additional layer of sputtered platinum on the oxygen electrode. Thus, the electrochemical round-trip efficiency can be improved by more than 4%. Treating the oxygen electrode with PTFE solution shows better performance in fuel cell and less performance in electrolysis mode. The increase of the round-trip efficiency is negligible. A layer sputtered directly on the membrane shows good impermeability, and hence results in high voltages at low current densities. The mass transportation is apparently constricted. The gas diffusion layer on the oxygen electrode, in this case a titanium foam, leads to flooding of the cell in fuel cell mode. Stable operation is achieved after pretreatment of the GDL with a PTFE solution.

  1. Dynamics of flat membranes and flickering in red blood cells

    NASA Astrophysics Data System (ADS)

    Frey, Erwin; Nelson, David R.

    1991-12-01

    A theory of the dynamics of polymerized membranes in the flat phase is presented. The dynamics of dilute membrane solutions is strongly influenced by long-ranged hydrodynamic interactions among the monomers, mediated by the intervening solvent. We discuss the renormalization of the kinetic coefficients for the undulation and phonon modes due to hydrodynamic “backflow” (Zimm behavior). The dynamics is also studied for free draining membranes (Rouse dynamics) corresponding to the Brownian dynamics method used in Monte Carlo simulations. The long time behavior of the dynamic structure factor is given by stretched exponentials with stretching exponents determined by the exponents of the elastic coefficients and the wave vector dependence of the Oseen tensor. We also study the dynamics of the thickness fluctuations in red blood cells (flicker phenomenon) taking into account the underlying polymerized spectrin skeleton. Qualitatively different dynamical behavior is predicted for spectrin skeletons isolated from heir natural lipid environment.

  2. Role of Cell Membrane-Vector Interactions in Successful Gene Delivery.

    PubMed

    Vaidyanathan, Sriram; Orr, Bradford G; Banaszak Holl, Mark M

    2016-08-16

    transported DNA is released from endosomes by free cationic polymer intercalated into the endosomal membrane. This cationic polymer initially interacts with the cell plasma membrane and appears to reach the endosome by lipid cycling mechanisms. The fraction of cells displaying release of intact DNA from endosomes quantitatively predicts the fraction of cells displaying gene expression for both linear poly(ethylenimine) (L-PEI; an effective vector) and generation five poly(amidoamine) dendrimer (G5 PAMAM; an ineffective vector). Moreover, intact OMB delivered with G5 PAMAM, which normally is confined to endosomes, was released by the subsequent addition of L-PEI with a corresponding 10-fold increase in transgene expression. These observations are consistent with experiments demonstrating that cationic polymer/membrane partition coefficients, not polyplex/membrane partition coefficients, predict successful gene expression. Interestingly, a similar partitioning of cationic polymers into the mitochondrial membranes has been proposed to explain the cytotoxicity of these materials. Thus, the proposed model indicates the same physicochemical property (partitioning into lipid bilayers) is linked to release from endosomes, giving protein expression, and to cytotoxicity. PMID:27459207

  3. 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

  4. Thermoase-derived flaxseed protein hydrolysates and membrane ultrafiltration peptide fractions have systolic blood pressure-lowering effects in spontaneously hypertensive rats.

    PubMed

    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

  5. Creating transient cell membrane pores using a standard inkjet printer.

    PubMed

    Owczarczak, Alexander B; Shuford, Stephen O; Wood, Scott T; Deitch, Sandra; Dean, Delphine

    2012-01-01

    Bioprinting has a wide range of applications and significance, including tissue engineering, direct cell application therapies, and biosensor microfabrication. Recently, thermal inkjet printing has also been used for gene transfection. The thermal inkjet printing process was shown to temporarily disrupt the cell membranes without affecting cell viability. The transient pores in the membrane can be used to introduce molecules, which would otherwise be too large to pass through the membrane, into the cell cytoplasm. The application being demonstrated here is the use of thermal inkjet printing for the incorporation of fluorescently labeled g-actin monomers into cells. The advantage of using thermal ink-jet printing to inject molecules into cells is that the technique is relatively benign to cells. Cell viability after printing has been shown to be similar to standard cell plating methods. In addition, inkjet printing can process thousands of cells in minutes, which is much faster than manual microinjection. The pores created by printing have been shown to close within about two hours. However, there is a limit to the size of the pore created (~10 nm) with this printing technique, which limits the technique to injecting cells with small proteins and/or particles. A standard HP DeskJet 500 printer was modified to allow for cell printing. The cover of the printer was removed and the paper feed mechanism was bypassed using a mechanical lever. A stage was created to allow for placement of microscope slides and coverslips directly under the print head. Ink cartridges were opened, the ink was removed and they were cleaned prior to use with cells. The printing pattern was created using standard drawing software, which then controlled the printer through a simple print command. 3T3 fibroblasts were grown to confluence, trypsinized, and then resuspended into phosphate buffered saline with soluble fluorescently labeled g-actin monomers. The cell suspension was pipetted into the

  6. Creating Transient Cell Membrane Pores Using a Standard Inkjet Printer

    PubMed Central

    Owczarczak, Alexander B.; Shuford, Stephen O.; Wood, Scott T.; Deitch, Sandra; Dean, Delphine

    2012-01-01

    Bioprinting has a wide range of applications and significance, including tissue engineering, direct cell application therapies, and biosensor microfabrication.1-10 Recently, thermal inkjet printing has also been used for gene transfection.8,9 The thermal inkjet printing process was shown to temporarily disrupt the cell membranes without affecting cell viability. The transient pores in the membrane can be used to introduce molecules, which would otherwise be too large to pass through the membrane, into the cell cytoplasm.8,9,11 The application being demonstrated here is the use of thermal inkjet printing for the incorporation of fluorescently labeled g-actin monomers into cells. The advantage of using thermal ink-jet printing to inject molecules into cells is that the technique is relatively benign to cells.8, 12 Cell viability after printing has been shown to be similar to standard cell plating methods1,8. In addition, inkjet printing can process thousands of cells in minutes, which is much faster than manual microinjection. The pores created by printing have been shown to close within about two hours. However, there is a limit to the size of the pore created (~10 nm) with this printing technique, which limits the technique to injecting cells with small proteins and/or particles. 8,9,11 A standard HP DeskJet 500 printer was modified to allow for cell printing.3, 5, 8 The cover of the printer was removed and the paper feed mechanism was bypassed using a mechanical lever. A stage was created to allow for placement of microscope slides and coverslips directly under the print head. Ink cartridges were opened, the ink was removed and they were cleaned prior to use with cells. The printing pattern was created using standard drawing software, which then controlled the printer through a simple print command. 3T3 fibroblasts were grown to confluence, trypsinized, and then resuspended into phosphate buffered saline with soluble fluorescently labeled g-actin monomers. The

  7. Difference in Membrane Repair Capacity Between Cancer Cell Lines and a Normal Cell Line.

    PubMed

    Frandsen, Stine Krog; McNeil, Anna K; Novak, Ivana; McNeil, Paul L; Gehl, Julie

    2016-08-01

    Electroporation-based treatments and other therapies that permeabilize the plasma membrane have been shown to be more devastating to malignant cells than to normal cells. In this study, we asked if a difference in repair capacity could explain this observed difference in sensitivity. Membrane repair was investigated by disrupting the plasma membrane using laser followed by monitoring fluorescent dye entry over time in seven cancer cell lines, an immortalized cell line, and a normal primary cell line. The kinetics of repair in living cells can be directly recorded using this technique, providing a sensitive index of repair capacity. The normal primary cell line of all tested cell lines exhibited the slowest rate of dye entry after laser disruption and lowest level of dye uptake. Significantly, more rapid dye uptake and a higher total level of dye uptake occurred in six of the seven tested cancer cell lines (p < 0.05) as well as the immortalized cell line (p < 0.001). This difference in sensitivity was also observed when a viability assay was performed one day after plasma membrane permeabilization by electroporation. Viability in the primary normal cell line (98 % viable cells) was higher than in the three tested cancer cell lines (81-88 % viable cells). These data suggest more effective membrane repair in normal, primary cells and supplement previous explanations why electroporation-based therapies and other therapies permeabilizing the plasma membrane are more effective on malignant cells compared to normal cells in cancer treatment. PMID:27312328

  8. 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.

    1995-01-01

    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 work performed at Lynntech. 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 unitized regenerative fuel cell and results obtained on testing it will be presented.

  9. 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.

  10. A novel unitized regenerative proton exchange membrane fuel cell

    NASA Astrophysics Data System (ADS)

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

    1995-04-01

    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 work performed at Lynntech. 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 unitized regenerative fuel cell and results obtained on testing it will be presented.

  11. Stem cell differentiation increases membrane-actin adhesion regulating cell blebability, migration and mechanics

    PubMed Central

    Sliogeryte, Kristina; Thorpe, Stephen D.; Lee, David A.; Botto, Lorenzo; Knight, Martin M.

    2014-01-01

    This study examines how differentiation of human mesenchymal stem cells regulates the interaction between the cell membrane and the actin cortex controlling cell behavior. Micropipette aspiration was used to measure the pressure required for membrane-cortex detachment which increased from 0.15 kPa in stem cells to 0.71 kPa following chondrogenic differentiation. This effect was associated with reduced susceptibility to mechanical and osmotic bleb formation, reduced migration and an increase in cell modulus. Theoretical modelling of bleb formation demonstrated that the increased stiffness of differentiated cells was due to the increased membrane-cortex adhesion. Differentiated cells exhibited greater F-actin density and slower actin remodelling. Differentiated cells also expressed greater levels of the membrane-cortex ezrin, radixin, moeisin (ERM) linker proteins which was responsible for the reduced blebability, as confirmed by transfection of stem cells with dominant active ezrin-T567D-GFP. This study demonstrates that stem cells have an inherently weak membrane-cortex adhesion which increases blebability thereby regulating cell migration and stiffness. PMID:25471686

  12. Membrane Stabilization and Detoxification of Acetaminophen-Mediated Oxidative Onslaughts in the Kidneys of Wistar Rats by Standardized Fraction of Zea mays L. (Poaceae), Stigma maydis.

    PubMed

    Sabiu, S; O'Neill, F H; Ashafa, A O T

    2016-01-01

    This study evaluated membrane stabilization and detoxification potential of ethyl acetate fraction of Zea mays L., Stigma maydis in acetaminophen-induced oxidative onslaughts in the kidneys of Wistar rats. Nephrotoxic rats were orally pre- and posttreated with the fraction and vitamin C for 14 days. Kidney function, antioxidative and histological analyses were thereafter evaluated. The acetaminophen-mediated significant elevations in the serum concentrations of creatinine, urea, uric acid, sodium, potassium, and tissue levels of oxidized glutathione, protein-oxidized products, lipid peroxidized products, and fragmented DNA were dose-dependently assuaged in the fraction-treated animals. The fraction also markedly improved creatinine clearance rate, glutathione, and calcium concentrations as well as activities of superoxide dismutase, catalase, glutathione reductase, and glutathione peroxidase in the nephrotoxic rats. These improvements may be attributed to the antioxidative and membrane stabilization activities of the fraction. The observed effects compared favorably with that of vitamin C and are informative of the fraction's ability to prevent progression of renal pathological conditions and preserve kidney functions as evidently supported by the histological analysis. Although the effects were prominently exhibited in the fraction-pretreated groups, the overall data from the present findings suggest that the fraction could prevent or extenuate acetaminophen-mediated oxidative renal damage via fortification of antioxidant defense mechanisms. PMID:27579048

  13. Membrane Stabilization and Detoxification of Acetaminophen-Mediated Oxidative Onslaughts in the Kidneys of Wistar Rats by Standardized Fraction of Zea mays L. (Poaceae), Stigma maydis

    PubMed Central

    Sabiu, S.; O'Neill, F. H.

    2016-01-01

    This study evaluated membrane stabilization and detoxification potential of ethyl acetate fraction of Zea mays L., Stigma maydis in acetaminophen-induced oxidative onslaughts in the kidneys of Wistar rats. Nephrotoxic rats were orally pre- and posttreated with the fraction and vitamin C for 14 days. Kidney function, antioxidative and histological analyses were thereafter evaluated. The acetaminophen-mediated significant elevations in the serum concentrations of creatinine, urea, uric acid, sodium, potassium, and tissue levels of oxidized glutathione, protein-oxidized products, lipid peroxidized products, and fragmented DNA were dose-dependently assuaged in the fraction-treated animals. The fraction also markedly improved creatinine clearance rate, glutathione, and calcium concentrations as well as activities of superoxide dismutase, catalase, glutathione reductase, and glutathione peroxidase in the nephrotoxic rats. These improvements may be attributed to the antioxidative and membrane stabilization activities of the fraction. The observed effects compared favorably with that of vitamin C and are informative of the fraction's ability to prevent progression of renal pathological conditions and preserve kidney functions as evidently supported by the histological analysis. Although the effects were prominently exhibited in the fraction-pretreated groups, the overall data from the present findings suggest that the fraction could prevent or extenuate acetaminophen-mediated oxidative renal damage via fortification of antioxidant defense mechanisms. PMID:27579048

  14. Tetraspanins regulate the protrusive activities of cell membrane

    SciTech Connect

    Bari, Rafijul; Guo, Qiusha; Zhongnan Hospital, Wuhan University, Wuhan ; Xia, Bing; Zhang, Yanhui H.; Giesert, Eldon E.; Levy, Shoshana; Zheng, Jie J.; Zhang, Xin A.

    2011-12-02

    Highlights: Black-Right-Pointing-Pointer Tetraspanins regulate microvillus formation. Black-Right-Pointing-Pointer Tetraspanin CD81 promotes microvillus formation. Black-Right-Pointing-Pointer Tetraspanin CD82 inhibits microvillus formation. Black-Right-Pointing-Pointer Based on this study, we extrapolated a general cellular mechanism for tetraspanins. Black-Right-Pointing-Pointer Tetraspanins engage various functions by regulating membrane protrusion morphogenesis. -- Abstract: Tetraspanins have gained increased attention due to their functional versatility. But the universal cellular mechanism that governs such versatility remains unknown. Herein we present the evidence that tetraspanins CD81 and CD82 regulate the formation and/or development of cell membrane protrusions. We analyzed the ultrastructure of the cells in which a tetraspanin is either overexpressed or ablated using transmission electron microscopy. The numbers of microvilli on the cell surface were counted, and the radii of microvillar tips and the lengths of microvilli were measured. We found that tetraspanin CD81 promotes the microvillus formation and/or extension while tetraspanin CD82 inhibits these events. In addition, CD81 enhances the outward bending of the plasma membrane while CD82 inhibits it. We also found that CD81 and CD82 proteins are localized at microvilli using immunofluorescence. CD82 regulates microvillus morphogenesis likely by altering the plasma membrane curvature and/or the cortical actin cytoskeletal organization. We predict that membrane protrusions embody a common morphological phenotype and cellular mechanism for, at least some if not all, tetraspanins. The differential effects of tetraspanins on microvilli likely lead to the functional diversification of tetraspanins and appear to correlate with their functional propensity.

  15. Fluconazole treatment hyperpolarizes the plasma membrane of Candida cells.

    PubMed

    Elicharova, Hana; Sychrova, Hana

    2013-11-01

    Five pathogenic Candida species were compared in terms of their osmotolerance, tolerance to toxic sodium and lithium cations, and resistance to fluconazole. The species not only differed, in general, in their tolerance to high osmotic pressure (C. albicans and C. parapsilosis being the most osmotolerant) but exhibited distinct sensitivities to toxic sodium and lithium cations, with C. parapsilosis and C. tropicalis being very tolerant but C. krusei and C. dubliniensis sensitive to LiCl. The treatment of both fluconazole-susceptible (C. albicans and C. parapsilosis) and fluconazole-resistant (C. dubliniensis, C. krusei and C. tropicalis) growing cells with subinhibitory concentrations of fluconazole resulted in substantially elevated intracellular Na(+) levels. Using a diS-C3(3) assay, for the first time, to monitor the relative membrane potential (ΔΨ) of Candida cells, we show that the fluconazole treatment of growing cells of all five species results in a substantial hyperpolarization of their plasma membranes, which is responsible for an increased non-specific transport of toxic alkali metal cations and other cationic drugs (e.g., hygromycin B). Thus, the combination of relatively low doses of fluconazole and drugs, whose import into the tested Candida strains is driven by the cell membrane potential, might be especially potent in terms of its ability to inhibit the growth of or even kill various Candida species. PMID:23547882

  16. Muscarinic receptor size on smooth muscle cells and membranes

    SciTech Connect

    Collins, S.M.; Jung, C.Y.; Grover, A.K.

    1986-08-01

    The loss of (/sup 3/H)quinuclidinyl benzilate ((/sup 3/H)QNB) binding following high-energy radiation was used to compare the muscarinic receptor size on single smooth muscle cells isolated by collagenase digestion from the canine stomach and on plasma membranes derived from intact gastric smooth muscle without exposure to exogenous proteolysis. Radiation inactivation of galactose oxidase (68 kdaltons), yeast alcohol dehydrogenase (160 kdaltons), and pyruvate kinase (224 kdaltons) activities were used as molecular-weight standards. Radiation inactivation of (/sup 3/H)QNB binding to rat brain membranes, which gave a target size of 86 kdaltons, served as an additional control. In isolated smooth muscle cells, the calculated size of the muscarinic receptor was 80 +/- 8 kdaltons. In contrast, in a smooth muscle enriched plasma membrane preparation, muscarinic receptor size was significantly smaller at 45 +/- 3 kdaltons. Larger molecular sizes were obtained either in the presence of protease inhibitors (62 +/- 4 kdaltons) or by using a crude membrane preparation of gastric smooth muscle 86 +/- 7 kdaltons).

  17. Determining TGF-β Receptor Levels in the Cell Membrane.

    PubMed

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

    2016-01-01

    Transforming growth factor-β (TGF-β) is a pleiotropic cytokine that signals via transmembrane TGF-β type I and type II serine/threonine kinases receptors, i.e., TβRI and TβRII. Upon TGF-β-induced receptor complex formation, the TβRII kinase phosphorylates TβRI. Subsequently, the activated TβRI 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 TβRI is an important determinant to control the intensity and duration of TGF-β signaling. TβRI is targeted for poly-ubiquitylation-mediated proteasomal degradation by the SMAD7-SMURF E3 ligase complex. We recently identified another important regulatory factor that controls TβRI levels in the cell membrane. As a strong inducer of TGF-β signaling, ubiquitin-specific protease (USP) 4 was found to directly interact with TβRI and act as a deubiquitylating enzyme, thereby stabilizing TβRI levels at the plasma membrane. This chapter introduces methods for examining cell membrane receptor (TβRI) levels. PMID:26520116

  18. Sterol-Rich Membrane Domains Define Fission Yeast Cell Polarity.

    PubMed

    Makushok, Tatyana; Alves, Paulo; Huisman, Stephen Michiel; Kijowski, Adam Rafal; Brunner, Damian

    2016-05-19

    Cell polarization is crucial for the functioning of all organisms. The cytoskeleton is central to the process but its role in symmetry breaking is poorly understood. We study cell polarization when fission yeast cells exit starvation. We show that the basis of polarity generation is de novo sterol biosynthesis, cell surface delivery of sterols, and their recruitment to the cell poles. This involves four phases occurring independent of the polarity factor cdc42p. Initially, multiple, randomly distributed sterol-rich membrane (SRM) domains form at the plasma membrane, independent of the cytoskeleton and cell growth. These domains provide platforms on which the growth and polarity machinery assembles. SRM domains are then polarized by the microtubule-dependent polarity factor tea1p, which prepares for monopolar growth initiation and later switching to bipolar growth. SRM polarization requires F-actin but not the F-actin organizing polarity factors for3p and bud6p. We conclude that SRMs are key to cell polarization. PMID:27180904

  19. 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.

  20. 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.

  1. 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

  2. Interaction of Boron Nitride Nanosheets with Model Cell Membranes.

    PubMed

    Hilder, Tamsyn A; Gaston, Nicola

    2016-06-01

    Boron nitride nanomaterials have attracted attention for biomedical applications, due to their improved biocompatibility when compared with carbon nanomaterials. Recently, graphene and graphene oxide nanosheets have been shown, both experimentally and computationally, to destructively extract phospholipids from Escherichia coli. Boron nitride nanosheets (BNNSs) have exciting potential biological and environmental applications, for example the ability to remove oil from water. These applications are likely to increase the exposure of prokaryotes and eukaryotes to BNNSs. Yet, despite their promise, the interaction between BNNSs and cell membranes has not yet been investigated. Here, all-atom molecular dynamics simulations were used to demonstrate that BNNSs are spontaneously attracted to the polar headgroups of the lipid bilayer. The BNNSs do not passively cross the lipid bilayer, most likely due to the large forces experienced by the BNNSs. This study provides insight into the interaction of BNNSs with cell membranes and may aid our understanding of their improved biocompatibility. PMID:26934705

  3. 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.

  4. Collaboration between primitive cell membranes and soluble catalysts.

    PubMed

    Adamala, Katarzyna P; Engelhart, Aaron E; Szostak, Jack W

    2016-01-01

    One widely held model of early life suggests primitive cells consisted of simple RNA-based catalysts within lipid compartments. One possible selective advantage conferred by an encapsulated catalyst is stabilization of the compartment, resulting from catalyst-promoted synthesis of key membrane components. Here we show model protocell vesicles containing an encapsulated enzyme that promotes the synthesis of simple fatty acid derivatives become stabilized to Mg(2+), which is required for ribozyme activity and RNA synthesis. Thus, protocells capable of such catalytic transformations would have enjoyed a selective advantage over other protocells in high Mg(2+) environments. The synthetic transformation requires both the catalyst and vesicles that solubilize the water-insoluble precursor lipid. We suggest that similar modified lipids could have played a key role in early life, and that primitive lipid membranes and encapsulated catalysts, such as ribozymes, may have acted in conjunction with each other, enabling otherwise-impossible chemical transformations within primordial cells. PMID:26996603

  5. Collaboration between primitive cell membranes and soluble catalysts

    PubMed Central

    Adamala, Katarzyna P.; Engelhart, Aaron E.; Szostak, Jack W.

    2016-01-01

    One widely held model of early life suggests primitive cells consisted of simple RNA-based catalysts within lipid compartments. One possible selective advantage conferred by an encapsulated catalyst is stabilization of the compartment, resulting from catalyst-promoted synthesis of key membrane components. Here we show model protocell vesicles containing an encapsulated enzyme that promotes the synthesis of simple fatty acid derivatives become stabilized to Mg2+, which is required for ribozyme activity and RNA synthesis. Thus, protocells capable of such catalytic transformations would have enjoyed a selective advantage over other protocells in high Mg2+ environments. The synthetic transformation requires both the catalyst and vesicles that solubilize the water-insoluble precursor lipid. We suggest that similar modified lipids could have played a key role in early life, and that primitive lipid membranes and encapsulated catalysts, such as ribozymes, may have acted in conjunction with each other, enabling otherwise-impossible chemical transformations within primordial cells. PMID:26996603

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

    SciTech Connect

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

    2003-01-01

    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 trypsin 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.

  7. 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

  8. 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.

  9. Stimulation of Erythrocyte Cell Membrane Scrambling by Mushroom Tyrosinase

    PubMed Central

    Frauenfeld, Leonie; Alzoubi, Kousi; Abed, Majed; Lang, Florian

    2014-01-01

    Background: Mushroom tyrosinase, a copper containing enzyme, modifies growth and survival of tumor cells. Mushroom tyrosinase may foster apoptosis, an effect in part due to interference with mitochondrial function. Erythrocytes lack mitochondria but are able to undergo apoptosis-like suicidal cell death or eryptosis, which is characterized by cell shrinkage and cell membrane scrambling leading to phosphatidylserine-exposure at the erythrocyte surface. Signaling involved in the triggering of eryptosis include increase of cytosolic Ca2+-activity ([Ca2+]i) and activation of sphingomyelinase with subsequent formation of ceramide. The present study explored, whether tyrosinase stimulates eryptosis. Methods: Cell volume has been estimated from forward scatter, phosphatidylserine-exposure from annexin V binding, [Ca2+]i from Fluo3-fluorescence, and ceramide abundance from binding of fluorescent antibodies in flow cytometry. Results: A 24 h exposure to mushroom tyrosinase (7 U/mL) was followed by a significant increase of [Ca2+]i, a significant increase of ceramide abundance, and a significant increase of annexin-V-binding. The annexin-V-binding following tyrosinase treatment was significantly blunted but not abrogated in the nominal absence of extracellular Ca2+. Tyrosinase did not significantly modify forward scatter. Conclusions: Tyrosinase triggers cell membrane scrambling, an effect, at least partially, due to entry of extracellular Ca2+ and ceramide formation. PMID:24647148

  10. A review of polymer electrolyte membrane fuel cell stack testing

    NASA Astrophysics Data System (ADS)

    Miller, M.; Bazylak, A.

    This paper presents an overview of polymer electrolyte membrane fuel cell (PEMFC) stack testing. Stack testing is critical for evaluating and demonstrating the viability and durability required for commercial applications. Single cell performance cannot be employed alone to fully derive the expected performance of PEMFC stacks, due to the non-uniformity in potential, temperature, and reactant and product flow distributions observed in stacks. In this paper, we provide a comprehensive review of the state-of-the art in PEMFC testing. We discuss the main topics of investigation, including single cell vs. stack-level performance, cell voltage uniformity, influence of operating conditions, durability and degradation, dynamic operation, and stack demonstrations. We also present opportunities for future work, including the need to verify the impact of stack size and cell voltage uniformity on performance, determine operating conditions for achieving a balance between electrical efficiency and flooding/dry-out, meet lifetime requirements through endurance testing, and develop a stronger understanding of degradation.

  11. 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.

  12. Self-humidified proton exchange membrane fuel cells: Operation of larger cells and fuel cell stacks

    SciTech Connect

    Dhar, H.P.; Lee, J.H.; Lewinski, K.A.

    1996-12-31

    The PEM fuel cell is promising as the power source for use in mobile and stationary applications primarily because of its high power density, all solid components, and simplicity of operation. For wide acceptability of this power source, its cost has to be competitive with the presently available energy sources. The fuel cell requires continuous humidification during operation as a power source. The humidification unit however, increases fuel cell volume, weight, and therefore decreases its overall power density. Great advantages in terms of further fuel cell simplification can be achieved if the humidification process can be eliminated or minimized. In addition, cost reductions are associated with the case of manufacturing and operation. At BCS Technology we have developed a technology of self-humidified operation of PEM fuel cells based on the mass balance of the reactants and products and the ability of membrane electrode assembly (MEA) to retain water necessary for humidification under the cell operating conditions. The reactants enter the fuel cell chambers without carrying any form of water, whether in liquid or vapor form. Basic principles of self-humidified operation of fuel cells as practiced by BCS Technology, Inc. have been presented previously in literature. Here, we report the operation of larger self-humidified single cells and fuel cell stacks. Fuel cells of areas Up to 100 cm{sup 2} have been operated. We also show the self-humidified operation of fuel cell stacks of 50 and 100 cm{sup 2} electrode areas.

  13. A comparative study of water uptake by and transport through ionomeric fuel cell membranes

    SciTech Connect

    Zawodzinski, T.A.Jr.; Springer, T.E.; Davey, J.; Jestel, R.; Lopez, C.; Valerio, J.; Gottesfeld, S. . Electronics Materials and Device Research)

    1993-07-01

    Water uptake and transport parameters measured at 30 C for several available perfluorosulfonic acid membranes are compared. The water sorption characteristics, diffusion coefficient of water, electroosmotic drag, and protonic conductivity were determined for Nafion 117, Membrane C, and Dow XUS 13204.10 developmental fuel cell membrane. The diffusion coefficient and conductivity of each of these membranes were determined as functions of membrane water content. Experimental determination of transport parameters, enables one to compare membranes without the skewing effects of extensive features such as membrane thickness which contributes in a nonlinear fashion to performance in polymer electrolyte fuel cells.

  14. Characterization of Flavonoid 3[prime],5[prime]-Hydroxylase in Microsomal Membrane Fraction of Petunia hybrida Flowers.

    PubMed Central

    Menting, JGT.; Scopes, R. K.; Stevenson, T. W.

    1994-01-01

    We have detected a flavonoid 3[prime],5[prime]-hydroxylase (F3[prime],5[prime]H) in the microsomal fraction of Petunia hybrida flowers. Activity varied with the development of flowers, peaking immediately prior to and during anthesis, but was absent in mature flowers. F3[prime],5[prime]H activity in flower extracts from genetically defined floral color mutants correlated strictly with the genotypes Hf1 and Hf2. No activity was detected in flowers from mutants homozygous recessive for both alleles. F3[prime],5[prime]H activity was dependent on NADPH and molecular oxygen; there was only slight activity with NADH. The enzyme catalyzes the hydroxylation of 5,7,4[prime]-trihydroxyflavonone at the 3[prime] and 5[prime] positions, and of 5,7,3[prime],4[prime]-tetrahydroxyflavonone and dihydroquercetin at the 5[prime] position. Hydroxylase activity was inhibited by plant growth regulators (1-aminobenzotriazole and tetcyclacis) and by CO, N-ethylmaleimide, diethyldithiocarbamate, and cytochrome (Cyt) c. Activity was not affected by diethylpyrocarbonate or phenylmethylsulfonyl fluoride, but was enhanced by 2-mercaptoethanol. A polyclonal antibody that inhibits higher plant NADPH-Cyt P450 reductase inhibited the F3[prime],5[prime]H. The data are consistent with the suggestion that the P. hybrida F3[prime],5[prime]H is a monooxygenase consisting of a Cyt P450 and a NADPH-Cyt P-450 reductase. Cyts P450 were detected in microsomal membranes and in solubilized detergent extracts of these membranes. F3[prime],5[prime]H activity was sensitive to low concentrations of all detergents tested, and therefore solubilization of the active enzyme was not achieved. Reaction products other than flavanones were observed in F3[prime],5[prime]H assays and these may be formed by enzymic oxidation of flavanones. The possibility of a microsomal flavone synthase of a type that has not been described in P. hybrida is discussed. PMID:12232356

  15. 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 β5 integrin-GFP (β5-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 β5-GFP and the tight junction marker ZO-1 in manipulated cells by confocal microscopy. Fewer than 5 % of cells expressed β5-GFP after liposome-mediated transfection. The percentage of cells with detectable β5-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 β5-GFP but increased variability of β5-GFP level among cells. In cells with low expression levels, β5-GFP localized mostly to the apical plasma membrane like endogenous αvβ5 integrin. In cells with high expression levels, β5-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

  16. Quantitative analysis of cell surface membrane proteins using membrane-impermeable chemical probe coupled with 18O labeling

    SciTech Connect

    Zhang, Haizhen; Brown, Roslyn N.; Qian, Weijun; Monroe, Matthew E.; Purvine, Samuel O.; Moore, Ronald J.; Gritsenko, Marina A.; Shi, Liang; Romine, Margaret F.; Fredrickson, Jim K.; Pasa-Tolic, Ljiljana; Smith, Richard D.; Lipton, Mary S.

    2010-05-03

    We report a mass spectrometry-based strategy for quantitative analysis of cell surface membrane proteome changes. The strategy includes enrichment of surface membrane proteins using a membrane-impermeable chemical probe followed by stable isotope 18O labeling and LC-MS analysis. We applied this strategy for enriching membrane proteins expressed by Shewanella oneidensis MR-1, a gram-negative bacterium with known metal-reduction capability via extracellular electron transfer between outer membrane proteins and environmental electron receptors. LC/MS/MS analysis resulted in the identification of about 79% membrane proteins among all proteins identified from the enriched sample. To illustrate the quantification of membrane proteome changes, enriched membrane protein samples from wild-type and mutant cells (generated from deletion of a type II secretion protein, GspD) were further labeled with 16O and 18O at the peptide level prior to LC-MS analysis. A chemical-probe-labeled pure protein has also been used as an internal standard for normalization purpose. The quantitative data revealed reduced abundances of many outer membrane proteins such as OmcA and MtrC in ΔgspD mutant cells, which agreed well with previously published studies.

  17. Quantitative analysis of cell surface membrane proteins using membrane-impermeable chemical probe coupled with 18O labeling

    PubMed Central

    Zhang, Haizhen; Brown, Roslyn N.; Qian, Wei-Jun; Monroe, Matthew E.; Purvine, Samuel O.; Moore, Ronald J.; Gritsenko, Marina A.; Shi, Liang; Romine, Margaret F; Fredrickson, James K.; Paša-Tolić, Ljiljana; Smith, Richard D.; Lipton, Mary S.

    2010-01-01

    We report a mass spectrometry-based strategy for quantitative analysis of cell surface membrane proteome changes. The strategy includes enrichment of surface membrane proteins using a membrane-impermeable chemical probe followed by stable isotope 18O labeling and LC-MS analysis. We applied this strategy for enriching membrane proteins expressed by Shewanella oneidensis MR-1, a gram-negative bacterium with known metal-reduction capability via extracellular electron transfer between outer membrane proteins and extracellular electron receptors. LC/MS/MS analysis resulted in the identification of about 400 proteins with 79% of them being predicted to be membrane localized. Quantitative aspects of the membrane enrichment were shown by peptide level 16O and 18O labeling of proteins from wild-type and mutant cells (generated from deletion of a type II secretion protein, GspD) prior to LC-MS analysis. Using a chemical probe labeled pure protein as an internal standard for normalization, the quantitative data revealed reduced abundances in ΔgspD mutant cells of many outer membrane proteins including the outer membrane c-cype cytochromes OmcA and MtrC, in agreement with previously investigation demonstrating that these proteins are substrates of the type II secretion system. PMID:20380418

  18. Risks of using membrane filtration for trace metal analysis and assessing the dissolved metal fraction of aqueous media--a study on zinc, copper and nickel.

    PubMed

    Hedberg, Yolanda; Herting, Gunilla; Wallinder, Inger Odnevall

    2011-05-01

    Membrane filtration is commonly performed for solid-liquid separation of aqueous solutions prior to trace metal analysis and when assessing "dissolved" metal fractions. Potential artifacts induced by filtration such as contamination and/or adsorption of metals within the membrane have been investigated for different membrane materials, metals, applied pressures and pre-cleaning steps. Measurements have been conducted on aqueous solutions including well-defined metal standards, ultrapure water, and on runoff water from corroded samples. Filtration using both non-cleaned and pre-cleaned filters revealed contamination and adsorption effects, in particular pronounced for zinc, evident for copper but non-significant for nickel. The results clearly show these artifacts to be non-systematic both for non-cleaned and pre-cleaned membranes. The applied pressure was of minor importance. Measurements of the labile fraction by means of stripping voltammetry clearly elucidate that membrane filtration followed by total metal analysis cannot accurately assess the labile or the dissolved metal fraction. PMID:21367497

  19. Response of human tumor cell lines in vitro to fractionated irradiation.

    PubMed

    Matthews, J H; Meeker, B E; Chapman, J D

    1989-01-01

    The surviving fraction of human tumor cell lines after 2 Gy (SF2) varies between 0.1 and 0.8. It has been postulated that differences in inherent radiosensitivity of tumor cells are a major determinant of radiation response in vivo. Assays of inherent radiosensitivity based on acute survival are being developed as predictors of tumor response which often assume that the same inherent radiosensitivity persists throughout a fractionated treatment. We have investigated the response of 2 human tumor cell lines (A549 and MCF7) with different inherent radiosensitivities to in vitro fractionated irradiation. A549 cells had an SF2 of 0.62 and a mean inactivation dose (D) of 3.07 Gy whereas MCF7 cells had an SF2 of 0.30 and a D of 1.52 Gy. Split dose repair capacity (at equal survival levels) was less for A549 than for MCF7 cells and recovery kinetics for both cell lines were substantially longer than those of rodent cell lines. Survival after 5 fractions of 2 Gy given 12 hr apart at 37 degrees C was near to that predicted from the acute survival curve, assuming complete repair and no proliferation. Acute survival of A549 cells which survived 5 fractions of 2 Gy given 12 hr apart was similar to the acute survival of unirradiated cells. When A549 cells were incubated at 22 degrees C between 5 fractions of 2 Gy given 12 hr apart, proliferation and split dose repair were substantially inhibited. These studies support the proposals to use in vitro inherent radiosensitivity assays for the prediction of in vivo response of tumors to fractionated treatment. PMID:2912934

  20. Migration of connexin in the membranes of living cells

    NASA Astrophysics Data System (ADS)

    Bledsoe, Matthew; Rana, Daharsh; May, Karl; Kreft, Jennifer

    2008-11-01

    Movement of connexins within cell lipid bilayers remains somewhat mysterious. In studying their movement, researchers hoped to shed more light on the mechanisms by which they are influenced. We examined this problem by observing the behavior of the connexins directly. Cancerous human liver cells were cultured and their membrane connexins labeled with green fluorescent protein through transvection. The connexins were then filmed by high speed camera and carefully analyzed. The study served to fine-tune the model used in simulations of connexin migration, enabling further study of connexins and their transmembrane environment.

  1. 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

  2. Fault tolerance control for proton exchange membrane fuel cell systems

    NASA Astrophysics Data System (ADS)

    Wu, Xiaojuan; Zhou, Boyang

    2016-08-01

    Fault diagnosis and controller design are two important aspects to improve proton exchange membrane fuel cell (PEMFC) system durability. However, the two tasks are often separately performed. For example, many pressure and voltage controllers have been successfully built. However, these controllers are designed based on the normal operation of PEMFC. When PEMFC faces problems such as flooding or membrane drying, a controller with a specific design must be used. This paper proposes a unique scheme that simultaneously performs fault diagnosis and tolerance control for the PEMFC system. The proposed control strategy consists of a fault diagnosis, a reconfiguration mechanism and adjustable controllers. Using a back-propagation neural network, a model-based fault detection method is employed to detect the PEMFC current fault type (flooding, membrane drying or normal). According to the diagnosis results, the reconfiguration mechanism determines which backup controllers to be selected. Three nonlinear controllers based on feedback linearization approaches are respectively built to adjust the voltage and pressure difference in the case of normal, membrane drying and flooding conditions. The simulation results illustrate that the proposed fault tolerance control strategy can track the voltage and keep the pressure difference at desired levels in faulty conditions.

  3. 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 β-tricalcium phosphate (β-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 β-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

  4. 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.

  5. A hybrid microbial fuel cell membrane bioreactor with a conductive ultrafiltration membrane biocathode for wastewater treatment.

    PubMed

    Malaeb, Lilian; Katuri, Krishna P; Logan, Bruce E; Maab, Husnul; Nunes, S P; Saikaly, Pascal E

    2013-10-15

    A new hybrid, air-biocathode microbial fuel cell-membrane bioreactor (MFC-MBR) system was developed to achieve simultaneous wastewater treatment and ultrafiltration to produce water for direct reclamation. The combined advantages of this system were achieved by using an electrically conductive ultrafiltration membrane as both the cathode and the membrane for wastewater filtration. The MFC-MBR used an air-biocathode, and it was shown to have good performance relative to an otherwise identical cathode containing a platinum catalyst. With 0.1 mm prefiltered domestic wastewater as the feed, the maximum power density was 0.38 W/m(2) (6.8 W/m(3)) with the biocathode, compared to 0.82 W/m(2) (14.5 W/m(3)) using the platinum cathode. The permeate quality from the biocathode reactor was comparable to that of a conventional MBR, with removals of 97% of the soluble chemical oxygen demand, 97% NH3-N, and 91% of total bacteria (based on flow cytometry). The permeate turbidity was <0.1 nephelometric turbidity units. These results show that a biocathode MFC-MBR system can achieve high levels of wastewater treatment with a low energy input due to the lack of a need for wastewater aeration. PMID:24016059

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

    PubMed

    Gioia, Magda; Vindigni, Giulia; 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 MβCD 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

  7. 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 MβCD 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

  8. A flexible portable proton exchange membrane fuel cell

    NASA Astrophysics Data System (ADS)

    Hsu, Fu-Kuang; Lee, Ming-San; Lin, Chi-Chang; Lin, Yu-Kuo; Hsu, Wei-Ting

    2012-12-01

    A flexible portable proton exchange membrane fuel cell (PEMFC) is developed with non-directional flexibility acquired through new carbon-fibre-made current collectors and a new cell structure. The performance of a pilot cell suffers no significant loss when bent to curvatures with various radii in multiple directions. It also compares well with a nonflexible cylindrical portable PEMFC composed of similar components. The new cell is made with a single cup-like flexible main body with the membrane glued to the inside rim. The current collector is composed of several bunches of carbon fibre, each with metal wires embedded in them. The soft and flexible fibres not only allow for close and evenly-distributed contact with the bent electrode, but also change the character of the contact so that a large compressional force is no longer required to acquire low contact resistance which is, above all, the key to the success of this flexible cell design. The metal wire provides the needed flexibility to cover large curved electrode areas. A wire spring is used to pressure the collector against the electrode while the main body bends.

  9. Establishment of subcellular fractionation techniques to monitor the intracellular fate of polymer therapeutics II. Identification of endosomal and lysosomal compartments in HepG2 cells combining single-step subcellular fractionation with fluorescent imaging.

    PubMed

    Manunta, Maria; Izzo, Lorella; Duncan, Ruth; Jones, Arwyn Tomos

    2007-01-01

    As they are often designed for lysosomotropic, endosomotropic and/or transcellular delivery, an understanding of intracellular trafficking pathways is essential to enable optimised design of novel polymer therapeutics. Here, we describe a single-step density gradient subcellular fractionation method combined with fluorescent detection analysis that provides a new tool for characterisation of endocytic traffic of polymer therapeutics. Hepatoma (HepG2) cells were used as a model and cell breakage was optimised using a cell cracker to ensure assay of the whole cell population. After removal of unbroken cells and nuclei, the cell lysate as a post-nuclear supernatant (PNS) was layered onto an iodixanol (OptiPrep) density gradient optimised to 5-20%. Early endosomes, late endosomes and lysosomes were identified from gradient fractions by immunoblotting for marker proteins early endosome antigen 1 (EEA 1) and lysosomal associated membrane protein 1 (LAMP 1) using horseradish peroxidase or fluorescently-labelled secondary antibodies. Lysosomes were also detected using N-acetyl-beta-glucosamindase (Hex A) activity. In addition, cells were incubated with Texas-red labelled transferrin (TxR-Tf) for 5 min to specifically label early endosomes and this was directly detected from SDS-PAGE gels. Internalised macromolecules and colloidal particles can potentially alter vesicle buoyant density. To see if typical macromolecules of interest would alter vesicle density or perturb vesicle traffic, HepG2 cells were incubated with dextran or a polyethyleneglycol (PEG)-polyester dendron G4 (1 mg/ml for 24 h). The PEG-polyester dendron G4 caused a slight redistribution of endocytic structures to lower density fractions but immunofluorescence microscopy showed no obvious dendron effects. In conclusion, the combined subcellular fractionation with fluorescent imaging approach described here can be used as a tool for both fundamental cell biology research and/or the quantitative localisation

  10. 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.

  11. Stimulatory Effects of Polysaccharide Fraction from Solanum nigrum on RAW 264.7 Murine Macrophage Cells

    PubMed Central

    Razali, Faizan Naeem; Ismail, Amirah; Abidin, Nurhayati Zainal; Shuib, Adawiyah Suriza

    2014-01-01

    The polysaccharide fraction from Solanum nigrum Linne has been shown to have antitumor activity by enhancing the CD4+/CD8+ ratio of the T-lymphocyte subpopulation. In this study, we analyzed a polysaccharide extract of S. nigrum to determine its modulating effects on RAW 264.7 murine macrophage cells since macrophages play a key role in inducing both innate and adaptive immune responses. Crude polysaccharide was extracted from the stem of S. nigrum and subjected to ion-exchange chromatography to partially purify the extract. Five polysaccharide fractions were then subjected to a cytotoxicity assay and a nitric oxide production assay. To further analyze the ability of the fractionated polysaccharide extract to activate macrophages, the phagocytosis activity and cytokine production were also measured. The polysaccharide fractions were not cytotoxic, but all of the fractions induced nitric oxide in RAW 264.7 cells. Of the five fractions tested, SN-ppF3 was the least toxic and also induced the greatest amount of nitric oxide, which was comparable to the inducible nitric oxide synthase expression detected in the cell lysate. This fraction also significantly induced phagocytosis activity and stimulated the production of tumor necrosis factor-α and interleukin-6. Our study showed that fraction SN-ppF3 could classically activate macrophages. Macrophage induction may be the manner in which polysaccharides from S. nigrum are able to prevent tumor growth. PMID:25299340

  12. Development of Nanoparticles Incorporating a Novel Liposomal Membrane Destabilization Peptide for Efficient Release of Cargos into Cancer Cells

    PubMed Central

    Ohgita, Takashi; Kogure, Kentaro

    2014-01-01

    In anti-cancer therapy mediated by a nanoparticle-based drug delivery system (DDS), overall efficacy depends on the release efficiency of cargos from the nanoparticles in the cancer cells as well as the specificity of delivery to tumor tissue. However, conventional liposome-based DDS have no mechanism for specifically releasing the encapsulated cargos inside the cancer cells. To overcome this barrier, we developed nanoparticles containing a novel liposomal membrane destabilization peptide (LMDP) that can destabilize membranes by cleavage with intramembranous proteases on/in cancer cells. Calcein encapsulated in liposomes modified with LMDP (LMDP-lipo) was effectively released in the presence of a membrane fraction containing an LMDP-cleavable protease. The release was inhibited by a protease inhibitor, suggesting that LMDP-lipo could effectively release its cargo into cells in response to a cancer-specific protease. Moreover, when LMDP-lipo contained fusogenic lipids, the release of cargo was accelerated, suggesting that the fusion of LMDP-lipo with cellular membranes was the initial step in the intracellular delivery. Time-lapse microscopic observations showed that the release of cargo from LMDP-lipo occurred immediately after association of LMDP-lipo with target cells. Consequently, LMDP-lipo could be a useful nanoparticle capable of effective release of cargos specifically into targeted cancer cells. PMID:25343714

  13. 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

  14. Alkaline direct alcohol fuel cells using an anion exchange membrane

    NASA Astrophysics Data System (ADS)

    Matsuoka, Koji; Iriyama, Yasutoshi; Abe, Takeshi; Matsuoka, Masao; Ogumi, Zempachi

    Alkaline direct alcohol fuel cells using an OH-form anion exchange membrane and polyhydric alcohols were studied. A high open circuit voltage of ca. 800 mV was obtained for a cell using Pt-Ru/C (anode) and Pt/C (cathode) at 323 K, which was about 100-200 mV higher than that for a DMFC using Nafion ®. The maximum power densities were in the order of ethylene glycol > glycerol > methanol > erythritol > xylitol. Silver catalysts were used as a cathode catalyst to fabricate alkaline fuel cells, since silver catalyst is almost inactive in the oxidation of polyhydric alcohols. Alkaline direct ethylene glycol fuel cells using silver as a cathode catalyst gave excellent performance because higher concentrations of fuel could be supplied to the anode.

  15. The degradation and turnover of fucosylated glycoproteins in the plasma membrane of a neuroblastoma-cell line

    PubMed Central

    Hudson, James E.; Johnson, Terry C.

    1977-01-01

    When monolayer cultures of neuroblastoma N2a cells were prelabelled with [3H]fucose to steady state, and then reincubated in complete medium in the presence of unlabelled 40mm-l-fucose, there was a rapid metabolism of fucosylated cellular macromolecules and the specific radioactivity of the acid-insoluble material decreased by 22% within 2h. After this period of time the remaining radioactive glycoproteins appeared to be more stable and the rate of loss of specific radioactivity markedly decreased. Since fucose is known to be associated predominantly with plasma-membrane components, the analysis of fucosylated glycoproteins was characterized in plasma-membrane fractions by polyacrylamide-gel electrophoresis. Two experimental approaches were used to measure glycoprotein degradation and turnover in the cell-surface membranes. In one set of experiments, with a similar incubation procedure to that used with intact cells, three membrane components were rapidly degraded (150000, 130000 and 48000 daltons), but another surface glycoprotein (68000 daltons) appeared to be more slowly metabolized than the mean rate of glycoprotein degradation. The relationship of the degradation of membrane glycoproteins to their turnover was analysed by dual-label experiments that used both [14C]fucose and [3H]fucose. Glycoproteins of the surface membrane of neuroblastoma cells were found to turn over at heterogeneous rates. The components mentioned above that exhibited significantly rapid rates of degradation, were also shown to turn over more rapidly than the average surface component. In addition to the membrane components detected by the use of only [3H]fucose, dual-label experiments illustrated that numerous surface glycoproteins were metabolized more rapidly or slowly than most of the cell-surface constituents. PMID:911319

  16. Quantitative proteomics of the Neisseria gonorrhoeae cell envelope and membrane vesicles for the discovery of potential therapeutic targets.

    PubMed

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

    2014-05-01

    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

  17. 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

  18. Long range physical cell-to-cell signalling via mitochondria inside membrane nanotubes: a hypothesis.

    PubMed

    Scholkmann, Felix

    2016-01-01

    Coordinated interaction of single cells by cell-to-cell communication (signalling) enables complex behaviour necessary for the functioning of multicellular organisms. A quite newly discovered cell-to-cell signalling mechanism relies on nanotubular cell-co-cell connections, termed "membrane nanotubes" (MNTs). The present paper presents the hypothesis that mitochondria inside MNTs can form a connected structure (mitochondrial network) which enables the exchange of energy and signals between cells. It is proposed that two modes of energy and signal transmission may occur: electrical/electrochemical and electromagnetic (optical). Experimental work supporting the hypothesis is reviewed, and suggestions for future research regarding the discussed topic are given. PMID:27267202

  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. 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

  1. Laser-photophoretic migration and fractionation of human blood cells.

    PubMed

    Monjushiro, Hideaki; Tanahashi, Yuko; Watarai, Hitoshi

    2013-05-13

    Laser photophoretic migration behavior of human blood cells in saline solution was investigated under the irradiation of Nd:YAG laser beam (532 nm) in the absence and the presence of the flow in a fused silica capillary. Red blood cells (RBC) were migrated faster than white blood cells (WBC) and blood pellets to the direction of propagation of laser light. The observed photophoretic velocity of RBC was about 11 times faster than those of others. This was understood from the larger photophoretic efficiency of RBC than that of WBC, which was simulated based on the Mie scattering theory. Furthermore, it was found that, during the photophoretic migration, RBCs spontaneously orientated parallel to the migration direction so as to reduce the drag force. Finally, it was demonstrated that RBC and WBC were separated in a micro-channel flow system by the laser photophoresis. PMID:23622969

  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. Chemically-modified Nafion ®/poly(vinylidene fluoride) blend ionomers for proton exchange membrane fuel cells

    NASA Astrophysics Data System (ADS)

    Song, Min-Kyu; Kim, Young-Taek; Fenton, James M.; Kunz, H. Russell; Rhee, Hee-Woo

    Miscible Nafion ®/poly(vinylidene fluoride) blend membranes are prepared and characterized PVdF = poly(vinylidene fluoride). The membranes have high miscibility above a 60 wt.% Nafion ® fraction when both polymers are dissolved in a solvent mixture of N, N'-dimethylacetamide and 2-propanol. Despite the high miscibility, the extremely hydrophobic PVdF component reduces the water uptake of Nafion ®/PVdF blend, and the proton conductivity is much lower than that of a Nafion ® 115 membrane even with a high weight fraction of Nafion ®. To improve water affinity and proton conductivity, PVdF is chemically-modified by means of a dehydrofluorination reaction and H 2SO 4 doping prior to solution blend. The chemically-modified Nafion ®/PVdF blend membrane shows similar conductance to Nafion ® 115 without any auxiliary fillers. Nafion ®/PVdF blend membranes of ˜35 μm thickness are hot-pressed between catalyzed carbon paper ELAT ® electrodes. A 25 cm 2 single cell delivers a maximum power of about 440 mW cm -2 at 900 mA cm -2 under H 2/O 2, which is comparable to the performance of Nafion ® 115 under the same operating conditions.

  4. The action of antidiuretic hormone on cell membranes

    PubMed Central

    Cuthbert, A. W.; Painter, Elisabeth

    1969-01-01

    1. The instantaneous impedance method has been used to study the effects of antidiuretic hormone (ADH) on frog skin. 2. The resting skin may be represented by a parallel RC network with a single time constant. 3. Antidiuretic hormone causes an increase in conductance and capacitance and in some cases the appearance of a polarization angle. 4. The structures in the skin responsible for the transients are located in the outermost membranes. 5. The effects of ADH have been interpreted in terms of the formation of water-filled sodium-permselective pores in the outer facing membranes which occupy, at most, 0.3% of the skin surface. These pores constitute a parallel, and hence additive, capacitance with that of the normally ion impermeable parts of the cell surface, and in addition are responsible for the increase in conductance. The polarization angle is due to the polydisperse nature of the skin after hormone treatment. PMID:5762042

  5. Influence of estrogenic pesticides on membrane integrity and membrane transfer of monosaccharide into the human red cell

    SciTech Connect

    Ingermann, R.L. )

    1989-09-01

    Some natural and synthetic estrogens inhibit carrier-mediated transport of glucose into human red blood cells and membrane vesicles from the placenta. The inhibitory action of these estrogens on transport appears to be a direct effect at the membrane and does not involve receptor binding and protein synthesis. It is not clear, however, whether such inhibition is a common feature among estrogenic agents. Several chlorinated hydrocarbon pesticides have been shown to possess estrogenic activity. These pesticides could have inhibitory effects on the human sodium-independent glucose transporter. Owing to the apparent importance of this membrane transporter in human tissues, direct interaction of hormones and xenobiotics with the glucose transporter is of fundamental significance. Some pesticides have been shown to alter membrane structure directly and alter the passive permeability of membranes. Whether the estrogenic pesticides influence passive diffusion of sugars across membranes has not been established. Finally, preliminary observations have suggested that some estrogens and pesticides have lytic effects on intact cells. Consequently, this study focuses on the ability of several estrogens and estrogenic pesticides to disrupt the cell membrane, influence the monosaccharide transporter, and alter the rate of monosaccharide permeation through the membrane by simple diffusion.

  6. 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

  7. 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

  8. Membrane-Bound TRAIL Supplements Natural Killer Cell Cytotoxicity Against Neuroblastoma Cells

    PubMed Central

    Sheard, Michael A.; Asgharzadeh, Shahab; Liu, Yin; Lin, Tsen-Yin; Wu, Hong-Wei; Ji, Lingyun; Groshen, Susan; Lee, Dean A.; Seeger, Robert C.

    2013-01-01

    Neuroblastoma cells have been reported to be resistant to death induced by soluble, recombinant forms of TRAIL (CD253/TNFSF10) due to low or absent expression of caspase-8 and/or TRAIL-receptor 2 (TRAIL-R2/DR5/CD262/TNFRSF10b). However, their sensitivity to membrane-bound TRAIL on natural killer (NK) cells is not known. Comparing microarray gene expression and response to NK cell-mediated cytotoxicity, we observed a correlation between TRAIL-R2 expression and the sensitivity of fourteen neuroblastoma cell lines to the cytotoxicity of NK cells activated with IL-2 plus IL-15. Even though most NK cytotoxicity was dependent upon perforin, the cytotoxicity was supplemented by TRAIL in fourteen of seventeen (82%) neuroblastoma cell lines as demonstrated using an anti-TRAIL neutralizing antibody. Similarly, a recently developed NK cell expansion system employing IL-2 plus lethally irradiated K562 feeder cells constitutively expressing membrane-bound IL-21 (K562 clone 9.mbIL21) resulted in activated NK cells derived from normal healthy donors and neuroblastoma patients that also utilized TRAIL to supplement cytotoxicity. Exogenous IFNγ up-regulated expression of caspase-8 in three of four neuroblastoma cell lines and increased the contribution of TRAIL to NK cytotoxicity against two of the three lines; however, relatively little inhibition of cytotoxicity was observed when activated NK cells were treated with an anti-IFNγ neutralizing antibody. Constraining the binding of anti-TRAIL neutralizing antibody to membrane-bound TRAIL but not soluble TRAIL indicated that membrane-bound TRAIL alone was responsible for essentially all of the supplemental cytotoxicity. Together, these findings support a role for membrane-bound TRAIL in the cytotoxicity of NK cells against neuroblastoma cells. PMID:23719242

  9. 160 C PROTON EXCHANGE MEMBRANE (PEM) FUEL CELL SYSTEM DEVELOPMENT

    SciTech Connect

    L.G. Marianowski

    2001-12-21

    The objectives of this program were: (a) to develop and demonstrate a new polymer electrolyte membrane fuel cell (PEMFC) system that operates up to 160 C temperatures and at ambient pressures for stationary power applications, and (b) to determine if the GTI-molded composite graphite bipolar separator plate could provide long term operational stability at 160 C or higher. There are many reasons that fuel cell research has been receiving much attention. Fuel cells represent environmentally friendly and efficient sources of electrical power generation that could use a variety of fuel sources. The Gas Technology Institute (GTI), formerly Institute of Gas Technology (IGT), is focused on distributed energy stationary power generation systems. Currently the preferred method for hydrogen production for stationary power systems is conversion of natural gas, which has a vast distribution system in place. However, in the conversion of natural gas into a hydrogen-rich fuel, traces of carbon monoxide are produced. Carbon monoxide present in the fuel gas will in time cumulatively poison, or passivate the active platinum catalysts used in the anodes of PEMFC's operating at temperatures of 60 to 80 C. Various fuel processors have incorporated systems to reduce the carbon monoxide to levels below 10 ppm, but these require additional catalytic section(s) with sensors and controls for effective carbon monoxide control. These CO cleanup systems must also function especially well during transient load operation where CO can spike 300% or more. One way to circumvent the carbon monoxide problem is to operate the fuel cell at a higher temperature where carbon monoxide cannot easily adsorb onto the catalyst and poison it. Commercially available polymer membranes such as Nafion{trademark} are not capable of operation at temperatures sufficiently high to prevent this. Hence this project investigated a new polymer membrane alternative to Nafion{trademark} that is capable of operation at

  10. Force Balance and Membrane Shedding at the Red-Blood-Cell Surface

    NASA Astrophysics Data System (ADS)

    Sens, Pierre; Gov, Nir

    2007-01-01

    During the aging of the red-blood cell, or under conditions of extreme echinocytosis, membrane is shed from the cell plasma membrane in the form of nanovesicles. We propose that this process is the result of the self-adaptation of the membrane surface area to the elastic stress imposed by the spectrin cytoskeleton, via the local buckling of membrane under increasing cytoskeleton stiffness. This model introduces the concept of force balance as a regulatory process at the cell membrane and quantitatively reproduces the rate of area loss in aging red-blood cells.

  11. 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

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

    DOEpatents

    Shore, Lawrence

    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.

  13. Triggering of erythrocyte cell membrane scrambling by salinomycin.

    PubMed

    Bissinger, Rosi; Malik, Abaid; Jilani, Kashif; Lang, Florian

    2014-11-01

    Salinomycin, a polyether ionophore antibiotic effective against a variety of pathogens, has been shown to trigger apoptosis of cancer cells and cancer stem cells. The substance is thus considered for the treatment of malignancy. Salinomycin compromises tumour cell survival at least in part by interference with mitochondrial function. Erythrocytes lack mitochondria but may undergo apoptosis-like suicidal cell death or eryptosis, which is characterized by scrambling of the cell membrane with phosphatidylserine exposure at the erythrocyte surface. Signalling involved in the triggering of eryptosis includes activation of oxidant-sensitive Ca(2+) permeable cation channels with subsequent increase in cytosolic Ca(2+) activity ([Ca(2+)]i). This study explored whether salinomycin stimulates eryptosis. Phosphatidylserine-exposing erythrocytes were identified by measurement of annexin-V binding, cell volume was estimated from forward scatter, haemolysis determined from haemoglobin release, [Ca(2+)]i quantified utilizing Fluo3-fluorescence and oxidative stress from 2',7' dichlorodihydrofluorescein diacetate (DCFDA) fluorescence in flow cytometry. A 48-hr exposure to salinomycin (5-100 nM) was followed by a significant increase in Fluo3-fluorescence, DCFDA fluorescence and annexin-V binding, as well as a significant decrease in forward scatter (at 5-10 nM, but not at 50 and 100 nM). The annexin-V binding after salinomycin treatment was significantly blunted but not abrogated in the nominal absence of extracellular Ca(2+) or in the presence of antioxidant n-acetyl cysteine (1 mM). Salinomycin triggers cell membrane scrambling, an effect at least partially due to oxidative stress and entry of extracellular Ca(2+). PMID:24717091

  14. Carbon monoxide poisoning of proton-exchange membrane fuel cells

    SciTech Connect

    Rodrigues, A.; Amphlett, J.C.; Mann, R.F.; Peppley, B.A.; Roberge, P.R.

    1997-12-31

    The platinum-alloy catalyst used in proton-exchange membrane (PEM) fuel cell anodes is highly susceptible to carbon monoxide (CO) poisoning. CO reduces the catalyst activity by blocking active catalyst sites normally available for hydrogen chemisorption and dissociation. The reaction kinetics at the anode catalyst surface can be used to estimate the decrease in cell voltage due to various levels of CO contamination in the inlet fuel streams on PEM fuel cell performance have been reviewed and analyzed in an attempt to further understand the electrochemical properties of the CO adsorption process. A fuel cell performance model of bipolar, Nafion 117 PEM fuel cell stack has been developed which predicts equilibrium cell output voltage as a function of current density and partial pressure of CO. The model contains both empirical and mechanistic parameters and evolved from a steady-state electrochemical model for a PEM fuel cell fed with a CO-free anode gas. Reaction kinetics and equilibrium surface coverage have been incorporated into the electrochemical model to predict the decrease in fuel cell performance at equilibrium. The effects of CO were studied at various concentrations of CO in hydrogen as the anode feed gas. Literature data were used to develop the model parameters and the resulting model is used to compare the model-predicted voltages, with and without CO, to data found in the literature.

  15. [LIGHT-DEPENDENT SYNTHESIS OF CELL MEMBRANES IN THE Brc-1 MUTANT OF CHLAMYDOMONAS REINHARDTII].

    PubMed

    Semenova, G A; Chekunova, E M; Ladygin, V G

    2015-01-01

    The structural organization of cells of the Brc-1 mutant of the unicellular green algae Chlamydomonas reinhardtii grown in the light and in the dark has been studied. The Brc-1 mutant contains the brc-1 mutation in the nucleus gene LTS3. In the light, all membrane structures in mutant cells form normally and are well developed. In the dark under heterotrophic conditions, the mutant cells grew and divided well, however, all its cell membranes: plasmalemma, tonoplast, mitochondrial membranes, membranes of the nucleus shell and chloroplast, thylakoids, and the membranes of dictiosomes of the Golgi apparatus were not detected. In the dark under heterotrophic conditions, mutant cells well grow and divide. It were shown that a short-term (1-10 min) exposure of Brc-1 mutant cells to light leads to the restoration of all above-mentioned membrane structures. Possible reasons for the alterations of membrane structures are discussed. PMID:26281212

  16. Regulation of Cell Contraction and Membrane Ruffling by Distinct Signals in Migratory Cells

    PubMed Central

    Cheresh, David A.; Leng, Jie; Klemke, Richard L.

    1999-01-01

    Cell migration and wound contraction requires assembly of actin into a functional myosin motor unit capable of generating force. However, cell migration also involves formation of actin-containing membrane ruffles. Evidence is provided that actin-myosin assembly and membrane ruffling are regulated by distinct signaling pathways in the migratory cell. Interaction of cells with extracellular matrix proteins or cytokines promote cell migration through activation of the MAP kinases ERK1 and ERK2 as well as the molecular coupling of the adaptor proteins p130CAS and c-CrkII. ERK signaling is independent of CAS/Crk coupling and regulates myosin light chain phosphorylation leading to actin-myosin assembly during cell migration and cell-mediated contraction of a collagen matrix. In contrast, membrane ruffling, but not cell contraction, requires Rac GTPase activity and the formation of a CAS/Crk complex that functions in the context of the Rac activating protein DOCK180. Thus, during cell migration ERK and CAS/Crk coupling operate as components of distinct signaling pathways that control actin assembly into myosin motors and membrane ruffles, respectively. PMID:10477763

  17. 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)

  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. Glycomics and glycoproteomics of membrane proteins and cell-surface receptors: Present trends and future opportunities.

    PubMed

    Chandler, Kevin Brown; Costello, Catherine E

    2016-06-01

    Membrane proteins mediate cell-cell interactions and adhesion, the transfer of ions and metabolites, and the transmission of signals from the extracellular environment to the cell interior. The extracellular domains of most cell membrane proteins are glycosylated, often at multiple sites. There is a growing awareness that glycosylation impacts the structure, interaction, and function of membrane proteins. The application of glycoproteomics and glycomics methods to membrane proteins has great potential. However, challenges also arise from the unique physical properties of membrane proteins. Successful analytical workflows must be developed and disseminated to advance functional glycoproteomics and glycomics studies of membrane proteins. This review explores the opportunities and challenges related to glycomic and glycoproteomic analysis of membrane proteins, including discussion of sample preparation, enrichment, and MS/MS analyses, with a focus on recent successful workflows for analysis of N- and O-linked glycosylation of mammalian membrane proteins. PMID:26872045